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#3270 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 2:01 am
Subject: News: Rover Spirit - Another Stall of Right-Rear Wheel Ends Drive
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Rover Spirit: Another Stall of Right-Rear Wheel Ends Drive
December 2nd, 2009 in Space & Earth / Space Exploration
Another Stall of Right-Rear Wheel Ends DriveThis blink comparison aids evaluation of a drive by NASA's Mars Exploration Rover Spirit during the rover's 2,099th Martian day, or sol (Nov. 28, 2009). Image Credit: NASA/JPL-Caltech

(PhysOrg.com) -- Spirit's right-rear wheel stalled again on Sol 2099 (Nov. 28, 2009) during the first step of a two-step extrication maneuver.

This stall is different in some characteristics from the stall on 2092 (Nov. 21). The Sol 2099 stall occurred more quickly and the inferred rotor resistance was elevated at the end of the stall. Investigation of past stall events along with these characteristics suggest that this stall might not be result of the terrain, but might be internal to the right-rear actuator. Rover project engineers are developing a series of diagnostics to explore the actuator health and to isolate potential terrain interactions. These diagnostics are not likely to be ready before Wednesday.

Plans for future driving will depend on the results of the diagnostic tests.

Before the Sol 2099 drive ended, Spirit completed 1.4 meters of wheel spin and the rover's center moved 0.5 millimeters (0.02 inch) forward, 0.25 millimeters (0.01 inch) to the left and 0.5 millimeters (0.02 inch) downward. Since Spirit began extrication on Sol 2088, the rover has performed 9.5 meters (31 feet) of wheel spin and the rover's center, in total, has moved 16 millimeters (0.63 inch) forward, 10 millimeters (0.39 inch) to the left and 5 millimeters (0.20 inch) downward.

Provided by JPL/NASA (news : web)
http://www.physorg.com/news178990566.html

Comment:
So, who forgot to pack the snow chains???

Posted by
Robert Karl Stonjek


#3269 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 2:11 am
Subject: News: Researchers create 'synthetic magnetic fields' for neutral atoms
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Researchers create 'synthetic magnetic fields' for neutral atoms
December 2nd, 2009 in Physics / Quantum Physics
Researchers create 'synthetic magnetic fields' for neutral atomsA pair of laser beams (red arrows) impinges upon an ultracold gas cloud of rubidum atoms (green oval) to create synthetic magnetic fields (labeled Beff). (Inset) The beams, combined with an external magnetic field (not shown) cause the atoms to "feel" a rotational force; the swirling atoms create vortices in the gas. Credit: JQI

(PhysOrg.com) -- Achieving an important new capability in ultracold atomic gases, researchers at the Joint Quantum Institute, a collaboration of the National Institute of Standards and Technology and the University of Maryland, have created "synthetic" magnetic fields for ultracold gas atoms, in effect "tricking" neutral atoms into acting as if they are electrically charged particles subjected to a real magnetic field. The demonstration, described in the latest issue of the journal Nature, not only paves the way for exploring the complex natural phenomena involving charged particles in magnetic fields, but may also contribute to an exotic new form of quantum computing.

As researchers have become increasingly proficient at creating and manipulating gaseous collections of atoms near absolute zero, these ultracold gases have become ideal laboratories for studying the complex behavior of material systems. Unlike usual crystalline materials, they are free of obfuscating properties, such as impurity atoms, that exist in normal solids and liquids. However, studying the effects of magnetic fields is problematic because the gases are made of neutral atoms and so do not respond to magnetic fields in the same way as charged particles do. So how would you simulate, for example, such important exotic phenomena as the quantum Hall effect, in which electrons can "divide" into quasiparticles carrying only a fraction of the electron's electric charge?

The answer Ian Spielman and his colleagues came up with is a clever physical trick to make the neutral atoms behave in a way that is mathematically identical to how charged particles move in a magnetic field. A pair of laser beams illuminates an ultracold gas of rubidium atoms already in a collective state known as a Bose-Einstein condensate. The laser light ties the atoms' internal energy to their external (kinetic) energy, modifying the relationship between their energy and momentum. Simultaneously, the researchers expose the atoms to a real magnetic field that varies along a single direction, so that the alteration also varies along that direction.

Researchers create 'synthetic magnetic fields' for neutral atomsA harbinger of the synthetic magnetic fields is the formation of vortices (spots). These spots, the number of which increases with increasing synthetic field, mark the points about which atoms swirled with a whirlpool-like motion. The measurement units in each panel indicate the size of the external magnetic field gradient applied to the gas of atoms, with larger external fields producing more vortices. Credit: JQI

In a strange inversion, the laser-illuminated neutral atoms react to the varying magnetic field in a way that is mathematically equivalent to the way a charged particle responds to a uniform magnetic field. The neutral atoms experience a force in a direction perpendicular to both their direction of motion and the direction of the magnetic field gradient in the trap. By fooling the atoms in this fashion, the researchers created vortices in which the atoms swirl in whirlpool-like motions in the gas clouds. The vortices are the "smoking gun," Spielman says, for the presence of synthetic magnetic fields.

Previously, other researchers had physically spun gases of ultracold atoms to simulate the effects of magnetic fields, but rotating gases are unstable and tend to lose atoms at the highest rotation rates. In their next step, the JQI researchers plan to partition a nearly spherical system of 20,000 rubidium atoms into a stack of about 100 two-dimensional "pancakes" and increase their currently observed 12 vortices to about 200 per-pancake. At a one-vortex-per-atom ratio, they could observe the and control it in unprecedented ways. In turn, they hope to coax to behave like a class of quasiparticles known as "non-abelian anyons," a required component of "topological quantum computing," in which anyons dancing in the gas would perform logical operations based on the laws of quantum mechanics.

Synthetic magnetism achieved by optical methods Credit: JQI

 
More information: Y.J. Lin, R.L. Compton, K. Jimenez-Garcia, J.V. Porto and I.B. Spielman. Synthetic magnetic fields for ultracold neutral atoms. Nature, Dec. 3, 2009.

Source: National Institute of Standards and Technology (news : web)
http://www.physorg.com/news178983240.html

Posted by
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#3268 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 1:56 am
Subject: News: NRL Sensor Observes First Light
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NRL Sensor Observes First Light
December 2nd, 2009 in Space & Earth / Space Exploration
NRL Sensor Observes First LightFirst light limb scan from the SSULI 002 instrument on DMSP F18. The x-axis represents wavelength, the y-axis is altitude and the color represents accumulated counts in 1 second. Source: Naval Research Laboratory

The Special Sensor Ultraviolet Limb Imager (SSULI) developed by NRL's Spacecraft Engineering Department and Space Science Division, launched October 18, 2009 on the U.S. Air Force Defense Meteorological Satellite Program (DMSP) F18 (flight 18) satellite, observed first light on December 1, 2009.

In a sample airglow profile (see figure above) the spectral emission features in the data are clean and show no anomalies.

"The SSULI team is very excited to continue with early orbit testing and begin the calibration and validation process with this instrument," said Andrew Nicholas, SSULI principal investigator, NRL Space Science Division.

Offering global observations, that yield near real-time altitude profiles of the ionosphere and neutral atmosphere, over an extended period of time, SSULI makes measurements from the extreme ultraviolet (EUV) to the far ultraviolet (FUV) over the wavelength range of 80 nanometers (nm) to 170 nm with 1.5 nm resolution.

SSULI data products, once calibrated and validated, will be used operationally at the Air Force Weather Agency (AFWA) as standalone operational data products and also as inputs into operational Space Weather models.

Provided by Naval Research Laboratory (news : web)
http://www.physorg.com/news178993932.html

Posted by
Robert Karl Stonjek


#3267 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 1:33 am
Subject: News: Extreme oil ~ Scraping the bottom of Earth's barrel
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Extreme oil: Scraping the bottom of Earth's barrel

The bitumen in tar sands gives the earth a thick, mushy feel. This non-conventional oil is difficult and expensive to extract (Image: Lara Solt/Dallas Morning News/Corbis)  
The bitumen in tar sands gives the earth a thick, mushy feel. This non-conventional oil is difficult and expensive to extract
Image: Lara Solt/Dallas Morning News/Corbis
 
Trouble ahead

More than enough?
 
 

Editorial: Plenty more oil, but use it wisely

EIGHTY-FIVE million barrels. That's how much oil we consume every day. It's a staggering amount - enough to fill over 5400 Olympic swimming pools - and demand is expected to keep on rising, despite the impending supply crunch.

The International Energy Agency forecasts that by 2030 it will rise to about 105 million barrels per day with a commensurate increase in production (see graph), although whistle-blowers recently told The Guardian newspaper in London that insiders at the IEA believe the agency vastly over-estimates our chances of plugging that gap. The agency officially denies this.

Wherever the truth lies, it is widely expected that by 2030 we will have passed the peak of conventional oil production - the moment that output from conventional oil reserves goes into terminal decline. A report from the UK Energy Research Centre (UKERC) published in August said there was a "significant risk" it would happen before 2020. And that means we will soon be staring down the barrel of the ultimate oil crisis.

Some governments and corporations are waking up to the idea and beginning to develop alternatives to keep the world's transport systems moving when cheap oil runs out. These include biofuels, more energy-efficient - or electric - carsMovie Camera, and hydrogen. But none of these is likely to make up the global shortfall in time. The pressure is on to keep the black stuff flowing and so the next two decades will see an unprecedented effort to exploit increasingly exotic and unconventional sources of oil. They include tar sands (a mixture of sand or clay and a viscous, black, sticky petroleum deposit called bitumen), oil shale (a sedimentary rock containing kerogen, a precursor to petroleum) and synthetic liquid fuels made from coal or gas.

Purely in terms of geological abundance, these sources look more than sufficient to meet global demand. According to the IEA, taken together, they raise the remaining global oil resource to about 9 trillion barrels (see map) - almost nine times the amount of oil humanity has consumed to date. The trouble is that the name "non-conventional oil" hides several dirty little secrets and a whole host of huge challenges.

Conventional oil refers to liquid hydrocarbons trapped in deep, highly pressurised reservoirs, which means that when the wells are drilled, the oil usually gushes to the surface of its own accord. Non-conventional oils are not so forthcoming, and need large amounts of energy, water and money to coax them from the ground and turn them into anything useful, like diesel or jet fuel.

As a result, non-conventional oil production to date has been slow to expand - with current output of just 1.5 million barrels per day. Not only that, because they take so much energy to produce, they are responsible for higher carbon emissions per barrel than conventional oil.

But, slowly, things are beginning to change. Growing awareness of the impending oil shortage and its ramifications - Deutsche Bank predicts a barrel price of $175 by 2016, for example - has driven a surge of investment in new technologies to recover non-conventional oil more effectively. "Canada could eclipse Saudi Arabia," says Julie Chan, vice-president of finance at E-T Energy, a Canadian company developing a new technique to extract oil from tar sands. So are non-conventionals poised to swoop in and confound the peak-oil doomsayers? Can we expect a new era of expensive, technologically demanding and environmentally damaging oil?

The most famous of the non-conventional resources are the Canadian tar sands, where proven reserves are second only in size to Saudi Arabia's conventional crude. Today, production stands at 1.2 million barrels per day. Tar sands containing bitumen are extracted from huge opencast mines and processed to produce oil. But mining and processing the raw bitumen is expensive and requires huge volumes of water (see diagram). In Canada, the industry is already reaching the legal limits of what can be drawn from the Athabasca river in winter. Worse, mining is only possible for deposits less than about 75 metres deep, and that's just 20 per cent of the total resource. So a whole range of new technologies is now being explored to extract the deeper bitumen.

...
 

Steamy business

Steam-assisted gravity drainage (SAGD) is one of the most established processes, accounting for almost half of tar sands production. Steam is injected into a well to melt the bitumen, which drains into a secondary shaft from where it is pumped out (see diagram). This is cheaper and uses much less water than mining, but more energy - usually from natural gas - to produce the required steam. An industry-sponsored report published by Alberta Chamber of Resources in 2005 found that if tar sands oil production rose to 5 million barrels per day by 2030, it would need 60 per cent of the gas consumed by western Canada, which it said would be "unthinkable".

But this brand of SAGD is not the only game in town. Nexen, a Canadian oil company, has developed a new twist on SAGD by dispensing with natural gas as fuel and using some of the bitumen to generate the energy needed to produce the steam. At its site in Long Lake, Alberta, the company gasifies asphaltenes - the heaviest fraction of bitumen. This synthetic gas is burned to generate steam for SAGD, and is also used to produce hydrogen which in turn is used to upgrade the bitumen on-site into high quality synthetic crude oil. This makes the process cheaper and energy self-sufficient - it even generates surplus power to export to the grid. The downside is that carbon dioxide emissions are higher than for mining or standard SAGD. The company aims to expand production from its current 14,000 barrels per day to 60,000 by 2013.

A method called "toe to heel air injection" takes a similar approach to SAGD, but does its burning underground. THAI involves a pair of wells. A vertical air-injecting well is drilled close to the "toe" of a horizontal production well (see THAI). Steam is pumped into both wells to heat the bitumen until it is hot enough to combust spontaneously when exposed to air. Then the steam is turned off, and air is pumped down the injector well to feed a horizontal fire front that moves slowly through the reservoir from the toe of the production well towards the heel, generating temperatures of up to 500 °C. The intense heat separates the bitumen into heavier and lighter fractions, with the heavier one (asphaltines) fuelling the fire while the lighter ones melt, flow to the production well and get pumped to the surface. That's a neat trick, because it means part of the refinery's job is done underground. This process uses between 10 and 30 per cent of the natural gas consumed by SAGD processes. It is even self-sufficient for its water needs, because groundwater is pumped up the production well along with the bitumen and recycled.

A third approach sounds a little more "out there", but in theory has the potential to be the least polluting of all the new bitumen-extraction techniques. Instead of heating the bitumen in a conventional fashion, the idea is to zap it with electricity, using a technique called electro-thermal dynamic stripping process (ET-DSP). A grid of vertical wells is drilled into the tar sands, each containing three large electrodes (see ET-DSP). Current is conducted between the wells via groundwater. The electrical resistance of the earth generates heat which liquefies the bitumen and allows it to flow into a central production well. Changing the voltage gradient between the electrodes allows the operators to direct the electric field to heat the richest parts of the bitumen deposit. Any water that comes up with the liquefied bitumen is re-injected to maintain conductivity. Since the process runs on grid electricity, there's no need for natural gas.

However, on the basis of Alberta's largely coal-fired power supply, the electricity used in ET-DSP means the production process is responsible for more carbon emissions than either mining or conventional crude production. E-T Energy, the company developing the technology, insists that emissions could be slashed if it were powered using hydro, wind or even gas-fired power. In a separate development, Bruce Power, an Alberta-based nuclear power generation company, has drawn up plans for new reactors sited near Canadian tar sands deposits to provide CO2-free electricity to the oil-extraction industry.

Although THAI and ET-DSP seem to have solved some of the practical problems of tar sands oil production, and the costs may fall in the future, they are still in their infancy. IHS CERA, an oil consultancy that recently produced a report on the growth prospects for tar sands production, estimates it will take between 5 and 15 years to commercialise the new technology. "It could be a decade before it is used in enough [tar sands] reservoirs to contribute meaningfully to production," says Jackie Forrest, one of the report's authors.

Putting the squeeze on

Tar sands

In a scenario most favourable to tar sands - high oil prices, growth in demand and a supportive regulatory framework - IHS CERA predicts output from the Canadian tar sands could reach 6.3 million barrels per day by 2035. That's a small fraction of forecast global demand, but to achieve even this, production would have to grow twice as fast as it ever has. That, says Forrest, "is really pushing it". So what of the other alternatives?

Oil shale is the next large unconventional resource under consideration, with around 2.5 trillion barrels of "oil equivalent" identified. It was used to produce oil before the oil industry took off in the late 19th century. To produce oil from it, you essentially need to speed up a geological process that takes millions of years.

