Houseflies stretch their legs to land. Bumblebees hover, then slowly descend. Now, insect-sized flying robots have a way to stick the landing, too.

A tiny aerial bot about the size of a bee (nicknamed RoboBee) uses static electricity to cling to the underside of a leaf and perch on other materials, study coauthor Robert Wood of Harvard University and colleagues report in the May 20 Science.

RoboBee, a bot with shiny, flapping wings and four pinlike legs, is the first of its size that can fly, perch on a surface and then take off again. This energy-saving feat could one day extend mission time in search and rescue operations, the researchers say.
For robots, tackling the problem of flight has been easier than figuring out how to land. “Engineers have been trying to build perching mechanisms for flying robots nearly as long as we have been creating flying robots,” Wood says.
Researchers have had success with bigger, bird-sized bots (SN: 2/7/15, p. 18), but their landing mechanisms are tricky to scale down. For the microbot, Wood and colleagues wanted something simple: lightweight and without moving parts.

The team created an “electroadhesive” patch with electrodes that can be charged, letting the patch stick to different surfaces, like a balloon sticking to the wall after being rubbed on someone’s hair.

Switch the electrodes on and the patch, a circular disc on top of the robot, helps RoboBee hang out on overhanging pieces of glass or plywood, for example. Switch the electrodes off and the bot detaches, free to fly again. The sticky contraption lets RoboBee rest between flights: The bot used about a thousandth as much energy perching than hovering, the researchers found.

The cooling effect of pollution may have been exaggerated.

Fossil fuel burning spews sulfuric acid into the air, where it can form airborne particles that seed clouds and cool Earth’s climate. But that’s not the only way these airborne particles can form, three new studies suggest. Tree vapors can turn into cooling airborne particles, too.

The discovery means these particles were more abundant before the Industrial Revolution than previously thought. Climate scientists have therefore overestimated cooling caused by air pollution, says atmospheric chemist Urs Baltensperger, who coauthored the three studies.
Simulating unpolluted air in a cloud chamber, Baltensperger and colleagues created microscopic particles from vapors released by trees. In the real world, cosmic rays whizzing into the atmosphere foster the development of these particles, the researchers propose in the May 26 Nature. Once formed, the particles can grow large enough to form the heart of cloud droplets, the researchers show in a second paper in Nature. After sniffing the air over the Swiss Alps, some of the same researchers report in the May 27 Science the discovery of the particles in the wild.

“These particles don’t just form in the laboratory, but also by Mother Nature,” says Baltensperger, of the Paul Scherrer Institute in Villigen, Switzerland.

Airborne particles, called aerosols, are microscopic bundles of molecules. Some aerosols start fully formed, such as dust and salts from sea spray, while others assemble from molecules in the atmosphere.

Since the 1970s, scientists have suspected that sulfuric acid is a mandatory ingredient for aerosols assembled in the air. Sulfuric acid molecules react with other molecules to form clusters that, if they grow large enough, can become stable. Human activities such as coal burning have boosted sulfuric acid concentrations in the atmosphere, subsequently boosting the abundance of aerosols that seed clouds and reflect sunlight like miniature disco balls. That aerosol boost partially offsets warming from greenhouse gases.

A cloud chamber at the CERN laboratory near Geneva allowed Baltensperger and his collaborators to simulate the atmosphere when sulfuric acid was scarce. The researchers added alpha-pinene, the organic vapor that gives pine trees their characteristic smell, to pristine air and watched for growing aerosols. Previous, though inconclusive, work suggested that the pine vapors might form aerosols.
Alpha-pinene molecules reacted with ozone in the air and formed molecules that reacted and bundled together to form aerosols, the researchers observed. The researchers added an extra layer of realism by using one of CERN’s particle beams to mimic ions from the cosmic rays bombarding Earth’s atmosphere. The “rays” led to the formation of as many as 100 times the number of aerosols. The added ions help stabilize the growing aerosols, the researchers propose.

Further testing showed that the newborn aerosols can rapidly grow from around 2 nanometers wide — roughly the diameter of a DNA helix — to 80 nanometers across, large enough to seed cloud droplets.

At a research station high in the Swiss Alps, researchers observed aerosol formation during atmospheric conditions with low sulfuric acid concentrations and abundant molecules akin to alpha-pinene. The researchers couldn’t confirm the rapid growth seen in the lab, though.

