Next-Generation Lens Promises Wider View, Greater Detail

A close-up view of the new lens. (Credit: Duke University Photography)

Duke University engineers have created a new generation of lens that could greatly improve the capabilities of telecommunications or radar systems to provide a wide field of view and greater detail.

But the lens they fashioned doesn’t look anything like a lens. While traditional lenses are made of clear substances — like glass or plastic — with highly polished surfaces, the new lens looks more like a miniature set of tan Venetian blinds. Yet its ability to focus the direction of electromagnetic rays passing through it dramatically surpasses that of a conventional lens, the engineers say.

The latest advance was made possible by the ability to fabricate exotic composite materials known as metamaterials. The metamaterial in these experiments is not so much a single substance, but the entire man-made structure which can be engineered to exhibit properties not readily found in nature.

The prototype lens, which measures four inches by five inches and less than an inch high, is made up of more than 1,000 individual pieces of the same fiberglass material used in circuit boards and is etched with copper. It is the precise arrangement of these pieces in parallel rows, that directs the rays as they pass through.

“For hundreds of years, lens makers have ground the surfaces of a uniform material in such a way as to sculpt the rays as they pass through the surfaces,” said Nathan Kundtz, post-doctoral associate in electrical and computer engineering at Duke’s Pratt School of Engineering. “While these lenses can focus rays extremely efficiently, they have limitations based on what happens to the rays as they pass through the volume of the lens.

“Instead of using the surfaces of the lens to control rays, we studied altering the material between the surfaces,” Kundtz said. “If you can control the volume, or bulk, of the lens, you gain much more freedom and control to design a lens to meet specific needs.”

The results of his experiments, which were conducted in the laboratory of senior researcher David R. Smith, the William Bevan Professor of Electrical and Computer Engineering, appeared as an advanced online publication of the journal Nature Materials. This is the first demonstration of what was thought to be theoretically possible.

Recognizing the limitations of traditional lenses, scientists have long been investigating other options, including those known as gradient index (GRIN) lenses. These are typically clear spheres, and while they have advantages over traditional lenses, they are difficult to fabricate and the focus point is spherical. Additionally, because most sensing systems are oriented in two dimensions, the spherical image doesn’t always translate clearly on a flat surface.

The new lens, however, has a wide angle of view, almost 180 degrees, and because its focal point is flat, it can be used with standard imaging technologies. The latest experiments were conducted with microwaves, and the researchers say it is theoretically possible to design lenses for wider frequencies.

“We’ve come up with what is in essence GRIN on steroids,” said Smith, whose team used similar metamaterials to create one of the first “cloaking” devices in 2006. “This first in a new class of lenses offers tantalizing possibilities and opens a whole new application for metamaterials.

“While these experiments were conducted in two dimensions, the design should provide a good initial step in developing a three-dimensional lens,” Smith said. “The properties of the metamaterials we used should also make it possible to use infrared and optical frequencies.”

The researchers say a single metamaterial lens could replace traditional optical systems requiring vast arrays of lenses and provide clearer images. They could also be used in large-scale systems such as radar arrays to better direct beams, a task not possible for traditional lenses, which would need to be too large to be practical.

The research was supported by the Army Research Office’s Multiple University Research Initiative (MURI).

Story Source:

Adapted from materials provided by Duke University, via EurekAlert!, a service of AAAS.

http://www.sciencedaily.com/releases/2009/12/091220143915.htm

Secrets of Mysterious ‘Night-Shining’ Clouds Unlocked by NASA’s AIM Satellite and Models

This image of Polar Mesospheric Clouds (PMC) from the Aeronomy of Ice in the Mesosphere Cloud Imaging and Particle Size (AIM-CIPS) instrument on July 14, 2009 in the northern polar region. The North Pole (90N) is in the center. Latitude bands of 80N, 70N, and 60N are also indicated by the light blue circles. (Credit: NASA)

NASA’s Aeronomy of Ice in the Mesosphere (AIM) satellite has captured five complete polar seasons of noctilucent (NLC) or “night-shining” clouds with an unprecedented horizontal resolution of 3 miles by 3 miles. Results show that the cloud season turns on and off like a “geophysical light bulb” and they reveal evidence that high altitude mesospheric “weather” may follow similar patterns as our ever-changing weather near the Earth’s surface.

These findings were unveiled today at the Fall Meeting of the American Geophysical Union today in San Francisco.

The AIM measurements have provided the first comprehensive global-scale view of the complex life cycle of these clouds, also called Polar Mesospheric Clouds (PMCs), over three entire Northern Hemisphere and two Southern Hemisphere seasons revealing more about their formation, frequency and brightness and why they appear to be occurring at lower latitudes than ever before.

“The AIM findings have altered our previous understanding of why PMCs form and vary,” stated AIM principal investigator Dr. James Russell III of Hampton University in Hampton, Va. “We have captured the brightest clouds ever observed and they display large variations in size and structure signifying a great sensitivity to the environment in which the clouds form. The cloud season abruptly turns on and off going from no clouds to near complete coverage in a matter of days with the reverse pattern occurring at the season end.”

