WASHINGTON — Researchers have devised a test to see if pairs of black holes — famous for creating gravitational waves when they merge — themselves formed from multiple mergers of smaller black holes.
The Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, has detected spacetime ripples from two sets of merging black holes (SN: 7/9/16, p. 8). Scientists typically assume that such black holes formed in the collapse of a massive star. But in especially crowded patches of the universe, black holes could have formed over generations of unions, astrophysicist Maya Fishbach of the University of Chicago explained January 28 at a meeting of the American Physical Society. Or the merging cycle could have occurred in the very early universe, starting with primordial black holes — objects that may have formed when extremely dense pockets of matter directly collapsed. Fishbach and colleagues studied how quickly black holes whirl around. In simulations, black holes that repeatedly merged reached a high rate of spin, the scientists found. That result didn’t depend on certain properties of the initial black holes, like whether they were spinning to begin with or not. “It’s cool,” says Fishbach. “The predictions from this in terms of spin are very robust,” making the idea easy to test.
So far, the spins of LIGO’s black holes are lower than the predictions. If the multiple merging process occurs, it could be very rare, so to conclusively test the idea would require tens to hundreds of black hole detections, Fishbach says.
A small, poorly understood segment of the population stays mentally healthy from age 11 to 38, a new study of New Zealanders finds. Everyone else encounters either temporary or long-lasting mental disorders.
Only 171 of 988 participants, or 17 percent, experienced no anxiety disorders, depression or other mental ailments from late childhood to middle age, researchers report in the February Journal of Abnormal Psychology. Of the rest, half experienced a transient mental disorder, typically just a single bout of depression, anxiety or substance abuse by middle age. “For many, an episode of mental disorder is like influenza, bronchitis, kidney stones, a broken bone or other highly prevalent conditions,” says study coauthor Jonathan Schaefer, a psychologist at Duke University. “Sufferers experience impaired functioning, many seek medical care, but most recover.”
The remaining 408 individuals (41 percent) experienced one or more mental disorders that lasted several years or more. Their diagnoses included more severe conditions such as bipolar and psychotic disorders.
Researchers analyzed data for individuals born between April 1972 and March 1973 in Dunedin, New Zealand. Each participant’s general health and behavior were assessed 13 times from birth to age 38. Eight mental health assessments occurred from age 11 to 38. Surprisingly, those who experienced lasting mental health did not display several characteristics previously linked to a lower likelihood of developing mental disorders. Those attributes consist of growing up in unusually affluent families, enjoying especially sound physical health and scoring exceptionally high on intelligence tests. Instead, mentally healthy participants tended to possess advantageous personality traits starting in childhood, Schaefer and colleagues found. These participants rarely expressed strongly negative emotions, had lots of friends and displayed superior self-control. Kiwis with rock-solid mental health also had fewer first- and second-degree relatives with mental disorders compared with their peers.
As adults, participants with enduring mental health reported, on average, more education, better jobs, higher-quality relationships and more satisfaction with their lives than their peers did. But lasting mental health doesn’t guarantee an exceptional sense of well-being, Schaefer says. Nearly one-quarter of never-diagnosed individuals scored below the entire sample’s average score for life satisfaction.
Less surprising was the 83 percent overall prevalence rate for mental disorders. That coincides with recent estimates from four other long-term projects. In those investigations — two in the United States, one in Switzerland and another in New Zealand — between 61 percent and 85 percent of participants developed mental disorders over 12- to 30-year spans.
Comparably high rates of emotional disorders were reported in 1962 for randomly selected Manhattan residents. Many researchers doubted those findings, which relied on a diagnostic system that was less strict than the three versions of psychiatry’s diagnostic manual that were introduced and used to evaluate New Zealand participants as they got older, says psychiatric epidemiologist William Eaton of Johns Hopkins Bloomberg School of Public Health. But the Manhattan study appears to have been on the right track, Eaton says.
Increased awareness that most people will eventually develop a mental disorder (SN: 10/10/09, p. 5), at least briefly, can reduce stigma attached to these conditions (SN Online: 10/13/16), he suspects.
Psychiatric epidemiologist Ronald Kessler suspects the numbers of people experiencing a mental disorder may be even higher than reported. Many participants deemed to have enduring mental health likely developed brief mental disorders that got overlooked, such as a couple of weeks of serious depression after a romantic breakup, says Kessler of Harvard Medical School, who directs U.S. surveys of mental disorders. Rather than focusing on rare cases of lasting mental health, “the more interesting thing is to compare people with persistent mental illness to those with temporary disorders,” he says.
