'Wobbling black hole' most extreme example ever detected

Researchers at Cardiff University have identified a peculiar twisting motion in the orbits of two colliding black holes, an exotic phenomenon predicted by Einstein's theory of gravity.

Their study, which is published in Nature and led by Professor Mark Hannam, Dr Charlie Hoy and Dr Jonathan Thompson, reports that this is the first time this effect, known as precession, has been seen in black holes, where the twisting is 10 billion times faster than in previous observations.

The binary black hole system was found through gravitational waves in early 2020 in the Advanced LIGO and Virgo detectors. One of the black holes, 40 times bigger than our Sun, is likely the fastest spinning black hole to be found through gravitational waves. And unlike all previous observations, the rapidly revolving black hole distorted space and time so much that the binary's entire orbit wobbled back and forth.

This form of precession is specific to Einstein's theory of general relativity. These results confirm its existence in the most extreme physical event we can observe, the collision of two black holes.

"We've always thought that binary black holes can do this," said Professor Mark Hannam of Cardiff University's Gravity Exploration Institute. "We have been hoping to spot an example ever since the first gravitational wave detections. We had to wait for five years and over 80 separate detections, but finally we have one!"

A more down-to-earth example of precession is the wobbling of a spinning top, which may wobble -- or precess -- once every few seconds. By contrast, precession in general relativity is usually such a weak effect that it is imperceptible. In the fastest example previously measured from orbiting neutron stars called binary pulsars, it took over 75 years for the orbit to precess. The black-hole binary in this study, colloquially known as GW200129 (named after the date it was observed, January 29, 2020), precesses several times every second -- an effect 10 billion times stronger than measured previously.

Dr Jonathan Thompson, also of Cardiff University, explained: "It's a very tricky effect to identify. Gravitational waves are extremely weak and to detect them requires the most sensitive measurement apparatus in history. The precession is an even weaker effect buried inside the already weak signal, so we had to do a careful analysis to uncover it."

Gravitational waves were predicted by Einstein in 1916. They were first directly detected from the merger of two black holes by the Advanced LIGO instruments in 2015, a breakthrough discovery that led to the 2017 Nobel Prize. Gravitational wave astronomy is now one of the most vibrant fields of science, with a network of the Advanced LIGO, Virgo and KAGRA detectors operating in the US, Europe and Japan. To date there have been over 80 detections, all of merging black holes or neutron stars.

"So far most black holes we've found with gravitational waves have been spinning fairly slowly," said Dr Charlie Hoy, a researcher at Cardiff University during this study, and now at the University of Portsmouth. "The larger black hole in this binary, which was about 40 times more massive than the Sun, was spinning almost as fast as physically possible. Our current models of how binaries form suggest this one was extremely rare, maybe a one in a thousand event. Or it could be a sign that our models need to change."

The international network of gravitational-wave detectors is currently being upgraded and will start its next search of the universe in 2023. They are likely to find hundreds more black holes colliding, and will tell scientists whether GW200129 was a rare exception, or a sign that our universe is even stranger than they thought.

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Clusters of genes help mice live longer

Researchers from the National Institute on Aging (NIA)-funded Interventions Testing Program recently reported the discovery of multiple candidate genes that influence longevity. The three Interventions Testing Program sites -- The University of Texas Health Science Center at San Antonio, The University of Michigan at Ann Arbor and The Jackson Laboratory at Bar Harbor, Maine -- collaborated on the study with the labs of Robert W. Williams, PhD, of the University of Tennessee Health Science Center at Memphis and Johan Auwerx, MD, PhD, of the École Polytechnique Fédérale de Lausanne in Lausanne, Switzerland.

"Some candidate genes impacted female life span while others affected the male life span," said Randy Strong, PhD, of the Sam and Ann Barshop Institute for Longevity and Aging Studies at UT Health San Antonio. "One cluster of genes increased longevity of both sexes. In a rarity for these types of studies, the findings were made in a population of mice with genetic diversity comparable to human populations."

The high-impact journal Science published the findings Sept. 30. Strong directs the Interventions Testing Program site at the Barshop Institute, which first attracted National Institute on Aging (NIA) grant funding for the Interventions Testing Program in 2003 and is in its 19th year of the NIA funding.

Genetic smorgasbord

"The study models what happens in people," said research coauthor James Nelson, PhD, of the Barshop Institute. "Unlike mice in many other studies, mice in this newly reported research are not all the same. Each has different genetic variants, resulting in slightly different proteins that do slightly different things, which together can impact aging."

