Friday, June 18, 2010


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Cycling crash helmets have just one purpose: to protect the cyclist's head. But only completely damage-free helmets do the job properly. It is therefore recommendable to buy a new one every now and again, but nobody wants to throw away a perfectly good helmet. It would be better to know for certain that this is really necessary.

A new process developed by research scientists at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg in cooperation with the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT in Oberhausen makes this possible. The polymer materials or plastics produced by the process start to smell if they develop small cracks. Large cracks really cause a stink. The smell comes from odoriferous oils enclosed in microcapsules. “Cyclists often replace their helmets unnecessarily after dropping them on the ground, because they cannot tell whether they are damaged or not. The capsules eliminate this problem. If cracks form, smelly substances are released,” explains Dr.-Ing. Christof Koplin, research scientist at the IWM. The capsules are added to a polypropylene mass which is injection-molded to form the final component. In the case of the bicycle helmet, the microcapsules are inserted in a thick foil made of polypropylene, which is fastened to the head gear.

A layer of melamine formaldehyde resin encloses the capsules so that they are completely airtight and mechanically sealed. It also protects the tiny pods, which are subjected to temperatures of 200 to 300 degrees during injection molding as well as static pressures of up to 100 bar. “Melamine formaldehyde resin proved to be the most suitable encapsulation material in the comparison we conducted of the material systems,” explains Koplin. “Inside the capsule there is a porous, hardly deformable silicon oxide core which absorbs the odoriferous substance. This core produced the best results,” he adds.

To determine the loads at which the miniscule capsules measuring just 1 to 50 micrometers break open, the scientists test them at the IWM with a Vickers indenter. The engineers calculate the number of capsules required by means of numerical computer simulation. The finished component is then subjected to bending and drawing tests. The tests are only deemed to be successfully completed if the capsules are found to open and exude the odoriferous substances just before the component fails. Koplin: “Our method of detection by smell offers several advantages. It not only indicates when safety-critical polymer components need to be replaced. The exuding smells also enable damage outside the safety range to be detected.”

The process is therefore suitable for all products which are difficult to test for defects, such as cycle, motorbike and construction helmets. But it can also be used to check pressure hoses, e.g. in washing machines, which are difficult to access. Smell sensors could also monitor plastic water and gas supply pipes to detect any cracks, because the odoriferous substances emitted are noticeable over long distances. “Smell detection is already in use for coated metal components. We are applying the process for the first time to polymer materials. The cycle helmet is being used as a demonstrator. Work on the capsules has finished and we are now completing characterizing tests on individual configurations,” states Koplin.

(Photo: © Fraunhofer IWM)

Fraunhofer Institute


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The Earth and Moon were created as the result of a giant collision between two planets the size of Mars and Venus. Until now it was thought to have happened when the solar system was 30 million years old or approx. 4,537 million years ago. But new research from the Niels Bohr Institute shows that the Earth and Moon must have formed much later – perhaps up to 150 million years after the formation of the solar system. The research results have been published in the scientific journal, Earth and Planetary Science Letters.

"We have determined the ages of the Earth and the Moon using tungsten isotopes, which can reveal whether the iron cores and their stone surfaces have been mixed together during the collision", explains Tais W. Dahl, who did the research as his thesis project in geophysics at the Niels Bohr Institute at the University of Copenhagen in collaboration with professor David J. Stevenson from the California Institute of Technology (Caltech).

The planets in the solar system were created by collisions between small dwarf planets orbiting the newborn sun. In the collisions the small planets melted together and formed larger and larger planets. The Earth and Moon are the result of a gigantic collision between two planets the size of Mars and Venus. The two planets collided at a time when both had a core of metal (iron) and a surrounding mantle of silicates (rock). But when did it happen and how did it happen? The collision took place in less than 24 hours and the temperature of the Earth was so high (7000º C), that both rock and metal must have melted in the turbulent collision. But were the stone mass and iron mass also mixed together?

Until recently it was believed that the rock and iron mixed completely during the planet formation and so the conclusion was that the Moon was formed when the solar system was 30 million years old or approximately 4,537 million years ago. But new research shows something completely different.

The age of the Earth and Moon can be dated by examining the presence of certain elements in the Earth's mantle. Hafnium-182 is a radioactive substance, which decays and is converted into the isotope tungsten-182. The two elements have markedly different chemical properties and while the tungsten isotopes prefer to bond with metal, hafnium prefers to bond to silicates, i.e. rock.

It takes 50-60 million years for all hafnium to decay and be converted into tungsten, and during the Moon forming collision nearly all the metal sank into the Earth's core. But did all the tungsten go into the core?

"We have studied to what degree metal and rock mix together during the planet forming collisions. Using dynamic model calculations of the turbulent mixing of the liquid rock and iron masses we have found that tungsten isotopes from the Earth's early formation remain in the rocky mantle", explains Tais W. Dahl, Niels Bohr Institute at the University of Copenhagen.

