星空女人频道

2013年5月10日星期五

Ice-free Arctic may be in our future

"While existing geologic records from the Arctic contain important hints about this time period, what we are presenting is the most continuous archive of information about past climate change from the entire Arctic borderlands. As if reading a detective novel, we can go back in time and reconstruct how the Arctic evolved with only a few pages missing here and there," says Brigham-Grette.

Results of analyses that provide "an exceptional window into environmental dynamics" never before possible were published this week in Science and have "major implications for understanding how the Arctic transitioned from a forested landscape without ice sheets to the ice- and snow-covered land we know today," she adds.

Their data come from analyzing sediment cores collected in the winter of 2009 from ice-covered Lake El'gygytgyn, the oldest deep lake in the northeast Russian Arctic, located 100 km north of the Arctic Circle. "Lake E" was formed 3.6 million years ago when a meteorite, perhaps a kilometer in diameter, hit the Earth and blasted out an 11-mile (18 km) wide crater. It has been collecting sediment layers ever since. Luckily for geoscientists, it lies in one of the few Arctic areas not eroded by continental ice sheets during ice ages, so a thick, continuous sediment record was left remarkably undisturbed. Cores from Lake E reach back in geologic time nearly 25 times farther than Greenland ice cores that span only the past 140,000 years.

"One of our major findings is that the Arctic was very warm in the middle Pliocene and Early Pleistocene [~ 3.6 to 2.2 million years ago] when others have suggested atmospheric CO2 was not much higher than levels we see today. This could tell us where we are going in the near future. In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier climate models," the authors state.

Important to the story are the fossil pollen found in the core, including Douglas fir and hemlock. These allow the reconstruction of vegetation around the lake in the past, which in turn paints a picture of past temperatures and precipitation.

Another significant finding is documentation of sustained warmth in the Middle Pliocene, with summer temperatures of about 59 to 61 degrees F [15 to 16 degrees C], about 14.4 degrees F [8 degrees C] warmer than today, and regional precipitation three times higher. "We show that this exceptional warmth well north of the Arctic Circle occurred throughout both warm and cold orbital cycles and coincides with a long interval of 1.2 million years when other researchers have shown the West Antarctic Ice Sheet did not exist," Brigham-Grette notes. Hence both poles share some common history, but the pace of change differed.

Her co-authors, Martin Melles of the University of Cologne and Pavel Minyuk of Russia's Northeast Interdisciplinary Scientific Research Institute, Magadan, led research teams on the project. Robert DeConto, also at UMass Amherst, led climate modeling efforts. These data were compared with ecosystem reconstructions performed by collaborators at universities of Berlin and Cologne.

The Lake E cores provide a terrestrial perspective on the stepped pacing of several portions of the climate system through the transition from a warm, forested Arctic to the first occurrence of land ice, Brigham-Grette says, and the eventual onset of major glacial/interglacial cycles. "It is very impressive that summer temperatures during warm intervals even as late as 2.2 million years ago were always warmer than in our pre-Industrial reconstructions."

Minyuk notes that they also observed a major drop in Arctic precipitation at around the same time large Northern Hemispheric ice sheets first expanded and ocean conditions changed in the North Pacific. This has major implications for understanding both what drove the onset of the ice ages

The sediment core also reveals that even during the first major "cold snap" to show up in the record 3.3 Million years ago, temperatures in the western Arctic were similar to recent averages of the past 12,000 years. "Most importantly, conditions were not 'glacial,' raising new questions as to the timing of the first appearance of ice sheets in the Northern Hemisphere," the authors add.

This week's paper is the second article published in Science by these authors using data from the Lake E project. Their first, in July 2012, covered the period from the present to 2.8 million years ago, while the current work addresses the record from 2.2 to 3.6 million years ago. Melles says, "This latest paper completes our goal of providing an overview of new knowledge of the evolution of Arctic change across the western borderlands back to 3.6 million years and places this record into a global context with comparisons to records in the Pacific, the Atlantic and Antarctica."

The new Lake E paleoclimate reconstructions and climate modeling are consistent with estimates made by other research groups that support the idea that Earth's climate sensitivity to CO2 may well be higher than suggested by the 2007 report of the Intergovernmental Panel on Climate Change.

