Experiments measure freezing point of extraterrestrial oceans to aid search for life

Researchers from the University of Washington and the University of California, Berkeley have conducted experiments that measured the physical limits for the existence of liquid water in icy extraterrestrial worlds. This blend of geoscience and engineering was done to aid in the search for extraterrestrial life and the upcoming robotic exploration of oceans on moons of other planets.

The results were recently published in Cell Reports Physical Sciences.

"The more a liquid is stable, the more promising it is for habitability," said co-corresponding author Baptiste Journaux, an acting assistant professor of Earth and space sciences at the UW. "Our results show that the cold, salty, high-pressure liquids found in the deep ocean of other planets' moons can remain liquid to much cooler temperature than they would at lower pressures. This extends the range of possible habitats on icy moons, and will allow us to pinpoint where we should look for biosignatures, or signs of life."

Jupiter and Saturn's icy moons -- including Europa, Ganymede and Titan -- are leading candidates within our solar system for hosting extraterrestrial life. These ice-encrusted moons are thought to harbor enormous liquid oceans, up to several dozen times the volume of oceans on Earth.

"Despite its designation as the 'blue marble,' Earth is remarkably dry when compared to these worlds," Journaux said.

The oceans on these moons may contain various types of salts and are expected to range from about 100 miles deep, on Europa, to more than 400 miles deep, on Titan.

"We know that water supports life, but the major part of the oceans on these moons are likely below zero degrees Celsius and at pressures higher than anything experienced on Earth," Journaux said. "We needed to know how cold an ocean can get before entirely freezing, including in its deepest abyss."

The study focused on eutectics, or the lowest temperature that a salty solution can remain liquid before entirely freezing. Salt and water are one example -- salty water remains liquid below the freezing temperature of pure water, one of the reasons people sprinkle salt on roads in winter to avoid the formation of ice.

The experiments used UC Berkeley equipment originally designed for the future cryopreservation of organs for medical applications and for food storage. For this research, however, the authors used it to simulate the conditions thought to exist on other planets' moons.

Journaux, a planetary scientist and expert on the physics of water and minerals, worked with UC Berkeley engineers to test solutions of five different salts at pressures up to 3,000 times atmospheric pressure, or 300 megapascals -- about three times the pressure in Earth's deepest ocean trench.

"Knowing the lowest temperature possible for salty water to remain a liquid at high pressures is integral to understanding how extraterrestrial life could exist and thrive in the deep oceans of these icy ocean worlds," said co-corresponding author Matthew Powell-Palm, who did the work as a postdoctoral researcher at UC Berkeley, also co-founder and CEO of the cryopreservation company BioChoric, Inc.

Journaux recently started working with NASA's Dragonfly mission team, which will send a rotorcraft in 2027 to Saturn's largest moon, Titan. NASA also is leading the Europa Clipper mission in 2024 to explore Europa, one of the many moons orbiting Jupiter. Meanwhile, the European Space Agency in 2023 will send its JUICE spacecraft, or Jupiter Icy Moons Explorer, to explore three of Jupiter's largest moons: Ganymede, Callisto and Europa.

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Neuroscientists find multiple brain regions control speech, challenging common assumption

Neurobiologists at the University of Pittsburgh School of Medicine give new meaning to the term "motor mouth" in a study published today in the Proceedings of the National Academy of Sciences. By carefully mapping neural networks in marmoset and macaque monkeys, they determined that multiple areas in the brain's frontal lobe control the muscles of vocalization and could provide a foundation for complex speech.

The findings -- which could lead to a better understanding of speech disorders -- refute a long-existing presumption that only the primary motor cortex, nicknamed M1, directly influences the larynx or voice box, said principal investigator Peter L. Strick, Ph.D., Thomas Detre Professor and chair of neurobiology at Pitt. Instead, several cortical regions send signals to laryngeal muscles to create greater vocal finesse in some nonhuman primates.

"This kind of parallel processing in our neural wiring might explain why humans are capable of highly sophisticated language that allows us to share information, express and perceive emotion, and tell memorable stories," said Strick, who also is scientific director of Pitt's Brain Institute. "Our remarkable speech skills are due to more evolved brains, not better muscles."

Led by Christina M. Cerkevich, Ph.D., research assistant professor of neurobiology, the investigators compared in marmosets and macaques neural networks that are the origin of descending command signals to control monkey vocalizations.

"We selected these two monkey species because of the striking differences in their vocal behavior," Cerkevich explained. "Marmosets readily vocalize in ways that are akin to humans by taking turns to speak and altering the volume, timing and pitch of their calls to each other. Macaques, on the other hand, make mostly simple, spontaneous calls."

The researchers injected a transneuronal tracer made from rabies virus into the cricothyroid muscle of the monkeys' larynxes. The tracer infects nerve cells and has the unique property of moving from one neuron to another only at synapses, which are the special sites where neurons interact with each other. This makes it possible to track neuronal circuits from the muscle back to the areas of the cerebral cortex that control it.

In addition to M1, both kinds of monkeys had multiple premotor areas in the frontal lobe that send descending command signals to the cricothyroid muscle. But two of the premotor areas provided a substantially larger source of descending output in marmosets, leading the researchers to propose that the enhanced vocal motor skills of marmosets are due, in part, to the expansion of neural signaling from these premotor areas.

"This result challenges the long-held view that improvements in motor skills of vocalization are due largely to changes in the output from M1, the primary motor cortex," Strick said. "It appears there is no single control center, but rather parallel processing sites that enable complex vocalization and, ultimately, speech."

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Hubble reveals surviving companion star in aftermath of supernova

It's not unheard of to find a surviving star at the scene of a titanic supernova explosion, which would be expected to obliterate everything around it, but the latest research from the Hubble Space Telescope has provided a long-awaited clue to a specific type of stellar death. In some supernova cases, astronomers find no trace of the former star's outermost layer of hydrogen. What happened to the hydrogen? Suspicions that companion stars are responsible -- siphoning away their partners' outer shell before their death -- are supported by Hubble's identification of a surviving companion star on the scene of supernova 2013ge.

The discovery also lends support to the theory that the majority of massive stars form and evolve as binary systems. It could also be the prequel to another cosmic drama: In time, the surviving, massive companion star will also undergo a supernova, and if both the stars' remnant cores are not flung from the system, they will eventually merge and produce gravitational waves, shaking the fabric of space itself.

NASA's Hubble Space Telescope has uncovered a witness at the scene of a star's explosive death: a companion star previously hidden in the glare of its partner's supernova. The discovery is a first for a particular type of supernova -- one in which the star was stripped of its entire outer gas envelope before exploding.

The finding provides crucial insight into the binary nature of massive stars, as well as the potential prequel to the ultimate merger of the companion stars that would rattle across the universe as gravitational waves, ripples in the fabric of spacetime itself.

Astronomers detect the signature of various elements in supernova explosions. These elements are layered like an onion pre-supernova. Hydrogen is found in the outermost layer of a star, and if no hydrogen is detected in the aftermath of the supernova, that means it was stripped away before the explosion occurred.

The cause of the hydrogen loss had been a mystery, and astronomers have been using Hubble to search for clues and test theories to explain these stripped supernovae. The new Hubble observations provide the best evidence yet to support the theory that an unseen companion star siphons off the gas envelope from its partner star before it explodes.

"This was the moment we had been waiting for, finally seeing the evidence for a binary system progenitor of a fully stripped supernova," said astronomer Ori Fox of the Space Telescope Science Institute in Baltimore, Maryland, lead investigator on the Hubble research program. "The goal is to move this area of study from theory to working with data and seeing what these systems really look like."

Fox's team used Hubble's Wide Field Camera 3 to study the region of supernova (SN) 2013ge in ultraviolet light, as well as previous Hubble observations in the Barbara A. Mikulski Archive for Space Telescopes. Astronomers saw the light of the supernova fading over time from 2016 to 2020 -- but another nearby source of ultraviolet light at the same position maintained its brightness. This underlying source of ultraviolet emission is what the team proposes is the surviving binary companion to SN 2013ge.

Two by two?

Previously, scientists theorized that a massive progenitor star's strong winds could blow away its hydrogen gas envelope, but observational evidence didn't support that. To explain the disconnect, astronomers developed theories and models in which a binary companion siphons off the hydrogen.

"In recent years many different lines of evidence have told us that stripped supernovae are likely formed in binaries, but we had yet to actually see the companion. So much of studying cosmic explosions is like forensic science -- searching for clues and seeing what theories match. Thanks to Hubble, we are able to see this directly," said Maria Drout of the University of Toronto, a member of the Hubble research team.

