Electronic News

2013-08-30

Bacteria supplemented their diet to clean up after Deep Water Horizon oil

Aug. 29, 2013 — Bacteria living in the Gulf of Mexico beaches were able to 'eat up' the contamination from the Deep Water Horizon oil spill by supplementing their diet with nitrogen, delegates at the Goldschmidt conference will be told today, Friday 30th August.

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Professor Joel Kostka will tell geochemists gathered in Florence for the conference that detailed genetic analysis showed some of the bacteria thrived on a diet of oil because they were able to fix nitrogen from the air. The research -- the first to use next generation sequencing technologies to dig into the detail of how the native beach microbes are metabolising the oil over time -- could open the door to much more sophisticated clean up techniques.

"Oil is a natural product, made of decayed plants and animals, and so is similar to the normal food sources for these bacteria." explains Professor Kostka, a microbiologist from Georgia Institute of Technology in Atlanta. "But because oil is low in nutrients such as nitrogen, this can limit how fast the bacteria grow and how quickly they are able to break down the oil. Our analysis showed that some bacteria are able to solve this problem themselves -- by getting their own nitrogen from the air."

Professor Kostka worked with Professor Markus Huettel, a biogeochemist from Florida State University, to take more than 500 samples over two years from Pensacola beach in the Gulf of Mexico, starting when the Deep Water Horizon oil slick first came ashore in June 2010. By analysing every gene of every bacteria in the sample, they were able to see which bacteria were present and how they responded as the conditions on the beach changed.The researchers looked at the prevalence of genes which encode for different types of activity -- such as nitrogen fixing or phosphorus uptake -- to identify exactly how the bacteria were degrading the oil.

"By understanding how the oil is degraded by microbes, which microbes do the work, and the impact of the surrounding environmental conditions, we can develop ways to intervene to support the natural clean-up process," says Professor Kostka. "However, we need to do this in a very measured and targeted way, to avoid long-term, unintended damage to the ecosystem. For example, in the past, nitrogen fertiliser has been sprayed onto contaminated beaches to speed up the work of the bacteria. Our analysis shows that, where bacteria can get this nitrogen naturally, such drastic intervention may not be necessary."

The genetic analysis carried out by Professor Kostka and his colleague Konstantinos Konstantinidis at Georgia Tech can show exactly how the oil-degrading bacteria are working at each part of an affected coastline, making it possible to identify which beaches are most effective at self-cleaning and target mitigation efforts -- such as offshore booms -- at the most vulnerable areas.But not all the bacteria thrived on a diet of oil. Professor Kostka's research showed that some bacteria which play an important role in the ecosystem of the beaches experienced a sharp decline following the contamination in June 2010.

"There's a tendency to focus on the short-term, visible effects of an oil spill on the beach and assume that once the beach looks 'clean' then all is back to normal," he says. "Our analysis shows some of the invisible impact in the loss of these important microbes. We need to be aware of the long-term chronic damage both a spill -- and in some cases our attempts to deal with it -- can cause."

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Spider venom reveals new secret: Once injected into a bite wound, venom of brown recluse spider causes unexpected reaction

University of Arizona researchers led a team that has discovered that venom of spiders in the genus Loxosceles, which contains about 100 spider species including the brown recluse, produces a different chemical product in the human body than scientists believed.

The finding has implications for understanding how these spider bites affect humans and for the development of possible treatments for the bites.

One of few common spiders whose bites can have a seriously harmful effect on humans, the brown recluse has venom that contains a rare protein that can cause a blackened lesion at the site of a bite, or a much less common, but more dangerous, systemic reaction in humans.

"This is not a protein that is usually found in the venom of poisonous animals," said Matthew Cordes, an associate professor in the UA's department of chemistry and biochemistry and member of the UA BIO5 Institute who led the study, published today in the journal PLOS ONE.

The protein, once injected into a bite wound, attacks phospholipid molecules that are the major component of cell membranes. The protein acts to cleave off the head portion of the lipids, leaving behind, scientists long have assumed, a simple, linear, headless lipid molecule.

The research team has discovered that in the test tube, the venom protein causes lipids to bend into a ring structure upon the loss of the head portion, generating a cyclical chemical product that is very different than the linear molecule it was assumed to produce.

"The very first step of this whole process that leads to skin and tissue damage or systemic effects is not what we all thought it was," Cordes said.

The lipid knocks off its own head by making a ring within itself, prompted by the protein from the spider venom, Cordes explained. "Part of the outcome of the reaction, the release of the head group, is the same. So initially scientists believed that this was all that was happening, then that became established in the literature."