These bright “night-shining” clouds, which form 50 miles above Earth’s surface, are seen by the spacecraft’s instruments, starting in late May and lasting until late August in the north and from late November to late February in the south. The AIM satellite reports daily observations of the clouds at all longitudes and over a broad latitude range extending from 60 to 85 degrees in both hemispheres.

The clouds usually form at high latitudes during the summer of each hemisphere. They are made of ice crystals formed when water vapor condenses onto dust particles in the brutal cold of this region, at temperatures around minus 210 to minus 235 degrees Fahrenheit. They are called “night shining” clouds by observers on the ground because their high altitude allows them to continue reflecting sunlight after the sun has set below the horizon. They form a spectacular silvery blue display visible well into the night time.

Sophisticated multidimensional models have also advanced significantly in the last few years and together with AIM and other space and ground-based data have led to important advances in understanding these unusual and provocative clouds. The satellite data has shown that:

1. Temperature appears to control season onset, variability during the season, and season end. Water vapor is surely important but the role it plays in NLC variability is only now becoming more understood,
2. Large scale planetary waves in the Earth’s upper atmosphere cause NLCs to vary globally, while shorter scale gravity waves cause the clouds to disappear regionally;
3. There is coupling between the summer and winter hemispheres: when temperature changes in the winter hemisphere, NLCs change correspondingly in the opposite hemisphere.

Computer models that include detailed physics of the clouds and couple the upper atmosphere environment where they occur with the lower regions of the atmosphere are being used to study the reasons the NLCs form and the causes for their variability. These models are able to reproduce many of the features found by AIM. Validation of the results using AIM and other data will help determine the underlying causes of the observed changes in NLCs.

The AIM results were produced by Mr. Larry Gordley and Dr. Mark Hervig and the Solar Occultation for Ice Experiment (SOFIE) team, Gats, Inc., Newport News, Va. and Dr. Cora Randall and the Cloud Imaging and Particle Size (CIPS) experiment team, University of Colorado, Laboratory for Atmospheric and Space Physics in Boulder and Dr. Scott Bailey, Va. Tech, Blacksburg, Va.; Modeling results were developed by Dr. Daniel Marsh of the National Center for Atmospheric Research in Boulder, Colorado and Professor Franz-Josef Lübken of the Leibniz-Institute of Atmospheric Physics, Kühlungsborn, Germany.

AIM is a NASA-funded SMall EXplorers (SMEX) mission. NASA’s Goddard Space Flight Center manages the program for the agency’s Science Mission Directorate at NASA Headquarters in Washington. The mission is led by the Principal Investigator from the Center for Atmospheric Sciences at Hampton University in VA. Instruments were built by the Laboratory for Atmospheric and Space Physics (LASP), University of Colorado, Boulder, and the Space Dynamics Laboratory, Utah State University. LASP also manages the AIM mission and controls the satellite. Orbital Sciences Corporation, Dulles, Va., designed, manufactured, and tested the AIM spacecraft, and provided the Pegasus launch vehicle.

For more information about the AIM mission, visit: http://www.nasa.gov/mission_pages/aim/news/nlc-secrets.html, http://www.nasa.gov/aim, and http://aim.hamptonu.edu

Story Source:

Adapted from materials provided by NASA/Goddard Space Flight Center.

http://www.sciencedaily.com/releases/2009/12/091215192216.htm

Scientists Decode Memory-Forming Brain Cell Conversations

Artist’s rendering of neurons. (Credit: iStockphoto)

The conversations neurons have as they form and recall memories have been decoded by Medical College of Georgia scientists.

The breakthrough in recognizing in real time the formation and recollection of a memory opens the door to objective, thorough memory studies and eventually better therapies, said Dr. Joe Tsien, neuroscientist and co-director of MCG’s Brain & Behavior Discovery Institute. He is corresponding author on the study published Dec. 16 in PLoS ONE.

“It’s a beginning, a first glimpse of a memory,” Dr. Tsien said. “For the first time it gives us the ability to look at the brain dynamic and tell what kind of memory is formed, what are the components of the memory and how the memory is retrieved at the network level.” The finding could help pinpoint at what stage memory formation is flawed and whether drugs are improving it.

For their studies, MCG scientists combined new technology and computational methods with century-old Pavlovian conditioning.

In the memory center of the brain, they used 128 electrodes capable of monitoring a handful of neurons each to simultaneously record the conversations of 200 to 300 neurons as mice learned to associate a certain tone with a mild foot shock 20 seconds later.

A computational algorithm translated the neuronal chatter into a discernable and dynamic activity pattern that provided scientists a trace or picture of what the memory looked like as it was formed and recalled.

“By listening to the neuronal activity we were able to decipher the real-time dynamic pattern and the meaning of those conversations so this is really satisfying,” said Dr. Tsien, the Georgia Research Alliance Eminent Scholar in Cognitive and Systems Neurobiology.

The trace changed slightly each time it was recalled — likely as the mood or situation of the rodent changed — but still remained recognizable as a specific memory.

