Thursday, April 15, 2010


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Fasting for one day does not lead to overeating the next day, or the following week, or to more than a temporary weight loss, reports a new Cornell study. The findings help explain why diets fail.

When people fast or diet and then eat freely, "we found they do not increase their food intake to compensate for a day without eating," said David Levitsky, professor of nutrition and psychology, whose new study was published in the journal Physiology and Behavior March 22.

However, they eventually regain their weight back anyway, he said, because metabolic rate is related to body weight. "Since you weigh less after fasting or dieting, your metabolism is slower, and so you regain the weight with normal eating," said Levitsky, a Stephen H. Weiss presidential fellow.

The results defy the notion that fasting or dieting leads to gorging later; they also counter the idea that people have a genetically determined set point weight.

However, the study suggests a new strategy for losing weight. Although chronic lifestyle changes (eating healthier foods and getting more exercise) are preferable ways to lose weight, Levitsky said, a weekly fast might be another way to go.

Since it takes 10 to 14 days to recover the body tissue lost from a one-day fast, "Going without food for one day each week should produce a significant reduction in body weight over time," Levitsky said, now that we know that "fasting does not lead to overeating, and total recovery of body tissue does not occur within the week."

In his study, 22 women, divided into three groups, ate meals Mondays through Fridays at the Cornell Human Metabolic Research Unit for four weeks. During the first week, all groups ate all they wanted. Each of the following three Mondays, one group was chosen to fast, one to consume only 1,200 calories, and one to eat unrestrained. For the rest of the week, all the women were free to eat as they liked. During each session, participants were weighed, and all food consumed was measured.

For those who fasted or ate a restricted diet on Monday, body weight declined significantly the following day, though it did not change for the unrestrained eaters.

By the end of the week, the fasters and dieters had recovered their lost weight (but not all their body tissue) -- without any increase in food consumption beyond normal levels. The fact they were burning fewer calories due to their slowed metabolism accounted for the weight gain; the paper estimates that it would take 10 days for the ratio of fat, bone and muscle to return to pre-fast levels.

"The women regained their weight within a week, because weight is a sloppy measure of body tissue -- weight includes body water, gastrointestinal tract contents, glycogen content and so on," said Levitsky. "Over time, however, the loss of body tissue would accumulate and result in significant weight loss," he said.

(Photo: Cornell U.)

Cornell University


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University students have developed a computer game that is operated by eye movements, which could allow people with severe physical disabilities to become ‘gamers’ for the first time.

The students, from Imperial College London, have adapted an open source game called ‘Pong’, where a player moves a bat to hit a ball as it bounces around the screen. The adaptation enables the player to move the bat using their eye.

To play the game, the user wears special glasses containing an infrared light and a webcam that records the movement of one eye. The webcam is linked to a laptop where a computer program syncs the player’s eye movements to the game.

The prototype game is very simple but the students believe that the technology behind it could be adapted to create more sophisticated games and applications such as wheelchairs and computer cursors controlled by eye movements.

One of the major benefits of the new technology is that it is inexpensive, using off-the-shelf hardware and costing approximately £25 to make. Eye movement systems that scientists currently use to study the brain and eye motion cost around £27,000, say the researchers.

Dr Aldo Faisal, the team’s supervisor from the Department of Computing and the Department of Bioengineering at Imperial College London, says:

“Remarkably, our undergraduates have created this piece of neurotechnology using bits of kit that you can buy in a shop, such as webcams. The game that they’ve developed is quite simple, but we think it has enormous potential, particularly because it doesn’t need lots of expensive equipment. We hope to eventually make the technology available online so anyone can have a go at creating new applications and games with it and we’re optimistic about where this might lead. We hope it could ultimately provide entertainment options for people who have very little movement. In the future, people might be able to blink to turn pages in an electronic book, or switch on their favourite song, with the roll of an eye.”

Mr Ian Beer, who is a third year undergraduate from the Department of Computing, adds: “This game is just an early prototype, but we’re really excited that from our student project we’ve managed to come up with something that could ultimately help people who have really limited movement. It would be fantastic to see lots of people across the world creating new games and applications using our software.”

Researchers in Dr Faisal’s lab are now refining the technology so that it can monitor movements in both eyes. This would enable a user to carry out more complicated tasks such as plotting a journey on screen. This might ultimately allow them to use eye movements to steer a motorised wheelchair.

(Photo: ICL)

Imperial College London


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University of British Columbia astronomer Ludovic Van Waerbeke with an international team has confirmed that the expansion of the universe is accelerating after looking at data from the largest-ever survey conducted by the Hubble Space Telescope.

