Tuesday, December 22, 2009

LIGHTNING-PRODUCED RADIATION A POTENTIAL HEALTH CONCERN FOR AIR TRAVELERS

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New information about lightning-emitted X-rays, gamma rays and high-energy electrons during thunderstorms is prompting scientists to raise concerns about the potential for airline passengers and crews to be exposed to harmful levels of radiation.

Scientists at the Florida Institute of Technology, University of California, Santa Cruz and the University of Florida have estimated that airplane passengers could be exposed to a radiation dose equal to that from 400 chest X-rays if their airplane happens to be near the start of a lightning discharge or related phenomena known as a terrestrial gamma ray flash.

The big unknown: how often — if ever — commercial airliners are exposed to these thunderstorm events, because the bursts of radiation occur only over extremely brief periods and extend just a few hundred feet in the clouds.

“We know that commercial airplanes are typically struck by lightning once or twice a year,” said Joe Dwyer, professor of physics and space sciences at Florida Tech. “What we don’t know is how often planes happen to be in just the right place or right time to receive a high radiation dose. We believe it is very rare, but more research is needed to answer the question definitively.”

The authors did not measure high radiation doses directly with airplanes. Instead, they estimated radiation based on satellite and ground-based observations of X-rays and gamma rays.

The authors “combined observations of lightning-produced X-rays and gamma rays with computer models of the movement of high-energy particles to estimate the amount of radiation that could be produced within, or very near, thunderclouds during lightning storms,” said Hamid Rassoul, a co-author and senior researcher from Florida Tech.

The observations included those made from orbiting satellites of “terrestrial gamma-ray flashes,” or TGFs, mysterious phenomena that appear to originate within thunderstorms at the same altitudes used by jet airliners. They also included measurements of X-rays and gamma rays from natural lightning on the ground, as well as artificial lightning triggered with wire-trailing rockets fired into storm clouds. Researchers believe the phenomena are linked, because both produce high levels of gamma rays and X-rays and occur along with the actual lightning flash.

The scientists concluded the radiation in a football field-sized space around these lightning events could reach “biologically significant levels,” up to 10 rem, according to their paper.

“If an aircraft happened to be in or near the high-field region when either a lightning discharge or a TGF event is occurring, then the radiation dose received by passengers and crew members inside the aircraft could potentially approach 10 rem in less than one millisecond,” the paper says.

Ten rem is considered the maximum safe radiation exposure over a person’s lifetime. It is equal to 400 chest X-rays, three CAT scans or 7,500 hours of flight time in normal conditions. All airplane passengers are exposed to slightly elevated radiation levels due to cosmic rays.

While the research raises obvious concerns, the scientists stressed that they don’t know how often the high-radiation events occur — or how often planes are nearby enough to expose passengers and flight crews to potential danger.

David Smith, an associate professor of physics at UC-Santa Cruz, said recent airborne research suggests the incidents are rare. Flying aboard a National Science Foundation/National Center for Atmospheric Research aircraft this past summer in Florida, Smith and several of the other researchers used a highly sophisticated instrument to measure gamma ray flashes from thunderstorms. Over the course of several flights, they were only able to detect one such flash, at a safe distance from the plane.

“These observations show that although thunderstorms do occasionally create intense gamma-ray flashes, the chance of accidently being directly hit by one is small,” Smith said.

Martin Uman, another author and a distinguished professor of electrical and computer engineering at UF, noted that airline pilots typically seek to avoid flying through storms.

However, he said, the fact that commercial planes are struck once or twice a year suggests more inquiry is needed. He said he would recommend to the Federal Aviation Administration that it place detectors aboard planes capable of measuring the storm-related, brief and intense radiation bursts to determine how often they occur. He also said more research on the phenomena that generates the bursts is clearly needed.

“What we need to do is supply the right kind of detectors to a lot of planes, and see if this ever happens,” he said. “We also need to spend more time looking at gamma and x-ray radiation from lightning and thunderstorms and trying to understand how it works.”

