Science Consciousness

Biologist Modifies Theory Of Cells' Engines

2008-12-25T21:59:00.000+06:00

Biologists have known for decades that cells use tiny molecular motors to move chromosomes, mitochondria, and many other organelles within the cell, but no one has been able to understand what "steers" these engines to their destinations. Now, researchers at the University of Rochester have shed new light on how cells accomplish this feat, and the results may eventually lead to new approaches to fighting pathogens and neurological diseases.

Michael Welte, associate professor of biology, shows in a paper published in the December 11 issue of Cell that the mechanisms that control the molecular motors are quite different from what biologists have previously believed. Before these findings, scientists assumed that the number of motors attached to an organelle determined how far and fast the organelle could travel, but Welte and colleagues have discovered that it is not the number of motors, but yet-to-be-discovered molecules that are likely the master regulators.

"The fact that motor number has nothing to do with regulating transport is extremely surprising, and somewhat unsettling to people working in vitro," says Welte. "It says we're really missing something when we study these motors only in the test tube instead of in a living cell."

Intracellular transport is crucial to a cell's health, says Welte. For instance, during cell division, one copy of each of the cell's chromosomes migrates to one side of the cell while the other copy moves to the other side. If this movement is disturbed, it could cause an imbalance of chromosomes in the daughter cells, which might die or become cancerous. Similarly, neurons, some of which are as much as three feet in length, manufacture proteins and organelles at one end and then must move that precious cargo all the way to the far end where they'll be used. This is an enormous task, says Welte, and defects in this transport are thought to cause a number of neurological diseases.

Given the difficulty of investigating these tiny motors acting within the cell, biologists have performed basic experiments on them outside of the cell in a carefully controlled environment. This led them to believe that the speed and distance an organelle could be transported depended on how many motors were pulling it, says Welte. Thus, the scientists reasoned, perhaps the cell simply attaches the right number of motors to an organelle to send it the right distance. Although this "multi-motor" hypothesis is very simple and elegant, says Welte, whether it actually holds true within living cells had never been tested.

Welte's graduate student, Susan Tran, decided to perform that test. She created fruit-fly eggs lacking a type of molecular motor called kinesin and found that certain organelles stopped moving—strong evidence that kinesin is responsible for their transport. Tran then made another type of mutant eggs, this time ones that produced only about half the number of kinesin motors of a regular egg. In both types of eggs, organelles were transported with the same speed and the same distance.

Welte needed to know if this equality was because the normal egg was simply utilizing only half the available kinesin motors, or if some master regulator was controlling the organelle's progress, regardless of the number of motors moving it. To do this, Welte turned to Steven Gross, associate professor of developmental and cell biology at the University of California. Gross' group uses an apparatus called "optical tweezers" that employs laser light to measure the tiny forces the motors generate. The team found that organelles in regular cells are pulled with twice the force of Tran's mutant, low-kinesin cells.

"That clinched it for us," says Welte. "Yes, there are multiple motors moving organelles around, but exactly how many doesn't matter. There is something else in the cell that's controlling all the motors. That opens up a big area for research—find what's driving these motors and maybe we can control them all by controlling one thing."

Welte and his team are now looking at where in the cell this signal comes from and how it influence the motors. Although Welte's team studied fruit fly eggs, the motors moving the organelles are present in all animals and employed for many tasks, including transport in human neurons.

Welte also points out that viruses, including HIV, make use of the same kind of motors to move about the cell, first to get from the site of penetration to the nucleus, where they multiply, and then to get progeny viruses back to the cell surface. If Welte and others can figure out how cells normally control these motors, it may be possible to prevent HIV from taking control of the motors and thus to keep it, and other intracellular pathogens, at the edge of the cell where they can do little harm.

This research was funded by the National Institutes of Health, and includes researchers from the University of Rochester, the University of California Irvine, and University of Texas at Austin.
Adapted from materials provided by University of Rochester.
ScienceDaily

Mathematical Model Gives Clearer Picture Of Physics Of Cells, Organelles

2008-12-25T21:56:00.000+06:00

Cells are filled with membrane-bound organelles like the nucleus, mitochondria and endoplasmic reticula. Over the years, scientists have made much progress in understanding the biomolecular details of how these organelles function within cells, but understanding the actual physical forces that maintain the structures of these organelles' membranes continues to be a challenge.

Now, UCLA Henry Samueli School of Engineering and Applied Science researcher William Klug and colleagues from the California Institute of Technology and the Whitehead Institute for Biomedical Research in Massachusetts have devised a mathematical procedure for accurately predicting the three-dimensional forces involved in creating and maintaining certain organelle membranes.

Their study, which appears Dec. 8 in Proceedings of the National Academy of Sciences and is currently available online, could potentially shed light on the life cycles of membrane-bound viruses such as HIV.

"The study is exciting because it provides a roadmap for ways we can do predictive computational science," said Klug, an assistant professor of mechanical and aerospace engineering. "The mathematical model is able to provide us with a quantitative understanding of the physics of cells that is essentially impossible to obtain directly by experiment."

To understand the researchers' mathematical description of how forces can lead to deformations in a membrane, one can consider the simple concept of a bathroom scale.

"When you step on a scale, a small spring in the scale defines how heavy you are or what force is being applied to the scale," said study co-author Paul Wiggins, a fellow at the Whitehead Institute. "Similarly, with membranes, springs or forces cause them to bend. In a sense, we wanted to see if we could play the same game with the organelles of a cell — to take the observed structure and see if we can predict what forces are applied to give rise to the structure and essentially hold the structure together."

The team used an artificial biomembrane to investigate the dynamic forces that act on a cell's membrane and organelles. With optical tweezers — a scientific instrument that uses a focused laser beam to provide an attractive or repulsive force — they were able to trap and move parts of the cell. This enabled the researchers to exert known forces in different ways, giving them an opportunity to analyze both the response of the membranes when their structures were changed dramatically and to validate their mathematical procedure for predicting forces based on the deformed shapes of the membranes.

"We have this geometry, so what are the forces?" said Klug. "It seems straightforward if you write it out mathematically but in practice, actually measuring the forces reliably where you can quantify the error is really tricky."

The researchers believe that understanding the forces and mechanisms that are responsible for maintaining the geometries of the organelles will help them uncover the crucial factors that lead to changes or malfunctions in organelles.

"When cells undergo oxygen damage, that usually leads to a change in the structure of the mitochondria — the specialized organelles often referred to as the powerhouses of cells," Wiggins said. "There is a close link between the ability of the mitochondria to function and its structure. By relating structure to force, we can uncover the crucial factors that lead to the change in the structure of the mitochondria and other organelles as well."

Membrane-bound viruses like HIV infect cells and then replicate and break from the cells by budding. This budding process eventually uses up the cell membrane and kills it.

"The forces that lead to the process of budding are essentially unknown," Klug said. "Researchers have looked at the image data of HIV in different stages of budding to try to understand the forces that lead up to it. If we can eventually understand what those forces are, we might be able to come up with a way to disrupt the viral assembly process. And that's a different strategy than what is being done today to treat retroviruses and HIV in particular."

Adapted from materials provided by University of California - Los Angeles.
ScienceDaily

Time Running Out On Coral Reefs As Climate Change Becomes Increasing Threat

2008-12-25T21:53:00.000+06:00

Located off the northeastern coast of Australia, the Great Barrier Reef is the largest coral reef system in the world. Increasing pressures from climate change will reach a tipping point in less than a decade triggering a significant decline in the health of the planet's coral reef ecosystems according to the findings in an international report. (Credit: iStockphoto)

Increasing pressures from climate change will reach a tipping point in less than a decade triggering a significant decline in the health of the planet's coral reef ecosystems according to the findings in an international report.

Released by the Global Coral Reef Monitoring Network and the International Coral Reef Initiative, international governmental and scientific partnerships, "Status of Coral Reefs of the World: 2008" provides both good and bad news while sounding the call for urgent global action to respond to climate change.

Coral reefs continue to be threatened from direct human activities of pollution and over-fishing, but now the threat of climate change is being recognized as the major threat to the future of reefs around the world. One fifth of the Earth's coral reefs have disappeared since 1950, and a NOAA authored report issued in July states that more that that nearly half of U.S. coral reef ecosystems are considered to be in "poor" or "fair" condition.

"Unless the world gets serious about reducing greenhouse gas emissions in the next few years, it is likely there will be massive bleaching and deaths of corals around the world," notes the report's lead editor and global coral authority Clive Wilkinson who coordinates the Global Coral Monitoring Network in Australia. "This will have significant impacts on the lives of the people in developing countries who are dependent on reefs for food, for tourism, and for protecting the land they live on."

This status report was put together from 370 contributors in 96 countries and states and is the most authoritative report on the world's coral reefs. The report presents regional assessments of the health coral reef ecosystems found throughout the world, the threats they face, and recommendations for action. A new feature of the 2008 reporting is publication of a separate report, "Socioeconomic Conditions along the World's Tropical Coasts: 2008," detailing socioeconomic data on how people use coral reefs in 27 developing tropical coastal countries.

The status report includes satellite date from NOAA's Coral Reef Watch project which measures stress to reefs from temperature globally and resulting bleaching. NOAA recently started tracking ocean acidification changes in the Caribbean.

Frequent or long-term bleaching kills or severely weakens corals, leaving them more vulnerable to disease, and resulting in a sea bottom covered with algae and sponges that may eventually smother remaining coral. Acidification is a growing threat that could imperil the ability of corals to build their skeletons. A number of recent studies demonstrate that ocean acidification is likely to harm coral reefs by slowing coral growth and making reefs more vulnerable to erosion and storms.

In good news the report, which is issued every four years, found that there was major recovery of reefs in the Indian Ocean and western Pacific from climate change induced bleaching events in 1998 - especially those reefs that were in protected areas. Other reefs cited as being in healthy condition included Australian reefs in general, most notably the Great Barrier Reef, the remote reef systems of the Pacific and Indian Ocean that suffer little human impacts and some small areas of the Caribbean.

The report also acknowledges that increased awareness such as that promoted by 2008 being designated "International Year of the Reef" is beginning to have an impact pointing to a series of major conservation initiatives that have been announced in recent years including the Coral Triangle Initiative in Asia, the Micronesia and Caribbean Challenges, and the creation of the two largest marine protected areas in the world: in the Phoenix Islands of Kiribati and the U.S. Papahanaumokuakea Marine National Monument.

