Wednesday, November 18, 2009

U OF A PHYSICIST IDS YOUNG NEUTRON STAR

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University of Alberta physics professor Craig Heinke has solved a mystery that lies 11,000 light years beyond Earth and has puzzled astronomers for years.

When a supernova, or exploding star 20 times heavier than our sun, blasted apart, it left behind a small core, a 20 kilometre-wide remnant, which Heinke and a colleague identified of as a neutron star.

It's the youngest neutron star ever identified, and its atmosphere, a thin layer of carbon, is one of a kind.

The mystery began unfolding more than 300 years ago when a star, now known as the Cassiopeia A supernova, literally lit up the universe. Heinke says the stars transition to supernova was a colossal explosion producing light as bright as all 100 billion stars in our universe. "The death of a star is that violent," said Heinke. "It took centuries for the dust to settle and when it did, just 10 years ago, the star's mysterious core was revealed."

The researchers used data from NASA's Chandra X-ray Observatory satellite. "X-ray imaging only sees the hottest things in the universe, such as neutron stars, and the material that falls into a black hole," said Heinke. "The neutron star we identified had a temperature of roughly a million degrees Celsius; that's 3,000 times hotter than boiling water."

Heinke eventually concluded that the core is a neutron star and that its unusual carbon atmosphere is due to its young age. Up until now researchers have only had much older neutron stars to examine and none of them had a carbon atmosphere. Heinke says it was the carbon atmosphere that caused a lot of confusion for astronomers. "The images sent back to Earth by the Chandra X-ray satellite simply didn't look like any neutron star pictures researchers had ever seen before," said Heinke.

Heinke's breakthrough reveals part of a neutron star's life cycle that had never been seen before.

Heinke and his collaborator, Wynn Ho of Southampton University in the United Kingdom, have published a paper on their research. It will be published this week in the prestigious journal, Nature.

"This discovery helps us understand how neutron stars are born in violent supernova explosions," said Heinke. "This neutron star was born so hot that nuclear fusion happened on its surface, producing a carbon atmosphere just 10 centimetres thick."

(Photo: NASA/CXC/SAO; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech/O. Krause)

University of Alberta

NANOSTRUCTURES ON OPTICAL FIBER PRODUCE "HIDDEN" PHOTOVOLTAIC CELLS

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Converting sunlight to electricity might no longer mean large panels of photovoltaic cells atop flat surfaces like roofs.

Using zinc oxide nanostructures grown on optical fibers and coated with dye-sensitized solar cell materials, researchers at the Georgia Institute of Technology have developed a new type of three-dimensional photovoltaic system. The approach could allow PV systems to be hidden from view and located away from traditional locations such as rooftops.

“Using this technology, we can make photovoltaic generators that are foldable, concealed and mobile,” said Zhong Lin Wang, a Regents professor in the Georgia Tech School of Materials Science and Engineering. “Optical fiber could conduct sunlight into a building’s walls where the nanostructures would convert it to electricity. This is truly a three dimensional solar cell.”

Details of the research were published in the early view of the journal Angewandte Chemie International on October 22. The work was sponsored by the Defense Advanced Research Projects Agency (DARPA), the KAUST Global Research Partnership and the National Science Foundation (NSF).

Dye-sensitized solar cells use a photochemical system to generate electricity. They are inexpensive to manufacture, flexible and mechanically robust, but their tradeoff for lower cost is conversion efficiency lower than that of silicon-based cells. But using nanostructure arrays to increase the surface area available to convert light could help reduce the efficiency disadvantage, while giving architects and designers new options for incorporating PV into buildings, vehicles and even military equipment.

Fabrication of the new Georgia Tech PV system begins with optical fiber of the type used by the telecommunications industry to transport data. First, the researchers remove the cladding layer, then apply a conductive coating to the surface of the fiber before seeding the surface with zinc oxide. Next, they use established solution-based techniques to grow aligned zinc oxide nanowires around the fiber much like the bristles of a bottle brush. The nanowires are then coated with the dye-sensitized materials that convert light to electricity.

Sunlight entering the optical fiber passes into the nanowires, where it interacts with the dye molecules to produce electrical current. A liquid electrolyte between the nanowires collects the electrical charges. The result is a hybrid nanowire/optical fiber system that can be up to six times as efficient as planar zinc oxide cells with the same surface area.

