Tuesday, March 9, 2010

ALIEN INVADERS PACK THE MILKY WAY

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Around a quarter of the globular star clusters in our Milky Way galaxy are invaders from other galaxies, according to a team of scientists from Swinburne University of Technology in Australia. In a paper accepted for publication in Monthly Notices of the Royal Astronomical Society, Swinburne astronomer Professor Duncan Forbes has shown that many of our galaxy’s globular star clusters are actually foreigners - having been born elsewhere and then migrated to our Milky Way.

“It turns out that many of the stars and globular star clusters we see when we look into the night sky are not natives, but aliens from other galaxies,” said Forbes. “They have made their way into our galaxy over the last few billion years.”

Previously astronomers had suspected that some globular star clusters, which each contain between 10000 and several million stars were foreign to our galaxy, but it was difficult to positively identify which ones.

Using Hubble Space Telescope data, Forbes, along with his Canadian colleague Professor Terry Bridges, examined globular star clusters within the Milky Way galaxy.

They then compiled the largest ever high-quality database to record the age and chemical properties of each of these clusters.

“Using this database we were able to identify key signatures in many of the globular star clusters that gave us tell-tale clues as to their external origin,” Forbes said.

“We determined that these foreign-born globular star clusters actually make up about one quarter of our Milky Way globular star cluster system. That implies tens of millions of accreted stars – those that have joined and grown our galaxy – from globular star clusters alone.”

The researchers’ work also suggests that the Milky Way may have swallowed up more dwarf galaxies than was previously thought.

“We found that many of the foreign clusters originally existed within dwarf galaxies - that is ‘mini’ galaxies of up to 100 million stars that sit within our larger Milky Way.

“Our work shows that there are more of these accreted dwarf galaxies in our Milky Way than was thought. Astronomers had been able to confirm the existence of two accreted dwarf galaxies in our Milky Way – but our research suggests that there might be as many as six yet to be discovered.

"Although the dwarf galaxies are broken-up and their stars assimilated into the Milky Way, the globular star clusters of the dwarf galaxy remain intact and survive the accretion process."

“This will have to be explored further, but it is a very exciting prospect that will help us to better understand the history of our own galaxy.”

(Photo: NASA / The Hubble Heritage Team / STScI / AURA)

Royal Astronomical Society

AN AFTERNOON NAP MARKEDLY BOOSTS THE BRAINS LEARNING CAPACITY

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If you see a student dozing in the library or a co-worker catching 40 winks in her cubicle, don't roll your eyes. New research from the University of California, Berkeley, shows that an hour’s nap can dramatically boost and restore your brain power. Indeed, the findings suggest that a biphasic sleep schedule not only refreshes the mind, but can make you smarter.

Conversely, the more hours we spend awake, the more sluggish our minds become, according to the findings. The results support previous data from the same research team that pulling an all-nighter — a common practice at college during midterms and finals — decreases the ability to cram in new facts by nearly 40 percent, due to a shutdown of brain regions during sleep deprivation.

"Sleep not only rights the wrong of prolonged wakefulness but, at a neurocognitive level, it moves you beyond where you were before you took a nap," said Matthew Walker, an assistant professor of psychology at UC Berkeley and the lead investigator of these studies.

In the recent UC Berkeley sleep study, 39 healthy young adults were divided into two groups — nap and no-nap. At noon, all the participants were subjected to a rigorous learning task intended to tax the hippocampus, a region of the brain that helps store fact-based memories. Both groups performed at comparable levels.

At 2 p.m., the nap group took a 90-minute siesta while the no-nap group stayed awake. Later that day, at 6 p.m., participants performed a new round of learning exercises. Those who remained awake throughout the day became worse at learning. In contrast, those who napped did markedly better and actually improved in their capacity to learn.

Matthew Walker, assistant psychology professor, has found that a nap clears the brain to absorb new information. These findings reinforce the researchers' hypothesis that sleep is needed to clear the brain’s short-term memory storage and make room for new information, said Walker, who presented his preliminary findings on Sunday, Feb. 21, at the annual meeting of the American Association of the Advancement of Science (AAAS) in San Diego, Calif.

Since 2007, Walker and other sleep researchers have established that fact-based memories are temporarily stored in the hippocampus before being sent to the brain's prefrontal cortex, which may have more storage space.

"It's as though the e-mail inbox in your hippocampus is full and, until you sleep and clear out those fact e-mails, you’re not going to receive any more mail. It's just going to bounce until you sleep and move it into another folder," Walker said.

In the latest study, Walker and his team have broken new ground in discovering that this memory-refreshing process occurs when nappers are engaged in a specific stage of sleep. Electroencephalogram tests, which measure electrical activity in the brain, indicated that this refreshing of memory capacity is related to Stage 2 non-REM sleep, which takes place between deep sleep (non-REM) and the dream state known as Rapid Eye Movement (REM). Previously, the purpose of this stage was unclear, but the new results offer evidence as to why humans spend at least half their sleeping hours in Stage 2, non-REM, Walker said.

