Protected areas not safe from light pollution

Protected areas, such as nature reserves and national parks, are thought to provide a refuge for wildlife, but according to a new study, many of these areas are not safe from light pollution. Thanks to increasing urbanization, many nocturnal skies are no longer dark. 

Although helpful for humans, artificial night lighting can impact nocturnal wildlife by disrupting natural reproductive cycles, disorienting migratory species, and increasing the risk of predation. To assess how well protected areas shelter wildlife from light pollution and preserve natural darkness, researchers analyzed satellite images of Earth collected at night by the Defense Meteorological Satellite Program between 1992 and 2010. Individual pixels, representative of approximately 3 square kilometers, were assigned a number based on their degree of illumination, ranging from 0 (complete darkness) to 63 (brightly lit urban areas). 

More than 170,000 unique protected areas were identified using the International Union for Conservation of Nature’s World Database on Protected Areas. 

The degree of nighttime illumination was then compared with unprotected areas for each continent over the 2 decades. Although 86% of the world’s landmasses remain in relative darkness at night, darkness declined slightly in all regions over the study period.

 Protected areas were still generally darker than unprotected areas, yet protected areas experienced widespread increases in nighttime light exposure between 1992 and 2010, the team reports online this month in Conservation Biology. In Europe, Asia, and South and Central America, up to 42% of protected areas have experienced significant increases in nighttime lighting. 

A smaller percentage of protected areas in Europe (24%) and North America (17%) exhibited high levels of nighttime lighting in all years. Based on their findings, researchers propose reduced lighting zones be established around existing refuges to preserve their natural darkness and biodiversity. 

A step closer to explaining high-temperature superconductivity?

For years some physicists have been hoping to crack the mystery of high-temperature superconductivity—the ability of some complex materials to carry electricity without resistance at temperatures high above absolute zero—by simulating crystals with patterns of laser light and individual atoms. Now, a team has taken—almost—the next-to-last step in such "optical lattice" simulation by reproducing the pattern of magnetism seen in high-temperature superconductors from which the resistance-free flow of electricity emerges.

"It's a very big improvement over previous results," says Tilman Esslinger, an experimentalist at the Swiss Federal Institute of Technology in Zurich, who was not involved in the work. "It's very exciting to see steady progress."

An optical lattice simulation is essentially a crystal made of light. A real crystal contains a repeating 3D pattern of ions, and electrons flow from ion to ion. In the simulation, spots of laser light replace the ions, and ultracold atoms moving among spots replace the electrons. Physicists can adjust the pattern of spots, how strongly the spots attract the atoms, and how strongly the atoms repel one another. 

That makes the experiments ideal for probing physics such as high-temperature superconductivity, in which materials such as mercury barium calcium copper oxide carry electricity without resistance at temperatures up to 138 K, far higher above absolute zero than ordinary superconductors such as niobium can.

Just how the copper-and-oxygen, or cuprate, superconductors work remains unclear. The materials contain planes of copper and oxygen ions with the coppers arranged in a square pattern. Repelling one another, the electrons get stuck in a one-to-a-copper traffic jam called a Mott insulator state. They also spin like tops, and at low temperatures neighboring electrons spin in opposite directions, creating an up-down-up-down pattern of magnetism called antiferromagnetism. Superconductivity sets in when impurities soak up a few electrons and ease the traffic jam. The remaining electrons then pair to glide freely along the planes.

Theorists do not yet agree how that pairing occurs. Some think that wavelike ripples in the antiferromagnetic pattern act as a glue to attract one electron to the other. Others argue that the pairing arises, paradoxically, from the repulsion among the electrons alone. Theorists can write down a mathematical model of electrons on a checkerboard plane, known as the Fermi-Hubbard model, but it is so hard to "solve" that nobody has been able to show whether it produces superconductivity.

Experimentalists hope to reproduce the Fermi-Hubbard model in laser light and cold atoms to see if it yields superconductivity. In 2002, Immanuel Bloch, a physicist at the Max Planck Institute for Quantum Optics (MPQ) in Garching, Germany, and colleagues realized a Mott insulator state in an optical lattice. Six years later, Esslinger and colleagues achieved the Mott state with atoms with the right amount of spin to mimic electrons. Now, Randall Hulet, a physicist at Rice University in Houston, Texas, and colleagues have nearly achieved the next-to-last step along the way: antiferromagnetism.

Hulet and colleagues trapped between 100,000 and 250,000 lithium-6 atoms in laser light. They then ramped up the optical lattice and ramped it back down to put them in order. Shining laser light of a specific wavelength on the atoms, they observed evidence of an emerging up-down-up-down spin pattern. The laser light was redirected, or diffracted, at a particular angle by the rows of atoms—just as x-rays diffract off the ions in a real crystal. Crucially, the light probed the spin of the atoms: The light wave flipped if it bounced off an atom spinning one way but not the other. Without that flipping, the diffraction wouldn't have occurred, so observation confirms the emergence of the up-down-up-down pattern, Hulet says.

