Thursday, January 14, 2010


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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.

(Photo: David R. Smith Lab, Pratt Engineering)

Duke University


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In excess of seven million barrels of gasoline are consumed by vehicles in the United States every day. As scientists race to find environmentally sound solutions to fuel the world’s ever-growing transportation needs, battery researchers are exploring the promise of lithium-air battery technology.

Li-air batteries use a catalytic air cathode that supplies oxygen, an electrolyte and a lithium anode. The technology has the potential to store almost as much energy as a tank of gasoline, and will have a capacity for energy storage that is five to 10 times greater than that of Li-ion batteries, a bridge technology. That potential, however, will not be realized until critical scientific challenges have been solved.

Researchers at the U. S. Department of Energy's (DOE) Argonne National Laboratory are leveraging their broad and deep understanding of safe, high-energy and long-life Li-ion battery development to leap the high hurdles required for the development of commercially viable Li-air batteries.

“The obstacles to Li-air batteries becoming a viable technology are formidable and will require innovations in materials science, chemistry and engineering," said Argonne Director Eric Isaacs. “We have a history of taking on scientific challenges and overcoming them. Argonne is committed to developing Li-air battery technologies. In fact, we’ve made it a ‘grand research challenge’ at the laboratory.”

Argonne has researched a variety of battery technologies during the last four decades, and in the process has built a deep well of scientific and engineering expertise. As a result, the lab has become a leader in the development of new materials for advanced batteries, including Li-ion batteries.

“This is not a near-term technology,” added Jeff Chamberlain, Senior Account Manager in Argonne’s Office of Technology Transfer. “It is going to take time and collaborations across several scientific disciplines to address the four main challenges of this battery development effort: safety, cost, life and performance.”

To accomplish this task, Argonne's research will continue to span basic, applied and theoretical sciences and will leverage the lab's world-class research facilities – the Advanced Photon Source, the Center for Nanoscale Materials and Argonne's Leadership Computing Facility.

While the potential of Li-air batteries is great, the research to get there will take time and involve working with industry, which will eventually adopt the technology for commercial application.

Argonne has worked with several industrial partners on the commercialization of Li-ion batteries and battery materials, including companies such as EnerDel, Envia, BASF and Toda America. The lab is working with the Commonwealth of Kentucky to develop the Kentucky-Argonne National Battery Manufacturing Center, which will support the development of a viable U.S. battery manufacturing industry. And more recently, DOE awarded the lab $8.8 million to build out and outfit three battery research facilities that will be used for battery prototyping, materials production scale-up and post-test analysis.

(Photo: Wes Agresta)

Argonne National Laboratory


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The timing of molar emergence and its relation to growth and reproduction in apes is being reported by two scientists at Arizona State University's Institute of Human Origins in the Dec. 28 online early edition of the Proceedings of the National Academy of Sciences (PNAS).

From the smallest South American monkeys to the largest African apes, the timing of molar development and eruption is closely attuned to many fundamental aspects of a primate's biology, according to Gary Schwartz, a researcher at the Institute of Human Origins and an associate professor in the School of Human Evolution and Social Change in ASU's College of Liberal Arts and Sciences.

"Knowing the age when the first molar appears in the mouths of most primates allows researchers to predict a host of life history attributes, such as gestation length, age at sexual maturity, birth spacing and overall lifespan," said Schwartz. "Humans are unique among primates because our life histories are so slow and thus our molars emerge relatively late. Given that apes are our closest living relatives, understanding the broader context of when the characteristic slower development of humans evolved is of great interest."

"We've known quite a bit about the timing of molar development in chimpanzees, which is important because they are our closest living relative. However, we've known virtually nothing about when this important event occurs in other wild-living ape species – until now," said lead author Jay Kelley, a research affiliate at ASU's Institute of Human Origins and an associate professor in the Department of Oral Biology at the University of Illinois, Chicago.

Because of the difficulties in obtaining tooth emergence ages from animals in the wild, Kelley opted for other means; he searched for specimens in museums. At the Zoologische Staatssammlung in Munich he found skulls of a wild-shot orangutan (Pongo pygmaeus pygmaeus) and gorilla (Gorilla gorilla gorilla) that preserved emerging first molars.

