Thursday, August 27, 2009

BEYOND THE LOOKING GLASS

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While the researchers can't promise delivery to a parallel universe or a school for wizards, books like Pullman's Dark Materials and JK Rowling's Harry Potter are steps closer to reality now that researchers in China have created the first tunable electromagnetic gateway.

The work, 'A simple route to a tunable electromagnetic gateway' is a further advance in the study of metamaterials, published Thursday, 14 August, in New Journal of Physics (co-owned by the Institute of Physics and German Physical Society). It has been published at http://stacks.iop.org/NJP/11/083012.

In the research paper, the researchers from the Hong Kong University of Science and Technology and Fudan University in Shanghai describe the concept of a "a gateway that can block electromagnetic waves but that allows the passage of other entities" like a "'hidden portal' as mentioned in fictions."

The gateway, which is now much closer to reality, uses transformation optics and an amplified scattering effect from an arrangement of ferrite materials called single-crystal yttrium-iron-garnet that force light and other forms of electromagnetic radiation in complicated directions to create a hidden portal.

Previous attempts at an electromagnetic gateway were hindered by their narrow bandwidth, only capturing a small range of visible light or other forms of electromagnetic radiation. This new configuration of metamaterials however can be manipulated to have optimum permittivity and permeability – able to insulate the electromagnetic field that encounters it with an appropriate magnetic reaction.

Because of the arrangement's response to magnetic fields it also has the added advantage of being tunable and can therefore be switched on and off remotely.

Dr Huanyang Chen from the Physics Department at Hong Kong University of Science and Technology has commented, "In the frequency range in which the metamaterial possesses a negative refraction index, people standing outside the gateway would see something like a mirror. Whether it can block all visible light depends on whether one can make a metamaterial that has a negative refractive index from 300 to 800 nanometres."

Metamaterials, the area of physics research behind the possible creation of a real Harry Potter-style invisibility cloak, are exotic composite materials constructed at the atomic (rather than the usual chemical) level to produce materials with properties beyond those which appear naturally.

(Photo: IoP)

Institute of Physics

BIPEDAL HUMANS DESCENDED FROM THE TREES, NOT UP FROM GROUND

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A detailed examination of the wrist bones of several primate species challenges the notion that humans evolved their two-legged upright walking style from a knuckle-walking ancestor.

The same lines of evidence also suggest that knuckle-walking evolved at least two different times, making gorillas distinct from chimpanzees and bonobos.

"We have the most robust data I've ever seen on this topic," said Daniel Schmitt, a Duke University associate professor of evolutionary anthropology. "This model should cause everyone to re-evaluate what they've said before."

The research, led by post-doctoral research associate Tracy Kivell, was supported by the Natural Sciences and Engineering Research Council in her native Canada, General Motors' Women in Science and Mathematics, and the University of Toronto, where Kivell did her Ph.D. work.

The debate over the origins of human bipedalism began during Charles Darwin's lifetime and continues vigorously to this day, commonly dividing into two competing models, the researchers explained.

One model "envisions the pre-human ancestor as a terrestrial knuckle-walker, a behavior frequently used by our closest living relatives, the African apes," they wrote in the PNAS report. The other model traces our two-legged walking to earlier tree-climbing, a mode of locomotion that is used by all living apes.

Supporters of the knuckle-walking origin think we and African apes evolved from a common knuckle walking ancestor. That connection, they contend, is still evident in wrist and hand bone features shared by African apes and by fossil and living humans.

But Kivell found otherwise when she began comparing juvenile and adult wrist bones of more than 100 chimps and bonobos, our closest living primate kin, with those of gorillas.

Significantly, two key features associated with knuckle walking were present in only 6 percent of the gorilla specimens she studied. But she found them in 96 percent of adult chimpanzees and 76 percent of bonobos. In all, she looked at specimens from 91 gorillas, 104 chimps and 43 bonobos.

Kivell and Schmitt suggested that one explanation for the absence of these features in gorillas is that they knuckle-walk in a fundamentally different way from chimps and bonobos. Gorillas stride with their arms and wrists extended straight down and locked in what Kivell called "columnar" stances that resemble how elephants walk. By contrast, chimps and bonobos walk more flexibly, "with their wrists in a bent position as opposed to being stacked-up," she said. "And with their wrists in bent positions there will be more stresses at those joints."

As a result, chimp and bonobo wrists have special features that gorillas lack -- little ridges and concavities that serve as "bony stops" to keep their wrists from over-bending. Gorillas don't need those, she added.

"When we first got together to work on this study that (difference) really jumped out in living color," Schmitt said.

"Then we sat down together and asked: 'What are the differences between them?' Schmitt said. "The answer is that chimps and bonobos spend a lot of time in the trees. And gorillas do not."

