The search for new materials for hydrogen storage

ScienceDaily (Sep. 20, 2012) — Hydrogen is the ideal fuel for new types of fuel cell vehicles, but one problem is how to store hydrogen. In his doctoral dissertation Serhiy Luzan studies new types of materials for hydrogen storage. He also shows that new materials with interesting properties can be synthesized by the reaction of hydrogen with carbon nano-structured materials. The dissertation will be publicly defended on September 28 at Umeå University in Sweden.

New car engines that run on hydrogen produce only water as exhaust and are three to four times more efficient than ordinary internal combustion engines. Just one "small" problem is hampering the development of hydrogen-powered vehicles: there is no good method for storing sufficient amounts of hydrogen, as it is a gas of very low density.

Serhiy Luzan devotes the first part of his dissertation to studies of hydrogen storage in exciting new types of materials: metal-organic frameworks (MOFs). They consist of zinc- and cobalt-based metal clusters linked together via organic linkers, and they are extremely porous. One gram of MOF has a hydrogen-absorbing surface that is larger than a football field! Dozens of new MOF materials are synthesized each year, which is highly promising for the next generation of hydrogen storage materials.

Serhiy studied the hydrogen absorption of several new MOFs and researched the effects of different surface areas, pore volumes, and pore forms on the hydrogen storage parameters. MOFs can store record amounts of hydrogen at very low temperatures, but the hydrogen capacity at room temperature is not good enough. Luzan therefore studied new methods to enhance this capacity. Addition of metal catalysts has previously been reported to improve hydrogen storage considerably.

"But in my study, the effect of metal catalysts addition on hydrogen absorption in MOFs was not confirmed," says Serhihy Luzan.

Hydrogen is of interest not only as a fuel but also for chemical modification of nano-structured carbon materials, such as carbon nanotubes, fullerenes, and graphene. Graphene is a single layer of carbon atoms. Carbon nanotubes also consist of pure carbon, in the form of graphene layers rolled into a cylinder. Fullerene, C60, consist of sixty carbon atoms arranged in five- or six-vertices figures, just like the pattern on a soccer ball. There are carbon materials that are stronger than steel, conduct current better than copper, and diffuse heat better than diamond.

In the second part of the dissertation Luzan describes the materials he created by the reaction of hydrogen with fullerenes and carbon nanotubes.

Luzan studied the reaction between fullerene C60 and hydrogen at elevated temperatures and hydrogen pressures, with and without the addition of metal catalysts. The reaction resulted in the formation of hydrogenated fullerenes, C60Hx. Upon extended hydrogen treatment, the fullerene structure fragmented and collapsed. This outcome shows that it is possible to break down fullerenes stepwise into smaller cup-like molecules, which are stabilized by hydrogen atoms. This is a structure that was previously difficult to achieve.

"With this method, we should be able to use fullerenes as a relatively inexpensive source material for creating new molecules that hopefully would retain interesting properties from the original carbon nano-material," says Serhihy Luzan.

Hydrogenated graphene (graphane) is expected to be an ideal material for new carbon-based electronics, but graphane is difficult to synthesize by a direct reaction between graphene and hydrogen. It is much easier first to hydrogenate carbon nanotubes and then to cut them along the tube axis into so-called nanoribbons, which have hydrogen covalently bonded to the surface.

Luzan's experiments showed that the reaction between single-wall carbon nanotubes and hydrogen is possible if a suitable catalyst is used, and he was able to observe that some of the nanotubes were converted to graphene or graphane nanoribbons.

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by Umeå University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/mJH4-1Dewnc/120920095241.htm
--
Manage subscription | Powered by rssforward.com

08.15 | 0 komentar | Read More

Antibiotic use aids MRSA spread in hospital and infection control measures do little to prevent it, says hospital study

ScienceDaily (Sep. 20, 2012) — The use of a commonly prescribed antibiotic is a major contributor to the spread of infection in hospitals by the 'superbug' MRSA, according to new research. The study also found that increasing measures to prevent infection -- such as improved hygiene and hand washing -- appeared to have only a small effect on reducing MRSA infection rates during the period studied.

MRSA -- methicillin-resistant Staphylococcus aureus -- is a bacteria that causes hospital-acquired infection and is resistant to all of the penicillin-type antibiotics frequently used in hospitals to prevent and treat infection. It can cause serious infections of the skin, blood, lungs and bones.

The researchers -- led by St George's, University of London -- tracked MRSA infection over 10 years from 1999 to 2009 at St George's Hospital, looking at how it has adapted to survive in a hospital environment and at factors that affected its prevalence. They found that a significant drop in MRSA rates coincided with a reduction in hospital prescriptions of ciprofloxacin, the most commonly prescribed antibiotic of the fluoroquinolone family.