"Like annual growth rings inside trees, the cells that produce teeth (both the enamel and underlying dentine) leave behind a trace of their presence, not as annual markers, but as growth lines that appear every day," said Kelley. By slicing the teeth in half, he and Schwartz were able to examine these incremental growth lines in ape individuals that died as their first molars were just erupting into their mouths.

"Because teeth preserve this phenomenal internal chronometer, we were able to count up how many days it took the first molars to form," said Schwartz. "In apes and monkeys, first molars start forming very close to the time of birth. As the first molars were still erupting in our specimens, development was incomplete and the final growth line was laid down on the day those animals died. Therefore, by counting backwards from the final growth line to the day of birth, we determined their age at death and thus the age at which that molar was erupting."

Using this novel approach, the two scientists were able to mark the age of the gorilla's first molar emergence at 3.8 years, nearly identical to that of a wild chimpanzee's. The orangutan's age at first molar emergence was surprisingly much later, at 4.6 years, which falls closer to the age of approximately 6 years in modern humans.

"We were excited to discover this much older age for the orangutan, since orangutans have much slower life histories than the other two great apes," said Kelly.

However, he and Schwartz caution that though the later emergence age in these large Asian apes is closer to that for modern humans, these latest findings should not be taken to indicate some special evolutionary relationship between the two.

"Rather, it is in keeping with what you would expect given the relatively slow pace of growth and long period of infant dependency that evolved separately in the lineage leading to orangutans and that leading to modern humans," said Schwartz.

The work by Kelley and Schwartz also has implications for understanding the evolution of human life history.

"We can use the same techniques to calculate ages at first molar emergence from the fossils of early hominids that just happened to die while their first molars were erupting," said Kelley. "The close correspondence between age at first molar emergence and the timing of life history events that we found in great apes and modern humans means that we can have confidence that first molar emergence ages in the early hominids will provide equally accurate knowledge about their life histories."

(Photo: Gary Schwartz/Arizona State University/Institute of Human Origins)

Arizona State University


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In Huntington's disease, a mutated protein in the body becomes toxic to brain cells. Recent studies have demonstrated that a small region adjacent to the mutated segment plays a major role in the toxicity. Two new studies supported by the National Institutes of Health show that very slight changes to this region can eliminate signs of Huntington's disease in mice.

Researchers do not fully understand why the protein (called mutant huntingtin) is toxic, but one clue is that it accumulates in ordered clumps of fibrils, perhaps clogging up the cells' internal machinery.

"These studies shed light on the structure and biochemistry of the mutant huntingtin protein and on potentially modifiable factors that affect its toxicity," said Margaret Sutherland, Ph.D., a program director at NIH's National Institute of Neurological Disorders and Stroke (NINDS). "They reveal sites within the huntingtin protein and within broader disease pathways that could serve as targets for drug therapy."

Both studies were published online. One study, published in the Journal of Cell Biology, was led by Leslie Thompson, Ph.D., and Joan Steffan, Ph.D., of the University of California, Irvine. The other study, in Neuron, was led by X. William Yang, M.D., Ph.D., of the University of California, Los Angeles in collaboration with Ron Wetzel, Ph.D., of the University of Pittsburgh School of Medicine.

Huntington's disease is inherited, and usually strikes in middle age, producing uncontrollable movements of the legs and arms, a loss of muscle coordination, and changes in personality and intellect. It is inexorably progressive and leads to death of affected persons usually within 20 years after symptoms first appear. Individuals with the disease carry mutations that affect the huntingtin protein. The mutations involve a triple repeat DNA sequence, a type of genetic miscue similarly found in Friedreich's ataxia, Kennedy's disease, fragile X syndrome, and other neurodegenerative disorders.

The normal huntingtin protein consists of about 3,150 amino acids (which are the building blocks for all proteins). In individuals with Huntington’s disease, the mutated protein contains an abnormally long string of a single amino acid repeat; lengthier chains are associated with worse symptoms and earlier onset of the disease. In recent years, however, researchers have begun looking at the effects of other, nearby amino acids in this large protein — and in particular, biochemical changes to those amino acids.

