A summertime cold snap can, quite literally, take the bloom off the rose. Not so for Scotch heather — and now scientists know why.

Thick cell walls and narrow plumbing in the alpine shrub’s stems stop deadly ice crystals from spreading to its fragile flowers during sudden summer freezes, researchers report September 15 in PLOS ONE. That lets the flowers survive and the plant make seeds even if temperatures dip below freezing.

Once ice crystals start to form inside of a plant, they can spread very quickly, says Gilbert Neuner, a botanist at the University of Innsbruck in Austria who led the study. Those sharp crystals can destroy plant cells — and flowers are particularly sensitive. So plants living in cold climes have developed strategies to confine ice damage to less harmful spots.
Neuner and his team used infrared imaging to measure heat given off by Scotch heather (Calluna vulgaris) plants as they freeze. That technique revealed where and when ice was forming. And looking at thin slices of the plant under a microscope let the scientists pick apart the structure of the plant’s ice barrier.
Cells at the base of the flower stalks had thicker walls and were packed more closely together than elsewhere in the plant, the team found. In the same area, the pipelines that carry water up the plant — called xylem — were narrower and had fewer points where ice could potentially sneak through. Those modifications let the plants “supercool” their flowers. That is, even when the flowers chilled to below zero degrees Celsius, they contained liquid water instead of ice. Ice didn’t form in the Scotch heather flowers until far below normal freezing temperatures, ‒22° C, and ice that formed elsewhere in the plant didn’t spread to the flowers.
Other species sometimes put up temporary ice blockades, for instance to protect overwintering buds. But that usually cuts off the flow of water through the xylem — fine if a plant is dormant over the winter, but flowers facing a sudden summer freeze need a continuous supply of water. Scotch heather gets around this problem by threading its xylem right through the icy barrier.

Membranes let water pass between the xylem cells, and these membranes might ultimately control the spread of ice crystals in C. vulgaris, Neuner suspects. Tiny pores in the membranes are too small to let ice crystals through the barrier. And when water molecules are found inside such small holes, the molecules are bound so tightly to the structures around them that they behave more like a gel instead of crystalizing into ice. The team hopes to test the idea in future studies.
Other flowering alpine plants could use a similar strategy. “I don’t think that this is unique to this plant,” says Sanna Sevanto, a tree physiologist at Los Alamos National Laboratory in New Mexico who wasn’t involved in the study. “It’s just that nobody has looked at it.”

Concussions, particularly those among children playing sports, are on parents’ minds. The fervor over NFL players’ brains and those of other elite athletes has trickled all the way down to mini-kicker soccer teams and peewee football leagues. And parents are right to be worried. Concussions seem to be on the rise. From 1990 to 2014, the rate of concussions in youth soccer players jumped by over 1,000 percent, a recent study estimated.

This increase might be driven in part by more inclusive definitions of concussion, a common form of traumatic brain injury that can come with headaches, confusion and memory trouble. More awareness might also drive numbers up; because parents, coaches and referees are more alert to the possibility of a concussion, more kids might be getting the diagnosis. But games may have become more competitive, too, leading to more body clashes that jolt the brain.

When a kid gets concussed, the instinct of many parents, myself included, is to cocoon their child, limiting social interaction, activity and even sleep, a recent poll conducted by researchers at UCLA suggests. The survey asked about 500 parents about how they would handle a child who had symptoms a week after a concussion. Eighty-four percent of the respondents said they would restrict their child’s physical activity for the week after the injury, 62 percent said they would take away their child’s electronics and 77 percent said they’d even wake their child up during the night. But those measures “can certainly be unhelpful,” says pediatric neurologist Christopher Giza of UCLA. “There’s some evidence it may be harmful.”

Giza points out that each child is unique, and the recovery process ought to be tailored by his or her medical team to best help the individual. But in general, excessive rest and isolation might work against kids. Last year, scientists found that children and teenagers who strictly rested for five days reported more symptoms than those who rested for one to two days. What’s more, recovery took longer for the kids who got the five-day break.

