Culture

While recent advances in ancient DNA analysis have established the major patterns of prehistoric human migration in western Eurasia, the population history of eastern Eurasia remains little understood. Northern China is of particular importance, as it harboured two of the world's earliest agricultural centres for millet farming: the Yellow and West Liao River basins. Both basins are famous for their rich archaeological cultures and their influence on nearby regions. However, little is known about their genetic interactions and how these affected the dispersal of millet farming over northern China and surrounding regions.

To tackle these questions, a team of researchers from the Max Planck Institute for the Science of Human History (MPI SHH) in Germany collaborated with geneticist Prof. Dr. Yinqiu Cui and her team at the School of Life Sciences at Jilin University in China. With joint forces, they were able to sequence 55 genomes from across northern China dating between 7,500 and 1,700 years ago, covering the Yellow River, West Liao River and Amur River regions. Their results add to discussions concerning the relationship between genetic contacts and subsistence change while providing the first comprehensive genetic overview of northern China.

Correlated changes of genes and subsistence

The researchers find that, contrary to the strong genetic continuity in the Amur basin, genetic profiles in the West Liao River region substantially changed over time. Yellow River, however, showed a general genetic stability but received genetic contribution from populations related to present-day groups in southern China since the middle Neolithic.

"Although the genetic changes in each region differ in timing and intensity, each shift is correlated with changes in subsistence strategy," says lead author Chao Ning of the MPI SHH's eurasia3angle team. "As we look backwards in time, an increase of Amur River affinity in West Liao River corresponds with the inclusion of a pastoral economy during the Bronze Age, prior to that, an increased Yellow River affinity in the same region is correlated with the intensification of millet farming in the late Neolithic. Finally, our earliest results show that an affinity of Yellow River to populations from southern China (e.g. from the Yangtze River basin) since the middle Neolithic is concordant with the northward dispersal of rice farming."

Corresponding author Choongwon Jeong, formerly a geneticist on the eurasia3angle team now affiliated with Seoul National University in South Korea, puts the findings in perspective. "We realize that our current dataset needs ancient genomes from people who brought rice agriculture into northeast China, such as ancient farmers from the Shandong and Lower Yangtze River regions, but nevertheless our study is a major step forward in understanding how this region developed."

"For me, as a linguist, our findings truly are an eye-opener," says senior author Martine Robbeets, principal investigator of the eurasia3angle team. "As the West Liao River Basin is associated with the origin of the Transeurasian language family and the Yellow River Basin with the Sino-Tibetan family, our results fuel the debate on the historical correlation between archaeological cultures, languages and genes."

The halo that surrounds our own Milky Way galaxy is much hotter than scientists once believed - and it may not be unique among galaxies.

The new findings were presented at the annual meeting of the American Astronomical Society, held online this week because of the COVID-19 pandemic.

In previous work, researchers at The Ohio State University found that parts of the Milky Way's halo - the hazy fog of dust, gas and dark matter that surrounds some galaxies - was at least 10 times hotter than anyone had known before.

This new research found that the extreme temperatures the researchers found in the original analysis - up to 10 million degrees Kelvin, or about 18 million degrees Fahrenheit - could possibly be found in the entire halo, said Smita Mathur, professor of astronomy at Ohio State.

"We can't say for sure that it is everywhere, because we have not analyzed the entire halo," Mathur said. "But we know now that the temperatures we saw in the first study definitely are not unique, and that is very exciting."

Mathur, senior researcher on the trio of studies presented, said the findings could help astronomers understand more about how the Milky Way and galaxies like it form and grow.

"We are trying to learn about the elements that form these halos, and about the temperatures there," she said. "Knowing those things can help us understand more about how galaxies connect with the rest of the universe, and how they formed and where elements might have come from."

Learning more about the halo, which is the final link between a galaxy and the wider universe around it, could help researchers understand the ways a galaxy grows and changes over time.

The data they analyzed came from an X-ray observatory telescope run by the European Space Agency. That telescope, called XMM-Newton, collects data in X-rays that would have otherwise been blocked by Earth's atmosphere.

The telescope collected that data from within the Milky Way, focused in one direction.

"It showed us that the halo was much hotter than we had known, but it didn't show us whether that was the case throughout the galaxy, or if the telescope had picked up an aberration caused by an unknown force coming from the direction where the telescope was pointed," Mathur said.

Anjali Gupta, a visiting astronomy researcher at Ohio State, analyzed data from the Japanese X-ray satellite telescope Suzaku, which collected spectrum from the Milky Way's halo in four different directions. That analysis confirmed their earlier finding, that the halo is much hotter than had previously been known, and also showed that the other parts of the halo likely are that hot.

The researchers also wondered if the temperatures they found in the Milky Way's halo might be found in other galaxies.

Mathur and Sanskriti Das, a graduate student at Ohio State who co-authored the previous study about Milky Way's halo, analyzed data from a galaxy about 200 million light years away from us. That galaxy, NGC 3221, is similar to the Milky Way in shape and size. The analysis found that the halo that surrounds that galaxy is about as hot as the halo surrounding the Milky Way.

Mathur, Das and Gupta all presented about the findings in separate presentations at AAS.

Nearly a century after insulin was discovered, an international team of researchers including University of Utah Health scientists report that they have developed the world's smallest, fully functional version of the hormone, one that combines the potency of human insulin with the fast-acting potential of a venom insulin produced by predatory cone snails. The finding, based on animal studies, could jumpstart the development of insulin treatments capable of improving the lives of those with diabetes.

"We now have the capability to create a hybrid version of insulin that works in humans and that also appears to have many of the positive attributes of cone snail insulin," says Danny Hung-Chieh Chou, Ph.D, a U of U Health assistant professor of biochemistry and one of the study's corresponding authors. "That's an important step forward in our quest to make diabetes treatment safer and more effective."