The scientists later correlated retrieval of the memory with the mice’s actions, such as freezing upon hearing the tone or returning to the chamber where the foot shock occurred. They found the traces tightly correlated with memory scores: the mice that had lower scores predictably had a fainter trace and those with stronger traces had better behavioral performance, such as freezing in anticipation of a shock. “At the behavioral level he is just frozen, but with this technique of decoding the real-time memory, it will tell you exactly what he is thinking,” Dr. Tsien said.

As expected, when mice were returned one hour later to the chamber where conditioning took place, they repeatedly froze, on average, 1.4 seconds after the recall pattern emerged in the brain. When placed in a setting with no history of the foot shock, the mice would freeze after they heard the tone.

One of the most surprising findings was that the memory trace of the foot shock was the sole memory that emerged in their brains 20 seconds after hearing the tone: just when the mild shock would have followed. “You think we are the only ones that can tell time?” Dr. Tsien said of this unexpected evidence of memory of time.

Problems with memory, the most fundamental cognitive function, can occur at any level — learning, consolidating, storing or retrieving. The ability to watch memories being made in real time should help pinpoint where problems lie, enabling more targeted research and eventual treatment, Dr. Tsien said.

“If you don’t know the basic biomarkers such as blood glucose or insulin level, it’s hard to assess and study diabetes. Without knowing what memory traces are, you really don’t have the precise physiological biomarkers to study memory and to reliably evaluate the effectiveness of treatment of memory disorders. We all know that behavior can be quite misleading sometime.” The ability to tell what memory is produced and how good that memory is could also dramatically shape development of machines that are controlled directly by the mind, rather than those using hands as an intermediary, he noted.

Studies were done in the CA1 region of the hippocampus, a well-documented center for forming associative memories. Similar tests are needed in other memory regions, Dr. Tsien said.

Related technology is already advancing patient care. For instance, primate studies of essential motor neuron connections are advancing the development of mind-controlled prosthetic limbs and electrodes can help identify where seizures originate. But it will take time and improved non-invasive recording technology before Dr. Tsien’s memory tests can be done on humans.

Dr. Guifen Chen, former MCG postdoctoral fellow, is first author on the paper, and Dr. L. Phillip Wang, MCG research scientist, is a co-author. The research was funded by the National Institutes of Health and the Georgia Research Alliance.

Story Source:

Adapted from materials provided by Medical College of Georgia, via EurekAlert!, a service of AAAS.

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Journal Reference:

1. Guifen Chen, L. Phillip Wang, Joe Z. Tsien. Neural Population-Level Memory Traces in the Mouse Hippocampus. PLoS ONE, 2009; DOI: 10.1371/journal.pone.0008256

http://www.sciencedaily.com/releases/2009/12/091215202322.htm

Yellowstone’s Plumbing Reveals Plume of Hot and Molten Rock 410 Miles Deep

Seismic imaging was used by University of Utah scientists to construct this 3-D picture of the Yellowstone hotspot plume of hot and molten rock that feeds the shallower magma chamber (not shown) beneath Yellowstone National Park, outlined in green at the surface, or top of the illustration. The Yellowstone caldera, or giant volcanic crater, is outlined in red. State boundaries are shown in black. The park, caldera and state boundaries also are projected to the bottom of the picture to better illustrate the plume’s tilt. Researchers believe “blobs” of hot rock float off the top of the plume, then rise to recharge the magma chamber located 3.7 miles to 10 miles beneath the surface at Yellowstone. The illustration also shows a region of warm rock extending southwest from near the top of the plume. It represents the eastern Snake River Plain, where the Yellowstone hotspot triggered numerous cataclysmic caldera eruptions before the plume started feeding Yellowstone 2.05 million years ago. (Credit: University of Utah)

The most detailed seismic images yet published of the plumbing that feeds the Yellowstone supervolcano shows a plume of hot and molten rock rising at an angle from the northwest at a depth of at least 410 miles, contradicting claims that there is no deep plume, only shallow hot rock moving like slowly boiling soup.

A related University of Utah study used gravity measurements to indicate the banana-shaped magma chamber of hot and molten rock a few miles beneath Yellowstone is 20 percent larger than previously believed, so a future cataclysmic eruption could be even larger than thought.

The study’s of Yellowstone’s plume also suggests the same “hotspot” that feeds Yellowstone volcanism also triggered the Columbia River “flood basalts” that buried parts of Oregon, Washington state and Idaho with lava starting 17 million years ago.

Those are key findings in four National Science Foundation-funded studies in the latest issue of the Journal of Volcanology and Geothermal Research. The studies were led by Robert B. Smith, research professor and professor emeritus of geophysics at the University of Utah and coordinating scientist for the Yellowstone Volcano Observatory.

“We have a clear image, using seismic waves from earthquakes, showing a mantle plume that extends from beneath Yellowstone,” Smith says.

The plume angles downward 150 miles to the west-northwest of Yellowstone and reaches a depth of at least 410 miles, Smith says. The study estimates the plume is mostly hot rock, with 1 percent to 2 percent molten rock in sponge-like voids within the hot rock.

Some researchers have doubted the existence of a mantle plume feeding Yellowstone, arguing instead that the area’s volcanic and hydrothermal features are fed by convection — the boiling-like rising of hot rock and sinking of cooler rock — from relatively shallow depths of only 185 miles to 250 miles.

