Monday, May 3, 2010

TRACKING DOWN RUST

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Concrete bridges have to be strong enough to cope with a wide variety of different impacts: frost, heavy traffic and emissions all take their toll on these structures. And then there are the various types of road salt used in winter to combat icy roads. The most common of these is sodium chloride, which is deployed in large amounts on Germany's roads. When the ice thaws, these salts break down into their ionic components that penetrate the concrete, destroying its five-centimeter thick protective alkaline layer. Any salt that leaches through to the steel rods used to reinforce the concrete pad will cause them to rust, resulting in structural damage. The result is cracks. In a worst-case scenario the bridge itself could collapse.

Until now there have been no effective tests to determine how deep the ions have penetrated the concrete and what damage they have already caused. Current practice is time-consuming and involves construction workers hammering on the reinforced concrete in search of cavities, which are a sure sign of corrosion damage. But experts at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS in Duisburg have now hit upon a more reliable and cost-effective method for detecting rust corrosion at an early stage. With a new sensor-transponder they can continuously measure and monitor how deep the ions have penetrated the concrete. While the sensor was developed by the building materials testing facility in Braunschweig (MPA Braunschweig), the integrated passive wireless transponder system is the work of IMS researchers. The sensor itself is crisscrossed by very fine iron wires, laid down at even distances. »If the dissolved salts reach the iron wires, these begin to corrode and break. The number of defective iron wires is an indicator of the extent of corrosion and the depth to which the concrete's protective layer has been penetrated. This allows us to determine when the next repair work needs to be carried out,« explains Frederic Meyer, a researcher at the IMS. The transponder transmits the measured data by wireless to the reading device carried by the construction workers. »Our transponder does not get the energy it needs to measure the corrosion from a battery, but from a magnetic field. This means it does not need to be replaced and can remain within the concrete structure permanently,« says Meyer.

The first field tests are already underway, with the sensor-transponder being integrated and put through its paces in a test bridge constructed by the MPA Braunschweig. The researchers will be exhibiting a prototype at the EURO ID trade fair, to be held in Cologne from May 4 through 6.

(Photo: Fraunhofer IMS)

Fraunhofer-Gesellschaft

TOPOGRAPHY OF MOUNTAINS COULD COMPLICATE RATES OF GLOBAL WARMING

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A new study concludes that the future effects of global warming could be significantly changed over very small distances by local air movements in complex or mountainous terrain - perhaps doubling or even tripling the temperature increases in some situations.

In an article to be published in the International Journal of Climatology, researchers from Oregon State University used the unique historical data provided by Oregon's H.J. Andrews Experimental Forest to study potential variations in temperature caused by steep hills and valleys.

Based on a regional temperature increase of about 5 degrees projected for western Oregon by 2100, the study concluded that some locations, such as mountain ridge tops, could actually increase as much as 14 degrees at some times, while cold air pools in the valleys below them with temperature increases similar to the regional average.

"Even if the predictions for average temperature changes are accurate, there's been very little work done on what that may mean in specific locations and situations," said Chris Daly, an OSU professor of geosciences, director of OSU's PRISM Climate Group and expert on the effects of elevation and topography on localized climatic effects.

"We are finding that there's a potential here for tremendous disparities in local effects that we need to learn more about," Daly said. "Some locations may get much warmer than the average while others nearby are affected less, with associated impacts on their ecology, the plant and animals species that live there."

The steep terrain and long-term climate records in the H.J. Andrews Forest near Blue River, Ore., in the central Oregon Cascade Range, have provided an unusual data set to study this phenomenon. In general, temperatures decrease as you go up in altitude – but not necessarily in the mountains. Some ridges in the H.J. Andrews are routinely warmer than protected valleys below them, especially at night and during winter, as cool air drains down their flanks and forms "cold pools" with fairly stable temperatures.

The formation of these cold pools is most pronounced during clear, calm weather. Since the zone of high pressure that provides California with many clear, calm days is projected to shift northward in a warming climate, the Pacific Northwest may see an increase in cold air pooling in many mountain valleys. This could lead to amplified warming on the ridges of several degrees, compared to that in the valleys.

