Tuesday, February 2, 2010


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Even simple insects can generate quite different movement patterns with their six legs. The animal uses various gaits depending on whether it crawls uphill or downhill, slowly or fast. Scientists from Göttingen have now developed a walking robot, which - depending on the situation - can flexibly and autonomously switch between different gaits.

The success of their solution lies in its simplicity: a small and simple network with just a few connections can create very diverse movement patterns. To this end, the robot uses a mechanism for "chaos control". This interdisciplinary work was carried out by a team of scientists at the Bernstein Center for Computational Neuroscience Göttingen, the Physics Department of the Georg-August-University of Göttingen and the Max Planck Institute for Dynamics and Self-Organization.

In humans and animals, periodically recurring movements like walking or breathing are controlled by small neural circuits called "central pattern generators" (CPG). Scientists have been using this principle in the development of walking machines. To date, typically one separate CPG was needed for every gait. The robot receives information about its environment via several sensors - about whether there is an obstacle in front of it or whether it climbs a slope. Based on this information, it selects the CPG controlling the gait that is appropriate for the respective situation.

The robot developed by the Göttingen scientists now manages the same task with only one CPG that generates entirely different gaits and which can switch between these gaits in a flexible manner. This CPG is a tiny network consisting of two circuit elements. The secret of its functioning lies in the so-called "chaos control". If uncontrolled, the CPG produces a chaotic activity pattern. This activity, however, can very easily be controlled by the sensor inputs into periodic patterns that determine the gait. Depending on the sensory input signal, different patterns - and thus different gaits - are generated.

The connection between sensory properties and CPG can either be preprogrammed or learned by the robot from experience. The scientists use a key example to show how this works: the robot can autonomously learn to walk up a slope with as little energy input as possible. As soon as the robot reaches a slope, a sensor shows that the energy consumption is too high. Thereupon, the connection between the sensor and the control input of the CPG is varied until a gait is found that allows the robot to consume less energy. Once the right connections have been established, the robot has learned the relation between slope and gait. When it tries to climb the hill a second time, it will immediately adopt the appropriate gait.

In the future, the robot will also be equipped with a memory device which will enable it to complete movements even after the sensory input ceases to exist. In order to walk over an obstacle, for instance, the robot would have to take a large step with each of its six legs. "Currently, the robot would not be able to handle this task - as soon as the obstacle is out of sight, it no longer knows which gait to use," says Marc Timme, scientist at the Max Planck Institute for Dynamics and Self-Organization. "Once the robot is equipped with a motor memory, it will be capable to use foresight and plan its movements".

(Photo: Network Dynamics Group, Max Planck Institute for Dynamics and Self-Organization)

Max Planck Institute


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Springtime ozone levels above western North America are rising primarily due to air flowing eastward from the Pacific Ocean, a trend that is largest when the air originates in Asia. These increases in ozone could make it more difficult for the United States to meet Clean Air Act standards for ozone pollution at ground level, according to a new international study. Published online in the journal Nature, the study analyzed large sets of ozone data captured since 1984.

“In springtime, pollution from across the hemisphere, not nearby sources, contributes to the ozone increases above western North America,” said lead author Owen R. Cooper, Ph.D., of the NOAA-funded Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder. “When air is transported from a broad region of south and east Asia, the trend is largest.”

The study focused on springtime ozone in a slice of the atmosphere from two to five miles above the surface of western North America, far below the protective ozone layer but above ozone-related, ground-level smog that is harmful to human health and crops. Ozone in this intermediate region constitutes the northern hemisphere background or baseline level of ozone in the lower atmosphere. The study was the first to pull together and then analyze the nearly 100,000 ozone observations gathered in separate studies by instruments on aircraft, balloons, and other platforms.

Combustion of fossil fuels releases pollutants like nitrogen oxides and volatile organic compounds, or VOCs, which react in the presence of sunlight to form ozone. North American emissions contribute to global ozone levels, but the researchers did not find any evidence that these local emissions are driving the increasing trend in ozone above western North America.