TAG:Climate Global Warming Ice Ages Early Climate Fossils Origin of Life

Heady mathematics: Describing popping bubbles in a foam

May 9, 2013 — Bubble baths and soapy dishwater, the refreshing head on a beer and the luscious froth on a cappuccino. All are foams, beautiful yet ephemeral as the bubbles pop one by one.

Two University of California, Berkeley, researchers have now described mathematically the successive stages in the complex evolution and disappearance of foamy bubbles, a feat that could help in modeling industrial processes in which liquids mix or in the formation of solid foams such as those used to cushion bicycle helmets.

Applying these equations, they created mesmerizing computer-generated movies showing the slow and sedate disappearance of wobbly foams one burst bubble at a time.

The applied mathematicians, James A. Sethian and Robert I. Saye, will report their results in the May 10 issue of Science. Sethian, a UC Berkeley professor of mathematics, leads the mathematics group at Lawrence Berkeley National Laboratory (LBNL). Saye will graduate from UC Berkeley this May with a PhD in applied mathematics.

"This work has application in the mixing of foams, in industrial processes for making metal and plastic foams, and in modeling growing cell clusters," said Sethian. "These techniques, which rely on solving a set of linked partial differential equations, can be used to track the motion of a large number of interfaces connected together, where the physics and chemistry determine the surface dynamics."

The problem with describing foams mathematically has been that the evolution of a bubble cluster a few inches across depends on what's happening in the extremely thin walls of each bubble, which are thinner than a human hair.

"Modeling the vastly different scales in a foam is a challenge, since it is computationally impractical to consider only the smallest space and time scales," Saye said. "Instead, we developed a scale-separated approach that identifies the important physics taking place in each of the distinct scales, which are then coupled together in a consistent manner."

Saye and Sethian discovered a way to treat different aspects of the foam with different sets of equations that worked for clusters of hundreds of bubbles. One set of equations described the gravitational draining of liquid from the bubble walls, which thin out until they rupture. Another set of equations dealt with the flow of liquid inside the junctions between the bubble membranes. A third set handled the wobbly rearrangement of bubbles after one pops.

Using a fourth set of equations, the mathematicians solved the physics of a sunset reflected in the bubbles, taking account of thin film interference within the bubble membranes, which can create rainbow hues like an oil slick on wet pavement. Solving the full set of equations of motion took five days using supercomputers at the LBNL's National Energy Research Scientific Computing Center (NERSC).

The mathematicians next plan to look at manufacturing processes for small-scale new materials.

"Foams were a good test that all the equations coupled together," Sethian said. "While different problems are going to require different physics, chemistry and models, this sort of approach has applications to a wide range of problems."

The work is supported by the Department of Energy, National Science Foundation and National Cancer Institute.

Video: http://www.youtube.com/watch?feature=player_embedded&v=ciciWBz8m_Y

TAG:Nature of Water Chemistry Physics Computer Modeling Math Puzzles Computer Science

Moon and Earth have common water source

Water inside the Moon's mantle came from primitive meteorites, new research finds, the same source thought to have supplied most of the water on Earth. The findings raise new questions about the process that formed the Moon.

The Moon is thought to have formed from a disc of debris left when a giant object hit Earth 4.5 billion years ago, very early in Earth's history. Scientists have long assumed that the heat from an impact of that size would cause hydrogen and other volatile elements to boil off into space, meaning the Moon must have started off completely dry. But recently, NASA spacecraft and new research on samples from the Apollo missions have shown that the Moon actually has water, both on its surface and beneath.

By showing that water on the Moon and on Earth came from the same source, this new study offers yet more evidence that the Moon's water has been there all along.

"The simplest explanation for what we found is that there was water on the proto-Earth at the time of the giant impact," said Alberto Saal, associate professor of Geological Sciences at Brown University and the study's lead author. "Some of that water survived the impact, and that's what we see in the Moon."

The research was co-authored by Erik Hauri of the Carnegie Institution of Washington, James Van Orman of Case Western Reserve University, and Malcolm Rutherford from Brown and published online in Science Express.

