Zebrafish embryos exposed to atrazine pass on health problems to their young

Jennifer Freeman, (center) an associate professor of toxicology in the School of Health Sciences, has found that atrazine exposure during embryonic development in zebrafish can cause later reproductive problems and physical deformations in their offspring. The research, co-authored by Maria S. Sepulveda, (left) professor of forestry and natural resources; and Sara E. Wirbisky, (right) a health sciences graduate student, is published in Nature’s Scientific Reports.

Credit: Purdue University photo/Charles Jischke

Atrazine exposure during embryonic development could cause later reproductive problems for female zebrafish, as well as physical deformations in their offspring, according to new research from Purdue University.

This approach to show the later-in-life consequences is novel because this is the first study of the offspring of female fish that were exposed to atrazine during their first 72 hours of life. Other studies expose the parents when they are adults and then study the offspring. But by exposing during embryogenesis, we will have a better idea of the total effects. For example, physical deformations in the offspring as well as complications with breeding and increases in progesterone for the parents was found.

Atrazine, an agricultural herbicide, is a suspected endocrine-disrupting chemical. It is used to kill broadleaf and grassy weeds in crops, such as corn, especially in the Midwest, and it often contaminates water supplies. The federally approved amount of atrazine in drinking water is 3 parts per billion, but workers can be exposed to larger levels, such as 30 parts per billion, and larger amounts may be present in surface water.

In this study, the fish were exposed during the 72-hour embryonic development time, which mirrors human prenatal development, to atrazine at levels of 0, 0.3, 3 or 30 parts per billion.

When the fish reached maturity, it was found that 5 percent of the females exposed to 30 parts per billion had swollen abdomens. The physical appearance was similar to what would happen if females became egg-bound because there were no males to mate with, but these fish were paired for breeding. Control for infection and bacteria was also taken. This is the hardest thing for us to explain right now; yes, this phenotype is seen in some of the fish, but why not in all of the females who were exposed to 30 ppb?

These fish with the swollen abdomens also had an increase in atretic ovarian follicles. It has been shown that atrazine affects the LH gene, which produces the hormone that triggers ovulation and plays a key role in follicle development. New findings and previous research suggest that a later-in-life effect of atrazine exposure could be due to the previously observed reduction in LH, providing a mechanism behind the observed reduction in spawning, atretic follicles and cystic ovarian degeneration.

In this study, when the fish reached maturity they were paired for breeding. Compared to the control group, females exposed to 30 parts per billion were not successful at breeding in general, whether their abdomens were swollen or not. For the fish that released eggs, their offspring hatched and survived.

There were no gross malformations, but a closer look showed that there was a decrease in head length to body length ratio at the highest dose of 30 ppb. At the middle doses of 0.3 and 3 ppb, a significant increase in head width to total body length ratio was seen.”

Previous research also found these physical effects in offspring that were exposed directly during their first 72 hours of life.

In this study, there also was an increase in progesterone levels in groups 3 and 30. There was a slight increase in the 0.3 parts per billion group, but it was not significant.

New RNA letter regulates gene expression

Rendering of DNA. DNA, RNA, protein — the end. Or is it?

Credit: © DigitalGenetics / Fotolia

DNA, RNA, protein — the end. Or is it? Until recently, the pattern used to encode genetic information into our cells was considered to be relatively straightforward: four letters (A,G,C,T) for DNA and four (A,G,C,U) for RNA. This equation, however, turned out to be oversimplified — RNA was holding out.

A new study published in Nature by a team of Tel Aviv University, Sheba Medical Center, and University of Chicago scientists finds that RNA, considered the DNA template for protein translation, often appears with an extra letter — and this letter is the regulatory key for control of gene expression. The discovery of a novel letter marking thousands of mRNA transcripts will offer insight into different RNA functions in cellular processes and contributions to the development of disease.

“Epigenetics, the regulation of gene expression beyond the primary information encoded by DNA, was thought until recently to be mediated by modifications of proteins and DNA,” said Prof. Gidi Rechavi, Djerassi Chair in Oncology at TAU’s Sackler Faculty of Medicine and head of the Cancer Research Center at Sheba Medical Center. “The new findings bring RNA to a central position in epigenetics.”