The paper drew on data from numerous observations and experiments, including experiments involving artificial “triggered” lightning at UF/Florida Tech International Center for Lightning Research and Testing at the Camp Blanding Army National Guard Base near Starke, Florida. UF and Florida Tech researchers at the center were the first to identify X-ray emissions from triggered lightning.

University of Florida

SCIENTISTS LOCATE DEEP ORIGINS OF "HAWAIIAN HOTSPOT"

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The Hawaiian Islands are one of the outstanding volcanic features on Earth, but their origins have been shrouded in mystery.

Still in debate has been a theory proposed 40 years ago, which states that mid-tectonic plate hotspots such as Hawaii are generated by upwelling plumes of lava from the base of Earth's lower mantle.

Cecily Wolfe, a geologist at the University of Hawai‘i at Mânoa School of Ocean and Earth Science and Technology, and a multi-institutional team of scientists put the theory to the test.

Their research findings will be published in the journal Science.

A deployment of a large network of sea-floor seismometers in Hawai‘i, through a National Science Foundation (NSF)-funded expedition called the Plume-Lithosphere Undersea Melt Experiment (PLUME), opened up a window into the Earth.

PLUME alllowed scientists to obtain the best picture yet of a mantle plume originating from the lower mantle, and revealed Hawai‘i's deep roots.

"The hypothesis that hot spots like Hawaii originate from mantle plumes is one of the longest-standing and most controversial topics in geology," says Robert Detrick, director of NSF's Division of Earth Sciences and a co-author of the paper. Detrick conducted the research while at the Woods Hole Oceanographic Institution

"This pioneering experiment combining large numbers of broadband seismometers on the seafloor with instruments on land has provided the most persuasive evidence yet for the existence of a mantle plume extending into the lower mantle beneath Hawaii."

The project involved four oceanographic research cruises to deploy and recover ocean bottom seismometers at 73 sites, led by Gabi Laske of the Scripps Institution of Oceanography and John Collins of the Woods Hole Oceanographic Institution.

Sean Solomon of the Carnegie Institution for Science provided a concurrent deployment of land seismometers on the main Hawaiian Islands.

The large, 1,000-km wide seafloor network yielded unprecedented results in a remote oceanic region.

The seismometers were used to record the timing of seismic shear waves from large earthquakes (magnitudes greater than 5.5) around the world.

This information was used to determine whether seismic waves travel more slowly through hot rock as they pass beneath Hawai‘i.

Combining the timing measurements from earthquakes recorded on many seismometers allowed Wolfe and colleagues to construct a sophisticated 3-dimensional image of the Hawaiian mantle.

In the upper mantle, the Hawaiian Islands are underlain by low shear-wave velocities, linked with hotter-than-average material from an upwelling plume.

Low velocities continue down into the Earth's transition zone, at 410 to 660 km depth, and extend even deeper into the Earth's lower mantle down to at least 1,500 km depth.

The location of the Hawaiian Islands in the middle of the Pacific Ocean had hampered past efforts to resolve its deep structure.

Seismometer deployments limited to land sites on the islands did not provide sufficient coverage for high-resolution imaging, and Hawaii is also far from the most active circum-Pacific zones of earthquakes.

As a result, scientists turned to a more technologically challenging, marine approach by placing temporary instrumentation on the seafloor to record seismic waves.

Results of the project make a strong case for the existence of a deep mantle plume, with implications not just for Hawaii, but for how convection in the solid Earth works; the Earth's composition with depth; and the inner Earth's evolution.

"This experiment was first conceived by our team a decade ago," says Wolfe. "The results have been worth the wait and exceeded all expectations. The success of such an ambitious seafloor experiment is a technological feat in itself, and signals a new era in the field of marine seismology."

Has the question of hot spots and mantle plumes been settled at last?

"It's a very strong vote," says Solomon, "in favor of the plume model."

(Photo: Paul Johnson, University of Hawaii)

NEW MEAT-EATING DINOSAUR ALTERS EVOLUTIONARY TREE

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Paleontologists, aided by amateur volunteers, have unearthed a previously unknown meat-eating dinosaur from a fossil bone bed in northern New Mexico, settling a debate about early dinosaur evolution, revealing a period of explosive diversification and hinting at how dinosaurs spread across the supercontinent Pangaea.

