Friday, July 2, 2010

ASTRONOMERS WITNESS A STAR BEING BORN

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Astronomers have glimpsed what could be the youngest known star at the very moment it is being born. Not yet fully developed into a true star, the object is in the earliest stages of star formation and has just begun pulling in matter from a surrounding envelope of gas and dust, according to a new study that appears in the current issue of the Astrophysical Journal.

The study’s authors—who include astronomers from Yale University, the Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Astronomy in Germany—found the object using the Submillimeter Array in Hawaii and the Spitzer Space Telescope. Known as L1448-IRS2E, it’s located in the Perseus star-forming region, about 800 light years away within our Milky Way galaxy.

Stars form out of large, cold, dense regions of gas and dust called molecular clouds, which exist throughout the galaxy. Astronomers think L1448-IRS2E is in between the prestellar phase, when a particularly dense region of a molecular cloud first begins to clump together, and the protostar phase, when gravity has pulled enough material together to form a dense, hot core out of the surrounding envelope.

“It’s very difficult to detect objects in this phase of star formation, because they are very short-lived and they emit very little light,” said Xuepeng Chen, a postdoctoral associate at Yale and lead author of the paper. The team detected the faint light emitted by the dust surrounding the object.

Most protostars are between one to 10 times as luminous as the Sun, with large dust envelopes that glow at infrared wavelengths. Because L1448-IRS2E is less than one tenth as luminous as the Sun, the team believes the object is too dim to be considered a true protostar. Yet they also discovered that the object is ejecting streams of high-velocity gas from its center, confirming that some sort of preliminary mass has already formed and the object has developed beyond the prestellar phase. This kind of outflow is seen in protostars (as a result of the magnetic field surrounding the forming star), but has not been seen at such an early stage until now.

The team hopes to use the new Herchel space telescope, launched last May, to look for more of these objects caught between the earliest stages of star formation so they can better understand how stars grow and evolve. “Stars are defined by their mass, but we still don’t know at what stage of the formation process a star acquires most of its mass,” said Héctor Arce, assistant professor of astronomy at Yale and an author of the paper. “This is one of the big questions driving our work.”

(Photo: NASA, ESA)

Yale University

REPORT DESCRIBES THE PHYSICS OF THE 'BENDS'

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As you go about your day-to-day activities, tiny bubbles of nitrogen come and go inside your tissues. This is not a problem unless you happen to experience large changes in ambient pressure, such as those encountered by scuba divers and astronauts. During large, fast pressure drops, these bubbles can grow and lead to decompression sickness, popularly known as "the bends."

A study in the Journal of Chemical Physics, which is published by the American Institute of Physics (AIP), may provide a physical basis for the existence of these bubbles, and could be useful in understanding decompression sickness.

A physiological model that accounts for these bubbles is needed both to protect against and to treat decompression sickness. There is a problem though. "These bubbles should not exist," says author Saul Goldman of the University of Guelph in Ontario, Canada.

Because they are believed to be composed mostly of nitrogen, while the surrounding atmosphere consists of both nitrogen and oxygen, the pressure of the bubbles should be less than that of the surrounding atmosphere. But if this were so, they would collapse.

"We need to account for their apparent continuous existence in tissues in spite of this putative pressure imbalance," says Goldman.

If, as is widely believed, decompression sickness is the result of the growth of pre-existing gas bubbles in tissues, those bubbles must be sufficiently stable to have non-negligible half-lives. The proposed explanation involves modeling body tissues as soft elastic materials that have some degree of rigidity. Previous models have focused on bubble formation in simple liquids, which differ from elastic materials in having no rigidity.

Using the soft-elastic tissue model, Goldman finds pockets of reduced pressure in which nitrogen bubbles can form and have enough stability to account for a continuous presence of tiny bubbles that can expand when the ambient pressure drops. Tribonucleation, the phenomenon of formation of new gas bubbles when submerged surfaces separate rapidly, provides the physical mechanism for formation of new gas bubbles in solution. The rapid separation of adhering surfaces results in momentary negative pressures at the plane of separation. Therefore, while these tiny bubbles in elastic media are metastable, and do not last indefinitely, they are replaced periodically. According to this picture, tribonucleation is the source, and finite half-lives the sink, for the continuous generation and loss small gas bubbles in tissues.

American Institute of Physics

LIQUID CRYSTALS LIGHT WAY TO BETTER DATA STORAGE

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As cell phones and computers continue to shrink, many companies are seeking better ways to store hundreds of gigabytes of data in small, low-power devices.

A special type of liquid crystal, similar to those used in computer displays and televisions, offers a solution. Unlike CDs and DVDs, which store information only on their surface, lasers can encode data throughout a liquid crystal. Known as holographic storage, the technique makes it possible to pack much more information in a tiny space.