Chimpanzees and bonobos have a more extended-wrist way of knuckle-walking which gives them added stability on branches, the researchers concluded. In contrast, gorillas' "columnar" style of knuckle-walking is consistent with ground transport.

Indeed, "from what we know about knuckle-walking among wild populations, gorillas and adult chimpanzees will both knuckle-walk about 85 percent of the time that they're moving," Kivell said. "But chimpanzees and bonobos are more arboreal than gorillas. So they're doing a lot more of it in the trees."

Kivell and Schmitt think this suggests independent evolution of knuckle-walking behavior in the two African ape lineages.

Some scientists point to features in the human anatomy as our own vestiges of a knuckle-walking ancestry. One notable example is the fusion a two wrist bones that could provide us extra stability, a feature we share with gorillas, chimps and bonobos.

But some lemurs have that feature too, and they do a variety of different movements in the trees but do not knuckle-walk, Kivell said.

Altogether, the evidence leans against the idea that our own bipedalism evolved from a knuckle-walking ancestor, the pair wrote. "Instead, our data support the opposite notion, that features of the hand and wrist found in the human fossil record that have traditionally been treated as indicators of knuckle-walking behavior in general are in fact evidence of arboreality."

In other words, a long-ago ancestor species that spent its time in the trees moved to the ground and began walking upright.

There are no fossils from the time of this transition, which likely occurred about seven million years ago, Kivell and Schmitt said. But none of the later fossils considered to be on the direct human line were knuckle-walkers.

Duke University

MARY HAD A LOT OF LAMBS: RESEARCHERS IDENTIFY WAY TO SPEED UP SHEEP BREEDING

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Mary had a little lamb, but only once a year. However, Cornell Sheep Program researchers have discovered an unusual form of a gene that prompts ewes to breed out of season as well as conceive at younger ages and more frequently.

They conducted a simple genetic test to identify the presence of the unusual form of the gene, the so-called M allele that other researchers had suspected might be correlated with out-of-season fertility, in their test flock and then validated the gene's relationship with aseasonal breeding by observing that trait in the flock.

The finding, published in the August issue of the Journal of Animal Science (Vol. 87, No. 8), may be a boon for the sheep industry worldwide, especially when combined with the Sheep Program's STAR system -- a method to manage ewes to lamb five times in three years rather than once a year.

"The primary biological limit for sheep production worldwide is the seasonality of breeding, but the market for high-quality lamb is a 52-week thing," said Doug Hogue, professor emeritus of animal science in the College of Agriculture and Life Sciences. His Cornell colleague Mike Thonney and former Cornell postdoctoral researcher Raluca Mateescu, now at Oklahoma State University, co-authored the paper with Andrea Lunsford, a graduate student at OSU.

Although the presence of the M allele has been definitively correlated with the ability to breed out of season, the researchers caution that it may only be a marker for the gene actually responsible for the trait.

"Breeding out of season is a complex trait," Mateescu said, "so there are a lot of genes controlling it." Mateescu observed the phenotype -- the physical expression of the gene -- in the researchers' flock during a postdoctoral fellowship at Cornell.

"In this case, we're talking about a receptor gene for melatonin," Thonney explained. Melatonin is a naturally produced hormone commonly found in many animals. The change in the DNA sequence of the M allele does not change the amino acid sequence of the protein. This means that it may be an accurate indicator for the phenotype of breeding out of season, though it's uncertain whether the gene actually impacts how the sheep's body reacts to melatonin. And there may be a risk of losing the association over generations, the researchers said, as recombination could occur between the marker and the functional gene.

Thus, the researchers stress that it will be very important to validate the gene's ability to indicate for aseasonal breeding each time the allele is bred into a new sheep population.

"I think it's very exciting … we only have one gene, but it's definitely a tool that farmers can use," said Mateescu, who is now focusing on placing markers across the sheep's entire genome to more accurately determine which gene or genes directly affect the trait of aseasonal reproduction.

The allele is particularly useful for management under the STAR system, developed by Hogue and Cornell sheep farm manager Brian Magee in the early 1980s, which uses nutrition and conventional breeding techniques to reduce the time between heats. "If a ewe doesn't get pregnant when she is supposed to, instead of a year, it's only 73 days [using the STAR system] until she has another opportunity," Thonney said.

While the STAR system requires better nutrition and more farm labor to manage the lambing, each lambing event involves fewer ewes than traditional yearly lambing.

The researchers hope that the discovery of the M allele may help the STAR system adapt to consistently high levels of production without any additional risk to flock health.

(Photo: Cornell U.)

Cornell University

UT SOUTHWESTERN PHYSICIANS BUST MYTHS ABOUT INSULIN

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People diagnosed with type 2 diabetes often resist taking insulin because they fear gaining weight, developing low blood sugar and seeing their quality of life decline.