In addition to climate change, negative impacts to corals in the past four years included the Indian Ocean tsunami, hurricane damage which combined with bleaching has endangered wide ranges of Caribbean coral reefs, and increasing human activity pressures including pollution, development, deforestation and overfishing in East Africa, South Asia, Southeast Asia, populated areas of the Pacific and Caribbean. One particular threat is the increase in "bomb" and cyanide fishing in Asia and in Tanzania.

The assessment includes detailed recommendations to preserve and better manage reef ecosystems. Human pollution and fishing pressures have to be reduced while the development of sustainable tourism activities can protect the reefs while stimulating economic growth. The report also encourages increased use of marine protected areas as a means of ensuring reefs can continue to protect important fish nursery areas and serve as reservoirs of marine biodiversity.

The Global Coral Reef Monitoring Network receives support from governmental and non-governmental organizations including the U.S. Department of State, NOAA (the National Oceanic and Atmospheric Administration), the World Bank and the WWF (World Wildlife Fund) to publish this survey of the health of the world's coral reefs and diagnoses solutions for halting and reversing their decline.

Adapted from materials provided by The Global Coral Reef Monitoring Network, via EurekAlert!, a service of AAAS.
ScienceDaily

Fraud In Science: How Prevalent Is It And What Can Be Done?

2008-12-25T21:51:00.000+06:00

Public confidence in the honesty of scientists is being harmed by a small minority of researchers who behave badly, a conference recently heard. European research organisations agreed to work more closely to tackle the problem of fraud and other misconduct in science.

The meeting in Madrid on 17-18 November was organised by the newly formed Research Integrity Forum of the European Science Foundation (ESF) in collaboration with the Spanish National Research Council (CSIC). It continued work set in motion by the first world conference on research integrity held in Lisbon in September 2007.

Fraud in science includes inventing data (fabrication), manipulating data to produce an unjustified result (falsification) or presenting the work of other researchers as one's own (plagiarism).

There is little hard evidence of the extent of the problem but various estimates suggest that between 0.1% and 1% of researchers commit fraud and perhaps as many as 10% to 50% engage in questionable practices. Most of these are relatively minor, said Dr John Marks, Director of Science and Strategy at ESF, "but if people get away with it and if no-one says anything about it, it might invite bigger issues of misconduct." He said that opinion polls showed that trust in scientists is still high "but that trust is easily lost by high profile cases of misconduct and that is why we are so concerned."

A survey by ESF earlier this identified 18 European countries that had put in place codes of conduct for good practice in research but they varied greatly in how they dealt with suspected cases. Many have set up research integrity offices to promote good practice and discourage misconduct.

No European country has yet followed the lead of the US National Science Foundation which, along with other federal agencies, has statutory powers to investigate allegations of fraud including power to subpoena evidence. Dr Peggy Fischer, of the NSF's Office of Inspector General, described how offenders can be required to take a course in scientific ethics or, in the most serious cases, banned from receiving any federal research funding for up to five years.

Systems in Europe tend to be more consensual and rely more on the self-governance of the scientific community. Professor Eero Vuorio, chair of the National Advisory Board on Research Ethics, said that all of Finland's universities and polytechnics and most research funding bodies had signed up to a national code of good scientific practice. Allegations of misconduct are investigated by individual institutions to an agreed procedure with the help of outside experts. Sanctions are in the hands of employers.

Although most countries agree on the core definition of what constitutes misconduct, they differ in how they regard other unethical behaviour and how they deal with it. The meeting heard reports on the situation in the United Kingdom, Portugal, the Czech Republic and France.

With much research now being done in international collaborations, problems can arise when fraud is committed within a cross-border partnership and there are no agreed rules on how cases are to be investigated and how sanctions can be imposed.

A move towards a common approach has been proposed by the Global Science Forum of the OECD, which would require potential collaborators to agree on what to do in cases of suspected misconduct. "When you're doing your collaborative planning you need to recognise that things can go wrong," said co-chair of the forum, Christine Boesz of NSF. She acknowledged that such an idea was new and was meeting resistance from some researchers.

The meeting also discussed the role of universities, national academies, international scientific bodies and scientific journals in promoting research integrity and heard of a project to compile a database of research papers known to be tainted by fraud. A proposal for a global clearinghouse to promote research integrity was also presented.

Members of the forum agreed to exchange information and good practice, to develop a code of conduct that could be used as a template for national codes, to develop a checklist to assist ESF members in setting up national and institutional structures to promote good practice and deal with misconduct, and to promote further research on the extent of misconduct.

Co-organiser Professor Juan José de Damborenea of CSIC told the meeting: "Society requires science and researchers to solve the problems that concern all of us. In general, public opinion has a good image of the honesty of scientists. We cannot allow it to be lost."

Adapted from materials provided by European Science Foundation.
ScienceDaily

4,000-year-old Amber Necklace Has Been Unearthed In England

2008-12-25T21:49:00.001+06:00

A 4,000-year-old amber necklace has been unearthed in England. (Credit: Image courtesy of University of Manchester)

A 4,000-year-old amber necklace has been unearthed in England. The rare find was unearthed from a stone-lined grave – known as a Cist - excavated by the team from The University of Manchester Field Archaeology Centre and Mellor Archaeological Trust.

It is the first time a necklace of this kind from the early Bronze Age has been found in north west England.

Peter Noble from The University of Manchester said: “An amber necklace of this sort was one of the most important ways that people of the early Bronze Age could display their power and influence.

“The fact that it has been found in the north west of England is pretty amazing and extremely rare.”

Dozens of different sized pierced amber beads are linked together on a length of fibre to form the beautiful artifact.

It was discovered by Vicky Nash from of the Mellor Archaeological Trust.

Peter Noble, who directed the dig added: “The necklace was made of amber – which is not found in this region.

“In fact, the nearest source is in the Baltic so we’re bound to ask, how did it get here and who brought it?”

Adapted from materials provided by University of Manchester.
ScienceDaily

Potential Links Between Breast Density And Breast Cancer Risk

2008-12-25T21:48:00.000+06:00

Having dense breasts - areas that show up light on a mammogram - is strongly associated with increased breast cancer risk, but "why" remains to be answered. Now, by examining dense and non-dense tissue taken from the breasts of healthy volunteers, researchers from Mayo Clinic have found several potential links.

In two studies being presented simultaneously in poster form at the Cancer Therapy & Research Center-American Association for Cancer Research (CTRC-AACR) San Antonio Breast Cancer Symposium, the researchers report that dense breast tissue contains more cells believed to give rise to breast cancer, compared to non-dense tissue. "We found a dramatic difference in tissue composition between dense and non-dense tissue in the breast," says Karthik Ghosh, M.D., a Mayo Clinic breast cancer researcher and physician who led one study.

In a second study, researchers also found that dense breast tissue has more aromatase enzyme than non-dense tissue. This is significant because aromatase helps convert androgen hormones into estrogen, and estrogen is important in breast cancer development, says that study's lead investigator, Celine Vachon, Ph.D.

"If aromatase is differentially expressed in dense and non-dense breast tissue, this could provide one mechanism by which density may increase breast cancer risk," Dr. Vachon says.

The researchers say these findings are unique because these studies are the first to examine areas of both dense and non-dense tissue taken from the same breast in healthy volunteers. Examination of healthy women is important, Dr. Ghosh says, because most prior studies of breast density have looked at tissue taken from women with known breast disease.

Sixty women, age 40 to 85, allowed Mayo Clinic researchers to take eight core-needle biopsies from their breasts; none had a history of breast cancer.

Dr. Ghosh and her team examined the biopsies to determine the percentage of epithelium tissue, stroma, and fat content in each. The epithelium is primarily composed of milk glands and ductal cells, and stroma is the connective tissue that supports epithelial cells. Dr. Vachon and her colleagues looked at aromatase expression within cells in both dense and non-dense tissue.

Results are now available from more than half of the participants who donated biopsy tissue. Dr. Ghosh found that areas of density contained much more epithelium (6 percent) and stroma (64 percent) and much less fat (30 percent), compared to non-dense tissue that contained less than 1 percent epithelium, about 20 percent stroma, and almost 80 percent fat. "This shows us that both the epithelium and stroma contribute to density, and suggests that the large difference in stroma content in dense breast tissue may play a significant role in breast cancer risk," Dr. Ghosh says.

She also looked at lobular involution, a decrease in the size and number of milk ducts that has been associated with decreased breast cancer risk, and found that 85 percent of non-dense tissue had complete involution compared to 35 percent of dense tissue.

Dr. Vachon and her team examined expression of aromatase in the biopsy samples and found that the stromal cells in dense breast tissue had more aromatase and intensity of expression in dense tissue, compared to non-dense. They say these findings may help explain why women with greater proportion of dense breast tissue are at greater risk for breast cancer than women with little or no density.

"These are initial findings from one of the first attempts to study breast density at the level of healthy tissue. It doesn't explain everything yet, but is providing really valuable insights," says Dr. Ghosh, who established the patient resource for both studies.

Drs. Ghosh and Vachon are finishing their analysis of the initial 60 volunteers, and they are also enrolling more participants in order to validate and expand their findings. "No one knows why density increases breast cancer risk, but we are attempting to connect the dots," Dr. Vachon says.

These studies were funded by the Mayo Clinic Breast Cancer Specialized Programs of Research Excellence (SPORE) grant, and a National Institutes of Health (NIH) career development award.
Adapted from materials provided by Mayo Clinic.
ScienceDaily

Why Climbers Die On Mount Everest

2008-12-25T21:46:00.000+06:00

Mountaineers climbing Mount Everest. (Credit: iStockphoto/Sandeep Subba)

An international research team led by Massachusetts General Hospital (MGH) investigators has conducted the first detailed analysis of deaths during expeditions to the summit of Mt. Everest. They found that most deaths occur during descents from the summit in the so-called "death zone" above 8,000 meters and also identified factors that appear to be associated with a greater risk of death, particularly symptoms of high-altitude cerebral edema.

"We know that climbing Everest is dangerous, but exactly how and why people have died had not been studied," says Paul Firth, MB, ChB, of the MGH Department of Anesthesia, who led the study "It had been assumed that avalanches and falling ice – particularly in the Khumbu Icefall on the Nepal route – were the leading causes of death and that high-altitude pulmonary edema would be a common problem at such extreme altitude. But our results do not support either assumption."

Thousands of climbers have attempted to reach the summit of 8,850-meter (29,000-foot) Mount Everest since the 1920s. In order to examine the circumstances surrounding all deaths on Everest expeditions, the research team – which included investigators from three British hospitals and the University of Toronto – reviewed available expedition records including the Himalayan Database, a compilation of information from all expeditions to 300 major peaks in the world's highest range. Of a total of reported 212 deaths on Everest from 1921 to 2006, 192 occurred above Base Camp, the last encampment before technical (roped) climbing begins.