The study appears in Nature Structural and Molecular Biology.

As cone snails slither across coral reefs, they are constantly on the prowl for prey. Some of these fish-hunting species, such as Conus geographus, release plumes of toxic venom that contain a unique form of insulin into the surrounding water. The insulin causes fish blood glucose levels to plummet, temporarily paralyzing them. As the fish flounders, the snail emerges from its shell to swallow the subdued victim whole.

In earlier research, Chou and colleagues discovered that this venomous insulin had many biochemical traits in common with human insulin. Plus, it appears to work faster than the swiftest-acting human insulin currently available.

Faster-acting insulin would diminish the risk of hyperglycemia and other serious complications of diabetes, says Helena Safavi, Ph.D., a study co-author and an assistant professor of biomedical sciences at the University of Copenhagen in Denmark. It also could improve the performance of insulin pumps or artificial pancreas devices, which automatically release insulin into the body as needed. "We want to help people with diabetes to more tightly and rapidly control their blood sugar," she says.

In pursuit of their goal, the researchers found that insulin derived from cone snail venom lacks a "hinge" component that causes human insulin to aggregate or clump together so it can be stored in the pancreas. These aggregates must break up into individual molecules before they can begin to work on blood sugar, a process that can take up to an hour. Since cone snail insulin doesn't aggregate, it is in essence primed and ready to work on the body's biochemical machinery almost immediately.

Intrigued, the researchers began to investigate ways to transform the insulin that cone snails use as a weapon into a different form: one that people who have Type-1 diabetes could use to rapidly restore equilibrium in their bodies.

"We had the idea of making human insulin more snail-like," says Safavi, who is also an adjunct professor of biochemistry at U of U Health. "So, we sought to basically take some of the advantageous properties from the snail and graft them onto the human compound."

The researchers thought this was possible because cone snail insulin essentially has the same basic structure or "backbone" as human insulin. However, they faced a dilemma: the snail's insulin is far less potent than human insulin. In fact, the researchers suspect that humans would require 20 to 30 times more of the cone snail insulin to lower their blood sugar levels.

In this new study, Chou and colleagues sought to overcome these problems. First, they used structural biology and medicinal chemistry techniques to isolate four amino acids that help the snail insulin bind to the insulin receptor. Then, they created a truncated version of a human insulin molecule without the region responsible for clumping.

The team integrated modified versions of these amino acids into the human molecule in hopes of creating a hybrid that does not clump and binds the human insulin receptor with high potency.

In tests with laboratory rats, this hybrid insulin molecule, which the scientists call "mini-insulin," interacted with insulin receptors in ways that cone snail insulin doesn't. These new interactions bound mini-insulin to insulin receptors in the rat's body just as strongly as normal human insulin would. As a result, mini-insulin had the same potency as human insulin but acted faster.

"Mini-insulin has tremendous potential," Chou says. "With just a few strategic substitutions, we have generated a potent, fast-acting molecular structure that is the smallest, fully active insulin to date. Because it is so small, it should be easy to synthesize, making it a prime candidate for the development of a new generation of insulin therapeutics."

CAMBRIDGE, MA -- Inspired by the Japanese art of paper cutting, MIT engineers have designed a friction-boosting material that could be used to coat the bottom of your shoes, giving them a stronger grip on ice and other slippery surfaces.

The researchers drew on kirigami, a variation of origami that involves cutting paper as well as folding it, to create the new coating. Laboratory tests showed that when people wearing kirigami-coated shoes walked on an icy surface, they generated more friction than the uncoated shoes.

Incorporating this coating into shoes could help prevent dangerous falls on ice and other hazardous surfaces, especially among the elderly, the researchers say.

"Through this work we set out to address the challenge of preventing falls, particularly on icy, slippery surfaces, and developed a kirigami-based system that facilitates an increase of friction with a surface," says Giovanni Traverso, an MIT assistant professor of mechanical engineering, a gastroenterologist at Brigham and Women's Hospital, and an assistant professor at Harvard Medical School.

Traverso and Katia Bertoldi, a professor of applied mechanics at Harvard University, are the senior authors of the study, which appears today in Nature Biomedical Engineering. MIT Research Scientist Sahab Babaee is the lead author of the paper, along with Simo Pajovic, an MIT graduate student, and Ahmad Rafsanjani, a former postdoc at Harvard University.

Inspired by art

Kirigami is an art form that involves cutting intricate patterns into sheets of paper and then folding them to create three-dimensional structures. Recently, some scientists have used this technique to develop new materials such as bandages that stick more securely to knees and other joints, and sensors that can be used to coat the skin of soft robots and help them orient themselves in space.

In this case, the team applied this approach to create intricate patterns of spikes in a sheet of plastic or metal. These sheets, applied to the sole of a shoe, remain flat while the wearer is standing, but the spikes pop out during the natural movement of walking.

"The novelty of this type of surface is that we have a shape transition from a 2D flat surface to a 3D geometry with needles that come out," Babaee says. "You can use those elements to control friction, because the sharp needles can pop in and out based on the stretch that you apply."

The researchers created and tested several different designs, including repeating patterns of spikes shaped like squares, triangles, or curves. For each shape, they also tested different sizes and arrangements, and they cut the patterns into both plastic sheets and stainless steel. For each of the designs, they measured the stiffness and the angle at which the spikes pop out when the material is stretched.

They also measured the friction generated by each design on a variety of surfaces, including ice, wood, vinyl flooring, and artificial turf. They found that all of the designs boosted friction, with the best results produced by a pattern of concave curves.

The researchers then used the concave curve coatings for tests with human volunteers. They attached the coatings to a variety of types of shoes, including sneakers and winter boots, and measured the friction produced when subjects walked across a force plate -- an instrument that measures the forces exerted on the ground -- covered with a 1-inch-thick layer of ice.