Even subtle differences can lead to different health outcomes as we age. Slight variations in the hemoglobin gene, for example, can cause the hemoglobin protein in red blood cells to be less effective at binding to oxygen and transferring it from the lungs to the body's tissues, Nelson noted. Anemia is one effect.

Female longevity

The discovery of genetic loci that influence longevity only in females is interesting and important, Strong said. Genetic loci are clusters of between 10 and 100 genes.

"Females and males differ in almost every aspect of aging you can explore," Strong said. "They each must be studied, both to understand aging in the two sexes and to develop effective treatments. If we offer the same drug therapies to females that we offer to males, and females' aging is caused by different genes, we are not going to be as effective in our treatments."

Confirmation in roundworms

The next steps are scrutinizing these candidate genes to find ones that are responsible for increased longevity. In the final part of the Science article, the team reported doing this. The researchers tested candidate genes in roundworms, which are often used in aging research because of their short life span. "A number of the candidate genes did affect longevity in the worms," Nelson said.

That doesn't prove that those same genes in humans are going to affect human life span, the researchers said. But it's another part of the case for continuing to study the genetic basis of longevity.

Powerful study design

As envisioned when the Interventions Testing Program began, having three sites where studies are conducted ensures statistical power and rigor and reproducibility of findings, Strong said.

The study is unique in that it is based on a large sample size of animals numbering several thousand, the authors said. "It is among the largest number of mice of any study that has attempted to identify genes that influence life span," Nelson said.

Barshop Institute excellence

The Interventions Testing Program is one of several NIA-funded centers at the Sam and Ann Barshop Institute. Among them, the Nathan Shock Center of Excellence in the Basic Biology of Aging provides core services to enhance research of the fundamental biological questions of aging. The Claude D. Pepper Older Americans Independence Center, named for the late U.S. representative, is a center of excellence aimed at increasing scientific knowledge to develop better ways of maintaining or restoring independence in senior adults. The Barshop Institute is the only institute or university in the nation to have these three centers.

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Heaviest element yet detected in an exoplanet atmosphere

Using the European Southern Observatory's Very Large Telescope (ESO's VLT), astronomers have discovered the heaviest element ever found in an exoplanet atmosphere -- barium. They were surprised to discover barium at high altitudes in the atmospheres of the ultra-hot gas giants WASP-76 b and WASP-121 b -- two exoplanets, planets which orbit stars outside our Solar System. This unexpected discovery raises questions about what these exotic atmospheres may be like.

"The puzzling and counterintuitive part is: why is there such a heavy element in the upper layers of the atmosphere of these planets?" says Tomás Azevedo Silva, a PhD student at the University of Porto and the Instituto de Astrofísica e Ciências do Espaço (IA) in Portugal who led the study published today in Astronomy & Astrophysics.

WASP-76 b and WASP-121 b are no ordinary exoplanets. Both are known as ultra-hot Jupiters as they are comparable in size to Jupiter whilst having extremely high surface temperatures soaring above 1000°C. This is due to their close proximity to their host stars, which also means an orbit around each star takes only one to two days. This gives these planets rather exotic features; in WASP-76 b, for example, astronomers suspect it rains iron.

But even so, the scientists were surprised to find barium, which is 2.5 times heavier than iron, in the upper atmospheres of WASP-76 b and WASP-121 b. "Given the high gravity of the planets, we would expect heavy elements like barium to quickly fall into the lower layers of the atmosphere," explains co-author Olivier Demangeon, a researcher also from the University of Porto and IA.

"This was in a way an 'accidental' discovery," says Azevedo Silva. "We were not expecting or looking for barium in particular and had to cross-check that this was actually coming from the planet since it had never been seen in any exoplanet before."

The fact that barium was detected in the atmospheres of both of these ultra-hot Jupiters suggests that this category of planets might be even stranger than previously thought. Although we do occasionally see barium in our own skies, as the brilliant green colour in fireworks, the question for scientists is what natural process could cause this heavy element to be at such high altitudes in these exoplanets. "At the moment, we are not sure what the mechanisms are," explains Demangeon.

In the study of exoplanet atmospheres ultra-hot Jupiters are extremely useful. As Demangeon explains: "Being gaseous and hot, their atmospheres are very extended and are thus easier to observe and study than those of smaller or cooler planets."

