tag:theconversation.com,2011:/id/topics/chemistry-730/articlesChemistry – The Conversation2024-03-22T12:32:08Ztag:theconversation.com,2011:article/2248152024-03-22T12:32:08Z2024-03-22T12:32:08ZWhat’s in tattoo ink? My team’s chemical analysis found ingredients that aren’t on the label and could cause allergies<figure><img src="https://images.theconversation.com/files/581794/original/file-20240313-30-tf41i8.jpg?ixlib=rb-1.1.0&rect=0%2C17%2C5751%2C3811&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Tattoo ink ingredients don't always match what's labeled on the bottle. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/CubaTattoos/b36471bdd2ff4e6e8a19a9b9644768d0/photo?Query=tattoo%20ink&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=406&digitizationType=Digitized&currentItemNo=0&vs=true&vs=true">AP Photo/Desmond Boylan</a></span></figcaption></figure><p>Tattoos are an incredibly common form of permanent self-expression that date back <a href="https://theconversation.com/tattoos-have-a-long-history-going-back-to-the-ancient-world-and-also-to-colonialism-165584">thousands of years</a>. Most tattoo artists follow strict health and sanitation regulations, so you might assume that tattoo inks are carefully regulated, too. </p>
<p>But as work done by <a href="https://scholar.google.com/citations?user=F2mp97YAAAAJ&hl=en">my team of chemistry researchers</a> suggests, <a href="https://doi.org/10.1021/acs.analchem.3c05687">up to 90%</a> of tattoo inks in the U.S. might be mislabeled. This isn’t just a case of a missing pigment or a minor discrepancy. These inks contained potentially concerning additives that weren’t listed on the packaging. </p>
<h2>What’s in an ink?</h2>
<p>All inks are made up of one or more pigments, which are molecules that give tattoos their color, and some kind of carrier for that pigment. Before the 20th century, <a href="https://www.trinitybj.com/blog/articles/tattoo-ink-throughout-time">pigments used in tattooing</a> included ash, charcoal, minerals or other natural materials. Around the middle of the 20th century, though, tattoo artists started making their own inks using synthetic pigments and dyes. </p>
<p>Today, nearly all pigments used in tattoos are made of <a href="https://f1000research.com/articles/6-2034/v2">synthetic molecules</a> that allow for bright colors – with the exception of white and black pigments.</p>
<p>In the past few decades, tattoo ink manufacturing has shifted from individual artists making their own to large companies manufacturing inks and selling them to artists. My team wanted to figure out whether these inks contained the ingredients advertised, so we <a href="https://doi.org/10.1021/acs.analchem.3c05687">analyzed 54 tattoo inks</a> from the U.S. market. </p>
<h2>Unlisted ingredients</h2>
<p>More than half the inks my research team analyzed contained unlisted polyethylene glycol, also known as PEG. A variety of <a href="https://en.wikipedia.org/wiki/Polyethylene_glycol">medical products</a> contain PEG, including laxatives. It can cause <a href="https://doi.org/10.1111/all.14711">allergic reactions</a>, however, and in the case of tattooing, <a href="https://doi.org/10.1007/s00204-016-1739-2">research has suggested</a> that repeated exposure to PEG could lead to kidney failure.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two carbon atoms, with OH groups at each end." src="https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=256&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=256&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=256&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=322&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=322&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=322&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Polyethylene glycol’s chemical structure.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:PEG_Structural_Formula_V1.svg">Jü/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>We also found <a href="https://pubchem.ncbi.nlm.nih.gov/compound/Propylene-Glycol">propylene glycol</a> in 15 inks, though it wasn’t listed as an ingredient in any of them. Propylene glycol is generally nontoxic and structurally similar to glycerin, which is used to thicken the ink. Even though propylene glycol is safe for most people, some people are highly allergic to it. In fact, it was the American Contact Dermatitis Society’s <a href="https://dermnetnz.org/topics/contact-allergy-to-propylene-glycol">2018 Allergen of the Year</a>. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three carbon atoms, with OH groups connected to the first and 2nd carbons." src="https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=457&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=457&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=457&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Propylene glycol’s chemical structure.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Propylene_glycol_chemical_structure.png">Edgar181/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>An <a href="https://www.contactdermatitisinstitute.com/pdfs/allergens/Propylene%20glycol.pdf">allergic reaction</a> to propylene glycol can cause a skin rash, itching and blistering. </p>
<p>In several inks, my research team found unlisted ingredients that are common in cosmetics but have not been tested in tattoo inks. <a href="https://doi.org/10.1080/10915810290096513">These include BHT</a>, <a href="https://www.paulaschoice.com/ingredient-dictionary/ingredient-dodecane.html">dodecane</a> and <a href="https://www.webmd.com/beauty/what-to-know-about-phenoxyethanol">2-phenoxyethanol</a>. In low concentrations, 2-phenoxyethanol can be a preservative. But the <a href="https://doi.org/10.1038/s41598-020-58170-9">Food and Drug Administration has warned</a> that it could get passed to infants through breastfeeding and lead to vomiting and dehydration in babies.</p>
<p>Of the 54 inks we analyzed, 29 reported the correct pigments, while the rest either did not report or reported the wrong pigments. <a href="https://www.kantonslabor.bs.ch/dam/jcr:ba246390-48da-406f-aa4e-9e1b24726a31/JB_Tattoo_PMU_2011_EN.pdf">This is a known</a> <a href="https://doi.org/10.1111/cod.13913">problem in tattoo inks</a> that ink manufacturers have not yet addressed. </p>
<h2>Pigment concerns</h2>
<p><a href="https://doi.org/10.3390/cosmetics10050141">Studies have found</a> that carbon black, the primary black pigment used in tattooing, can be contaminated with some of the same <a href="https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon">cancer-causing molecules</a> found in car exhaust and cigarette smoke.</p>
<p>Many red, yellow and orange pigments are azo pigments, which contain two connected nitrogen atoms. These pigments give ink bright, vivid colors, but over time they may <a href="https://doi.org/10.1007/s00204-016-1739-2">break down into carcinogens</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tattoo artist wearing latex gloves holding a tattooing needle inks a geometric design on an arm." src="https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The pigments in many tattoo inks are made up of synthetic molecules.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/InkcarcerationMusicandTattooFestival-Day1/7d0d0d2e40d64d4bbe7a0985aa992734/photo?Query=tattooing&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=382&digitizationType=Digitized&currentItemNo=7&vs=true&vs=true">Amy Harris/Invision/AP</a></span>
</figcaption>
</figure>
<p><a href="https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32020R2081#document1">Regulations in Europe</a> prohibit the use of copper-containing pigment blue 15 and pigment green 7, which my work observed to be the only blue and green pigments in the inks we tested. The EU banned these pigments over concern that their use in hair dyes <a href="https://mobil.bfr.bund.de/cm/349/tattoo-inks-risk-assessment-for-pigment-blue-15-3-and-pigment-green-7.pdf">may cause bladder cancer</a>, though researchers haven’t studied that connection in tattoos yet. </p>
<h2>A new focus on regulation</h2>
<p>The FDA is beginning to pay more attention to what is in tattoo inks. In 2022, Congress passed the <a href="https://www.fda.gov/cosmetics/cosmetics-laws-regulations/modernization-cosmetics-regulation-act-2022-mocra">Modernization of Cosmetics Regulation Act, or MoCRA</a>, which gave the FDA expanded authority to regulate tattoo inks. </p>
<p>The FDA is still deciding how to implement MoCRA, but the act will require accurate ingredient labeling and expand the FDA’s authority to recall ink. In the past, tattoo inks have very rarely, and only voluntarily, been recalled because of <a href="https://doi.org/10.3389/fpubh.2023.1279884">bacterial contamination</a>.</p>
<p>So what does this mean for tattoo clients and artists? Right now, there’s no clear research consensus on whether tattoos are safe or not, as they can cause infection and allergic reactions. Plus, tattoos vary widely in size, color and physical location on the body.</p>
<p>Studies like the one from my lab are an important piece in establishing what is actually in a tattoo, so that researchers can better understand any adverse events, such as long-term allergic reactions, that they might cause.</p>
<p>Understanding what is in ink also helps physicians identify what particular health concerns they should look for in tattooed individuals.</p>
<p>The tattoo-related health issues that researchers <a href="https://www.aerzteblatt.de/int/archive/article/182859">do know about</a> come from unskilled artists following poor sanitation protocols. To prevent potential health concerns, those considering a tattoo can work with an experienced and trained artist who follows best practices for hygiene and tattoo aftercare.</p><img src="https://counter.theconversation.com/content/224815/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Swierk receives funding from National Institute of Health, National Science Foundation, and American Chemical Society Petroleum Research Fund. </span></em></p>Some tattoo inks contain unlabeled materials that can cause allergic reactions.John Swierk, Assistant Professor, Chemistry, Binghamton University, State University of New YorkLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2240642024-03-14T19:24:44Z2024-03-14T19:24:44ZWhat washing machine settings can I use to make my clothes last longer?<figure><img src="https://images.theconversation.com/files/581554/original/file-20240313-30-b0w0se.jpg?ixlib=rb-1.1.0&rect=194%2C310%2C4780%2C3135&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-accidentally-dyeing-laundry-inside-washing-236885413">Monkey Business Images/Shutterstock</a></span></figcaption></figure><p>Orbiting 400 kilometres above Earth’s surface, the astronauts on the International Space Station live a pretty normal social life, if not for one thing: they happily wear their unwashed clothes <a href="https://www.nasa.gov/centers-and-facilities/glenn/nasa-glenn-interns-take-space-washing-machine-designs-for-a-spin/">for days and weeks at a time</a>. They can’t do their laundry <a href="https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Keeping_your_underwear_clean_on_the_Moon">just yet</a> because water is scarce up there.</p>
<p>But down here on Earth, washing clothes is a large part of our lives. <a href="https://bigee.net/media/filer_public/2013/03/28/bigee_domestic_washing_machines_worldwide_potential_20130328.pdf">It’s estimated</a> that a volume of water equivalent to 21,000 Olympic swimming pools is used every day for domestic laundry worldwide.</p>
<p>Fibres from our clothes make their way into the environment via the air (during use or in the dryer), water (washing) and soil (lint rubbish in landfill). Most of this fibre loss is invisible – we often only notice our favourite clothing is “disappearing” when it’s too late.</p>
<p>How can you ensure your favourite outfit will outlast your wish to wear it? Simple question, complex answer.</p>
<h2>Washing machines are not gentle</h2>
<p>When you clean the filters in your washing machine and dryer, how often do you stop to think that the lint you’re holding <a href="https://theconversation.com/uk-laundry-releases-microfibres-weighing-the-equivalent-of-1-500-buses-each-year-199712"><em>was</em>, in fact, your clothes</a>?</p>
<p>Laundering is harsh on our clothes, and <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0250346">research confirms this</a>. Several factors play a role: the type of washing machine, the washing cycle, detergents, temperature, time, and the type of fabric and yarn construction. </p>
<p>There are two types of domestic washing machines: top-loader and front-loader. Mechanical agitation (the way the machine moves the clothes around) is one of the things that helps ease dirt off the fabric.</p>
<p>Top-loaders have a vertical, bucket-like basket with a paddle, which sloshes clothes around in a large volume of water. Front-loaders have a horizontal bucket which rotates, exposing the clothes to a smaller volume of water – it takes advantage of gravity, not paddles.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/581556/original/file-20240313-26-zgawjl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A person selecting a program on a front loader washing machine panel with buttons." src="https://images.theconversation.com/files/581556/original/file-20240313-26-zgawjl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581556/original/file-20240313-26-zgawjl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581556/original/file-20240313-26-zgawjl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581556/original/file-20240313-26-zgawjl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581556/original/file-20240313-26-zgawjl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581556/original/file-20240313-26-zgawjl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581556/original/file-20240313-26-zgawjl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Washing machine programs tend to be carefully programmed to ensure minimal damage to the garments.</span>
<span class="attribution"><a class="source" href="https://www.pexels.com/photo/person-using-washing-machine-5591460/">RDNE Stock Project/Pexels</a></span>
</figcaption>
</figure>
<p>Top-loading machines <a href="https://link.springer.com/article/10.1007/s12541-010-0047-7">tend to be more aggressive</a> towards fabrics than front-loaders due to the different mechanical action and larger volumes of water. </p>
<p>Washing machine panels also present many choices. Shorter, low-temperature programs <a href="https://clevercare.info/more-eco-temperature-tips">are usually sufficient for everyday stains</a>. Choose longer or <a href="https://iprefer30.eu/animations/UK/wash-brochure-uk.pdf">high-temperature programs</a> only for clothing you have concerns about (healthcare uniforms, washable nappies, etc.).</p>
<p>Generally, washing machine programs are carefully selected combinations of water volume, agitation intensity and temperature recommended by the manufacturer. They take into consideration the type of fabric and its level of cleanliness.</p>
<p>Select the wrong program and you can say goodbye to your favourite top. For example, high temperatures or harsh agitation may cause some fibres to weaken and break, causing holes in the garment.</p>
<h2>Some fabrics lose fibres more easily than others</h2>
<p>At a microscopic level, the fabric in our clothes is made of yarns – individual fibres twisted together. The nature and length of the fibres, the way they are twisted and the way the yarns form the fabric can determine how many fibres will be lost during a wash.</p>
<p>In general, if you want to lose fewer fibres, you should wash less frequently, but some fabrics are affected more than others. </p>
<p>Open fabric structures (knits) with loose yarns <a href="https://www.nature.com/articles/s41598-021-98836-6">can lose more fibres</a> than tighter ones. Some sports clothing, like running shirts, are made of continuous filament yarn. These fibres are less likely to come loose in the wash. </p>
<p>Cotton fibres are only a few centimetres long. Twisted tightly together into a yarn, they can still escape.</p>
<p>Wool fibres are also short, but have an additional feature: scales, which make wool clothes much more delicate. Wool fibres can come loose like cotton ones, but also tangle with each other during the wash due to their scales. This last aspect is what causes wool garments to shrink when <a href="https://journals.sagepub.com/doi/abs/10.1177/004051756403400303">exposed to heat</a> and agitation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/581557/original/file-20240313-22-s1rv88.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tangle of white fibres in a loose web." src="https://images.theconversation.com/files/581557/original/file-20240313-22-s1rv88.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581557/original/file-20240313-22-s1rv88.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581557/original/file-20240313-22-s1rv88.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581557/original/file-20240313-22-s1rv88.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581557/original/file-20240313-22-s1rv88.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581557/original/file-20240313-22-s1rv88.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581557/original/file-20240313-22-s1rv88.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cotton fibres under a microscope, magnified 100 times.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/fibres-under-microscope-100x-1013172277">Dr. Norbert Lange/Shutterstock</a></span>
</figcaption>
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Read more:
<a href="https://theconversation.com/laundry-is-a-top-source-of-microplastic-pollution-heres-how-to-clean-your-clothes-more-sustainably-217072">Laundry is a top source of microplastic pollution – here's how to clean your clothes more sustainably</a>
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</em>
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<h2>Go easy on the chemicals</h2>
<p>The type of detergent and other products you use also makes a difference.</p>
<p>Detergents contain a soap component, enzymes to make stains easier to remove at low temperature, and fragrances. Some contain harsher compounds, such as bleaching or whitening agents.</p>
<p>Modern detergents are very effective at <a href="https://www.choice.com.au/home-and-living/laundry-and-cleaning/laundry-detergents/review-and-compare/laundry-detergents">removing stains such as food</a>, and you don’t need to use much.</p>
<p>An incorrect choice of wash cycles, laundry detergent and bleaching additives could cause disaster. Certain products, like bleach, can <a href="https://site.extension.uga.edu/textiles/textile-basics/understand-your-fibers/">damage some fibres like wool and silk</a>.</p>
<p>Meanwhile, research on <a href="https://www.sciencedirect.com/science/article/pii/S0269749120366872?via%3Dihub">fabric softeners and other treatments</a> <a href="https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0233332&type=printable">continues</a> – there’s no one-size-fits-all answer about their potential impact on our clothes.</p>
<h2>Just skip laundry day</h2>
<p>So, how to ensure your clothes last longer? The main tip is to wash them less often.</p>
<p>When it’s time for a wash, carefully read and follow the care labels. In the future, our washing machines will <a href="https://www.teknoscienze.com/tks_article/trends-in-laundry-by-2030/">recognise fabrics and select the wash cycle</a>. For now, that’s our responsibility.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-make-your-clothes-last-longer-its-good-for-your-bank-account-and-the-environment-too-201823">How to make your clothes last longer – it's good for your bank account and the environment too</a>
</strong>
</em>
</p>
<hr>
<p>And the next time you throw your shirt into the dirty laundry basket, stop. Think of the astronauts orbiting above Earth and ask yourself: if they can go without clean laundry for a few days, maybe I can too? (Although we don’t recommend just burning your dirty undies, either.)</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/C1j6KLP492E?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure><img src="https://counter.theconversation.com/content/224064/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alessandra Sutti has received research funding from the Australian Research Council, the Marine Bioproducts Cooperative Research Centre, the Innovative Manufacturing Cooperative Research Centre and by companies participating in associated projects such as the ARC Research Hub for Functional and Sustainable Fibres and the ARC Industrial Transformation Training Centre for Green Chemistry, as well as from industry partners associated with these grants, such as HeiQ Pty Ltd, Xefco Pty Ltd, C. Sea Solutions Pty Ltd (trading as ULUU) and Simba Global Pty/Ltd. Alessandra is a paid member of the HeiQ Innovation Advisory Board, is a member of the American Chemical Society and serves as a volunteer member on Standards Australia ME-009 Committee (Microplastics). She collaborates closely with The GLOBE Program (through GLOBE Italy), The University of California Berkeley and San Francisco State University, co-developing microplastics monitoring protocols and is involved in environmental education programmes.</span></em></p><p class="fine-print"><em><span>Amol Patil is engaged at the ARC Research Hub for Functional and Sustainable Fibres, a collaboration between Deakin University, the Australian Research Council and industry partners such as Simba Global Pty Ltd, Xefco Pty Ltd, HeiQ Pty Ltd, and Sea Solutions P/L (trading as ULUU). He is also working on a joint project sponsored by HeiQ-Marine bioproducts (MBCRC). </span></em></p><p class="fine-print"><em><span>Maryam Naebe is the recipient of Discover Natural Fibre Initiative Innovation Award. She has received funding through competitive grants and industry projects including Australian Research Council ARC Research Hub, ARC Discovery Project, Australian Wool Innovation, Cotton Research and Development Corporation, Cotton Incorporated (USA), Ford Motor Company (USA).