Quantifying the overall climate influence of fossil fuel burning in light of the new discovery will be tricky, says Renyi Zhang, an atmospheric chemist at Texas A&M University in College Station. “Atmospheric processes are complex,” he says. “They had a pure setup, but in reality the atmosphere is loaded with chemicals. It’s hard to draw direct conclusions at this point.”

Painkillers in the opium family may actually make pain last longer. Morphine treatment after a nerve injury doubled the duration of pain in rats, scientists report the week of May 30 in the Proceedings of the National Academy of Sciences.

The results raise the troubling prospect that in addition to having unpleasant side effects and addictive potential, opioids such as OxyContin and Vicodin could actually extend some types of pain. If a similar effect is found in people, “it suggests that the treatment is actually contributing to the problem,” says study coauthor Peter Grace, a neuroscientist at the University of Colorado Boulder.
Scientists have known that opioid-based drugs can cause heightened sensitivity to pain for some people, a condition called opioid-induced hyperalgesia. The new study shows that the effects linger weeks after use of the drugs is stopped. Male rats underwent surgery in which their sciatic nerves, which run down the hind legs, were squeezed with a stitch — a constriction that causes pain afterward. Ten days after surgery, rats received a five-day course of either morphine or saline.

Rats that didn’t receive morphine took about four weeks to start recovering, showing less sensitivity to a poke. Rats that got morphine took about eight weeks to show improvements — double the time. “That’s far bigger than we had anticipated,” Grace says. “We were definitely surprised by that.”

These experiments were done with male rats, but unpublished data indicate that morphine extends pain even longer in female rats, Grace says, results that fit with what’s known about differences in how males and females experience pain.

Longer-lasting pain in the rats came courtesy of an inflammatory response in the spinal cord. The immune system sees morphine as a threat, the researchers suspect, and responds by revving up inflammation through specialized cells called microglia. Experiments that shut down this process in microglia shortened the duration of the pain.

Many questions remain. Scientists don’t yet know if a similar immune reaction happens in people. Nor is it known whether all opioid-based painkillers would behave like morphine.
Understanding the details of how the process works has important implications for doctors, many of whom may be unaware of opioids’ complex relationship with pain, says internal medicine physician Jonathan Chen of Stanford University School of Medicine. Clarity on how opioids influence pain could change doctors’ prescribing habits and encourage the search for better pain treatments, he says.

Grace points out that the experiments were done in genetically similar rats, and that people may have more varied responses to opioids. That variability might mean that not everyone would be at risk for such long-lasting pain, he says. “But clearly these data suggest that there may be a subset of people who might be in trouble.”

Radiation from the 23 nuclear tests conducted near Bikini Atoll in the 1940s and ’50s has lingered far longer than previously predicted.

Radioactive material such as cesium-137 currently produces, on average, 184 millirems of radiation per year on Bikini Atoll. And some parts of the island hit 639 millirems per year, researchers report online the week of June 6 in the Proceedings of the National Academy of Sciences. Those measurements, made last year, surpass the 100 millirems per year safety standard set by the United States and the Republic of the Marshall Islands, which controls the island.

Scientists had predicted that, by now, radiation levels would have dropped to 16 to 24 millirems per year. But those estimates came from extrapolating from measurements made in the 1970s. The mismatch probably stems from incorrect assumptions about how rapidly radioactive material washes off the island, proposes study coauthor Emlyn Hughes, a physicist at Columbia University.

Whether the higher radiation levels pose a serious health risk to caretakers who live on the island for part of the year depends on how long they stay on the island and whether the local fruit they eat is safe, Hughes says.

A new technique turns climate-warming carbon emissions to stone. In a test program in Iceland, more than 95 percent of the carbon dioxide injected into basaltic lava rocks mineralized into solid rock within two years. This surprisingly fast transformation quarantined the CO2 from the atmosphere and could ultimately help offset society’s greenhouse gas emissions, scientists report in the June 10 Science.