The research, led jointly by Prof. Rechavi and Prof. Chuan He, John T. Wilson Distinguished Service Professor in Chemistry and Investigator of the Howard Hughes Medical Institute at the University of Chicago, and conducted by a team of researchers at TAU, Sheba, and Chicago, represents a breakthrough in understanding how RNAs are regulated.
“This discovery further opens the window on a whole new world of biology for us to explore,” said Prof. He. “These modifications have a major impact on almost every biological process.”

The number of modified nucleotides (letters) in RNA is 10 times larger than that of the letters found in DNA. But what accounts for the evolutionary drive for a large RNA alphabet? RNA molecules have a wide variety of functions, including storage of genetic information as well as catalytic, structural, and regulatory activities. This is in contrast to the important but one-dimensional function of DNA in encoding genetic information.

“The 140 or so different modifications that decorate RNA increase significantly the vocabulary of RNA and enable the various types of RNA, including mRNA, rRNA, tRNA, siRNA, miRNA and, lncRNA, to implement their versatile activities,” said Prof. Rechavi.

Prof. Rechavi’s group, led by Dan Dominissini and Sharon Moshkovitz, began exploring the landscape of chemical modifications of messenger RNA (mRNA) four years ago through a specific modification: the addition of a methyl group in position 6 of Adenosine (m6A) in mRNA. The research team then showed that this modification is specific to unique regions of the mRNA molecules and that the modification can be “read” by specific proteins. They also showed that this modification is dynamic and responds to environmental stimuli.

These findings complemented the identification by Prof. He’s University of Chicago group at the time of an enzyme (FTO) that removes the m6A marks from mRNA. The demonstration of a reversible process that decorates mRNA and affects its stability, translatability, splicing, and localization established a new field of RNA “epigenetics” known as “epitranscriptomics.”

In their new study, the researchers unraveled a new dynamic modification of mRNA — the methylation of position 1 of Adenosine (m1A). Importantly, this modification was shown to be localized in a telltale position near the start of protein translation and linked to increased protein synthesis. Thousands of genes are decorated by this modification, allowing cells to regulate the expression of proteins needed for key biological processes.

“We expect disruption of this new regulatory mechanism to be associated with disease states such as cancer and neurodegenerative disorders,” said Prof. Rechavi.

The research groups are currently studying the cellular processes involved in “writing” and “erasing” m1A, as well as the biochemical pathways regulated by this new RNA modification. In the future, they plan to explore the role of m1A methylation in embryonic development and its involvement in cancer and neurodegenerative disorders.

Motorboat noise gives predators a deadly advantage

The rate that fish are captured by predators can double when boats are motoring nearby.

Credit: Chris Mirbach

The rate that fish are captured by predators can double when boats are motoring nearby, according to pioneering work led by a University of Exeter marine biologist.

Dr Stephen Simpson and his international research team found that noise from passing motorboats increases stress levels in young coral reef fish and reduces their ability to flee from predators. As a consequence they are captured more easily and their survival chances are halved.

This is the first study to show that real-world noise, in this case the common noise of motorboats, can have a direct consequence on fish survival. The team hope the findings will inspire better environmental noise management in coastal areas.

“We found that when real boats were motoring near to young damselfish in open water, they became stressed and were six times less likely to startle to simulated predator attacks compared to fish tested without boats nearby,” said Dr Simpson, a senior lecturer in the University’s Biosciences department, whose work is funded by the Natural Environment Research Council (NERC) and the ARC Centre of Excellence for Coral Reef Studies.

“The combination of stress and poor responses to strikes by predators is why these fish became such easy prey,” said collaborator Dr Andy Radford, University of Bristol.

The team of scientists, which included Australian and Canadian researchers specialising in predator¬-prey interactions and bioacousticians from the University of Bristol, combined laboratory and field experiments, using playbacks and real boat noise, to test the impact of motorboat noise on survival of young Ambon damselfish during encounters with their natural predator the dusky dottyback.

Rather than being despondent, the team is optimistic about the possibilities for management of noise and its potential impact. “If you go to the Great Barrier Reef, there is a lot of noise from motorboats in some places. But unlike many pollutants we can more easily control noise. We can choose when and where we make it, and with new technologies, we can make less noise. For example, we could create marine quiet zones or buffer zones, and avoid known sensitive areas or times of year when juveniles are abundant,” said Dr Simpson.

Managing local environmental stressors such as noise is an essential first step in protecting the marine environment. “You might argue that climate change is a bigger threat to reef life, but if we can reduce the effect of local noise pollution we build greater resilience in reef communities to looming threats such as global warming and ocean acidification,” said collaborator Dr Mark Meekan, Australian Institute of Marine Science.