“In each reflection within the fiber, the light has the opportunity to interact with the nanostructures that are coated with the dye molecules,” Wang explained. “You have multiple light reflections within the fiber, and multiple reflections within the nanostructures. These interactions increase the likelihood that the light will interact with the dye molecules, and that increases the efficiency.”

Wang and his research team have reached an efficiency of 3.3 percent and hope to reach 7 to 8 percent after surface modification. While lower than silicon solar cells, this efficiency would be useful for practical energy harvesting.

By providing a larger area for gathering light, the technique would maximize the amount of energy produced from strong sunlight, as well as generate respectable power levels even in weak light. The amount of light entering the optical fiber could be increased by using lenses to focus the incoming light, and the fiber-based solar cell has a very high saturation intensity, Wang said.

Wang believes this new structure will offer architects and product designers an alternative PV format for incorporating into other applications.

“This will really provide some new options for photovoltaic systems,” Wang said. “We could eliminate the aesthetic issues of PV arrays on building. We can also envision PV systems for providing energy to parked vehicles, and for charging mobile military equipment where traditional arrays aren’t practical or you wouldn’t want to use them.”

Wang and his research team, which includes Benjamin Weintraub and Yaguang Wei, have produced generators on optical fiber up to 20 centimeters in length. “The longer the better,” said Wang, “because longer the light can travel along the fiber, the more bounces it will make and more it will be absorbed.”

Traditional quartz optical fiber has been used so far, but Wang would like to use less expensive polymer fiber to reduce the cost. He is also considering other improvements, such as a better method for collecting the charges and a titanium oxide surface coating that could further boost efficiency.

Though it could be used for large PV systems, Wang doesn’t expect his solar cells to replace silicon devices any time soon. But he does believe they will broaden the potential applications for photovoltaic energy.

“This is a different way to gather power from the sun,” Wang said. “To meet our energy needs, we need all the approaches we can get.”

Georgia Institute of Technology

MODIFIED ENZYME AND DELIVERY SYSTEM ENABLE SPINAL CORD REGENERATION

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Researchers have developed an improved version of an enzyme that degrades the dense scar tissue that forms when the central nervous system is damaged. By digesting the tissue that blocks re-growth of damaged nerves, the improved enzyme – and new system for delivering it – could facilitate recovery from serious central nervous system injuries.

The enzyme, chrondroitinase ABC (chABC), must be supplied to the damaged area for at least two weeks following injury to fully degrade scar tissue. But the enzyme functions poorly at body temperature and must therefore be repeatedly injected or infused into the body.

In a paper published November 2 in the early edition of the journal Proceedings of the National Academy of Sciences, researchers describe how they eliminated the thermal sensitivity of chABC and developed a delivery system that allowed the enzyme to be active for weeks without implanted catheters and pumps. This work was supported by the National Institutes of Health.

“This research has made digesting scar clinically viable by obviating the need for continuous injection of chABC by thermally stabilizing the enzyme and harnessing bioengineered drug delivery systems,” said the paper’s lead author Ravi Bellamkonda, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.

At physiological body temperature, chABC enzyme loses half of its enzymatic activity within one hour and the remaining functionality within three to five days. To thermostabilize the enzymes, Bellamkonda, Emory University cell biology associate professor Robert McKeon and Georgia Tech graduate student Hyun-Jung Lee mixed the enzyme with the sugar trehalose. The result -- the enzyme’s activity was stabilized at internal body temperature for up to four weeks during in vitro tests.

The researchers then used a lipid microtube-hydrogel scaffold system to deliver the thermostabilized enzymes into animals via a single injection. The scaffold provided sustained delivery of the enzyme for two weeks, with the microtubes enabling slow release and the hydrogel localizing the tubes to the lesion site. This delivery system also allowed the enzyme to diffuse deeper into the tissue than did catheter delivery.

In animal studies, the enzyme’s ability to digest the scar was retained for two weeks post-injury and scar remained significantly degraded at the lesion site for at least six weeks. The researchers also observed enhanced axonal sprouting and recovery of nerve function at the injury site when the thermostabilized enzyme was delivered.

