Monday, October 12, 2009

FIRST LIGHT FOR BOSS -- A NEW KIND OF SEARCH FOR DARK ENERGY

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BOSS, the Baryon Oscillation Spectroscopic Survey, is the most ambitious attempt yet to map the expansion history of the Universe using the technique known as baryon acoustic oscillation (BAO). A part of the Sloan Digital Sky Survey III (SDSS-III), BOSS achieved "first light" on the night of September 14-15, when it acquired data with an upgraded spectrographic system across the entire focal plane of the Sloan Foundation 2.5-meter telescope at Apache Point Observatory in New Mexico.

BOSS is the largest of four surveys in SDSS-III, with 160 participants from among SDSS-III's 350 scientists and 42 institutions. BOSS's principal investigator is David Schlegel, its survey scientist is Martin White, and its instrument scientist is Natalie Roe; all three are with the Physics Division of the U.S. Department of Energy's Lawrence Berkeley National Laboratory. Daniel Eisenstein of the University of Arizona is the director of SDSS-III.

"Baryon oscillation is a fast-maturing method for measuring dark energy in a way that's complementary to the proven techniques of supernova cosmology," says Schlegel. "The data from BOSS will be some of the best ever obtained on the large-scale structure of the Universe."

BOSS's first exposure was made after many nights of clouds and rain in the Sacramento Mountains when spectroscopy was obtained of some 800 galaxies and 200 quasars in the constellation Aquarius. Team member Vaishali Bhardwaj, a graduate student at the University of Washington fresh from a summer internship at Berkeley Lab, helped operate the telescope. Bhardwaj's teammate, Berkeley Lab postdoc Nic Ross, quipped that given the constellation where first light was obtained, the accomplishment marked the "dawning of the Age of Aquarius."

Baryon oscillations began as pressure waves propagated through the hot plasma of the early universe, creating regions of varying density that can be read today as temperature variations in the cosmic microwave background. The same density variations left their mark as the Universe evolved, in the periodic clustering of visible matter in galaxies, quasars, and intergalactic gas, as well as in the clumping of invisible dark matter.

Comparing these scales at different eras makes it possible to trace the details of how the Universe has expanded throughout its history – information that can be used to distinguish among competing theories of dark energy.

BOSS will measure 1.4 million luminous red galaxies at redshifts up to 0.7 (when the Universe was roughly seven billion years old) and 160,000 quasars at redshifts between 2.0 and 3.0 (when the Universe was only about three billion years old). BOSS will also measure variations in the density of hydrogen gas between the galaxies. The observation program will take five years.

"BOSS will survey the immense volume required to obtain percent-level measurements of the BAO scale and transform the BAO technique into a precision cosmological probe," says survey scientist White. "The high precision, enormous dynamic range, and wide redshift span of the BOSS clustering measurements translate into a revolutionary data set, which will provide rich insights into the origin of cosmic structure and the contents of the Universe."

Existing SDSS spectrographs were upgraded to include new red cameras more sensitive to the red portion of the spectrum, featuring CCDs designed and fabricated at Berkeley Lab, with much higher efficiency than standard astronomical CCDs in the near infrared.

"Visible light emitted by distant galaxies arrives at Earth redshifted into the near-infrared, so the improved sensitivity of these CCDs allows us to look much further back in time," says BOSS instrument scientist Roe.

To make these measurements BOSS will craft two thousand metal plates to fit the telescope's focal plane, plotting the precise locations of two million objects across the northern sky. Each morning astronomers begin plugging optical fibers into a thousand tiny holes in each of the "plug plates" to carry the light from each specific target object to an array of spectrographs.

Steering each optical fiber to the right CCD was no trivial task, says Schlegel. "The new BOSS fiber cartridges are snake pits of a thousand fibers each. It would be a disaster if you didn't know which one went where."

With a thousand holes in each plug plate, stopping to seek out specific holes to plug a fiber into, or tracing where each fiber ends up, would take an impossibly long time. Instead a computer assigns the correct target identity to each fiber as a fiber-mapping laser beam moves over the plugged-in fibers and records where the light from each emerges.

