Wednesday, July 8, 2009

NATURAL DEEP EARTH PUMP FUELS EARTHQUAKES AND ORE

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For the first time scientists have discovered the presence of a natural deep earth pump that is a crucial element in the formation of ore deposits and earthquakes.

The process, called creep cavitation, involves fluid being pumped through pores in deformed rock in mid-crustal shear zones, which are approximately 15 km below the Earth’s surface.

The fluid transfer through the middle crust also plays a key role in tectonic plate movement and mantle degassing.

The discovery was made by examining one millimetre sized cubes of exposed rock in Alice Springs, which was deformed around 320 million years ago during a period of natural mountain formation.

“We are seeing the direct evidence for one of the processes that got ore forming fluids moving up from the mantle to the shallow crust to form the ore deposits we mine today, it is also one of the mechanisms that can lead to earthquakes in the middle crust,” Dr Hough said.The evidence is described in a paper published in the latest edition of Nature entitled Creep cavitation can establish a dynamic granular fluid pump in ductile shear zones.

One of the paper’s author’s CSIRO Exploration and Mining scientist Dr Rob Hough said that this was the first direct observation of fluids moving through the mid-crustal shear zone.

“We are seeing the direct evidence for one of the processes that got ore forming fluids moving up from the mantle to the shallow crust to form the ore deposits we mine today, it is also one of the mechanisms that can lead to earthquakes in the middle crust,” Dr Hough said.

Research leader Dr Florian Fusseis, from the University of Western Australia, said that the discovery could provide valuable information in understanding how earthquakes are formed.

“While we understand reasonably well why earthquakes happen in general, due to stress build-up caused by motions of tectonic plates, the triggering of earthquakes is much more complex,” Dr Fusseis said.

“To understand the ‘where’ and ‘when’ of earthquakes, the ‘how’ needs to be understood first. We know that earthquakes nucleate by failure on a small part of a shear zone.”

Dr Fusseis said that while their sample did not record an earthquake it gave them an insight into the structures that could be very small and localized precursors of seismic failure planes.

The discovery was made possible through the use of high-resolution Synchrotron X-ray tomographic, scanning electron microscope observations at the nanoscale and advanced visualisation using iVEC in Western Australia.

The authors of the paper propose that the fluid movement, described as the granular fluid pump, is a self sustaining process where pores open and close allowing fluid and gas to be pumped out.

(Photo: University of Western Australia Dr Florian Fusseis)

Commonwealth Scientific and Industrial Research Organisation (CSIRO)

A MYSTERY SOLVED: SPACE SHUTTLE SHOWS 1908 TUNGUSKA EXPLOSION WAS CAUSED BY COMET

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The mysterious 1908 Tunguska explosion that leveled 830 square miles of Siberian forest was almost certainly caused by a comet entering Earth's atmosphere, says new Cornell research. The conclusion is supported by an unlikely source: the exhaust plume from the NASA space shuttle launched a century later.

The research, accepted for publication (June 24) by the journal Geophysical Research Letters, published by the American Geophysical Union, connects the two events by what followed each about a day later: brilliant, night-visible clouds, or noctilucent clouds, that are made up of ice particles and only form at very high altitudes and in extremely cold temperatures.

"It's almost like putting together a 100-year-old murder mystery," said Michael Kelley, the James A. Friend Family Distinguished Professor of Engineering at Cornell, who led the research team. "The evidence is pretty strong that the Earth was hit by a comet in 1908." Previous speculation had ranged from comets to meteors to black holes.

The researchers contend that the massive amount of water vapor spewed into the atmosphere by the comet's icy nucleus was caught up in swirling eddies with tremendous energy by a process called two-dimensional turbulence, which explains why the noctilucent clouds formed a day later many thousands of miles away.

Noctilucent clouds are the Earth's highest clouds, forming naturally in the mesosphere at about 55 miles over the polar regions during the summer months when the mesosphere is around minus 180 degrees Fahrenheit (minus 117 degrees Celsius).

The space shuttle exhaust plume, the researchers say, resembled the water vapor from the comet. A single space shuttle flight injects 300 metric tons of water vapor into the Earth's thermosphere, and the water particles have been found to travel to the Arctic and Antarctic regions, where they form the clouds after settling into the mesosphere. The thermosphere is the layer of the atmosphere above the mesosphere.

