Culture

Phytophthora infestans is an oomycete, or water mold, that causes the devastating potato disease known as late blight or potato blight and was responsible for the famous Irish Famine of the 1840s. In a recently published study, a group of scientists focused on the effectors of that pathogen and confirmed that plant pathogens employ an array of mechanisms to escape plant immunity response. These mechanisms explain why integrated resistance in plants cannot last long.

The scientists analyzed the genomic characters of the pathogen's AVR2 gene and the physical and biochemical properties of its effectors and found a substantial variation in the nucleotide sequences of the AVR2 genes generated from different P. infestans isolates and that these sequence variations were generated by many genetic mechanisms, including base substations, partial translation of the gene to the effectors, a small loss/gain of DNA sequence, and recombination.

"Bioinformatics analyses indicate that the virulent AVR2 effectors are proteins partially lacking three-dimension structure, known as disordered proteins, while avirulent effectors are ordered proteins with predicted crystal structures," explained Jiasui Zhan, one of the scientists involved in the study. "Each of the virulent effectors has one or two short linear interaction regions of ear-marked characters of disordered proteins. No such regions are found in the avirulent effectors. Furthermore, virulent AVR2 effectors are predicted to be less stable and have a shorter protein half-life than the avirulent effectors."

These results suggest that plant pathogens adopt a novel mechanism to escape plant recognition through reordering the physical structures of effector proteins. Through combining population genome and in vivo analyses of pathogenicity, Zhan and colleagues were able to draw the evolutionary pattern in groups rather than ad hoc phenomenon of single or a few samples in the similar studies and to verify the evolutionary inferences experimentally with statistical rigidness and robustness.

"This study highlights the fact that a subtle modification in gene sequence such as single base substitution may generate a huge corresponding change in protein properties of effectors and maybe other proteins as well," Zhan said. "The most surprising discovery is that there is clear difference in protein ordering between virulent and avirulent effectors: all 31 avirulent effectors are ordered proteins with defined structure while all 27 virulent are disordered proteins."

Multidisciplinary collaboration is essential for durable disease management and evolutionary genetics should play a central role in developing management practices that can minimize pathogen evolution's to evolve. For more information, read "The Phytophthora infestans AVR2 Effector Escapes R2 Recognition Through Effector Disordering" in the July issue of MPMI.

A new paper in The Economic Journal finds that bus drivers are more likely to let white riders ride for free and less likely to let Black riders ride without paying the fee.

Police officers must issue tickets to drivers exceeding the speed limit. A grocery store worker is not allowed to hand out goods free of charge. Similarly, bus drivers require all passengers to have valid tickets before being allowed onto the bus.

This study set out to test what happens when decisionmakers have to make unmonitored judgments. Do they voluntarily provide favours? And, if so, do they reward and accommodate some people more than others?

This study tested for discretionary favours, i.e., private accommodations, in everyday consumer transactions. In the study, the researchers hired test customers randomly assigned to board public buses where they presented a travel card with a zero monetary balance and asked the bus driver if they can have a free ride to a bus stop. While the public bus company's official rules and policies mostly discourage employees from providing a service free of monetary charge, close to two-thirds of observed bus drivers granted such favours, and predominantly to lighter-skinned people.

Based on 1,552 transactions in Queensland, Australia, the authors uncovered strong evidence of racial bias: bus drivers were twice as willing to let white testers ride free as Black testers (72% versus 36% of the time). Indian testers were accepted at 51%, while Asian testers were treated similarly to whites; being offered a free ride 73% of the time. Such racial bias against Black citizens still existed after controlling for several other variables including the bus driver's age, gender, and race. Based on the data, researchers found no evidence of own-group bias: bus drivers were just as likely to grant free rides to customers from other races as they were to customers of their own race.

The study revealed strong evidence of racial discrimination. A key feature in the field experiment is that the bus drivers had only a few seconds to decide regarding a person standing in front of them. Here the bus drivers appeared to use a customer's skin colour as a proxy for other unobservable group characteristics. The uncovered white privilege was reduced but still present when test customers wore business attire or dressed in army uniforms.

"Our findings show that white privilege extends into marketplace favours, or private accommodations, that are often hidden and unregulated," said Redzo Mujcic, one of the paper's authors. "The level of white privilege found is markedly greater than previously documented in other markets and public services, such as employment and housing, where discrimination is already illegal. As a society, we need to think about ways to eliminate such bias in daily interactions, especially given the large economic and social costs that accrue to discriminated minorities. For example, white citizens can simply refuse any such gifts in future transactions."

Enteroviruses and other pathogenic viruses that make their way into surface waters can be inactivated by heat, sunshine and other microbes, thereby reducing their ability to spread disease. But researchers report in ACS' Environmental Science & Technology that global warming could cause viruses to evolve, rendering them less susceptible to these and other disinfectants, such as chlorine.

Enteroviruses can cause infections as benign as a cold or as dangerous as polio. Found in feces, they are released into the environment from sewage and other sources. Their subsequent survival depends on their ability to withstand the environmental conditions they encounter. Because globalization and climate change are expected to alter those conditions, Anna Carratalà, Tamar Kohn and colleagues wanted to find out how viruses might adapt to such shifts and how this would affect their disinfection resistance.

The team created four different populations of a human enterovirus by incubating samples in lake water in flasks at 50 F or 86 F, with or without simulated sunlight. The researchers then exposed the viruses to heat, simulated sunlight or microbial "grazing" and found that warm-water-adapted viruses were more resistant to heat inactivation than cold-water-adapted ones. Little or no difference was observed among the four strains in terms of their inactivation when exposed to either more simulated sunlight or other microbes. When transplanted to cool water, warm-water-adapted viruses also remained active longer than the cool-water strains. In addition, they withstood chlorine exposure better. In sum, adaptation to warm conditions decreased viral susceptibility to inactivation, so viruses in the tropics or in regions affected by global warming could become tougher to eliminate by chlorination or heating, the researchers say. They also say that this greater hardiness could increase the length of time heat-adapted viruses would be infectious enough to sicken someone who comes in contact with contaminated water.

For all its vast emptiness, the universe is humming with activity in the form of gravitational waves. Produced by extreme astrophysical phenomena, these reverberations ripple forth and shake the fabric of space-time, like the clang of a cosmic bell.