Ecological and hydrological impacts are likely, but difficult to predict. Douglas-fir forests tolerate a wide range of temperature conditions and are fairly resilient, Daly said, but some plant or animal species that can't readily move may face challenges.

Cool valley bottoms with more stable temperatures could actually act as refuges from the hotter ridge tops for some species, but are not expected to escape the overall warming that will affect the region. Variations in snowmelt between ridge tops and valleys are also likely to become more complex.

"At a larger scale, these changes in regional airflow patterns may also alter the flow of marine air from the Pacific Ocean that helps cool and ventilate the interior valleys during summer," Daly said. "If there are more times when that ocean air flow pattern shuts down, the valleys where most of the population lives could become much hotter than expected."

Similar forces could be found in many Mediterranean climates around the world, such as in Europe, South America and parts of the western U.S., which have climates that are controlled by the seasonal movement of high pressure belts, Daly said.

"There is more we need to be concerned about than overall warming, and we really haven't given these localized issues much consideration," he said.

Research will continue in the Andrews Forest to study these changes as they evolve, scientists said. Although not all U.S. mountains are topographically similar to this area, such steep terrain and poorly ventilated valleys are common in many parts of the Cascade Range, Sierra Nevada mountains, and Rocky Mountains.

(Photo: Oregon State University)

Oregon State University

RATTLESNAKES SOUND WARNING ON BIODIVERSITY AND HABITAT FRAGMENTATION

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Like the canary in the coal mine, the timber rattlesnake may be telling us something about the environment we share.

Cornell University researchers – using cutting-edge tools including fine-scale molecular genetics and microsatellite markers – tracked the rattlesnakes to understand how wildlife habitats are affected by even modest human encroachment.

"We used this species as a model to investigate general processes underlying population-level responses to habitat fragmentation," said the authors, led by Cornell post-doctoral researcher Rulon Clark, in the paper "Roads, Interrupted Dispersal and Genetic Diversity in Timber Rattlesnakes," currently available online and to be published in the journal Conservation Biology (August 2010).

Researchers discovered that fragmentation of natural habitats by roads – even smaller, low-traffic highways – has had a significant effect over the past 80 years on genetic structure of timber rattlesnakes in four separate regions of upstate New York. Less genetic diversity means populations become more susceptible to illness or environmental changes that threaten their survival.

"Our study adds to a growing body of literature indicating that even anthropogenic habitat modifications that does not destroy a large amount of habitat can create significant barriers to gene flow," said researchers.

While the rattlesnakes shorter lifespan and method of travel may help make the impact of roadways relatively quick and dramatic, the new findings reinforce earlier work on other terrestrial animals – from grizzly bears to frogs – and provides a fresh warning about habitat fragmentation that all plans for future human development must consider.

Researchers used fine-scale molecular genetics as well as behavioral and ecological data to look at timber rattlesnakes from 19 different hibernacula – shared wintering quarters – in four regions in New York: the Adirondacks, Sterling Forest, Bear Mountain and Chemung County. In each case they used microsatellite markers to track how populations dispersed from their winter dens, their subsequent reproductive patterns, and how roads in these areas altered that gene flow. The roads themselves – all paved roadways built in the late 1920s to early 19030s for motorized traffic – were examined for use and relationship to natural barriers. Tissue samples were examined from more than 500 individual snakes.

"Over all four regions and 19 hibernacula, none of the genetic clusters … spanned either major or minor roads; hibernacula belonging to the same genetic deme were always on the same side of the road," the paper states. "This fine-scaled analysis, repeated over four geographic regions, underscores the significance of roads as barrier to dispersal and natural population processes for timber rattlesnakes and perhaps other species."

Cornell University

CONTRABAND COULD HIDE IN PLAIN SIGHT

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As airport security employees scan luggage for a large variety of banned items, they may miss a deadly box cutter if they find a water bottle first.