</span></em></p>Next time you do your laundry, think like an astronaut – wash your clothes as little as possible.Alessandra Sutti, Associate Professor, Institute for Frontier Materials, Deakin UniversityAmol Patil, Reseach Engineer, Deakin UniversityMaryam Naebe, Associate professor, Deakin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2251772024-03-13T19:15:03Z2024-03-13T19:15:03ZVinegar and baking soda: a cleaning hack or just a bunch of fizz?<figure><img src="https://images.theconversation.com/files/581208/original/file-20240312-20-t421p3.jpg?ixlib=rb-1.1.0&rect=270%2C48%2C3915%2C2868&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/caucasian-man-green-sponge-his-hand-2020591898">Daniele De Vivo/Shutterstock</a></span></figcaption></figure><p>Vinegar and baking soda are staples in the kitchen. Many of us have combined them in childhood scientific experiments: think fizzy volcanoes and geysers. </p>
<p>But people also frequently mix vinegar and baking soda to produce a reportedly effective household cleaner. Unfortunately, the chemistry behind the bubbly reaction doesn’t support the cleaning hype. The fizzy action is essentially <a href="https://theconversation.com/six-surprising-things-about-placebos-everyone-should-know-220829">a visual “placebo</a>”, formed by the combination of an acid and a base. </p>
<p>So, how does it work, and is it worth using these chemicals for cleaning? To understand all this, it helps to know a little more about chemistry. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-new-tiktok-trend-has-people-drinking-toxic-borax-an-expert-explains-the-risks-and-how-to-read-product-labels-210278">A new TikTok trend has people drinking toxic borax. An expert explains the risks – and how to read product labels</a>
</strong>
</em>
</p>
<hr>
<h2>What’s an acid?</h2>
<p>Foods with a sour taste typically contain acids. These include citric acid in lemon juice, malic acid in apples, lactic acid in yoghurt and <a href="https://theconversation.com/kitchen-science-everything-you-eat-is-made-of-chemicals-56583">phosphoric acids in soft drinks</a>. Most vinegars contain around 4–10% acetic acid, the rest is water and small amounts of flavour chemicals.</p>
<p>There are other naturally occurring acids, such as formic acid in ant bites and hydrochloric acid in our stomachs. Industrially, sulfuric acid is used in mineral processing, nitric acid for <a href="https://theconversation.com/what-is-ammonium-nitrate-the-chemical-that-exploded-in-beirut-143979">fertiliser manufacturing</a> and the highly potent hydrofluoric acid is used to etch glass.</p>
<p>All of these acids share similar properties. They can all release hydrogen ions (positively charged atoms) into water. Depending on their potency, acids can also dissolve minerals and metals through various chemical reactions.</p>
<p>This is why vinegar is an excellent cleaner for showers or kettles – it can react with and dissolve mineral deposits like limescale. </p>
<p>Other common acidic cleaning ingredients are oxalic acid, used for revitalising timber decks, hydrochloric acid in concrete and masonry cleaners, and sulfamic acid in potent toilet cleaners.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/581224/original/file-20240312-18-tb4sa3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hand in a yellow glove cleaning the inside of a shower screen with a squeegee." src="https://images.theconversation.com/files/581224/original/file-20240312-18-tb4sa3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581224/original/file-20240312-18-tb4sa3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=440&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581224/original/file-20240312-18-tb4sa3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=440&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581224/original/file-20240312-18-tb4sa3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=440&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581224/original/file-20240312-18-tb4sa3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=552&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581224/original/file-20240312-18-tb4sa3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=552&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581224/original/file-20240312-18-tb4sa3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=552&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Adding some vinegar to your shower cleaning routine can help to dissolve away the limescale deposits on the glass.</span>
<span class="attribution"><a class="source" href="https://www.pexels.com/photo/crop-person-cleaning-glass-shower-unit-4239091/">Karolina Grabowska/Pexels</a></span>
</figcaption>
</figure>
<h2>What’s a base?</h2>
<p>In chemistry, bases – the opposite of acids in many ways – can bind, rather than release hydrogen ions. This can help lift and dissolve insoluble grime into water. Bases can also break apart fat molecules. </p>
<p>Baking soda (also known as sodium hydrogen carbonate, sodium bicarbonate, or bicarb) is a relatively weak base. Stronger common bases include sodium carbonate (washing soda), sodium hydroxide (lye) and ammonia.</p>
<p><a href="https://theconversation.com/spill-at-a-nuclear-facility-shows-potential-burn-risks-from-a-household-chemical-112763">Sodium hydroxide</a> is a potent drain cleaner – its strong base properties can dissolve fats and hair. This allows blockages to be broken down and easily flushed away.</p>
<h2>Mixing a base and an acid</h2>
<p>Mixing vinegar and baking soda causes an immediate chemical reaction. This reaction forms water, sodium acetate (a salt) and carbon dioxide – the fizzy part. </p>
<p>The amount of carbon dioxide gas that is produced from baking soda is remarkable – one tablespoon (around 18 grams) can release over <a href="https://www.chemedx.org/JCESoft/jcesoftSubscriber/CCA/CCA8/MAIN/8/06/2/4/movie.html">five litres of gas</a>! But only if you add enough acid.</p>
<p>Reactions in chemistry often use equal quantities of chemical reagents. A perfect balance of acetic acid and baking soda would give you just water, carbon dioxide and sodium acetate. </p>
<p>But the majority of vinegar and bicarb cleaner recipes use a large excess of one or the other components. An example from TikTok for a DIY oven cleaner calls for one and a half cups of baking soda and one quarter cup of vinegar. </p>
<p>Crunching the numbers behind the chemical reaction shows that after the fizz subsides, over 99% of the added baking soda remains. So the active cleaning agent here is actually the baking soda (and the “elbow grease” of scrubbing).</p>
<p><div data-react-class="TiktokEmbed" data-react-props="{"url":"https://www.tiktok.com/@carmsssdi/video/6846229758724885765"}"></div></p>
<p>Ovens can be cleaned much more rigorously with stronger, sodium hydroxide based cleaners (although these are also more caustic). Many modern ovens also have a self-cleaning feature, so read your product manual before reaching for a chemical cleaner of any sort.</p>
<h2>What about the sodium acetate?</h2>
<p>Devotees of vinegar and baking soda mixtures might be wondering if the product of the fizzy reaction, sodium acetate, is the undercover cleaning agent. </p>
<p>Unfortunately, sodium acetate is an even weaker base than baking soda, so it doesn’t do much to clean the surface you’re trying to scrub.</p>
<p>Sodium acetate is used in <a href="https://www.youtube.com/watch?v=vABpel-11Nc">crystallisation-based heating packs</a> and as a concrete sealant, but not typically as a cleaner. </p>
<p>Fun fact: sodium acetate can be combined with acetic acid to make a crystalline <a href="https://theconversation.com/busting-the-myth-that-all-food-additives-are-bad-a-quick-guide-for-label-readers-82883">food additive</a> called sodium diacetate. These crystals give the vinegar flavour to <a href="https://www.youtube.com/watch?v=N0hEutu_goY">salt and vinegar chips</a> without making them soggy.</p>
<h2>Sorry to burst your bubbles</h2>
<p>There are a few rare cases where mixing vinegar and baking soda may be useful for cleaning. This is where the bubbling has a mechanical effect, such as in a blocked drain. </p>
<p>But in most cases you’ll want to use either vinegar or baking soda by itself, depending on what you’re trying to clean. It will be less <a href="https://theconversation.com/visually-striking-science-experiments-at-school-can-be-fun-inspiring-and-safe-banning-is-not-the-answer-195362">visually exciting</a>, but it should get the job done.</p>
<p>Lastly, remember that mixing cleaning chemicals at home can be risky. Always carefully read the product label and directions before engaging in DIY concoctions. And, to be extra sure, you can find out more safety information by reading the product’s <a href="https://theconversation.com/a-new-tiktok-trend-has-people-drinking-toxic-borax-an-expert-explains-the-risks-and-how-to-read-product-labels-210278">safety data sheet</a>.</p><img src="https://counter.theconversation.com/content/225177/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Kilah does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A mix of vinegar and baking soda is a popular DIY cleaner – but it’s really inefficient. A chemist explains why you should reconsider using this fizzy mixture.Nathan Kilah, Senior Lecturer in Chemistry, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2225712024-03-05T14:00:28Z2024-03-05T14:00:28ZLithium-ion batteries don’t work well in the cold − a battery researcher explains the chemistry at low temperatures<figure><img src="https://images.theconversation.com/files/579001/original/file-20240229-20-z7oy0y.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2120%2C1414&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Why do batteries lose charge more quickly when it's cold? </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/man-charging-electric-car-in-front-his-cabin-in-royalty-free-image/1977511649?phrase=battery+cold&adppopup=true">Halfpoint Images/Moment</a></span></figcaption></figure><p>Rechargeable batteries are great for storing energy and powering electronics from smartphones to electric vehicles. In cold environments, however, they can be more difficult to charge and may even catch on fire. </p>
<p>I’m a mechanical engineering professor who’s been interested in batteries since college. I now lead a <a href="https://research.drexel.edu/mem/changlab">battery research group</a> at Drexel University. </p>
<p>In just this past decade, I have watched the <a href="https://about.bnef.com/blog/lithium-ion-battery-pack-prices-hit-record-low-of-139-kwh/">price of lithium-ion batteries drop</a> as the production market <a href="https://www.iea.org/reports/global-ev-outlook-2023/trends-in-batteries">has grown much larger</a>. Future projections predict the market could reach <a href="https://www.mckinsey.com/industries/automotive-and-assembly/our-insights/battery-2030-resilient-sustainable-and-circular">thousands of GWh per year by 2030</a>, a significant increase. </p>
<p>But, lithium-ion batteries aren’t perfect – this rise comes with risks, such as their tendency to slow down during cold weather and even catch on fire.</p>
<h2>Behind the Li-ion battery</h2>
<p>The <a href="https://www.sciencedirect.com/topics/chemistry/electrochemical-energy-storage">electrochemical energy storage</a> within batteries works by storing electricity <a href="https://www.britannica.com/science/ion-physics">in the form of ions</a>. Ions are atoms that have a nonzero charge because they have either too many or not enough electrons. </p>
<p>When you plug in your electric car or phone, the electricity provided by the outlet <a href="https://www.youtube.com/watch?v=4-1psMHSpKs&ab_channel=TheLimitingFactor">drives these ions</a> from the battery’s positive electrode into its negative electrode. The electrodes are solid materials in a battery that can store ions, and all batteries have both a positive and a negative electrode. </p>
<p>Electrons pass through the battery as electricity. With each electron that passes to one electrode, a lithium ion also passes into the same electrode. This ensures the balance of charges in the battery. As you drive your car, the stored ions in the negative electrode move back to the positive electrode, and the resulting flow of electricity powers the motor. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578759/original/file-20240228-8828-q6kh1t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing three boxes, one labeled cathode, one labeled electrolyte, and one labeled anode. Small circles representing lithium ions move to the anode to charge and the cathode to discharge." src="https://images.theconversation.com/files/578759/original/file-20240228-8828-q6kh1t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578759/original/file-20240228-8828-q6kh1t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=564&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578759/original/file-20240228-8828-q6kh1t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=564&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578759/original/file-20240228-8828-q6kh1t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=564&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578759/original/file-20240228-8828-q6kh1t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=708&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578759/original/file-20240228-8828-q6kh1t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=708&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578759/original/file-20240228-8828-q6kh1t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=708&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When a lithium-ion battery delivers energy to a device, lithium ions – atoms that carry an electrical charge – move from the negative electrode, the anode, to the positive electrode, the cathode. The ions move in reverse when recharging.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/argonne/5029455937">Argonne National Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>While AA or AAA batteries can power small electronics, they can be used only once and cannot be charged. Rechargeable Li-ion batteries can operate for thousands of cycles of full charge and discharge. For each cycle, they can also store a much higher amount of charge than an AA or AAA battery.</p>
<p>Since lithium is the lightest metal, it has a high <a href="https://doi.org/10.1039/C3EE40795K">specific capacity</a>, meaning it can store a <a href="https://chang-lab.notion.site/How-To-Become-a-Battery-Expert-20a8edebe395403c9a158d7caca06ef4?pvs=4">huge amount of charge per weight</a>. This is why lithium-ion batteries are useful not just for portable electronics but for powering modes of transportation with limited weight or volume, such as electric cars. </p>
<h2>Battery fires</h2>
<p>However, lithium-ion batteries have risks that AA or AAA batteries don’t. For one, they’re more likely to catch on fire. For example, the number of <a href="https://gothamist.com/news/e-bike-battery-fires-keep-climbing-in-nyc">electric bike battery fires</a> reported in New York City has increased from 30 to nearly 300 in the past five years. </p>
<p>Lots of different issues can cause a battery fire. Poorly manufactured cells could contain defects, such as trace impurities or particles left behind from the manufacturing process, that increase the risk of an internal failure. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578754/original/file-20240228-30-b8mmfs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A car in a garage is on fire with the door cracked open, a firefighter carrying a hose runs towards it." src="https://images.theconversation.com/files/578754/original/file-20240228-30-b8mmfs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578754/original/file-20240228-30-b8mmfs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578754/original/file-20240228-30-b8mmfs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578754/original/file-20240228-30-b8mmfs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578754/original/file-20240228-30-b8mmfs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578754/original/file-20240228-30-b8mmfs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578754/original/file-20240228-30-b8mmfs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=497&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The lithium-ion batteries in electric vehicles have a higher risk of catching on fire when it’s cold out.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/ElectricCarsBatteryFires/0624a4c4cadb4ee0be42d58b8aab0161/photo?Query=ev%20battery%20fire&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=300&digitizationType=Digitized&currentItemNo=0&vs=true&vs=true">Orange County Sheriff’s Department/National Transportation Safety Board via AP</a></span>
</figcaption>
</figure>
<p>Climate can also affect battery operation. <a href="https://about.bnef.com/electric-vehicle-outlook/">Electric vehicle sales</a> have increased across the U.S., particularly in cold regions such as the Northeast and Midwest, where the frigid temperatures can hinder battery performance. </p>
<p>Batteries contain fluids called electrolytes, and cold temperatures cause fluids to flow more slowly. So, the electrolytes in batteries slow and thicken in the cold, causing the lithium ions inside to move slower. This slowdown can prevent the lithium ions from properly inserting into the electrodes. Instead, they may deposit on the electrode surface and form <a href="https://doi.org/10.1016/j.xcrp.2020.100035">lithium metal</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/G_TCFgEdEGc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The molecules in fluids move slower at colder temperatures – the same thing happens inside batteries.</span></figcaption>
</figure>
<p>If too much lithium deposits on the electrode’s surface during charging, it may cause an internal short circuit. This process can <a href="https://theconversation.com/lithium-ion-battery-fires-are-a-growing-public-safety-concern-heres-how-to-reduce-the-risk-209359">start a battery fire</a>.</p>
<h2>Making safer batteries</h2>
<p><a href="https://research.coe.drexel.edu/mem/changlab">My research group</a>, along with many others, is studying how to make batteries that operate more efficiently in the cold. </p>
<p>For example, researchers are exploring swapping out the usual battery electrolyte and replacing it with an alternative electrolyte that doesn’t thicken at cold temperatures. Another potential option is <a href="https://www.washingtonpost.com/climate-solutions/2024/01/19/electric-vehicle-battery-cold/">heating up the battery pack</a> before charging so that the charging process occurs at a warmer temperature. </p>
<p>My group is also investigating new types of batteries beyond lithium ion. These could be battery types that are more stable at wider temperature ranges, types that don’t even use liquid electrolytes at all, or batteries that use sodium instead of lithium. <a href="https://www.technologyreview.com/2023/05/11/1072865/how-sodium-could-change-the-game-for-batteries/">Sodium-ion batteries</a> could work well and cost less, as sodium is a very abundant resource.</p>
<p><a href="https://doi.org/10.1038/s41560-023-01208-9">Solid-state batteries</a> use solid electrolytes that aren’t flammable, which reduces the risk of fire. But these batteries don’t work quite as well as Li-ion batteries, so it’ll take more research to tell whether these are a good option.</p>
<p>Lithium-ion batteries power technologies that people across the country use every day, and research in these areas aims to find solutions that will make this technology even safer for the consumer.</p><img src="https://counter.theconversation.com/content/222571/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wesley Chang receives funding from Solid Energy Systems, Inc., Electric Power Research Institute, Drexel University. Wesley Chang consults for The Electrochemical Society. </span></em></p>Electric vehicles are catching on across the US, but they’re also catching on fire in colder regions like the Northeast and Midwest.Wesley Chang, Assistant Professor of Mechanical Engineering and Mechanics, Drexel UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2172752024-02-20T19:57:01Z2024-02-20T19:57:01ZFire is a chemical reaction. Here’s why Australia is supremely suited to it<p>Over the last 15 million years, Australia has slowly dried out. After humans arrived more than 65,000 years ago, they learned to use fire to their advantage. Today, fire weather is getting more frequent – and <a href="https://www.nature.com/articles/s41467-021-27225-4">fires are following</a> as the world heats up. This month, fires have flared in Victoria, destroying 46 houses, while Western Australia endures a heatwave and braces for <a href="https://www.watoday.com.au/national/western-australia/extreme-fire-danger-conditions-on-tuesday-to-close-wa-schools-dfes-warns-20240219-p5f65r.html">potential fires</a>. </p>
<p>We use controlled fire for food, industry and many other uses. But we fear it when it is uncontrolled. For something so common, it’s not well understood. </p>
<p>Fire is chemistry – a set of reactions known as combustion. Here’s what that means – and why parts of Australia are so well suited to fire. </p>
<h2>What is fire?</h2>
<p>For a fire to start, it needs three things: fuel, an oxidising agent and heat. </p>
<p>In bushfires, the fuel is plant material, the oxidising agent is oxygen in the atmosphere, and the heat could come from lightning or the fire itself once it starts. </p>
<p>First, the heat has to get to the fuel. Plants are mostly comprised of cellulose (a natural carbohydrate polymer we can’t digest) and lignin (a complex aromatic hydrocarbon), alongside other organic molecules. </p>
<p>But big molecules such as cellulose and lignin don’t burn easily, unlike small molecules such as propane or ethanol. It takes an external heat source to get them to burn. This is normally in the form of lightning, the cause of <a href="https://fennerschool.anu.edu.au/news-events/events/which-lightning-strikes-ignite-bushfires-review-fire-neural-network-fnn-high-risk">most large bushfires</a>. But humans have added other sources – a flicked cigarette, angle-grinders, or sparks from a downed powerline. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="lightning striking tree" src="https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">To start a fire, you need an external heat source such as lightning.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/lightning-oak-tree-625416632">David Wheat/Shutterstock</a></span>
</figcaption>
</figure>
<p>A little bit of extra heat won’t do it. But when cellulose and lignin are heated to 300°C, pyrolysis begins and the natural polymers begin to break down into small organic molecules, which promptly evaporate and form a gas. </p>
<p>At these temperatures, this gas rapidly reacts with oxygen in the air to produce carbon dioxide, water vapour – and heat. This is combustion. </p>
<p>As it burns, the gas becomes hot enough to glow, as do any solid particles within it. When we gaze at a campfire, that’s what we’re seeing – burning gas, glowing particles. </p>
<p>Many believe it’s the breaking of chemical bonds in the fuel that produces heat. But it’s actually the opposite. When we break any chemical bond, heat is absorbed. It’s making new chemical bonds that releases heat – the creation of water vapour and carbon dioxide. </p>
<p>These newly formed bonds are stronger than the bonds in the hydrocarbon fuel, meaning heat is released overall. So much heat that pyrolysis is sustained, consuming more fuel and spreading the fire. </p>
<h2>What about the water in plants?</h2>
<p>Plant material contains water as well as organic compounds. </p>
<p>There’s a unique bit of chemistry which takes place here. When heat first hits plant material, the water within begins to warm. But water has an extraordinarily high ability to store heat. </p>
<p>As water heats up, it begins to evaporate. Evaporation is endothermic, meaning it absorbs heat. That’s why we use it to stop ourselves overheating – we rely on sweat evaporating off our skin and taking heat with it. </p>
<p>This means you need still more energy to increase the temperature and overcome water’s heat absorbing properties. For pyrolysis to occur at all, the water in the plant matter has to evaporate. If there’s still water in the leaves or bark, it won’t burn. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-does-the-stuff-in-a-fire-extinguisher-stop-a-fire-120859">How does the stuff in a fire extinguisher stop a fire?</a>
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</em>
</p>
<hr>
<h2>Fire weather and gum trees</h2>
<p>Australia’s forests and bushlands are mostly on the east coast, avoiding the arid interior. But they can’t avoid the extremely hot and dry air the deserts produce, especially over summer. </p>
<p>Hot air can hold a remarkable amount of water. Its ability to soak up water roughly doubles every 10°C. So hot, dry air acts like a sponge. It scours the water from plant matter and soaks it up. </p>
<p>Plant material largely comes from gum trees. Our hundreds of species are famously messy, dropping bark, leaves and limbs on the forest floor. </p>
<p>Eucalyptus leaves often contain large amounts of volatile organic oils. In dry conditions, these leaves act as like natural lighter fluid, or “pre-pyrolysed material”. </p>
<p>This is because eucalypts like fire. Fire wipes out competitor species and can trigger gumnut germination.</p>
<p>When a bushfire begins and starts to spread, it’s usually burning the dead, dry litter and grasses, not large living trees with plenty of water. </p>
<p>Dry fuel is one thing. But a bushfire needs wind to spread. </p>
<p>Hot days in Australia are often windy, due to the temperature difference between hot deserts and cold oceans. If a lightning triggers pyrolysis and starts a fire, wind is what makes it spread. </p>
<p>Wind provides fresh oxygen to the fire front, making it more intense. It also blows hot dry air over fresh fuel ahead of the fire front, drying it out. If there’s no wind, fire spreads much more slowly. </p>
<p>What does it take to end a bushfire? A large fire will naturally burn itself out if there’s no more fuel for it. Heavy rain can douse a fire, though coals can keep smouldering and restart fires if dry, hot air arrives again. </p>
<p>Firefighters make firebreaks to try to starve the fire of its fuel, spray water to wet and cool the fuel or apply chemical agents such as fire-fighting foam to prevent oxygen getting in. </p>
<p>If we add more and more carbon dioxide to the atmosphere it traps more heat, leading to hotter days. More heat means fire weather – hot, dry and windy conditions – is more likely. And that means combustion will be more likely in some places. Under climate change, there’s more fire in our future. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/before-fusion-a-human-history-of-fire-55198">Before fusion: a human history of fire</a>
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</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/217275/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Dutton receives funding from The Australian Research Council. </span></em></p>We’re all familiar with fire. But do you really know what it is and how it starts? Here’s the chemistry of fire – and why Australia is so prone to going up in flames.Jason Dutton, Professor of Chemistry, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2020362024-02-19T00:42:34Z2024-02-19T00:42:34ZRun out of butter or eggs? Here’s the science behind substitute ingredients<figure><img src="https://images.theconversation.com/files/575492/original/file-20240213-28-yaukh5.jpg?ixlib=rb-1.1.0&rect=80%2C35%2C5784%2C3952&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/white-soup-on-brown-ceramic-bowl-wg5kaMtJ3Ts">Joanna Lopez/Unsplash</a></span></figcaption></figure><p>It’s an all too common situation – you’re busy cooking or baking to a recipe when you open the cupboard and suddenly realise you are missing an ingredient.</p>
<p>Unless you can immediately run to the shops, this can leave you scrambling for a substitute that can perform a similar function. Thankfully, such substitutes can be more successful than you’d expect.</p>
<p>There are a few reasons why certain ingredient substitutions work so well. This is usually to do with the chemistry and the physical features having enough similarity to the original ingredient to still do the job appropriately. </p>
<p>Let’s delve into some common ingredient substitutions and why they work – or need to be tweaked.</p>
<p><iframe id="IitfH" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/IitfH/1/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Oils versus butter</h2>
<p>Both butter and oils belong to a chemical class called <a href="https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Map%3A_Fundamentals_of_General_Organic_and_Biological_Chemistry_(McMurry_et_al.)/23%3A_Lipids/23.01%3A_Structure_and_Classification_of_Lipids">lipids</a>. It encompasses solid, semi-solid and liquid fats.</p>
<p>In a baked product the “job” of these ingredients is to provide flavour and influence the structure and texture of the finished item. In cake batters, lipids contribute to creating an emulsion structure – this means combining two liquids that wouldn’t usually mix. In the baking process, this helps to create a light, fluffy crumb.</p>
<p>One of the primary differences between butter and oil is that butter is only about 80% lipid (the rest being water), while <a href="https://www.nutritionadvance.com/types-of-cooking-fats-and-oils/">oil is almost 100% lipid</a>. Oil creates a softer crumb but is still a great fat to bake with.</p>
<p>You can use a wide range of oils from different sources, such as olive oil, rice bran, avocado, peanut, coconut, macadamia and many more. Each of these may impart different flavours.</p>
<p>Other “butters”, such as peanut and cashew butter, aren’t strictly butters but pastes. They impart different characteristics and can’t easily replace dairy butter, unless you also add extra oil.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/575161/original/file-20240213-30-j0czv9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A block of yellow butter in an open silver foil wrapper" src="https://images.theconversation.com/files/575161/original/file-20240213-30-j0czv9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/575161/original/file-20240213-30-j0czv9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/575161/original/file-20240213-30-j0czv9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/575161/original/file-20240213-30-j0czv9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/575161/original/file-20240213-30-j0czv9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=491&fit=crop&dpr=1 754w, https://images.theconversation.com/files/575161/original/file-20240213-30-j0czv9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=491&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/575161/original/file-20240213-30-j0czv9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=491&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Nut ‘butters’ can’t replace dairy butter because their composition is too different.</span>
<span class="attribution"><a class="source" href="https://pixabay.com/photos/butter-good-butter-fat-nourishment-3411126/">congerdesign/Pixabay</a></span>
</figcaption>
</figure>
<h2>Aquafaba or flaxseed versus eggs</h2>
<p>Aquafaba is the liquid you drain from a can of legumes – such as chickpeas or lentils. It contains proteins, kind of how egg white also contains proteins.</p>
<p>The proteins in egg white include albumins, and <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5912395/">aquafaba also contains albumins</a>. This is why it is possible to make meringue from egg whites, or from aquafaba if you’re after a vegan version.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-make-the-perfect-pavlova-according-to-chemistry-experts-196485">How to make the perfect pavlova, according to chemistry experts</a>
</strong>
</em>
</p>
<hr>
<p>The proteins act as a foam stabiliser – they hold the light, airy texture in the product. The concentration of protein in egg white is a bit higher, so it doesn’t take long to create a stable foam. Aquafaba requires more whipping to create a meringue-like foam, but it will bake in a similar way. </p>
<p>Another albumin-containing alternative for eggs is <a href="https://foodstruct.com/compare/seeds-flaxseed-vs-egg">flaxseed</a>. These seeds form a thick gel texture when mixed with a little water. The texture is similar to raw egg and can provide structure and emulsification in baked recipes that call for a small amount of egg white. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/eggs-are-so-expensive-right-now-what-else-can-i-use-207837">Eggs are so expensive right now. What else can I use?</a>
</strong>
</em>
</p>
<hr>
<h2>Lemon plus dairy versus buttermilk</h2>
<p>Buttermilk is the liquid left over after churning butter – it can be made from sweet cream, cultured/sour cream or whey-based cream. Buttermilk mostly <a href="https://www.journalofdairyscience.org/article/S0022-0302(06)72115-4/fulltext">contains proteins and fats</a>.</p>
