Posted: 28 Dec 2010 01:52 PM PST

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Construction of the world's largest particle detector is now complete after 10 years of drilling deeper than a mile into ultraclear Antarctic ice.

Called the IceCube, the three-dimensional array of sensors can detect neutrinos expelled by some of the universe's most violent sources, including black holes, supernovas and energetic stars.

Neutrinos weigh hardly anything, so the particles usually travel through matter — including the sun and Earth — without interacting. But every now and then they slam into the cores of atoms to create nuclear particle showers. The events emit faint blue trails of light which IceCube's 5,160 sensors can track with extreme precision.

"About one in a million neutrinos crash into a proton. We're measuring the energy and the directions of those nuclear reactions to build a neutrino-based map of the sky," said Francis Halzen, a theoretical physicist at the University of Wisconsin-Madison and leader of IceCube.

The $100-million neutrino-detection effort is one of the most challenging ever attempted by engineers and physicists, Halzen said.

"Nobody would have bet on the success of this project, and rightfully so," Halzen said. "If we knew how complex it would be to build, we may have never started."

In this gallery, take a tour of the world's biggest, iciest particle detector.

Video: Animations show the drilling of IceCube's 1.5-mile-deep holes, the completed array of light-detecting sensors and a simulation of a neutrino collision event.
Credit: NSF, IceCube/University of Madison-Wisconsin and Chris Bickel.

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Rare Cambodian Elephant Captured on Video

Posted: 28 Dec 2010 11:11 AM PST

A rare Cambodian elephant has finally been caught on video.

The footage was taken in August by photographer Allan Michaud for the Wildlife Conservation Society, who say it's the first high-quality video of an Asian elephant in Cambodia.

Michaud filmed the adult male in the Seima Forest, a Rhode Island–sized sanctuary along the country's border with Vietnam.

Newly protected by Cambodia's government and the WCS, the forest is home to some of Asia's rarest creatures: tigers, forest bison, langurs and, of course, elephants. But decades of war and instability, followed by contemporary threats from poaching and development, have spooked the gentle, highly social creatures.

From their droppings, a 2006 survey of Seima's elephants counted 116, but without actually seeing a single animal. Most photos have come from camera traps. According to WCS researcher Edward Pollard, the video is "visual confirmation that Seima is vitally important for biodiversity."

And for those people less moved by biodiversity than life, it's a rare glimpse of a magnificent animal.

Video: Allan Michaud, Wildlife Conservation Society.

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Brain Volume Linked to Social Networking

Posted: 28 Dec 2010 10:00 AM PST

By Yun Xie, Ars Technica

The size of your amygdala might indicate how large and complex your social network is. Amygdala volume has been connected to social network and behavior in past research, as scientists have found that nonhuman primate species with larger social groups tend to have greater amygdala volumes. Kevin Bickart and his coauthors took the next logical step and examined how amygdala volume varies in humans with different social networks. Their results appear in a recent issue of Nature Neuroscience.

The researchers measured two social network factors in 58 adults. First, they calculated the size of a participant's network, which is simply the total number of people who are in regular contact with the participant. Second, they measured the network's complexity, based on how many different groups a participant's contacts can be divided into. The authors then examined how well those two factors correlated with the size of a participant's amygdala and hippocampus. The hippocampus served as a negative control, as it should not vary based on social networks.

Linear regression revealed a positive correlation in amygdala size with both social network size and complexity. This effect showed no lateralization, meaning both left and right amygdala volumes followed this relationship. In addition, the effect is relatively specific, as other social factors like life satisfaction and perceived social support failed to correlate with amygdala volume.

Social network size and complexity did not significantly correspond with the size of the hippocampus or other subcortical areas. The authors did find that three regions in the cerebral cortex of the brain (caudal inferior temporal sulcus, caudal superior frontal gyrus, and subgenual anterior cingulate cortex) might correlate with social networks. They propose that those regions might have evolved along with amygdala to deal with the complexities of growing social circles.

This is one of the first publications that demonstrates a relationship between amygdala volume and social networks in humans. It would be fascinating to determine if a cause-and-effect relationship can be established. Are certain people born with larger amygdala and therefore create bigger social networks, or does the amygdala grow as we gain more friends and foes?

Images: 1) Flickr/AJ Cann. 2) Amygdala position./NIH.

Nature Neuroscience, 2010. DOI: 10.1038/nn.2724

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