The astronomers studied more than 446,000 galaxies to map the matter distribution and the expansion history of the universe. This study enabled them to observe precisely how dark matter evolved in the universe and to reconstruct a three-dimensional map of the dark matter and use this to test Albert Einstein’s theory of general relativity.

The findings will appear in a forthcoming issue of the journal Astronomy & Astrophysics. The study’s lead author is Tim Schrabback, an astronomer from Leiden University in the Netherlands.

“Our results confirmed that there is an unknown source of energy in the universe which is causing the cosmic expansion to speed up, stretching the dark matter further apart exactly as predicted by Einstein’s theory,” says Van Waerbeke, an associate professor in the Dept. of Physics and Astronomy.

Einstein’s theory of general relativity predicts that space and time is a soft geometrical structure of which the shape and evolution are entirely determined by the matter within it. Scientists posit that the universe is composed of dark matter and normal matter with a third constituent called “dark energy,” which over the past two billion years has been the force behind the accelerated expansion of the universe.

“The data from our study are consistent with these predictions and show no deviation from Einstein’s theories,” says Van Waerbeke, who is also a scholar in the Cosmology and Gravity program of the Canadian Institute for Advanced Research.

In the late 1990s, Van Waerbeke pioneered weak gravitational lensing to measure the invisible web of dark matter that makes up 80 per cent of the mass of the universe. This technique is similar to taking an X-ray of the body to reveal the underlying skeleton. It allows astronomers to observe how light from distant galaxies is bent and distorted by the web of invisible dark matter as it travels toward Earth. By measuring the distortions seen in these galaxy light patterns, astronomers can then map dark matter structures.

Along with weak gravitational lensing, the study uses data from the Cosmic Evolution Survey (COSMOS), one of the most ambitious undertakings by the Hubble Space Telescope. COSMOS is a joint project of the European Space Agency (ESA) and NASA involving more than 100 scientists from a dozen countries.

To generate the COSMOS survey, a camera aboard the Hubble photographed 575 slightly overlapping views of the same part of the universe. This required nearly 1,000 hours of observations, during which Hubble circled the Earth almost 600 times.

In addition to the Hubble data, the researchers used ground-based telescope data to assign distances to 194,000 of the galaxies surveyed, which was a key factor for reconstructing the three-dimensional picture of the dark matter distribution.

The University of British Columbia


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Self-repairing materials within nuclear reactors may one day become a reality as a result of research by Los Alamos National Laboratory scientists.

In a paper appearing in the journal Science, Los Alamos researchers report a surprising mechanism that allows nanocrystalline materials to heal themselves after suffering radiation-induced damage. Nanocrystalline materials are those created from nanosized particles, in this case copper particles. A single nanosized particle—called a grain—is the size of a virus or even smaller. Nanocrystalline materials consist of a mixture of grains and the interface between those grains, called grain boundaries.

When designing nuclear reactors or the materials that go into them, one of the key challenges is finding materials that can withstand an outrageously extreme environment. In addition to constant bombardment by radiation, reactor materials may be subjected to extremes in temperature, physical stress, and corrosive conditions. Exposure to high radiation alone produces significant damage at the nanoscale.

Radiation can cause individual atoms or groups of atoms to be jarred out of place. Each vagrant atom becomes known as an interstitial. The empty space left behind by the displaced atom is known as a vacancy. Consequently, every interstitial created also creates one vacancy. As these defects—the interstitials and vacancies—build up over time in a material, effects such as swelling, hardening or embrittlement can manifest in the material and lead to catastrophic failure.

Therefore, designing materials that can withstand radiation-induced damage is very important for improving the reliability, safety and lifespan of nuclear energy systems.

Because nanocrystalline materials contain a large fraction of grain boundaries—which are thought to act as sinks that absorb and remove defects—scientists have expected that these materials should be more radiation tolerant than their larger-grain counterparts. Nevertheless, the ability to predict the performance of nanocrystalline materials in extreme environments has been severely lacking because specific details of what occurs within solids are very complex and difficult to visualize.

Recent computer simulations by the Los Alamos researchers help explain some of those details.

In the Science paper, the researchers describe the never-before-observed phenomenon of a "loading-unloading" effect at grain boundaries in nanocrystalline materials. This loading-unloading effect allows for effective self-healing of radiation-induced defects. Using three different computer simulation methods, the researchers looked at the interaction between defects and grain boundaries on time scales ranging from picoseconds to microseconds (one-trillionth of a second to one-millionth of a second).