But attempts to use liquid crystals for data storage have had limited success. In order to reliably record and rewrite data, researchers must figure out a way to uniformly control the orientation of liquid crystal molecules. Currently, most liquid crystal technologies rely on physical or chemical manipulation, such as rubbing in one direction, to align molecules in a preferred direction.

In an important advance, scientists at the Tokyo Institute of Technology have created a stable, rewritable memory device that exploits a liquid crystal property called the "anchoring transition." The work is described in the latest issue of the Journal of Applied Physics, which is published by the American Institute of Physics (AIP).

Using either a laser beam or an electric field, the researchers can align rod-like liquid crystal molecules in a polymer. Their tests show that the liquid crystal created by the team can store data, be erased and used again.

"This is the first rewritable memory device utilizing anchoring transition," said Hideo Takezoe, who led the research. And because the device is bi-stable -- the liquid crystals retain their orientation in one of two directions -- it needs no power to keep images, adds Takezoe.

American Institute of Physics

WHEN DO NEWBORNS FIRST FEEL COLD?

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Cold sensing neural circuits in newborn mice take around two weeks to become fully active, according to a new study.

The finding adds to understanding of the cold sensing protein TRPM8 (pronounced trip-em-ate), first identified in a Nature paper in 2002 by USC College professor David McKemy.

McKemy’s study, published online by Neuroscience, shows that the cold sensing circuit starts to develop in utero but does not mature until well after birth.

“About three or four days before the animal is born, the protein is expressed. However, the axons of these nerves going into the spinal cord are not fully formed until probably two weeks after birth,” said McKemy, an assistant professor of neurobiology.

The delay in development of cold sensing is plausible, McKemy added.

“In the womb, when would we ever feel cold?”

By contrast, mice are born with a keen sense of smell, which they need to breast feed successfully.

Direct study of the cold sensing protein TRPM8 in humans is not yet possible. While sensory development differs in mice and humans - mice are born blind, for example - the study suggests a possible biological basis for findings of altered cold sensitivity in premature infants.

In a 2008 study of temperature sensation by the Institute of Child Health at University College London, researchers found that 11-year-old children born prematurely were less sensitive to temperature than those born at term.

“This is consistent with our observations that the circuitry is not fully developed until after birth, thus anything that disrupts this formation at this important stage could have long-term effects,” McKemy noted.

“There are other reports that injury and inflammation in rodent models that occur during the [prenatal] period lead to altered temperature sensitivity as well as altered neural circuits.”

The USC researchers tracked development of cold sensing through mice genetically engineered to express a green fluorescent protein whenever TRPM8 was produced.

TRPM8 is one in a class of proteins known as ion channels. Their purpose is to “turn on the cell” when they receive a stimulus. TRPM8 senses both painful cold and the soothing cold of menthol-based creams.

How one protein can convey both sensations is unknown. McKemy speculated that neurons differ in their internal architecture, with each tuned to accept either painful or pleasant cold signals from TRPM8.

One goal of TRPM8 research is to understand the molecular mechanisms of sensation, in the hope of developing better drugs for relief of chronic pain states, such as the extreme sensitivity to cold experienced by some diabetes patients.

“If you want to understand conditions like cold allodynia, which is cold pain, you need to find exactly what are the targets,” McKemy said.

“If we understand the basic nuts and bolts of the molecules and neurons and how they detect pain normally,” McKemy said, “then perhaps we can figure out why we detect pain when we shouldn’t.”

(Photo: Alexandra Bissonnett)

USC

LOVE BALLAD LEAVES WOMEN MORE OPEN TO A DATE

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If you're having trouble getting a date, French researchers suggest that picking the right soundtrack could improve the odds. Women were more prepared to give their number to an 'average' young man after listening to romantic background music, according to research that appears in the journal Psychology of Music, published by SAGE.

There's plenty of research indicating that the media affects our behaviour. Violent video games or music with aggressive lyrics increase the likelihood of aggressive behaviour, thoughts and feelings – but do romantic songs have any effect? This question prompted researchers Nicolas Guéguen and Céline Jacob from the Université de Bretagne-Sud along with Lubomir Lamy from Université de Paris-Sud to test the power of romantic lyrics on 18-20 year old single females. And it turns out that at least one romantic love song did make a difference.

Guéguen and Jacob were part of a research team that had already shown how romantic music played in a flower shop led to male customers spending more money. This time the researchers used questionnaires to pinpoint agreed-upon neutral and romantic songs. They chose 'Je l'aime à mourir', a well-known love song by French songwriter Francis Cabrel, and the neutral song 'L'heure du thé', by Vincent Delerm. A group of young women separate from the main study rated 12 young male volunteers for attractiveness, and the researchers picked the one rated closest to 'average' to help with the experiment.

