The chorion is a part of the afterbirth and is normally discarded after delivery, but it contains stem cells of fetal origin that appear to be pluripotent — i.e., they can differentiate into different types of human cells, such as lung, liver, or brain cells. Since these functional placental stem cells can be isolated from either fresh or frozen term human placentas, this implies that if each individual’s placenta is stored at birth instead of thrown away, these cells can be harvested in the future if therapeutic need arises. This potential represents a major breakthrough in the stem cell field.

In previous work, Drs. Serikov and Kuypers reported a novel technology to harvest blood-forming stem cells from the placenta to augment cord blood cells. These cells are “siblings” of the cord blood derived stem cells. Cord blood stem cells, unlike embryonic stem cells, have been used for many hundreds of successful bone marrow transplants. These transplants are mainly performed in children, as the amount of cells that can be harvested from cord blood is usually not sufficient for a successful transplant in adults. Adding placental-derived stem cells to the cord blood stem cells could make successful adult bone marrow transplants routinely possible.

The current report demonstrates that placental stem cells have much broader therapeutic potential than bone-marrow transplants, because they are pluripotent — i.e. able to differentiate into many different cell types — and they also generate growth factors that help in tissue repair. These cells are shown to integrate into different tissues when transplanted into mice, but like cord blood stem cells, and in contrast to embryonic pluripotent stem cells, they do not form tumor-like structures in mice.

Placental-derived stem cells are often viewed as “adult” stem cells in contrast to “embryonic” stem cells, which are the dominant focus in the stem cell research field. However, this report shows that these fetal stem cells can be harvested in large numbers, and without the ethical concerns attached to the use of embryonic stem cells. These stem cells may thus be a more practical source for regenerative medicine, particularly since, if placentas are routinely saved instead of thrown away, each individual will be able to draw on their own fetal stem cells if future therapeutic needs arise.

Placental stem cells are only 9 months old, and in contrast to adult stem cells, do not need to be reprogrammed to become pluripotent. Placental-derived stem cells have characteristics of young and vigorous cells, including young mitochondria. Future research will be aimed to bring this to the clinic and to test their efficacy in translational therapeutic applications.

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The above story is reprinted from materials provided by Children’s Hospital Research Center Oakland, via Newswise.

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Journal Reference:

1. Igor Nazarov,
   Jae W. Lee,
   Eric Soupene,
   Sara Etemad,
   Derrick Knapik,
   William Green,
   Elizaveta Bashkirova,
   Xiaohui Fang,
   Michael A. Matthay,
   Frans A. Kuypers,
   Vladimir B. Serikov. Multipotent Stromal Stem Cells from Human Placenta Demonstrate High Therapeutic Potential. Stem Cells Trans Med, May 8, 2012 DOI: 10.5966/sctm.2011-0021

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Article source: http://www.sciencedaily.com/releases/2012/05/120518132250.htm

Coffee drinkers were less likely to die from heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections, although the association was not seen for cancer. These results from a large study of older adults were observed after adjustment for the effects of other risk factors on mortality, such as smoking and alcohol consumption. Researchers caution, however, that they can’t be sure whether these associations mean that drinking coffee actually makes people live longer. The results of the study were published in the May 17, 2012 edition of the New England Journal of Medicine.

Neal Freedman, Ph.D., Division of Cancer Epidemiology and Genetics, NCI, and his colleagues examined the association between coffee drinking and risk of death in 400,000 U.S. men and women ages 50 to 71 who participated in the NIH-AARP Diet and Health Study. Information about coffee intake was collected once by questionnaire at study entry in 1995-1996. The participants were followed until the date they died or Dec. 31, 2008, whichever came first.

The researchers found that the association between coffee and reduction in risk of death increased with the amount of coffee consumed. Relative to men and women who did not drink coffee, those who consumed three or more cups of coffee per day had approximately a 10 percent lower risk of death. Coffee drinking was not associated with cancer mortality among women, but there was a slight and only marginally statistically significant association of heavier coffee intake with increased risk of cancer death among men.

“Coffee is one of the most widely consumed beverages in America, but the association between coffee consumption and risk of death has been unclear. We found coffee consumption to be associated with lower risk of death overall, and of death from a number of different causes,” said Freedman. “Although we cannot infer a causal relationship between coffee drinking and lower risk of death, we believe these results do provide some reassurance that coffee drinking does not adversely affect health.”

The investigators caution that coffee intake was assessed by self-report at a single time point and therefore might not reflect long-term patterns of intake. Also, information was not available on how the coffee was prepared (espresso, boiled, filtered, etc.); the researchers consider it possible that preparation methods may affect the levels of any protective components in coffee.

