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December 31, 2005, 8:32 PM CT

Galaxy Collisions And The Universe

Galaxy Collisions And The Universe
More than half of the largest galaxies in the nearby universe have collided and merged with another galaxy in the past two billion years, according to a Yale astronomer in a study using hundreds of images from two of the deepest sky surveys ever conducted.

The idea of large galaxies being assembled primarily by mergers rather than evolving by themselves in isolation has grown to dominate cosmological thinking. However, a troubling inconsistency within this general theory has been that the most massive galaxies appear to be the oldest, leaving minimal time since the Big Bang for the mergers to have occurred.

"Our study found these common massive galaxies do form by mergers. It is just that the mergers happen quickly, and the features that reveal the mergers are very faint and therefore difficult to detect," said Pieter van Dokkum, assistant professor of astronomy at Yale University, and sole author of the paper appearing in the December 2005 issue of the Astronomical Journal.

The paper uses two recent deep surveys done with the National Science Foundation's 4-meter telescopes at Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory, known as the NOAO Deep Wide-Field Survey and the Multiwavelength Survey by Yale/Chile. Together, these surveys covered an area of the sky 50 times larger than the size of the full Moon and more than 5,000 times larger than the famous Hubble Deep Field........

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December 31, 2005, 8:02 PM CT

How Running Made Us Human

How Running Made Us Human Credit: Laszlo Meszoly, Harvard University
Humans evolved from ape-like ancestors because they needed to run long distances - perhaps to hunt animals or scavenge carcasses on Africa's vast savannah - and the ability to run shaped our anatomy, making us look like we do today.

That is the conclusion of a study published in the Nov. 18 issue of the journal Nature by University of Utah biologist Dennis Bramble and Harvard University anthropologist Daniel Lieberman. The study is featured on Nature's cover.

Bramble and Lieberman argue that our genus, Homo, evolved from more ape-like human ancestors, Australopithecus, 2 million or more years ago because natural selection favored the survival of australopithecines that could run and, over time, favored the perpetuation of human anatomical features that made long-distance running possible.

"We are very confident that strong selection for running - which came at the expense of the historical ability to live in trees - was instrumental in the origin of the modern human body form," says Bramble, a professor of biology. "Running has substantially shaped human evolution. Running made us human - at least in an anatomical sense. We think running is one of the most transforming events in human history. We are arguing the emergence of humans is tied to the evolution of running".........

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December 31, 2005, 7:28 PM CT

How Roots Control Plant Shoots

How Roots Control Plant Shoots
University of Utah biologists discovered a gene that allows a plant's roots to tell the leaves to stop growing, presumably when water is scarce, soil is too compacted or other conditions are bad.

While roots obviously carry food and water to the leaves, the new findings help show how roots also send chemical signals that control whether or not leaves grow. How leaves grow is a crucial matter given that leafy plants supply food for humans and other creatures, produce oxygen for all animals to breathe, influence global climate and grace us with the current season of brilliant fall colors.

"When we look at plants, it's easy to think only about the above-ground parts you can see," says Leslie Sieburth, who led the study and is an associate professor of biology at the University of Utah. "But this study shows that the roots potentially play a huge role - in addition to supplying water and nutrients - in controlling how the plant comes to look as it does. It's very easy to ignore the root, but our study shows we shouldn't".

Manipulating the process someday might allow researchers to genetically engineer crops and other plants to be more productive in dry conditions - for example, so that crops could keep producing abundant leaves in a drought by irrigating them while overriding the genetic signal that normally would inhibit growth, Sieburth says.........

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December 31, 2005, 7:20 PM CT

Molecular 'zipcode' guides nerves

Molecular 'zipcode' guides nerves
During embryonic development, thousands of nerves must be connected to muscles as part of a communication network that allows the newborn to move, breathe and lead a normal life. The question is, how does this complicated 'telephone system' get wired up?.

In the April 8th edition of Cell, researchers at the Salk Institute for Biological Studies report that they have identified a molecular 'zip code' on the growing end of the nerve cell that guides it to the correct 'address' in the muscles. The discovery adds to developing knowledge about how the nervous system is assembled during fetal development. With such knowledge, scientists hope to use nature's own tricks for repairing the nervous system damaged by injury or neurodegenerative disorders such as Lou Gehrig's disease.