The description of the new species, named Tawa after the Hopi word for the Puebloan sun god, appears in the Dec. 10 issue of the journal Science in a paper lead-authored by Sterling Nesbitt, a postdoctoral researcher at The University of Texas at Austin's Jackson School of Geosciences. Nesbitt conducted the research with his colleagues while a graduate student at Columbia University's Lamont-Doherty Earth Observatory and the American Museum of Natural History.

The fossil bones of several individuals were recovered, but the type specimen is a nearly complete skeleton of a juvenile that stood about 28 inches (70 cm) tall at the hips and was about 6 feet (2 meters) long from snout to tail. Its body was about the size of a large dog, but with a much longer tail. It lived about 214 million years ago, plus or minus a million. The specimens are remarkable because they show little sign of being flattened during fossilization.

Tawa is part of a group of dinosaurs known as theropods, which includes T. Rex and Velociraptor. Theropods for the most part ate meat, walked on two legs and had feathers. Though most went extinct by 65 million years ago, some lineages survived to spawn modern birds.

One of Tawa's most important contributions to science has to do with what it says about another dinosaur, Herrerasaurus, the center of a lively debate since its discovery in Argentina in the 1960s. Herrerasaurus had some traits in common with theropods—including large claws, carnivorous teeth and certain pelvic features—but lacked other theropod traits such as pockets in vertebrae for airsacs. Some paleontologists claimed it was so unusual it was outside the evolutionary tree of theropods, or even of dinosaurs. Others placed it among the earliest theropods.

"The question was did those carnivorous traits arise in Herrerasaurus and in theropods independently or were they traits from a recent common ancestor that got passed down," said Nesbitt. "We had so few specimens of early theropods that it was hard to answer that question. But now that we have Tawa, we think we have an answer."

Tawa had a mix of Herrerasaurus-like characteristics (for example, in the pelvis) and features found in firmly established theropod dinosaurs (for example, pockets for airsacs in the backbone). Therefore, the characteristics that Herrerasaurus shares uniquely with theropods such as Tawa confirm the characteristics didn't arise independently and that Herrerasaurus is indeed a theropod.

The firm placement of Herrerasaurus within the theropod lineage points up an interesting fact about dinosaur evolution: once they appeared, they very rapidly diversified into the three main dinosaur lineages that persisted for more than 170 million years. Herrerasaurus was found in a South American rock layer alongside the oldest members of two major lineages—the sauropods and the ornithischians.

"Tawa pulls Herrerasaurus into the theropod lineage, so that means all three lineages are present in South America pretty much as soon as dinosaurs evolved," said Nesbitt. "Without Tawa, you can guess at that, but Tawa helps shore up that argument."

Tawa skeletons were found beside two other theropod dinosaurs from around the same period. Nesbitt noted that each of the three is more closely related to a known dinosaur from South America than they are to each other. This suggests these three species each descended from a separate lineage in South America, rather than all evolving from a local ancestor, and then later dispersed to North America and other parts of the supercontinent Pangaea. It also suggests there were multiple dispersals out of South America.

The first Tawa fossils were discovered in 2004 by volunteers taking a week-long paleontology seminar with experts at the Ruth Hall Museum of Paleontology in Abiquiu, New Mexico. The dig site, known as Hayden Quarry, is in a hillside on Ghost Ranch made famous by the painter Georgia O'Keefe. Alex Downs, an instructor for the course, contacted Nesbitt and a colleague to ask if they'd like to take a look at the fossils. There was a thigh bone, part of a hip and what later turned out to be some unrelated vertebrae.

"When we saw them, our jaws dropped," said Nesbitt. "A lot of these theropods have really hollow bones, so when they get preserved, they get really crunched. But these were in almost perfect condition."

He was also surprised by how much material was preserved at this one site. He and his colleagues began a full-scale excavation in 2006. Every summer since then, they've continued to unearth new material. The fossil bone bed extends for tens of meters along the hillside, promising years of painstaking work and perhaps additional significant discoveries.