The optical stimulation of neurons in a region of the fruit fly brain are known to control courtship decision

The optical stimulation of neurons in a region of the fruit fly brain are known to control courtship decision-making.

Credit: Image courtesy of Tohoku University

A genetic study on the courtship behavior of mutant fruit flies may illuminate human sexual orientation.

Two Tohoku University scientists have discovered that homosexual behavior in certain groups of male fruit flies can be altered by their environment. Specifically, they have shown that the sexual preferences of male fruit flies with a mutant version of a gene known to affect male sexual behavior can vary depending on whether the flies are reared in groups or alone.

The neurons that express the fruitless (fru) gene “basically govern the whole aspect of male sexual behavior,” explains neurogenetics professor Daisuke Yamamoto, who conducted the study with postdoctoral fellow Soh Kohatsu.
Yamamoto has been researching the sexual behavior of mutant fruit flies since the late 1980s. Normal male fruit flies tap the abdomen of a female to get a whiff of her sex pheromones before pursuing her to mate. In contrast, males with a mutant version of the fru gene show no interest in females; instead, they set off in vigorous pursuit of other males.

In his most recent study, Yamamoto wanted to analyze the role of vision in the courtship behavior of normal and mutant fruit flies. He optically stimulated neurons in a region of the fruit fly brain known to control courtship decision-making. The fruit flies were shown spots of white light flashing across a screen that represented walking females.

Normal fruit flies courted the spots only after priming with pheromones, but mutant males did not need pheromone priming or direct brain stimulation. The mutant fruit flies immediately followed the moving light spots and vibrated their wings in courtship.

However, this behavior was only displayed in mutant males reared in groups. “We found that this kind of visually induced courtship behavior in the fru mutant males was blocked by isolating them right after their emergence from the pupa,” says Yamamoto. The males reared by themselves did not react to the light spots, he says.

Yamamoto admits he was “terribly surprised” by the results, because he had previously never doubted that male-to-male courtship in fru mutant males was “solely genetically programmed”. It appears that social interaction activates neurons that make mutant males hypersensitive to visual stimuli.

While Yamamoto is cautious about drawing conclusions on human sexual orientation from studies of fruit flies, he believes some aspects of sexual orientation in humans could have a similar mechanistic basis to that of flies. “Our study offers a conceptual basis to explain how nature and nurture interact in shaping human sexual orientation,” he says.

Neanderthals mated with modern humans much earlier than previously thought, study finds

Scenario of interbreeding between modern humans and Neanderthals: Neanderthal DNA in present-day humans outside Africa originates from interbreeding that occurred 47,000 — 65,000 years ago (green arrow). Modern human DNA in Neanderthals is likely a consequence of earlier contact between the two groups roughly 100,000 years ago (red arrow).

Credit: © Ilan Gronau

Using several different methods of DNA analysis, an international research team has found what they consider to be strong evidence of an interbreeding event between Neanderthals and modern humans that occurred tens of thousands of years earlier than any other such event previously documented.

Today in Nature the team publishes evidence of interbreeding that occurred an estimated 100,000 years ago. More specifically the scientists provide the first genetic evidence of a scenario in which early modern humans left the African continent and mixed with archaic (now-extinct) members of the human family prior to the migration “out of Africa” of the ancestors of present-day non-Africans, less than 65,000 years ago.

“It’s been known for several years, following the first sequencing of the Neanderthal genome in 2010, that Neanderthals and humans must have interbred,” says Professor Adam Siepel, a co-team leader and Cold Spring Harbor Laboratory (CSHL) quantitative biologist. “But the data so far refers to an event dating to around 47,000-65,000 years ago, around the time that human populations emigrated from Africa. The event we found appears considerably older than that event.”

In addition to Siepel, who is Chair of CSHL’s Simons Center for Quantitative Biology, the team included several members of the Max Plank Institute for Evolutionary Anthropology, including Martin Kuhlwilm, Svante Pääbo, Matthias Meyer and co-team leader Sergi Castellano. Kuhlwilm was co-first author of the new paper with Ilan Gronau, a former member of Siepel’s Lab who is now at the Herzliya Interdisciplinary Center, Israel. Melissa Hubisz, a Ph.D. student with Siepel at Cornell University, also made major contributions to the work. The full international research team included 15 additional co-authors.