They found that with the kirigami coatings attached, the amount of friction generated was 20 to 35 percent higher than the friction generated by the shoes alone.

Preventing falls

The researchers are now working on determining the best way to attach and incorporate the kirigami surfaces. They are considering embedding them into the soles or designing them as a separate element that could be attached when needed. They are also exploring the possibility of using different materials, such as a rubber-like polymer with a reinforced steel tip.

While the researchers' original motivation was preventing slips on icy surfaces, they expect that this kind of shoe grip could also be useful in other settings, such as wet or oily working environments.

"We're looking at potential routes to commercialize the system, as well as further development of the system through different use cases," Traverso says.

Astronomers using European Southern Observatory (ESO) telescopes have discovered giant spots on the surface of extremely hot stars hidden in stellar clusters. Not only are these stars plagued by magnetic spots, some also experience superflare events, explosions of energy several million times more energetic than similar eruptions on the Sun. The findings, published today in Nature Astronomy, help astronomers better understand these puzzling stars and open doors to resolving other elusive mysteries of stellar astronomy.

The team, led by Yazan Momany from the INAF Astronomical Observatory of Padua in Italy, looked at a particular type of star known as extreme horizontal branch stars -- objects with about half the mass of the Sun but four to five times hotter. "These hot and small stars are special because we know they will bypass one of the final phases in the life of a typical star and will die prematurely," says Momany, who was previously a staff astronomer at ESO's Paranal Observatory in Chile. "In our Galaxy, these peculiar hot objects are generally associated with the presence of a close companion star."

Surprisingly, however, the vast majority of these extreme horizontal branch stars, when observed in tightly packed stellar groups called globular clusters, do not appear to have companions. The team's long-term monitoring of these stars, made with ESO telescopes, also revealed that there was something more to these mysterious objects. When looking at three different globular clusters, Momany and his colleagues found that many of the extreme horizontal branch stars within them showed regular changes in their brightness over the course of just a few days to several weeks.

"After eliminating all other scenarios, there was only one remaining possibility to explain their observed brightness variations," concludes Simone Zaggia, a study co-author from the INAF Astronomical Observatory of Padua in Italy and a former ESO Fellow: "these stars must be plagued by spots!"

Spots on extreme horizontal branch stars appear to be quite different from the dark sunspots on our own Sun, but both are caused by magnetic fields. The spots on these hot, extreme stars are brighter and hotter than the surrounding stellar surface, unlike on the Sun where we see spots as dark stains on the solar surface that are cooler than their surroundings. The spots on extreme horizontal branch stars are also significantly larger than sunspots, covering up to a quarter of the star's surface. These spots are incredibly persistent, lasting for decades, while individual sunspots are temporary, lasting only a few days to months. As the hot stars rotate, the spots on the surface come and go, causing the visible changes in brightness.

Beyond the variations in brightness due to spots, the team also discovered a couple of extreme horizontal branch stars that showed superflares -- sudden explosions of energy and another signpost of the presence of a magnetic field. "They are similar to the flares we see on our own Sun, but ten million times more energetic," says study co-author Henri Boffin, an astronomer at ESO's headquarters in Germany. "Such behaviour was certainly not expected and highlights the importance of magnetic fields in explaining the properties of these stars."

After six decades of trying to understand extreme horizontal branch stars, astronomers now have a more complete picture of them. Moreover, this finding could help explain the origin of strong magnetic fields in many white dwarfs, objects that represent the final stage in the life of Sun-like stars and show similarities to extreme horizontal branch stars. "The bigger picture though," says team member, David Jones, a former ESO Fellow now at the Instituto de Astrofísica de Canarias, Spain, "is that changes in brightness of all hot stars -- from young Sun-like stars to old extreme horizontal branch stars and long-dead white dwarfs -- could all be connected. These objects can thus be understood as collectively suffering from magnetic spots on their surfaces."

We are free to wander but usually when we go somewhere it's for a reason. In a new study, researchers at The Picower Institute for Learning and Memory show that as we pursue life's prizes a region of the brain tracks our location with an especially strong predilection for the location of the reward. This pragmatic bias of the lateral septum suggests it's a linchpin in formulating goal-directed behavior.

"It appears that the lateral septum is, in a sense, 'prioritizing' reward-related spatial information," said Hannah Wirtshafter, lead author of the study in eLife and a former graduate student in the MIT lab of senior author Matthew Wilson, Sherman Fairchild Professor of Neurobiology. Wirtshafter is now a postdoc at Northwestern University.

Last year, Wirtshafter and Wilson, a professor of biology and of brain and cognitive sciences, analyzed measurements of the electrical activity of hundreds of neurons in the LS and the hippocampus, a region known for encoding many forms of memory including spatial maps, as rats navigated a maze toward a reward. In Current Biology they reported that the LS directly encodes information about the speed and acceleration of the rats as they navigated through the environment.

The new study continued this analysis, finding that while the LS dedicates a much smaller proportion of its cells to encoding location than does the hippocampus, a much larger proportion of those cells respond when the rat is proximate to where the reward lies. Moreover, as rats scurried toward the reward point and back again within the H-shaped maze, the pace of their neural activity peaked closest to those reward locations, skewing the curve of their activity in association with where they could find a chocolate treat. Finally, they found that neural activity between the hippocampus and the LS was most highly correlated among cells that represented reward locations.

"Understanding how reward information is linked to memory and space through the hippocampus is crucial for our understanding of how we learn from experience, and this finding points to the role the lateral septum may play in that process," Wilson said.