Now researchers have detected a signal from what may be the most massive black hole merger yet observed in gravitational waves. The product of the merger is the first clear detection of an “intermediate-mass” black hole, with a mass between 100 and 1,000 times that of the sun.

They detected the signal, which they have labeled GW190521, on May 21, 2019, with the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO), a pair of identical, 4-kilometer-long interferometers in the United States; and Virgo, a 3-kilometer-long detector in Italy.

The signal, resembling about four short wiggles, is extremely brief in duration, lasting less than one-tenth of a second. From what the researchers can tell, GW190521 was generated by a source that is roughly 5 gigaparsecs away, when the universe was about half its age, making it one of the most distant gravitational-wave sources detected so far.

As for what produced this signal, based on a powerful suite of state-of-the-art computational and modeling tools, scientists think that GW190521 was most likely generated by a binary black hole merger with unusual properties.

Almost every confirmed gravitational-wave signal to date has been from a binary merger, either between two black holes or two neutron stars. This newest merger appears to be the most massive yet, involving two inspiraling black holes with masses about 85 and 66 times the mass of the sun.

The LIGO-Virgo team has also measured each black hole’s spin and discovered that as the black holes were circling ever closer together, they could have been spinning about their own axes, at angles that were out of alignment with the axis of their orbit. The black holes’ misaligned spins likely caused their orbits to wobble, or “precess,” as the two Goliaths spiraled toward each other.

The new signal likely represents the instant that the two black holes merged. The merger created an even more massive black hole, of about 142 solar masses, and released an enormous amount of energy, equivalent to around 8 solar masses, spread across the universe in the form of gravitational waves.

“This doesn’t look much like a chirp, which is what we typically detect,” says Virgo member Nelson Christensen, a researcher at the French National Centre for Scientific Research (CNRS), comparing the signal to LIGO’s first detection of gravitational waves in 2015. “This is more like something that goes ‘bang,’ and it’s the most massive signal LIGO and Virgo have seen.”

The international team of scientists, who make up the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration, have reported their findings in two papers published today. One, appearing in Physical Review Letters, details the discovery, and the other, in The Astrophysical Journal Letters, discusses the signal’s physical properties and astrophysical implications.

“LIGO once again surprises us not just with the detection of black holes in sizes that are difficult to explain, but doing it using techniques that were not designed specifically for stellar mergers,” says Pedro Marronetti, program director for gravitational physics at the National Science Foundation. “This is of tremendous importance since it showcases the instrument’s ability to detect signals from completely unforeseen astrophysical events. LIGO shows that it can also observe the unexpected.”

In the mass gap

The uniquely large masses of the two inspiraling black holes, as well as the final black hole, raise a slew of questions regarding their formation.

All of the black holes observed to date fit within either of two categories: stellar-mass black holes, which measure from a few solar masses up to tens of solar masses and are thought to form when massive stars die; or supermassive black holes, such as the one at the center of the Milky Way galaxy, that are from hundreds of thousands, to billions of times that of our sun.

However, the final 142-solar-mass black hole produced by the GW190521 merger lies within an intermediate mass range between stellar-mass and supermassive black holes — the first of its kind ever detected.

The two progenitor black holes that produced the final black hole also seem to be unique in their size. They’re so massive that scientists suspect one or both of them may not have formed from a collapsing star, as most stellar-mass black holes do.

According to the physics of stellar evolution, outward pressure from the photons and gas in a star’s core support it against the force of gravity pushing inward, so that the star is stable, like the sun. After the core of a massive star fuses nuclei as heavy as iron, it can no longer produce enough pressure to support the outer layers. When this outward pressure is less than gravity, the star collapses under its own weight, in an explosion called a core-collapse supernova, that can leave behind a black hole.

This process can explain how stars as massive as 130 solar masses can produce black holes that are up to 65 solar masses. But for heavier stars, a phenomenon known as “pair instability” is thought to kick in. When the core’s photons become extremely energetic, they can morph into an electron and antielectron pair. These pairs generate less pressure than photons, causing the star to become unstable against gravitational collapse, and the resulting explosion is strong enough to leave nothing behind. Even more massive stars, above 200 solar masses, would eventually collapse directly into a black hole of at least 120 solar masses. A collapsing star, then, should not be able to produce a black hole between approximately 65 and 120 solar masses — a range that is known as the “pair instability mass gap.”

But now, the heavier of the two black holes that produced the GW190521 signal, at 85 solar masses, is the first so far detected within the pair instability mass gap.

“The fact that we’re seeing a black hole in this mass gap will make a lot of astrophysicists scratch their heads and try to figure out how these black holes were made,” says Christensen, who is the director of the Artemis Laboratory at the Nice Observatory in France.

One possibility, which the researchers consider in their second paper, is of a hierarchical merger, in which the two progenitor black holes themselves may have formed from the merging of two smaller black holes, before migrating together and eventually merging.

“This event opens more questions than it provides answers,” says LIGO member Alan Weinstein, professor of physics at Caltech. “From the perspective of discovery and physics, it’s a very exciting thing.”

“Something unexpected”

There are many remaining questions regarding GW190521.

As LIGO and Virgo detectors listen for gravitational waves passing through Earth, automated searches comb through the incoming data for interesting signals. These searches can use two different methods: algorithms that pick out specific wave patterns in the data that may have been produced by compact binary systems; and more general “burst” searches, which essentially look for anything out of the ordinary.

LIGO member Salvatore Vitale, assistant professor of physics at MIT, likens compact binary searches to “passing a comb through data, that will catch things in a certain spacing,” in contrast to burst searches that are more of a “catch-all” approach.

In the case of GW190521, it was a burst search that picked up the signal slightly more clearly, opening the very small chance that the gravitational waves arose from something other than a binary merger.

“The bar for asserting we’ve discovered something new is very high,” Weinstein says. “So we typically apply Occam’s razor: The simpler solution is the better one, which in this case is a binary black hole.”

But what if something entirely new produced these gravitational waves? It’s a tantalizing prospect, and in their paper the scientists briefly consider other sources in the universe that might have produced the signal they detected. For instance, perhaps the gravitational waves were emitted by a collapsing star in our galaxy. The signal could also be from a cosmic string produced just after the universe inflated in its earliest moments — although neither of these exotic possibilities matches the data as well as a binary merger.