<p>Cultured buttermilk has a somewhat tangy flavour. Slightly soured milk can be a good substitute as it contains similar components and isn’t too different from “real” buttermilk, chemically speaking.</p>
<p>One way to achieve slightly soured milk is by adding some lemon juice or cream of tartar to milk. Buttermilk is used in pancakes and baked goods to give extra height or volume. This is because the acidic (sour) components of buttermilk interact with baking soda, producing a light and airy texture. </p>
<p>Buttermilk can also influence flavour, imparting a slightly tangy taste to pancakes and baked goods. It can also be used in sauces and dressings if you’re looking for a lightly acidic touch. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/575163/original/file-20240213-16-ol6va7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A stack of fluffy pancakes dusted with sugar with a strawberry on top" src="https://images.theconversation.com/files/575163/original/file-20240213-16-ol6va7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/575163/original/file-20240213-16-ol6va7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/575163/original/file-20240213-16-ol6va7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/575163/original/file-20240213-16-ol6va7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/575163/original/file-20240213-16-ol6va7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/575163/original/file-20240213-16-ol6va7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/575163/original/file-20240213-16-ol6va7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Buttermilk is a common ingredient for making fluffy pancakes.</span>
<span class="attribution"><a class="source" href="https://pixabay.com/photos/pancakes-food-strawberry-plate-2801959/">Matthias_Groeneveld/Pixabay</a></span>
</figcaption>
</figure>
<h2>Honey versus sugar</h2>
<p>Honey is a <a href="https://resources.perkinelmer.com/lab-solutions/resources/docs/APP_Analysis-of-Sugars-in-Honey-012101_01.pdf">complex sugar-based syrup</a> that includes floral or botanical flavours and aromas. Honey can be used in cooking and baking, adding both flavour and texture (viscosity, softness) to a wide range of products.</p>
<p>If you add honey instead of regular sugar in baked goods, keep in mind that honey imparts a softer, moister texture. This is because it contains more moisture and is a humectant (that is, it likes to hold on to water). It is also less crystalline than sugar, unless you leave it to crystallise.</p>
<p>The intensity of sweetness can also be different – some people find honey is sweeter than its granular counterpart, so you will want to adjust your recipes accordingly.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/575164/original/file-20240213-26-6c2r7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Close-up of a slice of bread with golden honey pooling on top" src="https://images.theconversation.com/files/575164/original/file-20240213-26-6c2r7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/575164/original/file-20240213-26-6c2r7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/575164/original/file-20240213-26-6c2r7t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/575164/original/file-20240213-26-6c2r7t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/575164/original/file-20240213-26-6c2r7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/575164/original/file-20240213-26-6c2r7t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/575164/original/file-20240213-26-6c2r7t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Honey has a complex flavour and can taste sweeter than regular sugar.</span>
<span class="attribution"><a class="source" href="https://pixabay.com/photos/honey-bread-spoon-bio-nature-752145/">estelheitz/Pixabay</a></span>
</figcaption>
</figure>
<h2>Gluten-free versus regular flour</h2>
<p>Sometimes you need to make substitutions to avoid allergens, such as gluten – the protein found in cereal grains such as wheat, rye, barley and others. </p>
<p>Unfortunately, gluten is also the component that gives a nice, stretchy, squishy quality to bread.</p>
<p>To build this characteristic in a gluten-free product, it’s necessary to have a mixture of ingredients that work together to mimic this texture. Common ingredients used are corn or rice flour, xanthan gum, which acts as a binder and moisture holder, and tapioca starch, which is a good water absorbent and can aid with binding the dough. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/thank-glutens-complex-chemistry-for-your-light-fluffy-baked-goods-216869">Thank gluten's complex chemistry for your light, fluffy baked goods</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/202036/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paulomi (Polly) Burey does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>In a pinch, the water from a can of beans can replace eggs. But how does that work, exactly?Paulomi (Polly) Burey, Associate Professor (Food Science), University of Southern QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2153112024-02-09T16:50:23Z2024-02-09T16:50:23ZYour unique smell can provide clues about how healthy you are<figure><img src="https://images.theconversation.com/files/574043/original/file-20240207-19-o4ehc8.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5291%2C3516&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/happy-calm-teen-girl-enjoying-good-1325627765">fizkes/Shutterstock</a></span></figcaption></figure><p>Hundreds of chemicals stream from our bodies into the air every second. These chemicals release into the air easily as they have high vapour pressures, meaning they boil and turn into gases at room temperature. They give clues about who we are, and how healthy we are. </p>
<p>Since ancient Greek times, we’ve known that we smell differently when we are unwell. While we rely on blood analysis today, ancient Greek physicians used smell to diagnose maladies. If they took a whiff of your breath and described it as <em>fetor hepaticus</em> (meaning bad liver), it meant you could be headed for liver failure.</p>
<p>If a person’s whiff was sweet or fruity, physicians thought this meant that sugars in the digestive system were not being broken down, and that person had probably diabetes. Science has since shown the ancient Greeks were right – liver failure and <a href="https://tisserandinstitute.org/human-volatilome/">diabetes</a> and many <a href="https://link.springer.com/article/10.1007/s00216-023-04986-z">other diseases</a> including infectious diseases give your breath a distinctive smell.</p>
<p>In 1971, <a href="https://www.nobelprize.org/prizes/peace/1962/pauling/facts/">Nobel Laureate chemist Linus Pauling</a> <a href="https://edu.rsc.org/feature/breath-analysis/2020106.article#:%7E:text=The%20'modern%20era'%20of%20breath,in%20an%20average%20breath%20sample.">counted 250 different</a> gaseous chemicals in breath. These gaseous chemicals are called volatile organic compounds or VOCs. </p>
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<p>Since Pauling’s discovery, other scientists have <a href="https://link.springer.com/article/10.1007/s40291-023-00640-7">discovered hundreds more VOCs</a> in our breath. We have learned that many of these VOCs have distinctive odours, but some have no odour that our noses can perceive. </p>
<p>Scientists believe that whether a VOC <a href="https://tisserandinstitute.org/human-volatilome/">has an odour</a> that our noses can detect or not, they can reveal information about how healthy someone is.</p>
<p>A Scottish man’s Parkinson’s disease onset was <a href="https://www.bbc.co.uk/news/uk-scotland-47627179">identified by his wife</a>, retired nurse Joy Milner, after she was convinced the way he smelled had changed, years before he was diagnosed in 2005. This discovery has <a href="https://www.manchester.ac.uk/discover/news/smell-of-skin-could-lead-to-early-diagnosis-for-parkinsons/">led to research programmes</a> involving Joy Milner to identify <a href="https://www.scientificamerican.com/article/a-supersmeller-can-detect-the-scent-of-parkinsons-leading-to-an-experimental-test-for-the-illness/">the precise smell</a> of this disease. </p>
<p>Dogs can <a href="https://www.nature.com/articles/d41586-022-01629-8">sniff out more diseases</a> than humans because of their more <a href="https://www.understandinganimalresearch.org.uk/news/the-science-of-sniffs-disease-smelling-dogs%20-%20I%20think%20the%20previous%20nature%20link%20has%20more%20credibility%20for%20here%20also">sophisticated olfactory talents</a>. But technological techniques, like <a href="https://www.britannica.com/science/mass-spectrometry">analytical tool mass spectrometry</a>, picks up even more subtle changes in VOC profiles that are being linked to <a href="https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(20)30100-6/fulltext">gut</a>, <a href="https://www-sciencedirect-com.dcu.idm.oclc.org/science/article/pii/S0165993618305168">skin</a> and <a href="https://err.ersjournals.com/content/28/152/190011">respiratory</a> diseases as well as neurological diseases like Parkinson’s. Researchers believe that one day some diseases will be diagnosed simply by breathing into a device. </p>
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<h2>Where do VOCs come from?</h2>
<p>Breath is not the only source of VOCs in the body. They are also emitted from skin, urine and faeces. </p>
<p>VOCs from skin are the result of millions of skin glands removing metabolic waste from the body, as well as waste generated by bacteria and other microbes that live on our skin. Sweating produces extra nutrients for these bacteria to metabolise which can result in particularly odorous VOCs. Odour from sweat only makes up a fraction of the scents from VOCs though.</p>
<p><a href="https://www.nature.com/articles/nrmicro.2017.157">Our skin</a> and also our gut microbiomes are made up from a delicate balance of these microbes. Scientists think <a href="https://journals.lww.com/co-gastroenterology/abstract/2015/01000/the_gut_microbiome_in_health_and_in_disease.12.aspx">they influence our health</a>, but we don’t yet understand a lot about how this relationship works. </p>
<p>Unlike the gut, the skin is relatively easy to study – you can collect skin samples from living humans without having to go deep into the body. <a href="https://www-sciencedirect-com.dcu.idm.oclc.org/science/article/pii/S1471492221002087">Scientists think</a> skin VOCs can offer insights into how the microbiome’s bacteria and the human body work together to maintain our health and protect us from disease.</p>
<p>In my team’s laboratory, <a href="https://iopscience.iop.org/article/10.1088/1752-7163/abf20a">we are investigating</a> whether the skin VOC signature can reveal different attributes of the person it belongs to. These signals in skin VOC signatures are probably how dogs distinguish between people by smell. </p>
<p>We are at a relatively early stage in this research area but we have shown that you can tell males from females based on how acidic the VOCs from skin are. We use mass spectrometry to see this as the average human nose is not sophisticated enough to detect these VOCs. </p>
<p>We can also predict a person’s age with reasonable accuracy to within a few years from their skin VOC profile. This is not surprising considering that oxidative stress in our bodies increases as we age.</p>
<p><a href="https://www.metabolismjournal.com/article/S0026-0495(00)80077-3/pdf">Oxidative stress</a> happens when your antioxidant levels are low and causes irreversible damage to our cells and organs. <a href="https://pubs.acs.org/doi/10.1021/jasms.3c00315">Our recent research</a> found by-products of this oxidative damage in skin VOC profiles. </p>
<p>Not only are these VOCs responsible for personal scent – they are used by plants, insects and animals as a communication channel. Plants are in a <a href="https://www.nature.com/articles/s41598-017-10975-x">constant VOC dialogue</a> with other organisms including pollinators, herbivores, other plants and their natural enemies such as harmful bacteria and insects. VOCs used for this back and forth dialogue are known as pheromones. </p>
<h2>What has science shown about love pheromones?</h2>
<p>In the animal kingdom, there is good evidence VOCs can act as aphrodisiacs. Mice for example have microbes which contribute to a particularly <a href="https://www.sciencedirect.com/science/article/pii/S0960982212012687">smelly compound called trimethylamine</a>, which allows mice to verify the species of a potential mate. <a href="https://www.sciencedirect.com/science/article/abs/pii/S0093691X21003083">Pigs</a> and <a href="https://www.nature.com/articles/4381097a">elephants</a> have sex pheromones too. </p>
<p>It is possible that humans also produce VOCs for attracting the perfect mate. Scientists have yet to fully decode skin – or other VOCs that are released from our bodies. But evidence for human love pheromones so far is <a href="https://www.science.org/content/article/do-human-pheromones-actually-exist">controversial at best</a>. <a href="https://www.newscientist.com/article/dn3835-colour-vision-ended-human-pheromone-use/">One theory suggests</a> that they were lost about 23 million years ago when primates developed full colour vision and started relying on their enhanced vision to choose a mate.</p>
<p>However, we believe that whether human pheromones exist or not, skin VOCs can reveal who and how we are, in terms of things like ageing, nutrition and fitness, fertility and even stress levels. This signature probably contains markers we can use to monitor our health and diagnose disease.</p><img src="https://counter.theconversation.com/content/215311/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aoife Morrin receives funding from Science Foundation Ireland.</span></em></p>The science of smell is an exciting area of research.Aoife Morrin, Associate Professor of Analytical Chemistry, Dublin City UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2194922024-02-08T19:17:16Z2024-02-08T19:17:16ZWhat is micellar water and how does it work?<figure><img src="https://images.theconversation.com/files/564426/original/file-20231208-19-wzr2mp.jpg?ixlib=rb-1.1.0&rect=0%2C15%2C3498%2C2313&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bottle-micellar-water-cotton-pad-1409151146">Geinz Angelina/Shutterstock</a></span></figcaption></figure><p>Micellar water, a product found in supermarkets, chemists and bathroom cabinets around the world, is commonly used to remove make-up. It’s a very effective cleanser and many people swear by it as part of their skincare routine. </p>
<p>So, what is micellar water and why is it so good at getting makeup and sunscreen off? Here’s the science.</p>
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Read more:
<a href="https://theconversation.com/how-should-i-add-sunscreen-to-my-skincare-routine-now-its-getting-hotter-213453">How should I add sunscreen to my skincare routine now it's getting hotter?</a>
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<h2>What are micelles?</h2>
<p>Oil and water generally don’t mix, which is why you’ll struggle to remove makeup and sunscreen (which both contain oils) with just plain water.</p>
<p>But micellar water products contain something called micelles – clusters of molecules that are <em>very</em> effective at removing oily substances. To understand why, you need to first know two chemistry terms: hydrophilic and hydrophobic.</p>
<p>A hydrophilic substance “loves” water and mixes easily with it. Salt and sugar are examples.</p>
<p>A hydrophobic substance “hates” water and generally refuses to mix with it. Examples include oil and wax. </p>
<p>Hydrophilic materials will happily mix with other hydrophilic materials. The same goes for hydrophobic substances. But if you try to combine hydrophilic and hydrophobic materials, they won’t mix.</p>
<h2>How are micelles formed? It’s all about surfactants</h2>
<p>The micelles in micellar water are formed by special molecules known as surfactants.</p>
<p>Surfactant stands for surface active agent. These molecules looked at their hydrophilic and hydrophobic brethren and said, why not both? They are typically comprised of two ends: a head group that is hydrophilic and a tail that is hydrophobic.</p>
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<a href="https://images.theconversation.com/files/573298/original/file-20240204-27-skrj1x.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram shows a surfactant, which has a head that is hydrophilic and a tail that is hydrophobic." src="https://images.theconversation.com/files/573298/original/file-20240204-27-skrj1x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/573298/original/file-20240204-27-skrj1x.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/573298/original/file-20240204-27-skrj1x.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/573298/original/file-20240204-27-skrj1x.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/573298/original/file-20240204-27-skrj1x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/573298/original/file-20240204-27-skrj1x.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/573298/original/file-20240204-27-skrj1x.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A surfactant has a head that is hydrophilic and a tail that is hydrophobic.</span>
<span class="attribution"><span class="source">Daniel Eldridge</span></span>
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<p>When a small amount of surfactant is added to water, the two ends of the molecule have competing interests. The hydrophilic head wants to be in the water, but the hydrophobic tail can’t stand water.</p>
<p>Add enough surfactant and, eventually, we will pass a critical micelle concentration and the surfactants will self-assemble into clusters of approximately 20 to 100 surfactant molecules. </p>
<p>All the hydrophilic heads will be pointing outwards, while the hydrophobic tails remain “hidden” at the centre. These clusters are micelles.</p>
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<a href="https://images.theconversation.com/files/573299/original/file-20240204-23-u7z1sn.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram shows surfactant molecules arranging themselves into a micelle, with the hydrophilic heads pointing outwards and the hydrophobic tails pointing inwards." src="https://images.theconversation.com/files/573299/original/file-20240204-23-u7z1sn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/573299/original/file-20240204-23-u7z1sn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/573299/original/file-20240204-23-u7z1sn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/573299/original/file-20240204-23-u7z1sn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/573299/original/file-20240204-23-u7z1sn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/573299/original/file-20240204-23-u7z1sn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/573299/original/file-20240204-23-u7z1sn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Surfactant molecules arrange themselves into a micelle, with the hydrophilic heads pointing outwards and the hydrophobic tails pointing inwards.</span>
<span class="attribution"><span class="source">Daniel Eldridge</span></span>
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<p>These micelles have a hydrophilic exterior, meaning that they are very happy to remain mixed throughout water. However, in the centre remains a hydrophobic pocket that’s very good at attracting oils.</p>
<p>This is very handy, and helps explain why adding some detergent (a surfactant) to water will allow you to wash an oily saucepan. The surfactant first helps lift of the oil, and then the oil can remained mixed into the water, finding a new home in the hydrophobic centre of the micelle.</p>
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<h2>Micellar water in action</h2>
<p>Surfactants are in your dishwashing detergent, your body wash, your shampoo, your toothpaste and even many foods. In all of these cases, they are there to help the water interact with the dirt and oils, and micellar water is no different.</p>
<p>When you apply some micellar water to a cotton pad, another convenient interaction occurs. The wet cotton is hydrophilic (loves water). Consequently, some of the micelles will unravel, with the hydrophilic heads being attracted to the wet cotton pad. </p>
<p>Now, sticking out from the surface will be a layer of hydrophobic tail groups. These hydrophobic tails cannot wait to attract themselves to makeup, sunscreen, oils, dirt, grease and other contaminants on your face. </p>
<p>As you sweep the cotton pad across your skin, these contaminants bind to the hydrophobic tails and are removed from the skin. </p>
<p>Some contaminants will also find themselves encapsulated in the hydrophobic centres of the micelle.</p>
<p>Either way, a cleaner surface is left behind.</p>
<p>Look at how a cotton wipe soaked in micellar water cleans up a small oil spill, in comparison to water alone.</p>
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<h2>So why shouldn’t I just use dishwashing detergent to wash my face?</h2>
<p>Technically, that would work as detergent does indeed contain lots of micelle-forming surfactants.</p>
<p>But these particular surfactants would probably cause a lot of skin and eye irritation, while also damaging and drying out your skin. Not nice.</p>
<p>The surfactants in micellar water are chosen to be mild and well tolerated by most people’s skin. But micellar water isn’t the only skincare product to contain micelles. There are many other face-cleaning products that also make great use of surfactant molecules and work very well too.</p>
<p>Now, it’s not perfect. While it is effective at removing a wide range of contaminants, thick or heavy makeup might not come off easily with micellar water (you might need to do a more vigorous clean).</p>
<p>Some products say there is “zero residue”, although the fine print clearly states this refers to visible residue.</p>
<p>Many products also state there is no rinse off required. Surfactants will remain on your skin after product use, but for many people they don’t cause irritation. If your skin is feeling irritated after using a micellar water product, you can try rinsing afterwards or discontinuing use.</p>
<p>And as is the case with many cosmetic products, you should test it first on a small patch of skin before using it all over your face.</p>
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Read more:
<a href="https://theconversation.com/what-is-a-paraben-and-why-are-so-many-products-advertised-as-paraben-free-198994">What is a paraben and why are so many products advertised as 'paraben-free'?</a>
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<img src="https://counter.theconversation.com/content/219492/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Eldridge does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The molecules that make micelles are in your dishwashing detergent, your body wash, your shampoo, your toothpaste and even many foods. They are there to help the water interact with the dirt and oils.Daniel Eldridge, Senior Lecturer in Chemistry, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2226672024-02-06T13:28:37Z2024-02-06T13:28:37ZSelf-extinguishing batteries could reduce the risk of deadly and costly battery fires<figure><img src="https://images.theconversation.com/files/573199/original/file-20240203-17-od3sxj.jpeg?ixlib=rb-1.1.0&rect=7%2C3%2C1270%2C674&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cutaway view of a Nissan Leaf electric vehicle showing part of its battery array (silver boxes).</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Electric_vehicle_battery#/media/File:Nissan_Leaf_012.JPG">Tennen-gas/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>In a <a href="https://doi.org/10.1038/s41893-024-01275-0">newly published study</a>, we describe our design for a self-extinguishing rechargeable battery. It replaces the most commonly used electrolyte, which is highly combustible – a medium composed of a lithium salt and an organic solvent – with materials found in a commercial fire extinguisher. </p>
<p>An electrolyte allows lithium ions that carry an electric charge to move across a separator between the positive and negative terminals of a lithium-ion battery. By modifying affordable commercial coolants to function as battery electrolytes, we were able to produce a battery that puts out its own fire.</p>
<p>Our electrolyte worked well across a wide temperature range, from about minus 100 to 175 degrees Fahrenheit (minus 75 to 80 degrees Celsius). Batteries that we produced in the lab with this electrolyte transferred heat away from the battery very well, and extinguished internal fires effectively. </p>
<p>We subjected these batteries to the nail penetration test, a common method for assessing lithium-ion battery safety. Driving a <a href="https://belltestchamber.com/why-do-we-need-to-do-the-nail-penetration-test.html">stainless steel nail through a charged battery</a> simulates an internal short circuit; if the battery catches fire, it fails the test. When we drove a nail through our charged batteries, they withstood the impact without catching fire.</p>
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<span class="caption">When a lithium-ion battery delivers energy to a device, lithium ions – atoms that carry an electrical charge – move from the anode to the cathode. The ions move in reverse when recharging.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/8Erh2x">Argonne National Laboratory/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
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<h2>Why it matters</h2>
<p>By nature, a battery’s temperature changes as it charges and discharges, due to <a href="https://data.energizer.com/pdfs/batteryir.pdf">internal resistance</a> – opposition within the battery to the flow of lithium ions. <a href="https://www.latimes.com/business/story/2023-07-13/how-a-heat-wave-will-hurt-your-ev-battery">High outdoor temperatures</a> or uneven temperatures within a battery pack seriously threaten batteries’ safety and durability. </p>
<p>Energy-dense batteries, such as the lithium-ion versions that are widely used in electronics and electric vehicles, contain an electrolyte formulation dominated by organic molecules that are highly flammable. This worsens the risk of <a href="https://www.sciencedirect.com/topics/chemistry/thermal-runaway">thermal runaway</a> – an uncontrollable process in which excess heat inside a battery speeds up unwanted chemical reactions that release more heat, triggering further reactions. Temperatures inside the battery can rise by hundreds of degrees in a second, <a href="https://www.youtube.com/watch?v=kHTlVmBbnPA&t=5s">causing a fire or explosion</a>.</p>
<p>Another safety concern arises when lithium-ion batteries are charged too quickly. This can cause chemical reactions that produce very sharp lithium needles called dendrites on the battery’s anode – the electrode with a negative charge. Eventually, the needles penetrate the separator and reach the other electrode, short-circuiting the battery internally and leading to overheating.</p>
<p>As scientists studying <a href="https://scholar.google.com/citations?user=jCXInTYAAAAJ&hl=en">energy generation</a>, <a href="https://scholar.google.com/citations?user=KsW8rMMAAAAJ&hl=en">storage and conversion</a>, we have a strong interest in developing energy-dense and safe batteries. Replacing flammable electrolytes with a flame-retardant electrolyte has the potential to make lithium-ion batteries safer, and can buy time for longer-term improvements that reduce inherent risks of overheating and thermal runaway. </p>
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<figcaption><span class="caption">Lithium-ion battery fires in vehicles have become a major concern for firefighters because the batteries burn at very high temperatures for long periods.</span></figcaption>
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<h2>How we did our work</h2>
<p>We wanted to develop an electrolyte that was nonflammable, would readily transfer heat away from the battery pack, could function over a wide temperature range, was very durable, and would be compatible with any battery chemistry. However, most known nonflammable organic solvents contain fluorine and phosphorus, which are expensive and can have <a href="https://www.usgs.gov/special-topics/water-science-school/science/phosphorus-and-water">harmful effects</a> <a href="https://www.stormwater.com/home/article/21146477/examining-the-impact-of-fluorine-on-soil-and-plant-health">on the environment</a>.</p>
<p>Instead, we focused on adapting affordable commercial coolants that already were widely used in fire extinguishers, electronic testing and cleaning applications, so that they could function as battery electrolytes. </p>
<p>We focused on a mature, safe and affordable commercial fluid called <a href="https://www.3m.com/3M/en_US/p/d/b40044871/">Novec 7300</a>, which has low toxicity, is nonflammable and does not contribute to global warming. By combining this fluid with several other chemicals that added durability, we were able to produce an electrolyte that had the features we sought and would enable a battery to charge and discharge over a full year without losing significant capacity. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/_pcqC4PLbQg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Standard lithium-ion batteries failing the nail penetration test.</span></figcaption>
</figure>
<h2>What still isn’t known</h2>
<p>Because lithium – an alkali metal - is scarce in our Earth’s crust, it is important to investigate how well batteries that use other, more abundant alkali metal ions, such as potassium or sodium, fare in comparison. For this reason, our study focused predominantly on self-extinguishing potassium-ion batteries, although it also showed that our electrolyte works well for making self-extinguishing lithium-ion batteries. </p>
<p>It remains to be seen whether our electrolyte can work equally well for other types of batteries that are in development, such as <a href="https://www.pnnl.gov/news-media/new-sodium-aluminum-battery-aims-integrate-renewables-grid-resiliency">sodium-ion, aluminum-ion</a> and <a href="https://www.technologyreview.com/2023/09/06/1079123/zinc-batteries-boost-eos/">zinc-ion</a> batteries. Our goal is to develop practical, environmentally friendly, sustainable batteries regardless of their ion type. </p>
<p>For now, however, since our alternative electrolyte has similar physical properties to currently used electrolytes, it can be readily integrated with current battery production lines. If the industry embraces it, we expect that companies will be able to manufacture nonflammable batteries using their existing lithium-ion battery facilities.</p>
<p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take on interesting academic work.</em></p><img src="https://counter.theconversation.com/content/222667/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Apparao Rao receives funding from the R. A. Bowen Endowed Professorship funds at Clemson University.</span></em></p><p class="fine-print"><em><span>Bingan Lu does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Lithium-ion battery fires are becoming increasingly common as electric vehicles spread, and are hard to extinguish. A new approach uses an electrolyte based on a commercial fire extinguisher.Apparao Rao, Professor of Physics, Clemson UniversityBingan Lu, Associate Professor of Physics and Electronics, Hunan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2168532024-02-05T13:30:30Z2024-02-05T13:30:30ZStudying lake deposits in Idaho could give scientists insight into ancient traces of life on Mars<figure><img src="https://images.theconversation.com/files/568753/original/file-20240110-30-i5trcc.JPG?ixlib=rb-1.1.0&rect=23%2C398%2C3128%2C1343&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists have been studying the Clarkia site for nearly five decades.</span> <span class="attribution"><span class="source">Robert Patalano</span></span></figcaption></figure><p>Does life exist elsewhere in the universe? If so, how do scientists search for and identify it? Finding life beyond Earth is extremely difficult, partly because other planets are so far away and partly because we are not sure what to look for.</p>
<p>Yet, astrobiologists have learned a lot about <a href="https://science.nasa.gov/astrobiology/">how to find life</a> in extraterrestrial environments, mainly by studying how and when the early Earth became livable.</p>
<p>While research teams at NASA are <a href="https://mars.nasa.gov/mars2020/mission/overview/">directly combing</a> the surface of Mars for signs of life, our <a href="https://news.bryant.edu/there-life-red-planet-faculty-earns-funding-explore-theory-earth">interdisciplinary research group</a> is <a href="https://news.bryant.edu/mars-mind-bryant-students-earn-funding-nasa-ri-space-grant-consortium">using a site here on Earth</a> to approximate ancient environmental conditions on Mars. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A rock face with several blocky layers of rock, in different stripes of color. The top layers are a darker clay, while the bottom layers are a lighter volcanic ash." src="https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A close-up view of the Clarkia site where you can see lacustrine clay and volcanic ash layers. This site represents Mars in our work.</span>