The delivery system also enabled the combination of therapies. Animals treated with thermostabilized chABC in combination with sustained delivery of neurotrophin-3 -- a protein growth factor that helps to support the survival and differentiation of neurons -- showed significant improvement in locomotor function and enhanced growth of sensory axons and sprouting of fibers for the neurotransmitter serotonin.

“These results bring us a step closer to repairing spinal cord injuries, which require multiple steps including minimizing the extent of secondary injury, bridging the lesion, overcoming inhibition due to scar, and stimulating nerve growth,” added Bellamkonda, who is also deputy director of research for GTEC, a regenerative medicine center based at Georgia Tech and Emory University, and a Georgia Cancer Coalition Distinguished Cancer Scholar.

Georgia Institute of Technology

SCIENTISTS PREPARE FOR LARGE-SCALE GLACIAL FLOODS

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Surging floods as powerful as the Amazon could hit parts of Europe within decades, according to new research.

Dr Andy Russell, of Newcastle University, is publishing the first comprehensive review in Developments in Quaternary Sciences (hard copy published Monday 9 November) of the impacts of flooding at a large Icelandic volcano-clad glacier.

These geological events - which can dramatically alter the surrounding landscape - are relatively frequent in Iceland, where a large sub-glacial eruption is long overdue.

This latest research has focussed on Mýrdalsjökull – Iceland’s southernmost glacier.

Melting glaciers and ice sheets are considered by many to be one of the greatest geological hazards associated with climate change.

Where glaciers are found on top of volcanoes enhanced glacier melting is likely to result in increased volcanic activity, enabling the sudden melt and release of large volumes of water as giant glacier outburst floods.

In Iceland enormous volumes of water and sediment suddenly entering the ocean during these floods have been known to generate tsunamis and extend the coastline by several kilometres within hours.

Volcanically triggered outburst floods are therefore a potent threat to surrounding communities and infrastructure.

Although subglacial volcanic eruptions are difficult to predict and impossible to prevent, Dr Russell and his research team have used evidence gathered within the routeways of former floods to gain a better understanding of what will happen during future outbursts.

“Knowledge of how outburst floods behaved previously enables us to better predict the impacts of future events and allows us to develop appropriate strategies to lessen their impact on the surrounding population,” explained Dr Russell. “We can’t predict or stop nature, but we can be prepared for it when she blows.”

Dr Russell has been working with academics and Earthwatch volunteers in Iceland for the last ten years. “There are still many gaps in our understanding and we are realising that meltwater can find its way out of glaciers much more quickly than previously thought,” he said. “We’re looking at the possibility of a flow the size of the Amazon being released within less than an hour and that doesn’t give people much time to get out of way.

“The potential impact of much of our work is in helping to inform both the local population and the civil defence authorities to ensure they are as prepared as possible.”

During this summer’s fieldwork, Dr Russell witnessed an event which made him realise just how quickly the environment can change in response to rapid glacier margin recession and ice surface lowering.

He watched the demise of Iceland’s largest glacial river, the Skeiðará, which started flowing on a new drainage path, along the glacier margin into the Gígjukvísl River.

During July 2009, Gígjukvísl’s flow rate increased steadily as the river ‘capture’ took hold. “The impacts of this event were spectacular,” said Dr Russell. “The levels in two iceberg-infested lakes at the glacier margin rose and water levels in a further three lakes dropped.

“Newly-routed water sliced through the glacier margin like a hot knife through butter. River channels between the lake basins experienced major growth over just ten days.

“This spectacular event illustrates dramatically how climate change can lead to sudden environmental change.”

Water no longer flows in the Skeiðará River system and, coupled with the nature of the whole outwash system, these changes so close to the glacier are likely to have significant impacts further down stream and within the coastal zone in the future.

(Photo: Newcastle U.)

New Castle University

MOBILE MICROSCOPES ILLUMINATE THE BRAIN

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By building a tiny microscope small enough to be carried around on a rats` head, scientists at the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, have found a way to study the complex activity of many brain cells simultaneously while animals are free to move around. With this new technology scientists can actually see how the brain cells operate while the animal is behaving naturally, giving rise to immense new insights into the understanding of perception and attention.

The majority of our life is spent moving around a static world and we generate our impression of the world using visual and other senses simultaneously. It is the ability to freely explore our environment that is essential for the view we form of our local surroundings. When we walk down the street and enter a shop to buy fruit, the street, shop and fruit are not moving, we are. What our brain is probably doing is constantly updating our position based on the information received from our sensory inputs such as eyes, ears, skin as well as our motor and vestibular systems, all in real time. The problem for researchers trying to understand how this occurs has always been how to record meaningful signals from the brain cells that do the calculations while we are in motion.