In prior observations of SN 2013ge, Hubble saw two peaks in the ultraviolet light, rather than just the one typically seen in most supernovae. Fox said that one explanation for this double brightening was that the second peak shows when the supernova's shock wave hit a companion star, a possibility that now seems much more likely. Hubble's latest observations indicate that while the companion star was significantly jostled, including the hydrogen gas it had siphoned off its partner, it was not destroyed. Fox likens the effect to a jiggling bowl of jelly, which will eventually settle back to its original form.

While additional confirmation and similar supporting discoveries need to be found, Fox said that the implications of the discovery are still substantial, lending support to theories that the majority of massive stars form and evolve as binary systems.

One to Watch

Unlike supernovae that have a puffy shell of gas to light up, the progenitors of fully stripped-envelope supernovae have proven difficult to identify in pre-explosion images. Now that astronomers have been lucky enough to identify the surviving companion star, they can use it to work backward and determine characteristics of the star that exploded, as well as the unprecedented opportunity to watch the aftermath unfold with the survivor.

As a massive star itself, SN 2013ge's companion is also destined to undergo a supernova. Its former partner is now likely a compact object, such as a neutron star or black hole, and the companion will likely go that route as well.

The closeness of the original companion stars will determine if they stay together. If the distance is too great, the companion star will be flung out of the system to wander alone across our galaxy, a fate that could explain many seemingly solitary supernovae.

However, if the stars were close enough to each other pre-supernova, they will continue orbiting each other as black holes or neutron stars. In that case, they would eventually spiral toward each other and merge, creating gravitational waves in the process.

That is an exciting prospect for astronomers, as gravitational waves are a branch of astrophysics that has only begun to be explored. They are waves or ripples in the fabric of spacetime itself, predicted by Albert Einstein in the early 20th century. Gravitational waves were first directly observed by the Laser Interferometer Gravitational-Wave Observatory.

"With the surviving companion of SN 2013ge, we could potentially be seeing the prequel to a gravitational wave event, although such an event would still be about a billion years in the future," Fox said.

Fox and his collaborators will be working with Hubble to build up a larger sample of surviving companion stars to other supernovae, in effect giving SN 2013ge some company again.

"There is great potential beyond just understanding the supernova itself. Since we now know most massive stars in the universe form in binary pairs, observations of surviving companion stars are necessary to help understand the details behind binary formation, material-swapping, and co-evolutionary development. It's an exciting time to be studying the stars," Fox said.

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Promising treatment for dementia

A Monash University led study has found a promising new treatment for patients with behavioural variant frontotemporal dementia, the second most common form of dementia in the under 60s -- resulting in a stabilising of what would normally be escalating behavioural issues, and a slowing of brain shrinkage due to the disease. It is the second clinical trial to show that the drug, sodium selenate, may slow cognitive decline and neurodegenerative damage that is the hallmark of many dementias including Alzheimer's Disease.

Behavioural variant frontotemporal dementia (bvFTD) is a rapidly progressing destructive disease and can occur in people as young as 35 years of age. It is characterised by behavioural disturbances and personality changes and can be highly disruptive and distressing for both patients and their families. Currently there are no treatments or cures for bvFTD and typical survival is 5-7 years from diagnosis.

The Phase 1 trial run in conjunction with the Royal Melbourne Hospital, the only one in Australia targeting non-genetic bvFTD, and one of a handful worldwide, showed that the drug, sodium selenate is safe and well-tolerated in patients with bvFTD over a period of 12 months. Importantly, the majority of patients receiving sodium selenate showed no change in their cognitive or behavioural symptoms, and reduced rates of brain atrophy over the trial period. The results from the trial, led by Dr Lucy Vivash, from the Monash University's Department of Neuroscience, have just been published in the journal, Alzheimer's and Dementia: Translational Research and Clinical Interventions.

In almost half of the cases with bvFTD, the damage to the neurons in the brain is caused by the build-up of a protein called tau. This protein is a major target for research in the prevention and treatment of Alzheimer's and other dementias, as a way to reverse the neurodegeneration caused by this tau accumulation.

According to Dr Vivash, sodium selenate upregulates an enzyme in the brain that effectively breaks down the tau protein. "We have previously shown, in a Phase 2 trial, that sodium selenate given to patients with mild to moderate Alzheimer's Disease resulted in less neurodegeneration than in those who did not," she said. Importantly those patients in the trial with higher levels of selenium, a breakdown product of sodium selenate, in their bloodstream showed less cognitive decline.

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Only 10 vaquita porpoises survive, but species may not be doomed, scientists say

The vaquita porpoise, the world's smallest marine mammal, is on the brink of extinction, with 10 or fewer still living in Mexico's Gulf of California, their sole habitat. But a genetic analysis by a team of UCLA biologists and colleagues has found that the critically endangered species remains relatively healthy and can potentially survive -- if illegal "gillnet" fishing ceases promptly.

"Interestingly, we found the vaquita is not doomed by genetic factors, like harmful mutations, that tend to affect many other species whose gene pool has diminished to a similar point," said Christopher Kyriazis, a UCLA doctoral student in ecology and evolutionary biology and a co-lead author of the research. "Outlawed fishing remains their biggest threat."

The small porpoises, which range from 4 to 5 feet in length, often become entangled and die in the large mesh gillnets used by poachers hunting the totoaba, an endangered fish highly valued in some countries for its perceived medicinal properties. While Mexico has outlawed totoaba fishing and made the use of these nets in the vaquitas' habitat illegal, many say the bans are not always enforced.

The researchers analyzed the genomes of 20 vaquitas that lived between 1985 and 2017 and conducted computational simulations to predict the species' extinction risk over the next 50 years. They concluded that if gillnet fishing ends immediately, the vaquita has a very high chance of recovery, even with inbreeding. If, however, the practice continues, even moderately, the prospects of recovery are less optimistic.

The research is published May 6 in the journal Science.

"Relative to other species, the vaquita has a higher chance of rebounding from an extreme population crash without suffering severe genetic consequences from inbreeding," said co-lead author Jacqueline Robinson, a postdoctoral scholar at UC San Francisco who earned her doctorate in biology at UCLA. "Genetic diversity in vaquitas is not so low that it constitutes a threat to their health and persistence. It simply reflects their natural rarity."

Genetic diversity is a measure of the differences that exist across the genome among individuals in a population. Large populations tend to have many differences, while naturally smaller or decimated ones have fewer, resulting in individuals that are more genetically similar. That similarity can often result in a greater incidence of harmful mutations that endanger the population since individuals are more likely to inherit the same muted gene from both parents, said senior author Kirk Lohmueller, UCLA associate professor of ecology and evolutionary biology and of human genetics.

"A prevailing view in conservation biology and population genetics is that small populations can accumulate deleterious mutations," Lohmueller said. "However, our finding that the vaquita likely has fewer strongly deleterious mutations hiding in the population means that they are better poised to survive future inbreeding, which bodes well for their overall recovery."

So what protects the vaquitas from the genetic perils of inbreeding? Much of it has to do with the fact that they have always been a small population in a very small habitat in the northern tip of the gulf, the researchers said. While their historic numbers are unknown, the first comprehensive survey in 1997 counted roughly 570 porpoises -- a number that has declined steadily over the last 25 years but which was not large to begin with.

"They're essentially the marine equivalent of an island species," said Robinson, who noted that the species has survived for tens of thousands of years with low genetic diversity. "The vaquitas' naturally low abundance has allowed them to gradually purge highly deleterious recessive gene variants that might negatively affect their health under inbreeding."

In fact, Robinson said, of the 12 marine mammal species -- including vaquitas -- the researchers genetically analyzed, vaquitas had the lowest number of potentially harmful mutations.

While the interplay among small population size, inbreeding and harmful genetic variations is complex, the approach used by the team in this study can help shed light on these dynamics.

"With genomic datasets, we now have the ability to address this complexity," Robinson said. "Species can vary in their levels of harmful genetic variation, and they will not all be affected exactly the same way by reduced population size or inbreeding. There are now many examples of species recovering from extreme declines."

"We hope our analysis is useful not only in demonstrating the potential for the vaquita to recover," Kyriazis said, "but also in highlighting a novel genomics-based simulation approach for endangered species."

Encouragingly, the surviving vaquitas in the northern Gulf of California are actively reproducing and appear healthy. But poachers' gillnets continue to pose an existential threat to the species, and unless further measures are taken to protect the porpoises, there is a distinct possibility they may go extinct. The loss would be a great tragedy, said the study's senior author, UCLA's Robert Wayne.