Hydras, petite pond polyps known for their seemingly eternal youth, exemplify the art of bouncing back (SN: 7/23/16, p. 26). The animals’ cellular scaffolding, or cytoskeleton, can regrow from a slice of tissue that’s just 2 percent of the original hydra’s full body size. Researchers thought that molecular signals told cells where and how to rebuild, but new evidence suggests there are other forces at play.
Physicist Anton Livshits and colleagues at the Technion-Israel Institute of Technology in Haifa genetically engineered Hydra vulgaris specimens so that stretchy protein fibers called actins, which form the cytoskeleton, lit up under a microscope. Then, the team sliced and diced to look for mechanical patterns in the regeneration process. Actin fibers in pieces of hydra exert mechanical force that lines up new cells and guides the growth of the animal’s head and tentacles, the researchers found. Turning off motor proteins that move actin stopped regeneration, and physically manipulating actin fiber alignment resulted in hydras with multiple heads. Providing hydras with further structural stability encouraged tissue slices to grow normally. Both mechanical and molecular forces may mold hydras in regeneration, the researchers report in the Feb. 7 Cell Reports. When researchers anchored rings of hydra tissue to a wire (right), they found that the added mechanical stability made a hydra grow normally along one body axis, and thus grow one head. Without this stability, the actin scaffolding was more disrupted and the animal grew two heads (left).
BOSTON — For a lawn that helps the environment — and doesn’t need to be mowed — look to the ocean. Meadows of underwater seagrass plants might lower levels of harmful bacteria in nearby ocean waters, researchers reported February 16 during a news conference at the annual meeting of the American Association for the Advancement of Science. That could make the whole ecosystem — from corals to fish to humans — healthier.
Not truly a grass, seagrasses are flowering plants with long, narrow leaves. They grow in shallow ocean water, spreading into vast underwater lawns. Seagrasses are “a marine powerhouse, almost equal to the rainforest. They’re one of the largest stores of carbon in the ocean,” says study coauthor Joleah Lamb, an ecologist at Cornell University. “But they don’t get a lot of attention.” It’s no secret that seagrasses improve water quality, says James Fourqurean, a biologist at Florida International University in Miami who wasn’t involved in the research, which appears in the Feb. 17 Science. The plants are great at removing excess nitrogen and phosphorus from coastal waters. But now, it seems, they might take away harmful bacteria, too.
A few years ago, Lamb’s colleagues became ill with amoebic dysentery while studying coral reefs in Indonesia, an archipelagic nation that straddles the Indian and Pacific oceans. When a city or village on one of the country’s thousands of islands dumps raw sewage into the ocean, shoreline bacteria populations can spike to dangerous levels. Water sampled close to the shores of four small and densely populated Indonesian islands had 10 times the U.S. Environmental Protection Agency’s recommended exposure limit of Enterococcusbacteria, which can cause illness in humans and often signals the presence of other pathogens. But water collected from offshore tidal flats and coral reefs with seagrass beds had lower levels of the bacteria compared with similar sites without the plants less than 20 meters away. The water had lower levels of numerous bacterial species that can make fish and marine invertebrates sick, too. And field surveys of more than 8,000 coral heads showed that those growing adjacent to or within seagrass beds had fewer diseases than those growing farther away. It’s unclear how far from seagrass beds this cleaner water extends, but the benefits can ripple through the entire ecosystem, Lamb said at the news conference. Healthier corals help protect the islands from erosion. And fish less contaminated with bacteria make a better source of food for people.
Lamb is planning follow-up studies to figure out exactly how the seagrasses clean the water. Like a shag carpet, seagrasses trap small particulates drifting through the ocean and prevent them from flowing on. The plants might ensnare bacteria in the same way, building up biofilms on their blades. Or, she suggests, the leaves could be giving off antimicrobial compounds that directly kill the bacteria.
The findings are one more reason to conserve seagrasses, study coauthor Jeroen van de Water, an ecologist at the Scientific Center of Monaco, said at the news conference. Worldwide, seagrass beds are declining by 7 percent each year, thanks to pollution and habitat loss. And while restoration efforts are underway in some areas, “it’s better to stop what we’re doing to the meadows than to try to replant them,” Lamb added. “Seagrasses are quite particular in the depth they want to be at and the environment they want to have. It’s hard to start doing restoration projects if the environment isn’t exactly what the seagrass prefers.”
Volcanoes that belch hydrogen could bump up the number of potentially habitable planets in the universe.