Specifically, Wilson and Wirtshafter interpret the results of the two studies to suggest that the LS plays a key role in helping to filter and convert raw information about location, speed and acceleration coming in from regions such as the hippocampus, into more reward-specific output for regions known to guide goal-directed behavior, such as the ventral tegmental area. In the paper they discuss ways in which the hippocampus and the LS might be wired together to do so. They theorize that the LS may dedicate neurons to receiving reward-related location information from the hippocampus and may blend non-reward location information within neurons also tasked for processing other information such as motion.

"This is supported by our previous work that shows somewhat overlapping populations of place-encoding and movement-encoding LS cells," Wirtshafter said.

Though it's easy for most of us to take the brain's ability to facilitate navigation for granted, scientists study it for several reasons, Wirtshafter said.

"Elucidating brain mechanisms and circuits involved in navigation, memory and planning may identify processes underlying impaired cognitive function in motor and memory diseases," she said. "Additionally, knowledge of the principles of goal directed behavior can also be used to model context-dependent brain behavior in machine models to further contribute to artificial intelligence development."

Maunakea, Hawaii - Determined to find a needle in a cosmic haystack, a pair of astronomers time traveled through archives of old data from W. M. Keck Observatory on Mauankea in Hawaii and old X-ray data from NASA's Chandra X-ray Observatory to unlock a mystery surrounding a bright, lensed, heavily obscured quasar.

This celestial object, which is an active galaxy emitting enormous amounts of energy due to a black hole devouring material, is an exciting object in itself. Finding one that is gravitationally lensed, making it appear brighter and larger, is exceptionally exciting. While slightly over 200 lensed unobscured quasars are currently known, the number of lensed obscured quasars discovered is in the single digits. This is because the feeding black hole stirs up gas and dust, cloaking the quasar and making it difficult to detect in visible light surveys.

Not only did the researchers uncover a quasar of this type, they found the object happens to be the first discovered Einstein ring, named MG 1131+0456, which was observed in 1987 with the Very Large Array network of radio telescopes in New Mexico. Remarkably, though widely studied, the quasar's distance or redshift remained a question mark.

"As we dug deeper, we were surprised that such a famous and bright source never had a distance measured for it," said Daniel Stern, senior research scientist at NASA's Jet Propulsion Laboratory and author of the study. "Having a distance is a necessary first step for all sorts of additional studies, such as using the lens as a tool to measure the expansion history of the universe and as a probe for dark matter."

Stern and co-author Dominic Walton, an STFC Ernest Rutherford Fellow at the University of Cambridge's Institute of Astronomy (UK), are the first to calculate the quasar's distance, which is 10 billion light-years away (or a redshift of z = 1.849).

The result is published in today's issue of The Astrophysical Journal Letters.

"This whole paper was a bit nostalgic for me, making me look at papers from the early days of my career, when I was still in graduate school. The Berlin Wall was still up when this Einstein ring was first discovered, and all the data presented in our paper are from the last millennium," said Stern.

METHODOLOGY

At the time of their research, telescopes around the planet were shuttered due to the coronavirus pandemic (Keck Observatory has since reopened as of May 16); Stern and Walton took advantage of their extended time at home to creatively keep science going by combing through data from NASA's Wide-field Infrared Survey Explorer (WISE) to search for gravitationally lensed, heavily obscured quasars. While dust hides most active galaxies in visible light surveys, that obscuring dust makes such sources very bright in infrared surveys, such as provided by WISE.

Though quasars are often extremely far away, astronomers can detect them through gravitational lensing, a phenomenon that acts as nature's magnifying glass. This occurs when a galaxy closer to Earth acts as a lens and makes the quasar behind it look extra bright. The gravitational field of the closer galaxy warps space itself, bending and amplifying the light of the quasar in the background. If the alignment is just right, this creates a circle of light called an Einstein ring, predicted by Albert Einstein in 1936.  More typically, gravitationally lensing will cause multiple images of the background object to appear around the foreground object.

Once Stern and Walton rediscovered MG 1131+0456 with WISE and realized its distance remained a mystery, they meticulously combed through old data from the Keck Observatory Archive (KOA) and found the Observatory observed the quasar seven times between 1997 and 2007 using the Low Resolution Imaging Spectrometer (LRIS) on the Keck I telescope, as well as the Near-Infrared Spectrograph (NIRSPEC) and the Echellette Spectrograph and Imager (ESI) on the Keck II telescope.

"We were able to extract the distance from Keck's earliest data set, taken in March of 1997, in the early years of the observatory," said Walton. "We are grateful to Keck and NASA for their collaborative efforts to make more than 25 years of Keck data publicly available to the world. Our paper would not have been possible without that."

The team also analyzed NASA's archival data from the Chandra X-ray Observatory in 2000, in the first year after the mission launched.

NEXT STEPS

With MG 1131+0456's distance now known, Walton and Stern were able to determine the mass of the lensed galaxy with exquisite precision and use the Chandra data to robustly confirm the obscured nature of the quasar, accurately determining how much intervening gas lies between us and its luminous central regions.

"We can now fully describe the unique, fortuitous geometry of this Einstein ring," said Stern. "This allows us to craft follow-up studies, such as using the soon-to-launch James Webb Space Telescope to study the dark matter properties of the lensing galaxy."

"Our next step is to find lensed quasars that are even more heavily obscured than MG 1131+0456," said Walton. "Finding those needles is going to be even harder, but they're out there waiting to be discovered. These cosmic gems can give us a deeper understanding of the universe, including further insight into how supermassive black holes grow and influence their surroundings," says Walton.

Ben-Gurion University Researchers Control Cattle Microbiomes to Produce Less Methane and Reduce Greenhouse Gases

BEER-SHEVA, Israel, June 1, 2020 - Ben-Gurion University of the Negev (BGU) researchers have learned to control the microbiome of cattle for the first time which could inhibit their methane production, and therefore reduce a major source of greenhouse gasses.