This is done by heating the rock to 500 °C until the kerogen decomposes into a synthetic crude oil and a solid residue. Traditionally that has meant digging up the shale and baking it in a huge oven. An expensive, energy-intensive process. It also leaves a greater volume of waste than the original shale, as testified by the hills of shale slag called "bings" that dot the West Lothian region of Scotland, where a century of shale oil production ended in the 1960s. What's needed is an in-situ production method similar to those developed for tar sands. Three-quarters of the global shale resource (see map) lies in Colorado, Utah and Wyoming, and Barack Obama's administration has recently restarted the process of leasing federal land for shale oil R&D. A number of technologies are being developed to heat the shale underground. These utilise microwaves, high-temperature gas injection, and radio waves combined with supercritical CO2. Such heating creates an oil reservoir that can then be extracted using conventional drilling (see diagram).

Microwaves, high-temperature gas injection, and radio waves combined with supercritical CO2 could all be used to extract oil from shale deposits

Oil multinational Shell has experimented with in-situ shale oil extraction at its development site in Cathedral Bluffs, Colorado. The company drilled bore holes 650 metres deep and inserted electrodes to heat the shale to between 340 °C and 370 °C over a period of months. However, the process is extremely power hungry, requiring energy to both heat the shale and to freeze the perimeter of the reservoir to block the flow of groundwater.

The company says it is unlikely to commercialise the process for at least another five years. The IEA estimates shale oil would cost between $50 and $100 per barrel to produce, without taking into account any carbon-emissions pricing that may come into force. It expects no significant shale oil production this side of 2030.

There's yet another old-school production method that may experience something of a renaissance in the coming decades. Just as shale oil is nothing new, neither is making liquid fuels from coal. Two German researchers developed the eponymous Fischer-Tropsch process in the 1920s, heating coal to produce a gas of carbon monoxide and hydrogen, which is then catalysed to produce diesel and kerosene. The technology was exploited by oil-strapped, coal-rich Germany during the second world war, and by South Africa in the 1980s and early 1990s to beat sanctions imposed during apartheid. South Africa has the world's only major coal-to-liquids (CTL) plant operating today and China has recently built a demonstration plant in Inner Mongolia.

So, could coal be the answer? Few doubt there is enough of the stuff to support a major expansion of CTL (New Scientist, 19 Jan 2008, p 38), and the fuels produced are of a high quality. The drawbacks are formidable: it takes about two tonnes of coal and up to 15 barrels of water to produce a single barrel of synthetic fuels. That makes it expensive. The IEA says that when it comes to US coal, to supply just 10 per cent of US transport fuel consumption would mean investing $70 billion, and raising coal production by 25 per cent - an additional 250 million tonnes per year.

Worse, because of the feedstock and energy demands of the production process, CTL fuels have roughly double the carbon emissions of conventional crude on a well-to-tank - or "mine-to-tank" - basis. Carbon capture and storage could be applied to the production plant, but the process is likely to be 90 per cent efficient at best. Then there are still the same emissions as petrol derived from oil when burning it in your car engine. So even with CCS, CTL is always likely to emit more carbon than conventional crude.

The Fischer-Tropsch process can also be used to make liquid fuels from natural gas. As with coal, there is no immediate shortage of feedstock. In fact, prices have slumped as rising gas production in the US and falling global demand combine to produce a worldwide glut which should last for at least the next few years. But, as with coal, there are major drawbacks.

The gas-to-liquids process (GTL) emits much less carbon than CTL, because the feedstock is cleaner, but still more than conventional crude. That's because almost half of the 280 cubic metres of gas it takes to produce a barrel of GTL fuel is burnt during the conversion process. Three small plants account for global production of 50,000 barrels of synthetic fuels per day. That should quadruple in the next few years with the opening of two larger plants in Qatar and Nigeria.

So with huge reserves and up-and-coming technologies, what are the prospects for unconventional sources? Will the non-conventionals be able to fill the gap left by diminishing crude oil, are we doomed to soaring emissions from ever dirtier oil?

Most analysts agree on one thing: despite the enormous size of the non-conventional resource, it will be decades before the new technologies can have a significant impact. In the meantime, any attempt to grow output quickly will have major regulatory and financial hurdles to overcome. In the US, federal bodies are effectively banned from buying non-conventional fuels because of their high CO2 emissions.

Furthermore, Obama has pledged to introduce a nationwide Low Carbon Fuel Standard (LCFS), requiring American fuel suppliers to cut carbon emissions from burning their fuels by 10 per cent between 2010 and 2020. Globally, non-conventionals would be penalised by any carbon-pricing regime that may result from the UN's climate change conference in Copenhagen, Denmark, next week. The IEA is pushing for a carbon-emissions price of $50 per tonne, which it says would add $5 to a barrel of fuel derived from tar sands, $12.50 to a barrel of GTL fuels and $30 to CTL ones.

Oil-price volatility is perhaps of even greater significance. Since the price slumped from its peak of $147 last year, tar sands projects aiming to deliver a total of 1.7 million barrels per day have been cancelled or delayed indefinitely, says the IEA. If price volatility persists - with oil shortages leading to a price spike, leading in turn to recession and a resumption of low oil prices - the halting investment in non-conventional oil development could become chronic.

The IEA's chief economist Fatih Birol says non-conventionals can defer global peak oil to "around 2030". Others are not convinced. "If everything goes well," says Steven Sorrel, the lead author of the UKERC report, "oil sands might produce 6 million barrels per day in 20 years' time, but by then we'll need to add at least 10 times that much capacity - without allowing for any growth in demand. It's very hard to see non-conventionals riding to the rescue."

Editorial: Plenty more oil, but use it wisely

Bibliography

  1. David Strahan is the author of The Last Oil Shock: A survival guide to the imminent extinction of petroleum man (John Murray, 2007)
 
Posted by
Robert Karl Stonjek

#3266 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 1:40 am
Subject: News: Both of NASA's Mars orbiters are down for the count
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Both of NASA's Mars orbiters are down for the count

  • 22:15 01 December 2009 by Rachel Courtland
  • For similar stories, visit the Spaceflight and Exploring Mars Topic Guides
Engineers are working to restore NASA's two Mars orbiters, Mars Odyssey (shown) and Mars Reconnaissance Orbiter, to normal operation (Illustration: NASA/JPL) 
Engineers are working to restore NASA's two Mars orbiters, Mars Odyssey (shown) and Mars Reconnaissance Orbiter, to normal operation
Illustration: NASA/JPL

The Red Planet is experiencing a partial radio blackout this week, as both of NASA's Mars orbiters have been felled by technical glitches. Until one of the probes can be brought back online later this week, the outages will delay operation of the twin Mars rovers, which use the orbiters to efficiently relay data back to Earth.

The main blow to rover operations comes from NASA's Mars Odyssey, which reached the Red Planet in 2001 and has been the prime communications relay for the rovers Spirit and Opportunity since they landed in 2004.

Odyssey has been down since 28 November, when its computers registered a memory error and sent the spacecraft into "safe mode", which minimises spacecraft operations.

Odyssey's most natural communications backup, NASA's Mars Reconnaissance Orbiter (MRO), has been kept on standby since August, when the spacecraft spontaneously rebooted for the fourth time this year.

Fast connection

The solar-powered Mars rovers can communicate with antennas on Earth directly, but the orbiters can relay information from the rovers to Earth at more than 10 times that speed, using a fraction of the energy.

The outages could delay attempts to free the Spirit rover from a sand pit that has been its home for more than six months (see Mars rover battles for its life). The rover team has been given until at least February to extricate Spirit.

"The rovers are safe. However, future activities are likely delayed, roughly on a day-for-day basis until Odyssey returns to relay operations," says John Callas, the rover programme manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

Unknown trigger

The causes of Odyssey's and MRO's technical problems are not yet clear.

Odyssey has experienced similar memory glitches in the past, and such events are not considered a big problem for the spacecraft, as they occur infrequently and there is a known recovery procedure, says Jeffrey Plaut, Mars Odyssey project scientist at JPL.

"[The glitch] causes a kind of a freeze-up. It's similar to something that might happen to your laptop," Plaut says. "In order to clear it, you reboot the computer."

Odyssey is now steering itself again so that it can keep its instruments pointed at Mars. But it will be at least several days before regular science operations and communications with the Mars rovers will begin. "We expect to be completely back on our feet by the end of the week," Plaut told New Scientist.

Total amnesia

Restoring MRO may take bit longer, as engineers work to update the spacecraft's memory to prevent a potentially catastrophic error.

MRO has been kept in suspended animation since 26 August, when the spacecraft rebooted itself. An investigation into that reboot as well as the three others MRO performed in 2009 revealed a potential problem: if the spacecraft's two sides rebooted within a minute of one another, MRO would lose all memory of being in orbit around Mars.

"It would believe it was at the stage of the mission when it was awaiting launch," says NASA spokesperson Guy Webster of JPL. To prevent irreversible amnesia, engineers have planned to begin uploading a set of revised data files to the spacecraft on Tuesday.

The files will rewrite MRO's default memory, so that it will know that it is in orbit if it experiences back-to-back reboots. The process is set to take a week, and it will take longer before the spacecraft is fully restored, Webster says.

A third spacecraft, the European Space Agency's Mars Express has occasionally acted as a communications relay for the Mars rovers. Unlike MRO and Odyssey, which take near-circular paths around the planet's poles, Mars Express has a highly elongated orbit. This typically reduces the rate by which it can relay data by a factor of four, Callas says.

Source: NewScientist
http://www.newscientist.com/article/dn18225-both-of-nasas-mars-orbiters-are-down-for-the-count.html?full=true&print=true

Posted by
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#3265 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 1:45 am
Subject: News: Transparent universe reveals hidden galaxies
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Transparent universe reveals hidden galaxies

Seeing blazars so clearly has called into question what we know about star formation and evolution (Image: NASA/Goddard Space Flight Center Conceptual Image Lab)  
Seeing blazars so clearly has called into question what we know about star formation and evolution
Image: NASA/Goddard Space Flight Center Conceptual Image Lab

THE universe is far more transparent at high energies than we thought. This discovery - based on sightings of unexpectedly bright objects that should be too far away to see so clearly - may call into question our understanding of how galaxies are born and evolve.

The universe is more transparent than expected, questioning what we know of galaxy formation

Most light travels through the cosmos unimpeded. But photons with very high energies of more than 100 gigaelectronvolts can collide with intergalactic infrared light. The longer these photons have to travel, the greater their chances of colliding and the less likely they are to reach Earth. As a result, distant blazars - galaxies with gluttonous black holes at their centres whose flares are pointing directly at Earth - are supposed to be much dimmer at higher energies than those that are not so far off.

Based on estimates of the amount of infrared light pervading the universe, blazars more than a billion years old were expected to be mostly invisible to telescopes looking for very high-energy gamma rays, says astrophysicist Simon Swordy of the University of Chicago.

But in 2006, the HESS telescope in Namibia reported the discovery of two unexpectedly bright blazars that are more than 2 billion years old. What's more, bright light from a blazar called 3C279, spotted one night in 2007 by the MAGIC telescope on La Palma in Spain's Canary Islands, survived some 5 billion years of travel. "We can see significantly further than we thought we could," says Swordy.

The mystery grew last month, when the VERITAS telescope in southern Arizona, following up on observations made by NASA's orbiting FERMI telescope, reported the discovery of yet another blazar that glows unusually brightly with very high-energy gamma rays. The new source, named 1ES 0502+675, is 4 billion years old. While it is not as distant as the one discovered by MAGIC, it could provide more useful information as it is bright, sits at a well-established distance and has been observed steadily for more than a month.

These blazars suggest that the amount of infrared light between galaxies must be quite low. This infrared background is light left over from star formation processes that occur early in the life of galaxies. We can estimate the background by counting galaxies in deep space, but now astrophysicists are beginning to question these estimates. "The amount of infrared is really right at the minimum you would expect from what we know about star formation and evolution," says Rene Ong of the University of California, Los Angeles, and spokesperson for VERITAS. "It's becoming a problem."

Continued observation of 1ES 0502+675 could help solve the puzzle. "This source could produce better and more reliable constraints on the extragalactic background than any source that has come before," says Ong.

Source: NewScientist
http://www.newscientist.com/article/mg20427373.800-highenergy-rays-pierce-foggy-fabric-of-universe.html?DCMP=NLC-nletter&nsref=mg20427373.800

Posted by
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#3264 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 12:13 am
Subject: News: European space missions given cost warning
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Page last updated at 11:42 GMT, Wednesday, 2 December 2009

European space missions given cost warning

By Jonathan Amos
Science correspondent, BBC News, Paris

Spica (Jaxa)
Only Spica sits well inside the budget envelope set by the agency

Europe's scientists have presented the six dream space missions they would like to fly before 2020.

The concepts ranged from a quest to map the "dark" components shaping the cosmos, to a plan to find far-off planets that most resemble Earth.

The European Space Agency (Esa) will probably carry just three or four of the ideas forward for further study.

And it warned some of the concept teams that their likely costs would bust the budget available to carry them out.

The wished-for missions are all competing for just two potential launch opportunities, in 2017 and 2018, under Esa's Cosmic Vision programme, which aims to answer the "big questions" in space science.

The consortia behind the proposed missions presented the details of their preparatory work to peers at the Oceanographic Institute of Paris, France.

Esa costs estimate (Esa)

The agency intends to allocate the best ventures up to 475 million euros (£430m) (at 2010 prices) each to implement their ideas.

But the early cost estimates indicate four of the competing consortia are already struggling to shape those ideas to the cash available, and two of the missions are projected to have a final price for Esa of 600 million euros (£540m) or more.

Mindful of the recent criticism the agency has received from member states on the issue of cost overruns, Professor David Southwood, Esa's director of science and robotics, told the teams: "Industry and the science community need to get to work on this; it's a collective responsibility."

The six consortia vying for the opportunity to fly a medium-class mission under Esa's Cosmic Vision programme are:

EUCLID - MAPPING THE 'DARK UNIVERSE'
"Frogspawn" map of dark matter (Nasa)
Hubble mapped the distribution of dark matter on a small patch of sky

This is a telescope designed to survey the unseen cosmos. It will map the distribution of "dark matter", the matter that cannot be detected directly but which astronomers know is there because of its gravitational effects on the matter we can see. Hubble has done this for a tiny portion of sky measuring two square degrees. Euclid will do it across 20,000 square degrees of sky. This should give scientists new insight not just into dark matter, but also into that other great mysterious cosmological phenomenon thought to be driving the expansion of the Universe at an ever increasing rate - so-called "dark energy". "We will get an incredible atlas of the sky out to about 10 billion light-years," said Dr Alexandre Refregier, from CEA Saclay, France. "We will be able to study all the structures and the evolution."

SPICA - TO FILL THE 'INFRARED GAP'

A joint mission with the Japanese space agency (Jaxa) to send the next generation of infrared telescope into orbit. Europe's contribution would include the 3.5m primary mirror and an instrument. Spica would see targets beyond the vision of the current state-of-the art infrared observatories - Esa's new Herschel telescope and Nasa's soon-to-launch James Webb telescope. "Spica will be much more sensitive," explained Professor Bruce Swinyard from the Rutherford Appleton Laboratory, UK. "It means we will be able to go from studying the formation of stars to being able to study the formation of planets. That's a big transition." Jaxa would launch Spica on one of its H-IIa rockets. A Jaxa director, Professor Tadayuki Takahashi, told the Paris meeting: "The European contribution is essential to the realisation of Spica."