On the shorter timescales, radiation-damaged materials underwent a "loading" process at the grain boundaries, in which interstitial atoms became trapped—or loaded—into the grain boundary. Under these conditions, the subsequent number of accumulated vacancies in the bulk material occurred in amounts much greater than would have occurred in bulk materials in which a boundary didn't exist. After trapping interstitials, the grain boundary later "unloaded" interstitials back into vacancies near the grain boundary. In so doing, the process annihilates both types of defects—healing the material.

This unloading process was totally unexpected because grain boundaries traditionally have been regarded as places that accumulate interstitials, but not as places that release them. Although researchers found that some energy is required for this newly-discovered recombination method to operate, the amount of energy was much lower than the energies required to operate conventional mechanisms—providing an explanation and mechanism for enhanced self-healing of radiation-induced damage.

Modeling of the "loading-unloading" role of grain boundaries helps explain previously observed counterintuitive behavior of irradiated nanocrystalline materials compared to their larger-grained counterparts. The insight provided by this work provides new avenues for further examination of the role of grain boundaries and engineered material interfaces in self-healing of radiation-induced defects. Such efforts could eventually assist or accelerate the design of highly radiation-tolerant materials for the next generation of nuclear energy applications.

Los Alamos National Laboratory


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A hitherto unknown reproductive system in a species closely related to the olive tree, Phillyrea angustifolia L., has been discovered by researchers at the Laboratoire de Génétique et Évolution des Populations Végétales (CNRS/Université de Lille 1) and the Centre d'Écologie Fonctionnelle et Évolutive (CNRS/Université de Montpellier 1, 2 and 3/ENSA Montpellier/CIRAD/Ecole Pratique des Hautes Études).

This system explains the high concentration of male individuals co-occurring with hermaphrodites in this species. The hermaphrodites, whose blossoms bear both male and female organs, are divided into two morphologically indistinguishable groups. The plants of each group are sterile among themselves but fully compatible with those of the other group. Under these conditions, the hermaphrodites can fertilize only half of the pollen recipients, whereas the males can pollinate all the hermaphrodites. The disadvantage weighing upon the males is thus neatly counterbalanced. This discovery proves for the first time the possibility of an evolutionary transition from hermaphroditism to dioecy. A report has been published in Science.

Researchers at the Laboratoire de Génétique et Évolution des Populations Végétales (CNRS/Université de Lille 1) and the Centre d'Écologie Fonctionnelle et Évolutive (CNRS/Université de Montpellier 1, 2 and 3/ENSA Montpellier/CIRAD/Ecole Pratique des Hautes Études) have discovered in Phillyrea angustifolia L., a species closely related to the olive tree, a hitherto unknown reproductive system characterized by incompatibility between hermaphrodite plants. This new reproductive mode explains the mystery of the high frequencies (up to 50%) of male individuals co-occurring with hermaphrodite individuals in this species. The hermaphrodite individuals, whose blossoms bear both male and female organs, are divided into two morphologically indistinguishable groups. The plants of each group are self-incompatible (they cannot fertilize each other) but fully compatible with plants of the other group. In such a system, a given hermaphrodite plant can pollinate only half of the other hermaphrodites, while a male can pollinate all the hermaphrodites in the population. These conditions neatly offset the reproductive disadvantage affecting the males, which have no female function (and are also referred to as "female-sterile" for this reason) and can thus transmit their genes only by male gametes, and not by both male and female gametes like the hermaphrodites.

In addition, this self-incompatibility within two morphologically identical groups of hermaphrodites could be a key reproductive mode, the origin of plant species with separate genders that evolve through "intermediary" reproductive systems. In the overall context of the evolution of reproductive systems from hermaphroditism toward dioecy (system in which individuals are exclusively either male or female), mixed systems involving the presence in the same species of both females and hermaphrodites (gynodioecy) or both males and hermaphrodites (androdioecy) are considered intermediaries derived from hermaphroditism. However, all previous empirical examples have shown that androdioecy had evolved from dioecious systems through the females' acquisition of a male function, and not from hermaphroditic systems through the loss of the female function by certain hermaphrodites. This new study shows for the first time that a transition from hermaphroditism to androdioecy is possible.

This discovery of a self-incompatibility system involving only two morphologically indistinguishable groups of hermaphrodite plants comes as a totally unexpected development. One of the researchers' next challenges will be to explain, from a functional point of view, how the number of self-incompatibility groups has been maintained at two.

Centre National de la Recherche Scientifique


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A major Australian study has provided new insights into the loss of structure in regions of the brain and its potential association with Alzheimer’s Disease.

The findings recently reported in Neurology suggest a build-up of deposits of the protein amyloid-beta in a region of the brain known as the temporal inferior cortex. The region is connected to the hippocampus, which is involved in memory.