“The mechanism by which coffee protects against risk of death — if indeed the finding reflects a causal relationship — is not clear, because coffee contains more than 1,000 compounds that might potentially affect health,” said Freedman. “The most studied compound is caffeine, although our findings were similar in those who reported the majority of their coffee intake to be caffeinated or decaffeinated.”

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The above story is reprinted from materials provided by National Institutes of Health.

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1. Neal D. Freedman, Yikyung Park, Christian C. Abnet, Albert R. Hollenbeck, Rashmi Sinha. Association of Coffee Drinking with Total and Cause-Specific Mortality. New England Journal of Medicine, 2012; 366 (20): 1891 DOI: 10.1056/NEJMoa1112010

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Article source: http://www.sciencedaily.com/releases/2012/05/120519071454.htm

Resistive RAM (or ‘ReRAM’) memory chips are based on materials, most often oxides of metals, whose electrical resistance changes when a voltage is applied — and they “remember” this change even when the power is turned off.

ReRAM chips promise significantly greater memory storage than current technology, such as the Flash memory used on USB sticks, and require much less energy and space.

The UCL team have developed a novel structure composed of silicon oxide, described in a recent paper in the Journal of Applied Physics, which performs the switch in resistance much more efficiently than has been previously achieved. In their material, the arrangement of the silicon atoms changes to form filaments of silicon within the solid silicon oxide, which are less resistive. The presence or absence of these filaments represents a ‘switch’ from one state to another.

Unlike other silicon oxide chips currently in development, the UCL chip does not require a vacuum to work, and is therefore potentially cheaper and more durable. The design also raises the possibility of transparent memory chips for use in touch screens and mobile devices.

The team have been backed by UCLB, UCL’s technology transfer company, and have recently filed a patent on their device. Discussions are ongoing with a number of leading semiconductor companies.

Dr Tony Kenyon, UCL Electronic and Electrical Engineering, said: “Our ReRAM memory chips need just a thousandth of the energy and are around a hundred times faster than standard Flash memory chips. The fact that the device can operate in ambient conditions and has a continuously variable resistance opens up a huge range of potential applications.

“We are also working on making a quartz device with a view to developing transparent electronics.”

For added flexibility, the UCL devices can also be designed to have a continuously variable resistance that depends on the last voltage that was applied. This is an important property that allows the device to mimic how neurons in the brain function. Devices that operate in this way are sometimes known as ‘memristors’.

This technology is currently of enormous interest, with the first practical memristor, based on titanium dioxide, demonstrated in just 2008. The development of a silicon oxide memristor is a huge step forward because of the potential for its incorporation into silicon chips.

The team’s new ReRAM technology was discovered by accident whilst engineers at UCL were working on using the silicon oxide material to produce silicon-based LEDs. During the course of the project, researchers noticed that their devices appeared to be unstable.

UCL PhD student, Adnan Mehonic, was asked to look specifically at the material’s electrical properties. He discovered that the material wasn’t unstable at all, but flipped between various conducting and non-conducting states very predictably.

Adnan Mehonic, also from the UCL Department of Electronic and Electrical Engineering, said: “My work revealed that a material we had been looking at for some time could in fact be made into a memristor.

“The potential for this material is huge. During proof of concept development we have shown we can programme the chips using the cycle between two or more states of conductivity. We’re very excited that our devices may be an important step towards new silicon memory chips.”

The technology has promising applications beyond memory storage. The team are also exploring using the resistance properties of their material not just for use in memory but also as a computer processor.

The work was funded by the Engineering and Physical Sciences Research Council.

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1. Adnan Mehonic, Sébastien Cueff, Maciej Wojdak, Stephen Hudziak, Olivier Jambois, Christophe Labbé, Blas Garrido, Richard Rizk, Anthony J. Kenyon. Resistive switching in silicon suboxide films. Journal of Applied Physics, 2012; 111 (7): 074507 DOI: 10.1063/1.3701581

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Article source: http://www.sciencedaily.com/releases/2012/05/120518132549.htm

Their findings shed light on how human disturbance of the natural world may lead to widespread, yet largely invisible, disruptions of ecological interaction chains. This, in turn, highlights the need to build non-traditional alliances — among marine biologists and foresters, for example — to address whole ecosystems across political boundaries.

This past fall, McCauley, a graduate student, and DeSalles, an undergraduate, were in remote Palmyra Atoll in the Pacific tracking manta rays’ movements for a predator-prey interaction study. Swimming with the rays and charting their movements with acoustic tags, McCauley and DeSalles noticed the graceful creatures kept returning to certain islands’ coastlines. Meanwhile, graduate student Hillary Young was studying palm tree proliferation’s effects on bird communities and native habitats.