To find the origin of the Moon's water, Saal and his colleagues looked at melt inclusions found in samples brought back from the Apollo missions. Melt inclusions are tiny dots of volcanic glass trapped within crystals called olivine. The crystals prevent water escaping during an eruption and enable researchers to get an idea of what the inside of the Moon is like.

Research from 2011 led by Hauri found that the melt inclusions have plenty of water -- as much water in fact as lavas forming on Earth's ocean floor. This study aimed to find the origin of that water. To do that, Saal and his colleagues looked at the isotopic composition of the hydrogen trapped in the inclusions. "In order to understand the origin of the hydrogen, we needed a fingerprint," Saal said. "What is used as a fingerprint is the isotopic composition."

Using a Cameca NanoSIMS 50L multicollector ion microprobe at Carnegie, the researchers measured the amount of deuterium in the samples compared to the amount of regular hydrogen. Deuterium is an isotope of hydrogen with an extra neutron. Water molecules originating from different places in the solar system have different amounts of deuterium. In general, things formed closer to the sun have less deuterium than things formed farther out.

Saal and his colleagues found that the deuterium/hydrogen ratio in the melt inclusions was relatively low and matched the ratio found in carbonaceous chondrites, meteorites originating in the asteroid belt near Jupiter and thought to be among the oldest objects in the solar system. That means the source of the water on the Moon is primitive meteorites, not comets as some scientists thought.

Comets, like meteorites, are known to carry water and other volatiles, but most comets formed in the far reaches of the solar system in a formation called the Oort Cloud. Because they formed so far from the sun, they tend to have high deuterium/hydrogen ratios -- much higher ratios than in the Moon's interior, where the samples in this study came from.

"The measurements themselves were very difficult," Hauri said, "but the new data provide the best evidence yet that the carbon-bearing chondrites were a common source for the volatiles in the Earth and Moon, and perhaps the entire inner solar system."

Recent research, Saal said, has found that as much as 98 percent of the water on Earth also comes from primitive meteorites, suggesting a common source for water on Earth and water on Moon. The easiest way to explain that, Saal says, is that the water was already present on the early Earth and was transferred to the Moon.

The finding is not necessarily inconsistent with the idea that the Moon was formed by a giant impact with the early Earth, but presents a problem. If the Moon is made from material that came from Earth, it makes sense that the water in both would share a common source. However, there's still the question of how that water was able to survive such a violent collision.

"The impact somehow didn't cause all the water to be lost," Saal said. "But we don't know what that process would be."

It suggests, the researchers say, that there are some important processes we don't yet understand about how planets and satellites are formed.

"Our work suggests that even highly volatile elements may not be lost completely during a giant impact," said Van Orman. "We need to go back to the drawing board and discover more about what giant impacts do, and we also need a better handle on volatile inventories in the Moon."

Funding for the research came from NASA's Cosmochemistry and LASER programs and the NASA Lunar Science Institute.

TAG:Moon Asteroids Comets and Meteors Solar System Water Near Earth Object Impacts Environmental Issues

Dust in the clouds: Cirrus clouds form around mineral dust and metallic particles

May 9, 2013 — At any given time, cirrus clouds -- the thin wisps of vapor that trail across the sky -- cover nearly one-third of the globe. These clouds coalesce in the upper layers of the troposphere, often more than 10 miles above the Earth's surface.

Cirrus clouds influence global climate, cooling the planet by reflecting incoming solar radiation and warming it by trapping outgoing heat. Understanding the mechanisms by which these clouds form may help scientists better predict future climate patterns.

Now an interdisciplinary team from MIT, the National Oceanic and Atmospheric Administration (NOAA), and elsewhere has identified the major seeds on which cirrus clouds form. The team sampled cirrus clouds using instruments aboard high-altitude research aircraft, analyzing particles collected during multiple flights over a nine-year period. They found that the majority of cloud particles freeze, or nucleate, around two types of seeds: mineral dust and metallic aerosols.

The absence of certain particles in the clouds also proved interesting. While scientists have observed that substances like black carbon and fungal spores readily form cloud particles in the lab, the team detected barely a trace of these particles in the upper atmosphere.