PLATO - SEARCHING FOR PLANETS LIKE OURS
Artist's impression of Corot-7b (Eso)
The hunt is one to find more rocky planets, but in the habitable zone

A spacecraft incorporating a suite of telescopes to hunt for planets around nearby bright stars. Crucially, these would include many rocky planets in the "habitable zone" - the region around a star where water can keep a liquid state. Plato would find these worlds by monitoring stars for the tiny dips in light that occur when planets move across their faces. "We will end up monitoring half the sky; it's incredible," enthused Dr Don Pollacco, from Queens University, Belfast, UK. "We will study these planets and their stars in intricate detail. And we can eventually use those planets to look for life in their atmospheres." Plato could dramatically increase the numbers of known rocky planets, enabling scientists to really refine their models of how planetary systems form and evolve over time.

CROSS-SCALE - SAMPLING THE SPACE AROUND US

A constellation of spacecraft that would fly around Earth to sample the charged gas, or plasma, that envelops our world. "Cross-Scale asks fundamental questions about the nature of the plasma Universe," said Professor Steve Schwartz from Imperial College, London, UK. "Ninety-nine percent of the Universe we see is in a plasma state. It's highly energised, highly charged. Its particles are accelerated up to energies that are far bigger than anything the Large Hadron Collider will ever do. The fundamental physics on all of this currently eludes us." Esa would provide seven spacecraft; Japan and Canada are considering their own mission (Scope) which could bring an additional five satellites. Together they would sample the plasma and detail its behaviour in three dimensions.

MARCO POLO - GRABBING SAMPLES FROM AN ASTEROID
Marco Polo (EADS Astrium)
Marco Polo would pick up a sample from the surface of the asteroid

A mission to a near-Earth asteroid to grab a handful of dust and pebbles off its surface to bring back to Earth labs for study. Marco Polo is a spacecraft that would land on the asteroid to try to drill or scoop up what would be perhaps just tens of grams of material. "It's really all about getting back a sample from what we would call a primitive asteroid, something which has been altered as little as possible since the formation of the Solar System," said Dr Simon Green, from the Open University, UK. "It's a time capsule back to 4.5 billion years ago. It tells you what conditions were like when the asteroids formed and the Earth formed." This material might contain organic (carbon-rich) molecules that could inform us about some of the precursor chemistry that eventually started life on our own planet.

SOLAR ORBITER - GETTING UP CLOSE TO THE SUN'S 'ENGINE'

This is one of the most advanced of the concepts in terms of planning. It would be a joint venture with the US. Solar Orbiter would be a successor, in European terms, to the Soho and Ulysses missions. It would circle the Sun, flying to within 35 million km of our star to make detailed measurements of the activity from the equator to the poles. The multi-instrumented probe would both observe the Sun and take in-situ measurements of its environment. "We want Solar Orbiter to help us understand how magnetic storms happen on the Sun and how they reach Earth, so we can predict them," said Dr Marco Velli of the University of Florence, Italy. "You have to go so close because you need to see the source. If you want to understand a supersonic engine, you have to go to where it is sub-sonic. That's where you can see how things work. You'll never get that information sitting out by the exhaust."

Although the first launch opportunity is in 2017, the current assessment is that none of the teams will be ready to meet this date.

Esa's Space Science Advisory Committee will convene in the New Year and rank the competitors. Their recommendations will then go to the Science Programme Committee who must decide in mid-February which of the projects should go forward for more detailed evaluation. It is expected at least two of the consortia's proposals will be discarded at this stage.

A final decision on the winning missions is not expected before the end of 2011.

Jonathan.Amos-INTERNET@...

Source: BBC
http://news.bbc.co.uk/2/hi/science/nature/8389906.stm

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#3263 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 12:24 am
Subject: News: Let the global technology race begin
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Nature 462, 570-571 (3 December 2009) | doi:10.1038/462570a; Published online 2 December 2009

Let the global technology race begin

Isabel Galiana1 & Christopher Green1

In the second of two pieces on decarbonization, Isabel Galiana and Christopher Green argue that fostering a technology revolution, not setting emissions targets, is the key to stabilizing the climate.

Summary

  • Reducing carbon emissions requires an energy-technology revolution that has not yet started
  • A slowly rising carbon price could provide long-term financing for energy research and development
  • A global technology race asks parties to use scientific capabilities rather than to sacrifice future development

The fixation on near-term targets for reducing greenhouse-gas emissions at the climate meeting in Copenhagen has resulted in insufficient attention towards the technological means of achieving them. Let us not forget that the true objective of climate-change policy is to limit global temperature increases. To achieve that requires a revolution in energy technology and the courage to dispense with target-focused climate policies. The race to solve the climate problem will be won by Aesop's tortoise — not the hare.

Stabilizing the climate is a huge technological challenge1, 2, 3 and the solution of ready-to-deploy, scalable low-carbon technologies is far from being a reality4, 5. We calculate that if global emissions are to be reduced by at least 80% by 2100 — a suggested goal if the rise in global temperature is to be limited to 2 °C — while maintaining global economic growth at 2.2% per year, two things are required. First, the energy intensity of the economy will need to be reduced to one-third of its 2000 level and, second, consumption of carbon-free energy will need to be almost three times greater than the total energy consumed globally in 2000, 85% of which was supplied by fossil fuels. To achieve this goal by 2100, energy-technology research and development (R&D) will be essential to decarbonize the global economy, through huge scale-ups of existing low-carbon technologies as well as breakthroughs.

Let the global technology race begin
S. LEEN/NATL GEOGRAPHIC/GETTY

Increasing the supply of low-carbon energy requires policy actions now.

To describe the required trade-offs of any climate policy, analysts use the Kaya identity C = P times (GDP/P) times (E/GDP) times (C/E), which relates carbon emissions, C, to its four driving factors: population (P); per capita gross domestic product (GDP/P); energy intensity of the economy (E/GDP); and emissions per unit of energy (C/E). Conventional climate policy considers only the emissions, C, and the political will needed to achieve reductions, but ignores the driving factors. Policy-makers are understandably reluctant to use population or economic growth to reduce greenhouse-gas emissions; hence policy should focus on the technological drivers. A useful way of looking at these is by combining E/GDP and C/E to yield the economy's carbon intensity (C/GDP).

In recent decades, although global GDP has grown at about 3% per year and global carbon intensity has declined by about 1.4% per year, emissions have grown well in excess of 1% per year. In view of this, the proposal by the Group of 8 rich nations (G8) to cut global emissions in half by 2050, consistent with limiting global long-term temperature increase to 2 °C — and to do this without slowing economic development — would require a tripling of the average annual rate of decline in carbon intensity for the next 40 years. This accelerated decline in carbon intensity requires a revolution in energy technology that has not yet started.

Can a technology-led approach avoid dangerous climate change? We proposed such a policy6 as part of the 2009 Copenhagen Consensus on Climate, in which a panel of leading economists ranked 15 policy responses to global warming. Our analyses show that cumulative emissions consistent with minimizing the rise in global temperature (climate stabilization) can be achieved by investing US$100 billion a year for the rest of the century in global energy R&D, testing, demonstration and infrastructure.

For two of the three technology paths we investigated, cumulative carbon emissions would be kept at levels that could limit long-term warming to 2 °C (ref. 7), despite the greatest emissions reductions occurring after 2050. Moreover, all of the paths we considered passed cost–benefit tests, usually by very large margins. A technology-led approach can stabilize the climate with higher probability and much lower cost than the emissions-target approach.

How would the technology-led approach work? First, governments would replace emissions targets with credible long-term global commitments to invest in energy R&D. To finance this, we propose a low carbon price of $5 per tonne of emitted carbon dioxide, which would raise almost $150 billion per year globally and $30 billion in the United States alone.

Second, the low carbon fee should be allowed to rise gradually over time, doubling, say, every 10 years. This would send a 'forward price signal' to deploy new or improved low-carbon technologies as they become scalable and cost-effective. Third, R&D funds should be isolated as far as possible from political interference by placing them in dedicated trust funds that are administered by independent committees drawn from the public and private sectors. Allocation of funds would be left to experts, akin to The Bill & Melinda Gates Foundation. Energy-technology competitions could be open to individual enterprises, nations or international coalitions. Countries that decide not to participate in R&D could use the funds raised to purchase successfully developed technologies from those that do participate.

Together, these three elements are catalysts for the development and deployment of an increasing flow of successful low-carbon energy innovations over the coming decades. These would span the technology spectrum: basic R&D in breakthrough technologies; 'enabling' R&D that allows scale-up of existing technologies (such as utility-scale storage for intermittent solar and wind energy); testing and demonstration projects; and energy-related infrastructure, such as 'smart grids' that help to manage intermittent energy sources. As these innovations diffuse, they will accelerate the decline in carbon intensity and reduce emissions to negligible levels by 2100 while maintaining economic growth.

Emission-target pitfalls

Our technology-led proposal inverts the usual relationship between carbon pricing and technology, whereby carbon pricing is naively expected to induce fundamental technological innovation. Experience shows that, even if there is successful innovation, the market is unlikely to undertake risky basic R&D when the benefits are difficult to appropriate. For example, public funds supported the basic scientific knowledge underlying radar, nuclear power, the Internet and the understanding of DNA — none of which are easy to patent. Also, governments cannot credibly convince current investors that future governments will set carbon prices high enough to compensate for up-front and risky R&D investments8. Moreover, potential pay-offs are decades rather than years in the future and are thus discounted away by myopic investors.

What if aggressive emissions-reduction targets were adopted and enforced without paying attention to the capabilities of existing technologies to deliver good low-carbon substitutes? The Kaya identity tells us that attempting to reduce emissions sharply would substantially reduce economic growth. For example, meeting the G8 goal of slashing global carbon emissions by 50% by 2050 — which would require developed countries to reduce emissions by up to 80% — could result in economic costs as high as 10% or more of their GDP.

Another problem with conventional policy is that high carbon prices fall heavily on energy-intensive industries and activities, which are often important to domestic production and employment. In populous, rapidly developing countries, the construction of new high-rise buildings and roads requires cement, steel, glass, copper and aluminium, all of which are highly energy-intensive. Understandably, most consumer-voters will be unwilling to pay the high carbon prices required by near-term emissions-reduction targets9 in the absence of reliable and inexpensive clean-energy sources. To be feasible, a carbon price must start low and rise slowly.

Proponents of a high carbon price (whether through a carbon market or tax) too easily assume that it will induce rapid technological change. But implementing high carbon prices now on the assumption of future technological pay-offs, without direct technological investment, is risky and expensive. Thus, we must address the technology challenge now. Still, supporters of conventional policy may argue that a technology-led approach lacks accountability for emissions reductions. Although we cannot predict exactly when emissions will be reduced because of the inherent uncertainty in deploying new technologies, we can predict that the carbon intensity of the economy will decline dramatically once such technologies become readily available.

Does a technology-led policy imply particular R&D funding choices? No. With $100 billion a year to spend, there will be various initiatives, including carbon-capture and storage technologies, advanced nuclear and deep-geothermal energy, next-generation biofuels, ocean-wave energy and storage for solar and wind energy. There should be no need to pick 'winners' or to get locked into inferior technologies.

What about the choice between R&D in 'enabling' and 'breakthrough' technologies? Both will be needed, and in many cases they overlap. Given the longer lead times needed for breakthrough technologies, a balance between investments in technologies with near- to medium-term pay-offs and those with long-term pay-offs seems sensible. No matter how one approaches climate change, stabilization is a long-term process with numerous paths10.

There are other advantages to a technology-led climate policy. It is attractive to developing countries such as China, India, Brazil and Indonesia because, instead of asking for emissions reductions, a technology-led policy invites them to participate in an energy-technology race. Many of these countries are already pressing ahead with R&D of low-carbon technologies.

A global technology race could attract new generations to the challenge of stabilizing climate by asking them to share their scientific and creative capabilities rather than to sacrifice future development. It would yield benefits in terms of spillovers to non-energy technologies and uses, just as the world is still benefiting from innovations developed in the race to put a man on the Moon. Ultimately, a technology-led policy is optimistic because it rewards success rather than punishing failure.

See Opinion, page 568. Discuss this article at http://go.nature.com/9eLudp and see online at http://www.nature.com/roadtocopenhagen.

References

  1. Hoffert. M. I. et al. Nature 395, 881–884 (1998). | Article | ISI | ChemPort |
  2. Caldeira, K., Jain, A. K. & Hoffert, M. I. Science 299, 2052–2054 (2003). | Article | PubMed | ChemPort |
  3. Pielke, R. Jr, Wigley, T. & Green, C. Nature 452, 531–532 (2008). | Article | PubMed | ChemPort |
  4. Hoffert, M. I. et al. Science 298, 981–987 (2002). | Article | PubMed | ChemPort |
  5. Barrett, S. J. Econ. Perspect. 23, 53–75 (2009). | Article
  6. Galiana, I. & Green, C. An Analysis of a Technology-led Climate Policy as a Response to Climate Change (Copenhagen Consensus Center, 2009).
  7. Meinshausen, M. et al. Nature 458, 1158–1162 (2009). | Article | PubMed | ChemPort |
  8. Montgomery, W. D. & Smith, A. E. in Human-induced Climate Change (Cambridge Univ. Press, 2007).
  9. Nemet, G. F. Res. Policy 38, 700–709 (2009). | Article
  10. Wigley, T. M. L. et al. Nature 379, 240–243 (1996). | Article | ChemPort |
  1. Isabel Galiana and Christopher Green are in the Department of Economics at McGill University, Montreal, Quebec H3A 2T7, Canada.
    Email: isabel.galiana@...; Email: chris.green@...
 
Posted by
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#3262 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 12:37 am
Subject: Paper: Extreme particle acceleration in the microquasar Cygnus X-3
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Nature 462, 620-623 (3 December 2009) | doi:10.1038/nature08578; Received 7 August 2009; Accepted 8 October 2009; Published online 22 November 2009

Extreme particle acceleration in the microquasar Cygnus X-3

M. Tavani1,2,3,4, A. Bulgarelli5, G. Piano1,4, S. Sabatini2,4, E. Striani2,4, Y. Evangelista1, A. Trois1, G. Pooley6, S. Trushkin7, N. A. Nizhelskij7, M. McCollough8, K. I. I. Koljonen9, G. Pucella10, A. Giuliani11, A. W. Chen3,11, E. Costa1, V. Vittorini1,3, M. Trifoglio5, F. Gianotti5, A. Argan1, G. Barbiellini3,12,13, P. Caraveo11, P. W. Cattaneo14, V. Cocco2, T. Contessi11, F. D'Ammando1,2, E. Del Monte1, G. De Paris1, G. Di Cocco5, G. Di Persio1, I. Donnarumma1, M. Feroci1, A. Ferrari3,15, F. Fuschino5, M. Galli16, C. Labanti5, I. Lapshov17, F. Lazzarotto1, P. Lipari18,19, F. Longo12,13, E. Mattaini11, M. Marisaldi5, M. Mastropietro20, A. Mauri5, S. Mereghetti11, E. Morelli5, A. Morselli4, L. Pacciani1, A. Pellizzoni21, F. Perotti11, P. Picozza2,4, M. Pilia21,22, M. Prest22, M. Rapisarda10, A. Rappoldi14, E. Rossi5, A. Rubini1, E. Scalise1, P. Soffitta1, E. Vallazza13, S. Vercellone23, A. Zambra3,11, D. Zanello18,19, C. Pittori24, F. Verrecchia24, P. Giommi24, S. Colafrancesco24, P. Santolamazza24, A. Antonelli25 & L. Salotti26

  1. INAF-IASF Roma, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy
  2. Dipartimento di Fisica, Università Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma, Italy
  3. Consorzio Interuniversitario Fisica Spaziale, Villa Gualino, Viale Settimio Severo 63, I-10133 Torino, Italy
  4. INFN Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma, Italy
  5. INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna, Italy
  6. Astrophysics Group, Cavendish Laboratory, 19 J. J. Thomson Avenue, Cambridge CB3 0HE, UK
  7. Special Astrophysical Observatory RAS, Karachaevo-Cherkassian Republic, Nizhnij Arkhyz 36916, Russia
  8. Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA
  9. TKK/Metsähovi Radio Observatory, Metsähovintie 114, Kylmälä 02540, Finland
  10. ENEA Frascati, Via Enrico Fermi 45, I-00044 Frascati (RM), Italy
  11. INAF-IASF Milano, Via E. Bassini 15, I-20133 Milano, Italy
  12. Dipartimento di Fisica, Università di Trieste, Via A. Valerio 2, I-34127 Trieste, Italy
  13. INFN Trieste, Padriciano 99, I-34012 Trieste, Italy
  14. INFN Pavia, Via Bassi 6, I-27100 Pavia, Italy
  15. Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, I-10125 Torino, Italy
  16. ENEA Bologna, Via don Fiammelli 2, I-40128 Bologna, Italy
  17. IKI, Profsoyuznaya Street 84, Moscow 117997, Russia
  18. INFN Roma 1, Piazza Aldo Moro 2, I-00185 Roma, Italy
  19. Dipartimento di Fisica, Università La Sapienza, Piazza Aldo Moro 2, I-00185 Roma, Italy
  20. CNR, IMIP, I-00016 Montelibretti (Rome), Italy
  21. INAF Osservatorio Astronomico di Cagliari, Poggio dei Pini, I-09012 Capoterra (Cagliari), Italy
  22. Dipartimento di Fisica, Università Insubria, Via Valleggio 11, I-22100 Como, Italy
  23. INAF-IASF Palermo, Via La Malfa 153, I-90146 Palermo, Italy
  24. ASI Science Data Center, ESRIN, I-00044 Frascati, Italy
  25. Osservatorio Astronomico di Roma, Via di Frascati 33, I-00040 Monte Porzio Catone, Italy
  26. Agenzia Spaziale Italiana, Viale Liegi 26, I-00198 Roma, Italy

Correspondence to: M. Tavani1,2,3,4 Correspondence and requests for materials should be addressed to M. Tavani (Email: pi.agile@...).