“One very interesting thing about our finding is that it shows a signal of breeding in the ‘opposite’ direction from that already known,” Siepel notes. “That is, we show human DNA in a Neanderthal genome, rather than Neanderthal DNA in human genomes.”

This finding, the result of several kinds of advanced computer modeling algorithms comparing complete genomes of hundreds of contemporary humans with complete and partial genomes of four archaic humans, has implications for our knowledge of human migration patterns.

People living today who are of European, Eurasian and Asian descent have well-identified Neanderthal-derived segments in their genome. These fragments are traces of interbreeding that followed the “out of Africa” human migration dating to about 60,000 years ago. They imply that children born of Neanderthal-modern human pairings outside of Africa were raised among the modern humans and ultimately bred with other humans, explaining how bits of Neanderthal DNA remain in human genomes.

Contemporary Africans, however, do not have detectable traces of Neanderthal DNA in their genomes. This indicates that whatever sexual contact occurred between modern humans and Neanderthals occurred among humans who left the African continent. “Ancestors of present-day African populations likely didn’t have the opportunity to interbreed with Neanderthals, who lived largely outside of Africa,” explains co-author Ilan Gronau.

The team’s evidence of “gene flow” from descendants of modern humans into the Neanderthal genome applies to one specific Neanderthal, whose remains were found some years ago in a cave in southwestern Siberia, in the Altai Mountains, near the Russia-Mongolia border. The modern human ancestor who contributed genes to this particular Neanderthal individual — called the “Altai Neanderthal,” and known from a tiny toe bone fragment — must have migrated out of Africa long before the migration that led Africans into Europe and Asia 60,000 years ago, the scientists say.

In contrast, the two Neanderthals from European caves that were sequenced for this study — one from Croatia, another from Spain — both lack DNA derived from ancestors of modern humans. The team also included in their analysis DNA from another archaic human relative, a Denisovan individual, whose remains were found in the same cave in the Altai Mountains. Denisovans, like Neanderthals, are members of the human line that eventually became extinct. Both of these archaic human cousins lived in the same cave, although at different times in the past.

The Denisovan analyzed in this study did not have traces of modern human DNA, unlike the Neanderthal found in the same cave. That doesn’t mean modern human ancestors never mated with Denisovans or European Neanderthals.

What is does mean, Siepel clarifies, is that “the signal we’re seeing in the Altai Neanderthal probably comes from an interbreeding event that occurred after this Neanderthal lineage diverged from its archaic cousins, a little more than 100,000 years ago.”

The modern human sequences in the Altai Neandertal appear to derive from a group of modern human ancestors from Africa that separated early from other humans, about the time present-day African populations diverged from one another, around 200,000 years ago. Thus, there must have been a long lag between the time when this group branched off the modern human family tree, roughly 200,000 years ago, and the time they left their genetic mark in the Altai Neandertal, about 100,000 years ago, before being lost to extinction themselves.

The team’s analysis included more than 500 genomes of contemporary Africans. “I was looking to see if I could find genomic regions where the Altai Neanderthal has sequences resembling those we see in humans,” says Martin Kuhlwilm. “We know that contemporary non-Africans have traces of Neanderthal in them, so they were not useful in this search. Instead, we used the genomes of contemporary individuals from five populations across Africa to identify mutations which most of them have in common.”

This was the data that provided evidence of “regions in the Altai Neanderthal genome that carry mutations observed in the Africans — but not in the Denisovan” or in Neanderthals found in European caves.

“This is consistent with the scenario of gene flow from a population closely related to modern humans into the Altai Neanderthal. After ruling out contamination of DNA samples and other possible sources of error, we are not able to explain these observations in any other way,” Siepel says.

The research described here was supported by the Special Foundation of the President of the Chinese Academy of Sciences, ICREA, EMBO YIP 2013, The Max Planck Society, the Krekeler Foundation, the MICINN and the U.S. National Institutes of Health.

Memory-loss man case ‘like nothing we have ever seen before’

A clinical psychologist has described treating an individual with a ‘Groundhog Day/Memento’- style memory loss as ‘like nothing we have ever seen before’. The amnesia patient suffered memory loss after root-canal treatment at a dentist and wakes up every morning thinking it is the day of his dentist appointment.

Credit: © alexmat46 / Fotolia

University of Leicester psychologist describes unique case as new to science. A 38-year-old fit and healthy man suffered memory loss after a local anaesthetic and root-canal treatment at his dentist. For the past decade he can only remember up to 90 minutes. And he awakes each day thinking it is the same day he went to the dentist. Symptoms are akin to those depicted in movies such as Groundhog Day and Memento. And, there is no evidence that the treatment at the dentist can be blamed for his condition.