(Photo: Jonathan Payne)

ASTRONAUT BALANCING ACT: TRAINING TO HELP EXPLORERS ADAPT TO A RETURN TO GRAVITY

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Astronauts returning from challenging long-duration missions face one more challenge when they get back to Earth – standing up and walking.

Upon returning to normal gravity, astronauts often suffer from balance problems that lead to dizziness and difficulty standing, walking and turning corners. Dr. Jacob Bloomberg is leading a group of National Space Biomedical Research Institute (NSBRI) scientists in a project to develop techniques to help astronauts adapt quickly to a new gravity environment and to overcome balance disturbances. This concept will also have benefits for non-astronaut populations such as the elderly or people with balance disorders.

Bloomberg of NASA Johnson Space Center Neurosciences Laboratory and his colleagues use a system that consists of a treadmill mounted on a base that can be actively moved in different directions to simulate balance disturbances. Called an Adaptability Training System, the treadmill has a projection screen in front of it that shows an image of a room or hallway that moves as the user walks. Disturbances are simulated by tilting the treadmill in one direction as the image is tilted in another.

“At first, people find it difficult to walk on the treadmill since its movement and images are out of sync. But over time, they learn to walk on it efficiently. We call this concept ‘learning to learn,’” said Bloomberg, who is the associate team leader of NSBRI’s Sensorimotor Adaptation Team and a senior research scientist at NASA.

In order to perform everyday activities, the brain interprets information provided by the body’s sensory systems: the eyes, the inner ear balance organs, the skin and muscle movement receptors. Bloomberg said the problems for astronauts occur during the transition period in which the brain is trying to adapt to a new gravity environment – either returning to Earth or in the future adjusting to lunar or martian gravity.

“In space, information from the sensory systems is different, particularly when you take away gravity. The brain reinterprets that information, makes adjustments and allows you to do the activities you need to do in space,” Bloomberg said. “The down side to that is when you return to Earth, the sensory systems are not used to a normal gravity environment.”

Former NASA astronaut Dr. Leroy Chiao experienced balance disturbances following his four spaceflights, one of which was a six-month stay on the International Space Station (ISS). He compared the effects to those experienced after stepping off a fast-spinning playground merry-go-round. “After a merry-go-round ride, the effects go away pretty quickly,” Chiao said. “But after a spaceflight, they linger.”

Post-flight data collected indicates a correlation between the length of the mission and how long effects linger. Bloomberg said if an astronaut has been in space on a typical two-week shuttle mission, it may take several days to recover. For six-month stays aboard the ISS, it could take at least several weeks to return to normal.

In addition to maximizing training efficiency, Bloomberg is looking at how long the benefit of the adaptability training lasts. Once subjects master the treadmill, they come back periodically for testing to see how well they perform. He is investigating if subjects can retain the training for up to six months, which would allow the training to take place before a long space mission.

Another goal of the researchers is to integrate a version of the system into the treadmill on a spacecraft, allowing astronauts to perform adaptability training on long missions. Integration would save space and power, both precious commodities on a spacecraft.

Chiao, who is the chairman of NSBRI’s User Panel, said the research could provide insight about much longer missions. “On a flight to Mars, astronauts will be in zero-gravity for six months or more. When they get to Mars, they will experience one-third gravity,” Chiao said. “Will systems like this allow them to go to work right away? Or will there need to be a recovery period or procedures before exploration can begin? These are important questions that this research is addressing.”

Project co-investigator Dr. Helen Cohen, professor of otolaryngology at Baylor College of Medicine, said, “It will not be a good situation if an astronaut lands on a new planet and has problems maintaining balance. The training could help maintain astronaut safety and help them accomplish mission objectives.”

Sensorimotor disturbances are not limited to standing up and walking. “Some people with inner ear trouble don’t steer a vehicle well,” said Cohen, associate director of the Center for Balance Disorders at BCM. “Adaptability training could also help people to perform these types of tasks better.”

Even though the cause of the sensorimotor problems is different, Bloomberg said the adaptability training concept could help prevent falls in the elderly.