"The vaquita is symbolic of the unique diversity found in the Gulf of California, which was described by John Steinbeck in his wonderful 1951 book 'The Log From the Sea of Cortez,'" said Wayne, a distinguished professor of ecology and evolutionary biology and a Howard Hughes Medical institute professor. "It represents a unique evolutionary lineage -- there is no similar species anywhere in the world -- and its loss would rob the ecosystem of an important predator adapted to this unique ecosystem."

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New tool to create hearing cells lost in aging

Hearing loss due to aging, noise and certain cancer therapy drugs and antibiotics has been irreversible because scientists have not been able to reprogram existing cells to develop into the outer and inner ear sensory cells -- essential for hearing -- once they die.

But Northwestern Medicine scientists have discovered a single master gene that programs ear hair cells into either outer or inner ones, overcoming a major hurdle that had prevented the development of these cells to restore hearing.

The study will be published in Nature May 4.

"Our finding gives us the us the first clear cell switch to make one type versus the other," said lead study author Jaime Garcia-Anoveros, professor of anesthesia, neurology and neuroscience at Northwestern University Feinberg School of Medicine. "It will provide a previously unavailable tool to make an inner or outer hair cell. We have overcome a major hurdle."

About 8.5 percent of adults aged 55 to 64 in the U.S. have disabling hearing loss. That increases to nearly 25 percent of those aged 65 to 74 and 50 percent of those who are 75 and older, reports the Centers for Disease Control.

Currently, scientists can produce an artificial hair cell, but it does not differentiate into an inner or outer cell, which provide different essential functions to produce hearing. The discovery is a major step towards developing these specific cells.

"It's like a ballet" as cells crouch and leap

The death of outer hair cells made by the cochlea are most often the cause of deafness and hearing loss. The cells develop in the embryo and do not reproduce. The outer hair cells expand and contract in response to the pressure of sound waves and amplify sound for the inner hair cells. The inner cells transmit those vibrations to the neurons to create the sounds we hear.

"It's like a ballet," Garcia-Anoveros says with awe as he describes the coordinated movement of the inner and outer cells. "The outers crouch and jump and lift the inners further into the ear.

"The ear is a beautiful organ. There is no other organ in a mammal where the cells are so precisely positioned. (I mean, with micrometric precision). Otherwise, hearing doesn't occur."

The master gene switch Northwestern scientists discovered that programs the ear hair cells is TBX2. When the gene is expressed, the cell becomes an inner hair cell. When the gene is blocked, the cell becomes an outer hair cell. The ability to produce one of these cells will require a gene cocktail, Garcia-Anoveros said. The ATOH1 and GF1 genes are needed to make a cochlear hair cell from a non-hair cell. Then the TBX2 would be turned on or off to produce the needed inner or outer cell.

The goal would be to reprogram supporting cells, which are latticed among the hair cells and provide them with structural support, into outer or inner hair cells.

"We can now figure out how to make specifically inner or outer hair cells and identify why the later are more prone to dying and cause deafness," Garcia-Anoveros said. He stressed this research is still in the experimental stage.

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Lunar soil has the potential to generate oxygen and fuel

Soil on the moon contains active compounds that can convert carbon dioxide into oxygen and fuels, scientists in China report May 5 in the journal Joule. They are now exploring whether lunar resources can be used to facilitate human exploration on the moon or beyond.

Nanjing University material scientists Yingfang Yao and Zhigang Zou hope to design a system that takes advantage of lunar soil and solar radiation, the two most abundant resources on the moon. After analyzing the lunar soil brought back by China's Chang'e 5 spacecraft, their team found the sample contains compounds -- including iron-rich and titanium-rich substances -- that could work as a catalyst to make desired products such as oxygen using sunlight and carbon dioxide.

Based on the observation, the team proposed an "extraterrestrial photosynthesis" strategy. Mainly, the system uses lunar soil to electrolyze water extracted from the moon and in astronauts' breathing exhaust into oxygen and hydrogen powered by sunlight. The carbon dioxide exhaled by moon inhabitants is also collected and combined with hydrogen from water electrolysis during a hydrogenation process catalyzed by lunar soil.

The process yields hydrocarbons such as methane, which could be used as fuel. The strategy uses no external energy but sunlight to produce a variety of desirable products such as water, oxygen, and fuel that could support life on a moonbase, the researchers say. The team is looking for an opportunity to test the system in space, likely with China's future crewed lunar missions.

"We use in-situ environmental resources to minimize rocket payload, and our strategy provides a scenario for a sustainable and affordable extraterrestrial living environment," Yao says.

While the catalytic efficiency of lunar soil is less than catalysts available on Earth, Yao says the team is testing different approaches to improve the design, such as melting the lunar soil into a nanostructured high-entropy material, which is a better catalyst.

Previously, scientists have proposed many strategies for extraterrestrial survival. But most designs require energy sources from Earth. For example, NASA's Perseverance Mars rover brought an instrument that can use carbon dioxide in the planet's atmosphere to make oxygen, but it's powered by a nuclear battery onboard.

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Global bird populations steadily declining

Staggering declines in bird populations are taking place around the world. So concludes a study from scientists at multiple institutions, published today in the journal Annual Review of Environment and Resources. Loss and degradation of natural habitats and direct overexploitation of many species are cited as the key threats to avian biodiversity. Climate change is identified as an emerging driver of bird population declines.

"We are now witnessing the first signs of a new wave of extinctions of continentally distributed bird species," says lead author Alexander Lees, senior lecturer at Manchester Metropolitan University in the United Kingdom and also a research associate at the Cornell Lab of Ornithology. "Avian diversity peaks globally in the tropics and it is there that we also find the highest number of threatened species."

The study says approximately 48% of existing bird species worldwide are known or suspected to be undergoing population declines. Populations are stable for 39% of species. Only 6% are showing increasing population trends, and the status of 7% is still unknown. The study authors reviewed changes in avian biodiversity using data from the International Union for Conservation of Nature's "Red List" to reveal population changes among the world's 11,000 bird species.

The findings mirror the results of a seminal 2019 study which determined that nearly 3 billion breeding birds have been lost during the past 50 years across the United States and Canada. The lead author of that study is also an author on this global status report.

"After documenting the loss of nearly 3 billion birds in North America alone, it was dismaying to see the same patterns of population declines and extinction occurring globally," says conservation scientist Ken Rosenberg from the Cornell Lab, now retired. "Because birds are highly visible and sensitive indicators of environmental health, we know their loss signals a much wider loss of biodiversity and threats to human health and well-being."

Despite their findings, study authors say there is hope for avian conservation efforts, but transformative change is needed.

"The fate of bird populations is strongly dependent on stopping the loss and degradation of habitats," says Lees. "That is often driven by demand for resources. We need to better consider how commodity flows can contribute to biodiversity loss and try to reduce the human footprint on the natural world."

"Fortunately, the global network of bird conservation organizations taking part in this study have the tools to prevent further loss of bird species and abundance," adds Rosenberg. "From land protection to policies supporting sustainable resource-use, it all depends on the will of governments and of society to live side by side with nature on our shared planet."

Information is key, and study authors point out that the growth of public participation in bird monitoring and the advent of easy-to-use tools, such as the Cornell Lab's eBird database, make continental-scale breeding bird surveys, distribution atlases, and abundance models possible and help inform conservation efforts.

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Quantum mechanics could explain why DNA can spontaneously mutate

The molecules of life, DNA, replicate with astounding precision, yet this process is not immune to mistakes and can lead to mutations. Using sophisticated computer modelling, a team of physicists and chemists at the University of Surrey have shown that such errors in copying can arise due to the strange rules of the quantum world.

The two strands of the famous DNA double helix are linked together by subatomic particles called protons -?the nuclei of atoms of hydrogen -- which provide the glue that bonds molecules called bases together. These so-called hydrogen bonds are like the rungs of a twisted ladder that makes up the double helix structure discovered in 1952 by James Watson and Francis Crick based on the work of Rosalind Franklin and Maurice Wilkins.

Normally, these DNA bases (called A, C, T and G) follow strict rules on how they bond together: A always bonds to T and C always to G. This strict pairing is determined by the molecules' shape, fitting them together like pieces in a jigsaw, but if the nature of the hydrogen bonds changes slightly, this can cause the pairing rule to break down, leading to the wrong bases being linked and hence a mutation. Although predicted by Crick and Watson, it is only now that sophisticated computational modelling has been able to quantify the process accurately.