Over a short period of the study, ciprofloxacin prescriptions fell from 70-100 daily doses for every thousand occupied beds to about 30 doses. In the same period, the number of patients identified by the laboratory to be infected with MRSA fell by half, from an average of about 120 a month to about 60. Following this, over the last two years of the study both the drug prescription level and MRSA rates remained at these reduced levels. Symptoms of MRSA infection can range from very mild to severe, but it is not known how many of the cases examined in the study were serious.

The study -- published in the Journal of Antimicrobial Chemotherapy -- looked at whether other factors such as improved infection control measures may have contributed to this decrease in infection. However, during a four-year period when more stringent infection control policies were introduced -- including improved cleaning and hand washing, and screening patients for MRSA on arrival at hospital -- the only major reduction in MRSA infection rates coincided with the reduction in ciprofloxacin prescriptions.

Lead author Dr Jodi Lindsay, a reader in microbial pathogenesis at St George's, University of London, said: "Surprisingly, it wasn't hygiene and hand washing that were the main factors responsible for the decrease in MRSA in the hospital. Rather, it seemed to be a change in the use of a particular group of antibiotics. Hand washing and infection control are important, but they were not enough to cause the decrease in MRSA we saw."

Dr Lindsay said the study suggested that MRSA relies on ciprofloxacin -- and fluoroquinolones in general -- to thrive in hospitals, as well as penicillin-type drugs, which was already assumed. The fluoroquinolone group of antibiotics have a similar enough mechanism of action to assume that the effect would be the same for them all.

She added that the findings suggest the most effective way to control MRSA and other hospital-based superbugs is to continue finding alternative ways to use antibiotics, rather than simply focusing on infection control techniques.

As well as identifying factors that influenced prevalence, the researchers identified the strain of MRSA that has become dominant. This strain -- CC22 -- has thrived by developing and maintaining multi-drug resistance, and becoming more fit to survive on hospital surfaces than other strains.

Dr Tim Planche, consultant microbiologist at St George's Healthcare NHS Trust and one of the co-authors of the study, said: "The Trust currently has infection rates among the lowest in London, having successfully driven acquisitions down over the past five or six years using a combination of both tough hygiene regimes and careful selective use of antibiotics. These findings, however, provide valuable insight and certainly warrant further investigation, which could lead to the development of even more effective infection control strategies in future."

Dr Lindsay said that studying the dynamic of how MRSA bacteria strains continue to evolve in hospitals in response to changing practice and interventions, such as infection control and antibiotic prescribing, will be essential to determine which interventions work, which are cost effective, and which are likely to have the best long-term outcomes.

She added: "But it seems that we now have an excellent opportunity to control superbugs in hospitals by re-examining how we prescribe antibiotics and ensuring we're using them in the most effective way possible."

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by University of St George's London.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal Reference:

1. G. M. Knight, E. L. Budd, L. Whitney, A. Thornley, H. Al-Ghusein, T. Planche, J. A. Lindsay. Shift in dominant hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) clones over time. Journal of Antimicrobial Chemotherapy, 2012; 67 (10): 2514 DOI: 10.1093/jac/dks245

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/OymIF6if2EY/120920082534.htm
--
Manage subscription | Powered by rssforward.com

07.44 | 0 komentar | Read More

Landing pads being designed for extraterrestrial missions

ScienceDaily (Sep. 20, 2012) — When the Mars Science Laboratory's Curiosity rover landed on Aug. 6, it was another step forward in the effort to eventually send humans to the Red Planet. Using the lessons of the Apollo era and robotic missions to Mars, NASA scientists and engineers are studying the challenges and hazards involved in any extraterrestrial landing.

The technology is known as "vertical takeoff-vertical landing." According to a group working in NASA's Engineering and Technology Directorate at the Kennedy Space Center in Florida, the best approach requires a landing pad already be in place.

"One of the greatest challenges to Apollo astronauts landing on the moon was dust, rocks and debris obscuring their vision during the final part of the descent," said Rob Mueller, a senior technologist in Kennedy's Surface Systems Office and Lunar Destination co-lead for NASA's Human Spaceflight Architecture Team. "When the Apollo lunar modules reached the 30-meter point (about 100 feet), the dust was like a fog making it difficult to see their landing site. Similarly, photographs show there were some rocks and dust kicked up by the rocket engines on the sky-crane lowering the Curiosity lander onto the Martian surface."

As the Mars Science Laboratory's descent stage used rocket engines to hover, its sky crane lowered the Curiosity rover with a 25-foot tether to a soft landing on the surface.