The research team includes Cordes; Vahe Bandarian, an associate professor also in the UA's department of chemistry and biochemistry; and Greta Binford, an associate professor of biology at Lewis and Clark College in Portland, Ore. who, completed her doctorate and a postdoc at the UA.

Cordes, Bandarian and Daniel Lajoie, a PhD candidate in Cordes's lab, tested venom from three species of brown recluse spiders from North and South America. Binford, an arachnologist who has traveled the world in search of the eight-legged creatures, collected the spiders, isolated their DNA and milked their venom, which was then frozen and shipped to the UA labs for analysis.

"We didn't find what we thought we were going to find," Cordes added. "We found something more interesting."

The cyclical shape of the headless molecule means that it has different chemical properties than the linear headless lipid believed to be generated by the protein, Cordes explained. The biological effects of either molecule in human membranes or insects aren't completely known, he said, but they are likely to be very different.

"We think it's something about that ring product generated by this protein that activates the immune system," Binford said.

"The properties of this cyclic molecule aren't well-known yet, but knowing that it's being produced by toxins in venoms might heighten interest," Cordes said. "Knowing how the protein is actually working and making this cyclic molecule could also lead to better insights on how to inhibit that protein."

For those who do have a reaction to the venom, the most common response is inflammation that after one to two days can develop into a dark lesion surrounding the bite site. The blackening, or necrosis, of the skin is dead skin cells, evidence of the immune system's efforts to prevent spread of the toxin by preventing blood flow to the affected area.

"Our bodies are basically committing tissue suicide," Binford said. "That can be very minor to pretty major, like losing a big chunk of skin. The only treatment in that case is usually to have a skin graft done by a plastic surgeon."

About once every five years, Binford said, someone develops a serious systemic reaction to a brown recluse bite, which can be fatal.

"If it goes systemic, then it can cause destruction of blood cells and various other effects that can in extreme cases lead to death by kidney failure or renal failure," Cordes said.

However, it is believed that the vast majority of brown recluse bites are so minor that they go unnoticed by those who were bitten.

It's not known what determines the type or severity of reaction a person is likely to get when bitten by a brown recluse, Cordes said, "but what is known is that this protein is the main cause of it."

"I think if we know how the toxin works, it opens a new door to understanding how the syndrome is initiated as well as the possibility of blocking that process."

"The discovery of this product may be crucial in understanding what exactly is going on in the human reaction," Binford said.

For the spider biologists and chemists, the work has just begun.

"These spiders have been around with this toxin for over 120 million years," Binford said. "I want to understand the full set of variation present in a single spider and across the entire genus and the activity of this compound."

"People think about the brown recluse with fear," she added. "When I think about a brown recluse or any other spider, I think about how a single spider can have 1,000 chemicals in its venom and there are about 44,000 species, so tens of millions of unique compounds in spider venom that we're in the process of discovering. We have a lot to learn about how these venom toxins work and potential for understanding new chemistry and developing new drugs or treatments."

Understanding how brown recluse venom produces harmful effects in humans is particularly relevant in Arizona, a hotbed for these spiders, Cordes said: "There are more variant species of Loxosceles here than anywhere else in the United States."

The UA-led study of brown recluse venom was supported initially by a pilot project award from the UA BIO5 Institute. Binford's venom collections were supported by a National Science Foundation Career Award.

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Learning how to migrate: Young whoopers stay the course when they follow a wise old bird

Aug. 29, 2013 — Scientists have studied bird migration for centuries, but it remains one of nature's great mysteries. How do birds find their way over long distances between breeding and wintering sites? Is their migration route encoded in their genes, or is it learned?

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Working with records from a long-term effort to reintroduce critically endangered whooping cranes in the Eastern U.S., a University of Maryland-led research team found evidence that these long-lived birds learn their migration route from older cranes, and get better at it with age.

Whooping crane groups that included a seven-year-old adult deviated 38% less from a migratory straight-line path between their Wisconsin breeding grounds and Florida wintering grounds, the researchers found. One-year-old birds that did not follow older birds veered, on average, 60 miles (97 kilometers) from a straight flight path. When the one-year-old cranes traveled with older birds, the average deviation was less than 40 miles (64 kilometers).

Individual whoopers' ability to stick to the route increased steadily each year up to about age 5, and remained roughly constant from that point on, the researchers found.

Many migration studies are done in short-lived species like songbirds, or by comparing a young bird to an older bird, said UMD biologist Thomas Mueller, an expert on animal migration and the study's lead scientist. "Here we could look over the course of the individual animals' lifetimes, and show that learning takes place over many years."