Kelley and collaborators saw the noctilucent cloud phenomenon days after the space shuttle Endeavour (STS-118) launched on Aug. 8, 2007. Similar cloud formations had been observed following launches in 1997 and 2003.

Following the 1908 explosion, known as the Tunguska Event, the night skies shone brightly for several days across Europe, particularly Great Britain -- more than 3,000 miles away. Kelley said he became intrigued by the historical eyewitness accounts of the aftermath, and concluded that the bright skies must have been the result of noctilucent clouds. The comet would have started to break up at about the same altitude as the release of the exhaust plume from the space shuttle following launch. In both cases, water vapor was injected into the atmosphere.

The scientists have attempted to answer how this water vapor traveled so far without scattering and diffusing, as conventional physics would predict.

"There is a mean transport of this material for tens of thousands of kilometers in a very short time, and there is no model that predicts that," Kelley said. "It's totally new and unexpected physics."

This "new" physics, the researchers contend, is tied up in counter-rotating eddies with extreme energy. Once the water vapor got caught up in these eddies, the water traveled very quickly -- close to 300 feet per second.

Scientists have long tried to study the wind structure in these upper regions of the atmosphere, which is difficult to do by such traditional means as sounding rockets, balloon launches and satellites, explained Charles Seyler, Cornell professor of electrical engineering and paper co-author.

"Our observations show that current understanding of the mesosphere-lower thermosphere region is quite poor," Seyler said.

(Photo: M.J. Taylor and C.D. Burton/Utah State University)

Cornell University

BIO-ACOUSTIC RECORDERS COULD ANSWER QUESTION: DO WIND FARMS POSE RISKS TO MIGRATORY BIRDS?

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Are wind turbines dangerous to migrating birds? Nobody really knows for sure because two-thirds of migrating bird species fly at night, making direct study of their habits and potential hazards a challenge, said Cornell researchers at the Cornell Workshop on Large-Scale Wind-Generated Power, June 13.

The workshop for U.S. and international experts took place in Hollister Hall, June 12-13 and scientists addressed issues associated with the growing use of wind power to generate electricity in the United States.

Radar, combined with state-of-the-art bio-acoustic listening devices, could be an effective way to record birds' flight calls at night and then quantify and identify species migrating past potential and existing wind-power sites, asserted Chris Clark, director of the Bioacoustics Research Program at Cornell's Lab of Ornithology, and Andrew Farnsworth, a postdoctoral associate at the lab and an expert on migrating birds, in a presentation. The bioacoustics program has developed such listening devices as well as the software to analyze them, Clark said.

Farnsworth showed a brief video of radar data from the network of weather surveillance radars in the continental United States, superimposed over a map of the country, revealing migrations in the night sky between sunset and sunrise on Oct. 1, 2008. The color-coded radar map illustrated areas of precipitation over the coasts as well as vast movements of tens of millions of birds, bats and insects across the entire country. In the densest areas, the color-scales indicated movement of 2,000 birds per cubic kilometer.

"You're talking about a massive movement of birds overnight," Farnsworth said.

Migrating birds evolved with past and present weather patterns, which means migration pathways tend to overlap with high-wind areas that have the greatest potential for wind-energy development, Farnsworth said. Though research shows that windows in tall buildings and housecats may be the greatest threat to migrating birds, the risks that wind turbines pose for these birds are not clear, he added.

Although radar data can show the magnitude, location, timing, speed and direction of migration patterns and provide information on key stopover sites, they do not identify types of birds or accurate flight altitudes, Farnsworth said. But combining radar data with data from flight call recordings and tracking tags on birds could allow researchers to identify many species in key areas.

Clark added that recorders are cost effective, can be automated for many months at remote sites, provide data on many species simultaneously, increase the probability of tracking secretive and endangered species, and could allow regulatory agencies to develop computer models to assess risks to birds from wind turbines.

He acknowledged, however, that using such acoustic technology could produce a massive "data crunch"; a single microphone over a three-to-four-month period can record 120 to 140 gigabytes of data, so data from several hundred microphones would be too much to process without advanced software. Also, researchers would need to better recognize the wide variety of flight calls and learn to integrate data from radar with those from acoustics and tracking tags, he added.

More research is needed, Clark stressed, to determine at what altitudes species tend to fly and whether birds sense turbine blades and avoid them.

Cornell has "opportunities and responsibilities" to make use of its multidisciplinary talents and resources, be proactive and engage the public to "do things today to save tomorrow," Clark asserted.