Mueller and others are working on ways to develop landing pads that could be robotically constructed in advance of future human expeditions to destinations such as the moon or Mars. These specially constructed landing sites could greatly reduce the potential for blowing debris and improve safety for astronauts who make the trip to Mars or another destination.

"Our best estimates indicate that descent engines of the Apollo landers were ejecting up to one-and-a-half tons of rocks and soil," said Dr. Phil Metzger, a research physicist in Kennedy's Granular Mechanics and Regolith Operations Laboratory. "It will be even more challenging when we land humans on Mars. The rocket exhaust will dig a deep hole under the lander and fluidize the soil. We don't know any way to make this safe without landing pads."

Building a landing site in advance of human arrival is part of the plan.

"Robotic landers would go to a location on Mars and excavate a site, clearing rocks, leveling and grading an area and then stabilizing the regolith to withstand impact forces of the rocket plume," Mueller said. "Another option is to excavate down to bedrock to give a firm foundation. Fabric or other geo-textile material could also be used to stabilize the soil and ensure there is a good landing site."

Metzger explained that one of the ways to ensure an on-target landing would be to have robotic rovers place homing beacons around the site.

"Tracking and homing beacons would help a spacecraft reach the specific spot where the landing pad had been constructed," he said.

Landing pad technology may be perfected on Earth well in advance of its use elsewhere in the solar system.

"Several commercial space companies are already discussing returning rocket stages to Kennedy or Cape Canaveral saving on the cost of sending payloads to low Earth orbit," Mueller said. "Rather than the first stage simply falling into the ocean, the rocket would land vertically back here at the Cape to be reused."

While landing pads will provide a smooth touchdown location, they will also require advanced technology design and decisions on how large the landing pad should be.

"One of the factors we have to consider is the atmosphere where a landing will take place," Metzger said. "The Earth has a dense atmosphere that focuses the rocket exhaust onto the ground, but also reduces how far the ejected material is dispersed. Mars, on the other hand, has an atmospheric density that is 1 percent that of Earth. It still focuses the plume into a narrow jet that digs into the soil, but it provides less drag so the ejected soil will actually travel farther.

"Then compare that to the moon with no atmosphere," he said. "The plume won't be focused so it won't dig a deep hole in the soil, but the ejected material will travel vast distances at high velocity. It is like a sandblaster on steroids. So the requirements for a landing pad are determined by the destination we're landing on."

Metzger envisions circular landing pads from about 50 to 100 meters (about 165 to 330 feet) in diameter.

"The specialized material taking the heat of the engine plume would be in the middle," he said. "The area surrounding the center would be designed to hold up support equipment."

Another issue is what substances to use in building the landing pads.

"Tests with prototype landers show that while pads are safer than touching down on natural surfaces, certain pad materials can produce debris of their own," Metzger said. "A supersonic rocket exhaust becomes extremely hot when it impacts a surface. Asphalt or concrete are out of the question because the temperature causes those materials to break apart, throwing chunks of material in all directions."

During investigations of prototype landers, various materials have been examined on the pads from which the vehicles have vertically taken off and landed.

"We've tested several types of materials and it seems that basalt regolith mixed with polymer binders hold up well," Metzger said.

However, the one substance for landing pads that shows the most promise is the material used on spacecraft heat shields.

"Of all the substances we studied, ablative materials seem to work best," Metzger said.

Ablative substances were used on the heat shields for spacecraft during Mercury, Gemini and Apollo. The heat of re-entry was dissipated by burning off successive layers.

"While ablative materials seem to work well, the layers will eventually all burn away," Mueller said. "So next we may try reusable thermal protection material similar to that used on the space shuttle tiles or the Orion capsules."

A human expedition to Mars is still many years away, but Mueller says now is the time to start planning for how to land on another planet.

"The technology we envision will take 10 to 15 years to develop," he said. "We need to begin verifying that these concepts will work, and that's why we are already involved in the research."

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by NASA.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/mAtm2NEa1QY/120920101035.htm
--
Manage subscription | Powered by rssforward.com

07.44 | 0 komentar | Read More

NASA app features inflatable spacecraft for returning station cargo

ScienceDaily (Sep. 20, 2012) — Want to try your hand at landing an inflatable spacecraft? All you need is a smart phone, a computer or a tablet.

NASA's new educational computer game based on its Hypersonic Inflatable Aerodynamic Decelerator (HIAD) project can be played on the Internet and downloaded free on Apple and Android mobile devices. (See: http://www.nasa.gov/offices/oct/game_changing_technology/game_changing_development/HIAD/index.html)

To make the HIAD inflatable spacecraft, giant cones of inner tubes are stacked together to form an innovative spacecraft for transporting cargo to other planets or bringing cargo back from the International Space Station. The ability to transport cargo to and from the station is essential to living and working on the orbiting platform, as food and supplies are ferried back and forth. It's also key to getting new investigations to the station and getting many results of experiments back for analysis on Earth.