The team, part of Surrey's research programme in the exciting new field of quantum biology, have shown that this modification in the bonds between the DNA strands is far more prevalent than has hitherto been thought. The protons can easily jump from their usual site on one side of an energy barrier to land on the other side. If this happens just before the two strands are unzipped in the first step of the copying process, then the error can pass through the replication machinery in the cell, leading to what is called a DNA mismatch and, potentially, a mutation.

In a paper published this week in the journal Nature Communications Physics, the Surrey team based in the Leverhulme Quantum Biology Doctoral Training Centre used an approach called open quantum systems to determine the physical mechanisms that might cause the protons to jump across between the DNA strands. But, most intriguingly, it is thanks to a well-known yet almost magical quantum mechanism called tunnelling -- akin to a phantom passing through a solid wall -- that they manage to get across.

It had previously been thought that such quantum behaviour could not occur inside a living cell's warm, wet and complex environment. However, the Austrian physicist Erwin Schrödinger had suggested in his 1944 book What is Life? that quantum mechanics can play a role in living systems since they behave rather differently from inanimate matter. This latest work seems to confirm Schrödinger's theory.

In their study, the authors determine that the local cellular environment causes the protons, which behave like spread out waves, to be thermally activated and encouraged through the energy barrier. In fact, the protons are found to be continuously and very rapidly tunnelling back and forth between the two strands. Then, when the DNA is cleaved into its separate strands, some of the protons are caught on the wrong side, leading to an error.

Dr Louie Slocombe, who performed these calculations during his PhD, explains that:

" The protons in the DNA can tunnel along the hydrogen bonds in DNA and modify the bases which encode the genetic information. The modified bases are called "tautomers" and can survive the DNA cleavage and replication processes, causing "transcription errors" or mutations."

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Combining certain meds with ibuprofen can permanently injure kidneys

Anyone who is taking a diuretic and a renin-angiotensin system (RSA) inhibitor for high blood pressure should be cautious about also taking ibuprofen, according to new research.

Diuretics and RSA inhibitors are commonly prescribed together for people with hypertension and are available under various pharmaceutical brand names. Painkillers such as ibuprofen are available over-the-counter in most pharmacies and stores in popular brands.

Researchers at the University of Waterloo used computer-simulated drug trials to model the interactions of the three drugs and the impact on the kidney. They found that in people with certain medical profiles, the combination can cause acute kidney injury, which in some cases can be permanent.

"It's not that everyone who happens to take this combination of drugs is going to have problems," said Anita Layton, professor of applied mathematics at Waterloo and Canada 150 Research Chair in mathematical biology and medicine. "But the research shows it's enough of a problem that you should exercise caution."

Computer-simulated drug trials can quickly produce results that would take much longer in human clinical trials. Layton and her team use mathematics and computer science to give medical practitioners a head start with issues like drug complications.

The research, in this case, can also speak directly to the many people who are taking drugs for hypertension and may reach for a painkiller with ibuprofen without giving it much thought.

"Diuretics are a family of drugs that make the body hold less water," Layton said. "Being dehydrated is a major factor in acute kidney injury, and then the RAS inhibitor and ibuprofen hit the kidney with this triple whammy. If you happen to be on these hypertension drugs and need a painkiller, consider acetaminophen instead."

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Astronomers discover a rare 'black widow' binary, with the shortest orbit yet

The flashing of a nearby star has drawn MIT astronomers to a new and mysterious system 3,000 light years from Earth. The stellar oddity appears to be a new "black widow binary" -- a rapidly spinning neutron star, or pulsar, that is circling and slowly consuming a smaller companion star, as its arachnid namesake does to its mate.

Astronomers know of about two dozen black widow binaries in the Milky Way. This newest candidate, named ZTF J1406+1222, has the shortest orbital period yet identified, with the pulsar and companion star circling each other every 62 minutes. The system is unique in that it appears to host a third, far-flung star that orbits around the two inner stars every 10,000 years.

This likely triple black widow is raising questions about how such a system could have formed. Based on its observations, the MIT team proposes an origin story: As with most black widow binaries, the triple system likely arose from a dense constellation of old stars known as a globular cluster. This particular cluster may have drifted into the Milky Way's center, where the gravity of the central black hole was enough to pull the cluster apart while leaving the triple black widow intact.

"It's a complicated birth scenario," says Kevin Burdge, a Pappalardo Postdoctoral Fellow in MIT's Department of Physics. "This system has probably been floating around in the Milky Way for longer than the sun has been around."

Burdge is the author of a study appearing in Nature that details the team's discovery. The researchers used a new approach to detect the triple system. While most black widow binaries are found through the gamma and X-ray radiation emitted by the central pulsar, the team used visible light, and specifically the flashing from the binary's companion star, to detect ZTF J1406+1222.

"This system is really unique as far as black widows go, because we found it with visible light, and because of its wide companion, and the fact it came from the galactic center," Burdge says. "There's still a lot we don't understand about it. But we have a new way of looking for these systems in the sky."

The study's co-authors are collaborators from multiple institutions, including the University of Warwick, Caltech, the University of Washington, McGill University, and the University of Maryland.

Day and night

Black widow binaries are powered by pulsars -- rapidly spinning neutron stars that are the collapsed cores of massive stars. Pulsars have a dizzying rotational period, spinning around every few milliseconds, and emitting flashes of high-energy gamma and X-rays in the process.

Normally, pulsars spin down and die quickly as they burn off a huge amount of energy. But every so often, a passing star can give a pulsar new life. As a star nears, the pulsar's gravity pulls material off the star, which provides new energy to spin the pulsar back up. The "recycled" pulsar then starts reradiating energy that further strips the star, and eventually destroys it.

"These systems are called black widows because of how the pulsar sort of consumes the thing that recycled it, just as the spider eats its mate," Burdge says.

Every black widow binary to date has been detected through gamma and X-ray flashes from the pulsar. In a first, Burdge came upon ZTF J1406+1222 through the optical flashing of the companion star.

It turns out that the companion star's day side -- the side perpetually facing the pulsar -- can be many times hotter than its night side, due to the constant high-energy radiation it receives from the pulsar.

"I thought, instead of looking directly for the pulsar, try looking for the star that it's cooking," Burdge explains.

He reasoned that if astronomers observed a star whose brightness was changing periodically by a huge amount, it would be a strong signal that it was in a binary with a pulsar.

Star motion

To test this theory, Burdge and his colleagues looked through optical data taken by the Zwicky Transient Facility, an observatory based in California that takes wide-field images of the night sky. The team studied the brightness of stars to see whether any were changing dramatically by a factor of 10 or more, on a timescale of about an hour or less -- signs that indicate the presence of a companion star orbiting tightly around a pulsar.

The team was able to pick out the dozen known black widow binaries, validating the new method's accuracy. They then spotted a star whose brightness changed by a factor of 13, every 62 minutes, indicating that it was likely part of a new black widow binary, which they labeled ZTF J1406+1222.

They looked up the star in observations taken by Gaia, a space telescope operated by the European Space Agency that keeps precise measurements of the position and motion of stars in the sky. Looking back through decades old measurements of the star? from the Sloan Digital Sky Survey, the team found that the binary was being trailed by another distant star. Judging from their calculations, this third star appeared to be orbiting the inner binary every 10,000 years.

Curiously, the astronomers have not directly detected gamma or X-ray emissions from the pulsar in the binary, which is the typical way in which black widows are confirmed. ZTF J1406+1222, therefore, is considered a candidate black widow binary, which the team hopes to confirm with future observations.

"The one thing we know for sure is that we see a star with a day side that's much hotter than the night side, orbiting around something every 62 minutes," Burdge says. "Everything seems to point to it being a black widow binary. But there are a few weird things about it, so it's possible it's something entirely new."

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Jaws hold crucial knowledge on the fate of sharks

Jaws was the only word needed to give the iconic 1970's thriller about a great white with a preference for humans its eerie title. Though a strong and important player at the top of the foodchain, sharks face a range of enemies: overfishing, habitat loss, pollution and climate change and human fear resulting in the use of shark control programs in some locations.

The fear and fascination for sharks have made people collect shark jaws for decades. These collections of shark jaws from museums, national fishery institutes and personal collections, including modern samples from fishery institutes represent a great opportunity for scientists.

Using genomic data retrieved from historical tiger shark jaws, an international group of scientists including Professor Einar Eg from the Technical University of Denmark has found evidence of the disappearance of a local southeastern Australian population of tiger sharks. A disappearance associated with a documented local decline in abundance of tiger sharks, likely caused by the ongoing shark control program.