The Hotspot: A Deep Plume, Blobs and Shallow Magma

Some 17 million years ago, the Yellowstone hotspot was located beneath the Oregon-Idaho-Nevada border region, feeding a plume of hot and molten rock that produced “caldera” eruptions — the biggest kind of volcanic eruption on Earth.

As North America slid southwest over the hotspot, the plume generated more than 140 huge eruptions that produced a chain of giant craters — calderas — extending from the Oregon-Idaho-Nevada border northeast to the current site of Yellowstone National Park, where huge caldera eruptions happened 2.05 million, 1.3 million and 642,000 years ago.

These eruptions were 2,500, 280 and 1,000 times bigger, respectively, than the 1980 eruption of Mount St. Helens. The eruptions covered as much as half the continental United States with inches to feet of volcanic ash. The Yellowstone caldera, 40 miles by 25 miles, is the remnant of that last giant eruption.

The new study reinforces the view that the hot and partly molten rock feeding volcanic and geothermal activity at Yellowstone isn’t vertical, but has three components:

• The 45-mile-wide plume that rises through Earth’s upper mantle from at least 410 miles beneath the surface. The plume angles upward to the east-southeast until it reaches the colder rock of the North American crustal plate, and flattens out like a 300-mile-wide pancake about 50 miles beneath Yellowstone. The plume includes several wider “blobs” at depths of 355 miles, 310 miles and 265 miles.”This conduit is not one tube of constant thickness,” says Smith. “It varies in width at various depths, and we call those things blobs.”
• A little-understood zone, between 50 miles and 10 miles deep, in which blobs of hot and partly molten rock break off of the flattened top of the plume and slowly rise to feed the magma reservoir directly beneath Yellowstone National Park.
• A magma reservoir 3.7 miles to 10 miles beneath the Yellowstone caldera. The reservoir is mostly sponge-like hot rock with spaces filled with molten rock.”It looks like it’s up to 8 percent or 15 percent melt,” says Smith. “That’s a lot.”

Researchers previously believed the magma chamber measured roughly 6 to 15 miles from southeast to northwest, and 20 or 25 miles from southwest to northeast, but new measurements indicate the reservoir extends at least another 13 miles outside the caldera’s northeast boundary, Smith says.

He says the gravity and other data show the magma body “is an elongated structure that looks like a banana with the ends up. It is a lot larger than we thought — I would say about 20 percent [by volume]. This would argue there might be a larger magma source available for a future eruption.”

Images of the magma reservoir were made based on the strength of Earth’s gravity at various points in Yellowstone. Hot and molten rock is less dense than cold rock, so the tug of gravity is measurably lower above magma reservoirs.

The Yellowstone caldera, like other calderas on Earth, huffs upward and puffs downward repeatedly over the ages, usually without erupting. Since 2004, the caldera floor has risen 3 inches per year, suggesting recharge of the magma body beneath it.

How to View a Plume

Seismic imaging uses earthquake waves that travel through the Earth and are recorded by seismometers. Waves travel more slowly through hotter rock and more quickly in cooler rock. Just as X-rays are combined to make CT-scan images of features in the human body, seismic wave data are melded to produce images of Earth’s interior.

The study, the Yellowstone Geodynamics Project, was conducted during 1999-2005. It used an average of 160 temporary and permanent seismic stations — and as many as 200 — to detect waves from some 800 earthquakes, with the stations spaced 10 miles to 22 miles apart — closer than other networks and better able to “see” underground. Some 160 Global Positioning System stations measured crustal movements.

By integrating seismic and GPS data, “it’s like a lens that made the upper 125 miles much clearer and allowed us to see deeper, down to 410 miles,” Smith says.

The study also shows warm rock — not as hot as the plume — stretching from Yellowstone southwest under the Snake River Plain, at depths of 20 miles to 60 miles. The rock is still warm from eruptions before the hotspot reached Yellowstone.

A Plume Blowing in the 2-inch-per-year Mantle Wind

Seismic imaging shows a “slow” zone from the top of the plume, which is 50 miles deep, straight down to about 155 miles, but then as you travel down the plume, it tilts to the northwest as it dives to a depth of 410 miles, says Smith.

That is the base of the global transition zone — from 250 miles to 410 miles deep — that is the boundary between the upper and lower mantle — the layers below Earth’s crust.

At that depth, the plume is about 410 miles beneath the town of Wisdom, Mont., which is 150 miles west-northwest of Yellowstone, says Smith.

He says “it wouldn’t surprise me” if the plume extends even deeper, perhaps originating from the core-mantle boundary some 1,800 miles deep.

Why doesn’t the plume rise straight upward? “This plume material wants to come up vertically, it wants to buoyantly rise,” says Smith. “But it gets caught in the ‘wind’ of the upper mantle flow, like smoke rising in a breeze.” Except in this case, the “breeze” of slowly flowing upper mantle rock is moving horizontally 2 inches per year.