Complete isolation and rest may cause children to grow anxious and despondent, Giza says. With their normal routines interrupted, they may focus more on their symptoms. Social interactions, even those that come via a screen, may help kids feel better sooner. Gentle exercise, such as walks and swimming, is also a good thing. And despite what parents may have heard, children with concussions need sleep to recover. “Waking the kid up every few hours only worsens symptoms,” Giza says. It’s not surprising that a week of poor sleep can dial up fatigue, irritability and slow thinking.

There is one very important limit that should still be respected for kids recovering from concussions: No more head knocks. Concussions in quick succession can be extra pernicious for the brain. That means kids shouldn’t return to any sport that puts them at risk for a second concussion until they are fully recovered. In a concussion’s aftermath, reflexes are blunted, balance may be off and thinking may be slow, Giza says. Those deficits put children at more risk for getting hit.

Some sports leagues have begun changing their rules to make the game safer. This season, 5- to 10-year-olds playing in a Pop Warner football game, for instance, will no longer have kickoffs, a game-starting play responsible for an inordinate amount of concussions. Game tweaks like that, along with more vigilant coaches and parents, will help protect these little brains.

Like two siblings with divergent personalities, a type of particle has shown signs of behaving differently than its antimatter partner. It’s the first time evidence of matter-antimatter differences have been detected in decays of a baryon — a category of particle that includes protons and neutrons. Such matter-antimatter discrepancies are key to explaining how the universe came to be made mostly of matter, scientists believe.

The result is “the first measurement of its kind,” says theoretical physicist Yuval Grossman of Cornell University. “Wow, we can actually see something that we’ve never seen before.”
Evidence of matter-antimatter differences in decays of baryons — particles which are composed of three smaller particles known as quarks — has eluded scientists until now. Previous experiments have found differences between matter and antimatter varieties of mesons, which are made up of one quark and one antiquark, but never in baryons.

For most processes, the laws of physics would be the same if matter were swapped with antimatter and the universe’s directions were flipped, as if reflected in a mirror. But when this principle, known as CP symmetry (for “charge parity”), is violated, matter and antimatter act differently. Now, scientists have found hints of CP violation in the decays of a particle known as a lambda-b baryon.

Scientists with the LHCb experiment, located at the Large Hadron Collider near Geneva, reported the result online September 16 at arXiv.org. They found that when the lambda-b baryon decays, the particles produced by the decay speed away at different angles and momenta for matter and antimatter versions of the baryon. (LHCb scientists declined to comment for this article, citing the embargo policy of Nature Physics, the journal to which the paper was submitted.)

After the Big Bang, the universe initially held equal parts antimatter and matter. But as the universe evolved, the laws of physics favored matter through CP violation, and antimatter became a rarity. Scientists’ well-tested theory of particle physics, the standard model, includes some CP violation, but not enough to explain the current imbalance. So physicists are searching for additional sources of the discrepancy.

It’s not surprising that differences in matter and antimatter appeared in baryons as well as mesons, says theoretical physicist David London of the University of Montreal. But precise measurements of baryons might eventually reveal deviations from the predictions of the standard model. Such a result could point the way to additional asymmetry that allowed the universe as we know it to form. “It’s just the first step, and hopefully there will be more such measurements,” says London.

You don’t need a degree in science to monitor backyard owls or measure trees. And anyone with a computer can help scientists track seal populations in Antarctica. Citizen science projects like these — which depend on crowdsourced data — are booming. And when faced with a planet scarred by industrialization and climate change, these efforts might be exactly what we need, environmental journalist Mary Ellen Hannibal argues in Citizen Scientist.
What we call “citizen science” was once just “science.” After all, many early conservationists and natural historians — people like John Muir — weren’t academics. As species disappear faster and faster, scientists can’t work alone. They need the eyes and ears of passionate people who are watching as flowers bloom earlier each year and butterflies become sparser.