The international study Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population has just been published in the journal Scientific Reports

"Our study shows that tiger sharks can have local and genetically isolated populations at a restricted geographical scale -- such as the south Eastern Australian coast -- and that these local populations are vulnerable to direct exploitation and shark control programs," says Einar Eg.

Top predator controls the ecosystem balance

The study shows that there are still tiger sharks in the area. However, these individuals belong to an, apparently, more widespread population found across the east/north coast of Australia.

"When we, through genetic analysis, better understand the distribution and migration of shark populations and their responses to human activities over historical time, we are better able to design proper management plans and actions at the appropriate geographical scale. Not only for the benefit of sharks, but for marine ecosystems as a whole," says Einar Eg and explains:

"Sharks are top predators. They control the abundance of other species below them, and sick fish, in the food chain, ensuring species diversity. I.e. they are important for maintaining ecosystem balance. They are generally long lived and slow reproducers, so a healthy shark fauna signals a healthy ocean and ecosystem."

Genetic diversity is the fuel that drives future evolution

Before the new study, it was believed that tiger sharks did not display local population structure. Thus, genetic differences among tiger shark populations were only found at a basin wide scale, such as between tiger sharks in the Pacific and Atlantic oceans. Accordingly, tiger sharks were expected to display low vulnerability towards local depletion. Therefore management of the species at a large geographical scale was in focus.

"From our samples alone, it appears that the historical local population has been extirpated or significantly reduced. This means that management of the species also has to focus on regional processes and exploitation patterns in order to protect local populations and biodiversity of the species as a whole," says Einar Eg and points to the crucial aspects of genetic research:

"Genetic diversity within a species, is the fuel that drives future evolution and adaptation to the environment, e.g. climate change. Without historical genetic/genomic data, there is no way of assessing the loss of genetic diversity within a species."

Fear and facts -- are sharks moving North?

With regards to the shark control programs having an impact on shark numbers, the obvious question arises "How afraid should one actually be to go swimming in Australia or South Africa?"

"In 2021, there were 73 cases of unprovoked shark bites worldwide, with a total of 11 fatalities. Most attacks were related to surfing and board sports. In Australia, there were three fatalities and 1 in SA. So, the chance of being attacked and killed by a shark is almost non-existing. One should definitely be more afraid of driving in your car writing txt messages," says Einar Eg.

As climate change causes sea temperatures to rise, some researchers say that we may be looking into a future with large sharks entering Danish/European waters. However, Einar Eg stresses that though changed temperature conditions could allow for more large sharks occurring in Danish/European waters, many other factors determine the distribution of a species.

"The Mediterranean, for instance, is very suitable for large sharks, but we do not see large assemblages of white, tiger, mako sharks there. If they come, it is highly unlikely that this would result in any bather-shark conflicts. As an example, there were no reported shark bites in Europe for 2021," says Einar Eg.

A future for sharks

On a global scale, the tiger shark is near threatened. According to Professor Einar Eg that covers a significant species depletion in some areas, while they're doing ok in other regions of the world: "We need to shift tiger shark management conceptually from an exclusive species view to also include the local population aspect. I.e. saving global populations has to go through protection and proper management of local populations," says Einar Eg.

"Now, by having our temporal genetic data, we can study the genetic impact of anthropogenic pressure on marine species, enabling us to improve management in order to secure biodiversity."

How can genetic research continue and help improve shark control and hunting in favour of sharks?

"Genetic research can help to elucidate the proper biological units (genetic populations), which should be the target for fisheries management, conservation and biodiversity protection," says Einar Eg and concludes:

"Studies like ours can illustrate the likely consequences of local over-exploitation in relation to shark control and make us realize what we can lose by not paying attention to the distribution of genetic variation within a species."

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Diet type can increase potentially harmful gas in the gut

Published in Clinical Nutrition, researchers from the University of Minnesota Medical School looked at colonic hydrogen sulfide -- a toxic gas in the body that smells like rotten eggs -- production in people in response to animal- and plant-based diet interventions.

"Although the role of hydrogen sulfide has long been a subject of great interest in the pathogenesis of multiple important diseases -- such as ulcerative colitis, colon cancer, and obesity -- past investigations have not been able to link dietary data, microbiome characterization and actual hydrogen sulfide production," said Alexander Khoruts, MD, a gastroenterologist in the U of M Medical School and M Health Fairview. "This is what we have done here."

From a human cohort, the study supports the general hypothesis that hydrogen sulfide produced by the gut microbiota increases with an animal-based diet. However, the results also suggested the existence of gut microbiome enterotypes that respond differentially and even paradoxically to different dietary input.

The study found that:
 

• In the majority of participants, a plant-based diet resulted in a lower hydrogen sulfide production compared to an animal-based (i.e., western) diet.
• As expected, a plant-based diet contained more fiber, while an animal-based diet contained more protein.
• In some individuals, plant-based diets did not lower hydrogen sulfide production and even led to some increases in it.
• Preliminary results suggested the existence of different compositions of gut microbiota (enterotypes) that correlate with differential responsiveness to diet in terms of hydrogen sulfide production.

"The study was consistent with the general understanding that regular intake of fiber-containing foods is beneficial to gut health," said Dr. Levi Teigen, a nutrition researcher in the Division of Gastroenterology in the U of M Medical School. "Future analyses of the gut microbiome may help to individualize nutrition interventions."

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How mosquito brains encode human odor so they can seek us out

Mosquitoes. Bane of backyard picnics -- and deadly in Zika- and dengue-prone regions.

Most of the world's mosquitos are opportunistic, willing to drink blood from any nearby source. But in some regions, the mosquitoes that carry Zika, dengue and yellow fever -- Aedes aegypti -- have evolved to bite humans almost exclusively. But to succeed as a specialized feeder, depending on just one species -- ours -- to survive, they must have evolved incredibly precise targeting strategies. How do they do it?

"We set out to try to understand how these mosquitoes distinguish human and animal odor," said Carolyn "Lindy" McBride, an assistant professor of ecology and evolutionary biology and neuroscience, "both in terms of what it is about human odor that they cue in on and what part of their brain allows them to cue in on those signals."

After years of dedicated work, including countless scientific and technological challenges, her team has discovered answers to both parts of this equation. What is it that the mosquitos are detecting, and how do they detect it? Their results appear in the current issue of Nature.

McBride described their mosquito-centric approach: "We sort of dove into the brain of the mosquito and asked, 'What can you smell? What lights up your brain? What's activating your neurons? And how is your brain activated differently when you smell human odor versus animal odor?'"

Then-graduate student Zhilei Zhao, a 2021 Ph.D. alumnus who is now at Cornell, pioneered their novel approach: imaging mosquito brains at very high resolution to watch how the mosquito identifies its next victim. To do that, he had to first genetically engineer mosquitos whose brains lit up when active, and then the team had to deliver human- and animal-flavored air in ways that the mosquitos could detect while inside the team's custom-built imaging equipment.

Human odor is composed of dozens of different compounds, and those same compounds, in slightly different ratios, are present in most mammal odors. None of those compounds is attractive to mosquitoes by itself, so the challenge was to determine the exact blend of components that mosquitos use to recognize human odor.

The team concluded that two chemicals, decanal and undecanal, are enriched in human odor. They patented a blend featuring decanal that they hope could lead to baits attracting mosquitoes to lethal traps, or repellents that interrupt the signal.

To provide comparison mammals to test, graduate student Jessica Zung worked with former research specialists Alexis Kriete and Azwad Iqbal to collect hair, fur and wool samples. For this paper, the team used odor from sixteen humans, two rats, two guinea pigs, two quail, one sheep and four dogs. Howell Living History Farm in Hopewell, N.J., donated several fleeces from their spring sheep shearing; for another domesticated mammal, Zung went to a grooming salon and gathered trimmed hairs from recently groomed pet dogs.

"For the human samples, we had a bunch of great volunteers," Zung said. "We had them not shower for a few days, then strip down naked and lie down in a Teflon bag." Why naked? Because cotton, polyester and other clothing fibers have their own smells that would distort the data.

Once they conquered the technical challenges -- retrieving the human and animal odors nondestructively, designing a system that allowed them to puff human odor at the mosquitos in the imaging setup, creating a wind tunnel to test simple blends or single compounds, and breeding viable strains of mosquitos whose brains respond to the equipment -- they began gathering data.

Very surprising data.

Before this study, researchers speculated that mosquito brains must have a complicated, sophisticated technique for distinguishing humans from other animals. Quite the opposite, it turned out.

