Tuesday, January 12, 2010

LOOKS CAN BE DECEIVING

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Does it matter if nature solves the same problem multiple ways? A NSF-supported study of lizard populations in White Sands, New Mexico has helped researcher Erica Rosenblum of the University of Idaho begin to answer that question. Published December 28 in the Proceedings of the National Academy of Sciences, the article describes genetic differences between lizards found in habitats that contain white or dark soils. These stark differences in color are an ideal environment to study natural selection and gene flow.

In three separate lizard species, Rosenblum and her team identified mutations in the gene encoding the melanocortin-1 receptor (Mc1r), all resulting in lizards with light skin. Further biochemical characterization of the mutations revealed that, although the same gene is affected in two of the species, the functional changes caused by the mutations were distinct. In one species the receptor is in the wrong location in the cell, while in a different species the receptor is in the correct location, but it is unable to transmit signal.

"The mutations we observed resulted in two distinct changes in how the Mc1 receptor functioned. Mc1r acts like a light switch for melanin, so even though the way the signaling is disrupted is different, outwardly we see the same result: light-skinned lizards," Rosenblum explained.

Although the end point, light skin, is the same, the different ways the reptiles achieve this have important implications for gene flow in each species. For instance, the dominance pattern of the mutated genes is different in the two species. The mutation that results in improperly located Mc1r protein is dominant, meaning it takes only one copy of the new gene to result in light-skinned lizards. In contrast, the lizards that appear white due to faulty receptor signal transmission must harbor two copies of the mutant gene because the trait is recessive.

Rosenblum added, "There is preliminary evidence that suggests the genes involved in adaptation can also affect speciation. Changes in melanin affect coloration on the top of the body, which predators see, and also the sides of the body, which other lizards use to decide who to mate with. Therefore both natural selection and sexual selection appear to play a role in this system."

This habitat provides researchers the unique opportunity to observe natural selection and speciation in progress. New species can form relatively quickly (over a few thousand years) in some selection environments, but catching organisms in the act is rare. The more researchers understand the speciation process, the better equipped we will be to try to preserve this process as our landscape changes.

(Photo: Erica Bree Rosenblum, University of Idaho)

National Science Foundation

COCKROACHES OFFER INSPIRATION FOR RUNNING ROBOTS

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The sight of a cockroach scurrying for cover may be nauseating, but the insect is also a biological and engineering marvel, and is providing researchers at Oregon State University with what they call “bioinspiration” in a quest to build the world’s first legged robot that is capable of running effortlessly over rough terrain.

If the engineers succeed, they may owe their success to what’s being learned from these insects and other animals, such as the guinea hen, that have their own remarkable abilities.

The latest findings – just published in the professional journal Bioinspiration and Biomimetics – outline how animals use their legs to manage energy storage and expenditure, and why this is so important for running stability. The work is being supported by the National Science Foundation.

“Humans can run, but frankly our capabilities are nothing compared to what insects and some other animals can do,” said John Schmitt, an assistant professor in the School of Mechanical, Industrial and Manufacturing Engineering at OSU. “Cockroaches are incredible. They can run fast, turn on a dime, move easily over rough terrain, and react to perturbations faster than a nerve impulse can travel.”

Within certain limitations, Schmitt said, cockroaches don’t even have to think about running – they just do it, with muscle action that is instinctive and doesn’t require reflex control. That, in fact, is part of what the engineers are trying to achieve. Right now some robots have been built that can walk, but none of them can run as well as their animal counterparts. Even walking robots absorb far too much energy and computing power to be very useful.

“If we ever develop robots that can really run over rough ground, they can’t afford to use so much of their computing abilities and energy demand to accomplish it,” Schmitt said. “A cockroach doesn’t think much about running, it just runs. And it only slows down about 20 percent when going over blocks that are three times higher than its hips. That’s just remarkable, and an indication that their stability has to do with how they are built, rather than how they react.”

If successful, Schmitt said, running robots could serve valuable roles in difficult jobs, such as military operations, law enforcement or space exploration. Related technology might also be applied to improve the function of prosthetic limbs for amputees, or serve other needs.

The OSU researchers are trying to identify some of the basic biological and mechanical principles that allow certain animals to run so well and effortlessly. A guinea hen, for instance, can change the length and angle of its spring-like legs to almost automatically adjust to an unexpected change in a ground surface as much as 40 percent of its hip height. That would be like a human running at full speed, stepping into a 16-inch-deep hole and never missing a beat.