"This game will help introduce new generations to NASA technologies that may change the way we explore other worlds," said Mary Beth Wusk, HIAD project manager at NASA's Langley Research Center in Hampton, Va. "It gives players an idea of some of the engineering challenges rocket scientists face in designing spacecraft, and does it in a fun way."

The game's goal is to create an inflatable heat shield that returns cargo from the space station to Earth. As the game's instructions put it, "to successfully guide an inflatable spacecraft through the super heat of atmospheric reentry requires the right stuff. If you inflate too early, your shape is incorrect or your material isn't strong enough -- you burn up. And if you get all that right and miss the target the mission is a bust."

The game offers four levels of engineering mastery and gives stars for each successful landing.

HIAD is more than just a game. It's a real technology being tested in laboratories and in flight. A prototype HIAD launched July 23 from NASA's Wallops Flight Facility on Virginia's Eastern Shore. The successful flight test demonstrated that lightweight, yet strong inflatable structures may become a practical way to help us explore other worlds.

NASA is developing the technology as part of the Space Technology Program's Game Changing Development Program. NASA's Space Technology Program is innovating, developing, testing and flying hardware for use in future science and exploration missions. NASA's technology investments provide cutting-edge solutions for our nation's future.

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by NASA.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/U5uew-qR9Eo/120920100909.htm
--
Manage subscription | Powered by rssforward.com

07.44 | 0 komentar | Read More

Space Shuttle Endeavour flyovers draw excited fans

ScienceDaily (Sep. 20, 2012) — Space shuttle Endeavour and the Shuttle Carrier Aircraft landed at Ellington Field in Houston this morning to complete the first day of its trek from Florida to Los Angeles where the shuttle will be placed on public display.

As the SCA approached Houston, it performed a low-level flyover carrying Endeavour over some of the city's landmarks. The flight made several flyovers during its trip across the American southeast.

The aircraft combination, weighing some 475,000 pounds, took off this morning from NASA's Kennedy Space Center in Florida then flew over the Space Coast in a salute to the region that hosted the shuttles during 30 years of launches and landings. The SCA and Endeavour also soared low over Disney World in Orlando during its trip west.

Later, the Michoud Assembly Facility near New Orleans, Stennis Space Center in Mississippi, were treated to a view of Endeavour atop the modified 747.

People took to Facebook and Twitter to share comments and photos of Endeavour as they saw the shuttle pass overhead.

› Flickr Gallery from Endeavour's Flyout

The flight will be the last ferry flight of the space shuttle era, capping nearly 35 years of shuttles riding atop modified 747s, counting the approach and landing tests conducted by Enterprise in 1977.

The SCA and Endeavour will depart at dawn on Thursday and make a fueling stop at Biggs Army Air Field in El Paso before proceeding to Dryden Flight Research Facility at Edwards Air Force Base, California. On Friday it will depart Dryden for a flyover of northern California and areas of the Los Angeles basin before landing at Los Angeles International Airport between 11 a.m. and noon PDT. In October, Endeavour will move to the California Science Center to begin a new mission inspiring future explorers. The pilots of the aircraft carrying space shuttle Endeavour across the country to California already know what it's like to lead an aerial parade.

"The Washington beltway was pretty packed with people," said Jeff Moultrie, chief pilot of the Shuttle Carrier Aircraft, or SCA, about the crowds the crew witnessed gathered around Washington, D.C., in April as they delivered Discovery to the Smithsonian's Air and Space Museum. "In fact, I think it stopped. We could see people stopped in their cars and up on buildings and such."

That ferry flight and a similar one a few days later that flew over New York City with Enterprise were two of a very few times a shuttle has been flown over northeastern cities. Enterprise was flown to the nation's capital in 1985 before going on display at the Smithsonian.

"We weren't sure what to expect, since we had never done something like this before with the space shuttle on top of the 747, what would be the reaction?" said SCA pilot Bill Rieke. "When that happened and we saw the reaction, that was priceless."

The flight crew for the SCA, a modified 747 airliner, is expecting much the same interest this time.

"We're proud to show off our work that NASA's done," Rieke said.

Moultrie said much more effort goes into setting the courses for the flights delivering the retired space shuttles to their display locations than did the ferry flights that carried the spacecraft back to Florida after a California landing.

Large aerial corridors are assigned for the ferry flight so no other planes can use the airspace while the shuttle and SCA are flying through, for example. Also, the flyovers call for the aircraft to pass into restricted airspace around some notable sites.