Cooper and colleagues from NOAA’s Earth System Research Laboratory in Boulder, Colo., and eight other research institutes used historical data of global atmospheric wind records and sophisticated computer modeling to match each ozone measurement with air-flow patterns for several days before it was recorded. This approach essentially let the scientists track ozone-producing emissions back to a broad region of origin.

This method is like imagining a box full of 40,000 tiny weightless balls at the exact location of each ozone measurement, explained Cooper. Considering winds in the days prior to the measurement, the computer model estimates which winds brought the balls to that spot and where they originated.

When the dominant airflow came from south and east Asia, the scientists saw the largest increases in ozone measurements. When airflow patterns were not directly from Asia, ozone still increased but at a lower rate, indicating the possibility that emissions from other places could be contributing to the ozone increases above North America. The study used springtime ozone measurements because previous studies have shown that air transport from Asia to North America is strongest in spring, making it easier to discern possible effects of distant pollution on the North American ozone trends.

Ozone-measuring research balloons and research aircraft collected a portion of the data. Commercial flights equipped with ozone measuring instruments also collected a large share of the data through the MOZAIC program, initiated by European scientists in 1994. The bulk of the data was collected between 1995 and 2008, but the team also included a large ozone dataset from 1984.

The analysis shows an overall significant increase in springtime ozone of 14 percent from 1995 to 2008. When they included data from 1984, the year with the lowest average ozone level, the scientists saw a similar rate of increase from that time through 2008 and an overall increase in springtime ozone of 29 percent.

“This study did not quantify how much of the ozone increase is solely due to Asia,” Cooper said. “But we can say that the background ozone entering North America increased over the past 14 years and probably over the past 25 years.”

The influence of ozone from Asia and other sources on ground-level air quality is a question for further study, Cooper said. Scientists will need to routinely measure ozone levels close to the surface at several locations along the West Coast to see whether similar trends are impacting ground-level air quality.

(Photo: NOAA)

National Oceanic and Atmospheric Administration


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Astronomers have found a giant magnetic loop stretched outward from one of the stars making up the famous double-star system Algol. The scientists used an international collection of radio telescopes to discover the feature, which may help explain details of previous observations of the stellar system.

"This is the first time we've seen a feature like this in the magnetic field of any star other than the Sun," said William Peterson, of the University of Iowa.

The pair, 93 light-years from Earth, includes a star about 3 times more massive than the Sun and a less-massive companion, orbiting it at a distance of 5.8 million miles, only about six percent of the distance between Earth and the Sun. The newly-discovered magnetic loop emerges from the poles of the less-massive star and stretches outward in the direction of the primary star. As the secondary star orbits its companion, one side -- the side with the magnetic loop -- constantly faces the more-massive star, just as the same side of our Moon always faces the Earth.

The scientists detected the magnetic loop by making extremely detailed images of the system using an intercontinental set of radio telescopes, including the National Science Foundation's Very Long Baseline Array, Very Large Array, and Robert C. Byrd Green Bank Telescope, along with the Effelsberg radio telescope in Germany. These radio telescopes were used as a single observing system that offered both great detail, or resolving power, and high sensitivity to detect very faint radio waves. When working together, these telescopes are known as the High Sensitivity Array.

Algol, in the constellation Perseus, is visible to the naked eye and well-known to amateur astronomers. As seen from Earth, the two stars regularly pass in front of each other, causing a notable change in brightness. The pair completes a cycle of such eclipses in less than three days, making it a popular object for amateur observers. The variability in brightness was discovered by an Italian astronomer in 1667, and the eclipsing-binary explanation was confirmed in 1889.

The newly-discovered magnetic loop helps explain phenomena seen in earlier observations of the Algol system at X-ray and radio wavelengths, the scientists said. In addition, they now believe there may be similar magnetic features in other double-star systems.

(Photo: Peterson et al., NRAO/AUI/NSF)

National Radio Astronomy Observatory


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A new study from the University of Leicester has found that most men in Europe descend from the first farmers who migrated from the Near East 10,000 years ago. The findings were published January 19 in the open-access journal PLoS Biology.