“Since we first turned on LIGO, everything we’ve observed with confidence has been a collision of black holes or neutron stars,” Weinstein says “This is the one event where our analysis allows the possibility that this event is not such a collision. Although this event is consistent with being from an exceptionally massive binary black hole merger, and alternative explanations are disfavored, it is pushing the boundaries of our confidence. And that potentially makes it extremely exciting. Because we have all been hoping for something new, something unexpected, that could challenge what we’ve learned already. This event has the potential for doing that.”

An international research collaboration including Northwestern University astronomers has witnessed the birth of an "intermediate-mass" black hole. This is the first conclusive discovery of an intermediate-mass black hole, an object which has long eluded astronomers. The cosmic event, its energy detected on Earth in the form of gravitational waves, is the most massive black hole merger yet observed in gravitational waves.

Two black holes likely collided and merged to create a more massive black hole with a final mass 142 times that of the sun, or 142 solar masses. This final black hole is the first to be found in an intermediate-mass range that lies between stellar-mass and supermassive black holes.

Another first is that the heavier of the two merging black holes, at 85 solar masses, is the first black hole so far detected within what is known as the "pair-instability mass gap."

Researchers detected the gravitational-wave signal on May 21, 2019, with the National Science Foundation's LIGO (Laser Interferometry Gravitational-wave Observatory (LIGO), a pair of identical, 4-kilometer-long interferometers in the United States, and Virgo, a 3-kilometer-long detector in Italy. The signal was dubbed GW190521.

The team of scientists, who make up the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration, has reported its findings in two papers to be published Sept. 2. One, appearing in Physical Review Letters, details the discovery of the gravitational wave signal, and the other, in the Astrophysical Journal Letters, discusses the signal's physical properties and astrophysical implications.

Christopher Berry, the CIERA Board of Visitors Research Professor in Northwestern's CIERA (Center for Interdisciplinary Exploration and Research in Astrophysics), was an LSC Editorial Board reviewer for the discovery paper. Chase Kimball, also an LSC member and a Northwestern astronomy Ph.D. student, contributed to the analysis of the astrophysical origins of GW190521 in the implications paper. Kimball is co-advised by Berry and Vicky Kalogera, the principal investigator of Northwestern's LSC group, director of CIERA and the Daniel I. Linzer Distinguished University Professor of Physics and Astronomy in the Weinberg College of Arts and Sciences.

"One of the great mysteries in astrophysics is how do supermassive black holes form?" Berry said. "They are the million solar-mass elephants in the room. Do they grow from stellar-mass black holes, which are born when a star collapses, or are they born via an undiscovered means? Long have we searched for an intermediate-mass black hole to bridge the gap between stellar-mass and supermassive black holes. Now, we have proof that intermediate-mass black holes do exist."

The signal of GW190521, resembling about four short wiggles, was extremely brief in duration, lasting less than one-tenth of a second. From what the researchers can tell, it was generated by a source that is roughly 5 gigaparsecs away, when the universe was about half its current age, meaning that the signal travelled across space for 7 billion years before reaching Earth. GW190521's source is the most distant gravitational-wave source detected so far.

"This doesn't look much like a chirp, which is what we typically detect," said Virgo member Nelson Christensen, a researcher at the French National Centre for Scientific Research, comparing the signal to LIGO's first detection of gravitational waves in 2015. "This is more like something that goes 'bang,' and it's the most massive signal LIGO and Virgo have seen."

Almost every confirmed gravitational-wave signal to date has been from a binary merger, either between two black holes or two neutron stars. This newest merger appears to be the most massive yet, involving two inspiraling black holes with masses about 85 and 66 solar masses.

"Gravitational-wave observations are revolutionary," Berry said. "Each new detection refines our understanding of how black holes form. With these gravitational-wave breakthroughs, it won't be long until we have enough data to uncover the secrets of how black holes are born and how they grow."

The LIGO-Virgo team has also measured each black hole's spin and discovered that as the black holes were circling ever closer together, they could have been spinning about their own axes, at angles that were out of alignment with the axis of their orbit. The black holes' misaligned spins likely caused their orbits to wobble, or "precess," as the two Goliaths spiraled toward each other.

The new signal likely represents the instant that the two black holes merged. The merger created an even more massive black hole, of about 142 solar masses, and released an enormous amount of energy, equivalent to around 8 solar masses, spread across the Universe in the form of gravitational waves.

"LIGO once again surprises us not just with the detection of black holes in sizes that are difficult to explain, but doing it using techniques that were not designed specifically for stellar mergers," said Pedro Marronetti, program director for gravitational physics at the National Science Foundation. "This is of tremendous importance since it showcases the instrument's ability to detect signals from completely unforeseen astrophysical events. LIGO shows that it can also observe the unexpected."

In the mass gap

The uniquely large masses of the two inspiraling black holes, as well as the final black hole, raise a slew of questions regarding their formation.

All of the black holes observed to date fit within either of two categories: stellar-mass black holes, which measure from a few solar masses up ¬to tens of solar masses and are thought to form when massive stars die; or supermassive black holes, such as the one at the center of the Milky Way galaxy, that are from hundreds of thousands to billions of times the mass of our sun.

However, the 142-solar-mass black hole produced by the GW190521 merger lies within an intermediate mass range between stellar-mass and supermassive black holes. And the two black holes that produced the final black hole also seem to be unique in their size. They're so massive that scientists suspect one or both of them may not have formed from a collapsing star, as most stellar-mass black holes do.

According to the physics of stellar evolution, outward pressure from the photons and gas in a star's core support it against the force of gravity pushing inward, so that the star is stable, like the sun. After the core of a massive star fuses nuclei as heavy as iron, it can no longer produce enough pressure to support the outer layers. When this outward pressure is less than gravity, the star collapses under its own weight, in an explosion called a core-collapse supernova, which can leave behind a black hole.

This process can explain how stars as massive as 130 solar masses can produce black holes that are up to 65 solar masses. But for heavier stars, a phenomenon known as "pair instability" is thought to kick in. When the core's photons become extremely energetic, they can morph into an electron and antielectron pair. These pairs generate less pressure than photons, causing the star to become unstable against gravitational collapse, and the resulting explosion is strong enough to leave nothing behind. Even more massive stars, above 200 solar masses, would eventually collapse directly into a black hole of at least 120 solar masses. A collapsing star, then, should not be able to produce a black hole between approximately 65 and 120 solar masses -- a range that is known as the "pair-instability mass gap."