The researchers' findings, to be published August 30 in the journal Science, are based on data from an intensive effort to restore the endangered bird to its native range. The whooping crane (Grus americana), is North America's largest bird, standing five feet tall, and one of its longest-lived, surviving 30 years or more in the wild. The species was near extinction in the 1940s, with fewer than 25 individuals. Today about 250 wild whoopers summer in Canada and migrate to Texas for the winter.

The Whooping Crane Eastern Partnership, made up of government and non-profit experts, has been working since 2001 to establish a second population in the Eastern U.S., which now numbers more than 100 birds. At Maryland's Patuxent Wildlife Research Refuge and other captive breeding sites, adult whooping cranes produce chicks and biologists hand-raise them, using special methods designed to prepare the chicks for life in the wild. Each summer in a Wisconsin marsh, experts train a group of captive-raised chicks to follow an ultralight aircraft, using techniques like those portrayed in the fictional 1996 movie "Fly Away Home" to lead them on a 1,300-mile journey to their Florida wintering grounds.

Only this first migration is human-assisted; from then on the young birds travel on their own, usually in the company of other whooping cranes. Their movements are monitored daily via satellite transmitters, radio telemetry and on-the-ground observers. The result is a record of the movements of individual birds over several years, all with known parentage and the same upbringing.

"This is a globally unique data set in which we can control for genetics and test for the effect of experience," said UMD Biology Professor William F. Fagan, a co-author of the paper, "and it gives us an indication of just how important this kind of socially learned behavior is."

Using data on all the ultralight-trained birds' spring and fall migrations from 2002 to 2009, the researchers found that neither genetic relatedness nor gender had any effect on the whooping cranes' tendency to stay on the shortest migratory route. They were surprised to find that the migrating groups' size also made no difference.

"Many biologists would have expected to find a strong effect of group size," Fagan said, "with input from more birds' brains leading to improved navigation, but we didn't see that effect."

Only one experienced bird per group was enough to keep the migration on track. The researchers hypothesize that older birds are better at recognizing landmarks and coping with bad weather. Stronger autumn winds may explain why the whoopers tended to stray further from their straight course during fall migration, Mueller said.

The study shows the migration training for captive-born whooping cranes is working, Mueller said. However, the reintroduced whoopers are having trouble breeding in the wild. Based on the migration study's finding, "we need to take into consideration that these birds may also reproduce more successfully as they age," he said.

Given the whooping cranes' recent plunge towards extinction, it wouldn't be surprising if the birds need to re-learn how best to raise their chicks, said Patuxent-based scientist Sarah J. Converse of the U.S. Geological Survey, a co-author of the paper.

"These birds' behaviors have evolved over millennia," Converse said. "Managers here are trying to restore a culture, that is, the knowledge that these birds accumulate over time. We need to give these birds the time and the opportunity to get the breeding right. We might need to be a little bit patient."

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From cancer treatment to ion thruster: The newest little idea for nanosat micro rockets

Nanosatellites borrow many of their components from terrestrial gadgets: miniaturized cameras, wireless radios and GPS receivers that have been perfected for hand-held devices are also perfect for spacecraft. However, according to Michigan Technological University's L. Brad King, there is at least one technology need that is unique to space: "Even the best smartphones don't have miniaturized rocket engines, so we need to develop them from scratch."

Miniature rockets aren't needed to launch a nanosatellite from Earth. The small vehicles can hitchhike with a regular rocket that is going that way anyway. But because they are hitchhikers, these nanosats don't always get dropped off in their preferred location. Once in space, a nanosatellite might need some type of propulsion to move it from its drop-off point into its desired orbit. This is where the micro rocket engine comes in.

For the last few years, researchers around the world have been trying to build such rockets using microscopic hollow needles to electrically spray thin jets of fluid, which push the spacecraft in the opposite direction. The fluid propellant is a special chemical known as an ionic liquid. A single thruster needle is finer than a human hair, less than one millimeter long and produces a thrust force equivalent to the weight of a few grains of sand. A few hundred of these needles fit in a postage-stamp-size package and produce enough thrust to maneuver a nanosatellite.

These new electrospray thrusters face some design challenges, however. "Because they are so small and intricate, they are expensive to make, and the needles are fragile," says King, the Ron and Elaine Starr Professor of Mechanical Engineering-Engineering Mechanics. "They are easily destroyed either by a careless bump or an electrical arc when they're running."

To get around the problem, King and his team have developed an elegant strategy: eliminate the expensive and tedious microfabrication required to make the needles by letting Mother Nature take care of the assembly. "We're working with a unique type of liquid called a ferrofluid that naturally forms a stationary pattern of sharp tips in the liquid surface," he says. "Each tip in this self-assembling structure can spray a jet of fluid just like a micro-needle, so we don't actually have to make any needles."