(Photo: Andrew Farnsworth/Lab of Ornithology)

Cornell University

'MORNING PEOPLE' AND 'NIGHT OWLS' SHOW DIFFERENT BRAIN FUNCTION

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Are you an "early bird" or a "night owl?" Scientists at the University of Alberta have found there are significant differences in the way our brains function depending on whether we're early risers or night owls.

Neuroscientists in the Faculty of Physical Education and Recreation looked at two groups of people: "morning people," those who wake up early and feel most productive in the morning, and those who were identified as "evening people," who typically felt livelier at night.

Eighteen study participants were placed in two groups (nine morning people and nine evening people) after completing a standardized questionnaire about their habits. The participants were tested four times throughout the day: at 9 a.m., then in the afternoon at 1, 5 and 9 p.m., using three different techniques.

"We measured how much muscle force the two different participant groups could each generate during maximum contractions [and] we applied electrical stimulation to a nerve in the back of the knee to assess pathways through the spinal cord," said graduate student Olle Lagerquist, who came up with the original idea for the experiments.

"We also used trans-cranial magnetic stimulation-a magnet that we hold over the cortex-to stimulate brain cells to send a signal to different muscles."

The research team, made up of Lagerquist and fellow student Alex Tamm, technician Alejandro Ley and neuroscientist Dave Collins, made three major discoveries, the biggest of which was the difference in brain activity between the two groups.

"In morning people their cortical excitability actually decreased throughout the day. It was highest in the morning and lowest in the evening," said Tamm. "It was the opposite for evening people; their brain activity was highest at 9 p.m."

"[Before now] no one's been able to actually show that your brain has more excitability in the morning if you're a morning person and in the evening when you're an evening person," said Lagerquist.

Researchers were surprised by the result of the spinal-cord stimulation, which tested reflex response throughout the day. "We saw the spinal-cord excitability increase for both groups throughout the day," said Tamm.

The test that measured maximum muscle force found that morning people fared less well than evening people, who became physically stronger during day. Morning people didn't experience any change in the force they generated during maximum contractions throughout the day.

"We are suggesting that morning people may never reach their true maximum performance because their brain [activity] is going one way and their spinal cord activity is going the other, so it's offsetting," said Collins. "In evening people, both brain and spinal cord are at maximum in the evening and they get maximum performance at night."

Researchers are excited by these findings and the possibilities of future research in the area.

"We had a lot of measures and a lot of questions, and oftentimes when you do that, things come out very muddy," said Lagerquist. "The fact we could find something robust enough was a very nice surprise."

"As a next step, we may look at whether we can take morning people and evening people and [make morning people behave like evening people and vice versa]. No one has done that and then tested pathways through the brain and spinal cord the way we have, but it would be a very long, time-consuming process," said Lagerquist.

"It would have implications for shift work - and there are many questions. How quickly can we switch this? How difficult is it for an evening person to work a morning shift and be able to exist in that environment?"

(Photo: U. Alberta)

University of Alberta

PROGRAMMING TOOLS ALLOW USE OF VIDEO GAME PROCESSORS FOR DEFENSE NEEDS

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Video gaming computers and video game consoles available today typically contain a graphics processing unit (GPU), which is very efficient at manipulating and displaying computer graphics. However, the unit’s highly parallel structure also makes it more efficient than a general-purpose central processing unit for a range of complex calculations important to defense applications.

Researchers in the Georgia Tech Research Institute (GTRI) and the Georgia Tech School of Electrical and Computer Engineering are developing programming tools to enable engineers in the defense industry to utilize the processing power of GPUs without having to learn the complicated programming language required to use them directly.

“As radar systems and other sensor systems get more complicated, the computational requirements are becoming a bottleneck,” said GTRI senior research engineer Daniel Campbell. “We are capitalizing on the ability of GPUs to process radar, infrared sensor and video data faster than a typical computer and at a much lower cost and power than a computing cluster.”

Mark Richards, a principal research engineer and adjunct professor in the School of Electrical and Computer Engineering, is collaborating with Campbell and graduate student Andrew Kerr to rewrite common signal processing commands to run on a GPU. This work is supported by the U.S. Defense Advanced Research Projects Agency and the U.S. Air Force Research Laboratory.