Fast and simple – but not quite foolproof. "In our first test images it looked like we'd just taken random spectra from all over," Schlegel says. After some hair-pulling, the problem turned out to be simple. "After we flipped the plus and minus signs in the program, everything worked perfectly."

Now BOSS is on its way to generating data of unprecedented precision on two million galaxies and quasars, and density variations in the intergalactic gas. The SDSS tradition of releasing data to the public will continue, with the first release from SDSS-III planned for December 2010.

(Photo: Dan Long, Senior Operations Engineer, Apache Point Observatory)

Lawrence Berkeley National Laboratory

COAL-MINING HAZARD RESEMBLES EXPLOSIVE VOLCANIC ERUPTION, STUDY SHOWS

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Worldwide, thousands of workers die every year from mining accidents, and instantaneous coal outbursts in underground mines are among the major killers. But although scientists have been investigating coal outbursts for more than 150 years, the precise mechanism is still unknown.

New research by scientists at the University of Michigan and Peking University in Beijing, China, suggests that the outbursts occur through a process very similar to what happens during explosive volcanic eruptions. The research is described in a paper in the October issue of the journal Geology.

"Just as magma can fragment when pressure on it is reduced, triggering an explosive eruption, gas-rich coal can also erupt when suddenly decompressed, as happens when excavation exposes a new layer of coal," said Youxue Zhang, professor of geology, whose previous work on volcanic eruptions, Africa's "exploding lakes" and theorized methane-driven ocean eruptions set the stage for the current research.

Zhang did much of the work on the coal outburst project in 2006 and 2007, during a part-time professorship at Peking University. Around that time, a number of deadly coal mine accidents---in China, Russia and the United States---had made headlines, and just before leaving for China in 2006, Zhang had printed out articles about the disasters to read during his flight.

"While reading a paper describing coal outbursts as violent ejection of pulverized coal particles and gas, the similarity of coal outbursts to magma fragmentation suddenly occurred to me," Zhang said.

When he arrived at Peking University, he discussed the idea with colleague Ping Guan, and the two decided to collaborate on experiments simulating coal outbursts. Zhang recruited undergraduate student Haoyue Wang to help with the project, in which the researchers used a shock tube apparatus similar to the one Zhang had used in previous experiments on explosive volcanic eruptions. Their experiments verified that coal outbursts are driven by high gas pressure inside coal and occur through a mechanism similar to magma fragmentation.

Before an explosive volcanic eruption, magma (molten rock in Earth's crust) contains a high concentration of dissolved gas, mainly water vapor. When pressure on the magma is reduced, as happened in the 1980 eruption of Mount St. Helens when overlying rock was suddenly removed, gas bubbles in the magma rapidly expand. Pressure is higher inside the bubbles than in the surrounding magma, and when pressure on the bubble walls builds to the breaking point, the bubbles burst and the magma fragments into pieces in an explosive eruption.

In deep coal beds, coal contains high concentrations of the gases carbon dioxide and methane. When a coal seam is exposed, pressure on the coal is reduced, but pressure on the gas inside the coal remains high. When the resulting stress exceeds the coal's strength, the coal fragments, releasing high-pressure gas that suddenly decompresses, ejecting outward and carrying pulverized coal with it.

The first recorded coal outburst was in France in 1834. Since then, outbursts have occurred in China, Russia, Turkey, Poland, Belgium, Japan and about a dozen other nations. They happen only in deep mines where coal contains gas at high pressure, but as deeper coals are mined to satisfy the world's energy demands, the risk of outbursts increases.

"Knowing the mechanism of coal outbursts is the first step toward predicting and preventing such disasters," said Zhang.

Next, the researchers plan more experiments to verify their results. Then, they hope to capture details of the outbursts with a high-speed camera and to study a variety of coal types from different mines.

University of Michigan

THE MAKING OF THE MALE BRAIN (ESTROGEN REQUIRED)

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It's often said that overly macho males suffer from "too much testosterone." But a new study in mice reveals how estrogen might share in that blame.

The report in the October 2nd issue of Cell, a Cell Press publication, reveals how early estrogen exposure "masculinizes" the brain circuitry, predisposing boys to be boys as it were. That early event is specifically critical in producing male mice that will pick fights with other males and that dutifully mark their territories with urine.