But now, the heavier of the two black holes that produced the GW190521 signal, at 85 solar masses, is the first so far detected confidently within the pair-instability mass gap. Astrophysicists think of black holes forming from stars collapsing, but an 85-solar-mass black hole should be impossible this way, Northwestern's Berry said.

"There are many ideas about how to get around this -- merging two stars together, embedding the black hole in a thick disc of material it can swallow, or primordial black holes created in the aftermath of the Big Bang," he said. "The idea I really like is a hierarchical merger where we have a black hole formed from the previous merger of two smaller black holes."

A hierarchical merger, in which the two progenitor black holes themselves may have formed from the merging of two smaller black holes, before migrating together and eventually merging, is one possibility which the researchers consider in their second paper. Kimball, Berry and Kalogera have been studying hierarchical mergers guided by independent theoretical predictions by other researchers at Northwestern.

"After so many gravitational-wave observations since the first detection in 2015, it's exciting that the universe is still throwing new things at us, and this 85-solar-mass black hole is quite the curveball," Kimball said.

For the implications paper on GW190521, Kimball calculated the merger rates, one of the key pieces of information for the astrophysical interpretation, and led the calculation of the probability that the source is the result of a hierarchical merger. The odds for or against a hierarchical merger are roughly even when considering mergers in globular clusters, dense balls of hundreds of thousands of stars and black holes, but the odds may be better for a merger in the dense heart of a galaxy.

Discussing results, Kimball said, "While GW190521's origin is a mystery, I'm particularly excited about the prospect of it being the result of a hierarchical merger. In the future, with more binary black hole mergers and a better understanding of the pair-instability mass gap, we should be able to tell more definitively whether GW190521's big black hole was itself the product of a previous merger."

"This event opens more questions than it provides answers," said LIGO member Alan Weinstein, professor of physics at the California Institute of Technology. "From the perspective of discovery and physics, it's a very exciting thing."

'Something unexpected'

There are many remaining questions regarding GW190521.

The LIGO and Virgo detectors can detect gravitational-wave signals from many sources. In the case of GW190521, the signal is sufficiently short that it may be interpreted as something other than a binary of black holes, opening the very small chance that the gravitational waves arose from a new source other than a binary merger.

"What if something entirely new produced these gravitational waves?" Kalogera said. "It's a tantalizing prospect, and in the implications paper, the scientists briefly consider other sources in the universe that might have produced the signal they detected. For instance, perhaps the gravitational waves were emitted by a collapsing star in our galaxy. The signal also could be from a cosmic string produced just after the universe inflated in its earliest moments -- although neither of these exotic possibilities matches the data as well as a binary merger."

The LIGO and Virgo detectors finished their latest observing run this past March. Data from this period are still being analyzed and are expected to contain many more gravitational-wave signals. The detectors are planned to resume observing next year after work is done to increase their detection range; the LIGO and Virgo detectors also will be joined for the first time by the Japanese KAGRA detector. The enhanced global detector network is expected to make more gravitational-wave discoveries than ever before.

"We're really in the dawn of gravitational-wave astronomy," graduate student Kimball said. "It's hard to pick a better time to come up as an astrophysicist."

Scientists observed what appears to be a bulked-up black hole tangling with a more ordinary one. The research team, which includes physicists from the University of Maryland, detected two black holes merging, but one of the black holes was 1 1/2 times more massive than any ever observed in a black hole collision. The researchers believe the heavier black hole in the pair may be the result of a previous merger between two black holes.
This type of hierarchical combining of black holes has been hypothesized in the past but the observed event, labeled GW190521, would be the first evidence for such activity. The Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration (LSC) and Virgo Collaboration announced the discovery in two papers published September 2, 2020, in the journals Physical Review Letters and Astrophysical Journal Letters.

The scientists identified the merging black holes by detecting the gravitational waves--ripples in the fabric of space-time--produced in the final moments of the merger. The gravitational waves from GW190521 were detected on May 21, 2019, by the twin LIGO detectors located in Livingston, Louisiana, and Hanford, Washington, and the Virgo detector located near Pisa, Italy.

"The mass of the larger black hole in the pair puts it into the range where it's unexpected from regular astrophysics processes," said Peter Shawhan, a professor of physics at UMD, an LSC principal investigator and the LSC observational science coordinator. "It seems too massive to have been formed from a collapsed star, which is where black holes generally come from."

The larger black hole in the merging pair has a mass 85 times greater than the sun. One possible scenario suggested by the new papers is that the larger object may have been the result of a previous black hole merger rather than a single collapsing star. According to current understanding, stars that could give birth to black holes with masses between 65 and 135 times greater than the sun don't collapse when they die. Therefore, we don't expect them to form black holes.

"Right from the beginning, this signal, which is only a tenth of a second long, challenged us in identifying its origin," said Alessandra Buonanno, a College Park professor at UMD and an LSC principal investigator who also has an appointment as Director at the Max Planck Institute for Gravitational Physics in Potsdam, Germany. "But, despite its short duration, we were able to match the signal to one expected of black-hole mergers, as predicted by Einstein's theory of general relativity, and we realized we had witnessed, for the first time, the birth of an intermediate-mass black hole from a black-hole parent that most probably was born from an earlier binary merger."

GW190521 is one of three recent gravitational wave discoveries that challenge current understanding of black holes and allow scientists to test Einstein's theory of general relativity in new ways. The other two events included the first observed merger of two black holes with distinctly unequal masses and a merger between a black hole and a mystery object, which may be the smallest black hole or the largest neutron star ever observed. A research paper describing the latter was published in Astrophysical Journal Letters on June 23, 2000, while a paper about the former event will be published soon in Physical Review D.

"All three events are novel with masses or mass ratios that we've never seen before," said Shawhan, who is also a fellow of the Joint Space-Science Institute, a partnership between UMD and NASA's Goddard Space Flight Center. "So not only are we learning more about black holes in general, but because of these new properties, we are able to see effects of gravity around these compact bodies that we haven't seen before. It gives us an opportunity to test the theory of general relativity in new ways."

For example, the theory of general relativity predicts that binary systems with distinctly unequal masses will produce gravitational waves with higher harmonics, and that is exactly what the scientists were able to observe for the first time.