Determining the composition of an exoplanet's atmosphere requires very specialised equipment. The team used the ESPRESSO instrument on ESO's VLT in Chile to analyse starlight that had been filtered through the atmospheres of WASP-76 b and WASP-121 b. This made it possible to clearly detect several elements in them, including barium.

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Study of over 5 million people's DNA reveals genetic links to height

The study, published today (12 October) in Nature, is the largest ever genome-wide association study, using the DNA of over 5 million people from 281 contributing studies. It plugs a sizeable gap in our understanding of how our genetic differences account for differences in height. Over 1 million of the study's participants are of non-European -- African, East Asian, Hispanic or South Asian -- ancestry.

The 12,111 variants, which cluster around parts of the genome associated with skeletal growth, provide a powerful genetic predictor for height. The variants identified explain 40% of the variation in height for people of European ancestry, and around 10-20% for those of non-European ancestry.

Adult height is mostly determined by the information encoded in our DNA -- children from tall parents tend to be taller and those from short parents are shorter, but these estimates aren't perfect. Growth from a small baby into an adult, and the role genetics play in this, have traditionally been a complex and poorly understood area of human biology. Previously, the largest genome-wide association study looking at height used a sample size of up to 700,000 individuals, the current sample is about seven times more than previous studies.

The unprecedented scale of the research provides new levels of detail and biological insight as to why people are tall or short, with heritability being linked to various specific genomic regions. The findings show that genetic variants associated with height are concentrated in regions covering just over 20% of the genome.

The study's findings could help doctors to identify people who are not able to reach their genetically predicted height, which may then aid in the diagnosis of hidden diseases or conditions that may be stunting their growth or impacting their health. The research also provides a valuable blueprint on how it could be possible to use genome-wide studies to identify a disease's biology and subsequently its hereditary components.

Greater genomic diversity needed

While this study has a large number of participants from non-European ancestries compared to previous studies, the researchers emphasise the need for more diversity in genomic research.

Most of the genetic data available is from people of European ancestry, so genome-wide studies don't capture the wide range of ancestral diversity across the globe. Increasing the size of genome-wide studies in non-European ancestry populations is essential to achieve the same level of saturation and close the gap in prediction accuracy in different populations.

Dr Eirini Marouli, co-first author of the study and Senior Lecturer in Computational Biology at Queen Mary University of London, said:

"We have accomplished a feat in studying the DNA of over 5 million people that was broadly considered impossible until recently.

"Genomic studies are revolutionary and might hold the key to solving many global health challenges -- their potential is tremendously exciting. If we can get a clear picture of a trait such as height at a genomic level, we may then have the model to better diagnose and treat gene-influenced conditions like heart disease or schizophrenia, for example.

"If we can map specific parts of the genome to certain traits, it opens the door to widespread targeted, personalised treatments further down the line that could benefit people everywhere."

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Red alert: Massive stars sound warning they are about to go supernova

Astronomers from Liverpool John Moores University and the University of Montpellier have devised an 'early warning' system to sound the alert when a massive star is about to end its life in a supernova explosion. The work was published in Monthly Notices of the Royal Astronomical Society.

In this new study, researchers determined that massive stars (typically between 8 and 20 solar masses) in the last phase of their lives, the so-called 'red supergiant' phase, will suddenly become around a hundred times fainter in visible light in the last few months before they die. This dimming is caused by a sudden accumulation of material around the star, which obscures its light.

Until now, it was not known how long it took the star to accrete this material. Now, for the first time, researchers have simulated how red supergiants might look when they are embedded within these pre-explosion 'cocoons'.

Old telescope archives show that images do exist of stars that went on to explode around a year after the image was taken. The stars appear as normal in these images, meaning they cannot yet have built up the theoretical circumstellar cocoon. This suggests that the cocoon is assembled in less than a year, which is considered to be extremely fast.

Benjamin Davies from Liverpool John Moores University, and lead author of the paper, says "The dense material almost completely obscures the star, making it 100 times fainter in the visible part of the spectrum. This means that, the day before the star explodes, you likely wouldn't be able to see it was there." He adds, "Until now, we've only been able to get detailed observations of supernovae hours after they've already happened. With this early-warning system we can get ready to observe them real-time, to point the world's best telescopes at the precursor stars, and watch them getting literally ripped apart in front of our eyes."