"It's been known for decades that estrogen may play a role in making males behave like males," said Nirao Shah of the University of California, San Francisco. "What we do here is to provide insight into the logic of how estrogen regulates that behavior."

The basis for differences between the sexes in such behaviors, they show, may reside in the neurons that are equipped with an enzyme, called aromatase, that converts testosterone into estrogen. The masculine brain has more of those testosterone-converting neurons in certain regions. The researchers now show that these neurons establish a unique neural circuitry in males, and that this difference in wiring depends on estrogen.

The researchers found that female mice exposed to estrogen as pups get wired to behave as "tomboys" of a sort. Their aromatase neurons now look like what is seen in the male brain, and the female mice take on aggressive and territorial behaviors typically reserved for males.

But if estrogen, the female hormone, establishes male behavior patterns, why don't girls act like boys? Shah explains that the ovaries normally don't pump out any hormone that early in life, but males do see a surge in testosterone at a young age, at least some of which gets converted by aromatase to estrogen.

The findings indicate that adult gonadal hormones are not the entire story when it comes to determining masculine versus feminine behavior, Shah said. "Rather than the gonadal hormones telling the adult brain what do to, the brain interprets signals based on its prior history," he said. Thus, female mice exposed to estrogen as pups respond to estrogen as adults by switching on the aggressive and territorial behaviors typically observed in males.

As for whether differences in early estrogen exposure or in the resulting brain circuitry can account for variation among males in stereotypically male behavior remains to be seen, Shah says.

"About eighty percent of male mice will fight with other males routinely, but there is always a fraction that fight poorly or not much at all," he said, a difference that may be explained by some combination of social experience along with early developmental events that wire the brain differently.

Testosterone itself isn't off the hook yet, however. Shah's team suspects it is also likely to have direct effects. As evidence of that, Shah notes that female mice whose brains are masculinized by exposure to estrogen in early development do fight, but they tend to fight with less intensity than males. But when these females have their ovaries -- their adulthood source of estrogen -- removed and are treated with male levels of testosterone, their will to fight goes up. "It suggests testosterone acts on its own receptor to increase the intensity of male-like fighting," Shah said.

Cell Press

NEW ANCIENT FUNGUS FINDING SUGGESTS WORLD'S FORESTS WERE WIPED OUT IN GLOBAL CATASTROPHE

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Tiny organisms that covered the planet more than 250 million years ago appear to be a species of ancient fungus that thrived in dead wood, according to new research published in the journal Geology.

The researchers behind the study, from Imperial College London and other universities in the UK, USA and The Netherlands, believe that the organisms were able to thrive during this period because the world's forests had been wiped out. This would explain how the organisms, which are known as Reduviasporonites, were able to proliferate across the planet.

Researchers had previously been unsure as to whether Reduviasporonites were a type of fungus or algae. By analysing the carbon and nitrogen content of the fossilised remains of the microscopic organisms, the scientists identified them as a type of wood-rotting fungus that would have lived inside dead trees.

Fossil records of Reduviasporonites reveal chains of microscopic cells and reflect an organism that lived during the Permian-Triassic period, before the dinosaurs, when the Earth had one giant continent called Pangaea.

Geological records show that the Earth experienced a global catastrophe during this period. Basalt lava flows were unleashed on the continent from a location centred on what is present day Siberia. Up to 96 per cent of all marine species and 70 per cent of land species became extinct. Traditionally, scientists had thought that land plants weathered the catastrophe without much loss.

Today's findings suggest that much of the vegetation on Pangaea did not survive and that the world's forests were wiped out, according to the researchers. Geological records show that there was a massive spike in the population of Reduviasporonites across Pangea as the Permian period came to an end. The scientists suggest that this means that there was in increase in the supply of wood for them to decay.

Professor Mark Sephton, one of the authors of the study from the Department of Earth Science and Engineering at Imperial College London, comments:

"Our study shows that neither plant nor animal life escaped the impact of this global catastrophe. Ironically, the worst imaginable conditions for plant and animal species provided the best possible conditions for the fungi to flourish."