Palmyra is a unique spot on Earth where scientists can compare largely intact ecosystems within shouting distance of recently disturbed habitats. A riot of life — huge grey reef sharks, rays, snapper and barracuda — plies the clear waters while seabirds flock from thousands of miles away to roost in the verdant forests of this tropical idyll.

Over meals and sunset chats at the small research station, McCauley, DeSalles, Young and other scientists discussed their work and traded theories about their observations. “As the frequencies of these different conversations mixed together, the picture of what was actually happening out there took form in front of us,” McCauley said.

Through analysis of nitrogen isotopes, animal tracking and field surveys, the researchers showed that replacing native trees with non-native palms led to about five times fewer roosting seabirds (they seemed to dislike palms’ simple and easily wind-swayed canopies), which led to fewer bird droppings to fertilize the soil below, fewer nutrients washing into surrounding waters, smaller and fewer plankton in the water and fewer hungry manta rays cruising the coastline.

“This is an incredible cascade,” said researcher Rodolfo Dirzo, a professor of environmental science and senior fellow with the Stanford Woods Institute for the Environment. “As an ecologist, I am worried about the extinction of ecological processes. This dramatically illustrates the significance of such extinctions.”

Equally important is what the study suggests about these cascades going largely unseen. “Such connections do not leave any trace behind,” said researcher Fiorenza Micheli, an associate professor of biology affiliated with the Stanford Woods Institute. “Their loss largely goes unnoticed, limiting our understanding of and ability to protect natural ecosystems.” McCauley put it another way: “What we are doing in some ecosystems is akin to popping the hood on a car and disconnecting a few wires and rerouting a few hoses. All the parts are still there — the engine looks largely the same — but it’s anyone’s guess as to how or if the car will run.”

By way of comparison, researcher Robert Dunbar, a professor of earth sciences and Stanford Woods Institute senior fellow, recalled the historical chain effects of increasing demands on water from Central California’s rivers. When salmon runs in these rivers slowed from millions of fish each year to a trickle, natural and agricultural land systems lost an important source of marine-derived fertilizer. These lost subsidies from the sea are now replaced by millions of dollars’ worth of artificial fertilizer applications. “Humans can really snip one of these chains in half,” Dunbar said.

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The above story is reprinted from materials provided by Stanford University. The original article was written by Rob Jordan.

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1. Douglas J. McCauley, Paul A. DeSalles, Hillary S. Young, Robert B. Dunbar, Rodolfo Dirzo, Matthew M. Mills, Fiorenza Micheli. From wing to wing: the persistence of long ecological interaction chains in less-disturbed ecosystems. Scientific Reports, 2012; 2 DOI: 10.1038/srep00409

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Article source: http://www.sciencedaily.com/releases/2012/05/120518132706.htm

“In the last several years there have been data suggesting that neurobiological changes are happening — [there are] very brain-specific mechanisms at work here,” says Bucci, an associate professor in the Department of Psychological and Brain Sciences.

From his studies, Bucci and his collaborators have revealed important new findings:

• The effects of exercise are different on memory as well as on the brain, depending on whether the exerciser is an adolescent or an adult.
• A gene has been identified which seems to mediate the degree to which exercise has a beneficial effect. This has implications for the potential use of exercise as an intervention for mental illness.

Bucci began his pursuit of the link between exercise and memory with attention deficit hyperactivity disorder (ADHD), one of the most common childhood psychological disorders. Bucci is concerned that the treatment of choice seems to be medication.

“The notion of pumping children full of psycho-stimulants at an early age is troublesome,” Bucci cautions. “We frankly don’t know the long-term effects of administering drugs at an early age — drugs that affect the brain — so looking for alternative therapies is clearly important.”

Anecdotal evidence from colleagues at the University of Vermont started Bucci down the track of ADHD. Based on observations of ADHD children in Vermont summer camps, athletes or team sports players were found to respond better to behavioral interventions than more sedentary children. While systematic empirical data is lacking, this association of exercise with a reduction of characteristic ADHD behaviors was persuasive enough for Bucci.

Coupled with his interest in learning and memory and their underlying brain functions, Bucci and teams of graduate and undergraduate students embarked upon a project of scientific inquiry, investigating the potential connection between exercise and brain function. They published papers documenting their results, with the most recent now available in the online version of the journal Neuroscience.

Bucci is quick to point out that “the teams of both graduate and undergraduates are responsible for all this work, certainly not just me.” Michael Hopkins, a graduate student at the time, is first author on the papers.

Early on, laboratory rats that exhibit ADHD-like behavior demonstrated that exercise was able to reduce the extent of these behaviors. The researchers also found that exercise was more beneficial for female rats than males, similar to how it differentially affects male and female children with ADHD.