According to new research at Duke University, identifying an easy-to-spot prohibited item such as a water bottle may hinder the discovery of other, harder-to-spot items in the same scan.

Missing items in a complex visual search is not a new idea: in the medical field, it has been known since the 1960s that radiologists tend to miss a second abnormality on an X-ray if they've found one already. The concept -- dubbed "satisfaction of search" -- is that radiologists would find the first target, think they were finished, and move on to the next patient's X-ray.

Does the principle apply to non-medical areas? That's what Stephen Mitroff, an assistant professor of psychology & neuroscience at Duke, and his colleagues set out to examine shortly after 2006, when the U.S. Transportation Security Administration banned liquids and gels from all flights, drastically changing airport luggage screens.

"The liquids rule has introduced a whole lot of easy-to-spot targets," Mitroff said.

In the new study, published online in the Journal of Experimental Psychology: Applied, Mitroff and his group asked college students to identify specific targets on a computer display – in this case, two perpendicular lines that form the letter "T" amid distracters, such as Ls and non-Ts. In some cases, Ts were easy to spot, and in other cases more difficult because they blended in with the background.

In an initial set of experiments, Mitroff and his colleagues altered the frequency of easy- and hard-to-spot targets. When the two kinds of targets appeared with equal frequency, subjects apparently had no trouble finding the hard-to-spot target in the presence of an easy one. But when the easy-to-spot item was two or three times more common, the subjects tended to overlook the hard-to-spot targets.

When Mitroff's group doubled the time allowed for each search, they saw that the students used barely a second of extra time but were significantly more accurate.

"It didn't seem to do with time itself, but it seems to be the time pressure," Mitroff said. "When you have the impending time pressure of going quickly, you are more likely to miss a second target."

Intriguingly, the data do not suggest subjects miss the second targets because they are too quick to end their search, an idea that would have bolstered the original satisfaction-of-search principle. "There seems to be some other mechanism, but it's not exactly clear what it is," Mitroff said.

One possible explanation is an idea called "attentional set," which suggests that finding one kind of target will make you more likely to find that same type of target rather than a new, different one. In radiology, it is like finding a fracture, which makes you more likely to find a second fracture rather than some other anomaly.

In an additional set of experiments, the researchers added time and accuracy pressure to the test by introducing small baggage icons that appeared along the top of the screen, mimicking a new bag on the security conveyer belt. One bag disappeared when subjects finished searching each display. They earned points for each display and the more quickly and accurately the subjects could identify the targets, the higher the points they received.

For one group of subjects, researchers set the speed of bags based on the each person's performance in a previous practice session. That group wasn't any worse at finding the second target than the first. In contrast, subjects following a brisk rate set by the researchers were worse at finding the second target.

"The results fit with what we think would happen if you remove the searcher from seeing the line," Mitroff said. In a remote search, the screeners will not know whether there is one person or 500 people waiting. "It's not in use, but these data suggest that it might be something worth trying."

Mitroff's group next has plans to replace T-targets with multiple targets of different types, such as tools and bottles.

Duke University

PERCEPTION: SKINNY PEOPLE AREN'T LAZY BUT OVERWEIGHT PEOPLE ARE

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Research at the University of Alberta shows that when a thin person is seen laying down watching television, people assume they're resting. But when people see an overweight person relaxing, it's automatically assumed they're lazy and unmotivated.

Tanya Berry, from the U of A's Faculty of Physical Education and Recreation, says these stereotypes about overweight people need to be addressed. Berry says just because a person is overweight, it doesn't mean they don't exercise, and just because a person is thin, it doesn't mean they are fit and healthy.

Berry had a group of study participants look at a number of pictures that would flash on a computer screen. After each photo a sedentary word such as "lazy" would appear. After the participants looked at each picture they were asked to say the colour of each word. Berry says when a picture of a thin "couch potato" came up, the participants were quick to say the colour of the word that appeared. But when a photo of an overweight person lying down appeared, the study participants paused. Berry concluded that the slow reaction resulted as the stereotyped thoughts automatically set in, with the participant thinking about the person being lazy rather than thinking about the colour of the word.