Firth and three physician co-authors – all experienced Himalayan mountaineers with expertise in managing high-altitude illness – reviewed records for all deaths and classified them according to available information. More detailed analysis was conducted on deaths occurring above 8,000 meters during the past 25 years. Deaths were categorized as traumatic, from falls or external hazards such as avalanches; nontraumatic, from high-altitude illness, hypothermia or other medical causes; or as disappearances. Expedition participants were classified as either 'climbers,' individuals from outside the Himalayan region, or 'sherpas' – high-altitude porters, most of them ethnic Sherpas or Tibetans, hired to transport equipment and otherwise assist the climbers.

The overall mortality rate for Everest mountaineers during the entire 86-year period was 1.3 percent; the rate among climbers was 1.6 percent and the rate among sherpas was 1.1 percent. During the past 25 years, a period during which a greater percentage of moutaineers climbed above 8,000 meters, the death rate for non-Himalayan climbers descending via the longer Tibetan northeast ridge was 3.4 percent, while on the shorter Nepal route it was 2.5 percent.

Factors most associated with the risk of death were excessive fatigue, a tendency to fall behind other climbers and arriving at the summit later in the day. Many of those who died developed symptoms such as confusion, a loss of physical coordination and unconsciousness, which suggest high-altitude cerebral edema, a swelling of the brain that results from leakage of cerebral blood vessels. Symptoms of high-altitude pulmonary edema, which is involved in most high-altitude-related deaths, were suprisingly rare.

"High-altitude cerebral edema symptoms were common among those that died, but signs of pulmonary edema, or excessive fluid in the lungs, were unusual" Firth says. "We also were surprised at how few people died due to avalanches and ice falls in recent years – those usually happen at lower altitudes, and overwhelmingly people died during summit bids above 8,000 feet – and that during descents, the mortality rate for climbers was six time that of sherpas."

While the reduced mortality rate among sherpas during descent suggests that taking time to acclimatize to high altitude could improve climber survival, Firth notes that many other factors may be involved. "Most of the sherpas are born and live their lives at high altitudes, and the competitive process for expedition employment probably selects those who are best adapted to and most skilled for the work. So the ability of lowlanders to acclimate to these very high altitudes needs further investigation."

During a 2004 Norwegian-American expedition from the north side of Everest led by Firth, equipment problems led the team to turn around at 8,300 meters, return to 7,900 meters and pool their oxygen supply. Half of the team successfully re-attempted the summit and returned safely, including Randi Skuag, the first Norwegian woman to climb Everest. Seven other climbers from other teams that year were not so fortunate – all dying above 8,000 meters, most while descending from the summit.

"The majority of those who have died on Everest were in the prime of their lives, with families and friends left bereft," stresses Firth, who is an instructor in Anaesthesia at Harvard Medical School. "Mountaineering is for fun; it's not worth dying or leaving others there to die. Appropriate caution is the hallmark of the elite mountaineer – the mountain will always be there next year."

The report, which will appear the December 20/27 issue of the British Medical Journal has been released online. The senior author of the British Medical Journal report is Richard Salisbury, who created and maintains the Himalayan Database. The other physician reviewers are Jeremy Windsor, MD, the Heart Hospital, London; Andrew Sutherland, MD, Radcliffe Hospital, Oxford; and Christopher Imray, MD, University Hospital, Coventry, all in the U.K. Additional co-authors are Hui Zheng, PhD, MGH Department of Medicine; G.W. Kent Moore, PhD, and John Semple, MD, University of Toronto; and Robert Roach, PhD, University of Colorado. The study was supported by the MGH Department of Anesthesia and Critical Care.

Adapted from materials provided by Massachusetts General Hospital, via EurekAlert!, a service of AAAS.
ScienceDaily

Toothbrushing Can Prevent Hospital-borne Pneumonia

2008-12-25T21:43:00.001+06:00

Ordinary tooth brushing could help prevent ventilator-associated pneumonia, new research shows. (Credit: iStockphoto/Michael Gatewood)

Hospital-borne infections are a serious risk of a long-term hospital stay, and ventilator-associated pneumonia (VAP), a lung infection that develops in about 15% of all people who are ventilated, is among the most dangerous. With weakened immune systems and a higher resistance to antibiotics, patients who rely on a mechanical ventilator can easily develop serious infections — as 26,000 Americans do every year.

Thanks to a proven new clinical approach developed by Tel Aviv University nurses, though, there is a new tool for stopping the onset of VAP in hospitals.

This new high-tech tool? An ordinary toothbrush.

Three Times a Day Keeps Pneumonia Away

“Pneumonia is a big problem in hospitals everywhere, even in the developed world,” says Nurse Ofra Raanan, the chief researcher in the new study and a lecturer at Tel Aviv University’s Department of Nursing. “Patients who are intubated can be contaminated with pneumonia only 2 or 3 days after the tube is put in place. But pneumonia can be effectively prevented if the right measures are taken.”

Raanan, who works at the Sheba Academic School of Nursing at The Chaim Sheba Medical Center, collaborated with a team of nurses at major medical centers around Israel. The nurses found that if patients — even unconscious ones — have their teeth brushed three times a day, the onset of pneumonia can be reduced by as much as 50%.

A Pioneering Study with Measurable Effects

It’s difficult to quantify the effects precisely, the researchers say. “While the research shows a definite improvement in reducing the incidence of hospital-borne pneumonia, it’s hard to say by exactly how much toothbrushing prevents VAP,” says Raanan, but the published evidence shows a direct correlation for intubated patients.

“Sometimes, however, doctors and nurses do everything right and the patient still gets pneumonia. But this approach will certainly improve the odds for survival.”

Normally, the teeth and oral cavity in a healthy mouth maintain a colony of otherwise harmless bacteria. Infection takes root when a breathing tube allows free passage of the “good” bacteria into the lower parts of the lung. The bacteria travel in small water droplets through the tube and colonize the lung. Once there, the bacteria take advantage of a patient’s weakened immune system and multiply. A regular toothbrushing kills the growth and subsequent spread of the bacterium that leads to VAP.

Augmenting the Preventative Routine

There are additional steps for preventing the onset of VAP. Today, nurses typically use a mechanical suction device to remove secretions from the mouth and throat. They also put patients in a seated position and change the position every few hours. Toothbrushing, say Tel Aviv University nurses, should be added to the routine.

Although nurses in some American hospitals already practice toothbrushing on ventilated patients, these new results may convince medical centers around the world to invest more resources in this routine practice, thereby saving lives.

The research and recommendations are scheduled for publication in a leading nursing journal.

Adapted from materials provided by Tel Aviv University.
ScienceDaily

Jupiter's Moon Europa Does The Wave To Generate Heat

2008-12-25T21:41:00.000+06:00

If the moon Europa is tilted on its axis even slightly as it orbits the giant planet Jupiter, then Jupiter's gravitational pull could be creating powerful waves in Europa's ocean. (Credit: NASA)

One of the moons in our solar system that scientists think has the potential to harbor life may have a far more dynamic ocean than previously thought.

If the moon Europa is tilted on its axis even slightly as it orbits the giant planet Jupiter, then Jupiter's gravitational pull could be creating powerful waves in Europa's ocean, according to Robert Tyler, an oceanographer with the University of Washington's Applied Physics Laboratory and author of a letter in the Dec. 11 Nature. As those waves dissipate, they would give off significant heat energy.

Depending on the amount of tilt, the heat generated by the ocean flow could be 100 to thousands of times greater than the heat generated by the flexing of Europa's rocky core in response to gravitational pull from Jupiter and the other moons circling that planet.

That's the current assumption – that oceans on moons are heated mainly by this flexing of their cores. In the case of Europa, it also has been thought that the thick ice covering its ocean probably generates some heat as two sides of cracked ice rub together in response to gravitational pull.

"If my work is correct then the heat source for Europa's ocean is the ocean itself rather than what's above or below it," Tyler says. "And we must form a new vision of the ocean habitat that involves strong ocean flow rather than the previously assumed sluggish flows."

Both are important considerations if exploratory missions are ever sent to Europa in search of life. Europa, which is slightly smaller than Earth's moon, is one of Jupiter's 63 moons. With surface temperatures as cold as minus 260 degrees Fahrenheit, Europa's surface is covered with a thick layer of ice. There is evidence of a liquid ocean beneath the ice and, if there is volcanic activity on the sea floor, this could be a recipe for generating microorganisms that live without sunlight, perhaps like the microorganisms found at hydrothermal vents and other places on Earth.

Many planets and moons are known to be tilted within their orbital plane. The Earth, for example, has an axial tilt of about 23 degrees. It's why the northern and southern hemispheres have different seasons, depending on whether they are tilted more toward or away from the sun.

Previous theoretical calculations expected Europa to have an axial tilt of at least 0.1 degrees. It hasn't been measured and could be bigger than this. But even at this minimum value the tidal flow on Europa using Tyler's new calculation is quite strong – some 10 centimeters a second – and enough to cause significant heating.

The new calculation differs from previous ones in that it allows a more realistic dynamic response of the ocean to the tidal forces.

His assumptions and calculations led him to say that he thinks this kind of wave action could be the dominant heat source in the oceans of Europa and other moons.

"But this proposal is a relatively new contender – so let's see how it does," he says. Tyler is the sole author of the letter in Nature. His work was supported by NASA's Outer Planets Research program.

Adapted from materials provided by University of Washington.
ScienceDaily

Astrophysicists Aim To Recreate Stars In The Lab

2008-12-25T21:40:00.000+06:00

Astronomers are recruiting the physics laboratory to unravel the high energy processes involved in formation of stars and other critical processes within the universe. Experiments with high energy radiation and plasmas in the laboratory involving temperatures and magnetic fields over a million times greater than normally encountered on earth are also producing spin off benefits for important applications, notably in the drive towards nuclear fusion as a source of clean carbon-neutral energy.

Although a great deal has been learnt through a combination of theoretical models and observation of the universe right across the electromagnetic spectrum including visible light with conventional optical telescopes, many questions on energetic processes taking place billions of miles away still remain unanswered.This is why astrophysicists are turning to a third ingredient, the high energy laboratory, fusing results obtained there with theoretical models and direct observation through instruments. The state of this highly promising field was discussed at a recent workshop organised by the European Science Foundation (ESF), which also set out a roadmap for future collaborative research in Europe over the next five years.

