上海千花419论坛

In a rare bright spot for global environmental news, atmospheric scientists reported in 2016 that the ozone hole that forms annually over Antarctica is beginning to heal. Their data nail the case that the Montreal Protocol, the international treaty drawn up in 1987 to limit the use of ozone-destroying chemicals, is working.

The Antarctic ozone hole forms every Southern Hemisphere spring, when chemical reactions involving chlorine and bromine break apart the oxygen atoms that make up ozone molecules. Less protective ozone means that more ultraviolet radiation reaches Earth, where it can damage DNA and lead to higher rates of skin cancer, among other threats.
The Montreal Protocol cut back drastically on the manufacture of ozone-destroying compounds such as chlorofluorocarbons, or CFCs, which had been used in air conditioners, refrigerators and other products. It went into force in 1989 and phased out CFCs by 2010.

Earlier studies had hinted that the ozone hole was on the mend. The new work, reported in Science in June, is the most definitive yet (SN: 7/23/16, p. 6). A team led by Susan Solomon, an atmospheric chemist at MIT, looked not only at the month of October, when Antarctic ozone loss typically peaks, but also at September, when the hole is growing. The healing trend was most obvious in September. Satellite measurements showed that from 2000 to 2015, the average extent of the September ozone hole shrank by about 4.5 million square kilometers, to approximately 18 million square kilometers. Soundings taken by weather balloons over Antarctica confirmed the findings.
CFC concentrations peaked above Antarctica in the late 1990s and early 2000s and have been dropping ever since, says Birgit Hassler, an atmospheric chemist at Bodeker Scientific in Alexandra, New Zealand. Each passing year allows scientists to gather more convincing data. The new study, Hassler says, “makes the whole development of the Antarctic ozone hole healing very transparent and understandable.”
It is a fitting capstone to Solomon’s career. In the 1980s she led a team that proposed that chlorine compounds were to blame for Antarctic ozone loss. She then traveled to the frozen continent to conduct pioneering experiments that measured the accumulating chemicals there. “It’s very humbling now to be 30 years later and be able to say we have a clear fingerprint that the ozone hole is starting to get better,” she says.

Solomon says that public engagement was key to solving the ozone problem, with people coming together to identify an issue that threatened society and develop new technologies to fix it. In that respect, the most successful environmental treaty in history holds lessons for dealing with a much bigger threat, she says — climate change.

To fix the ozone layer, industry stopped using CFCs and similar compounds and replaced them with hydrofluorocarbons. Those chemicals, however, turned out to be powerful greenhouse gases that accelerated global warming. In October, the nations that ratified the Montreal Protocol agreed to expand it to cover hydrofluorocarbons as well (SN: 11/26/16, p. 13).

When looking for love, some small-mouthed salamanders can really go the distance.

These intrepid amphibians (Ambystoma texanum) will risk death and dehydration to travel almost nine kilometers on average and as far as 14 to find a mate, researchers report December 20 in Functional Ecology. But all-female populations of a closely related group of salamanders that reproduce by cloning can’t go nearly as far.

Scientists tested the amphibians’ endurance on tiny treadmills. Then the team analyzed genetic differences between salamanders in patches of Ohio wetlands to see how far the amphibians might roam in the wild. Unisexual salamanders could only go a quarter of the treadmill distance that the small-mouthed salamanders could. And in the wild, they only dispersed about half as far from the pools where they were born.
By making the treacherous trek to a different pool to mate, A. texanum salamanders can mix up their genes and keep healthy variation in each population. Unisexual salamanders may have less stamina because they don’t mate in the usual way. Instead of searching for the perfect partner, they steal sperm from nearby male salamanders of different species. The sperm kick-start egg production but rarely actually fertilize eggs; only occasionally does a male’s DNA sneak into a female’s offspring.

Ditching the guys can be efficient — every member of an all-female population can give birth, and that means more babies. But it seems that going it alone has drawbacks, too: These salamanders’ poorer endurance could be a disadvantage if environmental changes forced them to colonize new territory.

Scientists have produced a new form of hydrogen in the lab — negatively charged hydrogen clusters.

Each cluster consists of hydrogen molecules arranged around a negatively charged hydrogen ion — a single hydrogen atom with an extra electron — at temperatures near absolute zero, the researchers report in the Dec. 30 Physical Review Letters. Similar, positively charged ion clusters have previously been found, but this is the first time scientists have seen negative hydrogen cluster ions beyond the simplest possible pairing of one molecule and one ion.
Physicist Michael Renzler of the University of Innsbruck in Austria and colleagues infused tiny droplets of liquid helium with hydrogen gas. Then, the scientists bombarded the droplets with a beam of electrons, which converted some hydrogen molecules into negatively charged hydrogen ions. Neighboring hydrogen molecules (two bonded hydrogen atoms) clustered around the ion, in groups of a few molecules to over 60.