"What we mean when we say higher harmonics is like the difference in sound between a musical duet with musicians playing the same instrument versus different instruments," said Buonanno, who developed the waveform models to observe the harmonics with her LSC group. "The more substructure and complexity the binary has -- for example the masses or spins of the black holes are different--the richer is the spectrum of the radiation emitted."

In addition to these three black hole mergers and a previously reported binary neutron star merger, the observational run from April 2019 through March 2020 identified 52 other potential gravitational wave events. The events were posted to a public alert system developed by LIGO and Virgo collaboration members in a program originally spearheaded by Shawhan so that other scientists and interested members of the public can evaluate the gravity wave signals.

"Gravitational wave events are being detected regularly," Shawhan said, "and some of them are turning out to have remarkable properties which are extending what we can learn about astrophysics."

The enigmatic variations of light in a binary system, located in Sagittarius constellation, could be explained by the presence of a variable gas disk around a hot star that revolves around a cooler star. These are the conclusions published in the journal Astronomy & Astrophysics and which brought by researchers from Chile, Serbia and Poland.

It is the binary system OGLE-BLG-ECL-157529, located at 10.567 light years from Earth, which had been reported in a catalog of binary stars in the direction of the Galactic center. The system showed a peculiar variation of its brightness, with a period close to 800 days, together with typical changes of an eclipsing binary star of 24.8 days. The data analyzed cover 18.5 years and were obtained at the Las Campanas observatory in Chile, as part of the Polish OGLE project.

The object was identified as a binary star, whose cooler and evolved star transfers mass to the hottest star, forming around it a disk of gas of about 30 solar radii of extension. The disk would have a temperature of about 3.000 Kelvin, and it would undergo changes in its size and temperature as a result of variations in the amount of material it receives from the cold star.

The team of researchers was integrated by Ronald Mennickent, Juan Garcés and Dominik Schleicher, from the Department of Astronomy of University of Concepción; Gojko Djurasevic, from the Astronomical Observatory Volgina, Patryk Iwanek, Radoslaw Poleski and Igor Soszy?ski, from the University of Warsaw. "The team of co-author have been in close collaboration since decades, and includes a PhD student of mine (Garcés) and colleagues who I have met at conferences and Dr. Schleicher who is from my institution", said Mennickent.

The article shows how changes in disc properties convincingly explain the changes in the brightness of the binary system. In particular, this system shows strange variations in the depth of its eclipses which can be explained by the evolution of this gaseous disk, according to the authors. "Many stars in the Universe are binary, and the most massive ones go through these mass transfer processes, which dramatically conditions their evolution. These objects can produce in the distant future, supernovae or even emitters of gravitational radiation", Dr. Mennickent explains.

The gravitational wave (1) detectors LIGO and Virgo have just chalked up their biggest catch yet, a black hole 142 times the mass of the Sun, resulting from the merger of two black holes of 85 and 65 solar masses. The remnant black hole is the most massive ever observed with gravitational waves, and it could give us some clues about the formation of the supermassive black holes that sit at the centres of some galaxies. The mass of one of the merging black holes, 85 solar masses, provides information that could improve our understanding of the final stages in the evolution of massive stars. The discovery, to which several CNRS teams contributed as part of the Virgo collaboration, is published on 2 September 2020 in the journals Physical Review Letters and Astrophysical Journal Letters.

At first sight, there is nothing particularly new about the detection of the birth of a black hole caused by the merger of two others, accompanied by the emission of a huge amount of energy: after all, a succession of similar events have been observed ever since 2015, when the gravitational waves produced by such phenomena were observed for the first time (2). However, GW190521, the signal recorded on 21 May 2019 by the LIGO and Virgo instruments, stands out from the crowd, for the signal is not only the most distant, and therefore the oldest, ever detected (the gravitational wave took seven billion years to reach us), but in addition the black hole resulting from the merger is also the most massive observed so far. Above all, the observation is the first direct evidence of the existence of 'intermediate-mass' black holes, which weigh in at 100 to 100 000 solar masses. Such intermediate-mass black holes are heavier than those resulting from the collapse of high mass stars, but much lighter than the supermassive black holes that sit at the centre of some galaxies. Until now, only indirect evidence obtained from electromagnetic observations hinted at their existence.

Intermediate-mass black holes are interesting since they may hold the key to one of the big puzzles in astrophysics and cosmology: the origin of supermassive black holes. Although the question remains an open one, one of the scenarios proposed to explain the formation of these cosmic monsters is precisely that of repeated mergers of intermediate-mass black holes.

With masses around 65 and 85 times that of the Sun, the two black holes that were observed to merge intrigue astrophysicists as well. This is because, based on our current knowledge, the gravitational collapse of a star cannot form black holes in the approximate range of 60 to 120 solar masses, since the most massive stars are completely blown apart by the supernova explosion that accompanies the collapse, leaving only gas and dust behind them. So, sitting right in the middle of this forbidden range, how did the black hole of 85 solar masses form? Is there something we haven't understood about the way in which massive stars end their lives? If it is not of stellar origin, could it too have resulted from an earlier merger of less massive black holes? Or alternatively, could it be a hypothetical primordial black hole, formed during the Big Bang? The observation of GW190521 clearly raises new questions about the formation of the enigmatic objects we call black holes.

Compared to earlier observations, the GW190521 signal detected by LIGO and Virgo is very short and harder to analyse. Due to its more complex nature, other hypotheses involving more exotic sources were also explored to explain it, and such possibilities are described in the article in Astrophysical Journal Letters. However, the most plausible source of this gravitational wave remains the merger of two black holes.

The populations of common animals are just as likely to rise or fall in number in a time of accelerating global change as those of rare species, a study suggests.

A study of more than 2,000 species reveals animal populations around the world - from the very common to endangered species - are going up and down as global change alters land, sea and freshwater ecosystems.

The findings highlight a need to look beyond only rare species in order to improve efforts to conserve global biodiversity, scientists say.

Critically endangered animals - such as the Hawksbill sea turtle - were previously thought to be at greater risk of decline than common species like red deer, but the study found a wide spectrum of changes in animal numbers.

Findings from the new study suggest the numbers within very common animal species are, in fact, as likely to increase or decrease as rare ones.

However, species with smaller population sizes were shown to be more likely to change from year to year, potentially increasing their extinction risk in the long term.