“It’s working, it’s feasible and it’s fast enough to be a permanent solution for storing CO2 emissions,” says study coauthor Juerg Matter, a geochemist at the University of Southampton in England.
Many existing carbon storage schemes pump CO2 underground, though the approach has been prone to leaks. Targeting basalt, the cooled remains of volcanic outpourings, may offer an advantage over other types of rock. As much as 25 percent of basalt is made up of elements that react with CO2 to form solid carbonate minerals such as limestone, a process that occurs naturally during rock weathering. Since it was thought that this mineralization process takes hundreds to thousands of years in most rock, it seemed far too slow to be useful in combating near-term climate change.
In Iceland, Matter and colleagues blended groundwater with 230 tons of CO2 emissions from a geothermal power plant to create a kind of seltzer water. The researchers then injected the mixture 400 to 800 meters belowground into basaltic rock. After about two years, the team collected samples of the deep rock — and discovered that almost all of the CO2 had mineralized.

At $17 per ton, mineralizing carbon emissions is roughly twice as expensive as existing storage methods, though doesn’t require long-term monitoring to prevent leaks, Matter says. Additionally, the approach only requires water and basalt, he says, and “we have enough basalt globally to take care of all anthropogenic CO2 emissions, theoretically.”

Another research group’s work backs up the new findings. Peter McGrail, a geochemist at the Pacific Northwest National Laboratory in Richland, Wash., and colleagues conducted similar tests using pure CO2 without water. The as-yet-unpublished findings revealed rapid mineralization similar to that reported by Matter and colleagues, McGrail says.

If you want to lock new information into your brain, try working up a sweat four hours after first encountering it.

This precisely timed trick, described June 16 in Current Biology, comes courtesy of 72 people who learned the location of 90 objects on a computer screen. Some of these people then watched relaxing nature videos, while others worked up a sweat on stationary bikes, alternating between hard and easy pedaling for 35 minutes. This workout came either soon after the cram session or four hours later.

Compared with both the couch potatoes and the immediate exercisers, the people who worked out four hours after their learning session better remembered the objects’ locations two days later. The delayed exercisers also had more consistent activity in the brain’s hippocampus, an area important for memory, when they remembered correctly. That consistency indicates that the memories were stronger, Eelco van Dongen of the Donders Institute in the Netherlands and colleagues propose.

The researchers don’t yet know how exercise works its memory magic, but they have a guess. Molecules sparked by aerobic exercise, including the neural messenger dopamine and the protein BDNF, may help solidify memories by reorganizing brain cell connections.

Australia has seen zero mass shootings in the 20 years since it enacted strict gun control laws and a mandatory gun buyback program, researchers report June 22 in JAMA.

Key to this success is probably the reduction in people’s exposure to semiautomatic weapons, Johns Hopkins University health policy researcher Daniel Webster writes in an accompanying editorial.

“Here’s a society that recognized a public safety threat, found it unacceptable, and took measures to address the problem,” Webster says.
In April 1996, a man with two semiautomatic rifles shot and killed 35 people in Tasmania and wounded at least 18 others. Two months after the shooting, known as the Port Arthur massacre, Australia began implementing a comprehensive set of gun regulations, called the National Firearms Agreement.

The NFA is famous for banning semiautomatic long guns (including the ones used by the Port Arthur shooter), but, as Webster points out, it also made buying other guns a lot harder too. People have to document a “genuine need,” pass a safety test, wait a minimum of 28 days, have no restraining orders for violence and demonstrate good moral character, among other restrictions, Webster writes.

“In Australia, they look at someone’s full record and ask, ‘Is this a good idea to let this person have a firearm?’” Webster says. In the United States, “we do pretty much the opposite. The burden is on the government to show that you are too dangerous to have a firearm.”

Australia also initiated a mandatory gun buyback program in 1996, leading to the purchase and destruction of more than 650,000 semiautomatic and pump-action rifles and shotguns.

Simon Chapman of the University of Sydney and colleagues tallied up mass shootings before and after the NFA and analyzed 35 years of mortality data from the Australian Bureau of Statistics.
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From 1979 to 1996, Australia had 13 fatal mass shootings involving five or more victims (not including the shooter), Chapman and colleagues report. From 1997 to May 2016, the country has had none. (Three shootings, however, have killed three or four victims.) Chapman’s team also found that the rate of gun deaths dropped rapidly after 1996 but can’t confirm that this reduction is due to the gun laws.

SAN DIEGO — The long-standing mystery of the Milky Way’s missing satellite galaxies has a credible culprit, new research suggests. Supernovas, the vigorous explosions of massive stars, might have shoved much of the matter surrounding our galaxy deep into space, preventing a horde of tiny companion galaxies from forming in the first place.