The invention of farming is perhaps the most important cultural change in the history of modern humans. Increased food production led to the development of societies that stayed put, rather than wandering in search of food. The resulting population growth culminated in the seven billion people who now live on the planet. In Europe, farming spread from the ‘Fertile Crescent’, a region extending from the eastern Mediterranean coast to the Persian Gulf and including the Tigris and Euphrates valleys.

There has been much debate about whether the westerly spread of agriculture from the Near East was driven by farmers actually migrating, or by the transfer of ideas and technologies to indigenous hunter-gatherers. Now, researchers have studied the genetic diversity of modern populations to throw light on the processes involved in these ancient events.

The new study, funded by the Wellcome Trust, examines the diversity of the Y chromosome, which is passed from father to son. Professor Mark Jobling, who led the research, said: “We focused on the commonest Y-chromosome lineage in Europe, carried by about 110 million men – it follows a gradient from south-east to north-west, reaching almost 100% frequency in Ireland. We looked at how the lineage is distributed, how diverse it is in different parts of Europe, and how old it is.” The results suggested that the lineage spread together with farming from the Near East.

Dr Patricia Balaresque, first author of the study, added: “In total, this means that more than 80% of European Y chromosomes descend from incoming farmers. In contrast, most maternal genetic lineages seem to descend from hunter-gatherers. To us, this suggests a reproductive advantage for farming males over indigenous hunter-gatherer males during the switch from hunting and gathering, to farming – maybe, back then, it was just sexier to be a farmer.”

(Photo: © Michael Greenhalgh)

University of Leicester


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The UK will not be able to achieve its target of reducing carbon emissions by 80 per cent by 2050 unless it urgently addresses carbon emissions from the built environment, according to a report published by the Royal Academy of Engineering.

Buildings currently account for 45 per cent of our carbon emissions but it is estimated that 80 per cent of the buildings we will be occupying in 2050 have already been built.

Many 20th century buildings are totally dependent on fossil fuel energy to make them habitable - in the 21st century buildings must be designed to function with much lower levels of energy dependency. The scale of this challenge is vast and will require both effective Government policy and a dramatic increase in skills and awareness in the construction sector.

Report author Doug King, founder of consulting engineers King Shaw Associates and Royal Academy of Engineering Visiting Professor in Building Engineering Physics at the University of Bath, says: “The sheer pace of change in the regulation of building energy performance has already created problems for the construction industry and the proposed acceleration of this process, aiming to achieve zero-carbon new buildings by 2020, will only widen the gulf between ambitious Government policy and the industry’s ability to deliver.”

The report introduces a new discipline; Building Engineering Physics, which supports the existing professions of architecture, structural engineering and building services engineering.

Building Engineering Physics investigates the areas of natural science that relate to the energy performance of buildings and their indoor and outdoor environments. The understanding and application of Building Engineering Physics allows us to design and construct high performance buildings which are comfortable and functional, yet use natural resources efficiently and minimise the environmental impacts of their construction and operation.

Before renewable energy generation is even considered it is vital to ensure that buildings are as energy efficient as possible, otherwise the potential benefits are simply wasted in offsetting un-necessary consumption.

Creative solutions to make buildings more energy efficient include basic techniques, known for thousands of years, such as using daylight, natural ventilation and thermal mass, where masonry is used to store heat and moderate temperature variations.

However, with the application of scientific analysis through Building Engineering Physics, these aspects of a building’s design can make a very substantial contribution to meeting the performance and comfort needs of the occupants without resorting to energy consuming building services installations.

One of the most pressing needs in the construction industry at present is for reliable information on the actual energy and carbon performance of newly built or refurbished buildings, to validate new designs and establish benchmarks.

Government, which has set ambitious policy on climate change, can lead by example, ensuring that full commissioning and post-occupancy evaluations against design targets are undertaken on all new publicly funded projects. Publication of this information would quickly build a database of successful low-carbon design solutions to inform other design teams.