Ferrofluids have been around since the 1960s. They are made of tiny magnetic particles suspended in a solvent that moves when magnetic force is applied. King illustrates with a tiny container holding a ferrofluid made of kerosene and iron dust. The fluid lies flat until he puts a magnet beneath it. Then suddenly, the liquid forms a regular series of peaks reminiscent of a mountain range or Bart Simpson's haircut. These peaks remain perfectly stable despite vigorous shaking and even turning the container upside down. It is, nonetheless, completely liquid, as a finger-tip touch proves undeniably. When the magnet is removed, the liquid relaxes to a perfectly flat surface.

King's team was trying to make an ionic liquid that behaved like a ferrofluid when they learned about a research team at the University of Sydney that was already making these substances. The Sydney team was using magnetic nanoparticles made by the life-sciences company Sirtex, which are used to treat liver cancer. "They sent us a sample, and we've used it to develop a thruster," King said. "Now we have a nice collaboration going. It's amazing that the same technology used to treat cancer can also function as a micro rocket for spacecraft."

King's first thruster is made of a one-inch block of aluminum containing a small ring of the special fluid. When a magnet is placed beneath the block, the liquid forms a tiny, five-tipped crown. When an electric force is then applied to the ferrofluid crown liquid jets emerge from each point, producing thrust. "It's fascinating to watch," King says. "The peaks get taller and skinnier, and taller and skinnier, and at some point the rounded tips instantly pop into nano-sharp points and start emitting ions."

The thruster appears to be almost immune to permanent damage. The tips automatically heal themselves and re-grow if they are somehow damaged. King's team has already demonstrated its self-healing properties, albeit inadvertently. "We accidentally turned the voltage up too high, and the tips exploded in a small arc," King says. While this would spell death for a typical thruster, "A completely new crown immediately formed from the remaining ferrofluid and once again resumed thrusting."

Their thruster isn't ready to push a satellite around in orbit just yet. "First we have to really understand what is happening on a microscopic level, and then develop a larger prototype based on what we learn," King said. "We're not quite there yet; we can't build a person out of liquid, like the notorious villain from the Terminator movies. But we're pretty sure we can build a rocket engine."

King has applied for a patent on the new technology. The research is funded by the Air Force Office of Scientific Research.

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Hydrogen fuel from sunlight

"We've developed a method by which molecular hydrogen-producing catalysts can be interfaced with a semiconductor that absorbs visible light," says Gary Moore, a chemist with Berkeley Lab's Physical Biosciences Division and principal investigator for JCAP. "Our experimental results indicate that the catalyst and the light-absorber are interfaced structurally as well as functionally."

Moore is the corresponding author, along with Junko Yano and Ian Sharp, who also hold joint appointments with Berkeley Lab and JCAP, of a paper describing this research in the Journal of the American Chemical Society (JACS). The article is titled "Photofunctional Construct That Interfaces Molecular Cobalt-Based Catalysts for H₂ Production to a Visible-Light-Absorbing Semiconductor." Co-authors are Alexandra Krawicz, Jinhui Yang and Eitan Anzenberg.

Earth receives more energy in one hour's worth of sunlight than all of humanity uses in an entire year. Through the process of photosynthesis, green plants harness solar energy to split molecules of water into oxygen, hydrogen ions (protons) and free electrons. The oxygen is released as waste and the protons and electrons are used to convert carbon dioxide into the carbohydrate sugars that plants use for energy. Scientists aim to mimic the concept but improve upon the actual process.

JCAP, which has a northern branch in Berkeley and a southern branch on the campus of the California Institute of Technology (Caltech), was established in 2010 by DOE as an Energy Innovation Hub. Operated as a partnership between Caltech and Berkeley Lab, JCAP is the largest research program in the United States dedicated to developing an artificial solar-fuel technology. While artificial photosynthesis can be used to generate electricity, fuels can be a more effective means of storing and transporting energy. The goal is an artificial photosynthesis system that's at least 10 times more efficient than natural photosynthesis.

To this end, once photoanodes have used solar energy to split water molecules, JCAP scientists need high performance semiconductor photocathodes that can use solar energy to catalyze fuel production. In previous efforts to produce hydrogen fuel, catalysts have been immobilized on non-photoactive substrates. This approach requires the application of an external electrical potential to generate hydrogen. Moore and his colleagues have combined these steps into a single material.

"In coupling the absorption of visible light with the production of hydrogen in one material, we can generate a fuel simply by illuminating our photocathode," Moore says. "No external electrochemical forward biasing is required."