Hannibal dips her toes into some of the citizen science projects happening within driving distance of her home in San Francisco. She chronicles efforts to count, track and save a variety of species, including sea otters and redwood trees.

Along the way, Hannibal discovers heroes both modern and historical: For instance, Rebecca Moore, who leads Google Earth Outreach, originally developed the mapping tool in the early 2000s to help stop logging in the Santa Cruz Mountains. And Alice Eastwood, botany curator at the California Academy of Sciences in the early 1900s, helped build the museum’s plant collection. Lacking a college degree, she collected specimens for nearly 60 years — and even saved part of the collection from the 1906 San Francisco earthquake.

While Hannibal is contemplating extinction and habitat destruction, her father is dying from cancer. Her field expeditions become a lens through which she processes her dad’s death. The parallels make Citizen Scientist part memoir, part science tale and part history book. Hannibal has a conversational writing style that moves quickly from topic to topic, punctuated with humorous and thoughtful asides.

Although centered in California, the book has a global message: Humans have much in common with the species we’re trying to save. Grizzlies and wolves, for instance, “leave their natal home, light out for a huge territory, find a mate, and establish a new base of operations,” Hannibal writes. The human heroes in our storybooks aren’t so different.

A genetic study of HIV viruses from the 1970s may finally clear the name of a man long identified as the source of the AIDS epidemic in the United States. HIV came to New York City between 1969 and 1973, long before the man known as Patient Zero became infected, researchers report October 26 in Nature.

Using techniques developed to decipher badly degraded ancient DNA from fossils, researchers reconstructed the genetic instruction books of eight HIV viruses from blood samples collected in 1978 and 1979 in New York City and San Francisco. The viral DNA was so genetically diverse that the viruses must have been circulating in the cities for years, picking up variations, says evolutionary biologist Michael Worobey of the University of Arizona in Tucson.
Worobey and colleagues calculate that the virus probably first jumped to the United States in 1970 or 1971. So HIV spread for about a decade before AIDS was recognized in 1981 and found to be caused by a retrovirus in 1983.
Examining the relationships between the New York City and San Francisco viruses with HIV strains from elsewhere let researchers trace the virus’s path. The eight American samples all came from the same branch of the HIV family tree as ones from the Caribbean. That suggests that HIV spread from Africa to the Caribbean before making its way to the United States. New York HIV samples were more diverse than those from California, indicating that New York City was probably the hub of early HIV spread and the virus arrived in San Francisco later.
Worobey and colleagues also examined HIV DNA from Patient Zero. Also known as Case 57, he was part a 1984 study of gay men with AIDS in Los Angeles who had either a rare cancer called Kaposi’s sarcoma or Pneumocystis carinii pneumonia, both complications of the disease. Researchers from the Centers for Disease Control and Prevention found that many of the men had had sexual contact with each other, helping to establish that HIV is sexually transmitted.
Later, in the book And the Band Played On, author Randy Shilts identified Patient Zero as an Air Canada flight attendant named Gaëtan Dugas. It was widely interpreted that Dugas was the first case of HIV in the United States, even though the CDC never claimed — and has repeatedly refuted — that, says epidemiologist James Curran, a coauthor of the 1984 study who is now at Emory University in Atlanta. Part of the confusion may have been that Patient Zero was supposed to be identified as Patient O (for “outside of California”).

Dugas became a flight attendant in 1974 and began traveling to the United States shortly after, says Richard McKay, coauthor of the new study and a medical historian at the University of Cambridge. Dugas estimated that he had about 250 male sexual partners each year between 1979 and 1981. Shilts and others contended that Dugas was intentionally spreading the virus to others, though he was diagnosed with Kaposi’s sarcoma in 1980 before anyone knew what AIDS was or that it was caused by a virus.

Now, the genetic analysis confirms that Dugas was not carrying the earliest version of the virus. “This individual was simply one of thousands infected before HIV/AIDS was recognized,” McKay says.