Until recently, scientists were still compiling data on how animal populations were shifting over time on a global scale across the different regions of the planet.

Making use of the newly available data, a team of University of Edinburgh researchers studied nearly 10,000 animal populations recorded in the Living Planet Database between 1970 and 2014 to provide a new perspective on animal population change. These include records of mammals, reptiles, sharks, fish, birds and amphibians.

The team found that 15 per cent of all populations declined during the period, while 18 per cent increased and 67 per cent showed no significant change.

Amphibians were the only group in which population sizes declined, while birds, mammals and reptiles experienced increases.

The overall decline in amphibians makes them a priority for conservation efforts, researchers say, as their loss could have knock-on effects in food chains and wider ecosystems.

The study, published in the journal Nature Communications, was funded by the Natural Environment Research Council and the Carnegie Trust.

Gergana Daskalova, of the University of Edinburgh's School of GeoSciences, who led the study, said: "We often assume that declines in animal numbers are prevalent everywhere. But we found that there are also many species which have increased over the last half of a century, such as those that do well in human-modified landscapes or those that are the focus of conservation actions."

Dr Isla Myers-Smith, also of the School of GeoSciences, who co-authored the study, said: "Only as we bring together data from around the world, can we begin to really understand how global change is influencing the biodiversity of our planet. The original idea for this study stemmed from a fourth year undergraduate class at the University of Edinburgh. It is so inspiring to see early career researchers tackle some of the big conservation questions of our time using advanced data science skills."

A simple test such as the strength of your handgrip could be used as a quick, low-cost screening tool to help healthcare professionals identify patients at risk of type 2 diabetes. In new research, scientists at the universities of Bristol and Eastern Finland measured the muscular handgrip strength of 776 men and women without a history of diabetes over a 20-year period and demonstrated that the risk of type 2 diabetes was reduced by around 50 per cent for every unit increase in handgrip strength value. The findings are published today in Annals of Medicine.

Diabetes in all forms is the ninth major cause of death in the world. Around 90 per cent of people with diabetes have type 2 diabetes. In the UK alone, one in ten people over 40 are now living with a diagnosis of type 2 diabetes. It is expected that if nothing changes, more than five million people will have developed diabetes by 2025.

Though older age, obesity, family history and lifestyle factors such as physical inactivity, smoking, unhealthy diet and excessive alcohol contribute substantially to the risk of developing type 2 diabetes, these factors alone do not explain all of the risk for type 2 diabetes. It appears other factors may be involved. Reduced muscular strength, which can be measured by handgrip strength, has consistently been linked to early death, cardiovascular disease, and disability.

Until recently, there was inconsistent evidence on the relationship between handgrip strength and type 2 diabetes. In a recent literature review of ten published studies on the topic the same researchers demonstrated that people with higher values of handgrip strength had a 27 per cent reduced risk of developing type 2 diabetes.

However, while findings from this review suggested handgrip strength could potentially be used to predict type 2 diabetes, researchers needed to test this formally using individual patient data.
In this latest study, the researchers from Bristol Medical School and Eastern Finland's Institute of Public Health and Clinical Nutrition followed 776 men and women aged 60-72 years without a history of diabetes over a 20-year period and measured the power of their hand grip strength using a handgrip dynamometer. Patients were asked to squeeze the handles of the dynamometer with their dominant hand with maximum isometric effort and maintain this for five seconds.

An analysis of the results demonstrated that the risk of type 2 diabetes was reduced by about 50 per cent for every unit increase in handgrip strength value. This association persisted even after taking into account several established factors that can affect type 2 diabetes such as age, family history of diabetes, physical activity, smoking, hypertension, waist circumference and fasting plasma glucose. When information on handgrip strength was added to these established factors which are already known to predict type 2 diabetes, the prediction of type 2 diabetes improved further.

According to lead author Dr Setor Kunutsor from Bristol's Musculoskeletal Research Unit: "These findings may have implications for the development of type 2 diabetes prevention strategies. Assessment of handgrip is simple, inexpensive and does not require very skilled expertise and resources and could potentially be used in the early identification of individuals at high risk of future type 2 diabetes."

Importantly, the findings appeared to be marked in women compared to men in sex-specific analyses, suggesting that women are likely to benefit from the use of this potential screening tool.

Principal investigator, Professor Jari Laukkanen from the University of Eastern Finland, added: "These results are based on a Finnish population. Given the low number of events in our analyses, we propose larger studies to replicate these findings in other populations and specifically in men and women."
The authors add that further research is needed to establish whether efforts to improve muscle strength such as resistance training are likely to reduce an individual's risk of type 2 diabetes.

The Korea Institute of Science and Technology (KIST) has announced that a research team led by Dr. Joong-Kee Lee of the Center for Energy Storage Research had developed a next-generation secondary battery that uses zinc metal as an electrode without any risk of explosion or fire. This battery is safe enough to be worn on the body and can be manufactured in the form of fiber shape, which means it may potentially be applied as a power source for wearable devices in the future.

Recently, the demand for safe batteries has been rising dramatically, mainly due to fires occurring in various electronic devices using lithium-ion batteries. The primary cause of such fires is the highly flammable electrolytes, but since Zn-ion secondary batteries use water-based electrolytes, there is no risk of explosion. This is why they are considered one of the more promising candidates to replace Li-ion batteries.

However, zinc anodes, which are the core material of existing Zn-ion batteries, present an inherent problem in that they undergo continuous corrosion in water-based electrolytes. Not only that, when zinc ions are stored on a metal surface, they accumulate as crystals in the form of branches (dendrites)* and trigger a short circuit between electrodes, resulting in a sharp decline in efficiency. Various studies have been carried out to come up with a solution to this problem through the means of a zinc metal complex, surface coating, and shape change, for example, but there have been major limitations in relation to processing cost and time.

The team headed by Dr. Lee from KIST developed a periodic anodizing method, which involves repeatedly permitting and blocking a flow of current on the surface of the metal electrode, thereby successfully controlling the surface coating morphologies and shape pattern array of the zinc oxide film simultaneously.