The findings from Prof. Itzhak Mizrahi's findings were published recently in Nature Communications. Prof. Mizrahi is a member of the Department of Life Sciences in the Faculty of Natural Sciences and the National Institute for Biotechnology in the Negev (NIBN).

The animal microbiome is a scientifically unexplored area. It protects against germs, breaks down food to release energy, and produces vitamins and exerts great control over many aspects of animal and human physical systems. Microbes are introduced at birth and produce a unique microbiome that evolves over time.

Mizrahi and his group have been conducting a three-year experiment with 50 cows divided into two groups. One group gave birth naturally, and the other through cesarean section. That difference was enough to change microbiome development and composition microbiome of the cows from each group.

This finding enabled Mizrahi's team together with Prof. Eran Halperin's group at UCLA to develop an algorithm that predicts the microbiome development and how it will evolve over time based on its present composition.

"Now that we know we can influence the microbiome development, we can use this knowledge to modulate microbiome composition to lower the environmental impact of methane from cows by guiding them to our desired outcomes," Mizrahi says.

Prof. Mizrahi has investigated the microbiome of cows, fish and other species to address world issues shaped by climate change. Reducing methane emissions from cows will reduce global warming. Engineering healthier fish, which is another of Mizrahi's projects, is especially important as the oceans empty of fish and aquaculture becomes the major source of seafood.

Major climate changes leading to great fluctuations in sea levels took place during the Quaternary period 2.58 million years ago. The sea receded during the glaciations, because the water ended up stored in huge ice masses; when the ice melted, the sea levels rose. So "in this work we analysed the rocky undersea coastal platforms formed throughout the period: the situation of all these terraces, their morphology, etc. Analysing these morphologies means studying the formation of this underwater landscape throughout the Quaternary, the main result of the change in sea levels and rise of the earth's crust", explained Peru Bilbao-Lasa, researcher in the UPV/EHU's Department of Mineralogy and Petrology.

"The rocky platforms are flat surfaces produced by swell waves. Just like sandpaper, they erode the seabed so flat surfaces are gradually formed, like the ones we can see today in the Basque Coast Geopark. These surfaces can also be found under the sea," confirmed the UPV/EHU researcher.

The researchers used an advanced technology to analyse all this; bathymetry enabled them to produce 3D maps of the sea bed to show what this hidden relief looks like.

In the studies conducted in the Bay of Biscay the researchers drew some important conclusions: new, rocky, submerged coastal platforms that had not been predefined and were irregularly distributed along the continental platform were defined. Six of them were found to be better defined. What is more, it was realised that some of them had not been formed since the most recent glaciation but prior to it. However, "we did not manage to associate the appearance of these rocky, underwater platforms with a single variable. Otherwise, the creation and degree of preservation of these surfaces appears to depend on the interaction among variables, such as wave climatology, lithography and direction of the sea bed, which would act simultaneously", said Bilbao.

A few minutes into the life of the universe, colliding emissions of light energy created the first particles of matter and antimatter. We are familiar with the reverse process—matter generating energy—which occurs in an atomic bomb, for example, but it has been difficult to recreate that critical transformation of light into matter.

Now, a new set of simulations by a research team led by UC San Diego's Alexey Arefiev point the way toward making matter from light. The process starts by aiming a high-power laser at a target to generate a magnetic field as strong as that of a neutron star. This field generates gamma ray emissions that collide to produce--for the very briefest instant--pairs of matter and antimatter particles.

The study published May 11 in Physical Review Applied offers a sort of recipe that experimentalists at the Extreme Light Infrastructure (ELI) high-power laser facilities in Eastern Europe could follow to produce real results in one to two years, said Arefiev, an associate professor of mechanical and aerospace engineering.

"Our results put scientists in a position to probe, for the first time, one of the fundamental processes in the universe," he said.

Harnessing high power

Arefiev, Ph.D. student Tao Wang and their colleagues at the Relativistic Laser-Plasma Simulation Group have been working for years on ways to create intense, directed beams of energy and radiation, work that is supported in part by the National Science Foundation and Air Force Office of Science Research. One way to accomplish this, they noted, would be to aim a high-power laser at a target to create a very strong magnetic field that would throw off intense energy emissions.

High-intensity, ultra-short laser pulses aimed at a dense target can render the target "relativistically transparent," as the electrons in the laser move at a velocity very close to the speed of light and effectively become heavier, Arefiev explained. This keeps the laser's electrons from moving to shield the target from the laser's light. As the laser pushes past these electrons, it generates a magnetic field as strong as the pull on the surface of a neutron star--100 million times stronger than Earth's magnetic field.

To say this all happens in the blink of an eye is a vast overstatement. The magnetic field exists for 100 femtoseconds. (A femtosecond is 10-15 of a second--a quadrillionth of a second.) But "from the point of the view of the laser, the field is quasi-static," said Arefiev. "Then again, from the point of view of the laser, our lives are probably longer than the life of the universe."

A high-power laser in this instance is one in the multi-petawatt range. A petawatt is a million billion watts. For comparison, the Sun delivers about 174 petawatts of solar radiation to the Earth's entire upper atmosphere. A laser pointer delivers about 0.005 watt to a Power Point slide.

Previous simulations suggested that the laser in question would have to be high powered and aimed at a tiny spot to produce the required intensity to create a strong enough magnetic field. The new simulations suggest that by increasing the size of the focal spot and boosting the laser power to around 4 petawatts, the laser's intensity could remain fixed and still create the strong magnetic field.

Under these conditions, the simulations show, the laser-accelerated electrons of the magnetic field spur the emission of high-energy gamma rays.

"We did not expect that we didn't need to go to a crazy intensity, that it's just sufficient to increase the power and you can get to very interesting things," said Arefiev.