"The simplicity surprised us," said McBride. "Despite the complexity of human odor, and the fact that it doesn't really have any kind of human-specific compounds in it, the mosquitoes have evolved a surprisingly simple mechanism for recognizing us. To me, it's an evolutionary story: if we created a statistical test to differentiate human odor, it would be very complex, but the mosquito does something remarkably simple, and simple usually works pretty well, when it comes to evolution."

In other words, simple solutions tend to breed true, over evolutionary time.

Mosquito brains have 60 nerve centers called glomeruli (singular: glomerulus). The team had hypothesized that many -- maybe even most -- would be involved in helping these human-dependent mosquitos find their favorite food.

"When I first saw the brain activity, I couldn't believe it -- just two glomeruli were involved," Zhao said. "That contradicted everything we expected, so I repeated the experiment several times, with more humans, more animals. I just couldn't believe it. It's so simple."

Of the two nerve centers, one responds to many smells including human odor, essentially saying, "Hey, look, there's something interesting nearby you should check out," while the other responds only to humans. Having two may help the mosquitos home in on their targets, the researchers suggest.

That was one of the biggest "Eureka!" moments in the project, said McBride. "Zhilei had worked for a couple years to get the transgenic mosquitoes that he needed, and then we found that we didn't have a good way to deliver human odor. So we worked for another year or two, coming up with ideas to try to figure out how to deliver enough human odor in a controlled enough way to see a response. Then, the first time we tried this new technology that we described in the paper -- this new way of delivering odors -- he actually saw a brain respond. It was incredible."

By determining the glomeruli that mosquitos use to detect humans, and identifying what it is they are detecting -- decanal and undecanal -- the team has an elegantly straightforward answer to their questions, noted Zung.

"If this were purely a neuro imaging paper, there would be some questions remaining," she said. "If this were purely an odor analysis paper, there would still be unanswered questions. A purely behavior paper, same thing. But one real strength of this project is that we were able to bring in so many different methods and the expertise of so many people. And Lindy was just amazing and willing to learn about and invest in all these different methods."

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Younger exoplanets are better candidates when looking for other Earths

As the scientific community searches for worlds orbiting nearby stars that could potentially harbor life, new Southwest Research Institute-led research suggests that younger rocky exoplanets are more likely to support temperate, Earth-like climates.

In the past, scientists have focused on planets situated within a star's habitable zone, where it is neither too hot nor too cold for liquid surface water to exist. However, even within this so-called "Goldilocks zone," planets can still develop climates inhospitable to life. Sustaining temperate climates also requires a planet have sufficient heat to power a planetary-scale carbon cycle. A key source of this energy is the decay of the radioactive isotopes of uranium, thorium and potassium. This critical heat source can power a rocky exoplanet's mantle convection, a slow creeping motion of the region between a planet's core and crust that eventually melts at the surface. Surface volcanic degassing is a primary source of CO2 to the atmosphere, which helps keep a planet warm. Without mantle degassing, planets are unlikely to support temperate, habitable climates like the Earth's.

"We know these radioactive elements are necessary to regulate climate, but we don't know how long these elements can do this, because they decay over time," said Dr. Cayman Unterborn, lead author of an Astrophysical Journal Letters paper about the research. "Also, radioactive elements aren't distributed evenly throughout the Galaxy, and as planets age, they can run out of heat and degassing will cease. Because planets can have more or less of these elements than the Earth, we wanted to understand how this variation might affect just how long rocky exoplanets can support temperate, Earth-like climates."

Studying exoplanets is challenging. Today's technology cannot measure the composition of an exoplanet's surface, much less that of its interior. Scientists can, however, measure the abundance of elements in a star spectroscopically by studying how light interacts with the elements in a star's upper layers. Using these data, scientists can infer what a star's orbiting planets are made of using stellar composition as a rough proxy for its planets.

"Using host stars to estimate the amount of these elements that would go into planets throughout the history of the Milky Way, we calculated how long we can expect planets to have enough volcanism to support a temperate climate before running out of power," Unterborn said. "Under the most pessimistic conditions we estimate that this critical age is only around 2 billion years old for an Earth-mass planet and reaching 5-6 billion years for higher-mass planets under more optimistic conditions. For the few planets we do have ages for, we found only a few were young enough for us to confidently say they can have surface degassing of carbon today, when we'd observe it with, say, the James Webb Space Telescope."

This research combined direct and indirect observational data with dynamical models to understand which parameters most affect an exoplanet's ability to support a temperate climate. More laboratory experiments and computational modeling will quantify the reasonable range of these parameters, particularly in the era of the James Webb Space Telescope, which will provide more in-depth characterization of individual targets. With the Webb telescope, it will be possible to measure the three-dimensional variation of exoplanet atmospheres. These measurements will deepen the knowledge of atmospheric processes and their interactions with the planet's surface and interior, which will allow scientists to better estimate whether a rocky exoplanet in habitable zones is too old to be Earth-like.

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Search reveals eight new sources of black hole echoes

Scattered across our Milky Way galaxy are tens of millions of black holes -- immensely strong gravitational wells of spacetime, from which infalling matter, and even light, can never escape. Black holes are dark by definition, except on the rare occasions when they feed. As a black hole pulls in gas and dust from an orbiting star, it can give off spectacular bursts of X-ray light that bounce and echo off the inspiraling gas, briefly illuminating a black hole's extreme surroundings.

Now MIT astronomers are looking for flashes and echoes from nearby black hole X-ray binaries -- systems with a star orbiting, and occasionally being eaten away by, a black hole. They are analyzing the echoes from such systems to reconstruct a black hole's immediate, extreme vicinity.

In a study appearing today in the Astrophysical Journal, the researchers report using a new automated search tool, which they've coined the "Reverberation Machine," to comb through satellite data for signs of black hole echoes. In their search, they have discovered eight new echoing black hole binaries in our galaxy. Previously, only two such systems in the Milky Way were known to emit X-ray echoes.

In comparing the echoes across systems, the team has pieced together a general picture of how a black hole evolves during an outburst. Across all systems, they observed that a black hole first undergoes a "hard" state, whipping up a corona of high-energy photons along with a jet of relativistic particles that is launched away at close to the speed of light. The researchers discovered that at a certain point, the black hole gives off one final, high-energy flash, before transitioning to a "soft," low-energy state.

This final flash may be a sign that a black hole's corona, the region of high-energy plasma just outside a black hole's boundary, briefly expands, ejecting a final burst of high-energy particles before disappearing entirely. These findings could help to explain how larger, supermassive black holes at the center of a galaxy can eject particles across vastly cosmic scales to shape a galaxy's formation.

"The role of black holes in galaxy evolution is an outstanding question in modern astrophysics," says Erin Kara, assistant professor of physics at MIT. "Interestingly, these black hole binaries appear to be 'mini' supermassive black holes, and so by understanding the outbursts in these small, nearby systems, we can understand how similar outbursts in supermassive black holes affect the galaxies in which they reside."

The study's first author is MIT graduate student Jingyi Wang; other co-authors include Matteo Lucchini and Ron Remillard at MIT, along with collaborators from Caltech and other institutions.

X-ray delays

Kara and her colleagues are using X-ray echoes to map a black hole's vicinity, much the way that bats use sound echoes to navigate their surroundings. When a bat emits a call, the sound can bounce off an obstacle and return to the bat as an echo. The time it takes for the echo to return is relative to the distance between the bat and the obstacle, giving the animal a mental map of its surroundings.

In similar fashion, the MIT team is looking to map the immediate vicinity of a black hole using X-ray echoes. The echoes represent time delays between two types of X-ray light: light emitted directly from the corona, and light from the corona that bounces off the accretion disk of inspiraling gas and dust.

The time when a telescope receives light from the corona, compared to when it receives the X-ray echoes, gives an estimate of the distance between the corona and the accretion disk. Watching how these time delays change can reveal how a black hole's corona and disk evolve as the black hole consumes stellar material.

Echo evolution

In their new study, the team developed search algorithm to comb through data taken by NASA's Neutron star Interior Composition Explorer, or NICER, a high-time-resolution X-ray telescope aboard the International Space Station. The algorithm picked out 26 black hole X-ray binary systems that were previously known to emit X-ray outbursts. Of these 26, the team found that 10 systems were close and bright enough that they could discern X-ray echoes amid the outbursts. Eight of the 10 were previously not known to emit echoes.

"We see new signatures of reverberation in eight sources," Wang says. "The black holes range in mass from five to 15 times the mass of the sun, and they're all in binary systems with normal, low-mass, sun-like stars."