The researchers are writing functions defined in the Vector, Signal and Image Processing Library (VSIPL) to run on GPUs. VSIPL is an open standard developed by embedded signal and image processing hardware and software vendors, academia, application developers and government labs. GPU VSIPL is available for download at (http://gpu-vsipl.gtri.gatech.edu/).

The researchers are currently writing the functions in Nvidia’s CUDA™ language, but the underlying principles can be applied to GPUs developed by other companies, according to Campbell. With GPU VSIPL, engineers can use high-level functions in their C programs to perform linear algebra and signal processing operations, and recompile with GPU VSIPL to take advantage of the speed of the GPU. Studies have shown that VSIPL functions operate between 20 and 350 times faster on a GPU than a central processing unit, depending on the function and size of the data set.

“The results are not surprising because GPUs excel at performing repetitive arithmetic tasks like those in VSIPL, such as signal processing functions like Fourier transforms, spectral analysis, image formation and noise filtering,” noted Richards. “We’ve just alleviated the need for engineers to understand the entire GPU architecture by simply providing them with a library of routines that they frequently use.”

The research team is also assessing the advantages of GPUs by running a library of benchmarks for quantitatively comparing high-performance, embedded computing systems. The benchmarks address important operations across a broad range of U.S. Department of Defense signal and image processing applications.

Preliminary studies have shown several of the benchmarks have straightforward parallelization schemes that result in faster operation without requiring significant optimization. For other benchmarks, additional research needs to be conducted into optimizing the use of multiple GPUs.

For the future, the researchers plan to continue expanding the GPU VSIPL, develop additional defense-related GPU function libraries and design programming tools to utilize other efficient processors, such as the cell broadband engine processor at the heart of the PlayStation 3 video game console.

(Photo: Georgia Tech/Gary Meek)

GT

SLEEP HELPS BUILD LONG-TERM MEMORIES

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Experts have long suspected that part of the process of turning fleeting short-term memories into lasting long-term memories occurs during sleep. Now, researchers at the RIKEN-MIT Center for Neural Circuit Genetics of MIT's Picower Institute for Learning and Memory have shown that mice prevented from "replaying" their waking experiences while asleep do not remember them as well as mice who are able to perform this function.

The work, which has a profound implication in the century-old search for the purpose of sleep, was reported in the June 25 issue of Neuron.

It is widely believed that memories of events and spaces are stored briefly in the hippocampus before they are consolidated in the neocortex for permanent storage. The seahorse-shaped hippocampus is thought to play a key role in learning and memory, but the precise circuits and mechanisms involved are not well understood.

"Our work demonstrates the molecular link between post-experience sleep and the establishment of long-term memory of that experience," said Susumu Tonegawa, the Picower Professor of Biology and Neuroscience at MIT and lead author of the study. "Ours is the first study to demonstrate this link between memory replay and memory consolidation. The sleeping brain must replay experiences like video clips before they are transformed from short-term into long-term memories."

The researchers looked at a circuit within the hippocampus known as the trisynaptic pathway, in which neuronal information passes through the hippocampus' three main substructures before moving on. "We demonstrated that this pathway is crucial for the transformation of a recent memory, formed within a day, to a remote memory that still exists at least six weeks later," Tonegawa said.

Creating a strain of engineered mice in which a change of diet shuts down trisynaptic circuits, the researchers implanted electrodes that monitored the activities of the animals' hippocampal cells as the animals ran a maze and then slept.

While they were still awake and running, the mice formed within their brains a pattern of place cells, or neurons that were firing in recognition of the maze the mice had learned to negotiate. During their post-run sleep, particularly during a deep sleep phase called slow-wave, the specific sequence of place cells that fired during the run was "replayed" in a similar sequence.

In human studies testing the role of slow-wave sleep in memory consolidation, the group that napped after memorizing word pairs such as "fruit-banana" and "tool-pliers," was able to recall a greater number of word pairs than those who did not nap.

This replay during sleep had been speculated, but has never been demonstrated, to be important for converting the recent memory stored in the hippocampus to a more permanent memory stored in the neocortex. "We have demonstrated that in the mutant mice in which the trisynaptic pathway is blocked, this replay process during the slow-wave sleep is impaired." Tonegawa said. The animals were able to form long-term memories of the maze only when their trisynaptic pathways were functioning after the formation of the short-term memory.

"Our conclusion is that the trisynaptic pathway-mediated replay of the hippocampal memory sequence during sleep plays a crucial role in the formation of a long-term memory," he said.

MIT

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