A study recently completed at UT Southwestern Medical Center suggests that those fears are largely unfounded and that patients and physicians should consider insulin as a front-line defense, as opposed to a treatment of last resort for non-insulin-dependent diabetes.

“We found that those patients who received insulin initially did just as well, if not better, than those who didn’t receive insulin,” said Dr. Ildiko Lingvay, assistant professor of internal medicine at UT Southwestern and lead author of the study appearing online and in a future issue of Diabetes Care. “This reinforces the idea that insulin treatment is a viable and safe option for patients, even in the very initial stages of their diagnoses.

“There is a myth out in the community, especially among certain ethnicities, that insulin is the last resort, and that somebody started on insulin is going to die,” Dr. Lingvay added. “We as physicians are responsible for teaching the patient that that’s not the case.”

More than 20 million Americans have type 2 diabetes. Obesity, age and lack of exercise all increase the risk for the disease, which is characterized by a progressive loss of insulin-producing beta cells. Diabetes is the single greatest independent risk factor for heart disease, as well as a contributor to a number of other medical problems, including blindness and kidney disease.

The standard initial treatment for type 2 diabetes is a single drug, often metformin, followed by the addition of more oral hypoglycemic agents as needed.

For this study, researchers evaluated the effectiveness of offering insulin-based therapy as an initial treatment option to newly diagnosed type 2 diabetes patients. They compared rates of compliance, satisfaction, effectiveness, safety and quality of life among the patients, who were randomized to receive either the standard triple oral therapy or insulin plus metformin, an oral drug that helps regulate blood sugar levels.

The patients, ranging in age from 21 to 70 years old, had been diagnosed with type 2 diabetes within the past two months. Researchers recruited study participants from Parkland Memorial Hospital or by self-referral to the Clinical Diabetes Research Clinic at UT Southwestern between November 2003 and June 2005.

After enrollment, every participant followed an insulin and metformin regimen for three months. The patients were then randomized to continue taking insulin and metformin or begin the triple oral therapy regimen. All participants were checked monthly for the first four months, at six months after randomization, and every three months thereafter for three years. Of the 58 patients randomized, 24 of the insulin-treated group and 21 of the triple oral therapy group completed the study.

The researchers found that the patients taking insulin plus metformin had fewer low-blood-sugar, or hypoglycemic, events, gained less weight and reported high satisfaction with the insulin.

Dr. Lingvay said she hopes physicians use these findings as the rationale to offer insulin-metformin as the first, rather than last, line of defense.

“Modern medicine uses insulin as a very effective and safe treatment tool,” she said. “With the new devices that we’re using, giving yourself an insulin shot is not much harder than taking pills.”

The data represent the first three years of a six-year study still under way at UT Southwestern. The next step, Dr. Lingvay said, is to begin analyzing how the insulin plus metformin and oral triple therapy regimens affect insulin production in beta cells.

(Photo: UT Southwestern)

UT Southwestern Medical Center

MODEL SUGGESTS HOW LIFES CODE EMERGED FROM PRIMORDIAL SOUP

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In 1953, Stanley Miller filled two flasks with chemicals assumed to be present on the primitive Earth, connected the flasks with rubber tubes and introduced some electrical sparks as a stand-in for lightning. The now famous experiment showed what amino acids, the building blocks of proteins, could easily be generated from this primordial stew. But despite that seminal experiment, neither he nor others were able to take the next step: that of showing how life’s code could come from such humble beginnings.

By working with the simplest amino acids and elementary RNAs, physicists led by Rockefeller University’s Albert J. Libchaber, head of the Laboratory of Experimental Condensed Matter Physics, have now generated the first theoretical model that shows how a coded genetic system can emerge from an ancestral broth of simple molecules. “All these molecules have different properties and these properties define their interactions,” says first author Jean Lehmann, whose work appears in the June issue of PLoS One. “What are the constraints that allow these molecules to self-organize into a code? We can play with that.”

The genetic code is a triplet code such that every triplet sequence of letters on messenger RNA (mRNA) corresponds to one of the 20 amino acids that make up proteins. Molecular adaptors called transfer RNAs (tRNAs) then convert this information into proteins that can achieve some specific tasks in the organism. Let’s say that each triplet sequence on mRNA, known as a codon, represents an outlet that can only accept a tRNA with a complementary anticodon. Translation works because each codon-anticodon match corresponds with an amino acid. As each tRNA is plugged in, a chain of amino acids is formed in the same order as the codons until translation is complete.

However, primitive tRNAs were not as finicky as tRNAs are today and could load any amino acid known to exist during the time of prebiotic Earth. Without the ability of tRNA to discriminate between various amino acids, such a random system might not be able to self-assemble into a highly organized code capable of supporting life.