The team suggest that the basalt lava, which flowed during Permian-Triassic catastrophe, unleashed toxic gases into the air. The gases had a dual effect, producing acid rain and depleting the ozone layer. The outcome was the destruction of forests, providing enough rotting vegetation to nourish Reduviasporonites so that they could proliferate across Pangaea.

The team reached their conclusions by analysing the carbon and nitrogen content of Reduviasporonites using a High Sensitivity Mass Spectrometer and comparing the results with those from modern fungi. They discovered that Reduviasporonites and modern fungi show similar chemical characteristics.

In the future, the team plan to carry out further comparisons between Reduviasporonites and potential counterparts among modern fungi, which they hope will provide further clues about how Reduviasporonites lived.

(Photo: ICL)

Imperial College London

SPECIAL BRAIN WAVE BOOST SLOWS MOTION

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Researchers have found that they can make people move in slow motion by boosting one type of brain wave. The findings offer some of the first proof that brain waves can have a direct influence on behavior, according to the researchers, who report their findings online on October 1 in Current Biology, a Cell Press publication.

"At last we have some direct experimental proof that brain waves influence behavior in humans, in this case how fast a movement is performed," said Peter Brown of University College London. "The implication is that it is not just how active brain cells are that is important, but also how they couple their activity into patterns like beta activity."

There are many types of brain waves, distinguished by their frequency and location, Brown explained. In the new study, the researchers injected a small electrical current into the brain through the scalps of fourteen people while the participants manipulated the position of a spot on a computer screen as quickly as they could with a joystick.

The electrical current used increased normal beta activity, a wave that earlier studies linked to sustained muscle activities, such as holding a book. Beta activity drops before people make a move.

Unlike most previous work, which used constant brain stimulation, the new study employed an oscillating current, more like that underlying normal brain activity. As a result, people's fastest times on the computer task were 10 percent slower.

Brown said the researchers were surprised that the electrical currents used in the study—which were very small and imperceptible to the participants—could have such a measurable effect.

The current findings provide the first interventional evidence of a causal link between increased beta synchrony and the slowing of voluntary movement in otherwise healthy individuals, the researchers report, noting that earlier studies have shown altered brain waves to influence memory.

In addition to the new insight into normal brain function, the results might have implications for treating conditions characterized by either uncontrolled or slowed movements.

"If we know what patterns of brain activity slow voluntary movement, then we can try and boost these patterns in conditions like chorea and dystonia, where there is excessive and uncontrolled movement," Brown said. "Conversely, we can try and suppress beta activity in conditions like Parkinson's disease typified by slow movement."

Cell Press

SIMULATION SUGGESTS ROCKY EXOPLANET HAS BIZARRE ATMOSPHERE

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So accustomed are we to the sunshine, rain, fog and snow of our home planet that we find it next to impossible to imagine a different atmosphere and other forms of precipitation.

To be sure, Dr. Seuss came up with a green gluey substance called oobleck that fell from the skies and gummed up the Kingdom of Didd, but it had to be conjured up by wizards and was clearly a thing of magic.

Not so the atmosphere of COROT-7b, an exoplanet discovered last February by the COROT space telescope launched by the French and European space agencies.

According to models by scientists at Washington University in St. Louis, COROT-7b's atmosphere is made up of the ingredients of rocks and when "a front moves in," pebbles condense out of the air and rain into lakes of molten lava below.

The work, by Laura Schaefer, research assistant in the Planetary Chemistry Laboratory, and Bruce Fegley Jr., Ph.D., professor of earth and planetary sciences in Arts & Sciences, appears in the Oct. 1 issue of The Astrophysical Journal.

Astronomers have found nearly 400 extra-solar planets, or exoplanets, in the past 20 years. But because of the limitations of the indirect means by which they are discovered, most are Hot Jupiters, chubby gas giants orbiting close to their parent stars. (More than 1,300 Earths could be packed inside Jupiter, which has 300 times the mass of Earth.)

COROT-7b, on the other hand, is less than twice the size of Earth and only five times its mass.