The new studies imply that the moon forming collision occurred after all of the hafnium had decayed completely into tungsten.

"Our results show that metal core and rock are unable to emulsify in these collisions between planets that are greater than 10 kilometres in diameter and therefore that most of the Earth's iron core (80-99 %) did not remove tungsten from the rocky material in the mantle during formation", explains Tais W. Dahl.

The result of the research means that the Earth and the Moon must have been formed much later than previously thought – that is to say not 30 million years after the formation of the solar system 4,567 million years ago but perhaps up to 150 million years after the formation of the solar system.

(Photo: U. Copenhagen)

University of Copenhagen


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A new study pinpoints the genetic changes that enable Tibetans to thrive at altitudes where others get sick.

In the online edition of Proceedings of the National Academy of Sciences, an international team has identified a gene that allows Tibetans to live and work more than two miles above sea level without getting altitude sickness.

A previous study published May 13 in Science reported that Tibetans are genetically adapted to high altitude. Now, less than a month later, a second study by scientists from China, England, Ireland, and the United States pinpoints a particular site within the human genome — a genetic variant linked to low hemoglobin in the blood — that helps explain how Tibetans cope with low-oxygen conditions.

The study sheds light on how Tibetans, who have lived at extreme elevation for more than 10,000 years, have evolved to differ from their low-altitude ancestors.

Lower air pressure at altitude means fewer oxygen molecules for every lungful of air. "Altitude affects your thinking, your breathing, and your ability to sleep. But high-altitude natives don't have these problems," said co-author Cynthia Beall of Case Western Reserve University. "They're able to live a healthy life, and they do it completely comfortably," she said.

People who live or travel at high altitude respond to the lack of oxygen by making more hemoglobin, the oxygen-carrying component of human blood. "That's why athletes like to train at altitude. They increase their oxygen-carrying capacity," said Beall.

But too much hemoglobin can be a bad thing. Excessive hemoglobin is the hallmark of chronic mountain sickness, an overreaction to altitude characterized by thick and viscous blood. Tibetans maintain relatively low hemoglobin at high altitude, a trait that makes them less susceptible to the disease than other populations.

"Tibetans can live as high as 13,000 feet without the elevated hemoglobin concentrations we see in other people," said Beall.

To pinpoint the genetic variants underlying Tibetans' relatively low hemoglobin levels, the researchers collected blood samples from nearly 200 Tibetan villagers living in three regions high in the Himalayas. When they compared the Tibetans' DNA with their lowland counterparts in China, their results pointed to the same culprit — a gene on chromosome 2, called EPAS1, involved in red blood cell production and hemoglobin concentration in the blood.

Originally working separately, the authors of the study first put their findings together at a March 2009 meeting at the National Evolutionary Synthesis Center in Durham, NC. "Some of us had been working on the whole of Tibetan DNA. Others were looking at small groups of genes. When we shared our findings we suddenly realized that both sets of studies pointed to the same gene — EPAS1," said Robbins, who co-organized the meeting with Beall.

While all humans have the EPAS1 gene, Tibetans carry a special version of the gene. Over evolutionary time individuals who inherited this variant were better able to survive and passed it on to their children, until eventually it became more common in the population as a whole.

"This is the first human gene locus for which there is hard evidence for genetic selection in Tibetans," said co-author Peter Robbins of Oxford University.

Researchers are still trying to understand how Tibetans get enough oxygen to their tissues despite low levels of oxygen in the air and bloodstream. Until then, the genetic clues uncovered so far are unlikely to be the end of the story. "There are probably many more signals to be characterized and described," said co-author Gianpiero Cavalleri of the Royal College of Surgeons in Ireland.

For those who live closer to sea level, the findings may one day help predict who is at greatest risk for altitude sickness. "Once we find these versions, tests can be developed to tell if an individual is sensitive to low-oxygen," said co-author Changqing Zeng of the Beijing Institute of Genomics.

"Many patients, young and old, are affected by low oxygen levels in their blood —perhaps from lung disease, or heart problems. Some cope much better than others," said co-author Hugh Montgomery, of University College London. "Studies like this are the start in helping us to understand why, and to develop new treatments."

(Photo: Wikimedia Commons)

National Evolutionary Synthesis Center


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The Yangtze River in China is 40 million years older than was previously thought, according to new research.

A study of minerals by a team led by Durham University reveals that the Yangtze River began to cut the Three Gorges area around 45 million years ago, making it much older than previously believed.

The Yangtze River, the third-longest river in the world, has played a central role in the development of Chinese culture, and the Three Gorges, which separate the Sichuan Basin in the west from the lowlands of central and eastern China to the east, have particular historical, cultural, and geomorphological significance.