Super-massive black holes in active galaxies can accelerate particles to relativistic energies, producing jets with associated gamma-ray emission. Galactic 'microquasars', which are binary systems consisting of a neutron star or stellar-mass black hole accreting gas from a companion star, also produce relativistic jets, generally together with radio flares. Apart from an isolated event detected in Cygnus X-1, there has hitherto been no systematic evidence for the acceleration of particles to gigaelectronvolt or higher energies in a microquasar, with the consequence that we are as yet unsure about the mechanism of jet energization. Here we report four gamma-ray flares with energies above 100 MeV from the microquasar Cygnus X-3 (an exceptional X-ray binary that sporadically produces radio jets). There is a clear pattern of temporal correlations between the gamma-ray flares and transitional spectral states of the radio-frequency and X-ray emission. Particle acceleration occurred a few days before radio-jet ejections for two of the four flares, meaning that the process of jet formation implies the production of very energetic particles. In Cygnus X-3, particle energies during the flares can be thousands of times higher than during quiescent states.

Source: Nature
http://www.nature.com/nature/journal/v462/n7273/abs/nature08578.html?lang=en

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#3261 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 12:41 am
Subject: Paper: Controlling photonic structures using optical forces
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Nature 462, 633-636 (3 December 2009) | doi:10.1038/nature08584; Received 24 June 2009; Accepted 7 October 2009; Published online 15 November 2009

Controlling photonic structures using optical forces

Gustavo S. Wiederhecker, Long Chen, Alexander Gondarenko & Michal Lipson
School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA

Correspondence to: Michal Lipson Correspondence and requests for materials should be addressed to M.L. (Email: ml292@...).

The use of optical forces to manipulate small objects is well known. Applications include the manipulation of living cells by optical tweezers and optical cooling in atomic physics. The miniaturization of optical systems (to the micro and nanoscale) has resulted in very compliant systems with masses of the order of nanograms, rendering them susceptible to optical forces. Optical forces have been exploited to demonstrate chaotic quivering of microcavities, optical cooling of mechanical modes, actuation of a tapered-fibre waveguide and excitation of the mechanical modes of silicon nano-beams. Despite recent progress in this field, it is challenging to manipulate the optical response of photonic structures using optical forces; this is because of the large forces that are required to induce appreciable changes in the geometry of the structure. Here we implement a resonant structure whose optical response can be efficiently statically controlled using relatively weak attractive and repulsive optical forces. We demonstrate a static mechanical deformation of up to 20 nanometres in a silicon nitride structure, using three milliwatts of continuous optical power. Because of the sensitivity of the optical response to this deformation, such optically induced static displacement introduces resonance shifts spanning 80 times the intrinsic resonance linewidth.

Source: Nature
http://www.nature.com/nature/journal/v462/n7273/abs/nature08584.html?lang=en

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#3260 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 12:32 am
Subject: Paper: Neutral atoms put in charge
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Nature 462, 584-585 (3 December 2009) | doi:10.1038/462584a; Published online 2 December 2009
 

Atomic physics: Neutral atoms put in charge

Martin Zwierlein

An elegant experiment shows that atoms subjected to a pair of laser beams can behave like electrons in a magnetic field, as demonstrated by the appearance of quantized vortices in a neutral superfluid.

Ultracold gases of atoms — a million times thinner than air and a million times colder than interstellar space — allow the observation and control of many-body quantum phenomena at macroscopic scales. They can thus serve as model materials for condensed-matter systems in which such phenomena arise.

Source: Nature
http://www.nature.com/nature/journal/v462/n7273/full/462584a.html

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Robert Karl Stonjek


#3259 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 12:38 am
Subject: Paper: Synthetic magnetic fields for ultracold neutral atoms
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Nature 462, 628-632 (3 December 2009) | doi:10.1038/nature08609; Received 7 August 2009; Accepted 20 October 2009

Synthetic magnetic fields for ultracold neutral atoms

Y.-J. Lin1, R. L. Compton1, K. Jiménez-García1,2, J. V. Porto1 & I. B. Spielman1

  1. Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, Maryland, 20899, USA
  2. Departamento de Física, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, México DF, 07360, México

Correspondence to: I. B. Spielman1 Correspondence and requests for materials should be addressed to I.B.S. (Email: ian.spielman@...).

Neutral atomic Bose condensates and degenerate Fermi gases have been used to realize important many-body phenomena in their most simple and essential forms, without many of the complexities usually associated with material systems. However, the charge neutrality of these systems presents an apparent limitation—a wide range of intriguing phenomena arise from the Lorentz force for charged particles in a magnetic field, such as the fractional quantum Hall effect in two-dimensional electron systems. The limitation can be circumvented by exploiting the equivalence of the Lorentz force and the Coriolis force to create synthetic magnetic fields in rotating neutral systems. This was demonstrated by the appearance of quantized vortices in pioneering experiments on rotating quantum gases, a hallmark of superfluids or superconductors in a magnetic field. However, because of technical issues limiting the maximum rotation velocity, the metastable nature of the rotating state and the difficulty of applying stable rotating optical lattices, rotational approaches are not able to reach the large fields required for quantum Hall physics. Here we experimentally realize an optically synthesized magnetic field for ultracold neutral atoms, which is evident from the appearance of vortices in our Bose–Einstein condensate. Our approach uses a spatially dependent optical coupling between internal states of the atoms, yielding a Berry's phase sufficient to create large synthetic magnetic fields, and is not subject to the limitations of rotating systems. With a suitable lattice configuration, it should be possible to reach the quantum Hall regime, potentially enabling studies of topological quantum computation.

Source: Nature
http://www.nature.com/nature/journal/v462/n7273/abs/nature08609.html?lang=en

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#3258 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Dec 3, 2009 12:31 am
Subject: Paper: Different stellar demise
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Nature 462, 579-580 (3 December 2009) | doi:10.1038/462579a; Published online 2 December 2009
 

Different stellar demise

Norbert Langer

A decades-old theory of stellar evolution — that the most massive stars end their life in a peculiar type of explosion termed a pair-instability supernova — finally seems to have been confirmed by observations.

Whereas the final evolutionary stage of a low-mass star such as the Sun is that of a simple white dwarf, the life of a massive star ends in a spectacular explosion called a supernova (SN). This theoretical view of stellar demise has been verified many times, most prominently through observations of SN 1987A, a supernova that occurred in a satellite galaxy of the Milky Way, the Large Magellanic Cloud.

Source: Nature
http://www.nature.com/nature/journal/v462/n7273/full/462579a.html

Posted by
Robert Karl Stonjek


#3257 From: "Robert Karl Stonjek" <stonjek@...>
Date: Wed Dec 2, 2009 1:22 pm
Subject: Wiley Interscience Content Alert: Monthly Notices of the Royal Astronomical Society 400, 3
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Online ISSN: 1365-2966    Print ISSN: 0035-8711
Monthly Notices of the Royal Astronomical Society
Volume400, Issue3,2009.
Early View (Articles Available Online in Advance of Print)
Journal compilation © 2009 RAS


  Papers
 
 1121-1131  A spatially resolved map of the kinematics, star formation and stellar mass assembly in a star-forming galaxy at z= 4.9
A. M. Swinbank, T. M. Webb, J. Richard, R. G. Bower, R. S. Ellis, G. Illingworth, T. Jones, M. Kriek, I. Smail, D. P. Stark, P. van Dokkum
Abstract
Published Online: 22 Oct 2009
DOI 10.1111/j.1365-2966.2009.15617.x

 1132-1138  Gravitational flexion by elliptical dark matter haloes
A. J. Hawken, S. L. Bridle
Abstract
Published Online: 3 Nov 2009
DOI 10.1111/j.1365-2966.2009.15539.x

 1139-1180  The properties of the stellar populations in ULIRGs – I. Sample, data and spectral synthesis modelling
J. Rodríguez Zaurín, C. N. Tadhunter, R. M. González Delgado
Abstract
Published Online: 11 Nov 2009
DOI 10.1111/j.1365-2966.2009.15444.x

 1181-1198  Resolved stellar mass maps of galaxies – I. Method and implications for global mass estimates
Stefano Zibetti, Stéphane Charlot, Hans-Walter Rix
Abstract
Published Online: 2 Oct 2009
DOI 10.1111/j.1365-2966.2009.15528.x

 1199-1207  Spectral energy distributions of type 2 quasi-stellar objects: obscured star formation at high redshifts
D. Rigopoulou, V. Mainieri, O. Almaini, A. Alonso-Herrero, J.-S. Huang, G. Hasinger, G. Rieke, J. Dunlop, I. Lehmann
Abstract
Published Online: 2 Oct 2009
DOI 10.1111/j.1365-2966.2009.15543.x

 1208-1224  Star clusters in the interacting galaxy system Arp 284
Bradley W. Peterson, Curtis Struck, Beverly J. Smith, Mark Hancock
Abstract
Published Online: 10 Oct 2009
DOI 10.1111/j.1365-2966.2009.15551.x

 1225-1240  Evolutionary paths to and from the red sequence: star formation and H i properties of transition galaxies at z∼ 0
L. Cortese, T. M. Hughes
Abstract
Published Online: 2 Oct 2009
DOI 10.1111/j.1365-2966.2009.15548.x

 1241-1246  Observations of 'wisps' in magnetohydrodynamic simulations of the Crab Nebula
N. F. Camus, S. S. Komissarov, N. Bucciantini, P. A. Hughes
Abstract
Published Online: 22 Sep 2009
DOI 10.1111/j.1365-2966.2009.15550.x

 1247-1263  The dynamics of satellite disruption in cold dark matter haloes
Jun-Hwan Choi, Martin D. Weinberg, Neal Katz
Abstract
Published Online: 29 Sep 2009
DOI 10.1111/j.1365-2966.2009.15556.x

 1264-1282  Are dry mergers dry, moist or wet?
P. Sánchez-Blázquez, B. K. Gibson, D. Kawata, N. Cardiel, M. Balcells
Abstract
Published Online: 6 Nov 2009
DOI 10.1111/j.1365-2966.2009.15557.x

 1283-1316  Cosmological radiative transfer comparison project – II. The radiation-hydrodynamic tests
Ilian T. Iliev, Daniel Whalen, Garrelt Mellema, Kyungjin Ahn, Sunghye Baek, Nickolay Y. Gnedin, Andrey V. Kravtsov, Michael Norman, Milan Raicevic, Daniel R. Reynolds, Daisuke Sato, Paul R. Shapiro, Benoit Semelin, Joseph Smidt, Hajime Susa, Tom Theuns, Masayuki Umemura
Abstract
Published Online: 14 Sep 2009
DOI 10.1111/j.1365-2966.2009.15558.x

 1317-1336  Cosmology and cluster halo scaling relations
Pablo A. Araya-Melo, Rien van de Weygaert, Bernard J. T. Jones
Abstract
Published Online: 12 Oct 2009
DOI 10.1111/j.1365-2966.2009.15565.x

 1337-1346  The outburst duration and duty cycle of GRS 1915+105
Patrick Deegan, Céline Combet, Graham A. Wynn
Abstract
Published Online: 29 Oct 2009
DOI 10.1111/j.1365-2966.2009.15573.x

 1347-1365  Chemical evolution of local galaxies in a hierarchical model
F. Calura, N. Menci
Abstract
Published Online: 10 Nov 2009
DOI 10.1111/j.1365-2966.2009.15440.x

 1366-1372  Applications of complex analysis to precession, nutation and aberration
Robin G. Stuart
Abstract
Published Online: 10 Nov 2009
DOI 10.1111/j.1365-2966.2009.15529.x

 1373-1382  Trapping in high-order orbital resonances and inclination excitation in extrasolar systems
A.-S. Libert, K. Tsiganis
Abstract
Published Online: 23 Oct 2009
DOI 10.1111/j.1365-2966.2009.15532.x

 1383-1388  Hemispheric variation of coronal mass ejections in cycle 23
Peng-Xin Gao, Ke-Jun Li, Xiang-Jun Shi
Abstract
Published Online: 21 Sep 2009
DOI 10.1111/j.1365-2966.2009.15534.x

 1389-1393  Orbital elements of comet C/1490 Y1 and the Quadrantid shower
Ki-Won Lee, Hong-Jin Yang, Myeong-Gu Park
Abstract
Published Online: 17 Nov 2009
DOI 10.1111/j.1365-2966.2009.15535.x

 1394-1412  AMI observations of Lynds dark nebulae: further evidence for anomalous cm-wave emission★
Anna M. M. Scaife, Natasha Hurley-Walker, David A. Green, Matthew L. Davies, Thomas M. O. Franzen, Keith J. B. Grainge, Michael P. Hobson, Anthony N. Lasenby, Guy G. Pooley, Carmen Rodríguez-Gonzálvez, Richard D. E. Saunders, Paul F. Scott, Timothy W. Shimwell, David J. Titterington, Elizabeth M. Waldram, Jonathan T. L. Zwart
Abstract
Published Online: 26 Oct 2009
DOI 10.1111/j.1365-2966.2009.15542.x

 1413-1426  Near-IR spectra of IPHAS extremely red Galactic AGB stars
N. J. Wright, M. J. Barlow, R. Greimel, J. E. Drew, M. Matsuura, Y. C. Unruh, A. A. Zijlstra
Abstract
Published Online: 18 Sep 2009
DOI 10.1111/j.1365-2966.2009.15536.x

 1427-1430  Measuring clustering in 2dv space
Annabel Cartwright
Abstract
Published Online: 9 Oct 2009
DOI 10.1111/j.1365-2966.2009.15540.x

 1431-1438  Timing observations of rotating radio transients
M. A. McLaughlin, A. G. Lyne, E. F. Keane, M. Kramer, J. J. Miller, D. R. Lorimer, R. N. Manchester, F. Camilo, I. H. Stairs
Abstract
Published Online: 6 Nov 2009
DOI 10.1111/j.1365-2966.2009.15584.x