“For astronauts, the sensory systems are working just fine but the information is being interpreted differently. For the elderly, it could be a combination of issues: the sensory systems may be deteriorated or the information may not be integrated by the brain as well as before,” he said. “We might use this training to improve some of the deficits that the elderly might experience. There are definitely applications in the clinical world in terms of fall prevention with the elderly population.”

(Photo: NASA)

REINVIGORATED HUBBLE SPACE TELESCOPE REVEALS MOST DISTANT GALAXIES YET

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Using the recently updated Hubble Space Telescope (HST) two teams of UK astronomers have identified galaxies which are likely to be the most distant yet seen. The UK teams, one led by Andrew Bunker and Stephen Wilkins at the University of Oxford and the other by Ross McLure and Jim Dunlop at the University of Edinburgh, analysed infrared images from the new Wide Field Camera 3 (WFC3) instrument on HST, installed during the most recent Space Shuttle servicing mission in May 2009. Infrared light is light invisible to the human eye, with wavelengths about twice as long as visible light - beyond the red.

"The expansion of the Universe causes the light from very distant galaxies to appear redder, so having a new camera on Hubble which is very sensitive in the infrared means we can identify galaxies at much greater distances than was previously possible" explained Stephen Wilkins, a postdoctoral researcher in astrophysics at Oxford University.

In a series of papers, to appear in the Monthly Notices of the Royal Astronomical Society, the UK teams present their analysis of the most sensitive images of the Universe yet taken in the infrared.

"The unique infrared sensitivity of Wide Field Camera 3 means that these are the best images yet for providing detailed information about the first galaxies as they formed in the early Universe", explained Dr Ross McLure from the Institute for Astronomy in Edinburgh.

The new images from Hubble include the region of sky known as the Hubble Ultra Deep Field, which Bunker and colleagues were the first to analyse 5 years ago using visible light images taken with Hubble's Advanced Camera for Surveys (ACS).

"Hubble has now revisited the Ultra Deep Field which we first studied 5 years ago, taking infrared images which are more sensitive than anything obtained before. We can now look even further back in time, identifying galaxies when the Universe was only 5 percent of its current age - within 1 billion years of the Big Bang" said Dr Daniel Stark, a postdoctoral researcher at the Institute of Astronomy in Cambridge who was involved in the work of both UK teams.

As well as identifying potentially the most distant objects yet, these new HST observations present an intriguing puzzle. "We know the gas between galaxies in the Universe was ionised (where electrons are removed from their host atomic nuclei) early in the history of the cosmos, but the total light from these new galaxies may not be sufficient to achieve this." said Andrew Bunker, a researcher at the University of Oxford.

The researchers are now looking forward to seeing these intriguing objects more clearly in the years ahead. "These new observations from HST are likely to be the most sensitive images Hubble will ever take, but the very distant galaxies we have now discovered will be studied in detail by Hubble's successor, the James Webb Space Telescope, which will be launched in 2014", commented Professor Jim Dunlop at the University of Edinburgh.

(Photo: NASA, ESA, STScI)

SOCIAL SCIENTISTS BUILD CASE FOR 'SURVIVAL OF THE KINDEST'

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Researchers at the University of California, Berkeley, are challenging long-held beliefs that human beings are wired to be selfish. In a wide range of studies, social scientists are amassing a growing body of evidence to show we are evolving to become more compassionate and collaborative in our quest to survive and thrive.

In contrast to "every man for himself" interpretations of Charles Darwin's theory of evolution by natural selection, Dacher Keltner, a UC Berkeley psychologist and author of "Born to be Good: The Science of a Meaningful Life," and his fellow social scientists are building the case that humans are successful as a species precisely because of our nurturing, altruistic and compassionate traits.

They call it "survival of the kindest."

"Because of our very vulnerable offspring, the fundamental task for human survival and gene replication is to take care of others," said Keltner, co-director of UC Berkeley's Greater Good Science Center. "Human beings have survived as a species because we have evolved the capacities to care for those in need and to cooperate. As Darwin long ago surmised, sympathy is our strongest instinct.”

Keltner's team is looking into how the human capacity to care and cooperate is wired into particular regions of the brain and nervous system. One recent study found compelling evidence that many of us are genetically predisposed to be empathetic.