"We had a massive coordination with the Federal Aviation Administration," Moultrie said. "The regular ferry flights required none of this. Other than some flyovers on arrival that we did as a bonus, we really didn't do flyovers."

Although they saw the crowds from inside the cockpit of the 747, Moultrie and Rieke said they made sure not to get distracted by them.

"We still have a mission to do and that is, we need to deliver it safely where it belongs and that is the part I'm focused on," Rieke said.

The flight also makes a few special demands of pilots as they line up the best way to approach a landmark so the flyby can be recorded in the best way.

"To do this type of flying, we need to consider the photography aspects, the sun angle, what the geometry with the chase ship needs to be, that type of thing," Moultrie said. "This is obviously the biggest thing I've done in aviation and probably the biggest thing I ever will do."

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by NASA.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/UdXg0Q3VlFU/120920101200.htm
--
Manage subscription | Powered by rssforward.com

07.44 | 0 komentar | Read More

Sudden cardiac death is associated with a thin placenta at birth, researchers find

ScienceDaily (Sep. 19, 2012) — Researchers studying the origins of sudden cardiac death have found that in both men and women a thin placenta at birth was associated with sudden cardiac death. A thin placenta may result in a reduced flow of nutrients from the mother to the fetus. The authors suggest that sudden cardiac death may be initiated by impaired development of the autonomic nervous system in the womb, as a result of fetal malnutrition.

The new study, published today in the International Journal of Epidemiology, also found that sudden death was associated independently with poor educational attainment. However, sudden cardiac death was not associated with maternal body size, fetal size at birth, or the length of gestation.

Professor David Barker and colleagues examined sudden death within the Helsinki Birth Cohort, which consists of 6075 men and 6370 women who were born in the city during 1934-1944 and attended child welfare clinics. Detailed information was recorded on the birth records of the group including the placental weight and the length and breadth of the placental surface as well as the child's weight, head circumference, and length.

Professor Barker, of the University of Southampton, comments that 'There is currently a growing body of research that shows that coronary heart disease is associated with alterations in prenatal growth and this has led to the hypothesis that coronary heart disease originates in the womb as a consequence of fetal malnutrition. In research recently carried out by myself and colleagues, we found that coronary heart disease among men was associated with altered shape and size of the placenta.'

'Our new research published today continues the investigation of the relationship between cardiac death and development within the womb. Our new findings suggest that sudden death may be initiated by the impaired development of the autonomic nervous system in the womb, due to placental thinness. A thin placenta may result in fetal malnutrition, due to a shallow invasion of the spiral arteries in the placenta which provide nutrients and blood to the baby. There is evidence that people who experience fetal malnutrition and who are small at birth have an increased sympopathoadrenal response to acute stress, which is known to be linked to death from cardiac arrest.'

Among women, sudden death was associated with a large placental area in comparison to the baby's weight. Placenta expansion in sheep is well documented and the findings in this study suggest that the placenta attempted to compensate for a thin surface by expanding the area of the surface. Professor Barker notes that 'there is evidence that compensatory placental expansion occurs in human and that this expansion may be beneficial in some circumstances. However, if the compensation is inadequate and the fetus continues to be under nourished then the need to share its nutrients with an enlarged placenta may become a metabolic burden and the quality of fetal development may be harmed. We believe that the female foetuses in our study compensated for placental thinness by expanding the placental surface.

Professor Barker and his team also found that sudden cardiac death was strongly associated with low socio-economic status and with low education attainment. He suggests that 'poor educational results may be due to a poor cognitive ability or other issues such as the inability to concentrate or maintain attention. We suggest that the association we have found between sudden death and poor educational attainment results from impaired prenatal development of the autonomic nervous system. These findings build upon a body of research that has consistently reported associations between sudden cardiac death and low socio-economic status.'

In the study, a total of one hundred and eighty-seven men (2.7%) and forty seven women (0.7%) suffered from sudden unexplained cardiac death outside of the hospital. The rate of sudden cardiac death among men and women increased with placental thinness, with a hazard ratio of 1.47. The authors restricted their analysis to deaths that occurred outside of hospital and were certified as coronary heart disease, with men and women who had never been admitted to hospital with coronary heart disease.

Professor Barker and his team do acknowledge that there are some limitations to the study. The placental measurements were made during routing obstetric practice 70 years ago and the quality of these measurements was not routinely checked and neither were other clinical measurements, such as blood pressure. The mean placental weight in this study was also more than the median recorded in a recent series of deliveries in Europe.