Without the transport pathway created by the Three Gorges, south-western China – including the rich agricultural area of Sichuan Province, known as China's 'rice bowl' – would have remained cut off from the rest of the country by the otherwise inaccessible mountains that surround the region.

The new findings, published in Geology, show that sediments from the Three Gorges, previously analysed by researchers and dated as being only 1-2 million years old, must have been deposited long after the Three Gorges were cut.

The research team, led by Dr Alexander Densmore from the Institute of Hazard, Risk and Resilience, Durham University, determined the onset of incision in the Three Gorges by looking at the cooling of minerals in the granite that underlies the Three Gorges Dam at Sandouping in Hubei Province. The granite containing these apatite grains was cooled to lower temperatures as the river cut down through it.

Prior work on the origin of the Three Gorges has shown that the Yangtze River most likely began as a set of small, non-descript streams that drained both west and east, out of a range of low mountains in central China.

It was argued that the merger of these streams gave rise to the progressive development of a much larger, east-flowing river system that became the Yangtze River. Many scientists agreed that the most likely point of merger of the streams was in the Three Gorges area.

Dr Alex Densmore said: "The fact that erosion had removed all of the evidence of the old, pre-merger river courses made dating the river particularly difficult.

"Prior attempts to date the Three Gorges placed their age at only 1-2 million years but this was based on sediments found within the gorges. If this were the case, the river would have had to have been carved into the rocks very quickly, and this would have required extremely high incision rates.

"We used the number of damage trails in the mineral apatite to tell us when the rocks were cooled below a particular temperature and thus when gorge incision began."

The research team, which involved scientists from Durham, Chengdu and Victoria universities, and researchers in the UK and Germany, found that samples near the gorges showed that cooling began about 45 million years ago, whereas samples taken farther away from the river show no evidence of that cooling. Thus, the cooling must have been caused by gorge incision, rather than by more regional erosion, according to the scientists.

Dr Densmore added: "The Yangtze River is much older than previously thought and extremely high incision rates were not required to create the distinctive gorges. It formed slowly, over a much longer time-span."

The research, funded by the Swiss Federal Institute of Technology, also helped to explain a mysterious episode of erosion that affected the eastern part of the Tibetan Plateau. 45 million years ago, sediment shed from the rising Tibetan Plateau to the west was trapped in a large basin upstream of the future Three Gorges area.

Dr Densmore said: "As the Gorges were cut, they acted as like a plughole in a giant bathtub, allowing that sediment to be eroded and flushed down into the growing Yangtze River and out into the East China Sea, depositing the sediment in the lowland areas of eastern China."

Durham University


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Scientists have for the first time determined the complete genome sequence of a brown alga and opened a new door to the understanding of multicellularity and photosynthesis.

With the world's first complete sequencing of a brown algal genome, an international research team has made a big leap towards understanding the evolution of two key prerequisites for higher life on Earth - multicellularity and photosynthesis. As the internationally renowned science magazine "Nature" reported in its latest issue, about 100 scientists and technicians, during a five-year research project, successfully decoded all hereditary information – commonly known as the "genome" - on Ectocarpus siliculosus, an up to 20 cm large brown seaweed, which occurs mainly along coastlines in temperate latitudes. They have analyzed approximately 214 million base pairs and assigned these to about 16,000 genes. The biologists, Dr. Klaus Valentin and Dr. Bank Beszteri of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association have been involved in this global project since the planning phase in 2005.

“As evolutionary scientists we are particularly interested in why the world has developed as we know it today” said Klaus Valentin about this project. “During earth’s history, complex multicellular life has evolved from unicellular organisms along five independent paths, which are: animals, plants, fungi, red algae and brown algae.” Evolutionary scientists have therefore set themselves the goal to decode a complete genome from a representative of each of these lines and to look for comparable genetic information. “This goal has now been achieved for the brown algal genome. The decoding of a red algal genome has already been completed, and we are currently evaluating the data” says Valentin on the future prospects of comparative genomics. “And indeed, in the brown alga, we found many genes for so called kinases, transporter and transcription factors. Such genes are also commonly found in land plants, and we suspect that they also play a key role in the origin of multicellular organisms”.

The sequencing of the brown algal genome is also a milestone in the efforts to reconstruct the evolution of photosynthesis. “We now know that oxygen-producing photosynthesis was ‘invented’ before about 3.8 billion years ago, by cyanobacteria, sometimes erroneously called ‘blue-green algae’”, says Valentin about the elemental capability of plants to convert sunlight into biologically usable energy, whilst releasing oxygen. “Green and red algae have developed this ability after their ancestors scavenged living cyanobacteria, and thus more or less captured photosynthesis, to the benefit of both sides, since this symbiosis resulted in tremendous competitive advantages in the primordial ocean”.