The complicated wiring process that occurs during embryonic development is controlled by chemical signaling molecules that guide the nerves to grow towards their targets. The Salk Institute study, involving a team of talented post-doctoral fellows led by Sam Pfaff and Tony Hunter, studied two key signaling molecules named ephrin and Eph.

Prior studies had established that the ephrin and Eph proteins work together as a tag team to guide the growth of neurons. Another Salk scientist, Dennis D.M. O'Leary previously revealed that.........

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December 31, 2005, 7:13 PM CT

Groundbreaking Combustion Research

Groundbreaking Combustion Research
Computational and combustion researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have earned national recognition in the Proceedings of the National Academy of Sciences (PNAS) with a cover article about unparalleled computer simulations of turbulent flames.

The research by researchers in Berkeley Lab's Center for Computational Sciences and Engineering and in the Environmental Energy Technologies Division has led to a three-dimensional combustion simulation of unmatched size without resorting to models for turbulence or turbulence-chemistry interactions. The article shows that the simulation closely matches a combustion experiment.

Gaining a better understanding of combustion, which powers everything from automobiles to aircraft to power generating plants, can help improve the efficiency of those system as well as help reduce the amount of pollution produced by burning fossil fuels.

"Eventhough collaborations between computational researchers and experimentalists are becoming increasingly common, the results from this project clearly demonstrate how scientific computing is coming into its own as an essential component of scientific discovery," said Horst Simon, Associate Laboratory Director for Computing Sciences at Berkeley Lab. "The simulation is unprecedented in several aspects - the number of chemical species included, the number of chemical processes modeled, and the overall size of the flame. This is truly breakthrough computational science."........

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December 31, 2005, 7:02 PM CT

Breakthrough Inspired by Experiment

Breakthrough Inspired by Experiment
Need to understand the details of how a molecule is put together? Want to see the effects of the intricate dance that its electrons do to make a chemical bond? Try blowing a molecule to bits and calculating what happens to all the pieces. That's the approach taken by an international group of collaborators from the University of California at Davis, universities in Spain and Belgium, and the Chemical Sciences Division of the Department of Energy's Lawrence Berkeley National Laboratory.

When a hydrogen molecule, H2, is hit by a photon with enough energy to send both its electrons flying, the two protons left behind - the hydrogen nuclei - repel each other in a so-called Coulomb explosion. In this event, called the double photoionization of H2, the paths taken by the fleeing electrons have much to say about how close together the two nuclei were at the moment the photon struck, and just how the electrons were correlated in the molecule.

Correlation means that properties of the particles like position and momentum cannot be calculated independently. When three or more particles are involved, calculations are notoriously intractable, both in classical physics and quantum mechanics. In the 16 December, 2005 issue of Science the scientists report on the first-ever complete quantum mechanical solution of a system with four charged particles.........

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December 31, 2005, 2:59 PM CT

Turning Semiconducting Nanotubes Into Metals

Turning Semiconducting Nanotubes Into Metals
A new study, published in today's issue of the journal Science, finds that the basic electrical properties of semiconducting carbon nanotubes change when they are placed inside a magnetic field. The phenomenon is unique among known materials, and it could cause semiconducting nanotubes to transform into metals in even stronger magnetic fields.

Researchers found that the "band gap" of semiconducting nanotubes shrank steadily in the presence of a strong magnetic force, said lead researcher Junichiro Kono, an assistant professor of electrical and computer engineering at Rice University. The research, which involved a multidisciplinary team of electrical engineers, chemists and physicists, helps confirm quantum mechanical theories offered more than four decades ago, and it sheds new light on the unique electrical properties of carbon nanotubes, tiny cylinders of carbon that measure just one-billionth of a meter in diameter.

"We know carbon nanotubes are exceptionally strong, very light and imbued with wonderful electrical properties that make them candidates for things like 'smart' spacecraft components, 'smart' power grids, biological sensors, improved body armor and countless other applications," said paper co-author Richard Smalley, director of Rice's Carbon Nanotechnology Laboratory. "These findings remind us that there are still unique and wonderful properties that we have yet to uncover about nanotubes".........