Nevertheless, the construction industry faces a serious skills issue in meeting the low-carbon building challenge. Few in the construction industry know how to apply the principles of Building Engineering Physics in the design of buildings and low-carbon design is scarcely taught at university level. The industry and educators are often still struggling to get to grips with the 2006 revision of the Building Regulations, which first required cuts in Carbon emissions against previous practice.

Yet within three years of the 2009 undergraduate intake graduating in 2013, they, and the rest of the industry, will be required to deliver not just reduced-carbon but zero-carbon new domestic buildings.

“We need engineers to think of buildings and their environments as complete energy systems,” says Doug King. “The work of the Royal Academy of Engineering Visiting Professors is clearly starting to make a difference in encouraging imaginative interdisciplinary design.

“One of the case studies featured in the report is a concept design project by students at the University of Cambridge for a house powered by hydrogen-producing algae.”

Dr Scott Steedman FREng says: “Our homes and buildings are the front line for the UK to reduce its consumption of energy and to manage resources in a more sustainable manner - yet we are not going to solve this challenge with loft insulation and double glazing alone.

“We need measures that go beyond the traditional solutions - new materials, new installation processes, new controls that are based on a engineering approach to the thermal upgrading of existing buildings and the design of new buildings. This Royal Academy of Engineering report on building engineering physics points the way forward.”

(Photo: Vaxomatic)

University of Bath


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Biologists at the University of Pennsylvania studying the processes of evolution appear to have resolved a longstanding conundrum: How can organisms be robust against the effects of mutations yet simultaneously adaptable when the environment changes?

The short answer, according to University of Pennsylvania biologist Joshua B. Plotkin, is that these two requirements are often not contradictory and that an optimal level of robustness maintains the phenotype in one environment but also allows adaptation to environmental change.

Using an original mathematical model, researchers demonstrated that mutational robustness can either impede or facilitate adaptation depending on the population size, the mutation rate and a measure of the reproductive capabilities of a variety of genotypes, called the fitness landscape. The results provide a quantitative understanding of the relationship between robustness and evolvability, clarify a significant ambiguity in evolutionary theory and should help illuminate outstanding problems in molecular and experimental evolution, evolutionary development and protein engineering.

The key insight behind this counterintuitive finding is that neutral mutations can set the stage for future, beneficial adaptation. Specifically, researchers found that more robust populations are faster to adapt when the effects of neutral and beneficial mutations are intertwined. Neutral mutations do not impact the phenotype, but they may influence the effects of subsequent mutations in beneficial ways.

To quantify this idea, the study’s authors created a general mathematical model of gene interactions and their effects on an organism’s phenotype. When the researchers analyzed the model, they found that populations with intermediate levels of robustness were the fastest to adapt to novel environments. These adaptable populations balanced genetic diversity and the rate of phenotypically penetrant mutations to optimally explore the range of possible phenotypes.

The researchers also used computer simulations to check their result under many alternative versions of the basic model. Although there is not yet sufficient data to test these theoretical results in nature, the authors simulated the evolution of RNA molecules, confirming that their theoretical results could predict the rate of adaptation.

“Biologists have long wondered how can organisms be robust and also adaptable,” said Plotkin, assistant professor in the Department of Biology in Penn’s School of Arts and Sciences. “After all, robust things don’t change, so how can an organism be robust against mutation but also be prepared to adapt when the environment changes? It has always seemed like an enigma.”

Robustness is a measure of how genetic mutations affect an organism’s phenotype, or the set of physical traits, behaviors and features shaped by evolution. It would seem to be the opposite of evolvability, preventing a population from adapting to environmental change. In a robust individual, mutations are mostly neutral, meaning they have little effect on the phenotype. Since adaptation requires mutations with beneficial phenotypic effects, robust populations seem to be at a disadvantage. The Penn-led research team has demonstrated that this intuition is sometimes wrong.

University of Pennsylvania




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