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Dinosaur 'mummies' might not be as unusual as we think

A process of desiccation and deflation explains why dinosaur "mummies" aren't as exceptional as we might expect, according to a study published October 12, 2022 in the open-access journal PLOS ONE by Stephanie Drumheller of the University of Tennessee-Knoxville and colleagues.

The term "mummy" is often used to describe dinosaur fossils with fossilized skin, which are relatively rare. It is commonly suggested that such fossils only form under exceptional circumstances and that a carcass must be shielded from scavenging and decomposition by rapid burial and/or desiccation in order for skin to become fossilized. In this study, Drumheller and colleagues combine fossil evidence with observations on modern animal carcasses to propose a new explanation for how such "mummies" might form.

The researchers examined a fossil of a dinosaur called Edmontosaurus from North Dakota which preserves large patches of desiccated and seemingly deflated skin on the limbs and tail. They identified bite marks from carnivores upon the dinosaur's skin. These are the first examples of unhealed carnivore damage on fossil dinosaur skin, and furthermore, this is evidence that the dinosaur carcass was not protected from scavengers, yet it became a mummy nonetheless.

Modern animal carcasses are known to be often emptied out as scavengers and decomposers target internal tissues, leaving behind skin and bone. The authors propose that damage to this dinosaur's skin from this incomplete scavenging would have exposed its insides and allowed a similar process to occur, after which the skin and bones became slowly desiccated and buried.

This process, which the authors call "desiccation and deflation," is common with modern carcasses and explains how dinosaur mummies might form under relatively ordinary circumstances. The authors stress that there are likely numerous pathways by which a dinosaur mummy might develop. Understanding these mechanisms will guide how paleontologists collect and interpret such rare and informative fossils.

Clint Boyd, Senior Paleontologist at the North Dakota Geological Survey, adds: "Not only has Dakota taught us that durable soft tissues like skin can be preserved on partially scavenged carcasses, but these soft tissues can also provide a unique source of information about the other animals that interacted with a carcass after death."

From Science Daily

Smelling in VR environment possible with new gaming technology

An odor machine, so-called olfactometer, makes it possible to smell in VR environments. First up is a "wine tasting game" where the user smells wine in a virtual wine cellar and gets points if the guess on aromas in each wine is correct. The new technology that can be printed on 3D printers has been developed in collaboration between Stockholm University and Malmö University. The research, funded by the Marianne and Marcus Wallenberg Foundation, was recently published in the International Journal of Human -- Computer Studies.

"We hope that the new technical possibilities will lead to scents having a more important role in game development, says Jonas Olofsson, professor of psychology and leader of the research project at Stockholm University.

In the past, computer games have focused mostly on what we can see -- moving images on screens. Other senses have not been present. But an interdisciplinary research group at Stockholm University and Malmö University has now constructed a scent machine that can be controlled by a gaming computer. In the game, the participant moves in a virtual wine cellar, picking up virtual wine glasses containing different types of wine, guessing the aromas. The small scent machine is attached to the VR system's controller, and when the player lifts the glass, it releases a scent.

"The possibility to move on from a passive to a more active sense of smell in the game world paves the way for the development of completely new smell-based game mechanics based on the players' movements and judgments," says Simon Niedenthal, interaction and game researcher at Malmö University.

The olfactometer consists of four different valves each connected to a channel. In the middle there is a fan sucking the air into a tube. With the help of the computer, the player can control the four channels so that they open to different degrees and provide different mixtures of scent. Scent blends that can mimic the complexity of a real wine glass. The game has different levels of difficulty with increasing levels of complexity.

"In the same way that a normal computer game becomes more difficult the better the player becomes; the scent game can also challenge players who already have a sensitive nose. This means that the scent machine can even be used to train wine tasters or perfumers," says Jonas Olofsson.

All code, blueprints and instructions for the machine are openly available online, as is code for the virtual wine tasting game. The research group, Sensory Cognitive Interaction Laboratory, which is located at the Department of Psychology, Stockholm University, now hopes that scented computer games can become useful for other purposes.

"For those who, for example, lost their sense of smell after COVID-19 or for other reasons, the new technology can mean an opportunity to regain their sense of smell with the help of game-based training," says Jonas Olofsson, research team leader.

Smell training is a method recommended by doctors for those who lose their sense of smell after colds and other viruses, but according to Jonas Olofsson, many people stop training because it becomes too boring.