Particle pairs

One of those interesting things is the production of electron-positron pairs--paired particles of matter and antimatter. These particles can be produced by colliding two gamma-ray beams or colliding one gamma-ray beam with blackbody radiation, an object that absorbs all radiation falling on it. The method produces a lot of them--tens to hundreds of thousands of pairs born out of one collision.

Scientists have performed the light-into-matter feat before, notably in one 1997 Stanford experiment, but that method required an extra stream of high-energy electrons, while the new method "is only light used to produce matter," said Arefiev. He also noted that the Stanford experiment "would produce one particle pair about every 100 shots."

An experiment that uses only light to create matter more closely mimics conditions during the first minutes of the universe, offering an improved model for researchers looking to learn more about this critical time period. The experiment could also provide more chances to study antimatter particles, which remain a mysterious part of the universe's composition. For instance, scientists are curious to learn more about why the universe appears to have more matter than antimatter, when the two should exist in equal amounts.

Arefiev and his colleagues were encouraged to do these simulations now because the laser facilities capable of carrying out the actual experiments are now available. "We specifically did the calculations for the lasers that have not been available until recently, but now should be available at these laser facilities," he said.

In an odd twist, the simulations proposed by the research team could also help the ELI scientists determine whether their lasers are as intense as they think they are. Firing a laser in the multi-petawatt range at a target only five microns in diameter "destroys everything," said Arefiev. "You shoot and it's gone, nothing is recoverable, and you can't actually measure the peak intensity that you produce."

But if the experiments produce gamma rays and particle pairs as predicted, "this will be a validation that the laser technology can reach such a high intensity," he added.

Last year, the UC San Diego researchers received a U.S. National Science Foundation grant that allows them to partner with ELI researchers to carry out these experiments. This partnership is critical, Arefiev said, because there are no facilities in the United States with powerful enough lasers, despite a 2018 report from the National Academies of Sciences warning that the U.S. has lost its edge in investing in intense ultrafast laser technology.

Arefiev said the ELI laser facilities will be ready to test their simulations in a couple years. "This is the reason why we wrote this paper, because the laser is operational, so we are not that far away from actually doing this," he said. "With science, that is what attracts me. Seeing is believing."

A new study reveals the diets of reef fish dictate how fast different species evolve. The breakthrough adds another piece to the fascinating evolutionary puzzle of coral reefs and the fishes that live on them.

"Up until now we knew that many factors could have influenced the pace of reef fish evolution, but these factors were never examined altogether," said Alexandre Siqueira, the study's lead author from the ARC Centre of Excellence for Coral Reef Studies at James Cook University (Coral CoE at JCU).

"By building an evolutionary 'tree of life' for nearly all fishes associated with reefs, we were able to examine the variation in rates of species formation and ask what drives it," said co-author Dr Peter Cowman, also from Coral CoE at JCU.

The 'tree of life' contains more than 6,000 fish species that live on coral reefs across the globe. Ecological and geographical data--such as diet and geographical range--were also gathered for the majority of these species.

The authors were surprised to find that what really matters in reef fish evolution isn't geography, but what fish eat and how big they get.

"We found that the fastest way to have more species, or biodiversity, on a reef is to be big and vegetarian," said co-author Professor David Bellwood, also from Coral CoE at JCU.

"Herbivores, such as surgeonfishes and parrotfishes, are key to the ecological diversity of coral reefs today."

The study suggests these fishes also made way for today's coral reefs to evolve and flourish.

"By feeding on the algae that compete with corals, herbivorous fishes may have also helped corals to expand through time," Mr Siqueira said.

"In turn, this expansion in the corals allowed the diversification of other reef fish groups that depend on them."

And these herbivorous fishes--big and small--still maintain coral reefs to this day.

The study offers a new way of looking at reefs with a functional, rather than taxonomic, approach. Very little is known about the functional evolution of reefs: what they do and how they work. Scientists previously only looked at how many reefs there were and what species were present.

"In this study it was important to understand the origins of the functional role a fish species plays on a reef--not just the species itself," Dr Cowman said.

Today's coral reefs differ from their early counterparts. It was only during the Miocene, less than 23 million years ago, that herbivorous fish species developed features that allowed them to explore different areas of the reef.

"Because of this, today's reefs are highly dynamic and have a fast turnover. These herbivores are the key element that established modern coral reefs," Prof Bellwood said.

"Understanding how reefs are constructed throughout their evolution means we can reach a better understanding of the fundamental processes that maintain them in a healthy state today," Mr Siqueira said.

Georg Winter's lab at CeMM uses chemical tools to understand the molecular basis of gene control and aberrations thereof in cancer. To do so, the team combines particularly fast-acting protein ablation systems ("degradation Tag"/ "dTAG", co-developed by Georg Winter in Jay Bradner's lab at the Dana Farber Cancer Institute, in Boston) with precise and unbiased measurements of gene activity at high kinetic resolution. Together with Patrick Cramer's lab and others, the international team of scientists now unveiled how the Mediator molecular machine mechanistically directs gene activation, which had long remained poorly understood owing to challenges in experimental manipulation.

Mediator was identified over 30 years ago as a molecular bridge that allows DNA-binding proteins, called transcription factors, to communicate with the cellular gene-copying machine, called RNA polymerase II (Pol II), to activate target genes. Understanding the direct role of Mediator in this process requires technologies that rapidly block Mediator function and measure changes in Pol II activity within the subsequent minutes. Using targeted protein degradation, scientists in the Winter lab now managed to rapidly remove individual parts of the Mediator complex to ask the question, whether the copying of all human genes depends to the same extent on Mediator integrity. In contrast to the existing paradigm, the study first-authored by CeMM PhD student Martin Jaeger suggests that Mediator is not generally required for transcription of all genes. Rather, the data imply that Mediator selectively safeguards the expression of a small set of genes, which form densely connected regulatory circuits to instruct cell-type-specific functions.