“One of our reasons for writing up this individual’s case was that we had never seen anything like this before in our assessment clinics, and we do not know what to make of it. We had never seen anything like it before.” — Lecturer in Clinical Psychology, Dr Gerald Burgess, University of Leicester
A University of Leicester clinical psychologist has described treating an individual with a ‘Groundhog Day/Memento’- style memory loss as ‘like nothing we have ever seen before’.

Now Dr Gerald Burgess has described the study of an amnesia patient — who suffered memory loss after root-canal treatment at a dentist — in an academic article in the journal Neurocase.

The work by Dr Burgess from the University of Leicester was done in collaboration with Bhanu Chadalavada Consultant Psychiatrist at Northamptonshire Healthcare Foundation NHS Trust, Northampton.

Dr Burgess is now appealing for people who know of someone who might have suffered similar symptoms of memory loss, or medical or allied health professionals working with someone like this, to contact him in order to build up knowledge and evidence in this field of study.

Dr Burgess, of the School of Psychology at the University of Leicester, was working as a clinical psychologist a decade ago when the patient was referred to him.

Dr Burgess said: “One of our reasons for writing up this individual’s case was that we had never seen anything like this before in our assessment clinics, and we do not know what to make of it, but felt an honest reporting of the facts as we assessed them was warranted, that perhaps there will be other cases, or people who know more than we do about what might have caused the patient’s amnesia.

“Our experience was that none of our colleagues in neurology, psychiatry, and clinical neuropsychology could explain this case, or had seen anything like it themselves before.”

The case revolves around a 38-year-old man from the UK who went to the dentist for a routine procedure and lost the ability to create new memories. Since the one-hour root-canal treatment, during which he was given a local anaesthetic, the individual cannot remember anything beyond 90 minutes.

He is fully aware of his identity and his personality did not change — but every day the man thinks it is the day of his dental appointment. He has to manage his life through an electronic diary and access to prompts.
Dr Burgess added: “Amongst our allied health professions, what we did know about from decades of research and hundreds of case studies, is that bilateral damage to the hippocampal and/or diencephalon structures causes profound amnesia, and in the absence of apparent structural damage to these structures, it left an explanation widely open to speculation.

“I think we learned so much, assessing and working with the patient. One thing is that we should perhaps not be so stuck in thinking that profound amnesia only occurs in the context of visible damage to the brain’s hippocampal and/or diencephalon structures — those structures appear just to be needed for the initial holding or retention of information before engrams then proceed slowly through several other neuro-electrical and neuro-chemical events, before finally permanent memories are stored, and that something can occur at some later point in this process to vanquish the memory trace permanently.

“An acquired or manifest deficiency of protein synthesis, required for permanent re-structuring of synapses in the brain, seemed an intriguing speculation, and one we hope there might be further human research into. This speculation was sparked by two seemingly key coincidences of one, timing when this protein synthesis stage occurs coincides with the patient’s forgetting at 90 minutes or thereabouts, and two, both ‘episodic’ and ‘procedural’ memories appear to require successful protein synthesis to occur for long-term memory permanence, and the patient cannot retain any new either episodic or procedural memories — and this is unusual compared to traditional cases of amnesia.

“I don’t think that at this point the dental anaesthetic or root canal can be blamed; it would be unethical and perhaps baseless scaremongering to do so, there is not sufficient evidence. I feel the story lies elsewhere, but that the preceding incident needed to be documented and not ignored.

“There is nothing more than that to go on now. Since publishing the article, web-based stories that have appeared have attracted a few people to write to me with theories or stories around anaesthesia and/or tooth extractions and subsequent memory difficulties. A few other profound anterograde amnesia cases in the literature, cited in the original article, followed on from an acute medical emergency involving the spinal column (e.g. whiplash), so no clear link to anaesthetic effects or tooth extraction that I am aware of. I would be most grateful if others have stories or theories of this or some kind to come forward.”

A metal that behaves like water

In a new paper published in Science, researchers at the Harvard and Raytheon BBN Technology have advanced our understanding of graphene’s basic properties, observing for the first time electrons in a metal behaving like a fluid.

Credit: Peter Allen/Harvard SEAS

Graphene is going to change the world — or so we’ve been told.