 1439-1444  Unusual glitch activity in the RRAT J1819−1458: an exhausted magnetar?
A. G. Lyne, M. A. McLaughlin, E. F. Keane, M. Kramer, C. M. Espinoza, B. W. Stappers, N. T. Palliyaguru, J. Miller
Abstract
Published Online: 6 Nov 2009
DOI 10.1111/j.1365-2966.2009.15668.x

 1445-1450  Upper limits on X-ray emission from two rotating radio transients
D. L. Kaplan, P. Esposito, S. Chatterjee, A. Possenti, M. A. McLaughlin, F. Camilo, D. Chakrabarty, P. O. Slane
Abstract
Published Online: 6 Nov 2009
DOI 10.1111/j.1365-2966.2009.15541.x

 1451-1460  The Millennium Galaxy Catalogue: the Mbh–Lspheroid derived supermassive black hole mass function
Marina Vika, Simon P. Driver, Alister W. Graham, Jochen Liske
Abstract
Published Online: 5 Oct 2009
DOI 10.1111/j.1365-2966.2009.15544.x

 1461-1471  The inhomogeneous ionizing background following reionization
Andrei Mesinger, Steven Furlanetto
Abstract
Published Online: 11 Nov 2009
DOI 10.1111/j.1365-2966.2009.15547.x

 1472-1478  A Keck/DEIMOS spectroscopic survey of the faint M 31 satellites And XV and And XVI
B. Letarte, S. C. Chapman, M. Collins, R. A. Ibata, M. J. Irwin, A. M. N. Ferguson, G. F. Lewis, N. Martin, A. McConnachie, N. Tanvir
Abstract
Published Online: 11 Nov 2009
DOI 10.1111/j.1365-2966.2009.15546.x

 1479-1492  The massive star binary fraction in young open clusters – II. NGC 6611 (Eagle Nebula)
H. Sana, E. Gosset, C. J. Evans
Abstract
Published Online: 16 Nov 2009
DOI 10.1111/j.1365-2966.2009.15545.x

 1493-1511  Probing re-ionization with quasar spectra: the impact of the intrinsic Lyman α emission line shape uncertainty
R. H. Kramer, Z. Haiman
Abstract
Published Online: 12 Oct 2009
DOI 10.1111/j.1365-2966.2009.15552.x

 1512-1520  Energetics of a black hole: constraints on the jet velocity and the nature of the X-ray emitting region in Cyg X-1
Julien Malzac, Renaud Belmont, Andrew C. Fabian
Abstract
Published Online: 9 Oct 2009
DOI 10.1111/j.1365-2966.2009.15553.x

 1521-1526  Accretion discs in blazars
E. J. D. Jolley, Z. Kuncic, G. V. Bicknell, S. Wagner
Abstract
Published Online: 10 Oct 2009
DOI 10.1111/j.1365-2966.2009.15554.x

 1527-1540  Modelling galaxy clustering: is new physics needed in galaxy formation models?
Han-Seek Kim, C. M. Baugh, S. Cole, C. S. Frenk, A. J. Benson
Abstract
Published Online: 9 Oct 2009
DOI 10.1111/j.1365-2966.2009.15560.x

 1541-1547  Peculiar velocities into the next generation: cosmological parameters from the SFI++ survey
Alexandra Abate, Pirin ErdoÄŸdu
Abstract
Published Online: 15 Oct 2009
DOI 10.1111/j.1365-2966.2009.15561.x

 1548-1562  Long-term monitoring in IC4665: fast rotation and weak variability in very low mass objects
Alexander Scholz, Jochen Eislöffel, Reinhard Mundt
Abstract
Published Online: 15 Oct 2009
DOI 10.1111/j.1365-2966.2009.15563.x

 1563-1573  The role of thermodynamics in disc fragmentation
Dimitris Stamatellos, Anthony P. Whitworth
Abstract
Published Online: 29 Oct 2009
DOI 10.1111/j.1365-2966.2009.15564.x

 1574-1582  Electromagnetic instabilities in rotating magnetized viscous objects
A. K. Nekrasov
Abstract
Published Online: 23 Oct 2009
DOI 10.1111/j.1365-2966.2009.15569.x

 1583-1592  Statistics of mass substructure from strong gravitational lensing: quantifying the mass fraction and mass function
Simona Vegetti, L. V. E. Koopmans
Abstract
Published Online: 10 Oct 2009
DOI 10.1111/j.1365-2966.2009.15559.x

 1593-1602  Probing the epoch of reionization with Milky Way satellites
Joseph A. Muñoz, Piero Madau, Abraham Loeb, Jürg Diemand
Abstract
Published Online: 10 Oct 2009
DOI 10.1111/j.1365-2966.2009.15562.x

 1603-1612  The evolution of the high-energy cut-off in the X-ray spectrum of GX 339−4 across a hard-to-soft transition
S. Motta, T. Belloni, J. Homan
Abstract
Published Online: 4 Nov 2009
DOI 10.1111/j.1365-2966.2009.15566.x

 1613-1624  Properties of long gamma-ray burst host galaxies in cosmological simulations
M. A. Campisi, G. De Lucia, L.-X. Li, S. Mao, X. Kang
Abstract
Published Online: 26 Oct 2009
DOI 10.1111/j.1365-2966.2009.15568.x

 1625-1631  Large Magellanic Cloud self-lensing for OGLE-II microlensing observations
S. Calchi Novati, L. Mancini, G. Scarpetta, Å. Wyrzykowski
Abstract
Published Online: 15 Oct 2009
DOI 10.1111/j.1365-2966.2009.15570.x

 1632-1642  Can stellar mass black holes be quark stars?
Z. Kovács, K. S. Cheng, T. Harko
Abstract
Published Online: 21 Oct 2009
DOI 10.1111/j.1365-2966.2009.15571.x

 1643-1664  Cosmological parameter constraints from SDSS luminous red galaxies: a new treatment of large-scale clustering
Ariel G. Sánchez, M. Crocce, A. Cabré, C. M. Baugh, E. Gaztañaga
Abstract
Published Online: 23 Oct 2009
DOI 10.1111/j.1365-2966.2009.15572.x



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#3256 From: "Robert Karl Stonjek" <stonjek@...>
Date: Wed Dec 2, 2009 3:43 pm
Subject: News: Splitting Time from Space—New Quantum Theory Topples Einstein's Spacetime
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Splitting Time from Space—New Quantum Theory Topples Einstein's Spacetime

Buzz about a quantum gravity theory that sends space and time back to their Newtonian roots

By Zeeya Merali

Was Newton right and Einstein wrong? It seems that unzipping the fabric of spacetime and harking back to 19th-century notions of time could lead to a theory of quantum gravity.

Physicists have struggled to marry quantum mechanics with gravity for decades. In contrast, the other forces of nature have obediently fallen into line. For instance, the electromagnetic force can be described quantum-mechanically by the motion of photons. Try and work out the gravitational force between two objects in terms of a quantum graviton, however, and you quickly run into trouble—the answer to every calculation is infinity. But now Petr Hořava, a physicist at the University of California, Berkeley, thinks he understands the problem. It’s all, he says, a matter of time.

More specifically, the problem is the way that time is tied up with space in Einstein’s theory of gravity: general relativity. Einstein famously overturned the Newtonian notion that time is absolute—steadily ticking away in the background. Instead he argued that time is another dimension, woven together with space to form a malleable fabric that is distorted by matter. The snag is that in quantum mechanics, time retains its Newtonian aloofness, providing the stage against which matter dances but never being affected by its presence. These two conceptions of time don’t gel.

The solution, Hořava says, is to snip threads that bind time to space at very high energies, such as those found in the early universe where quantum gravity rules. “I’m going back to Newton’s idea that time and space are not equivalent,” Hořava says. At low energies, general relativity emerges from this underlying framework, and the fabric of spacetime restitches, he explains.

Hořava likens this emergence to the way some exotic substances change phase. For instance, at low temperatures liquid helium’s properties change dramatically, becoming a “superfluid” that can overcome friction. In fact, he has co-opted the mathematics of exotic phase transitions to build his theory of gravity. So far it seems to be working: the infinities that plague other theories of quantum gravity have been tamed, and the theory spits out a well-behaved graviton. It also seems to match with computer simulations of quantum gravity.

Hořava’s theory has been generating excitement since he proposed it in January, and physicists met to discuss it at a meeting in November at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario. In particular, physicists have been checking if the model correctly describes the universe we see today. General relativity scored a knockout blow when Einstein predicted the motion of Mercury with greater accuracy than Newton’s theory of gravity could.

Can Hořřava gravity claim the same success? The first tentative answers coming in say “yes.” Francisco Lobo, now at the University of Lisbon, and his colleagues have found a good match with the movement of planets.

Others have made even bolder claims for Hořava gravity, especially when it comes to explaining cosmic conundrums such as the singularity of the big bang, where the laws of physics break down. If Hořava gravity is true, argues cosmologist Robert Brandenberger of McGill University in a paper published in the August Physical Review D, then the universe didn’t bang—it bounced. “A universe filled with matter will contract down to a small—but finite—size and then bounce out again, giving us the expanding cosmos we see today,” he says. Brandenberger’s calculations show that ripples produced by the bounce match those already detected by satellites measuring the cosmic microwave background, and he is now looking for signatures that could distinguish the bounce from the big bang scenario.

Hořava gravity may also create the “illusion of dark matter,” says cosmologist Shinji Mukohyama of Tokyo University. In the September Physical Review D, he explains that in certain circumstances Hořava’s graviton fluctuates as it interacts with normal matter, making gravity pull a bit more strongly than expected in general relativity. The effect could make galaxies appear to contain more matter than can be seen. If that’s not enough, cosmologist Mu-In Park of Chonbuk National University in South Korea believes that Hořava gravity may also be behind the accelerated expansion of the universe, currently attributed to a mysterious dark energy. One of the leading explanations for its origin is that empty space contains some intrinsic energy that pushes the universe outward. This intrinsic energy cannot be accounted for by general relativity but pops naturally out of the equations of Hořava gravity, according to Park.

Hořava’s theory, however, is far from perfect. Diego Blas, a quantum gravity researcher at the Swiss Federal Institute of Technology (EPFL) in Lausanne has found a “hidden sickness” in the theory when double-checking calculations for the solar system. Most physicists examined ideal cases, assuming, for instance, that Earth and the sun are spheres, Blas explains: “We checked the more realistic case, where the sun is almost a sphere, but not quite.” General relativity pretty much gives the same answer in both the scenarios. But in Hořava gravity, the realistic case gives a wildly different result.

Along with Sergei M. Sibiryakov, also at EPFL, and Oriol Pujolas of CERN near Geneva, Blas has reformulated Hořava gravity to bring it back into line with general relativity. Sibiryakov presented the group’s model in September at a meeting in Talloires, France.

Hořava welcomes the modifications. “When I proposed this, I didn’t claim I had the final theory,” he says. “I want other people to examine it and improve it.”

Gia Dvali, a quantum gravity expert at CERN, remains cautious. A few years ago he tried a similar trick, breaking apart space and time in an attempt to explain dark energy. But he abandoned his model because it allowed information to be communicated faster than the speed of light.

“My intuition is that any such models will have unwanted side effects,” Dvali thinks. “But if they find a version that doesn’t, then that theory must be taken very seriously.”

Note: This article was originally printed with the title, "Splitting Time from Space."


#3255 From: "Robert Karl Stonjek" <stonjek@...>
Date: Tue Dec 1, 2009 12:24 am
Subject: News: Black hole caught zapping galaxy into existence?
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Black hole caught zapping galaxy into existence?
November 30th, 2009 in Space & Earth / Astronomy
Black hole caught zapping galaxy into existence?This artist's impression shows how jets from supermassive black holes could form galaxies, thereby explaining why the mass of black holes is larger in galaxies that contain more stars. Credit: ESO/L. Calçada

(PhysOrg.com) -- Which come first, the supermassive black holes that frantically devour matter or the enormous galaxies where they reside? A brand new scenario has emerged from a recent set of outstanding observations of a black hole without a home: black holes may be “building” their own host galaxy. This could be the long-sought missing link to understanding why the masses of black holes are larger in galaxies that contain more stars.

"The 'chicken and egg' question of whether a galaxy or its black hole comes first is one of the most debated subjects in astrophysics today," says lead author David Elbaz. "Our study suggests that supermassive black holes can trigger the formation of stars, thus 'building' their own host galaxies. This link could also explain why galaxies hosting larger black holes have more stars."

To reach such an extraordinary conclusion, the team of astronomers conducted extensive observations of a peculiar object, the nearby quasar HE0450-2958, which is the only one for which a host galaxy has not yet been detected. HE0450-2958 is located some 5 billion light-years away.

Until now, it was speculated that the quasar's host galaxy was hidden behind large amounts of dust, and so the astronomers used a mid-infrared instrument on ESO's Very Large Telescope for the observations. At such wavelengths, dust clouds shine very brightly, and are readily detected. "Observing at these wavelengths would allow us to trace dust that might hide the host galaxy," says Knud Jahnke, who led the observations performed at the VLT. "However, we did not find any. Instead we discovered that an apparently unrelated galaxy in the quasar's immediate neighbourhood is producing stars at a frantic rate."

These observations have provided a surprising new take on the system. While no trace of stars is revealed around the black hole, its companion galaxy is extremely rich in bright and very young stars. It is forming stars at a rate equivalent to about 350 Suns per year, one hundred times more than rates for typical galaxies in the local Universe.

Black hole caught zapping galaxy into existence?

Colour composite image of a peculiar object, the nearby quasar HE0450-2958, which is the only one for which no sign of a host galaxy has yet been detected. A team of astronomers has identified black hole jets as a possible driver of galaxy formation, which may also represent the long-sought missing link to understanding why the mass of black holes is larger in galaxies that contain more stars. The mid-infrared part of this image was obtained with the VISIR instrument on ESO’s Very Large Telescope, while the visible image comes courtesy of the Hubble Space Telescope and the Advanced Camera for Surveys.

Earlier observations had shown that the companion galaxy is, in fact, under fire: the quasar is spewing a jet of highly energetic particles towards its companion, accompanied by a stream of fast-moving gas. The injection of matter and energy into the galaxy indicates that the quasar itself might be inducing the formation of stars and thereby creating its own host galaxy; in such a scenario, galaxies would have evolved from clouds of gas hit by the energetic jets emerging from quasars.

"The two objects are bound to merge in the future: the quasar is moving at a speed of only a few tens of thousands of km/h with respect to the companion galaxy and their separation is only about 22 000 light-years," says Elbaz. "Although the quasar is still 'naked', it will eventually be 'dressed' when it merges with its star-rich companion. It will then finally reside inside a host galaxy like all other quasars."

Hence, the team have identified black hole jets as a possible driver of galaxy formation, which may also represent the long-sought missing link to understanding why the mass of black holes is larger in galaxies that contain more stars.

"A natural extension of our work is to search for similar objects in other systems," says Jahnke.

Future instruments, such as the Atacama Large Millimeter/submillimeter Array, the European Extremely Large Telescope and the NASA/ESA/CSA James Webb Space Telescope will be able to search for such objects at even larger distances from us, probing the connection between black holes and the formation of galaxies in the more distant Universe.

More information: This research was presented in papers published in the journal Astronomy & : "Quasar induced galaxy formation: a new paradigm?" by Elbaz et al., and in the Astrophysical Journal "The QSO HE0450-2958: Scantily dressed or heavily robed? A normal quasar as part of an unusual ULIRG" by Jahnke et al. Research papers: http://www.aanda.org/10.1051/0004-6361/200912848/pdf and http://arxiv.org/abs/0906.0365

Source: ESO (news : web)
http://www.physorg.com/news178804126.html

Posted by
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#3254 From: "Robert Karl Stonjek" <stonjek@...>
Date: Mon Nov 30, 2009 8:55 pm
Subject: News: Large Hadron Collider sets world energy record
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Page last updated at 09:57 GMT, Monday, 30 November 2009
 

Large Hadron Collider sets world energy record

By Paul Rincon
Science reporter, BBC News

Large Hadron Collider (LHC) Courtesy: cern
The LHC is built inside a27km-long circular tunnel

The Large Hadron Collider (LHC) experiment on the French-Swiss border has set a new world record for energy.