The scientists also determined the geometric structures of the clusters. Hydrogen molecules organized into shells that surrounded the central ion. Clusters were most stable, and most common, when molecules filled shells to their capacity. In the first shell, for example, the cluster formed an icosahedron — a 3-D shape with 12 vertices — when 12 molecules filled this shell.

In space, hydrogen cluster ions might form naturally in cold, dense clouds of hydrogen or in atmospheres of gas giant planets.

Some ants are so good at navigating they can do it backward.

Researchers think that foraging ants memorize scenes in front of them to find their way back to the nest. But that strategy only works when facing forward. Still, some species have been observed trekking in reverse to drag dinner home.

To find out how the ants manage this feat, Antoine Wystrach of the University of Edinburgh and colleagues captured foraging desert ants (Cataglyphis velox) near a nest outside Seville, Spain. In a series of tests, the researchers gave the ants cookie crumbles and then released the ants at a fork in the route back to their nest.

Regardless of which direction they took, ants walking backward with cookie bits in tow maintained a straight path. The researchers suspect the ants relied on some sort of sunlight cues. Ants also appeared to peek behind themselves to check and adjust course. After making adjustments, ants maintained their new direction no matter their body orientation. Desert ants combine their celestial compass and long-term visual memories of the route to find their way home, the team concludes online January 19 in Current Biology.

Blobs of gas near the Milky Way’s center may be just the right mass to harbor young stars and possibly planets, too. Any such budding stellar systems would face an uphill battle, developing only about two light-years from the galaxy’s central supermassive black hole with its intense gravity and ultraviolet radiation. But it’s not impossible for the small stars to survive in the hostile place, a new study suggests.

“Nature is very clever. It finds ways to work in extreme environments,” says Farhad Yusef-Zadeh, an astrophysicist at Northwestern University in Evanston, Ill. Four blobs of gas near the galactic center have the right amount of mass to be planetary systems with small, young stars, Yusef-Zadeh and colleagues report online January 20 at arXiv.org. The paper is also slated for publication in the Monthly Notices of the Royal Astronomical Society.
“It is fairly likely that planets and low-mass stars do form near the galactic center. But we do not know it for sure at the moment,” says Avi Loeb, an astrophysicist at Harvard University. Loeb, who was not involved in the study, says the new evidence is “tentative at best.”

Yusef-Zadeh and colleagues used ALMA, the Atacama Large Millimeter/submillimeter Array, in Chile to study emissions from five of the 44 blobs of gas that the team discovered in 2014 (SN Online: 3/24/15). Four of the clouds had between 0.03 and 0.05 as much mass as the sun, the team calculated. That’s right in line with what’s needed to generate low-mass stars — ones about the size of the sun or a little bigger — and the planets that orbit them, Yusef-Zadeh says. He points out that the team has not detected these stars or planets, just that conditions are ripe for them to exist.

Loeb notes that the team had to infer the clouds’ entire masses from the ALMA measurements, which may reveal only a surface look at the blobs. The clouds may actually be denser; as a result, they would form more massive stars, challenging the team’s claim that low-mass stars are forming.

Yusef-Zadeh and colleagues are planning additional studies with ALMA and are also working on research that suggests that black holes may, in fact, help star formation. “It’s paradoxical,” Yusef-Zadeh says. “Black holes eat everything that comes too close to them. They tear everything apart. But they may actually make the formation of stars more efficient.”

The breath of oxygen that enabled the emergence of complex life kicked off around 100 million years earlier than previously thought, new dating suggests.

Previous studies pegged the first appearance of relatively abundant oxygen in Earth’s atmosphere, known as the Great Oxidation Event, or GOE, at a little over 2.3 billion years ago. New dating of ancient volcanic outpourings, however, suggests that oxygen levels began a wobbly upsurge between 2.460 billion and 2.426 billion years ago, researchers report the week of February 6 in Proceedings of the National Academy of Sciences.

That time difference is a big deal, says study coauthor and sedimentary geologist Andrey Bekker of the University of California, Riverside. The new date shakes up scientists’ understanding of the environmental conditions that led to the GOE, which prompted the evolution of oxygen-dependent life-forms called eukaryotes. Voluminous volcanic eruptions at the time poured fresh rock over a supercontinent near the equator, and the planet dipped into a frigid period known as a Snowball Earth.