"We think we're really looking at the seed, the nucleus of these ice crystals," says Dan Cziczo, an associate professor of atmospheric chemistry at MIT. "These results are going to allow us to better understand the climatic implications of these clouds in the future."

Cziczo and his colleagues have published their results this week in Science.

Up in the air

Cirrus clouds typically form at altitudes higher than most commercial planes fly. To sample at such heights, the team enlisted three high-altitude research aircraft from NASA and the National Science Foundation (NSF): a B-57 bomber, a DC-8 passenger jet, and a G-V business jet, all of which were repurposed to carry scientific instruments.

From 2002 to 2011, the team conducted four flight missions in regions of North America and Central America where cirrus clouds often form. Before takeoff, the team received weather forecasts, including information on where and when clouds might be found.

"More often than not, the forecast is solid, and it's up to the pilot to hit a cloud," Cziczo says. "If they find a good spot, they can call back on a satellite phone and tell us if they're inside a cloud, and how thick it is."

For each mission, Cziczo and Karl Froyd, of NOAA's Earth System Resource Laboratory, mounted one or two instruments to the nose of each plane: a single particle mass spectrometer and a particle collector.

Each flight followed essentially the same protocol: As a plane flew through a cloud, ice particles flowed through a specialized inlet into the nose of the plane. As they flowed in, the particles thawed, evaporating most of the surrounding ice. What's left was a tiny kernel, or seed, which was then analyzed in real time by the onboard mass spectrometer for size and composition. The particle collector stored the seeds for further analysis in the lab.

A human effect on cloud formation

After each flight, Cziczo and his colleagues analyzed the collected particles in the lab using high-resolution electron microscopy. They compared their results with analyses from the onboard mass spectrometer and found the two datasets revealed very similar cloud profiles: More than 60 percent of cloud particles consisted of mineral dust blown into the atmosphere, as well as metallic aerosols.

Cziczo notes that while mineral dust is generally regarded as a natural substance originating from dry or barren regions of the Earth, agriculture, transportation and industrial processes also release dust into the atmosphere.

"Mineral dust is changing because of human activities," Cziczo says. "You may think of dust as a natural particle, but some percentage of it is manmade, and it really points to a human ability to change these clouds."

He adds that some global-modeling studies predict higher dust concentrations in the future due to desertification, land-use change and changing rainfall patterns due to human-induced climate effects.

Cziczo's team also identified a "menagerie of metal compounds," including lead, zinc and copper, that may point to a further human effect on cloud formation. "These things are very strange metal particles that are almost certainly from industrial activities, such as smelting and open-pit burning of electronics," Cziczo adds. Lead is also emitted in the exhaust of small planes.

Contrary to what many lab experiments have found, the team observed very little evidence of biological particles, such as bacteria or fungi, or black carbon emitted from automobiles and smokestacks. Froyd says knowing what particles are absent in clouds is just as important as knowing what's present: Such information, he says, can be crucial in developing accurate models for climate change.

"There's been a lot of research efforts spent on looking at how these particle types freeze under various conditions," Froyd says. "Our message is that you can ignore those, and can instead look at mineral dust as the dominant driving force for the formation of this type of cloud."

The group's experimental approach was an impressive feat in itself, says Brian Toon, a professor of atmospheric and oceanic sciences at the University of Colorado. In a typical cirrus cloud, only one particle in 100,000 forms an ice crystal, making the odds of capturing such crystals slim at best.

"This group has used an instrument in a plane flying at speeds of two football fields per second to catch individual ice crystals, evaporate them and measure the composition of the tiny remnant particles -- an amazing technological achievement," says Toon, who was not involved in the research. "Now these measurements need to be repeated over a wide range of locations to be sure they are general."

This research was funded by NASA and the NSF.

TAG:Atmosphere Climate Global Warming Storms Severe Weather Air Pollution

Using bacteria to stop malaria

A study in the current issue of Science shows that the transmission of malaria via mosquitoes to humans can be interrupted by using a strain of the bacteria Wolbachia in the insects. In a sense, Wolbachia would act as a vaccine of sorts for mosquitoes that would protect them from malaria parasites. Treating mosquitoes would prevent them from transmitting malaria to humans, a disease that in 2010 affected 219 million people and caused an estimated 660,000 deaths.