Moving forward, they investigated a mechanism through which exercise seems to improve learning and memory. This is “brain derived neurotrophic factor” (BDNF) and it is involved in growth of the developing brain. The degree of BDNF expression in exercising rats correlated positively with improved memory, and exercising as an adolescent had longer lasting effects compared to the same duration of exercise, but done as an adult.

“The implication is that exercising during development, as your brain is growing, is changing the brain in concert with normal developmental changes, resulting in your having more permanent wiring of the brain in support of things like learning and memory,” says Bucci. “It seems important to [exercise] early in life.”

Bucci’s latest paper was a move to take the studies of exercise and memory in rats and apply them to humans. The subjects in this new study were Dartmouth undergraduates and individuals recruited from the Hanover community.

Bucci says that, “the really interesting finding was that, depending on the person’s genotype for that trophic factor [BDNF], they either did or did not reap the benefits of exercise on learning and memory. This could mean that you may be able to predict which ADHD child, if we genotype them and look at their DNA, would respond to exercise as a treatment and which ones wouldn’t.”

Bucci concludes that the notion that exercise is good for health including mental health is not a huge surprise. “The interesting question in terms of mental health and cognitive function is how exercise affects mental function and the brain.” This is the question Bucci, his colleagues, and students continue to pursue.

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The above story is reprinted from materials provided by Dartmouth College. The original article was written by Joseph Blumberg.

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Journal Reference:

1. M.E. Hopkins, F.C. Davis, M.R. VanTieghem, P.J. Whalen, D.J. Bucci. Differential effects of acute and regular physical exercise on cognition and affect. Neuroscience, 2012; DOI: 10.1016/j.neuroscience.2012.04.056

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Article source: http://www.sciencedaily.com/releases/2012/05/120518132812.htm

“I knew there would be rare variation but had no idea there would be so much of it,” said the senior author of the research, John Novembre, an assistant professor of ecology and evolutionary biology and of bioinformatics at UCLA.

A team of life scientists studied 202 genes in 14,002 people. The human genome contains some 3 billion base pairs; the scientists studied 864,000 of these pairs. While this is only a small part of the genome, the sample size of 14,002 people is one of the largest ever in a sequencing study in humans.

“Our results suggest there are many, many places in the genome where one individual, or a few individuals, have something different,” Novembre said. “Overall, it is surprisingly common that there is a rare variant in the population.

“This study doesn’t tell us how to cure a particular disease but suggests that disease in general may be caused by rare variants, and if you’re trying to find the genetic basis of disease, it’s important to focus on those variants. Understanding the genetic basis of disease provides clues to how the diseases work and clues about how to treat them.”

The scientists discovered one genetic variant every 17 bases, which was a dramatically higher rate than they expected, said Novembre, a population geneticist who is a member of UCLA’s interdepartmental program in bioinformatics.

Most of the time, only one person has the genetic variant and the other 14,001 do not.

“We saw lots of that,” he said. “We discovered there are many places in these 202 genes where there is variation and only a few individuals differ from the whole group, or only one differs. We also see evidence that a substantial fraction of these rare genetic variants appear to be deleterious in a long-term evolutionary sense and might impact disease.”

The research team included Daniel Wegmann, a former UCLA postdoctoral scholar in Novembre’s laboratory and a co-first author of the study; Darren Kessner, a UCLA graduate student in the bioinformatics interdepartmental Ph.D. program; colleagues from the University of Michigan, Ann Arbor (in fields including human genetics and biostatistics); and geneticists from international health care company GlaxoSmithKline, including project leader Matthew Nelson. The UCLA life scientists were involved in the population genetic analysis of the data.

In the study, 10,621 people had one of 12 diseases, including coronary artery disease, multiple sclerosis, bipolar disorder, schizophrenia, osteoarthritis and Alzheimer’s disease; 3,381 did not have any of the diseases.

“The large sample size allows us to see patterns with more clarity than ever before,” Novembre said. “If rare variants are like distant stars, this kind of large sample size is like having the Hubble Telescope; it’s allowing us to see more than before. We see a ton of rare variation, and these rare variants more often make changes to proteins than not. In that way, this study has important implications for the genetic basis of disease in humans. It’s consistent with the idea that many diseases may be partly caused by rare variants.”

Human population growth helps to explain the large number of genetic variants, the scientists said.

“The fact that we see so many rare variants is in part due to the fact that human populations have been growing very rapidly,” Novembre said. “Because the human population has grown so much, the opportunity for mutations to occur has also grown. Some of the variants we are seeing are very young, dating to population growth since the invention of agriculture and even the Industrial Revolution; this growth has created many opportunities for mutation in the genome because there are so many transmissions of chromosomes from parent to child in large populations.”