The workshop is setting up a European framework for conducting coordinated experiments in Extreme Laboratory Astrophysics (ELA), aiming to simulate the high temperatures and magnetic fields experienced in a variety of formative processes occurring throughout the universe's history. Full blown ELA builds on earlier more tentative initiatives, such as the JETSET network, which is a four-year Marie Curie Research Training Network (RTN) funded by the European Commission, designed to build a vibrant interdisciplinary European Research and Training community centred on rigorous and novel approaches to plasma jet studies, with a focus on flows produced during star formation. Plasma jets comprise high energy atomic nuclei stripped of their electrons, expelled from stars during their formation and early in their lives.

ELA experiments however, as discussed at the ESF workshop, go much further than the study of plasma jets, and therefore expand on the foundations created by JETSET. "The JETSET network was truly innovative in that it combined not only theoretical and observational astrophysics, but also for the first time experiments," said Andrea Ciardi, convenor of the ESF workshop and plasma physicist at the Ecole Normale Superieure in Paris. "However JETSET was limited in terms of astrophysical phenomena studied (jets from young stars) and in terms of groups involved. The workshop aims at the creation of an XLA framework combining numerical modelling, experiments and theory, to complement observations in the study of a broader range of astrophysical phenomena."

The workshop fulfilled its objectives of stimulating the required interdisciplinary research effort, and providing a broad outlook of future objectives. Furthermore it generated great excitement about prospects for the field, according to Ciardi. "The workshop covered a large spectrum of research both in astrophysics and in laboratory plasma physics: from cosmic rays acceleration, to the properties of fast winds in stars, and from high-power lasers aimed at achieving fusion to experiments producing magnetic bubbles expanding at hundreds of kilometres per second," said Ciardi. "Indeed the excitement comes from being able to re-create in the laboratory astrophysical phenomena taking place in some of the most extreme and exotic objects in the universe."

The ELA experiments should also have practical benefits. "ELA research has an inherent duality: experiments developed initially for laboratory astrophysics, including new diagnostics, theoretical and numerical models, can be useful for example to fusion research, which is pursuing a clean source of energy, which in some cases uses similar theoretical and experimental techniques," said Ciardi.

ELA research could also help improve weather forecasts by leading to better understanding of cosmic rays that strike the earth's atmosphere and have a significant effect on cloud formation and thunderstorm activity.

The ESF workshop, Extreme Laboratory Astrophysics: Advances and Opportunities in High-Energy Density Experiments, was held in Paris (France), in September 2008.

Adapted from materials provided by European Science Foundation.
ScienceDaily

Dwarf Crocodiles Split Into Three Species

2008-12-25T21:37:00.000+06:00

O. tetraspis eats a captures a land crab at Loango National Park, Gabon. (Credit: Mitchell J. Eaton)

You'd think that if scientists were to discover a new species, it would be in some remote, uncharted tropical forest, not a laboratory in New York. But a team from the Sackler Institute for Comparative Genomics at the American Museum of Natural History has done the unexpected. Looking at the genes of the African dwarf crocodile, researchers found that the group — genetically speaking — comprises three distinct species rather than one.

This not only ends a long debate about the taxonomy of this group, previously thought to consist of two closely related subspecies, but also defines a new, distinct species from genetic samples.

"In the past, the two morphologically distinct crocodile populations were believed to be different genera, then later different species, and then finally different subspecies," explains first-author Mitchell Eaton. Eaton conducted the research at the Sackler Institute and is finishing his doctoral degree at the University of Colorado. "We collected samples in Africa to explore this taxonomic question, and we found a great deal of evolutionary divergence between populations in the Congo Basin and on the west coast of Central Africa. We also — quite unexpectedly — found a completely new species from far West Africa; there may be even more species that we haven't sampled yet!"

African dwarf crocodiles, genus Osteolaemus, live in the tropical forests of Central and West Africa. Adults typically grow to no more than 5 feet in length and are the smallest living members of the crocodilian family. The three groups identified in this current research include a species from the Congo Basin (O. osborni), another from Central Africa's Ogooué Basin (O. tetraspis), and the new, yet unnamed species from West Africa. All of these crocodiles look very similar, and all are widely hunted by local people as a source of food. In fact, these animals provide up to a quarter of the non-fish bush meat consumed in some areas of Central Africa, but over-hunting to supply commercial 'bushmeat' markets may threaten many populations with extinction. Dwarf crocodiles are listed as vulnerable on the International Union for Conservation of Nature's Red List.

In the laboratory, the researchers sequenced more than 4,000 base pairs of both mitochondrial and nuclear DNA from as many as 82 individuals sampled across Central and West Africa. The results confirmed species-level separations between three different groups of dwarf crocodiles. Crocodiles from the Congo Basin appear to be the oldest of the three species, with some morphological characteristics placing them closer to a shared ancestor of the Nile crocodile. The dwarf crocodiles of the Ogooué and West Africa, on the other hand, are more recently evolved and are more closely related to each other than either is to the Congo Basin species.

"These species have been on their own evolutionary trajectory for a long time," says George Amato, Director of the Sackler Institute. "They are diagnostically distinct — every individual in one species has characteristics that are not found in the other species, and the number of diagnostic characteristics is large."

The new taxonomic discovery has implications for the conservation strategy of African dwarf crocodiles. "Without these genetic results, the level of biodiversity was cryptic, hidden," Amato continues. "Accurate taxonomy is necessary for conservation management of each species, and now we can calculate subsistence hunting levels that are manageable."

In addition to Amato and Eaton, coauthors include Andrew Martin of the University of Colorado and John Thorbjarnarson of the Wildlife Conservation Society (WCS). The research was funded in part by AMNH, the National Geographic Society, WCS, Lincoln Park Zoo, the Rufford Foundation, and the University of Colorado's Natural History Museum and Rozella Smith Fellowship. It is published in the early online edition of Molecular Phylogenetics and Evolution.

Adapted from materials provided by American Museum of Natural History, via EurekAlert!, a service of AAAS.
ScienceDaily

Immunity Stronger At Night Than During Day

2008-12-25T21:36:00.000+06:00

A fruit fly's immune system can tell time, researchers at the Stanford University School of Medicine have found, and how hard it punches back against infections depends on whether the fly is snoozing or cruising. The discovery could have implications for human health, too.

Working with jerry-rigged, light-bulb-laden shoeboxes to manipulate the flies' daily cycle and with syringes small enough to inject measured amounts of germs into the wee winged ones, the investigators have shown that the insects' immune response waxes and wanes with the diurnal oscillations called circadian rhythms.

Mimi Shirasu-Hiza, PhD, a postdoctoral scholar in the laboratory of David Schneider, PhD, assistant professor of microbiology and immunology, presented the findings Dec. 14 at the annual meeting of the American Society for Cell Biology, held in San Francisco.*

Insects do not have the advanced artillery that characterizes vertebrate immune systems — antibody-secreting B-cells, and killer and helper T-cells that precisely target specific pathogens for attack. But they do share with vertebrate organisms a primitive, but critical, rough-and-ready response to unwanted microbes: the innate immune system. This all-important first line of defense, without which we wouldn't survive an infection for the week or two it takes for our more-sophisticated antibodies and T-cells to kick into high gear, whirls into action at once, based on its ability to recognize generic patterns that distinguish microbial pests.

One feature of the fruit fly's innate immune system is the presence of circulatory cells called phagocytes that, like our own white blood cells, engulf and digest bacteria. In their new research, Shirasu-Hiza and Schneider have found that phagocytes' activity oscillates throughout the day.

Like the mosquito, platypus and whitetail deer, fruit flies are crepuscular — they are most active at dawn and dusk, tend to roam a bit during the daytime, and engage in what passes for sleep during the nighttime. (Flies don't have eyelids, so it's hard to tell if they're really asleep. Researchers instead characterize cyclical patterns of rest and activity in terms of the number of movements per five-minute cycle.)

Shirasu-Hiza flummoxed flies into a 12-hour circadian-rhythm phase shift by raising them in shoeboxes, wired by Schneider with timers that controlled batteries of light bulbs. This enabled the researchers to infect two sets of flies (from "nighttime" or "daytime" shoeboxes) in a single experimental session. This Shirasu-Hiza did, using syringes fashioned from glass capillary tubes heated and then stretched so that they were extremely thin, but still hollow. Armed with these syringes — which are powered by a machine called a "Picospritzer" — she spent hours on end in a dark room lit only by a red bulb (red light doesn't seem to perturb the daily rhythms of the flies) while injecting, one by one, multiple hundreds of tiny, week-old male flies (half of them sleeping, the other half awake) per session with precise volumes of solutions containing different pathogenic bacteria.

In previously published research, when Shirasu-Hiza and her colleagues had infected normal flies with measured doses of two noted human pathogens, Streptococcus pneumoniae or Listeria monocytogenes, the sickened flies' circadian rhythms were disturbed. They stumbled around more randomly, and stood still for relatively shorter periods. Moreover, genetic mutants lacking circadian cycles of rest and activity died more quickly on infection with these pathogens than normal flies did.

In the new round of experiments, the researchers observed that, consistent with those earlier findings, the activity of phagocytes in normal fruit flies oscillates with their circadian rhythms. Flies infected with S. pneumonia or L. monocytogenes during resting periods ("nighttime") also survive significantly longer than those infected during active periods ("daytime"). Further, by injecting fluorescently labeled dead bacteria into flies at different points in their circadian cycle, the investigators could see increased phagocyte function at night for those two pathogens: there was an increase in the number of bacteria ingested by phagocytes in flies infected during resting versus active phases. Likewise, circadian-mutant flies "trapped" in the active phase had decreased phagocyte function, demonstrating that phagocyte activity is subject to regulation by circadian proteins whose activity, in turn, is disrupted by these mutations.

Strangely, though, infecting the flies with a third bacterial pathogen, Burkholderia cepacia, produced the opposite result. Circadian-mutant flies coped better with the infection than did normal flies, suggesting that in this case, a disrupted circadian rhythm might actually be good for the flies.

That poses an intellectual challenge, Schneider said: "If a sick fruit fly were to walk into my office, and it were infected with Burkholderia, I would know that I should deprive it of sleep. But I don't know the rules for people. In hospitals, nurses and orderlies are going in and out all the time, and you never get any sleep. Is that good, or bad? There are probably conditions where that's going to make things much worse. But maybe there are some conditions where it's actually better for you to have your sleep continuously interrupted. We're trying to figure out the rules for the fly, and hopefully someone else can translate it into human biology: Do they put you in a quiet room, or do they keep coming in and fiddling with your IV on purpose?"

