Tuesday, September 8, 2009

DARTMOUTH RESEARCHERS PROPOSE NEW WAY TO REPRODUCE A BLACK HOLE

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Despite their popularity in the science fiction genre, there is much to be learned about black holes, the mysterious regions in space once thought to be absent of light. In a paper published in the August 20 issue of Physical Review Letters, the flagship journal of the American Physical Society, Dartmouth researchers propose a new way of creating a reproduction black hole in the laboratory on a much-tinier scale than their celestial counterparts.

The new method to create a tiny quantum sized black hole would allow researchers to better understand what physicist Stephen Hawking proposed more than 35 years ago: black holes are not totally void of activity; they emit photons, which is now known as Hawking radiation.

"Hawking famously showed that black holes radiate energy according to a thermal spectrum," said Paul Nation, an author on the paper and a graduate student at Dartmouth. "His calculations relied on assumptions about the physics of ultra-high energies and quantum gravity. Because we can't yet take measurements from real black holes, we need a way to recreate this phenomenon in the lab in order to study it, to validate it."

In this paper, the researchers show that a magnetic field-pulsed microwave transmission line containing an array of superconducting quantum interference devices, or SQUIDs, not only reproduces physics analogous to that of a radiating black hole, but does so in a system where the high energy and quantum mechanical properties are well understood and can be directly controlled in the laboratory. The paper states, "Thus, in principle, this setup enables the exploration of analogue quantum gravitational effects."

"We can also manipulate the strength of the applied magnetic field so that the SQUID array can be used to probe black hole radiation beyond what was considered by Hawking," said Miles Blencowe, another author on the paper and a professor of physics and astronomy at Dartmouth.

This is not the first proposed imitation black hole, says Nation. Other proposed analogue schemes have considered using supersonic fluid flows, ultracold bose-einstein condensates and nonlinear fiber optic cables. However, the predicted Hawking radiation in these schemes is incredibly weak or otherwise masked by commonplace radiation due to unavoidable heating of the device, making the Hawking radiation very difficult to detect. "In addition to being able to study analogue quantum gravity effects, the new, SQUID-based proposal may be a more straightforward method to detect the Hawking radiation," says Blencowe.

(Photo: Joseph Mehling '69)

ARE YOU THE NEXT USAIN BOLT? THE ANSWER COULD BE IN YOUR SALIVA

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Scientists at Newcastle University are launching a ground-breaking study to find out why some of us can run faster than others - despite doing the same amount of training.

The research team, led by Professor Patrick Chinnery, is asking the 54,000 people taking part in next month’s Bupa Great North Run to provide a saliva sample in a bid to find out whether our DNA is linked to race performance.

DNA - the genetic code we inherit from our parents - is important for our physical ability and previous work has shown that variations in the protein-building blocks of muscle can influence performance.

Now Newcastle University researchers want to examine energy production over a long distance.

They think that subtle differences in the DNA that is the blueprint for the energy-producing parts of the muscle - called mitochondria - influence physical fitness. They are now asking for the help of the thousands of Great North runners who will be tackling the 13.1 mile course.

With the help of race organisers, Nova International, an email has been sent to every runner asking if they would be willing to provide a saliva sample and their race number. The scientists will then find out the race time and see whether the DNA variants are linked to performance.

Professor Patrick Chinnery says, “The aim of this study is to find out whether our physical fitness is influenced by DNA - the genetic code that we have inherited from our parents.

“By comparing how many hours of training people have done against the genetic make-up of the energy-burning parts of their cells we hope to work out if there’s a link.

“We’re keen for as many as possible of the 54,000 runners to help us in this ground-breaking research – and the results could revolutionise the way people train in the future.”

The findings will develop understanding of the biology that underpins physical fitness and stamina – and could provide benefits for long-distance runners who wish to improve their performance and yet avoid dangerous complications.

(Photo: Bupa Great Run)

LOWER-COST SOLAR CELLS TO BE PRINTED LIKE NEWSPAPER, PAINTED ON ROOFTOPS

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Solar cells could soon be produced more cheaply using nanoparticle "inks" that allow them to be printed like newspaper or painted onto the sides of buildings or rooftops to absorb electricity-producing sunlight.

Brian Korgel, a University of Texas at Austin chemical engineer, is hoping to cut costs to one-tenth of their current price by replacing the standard manufacturing process for solar cells—gas-phase deposition in a vacuum chamber, which requires high temperatures and is relatively expensive.

"That's essentially what's needed to make solar-cell technology and photovoltaics widely adopted," Korgel said. "The sun provides a nearly unlimited energy resource, but existing solar energy harvesting technologies are prohibitively expensive and cannot compete with fossil fuels."