"I hope that the fact that drawings and code are openly available as "open source" will lead to an opportunity for game companies to start creating new, commercial products for scent training using the new technology," says Jonas Olofsson.

According to Simon Niedenthal, "open source" leads to promoting accessibility, reproducibility and comparison of results in research. It also contributes to creating a cohesive research and design community within the game development field.

"But it also means that the costs of the equipment are greatly reduced, which makes it available to more people. To us that is important," says Simon Niedenthal.

"We believe in open science, that research results should be made available to the public and that other researchers should be able to repeat our results. With the help of our research, others can build scent machines and explore new ways of using scents in games," says Jonas Olofsson.

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A new species of deep-sea fish discovered in the Atacama Trench

A new small blue snailfish is changing our understanding of the world's deepest fishes.

In 2018, an international team of scientists studied the Atacama Trench, an expansive trench that runs along the west coast of South America as a deep underwater valley that mirrors the Andes Mountains. The team, including Newcastle University scientists, deployed free-falling landers to sample the sparse deep-sea creatures around cameras and traps with bait. Two lander systems from Newcastle University recorded three types of hadal snailfish and one of them was not like the others.

The small blue fish, seen from about 6,000 to 7,600 m deep, doesn't look like other hadal snailfish. With large eyes and striking colour, it resembles other species of snailfishes that are found living in much shallower waters. The team used a 3D x-ray technique called microcomputed tomography (micro-CT) and DNA barcoding to see where the new species fit within the snailfish family.

To the team's surprise, the new species appears to be a separate coloniser of the Atacama Trench. The new species belongs is a member of the genus Paraliparis. Species in this genus are particularly abundant in the Southern Ocean of the Antarctic and are rarely found deeper than 2,000 m. Significantly, this is the first time this genus has been found living in the hadal zone.

The team named the new species Paraliparis selti, meaning blue in the Kunza language of the indigenous peoples of the Atacama Desert. The description is published in the journal Marine Biodiversity.

Study lead author, Dr Thom Linley, a visiting researcher at Newcastle University said: "I find this family of fishes absolutely fascinating. They are not at all what we expect from a deep-sea fish and I love to show people that the world's deepest fishes are actually pretty cute.

"For me to get a camera down to where these animals live, it's made of inches thick stainless steel and sapphire glass. It then films these delicate and beautiful animals perfectly adapted to this extreme environment. With engineering-built force we can only clumsily visit these animals for a short time.

"We have been wondering for some time just what makes this type of fish so good at living deep. Maybe it was a series of lucky accidents, a chance fluke, that happened in one lineage. Finding this new species tells us that it's bigger than that. Lightning struck twice and there is something special about this Family.

"Paraliparis selti provides a fantastic opportunity to explore what allows fish to live so deep. If we only had a single lineage to study, we could never be sure which traits were just part of that lineage and which are the deep-sea secret sauce."

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Dust plumes observed being 'pushed' into interstellar space by intense starlight

The results, made using infrared images of the binary star system WR140 taken over 16 years, are reported in the journal Nature.

In a complementary study of WR140, published in Nature Astronomy, NASA's James Webb Space Telescope (JWST) was able to see much deeper to snap an image of not just a single accelerating dust plume, but almost 20 of them, nested inside each other like a giant set of onion skins.

WR140 is comprised of a huge Wolf-Rayet star and an even bigger blue supergiant star, gravitationally bound in an eight-year orbit. This binary star, in the Cygnus constellation, has been monitored for two decades with one of the world's largest optical telescopes at the Keck Observatory in Hawaii.

WR140 episodically puffs out plumes of dust stretching thousands of times the distance from the Earth to the Sun. These dust plumes, produced every eight years, give astronomers a unique opportunity to observe how starlight can affect matter.

It's known that light carries momentum, exerting a push on matter known as radiation pressure. Astronomers often witness the outcome of this phenomenon in the form of matter coasting at high speed around the cosmos, but it's been a difficult process to catch in the act. Direct recording of acceleration due to forces other than gravity is rarely witnessed, and never in a stellar environment like this.

"It's hard to see starlight causing acceleration because the force fades with distance, and other forces quickly take over," said Yinuo Han from Cambridge's Institute of Astronomy, first author of the Nature paper. "To witness acceleration at the level that it becomes measurable, the material needs to be reasonably close to the star or the source of the radiation pressure needs to be extra strong. WR140 is a binary star whose ferocious radiation field supercharges these effects, placing them within reach of our high-precision data."