Millions of teeny galaxies should be buzzing around the Milky Way, according to theories about how galaxies evolve, but observations have turned up only a few dozen (SN: 9/19/15, p. 6). And the brightest of those that have been found are lightweights compared with what theorists expect to find. But new computer simulations designed to track the growth of galaxies down to the level of individual stars reveal the critical role that supernovas might play in resolving these conundrums.
Philip Hopkins, an astrophysicist at Caltech, presented the results June 13 during a news briefing at a meeting of the American Astronomical Society.

“Galaxies don’t just form stars and sit there,” Hopkins said. “If you [add] up all the energy that supernovae emitted during a galaxy’s lifetime, it’s greater than the gravitational energy holding the galaxy together. You cannot ignore it.”

Simulations are typically limited by computing power, and efforts to simulate galaxy evolution have to brush over some details. For instance, rather than capture everything that’s going on in a galaxy, simulations slap on the additive effects of supernovas in an ad hoc fashion. These limitations don’t fully capture all the physics of stellar winds and supernova shocks that ripple through a galaxy.

Hopkins’ simulations grow a galaxy organically within a computer, tracing the evolution of a system such as the Milky Way over 13 billion years. Within a massive virtual blob of dark matter — the elusive substance thought to bind galaxies together — gas collects and fragments into stellar nurseries. Stars are born and die in this digital universe. A volley of life-ending explosions from the most massive of these stars lead to a turbulent galactic history, Hopkins finds.

“As these stars form rapidly in the early universe, they also live briefly and explode and die violently, ejecting material far from the galaxy,” he said. “They’re not just getting rid of gas.” They’re stirring up the dark matter as well, preventing a multitude of satellite galaxies from forming, and whittling away at those few that survive. “It’s not until quite late times … that [the galaxy] settles down and forms what we would call a recognizable galaxy today,” Hopkins said.
The idea that stellar tantrums could chip away at the gas and dark matter around a galaxy is not new, says Janice Lee, an astronomer at the Space Telescope Science Institute in Baltimore. But Hopkins’ simulations bring a lot more detail to that story and show that it’s a plausible reason for our galaxy’s satellite shortfall.

Before declaring that the mystery of the missing satellite galaxies is solved, however, astronomers need to run a few more checks against reality, says Lee. There are still assumptions in the calculations about how energy from dying stars interacts with interstellar gas, for example. The precise details of that interaction can affect how many stellar runts versus behemoths form in star clusters.

NASA’s James Webb Space Telescope, scheduled to launch in 2018, could probe star clusters in several relatively nearby galaxies, she says. Those observations could be compared with virtual clusters that appear in the simulations to see how close they match the real universe.

Even Amelia Earhart couldn’t compete with the great frigate bird. She flew nonstop across the United States for 19 hours in 1932; the frigate bird can stay aloft up to two months without landing, a new study finds. The seabird saves energy on transoceanic treks by capitalizing on the large-scale movement patterns of the atmosphere, researchers report in the July 1 Science. By hitching a ride on favorable winds, the bird can spend more time soaring and less time flapping its wings.

“Frigate birds are really an anomaly,” says Scott Shaffer, an ecologist at San Jose State University in California who wasn’t involved in the study. The large seabird spends much of its life over the open ocean. Both juvenile and adult birds undertake nonstop flights lasting weeks or months, the scientists found. Frigate birds can’t land in the water to catch a meal or take a break because their feathers aren’t waterproof, so scientists weren’t sure how the birds made such extreme journeys.

Researchers attached tiny accelerometers, GPS trackers and heart rate monitors to great frigate birds flying from a tiny island near Madagascar. By pooling data collected over several years, the team re-created what the birds were doing minute-by-minute over long flights — everything from how often the birds flapped their wings to when they dived for food.
The birds fly more than 400 kilometers, about equivalent to the distance from Boston to Philadelphia, every day. They don’t even stop to refuel, instead scooping up fish while still in flight.

And when frigate birds do take a break, it’s a quick stopover.

“When they land on a small island, you’d expect they’d stay there for several days. But in fact, they just stay there for a couple hours,” says Henri Weimerskirch, a biologist at the French National Center for Scientific Research in Villiers-en-Bois who led the study. “Even the young birds stay in flight almost continually for more than a year.”