Researchers are getting closer to their goal.

In a computer model, they’ve created a concept that would allow a running robot to recover from a change in ground surface almost as well as a guinea hen. They are studying how the interplay of concepts such as energy storage and expenditure, sensor and feedback requirements, and leg angles can produce recovery from such perturbations. Ultimately, a team of OSU engineers hopes to use knowledge such as this to actually build robots that can efficiently run over rough terrain without using significant computing power.

And some day, a robot – instead of a human – might be used to run into a dangerous area, check things out and report back for further instructions.

Oregon State University

GLACIER MELT ADDS ANCIENT EDIBLES TO MARINE BUFFET

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Glaciers along the Gulf of Alaska are enriching stream and near shore marine ecosystems from a surprising source – ancient carbon contained in glacial runoff, researchers from four universities and the U.S. Forest Service report in the Dec. 24, 2009, issue of the journal "Nature."

In spring 2008, Eran Hood, associate professor of hydrology with the Environmental Science Program at the University of Alaska Southeast, set out to measure the nutrients that reach the gulf from five glaciated watersheds he can drive to from his Juneau office. “We don’t currently have much information about how runoff from glaciers may be contributing to productivity in downstream marine ecosystems. This is a particularly critical question given the rate at which glaciers along the Gulf of Alaska are thinning and receding” said Hood.

Hood then asked former graduate school colleague Durelle Scott, now an assistant professor of biological systems engineering at Virginia Tech, to help analyze the organic matter and nutrient (nitrogen and phosphorus) loads being exported from the Juneau-area study watersheds. "Because there are few reports of nutrient yields from glacial watersheds, Eran and I decided to compare the result from a non-glacial watershed with those of a watershed partially covered by a glacier and a watershed fully covered by a glacier," said Scott.

Hood and Scott’s initial findings, reported in the September 2008 issue of the journal Nature Geoscience, presented something of a mystery. As might be expected, there is more organic matter from a forested watershed than from a fully or partially glacier-covered watershed. With soil development, organic matter is transported from the landscape during runoff events. However, there was still a considerable amount of organic carbon exported from the glaciated landscape.

How can a glacier be a source of the organic carbon? His curiosity peeked, in spring 2009, Hood's Ph.D. student, Jason Fellman, collected samples from 11 watersheds along the Gulf of Alaska from Juneau to the Kenai Peninsula. The samples were analyzed to determine the age, source, and biodegradability of organic matter derived from glacier inputs.

"We found that the more glacier there is in the watershed, the more carbon is bioavailable. And the higher the percentage of glacier coverage, the older the organic material is – up to 4,000 years old," said Scott.

Hood and Scott hypothesize that forests that lived along the Gulf of Alaska between 2,500 to 7,000 years ago were covered by glaciers, and this organic matter is now coming out. "The organic matter in heavily glaciated watersheds is labile, like sugar. Microorganisms appear to be metabolizing ancient carbon and as the microorganisms die and decompose, biodegradable dissolved organic carbon is being flushed out with the glacier melt," said Scott.

How much? "Our findings suggest that runoff from glaciers may be a quantitatively important source of bioavailable organic carbon for coastal ecosystems in the Gulf of Alaska and, as a result, future changes in glacier extent may impact the food webs in this region that support some of the most productive fisheries in the United States," said Hood.

(Photo: Virginia Tech)

Virginia Tech News

SHAPE SHIFTERS: NC STATE CREATES NEW BREED OF ANTENNAS

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Antennas aren’t just for listening to the radio anymore. They’re used in everything from cell phones to GPS devices. Research from North Carolina State University is revolutionizing the field of antenna design – creating shape-shifting antennas that open the door to a host of new uses in fields ranging from public safety to military deployment.

Modern antennas are made from copper or other metals, but there are limitations to how far they can be bent – and how often – before they break completely. NC State scientists have created antennas using an alloy that “can be bent, stretched, cut and twisted – and will return to its original shape,” says Dr. Michael Dickey, assistant professor of chemical and biomolecular engineering at NC State and co-author of the research.

The researchers make the new antennas by injecting an alloy made up of the metals gallium and indium, which remains in liquid form at room temperature, into very small channels the width of a human hair. The channels are hollow, like a straw, with openings at either end – but can be any shape. Once the alloy has filled the channel, the surface of the alloy oxidizes, creating a “skin” that holds the alloy in place while allowing it to retain its liquid properties.