"Wolbachia-based malaria control strategy has been discussed for the last two decades," said Zhiyong Xi, MSU assistant professor of microbiology and molecular genetics. "Our work is the first to demonstrate Wolbachia can be stably established in a key malaria vector, the mosquito species Anopheles stephensi, which opens the door to use Wolbachia for malaria control."

First, Xi's team successfully demonstrated how Wolbachia can be carried by this malaria mosquito vector and how the insects can spread the bacteria throughout the entire mosquito population. Secondly, researchers showed that the bacteria can prevent those mosquitoes from transmitting malaria parasites to humans.

"We developed the mosquito line carrying a stable Wolbachia infection," Xi said. "We then seeded them into uninfected populations and repeatedly produced a population of predominantly Wolbachia-infected mosquitoes."

The basis for Xi's latest findings is connected to the success of his work using Wolbachia to halt Dengue fever. For this research, Xi focused on the mosquito species Aedes albopictus and Aedes aegypti. This work helped launch a global effort to develop Wolbachia-based strategies to eliminate dengue and other diseases.

The key to the malaria research was identifying the correct species of Wolbachia -- wAlbB -- and then injecting it into mosquito embryos. Out of the thousands of embryos injected by research associate Guowu Bian, one developed into a female that carried Wolbachia. The mosquito line derived from this female has maintained Wolbachia wAlbB infection with a 100 percent infection frequency through 34 generations. The number could grow higher as this is simply the last generation the researchers have bred thus far, Xi said.

The team then introduced various ratios of Wolbachia-infected females into a noninfected mosquito population. In each case, the entire population carried the bacteria in eight generations or less.

Using this promising approach to tackle malaria -- the biggest vector-borne disease -- gives scientists and world health officials another important tool to fight malaria.

Once Wolbachia has been released into a mosquito population, it is quite possible that it won't need to be reapplied, making it more economical than other methods like pesticide or human vaccine. This adds special value to the feasibility of this control strategy, considering most of the malaria endemic areas are suffering from poverty, Xi said.

TAG:Malaria Infectious Diseases Dentistry Bacteria Pests and Parasites Insects (including Butterflies)

Coral reefs suffering, but collapse not inevitable

"People benefit by reefs' having a complex structure -- a little like a Manhattan skyline, but underwater," said Peter Mumby of The University of Queensland and University of Exeter. "Structurally complex reefs provide nooks and crannies for thousands of species and provide the habitat needed to sustain productive reef fisheries. They're also great fun to visit as a snorkeler or diver. If we carry on the way we have been, the ability of reefs to provide benefits to people will seriously decline."

To predict the reefs' future, the researchers spent two years constructing a computer model of how reefs work, building on hundreds of studies conducted over the last 40 years. They then combined their reef model with climate models to make predictions about the balance between forces that will allow reefs to continue growing their complex calcium carbonate structures and those such as hurricanes and erosion that will shrink them.

Ideally, Mumby said, the goal is a carbonate budget that remains in the black for the next century at least. Such a future is possible, the researchers' model shows, but only with effective local protection and assertive action on greenhouse gases.

"Business as usual isn't going to cut it," he said. "The good news is that it does seem possible to maintain reefs -- we just have to be serious about doing something. It also means that local reef management -- efforts to curb pollution and overfishing -- are absolutely justified. Some have claimed that the climate change problem is so great that local management is futile. We show that this viewpoint is wrongheaded."

Mumby and his colleagues also stress the importance of reef function in addition to reef diversity. Those functions of reefs include the provision of habitat for fish, the provision of a natural breakwater to reduce the size of waves reaching the shore, and so on. In very practical terms, hundreds of millions of people depend directly on reefs for their food, livelihoods, and even building materials.

"If it becomes increasingly difficult for people in the tropics to make their living on coral reefs, then this may well increase poverty," said the study's first author, Emma Kennedy. It's in everyone's best interest to keep that from happening.