While the crustal plate moves southwest, the warm, underlying mantle slowly boils due to convection, with warm areas moving upward and cooler areas downward. Northwest of Yellowstone, this convection is such that the plume is “blown” east-southeast by mantle convection, so it angles upward toward Yellowstone.

Scientists have debated for years whether Yellowstone’s volcanism is fed by a plume rising from deep in the Earth or by shallow churning in the upper mantle caused by movements of the overlying crust. Smith says the new study has produced the most detailed image of the Yellowstone plume yet published.

But a preliminary study by other researchers suggests Yellowstone’s plume goes deeper than 410 miles, ballooning below that depth into a wider zone of hot rock that extends at least 620 miles deep.

The notion that a deep plume feeds Yellowstone got more support from a study published this month indicating that the Hawaiian hotspot — which created the Hawaiian Islands — is fed by a plume that extends downward at least 930 miles, tilting southeast.

A Common Source for Yellowstone and the Columbia River Basalts?

Based on how the Yellowstone plume slants now, Smith and colleagues projected on a map where the plume might have originated at depth when the hotspot was erupting at the Oregon-Idaho-Nevada border area from 17 million to almost 12 million years ago.

They saw overlap, between the zones within the Earth where eruptions originated near the Oregon-Idaho-Nevada border and where the famed Columbia River Basalt eruptions originated when they were most vigorous 17 million to 14 million years ago.

Their conclusion: the Yellowstone hotspot plume might have fed those gigantic lava eruptions, which covered much of eastern Oregon and eastern Washington state.

I argue it is the common source,” Smith says. “It’s neat stuff and it fits together.”

Smith conducted the seismic study with six University of Utah present or former geophysicists — former postdoctoral researchers Michael Jordan, of SINTEF Petroleum Research in Norway, and Stephan Husen, of the Swiss Federal Institute of Technology; postdoc Christine Puskas; Ph.D. student Jamie Farrell; and former Ph.D. students Gregory Waite, now at Michigan Technological University, and Wu-Lung Chang, of National Central University in Taiwan. Other co-authors were Bernhard Steinberger of the Geological Survey of Norway and Richard O’Connell of Harvard University.

Smith conducted the gravity study with former University of Utah graduate student Katrina DeNosaquo and Tony Lowry of Utah State University in Logan.

Story Source:

Adapted from materials provided by University of Utah.

http://www.sciencedaily.com/releases/2009/12/091214075225.htm

Old Math Reveals New Thinking in Children’s Cognitive Development

Five-year-olds can reason about the world from multiple perspectives simultaneously, according to a new theory by researchers in Japan and Australia. Using an established branch of mathematics called Category Theory, the researchers explain why specific reasoning skills develop in children at certain ages, particularly at age five. The new theory, published December 11 in the open-access journal PLoS Computational Biology, shows that these reasoning skills have similar profiles of development because they involve related sorts of processes.

Around age five, children begin to understand that if John is taller than Mary, and Mary is taller than Sue, then John is also taller than Sue — Transitive Inference. They also begin to understand that there are more fruit than apples in a grocery store — Class Inclusion. Despite decades of previous experiments, the causes of the remarkably similar profiles of cognitive development across such apparently dissimilar paradigms of reasoning have largely been a mystery.

Steven Phillips, at the National Institute of Advanced Industrial Science and Technology (AIST, Japan), and colleagues show that both Transitive Inference and Class Inclusion develop around age five because they involve the ability to apply two lines of thinking about a problem at the same time, whereas younger children are limited to one. In category theory, the emphasis is on the relations (maps) between objects, rather than their contents.

In the Transitive Inference example, children must think about a person (i.e., Mary) who is both taller than John and shorter than Sue to make the inference. The relationships between objects in Class Inclusion are similar, but the directions of the maps are reversed. In category theory, two things that are related by map reversal are called duals. Transitive Inference and Class Inclusion involve similar difficulties for children under five years because they involve the “same” (i.e. dual or isomorphic) processes, in the category theory sense.

So far, the theory provides a good account of Transitive Inference, Class Inclusion and five other forms of inference: Matrix Completion, Cardinality, Card Sorting, Balance Scale, and Theory of Mind. Further experiments will test theory-based predictions regarding other paradigms and more complex levels of reasoning.

Story Source:

Adapted from materials provided by Public Library of Science, via EurekAlert!, a service of AAAS.

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Journal Reference:

1. Phillips S, Wilson WH, Halford GS. What Do Transitive Inference and Class Inclusion Have in Common? Categorical (Co)Products and Cognitive Development. PLoS Comput Biol, 2009; 5 (12): e1000599 DOI: 10.1371/journal.pcbi.1000599

http://www.sciencedaily.com/releases/2009/12/091210203423.htm

The Puzzling Paradox of Sign Language

It takes longer to sign words than to say them. So how is it possible to sign and speak at the same rate?

Here’s a curious paradox related to American Sign Language, the system of hand-based gestures used by around 2 million deaf people in the US and elsewhere to communicate.

Almost 40 years ago, researchers discovered that although it takes longer to make signs than to say the equivalent words, on average sentences can be completed in about the same time. How can that be possible?