*The paper, "Circadian rhythm and immunity in Drosophila: a model for neuroimmune communication," was presented on Dec. 14, at the Moscone Center.

The work was funded by the National Institutes of Health.

Adapted from materials provided by Stanford University Medical Center, via EurekAlert!, a service of AAAS.
ScienceDaily

Predecessor of Cows, The Aurochs, Were Still Living In The Netherlands Around AD 600

2008-12-25T21:34:00.001+06:00

Archaeological researchers at the University of Groningen have discovered that the aurochs, the predecessor of our present-day cow, lived in the Netherlands for longer than originally assumed. Remains of bones recently retrieved from a horn core found in Holwerd (Friesland, Netherlands), show that the aurochs became extinct in around AD 600 and not in the fourth century.

The last aurochs died in Poland in 1627. In January 2008, the bony core horn was unearthed in a mound near Holwerd by amateur-archaeologist Lourens Olivier from Ternaard. The Groningen Institute for Archaeology at the University of Groningen has established that it came from the left horn of an aurochs bull, and C14 dating reveals that the horn dates back to between AD 555 and 650.

The horn core is the bony core of the horn of a bovine animal. While the aurochs was still alive, the horn core would have been covered by a sheath of horn. This horn sheath has since decomposed in the soil. The largest curve in the horn core found in Holwerd measures 59 cm. The whole horn, including the horn sheath, must have been at least 70 cm long.

The aurochs was much larger than the common cows we know today, with aurochs bulls measuring between 160 and 180 cm at the withers, and aurochs cows between 140 and 150 cm. The cattle bred on the Frisian mounds around AD 600 measured between 90 and 120 cm and their horn cores were 25 cm long at the most.

Hunters and the first Dutch farmers hunted the aurochs. The species eventually became extinct in the Netherlands, not only because it was hunted, but also because more and more land was being used for agriculture and the human population was increasing.

Aurochs bones dating back to Roman times have previously been found at various sites in the Dutch river regions. They have also been unearthed in the terps and mounds of Friesland and Groningen. An almost complete skeleton of an aurochs was found in a terp in Britsum (Friesland), 15 km from Holwerd. It dates back to between AD 257 and 421. It was long thought that this was the most recent evidence of the aurochs that would be found, and that the aurochs had therefore become extinct in the Netherlands sometime in the fourth century AD. However, the horn core from Holwerd shows that the aurochs must have been grazing the Frisian meadows for at least another 150 to 250 years.

The find is reported in the newsletter ‘Van Warden en Terpen’ (From Mounds and Terps), published on 4 December 2008 by the Terp Research Association.

Adapted from materials provided by University of Groningen.
ScienceDaily

Robotic Aircraft Designed For Weather Forecasting

2008-12-25T21:32:00.001+06:00

Improving weather forecasting could also save lives. The more time to prepare for a storm and evacuate the area, the better. Currently, forecasts made more than 48 hours in the future aren't considered highly reliable. (Credit: iStockphoto/Mike Bentley)

At MIT, planning for bad weather involves far more than remembering an umbrella. Researchers in the Department of Aeronautics and Astronautics are trying to improve weather forecasting using robotic aircraft and advanced flight plans that consider millions of variables.

"Weather affects huge sectors of our economy, such as agriculture and transportation," said Nicholas Roy, an assistant professor and one of the researchers who worked on the project. With more time for advanced planning, farmers could bring in their crop before a big storm hits. Airlines could adjust their flight schedules further in advance, reducing the impact on customers.

Improving weather forecasting could also save lives. "People do get killed in these storms," said Aero-Astro Professor Jonathan How, the principal investigator. The more time to prepare for a storm and evacuate the area, the better. Currently, forecasts made more than 48 hours in the future aren't considered highly reliable.

The researchers hope to gain some lead-time by improving the way data about current weather conditions are collected. Existing forecasting systems depend on pressure, temperature, and other sensors aboard a single piloted airplane that flies scripted routes. But the data that are collected can't be processed fast enough to alter the flight plan if a storm starts brewing. "The response time is fairly slow," How said. "Today's flight path is based on yesterday's weather."

Ideally, teams of unmanned aircraft would be used to gather data. Current sensor readings from one plane would be used to guide the deployment of additional planes to areas with especially interesting or changing weather. By gathering information from several key areas at the same time, the researchers believe they could offer more accurate forecasts.

"We'd like to better predict the weather three to five days in advance," said Han-Lim Choi, a postdoctoral associate in How's lab.

But this is no easy task, largely because weather involves extremely complicated interactions between a lot of different factors. And while the researchers focused their work on the area over the Pacific Ocean, this was still a vast expanse to consider in terms of automated flight planning. Traditional robotic planning algorithms don't scale well to problems of that size, How explained. So the key challenge was creating an algorithm that could develop an effective flight plan quickly, based on millions of variables.

After three years of research using computerized weather simulations, the team believes their algorithm can quickly and efficiently determine where aircraft should be sent to take the most important measurements. Essentially, the algorithm works by determining the relative utility of taking different flight paths to gather measurements. How said their system can create a new flight plan within six hours of collecting data.

Choi, who recently earned an MIT PhD for his work on the project, will describe the research at this month's IEEE Conference on Decision and Control.

How said the results of the research could reach far beyond weather prediction. Intelligent path planning is essential for all kinds of mobile robots, be they autonomous cars or mail-carrying robots. The research also be used, How noted, to help environmental engineers determine where best to take samples to determine the source of a contaminant.

Although the system has not yet been used with real aircraft, How's team continues to test their algorithm against increasingly complex weather models with the help of former MIT meteorologist James Hansen, who is now with the Naval Research Laboratory.

The research was funded by the National Science Foundation.

Adapted from materials provided by Massachusetts Institute of Technology.
ScienceDaily

How Mutations Are Transmitted From One Generation To The Next

2008-12-25T21:30:00.000+06:00

A fundamental process in the transmission of genes from mother to child has been identified by researchers at the Montreal Neurological Institute, McGill University. The new study published in the December issue of the journal Nature Genetics identifies a mechanism that plays a key role in how mutations are transmitted from one generation to the next, providing unprecedented insight into metabolic diseases.

DNA that is only passed on from mothers to their children is stored in mitochondria, a compartment of cells which functions to supply energy to the body. Mutations in mitochondrial DNA (mtDNA) are important causes of over 40 known types of diseases and disorders which primarily affect brain and muscle function, some of which are severely debilitating, with symptoms including stroke, epilepsy, deafness and blindness. One very common mutation in Quebec causes maternally inherited blindness which has now been traced back to a Fille du Roi sent by the king of France in the 1600s to rectify the imbalance of gender in the newly colonized country.

MNI researchers have located a genetic bottleneck that determines the proportion of mutated mtDNA that mothers transmit to their offspring. This is important because there are many copies of mitochondria in cells and their distribution in tissues has a role in the severity and symptoms of the disease. Therefore knowing how mtDNA is transmitted is essential for the understanding and treatment of a range of maternally inherited diseases, and provides an opportunity for genetic counselling and treatment.

"The proportion of mutated DNA copies shifts rapidly and unpredictably from mother to child making it very hard to predict what proportion of mutated DNA will be passed on." says Dr. Eric Shoubridge, neuroscientist at the MNI and lead investigator in the study. "We now understand that this is partly due to the genetic bottleneck, in which just a small number of the original mtDNA copies from the mother are actually transmitted to the child. This bottleneck occurs during the development of eggs in affected females.

Only a small set of the female's mtDNA is selected to replicate resulting in the individual producing eggs with a wide range of proportions of mutated mtDNA. These eggs give rise to offspring with proportions of mutated mtDNA that differ from each other and are different from the proportion of mutated mtDNA in the mother. This explains why the occurrence and severity of a disease from mutated mtDNA can vary in offspring of an affected mother. The identification and location of the genetic bottleneck in our study strengthens our knowledge of the rules and processes of transmission and improves our capacity for genetic counselling."

An important application of this study is in the prevention of the disease at the prenatal stage because therapies for sick patients are usually ineffective, and the diseases are often fatal. The study locates the bottleneck as occurring during the process of egg maturation in early postnatal life of a female, supporting the knowledge that mature oocytes or egg cells contain the full set of copies of mtDNA. This evidence makes possible pre-implantation genetic diagnosis, in which an oocyte is screened for harmful mutations prior to fertilization, for in-vitro fertilization for example. This prevents the transmission of harmful mutations and can avoid the termination of a pregnancy in cases where an embryo is carrying a fatal neurological disorder.

This research was supported by the Canadian Institutes of Health Research and the US National Institutes of Health. Eric Shoubridge is an International Scholar of the Howard Hughes Institute.

Adapted from materials provided by Montreal Neurological Institute and Hospital.
ScienceDaily

As Ice Melts, Antarctic Bedrock Is On The Move

2008-12-25T21:28:00.001+06:00

Eric Kendrick, a senior research associate at Ohio State, shown at a POLENET GPS site in West Antarctica. He is standing in front of solar panels, battery boxes, and wind generators used to power the GPS station. (Credit: Photo courtesy of Ohio State University.)

As ice melts away from Antarctica, parts of the continental bedrock are rising in response -- and other parts are sinking, scientists have discovered.

The finding will give much needed perspective to satellite instruments that measure ice loss on the continent, and help improve estimates of future sea level rise.

"Our preliminary results show that we can dramatically improve our estimates of whether Antarctica is gaining or losing ice," said Terry Wilson,* associate professor of earth sciences at Ohio State University.

These results come from a trio of global positioning system (GPS) sensor networks on the continent.

Wilson leads POLENET, a growing network of GPS trackers and seismic sensors implanted in the bedrock beneath the West Antarctic Ice Sheet (WAIS). POLENET is reoccupying sites previously measured by the West Antarctic GPS Network (WAGN) and the Transantarctic Mountains Deformation (TAMDEF) network.

In separate sessions at the meeting, Michael Bevis, Ohio Eminent Scholar in geodyamics and professor of earth sciences at Ohio State, presented results from WAGN, while doctoral student Michael Willis presented results from TAMDEF.

Taken together, the three projects are yielding the best view yet of what's happening under the ice.

When satellites measure the height of the WAIS, scientists calculate ice thickness by subtracting the height of the earth beneath it. They must take into account whether the bedrock is rising or falling. Ice weighs down the bedrock, but as the ice melts, the earth slowly rebounds.