<span class="attribution"><span class="source">Taylor Vahey</span></span>
</figcaption>
</figure>
<p>Contained within northern Idaho’s <a href="https://doi.org/10.1130/G48901.1">Clarkia Middle Miocene Fossil Site</a> are sediments that preserve some of Earth’s most diverse biological marker molecules, or <a href="https://doi.org/10.1016/j.epsl.2008.07.012">biomarkers</a>. These are remains of past life that offer glimpses into Earth’s history.</p>
<h2>An ancient lake</h2>
<p>About 16 million years ago, a lava flow in what would one day become Clarkia, Idaho, dammed a local drainage system and created a deep lake in a <a href="https://archive.org/details/latecenozoichist0000unse/page/424/mode/2up">narrow, steep-sided valley</a>. Although the lake has since dried up, weathering, erosion and <a href="https://www.facebook.com/p/Fossil-Bowl-100063724775941/">human activity</a> have exposed sediments of the former lake bed.</p>
<p>For nearly five decades, research teams like ours – being led by <a href="https://www.radcliffe.harvard.edu/people/hong-yang">Dr. Hong Yang</a> and <a href="https://www.bryant.edu/academics/faculty/leng-qin">Dr. Qin Leng</a> – have used <a href="https://doi.org/10.7717/peerj.4880">fossil remains</a> and <a href="https://doi.org/10.1016/0146-6380(95)80001-8">biogeochemistry</a> to reconstruct past environments of the Clarkia Miocene Lake region. </p>
<p>The lake’s depth created the <a href="https://www.jstor.org/stable/1303276">perfect conditions</a> for protecting microbial, plant and animal remains that fell to the lake’s bottom. In fact, the sediments are so well preserved that some of the fossilized leaves still show their autumn colors from when they sank into the water millions of years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A reddish brown long, thin leaf shown embedded on a piece of smooth sediment." src="https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A fossil magnolia leaf showing fall (reddish) colors. This leaf likely fell off a tree in the fall once the trees paused photosynthesis for the winter and sank to the bottom of the lake, where it was buried. The leaf retained its fall coloring for 16 million years, though once being dug up and exposed to air, it quickly oxidized and lost its color.</span>
<span class="attribution"><span class="source">Robert Patalano</span></span>
</figcaption>
</figure>
<p>Today, ancient lake beds on Earth are becoming <a href="https://doi.org/10.1146/annurev-earth-053018-060332">important settings</a> for learning about habitable environments on other planets. </p>
<h2>Biological marker molecules</h2>
<p>Clarkia’s lake sediments <a href="https://doi.org/10.1016/0146-6380(94)90045-0">contain a suite</a> of ancient biomarkers. These compounds, or classes of compounds, can reveal how organisms and their <a href="https://doi.org/10.1016/j.quascirev.2011.07.009">environments functioned</a> in the past.</p>
<p>Since the discovery of the <a href="https://www.idahogeology.org/pub/Information_Circulars/IC-33.pdf">Clarkia fossil site in 1972</a>, multiple research teams have used various <a href="https://doi.org/10.1016/S0146-6380(02)00212-7">cutting-edge technologies to analyze</a> different biomarkers. </p>
<p>Some of those found at Clarkia <a href="https://doi.org/10.1073/pnas.90.6.2246">include lignin</a>, which is the structural support tissue of plants, <a href="https://doi.org/10.1016/S0146-6380(00)00107-8">lipids like fats and waxes</a>, and possibly <a href="https://doi.org/10.1038/344656a0">DNA and amino acids</a>.</p>
<p>Understanding the origins, history and environmental factors that have allowed these biosignatures to stay so well preserved at Clarkia may also allow our team to predict the potential of organic matter preservation in ancient lake deposits on Mars.</p>
<h2>Studying life signatures on Mars</h2>
<p>In 2021, the <a href="https://mars.nasa.gov/mars2020/">Mars Perseverance Rover</a> landed on top of lake deposits in Mars’ <a href="https://doi.org/10.1126/science.abl4051">Jezero Crater</a>. Jezero is a meteorite impact crater believed to have once been flooded with water and home to an ancient river delta. Microbial life may have lived in Jezero’s crater lake, and their biomarkers might be found in lake bed sediments today. Perseverance has been drilling into the crater’s surface to collect samples that could contain ancient signs of life, with the intent of <a href="https://mars.nasa.gov/msr/#Facts">returning the samples to Earth in 2033</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&rect=14%2C7%2C4977%2C2799&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's rendition of the Perseverence rover, made of metal with six small wheels, a camera and a robotic arm." src="https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&rect=14%2C7%2C4977%2C2799&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Perseverance Rover is collecting samples to learn more about Mars’ environment.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/MarsLanding/c835b14b3e6645d7a0cd46558745752b/photo?Query=mars%20rover&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=530&currentItemNo=11&vs=true">NASA/JPL-Caltech via AP</a></span>
</figcaption>
</figure>
<p>Clarkia has many similarities to the Jezero Crater. Both Clarkia and Jezero Crater have ancient <a href="https://doi.org/10.1006/icar.2000.6530">lake deposits</a> derived from silica-rich, <a href="https://doi.org/10.1029/2017JE005478">basaltic rock</a> that formed under <a href="https://doi.org/10.1016/j.gloplacha.2022.103737">a climate with</a> higher temperatures, high humidity and a carbon dioxide-rich atmosphere. </p>
<p>At Clarkia, these conditions preserved microbial biomarkers in the ancient lake. Similar settings could have <a href="https://doi.org/10.1029/2012JE004115">formed lakes</a> on the surface of Mars. </p>
<p>The samples <a href="https://mars.nasa.gov/mars-rock-samples/#23">Perseverance is collecting</a> contain the geologic and climate history of the Jezero Crater landing site and may even contain preserved biomarkers of ancient life.</p>
<p>While Perseverance continues its mission, our group is <a href="https://agu.confex.com/agu/fm23/meetingapp.cgi/Paper/1367388">establishing criteria</a> for biomolecular authentication. That means we are developing ways to figure out whether ancient biomarkers from Earth, and hopefully Mars, are true echoes of life – rather than recent contamination or molecules from nonliving sources.</p>
<p>To do so, we are studying biomarkers from Clarkia’s fossil leaves and sediments and developing laboratory experiments using <a href="https://spaceresourcetech.com/collections/regolith-simulants">Martian simulants</a>. This material simulates the chemical and physical properties of Jezero Crater’s lake sediments.</p>
<p>By deciphering the sources, history and preservation of biomarkers connected with Clarkia’s ancient lake deposits, we hope to develop new strategies for studying the Perseverance Rover samples once they are back on Earth.</p><img src="https://counter.theconversation.com/content/216853/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Patalano receives funding from the NASA Rhode Island Space Grant Program. </span></em></p>While NASA rovers on the surface of Mars look for hints of life, researchers back on Earth are studying ‘echoes of life’ from ancient basins – hoping that the two sites might be similar.Robert Patalano, Lecturer of Biological and Biomedical Sciences, Bryant UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2154542024-02-02T23:11:54Z2024-02-02T23:11:54ZAnimals keep eating precious plants – we used ‘smell misinformation’ to keep them away<figure><img src="https://images.theconversation.com/files/555510/original/file-20231024-29-o85ef8.jpg?ixlib=rb-1.1.0&rect=143%2C294%2C4476%2C3218&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/swamp-wallaby-eating-some-eucalyptus-leaves-2243439195">Gert-Jan van Stein/Shutterstock</a></span></figcaption></figure><p>In places where we need to protect valuable plants – whether for ecological or economic reasons – local herbivores can cause significant damage.</p>
<p>Current solutions often involve killing the problem animals. But this is increasingly unacceptable due to animal welfare concerns and social pressures. Physical barriers such as fences can be expensive, and aren’t always practical. We need other options.</p>
<p>Recently, <a href="https://pubmed.ncbi.nlm.nih.gov/27368609/">our team</a> <a href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.12748">discovered</a> that herbivores – plant-eating mammals – primarily use their sense of smell to tell which plants they want to eat or avoid.</p>
<p>In our study <a href="https://www.nature.com/articles/s41559-024-02330-x">published today in Nature Ecology & Evolution</a>, we show how we can use this reliance on smell to nudge wallabies away from vulnerable native tree seedlings. We artificially created and deployed the key smells of a shrub wallabies avoid. </p>
<h2>Herbivore-induced headaches</h2>
<p>Hungry plant eaters are a concern for conservationists, farmers and foresters alike. They can devastate revegetation efforts and post-fire recovery, <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1442-9993.2004.01374.x">destroying more than half the seedlings</a> in these areas.</p>
<p>Every year, they cause <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12587">billions of dollars of damage</a> in forestry and agriculture. Herbivores also pose a risk to the long-term survival of many threatened plant species.</p>
<p>The most effective control strategies will likely <a href="https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(16)30152-5">work with a herbivore’s natural motivations</a> – understanding and harnessing what drives the animal to find or avoid certain plants.</p>
<p>Previously, research had primarily focused on what herbivores were eating, but had never really asked <em>how</em> they find the food in the first place.</p>
<p>Our approach puts a new twist on “olfactory (smell) misinformation” or “chemical camouflage” approaches. In recent studies, these methods have substantially reduced invasive predators eating <a href="https://www.science.org/doi/10.1126/sciadv.abe4164">threatened bird eggs</a> in New Zealand, and house mice eating agricultural <a href="https://www.nature.com/articles/s41893-023-01127-3">wheat grain</a> in Australia.</p>
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Read more:
<a href="https://theconversation.com/how-to-fool-a-mouse-chemical-camouflage-can-hide-crops-and-cut-losses-by-over-60-202042">How to fool a mouse: ‘chemical camouflage’ can hide crops and cut losses by over 60%</a>
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<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/555509/original/file-20231024-25-i6una0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small brown marsupial with dark ears eating spare but tall green grass" src="https://images.theconversation.com/files/555509/original/file-20231024-25-i6una0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/555509/original/file-20231024-25-i6una0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/555509/original/file-20231024-25-i6una0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/555509/original/file-20231024-25-i6una0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/555509/original/file-20231024-25-i6una0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/555509/original/file-20231024-25-i6una0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/555509/original/file-20231024-25-i6una0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A swamp wallaby munching on some grass. Like other plant-eating mammals, they use their sense of smell to find delicious plants.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/swamp-wallaby-wallabia-bicolor-eating-grass-2336437925">Joshua Prieto/Shutterstock</a></span>
</figcaption>
</figure>
<h2>A landscape of smells</h2>
<p>In navigating <a href="https://academic.oup.com/bioscience/article/72/8/745/6618787">a scent landscape</a>, herbivores use odour to recognise and select among plants and plant patches. Odour is key in guiding the foraging of <a href="https://link.springer.com/article/10.1007/s00442-016-3678-2">marsupials in Australia</a>, <a href="https://www.sciencedirect.com/science/article/pii/S0003347218301258">elephants in Africa</a> and <a href="https://www.pnas.org/doi/10.1073/pnas.1818284116">Asia</a>, and <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1600-0706.2011.19515.x">deer in the United States</a>.</p>
<p>With this in mind, we explored whether the smell of a plant they don’t like could be enough to nudge animals away from highly palatable native tree seedlings.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/553860/original/file-20231015-25-ot7z6b.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Image of a deer surrounded by green and red 'bubbles' of things represented by smell" src="https://images.theconversation.com/files/553860/original/file-20231015-25-ot7z6b.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553860/original/file-20231015-25-ot7z6b.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=423&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553860/original/file-20231015-25-ot7z6b.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=423&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553860/original/file-20231015-25-ot7z6b.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=423&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553860/original/file-20231015-25-ot7z6b.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=531&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553860/original/file-20231015-25-ot7z6b.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=531&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553860/original/file-20231015-25-ot7z6b.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=531&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mammalian herbivores use their noses to navigate complex smell landscapes where odour is emitted from food, predators, competitors and potential mates.</span>
<span class="attribution"><a class="source" href="https://academic.oup.com/bioscience/article/72/8/745/6618787">Finnerty et al., BioScience, 2022</a></span>
</figcaption>
</figure>
<p>To test this idea, we focused on swamp wallabies foraging in a eucalypt woodland in eastern Australia. <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/emr.12437">Studies have shown</a> having too many swamp wallabies around can limit the number of eucalypt seedlings that survive to become trees. Swamp wallabies also have a fantastic sense of smell – they can find just <a href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.12748">a few eucalypt leaves buried underground</a> among complex vegetation. </p>
<p>Using an approach <a href="https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.18432">we recently developed</a>, we found the key scent compounds of a plant we know wallabies avoid – the native shrub <em>Boronia pinnata</em>.</p>
<p>We then mixed these compounds together to create “informative virtual neighbours”. They were “informative” as our mix of compounds mimicked what a wallaby would recognise as <em>Boronia pinnata</em>, “virtual” as we were not actually deploying the real shrub, and “neighbours” as we placed these smells in the bush next to eucalypt seedlings we were trying to protect.</p>
<p>In our study, a virtual neighbour was a small glass vial with a few millilitres of the mixture, with a tube pierced through the lid so the smell could waft out.</p>
<p>Using odours instead of real plants is a type of <a href="https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/fee.2534">olfactory misinformation</a> – it sends a deceptive message to the animals. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/553872/original/file-20231015-21-f0ar90.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A side by side photo of a glass bottle with a tube sticking out and a black plastic cup on leaf litter" src="https://images.theconversation.com/files/553872/original/file-20231015-21-f0ar90.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553872/original/file-20231015-21-f0ar90.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553872/original/file-20231015-21-f0ar90.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553872/original/file-20231015-21-f0ar90.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553872/original/file-20231015-21-f0ar90.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=515&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553872/original/file-20231015-21-f0ar90.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=515&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553872/original/file-20231015-21-f0ar90.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=515&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">We deployed the virtual neighbour vials in custom-built contraptions that secured vials to the ground and provided protection from the weather.</span>
<span class="attribution"><span class="source">Finnerty et al., Nature Ecology & Evolution, 2024</span></span>
</figcaption>
</figure>
<h2>Real and virtual neighbours</h2>
<p>We also compared if virtual neighbours were as good as the real thing in protecting eucalypt seedlings from being eaten by wallabies.</p>
<p>Five virtual neighbour vials or real <em>Boronia pinnata</em> plants were spaced evenly around single eucalypt seedlings the wallabies would find highly palatable. (We also had two types of controls: a seedling with nothing around it, and a seedling surrounded by five empty vials.)</p>
<p>Using remote cameras for 40 days, we recorded how long it took wallabies to find and munch on the eucalypt seedlings.</p>
<p>The results were staggering. Seedlings were 20 times less likely to be eaten when surrounded by virtual neighbours than for both controls. This was equivalent to using real <em>B. pinnata</em> plants, but better because vials don’t compete with seedlings for water and other resources.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/572623/original/file-20240131-27-wkm6rq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/572623/original/file-20240131-27-wkm6rq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/572623/original/file-20240131-27-wkm6rq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/572623/original/file-20240131-27-wkm6rq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/572623/original/file-20240131-27-wkm6rq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/572623/original/file-20240131-27-wkm6rq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=494&fit=crop&dpr=1 754w, https://images.theconversation.com/files/572623/original/file-20240131-27-wkm6rq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=494&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/572623/original/file-20240131-27-wkm6rq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=494&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A single eucalypt seedling surrounded by five virtual neighbours (a) and five real plant neighbours (b).</span>
<span class="attribution"><span class="source">Finnerty et al., Nature Ecology & Evolution, 2024</span></span>
</figcaption>
</figure>
<h2>A highly effective approach</h2>
<p>The success of our study indicates we could use this approach as a new management tool – one that works by influencing the animals’ behaviour rather than trying to get rid of them.</p>
<p>We believe the concept behind developing virtual neighbours is directly transferable to any herbivore, mammal or otherwise, that uses plant odour to forage.</p>
<p>All herbivores avoid some plant species. With future development, we can deploy smelly virtual neighbours as a non-deadly and cost-effective tool to reduce the problems caused by overzealous herbivores.</p>
<hr>
<p><em>We acknowledge all other co-authors who contributed to this work: Catherine Price, Malcolm Possell and Cristian Gabriel Orlando from the University of Sydney, and Adrian Shrader from the University of Pretoria. We thank Paul Finnerty for assistance in designing and constructing virtual neighbour holders.</em></p><img src="https://counter.theconversation.com/content/215454/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Patrick Finnerty received funding for this work from the Royal Zoological Society of New South Wales, the Ecological Society of Australia, the Australian Academy of Science, NSW Dept of Planning and Environment, the Australian Wildlife Society, and the Australian Research Council.
</span></em></p><p class="fine-print"><em><span>Clare McArthur receives funding from the Australian Research Council, NSW Environmental Trust and NSW Department of Planning and Environment. She is a member of the Ecological Society of Australia, the Australian Mammal Society and the Australasian Wildlife Management Society.</span></em></p><p class="fine-print"><em><span>Peter Banks receives funding from the Australian Research Council, NSW Environmental Trust and NSW Department of Planning and Environment, Hermon Slade Foundation and Manaaki Whenua.</span></em></p>Each year, hungry plant-eating animals do billions of dollars of damage to valuable plants. We need prevention methods that don’t involve killing them.Patrick Finnerty, PhD candidate - Behavioural Ecology and Conservation Research, University of SydneyClare McArthur, Professor of Behavioural Ecology, University of SydneyPeter Banks, Professor of Conservation Biology, School of Life and Environmental Sciences, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2186682024-01-17T13:36:47Z2024-01-17T13:36:47ZHelium is an essential material for research and medical equipment, but it’s nonrenewable and difficult to recycle<figure><img src="https://images.theconversation.com/files/567962/original/file-20240104-29-yf3a44.jpg?ixlib=rb-1.1.0&rect=0%2C14%2C3264%2C1812&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A bag full of gas used in a helium recovery system.</span> <span class="attribution"><span class="source">Bluefors Cryocooler Technology, Inc.</span></span></figcaption></figure><p>The next time you pick up balloons for your big party, remember the helium gas in those balloons is destined for the stars. Helium is so light that it easily escapes Earth’s gravity, and all helium will eventually make its way into space. Like fossil fuels, helium is a limited resource. </p>
<p>Helium shortages have become an acute problem for many researchers. Since early 2022, a variety of factors have put pressure on the global helium market, including <a href="https://www.doi.org/10.1126/science.adm7941">the potential sale</a> of the U.S.’s publicly held helium reserves and production infrastructure, <a href="https://www.barrons.com/news/sanctions-on-russia-add-to-troubles-facing-global-helium-industry-01646337907">sanctions against Russia</a> and a series of <a href="https://www.gasworld.com/story/kornbluth-latest-amur-fire-tightens-helium-supply-for-2022/">breakdowns at helium plants</a>.</p>
<p><a href="https://www.gasworld.com/story/helium-shortage-4-0-continuing-uncertainty-in-the-market/">Four helium shortages</a> have occurred over the past decade, and these disruptions affect several high-tech industries. Beyond inflating balloons, helium plays a part in welding for certain metals and in making semiconductors.</p>
<p>Medical imaging and chemical analysis research also use helium. Liquid helium cooled to minus-450 degrees Fahrenheit (minus-268 degrees Celsius) keeps the superconducting magnets in instruments like magnetic resonance imaging, or MRI, and nuclear magnetic resonance, or NMR, systems cool. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568307/original/file-20240108-14-w0b91g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A white MRI machine, which has a tube with a cot inside and a white monitor in the background, and a black monitor with blurred images of a human skull, in the foreground." src="https://images.theconversation.com/files/568307/original/file-20240108-14-w0b91g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568307/original/file-20240108-14-w0b91g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568307/original/file-20240108-14-w0b91g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568307/original/file-20240108-14-w0b91g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568307/original/file-20240108-14-w0b91g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568307/original/file-20240108-14-w0b91g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568307/original/file-20240108-14-w0b91g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">MRI machines need liquid helium to keep the magnetic field functioning.</span>
<span class="attribution"><a class="source" href="https://mapi.associatedpress.com/v1/items/a6faf0ae96d649cdb2c8af3625eb34d5/preview/AP16295528547224.jpg?wm=api&tag=app_id=1,user_id=925287,org_id=101781">AP Photo/Keith Srakocic</a></span>
</figcaption>
</figure>
<p>Helium shortages put pressure on many industries, and when a shortage hits, helium <a href="https://doi.org/10.1126/science.adm7941">costs can spike dramatically</a>. Even consumers can be affected – prices for inflated party balloons and helium tank kits <a href="https://www.bbc.com/news/business-49715838">have increased substantially</a>.</p>
<h2>Helium in research – a cold conundrum</h2>
<p>Both MRI and NMR instruments require extremely strong magnetic fields to operate. The most efficient way to generate those fields <a href="https://theconversation.com/how-do-superconductors-work-a-physicist-explains-what-it-means-to-have-resistance-free-electricity-202308">uses superconducting wire</a>. A superconducting electrical current generates a magnetic field, and once started, these currents can continue for decades <a href="https://doi.org/10.1088/1742-6596/286/1/012016">without additional electrical input</a>.</p>
<p>But there is a catch. Without liquid helium, the wires quickly warm up. Over time, the helium used to cool the magnets evaporates. The superconductivity goes away, and the magnetic field dissipates. </p>
<p>Earlier this year, LK-99, a potential new <a href="https://theconversation.com/scientists-have-been-researching-superconductors-for-over-a-century-but-they-have-yet-to-find-one-that-works-at-room-temperature-3-essential-reads-216806">room-temperature superconductor</a> made headlines worldwide. Such a material, if found, could eliminate the need for helium in MRI and NMR systems. </p>
<p>So far, LK-99 has not produced a <a href="https://www.nature.com/articles/d41586-023-02585-7">breakthrough in superconductivity</a>, although scientists are still hunting for <a href="https://theconversation.com/physicists-hunt-for-room-temperature-superconductors-that-could-revolutionize-the-worlds-energy-system-80707">new superconducting materials</a>.</p>
<p>Until scientists find a functional room temperature superconductor, MRI and NMR facilities need helium. A small to midsize university or hospital may spend <a href="https://info.blockimaging.com/how-much-will-it-cost-to-refill-helium-in-my-mri-machine">US$20,000 per year on liquid helium</a>, as every few months, their liquid helium supplies need replenishing. </p>
<p>Larger facilities need more, and over the past two to three years, <a href="https://doi.org/10.1126/science.adm7941">the price of helium</a> has doubled. <a href="https://ivanmr.com/event/helium-crisis-4-0-as-it-pertains-to-the-nmr-community/">Some institutions</a> have been forced to de-energize their instruments as a result. This process shuts down the magnetic field, effectively halting the instrument’s activity until the facility can buy helium again.</p>
<p><iframe id="btsb0" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/btsb0/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>New helium on the horizon</h2>
<p>One approach to address the helium shortage involves seeking additional helium sources. Helium is normally obtained as a <a href="https://www.blm.gov/programs/energy-and-minerals/helium/about-helium">byproduct of drilling for natural gas</a>, since helium collects underground in pockets containing methane and other hydrocarbons. </p>
<p>Methane is a greenhouse gas, and burning natural gas <a href="https://www.eia.gov/energyexplained/natural-gas/natural-gas-and-the-environment.php">releases carbon dioxide</a> into the atmosphere. Methane and carbon dioxide in the atmosphere contribute to climate change. </p>
<p>But pockets of helium that aren’t mixed with natural gas could exist in places underground. <a href="https://www.earth.ox.ac.uk/2016/06/huge-helium-discovery-a-life-saving-find/">Researchers searching</a> in Africa have identified what could be a major store of helium in Tanzania’s Rukwa Region. </p>
<p><a href="https://www.dhakatribune.com/financial-markets/329840/noble-helium-asx-nhe-down-16%25-an-awkward">At least two companies</a> are actively trying to locate these pockets, which originate from <a href="https://www.earth.ox.ac.uk/2016/06/huge-helium-discovery-a-life-saving-find/">unique volcanic activity in the area</a>. Drilling at these sites could be a more climate-friendly alternative – although any form of drilling has local environmental impacts. </p>
<p>As of early December 2023, the helium levels found from drilling these pockets seem promising. <a href="https://www.investi.com.au/api/announcements/nhe/adc30bea-f91.pdf">The most recent exploration</a> reveals helium levels of at least 2% to 3%, more than 1,000 times normal atmospheric levels. This is <a href="https://doi.org/10.7569/jnge.2016.692506">on par with other drilling sites</a> that produce helium.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/567958/original/file-20240104-15-1owtjn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tall steel drilling rig and a large yellow container, with a red flag on top of the container." src="https://images.theconversation.com/files/567958/original/file-20240104-15-1owtjn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/567958/original/file-20240104-15-1owtjn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/567958/original/file-20240104-15-1owtjn.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/567958/original/file-20240104-15-1owtjn.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/567958/original/file-20240104-15-1owtjn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/567958/original/file-20240104-15-1owtjn.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/567958/original/file-20240104-15-1owtjn.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A helium drilling system.</span>
<span class="attribution"><span class="source">Lorna Blaisse, Helium One Global Ltd.</span></span>
</figcaption>
</figure>
<p>Two companies are currently searching for helium in Africa, and both plan to continue searching for higher helium levels. However, <a href="https://www.gasworld.com/story/the-2023-worldwide-helium-market/2128890.article/">independent industry assessments</a> estimate that new helium facilities may not come online until 2025 or later. </p>
<p>Even so, these efforts do not solve the bigger problem – the need for a renewable helium source.</p>
<h2>Reusing existing helium</h2>
<p>Until scientists have reliable, room-temperature superconductors or find an unlimited helium supply, conserving available helium is the best route forward. Fortunately, this is becoming easier to do. </p>
<p>Researchers at <a href="https://www.ameslab.gov/insider-april-2022">Iowa State University</a> began recycling their helium in the 1960s. Since then, this technology has become cheaper, and both the <a href="https://mcbblog.nsfbio.com/2022/05/24/nsf-bio-and-che-will-fund-acquisition-of-helium-recovery-systems/">U.S. National Science Foundation</a> and the <a href="https://loop.nigms.nih.gov/2020/02/nigms-administrative-supplements-for-helium-recovery-systems-2/">U.S. National Institutes of Health</a> have funded efforts to install helium recovery equipment in academic research settings. </p>
<p>These systems are becoming more common, even in smaller NMR facilities. And scientists, including researchers in my lab, are helping each other by <a href="https://www.youtube.com/@FitzkeeLab/">sharing their experiences</a> installing this equipment.</p>
<p>Helium recovery systems involve three main components. First, there is a system that <a href="https://cbic.yale.edu/about-us/helium-recovery">transports evaporated helium</a> from the superconducting magnets. This component monitors the evaporation rate and ensures a steady flow through the system.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568305/original/file-20240108-25-xdlll4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large metal structure next to a truck and a cylindrical red tank, with the setting sun in the background." src="https://images.theconversation.com/files/568305/original/file-20240108-25-xdlll4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568305/original/file-20240108-25-xdlll4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568305/original/file-20240108-25-xdlll4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568305/original/file-20240108-25-xdlll4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568305/original/file-20240108-25-xdlll4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568305/original/file-20240108-25-xdlll4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568305/original/file-20240108-25-xdlll4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A helium drilling facility at sunset.</span>