For the past two years, Korgel and his team have been working on this low-cost, nanomaterials solution to photovoltaics—or solar cell—manufacturing. Korgel is collaborating with professors Al Bard and Paul Barbara, both of the Department of Chemistry and Biochemistry, and Professor Ananth Dodabalapur of the Electrical and Computer Engineering Department. They recently showed proof-of-concept in the Journal of the American Chemical Society.

The inks could be printed on a roll-to-roll printing process on a plastic substrate or stainless steel. And the prospect of being able to paint the "inks" onto a rooftop or building is not far-fetched.

"You'd have to paint the light-absorbing material and a few other layers as well," Korgel said. "This is one step in the direction towards paintable solar cells."

Korgel uses the light-absorbing nanomaterials, which are 10,000 times thinner than a strand of hair, because their microscopic size allows for new physical properties that can help enable higher-efficiency devices.

In 2002, he co-founded a company called Innovalight, based in California, which is producing inks using silicon as the basis. This time, Korgel and his team are using copper indium gallium selenide or CIGS, which is both cheaper and benign in terms of environmental impact.

"CIGS has some potential advantages over silicon," Korgel said. "It's a direct band gap semiconductor, which means that you need much less material to make a solar cell, and that's one of the biggest potential advantages."

His team has developed solar-cell prototypes with efficiencies at one percent; however, they need to be about 10 percent.

"If we get to 10 percent, then there's real potential for commercialization," Korgel said. "If it works, I think you could see it being used in three to five years."

He also said that the inks, which are semi-transparent, could help realize the prospect of having windows that double as solar cells. Korgel said his work has attracted the interest of industrial partners.

Funding for the research comes from the National Science Foundation, the Welch Foundation and the Air Force Research Laboratory.

(Photo: UTA)

University of Texas at Austin

WALKING IN CIRCLES

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Scientists in the Multisensory Perception and Action Group at the Max Planck Institute for Biological Cybernetics in Tübingen, led by Jan Souman and Marc Ernst, have now presented the first empirical evidence that people really walk in circles when they do not have reliable cues to their walking direction. Their study, published today in the journal Current Biology, examined the walking trajectories of people who walked for several hours in the Sahara desert (Tunisia) and in the Bienwald forest area (Germany). The scientists used the global positioning system (GPS) to record these trajectories. The results showed that participants were only able to keep a straight path when the sun or moon was visible. However, as soon as the sun disappeared behind some clouds, people started to walk in circles without even noticing it.

Speaking about the study, Jan Souman said: "One explanation offered in the past for walking in circles is that most people have one leg longer or stronger than the other, which would produce a systematic bias in one direction. To test this explanation, we instructed people to walk straight while blindfolded, thus removing the effects of vision. Most of the participants in the study walked in circles, sometimes in extremely small ones (diameter less than 20 metres)."

However, it turned out that these circles were rarely in a systematic direction. Instead, the same person sometimes veered to the left, sometimes to the right. Walking in circles is therefore not caused by differences in leg length or strength, but more likely the result of increasing uncertainty about where straight ahead is. "Small random errors in the various sensory signals that provide information about walking direction add up over time, making what a person perceives to be straight ahead drift away from the true straight ahead direction," according to Souman.

Marc Ernst, Group Leader at the MPI for Biological Cybernetics, added: "The results from these experiments show that even though people may be convinced that they are walking in a straight line, their perception is not always reliable. Additional, more cognitive, strategies are necessary to really walk in a straight line. People need to use reliable cues for walking direction in their environment, for example a tower or mountain in the distance, or the position of the sun." In future research, Souman and Ernst will focus on how people use these and various other sources of information to guide their walking direction. For this, the scientists will use state-of-the-art Virtual Reality equipment, including a revolutionary new omnidirectional treadmill (("Cyber-carpet", www.youtube.com/watch?v=bmWD1bIKc44). Participants will try to find their way through a virtual forest, while walking in place on the treadmill and never leaving the laboratory. This will allow the scientists to have much more control over the information available to participants, making it possible to better test specific explanations, for example how people use the position of the sun to orient themselves.

(Photo: Jan Souman, Google Earth)

Max Planck Institute

THE BLOSSOMS OF MATURITY

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Why do some plants blossom even when days are short and gray? Scientists at the Max Planck Institute for Developmental Biology have found the answer to this question: An endogenous mechanism allows them to flower in the absence of external influences such as long days. A small piece of RNA, a so-called microRNA, has a central role in this process, as a decline of its concentration in the shoot apex triggers flowering.