Gravity measurements, too, rely on knowledge of the bedrock. As the crust under Antarctica rises, the mantle layer below it flows in to fill the gap. That mass change must be subtracted from Gravity Recovery and Climate Experiment (GRACE) satellite measurements in order to isolate gravity changes caused by the thickening or thinning of the ice.

Before POLENET and its more spatially limited predecessors, scientists had few direct measurements of the bedrock. They had to rely on computer models, which now appear to be incorrect.

"When you compare how fast the earth is rising, and where, to the models of where ice is being lost and how much is lost -- they don't match," Wilson said. "There are places where the models predict no crustal uplift, where we see several millimeters of uplift per year. We even have evidence of other places sinking, which is not predicted by any of the models."

A few millimeters may sound like a small change, but it's actually quite large, she explained. Crustal uplift in parts of North America is measured on the scale of millimeters per year.

POLENET's GPS sensors measure how much the crust is rising or falling, while the seismic sensors measure the stiffness of the bedrock -- a key factor for predicting how much the bedrock will rise in the future.

"We're pinning down both parts of this problem, which will improve the correction made to the satellite data, which will in turn improve what we know about whether we're gaining ice or losing ice," Wilson said. Better estimates of sea level rise can then follow.

POLENET scientists have been implanting sensors in Antarctica since December 2007. The network will be complete in 2010 and will record data into 2012. Selected sites may remain as a permanent Antarctic observational network.

Scientists around the world can access POLENET data online, and schools can access educational resources as part of the International Polar Year.

Ohio State's POLENET partners in the United States are Pennsylvania State University, the University of Texas at Austin, New Mexico Tech, Washington University, the Jet Propulsion Laboratory, and the University of Memphis. A host of international partners are part of the effort as well. POLENET is funded by the National Science Foundation.

*Wilson reported the research in a press conference December 15, 2008 at the American Geophysical Union meeting in San Francisco.
Adapted from materials provided by Ohio State University.
ScienceDaily

Effects Of Unconscious Exposure To Advertisements

2008-12-25T21:26:00.000+06:00

Fads have been a staple of American pop culture for decades, from spandex in the 1980s to skinny jeans today. But while going from fad to flop may seem like the result of fickle consumers, a new study suggests that this is exactly what should be expected for a highly efficient, rationally evolved animal.

The new research, led by cognitive scientist Mark Changizi of Rensselaer Polytechnic Institute, shows why direct exposure to repeated ads initially increases a consumer’s preference for promoted products, and why the most effective advertisements are the ones consumers don’t even realize they have seen.

It has long been known that repeated visual exposure to an object can affect an observer’s preference for it, initially rapidly increasing preference, and then eventually lowering preference again. This can give way to short-lived fads. But while this may seem illogical, Changizi argues that it makes perfect cognitive sense.

“A rational animal ought to prefer something in proportion to the probable payoff of acting to obtain it,” said Changizi, assistant professor of cognitive science at Rensselaer and lead author of the study, which appears in the online version of the journal Perception. “The frequency at which one is visually exposed to an object can provide evidence about this expected payoff, and our brains have evolved mechanisms that exploit this information, rationally modulating our preferences.”

A small number of visual exposures to an object typically raises the probability of acquiring the object, which enhances preference, according to Changizi.

On the other hand, Changizi says overexposure to an object provides the brain with evidence that the object is overabundant, and is likely not valuable, thereby lowering the individual’s preference for it.

“An individual’s preference for an object based on a large number of visual exposures will almost always take the shape of an inverted ‘U’, with an initial rapid rise in preference based on the enhanced probability that an object can be obtained, followed by a plateau and a gradual decrease in preference as the evidence begins to suggest that the object is overly common and thus not valuable,” Changizi said.

One of the most surprising aspects of visual exposure effects, according to Changizi, is that they are enhanced when visual exposure occurs without conscious recognition.

“This non-conscious mechanism exists because visual exposure information alone, without conscious judgment, has implications for the expected payoff of one’s actions,” Changizi said. “In many natural situations, observers potentially have both exposure schedule information and consciously accessible information about the object, in which case the predicted degree of preference modulations from visual exposure will be dampened, as the visual information is competing with the information from conscious recognition of the object and any subsequent judgment.”

These non-conscious mechanisms for rationally modulating preference are the kind animals without much of a cognitive life can engage in, and Changizi speculates that they are much more ancient.

Advertising that takes the form of apparel branded with company’s names, and products strategically placed in movies and television shows, often go unnoticed by consumers, capitalizing on our brain’s mechanisms to modulate preference based on non-conscious exposure.

Changizi’s research suggests that such advertising tactics work because they tap into our non-conscious mechanisms for optimal preferences, hijacking them for selling a company’s products. The research could hold potential for marketers interested in optimizing their advertising for the human mind, Changizi says.

Changizi conducted his research with Shinsuke Shimojo, professor of biology at the California Institute of Technology. The project was funded by a grant from the National Institutes of Health.

Adapted from materials provided by Rensselaer Polytechnic Institute.
ScienceDaily

Supercomputer Center Director Offers Tips On Data Preservation In The Information Age

2008-12-25T21:24:00.001+06:00

The world has gone digital in just about everything we do. Almost every iota of information we access these days is stored in some kind of digital form and accessed electronically -- text, charts, images, video, music, you name it. The key questions are: Will your data be there when you need it? And who’s going to preserve it?

In the December 2008 edition of Communications of the ACM, the monthly magazine of the Association for Computing Machinery, Dr. Fran Berman, director of the San Diego Supercomputer Center (SDSC) at the University of California, San Diego, provides a guide for surviving what has become known as the “data deluge.”

Managing this deluge and preserving what’s important is what Berman refers to as one of the “grand challenges” of the Information Age. The amount of digital data is immense: A 2008 report by the International Data Corporation (IDC), a global provider of information technology intelligence based in Framingham, Mass., predicts that by 2011, our “digital universe” will be 10 times the size it was in 2006 - and almost half of this universe will not have a permanent home as the amount of digital information outstrips storage space.

“As a society, we have only begun to address this challenge at a scale concomitant with the deluge of data available to us and its importance in the modern world,” writes Berman, a longtime pioneer in cyberinfrastructure – an open but organized aggregate of information technologies including computers, data archives, networks, software, digital instruments, and other scientific endeavors that support 21st century life and work.

Berman is a strong advocate of cyberinfrastructure that supports the management and preservation of digital data in the Information Age – data cyberinfrastructure: “Just like the physical infrastructures all around us -- roads, bridges, water and electricity – we need a data cyberinfrastructure that is stable, predictable, and cost-effective.”

In her article, Berman explores key trends and issues associated with preserving digital data, and what’s required to keep it manageable, accessible, available, and secure. However, she warns that there is no “one-size-fits-all” solution for data stewardship and preservation.

“The ‘free rider’ solution of ‘Let someone else do it’-- whether that someone else is the government, a library, a museum, an archive, Google, Microsoft, the data creator, or the data user -- is unrealistic and pushes responsibility to a single company, institution, or sector. What is needed are cross-sector economic partnerships,” says Berman. She adds that the solution is to “take a comprehensive and coordinated approach to data cyberinfrastructure and treat the problem holistically, creating strategies that make sense from a technical, policy, regulatory, economic, security, and community perspective.”

Berman’s ACM article closes with a set of “Top 10” guidelines for data stewardship:

1. Make a plan. Create an explicit strategy for stewardship and preservation for your data, from its inception to the end of its lifetime; explicitly consider what that lifetime may be.
2. Be aware of data costs and include them in your overall IT budget. Ensure that all costs are factored in, including hardware, software, expert support, and time. Determine whether it is more cost-effective to regenerate some of your information rather than preserve it over a long period.
3. Associate metadata with your data. Metadata is needed to be able to find and use your data immediately and for years to come. Identify relevant standards for data/metadata content and format, following them to ensure the data can be used by others.
4. Make multiple copies of valuable data. Store some of them off-site and in different systems.
5. Plan for the transition of digital data to new storage media ahead of time. Include budgetary planning for new storage and software technologies, file format migrations, and time. Migration must be an ongoing process. Migrate data to new technologies before your storage media becomes obsolete.
6. Plan for transitions in data stewardship. If the data will eventually be turned over to a formal repository, institution, or other custodial environment, ensure it meets the requirements of the new environment and that the new steward indeed agrees to take it on.
7. Determine the level of “trust” required when choosing how to archive data. Are the resources of the U.S. National Archives and Records Administration necessary or will Google do?
8. Tailor plans for preservation and access to the expected use. Gene-sequence data used daily by hundreds of thousands of researchers worldwide may need a different preservation and access infrastructure from, for example, digital photos viewed occasionally by family members.
9. Pay attention to security. Be aware of what you must do to maintain the integrity of your data.
10. Know the regulations. Know whether copyright, the Health Insurance Portability and Accountability Act of 1996, the Sarbanes-Oxley Act of 2002, the U.S. National Institutes of Health publishing expectations, or other policies and/or regulations are relevant to your data, ensuring your approach to stewardship and publication is compliant.

Berman is a national leader in this area and also co-chairs of the Blue Ribbon Task Force on Sustainable Digital Preservation and Access with OCLC economist Brian Lavoie. The task force was formed late last year to explore and ultimately present a range of economic models, components, and actionable recommendations for sustainable preservation and access of digital data in the public interest. Commissioned for two years, the task force will publish an interim report outlining economic issues and systemic challenges associated with digital preservation later this month on its website.

Adapted from materials provided by University of California - San Diego.
ScienceDaily

Practice As Well As Sleep May Help Birds Learn New Songs

2008-12-25T21:21:00.001+06:00

Zebra finches. Practice as well as sleep may help birds learn new songs. The reorganization of neural activity during sleep helps young songbirds to develop the vocal skills they display while awake, University of Chicago researchers have found. (Credit: iStockphoto/Andrew Corney)

Practice as well as sleep may help birds learn new songs. The reorganization of neural activity during sleep helps young songbirds to develop the vocal skills they display while awake, University of Chicago researchers have found.

Sleep is well known to have a role in a broad range of learning processes studied in humans, including acquiring complex skills such as video game playing and learning new speech dialects. However, the neural mechanisms involved in the nighttime consolidation of learning are not well understood. To study this, researchers turned to an animal model system, the developmental learning of song in songbirds, which long has been known to share features with learning speech and language.