<span class="attribution"><span class="source">Noble Helium Ltd</span></span>
</figcaption>
</figure>
<p>Second, there is a collection system. For large facilities, this consists of <a href="https://nationalmaglab.org/about-the-maglab/around-the-lab/what-is-that/helium-recovery-bag/">a large, flexible bag</a>. The bag expands as it collects the evaporated helium, storing it temporarily. This bag is the size of a small car, and where space is a concern, smaller facilities can use helium tanks for storage. </p>
<p>Third, there is a system that <a href="https://doi.org/10.1088/1757-899X/101/1/012103">reliquefies the gaseous helium</a>. This is the most expensive component, and it uses electrical energy to cool the helium. Once liquefied, the facility staff transfers the helium back to the magnets.</p>
<p>While the helium shortage has led to significant challenges, many scientists are optimistic about the future. Researchers continue to search for room-temperature superconductors. New helium facilities in Tanzania could increase supply. And more widespread access to helium recovery equipment is allowing scientists to conserve this valuable resource.</p><img src="https://counter.theconversation.com/content/218668/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Fitzkee receives funding from The National Science Foundation (DBI 2215258, CHE/MCB 2304919) and the National Institutes of Health (R01GM113152). Any opinions, findings, conclusions, or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation or National Institutes of Health.</span></em></p>With the fourth significant shortage of helium in a decade continuing, companies and researchers are looking for alternative sources.Nicholas Fitzkee, Professor of Chemistry, Mississippi State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2162442024-01-16T13:40:18Z2024-01-16T13:40:18ZYour fingerprint is actually 3D − research into holograms could improve forensic fingerprint analysis<figure><img src="https://images.theconversation.com/files/565336/original/file-20231212-25-54j3sc.jpg?ixlib=rb-1.1.0&rect=4%2C17%2C2895%2C2056&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fingerprints have been used as unique identifiers for decades. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/BabeRuthAuction/02eed90749c4440d91a7a4e4ea305c6b/photo?Query=fingerprint&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=949&currentItemNo=18">AP Photo/Patrick Semansky</a></span></figcaption></figure><p>When you use your fingerprint to unlock your smartphone, your phone is looking at a two-dimensional pattern to determine whether it’s the correct fingerprint before it unlocks for you. But the imprint your finger leaves on the surface of the button is actually a 3D structure called a fingermark. </p>
<p>Fingermarks are made up of tiny ridges of oil from your skin. Each ridge is only a few microns tall, or a few hundredths of the thickness of human hair.</p>
<p>Biometric identifiers record fingermarks only as 2D pictures, and although these carry a lot of information, there’s a lot missing. A 2D fingerprint neglects the depth of the fingermark, including pores and scars buried in the ridges of fingers that are difficult to see.</p>
<p>I’m an <a href="https://udayton.edu/directory/engineering/electrical_and_computer/banerjee_partha.php">educator and scientist</a> who studies holography, a field of research that focuses on how to display 3D information. My lab has created a way to map and visualize fingermarks in three dimensions from any perspective on a computer – <a href="https://theconversation.com/five-surprising-ways-holograms-are-revolutionising-the-world-77886">using digital holography</a>.</p>
<h2>Fingermark types</h2>
<p>Scientists categorize fingermarks as either patent, plastic or latent, depending on how visible they are when left on a surface.</p>
<p>Patent fingermarks are the most visible type – bloody fingerprints at crime scenes are one example. Plastic fingermarks are found on soft surfaces, such as clay, Play-Doh or chocolate bars. The human eye can see both <a href="https://doi.org/10.1201/b12882">patent and plastic fingermarks quite easily</a>.</p>
<p>The least visible are latent fingermarks. These are usually found on hard surfaces such as <a href="https://doi.org/10.1201/b12882">glass, metals, woods and plastics</a>. To make them out, a fingerprint examiner has to use physical or chemical methods such as dusting with powder, creating chemical reactions with appropriate reagents or <a href="https://doi.org/10.1186/s41935-017-0009-7">cyanoacrylate fuming</a>. </p>
<p>Cyanoacrylate makes super glue in <a href="https://nij.ojp.gov/library/publications/fingerprint-sourcebook">its liquid form</a>, but as a gas it can make latent fingermarks visible. Researchers develop the prints by letting cyanoacrylate vapor molecules react with components in the latent fingerprint residue.</p>
<p>The geometric details on fingermarks are categorized into three levels. Level 1 encompasses <a href="https://www.forensicsciencesimplified.org/prints/principles.html">visible ridge patterns</a>, so loops, whorls and arches. Level 2 refers to <a href="https://nij.ojp.gov/library/publications/fingerprint-sourcebook">minutiae or small details</a>, such as bifurcations, endings, eyes and hooks. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/565337/original/file-20231212-15-ry9tua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three fingerprint ridge patterns shown in black and white. The ridges on the left look like a hill, the center looks like a hill with a loop on top, and on the right the ridges form a circle." src="https://images.theconversation.com/files/565337/original/file-20231212-15-ry9tua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/565337/original/file-20231212-15-ry9tua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=233&fit=crop&dpr=1 600w, https://images.theconversation.com/files/565337/original/file-20231212-15-ry9tua.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=233&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/565337/original/file-20231212-15-ry9tua.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=233&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/565337/original/file-20231212-15-ry9tua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=293&fit=crop&dpr=1 754w, https://images.theconversation.com/files/565337/original/file-20231212-15-ry9tua.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=293&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/565337/original/file-20231212-15-ry9tua.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=293&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fingerprints have visible ridge structures, such as arches (left), whorls (middle) and loops (right), but at the microscopic level they have much finer patterns and structures.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:%D0%9F%D0%B0%D0%BB%D1%8C%D1%86%D0%B5%D0%B2%D1%8B%D0%B5_%D1%83%D0%B7%D0%BE%D1%80%D1%8B.jpg">ValeriyPolunovskiy/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Finally, Level 3 features, such as pores, scars and creases, are too small for the human eye to resolve. This is where <a href="https://doi.org/10.1117/1.OE.56.3.034117">optical techniques</a> like holography come in handy, since optical wavelengths are in the order of microns, small enough to make out small details on an object.</p>
<h2>Developing fingermark holograms</h2>
<p>Since fingermarks are usually collected as 2D pictures, and holograms display 3D information, my team wanted to develop a technique that can show all the 3D topological characteristics of a fingermark.</p>
<p>To do this, we’ve been collaborating with <a href="https://scholar.google.com/citations?user=wC7o_VAAAAAJ&hl=en">Akhlesh Lakhtakia’s group</a> at Penn State. They developed a specialized technique that deposits a <a href="https://doi.org/10.1117/1.OE.56.3.034117">nanoscale columnar thin film</a> layer, called a CTF, on top of the fingermark to develop and preserve it. </p>
<p>Columnar thin films are dense pillars of <a href="https://doi.org/10.1117/1.OE.56.3.034117">glassy material</a> that uniformly cover the fingermark, like a dense growth of identical trees in a forest. Just as the tops of these trees would reflect the topology of the ground, the tops of these columnar thin films <a href="https://doi.org/10.1016/j.ijleo.2023.171541">replicate the 3D structure</a> of the fingermarks on which they are deposited. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/558698/original/file-20231109-15-x4lbc9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A man wearing a blue shirt and green vest, as well as a blue glove, holds a clear petri dish upright, which has three small red squares with fingermarks on them inside." src="https://images.theconversation.com/files/558698/original/file-20231109-15-x4lbc9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558698/original/file-20231109-15-x4lbc9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558698/original/file-20231109-15-x4lbc9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558698/original/file-20231109-15-x4lbc9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558698/original/file-20231109-15-x4lbc9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558698/original/file-20231109-15-x4lbc9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558698/original/file-20231109-15-x4lbc9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Samples collected using CTF film.</span>
<span class="attribution"><span class="source">Banerjee Lab</span></span>
</figcaption>
</figure>
<p><a href="https://science.howstuffworks.com/hologram.htm">To make a hologram</a> of something like a 3D fingermark, researchers split light from a laser into two parts. One part, called the reference wave, shines directly on a digital camera. The other wave shines on the object, in this case the fingermark. </p>
<p>If the object is reflective, the reflected light is also <a href="https://doi.org/10.1117/1.OE.56.3.034117">directed to the digital camera</a> and <a href="https://spie.org/publications/book/2190843?SSO=1">superimposed on the reference wave</a>.</p>
<p>The superposition of waves – both from the reference and the object – creates an interference pattern, which is called a hologram. In digital holography, this hologram, which is a 2D picture, is recorded in the digital camera. Researchers then import the hologram to a computer, where they can use the physical laws of wave propagation to figure out where the light waves from the laser bounced off different parts of the object. </p>
<p>This process allows them <a href="https://spie.org/publications/book/2190843?SSO=1">to reconstruct the object</a> as a 3D picture.</p>
<p>So, the reconstructed hologram has <a href="https://www.biblio.com/book/principles-applied-optics-banerjee-partha-p/d/1473721348">all the 3D details of the object</a>, and you can now visualize the 3D object on a laptop <a href="https://spie.org/publications/book/2190843?SSO=1">from any perspective</a>. </p>
<h2>Picking up fingermarks</h2>
<p>In 2017, our collaboration <a href="https://doi.org/10.1117/1.OE.56.3.034117">reported our first results</a>, where we made 3D pictures of latent fingermarks using the CTF technique. We recorded holograms of the CTF-developed fingermarks with two different wavelengths of light – green and blue – generated from a laser. Using two different wavelengths allowed us to make out tiny details such as pores in the 3D reconstructions. </p>
<p>Lakhtakia’s research group has deposited hundreds of fingermarks on glass, wood and plastic. They’ve then let them age in different environments, at various temperatures and humidity levels, before coating them with CTF film to pick up the fingerprint. My group records the digital holograms of these fingermarks and visualizes them in 3D on a computer. </p>
<p>We have also started working on a better 3D fingermark analysis plan to help identify crime suspects.</p>
<p>The <a href="https://www.mcohio.org/816/Miami-Valley-Regional-Crime-Lab">Miami Valley Regional Crime Lab</a> in Dayton, Ohio, has graded the quality of the fingermarks captured by Lakhtakia’s research group. It will also help us develop a new method for grading the 3D holographic reconstructions, something that does not currently exist. This may involve creating categories to classify how clear the 3D renderings of the fingermarks are.</p>
<p>The use of fingerprints as unique identifiers has a long history, going back to <a href="https://nij.ojp.gov/library/publications/fingerprint-sourcebook">ancient Babylonian and Chinese civilizations</a>. They’ve been used for forensic purposes <a href="https://doi.org/10.1016/j.endeavour.2023.100863">since the late 1890s</a>, starting in Calcutta, India. Our work aims to build on this rich history and use cutting-edge technologies to improve fingermark analysis.</p><img src="https://counter.theconversation.com/content/216244/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Partha Banerjee’s Holography and Metamaterials (HaM) Lab has used Digital Holography for many applications funded by DARPA, Air Force and Army. The current joint work on fingermarks is supported by a grant from the Criminal Investigations and Network Analysis (CINA) Center of the Department of Homeland Security (DHS). </span></em></p>Using fingerprints to catch criminals isn’t 100% accurate, but analyzing fingerprints in 3D, rather than 2D, could improve the process.Partha Banerjee, Professor of Electrical and Computer Engineering, University of DaytonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2161592023-12-26T20:30:30Z2023-12-26T20:30:30ZThe science of the ideal salad dressing<figure><img src="https://images.theconversation.com/files/558179/original/file-20231107-19-8sujdg.jpg?ixlib=rb-1.1.0&rect=626%2C107%2C3159%2C2310&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/salad-dressing-ingredients-olive-oil-honey-1808249242">HannaTor/Shutterstock</a></span></figcaption></figure><p>Summer means salads. And salads are even more delicious with a good dressing.</p>
<p>Most salad dressings are temporarily stable mixtures of oil and water known as emulsions.</p>
<p>But how do salad dressing emulsions form? And how can we enhance our emulsions for better salads and more?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-make-the-perfect-pavlova-according-to-chemistry-experts-196485">How to make the perfect pavlova, according to chemistry experts</a>
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</em>
</p>
<hr>
<h2>Oil and water don’t mix</h2>
<p>It’s accepted wisdom that oil and water don’t mix. The water and oil molecules have distinct chemical properties that don’t interact well together. </p>
<p>You may have seen this if you’ve attempted to make a salad dressing by shaking together oil and vinegar (which is mostly water), which gives a temporary suspension that quickly separates.</p>
<p>There is a large energy cost to breaking apart and mixing the water and oil layers. The secret to blending them together is to add an extra ingredient known as a “surfactant” or emulsifier.</p>
<p>The name surfactant is derived from “surface active”. It highlights that these molecules work at the surface or interface to bridge the interactions between the oil and water. This is similar to how <a href="https://theconversation.com/what-is-sodium-lauryl-sulfate-and-is-it-safe-to-use-125129">detergents</a> are able to remove grease from your dishes.</p>
<p>Many vinaigrette recipes call for emulsifiers without specifically mentioning their crucial emulsifying role. </p>
<p>Key examples are mustard and garlic, which contain “mucilage” – a mix of carbohydrates – that can act as emulsifiers. </p>
<p>So if your vinegar/oil salad dressings are separating, make sure you’re adding enough of these ingredients (which also contain <a href="https://theconversation.com/hate-vegetables-you-might-have-super-taster-genes-74428">wonderful flavour chemicals</a>).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/557661/original/file-20231106-21-zqku7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three salad dressings sit on a bench; one with chilli seeds, one creamy yoghurt-based dressing and one mustard and oil emulsion." src="https://images.theconversation.com/files/557661/original/file-20231106-21-zqku7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557661/original/file-20231106-21-zqku7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557661/original/file-20231106-21-zqku7t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557661/original/file-20231106-21-zqku7t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557661/original/file-20231106-21-zqku7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557661/original/file-20231106-21-zqku7t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557661/original/file-20231106-21-zqku7t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many vinaigrette recipes call for emulsifiers such as mustard.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/variety-homemade-sauces-salad-dressings-mason-571747333">Shutterstock</a></span>
</figcaption>
</figure>
<p>Commercial salad dressings also contain naturally sourced emulsifying carbohydrates. These will often be listed on the ingredients as generic “vegetable gum” or similar, and you may need to <a href="https://theconversation.com/busting-the-myth-that-all-food-additives-are-bad-a-quick-guide-for-label-readers-82883">read the label</a> and delve a little deeper into the <a href="https://www.foodstandards.gov.au/consumer/additives/additiveoverview/Documents/Food%20Additive%20Code%20Numbers%20%28July%202014%29.pdf">food additive number</a> to find out the source. </p>
<p>Researchers have raised questions about <a href="https://theconversation.com/food-additives-and-chronic-disease-risk-what-role-do-emulsifiers-play-38492">synthetic emulsifiers used in processed food</a>, as studies in mice suggest they have health risks. It’s too early to say exactly what this means for humans. </p>
<h2>Shake it ‘til you make it</h2>
<p>Mixing is key to dispersing oil in water. While shaking a jar is convenient, a whisk or food processor will give a more complete emulsion. The white (or opaque) colour of many emulsions is due to the formation of microdroplets that scatter light. </p>
<p>These mechanical mixing methods are even more essential for the formation of so-called “permanent emulsions” such as mayonnaise. </p>
<p>Mayonnaise is an emulsion of oil in water, but egg yolk is the key emulsifier. Egg yolks contain long molecules called <a href="https://link.springer.com/referenceworkentry/10.1007/978-3-642-36605-5_28">phospholipids</a> that are able to interact with both the oil layer and the water. Mayonnaise is an impressively stable emulsion, which is why is can be sold in a shelf-stable form.</p>
<p>But it isn’t infinitely stable; heating the mayonnaise emulsion will cause it to split. Perhaps you’ve hurriedly prepared a potato salad and added a mayonnaise-based dressing before the potatoes have cooled down?</p>
<p>Or toasted a sandwich spread with mayonnaise? (Incidentally, adding mayonnaise to the <em>outside</em> of a toasted sandwich is an excellent path to some <a href="https://theconversation.com/kitchen-science-from-sizzling-brisket-to-fresh-baked-bread-the-chemical-reaction-that-makes-our-favourite-foods-taste-so-good-58577">delicious and crispy chemical reactions</a>.) </p>
<p>The heat destabilises the emulsion and the separate oil and water phases will reform. Depending on the mixture, split emulsions may be recovered by adding more emulsifier and re-whisking or re-mixing.</p>
<p>Hollandaise sauce is a notoriously difficult emulsion to prepare. The traditional hollandaise method involves whisking egg yolk, water, and lemon juice over a low heat, then slowly adding melted butter with further whisking. Not only can the emulsion split, but you can also overcook the added emulsifying egg yolk. </p>
<p>The key to a successful hollandaise emulsion is separating the butter into fine, dispersed droplets, giving a thick and opaque mixture, but without cooking the eggs. Adding the butter too quickly or without sufficient mixing can give a split sauce. </p>
<p>Using an <a href="https://www.seriouseats.com/foolproof-2-minute-hollandaise-recipe">immersion blender</a> can help, as can controlling the temperature of the melted butter. You might get a more consistently emulsified sauce with far less strain on your wrists. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/557663/original/file-20231106-28-8oczkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A person makes mayonnaise using a mechanical stick blender." src="https://images.theconversation.com/files/557663/original/file-20231106-28-8oczkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557663/original/file-20231106-28-8oczkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557663/original/file-20231106-28-8oczkp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557663/original/file-20231106-28-8oczkp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557663/original/file-20231106-28-8oczkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=466&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557663/original/file-20231106-28-8oczkp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=466&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557663/original/file-20231106-28-8oczkp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=466&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mechanical mixing methods are even more essential for the formation of ‘permanent emulsions’ such as mayonnaise.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/concept-making-homemade-mayonnaise-natural-healthy-1829111036">Shutterstock</a></span>
</figcaption>
</figure>
<h2>You’ve got me feeling emulsions</h2>
<p>Emulsions are used in many more places than salads and sauces. Most medicated creams, cosmetics and lotions are emulsions of oils and water, which is why they look white. </p>
<p>Gardeners might be familiar with a mixture known as “<a href="https://www.abc.net.au/gardening/how-to/horticultural-oils/9428876">white oil</a>” – a mixture of vegetable oil and detergent. This brew, when diluted in water, is an inexpensive, effective, yet mild insecticide. Commercial versions often contain other pesticides, so make sure you read the label.</p>
<p>Modern <a href="https://www.acs.org/education/whatischemistry/landmarks/acrylicemulsion.html">acrylic paints use emulsions</a> for both their manufacturing and application. The emulsions suspend the paint polymers in a water base.</p>
<p>The water from the paint evaporates, leaving a film of paint polymers that can’t be re-dispersed into water. This clever chemical trick has saved huge quantities of oil-derived solvents from being used, <a href="https://theconversation.com/why-solvents-can-affect-brain-health-even-at-low-levels-of-exposure-98081">inhaled</a>, and emitted into the environment from traditional oil-based paints.</p>
<p>Modern vaccines use <a href="https://theconversation.com/adjuvants-the-unsung-heroes-of-vaccines-156548">emulsions to increase the immune systems response</a>. Other common emulsions are inks, <a href="https://theconversation.com/how-does-ice-cream-work-a-chemist-explains-why-you-cant-just-freeze-cream-and-expect-results-205038">ice cream</a>, margarine and hair products, to name just a few.</p>
<p>So next time you’re making a salad, check your emulsions. Opposites don’t attract, but mixing them with the right chemistry can give a delicious result.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/kitchen-science-the-many-wonders-of-humble-flour-59310">Kitchen Science: the many wonders of humble flour</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/216159/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Kilah does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There is a large energy cost to breaking apart and mixing the water and oil layers. The secret to blending them is to add an extra ingredient known as a ‘surfactant’ or emulsifier, like mustard.Nathan Kilah, Senior Lecturer in Chemistry, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2195892023-12-20T22:11:26Z2023-12-20T22:11:26ZHow to make gravy (using chemistry)<figure><img src="https://images.theconversation.com/files/566166/original/file-20231217-26-g6qyx4.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C5472%2C3628&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/caucasian-male-hand-pouring-gravy-on-1256033632">OKMG/Shutterstock</a></span></figcaption></figure><p>“Gravy Day” is a relatively new date in the Australian calendar. Paul Kelly’s song <a href="https://theconversation.com/humbug-tinsel-and-gravy-in-search-of-the-perfect-christmas-pop-song-88924">How to Make Gravy</a> tells the story of a prisoner (Joe) writing to his brother on December 21. Joe laments missing the family Christmas celebrations and asks who will make gravy for the roast lunch in his absence.</p>
<p>While a roast may not be everyone’s idea of the perfect <a href="https://theconversation.com/a-festive-feast-of-fish-and-fruit-the-creation-of-the-australian-christmas-dinner-151201">Christmas feast</a>, “Gravy Day” does give the opportunity to discuss the chemistry involved in making gravy – a thickened sauce made from drippings collected from roasted meats.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/FozoWgvh-m4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Paul Kelly performs his song How To Make Gravy.</span></figcaption>
</figure>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-does-ice-cream-work-a-chemist-explains-why-you-cant-just-freeze-cream-and-expect-results-205038">How does ice cream work? A chemist explains why you can't just freeze cream and expect results</a>
</strong>
</em>
</p>
<hr>
<h2>Give my love to Angus (beef?)</h2>
<p>Roasting meat sets off a cascade of chemical reactions, producing myriad new flavour chemicals. More than <a href="https://link.springer.com/chapter/10.1007/978-1-4615-2143-3_10#:%7E:text=This%20has%20resulted%20in%20the,and%20lean%20components%20of%20meat.">1,000</a> flavour compounds have been identified in roasted meats.</p>
<p>Each chemical gives its unique characteristics to the taste and smell of the finished roast. The chemical <a href="https://www.sciencedirect.com/science/article/pii/S0308814698000764">12-methyltridecanal</a> helps give roast beef its “beefy” flavour, while the sulfur-containing compound <a href="https://www.sciencedirect.com/science/article/pii/S0963996922004422">2-methyl-3-furanthiol</a> is more often found in roast chicken.</p>
<p>There are three main types of chemical reactions taking place when roasting meats that produce flavour chemicals. </p>
<p>The <a href="https://theconversation.com/kitchen-science-from-sizzling-brisket-to-fresh-baked-bread-the-chemical-reaction-that-makes-our-favourite-foods-taste-so-good-58577">Maillard reaction</a> is responsible for both colour and flavour. This broad reaction type takes place between amino acids from the protein and sugars and simple carbohydrates found in the meat. </p>
<p>The Maillard reaction is also the chemistry responsible for many favourite flavours, including roasted coffee, chocolate, steak, toast and more. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566164/original/file-20231217-27-m8n75f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A roast chicken is displayed on a table." src="https://images.theconversation.com/files/566164/original/file-20231217-27-m8n75f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566164/original/file-20231217-27-m8n75f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566164/original/file-20231217-27-m8n75f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566164/original/file-20231217-27-m8n75f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566164/original/file-20231217-27-m8n75f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566164/original/file-20231217-27-m8n75f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566164/original/file-20231217-27-m8n75f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The sulfur-containing compound 2-methyl-3-furanthiol is often found in roast chicken.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/homemade-chicken-rotisserie-thyme-lemon-closeup-1574170006">AS Foodstudio/Shutterstock</a></span>
</figcaption>
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<h2>A hundred degrees, even more maybe</h2>
<p>The other main type of reaction occurring in a hot oven is the breakdown of fats by “<a href="https://doi.org/10.1016/j.foodres.2022.111385">lipid degradation</a>”. This can form hundreds of different chemical compounds. Many of these chemicals are described as “fatty”, “tallowy”, or smell like fried foods. </p>
<p>The unique fat profiles found in different animals translate to the profile of flavour chemicals that form from lipid degradation when roasted. Further flavour compounds can arise through the third type of reactions combining products of Maillard reactions and lipid degradation.</p>
<p>One specific flavour compound identified as having a “gravy aroma” is known as <a href="https://pubs.acs.org/doi/10.1021/jf9023189">3-mercapto-2-methylpentan-1-ol</a>. This compound comes from roasted vegetables, so including some veggies in your roasting pan will give you more depth of gravy flavour. Also, “cutting onions” is a useful excuse if listening to How to Make Gravy gets you feeling emotional.</p>
<h2>The treasure and the trash</h2>
<p>Roasting meats causes the fats to “render” and separate from the meat as a liquid. The fat pools in the tray with flavour-rich meat juices.</p>
<p>While the fat and the water both carry flavour compounds, too much fat can give the finished gravy an unpleasant mouth feel, or can separate into layers when served.</p>
<p>It’s worth pouring off the pan juices into a jug to allow the fat to separate from the liquid so you can control how much fat you’re adding. Be sure to dispose of the excess fat responsibly – <a href="https://theconversation.com/why-shouldnt-i-pour-oil-or-paint-down-the-sink-and-what-should-i-do-instead-206604">don’t pour it down the drain</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566165/original/file-20231217-19-yw2q11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Meat juices drip off a spoon into a tray of roasted meats." src="https://images.theconversation.com/files/566165/original/file-20231217-19-yw2q11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566165/original/file-20231217-19-yw2q11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566165/original/file-20231217-19-yw2q11.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566165/original/file-20231217-19-yw2q11.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566165/original/file-20231217-19-yw2q11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566165/original/file-20231217-19-yw2q11.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566165/original/file-20231217-19-yw2q11.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Roasting meats causes the fats to ‘render’ and separate from the meat as a liquid.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/closeup-spoon-juice-sauce-over-cooked-1005879244">Jevanto Productions/Shutterstock</a></span>
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</figure>
<h2>Just add flour…</h2>
<p>Flour (or, more specifically, starch) is the secret ingredient of a good gravy. Starches are <a href="https://www.sciencedirect.com/science/article/pii/S0168945222000474">large complex chemicals</a> that are made up of lots of sugars joined together. </p>
<p>Starch granules are tightly packed and swell greatly when they absorb water. The swollen starch molecules forms a gel-like network that traps water and oil to give a thickened gravy.</p>
<p>Wheat flour is most often used as the starch source. Corn and arrowroot starch can also be used. They have a higher percentage of starch than flour and a more neutral flavour. </p>
<p>Wheat starch typically requires a larger quantity to be added and longer cooking to form a paste. Whichever starch you use, don’t add it too quickly or without mixing as you’ll form lumps.</p>
<h2>…salt, red wine, and a dollop of tomato sauce</h2>
<p>Salt is a common ingredient when preparing roast meats, both on the surface of the meat to draw out moisture and as a flavouring agent. The pan juices are typically concentrated as part of the gravy making process. </p>
<p>Make sure you taste the gravy before seasoning, as salt will be concentrated by heating. </p>
<p>Additional flavour components can be introduced by adding red wine, sherry, stock, or tomato sauce. These ingredients will broaden the flavour profile through sweetness (sugar), acidity (vinegar, citric and malic acids), and umami in the case of tomato sauce (natural glutamates, such as those found in MSG). Some folk even add Vegemite to their gravy for an extra umami boost.</p>
<h2>I bet it will taste the same</h2>
<p>If you happen to have screwed up your gravy this time, or are after convenience, then you can turn to an instant gravy powder. The main ingredient is typically maltodextrin or another corn-derived (and possibly chemically modified) starch.</p>