The LHC pushed the energy of its particle beams beyond one trillion electron volts, making it the world's highest-energy particle accelerator.

The previous record was held by the Tevatron particle accelerator in Chicago.

Officials say it is another milestone in the LHC's drive towards its main scientific tests set for 2010.

The LHC is designed to smash together beams of sub-atomic particles at just under the speed of light. Researchers hope to see signs of new physics in the aftermath of the collisions, helping them unlock the secrets of the Universe.

Operated by the European Organisation for Nuclear Research (better known by its French acronym Cern), the LHC is built inside a 27km-long circular tunnel.

'Pilot beam'

"We are still coming to terms with just how smoothly the LHC commissioning is going," said Cern's director general Rolf Heuer.

"It is fantastic. However, we are continuing to take it step-by-step, and there is still a lot to do before we start physics in 2010. I'm keeping my champagne on ice until then."

Until now the LHC had been operating at a relatively low energy of 450 billion electron volts.

On Sunday, engineers increased the energy of this "pilot beam", reaching 1.18 trillion electron volts at 2344 GMT.

The previous record of 0.98 trillion electron volts has been held by the Tevatron accelerator since 2001.

The LHC is eventually expected to operate at some seven trillion electron volts.

Last week, the machine circulated two beams of protons for the first time and carried out its first low-energy beam collisions.

Researchers working on the collider have said they are delighted with the quick progress made since the machine restarted on 20 November.

The LHC had to be shut down for repairs shortly after its inauguration in September 2008 when an electrical fault caused one tonne of liquid helium to leak into the collider's tunnel.

Source: BBC
http://news.bbc.co.uk/2/hi/science/nature/8385891.stm

Comment:
Pull the choke right out, turn the key, gun the throttle when she starts to fire...what's so hard about that??

Posted by
Robert Karl Stonjek


#3253 From: "Robert Karl Stonjek" <stonjek@...>
Date: Mon Nov 30, 2009 8:47 pm
Subject: This Week in Physics - November 30, 2009
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This week in Physics — November 30, 2009
Viewpoint: A 21st century Rutherford experiment
Dieter Ackermann, Haik Simon, Physics 2, 101 (2009) – Published November 30, 2009

Collisions of neutron-rich helium nuclei with gold targets show how the internal arrangement of nucleons influences nuclear fusion reaction mechanisms.

   
Viewpoint: Nodes to the grindstone
Peter J. Hirschfeld, Physics 2, 100 (2009) – Published November 30, 2009

Raman spectroscopy of a cobalt-doped iron-pnictide superconductor reveals the complex electronic structure of the superconducting state in this material.

   
Synopsis: May cooler molecules prevail
Published November 30, 2009

Improved optical techniques may permit direct cooling of molecules to form ultracold gases, instead of cooling the atoms first.

   
Synopsis: Out of the substrate, an atomic chain
Published November 30, 2009

Under certain conditions, nanowires that form when a metal is deposited on a surface are primarily made of the substrate.

   
Synopsis: Outsmarting decoherence in a trapped ion quantum computer
Published November 30, 2009

Ion traps can store quantum information with long coherence times and support universal quantum computations.

   
Synopsis: A clean slate
Published November 30, 2009

Scanning tunneling spectroscopy can take advantage of the high-quality surface of Fe1+δSe1-xTex to learn more about iron-based superconductivity.

   
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#3252 From: "Robert Karl Stonjek" <stonjek@...>
Date: Sun Nov 29, 2009 11:27 pm
Subject: News: Spinons -- confined like quarks
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Spinons -- confined like quarks
November 29th, 2009 in Physics / General Physics

The concept of confinement is one of the central ideas in modern physics. The most famous example is that of quarks which bind together to form protons and neutrons. Now Prof. Bella Lake from Helmholtz-Zentrum Berlin (Germany) together with an international team of scientists report for the first time an experimental realization and a proof of confinement phenomenon observed in a condensed matter system.

The concept of confinement states that in certain systems the constituent particles are bound together by an interaction whose strength increases with increasing particle separation. In the case of quarks they are held together by the so called strong force, a force that grows stronger with increasing distance. As a consequence individual particles like quarks don't exist in a free state and their properties can be observed only indirectly.

In the 1990s Prof Alexei Tsvelik from Brookhaven National Laboratory (USA) and co-workers predicted an analogous confinement process in systems known as spin-ladders found in condensed mat-ter physics. Experimental confirmation of this phenomenon has however only been achieved recently as described by Bella Lake et al in the current issue of the journal .

Spin-ladders consist of two chains of copper oxide chemically bonded together. This makes the electrons interact strongly with each other. A remarkable feature of a single chain is that the individual electrons, which behave as an elementary charge combined with magnetic spin, co-operate in concert to separate into independent spin and charge parts. According to Bella Lake "The spin parts, known as spinons, have different properties to those of the original electrons. In fact they are analogous to quarks, the building blocks of protons and neutrons." On coupling two chains together to form a spin ladder the spin parts are found to recombine, but in a new way. "We have found, that excitations of individual chains, so called spinons, are confined in a similar way to that in which elementary quarks are held together", Bella Lake said.

The team of scientists have found evidence for the confinement idea by neutron scattering experiments on magnetic crystals of calcium cuprate (a copper-oxide material synthesized at the Leibniz Institute for Solid State and materials research in Dresden). The neutron experiments were performed using the MAPS spectrometer at the ISIS pulsed neutron source at Rutherford Appleton Laboratory, UK. Further the crystal and magnetic structure were investigated from neutron data collected on the E5 instrument at the research reactor BER II in Berlin.

The neutron scattering data show that the electrons essentially first split into spins and charges on the chains, then the spinons pair up again due to ladder effects. Prof Alan Tennant, the head of "Institute Complex Magnetic Materials" at HZB, explained: "The geometry of the ladder in fact plays a special role: the spinons always appear in pairs and when they move apart, they force a reorganisation of the intervening electrons that costs energy. The energy cost grows with separation - like a rubber band." According to Bella Lake "This strong pairing up of two spinons is like quarks binding together to form subatomic particles like hadrons and mesons."

Prof Alexei Tsvelik who developed the theoretical description explained "The formation of hadrons is well established on a qualitative level, but its quantitative aspects remain unresolved. It is unknown how to relate the theoretical parameters to the observed hadron masses. This is one of the reasons why condensed matter analogues are interesting. They provide examples of confinement for which detailed descriptions have been achieved."

More information: Nature Physics, DOI: 10.1038/NPHYS1462

Source: Helmholtz Association of German Research Centres (news : web)
http://www.physorg.com/news178724926.html

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#3251 From: "Robert Karl Stonjek" <stonjek@...>
Date: Sun Nov 29, 2009 2:26 am
Subject: News: Milky Way Grew by Swallowing Other Galaxies
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Picture of globular clusters
Ingested. Globular clusters such as Terzan 5 and M22 (inset) are the remnants of other galaxies swallowed by the Milky Way.

Credit: F. R. Ferraro/Università di Bologna (main image); Jae-Woo Lee/Sejong University (inset)

Milky Way Grew by Swallowing Other Galaxies

By Phil Berardelli
ScienceNOW Daily News
25 November 2009

The motto "E Pluribus Unum" ("out of many, one") could be applied to the Milky Way. Astronomers have obtained new evidence that our home galaxy contains pieces of many former galaxies. The findings strengthen the idea that large galaxies don't emerge whole from single, gigantic clouds of dust and gas. Rather, they grow by swallowing their neighbors.

The clues come from globular clusters--spherical concentrations of up to millions of stars, orbiting the galactic center as self-contained neighborhoods. Aside from our galaxy's huge spiral arms, globular clusters constitute some of its most striking features. Astronomers have long thought they formed from concentrated clouds of gas and dust in the early Milky Way. But two papers in tomorrow's issue of Nature paint an entirely different portrait.

In one paper, a team of Korean astronomers measured the calcium content of stars in 37 of the Milky Way's 158 known globular clusters. About half contained significant amounts of the element, indicating that they had formed from the remnants of supernovae, the titanic explosions of giant stars that once manufactured calcium and other heavy elements in their cores. This finding is significant, says lead author Jae-Woo Lee of Sejong University in Seoul, because it indicates the globular clusters must have once been much larger than they are today. Otherwise, they wouldn't have exerted the gravitational force needed to trap the supernovae remnants so that they could condense into new stars. "This led us to believe that many of the globular clusters we studied are most likely the relics of more massive, primeval dwarf galaxies that merged with [the Milky Way]," he says.

In the second paper, an international team found further evidence for this idea in a globular cluster called Terzan 5. Located above the center of the Milky Way in an area called the galaxy's bulge, the cluster contains an extraordinary number of pulsars, the ultradense, rapidly spinning remnants of supernovae. Chemical analysis revealed that the material ejected in these explosions, rather than escaping from the cluster at high velocity, stuck around to form new stars. This feat required the gravity of a galaxy with up to 1000 times more mass than Terzan 5 currently has. As in the other study, the most likely explanation is that Terzan 5 was once a much larger galaxy that was swallowed by the Milky Way, says lead author Francesco Ferraro of the Università di Bologna in Italy. When Terzan 5 and the other dwarf galaxies merged with the Milky Way, he explains, the collision sheared off many of their stars, leaving the smaller clusters we see today.

Ferraro says further studies of globular clusters should produce more such surprises. "These systems are real gold mines of information," he says, "and each time we observe them they reveal a new, unexpected secret."

The findings could turn previous assumptions about globular clusters on their head, says astronomer David Weinberg of Ohio State University, Columbus. Researchers used to think that one of the Milky Way's clusters, Omega Centauri, was an anomaly because it used to be its own galaxy. Now, Weinberg says, "it looks like anomalous is becoming the new normal."

Source: Science
http://sciencenow.sciencemag.org/cgi/content/full/2009/1125/2?etoc

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#3250 From: "Robert Karl Stonjek" <stonjek@...>
Date: Sun Nov 29, 2009 2:22 am
Subject: News: An Update on the Leaked Climate E-mails and a "Dating Service" for Scientists and Teachers
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Picture of spintronics
Novel twist. Ordinary electronics uses only the electrons charge; spintronics would also encode information in an electron’s spin, which causes the particle to be magnetized along its axis.

Credit: Lawrence Berkeley National Laboratory

A New Spin on Electronics

By Adrian Cho
ScienceNOW Daily News
25 November 2009

You're reading this story on a computer whose chips shift tiny packets of electric charge through circuits etched in the ubiquitous semiconductor silicon. But some physicists aim to develop a whole new technology called "spintronics" that would encode information in the directions in which electrons spin as well. Those efforts could lead to ultra-low-power electronics and even futuristic quantum computers. Now, such technologies may be an important step closer to reality thanks to a group of researchers that has managed to polarize the spinning electrons in silicon, the most common commercial semiconductor.

Such "spin injection" had been achieved before in more exotic semiconductors, such as gallium arsenide and indium arsenide. The trick is to lay a patch of magnetic metal such as nickel iron on top of the semiconductor. The whole reason the metal is magnetic is that more of its electrons' spins point in one way than in the opposite way. So if a current can be driven from the metal into the semiconductor, it should deposit spin-polarized electrons in it. Physicists have shown that those electrons will hold their polarization long enough to flow micrometers through the semiconductor, which should be far enough to use them in circuits.

Incorporating both the magnetic leads and the underlying semiconductor, a spintronics circuit could hold its memory when turned off, as the magnetic elements remain magnetized. Manipulating spin could also require far less power than steering charges does, says Ron Jansen of the University of Twente in Enschede, Netherlands. Some physicists even aspire to create a spooky quantum connection called "entanglement" between spin-polarized currents to make a quantum computer that could crack problems that stymie an ordinary one.

Spin injection had been achieved at room temperature, however, only in materials like gallium arsenide. In silicon it had been done only at temperatures below 150 kelvin. Now Jansen, Saroj Dash, and colleagues at Twente have brought silicon in from the cold, too. To do that, they relied on a simple and elegant scheme to inject and detect the spins with a single nickel iron electrode separated from the silicon with a very even layer of aluminum oxide. As current flowed out of the electrode, it produced a puddle of polarized electrons in the silicon below it. But the researchers could dissipate this polarized puddle by applying a magnetic field, which for a fixed current would cause the voltage across the contact to decrease in a telltale way. And that's exactly what they observed, as the team reports tomorrow in Nature.

To prove that the voltage change wasn't caused by something else, the researchers conducted a control experiment in which they separated the aluminum oxide and the nickel iron with a layer of the metal ytterbium, which destroyed the spin polarization. In that case, the voltage across the contact remained constant even when the magnetic field was ramped up, proving that polarized electrons caused the original effect.

It's a "compelling demonstration," says Paul Crowell, a physicist at the University of Minnesota, Twin Cities. The next step, he says, is to conduct multielectrode measurements that show spin-polarized currents actually flowing through the silicon. The result raises the possibility of quick and simple spintronics applications, he says. "For a chip that needs a relatively simple memory, I think this could be realized in silicon fairly easily." But the grand goals of spintronics, such as ultralow power consumption, remain years away, Crowell says--and Jansen agrees.

Soure: Science
http://sciencenow.sciencemag.org/cgi/content/full/2009/1125/4?etoc

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#3249 From: "Robert Karl Stonjek" <stonjek@...>
Date: Fri Nov 27, 2009 11:51 pm
Subject: News: Spin polarization achieved in room temperature silicon
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Spin polarization achieved in room temperature silicon
November 27th, 2009 in Physics / General Physics
Spin polarization achieved in room temperature silicon

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(PhysOrg.com) -- A group in The Netherlands has achieved a first: injection of spin-polarized electrons in silicon at room temperature. This has previously been observed only at extremely low temperatures, and the achievement brings spintronic devices using silicon as a semiconductor a step closer.

Spintronics, or spin electronics, is an emerging field of electronics that aims to be able to represent digital information by using the spin of electrons as well as their charge. When fully developed, spintronic devices could profoundly change data storage devices, computer architecture and so on, and they could reduce energy use to ultra-low levels.

Electrons are basically a two-state system with their spins either "up" or "down". For a spintronics device to work, it must have a system (the spin injector) that produces a spin-polarized electric current, which has more of its electrons in one spin state than the other. It also needs a spin detector that can detect whether the electrons are up or down.

In metallic systems spin polarization is generally achieved by passing an electric current through a ferromagnet. (It is magnetic because the electrons within it are polarized, and as they pass from the magnet to the metal they remain polarized for a short time.) Spin polarization has also been achieved at room temperature in ferromagnetic semiconductors such as manganese-doped gallium arsenide.

Until recently spin polarization in non-magnetic semiconductors like silicon has only been achieved at temperatures of 150 K, but new research has achieved spin polarization at ambient temperature. Scientists Saroj P. Dash and colleagues at the MESA Institute for Nanotechnology at the University of Twente in The Netherlands used a single nickel-iron electrode on top of silicon, with a layer of aluminum oxide between them. When they applied a current to the electrode they observed a "puddle" of electrons in the silicon, which could then be dissipated by applying a magnetic field. This caused an observable voltage drop across the contact.

As a control they inserted a layer of ytterbium between the electrode and the aluminum oxide, since ytterbium is known to destroy spin polarization. When the current and magnetic field were applied, no voltage drop was observed, which indicates that spin polarized electrons had caused the effect.

Spintronics could eventually lead to extremely low energy use devices, and perhaps ultimately to quantum computers. More research is needed to prove the spin-polarized currents really flow through the silicon, and it may still be several years before the promised ultra-low power devices are developed.

The research was published yesterday in the journal, Nature.