Sylvan Shank, a recent Ph.D. graduate in Psychology, and Daniel Margoliash, Professor in Organismal Biology & Anatomy and in Psychology, report in this week's issue of Nature that when young zebra finches listen to an adult tutor's song and then practice singing, the activity of premotor neurons in the brain is altered during the following night's sleep. The newly formed pattern of spikes in nighttime activity carries information both about the tutor song and auditory feedback the birds hear while singing. These nighttime changes lead to improvements the young birds' singing that can be observed the following day.

The study is the first direct observation of the nighttime activity related to vocal learning.

"This study takes big steps forward in finding out how sleep impacts learning," Margoliash said. "We looked at juvenile birds at the first moments of learning. We gained insight into the role of auditory information in structuring sleep activity, which in turn, we speculate interacts with daytime activity to drive vocal learning.

Since the changes occur in the region of the brain that drives singing during the day, but occur prior to the changes in singing, this discovery provides a compelling hypothesis for how this learning might happen. Juvenile songbirds show a complex, sleep-dependent circadian patterns of singing that have been observed during developmental vocal learning.

Their songs have less structure each morning and regain their complexity each afternoon. This daily pattern of variation is important for song learning—birds that have the greatest variation early in development are the ones that ultimately learn the best.

"We now have a new model for how this works," said Margoliash. "At night, the auditory information that the bird was exposed to during the day is reactivated, [carried by the spontaneous activity of neurons], changing the structure of the neural networks. These changes interact with changes during the day as birds listen to tutor songs and practice singing." The authors suggest that reactivation of sensory information at night might be a general mechanism for learning a new skill.

In previous work, Margoliash and his team identified places in the brain where nighttime activity is reactivated. In adult birds, individual cells spontaneously emitted patterns of bursts during sleep that were very similar to the burst patterns emitted when the bird sang during the day.

In the current study, the University team was able, for the first time, to look at juvenile zebra finches. Using microelectrodes, the team observed changes in neuronal activity during sleep in a region of the young zebra finch brain involved in singing—the acropalium (RA).

Shank and Margoliash first looked at the effects of exposing birds to different tutor songs. They then extended that work to the role of auditory feedback in driving learning. They wanted to see whether changes in the brain brought on during sleep after exposure to a new song were reinforced by practice as well as daytime listening. They theorized that the interaction of the listening followed by practice and sleep consolidation could explain how birds learn to sing new calls.

To test the role of auditory feedback on the bird's learning, the team used white noise at 100 decibels to prevent the birds from hearing themselves. In subsequent tests of their brain activity, the team found no increase in the activity after the exposure to white noise, even if the birds had listened to tutor songs. This finding demonstrated the importance of auditory feedback; after the white noise was eliminated, the birds began to learn normally.

"There is a very famous theory called the 'template theory' of birdsong learning," Margoliash said. "This theory postulates that a sensory template is formed when listening to an adult tutor, and that this template is then used to evaluate auditory feedback. We knew neither the form nor the mode of action of the template. Now we understand that the template can influence learning via sleep, and that new template information is rapidly distributed throughout the brain."

Neurons in RA do not exhibit auditory activity during the day, yet their nighttime activity patterns reflect auditory signals. Margoliash speculates that "perhaps dreams are so compelling because additional areas are recruited to process the sensory experience."

Journal reference:

1. Shank et al. Sleep and sensorimotor integration during early vocal learning in a songbird. Nature, 2008; DOI: 10.1038/nature07615

Adapted from materials provided by University of Chicago, via EurekAlert!, a service of AAAS.
SC

Computer Scientists Launching Indoor Navigation System

2008-12-25T21:20:00.000+06:00

Now that navigation systems are here to stay, we can hardly imagine life without them. Aside from private use for getting about on roads, they play an essential role in air and ocean traffic, and even in rail transport for guiding and monitoring trains. With its Galileo navigation system, the European Union intends to become independent of America’s GPS (Global Positioning System).*

The Federal Ministry of Education and Research recently approved the two-year project “Indoor”, which will run until the end of 2010. In this project, LMU computer scientists working with Professor Claudia Linnhoff-Popien are developing positioning and navigation technologies to be used in the field of traffic logistics and for emergency services. What they are focusing on in particular is indoor positioning and navigation.

The project aims at a fundamentally new development: Solutions so far have relied on the terminal device periodically sending position data to a server, even when the user, and therefore the terminal, is not moving at all. The LMU computer scientists, on the other hand, assign boundary circles to the users according to given queries and the movement of the persons or objects being monitored. The terminal only gets in touch with the server if the user moves beyond his circle. This method is more effective and economical, since the position data is only sent to the server when there is movement, and costs are only incurred at that moment.

This technology so far works best with GPS-supported terminals – and it will now be exciting to see how the new challenges of a Galileo module and the addition of indoor positioning will be met. As it is, the crux of the problem with large buildings is the given architecture and furnishing, both of which can lead to all kinds of wild shadowing effects and reflections. The present technology goes back to research done in the Mobile and Distributed Systems Group, which has been being published in prestigious international journals over the past five years, and which has led to numerous dissertations, one habilitation and a number of patent applications.

The aim of the “Indoor” project is to improve certain algorithms that will increase the energy and cost efficiency of location-based service applications. Localization algorithms for indoor applications shall be enhanced, existing platforms and concepts technically evaluated, and a user study conducted.

The scientists have daunting challenges ahead as they forge on with the project, since precise localization inside a large building is considerably more difficult to achieve than outdoors. Aside from the technical difficulty of achieving this, there is one nasty problem that stands in their way: the “semantics” of buildings. There is no way of knowing from a public building’s floor plan alone, for example, whether a door drawn on the plan is actually accessible to every public person, or whether it is perhaps only accessible to certain staff or to certain groups of people.

Together with a spin-off of the Mobile and Distributed Systems Group, Aloqa GmbH Munich, and a hardware developer for satellite navigation systems, Ifen GmbH Poing, a prototype shall be developed during the project, which shall implement the methods developed at the group as a tangible hardware module. And there is one more partner who will be involved in the testing phase: the Walt Disney Company, Germany. Disney is namely interested in this budding technology because it could be just what they need for their theme parks.

*Now the Mobile and Distributed Systems Group of Ludwig-Maximilians-Universität (LMU), München, is also involved in developing Galileo services.The introduction of Galileo will mark the independence of the European Union from America’s GPS (Global Positioning System) and the Russian Federation’s global navigation satellite system GLONASS. While Galileo, a joint project of the EU and the ESA (European Space Agency), is compatible with GPS, it guarantees independent and reliable availability in Europe.

Adapted from materials provided by Ludwig-Maximilians-Universitaet Muenchen (LMU).
ScienceDaily

The European Eel: To Migrate Or Not To Migrate In Freshwaters?

2008-12-25T21:18:00.001+06:00

The European eel’s biology and ecology never cease to amaze us. At the elver stage, certain individuals swim up estuaries to grow in rivers, whereas others spend their entire life cycle at sea. In Bordeaux, researchers have looked into the origin of this divergence in migratory behaviour. What if it was only a question of energy reserves and feeding behaviour?

Over-fishing, pollution, river development, global climate changes, etc. are threatening a large number of migratory fish. Among the endangered species, one can cite the European eel whose numbers have been divided by 10 over the two last decades. To save the species, the priority is better management of the populations subjected to the pressures of the environment. However, this first assumes better knowledge of the species’ biology and ecology.

The exercise is complex, because the European eel’s life cycle is still not fully understood. The species has long been considered a migratory fish that reproduces at sea and grows in rivers. Yet studies conducted over the last 10 years have shown that certain individuals do not spend their growth period in freshwaters. Migratory divergences may exist at the elver stage. At Bordeaux and Saint-Pée-sur-Nivelle, in doctoral work co-supervised by Cemagref and the INRA, Sarah Bureau du Colombier has been studying the source of these different migratory patterns in European eel elvers.

Sorting migrant fish and sedentary fish

What morphological characteristics differentiate a sedentary elver from a migratory elver in the natural environment? Today the response is “none”. To sort individuals by their propensity to migrate, the young doctoral student chose to concentrate on behavioral studies. To swim up the estuaries, the migratory elvers use the current from the ebb tide. Since light inhibits migration, they prefer to move in darkness, therefore especially at night. By reproducing the two main stimuli of migration in experimental conditions, it was possible to distinguish highly mobile individuals (with a strong propensity to migrate) from more passive individuals, buried in the gravel (with a weak propensity to migrate). The hundreds of elvers tracked during this study were captured upon entering the estuary or in the middle of the Adour estuary.

A question of an individual energy threshold

When they swim up the Adour estuary, the young elvers stop feeding more or less totally. This is a true obstacle course which requires good energy reserves upon entering the mouth of the estuary and then rapidly resuming feeding once the river has been reached. To verify these hypotheses, the young scientist compared the energy state of the two categories of elver as well as their capacity to resume feeding. In the estuary environment, elvers with a strong propensity to migrate seemed better equipped, in terms of energy stores, to conquer the freshwater environment and pursue their growth. Upon entering the estuary, the differences are not significant. This result points towards the existence of an individual energy threshold determining whether the individual will pursue its migration. In addition, the results have also underscored the greater energy expenditures and slower and/or lower resumption of feeding in sedentary elvers.

All of these data were then used to feed an estuarial migration model that will eventually be used to simulate the migratory behaviour of elvers according to different parameters, some of which are related to global climate changes.

A complex life cycle

The European eel reproduces near the North American coast in the Sargasso Sea. The young larvae, called leptocephalus, cross the Atlantic Ocean on the ocean currents. Near the European and North African coasts, they metamorphose into elvers (young yellow eels). These individuals then settle in coastal zones or in estuaries, or swim up rivers. After they have metamorphosed into silver eels, the adults embark on their migration and reproduction in the Sargasso Sea.

Adapted from materials provided by Cemagref, via AlphaGalileo.
ScienceDaily

UV-B Light Sensing Mechanism Discovered In Plant Roots

2008-12-25T21:15:00.001+06:00

An Arabidopsis early seedling developing normally (left) compared with the same plant with a mutated RUS1 gene (right) which shows stunted growth. (Credit: SFSU)

Scientists have discovered that plant roots can sense UV-B light and have identified a specific gene that is a vital player in UV-B signaling, the communication between cells.

A study published Dec. 8 in the Early Edition of PNAS reveals that the gene RUS1 measures UV-B light levels and passes this information on to other parts of the plant responsible for growth and development. A low dosage of UV-B light, for example the levels found in shady conditions or under fluorescent lighting, can provide important signals to the rest of the plant and is therefore beneficial to normal plant growth. It helps young plants stay on the right track of development and aids seedling morphogenesis, but too much UV-B light can be toxic.