<p>Shelf-stable powdered fats, salt, colours, and a range of <a href="https://theconversation.com/busting-the-myth-that-all-food-additives-are-bad-a-quick-guide-for-label-readers-82883">flavour additives</a> will be present in varying amounts depending on the style and price point of the product.</p>
<p>The advantages of the instant version are speed and uniformity due to the carefully controlled commercial production.</p>
<p>So unlike Joe’s concerns for his family’s gravy, an instant gravy will be more likely to taste the same, regardless of who ends up making it.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-make-the-perfect-pavlova-according-to-chemistry-experts-196485">How to make the perfect pavlova, according to chemistry experts</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/219589/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Kilah does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Roasting meat sets off a cascade of chemical reactions. With a bit of kitchen chemistry know-how, you can use these reactions to your advantage when you make gravy.Nathan Kilah, Senior Lecturer in Chemistry, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2192842023-12-19T13:14:58Z2023-12-19T13:14:58ZHow active are the microorganisms in your yogurt? We created a new tool to study probiotic activity — and made it out of cardboard<figure><img src="https://images.theconversation.com/files/565830/original/file-20231214-19-q51cra.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4244%2C2920&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fermented foods can be a good source of probiotics. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/fermented-vegetables-sauerkraut-with-carrots-and-royalty-free-image/1279140719?phrase=probiotic+food&adppopup=true">Yulia Naumenko/Moment via Getty Images</a></span></figcaption></figure><p>Humans have been fermenting food and drinks — everything from kimchi and yogurt to beer and kombucha — for <a href="https://doi.org/10.3390%2Ffoods10112861">more than 13,000 years</a>. </p>
<p>Fermentation – a natural process that uses microorganisms to create alcohols and acids from carbohydrates – can preserve food so it lasts longer, and it can enhance the quality of a food by turning some components into more easily digestible forms. </p>
<p>Some fermented foods that contain live microorganisms are <a href="https://www.nccih.nih.gov/health/probiotics-what-you-need-to-know">called probiotics</a>, which can increase the shelf life of food and provide a range of additional benefits, like promoting a healthy <a href="https://theconversation.com/which-microbes-live-in-your-gut-a-microbiologist-tries-at-home-test-kits-to-see-what-they-reveal-about-the-microbiome-181392">gut microbiome</a> and lowering cholesterol levels.</p>
<p><a href="https://scienceweb.clemson.edu/uacl/">We are</a> <a href="https://scholar.google.com/citations?user=0kmXuxYAAAAJ&hl=en">chemists</a>, and our team wanted to figure out a way to understand which probiotics are the most active in the body. So we developed a cardboard sensor that could monitor the metabolic activity of probiotics.</p>
<h2>Probiotic health benefits</h2>
<p>As they are generally <a href="https://doi.org/10.1086/523331">considered safe</a>, probiotics are also one of the most popular dietary supplements in today’s market, accounting for more than <a href="https://finance.yahoo.com/news/global-probiotics-market-size-worth-075000774.html">US$50 billion</a> per year. </p>
<p><em>Lactobacillus</em>, <em>Bifidobacterium</em> and <em>Saccharomyces</em> are the most common probiotics. For example, food manufacturers use starter cultures of <em><a href="https://www.healthline.com/health/digestive-health/lactobacillus-bulgaricus">Lactobacillus bulgaricus</a></em> and <em><a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/streptococcus-thermophilus">Streptococcus thermophilus</a></em> to clot milk and make yogurt.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Z-DfrsyAMTw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Probiotic-packed foods can help with gut health.</span></figcaption>
</figure>
<p><a href="https://doi.org/10.1038/s41575-019-0173-3">Recent studies</a> have also found that probiotics may prevent the development of harmful bacteria in the body, lower cholesterol levels, reduce constipation, control blood pressure, enhance the production of vitamins, improve calcium absorption and boost the immune system. </p>
<p>However, probiotics can only provide health effects when the microorganisms are alive, meaning they’re metabolically active and <a href="https://www.nature.com/articles/s41575-019-0173-3/figures/1">interacting with the host’s body</a>. So, the type of probiotic, its formulation, and how it’s processed become critically important. </p>
<h2>Analyzing probiotics</h2>
<p>Probiotics grow from individual cells into colonies. Food scientists can study probiotics by counting the number of viable cells – also called colony forming units – in the food to figure out how much they might grow and how active they’ll be. They can also study how probiotics respond to <a href="https://doi.org/10.1016/j.crfs.2021.04.006">a gastric juice made in the lab</a> to simulate how probiotics act in your gut. <a href="https://www.britannica.com/science/human-digestive-system/Gastric-secretion">Gastric juice</a> is the fluid secreted in your stomach during digestion. </p>
<p>But most of these tests are slow and involve expensive instruments and skilled personnel. That’s where our cardboard sensors come in.</p>
<p>Our research team has collaborated with a research <a href="https://www.iq.usp.br/trlcp/">team from Brazil</a> to develop a simple sensor that can measure the <a href="https://doi.org/10.1002/anse.202300056">metabolic activity of probiotic foods</a>. </p>
<p>We built the sensors using standard cardboard and a process called laser scribing. We use a laser to convert a small amount of the cardboard into carbon, making it electrically conductive. We also used gold nanoparticles, which further improve the sensor’s response by decreasing the material’s resistivity.</p>
<p>Lowering the resistivity of the material is important because the sensor detects the metabolic activity of bacteria via a type of chemical reaction called a <a href="https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:chemical-reactions/x2eef969c74e0d802:oxidation-reduction-redox-reactions/a/oxidation-number">redox reaction</a>. It can detect the oxidation of a molecule that is produced by one of the probiotics. </p>
<h2>Sensor findings</h2>
<p>Before testing, the team first calibrated the sensor using a popular probiotic yogurt widely available in U.S. stores as a model. For each test, we only needed to incubate 100 microliters of sample — about 1/50th of a teaspoon — for 10 minutes at room temperature. </p>
<p>Once we calibrated the sensors, we tested how metabolically active the microorganisms present in the sample were. We tested both beer and yogurt and found that the sensors could determine the metabolic activity more accurately than other tests that scientists usually use. </p>
<p><a href="https://doi.org/10.1002/anse.202300056">We also found</a> that the bacteria in the beer we tested, an unfiltered IPA, had more metabolic activity than the yogurts, which were popular brands Siggi’s, Yakult and Activia.</p>
<p>But, before you run to your local brewery, it’s important to note that the sensor only measures the total metabolic activity of the microorganisms present in the sample. It doesn’t detect anything about the type of activity or potential health effects.</p>
<p>While several groups have reported on the potential <a href="https://doi.org/10.3390%2Fnu15040844">health benefits of beer</a>, not all beers will provide these benefits. And keep in mind that a pint of an IPA carries beneficial bacteria, but also a typical alcohol content of between 6% and 8% and 180-200 calories.</p>
<p>Many <a href="https://doi.org/10.1016/j.tifs.2023.06.013">researchers have performed studies in this field</a> using more traditional probiotic foods that contain many of the microorganisms in your gut. Even in these cases, they’ve found that probiotics’ ability to correct specific health issues is probably limited. </p>
<p>Also, considering the way supplements containing probiotics <a href="https://www.forbes.com/sites/linhanhcat/2019/03/13/probiotics/?sh=35d1926719e8">are regulated</a>, it’s hard to say whether the products actually contain the type and amount of viable bacteria advertised on the label.</p>
<p>All things considered, the proposed sensor aims to provide a simple, portable and low-cost way to detect the activity of live bacteria. These sensors could one day help out in fields like health care.</p><img src="https://counter.theconversation.com/content/219284/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Financial support for this project has been provided by the Department of Chemistry at Clemson University and by CAPES (Brazil).</span></em></p><p class="fine-print"><em><span>George Chumanov does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Probiotics are great for your gut, but which sources contain the most beneficial bacteria? Newly developed sensors are helping scientists figure it out.Carlos D. Garcia, Professor of Chemistry, Clemson UniversityGeorge Chumanov, Professor of Chemistry, Clemson UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2191952023-12-06T19:39:11Z2023-12-06T19:39:11ZEarth may have had all the elements needed for life within it all along − contrary to theories that these elements came from meteorites<figure><img src="https://images.theconversation.com/files/563960/original/file-20231206-27-mh7rrg.jpg?ixlib=rb-1.1.0&rect=5%2C11%2C1994%2C1485&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists still debate the origins of Earth's life-sustaining elements.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/hot-sunrise-in-space-royalty-free-image/160306742?phrase=Tobias+Roetsch+Future+Publishing+earth&adppopup=true">BlackJack3D/E+ via Getty Images</a></span></figcaption></figure><p>For many years, scientists have predicted that many of the <a href="https://www.khanacademy.org/science/ap-biology/chemistry-of-life/elements-of-life/a/matter-elements-atoms-article">elements that are crucial ingredients for life</a>, like sulfur and nitrogen, first came to Earth when asteroid-type objects carrying them crashed into our planet’s surface. </p>
<p>But new research <a href="https://doi.org/10.1126/sciadv.adh0670">published by our team</a> in Science Advances suggests that many of these elements, called volatiles, may have existed in the Earth from the beginning, while it formed into a planet.</p>
<p>Volatiles evaporate more readily than other elements. Common examples include carbon, hydrogen and nitrogen, though our research focused on a <a href="https://www.sciencedirect.com/topics/chemistry/chalcogen">group called chalcogens</a>. Sulfur, selenium and tellurium are all chalcogens.</p>
<p>Understanding how these volatile elements made it to Earth helps <a href="https://scholar.google.com/citations?user=DpHUpCwAAAAJ&hl=en">planetary scientists</a> <a href="https://scholar.google.com/citations?user=h0uFkzgAAAAJ&hl=zh-CN">like us</a> better understand Earth’s geologic history, and it could teach us more about the habitability of terrestrial planets beyond Earth. </p>
<h2>Why it matters</h2>
<p>The popular “late veneer” theory predicts that Earth first formed from <a href="https://www.ox.ac.uk/news/2017-09-27-volatile-processes-shaped-earth">materials that are low in volatiles</a>. After the formation of the Earth’s core, the theory says, the <a href="https://doi.org/10.1126/science.1186239">planet got volatiles</a> when volatile-rich bodies from the outer solar system hit the surface. </p>
<p>These objects brought <a href="https://doi.org/10.1007/978-3-642-11274-4_870">around a half a percent of Earth’s mass</a>. If the late veneer theory is right, then most elements that make up life arrived on Earth sometime <a href="https://physicsworld.com/a/how-the-earths-core-was-formed/">after the Earth’s core had formed</a>.</p>
<p>But our new research suggests that Earth had all its life-essential volatile elements from the very beginning, during the planet’s formation. These results challenge the late veneer theory and are consistent with another study <a href="https://newsroom.ucla.edu/releases/earth-like-planets-may-be-an-inevitability">tracing the origin of water on Earth</a>. </p>
<h2>How we did our work</h2>
<p>To study the origin of volatiles in the Earth, we used a computational technique called <a href="https://www.jeol.com/words/emterms/20121023.055758.php#gsc.tab=0">first-principles calculation</a>. This technique describes the <a href="https://www.ducksters.com/science/chemistry/radiation_and_radioactivity.php">behaviors of isotopes</a>, which are atoms of an element that have varying numbers of neutrons. You can think of an element as a family – every atom has the same number of protons, but <a href="https://theconversation.com/hunting-for-rare-isotopes-the-mysterious-radioactive-atomic-nuclei-that-will-be-in-tomorrows-technology-86177">different isotope cousins</a> have different numbers of neutrons.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/42gUZNYco0c?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Isotopes have a host of useful applications, from archaeology and medicine to planetary science.</span></figcaption>
</figure>
<p>Different isotopes behaved slightly differently during each stage of Earth’s formation. And the isotopes left behind a signature after each formation stage that scientists can use as a kind of fingerprint to track where they were throughout Earth’s formation. </p>
<p>First-principles calculation allowed us to calculate what isotope signatures we’d expect to see for different chalcogens, depending on how the Earth formed. We ran a few models and compared our isotope predictions for each model with the actual measurements of chalcogen isotopes on Earth.</p>
<p><a href="https://doi.org/10.1126/sciadv.adh0670">We found that</a> while many volatiles evaporated during Earth’s formation, when it was hot and glowing, many more are still left over today. Our findings suggest that most of the volatiles on Earth now are likely left over from the early stage of Earth’s formation.</p>
<h2>What’s next</h2>
<p>While chalcogens are interesting to study, future research should look at other critical-for-life volatiles, like nitrogen. And more research into how these volatiles behave <a href="https://education.nationalgeographic.org/resource/core/">under extreme conditions</a> could help us know more about how isotopes were behaving during each of the growth stages of Earth’s formation. </p>
<p>We also hope to use this approach to see <a href="https://theconversation.com/nasas-tess-spacecraft-is-finding-hundreds-of-exoplanets-and-is-poised-to-find-thousands-more-122104">whether some exoplanets</a> – planets beyond our solar system – could be <a href="https://theconversation.com/distant-star-toi-700-has-two-potentially-habitable-planets-orbiting-it-making-it-an-excellent-candidate-in-the-search-for-life-198274">habitable to life</a>.</p>
<p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p><img src="https://counter.theconversation.com/content/219195/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shichun Huang is funded by National Science Foundation, and UTK Gerald D. Sisk Endowed Professorship.</span></em></p><p class="fine-print"><em><span>Wenzhong Wang receives funding from the National Natural Science Foundation of China. </span></em></p>Scientists analyzing isotope ratios have found that many of the elements that make up life could be left over from Earth’s formation.Shichun Huang, Associate Professor of Earth and Planetary Sciences, University of TennesseeWenzhong Wang, Professor of Planetary Science, University of Science and Technology of ChinaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2175942023-12-01T16:05:52Z2023-12-01T16:05:52ZPFAS forever chemicals found in English drinking water – why are they everywhere and what are the risks?<figure><img src="https://images.theconversation.com/files/561547/original/file-20231124-23-32rcjz.jpg?ixlib=rb-1.1.0&rect=23%2C57%2C7693%2C5078&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/senior-hand-holding-glass-clean-water-2289733331">husjur02/Shutterstock</a></span></figcaption></figure><p><a href="https://www.dwi.gov.uk/pfas-and-forever-chemicals/">PFAS chemicals</a> (per-and poly fluoroalkyl substances), also known as forever chemicals, are rarely <a href="https://www.theguardian.com/environment/2023/oct/13/pfas-pollution-us-military-bases-forever-chemicals">out of the news</a> at the moment. The latest concern about this chemical group <a href="https://www.theguardian.com/environment/2023/nov/28/forever-chemicals-found-in-drinking-water-sources-across-england">is their presence</a> in <a href="https://www.bbc.co.uk/news/science-environment-67101179">drinking water</a> in England. </p>
<p>The Royal Society of Chemistry found that the UK’s drinking water standard is not stringent enough to protect us against the dangerous health effects of PFAS. The health risks include links to cancer and fertility problems. </p>
<p>But PFAS are a problem that is not going away anytime soon. Even if we stopped using them in products today, there are already huge amounts of them in the environment and some types of PFAS simply <a href="https://www.cdc.gov/biomonitoring/PFAS_FactSheet.html">do not degrade</a>. <a href="https://www.lancaster.ac.uk/news/new-antarctic-study-shows-levels-of-forever-chemicals-reaching-the-remote-continent-have-been-increasing">Our research</a> has even found growing evidence of these chemicals in some of the most remote places on Earth, including the Antarctic. </p>
<p>To make matters worse, the PFAS chemicals that do degrade often break down into the more recalcitrant PFAS types, which then <a href="https://setac.onlinelibrary.wiley.com/doi/full/10.1002/etc.2663">cycle around the environment</a> endlessly. </p>
<h2>What are PFAS?</h2>
<p>Media coverage of the problem can be hard to follow because the PFAS group includes more than 5,000 different chemical substances. </p>
<p>It <a href="https://www.edf.org/blog/2013/04/30/chemicals-called-pfcs-are-everywhere-and-thats-problem">used to be common</a> to read stories about <a href="https://www.sciencedirect.com/topics/chemistry/perfluorinated-compound">poly- /perfluoro compounds</a> (PFCs) and poly- /perfluoro alkyl acids (PFAs) rather than PFAS. Even now it is not uncommon to see products like outdoor clothing labelled as PFC free. </p>
<p>But a lot of PFCs are non-toxic and include a lot of widely used <a href="https://pubs.acs.org/doi/10.1021/acsomega.0c00830">medical drugs</a>. PFCs mean drugs with a carbon-fluorine bond, which is not a problem in itself. PFAS are a sub group of PFCs and they are toxic and extremely difficult to break down. </p>
<p>PFAs are a sub-group of PFAS chemicals. Over the <a href="https://www.sciencedirect.com/science/article/pii/S0304389422009104">last few years</a> research has increasingly highlighted problems with the wider PFAS group than just PFAs. PFAS can be broadly split into two groups: fluoropolymers and non-polymers. </p>
<h2>Fluoropolymers</h2>
<p>The most well-known fluoropolymer is polytetrafluoroethylene (PTFE) with its trademark name Teflon, first produced by <a href="https://theconversation.com/dark-waters-what-dupont-scandal-can-teach-companies-about-doing-the-right-thing-132480">Dupont in the 1940s</a>. PTFE is the non-stick coating to cookware. Its stability to high temperatures, non-reactivity and low friction properties makes it ideal for this application. We can ingest flakes of the polymer, but it is not absorbed by the body so just passes through us. </p>
<p>PTFE film is also used in some types of <a href="https://core.ac.uk/download/pdf/212817141.pdf">waterproof, breathable outdoor clothing</a>. The micropores allow the passage of water vapour (from sweat for example) but prevent water droplets seeping through, keeping the wearer dry. </p>
<p>Other fluoropolymers include polyvinylidene fluoride (PVDF) used in <a href="https://www.sciencedirect.com/science/article/abs/pii/B9780128006795000105">sensors and batteries</a> because of its ability to hold an electrical charge. While fluoropolymers are not considered toxic, <a href="https://pubs.acs.org/doi/10.1021/acs.est.0c03244">their production relies on</a> large quantities of other toxic chemicals, like non-polymers. They are better for us because the end product doesn’t bring us into direct contact with non-polymers, but bad news for the environment as that is where the non-polymers will probably end up.</p>
<h2>Non-polymers</h2>
<p>The <a href="https://www.researchgate.net/publication/264002410_Polymers_and_non-polymers_-_A_new_systematisation_of_substances_and_materials">non-polymer group</a> has by far the biggest number of substances and their use is myriad – including in food packaging, cosmetics, medical applications, fabric coatings and electronics.</p>
<p>This group also includes refrigerant and cleaning solvents (replacement chemicals to the <a href="https://www.unep.org/ozonaction/who-we-are/about-montreal-protocol">infamous CFCs</a> banned to protect the ozone). They have high water and oil repellency and chemical stability. For industrial uses chemicals must be stable so that they do their job without reacting or breaking down. If you bought a cosmetic and it lost its colour or wouldn’t spread after a few days, for example, that wouldn’t be good.</p>
<p>Non-polymers also have <a href="https://www.sciencedirect.com/topics/materials-science/thermal-stability">good thermal stability</a>. This makes it very useful for making food packaging such as pizza boxes and popcorn wrapping.</p>
<figure class="align-center ">
<img alt="Pepperoni inside cardboard box on table" src="https://images.theconversation.com/files/561548/original/file-20231124-19-hpu6dn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/561548/original/file-20231124-19-hpu6dn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/561548/original/file-20231124-19-hpu6dn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/561548/original/file-20231124-19-hpu6dn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/561548/original/file-20231124-19-hpu6dn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/561548/original/file-20231124-19-hpu6dn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/561548/original/file-20231124-19-hpu6dn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">There’s a good chance non-polymers were used to make this pizza box.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/food-delivery-ordering-dinner-online-restaurant-1745084690">Regina Foster/Shutterstock</a></span>
</figcaption>
</figure>
<p>They are used in a <a href="https://pubs.acs.org/doi/10.1021/acs.estlett.1c00240">lot of cosmetic products</a> and toiletries because they make the product smoother, water resistant and easier to apply. </p>
<p>They have an <a href="https://nora.nerc.ac.uk/id/eprint/527128/1/N527128JA.pdf">eight-carbon chain</a> (C8) with acidic heads. The longer chain length provides better stability and less friction which means they are useful as processing aids in polymer manufacture. </p>
<p>Since 2000, industry has moved away from C8 chemistry and shifted towards <a href="https://pubs.acs.org/doi/10.1021/cen-v088n005.p012">shorter chain length</a> chemicals because of concerns over toxicity of the longer-chain compounds and their harm to the environment. </p>
<p>The shorter chain length does help them break down faster and makes them less toxic. However they don’t perform as well as the longer chain chemicals. So manufacturers use more of them in products and more of them get into the environment. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/561583/original/file-20231124-17-g6wjlq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/561583/original/file-20231124-17-g6wjlq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/561583/original/file-20231124-17-g6wjlq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=432&fit=crop&dpr=1 600w, https://images.theconversation.com/files/561583/original/file-20231124-17-g6wjlq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=432&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/561583/original/file-20231124-17-g6wjlq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=432&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/561583/original/file-20231124-17-g6wjlq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=543&fit=crop&dpr=1 754w, https://images.theconversation.com/files/561583/original/file-20231124-17-g6wjlq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=543&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/561583/original/file-20231124-17-g6wjlq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=543&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The long, fluorinated (F) eight-carbon ‘backbone’ provides thermal and chemical stability and is hydrophobic while the acid head is hydrophilic.</span>
<span class="attribution"><span class="source">Crispin Halsall</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Toxic effects</h2>
<p>The widespread of these chemical groups comes at a cost. PFAS <a href="https://www.niehs.nih.gov/health/topics/agents/pfc/index.cfm">enter the environment</a> through the everyday use and disposal of products that contain them. Emissions from fluoropolymer manufacturing sites is another source.</p>
<p><a href="https://www.sciencedirect.com/science/article/abs/pii/S0957582022004839">Domestic and commercial wastewater</a> contains PFAS, which is released into rivers and ocean currents and into remote parts of the planet as evidenced by my team’s <a href="https://pubs.acs.org/doi/10.1021/acs.est.1c01676">recent work</a> investigating high levels of PFAS in Arctic sea ice. </p>
<p>Humans are <a href="https://www.nature.com/articles/s41370-018-0094-1">typically exposed</a> to these chemicals through drinking water, food and household dust. They are a problem for our health because these chemicals have an acid head which tends to interact with and bind to <a href="https://www-webofscience-com.ezproxy.lancs.ac.uk/wos/woscc/full-record/WOS:000296230300005">protein molecules in blood</a>. This has knock-on effects on health. </p>
<p>There is strong evidence to demonstrate that exposure to specific PFAS is linked with <a href="https://setac.onlinelibrary.wiley.com/doi/full/10.1002/etc.4890">liver disease, cancer</a> and damages people’s reproductive systems and children’s development. Another area of concern is <a href="https://www.mdpi.com/1660-4601/19/9/5375">repression of the immune system</a> and lowered response to vaccines. </p>
<p>Many other countries such as the US and Denmark have revised their drinking water standards. It’s time UK drinking water standards caught up.</p><img src="https://counter.theconversation.com/content/217594/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Crispin Halsall is a Professor of Environmental Organic Chemistry and receives funding from the Natural Environment Research Council (NERC) for his work on PFAS</span></em></p>They have properties that make them essential for many products.Crispin Halsall, Professor in Environmental Chemistry, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2139982023-11-27T13:40:53Z2023-11-27T13:40:53ZChlorine is a highly useful chemical that’s also extremely dangerous − here’s what to know about staying safe around it<figure><img src="https://images.theconversation.com/files/560460/original/file-20231120-27-fge83s.jpg?ixlib=rb-1.1.0&rect=10%2C0%2C3484%2C2326&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Jordanian forensics experts inspect the site of a chlorine gas explosion in the Port of Aqaba in June 2022. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/jordanian-forensics-experts-inspect-the-site-of-a-toxic-gas-news-photo/1241583752">Khalil Mazraawi/AFP via Getty Images</a></span></figcaption></figure><p>Many people encounter chlorine in their daily lives, whether it’s as an ingredient in household bleach or an additive that sanitizes water in swimming pools. Chlorine is also used as an antiseptic, a bleaching agent in the production of paper and cloth, and to kill microorganisms in drinking water.</p>
<p>But this familiar chemical is also extremely toxic. And because it’s ubiquitous in many industries across the U.S., it often is released in chemical accidents and spills. </p>
<p>As a <a href="https://scholar.google.com/citations?user=yI9ON-UAAAAJ&hl=en">pharmaceutical scientist</a>, I study ways in which chemicals and other materials affect the human body. Currently, I am working to develop <a href="https://ehsrc.public-health.uiowa.edu/ehsrc-investigators-receive-niehs-award-to-develop-cationic-camkiin-nanoparticles-that-reduce-chlorine-induced-airway-oxidative-stress/">therapies to counteract chlorine gas exposure</a> and to understand the mechanism by which chlorine harms people. One promising therapy that we are developing is inhalable nanoparticles that counteract lung damage following chlorine gas exposure. </p>
<h2>A common and dangerous chemical</h2>
<p><a href="https://www.rsc.org/periodic-table/element/17/chlorine">Chlorine</a> is an extremely toxic and widely used chemical. In the U.S., it is one of the top five chemicals by production volume, with an output of about 12 million tons (11 million metric tons) <a href="https://www.statista.com/statistics/299725/total-us-plastics-and-chemicals-shipments-by-type/">per year</a>. </p>
<p>A yellow-green gas at room temperature, chlorine is highly reactive, which means that it <a href="https://chemistrytalk.org/chlorine-element/">readily forms compounds with many other chemicals</a>. These reactions often are very intense. Chlorine <a href="https://www.cdc.gov/niosh/ershdb/emergencyresponsecard_29750024.html">reacts explosively or forms explosive compounds</a> with many common substances, including hydrogen, turpentine and ammonia.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/560471/original/file-20231120-26-48hv06.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Poster explaining how to use chlorine and other pool chemicals safely." src="https://images.theconversation.com/files/560471/original/file-20231120-26-48hv06.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560471/original/file-20231120-26-48hv06.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=785&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560471/original/file-20231120-26-48hv06.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=785&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560471/original/file-20231120-26-48hv06.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=785&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560471/original/file-20231120-26-48hv06.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=986&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560471/original/file-20231120-26-48hv06.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=986&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560471/original/file-20231120-26-48hv06.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=986&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Even in everyday uses, chlorine requires special handling and precautions.</span>
<span class="attribution"><a class="source" href="https://www.cdc.gov/healthywater/swimming/pdf/Pool-Chemical-Safety-USE-poster-p.pdf">CDC</a></span>
</figcaption>
</figure>
<p>Chlorine gas exposure, even for short periods of time and <a href="http://dx.doi.org/10.1513/pats.201001-008SM">at low levels</a>, leads to eye, throat and nose irritation and causes coughing and breathing problems and burning in the eyes. <a href="http://dx.doi.org/10.1513/pats.201001-008SM">Higher exposure levels</a> can cause chest pain, severe breathing difficulties, pneumonia, vomiting and fluid in the lungs. Very high levels can cause death. Chlorine also can be absorbed through the skin, resulting in pain, swelling, inflammation and blistering. </p>
<p>Our research has shown that exposure to chlorine gas leads to airway inflammation and <a href="http://dx.doi.org/10.1378/chest.123.3_suppl.411s">airway hyperreactivity</a> – swelling and narrowing of the bronchial tubes that carry air to and from your lungs, which makes it harder to breathe. This condition is a characteristic feature of asthma. </p>
<p>Chlorine’s toxicity made it one of the first chemical weapons used on a large scale in warfare. German troops <a href="https://www.denix.osd.mil/rcwmprogram/history/">released it against French and Canadian forces</a> in World War I. More recently, international observers report that <a href="https://apnews.com/article/syria-government-bashar-assad-3b283b4dd01f1765027aa567e53c24be">Syria has used chlorine weapons repeatedly</a> in that country’s civil war. In Iraq, insurgents <a href="https://www.reuters.com/article/us-iraq1/chlorine-bombs-mark-new-guerrilla-tactics-u-s-idUSKRA14854020070222/">used chlorine bombs against U.S. forces</a> in 2007 in and around Baghdad, and the Islamic State reportedly later <a href="https://www.bbc.com/news/world-middle-east-31847427">used chlorine in crude roadside bombs</a> in Iraq.</p>
<h2>Large-scale releases worldwide</h2>