The new study is a cautionary tale against trying to pin the spread of an infectious disease on any one person, says Robert Remien, a behavioral scientist at Columbia University Medical Center. “There’s no blame or cause to be laid on any of those people in those early years.”

Editor’s note: This story was updated November 10, 2016, to fix the alignment of the timeline with the phylogenetic tree and to update the number of sequential diagnoses in the Patient Zero cluster of AIDS cases.

SAN DIEGO — A nerve-zapping headset caused people to shed fat in a small preliminary study.

Six people who had received the stimulation lost on average about 8 percent of the fat on their trunks in four months, scientists reported November 12 at the annual meeting of the Society for Neuroscience.

The headset stimulated the vestibular nerve, which runs just behind the ears. That nerve sends signals to the hypothalamus, a brain structure thought to control the body’s fat storage. By stimulating the nerve with an electrical current, the technique shifts the body away from storing fat toward burning it, scientists propose.
Six overweight and obese people received the treatment, consisting of up to four one-hour-long sessions of stimulation a week. Because it activates the vestibular system, the stimulation evoked the sensation of gently rocking on a boat or floating in a pool, said study coauthor Jason McKeown of the University of California, San Diego.

After four months, body scans measured the trunk body fat for the six people receiving the treatment and three people who received sham stimulation. All six in the treatment group lost some trunk fat, despite not having changed their activity or diet. In contrast, those in the sham group gained some fat. Researchers suspect that metabolic changes are behind the difference. “The results were a lot better than we thought they’d be,” McKeown said.

Earlier studies had found that vestibular nerve stimulation causes mice to drop fat and pack on muscle, resulting in what McKeown called Schwarzenegger mice. Though small, the current study suggests that the approach has promise in people. McKeown and colleagues have started a company based on the technology and plan to test it further, he said.

Building mountains in minutes requires deep rocks and a big bang.

Rings of mountainous peaks sit inside large impact craters, but scientists weren’t sure how these features formed. One explanation proposed that these mountains form from deep rocks jolted to the surface by the impact. Another theory suggested that uplift caused surface rocks to congregate in heaps around the crater.

Rocks extracted from ground zero of the impact that devastated the dinosaurs have now resolved this debate. That crater’s peak ring is made up of deep rocks, researchers report in the Nov. 18 Science.
Confirming this explanation of peak ring formation will help scientists study the depths of other planets, says study coauthor Sean Gulick, a geophysicist at the University of Texas at Austin. It will also help better estimate the environmental damage wrought by the dinosaur-killing impact.、
“Unlike tectonic mountains that take millions of years to form, these mountains are made in less than 10 minutes,” Gulick says. Knowing the forces involved in sculpting those mountains will allow scientists to better estimate the total energy released during the catastrophic crash.
The Chicxulub impactor whacked into Mexico’s Yucatán Peninsula around 66 million years ago, leaving behind a 200-kilometer-wide hole in the ground. Rising around 600 meters from the crater floor — though now buried under sediment – is the peak ring. While similar rings of mountains have been spotted inside large craters on other planetary bodies such as the moon and Mercury, Chicxulub is the only crater on Earth with an intact peak ring structure. And “it’s a lot cheaper to get to the one in Mexico,” Gulick says.

Last spring, Gulick and colleagues drilled into Chicxulub’s peak ring off the coast of Mexico using a special ship that can convert into a stable platform using three long legs. Rock samples, collected from about 750 to 1,300 meters below the seafloor, contained bits of granite and other minerals that would have been buried many kilometers belowground just before the impact. That means that the same process that built the peak ring must have churned those deep rocks to the surface, the researchers concluded.
That result does not mesh with the idea that the peak ring material instead came from much closer to the surface. Under that theory, after impact, surface material slides down the crater rim onto the floor. The middle of the floor then rebounds upward due to the removal of the weight of the overlying rock. That uplift shifts the fallen material, forming a peak ring.
Instead, the dynamic collapse theory of peak ring formation explains what happened at Chicxulub, researchers say. After the initial strike, churned-up material rushed in to fill the deep void left by the impact, like water when a stone is dropped into a pond. The flowing material met in the middle of the crater and surged upward into a towering central peak that then collapsed outward, dumping rocks previously buried several kilometers underground onto the crater’s surface.
These rocks became more porous and less dense during their dramatic rise, the researchers found. While typical deep rocks in the region have an average density of more than 2.6 grams per cubic centimeter, the peak ring rocks average just 2.41 grams per cubic centimeter and are heavily fractured.