It was the first planet found orbiting the star COROT-7, an orange dwarf in the constellation Monoceros, or the Unicorn. (This priority is designated by the letter b.)

In August 2009 a consortium of European observatories led by the Swiss reported the discovery of COROT-7c, a second planet orbiting COROT-7.

Using the data from both planets, they were able to calculate that COROT-7b has an average density about the same as Earth's. This means it is almost certainly a rocky planet made up of silicate rocks like those in Earth's crust, says Fegley.

Not that anyone would call it Earth-like, much less hospitable to life. The planet and its star are separated by only 1.6 million miles, 23 times less than the distance between the parboiled planet Mercury and our Sun.

Because the planet is so close to the star, it is gravitationally locked to it in the same way the Moon is locked to Earth. One side of the planet always faces its star, just as one side of the Moon always faces Earth.

This star-facing side has a temperature of about 2600 degrees Kelvin (4220 degrees Fahrenheit). That's infernally hot—hot enough to vaporize rocks. The global average temperature of Earth's surface, in contrast, is only about 288 degrees Kelvin (59 degrees Fahrenheit).

The side in perpetual shadow, on the other hand, is positively chilly at 50 degrees Kelvin (-369 degrees Fahrenheit).

Perhaps because they were cooked off, COROT-7b's atmosphere has none of the volatile elements or compounds that make up Earth's atmosphere, such as water, nitrogen and carbon dioxide.

"The only atmosphere this object has is produced from vapor arising from hot molten silicates in a lava lake or lava ocean," Fegley says.

What might that atmosphere be like? To find out Schaefer and Fegley have used thermochemical equilibrium calculations to model COROT-7b's atmosphere.

The calculations, which reveal which mineral assemblages are stable under different conditions, were carried out with MAGMA, a computer program Fegley developed in 1986 with the late A. G. W. Cameron, a professor of astrophysics at Harvard University.

Schaefer and Fegley modified the MAGMA program in 2004 in order to study high-temperature volcanism on Io, Jupiter's innermost Galilean satellite. This modified version was used in their present work.

Because the scientists didn't know the exact composition of the planet, they ran the program with four different starting compositions. "We got essentially the same result in all four cases," says Fegley.

"Sodium, potassium, silicon monoxide and then oxygen — either atomic or molecular oxygen — make up most of the atmosphere." But there are also smaller amounts of the other elements found in silicate rock, such as magnesium, aluminum, calcium and iron.

Why is there oxygen on a dead planet, when it didn't show up in Earth's atmosphere until 2.4 billion years ago, when plants started to produce it?

"Oxygen is the most abundant element in rock," says Fegley, "so when you vaporize rock what you end up doing is producing a lot of oxygen."

The peculiar atmosphere has its own singular weather. "As you go higher the atmosphere gets cooler and eventually you get saturated with different types of 'rock' the way you get saturated with water in the atmosphere of Earth," explains Fegley. "But instead of a water cloud forming and then raining water droplets, you get a 'rock cloud' forming and it starts raining out little pebbles of different types of rock."

Even more strangely, the kind of rock condensing out of the cloud depends on the altitude. The atmosphere works the same way as fractionating columns, the tall knobby columns that make petrochemical plants recognizable from afar. In a fractionating column, crude oil is boiled and its components condense out on a series of trays, with the heaviest one (with the highest boiling point) sulking at the bottom, and the lightest (and most volatile) rising to the top.

Instead of condensing out hydrocarbons such as asphalt, petroleum jelly, kerosene and gasoline, the exoplanet's atmosphere condenses out minerals such as enstatite, corundum, spinel, and wollastonite. In both cases the fractions fall out in order of boiling point.

Elemental sodium and potassium, which have very low boiling points in comparison with rocks, do not rain out but would instead stay in the atmosphere, where they would form high gas clouds buffeted by the stellar wind from COROT-7.

These large clouds may be detectable by Earth-based telescopes. The sodium, for example, should glow in the orange part of the spectrum, like a giant but very faint sodium vapor streetlamp.

Observers have recently spotted sodium in the atmospheres of two other exoplanets.

The atmosphere of COROT-7b may not be breathable, but it is certainly amusing.

Washington University in St. Louis

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