"I can’t imagine Mother Nature would have us spend 50 percent of the night going from one sleep stage to another for no reason," Walker said. "Sleep is sophisticated. It acts locally to give us what we need."

Walker and his team will go on to investigate whether the reduction of sleep experienced by people as they get older is related to the documented decrease in our ability to learn as we age. Finding that link may be helpful in understanding such neurodegenerative conditions as Alzheimer’s disease, Walker said.

(Photo: Matthew Walker)

University of California, Berkeley

TV ADS MAY BE MORE EFFECTIVE IF WE PAY LESS ATTENTION

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Viewers pay less attention to creative television advertisements, shows new research from the University of Bath, but may make themselves more vulnerable to the advertiser’s message.

The findings overturn the long-held assumption within the advertising industry that ads with high levels of emotional content encourage viewers to pay more attention.

The study, published in the Journal of Advertising Research, used an eye-tracking device to measure the real-time attention paid to a range of adverts with different levels of emotional content.

The adverts were embedded in an episode of the sitcom Frasier and participants were unaware that advertising was the subject of the research.

Results showed that viewers paid less attention to likeable, creative adverts, and more attention to factual information-giving adverts, even when they didn’t like them.

Dr Robert Heath, from the University’s School of Management, who led the research team, said: “There has been a lot of research which shows that creative TV ads are more effective than those which simply deliver information, and it has always been assumed that it is because viewers pay more attention to them.

“But in a relaxed situation like TV watching, attention tends to be used mainly as a defence mechanism. If an ad bombards us with new information, our natural response is to pay attention so we can counter-argue what it is telling us. On the other hand, if we feel we like and enjoy an ad, we tend to be more trustful of it and therefore we don’t feel we need to pay too much attention to it.

“The sting in the tail is that by paying less attention, we are less able to counter-argue what the ad is communicating. In effect we let our guard down and leave ourselves more open to the advertiser’s message.

“This has serious implications for certain categories of ads, particularly ads for products that can be harmful to our health, and products aimed at children.

“The findings suggest that if you don’t want an ad to affect you in this way, you should watch it more closely.”

(Photo: U. Bath)

University of Bath

THE SAFE WAY TO USE ONE INTERNET PASSWORD

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A little-used Internet authentication system from the 1980s could provide the answer for enabling web users to securely log in only once per Internet session, a Queensland University of Technology researcher has found.

PhD researcher Suriadi, from QUT's Information Security Institute, said a secure single-sign on system was more than simply using the same password for multiple accounts.

Mr Suriadi said any future single-sign on systems, which could potentially give web users access to a multitude of accounts, including email, bank and shopping, would require extreme privacy to avoid information spies and account hackers.

"Single-sign on systems are already being used by organisations," he said.

"For example, a bank could link their Internet banking site to an online trading site, thus relieving users from having to perform an extra log in step.

"However, if one of the parties is compromised, for example by a virus, a 'denial of service' attack or insecure set-up, it puts all the user's linked accounts at risk."

Mr Suriadi said his research investigated a little-used "anonymous credential system" which dates back to the 1980s, but recently received renewed interest from the research community.

"Using this credential system, we could enhance the security and privacy of a single sign-on system," he said.

"The system works by revealing as little information about who you are as necessary for logging into an account, therefore allowing you to remain anonymous.

"This way, a company wouldn't be able to track your shopping habits and target spam or marketing at you. This method could also confirm you are over 18 and not reveal your birthday."

Mr Suriadi said a single sign-on system backed by the anonymous credential system required the cooperation of businesses and organisations to enable it.

"One use of this could be for the research community, with online libraries and databases applying the anonymous credential system so that the privacy of researchers can be preserved," he said.

"This would be useful for people researching sensitive issues."

Mr Suriadi said for the purposes of accountability, such a system would also allow authorities to revoke users' anonymity in cases of illegal activity.

(Photo: QUT)

Queensland University of Technology

FIELD STUDY EXPOSES HOW SEA TURTLE HATCHLINGS USE THEIR FLIPPERS TO MOVE QUICKLY ON SAND

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Life can be scary for endangered loggerhead sea turtles immediately after they hatch. After climbing out of their underground nest, the baby turtles must quickly traverse a variety of terrains for several hundred feet to reach the ocean.

While these turtles' limbs are adapted for a life at sea, their flippers enable excellent mobility over dune grass, rigid obstacles and sand of varying compaction and moisture content. A new field study conducted by researchers at the Georgia Institute of Technology is the first to show how these hatchlings use their limbs to move quickly on loose sand and hard ground to reach the ocean. This research may help engineers build robots that can travel across complex environments.

"Locomotion on sand is challenging because sand surfaces can flow during limb interaction and slipping can result, causing both instability and decreased locomotor performance, but these turtles are able to adapt," said Daniel Goldman, an assistant professor in the Georgia Tech School of Physics. "On hard-packed sand at the water's edge, these turtles push forward by digging a claw on their flipper into the ground so that they don't slip, and on loose sand they advance by pushing off against a solid region of sand that forms behind their flippers."