The new JCAP photocathode construct consists of the semiconductor gallium phosphide and a molecular cobalt-containing hydrogen production catalyst from the cobaloxime class of compounds. As an absorber of visible light, gallium phosphide can make use of a greater number of available solar photons than semiconductors that absorb ultraviolet light, which means it is capable of producing significantly higher photocurrents and rates of fuel production. However, gallium phosphide can be notoriously unstable during photoelectrochemical operations.

Moore and his colleagues found that coating the surface of gallium phosphide with a film of the polymer vinylpyridine alleviates the instability problem, and if the vinylpyridine is then chemically treated with the cobaloxime catalyst, hydrogen production is significantly boosted.

"The modular aspect of our method allows independent modification of the light-absorber, linking material and catalyst, which means it can be adapted for use with other catalysts tethered over structured photocathodes as new materials and discoveries emerge," Moore says. "This could allow us, for example, to replace the precious metal catalysts currently used in many solar-fuel generator prototypes with catalysts made from earth-abundant elements."

Despite its promising electronic properties, gallium phosphide features a mid-sized optical band gap which ultimately limits the total fraction of solar photons available for absorption. Moore and his colleagues are now investigating semiconductors that cover a broader range of the solar spectrum, and catalysts that operate faster at lower electrical potentials. They also plan to investigate molecular catalysts for carbon dioxide reduction.

"We look forward to adapting our method to incorporate materials with improved properties for converting sunlight to fuel," Moore says. "We believe our method provides researchers at JCAP and elsewhere with an important tool for developing integrated photocathode materials that can be used in future solar-fuel generators as well as other technologies capable of reducing net carbon dioxide emissions."

This research was funded by the DOE Office of Science.

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Transparent artificial muscle plays music to prove a point

Aug. 29, 2013 — In a materials science laboratory at Harvard University, a transparent disk connected to a laptop fills the room with music -- it's the "Morning" prelude from Peer Gynt, played on an ionic speaker.

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No ordinary speaker, it consists of a thin sheet of rubber sandwiched between two layers of a saltwater gel, and it's as clear as a window. A high-voltage signal that runs across the surfaces and through the layers forces the rubber to rapidly contract and vibrate, producing sounds that span the entire audible spectrum, 20 hertz to 20 kilohertz.

But this is not an electronic device, nor has it ever been seen before. Published in the August 30 issue of Science, it represents the first demonstration that electrical charges carried by ions, rather than electrons, can be put to meaningful use in fast-moving, high-voltage devices.

"Ionic conductors could replace certain electronic systems; they even offer several advantages," says co-lead author Jeong-Yun Sun, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS).

For example, ionic conductors can be stretched to many times their normal area without an increase in resistivity -- a problem common in stretchable electronic devices. Secondly, they can be transparent, making them well suited for optical applications. Thirdly, the gels used as electrolytes are biocompatible, so it would be relatively easy to incorporate ionic devices -- such as artificial muscles or skin -- into biological systems.

After all, signals carried by charged ions are the electricity of the human body, allowing neurons to share knowledge and spurring the heart to beat. Bioengineers would dearly love to mesh artificial organs and limbs with that system.

"The big vision is soft machines," says co-lead author Christoph Keplinger, who worked on the project as a postdoctoral fellow at Harvard SEAS and in the Department of Chemistry and Chemical Biology. "Engineered ionic systems can achieve a lot of functions that our body has: they can sense, they can conduct a signal, and they can actuate movement. We're really approaching the type of soft machine that biology has to offer."

The audio speaker represents a robust proof of concept for ionic conductors because producing sounds across the entire audible spectrum requires both high voltage (to squeeze hard on the rubber layer) and high-speed actuation (to vibrate quickly) -- two criteria which are important for applications but which would have ruled out the use of ionic conductors in the past.

The traditional constraints are well known: high voltages can set off electrochemical reactions in ionic materials, producing gases and burning up the materials. Ions are also much larger and heavier than electrons, so physically moving them through a circuit is typically slow. The system invented at Harvard overcomes both of these problems, opening up a vast number of potential applications including not just biomedical devices, but also fast-moving robotics and adaptive optics.

"It must seem counterintuitive to many people, that ionic conductors could be used in a system that requires very fast actuation, like our speaker," says Sun. "Yet by exploiting the rubber layer as an insulator, we're able to control the voltage at the interfaces where the gel connects to the electrodes, so we don't have to worry about unwanted chemical reactions. The input signal is an alternating current (AC), and we use the rubber sheet as a capacitor, which blocks the flow of charge carriers through the circuit. As a result, we don't have to continuously move the ions in one direction, which would be slow; we simply redistribute them, which we can do thousands of times per second."