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by Oxford University Press, via EurekAlert!, a service of AAAS.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal Reference:

1. David JP Barker, Gail Larsen, Clive Osmond, Kent L Thornburg, Eero Kajantie, and Johan G Eriksson. The placental origins of sudden cardiac death. International Journal of Epidemiology, 2012; DOI: 10.1093/ije/dys116

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/LzlHK8Vnrqo/120920082705.htm
--
Manage subscription | Powered by rssforward.com

07.15 | 0 komentar | Read More

Adolescent male chimps in large community strive to be alphas

ScienceDaily (Sep. 19, 2012) — An Ohio University anthropologist reports the first observation of dominance relationships among adolescent male chimpanzees, which he attributes to the composition of their community. Hogan Sherrow spent eight years studying the Ngogo community of chimpanzees in Kibale National Park in western Uganda. Ngogo is the biggest chimpanzee community on record, with more than 150 members and about twice as many males as found in other chimp communities across Africa.

Unlike their adult male counterparts, which have a well-documented dominance hierarchy, adolescent males have not been known to establish dominance relationships. During four field seasons between 2000 and 2004, however, Sherrow found that some adolescent males pant grunted to other adolescent males on a consistent basis. Research by Jane Goodall established that pant grunts are made by subordinate individuals to dominant ones, Sherrow explained.

"It calms hostilities. It means, 'I know that you're stronger than me, so don't beat me up.' It's like they're sending up the white flag," said Sherrow, an assistant professor of anthropology who published his recent findings in the journal Folia Primatologica.

After ranking the 17 adolescent males in order of dominance, Sherrow concluded that the biggest and oldest animals were at the top of the hierarchy. There were only two exceptions, males that appeared to act in a subordinate manner due to physical injuries.

Sherrow suggests that he observed dominance relationships in the adolescent males of this chimpanzee community due to its size and heightened competition for females. Each male in Ngogo must contend with 35 to 40 others, whereas most communities contain 10 to 15 competitors for mating. Adolescent male chimps also may vie for access to high-ranking adult males as a competitive strategy.

Adult male chimpanzees have clear and defined dominance relationships that depend on size, strength and the ability to form alliances in the community. The most dominant males have priority access to resources and potential mates and usually father more offspring.

"We should not be surprised that adolescent males can form these dominance relationships. Adults males form them, and adolescent males need to learn them at some point," Sherrow said.

Studies of other immature males in primate, mammal and even human communities with intense competition for resources also have found adolescent dominance hierarchies, he added.

Because the Ngogo community is unusually large, Sherrow noted that scientists should seek to observe this behavior in another neighboring community of this size to determine if a similar hierarchy can be documented. The Ngogo study site, located in the Ugandan rain forest, was established in 1995 and has been observed daily by researchers.

The recent study not only offers a new view of chimpanzee behavior, but could shed light on human power and dominance as well, Sherrow suggested.

"Because chimpanzees, along with bonobos, are our closest living relatives, understanding things like how and why they form dominance relationships helps us understand the drive for status and prestige in humans," he said.

The L.S.B. Leakey Foundation, the American Society of Primatologists, the Sigma Xi Foundation, the John F. Enders Foundation and Yale University provided support for the research.

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by Ohio University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal Reference:

1. Hogan M. Sherrow. Adolescent Male Chimpanzees at Ngogo, Kibale National Park, Uganda, Have Decided Dominance Relationships. Folia Primatologica, 2012; 83 (2): 67 DOI: 10.1159/000341168

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/UX94_0bMXmc/120920095326.htm
--
Manage subscription | Powered by rssforward.com

07.15 | 0 komentar | Read More

Computer simulations for multiscale systems can be faster, better, more reliable

ScienceDaily (Sep. 20, 2012) — University of Oregon scientists have found a way to correctly reproduce not only the structure but also important thermodynamic quantities such as pressure and compressibility of a large, multiscale system at variable levels of molecular coarse-graining.

The method is a mathematically driven predictive modeling of a real system, built on liquid state theory, and utilizing powerful computing resources. The team's theory appears in the Sept. 21 issue of the journal Physical Review Letters.

Understanding multiscale systems is of vital importance in biology and material engineering. Because physical properties of multiscale systems develop on an extended range of times and lengths -- with changes involving many orders of magnitude -- computer simulations at the atomic resolution can exceed even the most advanced computational capabilities.

In recent years theoretical coarse-graining methods have gained attention in the scientific community because they provide an efficient alternative to traditional simulations, which represent explicitly every atom of the molecular system. In course graining, atomistic-level information is removed to make computations at long time- and large length-scales possible. The key issue is how to develop reliable and controllable coarse-graining procedures. Most coarse-graining methods correctly predict the structure of a liquid, but they fall short in predicting thermodynamic properties such as pressure or compressibility.

The new theory has the capability to ensure both structural and thermodynamic consistency, said Marina G. Guenza, professor of theoretical physical chemistry and project leader.