In their study, Drs. Steffan and Thompson investigated how a process called phosphorylation affects huntingtin. Phosphorylation is the attachment of chemical tags, known as phosphates, onto the amino acids in a protein. The process occurs naturally and is a way of marking proteins for destruction by cellular waste handling systems. The researchers liken it to putting a sign on a pile of junk that tells the garbage collectors to take it away. Their study shows that phosphorylation of just two amino acids, located at one end of huntingtin, targets the protein for destruction and protects against the toxic effects of the mutant protein.

"Clearance of mutant huntingtin is likely regulated at many levels, but our data establish that these two amino acids are critical," Dr. Steffan said.

Could boosting phosphorylation of those two amino acids reduce the buildup of huntingtin and improve symptoms of the disease? In parallel with the UC Irvine research, Dr. Yang and his team at UCLA were asking that question using an animal model of Huntington’s disease. Previously, Dr. Yang had created mice that carry the mutant huntingtin gene. These mice develop symptoms reminiscent of Huntington’s disease in humans, including poor coordination, mental changes such as increased anxiety, loss of brain tissue, and accumulation of clumps of huntingtin in brain cells.

Through further genetic engineering, Dr. Yang altered the same two critical amino acids at the end of the mutant huntingtin protein to either mimic phosphorylation (phosphomimetic) or resist it (phosphoresistant). Mice with the phosphoresistant version of the protein developed symptoms of Huntington's, but mice with the phosphomimetic version remained free of symptoms and huntingtin clumps up to one year.

Meanwhile, test tube experiments by Dr. Wetzel's group in Pittsburgh showed that phosphomimetic modification of a huntingtin fragment reduced its tendency to form clumps. Together, data from the mouse and test tube experiments provide strong support for the idea that phosphorylation acts as a molecular switch to alter clumping of the mutant protein, the researchers said.

The nearly complete lack of any signs of disease in the phosphomimetic Huntington mice may point toward new strategies to treat the disorder someday. Dr. Yang said, "Drugs that enhance or mimic the effects of phosphorylation may help to detoxify the mutant huntingtin protein."

If such drugs could be developed, Drs. Steffan and Thompson theorize, they would likely be most effective at early stages of the disease, but less so at later stages, when the clearance machinery appears to run down. Dr. Yang said he plans to examine older mice carrying the phosphomimetic version of mutant huntingtin to determine how long they are protected from the disease.

National Institutes of Health


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Two nearby stars have been found to harbor “super-Earths”― rocky planets larger than the Earth but smaller than ice giants such as Uranus and Neptune. Unlike previously discovered stars with super-Earths, both of the stars are similar to the Sun, suggesting to scientists that low-mass planets may be common around nearby stars.

“Over the last 12 years or so nearly 400 planets have been found, and the vast majority of them have been very large―Jupiter mass or even larger,” says researcher Paul Butler of the Carnegie Institution’s Department of Terrestrial Magnetism. “These latest planets are part of a new trend of finding much smaller planets – planets that are more comparable to Earth.”

The international team of researchers, co-led by Butler and Steven Vogt of the University of California, Santa Cruz, was able to detect the new planetary systems by combining data from observations spanning several years at the W. M. Keck Observatory in Hawaii and the Anglo-Australian Telescope in New South Wales, Australia. The researchers used the subtle “wobbling” of the stars caused by the planets’ gravitational pull to determine the planets’ size and orbits. Greg Henry at Tennessee State University independently monitored the brightness of the stars to rule out stellar “jitter”―roiling of gases on a star’s surface that can be confused with a planet-induced wobble.

The bright star 61 Virginis, visible with the naked eye in the constellation Virgo, is only 28 light-years from Earth and closely resembles the Sun in size, age and other properties. Earlier studies had eliminated the possibility of a Jupiter-sized planet orbiting 61 Virginis. In this study, the researchers found evidence of three low-mass planets, the smallest of which is five times the mass of Earth and speeds around the star once every four days.