The study found that plants with a mutated UV-B light sensor gene become hypersensitive to UV-B light and even under low intensity levels of UV-B light, their root growth is stunted and they fail to grow leaves. Therefore the RUS1 gene is responsible for ensuring that young seedlings develop normally even when their roots are exposed to UV-B light.

It's unusual that roots, normally covered in soil, should have sensors for UV-B light, but the RUS1 gene is crucial at the young seedling stage when a plant's roots are resting on the soil surface. Later in a plant's life, roots can be exposed after rainwash, geological movements or animal activity.

The discovery of RUS1 provides scientists with a platform to examine other key genes that receive UV-B light and translate light information into how the plant should develop.

The paper's corresponding author is Zheng-Hui He, professor of biology at San Francisco State University. In addition to He, co-authors include SF State researchers Hongyun Tong, Colin D. Leasure, Xuewen Hou, Gigi Yuen, and Winslow Briggs from the Carnegie Institute of Washington.

Adapted from materials provided by San Francisco State University, via EurekAlert!, a service of AAAS.
ScienceDaily

New Mechanism For Attentional Control In The Human Brain Discovered

2008-12-25T21:14:00.000+06:00

A study by UC Davis researchers appearing in the journal Science on December 12, reports the discovery of a new mechanism of attention in the human brain. Previous studies in animals implicated changes in the state of a portion of the brainstem, called the locus ceruleus (LC), in shifts from distractible to attentive states.

By administering a drug that modifies the state of the LC, which was visualized using functional magnetic resonance (fMRI) brain imaging techniques, the researchers were able to shift volunteers into a more attentive state in which they showed enhanced coordinated brain activity and performance on a test of attention control.

The UC Davis study also provides new insights into the workings of a stimulant-like drug that could have broad applications for enhancing the cognition of people with conditions ranging from autism to schizophrenia.

The drug modafinil is approved by the Food and Drug Administration (FDA) for treating narcolepsy, shift-work related sleep disorders and obstructive sleep apnea, and indicated for conditions including ADHD, Parkinson's disease and depression. But how it works has not been well understood until now.

"We have shown that the way modafinil works is by quieting activity in the LC and increasing its connections with the frontal cortex," said Cameron Carter, a UC Davis professor of psychiatry and behavioral sciences and senior author of the study.

"Now that we know how it works, we can develop better cognitive enhancers that can treat more people suffering from a wider variety of neurodevelopmental disorders, like ADHD, autism and schizophrenia," he said.

Clues to the drug's mechanism came from work done in animals, said Michael Minzenberg, lead author of the paper and a UC Davis assistant professor of clinical psychiatry. The animal studies indicated that it was the shift in brain activity of the pre-frontal cortex caused by norepinephrine that was responsible for improvements in cognition. Studies in primates also showed that norepinephrine increased attentiveness.

"Now we know that, although these parts of the brain are far from each other, their activity is correlated," said Minzenberg.

Previous studies in primates showed that, when not performing a complex task, neurons in the prefrontal cortex fire often and seemingly at random. During the performance of a focused task, however, that area of the brain is quiet and the cells fire only in concert with actions associated with the task. These modes are called exploration and exploitative, respectively.

"We found that modafinil shifts the human brain into exploitation mode and study subjects perform better on tasks," Minzenberg said.

In the current study the research team used fMRI to look at brain activity in real time in 21 healthy adults who were asked to perform a standardized test called a POP Task (Preparing to Overcome Prepotency) that requires the subject to pay close attention.

The subjects performed this task on different days after taking either a sugar pill or a dose of modafinil. Researchers then looked at the differences in brain-activity patterns.

"Subjects performed much better on these tasks after taking modafinil, but, more importantly, using fMRI we were able to see the shift to quieter, more focused brain activity ," Minzenberg said.

According to Minzenberg, this study is one of the few to look at the pharmacological activity of a drug in real time using a non-invasive method.

"This is a proof-of-concept study supporting the use of fMRI to study drug effects on the brain as a way of gaining insight into how the drugs work," he said.

While fMRI may help speed up the drug development process in general, the results of the study promise to accelerate development of drugs to treat neurodevelopmental disorders in particular, Carter said.

"Future development will be more targeted because this study builds a bridge between basic science and human cognition," he said.

The study was funded by the National Institute of Mental Health (NIMH) and a Translational Clinical Scientist career development grant to professor Carter from the Burroughs Wellcome Fund.

Other study authors include UC Davis researchers Andrew Watrous, of the UC Davis Center for Neuroscience and Jong Yoon and Stefan Ursu of the UC Davis Medical Center Department of Psychiatry.

Adapted from materials provided by University of California - Davis - Health System.
ScienceDaily

Solar Flare Surprise: Stream Of Perfectly Intact Hydrogen Atoms Detected

2008-12-25T21:09:00.001+06:00

The X9-class solar flare of Dec. 5, 2006, observed by the Solar X-Ray Imager aboard NOAA's GOES-13 satellite. (Credit: NOAA's Space Weather Prediction Center)

Solar flares are the most powerful explosions in the solar system. Packing a punch equal to a hundred million hydrogen bombs, they obliterate everything in their immediate vicinity. Not a single atom should remain intact.

At least that’s how it’s supposed to work.

"We’ve detected a stream of perfectly intact hydrogen atoms shooting out of an X-class solar flare," says Richard Mewaldt of the California Institute of Technology. "What a surprise! If we can understand how these atoms were produced, we'll be that much closer to understanding solar flares."

The event occurred on Dec. 5, 2006. A large sunspot rounded the sun’s eastern limb and with little warning it exploded. On the "Richter scale" of flares, which ranks X1 as a big event, the blast registered X9, making it one of the strongest flares of the past 30 years.

NASA managers braced themselves. Such a ferocious blast usually produces a blizzard of high-energy particles dangerous to both satellites and astronauts. An hour later they arrived, but they were not the particles researchers expected.

NASA’s twin Solar TErrestrial RElations Observatory (STEREO) spacecraft made the discovery: "It was a burst of hydrogen atoms," says Mewaldt. "No other elements were present, not even helium (the sun’s second-most abundant atomic species). Pure hydrogen streamed past the spacecraft for a full 90 minutes."

Next came 30 minutes of quiet. The burst subsided and STEREO’s particle counters returned to low levels. The event seemed to be over when a second wave of particles enveloped the spacecraft. These were the "broken atoms" flares are supposed to produce—protons and heavier ions such as helium, oxygen and iron. "Better late than never," he says.

At first, this unprecedented sequence of events baffled scientists, but now Mewaldt and colleagues believe they’re getting to the bottom of the mystery.

First, how did the hydrogen atoms resist destruction?

"They didn’t," says Mewaldt. "We believe they began their journey to Earth in pieces, as protons and electrons. Before they escaped the sun’s atmosphere, however, some of the protons captured an electron, forming intact hydrogen atoms. The atoms left the sun in a fast, straight shot before they could be broken apart again." (For experts: The team believes the electrons were recaptured by some combination of radiative recombination and charge exchange.)

Second, what delayed the ions?

"Simple," says Mewaldt. "Ions are electrically charged and they feel the sun’s magnetic field. Solar magnetism deflects ions and slows their progress to Earth. Hydrogen atoms, on the other hand, are electrically neutral. They can shoot straight out of the sun without magnetic interference."

Imagine two runners dashing for the finish line. One (the ion) is forced to run in a zig-zag pattern with zigs and zags as wide as the orbit of Mars. The other (the hydrogen atom) runs in a straight line. Who’s going to win?

"The hydrogen atoms reached Earth almost two hours before the ions," says Mewaldt.

Mewaldt believes that all strong flares might emit hydrogen bursts, but they simply haven’t been noticed before. He’s looking forward to more X-flares now that the two STEREO spacecraft are widely separated on nearly opposite sides of the Sun. (In 2006 they were still together near Earth.) STEREO-A and –B may be able to triangulate future bursts and pinpoint the source of the hydrogen. This would allow the team to test their ideas about the surprising phenomenon.

"All we need now," he says, "is some solar activity."

For more information about this research, look for the article "STEREO Observations of Energetic Neutral Atoms during the 5 December 2006 Solar Flare" by R. A. Mewaldt et al., in a future issue of the Astrophysical Journal Letters.

For more information about STEREO, please visit: http://www.nasa.gov/stereo
Adapted from materials provided by NASA/Goddard Space Flight Center.
ScienceDaily

Wobbly Planets Could Reveal Earth-like Moons

2008-12-25T21:02:00.001+06:00

Artist's representation of a gas giant exoplanet with a habitable moon. (Credit: Andy McLatchie)

Moons outside our Solar System with the potential to support life have just become much easier to detect, thanks to research by an astronomer at University College London (UCL).

David Kipping has found that such moons can be revealed by looking at wobbles in the velocity of the planets they orbit. His calculations, which appear in the Monthly Notices of the Royal Astronomical Society December 11, not only allow us to confirm if a planet has a satellite but to calculate its mass and distance from its host planet – factors that determine the likely habitability of a moon.

Out of the 300+ exoplanets (planets outside our Solar System) currently known, almost 30 are in the habitable zone of their host star but all of these planets are uninhabitable gas giants. The search for moons in orbit around these planets is important in our search for alien life as they too will be in the habitable zone but are more likely to be rocky and Earth-like, with the potential to harbour life.

“Until now astronomers have only looked at the changes in the position of a planet as it orbits its star. This has made it difficult to confirm the presence of a moon as these changes can be caused by other phenomena, such as a smaller planet,” said David Kipping. “By adopting this new method and looking at variations in a planet’s position and velocity each time it passes in front of its star, we gain far more reliable information and have the ability to detect an Earth-mass moon around a Neptune-mass gas planet.”

The appearance of wobbles in a planet’s position and velocity are caused by the planet and its moon orbiting a common centre of gravity. While the old method of looking at the wobbles in position allowed astronomers to search for moons, it did not allow them to determine either their mass or their distance from the planet.

Professor Keith Mason, Chief Executive of the Science and Technology Facilities Council, said, “It’s very exciting that we can now gather so much information about distant moons as well as distant planets. If some of these gas giants found outside our Solar System have moons, like Jupiter and Saturn, there’s a real possibility that some of them could be Earth-like.”

Kippings work is funded by the UK’s Science and Technology Facilities Council (STFC).
Adapted from materials provided by Science and Technology Facilities Council, via AlphaGalileo.
ScienceDaily