Ramses Ramirez and Lisa Kaltenegger, both of Cornell University, modeled the atmospheres of planets blemished with hydrogen-spewing volcanoes. These gaseous eruptions could warm planets and ultimately widen a star’s habitable zone, the region where liquid water can exist on a planet’s surface, by about 30 to 60 percent, researchers report in the March 1 Astrophysical Journal Letters. That would be like extending the outer edge of the sun’s habitable zone from about 254 million kilometers — just beyond Mars’ orbit — to 359 million kilometers, or roughly to the asteroid belt between Mars and Jupiter.
Exoplanets that astronomers had previously thought too cold to support life might, in fact, be ripe for habitability if they have hydrogen volcanoes, the researchers say. One example is TRAPPIST-1h, the farthest-out planet identified in an odd system of seven Earth-sized planets 39 light-years from Earth (SN Online: 2/22/17). That world is thought to be icy like Jupiter’s moon Europa.
Adding planets to a star’s habitable zone means more exotic worlds could be targets in the search for signatures of life beyond our solar system. Astronomers plan to search for these signatures with the James Webb Space Telescope, slated to launch in 2018, and later with the European Extremely Large Telescope, scheduled to begin operations in 2024.
Just six weeks of training can turn average people into memory masters.
Boosting these prodigious mnemonic skills came with overhauls in brain activity, resulting in brains that behaved more like those of experts who win World Memory Championships competitions, scientists report March 8 in Neuron.
The findings are notable because they show just how remarkably adaptable the human brain is, says neuroscientist Craig Stark of the University of California, Irvine. “The brain is plastic,” he says. “Through use, it changes.” It’s not yet clear how long the changes in the newly trained brains last, but the memory gains persisted for four months.
In an initial matchup, a group of 17 memory experts, people who place high in World Memory Championships, throttled a group of people with average memories. Twenty minutes after seeing a list of 72 words, the experts remembered an average of 70.8 words; the nonexperts caught, on average, only 39.9 words.
In subsequent matchups, some nonexperts got varying levels of help. Fifty-one novices were split into three groups. A third of these people spent six weeks learning the method of loci, a memorization strategy used by ancient Greek and Roman orators. To use the technique, a person must imagine an elaborate mental scene, such as a palace or a familiar walking path, and populate it with memorable items. New information can then be placed onto this scaffold, offering a way to quickly “see” long lists of items.
Other participants spent six weeks training to improve short-term memory, performing a tricky task that required people to simultaneously keep track of series of locations they see and numbers they hear. The rest of the participants had no training at all.
After the training, the people who learned the method of loci performed nearly as well as the memory experts. But the rest didn’t show such improvement. Study coauthor Martin Dresler, a neuroscientist at the Radboud University Medical Center in the Netherlands, knew that the method of loci works quite well; he wasn’t surprised to see those memory scores spike. To him, the more interesting changes happened in the trained people’s brains. Before and after training, nonexperts underwent scans that pinpointed brain areas that were active at the same time, an indication that these brain areas work together closely. Dresler and colleagues looked at 2,485 connections in brain networks important for memory and visual and spatial thinking. Training in the method of loci seemed to reconfigure many of those connections, making some of the connections stronger and others weaker. The overall effect of training was to make brains “look like those of the world’s best memorizers,” Dresler says. The results suggest that large-scale changes across the brain, as opposed to changes in individual areas, drive the increased memory capacity.
These new memory skills were still obvious four months after training ended, particularly for the people whose brain behavior became more similar to that of the memory experts. The researchers didn’t scan participants’ brains four months out, so they don’t know whether the brain retains its reshaped connections. No such brain changes or big increases in memory skills were seen in the other groups.
Memorization techniques have been criticized as interesting tricks that have little use in real life. But “that’s not the case,” Dresler says. Boris Konrad, a coauthor of the study also at Radboud, is a memory master who trained in the method of loci. The technique “really helped him get much better grades” in physics and other complex studies, Dresler says.
Improvements in mnemonic memory, like other types of cognitive training, might not improve a broader range of thinking skills. The current study can’t answer bigger questions about whether brain training has more general benefits.
Mosquitoes take weird insect flight to new heights.
The buzzing bloodsuckers flap their long wings in narrow strokes really, really fast — more than 800 times per second in males. That’s four times faster than similarly sized insects. “The incredibly high wingbeat frequency of mosquitoes is simply mind-boggling,” says David Lentink, who studies flight at Stanford University.