A similar series of geologic events around 700 million years ago coincided with a second rise of oxygen, to near-modern levels, and some eukaryotes evolving into the first animals. Both oxygen upswings pushed life toward complexity and the ultimate emergence of humans, Bekker says. “For the first time, we see parallels between these two time intervals,” he says.
Oxygen-producing microbes probably first appeared more than 3 billion years ago (SN Online: 9/8/15). But oxygen remained scant until the GOE when, for unknown reasons, atmospheric concentrations of the gas rose from near zero to around 0.1 percent of modern levels.

Dating the GOE’s start has been tricky, though, because few rocks from back then remain. Geologist Ashley Gumsley of Lund University in Sweden, Bekker and colleagues studied ancient volcanic rocks from South Africa that neighbor a layer of minerals that could have formed only in the presence of oxygen. Using an old technique, geologists had previously determined those volcanic rocks to be from around 2.222 billion years ago, well after the GOE’s start.

Applying modern techniques that measure the gradual decay of radioactive uranium in the rocks, the researchers revised the volcanism’s timing to about 2.426 billion years ago. That new date — plus a separate volcanic eruption previously dated to around 2.460 billion years ago that clearly happened before the oxygen rise — helps constrain the potential GOE start date.

The GOE isn’t the only global event to have its timeline tweaked. The oldest known evidence of global glaciation, called a Snowball Earth, lies underneath and alongside the South African rocks. The new eruption dating pushes that Snowball Earth event earlier as well — to around the same time as the start of the GOE.

The oxygen rise and the temperature drop may have been related, the researchers propose.

The new data and existing chemical evidence suggest that oxygen levels during the GOE wavered between pitiful and plentiful several times, rather than steadily rising (SN: 2/18/17, p. 16). (Oxygen concentrations stabilized around 2.250 billion years ago and remained largely unchanged until levels rose again more than a billion years later.) These oscillations coincided with Snowball Earths and volcanic eruptions, Gumsley says.

Climate, oxygen and volcanism were intertwined during the GOE, the researchers propose. Volcanic eruptions covered the supercontinent with fresh rock. That rock formed near the equator where heavy precipitation weathered the rock, drawing carbon dioxide from the air and washing nutrients into the ocean. Those nutrients nourished photosynthetic microbes, which produced an abundance of oxygen. Oxygen built up in the atmosphere and reacted with methane, reducing levels of that greenhouse gas (SN: 10/29/16, p. 17).

With less CO2 and methane warming the climate, Earth froze and oxygen-producing biological activity decreased. The ongoing volcanism spewed replacement CO2 into the atmosphere over time and eventually reheated the planet.

“This is further evidence that oxygen’s history has really been a roller coaster ride rather than a unidirectional rise,” says Yale University geochemist Noah Planavsky. While he’s uncertain about the role rock weathering played in controlling ancient oxygen levels, Planavsky believes the new age will allow scientists to delve into the question of why the GOE began when it did. “Without dates,” he says, it’s impossible “to have any real grounding to tackle these problems.”

People who undergo gastric bypass surgery are more likely to experience a remission of their diabetes than patients who receive a gastric sleeve or intensive management of diet and exercise, according to a new study. Bypass surgery had already shown better results for diabetes than other weight-loss methods in the short term, but the new research followed patients for five years.

“We knew that surgery had a powerful effect on diabetes,” says Philip Schauer of the Bariatric & Metabolic Institute at the Cleveland Clinic. “What this study says is that the effect of surgery is durable.” The results were published online February 15 in the New England Journal of Medicine.
The study followed 134 people with type 2 diabetes for five years in a head-to-head comparison of weight-loss methods. At the end of that time, two of 38 patients who only followed intensive diet and exercise plans were no longer in need of insulin to manage blood sugar levels. For comparison, 11 of 47 patients who had a gastric sleeve, which reduces the size of the stomach, and 14 of 49 who underwent gastric bypass, a procedure that both makes the stomach smaller and shortens digestion time, did not need the insulin anymore. In general, patients who had been diabetic for fewer than eight years were more likely to be cured, Schauer says.

Even those surgical patients who still needed to take insulin had greater weight loss and lower median glucose levels than others in the study. This study was also one of the few to show that bariatric surgery could help those with only mild obesity, defined as a body mass index between 27 and 34. How bariatric surgery might improve diabetes is still unknown, but scientists have pointed to effects on the body’s metabolism (SN: 8/24/13, p. 14) and gut microbes (SN: 9/5/15, p. 16).
The same research team had published similar results at one and three years after surgery, but few studies looked further, says Kristoffel Dumon, a bariatric surgeon with the University of Pennsylvania Health System in Philadelphia. “The criticism of bariatric research has been that there are no good long-term results. With weight-loss surgery, you often see rapid initial results, but you want to see that to a five-year time point.”
Dumon also notes that the patients who received only intensive medical therapy did not report an improvement in their quality of life, and their emotional well-being worsened. People in the surgical group reported improvements in quality of life, but not in emotional well-being, a finding that Schauer says has more to do with stress management and other characteristics that wouldn’t necessarily be affected by surgery.