Sun works in a research group led by Zhigang Suo, the Allen E. and Marilyn M. Puckett Professor of Mechanics and Materials at Harvard SEAS. An expert in the mechanical behaviors of materials, Suo is also a Kavli Scholar at the Kavli Institute for Bionano Science & Technology, which is based at SEAS.

Suo teamed up with George M. Whitesides, a prominent chemist who specializes in soft machines, among many other topics. Whitesides is the Woodford L. and Ann A. Flowers University Professor in the Department of Chemistry and Chemical Biology, co-director of the Kavli Institute at Harvard, and a Core Faculty Member at the Wyss Institute for Biologically Inspired Engineering at Harvard.

"We'd like to change people's attitudes about where ionics can be used," says Keplinger, who now works in Whitesides' research group. "Our system doesn't need a lot of power, and you can integrate it anywhere you would need a soft, transparent layer that deforms in response to electrical stimuli -- for example, on the screen of a TV, laptop, or smartphone to generate sound or provide localized haptic feedback -- and people are even thinking about smart windows. You could potentially place this speaker on a window and achieve active noise cancellation, with complete silence inside."

Sam Liss, Director of Business Development in Harvard's Office of Technology Development, is working closely with the Suo and Whitesides labs to commercialize the technology. Their plan is to work with companies in a range of product categories, including tablet computing, smartphones, wearable electronics, consumer audio devices, and adaptive optics.

"With wearable computing devices becoming a reality, you could imagine eventually having a pair of glasses that toggles between wide-angle, telephoto, or reading modes based on voice commands or gestures," suggests Liss.

For now, there is much more engineering and chemistry work to be done. The Harvard team chose to make its audio speaker out of very simple materials -- the electrolyte is a polyacrylamide gel swollen with salt water -- but they emphasize that an entire class of ionically conductive materials is available for experimentation. Future work will focus on identifying the best combinations of materials for compatibility, long life, and adhesion between the layers.

In addition to Keplinger, Sun, Whitesides, and Suo, coauthors included Keith Choon Chiang Foo, a former postdoctoral fellow at Harvard SEAS, now at the Institute of High Performance Computing in Singapore; and Philipp Rothemund, a graduate student at Harvard SEAS.

This research was supported by the National Science Foundation through a grant to the Materials Research Science and Engineering Center at Harvard University (DMR-0820484) and by the Army Research Office (W911NF-09-1-0476). It was also enabled in part by the Department of Energy (ER45852) and the Agency for Science, Technology, and Research (A*STAR), Singapore.

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NASA data reveals mega-canyon under Greenland ice sheet

Aug. 29, 2013 — Data from a NASA airborne science mission reveals evidence of a large and previously unknown canyon hidden under a mile of Greenland ice.

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The canyon has the characteristics of a winding river channel and is at least 460 miles (750 kilometers) long, making it longer than the Grand Canyon. In some places, it is as deep as 2,600 feet (800 meters), on scale with segments of the Grand Canyon. This immense feature is thought to predate the ice sheet that has covered Greenland for the last few million years.

"One might assume that the landscape of the Earth has been fully explored and mapped," said Jonathan Bamber, professor of physical geography at the University of Bristol in the United Kingdom, and lead author of the study. "Our research shows there's still a lot left to discover."

Bamber's team published its findings Thursday in the journal Science.

The scientists used thousands of miles of airborne radar data, collected by NASA and researchers from the United Kingdom and Germany over several decades, to piece together the landscape lying beneath the Greenland ice sheet.

A large portion of this data was collected from 2009 through 2012 by NASA's Operation IceBridge, an airborne science campaign that studies polar ice. One of IceBridge's scientific instruments, the Multichannel Coherent Radar Depth Sounder, can see through vast layers of ice to measure its thickness and the shape of bedrock below.

In their analysis of the radar data, the team discovered a continuous bedrock canyon that extends from almost the center of the island and ends beneath the Petermann Glacier fjord in northern Greenland.

At certain frequencies, radio waves can travel through the ice and bounce off the bedrock underneath. The amount of times the radio waves took to bounce back helped researchers determine the depth of the canyon. The longer it took, the deeper the bedrock feature.

"Two things helped lead to this discovery," said Michael Studinger, IceBridge project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "It was the enormous amount of data collected by IceBridge and the work of combining it with other datasets into a Greenland-wide compilation of all existing data that makes this feature appear in front of our eyes."

The researchers believe the canyon plays an important role in transporting sub-glacial meltwater from the interior of Greenland to the edge of the ice sheet into the ocean. Evidence suggests that before the presence of the ice sheet, as much as 4 million years ago, water flowed in the canyon from the interior to the coast and was a major river system.

"It is quite remarkable that a channel the size of the Grand Canyon is discovered in the 21st century below the Greenland ice sheet," said Studinger. "It shows how little we still know about the bedrock below large continental ice sheets."