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December 31, 2005, 2:24 PM CT

Hubble To 'weigh' Dog Star's Companion

Hubble To 'weigh' Dog Star's Companion
White dwarfs are important to theories of both stellar and cosmological evolution. New results published in the Monthly Notices of the Royal Astronomical Society provide for the first time an accurate measurement of the weight of the nearest white dwarf, Sirius B, companion of the brightest star in the sky. It turns out that Sirius's companion, despite being smaller than the Earth, has a mass that is 98% that of our own Sun.

For astronomers, it's always been a source of frustration that the nearest white-dwarf star is buried in the glow of the brightest star in the nighttime sky. This burned-out stellar remnant is a faint companion of the brilliant blue-white Dog Star, Sirius, located in the winter constellation Canis Major.

Now, an international team of astronomers has used the keen eye of the NASA/ESA Hubble Space Telescope to isolate the light from the white dwarf, called Sirius B. The new results allow them to measure precisely the white dwarf's mass based on how its intense gravitational field alters the wavelengths of light emitted by the star.

"Studying Sirius B has challenged astronomers for more than 140 years," said Martin Barstow of the University of Leicester, U.K., who is the leader of the observing team. "Only with Hubble have we at last been able to obtain the observations we need, uncontaminated by the light from Sirius, in order to measure its change in wavelengths".........

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December 31, 2005, 2:21 PM CT

Most detailed image of the Crab Nebula

Most detailed image of the Crab Nebula
A new Hubble image - among the largest ever produced with the Earth-orbiting observatory - gives the most detailed view so far of the entire Crab Nebula. The Crab is arguably the single most interesting object, as well as one of the most studied, in all of astronomy. The image is the largest ever taken with Hubble's WFPC2 workhorse camera.

The Crab Nebula is one of the most intricately structured and highly dynamical objects ever observed. The new Hubble image of the Crab was assembled from 24 individual exposures taken with the NASA/ESA Hubble Space Telescope's Wide Field and Planetary Camera 2 (WPFC2) and is the highest resolution image of the entire Crab Nebula ever made.

The Crab Nebula is a six-light-year-wide expanding remnant of a star's supernova explosion. Japanese and Chinese astronomers witnessed this violent event nearly 1,000 years ago in 1054.

The filaments are the tattered remains of the star and consist mostly of hydrogen. The rapidly spinning neutron star embedded in the centre of the nebula, only barely visible in this Hubble image, is the dynamo powering the nebula's eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second due to the neutron star's rotation. A neutron star is the crushed ultra-dense core of the exploded star.........

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December 31, 2005, 2:18 PM CT

Young stars sculpt gas with powerful outflows

Young stars sculpt gas with powerful outflows
This Hubble Space Telescope view shows one of the most dynamic and intricately detailed star-forming regions in space, located 210,000 light-years away in the Small Magellanic Cloud (SMC), a satellite galaxy of our Milky Way. At the centre of the region is a brilliant star cluster called NGC 346. A dramatic structure of arched, ragged filaments with a distinct ridge surrounds the cluster.

A torrent of radiation from the hot stars in the cluster NGC 346, at the centre of this Hubble image, eats into denser areas around it, creating a fantasy sculpture of dust and gas. The dark, intricately beaded edge of the ridge, seen in silhouette, is especially dramatic. It contains several small dust globules that point back towards the central cluster, like windsocks caught in a gale.

Energetic outflows and radiation from hot young stars are eroding the dense outer portions of the star-forming region, formally known as N66, exposing new stellar nurseries. The diffuse fringes of the nebula prevent the energetic outflows from streaming directly away from the cluster, leaving instead a trail of filaments marking the swirling path of the outflows.

The NGC 346 cluster is resolved into at least three sub-clusters and collectively contains dozens of hot, blue, high-mass stars, more than half of the known high-mass stars in the entire SMC galaxy. A myriad of smaller, compact clusters is also visible throughout the region.........

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