TAG:Extinction Fisheries Coral Reefs Ecology Ocean Policy Environmental Policies

Rejuvenating hormone found to reverse symptoms of heart failure

May 9, 2013 — Heart failure is one of the most debilitating conditions linked to old age, and there are no specific therapies for the most common form of this condition in the elderly. A study published by Cell Press May 9th in the journal Cell reveals that a blood hormone known as growth differentiation factor 11 (GDF11) declines with age, and old mice injected with this hormone experience a reversal in signs of cardiac aging. The findings shed light on the underlying causes of age-related heart failure and may offer a much-needed strategy for treating this condition in humans.

"There has been evidence that circulating bloodstream factors exist in mammals that can rejuvenate tissues, but they haven't been identified. This study found the first factor like this," says senior study author Richard Lee of the Harvard Stem Cell Institute and Brigham and Women's Hospital.

Heart failure is a condition in which the heart can't pump enough blood to meet the body's needs, causing shortness of breath and fatigue, and it is becoming increasingly prevalent in the elderly. The most common form of age-related heart failure involves thickening of heart muscle tissue. But until now, the molecular causes and potential treatment strategies for this condition have been elusive.

To identify molecules in the blood responsible for age-related heart failure, a team led by Lee and Amy Wagers of the Harvard Stem Cell Institute and Joslin Diabetes Center used a well-established experimental technique: they surgically joined pairs of young and old mice so that their blood circulatory systems merged into one. After being exposed to the blood of young mice, old mice experienced a reversal in the thickening of heart muscle tissue. The researchers then screened the blood for molecules that change with age, discovering that levels of the hormone GDF11 were lower in old mice compared with young mice.

Moreover, old mice treated with GDF11 injections experienced a reversal in signs of cardiac aging. Heart muscle cells became smaller, and the thickness of the heart muscle wall resembled that of young mice. "If some age-related diseases are due to loss of a circulating hormone, then it's possible that restoring levels of that hormone could be beneficial," Wagers says. "We're hoping that some day, age-related human heart failure might be treated this way."

TAG:Heart Disease Stroke Prevention Healthy Aging Vioxx Cholesterol Diseases and Conditions

Mapping the embryonic epigenome: How genes are turned on and off during early human development

After an egg has been fertilized, it divides repeatedly to give rise to every cell in the human body -- from the patrolling immune cell to the pulsing neuron. Each functionally distinct generation of cells subsequently differentiates itself from its predecessors in the developing embryo by expressing only a selection of its full complement of genes, while actively suppressing others. "By applying large-scale genomics technologies," explains Bing Ren, PhD, Ludwig Institute member and a professor in the Department of Cellular and Molecular Medicine at the UC San Diego School of Medicine, "we could explore how genes across the genome are turned on and off as embryonic cells and their descendant lineages choose their fates, determining which parts of the body they would generate."

One way cells regulate their genes is by DNA methylation, in which a molecule known as a methyl group is tacked onto cytosine -- one of the four DNA bases that write the genetic code. Another is through scores of unique chemical modifications to proteins known as histones, which form the scaffolding around which DNA winds in the nucleus of the cell. One such silencing modification, called H3K27me3, involves the highly specific addition of three methyl groups to a type of histone named H3. "People have generally not thought of these two 'epigenetic' modifications as being very different in terms of their function," says Ren.

The current study puts an end to that notion. The researchers found in their analysis of those modifications across the genome -- referred to, collectively, as the epigenome -- that master genes that govern the regulation of early embryonic development tend largely to be switched off by H3K27me3 histone methylation. Meanwhile, those that orchestrate the later stages of cellular differentiation, when cells become increasingly committed to specific functions, are primarily silenced by DNA methylation.

"You can sort of glean the logic of animal development in this difference," says Ren. "Histone methylation is relatively easy to reverse. But reversing DNA methylation is a complex process, one that requires more resources and is much more likely to result in potentially deleterious mutations. So it makes sense that histone methylation is largely used to silence master genes that may be needed at multiple points during development, while DNA methylation is mostly used to switch off genes at later stages, when cells have already been tailored to specific functions, and those genes are less likely to be needed again."