More information: Electrical creation of spin in at room temperature, Nature 462, 491-494 (26 November 2009), doi:10.1038/nature08570

© 2009 PhysOrg.com
http://www.physorg.com/news178526124.html

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#3248 From: "Robert Karl Stonjek" <stonjek@...>
Date: Fri Nov 27, 2009 11:47 pm
Subject: News: Herschel takes a peek at the ingredients of the galaxies
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Herschel takes a peek at the ingredients of the galaxies
November 27th, 2009 in Space & Earth / Astronomy
Herschel takes a peek at the ingredients of the galaxiesEnlarge

Figure 1. Credit: ESA

(PhysOrg.com) -- The European Space Agency has today released spectacular new observations from the Herschel Space Observatory, including the UK-led SPIRE instrument. Spectrometers on board all three Hershel instruments have been used to analyse the light from objects inside our galaxy and from other galaxies, producing some of the best measurements yet of atoms and molecules involved in the birth and death of stars.

The SPIRE Fourier Transform Spectrometer (FTS), which covers the whole submillimetre wavelength range between 194 and 672 microns, will be invaluable to astronomers in determining the composition, temperature, density and mass of interstellar material in nearby galaxies and in star-forming clouds in our own galaxy.

Professor Keith Mason, Chief Executive of the Science and Technology Facilities Council (STFC), which provides the UK funding for Herschel, said “Herschel has once again returned some spectacular indications of what is to come. This wealth of new data exists because of the dedication and skill of the scientists working on this project and will vastly expand our knowledge of the life cycle of stars.”

Professor Matt Griffin of Cardiff University, who is the SPIRE Principal Investigator, said: “Some trial observations have been made during initial testing of the spectrometer, and it is clear that the data are of excellent quality, and even these initial results are very exciting scientifically, especially our ability to trace the presence of water throughout the Universe. The spectrometer was technically very challenging to build, and the whole team is delighted that it works so well.”

Herschel takes a peek at the ingredients of the galaxies

Enlarge

Figure 2. Credit: ESA

Professor Glenn White, of the Open University and STFC’s Rutherford Appleton Laboratory, and an expert in the field of molecular astronomy for which the SPIRE spectrometer is designed, said: "The exquisite sensitivity and quality of these early data reveal spectacular spectroscopic signatures that show the diversity and complexity of the birth processes common to the formation of star and planets. Herschel is going to help us trace the evolution and life of stars, to map the chemistry in our galactic neighbourhood, and allow us to detect water and complex molecules in distant galaxies."

Professor Mike Barlow of University College London, who will use the SPIRE instrument to study the material ejected into space by stars near the end of their lives, said: “The unprecedented spectral range and the wealth of detail revealed by the SPIRE spectrometer, in a hitherto almost unexplored region of the spectrum, promises to revolutionise our understanding of the formation of molecules and dust particles during the final stages of the lives of stars. These dust particles go on to play a crucial role in the formation of new stars and provide the raw material for the planetesimals and planets that form around them."

Figure 1 shows part of the SPIRE spectrum of VY Canis Majoris (VY CMa), a giant star near the end of its life, which is ejecting huge amounts of gas and dust into interstellar space, including elements such as carbon, oxygen and nitrogen (which form the raw material for future planets, and eventually life). The inset is a SPIRE camera image of VY CMa, in which it appears as a bright point-source near the edge of a large extended cloud. The spectrum is amazingly rich, with prominent features from carbon monoxide (CO) and water (H2O). More than 200 other spectral features have also been identified, many due to water, showing that the star is surrounded by large quantities of hot steam. Observations like these will help to establish a detailed picture of the mass loss from stars and the complex chemistry occurring in their extended envelopes.

Herschel takes a peek at the ingredients of the galaxies

Enlarge

Figure 3. Credit: ESA

Figure 2 is a spectrum of one position on the Orion Bar, part of the Orion nebula in which the gas on the edge of the nebula is partly ionised by intense radiation from nearby hot young stars. The inset shows a near infrared picture from NASA’s Spitzer Space Telescope. The SPIRE spectrum has many features from CO, appearing as the dominating narrow lines, seen here for the first time together in a single spectrum. These mean that the entire spectrum is observed at the same time and calibrated together. The brightness of the spectral features will allow astronomers to estimate the temperature and density of interstellar gas. The spectrum also shows the first detection of an emission feature from the molecular ion methylidynium (CH+), a key building block for larger carbon-bearing molecules. This and similar regions are large, and the SPIRE spectrometer’s will be extremely powerful in characterising how the gas properties vary within such sources.

Figure 3 shows a SPIRE spectrum of Arp 220, a galaxy 250 million light years away from Earth with very active star formation triggered when two large spiral galaxies collided to produce the complex object we see today. Arp 220 is an important template for understanding even more distant galaxies and galaxy formation in the early universe. The spectrum shows many emission features of CO, and H2O features are seen both in emission and absorption. The inset is an optical image of Arp 220 made with the Hubble Space Telescope.

Figure 4 shows the spectrum of Messier 82 (M82), a nearby galaxy (only 12 million light years away) with very active star formation. It is part of an interacting group of galaxies including the large spiral M81. The accompanying image (inset) is a spectacular three-colour composite picture of the two galaxies made with the SPIRE camera, showing material being stripped from M81 by the gravitational interaction with M82. The SPIRE spectrum of M82 shows strong emission lines from CO over the whole range, as well as emission lines from atomic carbon and ionized nitrogen.

Herschel takes a peek at the ingredients of the galaxies

Enlarge

Figure 4. Credit: ESA

The SPIRE FTS observations were carried out as part of the performance verification of the observatory. The scientific rights of some of these observations are owned by Key Programme consortia: for Arp 220 and M82, the Nearby Galaxies consortium lead by C. Wilson; for VY CMa the MESS consortium led by M. Groenewegen; for the Orion Bar, the Evolution of Interstellar Dust consortium led by A. Abergel.

Provided by Science and Technology Facilities Council (news : web)
http://www.physorg.com/news178551842.html

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#3247 From: "Robert Karl Stonjek" <stonjek@...>
Date: Fri Nov 27, 2009 11:50 pm
Subject: News: Multiferroic compounds used to produce smaller and cheaper digital memories
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Multiferroic compounds used to produce smaller and cheaper digital memories
November 27th, 2009 in Physics / Condensed Matter
Multiferroic compounds used to produce smaller and cheaper digital memoriesImage of the ferroelectric domains of the multiferroic compound BiFeO3. © A. Mougin, CNRS 2009

(PhysOrg.com) -- Is it possible to make even more compact digital memories for portable electronic devices and which consume even less energy? A team of French researchers has recently demonstrated that it is feasible, thanks to a new class of materials known as multiferroics, which combine unusual electric and magnetic properties.

At a microscopic scale, atoms and molecules produce electric and magnetic fields. At our own scale, in the majority of crystals, the electric and magnetic properties of the various atoms offset one another and cancel each other out. Sometimes, however, this is not the case and in certain compounds, known as ferromagnetics, magnetic properties subsist at a macroscopic scale and can therefore act as a magnet.

Less commonly, an electric order can exist at the macroscopic scale; such is the case with what are known as ferroelectric compounds. Even more rarely, electric and magnetic orders exist at one and the same time, as is the case with multiferroic materials. Moreover, in these materials, the electric and magnetic orders interact. Such interaction offers the opportunity of controlling the spins (the magnetic moments) of the atoms via an electric field, thus opening whole new perspectives particularly as regards information storage.

Researchers at the Laboratoire de Physique des Solides, the Institut Rayonnement-Matičre de Saclay and the Institut Néel first synthesized the multiferroic compound BiFeO3 and then demonstrated the interaction between its electric and magnetic orders. They then produced a material formed of a layer of BiFeO3 and a ferromagnetic film and showed that they were able to modify the preferential orientation of the magnetization of the ferromagnetic film by applying an electric field. These pioneering results validate the concept of storing and writing magnetic data using an electric field.

In today's hard discs, data - or bits - are written using a magnetic field that directs the magnetization, which imposes the bit value. There are two possible magnetization states and thus two possible bit values (designated 0 or 1). With a multiferroic material, each memory element could be placed in four distinct states instead of two (two electrical polarization states and two magnetization states). Magnetic memories with two states (like existing memories), but which can be modified through the application of an electric field, could also be envisaged.

This possibility of writing and erasing data using an electric field constitutes a decisive advantage in mobile electronic devices (mobile phones, laptop computers, GPS, etc.) from two points of view. Firstly, the application of an electric field requires less energy than the application of a magnetic field and therefore batteries would last longer. Secondly, the electric field would be more local, which would mean more memory elements could be packed onto a given surface and thus enable component miniaturization to be pushed even further.

More information: Electric field switching of the magnetic anisotropy of a ferromagnetic layer exchange coupled to the multiferroic compound BiFeO3. D. Lebeugle, A. Mougin, M. Viret, D. Colson, L. Ranno. Physical Review Letters, 18 November 2009.

Provided by CNRS
http://www.physorg.com/news178546236.html

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#3246 From: "Robert Karl Stonjek" <stonjek@...>
Date: Fri Nov 27, 2009 4:36 am
Subject: News: Gullies and Flow Features on Crater Wall
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Gullies and Flow Features on Crater Wall
November 26th, 2009 in Space & Earth / Space Exploration
Gullies and Flow Features on Crater WallThis image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter shows a sample of the variety and complexity of processes that may occur on the walls of Martian craters, well after the impact crater formed. Image Credit: NASA/JPL-Caltech/University of Arizona

(PhysOrg.com) -- This image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter shows a sample of the variety and complexity of processes that may occur on the walls of Martian craters, well after the impact crater formed.

At the very top of the image is the high crater rim. At the bottom of the image is the crater's central peak, a dome of material rising above the surrounding crater floor. The central peak was uplifted during the impact event.

Reaching down the walls of the crater are winding and crooked troughs, or gullies. Some of these gullies may have formed with the help of liquid water, melted from ice or snowpack on the crater walls or from groundwater within the walls. Also notable is the long tongue-like lobe stretching down the middle of the image, with a darker, rounded snout and prominent parallel grooves on its surface. These characteristics, together with faint cracks on its surface, suggest that this lobe may have formed by movement of ice-rich material from up on the crater wall down to the crater floor.

Because surface features on this lobe and on most of the gullies do not appear sharp and pristine, and because wind-blown dunes have blown up on the front snout of the lobe, and because there are several small craters on the lobe's surface, the movements of ice-rich material and possibly water have probably not occurred very recently.

This image covers a swath of ground about 6 kilometers (4 miles) wide, centered at 32.4 degrees south latitude, 103.2 degrees east longitude. It is one product from HiRISE observation ESP_013726_1475, made on July 1, 2009. Other image products from this observation are available at http://hirise.lpl.arizona.edu/ESP_013726_1475 .

Provided by JPL/NASA (news : web)
http://www.physorg.com/news178453746.html

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#3245 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Nov 26, 2009 9:20 am
Subject: News: Without maths we’re lost in a dark labyrinth
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Without maths we’re lost in a dark labyrinth | Marcus du Sautoy - Times Online

It’s the glue that binds scientific and artistic cultures. The language of number and symmetry is spoken everywhere

When I was a kid I hadn’t wanted to be a mathematician at all. My dream had been to become a spy. This ambition was fuelled by too many visits to see Roger Moore playing 007 at our local cinema combined with the misconception that my mum, who was once in the diplomatic corps, had been a spy. To realise my dream I decided I would follow in my mum’s footsteps and join the Foreign Office.

Speaking foreign languages seemed to be the key to fulfilling my dream, so when I went to secondary school I signed up for all the languages my school taught. It did French and German. It was one of the few comprehensive schools still teaching Latin. There was a course on the BBC teaching Russian. Being a boy of the Cold War I thought that was an ideal language for anyone dreaming to become a spy. So I got my French teacher to help me with Russian.

But as I battled away with these languages I became increasingly frustrated with the illogical spellings, the endless irregular verbs that didn’t make any sense and which you just had to learn. I’ve always had a terrible memory and yearned for a sense of order and logic.

At the height of this crisis my maths teacher pulled me aside. Almost conspiratorially he let on that the maths we were doing in the classroom wasn’t really what mathematics was about and he suggested a few books that he thought might open up the real world of mathematics to me. One of the books was called The Language of Mathematics. I was intrigued. I’d never thought of mathematics as a language. As I read further through the book I realised that this was the language I’d been hankering after.

First, it didn’t seem to have any irregular verbs. Everything made logical sense, evolving naturally from a few natural assumptions. That’s not to say that there weren’t surprising twists and turns throughout the story, but they all made sense. The most exciting discovery was the power of this language to describe the natural world. It had the power to reveal where it had all come from but, more excitingly, to predict what will happen next: for example, to make sense of what is happening (or almost happening) in the Large Hadron Collider, which uses the mathematics of strange symmetrical objects in hyperspace. To assess the potential effect of travel restrictions or vaccinations on the spread of the H1N1 virus requires mathematical modelling. And climate change is a mathematical problem: it’s only by understanding the delicate mathematical relationship between different factors in the environment that we can understand why temperatures are rising.

Mathematics brings a transparency to these complex systems. But it isn’t only the scientists who are speaking this language. It is extraordinary how many interesting mathematical ideas one can find bubbling beneath the surface of the work of many artists. Either consciously or subconsciously they are drawn to the same mathematical structures that fascinate me.

Messiaen consciously exploited the asynchronicity of the prime numbers 17 and 29 to create a sense of timelessness in the Quartet for the End of Time. In another piece, Île de Feu, I cannot believe he was aware that the two twelve-note sequences he uses are the basis for generating one of the strangest symmetrical objects discovered by mathematicians in our mathematical journey through symmetry. But it is a sensitivity to similar structures that drew him to these two themes. From the magnificence of the Baroque to the modern architecture of Arup, Foster and Hadid, one can find complex mathematical curves running through the buildings that surround us. The writing of Borges is infused with a fascination with infinity and the nature of space.

With mathematics acting like a glue binding all these different scientific and artistic cultures together I believe that mathematics provides a perfect platform for my job as the new Simonyi Professor for the Public Understanding of Science, which I have held for a year. In some strange sense I have found myself realising my dream to join the Foreign Office. I see my role rather like an ambassador for the often alien world of science, trying to provide bridges for a society that is sometimes suspicious of this powerful territory.

Given how much scientific and technological developments permeate modern life, it is essential that society understands what is happening in our world. The Jenkins report in 2000 identified that more dialogue was needed between the scientific community and society. But I believe one can only have genuine dialogue if you’ve got understanding. How can you have a debate about stem-cell research if you don’t understand what a stem cell is? That’s not to say that the scientists know all the answers. Many of the interactions between science and society need input from many different perspectives. Scientific research is key to understanding the relative dangers of different drugs but scientists need to understand that drugs are not purely a scientific question, that there is a social and political dimension. But without the understanding of the science, this debate doesn’t get going.

The challenging thing for me is that science is not just a single country. It is a continent full of very different cultures. I was out of my depth when I was phoned up by a news channel to explain on the spot the work of the Nobel Prize for Medicine announced that morning. By the following day I’d talked to colleagues enough to download in my Sexy Science column the essence of how telomeres protect chromosomes as they divide and multiply. Just imagine a professorship for the Public Understanding of the Humanities who had to represent everything from philosophy to medieval painting, from South American literature to the music of the Baroque.

It is one of my aspirations during the tenure of my professorship to encourage government, research councils and universities that the more scientific ambassadors we can support the better chance we have of integrating the foreign world of science with the rest of society. Without an understanding of the language of science and mathematics, as Galileo once wrote, we will all be wandering around lost in a dark labyrinth.

From Marcus du Sautoy’s inaugural lecture as the Simonyi Professor for the Public Understanding of Science at the University of Oxford.

Source: Times Online
http://www.timesonline.co.uk/tol/comment/columnists/guest_contributors/article6932402.ece

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#3244 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Nov 26, 2009 7:57 am
Subject: Book review: Kettle as myth, engineer as chemist
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Kettle as myth, engineer as chemist

David Philip Miller: James Watt, chemist: understanding the origins of the steam age
Pickering & Chatto, London, 2009. Pp. , £60.00 (hardback). ISBN 978-1-85196-974-6.
 