The researchers then set up a scenario where the 87 females each spent time in a waiting room with background music playing, before moving to a different room where the experimenter instructed her to discuss the difference between two food products with the young man. Once the experimenter returned, she asked them to wait for a few moments alone, and this gave the 'average' male a chance to use his standard chat up line: "My name is Antoine, as you know, I think you are very nice and I was wondering if you would give me your phone number. I'll phone you later and we can have a drink together somewhere next week.'

The love song in the waiting room almost doubled Antoine's chances of getting a woman's number – 52% of participants responded to his advances under the influence of Francis Cabrel, whereas only 28% of those who had heard the 'neutral' song by Vincent Delerm offered their details.

"Our results confirm that the effect of exposure to media content is not limited to violence and could have the potential to influence a high spectrum of behaviour," says Guéguen. "The results are interesting for scientists who work on the effect of background music on individuals' behaviour."

The results also add weight to a general learning model proposed by Buckley and Anderson in 2006 to explain the effect of media exposure. Their model states that media exposure in general, and not only aggressive or violent media, affects individuals' internal states, which explains why prosocial media fosters prosocial outcomes.

Why did the music have this effect? It may be that, as shown in earlier research, the music induced positive affect (in psychological terms, affect is the experience of feeling or emotion). Positive affect is associated with being more receptive to courtship requests. Alternatively, the romantic content of the song may have acted as a prime that then led to displays of behaviour associated with that prime. In either case, further research is needed before the researchers will commit to wider generalisations on the targeted use of love songs. But if you're a hopeful single, awareness of the background music certainly won't do any harm.

SAGE

HUMANS HAVE A MIGHTY BITE

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The robust jaws and formidable teeth of some of our ancestors and ape cousins may suggest that humans are wimps when it comes to producing a powerful bite: but a new study has found the opposite is true, with major implications for our understanding of diet in ancestral humans.

The surprise findings suggest that early modern humans did not necessarily need to use tools and cooking to process high-nutrient hard foods, such as nuts - and perhaps less tough foods such as meat - but may have lost an ability to eat very tough items, such as tubers or leaves.

In the first comparison of its kind, Australian researchers have found that the lightly built human skull has a far more efficient bite than those of the chimp, gorilla and orang-utan, and of two prehistoric members of our family, Australopithecus africanus and Paranthropus boisei.

They found that modern humans can achieve relatively high bite forces using less-powerful jaw muscles. In short, the human skull does not have to be as robust because, for any given bite force, the sum of forces acting on the human skull is much less.

These results also explain the apparent inconsistency of very thick tooth enamel in modern humans - a feature typically associated with high bite forces in other species. Thick enamel and large human tooth roots are well adapted to take high loads when biting.

The study appears in a paper in the journal Proceedings of the Royal Society B by a team led by Dr Stephen Wroe, of the Computational Biomechanics Research Group in the UNSW's School of Biological, Earth and Environmental Sciences. They used sophisticated three-dimensional (3D) finite element analysis to compare digital models of actual skulls that had been CAT-scanned.

The technique, adapted from engineering, provides a highly detailed view of where stresses occur in materials under loads designed to mimic actual scenarios. Wroe's team has previously used this approach to study the jaw mechanics of living and extinct species as varied as the great white shark and the sabre-toothed tiger.

These result calls into question previous suggestions that the evolution of a less robust skull in modern humans involved a trade-off for a weaker bite or was necessarily a response to behavioural changes, such as switching to softer foods or more processing of foods with tools and cooking. It has also been suggested that human jaw muscles were reduced to make way for a larger brain.

"However plausible those ideas may seem they have been based on very little by way of comparative data: for example, there are no actual records of bite force collected from living members of any other ape species, " says Dr Wroe. "It turns out that we don't have a wimpish bite at all - it is very efficient and powerful.

"When we're biting down in vertical plane, at the back of the jaw our bite is about 40-50% more efficient than it is for all great apes. It's even more efficient when biting at the front of the jaw.

"We've only looked at two extinct hominins in this study, but, for our size, we humans are comparable in terms of maximum bite force to these fossil species, which include ‘nutcracker man', renowned for its particularly massive skull and jaw muscles. Size matters, but efficiency matters more - and humans are very efficient biters.

"Importantly though, our study focuses on the generation of peak bite forces over short time spans. The jaws of other species may be better adapted to maintain chewing over long periods. This means that although humans are up there with great apes in their ability to quickly crack open a hard item, such as a large nut, or process less tough foods, such as meat, they may be less well adapted to process tough material, such as leaves or bamboo, which requires sustained chewing over a long period".

(Photo: UNSW)

UNSW

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