The researchers also found that the human genome is peppered with more than 1,200 large regions that are consistently devoid of DNA methylation throughout development. It turns out that many of the genes considered master regulators of development are located in these regions, which the researchers call DNA methylation valleys (DMVs). Further, the team found that the DMVs are abnormally methylated in colon cancer cells. While it has long been known that aberrant DNA methylation plays an important role in various cancers, these results suggest that changes to the cell's DNA methylation machinery itself may be a major step in the evolution of tumors.

Further, the researchers catalogued the regulation of DNA sequences known as enhancers, which, when activated, boost the expression of genes. They identified more than 103,000 possible enhancers and charted their activation and silencing in six cell types. Researchers will in all likelihood continue to sift through the data generated by this study for years to come, putting the epigenetic phenomena into biological context to investigate a variety of cellular functions and diseases.

"These data are going to be very useful to the scientific community in understanding the logic of early human development," says Ren. "But I think our main contribution is the creation of a major information resource for biomedical research. Many complex diseases have their roots in early human development."

Laboratories led by Michael Zhang, at the University of Texas, Dallas, and Wei Wang, at the University of California, La Jolla, contributed extensively to the computational analysis of data generated by the epigenetic mapping.

TAG:Genes Human Biology Epigenetics Developmental Biology Epigenetics Research Biotechnology

Social connections drive the 'upward spiral' of positive emotions and health

The research, led by Barbara Fredrickson of the University of North Carolina at Chapel Hill and Bethany Kok of the Max Planck Institute for Human Cognitive and Brain Sciences also found it is possible for a person to self-generate positive emotions in ways that make him or her physically healthier.

"People tend to liken their emotions to the weather, viewing them as uncontrollable," says Fredrickson. "This research shows not only that our emotions are controllable, but also that we can take the reins of our daily emotions and steer ourselves toward better physical health."

To study the bodily effects of up-regulating positive emotions, the researchers zeroed in on vagal tone, an indicator of how a person's vagus nerve is functioning. The vagus nerve helps regulate heart rate and is also a central component of a person's social-engagement system.

Because people who have higher vagal tone tend to be better at regulating their emotions, the researchers speculated that having higher vagal tone might lead people to experience more positive emotions, which would then boost perceived positive social connections. Having more social connections would in turn increase vagal tone, thereby improving physical health and creating an "upward spiral."

To see whether people might be able to harness this upward spiral to steer themselves toward better health, Kok, Fredrickson, and their colleagues conducted a longitudinal field experiment.

Half of the study participants were randomly assigned to attend a 6-week loving-kindness meditation (LKM) course in which they learned how to cultivate positive feelings of love, compassion, and goodwill toward themselves and others. They were asked to practice meditation at home, but how often they meditated was up to them. The other half of the participants remained on a waiting list for the course.

Each day, for 61 consecutive days, participants in both groups reported their "meditation, prayer, or solo spiritual activity," their emotional experiences, and their social interactions within the last day. Their vagal tone was assessed twice, once at the beginning and once at the end of the study.

The data provided clear evidence to support the hypothesized upward spiral, with perceived social connections serving as the link between positive emotions and health.

Participants in the LKM group who entered the study with higher vagal tone showed steeper increases in positive emotions over the course of the study. As participants' positive emotions increased, so did their reported social connections. And, as social connections increased, so did vagal tone. In contrast, participants in the wait-list group showed virtually no change in vagal tone over the course of the study.

"The daily moments of connection that people feel with others emerge as the tiny engines that drive the upward spiral between positivity and health," Fredrickson explains.

These findings add another piece to the physical health puzzle, suggesting that positive emotions may be an essential psychological nutrient that builds health, just like getting enough exercise and eating leafy greens.

"Given that costly chronic diseases limit people's lives and overburden healthcare systems worldwide, this is a message that applies to nearly everyone, citizens, educators, health care providers, and policy-makers alike," Fredrickson observes.

This work was supported National Institute of Mental Health Grant MH59615.