<p>Some recent accidents show how commonly the release or mishandling of chlorine can create life-threatening situations. For example, on April 27, 2023, five workers at a spa in Brooklyn were hospitalized after employees <a href="https://abc7ny.com/midwood-brooklyn-world-spa-hazmat/13190043/">mixed two cleaning chemicals</a>, releasing chlorine gas – a reaction that is <a href="https://doh.wa.gov/community-and-environment/contaminants/bleach-mixing-dangers">surprisingly easy to generate</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/560483/original/file-20231120-27-e5h8a7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A huge grey plume billows from an industrial facility." src="https://images.theconversation.com/files/560483/original/file-20231120-27-e5h8a7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560483/original/file-20231120-27-e5h8a7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560483/original/file-20231120-27-e5h8a7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560483/original/file-20231120-27-e5h8a7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560483/original/file-20231120-27-e5h8a7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560483/original/file-20231120-27-e5h8a7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560483/original/file-20231120-27-e5h8a7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A fire burns at the BioLab Inc. chemical plant in Westlake, La., on Aug. 27, 2020. Winds from Hurricane Laura damaged several buildings, and rainwater reached the chemicals stored there, triggering a fire that released a chlorine plume. The U.S. Chemical Safety and Hazard Investigation Board later concluded that the facility was not adequately prepared for extreme weather.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/TropicalWeatherLouisiana/d351c48226b3451d91311a08a5f5ff31/photo">AP Photo/Gerald Herbert</a></span>
</figcaption>
</figure>
<p>In a larger event, on April 18, 2022, a compressor fire caused a chlorine gas spill inside a <a href="https://www.theadvocate.com/baton_rouge/news/environment/at-least-23-hospitalized-after-chlorine-leak-at-chemical-plant-near-plaquemine-officials-say/article_bef9acf0-c1b8-11ec-98d7-5b060fdac504.html">Dow Chemicals facility</a> close to Plaquemine, Louisiana. Liquid chlorine quickly vaporized into the air and spread into adjoining neighborhoods. At least 23 people were hospitalized. </p>
<p>Large-scale shipments of chlorine can cause widespread injuries and even deaths in the event of accidents. For example, when a freight train derailed in Graniteville, South Carolina, in 2005, a tanker car ruptured and <a href="https://doi.org/10.1177/003335490712200610">released 60 tons of chlorine</a>. Nine people died, 72 were hospitalized and 525 received outpatient medical treatment.</p>
<p>The most dramatic recent case occurred at the <a href="https://www.reuters.com/world/middle-east/four-dead-70-injured-toxic-gas-leak-jordans-aqaba-port-state-tv-2022-06-27/">Port of Aqaba in Jordan</a> on June 27, 2022. A crane dropped a container loaded with 25 tons of chlorine onto a docked ship, where it broke and produced a massive release of toxic gas. The spill killed 13 people and injured more than 260.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Gbng95zULgE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A deadly cloud of chlorine fumes was released after a tank fell onto the deck of a ship while being moved in the Jordanian Port of Aqaba on June 27, 2022.</span></figcaption>
</figure>
<h2>Protecting people from chlorine gas exposure</h2>
<p>Although the risks from chlorine gas exposure have been well understood for over a century, there are no current antidotes. This is because chlorine is a strong oxidizing agent that can <a href="https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx">cause major tissue damage</a> in the body.</p>
<p>People who handle chlorine in the workplace should use respiratory equipment that meets <a href="https://www.cdc.gov/niosh/npg/npgd0115.html">federal regulatory standards</a>. They also should have rubber gloves, a protective apron or other protective clothing, goggles or a face mask, and access to a shower and eye-washing station.</p>
<p>Signs that <a href="https://chemtech-us.com/articles/what-does-chlorine-gas-smell-like-7-telling-signs-of-a-chlorine-gas-leak/">chlorine may be present</a> include a pungent, irritating odor, like very strong cleaning products; a yellowish-green gas; and irritation to the eyes and throat. If you suspect that you may have been exposed to chlorine gas, the <a href="https://www.cdc.gov/chemicalemergencies/factsheets/chlorine.html#anchor_63694">Centers for Disease Control and Prevention recommend</a> moving away from the area and removing all clothing and showering if possible. </p>
<p>Symptoms of chlorine exposure can be treated in a hospital. Therapies include providing patients with humidified oxygen, which is less irritating to the nose and throat than conventional oxygen, and inhaled <a href="https://www.ncbi.nlm.nih.gov/books/NBK548685/">beta-adrenergic agents</a> – medications that are widely used to manage bronchial asthma by relieving lung spasms and reducing airway resistance.</p>
<p>Researchers are studying <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908650/">other medications</a> that may help reduce the severity of lung injury and help patients recover lung function. These include inhalable therapies that reduce lung damage following chlorine gas exposure and oral tablets or injectable therapies that reduce lung inflammation.</p>
<p>Chlorine is a safe and effective disinfectant <a href="https://www.ready.gov/household-chemical-emergencies">when handled appropriately</a>. But as with other household chemicals, it is very important to understand its risks, read labels before using it, store it in its original container in a secure place and dispose of it safely.</p><img src="https://counter.theconversation.com/content/213998/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aliasger K. Salem receives funding from the National Institutes of Health. He serves on the Executive Board of the American Association for Pharmaceutical Scientists.</span></em></p>Chlorine is a widely used industrial chemical that’s frequently a factor in toxic accidents and workplace injuries. A pharmaceutical expert explains why it’s so hazardous.Aliasger K. Salem, Associate Vice President for Research and Bighley Chair and Professor of Pharmaceutical Sciences, University of IowaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2168692023-11-20T15:12:59Z2023-11-20T15:12:59ZThank gluten’s complex chemistry for your light, fluffy baked goods<figure><img src="https://images.theconversation.com/files/560048/original/file-20231116-27-u7q41v.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1996%2C1496&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Gluten is in a variety of breads and baked goods − it helps them rise and gives bread its characteristic texture. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/woman-kneading-dough-royalty-free-image/147205762?phrase=gluten&adppopup=true">Adam Gault/OJO Images via Getty Images</a></span></figcaption></figure><p>Within the bread, rolls and baked goods on many tables this holiday season is an extraordinary substance – gluten. Gluten’s unique chemistry makes foods airy and stretchy.</p>
<p><a href="https://chemistry.richmond.edu/faculty/knolin/">I’m a chemist</a> who teaches a chemistry of cooking class, and every year I ask my students, “What is gluten?” Common answers are “a sugar” or “a carbohydrate.” But rarely does anyone get it right. </p>
<h2>So, what is gluten?</h2>
<p>Gluten is a <a href="https://doi.org/10.3389/fnut.2019.00101">complex mixture of proteins</a>. It makes up <a href="https://doi.org/10.1111/jgh.13703">85%-90% of the protein in flour</a>. Proteins are natural biological macromolecules composed of <a href="https://www.britannica.com/science/amino-acid">chains of amino acids</a> that fold upon themselves to adopt a variety of shapes. </p>
<p>Gluten comes from the endosperm of <a href="https://doi.org/10.1093/aob/mcr098">wheat, rye, barley and related plants</a>. The endosperm is a tissue in the plant’s seeds that serves as a storage location for starch and protein. The milling process that creates flour releases the contents of the endosperm, including gluten.</p>
<p>The main proteins in the gluten mixture are <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/gliadin">gliadin</a> and <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/glutenin">glutenin</a>. These proteins make up much of <a href="https://modernistcuisine.com/mc/gluten-how-does-it-work/">flour-based food products’ structure</a>. During the kneading or mixing part of making dough, these proteins form an elastic mesh, often referred to as the gluten network.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/560047/original/file-20231116-27-zi3eck.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A close up of a slice of bread, showing the white gluten network with darker holes." src="https://images.theconversation.com/files/560047/original/file-20231116-27-zi3eck.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560047/original/file-20231116-27-zi3eck.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560047/original/file-20231116-27-zi3eck.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560047/original/file-20231116-27-zi3eck.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560047/original/file-20231116-27-zi3eck.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560047/original/file-20231116-27-zi3eck.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560047/original/file-20231116-27-zi3eck.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The texture of your bread will depend on how much you knead and work the dough and how the gluten network forms.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/cut-loaf-of-round-shaped-wheat-bread-royalty-free-image/1468126179?phrase=bread">ligora/iStock via Getty Images</a></span>
</figcaption>
</figure>
<h2>Creating a gluten network</h2>
<p>Forming a gluten network is key for getting dough to rise. The network acts as a balloon that traps gases during the rising, proofing and baking processes. During <a href="https://www.theperfectloaf.com/guides/proofing-bread-dough/">rising and proofing</a>, when the dough is given time to expand, yeast in the dough releases carbon dioxide as it eats and digests the sugars present. <a href="https://doi.org/10.3390/microorganisms8081142">This process is called fermentation</a>. </p>
<p>The baking process produces a number of <a href="https://www.campdenbri.co.uk/blogs/bread-dough-rise-causes.php">different gases</a>, such as carbon dioxide, water in the form of steam, ethanol vapors and nitrogen. The gluten network traps these gases and the dough expands like a balloon. If the gluten network is too strong, the gases will not produce enough pressure to make the dough rise. If it’s too weak, the balloon will burst and the dough will not stay risen. How strong the gluten network ends up being depends on how long you knead and mix the dough. </p>
<p>For the <a href="https://www.seriouseats.com/what-is-gluten-free-bread-dough-pasta">gluten network to form</a>, you need to knead or mix the dough with some water – this aligns the proteins.</p>
<p>The glutenin proteins come in long and short chains that adopt coiled structures. These coils are held together through attractive forces between the loops of the coils known as <a href="https://www.britannica.com/science/hydrogen-bonding">intramolecular hydrogen bonds</a>. Kneading and mixing break some of the attractive forces and align the glutenin proteins. </p>
<p>Bonds form between the individual glutenin chains through sulfur atoms on some of the amino acids that make up glutenin. When these amino acids – called cysteines – are brought into contact with each other, the sulfur atoms bond to one another, creating a linkage called a <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/disulfide-bond">disulfide bond</a>.</p>
<p>As more and more cysteines form disulfide bonds with cysteines on neighboring proteins, the network grows. So, the more proteins present and the longer the kneading process, the stronger the gluten network. Bread flour has <a href="https://www.healthline.com/nutrition/high-gluten-flour#what-it-is">higher protein concentrations</a> – 12%-14% – than other flours, so bread flour leads to a stronger gluten network and more rise.</p>
<p>The gliadin proteins are smaller and more compact than glutenin proteins. During the kneading process, gliadin disperses throughout the glutenin polymers. While glutenin provides elasticity and strength to dough, the <a href="https://doi.org/10.1007/s12551-017-0367-2">gliadin proteins</a> make the dough viscous, or fluidlike, and dense.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/qWB14oUtBhQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Gluten is made up of two proteins: glutenin and gliadin.</span></figcaption>
</figure>
<h2>Strengthening and shortening</h2>
<p><a href="https://www.cargill.com/salt-in-perspective/salt-in-bread-dough">Adding salt</a> neutralizes any charges that may be present on the proteins. This minimizes any repulsion between the proteins and brings them closer together. This process forces water out from between the proteins, which both brings the proteins closer together and stabilizes the network. So, adding salt will create a stronger network that increases the amount of stretching and pulling the dough can withstand. </p>
<p>Fats like butter or margarine will <a href="https://www.ifst.org/lovefoodlovescience/resources/fats-and-oils-shortening">weaken, or “shorten,”</a> the gluten network. Typically, recipes ask you to mix the fats with the flour before adding water or milk. This is so the fats coat the flour. And because fats are hydrophobic, or water-repellent, this process prevents the water that helps the gluten network form from reaching the proteins. This results in a softer, more tender baked good. </p>
<p>Without the formation of the gluten network, baked goods would not rise into the light and fluffy delicious dishes we love.</p><img src="https://counter.theconversation.com/content/216869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kristine Nolin does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Ever wonder why bakers spend so long kneading their dough? They’re trying to form a gluten network, which helps the bread rise.Kristine Nolin, Associate Professor of Chemistry, University of RichmondLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2132022023-11-20T13:15:30Z2023-11-20T13:15:30ZHow do crystals form?<figure><img src="https://images.theconversation.com/files/557894/original/file-20231106-25-rk3zxx.jpg?ixlib=rb-1.1.0&rect=33%2C0%2C5595%2C3713&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Two crystalline materials together: kyanite (blue) embedded in quartz (white).</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/bladed-crystals-of-kyanite-in-quartz-from-brazil-news-photo/869774444">Photo 12/Universal Images Group via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>How do crystals form? – Alyssa Marie, age 5, New Mexico</strong></p>
</blockquote>
<hr>
<p>Scientifically speaking, the term “crystal” refers to any solid that has an <a href="https://theconversation.com/why-does-nature-create-patterns-a-physicist-explains-the-molecular-level-processes-behind-crystals-stripes-and-basalt-columns-186433">ordered chemical structure</a>. This means that its parts are arranged in a precisely ordered pattern, like bricks in a wall. The “bricks” can be <a href="https://australian.museum/learn/minerals/what-are-minerals/crystal-shapes/">cubes or more complex shapes</a>.</p>
<p>I’m <a href="https://scholar.google.com/citations?user=EqUjQbwAAAAJ&hl=en">an Earth scientist and a teacher</a>, so I spend a lot of time thinking about minerals. These are solid substances that <a href="https://www.britannica.com/science/mineral-chemical-compound">are found naturally in the ground</a> and can’t be broken down further into different materials other than <a href="https://www.youtube.com/watch?v=wzTRPlG1L0o">their constituent atoms</a>. Rocks are mixtures of different minerals. <a href="https://www.geologyin.com/2016/03/what-is-difference-between-minerals-and.html">All minerals are crystals</a>, but not all crystals are minerals. </p>
<p>Most rock shops sell mineral crystals that occur in nature. One is <a href="https://theconversation.com/not-so-foolish-after-all-fools-gold-contains-a-newly-discovered-type-of-real-gold-161819">pyrite, which is known as fool’s gold</a> because it looks like real gold. Some shops also feature showy, human-made crystals such as <a href="https://www.zmescience.com/feature-post/natural-sciences/geology-and-paleontology/rocks-and-minerals/the-bismuth-crystal-why-it-looks-so-amazingly-trippy-and-why-its-actually-a-big-deal-for-science/">bismuth</a>, a natural element that forms crystals when it is melted and cooled. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A dark gray rock with a large concentration of shiny yellow material covering part of its surface." src="https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=569&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=569&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=569&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pyrite in black shale rock from a quarry in Indianapolis, Ind.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/uJq9jj">James St. John/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Why and how crystals form</h2>
<p>Crystals grow when molecules that are alike get close to each other and stick together, forming chemical bonds that act like Velcro between atoms. Mineral crystals cannot just start forming spontaneously – they need special conditions and a <a href="https://www.thoughtco.com/definition-of-nucleation-605425">nucleation site</a> to grow on. A nucleation site can be a rough edge of rock or a speck of dust that a molecule bumps into and sticks to, starting the crystallization chain reaction.</p>
<p>At or near the Earth’s surface, many molecules are dissolved in water that flows through or over the ground. If there are enough molecules in the water that are alike, they will separate from the water as solids – a process called precipitation. If they have a nucleation site, they will stick to it and start to form crystals. </p>
<p>Rock salt, which is actually <a href="https://www.britannica.com/science/halite">a mineral called halite</a>, grows this way. So does <a href="https://www.britannica.com/science/travertine">another mineral called travertine</a>, which sometimes forms flat ledges in caves and around hot springs, where water causes chemical reactions between the rock and the air. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="White rock terraces around a vent in the earth's surface releasing steam." src="https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Travertine ledges at Mammoth Hot Springs in Yellowstone National Park in Wyoming. Terraced pools form due to deposition of travertine from the hot spring fluids as they cool and release carbon dioxide.</span>
<span class="attribution"><a class="source" href="https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/thumbnails/image/P7190038.JPG">USGS</a></span>
</figcaption>
</figure>
<p>You can make “<a href="http://www.sciencekidsathome.com/science_experiments/growing_stalactites.html">salt stalactites</a>” at home by growing salt crystals on a string. In this experiment, the string is the nucleation site. When you dissolve Epsom salts in water and lower a string into it, then leave it for several days, the water will slowly evaporate and leave the Epsom salts behind. As that happens, salt crystals precipitate out of the water and grow crystals on the string.</p>
<p>Many places in the Earth’s crust are hot enough for <a href="https://www.britannica.com/science/magma-rock">rocks to melt into magma</a>. As that magma cools down, mineral crystals grow from it, just like water freezing into ice cubes. These mineral crystals form at much higher temperatures than salt or travertine precipitating out of water. </p>
<h2>What crystals can tell scientists</h2>
<p>Earth scientists can learn a lot from different types of crystals. For example, the presence of certain mineral crystals in rocks can reveal the rocks’ age. This dating method is called <a href="https://www.britannica.com/science/geochronology">geochronology</a> – literally, measuring the age of materials from the Earth. </p>
<p>One of the most valued mineral crystals for geochronologists is <a href="https://geology.com/minerals/zircon.shtml">zircon</a>, which is so durable that it quite literally stands the test of time. The <a href="https://www.si.edu/newsdesk/releases/earths-oldest-minerals-date-onset-plate-tectonics-36-billion-years-ago">oldest zircons ever found</a> come from Australia and are about 4.3 billion years old – almost as <a href="https://www.amnh.org/exhibitions/darwin/the-world-before-darwin/how-old-is-earth">old as our planet itself</a>. Scientists use the chemical changes recorded within zircons as they grew as a reliable “clock” to <a href="https://knowablemagazine.org/article/physical-world/2021/keeping-time-zircons">figure out how old the rocks containing them are</a>.</p>
<p>Some crystals, including zircons, have growth rings, like the <a href="https://naturalsciences.org/calendar/news/science-at-home-tree-rings/">rings of a tree</a>, that form when layers of molecules accumulate as the mineral grows. These rings can tell scientists all kinds of things about <a href="https://theconversation.com/1-000-year-old-stalagmites-from-a-cave-in-india-show-the-monsoon-isnt-so-reliable-their-rings-reveal-a-history-of-long-deadly-droughts-189222">the environment in which they grew</a>. For example, changes in pressure, temperature and magma composition can all result in growth rings.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="White rectangular feldspar crystals with faintly visible growth rings are prominent against grey granodiorite rock." src="https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=530&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=530&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=530&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=666&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=666&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=666&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Feldspar crystals with growth rings in granodiorite rock near Squamish, British Columbia.</span>
<span class="attribution"><span class="source">Natalie Bursztyn</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Sometimes mineral crystals grow as high pressure and temperatures within the Earth’s crust change rocks from one type to another in a process called <a href="https://www.amnh.org/exhibitions/permanent/planet-earth/how-do-we-read-the-rocks/three-types/metamorphic">metamorphism</a>. This process causes the elements and chemical bonds in the rock to rearrange themselves into new crystal structures. Lots of spectacular crystals grow in this way, including <a href="https://geology.com/minerals/garnet.shtml">garnet</a>, <a href="https://geology.com/minerals/kyanite.shtml">kyanite</a> and <a href="https://geology.com/minerals/staurolite.shtml">staurolite</a>.</p>
<h2>Amazing forms</h2>
<p>When a mineral precipitates from water or crystallizes from magma, the more space it has to grow, the bigger it can become. There is a <a href="https://cen.acs.org/physical-chemistry/geochemistry/Naicas-crystal-cave-captivates-chemists/97/i6">cave in Mexico full of giant gypsum crystals</a>, some of which are 40 feet (12 meters) long – the size of telephone poles.</p>
<p>Especially showy mineral crystals are also valuable as gemstones for jewelry once they are cut into new shapes and polished. The highest price ever paid for a gemstone was $71.2 million for the <a href="https://www.npr.org/sections/thetwo-way/2017/04/05/522739361/pink-star-diamond-sells-for-71-million-smashing-auction-record">CTF Pink Star diamond</a>, which went up for auction in 2017 and sold in less than five minutes.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/213202/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Natalie Bursztyn does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There are a lot of myths about crystals − for example, that they are magical rocks with healing powers. An earth scientist explains some of their amazing true science.Natalie Bursztyn, Lecturer in Geosciences, University of MontanaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2176222023-11-17T13:29:07Z2023-11-17T13:29:07ZThanksgiving sides are delicious and can be nutritious − here’s the biochemistry of how to maximize the benefits<figure><img src="https://images.theconversation.com/files/560008/original/file-20231116-25-qa3919.jpg?ixlib=rb-1.1.0&rect=371%2C19%2C1212%2C1371&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Side dishes made with colorful vegetables are a holiday staple for many. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/thanksgiving-table-with-turkey-and-sides-royalty-free-image/1036967058?phrase=thanksgiving+vegetables&adppopup=true">VeselovaElena/iStock via Getty Images</a></span></figcaption></figure><p>While people usually think first about the turkey or the ham during holiday meals, the sides are what help balance your plate. Colorful vegetables like green beans, collard greens, roasted carrots and mashed sweet potatoes are loaded with important micronutrients. But how you prepare them will help determine whether you get the most nutritional value out of each bite this holiday season.</p>
<p>As <a href="https://blog.richmond.edu/pollocklab/">a biochemist</a>, I know that food is made up of many chemical substances that are crucial for human growth and function. These chemical substances are called nutrients and can be divided into macronutrients, such as carbohydrates, fats and proteins, and micronutrients, such as vitamins and minerals.</p>
<p>Vegetables are <a href="https://www.cdc.gov/nutrition/micronutrient-malnutrition/micronutrients/index.html">full of micronutrients</a> that human bodies need for metabolism – or converting food into energy – as well as to form and maintain cells and tissues. These micronutrients can be classified into three types: minerals, water-soluble vitamins and fat-soluble vitamins.</p>
<h2>Minerals</h2>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559444/original/file-20231114-25-uczoq8.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Alt text" src="https://images.theconversation.com/files/559444/original/file-20231114-25-uczoq8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559444/original/file-20231114-25-uczoq8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=135&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559444/original/file-20231114-25-uczoq8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=135&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559444/original/file-20231114-25-uczoq8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=135&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559444/original/file-20231114-25-uczoq8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=169&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559444/original/file-20231114-25-uczoq8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=169&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559444/original/file-20231114-25-uczoq8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=169&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The dietary minerals found in vegetables.</span>
<span class="attribution"><span class="source">Julie Pollock</span></span>
</figcaption>
</figure>
<p>The greens – collard greens, kale, spinach, green beans – on your table are rich sources of the elements <a href="https://ods.od.nih.gov/factsheets/Magnesium-Consumer/">magnesium</a> and <a href="https://ods.od.nih.gov/factsheets/Calcium-Consumer/">calcium</a>. Your body needs these two major minerals for muscle movement and bone health. </p>
<p>Magnesium is essential for many of the enzymes that play important roles in DNA synthesis and repair, as well as protein production and metabolic function. The cellular processes, especially <a href="https://www.sciencedirect.com/topics/neuroscience/dna-synthesis">accurate DNA synthesis</a>, are important in protecting your body from developing diseases such as cancer. Calcium helps regulate <a href="https://www.news-medical.net/health/pH-in-the-Human-Body.aspx">the pH in your body</a>, influences your metabolism and strengthens your nerve impulses. Nerve impulses are important for your senses and your memory. </p>
<p>Greens are also <a href="https://ods.od.nih.gov/factsheets/Iron-Consumer/">a source of iron</a> – you were right, Popeye! – which is particularly important for the oxygen-binding proteins hemoglobin and myoglobin that transfer and store oxygen in your body, respectively. In addition, human bodies require iron for processes that help generate energy, protect against oxidative damage and make hormones.</p>
<p>Orange vegetables – carrots, pumpkin, sweet potatoes and squash – contain some levels of calcium and iron as well as <a href="https://doi.org/10.3945/an.112.003533">high levels of potassium</a>. Potassium is important for muscle movement, nerve impulses and maintaining low blood pressure. Although not a colorful vegetable, white potatoes also contain very <a href="https://doi.org/10.3945/an.112.003533">high levels of potassium</a>. </p>
<h2>Water-soluble vitamins</h2>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559445/original/file-20231114-15-is56e7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two diagrams showing Vitamin B6, a hexagon with three branches with 'OH' attached, and vitamin C, a hexagon with two Os and four branches with OH coming off." src="https://images.theconversation.com/files/559445/original/file-20231114-15-is56e7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559445/original/file-20231114-15-is56e7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=255&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559445/original/file-20231114-15-is56e7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=255&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559445/original/file-20231114-15-is56e7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=255&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559445/original/file-20231114-15-is56e7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=320&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559445/original/file-20231114-15-is56e7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=320&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559445/original/file-20231114-15-is56e7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=320&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The structures of water-soluble vitamins found in vegetables.</span>
<span class="attribution"><span class="source">Julie Pollock</span></span>
</figcaption>
</figure>
<p>Most green and orange vegetables contain <a href="https://doi.org/10.1146/annurev.nu.14.070194.002103">high levels of vitamin C</a>. Vitamin C is an important water-soluble vitamin because it acts as an antioxidant. <a href="https://theconversation.com/13-ways-to-get-more-antioxidants-and-why-you-need-to-70035">Antioxidants protect your cells</a> against certain types of damage caused by very reactive molecules known as free radicals. </p>
<p>In addition, vitamin C can enhance immune response and is essential for the <a href="https://www.healthline.com/nutrition/collagen">synthesis of collagen</a> – the major protein in your skin. Although taking large levels of vitamin C will not <a href="https://www.ncbi.nlm.nih.gov/books/NBK279544/">keep you from ever getting sick</a>, a healthy amount can help your skin stay soft, help you avoid diseases like scurvy and potentially shorten the length of a cold.</p>
<p>The white potatoes on the table have high levels of <a href="https://doi.org/10.3390/nu13093229">vitamin B6</a>, which is a component of enzymes essential for carbohydrate, fat and protein metabolism. It also helps create healthy blood cells and is important in the production of neurotransmitters such as <a href="https://brain.harvard.edu/hbi_news/exploring-how-serotonin-and-dopamine-interact/">serotonin and dopamine</a>, which both regulate pleasure and happiness.</p>
<h2>Fat-soluble vitamins</h2>
<figure class="align-center ">
<img alt="Two diagrams, the left showing the chemical structure of Vitamin K, the right showing the chemical structure of Vitamin A" src="https://images.theconversation.com/files/559446/original/file-20231114-29-d1rqea.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559446/original/file-20231114-29-d1rqea.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=151&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559446/original/file-20231114-29-d1rqea.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=151&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559446/original/file-20231114-29-d1rqea.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=151&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559446/original/file-20231114-29-d1rqea.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=190&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559446/original/file-20231114-29-d1rqea.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=190&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559446/original/file-20231114-29-d1rqea.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=190&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The structures of fat-soluble vitamins found in vegetables.</span>