Mosquitoes mostly hover. Still, it takes a lot of oomph and some unorthodox techniques to fly that slowly. Mosquitoes manage to stay aloft thanks primarily to two novel ways to generate lift when they rotate their wings, Richard Bomphrey and colleagues write March 29 in Nature. The insects essentially recycle the energy from the wake of a preceding wing stroke and then tightly rotate their wings to remain in flight. Most insects (and some birds and bats) rely on long wing strokes that create tiny low-pressure tornadoes called leading-edge vortices. The sharp front edge of the wing splits airflow in two, creating a bubble of swirling air along the front of the wing. Having low-pressure air above a wing and high-pressure air below generates lift.
But mosquitoes rapidly flap their wings up and down around a roughly 40-degree angle on average. Such short, speedy wingbeats make it impossible to generate enough lift from leading-edge vortices to stay in the air. “We knew something funny had to be going on. We just didn’t know what,” says Bomphrey, a biomechanist at the Royal Veterinary College of the University of London. So his team aimed eight high-speed cameras at hovering house mosquitoes (Culex quinquefasciatus) to model the physics of mosquito flight. It turns out the insects flap their wings in a tight figure eight formation. Leading-edge vortices generate some lift as the wings briefly cut through the air horizontally. Then, as the wings start to rotate into the curve of the figure eight, they trap the wake of the previous stroke to create another series of low-pressure swirling vortices, this time along the back edge of the wing. “This doesn’t require any power. It’s a particularly economical way of generating lift,” says Bomphrey. As the wings rotate, they also push air down, redirecting low-pressure air across the top of the wings. The wings rotate around an axis at their front edge, but if they go too far past vertical, they start to lose lift. So, the mosquito subtly shifts its wings’ turning axis from the front to the back of the wing, creating a more horizontal surface that allows the wings to continue to push air down. This also sets up the insect to benefit from the vortices along the trailing edge of the wing coming out of the turn.
Switching the axis mid-rotation “is impressive, especially since mosquito nerve cells fire just once for every few wingbeats,” says Itai Cohen, a Cornell University physicist not affiliated with the work. “Somehow this animal has evolved a complex wing stroke that takes advantage of aerodynamic forces and the mechanical infrastructure of the wing to generate complex motions with very few signals from the brain,” he says.
Bomphrey suspects that using these lift-driving forces may be common in mosquitoes and other insects that hover. But Lentink, who was not affiliated with the work, thinks it’s unlikely that lots of insects fly this way “because it seems so inefficient.”
Another force of nature may have driven mosquitoes to such illogical flight patterns: sex. Mosquito wingbeats make high-pitched tones, and males and females harmonize these tones in their search for a mate (SN: 01/31/09, p. 10). A flight style that entails fast flapping may have evolved as a result of sexual pressure to reach higher frequencies. That’s one theory anyway, and Cohen thinks it’s an interesting idea: “You’re talking about an insect sacrificing its flying capabilities in order to mate.”
A severe coral bleaching event spurred by high ocean temperatures has struck the Great Barrier Reef for an unprecedented second time in 12 months, reveal aerial surveys released April 10 by scientists at James Cook University in Townsville, Australia. While last year the northern third of the reef was hardest hit, this time around the reef’s midsection experienced the worst bleaching. The two bleaching events together span around 1,500 kilometers of the 2,300-kilometer-long reef.
“It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016,” James Kerry, one of the researchers behind the finding, said in a statement.
Bleached corals aren’t dead. Trauma, disease or warm water can cause an exodus of the symbiotic algae that provide corals with food and vibrant color schemes. If better conditions, such as cooler waters, return, the algae may return to their homes. If they don’t come back, though, the corals starve.
Warming caused by El Niño exacerbated last year’s bleaching event. With El Niño now long gone, the researchers blame this year’s bleaching largely on global warming. If humans don’t curb emissions of planet-warming greenhouse gases, scientists warn that the entire reef could be in jeopardy.
A handful of measurements of decaying particles has seemed slightly off-kilter for years, intriguing physicists. Now a new decay measurement at the Large Hadron Collider in Geneva has amplified that interest into tentative enthusiasm, with theoretical physicists proposing that weird new particles could explain the results. Scientists with the LHCb experiment reported the new result on April 18 in a seminar at the European particle physics lab CERN, which hosts the LHC.
“It’s incredibly exciting,” says theoretical physicist Benjamin Grinstein of the University of California, San Diego. The new measurement is “a further hint that there’s something new and unexpected happening in very fundamental interactions.” Other physicists, however, are more cautious, betting that the series of hints will not lead to a new discovery. “One should always remain suspicious of an effect that does not show up in a clear way” in any individual measurement, Carlos Wagner of the University of Chicago wrote in an e-mail.