Last year, in the journal Physical Review E, Guenza and doctoral student Ivan Lyubimov, a co-author of the new paper, documented a procedure to reconstruct the realistic dynamics of multiscale systems from the motion measured in dynamic simulations of coarse-grained macromolecules. In this newly published article, the same coarse-graining formalism is shown to reproduce correctly the pressure and compressibility of the system, providing a reliable method to simulate complex macromolecular systems in an extended range of length and timescales.

Thermodynamic properties are important in the mixing of liquid materials used in making plastics, said Anthony J. Clark, a UO doctoral student in physics and lead author of the new paper. "Pressure has been a high-level issue in coarse-graining," he said. "It is important to be able to reproduce the distribution of molecules in a system, and pressure is a hard physical quantity to predict. Our theory now will provide the interaction potentials of coarse-grained molecules, which correctly predict both the structure and the thermodynamics of the sample."

The improvements to the formula for the computational simulation mean that manufacturers soon may be able to use a computer code and input information for the materials they plan to mix and quickly determine the behavior of a finished product, said Guenza, a member of the UO's Institute of Theoretical Science, Materials Science Institute and Institute of Molecular Biology.

A problem in working with polymers, for example, is that they often don't blend easily. Controlling for thermodynamic components is vital.

"These molecules are very complex," said co-author Jay McCarty, a doctoral student in chemistry who derived the equations that prove the thermodynamic consistency of Clark's potential and ran the atomistic simulations the test the theory. "They move at different timescales and cover many lengthscales. Our goal is to bridge phenomena that happen at different scales at the molecular level."

Many manufacturing processes rely on often costly, time-consuming and wasteful trial-and-error procedures. While the scientific program is still under development to be extended to a larger number of systems, Guenza said, the recent developments have addressed major stumbling blocks.

On the horizon, she said, is a web-based computer program at the UO, which manufacturers and researchers will be able to access to run predictive coarse-graining simulations that will facilitate the study of polymeric systems and improve the efficiency of working with these samples.

"Dr. Guenza's work to improve our understanding of multi-scale systems has the potential to create new efficiencies in research and manufacturing," said Kimberly Andrews Espy, vice president for research and innovation, and dean of the graduate school. "It reflects the University of Oregon's commitment to re-engineering the science, manufacturing and business processes related to critical products with the aim of fostering a more sustainable future for our planet and its people."

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by University of Oregon, via EurekAlert!, a service of AAAS.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/8lK3woXJhn0/120920082703.htm
--
Manage subscription | Powered by rssforward.com

06.15 | 0 komentar | Read More

Invisible plastic particles in seawater damaging to sea animals

ScienceDaily (Sep. 20, 2012) — Plastic nanoparticles in seawater can have an adverse effect on sea organisms. Particles measuring about a thirty millionth of a millimetre, and therefore invisible to the naked eye, are responsible. Mussels that have been exposed to such particles eat less, and thus grow less well, according to research carried out by scientists and students at Wageningen University and IMARES, both part of Wageningen UR. They wrote about their research in the most recent issue of Environmental Toxicology and Chemistry.

The presence of 'plastic soup' in the oceans is regarded as a big problem. Tiny plastic particles enter the sea when plastic debris decomposes. Such particles are probably also released from cosmetics and from clothes in the wash, subsequently entering the sewage system and surface waters and eventually reaching the sea.

The EU and the Dutch government recognise the problem and the need to monitor the existence of plastics in the seas in order to learn more about present and future concentrations of plastic micro- and nanoparticles in marine environments. Very little is known about the effects plastic nanoparticles have on sea life. The effects now discovered do not yet prove that plastic in the North Sea is a big problem, but they do suggest that further research is extremely important, the researchers remark.

Professor Bart Koelmans' research team, from Wageningen University and IMARES, exposed mussels to various concentrations of nanoplastic in order to discover the concentration at which an effect was noticeable. The team also varied the quantity of algae -- the normal food source for mussels. By giving the plastic nanoparticles colour, and by measuring them using dynamic light scattering, it was possible to determine the particle concentration that exerted an effect. The researchers described in their publication that the extent to which the tiny plastic particles clump together is also extremely important for understanding particle uptake and the resulting effects in marine organisms. "It means that those effects are not easy to predict because the biological availability of the particles can differ enormously from one organism to another, and because variation in water quality also plays a role," says Prof. Koelmans.

Four research studies

This publication is the first of four by Wageningen University and IMARES into the effects of plastic in the North Sea. The other studies will be published in the near future. The first of these is research into the effect of plastic on lugworms, which lose weight due to uptake of plastic particles. The worms, as a result, take in more toxic substances such as polychlorinated biphenyls (PCBs), which bind to plastics.