“Because the alloy remains a liquid,” Dickey says, “it takes on the mechanical properties of the material encasing it.” For example, the researchers injected the alloy into elastic silicone channels, creating wirelike antennas that are incredibly resilient and that can be manipulated into a variety of shapes. “This flexibility is particularly attractive for antennas because the frequency of an antenna is determined by its shape,” says Dickey. “So you can tune these antennas by stretching them.”

While the alloy makes an effective antenna that could be used in a variety of existing electronic devices, its durability and flexibility also open the door to a host of new applications. For example, an antenna in a flexible silicone shell could be used to monitor civil construction, such as bridges. As the bridge expands and contracts, it would stretch the antenna – changing the frequency of the antenna, and providing civil engineers information wirelessly about the condition of the bridge.

Flexibility and durability are also ideal characteristics for military equipment, since the antenna could be folded or rolled up into a small package for deployment and then unfolded again without any impact on its function. Dickey thinks these new applications are the most likely uses for the new antennas, since the alloy is more expensive than the copper typically used in most consumer electronics that contain antennas.

Dickey’s lab is performing further research under a National Science Foundation grant to better understand the alloy’s properties and means of utilizing it to create useful devices.

(Photo: NCSU)

North Carolina State University

'PARTICLE SOUP' DISCOVERY WILL IMPROVE CLIMATE PREDICTIONS

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New research from scientists at The University of Manchester is set to improve predictions about climate and air quality – and make life easier for those suffering from respiratory problems.

Atmospheric researchers from the Centre for Atmospheric Science in the School of Earth, Atmospheric and Environmental Science (SEAES) worked with an international team of 60 scientists to study the behaviour of organic particulate once it has been released into the atmosphere.

Their findings appear in the world-leading journal Science.

Scientists have previously struggled to work out where the organic particulate comes from, why there is so much in the air and what happens to it.

A lack of information about their behaviour has led to incomplete or inaccurate prediction models for climate and air quality.

This is important for people suffering from respiratory illnesses like asthma, as better modelling and predictions could help them avoid atmospheric conditions which will adversely affect their health.

Now Manchester researchers and international colleagues have taken a more holistic approach to tracking the life cycles of airbourne compounds – and this promises to improve future predictions.

Organic compounds coat airbourne particles and make up as much as 90 per cent of all fine particle mass floating around in the atmosphere.

These particles influence cloud formation and therefore rainfall, as well as contributing to human disease and illness.

Through field observations and lab experiments, scientists have now found that organic matter tends to end up as a type of ‘goo’ with very similar physical and chemical properties – regardless of the source or where it is found in the atmosphere.

Researchers were surprised to find that organic matter found in airbourne particles looked very similar, whether collected in the heart of Mexico City, in an island in Japan, in a forest in Finland or up a mountain in the Swiss Alps.

As part of the new study, scientists have also created a chemical ‘map’, which provides some clear visualisation of how organic aerosols change once they become part of the particle soup. This promises to let people predict the ability of the organics to participate in cloud formation.

The research paper’s co-author Prof Hugh Coe of The University of Manchester said: “The organic content of airbourne particles is highly complex, but the approach we have taken in our research greatly simplifies our understanding.

“The particle soup we have found can be boiled down into a few measureable characteristics, such as oxygen to carbon ratio and the volatility of the particles, which are key variables for predicting climate and air quality.

“This international research provides a new framework for improving our knowledge of how organic material forms and how it evolves over time. It shows how in future air quality and climate models can incorporate this complexity in a simple but inclusive way.”

(Photo: U. Manchester)

The University of Manchester

SUN AND MOON TRIGGER DEEP TREMORS ON SAN ANDREAS FAULT

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The faint tug of the sun and moon on the San Andreas Fault stimulates tremors deep underground, suggesting that the rock 15 miles below is lubricated with highly pressurized water that allows the rock to slip with little effort, according to a new study by University of California, Berkeley, seismologists.

"Tremors seem to be extremely sensitive to minute stress changes," said Roland Bürgmann, UC Berkeley professor of earth and planetary science. "Seismic waves from the other side of the planet triggered tremors on the Cascadia subduction zone off the coast of Washington state after the Sumatra earthquake last year, while the Denali earthquake in 2002 triggered tremors on a number of faults in California. Now we also see that tides – the daily lunar and solar tides – very strongly modulate tremors."