To find out if it could, Libchaber and Lehmann, together with Michel Cibils at Ecole Polytechnique Federale de Lausanne in Laussane, Switzerland, worked with a simple theoretical system. They took two of the simplest amino acids thought to exist billions of years ago, two primitive tRNAs and an RNA template with two complementary codons, and then developed an algorithm to incrementally change the concentration of each molecule. Their goal was to see which conditions, if any, could coax the system to specifically translate codons in a non-random fashion. They found that the properties of the molecules set the concentrations at which the molecules needed to exist for a coded regime to emerge.

At these concentrations, the scientists found that a vetting process began to unfold whereby the tRNA and the amino acid began to seek each other out. All in all, an elementary translation process depended on two time scales: the time during which a tRNA remains bound to its codon (hybridization) and the time it takes for the amino acid on that tRNA to form a new chemical bond with the amino acid next to it (polymerization).

“It takes a lifetime for the tRNA to dissociate from its codon,” says Libchaber, who is also Detlev W. Bronk Professor at Rockefeller. “If it takes the amino acid loaded on the RNA longer than a lifetime to polymerize to an amino acid nearby, the selection of tRNA and amino acid doesn’t occur. But when the two lifetimes are comparable, even when there is nonspecific loading of an amino acid, a selection process begins to take hold because some amino acids would be more adaptive during that time span -- and start what would be the beginning of a code.”

Although Libchaber and Lehmann point out that the analysis certainly does not provide a full picture of the problem, the work nonetheless brings us one step closer to understanding how Life first began. “The dream of physicists is to create elementary life,” Libchaber says. “Then we would know that we understand something.”

Rockefeller University

LIFE AND DEATH IN THE LIVING BRAIN: RECRUITMENT OF NEW NEURONS SLOWS WHEN OLD BRAIN CELLS KEPT FROM DYING

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Like clockwork, brain regions in many songbird species expand and shrink seasonally in response to hormones. Now, for the first time, University of Washington neurobiologists have interrupted this natural "annual remodeling" of the brain and have shown that there is a direct link between the death of old neurons and their replacement by newly born ones in a living vertebrate.

The scientists introduced a chemical into one side of sparrow brains in an area that helps control singing behavior to halt apoptosis, a cell suicide program. Twenty days after introduction of the hormones the researchers found that there were 48 percent fewer new neurons than there were in the side of the brain that did not receive the cell suicide inhibitor.

"This is the first demonstration that if you decrease apoptosis you also decrease the number of new brain cells in a live animal. The next step is to understand this process at the molecular level," said Eliot Brenowitz, a UW professor of psychology and biology and co-author of a new study. His co-author is Christopher Thompson, who earned his doctorate at the UW and is now at the Free University of Berlin.

"The seasonal hormonal drop in birds may mimic what is an age-related drop in human hormone levels. Here we have a bird model that is natural and maybe similar genes have a similar function in humans with degenerative diseases such as Alzheimer's and Parkinson's, as well as strokes, which are associated with neuron death."

The research involved Gambel's white-crowned sparrows, a songbird subspecies that winters in California and migrates to Alaska in the spring and summer to breed and raise its young. The sparrow's brain regions, including one called the HVC, which control learned song behavior in males, expand and shrink seasonally. Thompson and Brenowitz previously found that neurons in the HVC begin dying within four days hours after the steroid hormone testosterone is withdrawn from the bird's brains. Thousands of neurons died over this time.

In the new work, the UW researchers received federal and state permission to capture 10 of the sparrows in Eastern Washington at the end of the breeding season. After housing the birds for three months, they castrated the sparrows and then artificially brought them to breeding condition by implanting testosterone and housing them under the same long-day lighting conditions that they would naturally be exposed to in Alaska. This induced full growth of the song control system in the birds' brains.

Next the researchers transitioned the birds to a non-breeding condition by reducing the amount of light they were exposed to and removing the implanted testosterone. They infused the HVC on one side of the brain with chemicals, called caspase inhibitors, that block apoptosis, and two chemical markers that highlight mature and new neurons. Twenty days later the birds were euthanized and sections of their brains were examined under a microscope.

These procedures were done with the approval of the UW's Institutional Animal Care and Use Committee and the National Institute of Mental Health. The latter funded the research.

The HVC straddles both hemispheres of the brain but the two sides are not directly connected. When Thompson counted the number of newly born neurons that had migrated to the HVC, he found only several hundred of them among the hundreds of thousands of mature neurons he examined. And there were nearly half the number of new neurons in the side of the HVC where brain cell death was inhibited compared with the other, untreated side of the HVC.

"This shows there is some direct link between the death of old neurons and the addition of new cells that were born elsewhere in the brain and have migrated," said Brenowitz. "What allows new cells to be incorporated into the brain is the big question. This is particularly true on a molecular level where we want to know what is the connection between cell death and neurogenesis and which genes are responsible."

(Photo: University of Washington)

University of Washington

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