The scientists isolated and sequenced the pieces of DNA from the 202 genes.

They estimated mutation rates from population genetic data, which has only rarely been done before.

“We have been able to estimate mutation rates for each of the genes, which has been difficult to do with smaller sample sizes,” Novembre said. “In future research, we can study mutation rates not just in these 202 genes, but genome-wide.”

Sequencing technologies are advancing rapidly, he said. “What seemed like science fiction in the past is science today.”

Rare genetic variants would not have been detectable in most previous studies, whose samples usually had fewer than 1,000 people.

Typically, in population genetics, it is difficult to estimate mutation rates separately from population sizes, but when you get to very large sample sizes, you can estimate the two separately, Novembre said.

“We estimate 202 mutation rates, one for each gene,” he said. “We show that the mutation rate varies from gene to gene. Follow-up studies may be able to reveal more about what factors affect mutation rates.”

Rare genetic variants are frequently geographically localized to small pockets around the globe rather than being widespread, Novembre said.

In the image accompanying this release, each vertical line represents one of the 202 genes. For each gene, the scientists plotted, at the top of the image, the number of genetic variants that have a frequency greater than 0.5 percent. When variants are greater than 0.5 percent, previous studies have been able to find most of them.

“With our large sample size, we can detect variants at a frequency less than 0.5 percent, and we see all of these, which have never been seen before,” Novembre said. “Previous studies have examined the tip of the iceberg of genetic variation, but there is all this rare variation that has been below the surface, below our threshold of detection. Now, with large sample sizes, we can see a more complete picture of human genetic diversity.”

The genetic code has changes that are “nonsynonymous” (they change the meaning of a protein) and “synonymous” (they don’t change the meaning of a protein).

“We see many nonsynonymous changes amongst the rare variants, and these are plausibly affecting disease in humans, though in ways that are not yet well understood,” Novembre said

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The above story is reprinted from materials provided by University of California – Los Angeles. The original article was written by Stuart Wolpert.

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Journal Reference:

1. M. R. Nelson, D. Wegmann, M. G. Ehm, D. Kessner, P. St. Jean, C. Verzilli, J. Shen, Z. Tang, S.-A. Bacanu, D. Fraser, L. Warren, J. Aponte, M. Zawistowski, X. Liu, H. Zhang, Y. Zhang, J. Li, Y. Li, L. Li, P. Woollard, S. Topp, M. D. Hall, K. Nangle, J. Wang, G. Abecasis, L. R. Cardon, S. Zollner, J. C. Whittaker, S. L. Chissoe, J. Novembre, V. Mooser. An Abundance of Rare Functional Variants in 202 Drug Target Genes Sequenced in 14,002 People. Science, 2012; DOI: 10.1126/science.1217876

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Article source: http://www.sciencedaily.com/releases/2012/05/120518132832.htm

The team found that the dusty planet circles its parent star every 15 hours — one of the shortest planet orbits ever observed. Such a short orbit must be very tight and implies that the planet must be heated by its orange-hot parent star to a temperature of about 3,600 degrees Fahrenheit. Researchers hypothesize that rocky material at the surface of the planet melts and evaporates at such high temperatures, forming a wind that carries both gas and dust into space. Dense clouds of the dust trail the planet as it speeds around its star.

“We think this dust is made up of submicron-sized particles,” says co-author Saul Rappaport, a professor emeritus of physics at MIT. “It would be like looking through a Los Angeles smog.”

The group’s findings, published in the Astrophysical Journal, are based on data from the Kepler Observatory, a space-based telescope that surveys more than 160,000 stars in the Milky Way. The observatory records the brightness of each star at regular intervals; scientists then analyze the data for signs of new planets outside our own solar system.

A curiously stellar case

Astronomers using the Kepler satellite typically identify exoplanets by looking for regular dips in a star’s brightness. For example, if a star dims every month, one possibility is that the dimming is due to a planet that travels around the star over the course of a month; each time the planet travels in front of the star, the planet blocks the same small amount of light.

However, Rappaport and his colleagues came across a curious light pattern from a star dubbed KIC 12557548. The group examined the star’s light curves, a graph of its brightness over time, and found that its light dropped by different intensities every 15 hours — suggesting that something was blocking the star regularly, but by varying degrees.

The team considered several explanations for the puzzling data, including the possibility that a planetary duo — two planets orbiting each other — also orbited the star. (Rappaport reasoned that the planetary pair would pass by the star at different orientations, blocking out different amounts of light during each eclipse.) In the end, the data failed to support this hypothesis: The dimming every 15 hours was judged far too short a period to allow sufficient room for two planetary bodies orbiting each other, in the same way that Earth and the moon together orbit the sun.