The IceBridge campaign will return to Greenland in March 2014 to continue collecting data on land and sea ice in the Arctic using a suite of instruments that includes ice-penetrating radar.

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NASA's Chandra Observatory catches giant black hole rejecting material

New Chandra images of Sagittarius A* (Sgr A*), which is located about 26,000 light-years from Earth, indicate that less than 1 percent of the gas initially within Sgr A*'s gravitational grasp ever reaches the point of no return, also called the event horizon. Instead, much of the gas is ejected before it gets near the event horizon and has a chance to brighten, leading to feeble X-ray emissions.

These new findings are the result of one of the longest observation campaigns ever performed with Chandra. The spacecraft collected five weeks' worth of data on Sgr A* in 2012. The researchers used this observation period to capture unusually detailed and sensitive X-ray images and energy signatures of super-heated gas swirling around Sgr A*, whose mass is about 4 million times that of the sun.

"We think most large galaxies have a supermassive black hole at their center, but they are too far away for us to study how matter flows near it," said Q. Daniel Wang of the University of Massachusetts in Amherst, who led of a study published Thursday in the journal Science. "Sgr A* is one of very few black holes close enough for us to actually witness this process."

The researchers found that the Chandra data from Sgr A* did not support theoretical models in which the X-rays are emitted from a concentration of smaller stars around the black hole. Instead, the X-ray data show the gas near the black hole likely originates from winds produced by a disk-shaped distribution of young massive stars.

"This new Chandra image is one of the coolest I've ever seen," said co-author Sera Markoff of the University of Amsterdam in the Netherlands. "We're watching Sgr A* capture hot gas ejected by nearby stars, and funnel it in towards its event horizon."

To plunge over the event horizon, material captured by a black hole must lose heat and momentum. The ejection of matter allows this to occur.

"Most of the gas must be thrown out so that a small amount can reach the black hole," said Feng Yuan of Shanghai Astronomical Observatory in China, the study's co-author. "Contrary to what some people think, black holes do not actually devour everything that's pulled towards them. Sgr A* is apparently finding much of its food hard to swallow."

The gas available to Sgr A* is very diffuse and super-hot, so it is hard for the black hole to capture and swallow it. The gluttonous black holes that power quasars and produce huge amounts of radiation have gas reservoirs much cooler and denser than that of Sgr A*.

The event horizon of Sgr A* casts a shadow against the glowing matter surrounding the black hole. This research could aid efforts using radio telescopes to observe and understand the shadow. It also will be useful for understanding the effect orbiting stars and gas clouds may have on matter flowing toward and away from the black hole.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

For Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra

For an additional interactive image, podcast, and video on the finding, visit: http://chandra.si.edu

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Poor concentration: Poverty reduces brainpower needed for navigating other areas of life

Aug. 29, 2013 — Poverty and all its related concerns require so much mental energy that the poor have less remaining brainpower to devote to other areas of life, according to research based at Princeton University. As a result, people of limited means are more likely to make mistakes and bad decisions that may be amplified by -- and perpetuate -- their financial woes.

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Published in the journal Science, the study presents a unique perspective regarding the causes of persistent poverty. The researchers suggest that being poor may keep a person from concentrating on the very avenues that would lead them out of poverty. A person's cognitive function is diminished by the constant and all-consuming effort of coping with the immediate effects of having little money, such as scrounging to pay bills and cut costs. Thusly, a person is left with fewer "mental resources" to focus on complicated, indirectly related matters such as education, job training and even managing their time.

In a series of experiments, the researchers found that pressing financial concerns had an immediate impact on the ability of low-income individuals to perform on common cognitive and logic tests. On average, a person preoccupied with money problems exhibited a drop in cognitive function similar to a 13-point dip in IQ, or the loss of an entire night's sleep.

But when their concerns were benign, low-income individuals performed competently, at a similar level to people who were well off, said corresponding author Jiaying Zhao, who conducted the study as a doctoral student in the lab of co-author Eldar Shafir, Princeton's William Stewart Tod Professor of Psychology and Public Affairs. Zhao and Shafir worked with Anandi Mani, an associate professor of economics at the University of Warwick in Britain, and Sendhil Mullainathan, a Harvard University economics professor.

"These pressures create a salient concern in the mind and draw mental resources to the problem itself. That means we are unable to focus on other things in life that need our attention," said Zhao, who is now an assistant professor of psychology at the University of British Columbia.

"Previous views of poverty have blamed poverty on personal failings, or an environment that is not conducive to success," she said. "We're arguing that the lack of financial resources itself can lead to impaired cognitive function. The very condition of not having enough can actually be a cause of poverty."