Today, Andrew Chong and buddies at Princeton University in New Jersey give us the answer. They say that the information content of the 45 handshapes that make up sign language is higher than the information content of phonemes, the building blocks of the spoken word. In other words, there is greater redundancy in spoken English than signed English.

In a way, that’s a trivial explanation, a mere restatement of the problem. What’s impressive about the Princeton contribution is the way they have arrived at this conclusion.

The team has determined the entropy of American Sign Language experimentally, by measuring the frequency of handshapes on video logs for deaf people uploaded to youtube.com, deafvideo.tv and deafread.com as well as from video recordings of signed conversations taken on campus.

It turns out that the information content of handshapes is on average just 0.5 bits per handshape less than the theoretical maximum. By contrast, the information content per phoneme in spoken English is some 3 bits lower than the maximum.

This raises an interesting question. The spoken word has all this redundancy for a reason: it allows us to be understood over a noisy channel. Lessen the redundancy and your capacity to deal with noise is correspondingly reduced.

Why would sign language need less redundancy? “Entropy might be higher for handshapes than English phonemes because the visual channel is less noisy than the auditory channel…so error correction is less necessary,” say Chong and co.

They go on to speculate that signers cope with errors in an entirely different way to speakers. “Difficulties in visual recognition of handshapes could be solved by holding or slowing the transition between those handshapes for longer amounts of time, while difficulties in auditory recognition of spoken phonemes cannot always be easily solved by speaking phonemes for longer amounts of time,” they say.

And why is all this useful? Chong and friends say that if sign language is ever to be encoded and transmitted electronically, a better understanding of its information content will be essential for developing encoders and decoders that do the job. A worthy pursuit by any standards.

Ref: arxiv.org/abs/0912.1768: Frequency of Occurrence and Information Entropy of American Sign Language

http://www.technologyreview.com/blog/arxiv/24521/

Deniergate: Turning the tables on climate sceptics

Looks great: what does it mean? (Image: Miguel Villagran/Getty)

by Michael Marshall and Michael Le Page

“Climategate” has put scientists on trial in the court of public opinion. If you believe climate sceptics, a huge body of evidence involving the work of tens of thousands of scientists over more than a century should be thrown out on the basis of the alleged misconduct of a handful of researchers, even though nothing in the hacked emails has been shown to undermine any of the scientific conclusions.

If we are going to judge the truth of claims on the behaviour of those making them, it seems only fair to look at the behaviour of a few of those questioning the scientific consensus. There are many similar examples we did not include. We leave readers to draw their own conclusions about who to trust.

1. Fun with the sun

In 1991, the journal Science published a paper by researchers Eigil Friis-Christensen and Knud Lassen, then at the Danish Meteorological Institute in Copenhagen. It included graphs that appeared to show a remarkably close correlation between solar activity and terrestrial temperatures – suggesting that other factors, such as carbon dioxide levels, have little influence on global temperatures.

The graphs were seized on by climate change sceptics and have been widely reproduced ever since. But according to Peter Laut of the Technical University of Denmark in Lyngby, the close correlations in the original graphs, and in updated versions published in 1995 and 2000, exist only because of what he describes as a “pattern of strange errors”.

Laut described his findings in a peer-reviewed paper (Journal of Atmospheric and Solar-Terrestrial Physics, vol 65, p 801) and also wrote them up in a less technical form for the geophysicists’ newspaper Eos (vol 85, p 370 (PDF)). His concerns about the 1991 paper are shared by a number of leading climate scientists.

Outcome: Little action has been taken following publication of Laut’s papers. The 1991 paper is still frequently cited by climate deniers.

2. The great swindle

A television programme called The Great Global Warming Swindle was commissioned by the British broadcaster Channel 4 and aired in 2007.

The documentary, written and directed by Martin Durkin, prompted a voluminous complaint to the UK’s broadcast regulator Ofcom, alleging 137 breaches of broadcasting regulations.

For instance, the programme showed a graph comparing temperature and solar activity since 1550, based on a 1995 paper by Friis-Christensen and Lassen. This was one of the graphs questioned by Peter Laut (see above).

In the original graph, there was a gap in the solar activity line between 1600 and 1700 because there were no sunspots at this time, as confirmed by sunspot records. In the TV programme, this gap had somehow been filled in. Friis-Christensen accused the programme makers of fabricating the data.

The programme was also alleged to have misrepresented the views of several scientists who were interviewed on camera.

Outcome: Ofcom upheld some complaints about scientists being misrepresented, but decided that the breaches of factual accuracy did not fall within its remit.

3. The Oregon petition

The Oregon Institute of Science and Medicine is a research centre in the small town of Cave Junction; it says it conducts research into “protein biochemistry, diagnostic medicine, nutrition, preventive medicine and ageing”. In 1998, it issued a petition urging the US government to reject all limits on greenhouse gas emissions. The petition was mailed to thousands of US scientists, who were asked to sign it.

It was accompanied by an article entitled “Environmental effects of increased atmospheric carbon dioxide“. One of the authors, Willie Soon, is a well-known climate sceptic. The article closely resembled the style of articles from the peer-reviewed journal Proceedings of the National Academy of Sciences, down to the typeface. It had not been published in that or any other journal, as the US National Academy of Sciences made clear in a statement.