A dusty idea

Instead, the researchers landed on a novel hypothesis: that the varying intensities of light were caused by a somewhat amorphous, shape-shifting body.

“I’m not sure how we came to this epiphany,” Rappaport says. “But it had to be something that was fundamentally changing. It was not a solid body, but rather, dust coming off the planet.”

Rappaport and his colleagues investigated various ways in which dust could be created and blown off a planet. They reasoned that the planet must have a low gravitational field, much like that of Mercury, in order for gas and dust to escape from the planet’s gravitational pull. The planet must also be extremely hot — on the order of 3,600° F.

Rappaport says there are two possible explanations for how the planetary dust might form: It might erupt as ash from surface volcanoes, or it could form from metals that are vaporized by high temperatures and then condense into dust. As for how much dust is spewed from the planet, the team showed that the planet could lose enough dust to explain the Kepler data. From their calculations, the researchers concluded that at such a rate, the planet will completely disintegrate within 100 million years.

The researchers created a model of the planet orbiting its star, along with its long, trailing cloud of dust. The dust was densest immediately surrounding the planet, thinning out as it trailed away. The group simulated the star’s brightness as the planet and its dust cloud passed by, and found that the light patterns matched the irregular light curves taken from the Kepler Observatory.

“We’re actually now very happy about the asymmetry in the eclipse profile,” Rappaport says. “At first we didn’t understand this picture. But once we developed this theory, we realized this dust tail has to be here. If it’s not, this picture is wrong.”

Dan Fabrycky, a member of the Kepler Observatory science team, says the model may add to the many different ways in which a planet can disappear.

“This might be another way in which planets are eventually doomed,” says Fabrycky, who was not involved in the research. “A lot of research has come to the conclusion that planets are not eternal objects, they can die extraordinary deaths, and this might be a case where the planet might evaporate entirely in the future.”

The research was funded by the National Science Foundation and the Natural Sciences and Engineering Research Council of Canada.

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The above story is reprinted from materials provided by Massachusetts Institute of Technology. The original article was written by Jennifer Chu, MIT News Office.

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Journal Reference:

1. S. Rappaport, A. Levine, E. Chiang, I. El Mellah, J. Jenkins, B. Kalomeni, E. S. Kite, M. Kotson, L. Nelson, L. Rousseau-Nepton, K. Tran. Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548. Astrophysical Journal, 2012; (accepted) [link]

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Article source: http://www.sciencedaily.com/releases/2012/05/120518192328.htm

Classical physics is deterministic: for example, we can determine the position and velocity of a particle at any time in the future. Quantum theory, on the other hand, states that there exist processes which are fundamentally random: for instance, the outcomes of measurements of quantum particles seem to be determined entirely by chance. This is why Einstein argued in a publication in 1935 that the quantum theory is incomplete, and yet another kind of higher theory must exist, but up to the present time there has been no proof either that the world is purely deterministic and all randomness is due solely to a lack of knowledge about certain events, or that everything happens purely by chance. However, ETH Zurich physicists have now succeeded in showing in a thought experiment that randomness can be amplified.

The results, published in the scientific journal Nature Physics, may also have practical applications.

Free choice is decisive for a representative outcome

Experiments in physics always depend on a large number of variables. To obtain a representative result, the choice of the variables — like the selection of the people questioned in an opinion survey — must be completely free and random. The entirely free — random — choice of variables is also important in information technology, for example, for efficient simulations. It is also extremely important for encoding messages, i.e. in cryptography, and for the random number generators in gambling casinos. If the latter work badly and a fraudster can see through them, he can exploit this to his advantage.

How random is a choice of variables?

In their study, the physicists Roger Colbeck, postdoctoral researcher, and Renato Renner, Professor at the Institute for Theoretical Physics of ETH Zurich, investigated which minimum conditions must be fulfilled in order for a selection of variables to count as absolutely free, and for this selection not to be already practically “pre-programmed” through earlier events. In this study the physicists defined that a variable counts as being chosen freely and at random if it is not correlated with other variables at this or an earlier moment in time.

In 1964 the physicist John Stuart Bell developed what is known as Bell’s inequality, which in simple terms states that there are measurements whose results are not pre-determined and are thus random. The experiments proposed by Bell to prove his theorem, which are based on measuring the entanglement of quantum-mechanical particles, did indeed show this, but only subject to the fundamental condition that the measurements performed during the experiment were chosen completely freely and at random. It is like arguing in a circle: the existence of randomness is again presupposed.