As a side project, Kara is working with MIT education and music scholars, Kyle Keane and Ian Condry, to convert the emission from a typical X-ray echo into audible sound waves.

Video Echos of a Black Hole: https://youtu.be/iIeIag2Ji8k

The researchers then ran the algorithm on the 10 black hole binaries and divided the data into groups with similar "spectral timing features," that is, similar delays between high-energy X-rays and reprocessed echoes. This helped to quickly track the change in X-ray echoes at every stage during a black hole's outburst.

The team identified a common evolution across all systems. In the initial "hard" state, in which a corona and jet of high-energy particles dominates the black hole's energy, they detected time lags that were short and fast, on the order of milliseconds. This hard state lasts for several weeks. Then, a transition occurs over several days, in which the corona and jet sputter and die out, and a soft state takes over, dominated by lower-energy X-rays from the black hole's accretion disk.

During this hard-to-soft transition state, the team discovered that time lags grew momentarily longer in all 10 systems, implying the distance between the corona and disk also grew larger. One explanation is that the corona may briefly expand outward and upward, in a last high-energy burst before the black hole finishes the bulk of its stellar meal and goes quiet.

Read more at Science Daily

Dinosaur extinction changed plant evolution

With the extinction of large, non-flying dinosaurs 66 million years ago, large herbivores were missing on Earth for the subsequent 25 million years. Since plants and herbivorous animals influence each other, the question arises whether, and how this very long absence and the later return of the so-called "megaherbivores" affected the evolution of the plant world.

To answer this question, a research team led by iDiv and Leipzig University analysed fossil and living palms today. Genetic analyses enabled the researchers to trace the evolutionary developments of plants during and after the absence of megaherbivores. Thus, they first confirmed the common scientific assumption that many palm species at the time of the dinosaurs bore large fruits and were covered with spines and thorns on their trunks and leaves.

However, the research team found that the "evolutionary speed" with which new palm species with small fruits arose during the megaherbivore gap decreased, whereas the evolutionary speed of those with large fruits remained almost constant. The size of the fruits themselves, however, also increased. So, there were palms with large fruits even after the extinction of the dinosaurs. Apparently, much smaller animals could also eat large fruits and spread the seeds with their excretions. "We were thus able to refute the previous scientific assumption that the presence of large palm fruits depended exclusively on megaherbivores," says the study's first author Dr Renske Onstein from iDiv and Leipzig University. "We therefore assume that the lack of influence of large herbivores led to denser vegetations in which plants with larger seeds and fruits had an evolutionary advantage."

However, the defence traits of the plants; spines and thorns on leaves and stems, showed a different picture: the number of palm species with defence traits decreased during the megaherbivore gap. "Defence traits without predators apparently no longer offered evolutionary advantages," says Onstein, who heads the junior research group Evolution and Adaptation at iDiv. "However, they returned in most palm species when new megaherbivores evolved, in contrast to the changes in fruits, which persisted."

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Researchers discover new species of salamander from Gulf Coastal plains hotspot

There are approximately 750 species of salamander known to science, a third of which reside in North America. Now, a team of researchers led by R. Alexander Pyron, the Robert F. Griggs Associate Professor of Biology at the George Washington University, has discovered a new species of swamp-dwelling dusky salamander from the Gulf Coastal Plain of southeastern Mississippi and southwestern Alabama.

The discovery increases knowledge of the biodiversity in the southeastern United States Coastal Plain, a candidate region meeting the global criteria for a biodiversity hotspot. According to the researchers, the region has been studied intensively for hundreds of years, but nonetheless still contains abundant undescribed diversity.

"This discovery shows us how much more there is to learn even in our own backyards," Pyron said. "The famed naturalist E.O. Wilson called this region 'America's Amazon,' where ivory-billed woodpeckers and red wolves once lived. We are losing biodiversity at a dramatic rate, while still discovering how much was originally there. Salamanders are among the most imperiled animals globally, and we've yet to understand their true biodiversity."

The researchers determined that the new species of salamander, known as Desmognathus pascagoula, is similar to another recently discovered species known as Desmognathus valentinei. However, certain morphological, genetic and geographic aspects of the new species differ. The researchers sequenced the genomes from D. valentinei and D. pascagoula specimens, revealing genetic variations in 881 different genes. They also compared the body structure of D. pascagoula with D. valentinei and Desmognathus conanti, another species that occurs in the area, using collections from the Smithsonian's National Museum of Natural History. They found subtle but significant differences: D. pascagoula has a longer, more slender body and a narrower head and nostrils.

"Many of these dusky salamanders are cryptic, meaning they can't easily be told apart with the naked eye, which is one reason they went undiscovered for so long," Pyron said. "Only with genome sequencing can we see how different they really are. Then, precise measurements of preserved specimens reveal tiny differences in things like the width of the head, which are otherwise imperceptible."

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'Resetting' the injured brain offers clues for concussion treatment

New research in mice raises the prospects for development of post-concussion therapies that could ward off cognitive decline and depression, two common conditions among people who have experienced a moderate traumatic brain injury.

The study in mice clarified the role of specific immune cells in the brain that contribute to chronic inflammation. Using a technique called forced cell turnover, researchers eliminated these cells in the injured brains of mice for a week and then let them repopulate for two weeks.

"It's almost like hitting the reset button," said senior study author Jonathan Godbout, professor of neuroscience in The Ohio State University College of Medicine.

Compared to brain-injured mice recovering naturally, mice that were given the intervention showed less inflammation in the brain and fewer signs of thinking problems 30 days after the injury.

Though temporarily clearing away these cells, called microglia, in humans isn't feasible, the findings shed light on pathways to target that could lower the brain's overall inflammatory profile after a concussion, potentially reducing the risk for behavioral and cognitive problems long after the injury.

"In a moderate brain injury, if the CT scan doesn't show damage, patients go home with a concussion protocol. Sometimes people come back weeks, months later with neuropsychiatric issues. It's a huge problem affecting millions of people," said Godbout, faculty director of Ohio State's Chronic Brain Injury Program and assistant director of basic science in the Institute for Behavioral Medicine Research.

"How do you treat that? At least in mice, by turning over the microglia in the brain we had a very positive effect on their behavior, cognitive status and level of inflammation in the brain. Now we can focus on cellular pathways that generate chronic inflammation as a target."

The research is published online in the Journal of Neuroscience.

About 85% of traumatic brain injuries are similar to the type of concussion examined in this study, involving dispersed impact to the head that causes brain tissue to bump against the skull. Previous research suggests that at least 75% of people who experience a moderate brain injury have long-term mental health and cognitive complications.

Godbout's lab previously linked depressive symptoms in mice to microglia's sustained "high alert" status after a head injury, which causes the cells to overreact to later challenges to the immune system and become excessively inflammatory. In a more recent study in mice, his team showed that forced turnover of microglia before a head injury could reduce later neuropsychiatric complications.

"That was a proof of principle to show that a lot of the inflammation, especially in the long term, is mediated by microglia," he said. "But there is an acute phase of inflammation -- you want to initiate that repair process. There's a positive to that early inflammatory response in the brain or spinal cord. If it lasts a long time and doesn't fully resolve, that's when it's dangerous."

In this new study, researchers waited for seven days after the brain injury to force the turnover of microglia, giving the cells time to carry out their work promoting initial healing. An experimental drug that inhibits a protein that microglia in mice need for survival was added to their food for a week, resulting in depletion of over 95% of microglia in their brains.

After allowing 16 days for the microglia to repopulate, researchers compared the intervention mice to injured mice that recovered without the cell turnover treatment. The intervention mice performed better than control mice on tasks testing their memory and depressive symptoms.

Further analyses of injured brain tissue suggested the cell turnover reversed some injury-related damage to neurons, lowered overall inflammation and improved the brain's ability to adapt to change. Researchers also injected mice with a molecule that triggers an immune response to mimic an infection, and found that sickness behavior was lower in the intervention mice.

Godbout said these combined findings suggest that the repopulating microglia returned in a less "primed" state of readiness, lowering chances for a lifetime of exaggerated inflammatory responses in the brain to any challenge to the immune system -- that brain inflammation being the likely culprit behind the neuropsychiatric complications that follow a head injury.

"If microglia in the human brain don't return to normal and chronic inflammation persists after a head injury, it's not just a secondary brain injury that causes problems. Even getting a viral infection after concussion recovery can progress into a cognitive or behavioral issue or amplify some other part of behavior, like depression," Godbout said. "There is a real connection between a head injury and mental health, and the risk doesn't go away.