“About 10 percent of the rock is pores, so there’s lots of space,” Gulick says. Microbes, he proposes, may have moved into those holes as life repopulated the impact site. Early life on Earth may have even gotten its first foothold in the porous rock inside similar impact craters, he speculates.

The high porosity of the Chicxulub rock could also explain why the moon’s crater-riddled crust is highly porous and help solve other planetary mysteries as well, says Ross Potter, a planetary scientist at Brown University.

“Impact craters are excavating material from depth, so they’re very good probes into the interior of planetary bodies,” he says. “You may be able to find very interesting samples that tell you a lot about not only the cratering process itself, but also the interior of the planet and how the planet formed.”

SAN ANTONIO — Early Christian monks’ vows of silence may have attracted not only the devout but also a fair number of hearing-impaired men with a sacred calling.

A team led by bioarchaeologist Margaret Judd of the University of Pittsburgh found that a substantial minority of Byzantine-era monks buried in a communal crypt at Jordan’s Mount Nebo monastery display skeletal signs of hearing impairments. Judd presented these results November 19 at the annual meeting of the American Schools of Oriental Research.
Judd has directed excavations at Mount Nebo since 2007. Her new results focus on a two-chambered crypt containing skeletons of at least 57 men presumed to have been monks. Oil lamps found in the crypt date to the 700s.

About 16 percent of these men displayed damage to middle ear bones caused by infections known as otitis media. This condition frequently occurs in childhood and can lead to lasting hearing problems even if the infection clears up quickly (SN Online: 3/10/10). Monks showing signs of otitis media probably suffered mild to moderate hearing loss.

Damage to one middle ear bone, the stapes, in two other individuals likely caused severe hearing loss in one ear each. In another case, a fracture above the left eye could have damaged middle ear bones, Judd proposed. Finally, one skull’s thickened bone may have resulted from Paget’s disease, a viral infection in adulthood that can impair hearing.

Hearing loss would have had little effect on monks’ daily lives, since they communicated with hand signals, nods and other gestures, Judd said. Even if some developed hearing ailments after joining the monastery, those conditions must have largely gone undetected by affected monks and their peers who rarely or never spoke, she suggested.

Without light, we cannot see. That’s why “dark galaxies” have eluded astronomers for so long. Two years ago, these star-starved entities were virtually unknown. But scientists now have better ways of seeing, even in dim conditions. New telescopes that can detect the faint light from these mysterious galaxies have enabled scientists to chalk up a considerable list: Dark galaxies seem to be much more common than anyone had thought. One rivals the Milky Way in size but holds only a hundredth as many stars.

Cataloging these dark galaxies, as Christopher Crockett reports (SN: 12/10/16, p. 18), is just the beginning. Scientists still don’t know how such galaxies might have formed or how their small populations of stars can fend off the gravitational grabs of other galaxies. Understanding dark galaxies will take more time and more intense study of their faint light.
Cleverly built telescopes may allow us to examine the cosmic darkness, but a different type of cleverness entirely is required to delve into the minds of animals. Specifically, researchers trying to understand the evolutionary roots of mathematics must resort to complex tests for evaluating how animals judge quantities, Susan Milius reports in “Animals give clues to the origins of human number crunching.” (SN: 12/10/16, p. 22).