By visualizing Pol II enzymes in cells, the scientists observed that Mediator nucleates large clusters of transcription machinery components that are thought to form around regulatory DNA regions, called super-enhancers. These super-enhancers direct the expression of cell-type-specific genes by physically touching their target genes, which are often millions of DNA bases away. When Mediator was degraded, the large Pol II clusters rapidly disappeared, but super-enhancers still seemed to touch their target genes, indicating that Mediator was not required to maintain these DNA contacts.

Together with experts from the Cramer lab in Goettingen, however, the team observed dramatic changes in the dynamics of Pol II turnover at super-enhancer-driven genes after Mediator loss. The data suggested that Mediator clusters drove highly efficient recruitment of Pol II enzymes to these cell-type-specific genes, allowing their copying at remarkable efficiency. At the same time, the majority of other genes seemed to be surprisingly mildly affected by acute Mediator loss, which made the scientists suspect that they undergo some unexpected type of compensatory boost.

The team went on to address this compensatory mechanism, and found that promoter-proximal pausing of Pol II was globally reduced in response to Mediator loss. Pausing is a phenomenon, where Pol II enzymes are held back for several minutes right after they started copying a gene. The waiting Pol II constitutes a roadblock that prevents the passing of other Pol II enzymes behind it, thus limiting the number of RNA copies produced in a given timespan. After Mediator degradation, the scientists observed that the main factor responsible for signaling pause release, called cyclin dependent kinase 9 (CDK9), more efficiently bound to DNA in cells and more actively tagged its protein targets with a phosphate group. Chemically blocking CDK9 activity made the transcriptional defects of Mediator ablation less selective for super-enhancer target genes, which highlights that the uncovered CDK9 activation shapes how cells react to acute Mediator loss. This unexpected finding suggested that pausing may have evolved as a buffering capacity to rapidly react to and partially compensate acute defects in Pol II recruitment.

The study opens up new avenues to understand the composition of Mediator-nucleated Pol II clusters and how CDK9 is so efficiently activated in response to transcriptional stresses. Furthermore, Georg Winter imagines future possibilities to perhaps tackle diseases, where Mediator function went awry: "Very preliminarily, our work might also have revealed some potential for Mediator as a drug target and next steps might be to develop direct degrader molecules against this complex."

Employers across the UK could face legal action from employees who return to work and contract the COVID-19 virus, a leading health and safety expert has warned.

Professor Andrew Watterson, of the University of Stirling, has questioned whether adequate procedures and resources are in place to identify and investigate all work-related illnesses and deaths linked to the virus, specifically in non-health or social care settings.

In such cases, employees and their families may not have the COVID-19 link recognised or compensated - which could, in turn, lead to civil court action, he explained.

The expert in occupational and environmental health believes further evidence and clarity is required on exactly how the 'test, trace and isolate' approach will protect workers - especially when untested workers may be asymptomatic - and he also reemphasised the "critical" importance of the use of appropriate personal protective equipment and two-metre social distancing.

Professor Watterson's concerns are outlined in a new paper published in peer-reviewed journal New Solutions and in a separate letter, published as a BMJ Rapid Response. The publications - based on policy analysis and data - suggest that science has been "ignored" at times and also highlight a lack of research on the impact and potential impact of the virus on many workers who are not employed in health or social care - such as those working in shops, construction, food processing, transport and small businesses. He said it was critical for employers and regulators to engage with workers and their representatives on health and safety issues linked to the virus.

Professor Watterson said: "Employers have a duty to report occupational diseases. However, COVID-19 is not yet classified as an occupational disease under the Prescribed Industrial Diseases scheme, which would generate workers' compensation. Under current legislation, incidents where a worker is exposed, or possibly exposed, to COVID-19 is reported to the Health and Safety Executive under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 2013.

"There are concerns that occupational COVID-19 cases will not be reported, and those that are may not be fully investigated, recognised or compensated for.

"At a later date, there could be civil actions in the courts by employees who contracted the virus at work, or by their families, if fatalities occurred."

The New Solutions paper cites previous research on COVID-19 transmission routes, especially relating to airborne as well as droplet transmission - the touching of contaminated surfaces, viral aerosolization in a confined space, and contact with asymptomatic infected people - and states: "Knowledge of these routes should have informed decisions weeks ago in the UK about occupational health and safety precautions, availability of sanitisers, what personal protective equipment was needed, by whom and in what settings."

Professor Watterson said a continued lack of planning was responsible for the threat posed by COVID-19 to workplace health and safety in the UK.

He added: "A catalogue has emerged in the UK of missed opportunities and failures by various government bodies, agencies and organisations, and employers to plan for the pandemic and to equip staff with the necessary health and safety equipment and procedures to protect themselves and the public from COVID-19. In contrast, UK trade unions and non-governmental organisations issued early warnings of a pandemic - and offered important guidance on solutions to mitigate its impact on workers and, hence, wider society.

"Prior to the pandemic, the Health and Safety Executive and other regulators in local authorities should have been checking pandemic health and safety planning, and the availability and capability of appropriate personal protective equipment for health and social care workers, as well as those employed in shops, warehouses, transport and other workplaces. It is not clear from information in the public domain that they did so."

In the BMJ Rapid Response letter, Professor Watterson highlights that workplace exposure to COVID-19 has occurred in four waves: with frontline healthcare workers in the first; social care workers in the second; key workers - such as transport and service sector staff - in the third; and, now, construction workers in the fourth.

He said: "COVID-19 has emerged in a very short period of time as an 'occupational disease' but gaining official recognition and establishing workplace exposures as its cause may well still prove highly problematic. The task may be easier for healthcare workers than other occupational groups. For that reason, it is critical that the health and safety need of the third and fourth waves of exposed workers are addressed and appropriate preventative action taken, supported by the necessary research."