Brown algae were assumed to have arisen from the fusion of photosynthetically inactive colourless cells with a unicellular red alga. However, as discovered in a previous research project on single-celled diatoms, AWI researchers showed that brown algae also arose from the fusion of a green alga with a red alga and thus refuted a widespread theory among experts. “Interestingly”, says Klaus Valentin, “In the brown alga we discovered, a high proportion of genes that are characteristic of green algae, including the kinases and transporters typical for multicellular land plants, as mentioned above. To which extent we have traced common origins of multicellular life, will have to be determined in future investigations”.

From an ecological point of view, however, brown algae are also an exciting study object. On the rocky shores of polar and temperate latitudes, their role in the ecosystem is similar to that of trees on the mainland. Some species can reach lengths of up to 160 meters. These “submarine forests” are not only an important habitat for marine animals, but in areas with strong tides, they often fall dry for several hours and reveal an incredible stress tolerance. “In the context of climate change, we have now become interested in how brown algae have adapted to UV light and increasing temperatures. How they adjust to changing living conditions,” mentions Klaus Valentin, is one of the aspects of research on ocean forests at the Alfred Wegener Institute. “In addition, brown algae are evolutionary speaking much older than terrestrial plants. They have multiple metabolic properties, but these have barely been studied. A better understanding of the properties locked up in the genes could also be a foundation for the development of new products and technologies”.

(Photo: Udo Schilling)

Alfred Wegener Institute


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The mystery of how the world's largest living reptile - the estuarine crocodile - has come to occupy so many South Pacific islands separated by huge stretches of ocean despite being a poor swimmer has at last been solved by a group of Australian ecologists. Publishing their new study in the British Ecological Society's Journal of Animal Ecology, they say that like a surfer catching a wave, the crocodiles ride ocean currents to cross large areas of open sea.

The estuarine crocodile (Crocodylus porosus) is a semi-aquatic reptile, living mainly in rivers, mangroves and estuaries. Its geographical range extends over 10,000 km2 of the South-East Pacific, from East India to Fiji and from southern China to North Australia. Although it spends most of its life in salt-water, it cannot be considered a marine reptile in the same way as a turtle is, for example, because it relies on land for food and water.

Many anecdotal accounts exist of large crocodiles being sighted far out to sea, but this is the first study to show – using underwater acoustic tags and satellite tracking – that estuarine crocodiles ride surface currents during long-distance travel, which would enable them to voyage from one oceanic island and another.

The results explain why, despite occupying such a large range, species diversification of the estuarine crocodile has not occurred.

Working in the remote Kennedy River in North Queensland, Australia, Dr Hamish Campbell from University of Queensland and colleagues from Queensland Parks and Wildlife Service and Australia Zoo tagged 27 adult estuarine crocodiles with sonar transmitters and used underwater receivers to track their every move over 12 months.

During that time they recorded 1.2 million data packets and found that both male and female adult crocodiles undertook long-distance journeys, regularly travelling more than 50km from their home area to the river mouth and beyond into open sea.

The data showed that crocodiles always began long-distance travel within an hour of the tide changing, allowing them to go with the flow, and that they halted their journeys by hauling out on to the river bank when the tide turned against them.

The team – which included the late Steve Irwin ("The Crocodile Hunter") – also re-analysed archival data from the few crocodiles that have been satellite tracked whilst undertaking ocean travel. By overlaying the crocodiles' movements with surface current estimates they found that ocean swimming crocodiles showed a similar behavioural strategy when at sea.

One satellite-tagged crocodile – a 3.84 metre-long male – left the Kennedy River and travelled 590 km over 25 days down the west coast of Cape York Peninsula timing its journey to coincide with a seasonal current system that develops in the Gulf of Carpentaria.

A second crocodile – a 4.84 metre-long male – travelled more than 411 km in only 20 days from the east coast of Cape York Peninsula through the Torres Straits to the Wenlock River on the west coast of Cape York. The Torres Straits are notorious for strong water currents, and when the crocodile arrived the currents were moving opposite to its direction of travel. It waited in a sheltered bay for four days and only passed through the Straits when the currents switched to favour its journey.

According to Dr Campbell: "The estuarine crocodile occurs as island populations throughout the Indian and Pacific ocean, and because they are the only species of salt-water living crocodile to exist across this vast area, regular mixing between the island populations probably occurs.

"Because these crocodiles are poor swimmers, it is unlikely that they swim across vast tracts of ocean. But they can survive for long periods in salt-water without eating or drinking, so by only travelling when surface currents are favourable, they would be able to move long distances by sea. This not only helps to explains how estuarine crocodiles move between oceanic islands, but also contributes to the theory that crocodilians have crossed major marine barriers during their evolutionary past."





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