The study, led by UC Berkeley graduate student Laura Saslow and Sarina Rodrigues of Oregon State University, found that people with a particular variation of the oxytocin gene receptor are more adept at reading the emotional state of others, and get less stressed out under tense circumstances.

Informally known as the "cuddle hormone,” oxytocin is secreted into the bloodstream and the brain, where it promotes social interaction, nurturing and romantic love, among other functions.

"The tendency to be more empathetic may be influenced by a single gene,” Rodrigues said.

While studies show that bonding and making social connections can make for a healthier, more meaningful life, the larger question some UC Berkeley researchers are asking is, "How do these traits ensure our survival and raise our status among our peers?"

One answer, according to UC Berkeley social psychologist and sociologist Robb Willer is that the more generous we are, the more respect and influence we wield. In one recent study, Willer and his team gave participants each a modest amount of cash and directed them to play games of varying complexity that would benefit the "public good.” The results, published in the journal American Sociological Review, showed that participants who acted more generously received more gifts, respect and cooperation from their peers and wielded more influence over them.

"The findings suggest that anyone who acts only in his or her narrow self-interest will be shunned, disrespected, even hated,” Willer said. "But those who behave generously with others are held in high esteem by their peers and thus rise in status.”

"Given how much is to be gained through generosity, social scientists increasingly wonder less why people are ever generous and more why they are ever selfish,” he added.

Such results validate the findings of such "positive psychology” pioneers as Martin Seligman, a professor at the University of Pennsylvania whose research in the early 1990s shifted away from mental illness and dysfunction, delving instead into the mysteries of human resilience and optimism.

While much of the positive psychology being studied around the nation is focused on personal fulfillment and happiness, UC Berkeley researchers have narrowed their investigation into how it contributes to the greater societal good.

One outcome is the campus's Greater Good Science Center, a West Coast magnet for research on gratitude, compassion, altruism, awe and positive parenting, whose benefactors include the Metanexus Institute, Tom and Ruth Ann Hornaday and the Quality of Life Foundation.

Christine Carter, executive director of the Greater Good Science Center, is creator of the "Science for Raising Happy Kids” Web site, whose goal, among other things, is to assist in and promote the rearing of "emotionally literate” children. Carter translates rigorous research into practical parenting advice. She says many parents are turning away from materialistic or competitive activities, and rethinking what will bring their families true happiness and well-being.

"I've found that parents who start consciously cultivating gratitude and generosity in their children quickly see how much happier and more resilient their children become,” said Carter, author of "Raising Happiness: 10 Simple Steps for More Joyful Kids and Happier Parents” which will be in bookstores in February 2010. "What is often surprising to parents is how much happier they themselves also become."

As for college-goers, UC Berkeley psychologist Rodolfo Mendoza-Denton has found that cross-racial and cross-ethnic friendships can improve the social and academic experience on campuses. In one set of findings, published in the Journal of Personality and Social Psychology, he found that the cortisol levels of both white and Latino students dropped as they got to know each over a series of one-on-one get-togethers. Cortisol is a hormone triggered by stress and anxiety.

Meanwhile, in their investigation of the neurobiological roots of positive emotions, Keltner and his team are zeroing in on the aforementioned oxytocin as well as the vagus nerve, a uniquely mammalian system that connects to all the body's organs and regulates heart rate and breathing.

Both the vagus nerve and oxytocin play a role in communicating and calming. In one UC Berkeley study, for example, two people separated by a barrier took turns trying to communicate emotions to one another by touching one other through a hole in the barrier. For the most part, participants were able to successfully communicate sympathy, love and gratitude and even assuage major anxiety.

Researchers were able to see from activity in the threat response region of the brain that many of the female participants grew anxious as they waited to be touched. However, as soon as they felt a sympathetic touch, the vagus nerve was activated and oxytocin was released, calming them immediately.

"Sympathy is indeed wired into our brains and bodies; and it spreads from one person to another through touch,” Keltner said.