Details of the study were published online on February 10, 2010 in the journal Biology Letters. This research was supported by the Burroughs Wellcome Fund, National Science Foundation, and the Army Research Laboratory.

In collaboration with the Georgia Sea Turtle Center, biology graduate student Nicole Mazouchova studied the movement of sea turtle hatchlings of the species Caretta caretta at Jekyll Island on the coast of Georgia. She and research technician Andrei Savu worked from a mobile laboratory that contained a nearly three-foot-long trackway filled with dry Jekyll Island sand.

The trackway contained tiny holes in the bottom through which air could be blown. The air pulses elevated the granules and caused them to settle into a loosely packed solid state, allowing the researchers to closely control the density of the sand.

In addition to challenging hatchlings to traverse loosely packed sand in the trackway, the researchers also studied the turtles' movement on hard surfaces -- a sandpaper-covered board placed on top of the sand. Two high-speed cameras recorded the movements of the hatchlings along the trackway, and showed how the turtles altered their locomotion to move on different surfaces.

"We assumed that the turtles would perform best on rigid ground because it would not give way under their flippers, but our experiments showed that while the turtles' average speed on sand was reduced by 28 percent relative to hard ground, their maximal speeds were the same for both surfaces," noted Goldman.

The researchers' investigations showed that on the rigid sandpaper surface, the turtles anchored a claw located on their wrists into the sandpaper and propelled themselves forward. During the thrusting process, one of the turtle's shoulders rotated toward its body and its wrist did not bend, keeping the limb fully extended.

In contrast, on loosely packed sand, pressure from the thin edge of one of the turtle's flippers caused the limb to penetrate into the sand. The turtle's shoulder then rotated as the flipper penetrated until the flipper was perpendicular to the surface and the turtle's body lifted from the surface.

"The turtles dug into the loosely packed sand, lifted their bellies off the ground, lurched forward, stopped, and did it again," explained Goldman.

To extend their biological observations, Goldman and physics graduate student Nick Gravish designed an artificial flipper system in the laboratory. The flipper consisted of a thin aluminum plate that was inserted into and dragged along the trackway filled with Jekyll Island sand. Calibrated strain gauges mounted on the flipper provided force measurements during the dragging procedure.

"Our model revealed that a major challenge for rapid locomotion of hatchling sea turtles on sand is the balance between high speed, which requires large inertial forces, and the potential for failure through fluidization of the sand," explained Goldman. "We believe that the turtles modulate the amount of force they use to push into the sand so that it remains below the force required for the ground to break apart and become fluidlike."

Goldman and his team plan to conduct further field studies and laboratory experiments to determine if and how the turtles control their limb movements on granular media to avoid sand fluidization. They are also developing robots that move along granular media like the sea turtle hatchings.

"These research results are valuable for roboticists who want to know the minimum number of appendage features necessary to move effectively on land and whether they can just design a robot with a flat mitt and a claw like these turtles have," noted Goldman.

(Photo: Alan Rees)

Georgia Institute of Technology

SCIENTISTS REVEAL DRIVING FORCE BEHIND EVOLUTION

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The team observed viruses as they evolved over hundreds of generations to infect bacteria. They found that when the bacteria could evolve defences, the viruses evolved at a quicker rate and generated greater diversity, compared to situations where the bacteria were unable to adapt to the viral infection.

The study shows, for the first time, that the American evolutionary biologist Leigh Van Valen was correct in his 'Red Queen Hypothesis'. The theory, first put forward in the 1970s, was named after a passage in Lewis Carroll's Through the Looking Glass in which the Red Queen tells Alice, 'It takes all the running you can do to keep in the same place'. This suggested that species were in a constant race for survival and have to continue to evolve new ways of defending themselves throughout time.

Dr Steve Paterson, from the University's School of Biosciences, explains: "Historically, it was assumed that most evolution was driven by a need to adapt to the environment or habitat. The Red Queen Hypothesis challenged this by pointing out that actually most natural selection will arise from co-evolutionary interactions with other species, not from interactions with the environment.

"This suggested that evolutionary change was created by 'tit-for-tat' adaptations by species in constant combat. This theory is widely accepted in the science community, but this is the first time we have been able to show evidence of it in an experiment with living things."

Dr Michael Brockhurst said: "We used fast-evolving viruses so that we could observe hundreds of generations of evolution. We found that for every viral strategy of attack, the bacteria would adapt to defend itself, which triggered an endless cycle of co-evolutionary change. We compared this with evolution against a fixed target, by disabling the bacteria's ability to adapt to the virus.

"These experiments showed us that co-evolutionary interactions between species result in more genetically diverse populations, compared to instances where the host was not able to adapt to the parasite. The virus was also able to evolve twice as quickly when the bacteria were allowed to evolve alongside it."

The team used high-throughput DNA sequencing technology at the Centre for Genomic Research to sequence thousands of virus genomes. The next stage of the research is to understand how co-evolution differs when interacting species help, rather than harm, one another.

University of Liverpool

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