"Now we're looking more closely at the pathways that cause changes in microglia, and targeting something specific in that pathway. That is a way forward."

Read more at Science Daily

Spinning stars shed new light on strange signal coming from galactic center

Researchers from The Australian National University (ANU) have found an alternative explanation for a mysterious gamma-ray signal coming from the centre of the galaxy, which was long claimed as a signature of dark matter.

Gamma-rays are the form of electromagnetic radiation with the shortest wavelength and highest energy.

Co-author of the study Associate Professor Roland Crocker said this particular gamma-ray signal -- known as the Galactic Centre Excess -- may actually come from a specific type of rapidly-rotating neutron star, the super-dense stellar remnants of some stars much more massive than our sun.

The Galactic Centre Excess is an unexpected concentration of gamma-rays emerging from the centre of our galaxy that has long puzzled astronomers.

"Our work does not throw any doubt on the existence of the signal, but offers another potential source," Associate Professor Crocker said.

"It is based on millisecond pulsars -- neutron stars that spin really quickly -- around 100 times a second.

"Scientists have previously detected gamma-ray emissions from individual millisecond pulsars in the neighbourhood of the solar system, so we know these objects emit gamma-rays. Our model demonstrates that the integrated emission from a whole population of such stars, around 100,000 in number, would produce a signal entirely compatible with the Galactic Centre Excess."

The discovery may mean scientists have to re-think where they look for clues about dark matter.

"The nature of dark matter is entirely unknown, so any potential clues garner a lot of excitement," Associate Professor Crocker said.

"But our results point to another important source of gamma-ray production.

"For instance, the gamma-ray signal from Andromeda, the next closest large galaxy to our own may be mostly due to millisecond pulsars."

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How a soil microbe could rev up artificial photosynthesis

Plants rely on a process called carbon fixation -- turning carbon dioxide from the air into carbon-rich biomolecules - for their very existence. That's the whole point of photosynthesis, and a cornerstone of the vast interlocking system that cycles carbon through plants, animals, microbes and the atmosphere to sustain life on Earth.

But the carbon fixing champs are not plants, but soil bacteria. Some bacterial enzymes carry out a key step in carbon fixation 20 times faster than plant enzymes do, and figuring out how they do this could help scientists develop forms of artificial photosynthesis to convert the greenhouse gas into fuels, fertilizers, antibiotics and other products.

Now a team of researchers from the Department of Energy's SLAC National Accelerator Laboratory, Stanford University, Max Planck Institute for Terrestrial Microbiology in Germany, DOE's Joint Genome Institute (JGI) and the University of Concepción in Chile has discovered how a bacterial enzyme -- a molecular machine that facilitates chemical reactions -- revs up to perform this feat.

Rather than grabbing carbon dioxide molecules and attaching them to biomolecules one at a time, they found, this enzyme consists of pairs of molecules that work in sync, like the hands of a juggler who simultaneously tosses and catches balls, to get the job done faster. One member of each enzyme pair opens wide to catch a set of reaction ingredients while the other closes over its captured ingredients and carries out the carbon-fixing reaction; then, they switch roles in a continual cycle.

A single spot of molecular "glue" holds each pair of enzymatic hands together so they can alternate opening and closing in a coordinated way, the team discovered, while a twisting motion helps hustle ingredients and finished products in and out of the pockets where the reactions take place. When both glue and twist are present, the carbon-fixing reaction goes 100 times faster than without them.

"This bacterial enzyme is the most efficient carbon fixer that we know of, and we came up with a neat explanation of what it can do," said Soichi Wakatsuki, a professor at SLAC and Stanford and one of the senior leaders of the study, which was published in ACS Central Science this week.

"Some of the enzymes in this family act slowly but in a very specific way to produce just one product," he said. "Others are much faster and can craft chemical building blocks for all sorts of products. Now that we know the mechanism, we can engineer enzymes that combine the best features of both approaches and do a very fast job with all sorts of starting materials."

Improving on nature

The enzyme the team studied is part of a family called enoyl-CoA carboxylases/reductases, or ECRs. It comes from soil bacteria called Kitasatospora setae, which in addition to their carbon-fixing skills can also produce antibiotics.

Wakatsuki heard about this enzyme family half a dozen years ago from Tobias Erb of the Max Planck Institute for Terrestrial Microbiology in Germany and Yasuo Yoshikuni of JGI. Erb's research team had been working to develop bioreactors for artificial photosynthesis to convert carbon dioxide (CO2) from the atmosphere into all sorts of products.

As important as photosynthesis is to life on Earth, Erb said, it isn't very efficient. Like all things shaped by evolution over the eons, it's only as good as it needs to be, the result of slowly building on previous developments but never inventing something entirely new from scratch.

What's more, he said, the step in natural photosynthesis that fixes CO2 from the air, which relies on an enzyme called Rubisco, is a bottleneck that bogs the whole chain of photosynthetic reactions down. So using speedy ECR enzymes to carry out this step, and engineering them to go even faster, could bring a big boost in efficiency.

"We aren't trying to make a carbon copy of photosynthesis," Erb explained. "We want to design a process that's much more efficient by using our understanding of engineering to rebuild the concepts of nature. This 'photosynthesis 2.0' could take place in living or synthetic systems such as artificial chloroplasts -- droplets of water suspended in oil."

Portraits of an enzyme

Wakatsuki and his group had been investigating a related system, nitrogen fixation, which converts nitrogen gas from the atmosphere into compounds that living things need. Intrigued by the question of why ECR enzymes were so fast, he started collaborating with Erb's group to find answers.

Hasan DeMirci, a research associate in Wakatsuki's group who is now an assistant professor at Koc University and investigator with the Stanford PULSE Institute, led the effort at SLAC with help from half a dozen SLAC summer interns he supervised. "We train six or seven of them every year, and they were fearless," he said. "They came with open minds, ready to learn, and they did amazing things."

The SLAC team made samples of the ECR enzyme and crystallized them for examination with X-rays at the Advanced Photon Source at DOE's Argonne National Laboratory. The X-rays revealed the molecular structure of the enzyme -- the arrangement of its atomic scaffolding -- both on its own and when attached to a small helper molecule that facilitates its work.

Further X-ray studies at SLAC's Stanford Synchrotron Radiation Lightsource (SSRL) showed how the enzyme's structure shifted when it attached to a substrate, a kind of molecular workbench that assembles ingredients for the carbon fixing reaction and spurs the reaction along.

Finally, a team of researchers from SLAC's Linac Coherent Light Source (LCLS) carried out more detailed studies of the enzyme and its substrate at Japan's SACLA X-ray free-electron laser. The choice of an X-ray laser was important because it allowed them to study the enzyme's behavior at room temperature -- closer to its natural environment -- with almost no radiation damage.

Meanwhile, Erb's group in Germany and Associate Professor Esteban Vo?hringer-Martinez's group at the University of Concepción in Chile carried out detailed biochemical studies and extensive dynamic simulations to make sense of the structural data collected by Wakatsuki and his team.

The simulations revealed that the opening and closing of the enzyme's two parts don't just involve molecular glue, but also twisting motions around the central axis of each enzyme pair, Wakatsuki said.

"This twist is almost like a rachet that can push a finished product out or pull a new set of ingredients into the pocket where the reaction takes place," he said. Together, the twisting and synchronization of the enzyme pairs allow them to fix carbon 100 times a second.

The ECR enzyme family also includes a more versatile branch that can interact with many different kinds of biomolecules to produce a variety of products. But since they aren't held together by molecular glue, they can't coordinate their movements and therefore operate much more slowly.

"If we can increase the rate of those sophisticated reactions to make new biomolecules," Wakatsuki said, "that would be a significant jump in the field."

From static shots to fluid movies

So far the experiments have produced static snapshots of the enzyme, the reaction ingredients and the final products in various configurations.

"Our dream experiment," Wakatsuki said, "would be to combine all the ingredients as they flow into the path of the X-ray laser beam so we could watch the reaction take place in real time."

The team actually tried that at SACLA, he said, but it didn't work. "The CO2 molecules are really small, and they move so fast that it's hard to catch the moment when they attach to the substrate," he said. "Plus the X-ray laser beam is so strong that we couldn't keep the ingredients in it long enough for the reaction to take place. When we pressed hard to do this, we managed to break the crystals."

An upcoming high-energy upgrade to LCLS will likely solve that problem, he added, with pulses that arrive much more frequently -- a million times per second -- and can be individually adjusted to the ideal strength for each sample.

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