The same goes for smaller mammals. UC Berkeley psychologist Darlene Francis and Michael Meaney, a professor of biological psychiatry and neurology at McGill University, found that rat pups whose mothers licked, groomed and generally nurtured them showed reduced levels of stress hormones, including cortisol, and had generally more robust immune systems.

Overall, these and other findings at UC Berkeley challenge the assumption that nice guys finish last, and instead support the hypothesis that humans, if adequately nurtured and supported, tend to err on the side of compassion.

“This new science of altruism and the physiological underpinnings of compassion is finally catching up with Darwin's observations nearly 130 years ago, that sympathy is our strongest instinct,” Keltner said.

(Photo: Jonathan Payne)

University of California, Berkeley

A SPECIAL KIND OF FLIGHT TRAINING

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Scientists from nine institutions and industrial enterprises aim to investigate motion perception in extreme situations as well as to improve flight simulators, thereby making an important contribution to enhanced aviation safety. Researchers from the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, will contribute to the biological foundations of understanding how pilots become disoriented in extreme flight conditions, and how balance and visual information combine in the brain.

Student pilots receive ever increasing amounts of training in simulators, combined with flight training in real aircraft. This saves money, helps protect the environment and above all, is a safer form of training. Standard flight manoeuvres, such as take-off and landing, can already be properly trained with current flight simulator technology. Extreme manoeuvres, such as recovery from loss of control are much more complex and difficult to simulate. One of the problems the interdisciplinary research team seeks to resolve is the lack of an appropriate algorithm to optimize the motion within the limited workspace of any simulator for such extreme conditions. Within the framework of the three-year SUPRA project (Simulation of Upset Recovery in Aviation), their goal is to improve the simulation of such complex flight manoeuvres and to develop a new generation of flight simulators.

At first, relevant training scenarios must be chosen for the experiments. This will be done in close cooperation with professional test pilots, who have already acquired much experience with such extreme conditions. The scientists, under the direction of Heinrich H. Bülthoff at the Max Planck Institute for Biological Cybernetics, hope to discover how pilots perceive aircraft motion during the extreme situations and why they can become spatially disoriented. They are particularly interested in the interaction of vision and signals the brain receives from the balance organs in the inner ear. With the help of a robotic arm, test persons will be exposed to a variety of accelerations, while simultaneously viewing a computer-generated virtual environment. By using the appropriate stimulation of both the visual and balance systems, it is possible to "trick" the brain in such a way that the pilot perceives an actual flight manoeuvre, rather than the laboratory. For example, the scientists are able to give an impression of acceleration with purely visual stimulation, although not actually providing real motion. This perception can be enhanced by providing a suitable actual motion. This type of illusion of motion is used in flight simulators to produce a perception of motion that would not otherwise be possible due to the limited workspace.

The international consortium makes use of two completely new types of simulators that exist in the Dutch research institute, TNO, and in the Max Planck Institute for Biological Cybernetics in Tübingen, Germany. "In these times of ever increasing mobility, thorough training of new pilots is an important theme. We are pleased that the European Union has provided us with the opportunity to work with an international team to make an important contribution to flight safety by improving pilot training", stated Heinrich H. Bülthoff at the start of the project.

(Photo: Anne Faden)

Max Planck Society

HOW TO READ BRAIN ACTIVITY?

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The electroencephalogram (EEG) has been widely used in research and medicine for more than 80 years. The ability to measure the electrical activity in the brain by means of electrodes on the head is a handy tool to study brain function as it is noninvasive and easy to apply. The interpretation of the EEG signal remains, however, difficult. The main reason for this is that the exact relationship between the activity generated in the brain compared to that measured on the scalp is unclear. Therefore, a question of paramount practical importance is how EEG can be used to deduce neural activity in the brain. Recently, Kevin Whittingstall and Nikos Logothetis from the Max Planck Institute for Biological Cybernetics in Tubingen have addressed this very question for the first time.