Alzheimer’s is characterised by two factors: a build-up of amyloid-beta plaques in the brain, and a loss of neurons.

CSIRO’s Preventative Health Flagship Theme Leader, Dr Cassandra Szoeke, said the puzzle for researchers was that the parts of the brain that had shrunk (atrophied) due to neuron loss were not the same as those showing increased deposits of amyloid-beta.

Using MRI scans to study Alzheimer's disease-affected brain tissue, the researchers found that shrinking (atrophy) of the hippocampus was associated with plaque deposits in the temporal inferior cortex.

The results indicate that the increased accumulation of amyloid in the temporal inferior cortex disrupts connections with the hippocampus, causing the neurons to die.

"By helping to better understand the mechanisms involved in the progression of the disease, the study may guide the development of new strategies for early diagnosis," Dr Szoeke said.

The study involved advanced techniques for analysing and comparing different types of brain scans. Lead researcher was Dr Perrick Bourgeat, from the Australian e-Health Research Centre - a joint venture between CSIRO and the Queensland Government.

(Photo: CSIRO)

The Commonwealth Scientific and Industrial Research Organisation (CSIRO)


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A mother monkey's milk sends signals to nursing infants that may program the infant’s behavior and temperament, according scientists at UC Davis and the Smithsonian Institution.

Infant monkeys whose mothers had higher levels of milk energy soon after their birth coped more effectively and showed greater confidence compared to those whose mothers had lower milk energy, the scientists report in the February issue of the American Journal of Primatology.

“This is the first study for any mammal that presents evidence that natural variation in available milk energy from the mother is associated with later variation in infant behavior and temperament,” said Katie Hinde, an anthropologist at the California National Primate Research Center and the nutrition laboratory at the Smithsonian’s National Zoo. Hinde is co-author of the paper with UC Davis psychology professor John Capitanio.

Among rhesus macaque monkeys, mothers who weigh more and have had previous pregnancies produce more and better breast milk for their babies than mothers who weigh less and are less experienced. Researchers used large groups of rhesus macaques living in an outdoor enclosure at the California National Primate Research Center at UC Davis to study how this natural variation in breast milk quality and quantity sends a signal to infants about their environment.

The researchers collected milk at two different times from 59 mothers: once when their infants were one month old and again when the infants were three and half months old. They recorded the quantity of milk produced by each mother and analyzed the energy value of each animal's milk sugars, proteins and fat. These figures were combined to calculate the available milk energy generated by each mother.

Although all of the monkeys in the study were fed the same diet, milk from mothers who weighed more and had had previous pregnancies contained higher available energy when their infants were one month old than the milk of lighter, less experienced mothers.

"Our results suggest that the milk energy available soon after birth may be a nutritional cue that calibrates the infant’s behavior to environmental or maternal conditions," Hinde said.

At three to four months old, each infant was assessed for behavior and temperament. Infants whose mothers had higher levels of milk energy soon after their birth coped more effectively (moved around more, explored more, ate and drank) and showed greater confidence (were more playful, curious and active). Infants whose mothers had lower milk energy had lower activity levels and were less confident when temporarily separated from their mother.

California National Primate Research Center)

University of California, Davis


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Imagine this scenario: A woman and her friend are touring a chemical factory. They come to a coffee machine and, next to it, a container labeled “toxic.” The woman sees the label but goes ahead and scoops a powdery white substance from the container into a cup of coffee she has brewed for her friend. The friend drinks the coffee but is unharmed, because it turns out the powder was only sugar.

Most people would say the woman’s actions were morally repugnant. However, in a new study, patients with damage to a part of the brain known as the ventromedial prefrontal cortex (VMPC) reacted very differently. They were unable to conjure a normal emotional response to the situation, and based their judgment only on the outcome — that is, no harm was done. In their view, the friend’s actions were morally permissible.

That suggests that the human brain’s ability to respond appropriately to intended harms — that is, with outrage toward the perpetrator — is seated in the VMPC, a brain region associated with regulating emotions.

The finding offers a new piece to the puzzle of how the human brain constructs morality, says Liane Young, a postdoctoral associate in MIT’s Department of Brain and Cognitive Sciences and lead author of a paper describing the findings in the March 25 issue of the journal Neuron.

“We’re slowly chipping away at the structure of morality,” says Young. “We’re not the first to show that emotions matter for morality, but this is a more precise look at how emotions matter.”

Working with researchers at the University of Southern California, led by Antonio Damasio, Young studied a group of nine patients with damage (caused by aneurisms or tumors) to the VMPC, a plum-sized area located above and behind the eyes.

