Sunday, September 6, 2009

NGC 4945 suggest

Seen edge-on, observations of NGC 4945 suggest that this hive of stars is a spiral galaxy much like our own Milky Way, with swirling, luminous arms and a bar-shaped centre. Sites of active star formation, known as H II regions, are seen prominently in the image, appearing bright pink. These resemblances aside, NGC 4945 has a brighter centre that likely harbours a supermassive black hole, which is devouring reams of matter and blasting energy out into space. NGC 4945 is about 13 million light-years away in the constellation of Centaurus (the Centaur) and is beautifully HTC Hero revealed in this image taken with data in five bands (B, V, R, H-alpha and S II) with the 2.2-metre MPG/ESO telescope at La Silla. The field of view is 30 x 30 arcminutes. North is up, East is to the le

Using brain scans in monkeys, Duke University Medical Center researchers are now able to predict when monkeys will switch from exploiting a known resource to exploring their options.

"Humans aren't the only animals who wonder if the grass is greener elsewhere, but it's hard to abandon what we know in hopes of finding something better," said John Pearson, Ph.D., research associate in the Duke Department of Neurobiology and lead author of a study published in this week's Current Biology.

"Studies like this one help reveal how the brain weighs costs and benefits in making that kind of decision," Pearson said. "We suspect that such a fundamental question engages many areas of the brain, but this is one of the first studies to show how individual neurons can carry signals for these kinds of strategic decisions."

The researchers looked at how nerve cells fired in a part of the brain known as the posterior cingulate cortex as the monkeys were offered a selection of rewards. Generally, these neurons fired more strongly when monkeys decided to explore new alternatives.

The monkeys started with four rewards to choose from, each a 200 microliter cup of juice. After that, the four targets began to slowly change in value, becoming larger or smaller. The monkeys were free to explore the other targets or stay with the initial target, whose value they knew for certain. Monkeys had to select an option to learn its current value and integrate this information with their knowledge of the chances of getting more juice at a different target.

By studying the individual neurons, the researchers could predict which strategy the monkey would employ.

"These data are interesting from a human health perspective, because the posterior cingulate cortex is the most metabolically active part of the brain when we are daydreaming or thinking to ourselves, and it is also one of the first parts of the brain to show damage in Alzheimer's disease," said Michael Platt, Ph.D., professor of neurobiology and evolutionary anthropology at Duke and senior author of the study.The process causes the disk of gas around the central black hole in NGC 1365 to produce copious X-rays, but the structure is much too small to resolve directly with a telescope. However, astronomers were able to measure the disk's size by observing how long it took for the black hole to go in and out of the eclipse. This was revealed duringring a peak in the temperature of hot gas in the center of the giant elliptical galaxy NGC 4649, scientists have determined the mass of the galaxy's supermassive black hole. The method, applied for the first time, gives results that are consistent with a traditional technique.

Astronomers have been seeking out different, independent ways of precisely weighing the largest supermassive black holes, that is, those that are billions of times more massive than the Sun. Until now, methods based on observations of the motions of stars or of gas in a disk near such large black holes had been used.

"This is tremendously important work since black holes can be elusive, and there are only a couple of ways to weigh them accurately," said Philip Humphrey of the University of California at Irvine, who led the study. "It's reass

"People with Alzheimer's become set in their ways and don't explore as much, which may be because this part of the brain is damaged," Platt said. "Likewise, in people with obsessive-compulsive disorder, they can become fixed on certain activities or patterns of activity and can't disengage from them, which may also relate to changes in this part of the brain that renders them mentally unable to switch gears between exploring and exploiting."

More research is needed to learn about how this part of the brain functions, which might be crucial to the flexible adaptation of strategy in response to changing e
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