Frigate birds need to be energy Scrooges to fly that far. To minimize wing-flapping time, they seek out routes upward-moving air currents that help them glide and soar over the water. For instance, the birds skirt the edge of the doldrums, a windless region near the equator. On either side of the region, consistent winds make for favorable flying conditions. Frigate birds ride a thermal roller coaster underneath the bank of fluffy cumulus clouds frequently found there, soaring up to altitudes of 600 meters.

Airplanes tend to avoid flying through cumulus clouds because they cause turbulence. So the researchers were surprised to find that frigate birds sometimes use the rising air inside the clouds to get an extra elevation boost — up to nearly 4,000 meters. The extra height means the birds have more time to gradually glide downward before finding a new updraft. That’s an advantage if the clouds (and the helpful air movement patterns they create) are scarce.

It’s not yet clear how frigate birds manage to sleep while on the wing. Weimerskirch suggests they might nap in several-minute bursts while ascending on thermals.

“To me, the most fascinating thing was how incredibly far these frigate birds go in a single flight, and how closely tied those flight patterns are to the long-term average atmospheric condition,” says Curtis Deutsch, an oceanographer at the University of Washington in Seattle. As these atmospheric patterns shift with climate change, frigate birds might change their path, too.

Even robots can use a heart. Or heart cells, at least.

A new stingray bot about the size of a penny relies on light-sensitive heart cells to swim. Zaps with light force the bot’s fins to flutter, letting researchers drive it through a watery obstacle course, Kit Parker of Harvard University and colleagues report in the July 8 Science.

The new work “extends the state of the art — very much so,” says bioengineer Rashid Bashir of the University of Illinois at Urbana-Champaign. “It’s the next level of sophistication for swimming devices.”
For decades, the field of robotics has been dominated by bulky, rigid machines made mostly of metal or hard plastic. But in recent years, some researchers have turned toward softer, squishier materials, such as silicones and rubbery plastics (SN: 11/1/14, p.11). And a small group of scientists have taken it one step further: combining soft materials with living cells.

So far, there’s just a handful of papers on these hybrid machines, says Bashir, whose own lab recently reported the invention of tiny, muscle-wrapped bots that inch along like worms in response to light.

In 2012, Parker’s team built a robotic jellyfish out of silicone and heart muscle cells. Electrically stimulating the cells let the jellyfish push itself through water by squeezing its body into a bell shape and then relaxing.

But, Parker says, “the jellyfish just swam.” He and his colleagues couldn’t steer it around a tank. They can, however, steer the new stingray.

He explains the team’s strategy with a story about his daughter. When she was little, Parker would point his laser pointer at the sidewalk and she’d try to stomp on the dot. He could guide her down a path as she followed the light. “She got to be independent and I got to make sure she didn’t step out into traffic.”
Parker guides his stingray bot in a similar way.

Layered on top of the bot’s body — a gold skeleton sandwiched between layers of silicone — lies a serpentine pattern of cells. The pattern is made up of about 200,000 these cells, harvested from rat hearts and then genetically engineered to contract when hit with pulses of blue light.
Flashing the light at the bot sets off a wave of contractions, making the fins undulate, like a flag rippling in the wind. To make the stingray turn, the team stimulates the bot’s right and left fins separately. Faster flashing on the right side makes the ray turn left and vice versa, Parker says.

By moving the lights slowly across a fluid-filled chamber, the researchers led the bot in a curving path around three obstacles.

“It’s very impressive,” says MIT computer scientist Daniela Rus. The stingray is “capable of a new type locomotion that had not been seen before” in robots, she says.

Bashir says he can envision such devices one day used in biomedicine or even environmental cleanup: Perhaps researchers could program cells on a swimming bot to suck toxicants out of lakes or streams. But the work is still in its early days, he says.

Parker, a bioengineer interested in cardiac cell biology, has something entirely different in mind. He wants to create an artificial heart that children born with malformed hearts could use as a replacement. Like a heart, a stingray’s muscular body is a pump, he says, designed to move fluids. The robot gave Parker a chance to work on assembling a pump made with living materials.

“Some engineers build things out of aluminum. I build things out of cells — and I need to practice,” he says. “So I practice building pumps.”

There’s another upside to the robot too, he adds: “It’s cool and fun.”