Counting seems an all-too-human concept, and yet many creatures can reliably pick out a greater number of treats. Figuring out how animals are making such a choice (is it surface area? volume? number?) has frustrated researchers and occasionally triggered disagreements. But the latest studies show signs that many animals do have some quantitative sense, even if it’s far less sophisticated than our own.

Much less illuminating are the results that supposedly would have provided the final answer about heart health risks posed by the anti-inflammatory pain medicine Celebrex. Like Vioxx, which was taken off the market years ago after it was linked to heart problems, Celebrex (generic name celecoxib) is what’s known as a COX-2 inhibitor. Many experts were concerned that the problems with Vioxx might also show up in people who took Celebrex. But there were little data, so the U.S. Food and Drug Administration asked for a large study to clear up the question. When the results were reported in November at a meeting of the American Heart Association, they brought little resolution, Laura Beil reports in “Popular painkiller doesn’t have more heart risks than others, study claims” (SN: 12/10/16, p. 6). Despite finding no elevated heart risk from Celebrex use, and fewer gastrointestinal side effects compared with ibuprofen and naproxen, the study was not done as cleverly as it needed to be. It enrolled people already at low risk of heart problems, for one. Dosages of medicines shifted during the long study. Many taking Celebrex dropped out before the study was completed. Far from settling the issue, the research leaves many questions unanswered.

In so many areas, science succeeds — seeing into the darkness, exploring the unknown and investigating fantastical ideas. But sometimes the signal is faint, the tools we use too crude, the logic shaky, the deeper understanding still elusive. That’s when scientists need to be more clever, more persistent, more wedded to reason and committed to revealing whatever truths can be found out there in the light.

Brilliant births and destructive deaths of stars might take a runt of a galaxy and stretch it to become a ghostly behemoth, new computer simulations show. This process could explain the origin of recently discovered dark galaxies, which can be as wide as the Milky Way but host roughly 1 percent as many stars.

Since 2015, astronomers have found hundreds of these shadowy systems lurking in and around several clusters of galaxies (SN: 12/10/16, p. 18). How these dark galaxies form is a puzzle. But prolific star formation and blast waves from exploding stars could be responsible, researchers suggest in a paper to appear in Monthly Notices of the Royal Astronomical Society Letters.
“The mystery is: Are these galaxies like the Milky Way, or are they dwarf galaxies?” says study coauthor Arianna Di Cintio, an astrophysicist at the University of Copenhagen in Denmark. “Our mechanism could be a nice formation scenario for these galaxies and prove that they are dwarfs.”

Di Cintio and colleagues ran computer simulations of galaxy evolution and found that some runts can be inflated by stellar energy. Radiation from young massive stars heats up interstellar gas, preventing it from forming more stars. And a flurry of supernova explosions can toss that gas out of the galaxy. The gravity of the galaxy drops, and so does its ability to hold on to stars and dark matter, an enigmatic substance thought to help hold galaxies together. “Dark matter particles fly outward and start the expansion,” says Di Cintio. “This happens to the stellar population as well.”

Those galaxies that remain as runts in the simulations go through this process just once, whereas giant dark galaxies regurgitate their gas multiple times. And that provides a way to test this idea, says Di Cintio. First astronomers need to find dark entities far away from galaxy clusters where the environment can also take its toll. Then researchers can estimate the ages of stars in the galaxy to see if there have been multiple bursts of star formation. If this hypothesis is correct, dark galaxies might also be loaded up with lots of hydrogen gas that allows them to sustain several rounds of gas purging.

“It is very interesting to see that, in some cases, [supernovas] can be efficient enough to expand dwarf galaxies,” says Nicola Amorisco, also at the University of Copenhagen. He helped put forth an idea that dark galaxies start as runts that get stretched because of rapid rotation. Recent observations also show that some dark systems have masses that are similar to dwarf galaxies (though one is as hefty as the Milky Way). “It is even possible that a combination of — or the interplay between — a few different mechanisms could be responsible,” says Amorisco. “It will be very exciting to understand whether that is the case.”