Using this method, the KIST research team inhibited the generation of dendrites during the electrochemical reaction by forming a functionalized shape in which hexagonal pyramids were arranged on the surface of zinc metal. According to the periodic anodizing method, the zinc oxide covering the upper part of the hexagonal pyramid is thick, whereas it is thin on the sides. The variation in thickness induces the zinc metal to accumulate on the side with a relatively thinner layer of zinc oxide. Dendrites are a problem as they accumulate vertically on the metal surface, but the newly developed technology in question induces the zinc metal film to grow in a horizontal direction on the electrode surface, and it was able to effectively suppress the generation of dendrite. As for the zinc oxide film that formed on the surface, direct contact with electrolytes was blocked, thereby preventing corrosion and side reaction at the same time.

The Zn-ion secondary battery developed through this study maintained nearly 100% of its capacity over 1,000 cycles, even though it was repeatedly charged and discharged under extreme conditions (9,000 mA/g, fully charged and discharged for about 2 minutes each), attributed to its structural and electrochemical stability.

Based on such stability, the KIST researchers made a Zn-ion secondary battery in the form of flexible fibers. In addition to being bent can be bent easily, it can be used incorporated into clothing, a bag if it is made into fabric. (ACS Appl. Mater. Interfaces 2020, 12, 5, 5820-5830)

Dr. Lee, a senior researcher at KIST, said, "The high-performance Zn-ion secondary battery developed in this study does not present any potential risks associated with Li-ion batteries coming into contact with the human body. At the same time, we expected it to garner attention as a next-generation secondary battery that is safe for the human body and doesn't present any risks of explosion or fire, along with its excellent electrochemical performance that is comparable to the existing commercial batteries in terms of battery capacity. (Advanced Functional Materials, 2020, 202004210, DOI: 10.1002/adfm.202004210) It appears that based on excellent stability, improved electrochemical performance, and simple processes, it will be possible to make the manufacturing process practical for real-life application."

The most massive black hole collision ever detected has been directly observed by the LIGO and VIRGO Scientific Collaboration, which includes scientists from The Australian National University (ANU).

The short gravitational wave signal, GW190521, captured by the LIGO and Virgo gravitational wave observatories in the United States and Europe on 21 May last year, came from two highly spinning, mammoth black holes weighing in at a massive 85 times and 66 times the mass of the Sun, respectively.

But that is not the only reason this system is very special. The larger of the two black holes is considered `impossible'. Astronomers predict that stars between 65 - 130 times the mass of the Sun undergo a process called pair instability, resulting in the star being blown apart, leaving nothing behind.

With a mass of 85 solar masses, the larger black hole falls squarely in that forbidden range, referred to as the upper black hole mass gap, and should be `impossible'. So if it wasn't created by the collapse of a star, how did it form?

"We think of black holes as the vacuum cleaners of the Universe. They suck in everything in their paths, including gas clouds and stars," said Professor Susan Scott?from the ANU Research School of Physics, a co-author on the publication.

"They also suck in other black holes and it is possible to produce bigger and bigger black holes by the ongoing collisions of earlier generations of black holes. The heavier `impossible' black hole in our detected collision may have been produced in this way."

The two black holes merged when the Universe was only about seven billion years old, which is roughly half its present age. They formed an even larger black hole weighing a whopping 142 times the mass of the Sun, by far the largest black hole ever observed through gravitational wave observations.

Black holes of mass 100 to 100,000 solar masses are called intermediate mass black holes (IMBHs). They are heavier than stellar mass black holes but lighter than supermassive black holes often located at the centres of galaxies. There have been no conclusive electromagnetic observations for IMBHs in the mass range 100 to 1,000 solar masses.

"The `impossible' black hole formed by the collision lies in the black hole desert between 100 and 1,000 times the mass of the Sun," Professor Scott, who is also the Chief Investigator with the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), said.

"We are very excited to have achieved the first direct observation of an IMBH in this mass range. We also saw how it formed, confirming that IMBHs can be produced through the merger of two smaller black holes."

Another recent study suggests scientists using Caltech's Zwicky Transient Facility may have spotted a light flare from the collision. This is surprising, as black holes and their mergers are normally dark to telescopes. One theory is the system may have been orbiting a supermassive black hole. The newly formed black hole may've received a kick from the collision, shooting off in a new direction and surging through the disk of gas surrounding the supermassive black hole, causing it to light up.

"There are a number of different environments in which this system of two black holes could have formed, and the disk of gas surrounding a supermassive black hole is certainly one of them," OzGrav postdoctoral researcher, Dr Vaishali Adya from ANU, said.

"But it is also possible that this system consisted of two primordial black holes that formed in the early Universe.

"Every observation we make of two black holes colliding gives us new and surprising information about the lives of black holes throughout the Universe. We are beginning to populate the black hole mass gaps previously thought to exist, with `impossible' black holes that have been revealed through our detections."

Recent estimates indicate a prevalence of autism spectrum disorder (ASD) in the United States of 1 in 59 children with a well-established 4:1 male predominance. Individual costs for care are estimated at about $2.4 million, yielding a societal burden that is expected to exceed $400 billion by 2025. Currently, there are no FDA-approved medications that improve the core symptoms of ASD.

Neuroscientists in the laboratory of Randy D. Blakely, Ph.D., professor of biomedical science in Florida Atlantic University's Schmidt College of Medicine and executive director of the FAU Brain Institute, are focused on serotonin, a mood-regulating molecule in the brain that regulates many brain synapses -- the gaps between nerve cells where signals are sent and received. The supply of serotonin is tightly regulated by a protein called the serotonin transporter (SERT), which sweeps away serotonin from synapses to limit its action. Shifts in the transporter's activity can significantly impact the ability of serotonin to act in the brain.

Changes in signaling by the neurotransmitter serotonin has been connected to autism for more than 50 years, dating back to findings of elevated serotonin levels in the blood of some people with the disorder, a feature termed hyperserotonemia. Since this time, multiple rare changes in the genetic code that impact SERT have been observed.

Recent studies of mice expressing the most common of these gene variants, called SERT Ala56, induces behavioral changes in animals that scientists connect to alterations in people with autism - repetitive behavior, altered communication, and atypical social interactions, as well as hyperserotonemia. Although the effects of the SERT Ala56 mutation are paralleled by other mutations in the SERT gene, none of these mutations are common enough to account for the number of individuals with autism demonstrating hyperserotonemia.

Blakely and collaborators have published a study in the journal Frontiers in Molecular Neuroscience, which now offers a possible explanation for this puzzle.