Since its discovery a decade ago, scientists and tech gurus have hailed graphene as the wonder material that could replace silicon in electronics, increase the efficiency of batteries, the durability and conductivity of touch screens and pave the way for cheap thermal electric energy, among many other things.
It’s one atom thick, stronger than steel, harder than diamond and one of the most conductive materials on earth.
But, several challenges must be overcome before graphene products are brought to market. Scientists are still trying to understand the basic physics of this unique material. Also, it’s very challenging to make and even harder to make without impurities.

In a new paper published in Science, researchers at the Harvard and Raytheon BBN Technology have advanced our understanding of graphene’s basic properties, observing for the first time electrons in a metal behaving like a fluid.

In order to make this observation, the team improved methods to create ultra-clean graphene and developed a new way measure its thermal conductivity. This research could lead to novel thermoelectric devices as well as provide a model system to explore exotic phenomena like black holes and high-energy plasmas.

This research was led by Philip Kim, professor of physics and applied physics in John A. Paulson School of Engineering and Applied Sciences (SEAS).

An electron super highway
In ordinary, three-dimensional metals, electrons hardly interact with each other. But graphene’s two-dimensional, honeycomb structure acts like an electron superhighway in which all the particles have to travel in the same lane. The electrons in graphene act like massless relativistic objects, some with positive charge and some with negative charge. They move at incredible speed — 1/300 of the speed of light — and have been predicted to collide with each other ten trillion times a second at room temperature. These intense interactions between charge particles have never been observed in an ordinary metal before.

The team created an ultra-clean sample by sandwiching the one-atom thick graphene sheet between tens of layers of an electrically insulating perfect transparent crystal with a similar atomic structure of graphene.

“If you have a material that’s one atom thick, it’s going to be really affected by its environment,” said Jesse Crossno, a graduate student in the Kim Lab and first author of the paper. “If the graphene is on top of something that’s rough and disordered, it’s going to interfere with how the electrons move. It’s really important to create graphene with no interference from its environment.”

The technique was developed by Kim and his collaborators at Columbia University before he moved to Harvard in 2014 and now have been perfected in his lab at SEAS.

Next, the team set up a kind of thermal soup of positively charged and negatively charged particles on the surface of the graphene, and observed how those particles flowed as thermal and electric currents.
What they observed flew in the face of everything they knew about metals.

A black hole on a chip
Most of our world — how water flows (hydrodynamics) or how a curve ball curves — is described by classical physics. Very small things, like electrons, are described by quantum mechanics while very large and very fast things, like galaxies, are described by relativistic physics, pioneered by Albert Einstein.

Combining these laws of physics is notoriously difficult but there are extreme examples where they overlap. High-energy systems like supernovas and black holes can be described by linking classical theories of hydrodynamics with Einstein’s theories of relativity.

But it’s difficult to run an experiment on a black hole. Enter graphene.

When the strongly interacting particles in graphene were driven by an electric field, they behaved not like individual particles but like a fluid that could be described by hydrodynamics.

“Instead of watching how a single particle was affected by an electric or thermal force, we could see the conserved energy as it flowed across many particles, like a wave through water,” said Crossno.

“Physics we discovered by studying black holes and string theory, we’re seeing in graphene,” said Andrew Lucas, co-author and graduate student with Subir Sachdev, the Herchel Smith Professor of Physics at Harvard. “This is the first model system of relativistic hydrodynamics in a metal.”

Moving forward, a small chip of graphene could be used to model the fluid-like behavior of other high-energy systems.

Industrial implications
So we now know that strongly interacting electrons in graphene behave like a liquid — how does that advance the industrial applications of graphene?
First, in order to observe the hydrodynamic system, the team needed to develop a precise way to measure how well electrons in the system carry heat. It’s very difficult to do, said co-PI Dr. Kin Chung Fong, scientist with Raytheon BBN Technology.

Materials conduct heat in two ways: through vibrations in the atomic structure or lattice; and carried by the electrons themselves.

“We needed to find a clever way to ignore the heat transfer from the lattice and focus only on how much heat is carried by the electrons,” Fong said.

To do so, the team turned to noise. At finite temperature, the electrons move about randomly: the higher the temperature, the noisier the electrons. By measuring the temperature of the electrons to three decimal points, the team was able to precisely measure the thermal conductivity of the electrons.

“Converting thermal energy into electric currents and vice versa is notoriously hard with ordinary materials,” said Lucas. “But in principle, with a clean sample of graphene there may be no limit to how good a device you could make.”