It is widely acknowledged that the process of HIV-1 infecting cells undergoes the following steps: membrane fusion, viral core release, reverse transcription, capsid disassembly in cytoplasm, nuclear entry of the viral genome, and viral genome integration, followed by reproducing themselves using the host cell system. However, recent studies have found that viral capsid also exist in the nucleus, and play functions such as integration site selection and immune escape. The latest report proves that the HIV-1 viral capsid uncoated near the site of chromosome integration. Considering that the size of the virus carrying the capsid is much larger than the nuclear pores, how the viral cores pass through the nuclear membrane barrier remains mysterious.

In response to this puzzle concerning, selected components of HIV-1 and the host cells are differentially labelled so that the Virus-host cell interaction can be dynamically tracked. It was found that after entering the cell, the viral particles moved along the microtubules and selectively gathered at the microtubule organization center (MTOC), leading the nearby nuclear envelope (NE) to undergo deformation, invagination and restoration to form a nuclear vesicle in which the viral particles were wrapped; then, the inner membrane of the nuclear vesicle ruptured to release HIV-1 into the nucleus. This phenomenon is similar to cell endocytosis and therefore called the "nuclear endocytosis-like pathway". Factors involving in the process were preliminarily investigated. This discovery expands our understanding of the complexity of HIV-1 nuclear entry, which may provide new insights to HIV-1 virology. The molecular details and viral biology of the mechanism need further elucidation.

A Finnish research group has found strong evidence for the presence of exotic quark matter inside the cores of the largest neutron stars in existence. The conclusion was reached by combining recent results from theoretical particle and nuclear physics to measurements of gravitational waves from neutron star collisions.

All normal matter surrounding us is composed of atoms, whose dense nuclei, comprising protons and neutrons, are surrounded by negatively charged electrons. Inside what are called neutron stars, atomic matter is, however, known to collapse into immensely dense nuclear matter, in which the neutrons and protons are packed together so tightly that the entire star can be considered one single enormous nucleus.

Up until now, it has remained unclear whether inside the cores of the most massive neutron stars nuclear matter collapses into an even more exotic state called quark matter, in which the nuclei themselves no longer exist. Researchers from the University of Helsinki now claim that the answer to this question is yes. The new results were published in the prestigious journal Nature Physics.

"Confirming the existence of quark cores inside neutron stars has been one of the most important goals of neutron star physics ever since this possibility was first entertained roughly 40 years ago," says Associate Professor Aleksi Vuorinen from the University of Helsinki's Department of Physics.

Existence very likely

With even large-scale simulations run on supercomputers unable to determine the fate of nuclear matter inside neutron stars, the Finnish research group proposed a new approach to the problem. They realised that by combining recent findings from theoretical particle and nuclear physics with astrophysical measurements, it might be possible to deduce the characteristics and identity of matter residing inside neutron stars.

In addition to Vuorinen, the group includes doctoral student Eemeli Annala from Helsinki, as well as their colleagues Tyler Gorda from the University of Virginia, Aleksi Kurkela from CERN, and Joonas Nättilä from Columbia University.

According to the study, matter residing inside the cores of the most massive stable neutron stars bears a much closer resemblance to quark matter than to ordinary nuclear matter. The calculations indicate that in these stars the diameter of the core identified as quark matter can exceed half of that of the entire neutron star. However, Vuorinen points out that there are still many uncertainties associated with the exact structure of neutron stars. What does it mean to claim that quark matter has almost certainly been discovered?

"There is still a small but nonzero chance that all neutron stars are composed of nuclear matter alone. What we have been able to do, however, is quantify what this scenario would require. In short, the behaviour of dense nuclear matter would then need to be truly peculiar. For instance, the speed of sound would need to reach almost that of light," Vuorinen explains.

Radius determination from gravitational wave observations

A key factor contributing to the new findings was the emergence of two recent results in observational astrophysics: the measurement of gravitational waves from a neutron star merger and the detection of very massive neutron stars, with masses close to two solar masses.

In the autumn of 2017, the LIGO and Virgo observatories detected, for the first time, gravitational waves generated by two merging neutron stars. This observation set a rigorous upper limit for a quantity called tidal deformability, which measures the susceptibility of an orbiting star's structure to the gravitational field of its companion. This result was subsequently used to derive an upper limit for the radii of the colliding neutron stars, which turned out to be roughly 13 km.

Similarly, while the first observation of a neutron star dates back all the way to 1967, accurate mass measurements of these stars have only been possible for the past 20 years or so. Most stars with accurately known masses fall inside a window of between 1 and 1.7 stellar masses, but the past decade has witnessed the detection of three stars either reaching or possibly even slightly exceeding the two-solar-mass limit.

Further observations expected

Somewhat counterintuitively, information about neutron star radii and masses has already considerably reduced the uncertainties associated with the thermodynamic properties of neutron star matter. This has also enabled completing the analysis presented by the Finnish research group in their Nature Physics article.

In the new analysis, the astrophysical observations were combined with state-of-the-art theoretical results from particle and nuclear physics. This enabled deriving an accurate prediction for what is known as the equation of state of neutron star matter, which refers to the relation between its pressure and energy density. An integral component in this process was a well-known result from general relativity, which relates the equation of state to a relation between the possible values of neutron star radii and masses.

Since the autumn of 2017, a number of new neutron star mergers have been observed, and LIGO and Virgo have quickly become an integral part of neutron star research. It is precisely this rapid accumulation of new observational information that plays a key role in improving the accuracy of the new findings of the Finnish research group, and in confirming the existence of quark matter inside neutron stars. With further observations expected in the near future, the uncertainties associated with the new results will also automatically decrease.

"There is reason to believe that the golden age of gravitational wave astrophysics is just beginning, and that we will shortly witness many more leaps like this in our understanding of nature," Vuorinen rejoices.