Berry says the research is important because stereotypes can influence the way people behave. She believes that more awareness of stereotypes can help people counter the effects. For example, if you're aware that you hold a stereotype about a couch potato you're less likely to be negatively influenced by those stereotypes.

University of Alberta

NEW METHODS IDENTIFY THOUSANDS OF NEW DNA SEQUENCES MISSING FROM THE HUMAN GENOME REFERENCE MAP

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Researchers have discovered 2,363 new DNA sequences corresponding to 730 regions on the human genome by using new approaches. These sequences represent segments of the genome that were not charted in the reference map of the human genome.

"A large portion of those sequences are either missing, fragmented or misaligned when compared to results from next-generation sequencing genome assemblies on the same samples," said Dr. Evan Eichler, senior author on the findings published April 19 in the advanced online edition of Nature Methods. Eichler is a University of Washington (UW) professor of genome sciences and an investigator with the Howard Hughes Medical Institute. "These findings suggest that new genome assemblies based solely on next-generation sequencing might miss many of these sites."

Dr. Jeffrey M. Kidd was lead author of the article, which described the new techniques the research team used to find some of the missing sequences.

Kidd headed the study while earning his Ph.D. at the University of Washington in the Eichler lab. Kidd is now a postdoctoral fellow at Stanford University.

"Over the past several years, the extent to which the structure of the genome varies among humans has become clearer. This variation suggested that there must be portions of the human genome where DNA sequences had yet to be discovered, annotated and characterized," he said "We hope that these sequences ultimately will be included as part of future releases of the reference human genome sequence."

The reference genome is a yardstick – or standard for comparison – for studies of human genetics.

The human reference genome was first created in 2001 and is updated every couple of years, Kidd explained. It's a mosaic of DNA sequences derived from several individuals. He went on to say that about 80 percent of the reference genome came from eight people. One of them actually accounts for more than 66 percent of the total.

Along with their collaborators at Agilent, the team designed ways to examine these newly identified sequences in a panel of people representing populations from around the world. The researchers found that, in some cases, the number of copies of these sequences varied from person to person.

The fact that a person can have one or more copies, or no copy at all, of a particular DNA sequence may account for why these sequences were missing from the reference genome. The researchers also found that some of these sequences were common or rare in different populations, depending on from which part of the globe their ancestors originated.

"Each segment of the reference genome is from a single person, and reflects the genome of that individual. If the donor sample was missing a sequence that many other people have, that sequence would not be represented in the reference genome." Kidd explained. "That is why some of the positions on the reference genome represent rare structural configurations or entirely omit sequences found in the majority of people." Kidd said that the study published in Nature Methods used information from nine individuals, representing various world populations, to search for and fill in some of the missing pieces.

By looking at genomes from seven kinds of animals, the researchers were also able to show that some of the newly identified DNA sequences appear to have been conserved during the evolution of mammals and man. The animals whose genomes were studied were chimpanzee, Bornean orangutan, Rhesus monkey, house mouse, Norway rat, dog, and horse.

"Some of the sequences were present in several different species, but were absent from the reference genome," Kidd said. "Some of the sequences present in several mammals actually correspond to sites of variations in humans – some people have retained a particular sequence, and others have lost it."

The researchers also developed a method to accurately genotype many of the newly found DNA sequences and created a way to look at variations in the number of copies of these sequences, thereby opening up regions of the human genome previously inaccessible to such studies.

"Scientists can now begin trying to understand the functional importance of these sequences and their variations," Kidd said.

The 1,000 Genomes Project (an international effort to fully sequence the genomes of a thousand anonymous individuals) and other genome studies are amassing massive amounts of data on DNA sequences that are then mapped to the reference genome, he added. Any study, he continued, that improves the completeness and quality of the reference genome assembly will thereby benefit these projects and lead to a fuller picture of the extent of human genomic variation.

The findings are published as "Characterization of missing human genome sequences and copy-number polymorphic insertions," in Nature Methods.

University of Washington

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