Making use of quantum mechanical laws

The scientists now made use of entanglement and locality — the fact that for example a local event on Earth does not exert any direct influence on another planet — to show that beyond a certain point “weakly” indeterministic situations can be amplified to such an extent that they are completely random.

This is achievable for example with two entangled quantum particles that are strongly coupled but are then measured independently of one another. The scientists’ calculations showed that the quantum correlation between the bits can be so strong that they cannot be correlated with anything existing previously. This means that the results are completely random, whereas only weak randomness is needed for the choice of the measurement.

The two scientists stress that they have not thereby proved that the world is non-deterministic. However, they say there is nothing in between. The existence of weak randomness automatically implies that there must be an unlimited amount of strong randomness. However, Colbeck says it is first of all necessary to achieve a particular “randomness threshold”: “Our method allows randomness to be amplified once a certain threshold has been reached. It would now be interesting to know whether this threshold can be made arbitrarily small by using improved methods.” This would then mean that an arbitrarily small amount of indetermisism would be sufficient to generate an unlimited amount of randomness.

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The above story is reprinted from materials provided by ETH Zürich, via AlphaGalileo.

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Journal Reference:

1. Roger Colbeck, Renato Renner. Free randomness can be amplified. Nature Physics, 2012; DOI: 10.1038/NPHYS2300

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

Article source: http://www.sciencedaily.com/releases/2012/05/120516093015.htm

Next Mother’s Day, say it with an evolved model of logistical efficiency — a flower. A new discovery about how nature’s icons of romance manage the distribution of sperm among female gametes with industrial precision helps explain why the delicate beauties have reproduced prolifically enough to dominate Earth.

In pollination, hundreds of sperm-carrying pollen grains stick to the stigma suspended in the middle of a flower and quickly grow a tube down a long shaft called a style toward clusters of ovules, which hold two female sex cells. This could be a chaotic frenzy, but for the plant to succeed, exactly two fertile sperm should reach the two cells in each ovule — no more, no less. No ovule should be left out, either because too many tubes have gone elsewhere, or because the delivered sperm don’t work.

In the journal Current Biology, Brown University biologists report that flowers have evolved an elegant safeguard system to ensure that only the minimum necessary number of pollen tubes will reach each ovule.

“There is a mechanism that prevents too many pollen tubes from delivering too many sperm,” said Mark Johnson, associate professor of biology at Brown and senior author on a new paper detailing the discovery. “But the other cool thing is that there is also a way to salvage fertilization if the first father is a dud.”

Essentially the successful fusion of sperm and female gametes immediately terminates the signaling that attracts pollen tubes to the ovule, a finding by first author Kristin Beale, a graduate student in Johnson’s lab.

“Previous models had said that pollen tube entry was sufficient — that once one pollen tube entered, others would be repelled,” Beale said. “But we show it’s the process of gamete fusion.”

Added Johnson: “Until fusion has happened, there’s no guarantee that you’ll have successful seed formation.”

A mystery solved with mutants

Although scientists have studied plant reproduction for centuries, the tools to make Beale’s finding have only become available in the last few years, Johnson said. Armed with these new capabilities, the team, including second author Alexander Leydon, conducted a series of experiments in Arabidopsis plants, a model plant for research.

The most important tool was a pollen mutant the team had discovered called hap2. The mutant grows a pollen tube to an ovule and bursts to release sperm, a normal course of events. But hap2′s sperm can’t fuse with the female gametes. It is a convenient dud. The team also employed new techniques that allow pollen tubes and the sperm they carry to fluoresce as green or red. That way they could watch as different tubes interacted with the ovules.

In their first experiment, the team sent in healthy sperm, half of which were carried by red-tagged tubes and half of which by green-tagged tubes. With nothing but healthy sperm in the mix, only about 1 percent of ovules ended up with multiple pollen tubes (a phenomenon that Beale calls “polytubey”). Ovules could block polytubey in the vast majority of cases.

Then the team unleashed a sampling of sperm in which one in four were duds. Polytubey increased tenfold. One unfortunate ovule ended up attracting four tubes, indicating polytubey is allowed until a fertile sperm comes along.

In another experiment with mutant sperm tagged red and normal, or “wild-type” pollen tubes tagged green, the researchers saw polytubey only where there was a red glow under the microscope.

“We did not observe ovules that were targeted by two pollen tubes carrying wild-type sperm,” they wrote in the journal. “Ovules first targeted by defective sperm can attract additional pollen tubes; but when wild-type sperm are attracted, subsequent pollen tubes are blocked.”

In the paper the team also showed that one of two cells responsible for attracting pollen tubes will persist in the ovule until gamete fusion occurs. While the team didn’t identify the exact signaling molecule responsible for blocking polytubey after gamete fusion, Johnson said, the study does help scientists determine what that signaling molecule must be like. He said it must be fast-acting and potent.