Such patients have difficulty processing social emotions such as empathy or embarrassment, but “they have perfectly intact capacity for reasoning and other cognitive functions,” says Young.

A 2007 study by Damasio, Young and their colleagues showed that such patients are more willing than non-brain-damaged adults to judge killing or harming another person as morally permissible if doing so would save others’ lives. That led the researchers to suspect that the brain-damaged patients lacked appropriate emotional responses to moral harms and relied instead on calculating, rational approach to moral dilemmas.

In the new Neuron study, the researchers tried to tease out the exact role of emotional responses in making moral judgments. They gave the subjects a series of 24 scenarios and asked for their reactions. The scenarios of most interest to the researchers were ones featuring a mismatch between the person’s intention and the outcome — either failed attempts to harm or accidental harms.

“Every time we make a judgment, there are lots of factors that influence it, and two of the most important are what the agent wants to do, and what actually happens,” says Young.

When confronted with failed attempts to harm, the patients had no problems understanding the perpetrator’s intentions, but they failed to hold them morally responsible. The patients even judged attempted harms as more permissible than accidental harms (such as accidentally poisoning someone) — a reversal of the pattern seen in normal adults.

“They can process what people are thinking and their intentions, but they just don’t respond emotionally to that information,” says Young. “They can read about a murder attempt and judge it as morally permissible because no harm was done.”

This supports the idea that making moral judgments requires at least two processes — a logical assessment of the intention, and an emotional reaction to it, says Michael Koenigs, a neuroscientist at the University of Wisconsin who has also studied patients with VMPC damage.

“There's no doubt that our moral sense is informed by our ability to infer the intentions of others, and to generate an affective response to those intentions,” says Koenigs. “This study implicates VMPC as a key area for integrating intention with affect [emotional feeling] to yield moral judgment.”

The ability to blame others who try to cause harm, even when they fail, may have evolved as a way to protect ourselves from those with malevolent intentions, says Young. “This information is critical for making judgments about whom to be friends with and whom to trust,” she says. “We don’t want people wishing harm on us, even if they fail.”

In future work, Young hopes to study patients who incurred damage to the VMPC when they were younger, to see if they have the same impaired judgment. She also plans to study patient reactions to situations where the harmful attempts may be directed at the patient and therefore more personal.

(Photo: Patrick Gillooly)

Massachusetts Institute of Technology


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Imagine if your computer only allowed you to see one line at a time, no matter what you were doing – reading e-mail, looking at a Web site, doing research. That’s the challenge facing blind computer users today. But new research from North Carolina State University is moving us closer to the development of a display system that would allow the blind to take full advantage of the Web and other computer applications.

“Right now, electronic Braille displays typically only show one line of text at a time. And they’re very expensive,” says Dr. Neil Di Spigna, a research assistant professor at NC State and co-author of a paper describing the research. In order to develop a more functional, and affordable, tool that would allow the blind to interface with their computers, Di Spigna and his colleagues are working to develop a full-page, refreshable Braille display. Braille uses a series of raised dots to represent letters and numbers, allowing blind people to read.

Such a display would also translate images into tactile displays, effectively mapping pixels in an image and allowing the full-page Braille display to represent the images as raised dots.

The researchers have developed a concept called a “hydraulic and latching mechanism,” which would allow the development of such a display system. The mechanism would be made of an electroactive polymer that is very resilient and inexpensive, when compared to current Braille display technologies. “This material will allow us to raise dots to the correct height, so they can be read,” says Dr. Peichun Yang, a postdoctoral research associate at NC State and co-author of the paper. “Once the dots are raised, a latching mechanism would support the weight being applied by a person’s fingers as the dots are read. The material also responds quickly, allowing a reader to scroll through a document or Web site quickly.”

Earlier this month, the researchers presented their findings on the hydraulic component of the mechanism, showing that it is a viable technology. The next step is to demonstrate a proof-of-concept model of the latching mechanism. “We hope to have a fully functioning prototype of the mechanism within a year,” Di Spigna says, “and that could serve as the functional building block of a full-screen refreshable display.”

“Reading Braille is essential to allowing blind people to find employment,” says Yang, who is blind. “We’re optimistic that this technology will give the blind additional opportunities in this area.”

“The last 20 years of computer technology have been relatively inaccessible – and today’s common mobile computing devices, from smart-phones to digital navigators and iPads, have been completely nonexistent – to blind people, because the display technology for the blind has not kept pace,” says David Winick, a researcher at NC State and co-author of the paper. “We hope to enable the development of applications that will give the blind more complete access to the internet and other computer resources, such as e-books.”

(Photo: Zina Deretsky, National Science Foundation)

North Carolina State University




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