Hulet's team solved a problem that has plagued other efforts. Usually, turning the optical lattice on heats the atoms. To avoid that, the researchers added another laser that slightly repelled the atoms, so that the most energetic ones were just barely held by the trap. Then, as the atoms heated, the most energetic ones "evaporated" like steam from hot soup to keep the other ones cool, the researchers report online this week in Nature. They didn't quite reach a full stable antiferromagnetic pattern: The temperature was 40% too high. But the technique might get there and further, 

Hulet says. "We don't have a good sense of what the limit of this method is," he says. "We could get a factor of two lower, we could get a factor of 10 lower."

"It is indeed very promising," says Tin-Lun "Jason" Ho, a theorist at Ohio State University, Columbus. Reducing the temperature by a factor of two or three might be enough to reach the superconducting state, he says. However, MPQ's Bloch cautions that it may take still other techniques to get that cold. 

"There are several cooling techniques that people are developing and interesting experiments coming up," he says.

Physicists are also exploring other systems and problems with optical lattices. The approach is still gaining steam, Hulet says: "It's an exciting time."

Article: ScienceMag

NIH sets aside more than $40 million for study of human placenta

The Human Placenta Project, launched last year by the National Institutes of Health (NIH) despite uncertainty over how much money would back in the effort, has just received a whopping $41.5 million in 2015 to study the vital mass of tissue that sustains a developing fetus.

The placenta carries nutrients and oxygen to a fetus from its mother’s bloodstream and removes waste; problems with its performance may contribute to health concerns ranging from preterm birth to adult diabetes. Yet it is the least understood human organ, according to Alan Guttmacher, director of NIH’s National Institute of Child Health and Human Development (NICHD). 

Last year, Science reported on a NICHD workshop where planning began for a Human Placenta Project that would aim to monitor the placenta during a woman’s pregnancy, using new imaging approaches, tests for fetal molecules shed into a mother’s blood, and other tools.

That plan is reflected in the title of a 26 February request for grant applications, from NICHD and the National Institute of Biomedical Imaging and Bioengineering (NIBIB), that calls for “Paradigm-Shifting Innovations” in how to assess the human placenta. One objective is to learn how environmental factors such as a mother’s diet and exposure to pollutants affect the placenta. The $41.5 million will support eight to nine awards lasting up to 4 years.

The new funding commitment for the project comes on top of about $4.5 million in 2015 that NICHD and NIBIB have already set aside for research on tools to study the placenta. An NIH representative says that some of the additional $41.5 million could come from leftover funding from the National Children’s Study (NCS), a controversial plan to follow the health of 100,000 children for 21 years that NIH canceled in December. NIH is now looking for ways to spend $140 million that Congress appropriated for the NCS in 2015 on related studies.

Article: ScienceMag

Astronauts breeze through spacewalk to rig station for U.S. space taxis

Two U.S. astronauts whipped through a third spacewalk outside the International Space Station on Sunday to rig parking spots for new U.S. space taxis.

Station commander Barry "Butch" Wilmore and flight engineer Terry Virts expected to spend about seven hours installing antennas, cables and navigation aides on the station's exterior truss. Instead, the astronauts, who were making their third spacewalk in eight days, were back inside the space station in 5.5 hours.

The purpose of the outings was to prepare berthing slips for spaceships being developed by Boeing and Space Exploration Technologies, or SpaceX.

Wilmore and Virts floated outside the Quest airlock shortly after 7 a.m. EST/1200 GMT, a NASA Television broadcast showed. Their job was to install more than 400 feet (122 meters) of cables, a pair of antennas and reflectors that the new spaceships will use to navigate toward and dock with the station, a $100 billion laboratory that flies about 260 miles (418 km) above Earth.

After the spacewalk, Virts reported that a small amount of water had seeped into his helmet, a situation that also occurred after a spacewalk last week.

"It's no issue to crew safety," mission commentator Daniel Huot said.

In July 2013, Italian astronaut Luca Parmitano nearly drowned when water began leaking into his helmet. NASA immediately aborted the spacewalk and suspended spacewalks while engineers figured out the cause of the problem. The incident with the suit Virts was wearing is unrelated, NASA said.

Sunday's outing followed two spacewalks last week to rig power and data cables for a pair of docking port adapters that are due to arrive later this year. One adapter will be installed at the berthing slip once used by NASA's space shuttles, which were retired in 2011. The second docking system will be located at an adjacent hatch on the Harmony connecting node.

Since the shuttles' retirement, the United States has been dependent on Russia to fly crew to and from the station, a joint project of 15 nations.

NASA aims to break Russia's monopoly before the end of 2017 by buying rides from Boeing and SpaceX.

Article: Reuters