Despite intense scientific criticism (see here (PDF) and here, for example) the petition attracted over 30,000 signatures – although the organisers admitted that they did little to verify the respondents’ credentials, allowing obviously fake names like “Dr Geri Halliwell” to be included.

Outcome: As of 2008, the petition was being recirculated. The accompanying article has acquired an aura of respectability, having finally been published in a journal, albeit not one specialising in climatology: – the Journal of American Physicians and Surgeons.

4. Peer review?

In 2008, the Forum on Physics and Society (FPS), a newsletter produced by the American Physics Society, published an article entitled “Climate sensitivity reconsidered“. The article claimed that “the IPCC’s estimates may be excessive and unsafe” and that attempts to cut CO₂ emissions “are pointless, may be ill-conceived and could even be harmful”.

The article was written by Christopher Monckton, a British journalist and consultant. Although apparently highly technical, the piece has been strongly criticised by professional climate scientists, including Gavin Schmidt, of NASA’s Goddard Institute for Space Studies, New York.

The piece was reported by the US Science and Public Policy Institute as having been “peer-reviewed”.

Article continues - http://www.newscientist.com/article/dn18279-deniergate-turning-the-tables-on-climate-sceptics.html

Real Human Bone Grown in Tissue Culture

The best way to prevent a fracture is to stop bones from reaching the point where they are prone to breaking, but understanding the process of how bones form and mature has been challenging. Now researchers at the University of Houston department of health and human performance have created a process that grows real human bone in tissue culture, which can be used to investigate how bones form and grow.

“We have manufactured a structure that has no synthetic components,” said Mark Clarke, associate professor and principal investigator. “It’s all made by the two cell types bones start with inside the body. What you end up with is a piece of material that is identical to newly-formed, human, trabecular bone, including its mineral components, its histology and its growth factor content.”

Being in a microgravity environment causes astronauts’ bodies to lose more bone mineral than they can replace, which makes them vulnerable to fractures and breaks. Even when they return to Earth, the bone loss continues as their bodies slowly begin the process of replacing the bone mineral content.

The NASA-funded study, which included Clarke’s collaborators at NASA-Johnson Space Center, Dr. Neal Pellis and Dr. Alamelu Sundaresan, used human osteoblasts and osteoclasts, the two major cell types involved in the formation of and breaking down of bone. The 3-dimensional bone constructs allowed for ideal conditions to investigate how bone forms and, more importantly, how bone is lost in environments such as space flight and conditions present in post-menopausal women and spinal cord patients.

Clarke has worked with NASA on other bone loss studies. He served as a principal investigator in a NASA study of micro-fabricated skin patches that collect sweat for analysis of biomarkers of bone loss, like calcium.

His research on bone formation also is proving to be market-ready, as a newly formed start-up company, OsteoSphere Inc., examines ways the breakthrough research can be used in a clinical setting for applications such as spinal fusions, facial reconstructions following bomb blasts or the re-growing of an individual bone outside of the patient,.

Story Source:

Adapted from materials provided by University of Houston.

http://www.sciencedaily.com/releases/2009/12/091209143753.htm

Earth’s Atmosphere Came from Outer Space, Scientists Find

New research suggests that the gases which formed Earth’s atmosphere — and probably its oceans — did not come from inside Earth but from outer space. (Credit: iStockphoto)

The gases which formed the Earth’s atmosphere — and probably its oceans — did not come from inside the Earth but from outer space, according to a study by University of Manchester and University of Houston scientists.

The report published in the journal Science means that textbook images of ancient Earth with huge volcanoes spewing gas into the atmosphere will have to be rethought.

According to the team, the age-old view that volcanoes were the source of the Earth’s earliest atmosphere must be put to rest.

Using world-leading analytical techniques, the team of Dr Greg Holland, Dr Martin Cassidy and Professor Chris Ballentine tested volcanic gases to uncover the new evidence.

The research was funded by Natural Environment Research Council (NERC).

“We found a clear meteorite signature in volcanic gases,” said Dr Greg Holland the project’s lead scientist.

“From that we now know that the volcanic gases could not have contributed in any significant way to the Earth’s atmosphere.

“Therefore the atmosphere and oceans must have come from somewhere else, possibly from a late bombardment of gas and water rich materials similar to comets.

“Until now, no one has had instruments capable of looking for these subtle signatures in samples from inside the Earth — but now we can do exactly that.”

The techniques enabled the team to measure tiny quantities of the unreactive volcanic trace gases Krypton and Xenon, which revealed an isotopic ‘fingerprint’ matching that of meteorites which is different from that of ’solar’ gases.

The study is also the first to establish the precise composition of the Krypton present in the Earth’s mantle.

Project director Prof Chris Ballentine of The University of Manchester, said: “Many people have seen artist’s impressions of the primordial Earth with huge volcanoes in the background spewing gas to form the atmosphere.

“We will now have to redraw this picture.”

Story Source:

Adapted from materials provided by University of Manchester, via EurekAlert!, a service of AAAS.