By combining recordings of both EEG and individual neurons in trained monkeys, Whittingstall and Logothetis found that a combination of specific waves in the EEG could indeed reliably predict the activity of cells in the brain. They presented different movie clips consisting of everyday natural scenes to trained monkeys. While the monkeys watched, their brain activity was recorded via EEG and via electrodes that were placed directly on the neurons, thus allowing for a direct comparison between data sets. Specifically, they observed that the firing pattern of cells was highest during periods where bursts of ‘fast’ EEG activity were embedded within the slow-wave EEG. As the degree of this so-called ‘frequency band coupling’ changed, so also did the cells firing rate.

"We succeeded in identifying which aspects of the EEG best represent changes in the activity from a population of neurons in the brain", explains Kevin Whittingstall. "With this information, we can now move to better understand the cause of abnormal EEG waveforms in patients with certain neurological disorders."

(Photo: Kevin Whittingstall)

Max Planck Society

A SEE-THROUGH SURPRISE

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Very often in science, the unexpected discovery turns out to be the most significant. Rice University Professor Junichiro Kono and his team weren't looking for a breakthrough in the transmission of terahertz signals, but there it was: a plasmonic material that would, with adjustments to its temperature and/or magnetic field, either stop a terahertz beam cold or let it pass completely.

The finding by Kono, a professor in electrical and computer engineering and in physics and astronomy, former graduate student Xiangfeng Wang and their colleagues helps close a knowledge gap in the electromagnetic spectrum between the ranges that address electronic and photonic devices.

Their paper, "Interference-Induced Terahertz Transparency in a Magneto-Plasma in a Semiconductor," appears in the online version of the journal Nature Physics and will be published in the Dec. 24 edition. Co-authors include Texas A&M theoretical physicist Alexey Belyanin, Los Alamos National Laboratory physicist Scott Crooker and Daniel Mittleman, a Rice professor in electrical and computer engineering.

Kono's team had been studying the conductivity of indium antimonide. "This is a classic material people started working on in the 1940s," he said. "It's a typical semiconductor, and if you dope it, it's highly conductive. But if you apply a magnetic field, it becomes an insulator, and that's what we planned to look at."

When Wang used terahertz spectroscopy to study the material, its unusual properties became apparent. "He started tuning various parameters -- the magnetic field, temperature and then the frequency -- and found that the terahertz transmission of the material changed drastically," Kono said. "It went from opaque to transparent."

They found that in a magnetic field, the doped indium antimonide, a solid-state plasma, transmitted circularly polarized waves that interfered with each other. This affected terahertz beams in much the same way polarized sunglasses interfere with visible light. To their surprise, at particular combinations of settings, the beams would pass right through.

"Terahertz is an exciting field right now," said Kono, a newly named fellow of the American Physical Society whose lab focuses on the physics and applications of semiconductor nanostructures and quantum devices. "This frequency range is considered to be the last frontier of the electromagnetic spectrum."

Kono said neither type of semiconductor device in common use today -- photonic and electronic -- works in the terahertz range. "Photonic devices work in the visible and near-infrared ranges and electronic devices work in the kilohertz, megahertz and gigahertz ranges. There's a clear gap where there's no mature solid-state technology. That's why a lot of people are working to fill it."

"I wouldn't say the terahertz region is unexplored, but it's less so," said Mittleman, who specializes in terahertz technologies and worked on the development of a terahertz version of Rice's famous single-pixel camera. "There are some open problems that people haven't thought about -- or have thought about, but haven't found good solutions for. The whole technology base is a lot less mature."

Kono said applications for terahertz technology include imaging, spectroscopy and communications, and having a device that can serve as a terahertz switch would be a step forward.

Still, there are hurdles to making the lab's discovery practical, one being the operating temperature. Wang worked with the indium antimonide at temperatures between 2 and 240 kelvins (approximately -456 to -27 degrees Fahrenheit).

"The temperature is certainly a concern," Mittleman said. "If it's going to have impact as a useful device for controlling terahertz beams, there is some work yet to do. I don't think that's impossible, but the route is not immediately clear.

"There's not a lot of shocking new physics here," he said, but the combination of techniques used to treat the indium antimonide made for interesting science. "People are going to think it's pretty cool.

"I think it's nice to find things like this, because it's a great example of an unexpected discovery that could turn out to be really useful."

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