The researchers believe this indicates the need for good research into other toxic substances that bind to plastic -- an additional consequence of the presence of microplastics. In order to analyse the interaction of plastic and other toxic substances in the food web, Koelmans' group has made a detailed computer model. This type of model is crucial for estimating the risks plastics impose in the sea. The last piece of research is into plastic debris in the stomachs of fish. An analysis of hundreds of fish has shown that 12% of them have debris in their stomachs. Around half of that debris is plastic.

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by Wageningen University and Research Centre.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal Reference:

1. A. Wegner, E. Besseling, E.M. Foekema, P. Kamermans, A.A. Koelmans. Effects of nanopolystyrene on the feeding behavior of the blue mussel (Mytilus edulis L.). Environmental Toxicology and Chemistry, 2012; DOI: 10.1002/etc.1984

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/QFWf-GX1xoo/120920082526.htm
--
Manage subscription | Powered by rssforward.com

06.15 | 0 komentar | Read More

Humans were already recycling 13,000 years ago, burnt artifacts show

ScienceDaily (Sep. 20, 2012) — A study at the Universitat Rovira i Virgili and the Catalan Institute of Human Paleoecology and Social Evolution (IPHES) reveals that humans from the Upper Palaeolithic Age recycled their stone artefacts to be put to other uses. The study is based on burnt artefacts found in the Molí del Salt site in Tarragona, Spain.

The recycling of stone tools during Prehistoric times has hardly been dealt with due to the difficulties in verifying such practices in archaeological records. Nonetheless, it is possible to find some evidence, as demonstrated in a study published in the 'Journal of Archaeological Science'.

"In order to identify the recycling, it is necessary to differentiate the two stages of the manipulation sequence of an object: the moment before it is altered and the moment after. The two are separated by an interval in which the artefact has undergone some form of alteration. This is the first time a systematic study of this type has been performed," as explained to SINC by Manuel Vaquero, researcher at the Universitat Rovira i Virgili.

The archaeologists found a high percentage of burnt remains in the Molí del Salt site (Tarragona), which date back to the end of the Upper Palaeolithic Age some 13,000 years ago. The expert ensures that "we chose these burnt artefacts because they can tell us in a very simple way whether they have been modified after being exposed to fire."

The results indicate that the recycling of tools was normal during the Upper Palaeolithic Age. However, this practice is not documented in the same way as other types of artefacts. The use of recycled tools was more common for domestic activities and seems to be associated with immediate needs.

Recycling domestic tools

Recycling is linked to expedited behaviour, which means simply shaped and quickly available tools as and when the need arises. Tools used for hunting, like projectile points for instance, were almost never made from recycled artefacts. In contrast, double artefacts (those that combine two tools within the same item) were recycled more often.

"This indicates that a large part of these tools were not conceived from the outset as double artefacts but a single tool was made first and a second was added later when the artefact was recycled," outlines the researcher. The history of the artefacts and the sequence of changes that they have undergone over time are fundamental in understanding their final morphology.

According to Vaquero, "in terms of the objects, this is mostly important from a cultural value point of view, especially in periods like the Upper Palaeolithic Age, in which it is thought that the sharper the object the sharper the mind."

Sustainable practices with natural resources

Recycling could have been determinant in hunter-gatherer populations during the Palaeolithic Age if we consider the behaviour of current indigenous populations nowadays.

"It bears economic importance too, since it would have increased the availability of lithic resources, especially during times of scarcity. In addition, it is a relevant factor for interpreting sites because they become not just places to live but also places of resource provision," states the researcher.

Reusing resources meant that these humans did not have to move around to find raw materials to make their tools, a task that could have taken them far away from camp. "They would simply take an artefact abandoned by those groups who previously inhabited the site."

Vaquero and the team believe that this practice needs to be borne in mind when analysing the site. "Those populating these areas could have moved objects from where they were originally located. They even could have dug up or removed sediments in search of tools," highlights the researcher.

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by Plataforma SINC, via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal Reference:

1. Manuel Vaquero, Susana Alonso, Sergio García-Catalán, Angélica García-Hernández, Bruno Gómez de Soler, David Rettig, María Soto. Temporal nature and recycling of Upper Paleolithic artifacts: the burned tools from the Molí del Salt site (Vimbodí i Poblet, northeastern Spain). Journal of Archaeological Science, 2012; 39 (8): 2785 DOI: 10.1016/j.jas.2012.04.024

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

20 Sep, 2012

-
Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/WwrQ7wAqIHw/120920082536.htm
--
Manage subscription | Powered by rssforward.com

06.15 | 0 komentar | Read More