To get around this problem researchers at the Max Planck Institute for Biological Cybernetics in Tübingen have developed a way of actually watching the activity of many brain cells simultaneously in an animal that is free to move around the environment. By developing a small, light-weight laser-scanning microscope, researchers were able to, for the first time, image activity from fluorescent neurons in animals that were awake and moving around, while tracking the exact position of the animal in space. The microscope uses a high-powered pulsing laser and fiber optics to scan cells below the surface of the brain, eliminating the need to insert electrodes, which are traditionally used. Because of this, the microscope is non-invasive to the brain tissue.

The traditional approach to solving these sorts of questions is to restrain the animal and present it with a series of scenes or movies or images. The miniaturized microscope allows the researchers to turn this paradigm around and allow the animal to freely move around in its environment, while still allowing the scientists to monitor the activity of the brain cells responsible for processing visual information. It is clear that the brain does not work one cell at a time to recognize the environment, so the microscope records from many cells at a time, allowing for the first time the ability to look at how the brain is able to generate an internal representation of the outside world, while using natural vision.

"We need to let the animal behave as naturally as possible if we want to understand how its brain operates during interaction with complex environments. The new technology is a major milestone on the way to helping us understand how perception and attention work", says Jason Kerr, lead author of the study.

(Photo: MPI for Biological Cybernetics)

Max Planck Institute

FIRST IMPRESSIONS COUNT WHEN MAKING PERSONALITY JUDGMENTS

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First impressions do matter when it comes to communicating personality through appearance, according to new research by psychologists Laura Naumann of Sonoma State University and Sam Gosling of The University of Texas at Austin.

Despite the crucial role of physical appearance in creating first impressions, until now little research has examined the accuracy of personality impressions based on appearance alone. These findings will be published in the December 2009 issue of Personality and Social Psychology Bulletin, co-written with Simine Vazire (Washington University in St. Louis) and Peter J. Rentfrow (University of Cambridge).

"In an age dominated by social media where personal photographs are ubiquitous, it becomes important to understand the ways personality is communicated via our appearance," says Naumann. "The appearance one portrays in his or her photographs has important implications for their professional and social life."

In the study, observers viewed full-body photographs of 123 people they had never met before. The targets were viewed either in a controlled pose with a neutral facial expression or in a naturally expressed pose. The accuracy of the judgments was gauged by comparing them to the aggregate of self-ratings and that of three informants who knew the targets well, a criterion now widely regarded as the gold standard in personality research.

Even when viewing the targets in the controlled pose, the observers could accurately judge some major personality traits, including extraversion and self-esteem. But most traits were hard to detect under these conditions. When observers saw naturally expressive behavior (such as a smiling expression or energetic stance), their judgments were accurate for nine of the 10 personality traits. The 10 traits were extraversion, agreeableness, conscientiousness, emotional stability, openness, likability, self-esteem, loneliness, religiosity and political orientation.

"We have long known that people jump to conclusions about others on the basis of very little information," says Gosling, "but what's striking about these findings is how many of the impressions have a kernel of truth to them, even on the basis of something as simple a single photograph."

Gosling cautioned that observers still make plenty of mistakes, but noted that this latest work is important because it sheds new light on the sources of accuracy and inaccuracy of judgments.

With this kind of knowledge, individuals can choose to alter their appearance in specific ways, either to make identity claims or shape others impressions of them, Naumann says.

"If you want potential employers or romantic suitors to see you as a warm and friendly individual, you should post pictures where you smile or are standing in a relaxed pose," suggests Naumann.

For example, whether you smile and how you stand (tense vs. relaxed, energetic vs. tired) are important cues to judge a variety of traits. Extraverts smile more, stand in energetic and less tense ways, and look healthy, neat and stylish. People who are more open to experience are less likely to have a healthy, neat appearance, but are more likely to have a distinctive style of dress.

The researchers also found males who have a neat and healthy appearance are often seen as more conscientious. However, defining personality in women was more difficult because they were more strongly influenced by cultural demands to look presentable.

University of Texas

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