Butler points out that the signal produced by this planet was one of the smallest ever detected. “One has to be very cautious when you claim a discovery,” he says. “What gives us confidence is that we see the signal from two separate telescopes, and the two signals match up perfectly.”

The other newly-discovered system orbits the star HD 1461, located 76 light-years from Earth. HD 1461 also closely resembles the Sun and is visible in the constellation Cetus. The researchers found clear evidence for one planet 7.5 times the mass of Earth and possible indications of two others. The 7.5-Earth-mass planet, designated HD 1461b, is intermediate in size between Earth and Uranus. It orbits its star once every six days.

These planets have orbits close to their stars and so they would be too hot to support life or liquid water. But Butler says that they point the way toward finding similar planets in similar orbits around nearby M-dwarfs, stars that are typically less than half the mass of the Sun and typically put out less than two percent the Sun’s energy. “These sorts of planets around M dwarfs actually would be in a liquid water zone,” he says. “So we are knocking on the door right now of being able to find habitable planets.”

Carnegie Institution of Washington


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A study carried out in Ivory Coast has shown that monkeys of a certain forest-dwelling species called Campbell's monkeys emit six types of alert calls. The primates combine these calls into long vocal sequences which allow them to convey messages about social cohesion or various dangers, including predation.

These results, obtained by researchers at the Ethologie Animale et Humaine research group (CNRS / Université Rennes 1), working with the universities of St Andrews in Scotland and Cocody-Abidjan in Ivory Coast, were published on the website of the Proceedings of the National Academy of Sciences. The results reveal the most complex example of "proto-syntax" yet discovered in a non-human species.

For two years, at the Taï Monkey Project research station in the Taï national park in Ivory Coast, researchers studied the behavior of Campbell's monkeys (Cercopithecus campbelli campbelli). These monkeys live in small groups of ten or so individuals, made up of an adult male, several adult females and their progeny.

Researchers from the Ethologie Animale et Humaine research group (CNRS / Université de Rennes 1), working with a psychologist and an ethologist from the universities of St Andrews in Scotland and Cocody-Abidjan in Ivory Coast, studied the loud calls of adult males, whose vocal repertory is very different from that of females. They observed the vocal response of males to various disturbances of their environment, notably encounters with natural predators (like the eagle and leopard). They also carried out visual simulation experiments (with stuffed leopards and eagles) as well as acoustic experiments (using a loud-speaker amplifying leopard or eagle calls and grunts) suggesting the presence of these predators.

These experiments showed that males have a repertory of six types of alert calls (Boom, Krak, Hok, Hok-oo, Krak-oo, Wak-oo) but only rarely use them in isolation, preferring to produce long vocal sequences of an average of 25 successive calls (each sequence being made up of 1 to 4 types of different calls). Furthermore, Campbell's monkeys combine calls in order to convey different messages. By modifying a call sequence or the order of calls within a sequence, the messages are changed, and can relay precise information about the nature of the danger (a falling tree, a predator), the type of predator (eagle, leopard), how the predator was detected (acoustically, visually) but also about social events unrelated to predation (gathering before the group moves to another site, an encounter with another group of the same species at territory boundaries...).

This study shows the capacity of this monkey species for very complex vocal communication, both in the range of transmitted messages and in the techniques used to encode these messages. The same team of researchers had previously shown that males used a suffix « oo » to duplicate the size of his vocal repertory (which allowed them to produce the sounds Hok and Krak as well as Hok-oo and Krak-oo). In this new study, the ethologists explain some of the rules that govern the semantic combinations of calls. For example, Campbell's monkeys can add a particular type of call to an existing sequence in order to make the message more precise or to alter it. They can also combine sequences relaying different messages in order to convey a third message.

This ability to combine calls may have appeared during the monkeys' evolution to compensate for limited vocal flexibility (monkeys have less vocal flexibility than birds and cetaceans) and provide a way to encode new messages. This study shows a form of proto-syntax in this tree-dwelling monkey species which, as they live in a habitat with limited visibility, can only communicate vocally. This study raises the question of the potential existence of precursors to human language in animal vocal communication.

(Photo: © A. Laurence)

Centre National de la Recherche Scientifique




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