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Journal Reference:

1. Greg Holland, Chris J. Ballentine, Martin Cassidy. Meteorite Kr in Earth’s Mantle Suggests a Late Accretionary Source for the Atmosphere. Science, 2009;

http://www.sciencedaily.com/releases/2009/12/091210153538.htm

First Evidence of Brain Rewiring in Children: Reading Remediation Positively Alters Brain Tissue

The left brain image shows the area of compromised white matter (blue area) among poor readers relative to good readers at the beginning of the study. THe center brain image shows the area where the structural integrity increased (red/yellow area) among poor readers who received the instruction, and it is very similar to the initially compromised area. The right brain image shows that following the instruction, there were no differences between the good and poor readers with respect to the integrity of their white matter. (Credit: Timothy Keller and Marcel Just)

Carnegie Mellon University scientists Timothy Keller and Marcel Just have uncovered the first evidence that intensive instruction to improve reading skills in young children causes the brain to physically rewire itself, creating new white matter that improves communication within the brain.

As the researchers report today in the journal Neuron, brain imaging of children between the ages of 8 and 10 showed that the quality of white matter — the brain tissue that carries signals between areas of grey matter, where information is processed — improved substantially after the children received 100 hours of remedial training. After the training, imaging indicated that the capability of the white matter to transmit signals efficiently had increased, and testing showed the children could read better.

“Showing that it’s possible to rewire a brain’s white matter has important implications for treating reading disabilities and other developmental disorders, including autism,” said Just, the D.O. Hebb Professor of Psychology and director of Carnegie Mellon’s Center for Cognitive Brain Imaging (CCBI).

Dr. Thomas R. Insel, director of the National Institute of Mental Health, agreed. “We have known that behavioral training can enhance brain function. The exciting breakthrough here is detecting changes in brain connectivity with behavioral treatment. This finding with reading deficits suggests an exciting new approach to be tested in the treatment of mental disorders, which increasingly appear to be due to problems in specific brain circuits,” Insel said.

Keller and Just’s study was designed to discover what physically changes in the brains of poor readers who make the transition to good reading. They scanned the brains of 72 children before and after they went through a six-month remedial instruction program. Using diffusion tensor imaging (DTI), a new brain imaging technique that tracks water movement in order to reveal the microscopic structure of white matter, Keller and Just found a brain change involving the white matter cabling that wires different parts of the brain together.

“Water molecules that are inside nerve fibers tend to move or diffuse parallel to the nerve fibers,” explained Keller, a CCBI research scientist and author of the first developmental study of compromised white matter in autism. “To track the nerve fibers, the scanner senses areas in which many water molecules are moving along in the same direction and produces a road-map of the brain’s wiring.”

Previous DTI studies had shown that both children and adults with reading difficulty displayed areas of compromised white matter. This new study shows that 100 hours of intensive reading instruction improved children’s reading skills and also increased the quality of the compromised white matter to normal levels. More precisely, the DTI imaging illustrated that the consistency of water diffusion had increased in this region, indicating an improvement in the integrity of the white matter tracts.

“The improved integrity essentially increases communication bandwidth between the two brain areas that the white matter connects, by a factor of 10,” Just said. “This opens a new era of being able to see the brain wiring change when an effective instructional treatment is applied. It lets us see educational interventions from a new perspective.”

Out of the 72 children, 47 were poor readers and 25 were reading at a normal level. The good readers and a group of 12 poor readers did not receive the remedial instruction, and their brain scans did not show any changes. “The lack of change in the control groups demonstrates that the change in the treated group cannot be attributed to naturally occurring maturation during the study,” Keller said.

Keller and Just also found that the amount of change in diffusion among the treated group was directly related to the amount of increase in phonological decoding ability. The children who showed the most white matter change also showed the most improvement in reading ability, confirming the link between the brain tissue alteration and reading progress.

Additional analyses indicated that the change resulted from a decrease in the movement of water perpendicular to the main axes of the underlying white matter fibers, a finding consistent with increased myelin content in the region. Although the authors caution that further research will be necessary to uncover the precise mechanism for the change in white matter, some previous findings indicate a role for electrical activity along axons in promoting the formation of myelin around them, providing a plausible physiological basis for intensive practice and instruction increasing the efficiency of communication among brain areas.

“We’re excited about these results,” Just said. “The indication that behavioral intervention can improve both cognitive performance and the microstructure of white matter tracts is a breakthrough for treating and understanding development problems.”

The research was funded by grants from the Richard King Mellon Foundation and the National Institute of Mental Health. For more information on Just, a pioneer in brain science discoveries, Keller and Carnegie Mellon’s Center for Cognitive Brain Imaging, visit www.ccbi.cmu.edu.

Story Source:

Adapted from materials provided by Carnegie Mellon University, via EurekAlert!, a service of AAAS.

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Journal Reference:

1. Timothy A. Keller, Marcel Adam Just. Altering Cortical Connectivity: Remediation-Induced Changes in the White Matter of Poor Readers. Neuron, 2009; 64 (5): 624-631 DOI: 10.1016/j.neuron.2009.10.018

http://www.sciencedaily.com/releases/2009/12/091209121200.htm