Schauer hopes to have even longer-term data in the future. His team will combine their results with those from similar research at three other U.S. sites with the goal of following patients for up to 10 years.

Eijiro Miyako gets emotional about the decline of honeybees.

“We need pollination,” he says. “If that system is collapsed, it’s terrible.”

Insects, especially bees, help pollinate both food crops and wild plants. But pollinators are declining worldwide due to habitat loss, disease and exposure to pesticides, among other factors (SN: 1/23/16, p. 16).

Miyako, a chemist at the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, became passionate about the loss of pollinators after watching a TV documentary. He remembers thinking: “I need to create something to solve this problem.”
His answer was in an 8-year-old jar in his lab.

In 2007, he had tried to make a gel that conducts electricity, but it was “a complete failure,” he says. So he poured the liquid into a jar, put it in a drawer and forgot about it. Cleaning out his lab in 2015, he accidentally dropped and broke the jar.
Surprisingly, the gel was still sticky and picked up dust from the floor. Miyako realized that the gel’s ability to capture the tiny particles was similar to how honeybee body hairs trap pollen. His thoughts jumped to artificial pollination.

First, he investigated whether non-pollinating insects could help do the job. He dabbed his gel onto ants and set them loose in a box of tulips. The ants were coated with pollen after three days.

Still, Miyako worried that predators would snack on his insect pollinators. To give them camouflage, he mixed four light-reactive compounds into the gel. He tested the new concoction on flies, placing a droplet on their backs and setting the insects in front of blue paper. Under ultraviolet light, the gel changed from clear to blue, mimicking the color of the backdrop.

Though this chemical invisibility cloak might protect the insects, Miyako wanted a pollinator that could be controlled and wouldn’t wander off at the first scent of a picnic.

He bought 10 kiwi-sized drones and taught himself to fly them, breaking all but one in the process. Miyako covered the bottom of the surviving drone with short horsehair, using electricity to make the hair stand up. Adding his gel made the horsehair work like bee fuzz.
In tests so far, the drone has successfully pollinated Japanese lilies more than a third of the time, brushing up against one flower to collect pollen, then flying into another to knock the grains off, his team reports in the Feb. 9 Chem.
Glad he saved that failed gel, Miyako thinks it is possible to automate a fleet of 100 drones, using GPS and artificial intelligence, to pollinate alongside bees and other insects. “It’s not science fiction,” he says.

One of Jupiter’s companions is a bit of a nonconformist.

The gas giant shares its orbit around the sun with a slew of asteroids, but scientists have now discovered one that goes against the flow. It journeys around the solar system in reverse — in the opposite direction of Jupiter and all the other planets. Asteroid 2015 BZ509 is the first object found that orbits in the same region as a planet but travels backward, researchers from Canada and the United States report March 30 in Nature.
The asteroid was discovered with the Pan-STARRS observatory in Hawaii in 2015, and the researchers made additional observations with the Large Binocular Telescope Observatory in Arizona.

Backward-going asteroids are rare — only 0.01 percent of known asteroids are in retrograde orbits. Until now, none were known to share a planet’s orbit. It was thought that asteroids going in reverse couldn’t coexist with a planet because interactions with the celestial body, twice each orbit, would knock the asteroid off track. But because 2015 BZ509 passes on alternating sides of Jupiter, the interactions cancel each other out, the researchers say. The first flyby in orbit pulls the asteroid outward, and the next tugs it inward — keeping the maverick asteroid in line.

The asteroid’s relationship with Jupiter is no short-term fling: The researchers determined that the two have shared an orbit for a million years.

The oldest known specimens of bedbug relatives have been unearthed in an Oregon cave system where ancient humans once lived. The partial fossils from three different species in the bedbug family date back 5,000 to 11,000 years, predating a previous find from 3,500 years ago, researchers report April 4 in the Journal of Medical Entomology.

“The bedbugs that we know in modern times originated as bat parasites, and it’s believed that they became human parasites when humans lived in caves with bats,” says study coauthor Martin Adams of Paleoinsect Research in Portland, Ore. When humans moved elsewhere, bedbugs came along for the ride.

These three species (Cimix antennatus, Cimex latipennis and Cimex pilosellus) probably coexisted with humans in Oregon’s Paisley Five Mile Point Caves, and probably snacked on people at least occasionally, Adams says. Even though all three species are still around today, they still feast mostly on bats.

Archaeologists think that ancient humans lived in the Paisley Caves only seasonally, which could explain why these particular species of bedbugs didn’t switch to a human-centric diet.