Johnson said the research may eventually have applications in agriculture, either because it could aid fertilization when it is hindered, for instance by bad environmental conditions, or commercial corn breeding. Seed companies create hybrids by fertilizing corn with hand-collected pollen, and to do this they need varieties where male fertility can be controlled.

Nature’s own system, however, appears to guarantee that virtually every ovule will have exactly the right amount of healthy sperm. By employing this newly understood mechanism, flowers thereby become the most prolific moms they can be.

The National Science Foundation and the National Institutes of Health Brown University Initiative to Maximize Student Development funded the work.

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

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Journal Reference:

1. Kristin M. Beale, Alexander R. Leydon, Mark A. Johnson. Gamete Fusion Is Required to Block Multiple Pollen Tubes from Entering an Arabidopsis Ovule. Current Biology, 2012; DOI: 10.1016/j.cub.2012.04.041

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Article source: http://www.sciencedaily.com/releases/2012/05/120517132053.htm

Most understanding at that level is theoretical, requiring the use of supercomputers to make innumerable calculations over periods of weeks to make educated guesses as to the arrangements and structure of water clusters before they form into liquid water or ice.

But a new study, using experimentation with a highly advanced spectrometer for molecular rotational spectroscopy, has removed some of the mystery and validates some very complex theory involving the way water molecules bond. It is published in the May 18 issue of the journal Science.

“We set out to determine quantitatively the structure that small assemblies of water adopt, and then compare them to theory to see how well current quantum chemistry predicts the properties of molecules,” said Brooks Pate, a chemist in the University of Virginia’s College of Arts Sciences who led the study. “We found experimentally that modern quantum chemistry has reached the point where its theories are proving out in the lab regarding the unusual directional bonding properties of water clusters.”

The properties of water, and how it interacts with itself and other molecules, is the basis for many processes in biology, and likely played a major role in the development of life on Earth. But understanding how those bonds form at the molecular level has been largely guesswork.

“For the first time, now we have an actual physical picture of what water’s molecules put together look like, and it turns out they adopt three different geometries,” Pate said. “This is in agreement with theory.”

Pate and his U.Va. team identified and imaged a three-dimensional geometry that a water molecule takes on that is the likely precursor structure for forming liquid water and ice.

“We found that the bonding strengths of liquid water actually begin to emerge even in a tiny cluster,” Pate said. “The challenge is figuring out how it interacts with other molecules and how the forces between two molecules of water can be described quantitatively, because the orientation of how the waters come at each other makes a big difference in the binding.”

There are innumerable possibilities for how this happens, and theorists, including Pate’s colleague on the paper, quantum chemist George Shields of Bucknell University, have been working on the details for years without direct validation from experiments.

The difficulty has been in developing techniques that are sensitive enough to image the tiny water molecules and how they orient themselves when interacting with other water molecules. The breakthrough came earlier this year when Pate’s U.Va. team used a new tool, a molecular rotational spectrometer developed during the last two years, to make precise measurements that ultimately validated what theory has expressed.

The improved sensitivity of the instrument comes from advances in high-speed digital electronics that provide unprecedented data throughput in the measurement. This core technology is being commercialized for applications in chemical analysis by a Charlottesville start-up venture, BrightSpec.

“This will allow chemists to transfer what we’ve learned to larger systems,” Pate said. “We are checking to see if theory can get right the structures of the arrangements of water molecules so that that information can be used to see how water interacts in larger systems.”

The larger systems could include bio-molecules, such as protein in DNA, and how surrounding water molecules might interact with those molecules through hydrogen bonds.

“It is very satisfying to see that the experimental work we did, completely independently of theory, came together so perfectly with the theory,” Pate noted.

He said his research is the behind-the-scenes workings of chemistry that ultimately makes up the big picture of how things come together at much larger scales.

“You may not want to know how a bridge was designed, but you sure want to know it was done right,” he said. “Likewise, if a theory is used to predict, for example, how a medicine might work, you ideally would want to be able to test the theory to make sure it’s right before making the medicine. That would be the ultimate goal — to have theory and experimentation in sync.”

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The above story is reprinted from materials provided by University of Virginia, via Newswise.

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Journal Reference:

1. C. Perez, M. T. Muckle, D. P. Zaleski, N. A. Seifert, B. Temelso, G. C. Shields, Z. Kisiel, B. H. Pate. Structures of Cage, Prism, and Book Isomers of Water Hexamer from Broadband Rotational Spectroscopy. Science, 2012; 336 (6083): 897 DOI: 10.1126/science.1220574

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Article source: http://www.sciencedaily.com/releases/2012/05/120518081147.htm