"We have known for some time that the activity and regulation of the SERT protein is critically dependent on a number of other proteins that tell the protein where to locate on nerve cells and how to act," said Blakely, lead author.

It turns out that the SERT Ala56 mutation changes the structure of the transporter in ways that keep these partner proteins from interacting with the transporter, a protein that Blakely's laboratory identified thirty years ago.

Last year, Blakely's former graduate student Meagan Quinlan, Ph.D., first author and a post-doctoral fellow at the University of Washington, demonstrated that the SERT Ala56 mutation impacts the structure of the SERT protein in cells in culture, revving up the transporter into a state of abnormally high activity.

"We think that this high-activity state results in removal of too much serotonin from sites in the brain where serotonin is needed, both during development and in adults," said Quinlan. "I suspect that the structural changes we have observed likely reflected changes in the regulatory ability of SERT-associated proteins to maintain serotonin inactivation at normal levels."

To test this concept, Quinlan purified the mutant transporter from the brain of SERT Ala56 expressing mice, as well as from normal mice, and then determined whether proteins normally bound to SERT were still attached.

"We found that only a few proteins seemed to interact with SERT Ala56 more than they should. In contrast, many more proteins appeared no longer tethered to the transporter, including some proteins we already knew to be SERT regulators and others that have been linked to ASD," said Quinlan.

Blakely was actually quite surprised at the findings. "It is quite amazing that one of the smallest changes you can make in SERT can alter its interactions with partners," said Blakely.

According to Blakely, further work could reveal more extensive links between SERT and other genes known to associate with autism, broadening the impact of SERT Ala56 to other neurotransmitter systems.

"Following the scent of serotonin may well take us to molecules and medications we had no clue about just a few years ago," said Blakely.

Blakely's team recently reported a new small molecule that can tone down SERT activity and normalize behaviors in the SERT Ala56 mouse, a molecule that he hopes may lead to a new therapeutic.

"A goal moving forward with this drug is to see if it can reverse the changes in SERT Ala56 protein associations, tying the molecular changes we see with the mutant to how the drug may work," said Blakely.

ASD is a serious developmental disorder with increased prevalence that impairs the ability to communicate and interact and impacts the nervous system. The range and severity of symptoms can vary widely and common symptoms can include difficulty with communication and social interactions, obsessive interests, and repetitive behaviors. No current medications treat the core features of ASD.

A blood test on hospital admission showing the presence or absence of SARS-CoV-2 can identify patients at a high risk of severe COVID-19. Admitted patients without virus in their blood have a good chance of rapid recovery. This according to researchers at Karolinska Institutet and Danderyd Hospital in a new study published in the scientific journal Clinical Infectious Diseases.

Blood samples were taken from patients with a confirmed COVID-19 infection within three days of admission to the Department of Infectious Diseases, Danderyd Hospital, Sweden. Patients with measurable levels of the new coronavirus SARS-CoV-2 in their blood were seven times more likely to develop critical symptoms and eight times more likely to die within 28 days.

"This readily available test allows us to identify patient groups at high or low risk of severe COVID-19, which enables us to better guide the treatment and monitoring of these patients", says the study's lead author Karl Hagman, infectious diseases consultant at Danderyd Hospital and doctoral student at Karolinska Institutet's Department of Clinical Sciences at the same hospital.

The researchers analysed the presence of viral RNA in the blood using a standard hospital technique called PCR on samples taken from a total of 167 patients. Sixty-one patients had measurable levels of the virus in their blood and 15/61 (25 per cent) died within 28 days of blood sampling. This can be compared with three deaths (three per cent) amongst the 106 patients who did not have measurable levels of virus in their blood. The presence of virus in the blood increased with age and was much more common in patients over the age of 60.

The researchers received no specific funding for this study. The paper's last author, Johan Ursing, has a clinical research position financed by Region Stockholm. One of the co-authors has reported receipt of payment from pharmaceutical company Pfizer outside this current study. No other potential conflicts of interest are declared in the paper.

The bacterium Helicobacter pylori is linked to increased risk of stomach cancer, and is genetically highly variable. A new study by researchers of Ludwig-Maximilians-Universitaet (LMU) in Munich explores the role played by this diversity in the early phase of infection in adult humans.

It is estimated that about half of the world's population is infected with the bacterium Helicobacter pylori. Most primary infections occur in childhood. In many cases, it causes no overt symptoms in the human host, although it can give rise to a variety of gastrointestinal problems. However, if the infection becomes chronic, approximately 1% of its victims go on to develop stomach cancer. One of the most striking features of the pathogen is the range of its genetic variability, which makes it highly adaptable. - Moreover, as a new report now shows, this versatility becomes apparent within weeks of the initial infection. Led by Professors Sebastian Suerbaum and Christine Josenhans of LMU's Max von Pettenkofer Institute, the study appears in the online journal mbio.

The researchers were able to make use of a unique set of samples obtained in the course of a vaccine trial performed in collaboration with colleagues from the Max Planck Institute for Infection Biology in Berlin in which adult volunteers were infected with H. pylori. Ten weeks later, bacterial samples were isolated from two different regions of the stomach in each case, and the donors were then treated with antibiotics to eliminate the pathogen. Complete genome sequences of single-cell isolates obtained from these samples were determined using state-of-the-art single-molecule, real-time (SMRT) sequencing methods and compared with that of the H. pylori strain with which the volunteers had been infected nearly 3 months previously.

The results revealed that the bacterial genomes had undergone a surprising degree of diversification within this relatively short time span. Many of the mutations detected were located in genes that are directly involved in molecular interactions between the pathogen and host cells. The set of proteins affected included polypeptides that are expressed on the cell wall of the bacterium, as well as transport proteins that are found in its outer membrane. These findings suggest that specific genes are being positively selected to enable the bacterium to exploit metabolites that are available in different cellular niches in the lining of the stomach. In addition to these genetic mutations (which alter gene products), the authors noted a variety of epigenetic changes (which alter gene regulation) in the bacterial DNA during the early phase of infection. H. pylori possesses many enzyme systems that attach methyl groups to specific DNA sequences. The authors identified 24 such systems, and at least some of these may serve to regulate the expression of sets of genes in the bacterium. These results further support the notion that alterations in gene products and patterns of gene activity during the weeks and months following the primary infection play an important role in enabling the bacterium to adapt to, and become established in different niches in the stomach.