In a paper in the Dec. 24 issue of the journal Nature, UC Berkeley graduate student Amanda M. Thomas, seismologist Robert Nadeau of the Berkeley Seismological Laboratory and Bürgmann argue that this extreme sensitivity to stress – and specifically to shearing stress along the fault – means that the water deep underground is under extreme pressure.

"The big finding is that there is very high fluid pressure down there, that is, lithostatic pressure, which means pressure equivalent to the load of all rock above it, 15 to 30 kilometers (10 to 20 miles) of rock," Nadeau said. "Water under very high pressure essentially lubricates the rock, making the fault very weak."

Though tides raised in the Earth by the sun and moon are not known to trigger earthquakes directly, they can trigger swarms of deep tremors, which could increase the likelihood of quakes on the fault above the tremor zone, the researchers say. At other fault zones, such as at Cascadia, swarms of tremors in the ductile zone deep underground correlate with slip at depth as well as increased stress on the shallower "seismogenic zone," where earthquakes are generated. The situation on the San Andreas Fault is not so clear, however.

"These tremors represent slip along the fault 25 kilometers (15 miles) underground, and this slip should push the fault zone above in a similar pattern," Bürgmann said. "But it seems like it must be very subtle, because we actually don't see a tidal signal in regular earthquakes. Even though the earthquake zone also sees the tidal stress and also feels the added periodic behavior of the tremor below, they don't seem to be very bothered."

Nevertheless, said Nadeau, "It is certainly in the realm of reasonable conjecture that tremors are stressing the fault zone above it. The deep San Andreas Fault is moving faster when tremors are more active, presumably stressing the seismogenic zone, loading the fault a little bit faster. And that may have a relationship to stimulating earthquake activity."

Seismologists were surprised when tremors were first discovered more than seven years ago, since the rock at that depth – for the San Andreas Fault, between 15 and 30 kilometers (10 to 20 miles) underground – is not brittle and subject to fracture, but deformable, like peanut butter. They called them non-volcanic tremors to distinguish them from tremors caused by fluid – water or magma – fracturing and flowing through rock under volcanoes. It was not clear, however, what caused the non-volcanic tremors, which are on the order of a magnitude 1 earthquake.

To learn more about the source of these tremors, UC Berkeley seismologists began looking for tremors five years ago in seismic recordings from the Parkfield segment of the San Andreas Fault obtained from sensitive bore-hole seismometers placed underground as part of the UC Berkeley's High-Resolution Seismic Network. Using eight years of tremor data, Thomas, Bürgmann and Nadeau correlated tremor activity with the effects of the sun and moon on the crust and with the effects of ocean tides, which are driven by the moon.

They found the strongest effect when the pull on the Earth from the sun and moon sheared the fault in the direction it normally breaks. Because the San Andreas Fault is a right-lateral strike-slip fault, the west side of the fault tends to break north-northwestward, dragging Los Angeles closer to San Francisco.

"When shear stress on a plane parallel to the San Andreas Fault most encourages slipping in its normal slip direction is when we see the maximum tremor rate," Bürgmann said. "The stress is many, many orders of magnitude less than the pressure down there, which was really, really surprising. You essentially could push it with your hand and it would move."

In fact, the shear stress from the sun, moon and ocean tides amount to around 100 Pascals, or one-thousandth atmospheric pressure, whereas the pressure 25 kilometers underground is on the order of 600 megaPascals, or 6 million times greater.

Nadeau and colleagues reported earlier this year that earthquakes in 2003 and 2004 near the Parkfield segment of the San Andreas Fault increased both tremor activity and stress on the fault itself.

In addition, Nadeau noted, other scientists have shown small tidal effects on tremors in the Cascadia subduction zone, with increased amplitude during certain periods, though they were unable to distinguish between tugs along the fault and tugs across, or normal to, the fault.

"We were really able to tighten the nuts down on whether it is a normal-fault stress change or an along-fault stress change that is stimulating the tremor," he said. The fact that tremors are triggered by along-fault shear stress "means that fluids are probably the explanation."

It may be that tremors only occur on faults where fluid is trapped deep underground with no cracks or fractures allowing it to squirt away, Nadeau added. That may explain why tremors are not observed on other faults, despite intense searching.

"There is still all lot to learn about tremor and earthquakes in fault zones," he said. "The fact that we find tremors adjacent to a locked fault, like the one at Parkfield, makes you think there are some more important relationships going on here, and we need to study it more."

University of California, Berkeley

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