<span class="attribution"><span class="source">Julie Pollock</span></span>
</figcaption>
</figure>
<p>One of the most important vitamins you get from the green vegetables, especially leafy ones like kale, spinach, collards and Brussels sprouts, is <a href="https://ods.od.nih.gov/factsheets/VitaminK-Consumer/">vitamin K</a>. Vitamin K is an essential component of enzymes that make proteins in bone and proteins that help clot blood after injuries. </p>
<p><a href="https://ods.od.nih.gov/factsheets/VitaminA-Consumer/">Vitamin A</a> is another important fat-soluble vitamin found in spinach and orange vegetables. The source of vitamin A in vegetables is actually <a href="https://www.healthline.com/health/beta-carotene-benefits">beta carotene</a>, which gets broken into two molecules of active vitamin A after consumption. Vitamin A is essential to vision as well as cell differentiation, reproduction, bone health and immune system function. </p>
<h2>Absorption of micronutrients</h2>
<p>Consuming vegetables that contain micronutrients is very important, but just as important is your body’s ability to absorb the nutrients and transport them to the cells that need them. Macronutrients like carbohydrates, fats and proteins that primarily make up the food we eat are very efficiently absorbed into your bloodstream. </p>
<p>However, only 3%-10% of some micronutrients <a href="https://www.pearson.com/en-us/subject-catalog/p/science-of-nutrition-the/P200000007016/9780135371565">actually get distributed throughout your body</a>. Other ingredients and factors in your food can moderate whether you absorb vitamins and minerals.</p>
<p>Therefore, it is important to prepare vegetables in a way that can enhance the body’s ability to absorb their essential vitamins and minerals.</p>
<p>One good example of this is iron – specifically, the <a href="https://doi.org/10.3390/nu11051049">iron in the food you consume</a>. Heme iron, which is the form necessary for incorporation into your body, comes only from animal products and is the most easily absorbed. </p>
<p>The plant-based iron contained in green and orange vegetables, on the other hand, is not bound to a heme, and your body can’t absorb it as readily. Consuming vitamin C alongside vegetables can <a href="https://doi.org/10.1111/j.1749-6632.1980.tb21325.x">increase the uptake of nonheme iron</a>. So, a squeeze of lemon or orange juice can not only enhance the flavor of your vegetables but the micronutrients you obtain from them.</p>
<p>Fat-soluble vitamins, like vitamin K and vitamin A, are best absorbed when the meal <a href="https://medlineplus.gov/ency/article/002399.htm">contains some dietary fat</a>, which you can get from oil. This is particularly important for vitamin K because green vegetables are its primary dietary source. This is in contrast to the other minerals and vitamins discussed that can also be obtained from animals or legumes that contain some amounts of dietary fat already.</p>
<p>After consumption, vitamin K must be packaged with other fats in <a href="https://doi.org/10.1093/nutrit/nuab061">structures called micelles or lipoproteins</a> that can move around in the bloodstream. That means that it’s a good idea to prepare your greens with some source of fat – olive oil, avocado oil, butter or even a little bacon grease.</p>
<p>So, if you’re staring at the southern style collard greens on your plate and wondering whether they’re as healthy as eating a raw green leaf, think about it in terms of the biochemistry. While raw greens provide you with plenty of fiber and minerals, they won’t help your vitamin K levels as greens cooked in oil will. </p>
<p>Enjoy your time around the holiday table. Load up your plate with everything you like to eat, and make sure to not go completely fat-free in order to help your body process and use all the micronutrients.</p><img src="https://counter.theconversation.com/content/217622/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Julie Pollock receives funding from the National Institutes of Health. </span></em></p>The turkey doesn’t have to be the star this Thanksgiving. Vegetable side dishes are packed with nutrients − depending on how you prepare them, they can help keep you energized this holiday season.Julie Pollock, Associate Professor of Chemistry, University of RichmondLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2146582023-11-15T12:17:52Z2023-11-15T12:17:52ZFlame retardant chemicals can cause serious health risks – and they only slow fire by a few seconds<figure><img src="https://images.theconversation.com/files/558056/original/file-20231107-23-uxqwi1.jpg?ixlib=rb-1.1.0&rect=70%2C30%2C6639%2C4436&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Many flame retardant additives have been banned. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/chemicals-production-factory-experienced-workers-fully-2287552083">Aleksandar Malivuk/Shutterstock</a></span></figcaption></figure><p>House fires are many people’s worst nightmare. But chemicals created decades ago to protect people’s homes from out of control flames opened our front doors to a new menace: toxic chemicals. Ones that we are consistently exposed to in our homes, offices and vehicles.</p>
<p>Plastics are everywhere and are highly flammable materials. To combat this, in around the <a href="https://iris.who.int/handle/10665/41961">mid to late 20th century</a>, a class of chemicals known as flame retardants (FRs) were developed to reduce the fire risks of plastic materials.</p>
<p>These were <a href="https://doi.org/10.1007/978-3-642-19269-2">widely used in plastic items with electrical componants</a> including domestic appliances like cookers and kettles, electronics like TVs and computers, and especially electric heaters. </p>
<p>Their use was later extended to other items such as household furniture, vehicles, building insulation and even some children’s products, such as changing mats and cot mattresses. These FRs work by starving a fire of oxygen for a short time, allowing us time to fight a fire <a href="https://doi.org/10.1007/978-3-642-19269-2">before it gets out of control</a>. </p>
<p>But, like for other chemicals such as pesticides <a href="https://www.hse.gov.uk/asbestos/dangerous.htm">and asbestos</a>, research caught up with the most widely used FRs in the early 2000s and found that the benefits of these chemicals may be outweighed by the dangers. These FRs <a href="https://doi.org/10.1016/j.scitotenv.2021.150747">leach out during everyday activities</a>, particularly from soft and flexible items like beds, couches and blankets. </p>
<p><a href="https://doi.org/10.1016/j.chemosphere.2017.11.068">Simply using these items</a> is enough to make FRs leach into indoor air and dust where we can inhale or ingest them, or <a href="https://doi.org/10.1016/j.envint.2018.05.027">even absorb them through our skin</a>. Research has shown these chemicals have <a href="https://www.sciencedirect.com/science/article/abs/pii/S0301479722021740">hazardous properties</a> when enough is absorbed into our bodies. For example, they have been shown to be carcinogenic and can lead to infertility.</p>
<h2>Legacy flame retardants</h2>
<p>Some of these FRs were <a href="http://data.europa.eu/eli/reg/2019/1021/oj">banned for use in these kinds of products</a>. But there is a danger from both legacy FRs still in circulation as well as so-called “emerging FRs” that replaced the banned chemicals. </p>
<p>New FRs, with slightly different properties to banned ones, are being introduced all the time. This is because, in many cases, regulations in the UK and Ireland require furniture products to meet fire-retardancy standards. The cheapest way is by using additive FRs. </p>
<p>Our <a href="https://www.epa.ie/publications/research/waste/research-434-persistent-organic-chemicals-in-the-irish-waste-stream.php">recent research project</a>, conducted by the University of Birmingham and the University of Galway, highlighted how these chemicals are still widely present in consumer goods. The research found restricted FRs in roughly half of the household furniture items we analysed. They were also prominently found in household electronics and building insulation foams. </p>
<figure class="align-center ">
<img alt="Man staining wood with white spray gun." src="https://images.theconversation.com/files/558059/original/file-20231107-253657-z3ridc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558059/original/file-20231107-253657-z3ridc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558059/original/file-20231107-253657-z3ridc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558059/original/file-20231107-253657-z3ridc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558059/original/file-20231107-253657-z3ridc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558059/original/file-20231107-253657-z3ridc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558059/original/file-20231107-253657-z3ridc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Additive FRs are often the cheapest way of meeting fire safety standards.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/staining-wood-white-spray-gun-application-1316976761">il21/Shutterstock</a></span>
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<p>When these items are recycled, we would hope that these banned harmful chemicals are removed from circulation. However, these chemicals are <a href="https://doi.org/10.1016/j.scitotenv.2018.05.132">very difficult to remove from waste</a>. Approximately 10% of hazardous waste containing restricted FRs goes into the recycling stream. </p>
<p>Research shows that products <a href="https://www.epa.ie/publications/research/waste/research-272.php#">made from recycled materials</a> contain banned FRs at relatively low concentrations. Banned FRs have been found in electronics, furniture and polystyrene packaging foams, but also, <a href="https://www.epa.ie/publications/research/waste/research-434-persistent-organic-chemicals-in-the-irish-waste-stream.php">more worryingly</a>, children’s toys, kitchen utensils and food packaging. </p>
<p>The low concentrations of banned FRs in these products are consistent with leftovers from recycled waste rather than deliberate treatment. </p>
<p>Additionally, almost all the mattresses, furniture and vehicle foams we investigated for our research project contained emerging FRs, which research shows have <a href="https://doi.org/10.1016/j.scitotenv.2022.160250">similar hazards to their banned predecessors</a>. </p>
<p>Unlike the UK and Ireland, most of Europe does not have such stringent furniture fire safety standards. However, <a href="https://ourworldindata.org/grapher/fire-death-rates">we do not see significantly fewer</a> fires or fire-related fatalities in the UK and Ireland. </p>
<p>Irish government <a href="https://www.gov.ie/en/collection/4c5e7-fire-fatality-statistics/">data suggests that other factors</a> such as the indoor smoking ban, requirements for smoke alarms in all rooms, reduced numbers of open fires in homes, and increased fire safety awareness have contributed more to the decrease in fire fatalities in Ireland over the last 20 years than FRs. </p>
<p>The recently published European Chemicals Agency (ECHA) <a href="https://echa.europa.eu/documents/10162/2082415/flame_retardants_strategy_en.pdf/">strategy on FRs</a> outlines the EU’s road map for removing hazardous FRs from circulation. It specifically cites the UK’s and Ireland’s stringent furniture foam fire safety standards as one of the reasons FRs are so prevalent in the EU market. </p>
<p>No one likes the idea of fires in their homes. But the amount of time a fire is slowed by these FRs is in the order of seconds. </p>
<p>In Ireland, <a href="https://www.gov.ie/en/collection/4c5e7-fire-fatality-statistics/">the majority of fatalities</a> from fires happen overnight, meaning people aren’t awake to take advantage of the few extra seconds before fire takes hold. The smoke produced by <a href="https://www.sciencedirect.com/science/article/abs/pii/S0045653518320496?via%3Dihub">burning FR-treated items</a> is also more toxic compared to non-FR- treated materials, leading to increased risk of asphyxiation, the leading cause of death from fires.</p>
<h2>Know the risks</h2>
<p>Few people are aware that these chemical additives are in so many items and fewer still know the hazards they pose. At the moment, it is difficult to know which FRs are used where and at what concentrations. </p>
<p>There should, at the very least, be a more robust labelling system which outlines exactly what chemicals are in these items so that consumers can make informed decisions. Not all products contain FRs but it’s hard for consumers to tell because manufacturers only have to state whether safety standards have been met, now how they have been met. </p>
<p>We need to ask ourselves: are these additive chemicals worth it? New FRs can be developed faster than research can determine their toxicity, making it difficult to tell how safe they really are. </p>
<p>It is vital we have a <a href="https://www.sciencedirect.com/science/article/pii/S0160412023000557">long overdue discussion</a> on fire safety regulations. The negatives of FRs seem to substantially outweigh the benefits. So perhaps the path forward is removing the need for these additives and finally revising fire standards to reflect modern research.</p><img src="https://counter.theconversation.com/content/214658/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Sharkey is a post-doctoral researcher at the University of Galway and received funding from the Environmental Protection Agency of Ireland. The research project referenced below was funded under the EPA Research Programme 2014-2020 (2018-RE-LS-3).</span></em></p>Flame retardants were developed to prevent house fires and help save lives. But they come with some serious health risks.Martin Sharkey, Senior Post-Doctoral Researcher, University of GalwayLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2168432023-11-14T19:06:34Z2023-11-14T19:06:34ZDid this chemical reaction create the building blocks of life on Earth?<figure><img src="https://images.theconversation.com/files/559203/original/file-20231114-21-xy4zlm.jpg?ixlib=rb-1.1.0&rect=53%2C0%2C6000%2C3997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/molecular-model-messenger-ribonucleic-acid-mrna-2202150169">Shutterstock</a></span></figcaption></figure><p>How did life begin? How did chemical reactions on the early Earth create complex, self-replicating structures that developed into living things as we know them?</p>
<p>According to one school of thought, before the current era of DNA-based life, there was a kind of molecule called RNA (or ribonucleic acid). RNA – which is still a crucial component of life today – can replicate itself and catalyse other chemical reactions.</p>
<p>But RNA molecules themselves are made from smaller components called ribonucleotides. How would these building blocks have formed on the early Earth, and then combined into RNA?</p>
<p>Chemists like me are trying to recreate the chain of reactions required to form RNA at the dawn of life, but it’s a challenging task. We know whatever chemical reaction created ribonucleotides must have been able to happen in the messy, complicated environment found on our planet billions of years ago.</p>
<p>I have been studying whether “autocatalytic” reactions may have played a part. These are reactions that produce chemicals that encourage the same reaction to happen again, which means they can sustain themselves in a wide range of circumstances. </p>
<p>In <a href="https://pubs.rsc.org/en/content/articlelanding/2023/SC/D3SC03185C">our latest work</a>, my colleagues and I have integrated autocatalysis into a well-known chemical pathway for producing the ribonucleotide building blocks, which could have plausibly happened with the simple molecules and complex conditions found on the early Earth.</p>
<h2>The formose reaction</h2>
<p>Autocatalytic reactions play crucial roles in biology, from regulating our heartbeats to forming patterns on seashells. In fact, the replication of life itself, where one cell takes in nutrients and energy from the environment to produce two cells, is a particularly complicated example of autocatalysis.</p>
<p>A chemical reaction called the formose reaction, first discovered in 1861, is one of the best examples of an autocatalytic reaction that could have happened on the early Earth.</p>
<figure class="align-right ">
<img alt="An old black and white photograph of a bald, bearded man wearing an old-fashioned coat." src="https://images.theconversation.com/files/559204/original/file-20231114-27-xbwbu9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/559204/original/file-20231114-27-xbwbu9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=951&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559204/original/file-20231114-27-xbwbu9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=951&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559204/original/file-20231114-27-xbwbu9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=951&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559204/original/file-20231114-27-xbwbu9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1196&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559204/original/file-20231114-27-xbwbu9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1196&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559204/original/file-20231114-27-xbwbu9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1196&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The formose reaction was discovered by Russian chemist Alexander Butlerov in 1861.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Alexander_Butlerov#/media/File:Butlerov,_A._M._1828-1886.jpg">Wikimedia</a></span>
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</figure>
<p>In essence, the formose reaction starts with one molecule of a simple compound called glycolaldehyde (made of hydrogen, carbon and oxygen) and ends with two. The mechanism relies on a constant supply of another simple compound called formaldehyde. </p>
<p>A reaction between glycolaldehyde and formaldehyde makes a bigger molecule, splitting off fragments that feed back into the reaction and keep it going. However, once the formaldehyde runs out, the reaction stops, and the products start to degrade from complex sugar molecules into tar.</p>
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Read more:
<a href="https://theconversation.com/can-bleach-help-solve-the-origin-of-life-in-the-primordial-soup-23512">Can bleach help solve the origin of life in the primordial soup?</a>
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<p>The formose reaction shares some common ingredients with a well-known chemical pathway to make ribonucleotides, known as the Powner–Sutherland pathway. However, until now no one has tried to connect the two – with good reason.</p>
<p>The formose reaction is notorious for being “unselective”. This means it produces a lot of useless molecules alongside the actual products you want.</p>
<h2>An autocatalytic twist in the pathway to ribonucleotides</h2>
<p>In our study, we tried adding another simple molecule called cyanamide to the formose reaction. This makes it possible for some of the molecules made during the reaction to be “siphoned off” to produce ribonucleotides.</p>
<p>The reaction still does not produce a large quantity of ribonucleotide building blocks. However, the ones it does produce are more stable and less likely to degrade.</p>
<p>What’s interesting about our study is the integration of the formose reaction and ribonucleotide production. Previous investigations have studied each separately, which reflects how chemists usually think about making molecules.</p>
<figure class="align-center ">
<img alt="A photo showing a drop of blue liquid about to fall from a pipette into one of several empty test tubes." src="https://images.theconversation.com/files/559206/original/file-20231114-26-ceqaiv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559206/original/file-20231114-26-ceqaiv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559206/original/file-20231114-26-ceqaiv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559206/original/file-20231114-26-ceqaiv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559206/original/file-20231114-26-ceqaiv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559206/original/file-20231114-26-ceqaiv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559206/original/file-20231114-26-ceqaiv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Chemistry often focuses on clean, efficient and productive reactions, rather than messy combinations.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/science-laboratory-test-tubes-equipment-1898590327">Shutterstock</a></span>
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<p>Generally speaking, chemists tend to avoid complexity so as to maximise the quantity and purity of a product. However, this reductionist approach can prevent us from investigating dynamic interactions between different chemical pathways.</p>
<p>These interactions, which happen everywhere in the real world outside the lab, are arguably the bridge between chemistry and biology. </p>
<h2>Industrial applications</h2>
<p>Autocatalysis also has industrial applications. When you add cyanamide to the formose reaction, another of the products is a compound called 2-aminooxazole, which is used in chemistry research and the production of many pharmaceuticals.</p>
<p>Conventional 2-aminooxazole production often uses cyanamide and glycolaldehyde, the latter of which is expensive. If it can be made using the formose reaction, only a small amount of glycolaldehyde will be needed to kickstart the reaction, cutting costs.</p>
<p>Our lab is currently optimising this procedure in the hope we can manipulate the autocatalytic reaction to make common chemical reactions cheaper and more efficient, and their pharmaceutical products more accessible. Maybe it won’t be as big a deal as the creation of life itself, but we think it could still be worthwhile.</p>
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<strong>
Read more:
<a href="https://theconversation.com/weve-been-wrong-about-the-origins-of-life-for-90-years-63744">We've been wrong about the origins of life for 90 years</a>
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<img src="https://counter.theconversation.com/content/216843/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Quoc Phuong Tran does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Scientists have known about the ‘formose reaction’ for 160 years. New research shows how it could have played a key role in the creation of life.Quoc Phuong Tran, PhD Candidate in Prebiotic Chemistry, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2170352023-11-08T19:05:23Z2023-11-08T19:05:23ZHow animals get their skin patterns is a matter of physics – new research clarifying how could improve medical diagnostics and synthetic materials<figure><img src="https://images.theconversation.com/files/558150/original/file-20231107-15-ksvdj8.png?ixlib=rb-1.1.0&rect=0%2C0%2C2121%2C1412&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Color patterns seen in fish and other animals evolved to serve various purposes.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-the-eye-of-a-yellowspot-rabbitfish-royalty-free-image/691700228">Lagunatic Photo/iStock via Getty Images Plus</a></span></figcaption></figure><p>Patterns on animal skin, such as zebra stripes and poison frog color patches, serve various biological functions, including <a href="https://doi.org/10.1080/00222933.2019.1607600">temperature regulation</a>, <a href="https://doi.org/10.1098/rsos.160824">camouflage</a> and <a href="https://doi.org/10.1111/j.1558-5646.2011.01257.x">warning signals</a>. The colors making up these patterns must be distinct and well separated to be effective. For instance, as a warning signal, distinct colors make them clearly visible to other animals. And as camouflage, well-separated colors allow animals to better blend into their surroundings.</p>
<p>In our newly published research in Science Advances, my student <a href="https://scholar.google.com/citations?user=ZYQyHkYAAAAJ&hl=en">Ben Alessio</a> <a href="https://scholar.google.com/citations?user=oiMqxxoAAAAJ&hl=en">and I</a> propose a <a href="http://www.science.org/doi/10.1126/sciadv.adj2457">potential mechanism</a> explaining how these distinctive patterns form – that could potentially be applied to medical diagnostics and synthetic materials.</p>
<p>A thought experiment can help visualize the challenge of achieving distinctive color patterns. Imagine gently adding a drop of blue and red dye to a cup of water. The drops will slowly disperse throughout the water due to the <a href="https://bio.libretexts.org/Learning_Objects/Worksheets/Biology_Tutorials/Diffusion_and_Osmosis">process of diffusion</a>, where molecules move from an area of higher concentration to lower concentration. Eventually, the water will have an even concentration of blue and red dyes and become purple. Thus, diffusion tends to create color uniformity.</p>
<p>A question naturally arises: How can distinct color patterns form in the presence of diffusion?</p>
<h2>Movement and boundaries</h2>
<p>Mathematician Alan Turing first addressed this question in his seminal 1952 paper, “<a href="https://doi.org/10.1098/rstb.1952.0012">The Chemical Basis of Morphogenesis</a>.” Turing showed that under appropriate conditions, the chemical reactions involved in producing color can interact with each other in a way that counteracts diffusion. This makes it possible for colors to self-organize and create interconnected regions with different colors, forming what are now called Turing patterns. </p>
<p>However, in mathematical models, the boundaries between color regions are fuzzy due to diffusion. This is unlike in nature, where boundaries are often sharp and colors are well separated.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Close-up of head of moray eel with dark brown patches separated by uneven white boundaries." src="https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Moray eels have distinctive patterns on their skin.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/laced-leopard-moray-in-indian-ocean-during-a-scuba-royalty-free-image/1306632894">Asergieiev/iStock via Getty Images</a></span>
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<p>Our team thought a clue to figuring out how animals create distinctive color patterns could be found in lab experiments on micron-sized particles, such as the <a href="https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Biology_(Kimball)/03%3A_The_Cellular_Basis_of_Life/3.22%3A_Chromatophores">cells involved in producing the colors</a> of an animal’s skin. <a href="https://doi.org/10.1039/D0SM00899K">My work</a> and work from <a href="https://doi.org/10.1073/pnas.1511484112">other labs</a> found that micron-sized particles form <a href="https://doi.org/10.1103/PhysRevLett.117.258001">banded structures</a> when placed between a region with a high concentration of other dissolved solutes and a region with a low concentration of other dissolved solutes.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of a large blue circle moving to the right as it's swept along with the medium-sized red circles surrounding it also moving to the right, where there is a higher concentration of small green circles" src="https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=551&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=551&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=551&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=693&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=693&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=693&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The blue circle in this diagram is moving to the right due to diffusiophoresis, as it is swept along with the motion of the red circles moving into an area where there are more green circles.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Schematic_of_particle_illustrating_diffusiophoresis.png">Richard Sear/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In the context of our thought experiment, changes in the concentration of blue and red dyes in water can propel other particles in the liquid to move in certain directions. As the red dye moves into an area where it is at a lower concentration, nearby particles will be carried along with it. This phenomenon is <a href="https://doi.org/10.1039/C6SM00052E">called diffusiophoresis</a>. </p>
<p>You benefit from diffusiophoresis whenever you <a href="https://doi.org/10.1103/PhysRevApplied.9.034012">do your laundry</a>: Dirt particles move away from your clothing as soap molecules diffuse out from your shirt and into the water.</p>
<h2>Drawing sharp boundaries</h2>
<p>We wondered whether Turing patterns composed of regions of concentration differences could also move micron-sized particles. If so, would the resulting patterns from these particles be sharp and not fuzzy? </p>
<p>To answer this question, we <a href="http://www.science.org/doi/10.1126/sciadv.adj2457">conducted computer simulations</a> of Turing patterns – including hexagons, stripes and double spots – and found that diffusiophoresis makes the resulting patterns significantly more distinctive in all cases. These diffusiophoresis simulations were able to replicate the intricate patterns on the skin of the ornate boxfish and jewel moray eel, which isn’t possible through Turing’s theory alone.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/pU-EB6fa0As?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video shows small particles moving due to a related phenomenon called diffusioosmosis.</span></figcaption>
</figure>
<p>Further supporting our hypothesis, our model was able to reproduce the findings of a <a href="https://doi.org/10.1038/s41567-021-01213-3">lab study</a> on how the bacterium <em>E. coli</em> moves molecular cargo within themselves. Diffusiophoresis resulted in sharper movement patterns, confirming its role as a physical mechanism behind biological pattern formation. </p>
<p>Because the cells that produce the pigments that make up the colors of an animal’s skin are also micron-sized, our findings suggest that diffusiophoresis may play a key role in creating distinctive color patterns more broadly in nature.</p>
<h2>Learning nature’s trick</h2>
<p>Understanding how nature programs specific functions can help researchers design synthetic systems that perform similar tasks. </p>
<p>Lab experiments have shown that scientists can use diffusiophoresis to create <a href="https://doi.org/10.1038/ncomms15181">membraneless water filters</a> and <a href="https://doi.org/10.1002/adma.201701516">low-cost drug development tools</a>.</p>
<p>Our work suggests that combining the conditions that form Turing patterns with diffusiophoresis could also form the basis of artificial skin patches. Just like adaptive skin patterns in animals, when Turing patterns change – say from hexagons to stripes – this indicates underlying differences in chemical concentrations inside or outside the body. </p>
<p>Skin patches that can sense these changes could diagnose medical conditions and monitor a patient’s health by detecting changes in biochemical markers. These skin patches could also sense changes in the concentration of harmful chemicals in the environment.</p>
<h2>The work ahead</h2>
<p>Our simulations exclusively focused on spherical particles, while the cells that create pigments in skin come in varying shapes. The effect of shape on the formation of intricate patterns remains unclear. </p>
<p>Furthermore, pigment cells move in a complicated biological environment. More research is needed to understand how that environment inhibits motion and potentially freezes patterns in place.</p>
<p>Besides animal skin patterns, Turing patterns are also crucial to other processes such as <a href="https://doi.org/10.1042%2FBST20200013">embryonic development</a> and <a href="https://doi.org/10.1016/j.neo.2020.09.008">tumor formation</a>. Our work suggests that diffusiophoresis may play an underappreciated but important role in these natural processes.</p>
<p>Studying how biological patterns form will help researchers move one step closer to mimicking their functions in the lab – <a href="https://doi.org/10.1038/s41427-021-00322-y">an age-old endeavor</a> that could benefit society.</p><img src="https://counter.theconversation.com/content/217035/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ankur Gupta receives funding from NSF (CBET - 2238412) and ACS Petroleum Research Fund (65836 - DNI9). </span></em></p>Understanding how the intricate spots and stripes, or Turing patterns, of many animals form can help scientists mimic those processes in the lab.Ankur Gupta, Assistant Professor of Chemical and Biological Engineering, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.