Jane Insley
Science Museum, South Kensington, London SW7 2DD, UK

James Watt (1736–1819) was deeply integrated into the intellectual and entrepreneurial circles of his day, which have been studied and described in many ways. In his book David Miller addresses the history of Watt's activities in chemistry firmly in the context of both his steam engine work and the rest of his intellectual environment.

In the introduction he gives a brief overview of Watt's life, and the cultivation of his public image and reputation. He also outlines the specific intent of his study, ‘to partially recast our understanding of James Watt's improvements of the steam engine and the natural philosophical basis for them’. This is in preference to a comprehensive history of Watt's chemical connections and activities. Miller asserts that a history of Watt's chemistry written apart from the steam engine activity would reinforce an artificial divide between the two and hinder the understanding of both. A broader purpose is to exemplify some of the ways in which historical sources can be profoundly misleading, through both accident and design, and also at the time and afterwards.

There are two main sections in the book. The first is ‘Representations’—of statues, kettles and engine indicators (including a bizarre story with a photograph of a visitor information office in the form of a giant yellow kettle), the demise of the ‘chemical Watt’ in the nineteenth century, and the rise of the ‘mechanical Watt’ as a philosophical engineer. The second part, ‘Realities’, discusses Watt's chemistry of heat, the steam engine as chemistry, and the evolution of the indicator, or ‘Why Watt was not a proto-thermodynamicist’.

For a short refresher survey of James Watt's chemical work, I would recommend a quick look at the 1985 paper1 by Jennifer S. Pugh and John Hudson (which is not mentioned in the bibliography). Alternatively, the first few pages of the second section cover it, but by then you are already halfway through. In this section, Miller emphasizes his belief that it is a mistake to separate Watt's philosophical chemistry (on the chemistry of water and airs, frequently presented as ‘failure’) from his ‘cookbook chemistry’ (on glazes, varnishes, inks, bleaching agents, medically promising airs and, of course, steam, which were ingenious, entrepreneurial and in a very real way successful). Miller's argument is that Watt was thoroughly convinced that there was a connection between the chemistry of airs and the chemistry of steam, so his practical and theoretical studies were interrelated as a result.

The health warning is that Watt was not a systematic chemist. He read widely and operated in a magpie fashion, picking up and developing ideas if they looked as though they might be useful. Eighteenth-century chemistry was in a complex and confused state, and Watt straddled the rival concepts of phlogiston and oxygen. Miller characterizes Watt as a ‘lumper’ rather than a ‘splitter’, believing in a fundamental unity of families of airs rather than seeing the newly discovered airs as having distinct chemical identities.

The temptation is to quote extensively from the text—Miller has an enjoyable writing style, and it is anything but a turgid read. The balance of the book is good—the two sections are topped and tailed with introduction and conclusions, one-fifth of the book is endnotes (given at the back of the book and keyed to the pages on which they occur, which in my view works well) and the 16-page bibliography is very wide-ranging, as it must be if one is scouring the literature for examples of representation and appropriation. The book looks handsome overall, but the pictures are halftone (oh, those dots—the pictures are screened photos, giving a pre-pixellation dotted appearance which is a little odd in these days of high-resolution digital imagery) and I did note two howler typographic errors on my first read through, which ruined their respective sentences (on pages 104 and 117, for any future editions or reprints).

The archival resources for James Watt may be finite, but they are also vast; there is plenty of scope still for revisiting and for the extraction of fruitful insights. References to them are not, however, immutable—the huge microfilm resource of his correspondence and papers generated at Birmingham Central Library from 1993 has been re-catalogued, and roll numbers have changed. Nevertheless the availability of microfilm allows historical study at a distance, a facility increasingly offered through the World Wide Web. This will have been useful for Miller, who is currently based at the University of New South Wales in Sydney, although as his acknowledgements make clear he has travelled extensively overseas to pursue his interest. And on the Web things can change—he has noted that a couple of his references are from Web pages that have been discontinued, a prospect it is worth remembering.

I read this book with considerable interest as I am currently privileged to be researching the chemicals in James Watt's garret workshop, preserved at the Science Museum, London. This is the kitchen cupboard for his cookbook chemistry. It is therefore a timely reminder for me that, as Miller says in conclusion, ‘James Watt was a chemist. He was also an engineer. We understand him, and the origins of the steam age, better if we can see him as both at the same time.’

Footnotes

  • 1 John Hudson and Jennifer S. Pugh, ‘The chemical work of James Watt, F.R.S.’, Notes Rec. R. Soc. 40, 41–52 (1985).

Source: The Royal Society
http://rsnr.royalsocietypublishing.org/content/early/2009/11/24/rsnr.2009.0069.full?papetoc

Posted by
Robert Karl Stonjek


#3243 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Nov 26, 2009 5:21 am
Subject: News: Researchers develop virtual streams to help restore real ones
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Researchers develop virtual streams to help restore real ones
November 24th, 2009 in Physics / General Physics

Researchers at the University of Minnesota have developed a unique new computer model called the Virtual StreamLab, designed to help restore real streams to a healthier state. The Virtual StreamLab, which demonstrates the physics of natural water flows at an unprecedented level of detail and realism, was unveiled for the first time this week at the 2009 American Physical Society Division of Fluid Dynamics meeting in Minneapolis, one of the largest conferences in fluid dynamics with more than 1,500 attendees from around the world.

The University of Minnesota team of researchers led by civil engineering professor Fotis Sotiropoulos, director of the University's St. Anthony Falls Laboratory (SAFL), developed the Virtual StreamLab to help improve stream restoration processes. They have completed their first simulation of SAFL's Outdoor StreamLab, a scaled natural stream along the Mississippi River. More than 90 million data points have been mapped into the team's computer model resulting in the most accurate model of a real stream to date. The Virtual StreamLab employs sophisticated numerical algorithms that can handle the arbitrarily complex geometry of natural waterways, features advanced turbulence models, and utilizes the latest advances in massively parallel supercomputers.

The ability to simulate water flow over topography with this degree of realism provides researchers with the insights necessary to improve sustainable stream restoration strategies, helping to optimize techniques to fight erosion, help prevent flooding and restore aquatic habitats in degraded waterways.

Recent national data shows that 44 percent of the nation's 3.5 million miles of rivers and streams have become degraded due to sedimentation and excess nutrients. This decline has led to impaired water quality over entire watersheds, rendering many streams unhealthy for recreation and public contact. The effects also have serious consequences for the health of aquatic life. Efforts to restore these bodies of water have resulted in an annual cost of more than $1 billion in the United States alone.

Historically, efforts have involved installing structures in the stream to change the direction and speed of the water, but with little ability to fine-tune a stream's reactions. Past computer models often oversimplify the stream systems and can't accurately simulate the beds, complicated bank shapes, turbulence, and natural or man-made structures within them.

"The practice of stream restoration has had a rocky rate of success as practitioners have struggled to alter a natural system with countless unknowns," Sotiropoulos said. "The need for more effective and reliable stream restoration strategies is clear, but the underlying physical processes which govern the behavior of a stream and its inhabitants are very complex. Our new Virtual StreamLab should provide researchers with a deeper understanding of those complexities."

Source: University of Minnesota (news : web)
http://www.physorg.com/news178315462.html

Posted by
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#3242 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Nov 26, 2009 5:16 am
Subject: News: Cosmic 'Dig' Reveals Vestiges of the Milky Way's Building Blocks
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Cosmic 'Dig' Reveals Vestiges of the Milky Way's Building Blocks
November 25th, 2009 in Space & Earth / Astronomy
Cosmic 'dig' reveals vestiges of the Milky Way's building blocksPeering through the thick dust clouds of our galaxy's central parts (the "bulge") with an amazing amount of detail, a team of astronomers has revealed an unusual mix of stars in the stellar grouping known as Terzan 5. Never observed anywhere in the bulge before, this peculiar cocktail of stars suggests that Terzan 5 is in fact one of the bulge's primordial building blocks, most likely the relic of a dwarf galaxy that merged with the Milky Way during its very early days. This near-infrared image was obtained with the Multi-conjugate Adaptive Optics Demonstrator (MAD) instrument on ESO's Very Large Telescope. Observations in two bands (J and K) were combined. The field of view is 40 arcseconds across. Credit: ESO/F. Ferraro

(PhysOrg.com) -- Peering through the thick dust clouds of our galaxy's "bulge" (the myriads of stars surrounding its center), a team of astronomers has unveiled an unusual mix of stars in the stellar grouping known as Terzan 5. Never observed anywhere in the bulge before, this peculiar "cocktail" of stars suggests that Terzan 5 is in fact one of the bulge's primordial building blocks, most likely the relic of a dwarf galaxy that merged with the Milky Way during its very early days.

"The history of the Milky Way is encoded in its oldest fragments, globular clusters and other systems of stars that have witnessed the entire evolution of our galaxy," says Francesco Ferraro, lead author of a paper appearing in this week's issue of the journal Nature. "Our new study opens a new window on yet another piece of our galactic past."

Like archaeologists, who dig through the dust piling up on top of the remains of past civilisations and unearth crucial pieces of the history of mankind, astronomers have been gazing through the thick layers of interstellar dust obscuring the bulge of the Milky Way and have unveiled an extraordinary cosmic relic.

The target of the study is the star cluster Terzan 5. The new observations show that this object, unlike all but a few exceptional globular clusters, does not harbour stars which are all born at the same time — what astronomers call a "single population" of stars. Instead, the multitude of glowing stars in Terzan 5 formed in at least two different epochs, the earliest probably some 12 billion years ago and then again 6 billion years ago.

"Only one globular cluster with such a complex history of star formation has been observed in the halo of the Milky Way: Omega Centauri," says team member Emanuele Dalessandro. "This is the first time we see this in the bulge."

The galactic bulge is the most inaccessible region of our galaxy for astronomical observations: only infrared light can penetrate the dust clouds and reveal its myriads of stars. "It is only thanks to the outstanding instruments mounted on ESO's Very Large Telescope," says co-author Barbara Lanzoni, "that we have finally been able to 'disperse the fog' and gain a new perspective on the origin of the galactic bulge itself."

Cosmic 'Dig' Reveals Vestiges of the Milky Way's Building BlocksThis wide-field image, based on data from Digitized Sky Survey 2, shows the whole region around the stellar grouping Terzan 5.

A technical jewel lies behind the scenes of this discovery, namely the Multi-conjugate Adaptive Optics Demonstrator (MAD), a cutting-edge instrument that allows the VLT to achieve superbly detailed images in the infrared. Adaptive optics is a technique through which astronomers can overcome the blurring that the Earth's turbulent atmosphere inflicts on astronomical images obtained from ground-based telescopes; MAD is a prototype of even more powerful, next-generation adaptive optics instruments.

Through the sharp eye of the VLT, the astronomers also found that Terzan 5 is more massive than previously thought: along with the complex composition and troubled star formation history of the system, this suggests that it might be the surviving remnant of a disrupted dwarf galaxy, which merged with the Milky Way during its very early stages and thus contributed to form the galactic bulge.

"This could be the first of a series of further discoveries shedding light on the origin of bulges in galaxies, which is still hotly debated," concludes Ferraro. "Several similar systems could be hidden behind the bulge's dust: it is in these objects that the formation history of our Milky Way is written."

More information: This research was presented in a paper that appears in the 26 November 2009 issue of Nature , "The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge", by F. R. Ferraro et al.

Source: ESO (news : web)
http://www.physorg.com/news178377940.html

Posted by
Robert Karl Stonjek


#3241 From: "Robert Karl Stonjek" <stonjek@...>
Date: Thu Nov 26, 2009 5:24 am
Subject: News: The Discrete Fourier Transform
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Explained: The Discrete Fourier Transform
November 25th, 2009 in Other Sciences / Mathematics
Explained: The Discrete Fourier Transform(PhysOrg.com) -- In 1811, Joseph Fourier, the 43-year-old prefect of the French district of Isčre, entered a competition in heat research sponsored by the French Academy of Sciences. The paper he submitted described a novel analytical technique that we today call the Fourier transform, and it won the competition; but the prize jury declined to publish it, criticizing the sloppiness of Fourier’s reasoning. According to Jean-Pierre Kahane, a French mathematician and current member of the academy, as late as the early 1970s, Fourier’s name still didn’t turn up in the major French encyclopedia the Encyclopædia Universalis.

Now, however, his name is everywhere. The Fourier transform is a way to decompose a signal into its constituent frequencies, and versions of it are used to generate and filter cell-phone and Wi-Fi transmissions, to compress audio, image, and video files so that they take up less bandwidth, and to solve differential equations, among other things. It’s so ubiquitous that “you don’t really study the Fourier transform for what it is,” says Laurent Demanet, an assistant professor of applied mathematics at MIT. “You take a class in signal processing, and there it is. You don’t have any choice.”

The Fourier transform comes in three varieties: the plain old Fourier transform, the Fourier series, and the discrete Fourier transform. But it’s the discrete Fourier transform, or DFT, that accounts for the Fourier revival. In 1965, the computer scientists James Cooley and John Tukey described an algorithm called the fast Fourier transform, which made it much easier to calculate DFTs on a computer. All of a sudden, the DFT became a practical way to process digital signals.

To get a sense of what the DFT does, consider an MP3 player plugged into a loudspeaker. The MP3 player sends the speaker audio information as fluctuations in the voltage of an electrical signal. Those fluctuations cause the speaker drum to vibrate, which in turn causes air particles to move, producing sound.

An audio signal’s fluctuations over time can be depicted as a graph: the x-axis is time, and the y-axis is the voltage of the electrical signal, or perhaps the movement of the speaker drum or air particles. Either way, the signal ends up looking like an erratic wavelike squiggle. But when you listen to the sound produced from that squiggle, you can clearly distinguish all the instruments in a symphony orchestra, playing discrete notes at the same time.

That’s because the erratic squiggle is, effectively, the sum of a number of much more regular squiggles, which represent different frequencies of sound. “Frequency” just means the rate at which air molecules go back and forth, or a voltage fluctuates, and it can be represented as the rate at which a regular squiggle goes up and down. When you add two frequencies together, the resulting squiggle goes up where both the component frequencies go up, goes down where they both go down, and does something in between where they’re going in different directions.

The DFT does mathematically what the human ear does physically: decompose a signal into its component frequencies. Unlike the analog signal from, say, a record player, the digital signal from an MP3 player is just a series of numbers, representing very short samples of a real-world sound: CD-quality digital audio recording, for instance, collects 44,100 samples a second. If you extract some number of consecutive values from a digital signal — 8, or 128, or 1,000 — the DFT represents them as the weighted sum of an equivalent number of frequencies. (“Weighted” just means that some of the frequencies count more than others toward the total.)

The application of the DFT to wireless technologies is fairly straightforward: the ability to break a signal into its constituent frequencies lets cell-phone towers, for instance, disentangle transmissions from different users, allowing more of them to share the air.

The application to data compression is less intuitive. But if you extract an eight-by-eight block of pixels from an image, each row or column is simply a sequence of eight numbers — like a digital signal with eight samples. The whole block can thus be represented as the weighted sum of 64 frequencies. If there’s little variation in color across the block, the weights of most of those frequencies will be zero or near zero. Throwing out the frequencies with low weights allows the block to be represented with fewer bits but little loss of fidelity.

Demanet points out that the DFT has plenty of other applications, in areas like spectroscopy, magnetic resonance imaging, and quantum computing. But ultimately, he says, “It’s hard to explain what sort of impact Fourier’s had,” because the Fourier transform is such a fundamental concept that by now, “it’s part of the language.”

Provided by Massachusetts Institute of Technology (news : web)
http://www.physorg.com/news178356724.html

Posted by
Robert Karl Stonjek


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