The mental tax that poverty can put on the brain is distinct from stress, Shafir explained. Stress is a person's response to various outside pressures that -- according to studies of arousal and performance -- can actually enhance a person's functioning, he said. In the Science study, Shafir and his colleagues instead describe an immediate rather than chronic preoccupation with limited resources that can be a detriment to unrelated yet still important tasks.

"Stress itself doesn't predict that people can't perform well -- they may do better up to a point," Shafir said. "A person in poverty might be at the high part of the performance curve when it comes to a specific task and, in fact, we show that they do well on the problem at hand. But they don't have leftover bandwidth to devote to other tasks. The poor are often highly effective at focusing on and dealing with pressing problems. It's the other tasks where they perform poorly."

The fallout of neglecting other areas of life may loom larger for a person just scraping by, Shafir said. Late fees tacked on to a forgotten rent payment, a job lost because of poor time-management -- these make a tight money situation worse. And as people get poorer, they tend to make difficult and often costly decisions that further perpetuate their hardship, Shafir said. He and Mullainathan were co-authors on a 2012 Science paper that reported a higher likelihood of poor people to engage in behaviors that reinforce the conditions of poverty, such as excessive borrowing.

"They can make the same mistakes, but the outcomes of errors are more dear," Shafir said. "So, if you live in poverty, you're more error prone and errors cost you more dearly -- it's hard to find a way out."

The first set of experiments took place in a New Jersey mall between 2010 and 2011 with roughly 400 subjects chosen at random. Their median annual income was around $70,000 and the lowest income was around $20,000. The researchers created scenarios wherein subjects had to ponder how they would solve financial problems, for example, whether they would handle a sudden car repair by paying in full, borrowing money or putting the repairs off. Participants were assigned either an "easy" or "hard" scenario in which the cost was low or high -- such as $150 or $1,500 for the car repair. While participants pondered these scenarios, they performed common fluid-intelligence and cognition tests.

Subjects were divided into a "poor" group and a "rich" group based on their income. The study showed that when the scenarios were easy -- the financial problems not too severe -- the poor and rich performed equally well on the cognitive tests. But when they thought about the hard scenarios, people at the lower end of the income scale performed significantly worse on both cognitive tests, while the rich participants were unfazed.

To better gauge the influence of poverty in natural contexts, between 2010 and 2011 the researchers also tested 464 sugarcane farmers in India who rely on the annual harvest for at least 60 percent of their income. Because sugarcane harvests occur once a year, these are farmers who find themselves rich after harvest and poor before it. Each farmer was given the same tests before and after the harvest, and performed better on both tests post-harvest compared to pre-harvest.

The cognitive effect of poverty the researchers found relates to the more general influence of "scarcity" on cognition, which is the larger focus of Shafir's research group. Scarcity in this case relates to any deficit -- be it in money, time, social ties or even calories -- that people experience in trying to meet their needs. Scarcity consumes "mental bandwidth" that would otherwise go to other concerns in life, Zhao said.

"These findings fit in with our story of how scarcity captures attention. It consumes your mental bandwidth," Zhao said. "Just asking a poor person to think about hypothetical financial problems reduces mental bandwidth. This is an acute, immediate impact, and has implications for scarcity of resources of any kind."

"We documented similar effects among people who are not otherwise poor, but on whom we imposed scarce resources," Shafir added. "It's not about being a poor person -- it's about living in poverty."

Many types of scarcity are temporary and often discretionary, said Shafir, who is co-author with Mullainathan of the book, "Scarcity: Why Having Too Little Means So Much," to be published in September. For instance, a person pressed for time can reschedule appointments, cancel something or even decide to take on less.

"When you're poor you can't say, 'I've had enough, I'm not going to be poor anymore.' Or, 'Forget it, I just won't give my kids dinner, or pay rent this month.' Poverty imposes a much stronger load that's not optional and in very many cases is long lasting," Shafir said. "It's not a choice you're making -- you're just reduced to few options. This is not something you see with many other types of scarcity."

The researchers suggest that services for the poor should accommodate the dominance that poverty has on a person's time and thinking. Such steps would include simpler aid forms and more guidance in receiving assistance, or training and educational programs structured to be more forgiving of unexpected absences, so that a person who has stumbled can more easily try again.

"You want to design a context that is more scarcity proof," said Shafir, noting that better-off people have access to regular support in their daily lives, be it a computer reminder, a personal assistant, a housecleaner or a babysitter.

"There's very little you can do with time to get more money, but a lot you can do with money to get more time," Shafir said. "The poor, who our research suggests are bound to make more mistakes and pay more dearly for errors, inhabit contexts often not designed to help."

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