Taken in isolation, none of the measurements rise beyond the level that can be explained by a statistical fluctuation, meaning that the discrepancies could easily disappear with more data. But, says theoretical physicist David London of the University of Montreal, there are multiple independent hints, “and they all seem to be pointing at something.”
The measurements all involve a class of particle called a B meson, which can be produced when protons are smashed together in the LHC. When a B meson decays, it can produce a type of particle called a kaon that is accompanied either by an electron and a positron (an antimatter version of an electron) or by a muon — the electron’s heavier cousin — and an antimuon.
According to physicists’ accepted theories, muons and electrons should behave essentially identically aside from the effects of their differing masses. That means the two kinds of particles should have an even chance of being produced in such B meson decays. But in the new result, the scientists found only about seven decays with muons for every 10 with electrons.
There are several varieties of B mesons. All are made up of one quark — a type of fundamental particle that also makes up protons and neutrons — and one antiquark. One of the two particles is a type called a “bottom” quark (or antiquark), hence the B meson’s name. Earlier measurements of another variety of B meson decay also found a muon shortage. What’s more, measurements of the angles at which particles are emitted in some types of B meson decay also appear slightly out of whack, adding to the sense that something funny may be going on in such decays.
“We are excited by how [the measurements] all seem to fit together,” says LHCb spokesperson Guy Wilkinson, an experimental physicist at the University of Oxford in England. If more data confirm that B mesons misbehave, a likely explanation would be a new particle that interacts differently with muons than it does with electrons. One such particle could be a leptoquark — a particle that acts as a bridge between quarks and leptons, the class of particle that includes electrons and muons. Or it could be a heavy, electrically neutral particle called a Z-prime boson.
Physicists spawned a similar hubbub in 2016, when the ATLAS and CMS experiments at the LHC saw hints of a potential new particle that decayed to two photons (SN: 5/28/16, p. 11). Those hints evaporated with more data, and the current anomalies could do likewise. Although the two sets of measurements are very different, says Wolfgang Altmannshofer of the University of Cincinnati, “from the point of the overall excitement, I would say the two things are roughly comparable.”
Luckily, LHCb scientists still have a lot more data to dig into. The researchers used particle collisions only from before 2013, when the LHC was running at lower energy than it is now. “We have to get back to the grindstone and try and analyze more of the data we have,” says Wilkinson. Updated results could be ready in about half a year, he says, and should allow for a more definitive conclusion.
Mapping the relationships between different dog breeds is rough (get it?), but a team of scientists at the National Institutes of Health did just that using the DNA of 1,346 dogs from 161 breeds. Their analysis, which appears April 25 in Cell Reports, offers a lot to chew on.
Here are five key findings from the work:
Dogs were bred for specific jobs, and this shows in their genes. As human lifestyles shifted from hunting and gathering to herding to agriculture and finally urbanization, humans bred dogs (Canis familiaris) accordingly. Then over the last 200 years, more and more breeds emerged within those categories. Humans crossed breeds to create hybrids based on appearance and temperament, and those hybrids eventually became new breeds.
DNA from hybrid dogs backs up historical records. Genetic backtracking indicates that, for example, mixing between bulldogs and terriers traces back to Ireland between 1860 and 1870. That timeframe and location coincides with historical records indicating a dog-fighting fad that’s linked with crossing breeds to make better fighters.
Geography also matters. While herder dog breeds showed a lot of genetic diversity, they fall into two general groups from the rural United Kingdom and the Mediterranean on the breed family tree. When humans switched from hunting to farming, herding breeds may have emerged independently in different areas. Geography could also explain why these two groups use different herding tactics.
New World dogs aren’t all immigrants. A genetic legacy of America’s early canine inhabitants lives on in some of today’s breeds. Dogs trekked to the Americas from Asia with people more than 10,000 years ago, but when European groups started to colonize the Americas, they brought European dog breeds with them. Past studies suggest that outside breeds largely replaced New World dogs, but the new dataset shows New World dog DNA actually does persist in a few modern New World breeds, such as Chihuahuas.
Big dogs evolved independently to be big. European mastiffs and Mediterranean sheepdogs don’t share recent changes in their DNA, meaning their size traits arose separately and for different reasons. While both breed groups specialize in guarding things, mastiffs use their size to intimidate humans, while sheepdogs use their size to overpower animal predators. Larger size may have been one of the first traits that human breeders zeroed in on, the researchers suspect.