All stars generate stellar winds, but those from Wolf-Rayet stars can be more like a stellar hurricane. Elements such as carbon in the wind condense out as soot, which remains hot enough to glow bright in the infrared. Like smoke in the wind, this gives telescopes something that can be observed.

The team used an imaging technology known as interferometry which was able to act like a zoom lens for the 10-metre Keck telescope mirror, enabling the researchers to recover sufficiently sharp images of WR140 for the study.

Han and his team found that the dust does not stream out from the star with the wind in a hazy ball. Instead, the dust forms where the winds from the two stars collide, on the surface of a cone-shaped shock front between them.

Because the orbiting binary star is in constant motion, the shock front also rotates. The sooty plume gets wrapped into a spiral, in the same way that droplets form a spiral in a garden sprinkler.

The researchers found that WR140 has other tricks up its sleeve. The two stars are not on circular but rather elliptical orbits, and dust production turns on and off as the binary nears and departs the point of closest approach. By modelling these effects into the three-dimensional geometry of the dust plume, the astronomers were able to measure to location of dust features in three-dimensional space.

"Like clockwork, this star puffs out sculpted smoke rings every eight years, with all this wonderful physics written then inflated in the wind like a banner for us to read," said co-author Professor Peter Tuthill from the University of Sydney. "Eight years later as the binary returns in its orbit, another appears the same as the one before, streaming out into space inside the bubble of the previous one, like a set of giant nested Russian dolls."

Because the dust produced by this Wolf-Rayet is so predictable and expands to such large distances, it offered the astronomers a unique laboratory to examine the acceleration zone.

"In the absence of external forces, each dust spiral should expand at a constant speed," said Han, who is also a co-author on the JWST paper. "We were puzzled at first because we could not get our model to fit the observations, until we finally realised that we were seeing something new. The data did not fit because the expansion speed wasn't constant, but rather that it was accelerating. We'd caught that for the first time on camera."

"In one sense, we always knew this must be the reason for the outflow, but I never dreamed we'd be able to see the physics at work like this," said Tuthill. "When I look at the data now, I see WR140's plume unfurling a like giant sail made of dust. When it catches the photon wind streaming from the star, like a yacht catching a gust, it makes a sudden leap forward."

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Toward a fully edible sensor showing if frozen food has previously thawed

When you're standing in the frozen food aisle, it's nearly impossible to know whether that Salisbury steak has thawed and refrozen -- a process with potentially harmful consequences. So, researchers reporting in ACS Sensors have designed a food-grade device from edible materials, including table salt, red cabbage and beeswax, that lets you know. The proof-of-concept sensor provides a color readout when it's warmed above a specific temperature, which is tunable from -58 F to 32 F.

Keeping food cold while it's transported and stored is essential to retaining its flavor and quality, reducing the risk of food poisoning and minimizing waste. While researchers have developed devices that alert manufacturers when cold items are exposed to unwanted temperatures, they only indicate changes above freezing. To create a sensor for frozen products, one solution could be to use materials with electrical properties that are altered upon melting. It would also be ideal if such changes could produce a signal, such as a visible color change. In addition, an edible electronic device, which uses only food and consumable components, would be the safest way to monitor food. So, Ivan Ilic, Mario Caironi and colleagues set out to develop the first fully edible, self-powered temperature sensor with a visible color indicator for use with frozen products.

The researchers started by building a device that generated an electrical current as it defrosted, connecting magnesium and gold electrodes through an electrolyte solution held in a plastic container. They tested the device with solutions of frozen edible electrolytes, including table salt and calcium-containing salts, and naturally electrolyte-rich foods, including a grape, melon and apple. As the solutions defrosted, they conducted current between -58 F and 32 F, which the researchers say could be fine-tuned, based on the amount and identity of the salt. Next, this device was connected to a color-changing system, containing tin and gold electrodes and red cabbage juice, that produced an irreversible shift from reddish purple to blue when current was applied.

In the final step, the team put all of the parts together in a block of beeswax that held the temperature-activated and indicator solutions in separate chambers, and demonstrated that the self-powered device could be used for frozen food monitoring. The researchers say that their proof-of-concept sensor paves the way for edible materials to be used in inexpensive, safe technologies that alert customers to a frozen product's storage history.

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