MicroRNAs are very short RNA snippets that have emerged in recent years as essential regulators of gene function in both plants and animals. By binding to complementary motifs in a messenger RNA, they inhibit its translation into protein. This process thus blunts the activity of the corresponding gene.

In Tübingen, developmental biologists have discovered that the common wallcress, Arabidopsis, uses this regulatory mechanism to switch from vegetative to reproductive development. A group of related regulators, the SPL proteins, play an important role in promoting the onset of flowering. In young plants, production of SPL proteins is prevented by high levels of microRNA156. Jia-Wei Wang and colleagues demonstrate that independent of external cues, the concentration of the microRNA declines over time, like sand running through an hourglass. When the microRNA concentration falls below a certain level, enough SPL proteins are produced to activate the flowering process even in the absence of other regulators that measure day length or external temperature. This in turns allows a sufficiently old plant to flower, even in an unfavorable environment.

Interestingly, the SPLs do double duty, since they have supporting roles when plants flower in response to long days. Furthermore, both the SPLs and other regulators eventually converge on a similar set of targets crucial for flowering. "Flowering is crucial for the long-term survival of plants. The redundancy of environment-dependent and -independent mechanisms ensures that plants do not wait forever until flowering. Better flower once, then never", explains Detlef Weigel, director at the Max Planck Institute for Developmental Biology.

(Photo: Jürgen Berger)

Max Planck Institute

FAT IN THE LIVER -- NOT THE BELLY -- IS A BETTER MARKER FOR DISEASE RISK

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New findings from nutrition researchers at Washington University School of Medicine in St. Louis suggest that it's not whether body fat is stored in the belly that affects metabolic risk factors for diabetes, high blood triglycerides and cardiovascular disease, but whether it collects in the liver.

Having too much liver fat is known as nonalcoholic fatty liver disease. The researchers report online in the journal PNAS Early Edition that when fat collects in the liver, people experience serious metabolic problems such as insulin resistance, which affects the body's ability to metabolize sugar. They also have increases in production of fat particles in the liver that are secreted into the bloodstream and increase the level of triglycerides.

For years, scientists have noted that where individuals carried body fat influences their metabolic and cardiovascular risk. Increased fat inside the belly, known as visceral fat, is associated with an increased risk of diabetes and heart disease.

"Data from a large number of studies shows that visceral fat is associated with metabolic risk, which has led to the belief that visceral fat might even cause metabolic dysfunction," says senior investigator Samuel Klein, M.D. "However, visceral fat tracks closely with liver fat. We have found that excess fat in the liver, not visceral fat, is a key marker of metabolic dysfunction. Visceral fat might simply be an innocent bystander that is associated with liver fat."

Klein, the Danforth Professor of Medicine and Nutritional Science, directs the Division of Geriatrics and Nutritional Science and the Center for Applied Research Studies, as well as Washington University's Center for Human Nutrition. He says most of our body fat, called subcutaneous fat, is located under our skin, but about 10 percent is present inside the belly, while much smaller amounts are found inside organs such as the liver and muscle.

This study compared obese people with elevated and normal amounts of liver fat. All subjects were matched by age, sex, body mass index, percent body fat and degree of obesity. Through careful evaluations of obese people with different amounts of visceral fat or liver fat, Klein's team determined that excess fat inside the liver identifies those individuals who are at risk for metabolic problems.

"We don't know exactly why some fats, particularly triglycerides, will accumulate inside the liver and muscle in some people but not in others," says first author Elisa Fabbrini, M.D., Ph.D., assistant professor of medicine. "But our data suggest that a protein called CD36, which controls the transport of fatty acids from the bloodstream into different tissues, is involved."

Fatty acids are the building blocks for making fats, known as triglycerides. Klein, Fabbrini and their colleagues found that CD36 levels were lower in fat tissue and higher in muscle tissue among people with elevated liver fat.

Fabbrini and Klein say changes in CD36 activity could be responsible for diverting circulating fatty acids away from fat tissue and into liver and muscle tissue, where they are converted to triglyceride. Increased tissue uptake of fatty acids could be responsible for metabolic dysfunction.

Klein says those who are obese but don't have high levels of fat in the liver should be encouraged to lose weight, but those with elevated liver fat are at particularly high risk for heart disease and diabetes. He says they need to be treated aggressively to help them lose weight because dropping pounds can make a big difference.

"Fatty liver disease is completely reversible," he says. "If you lose a small amount of weight, you can markedly reduce the fat content in your liver. In fact, even two days of calorie restriction can cause a large reduction in liver fat and improvement in liver insulin sensitivity."

Washington University School of Medicine in St. Louis

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