TAG:Health Policy Mental Health Research Psychology Perception Social Issues Public Health

2012年6月26日星期二

对症下药不同双眼皮术失败解决方法_整形

核心提示：割双眼皮术可以让我们拥有一双后天加工的美丽大眼，但是却不一定每一双双眼皮都会手术成功，那么，如果双眼皮手术失败的时候，我们该如何修复？下面一起来了解下不同的失败个案的解决办法。

　　割双眼皮手术是时下许多爱美人士多喜欢做的一种美容手术，割双眼皮术的技术在美容界已经比较成熟，因为很少会出现副作用，但是这并不代表失败的例子不存在，失败的原因有许多，譬如医院医生的专业操作不达标，医院的手术程序不当，以及术后患者本身护理不好，也会让双眼皮手术失败。

割双眼皮手术效果前后对比

　　一、双眼皮术失败的临床表现及原因：

　　1、切口疤痕。原因为切口感染，切口缘不整齐对合不良，或患者是疤痕体质。

　　2、双眼皮过宽，过窄，过长，过短，双侧不对称。原因为设计不当，设计线过宽，过窄过长，过短，双侧不对称，切开时未按设计线切开；设计时未考虑患者本身双侧不对称。

　　3、三眼皮形成。原因为原有双眼皮粘连线未分开，原有双眼皮线与新设计的双眼皮线形成三眼皮，多见于埋线法；切口上方眼轮匝肌去处过多，致使上睑皮肤与深部组织粘连形成三眼皮。

　　4、外形不美。患者眼裂短，形成双眼皮宽，眼睛变圆；切口下缘眼轮切除不够双眼皮臃肿不自然；双眼皮外形与五官不协调。

　　5、睁眼乏力。术前患者有轻度上睑下垂或提上睑肌力弱；术中切开过深损伤提上睑肌腱膜；早期疤痕增生挛缩可引起。

　　6、双眼皮线消失。原因为双眼皮设计线过低形成内双；睑板前眼轮匝肌去除不够防碍皮肤与睑板粘连；缝合时没固定于睑板腱膜上；拆线过早粘连不够牢固。

　　7、眼睑凹陷。眶隔脂肪去除过多。

　　二、双眼皮手术失败案例

　　双眼皮手术失败案例一：重睑线消失

　　李小姐是某家跨国公司白领，在两年前做了埋线双眼皮手术，然而最近李小姐发现双眼皮居然消失了，完全"回归"了以前的自己，这让她不知所措，整天愁眉苦脸，给她的生活和工作带来了不小的影响，面对朋友问起双眼皮怎么没了的时候，李小姐是有苦难言。

　　双眼皮手术失败修方法：重睑线消失有两种情况，一种是部分消失，一种是完全消失。

　　如果是部分消失可按照原来保留的双眼皮在重新"接"一段，新的重睑线和原有的弧度保持一致，并且看起来非常自然就可以了，如果是重睑线完全消失，就需要重新做双眼皮手术，对于上睑皮肤不松弛，脂肪较少的求美者可用埋线双眼皮，对于皮肤松弛但是脂肪少的可用韩式双眼皮，而切开双眼皮适用于身体条件允许，心理健康有需要做双眼皮的所有求美者。

　　双眼皮手术失败案例二：手术后出现隐双

　　张小姐是大三学生，为了能在毕业后找到一份理想的工作，张小姐在增加自己"内功"的同时也在外貌上下了不少功夫，在说服家长后张小姐去某整形医院做了切开双眼皮手术，可是术后张小姐发现双眼皮竟然是隐双，马上就要毕业找工作了，这下张小姐急得像热锅上的蚂蚁，逢人就问该怎么办。

　　双眼皮手术失败修复方法：如果手术后出现隐双，可按原切口重新将皮肤切开，去除部位多余的脂肪和眼轮匝肌，上睑皮肤有一定的伸展性，可以在缝合的时候将切口上提以增加双眼皮的宽度。

　　双眼皮手术失败案例三：术后双眼皮不对称

　　陈小姐是某所高校教师，觉得自己单眼皮不好看就在暑假的时候去整形医院做了双眼皮手术，当时采用的是切开双眼皮方法，然而在术后陈小姐发现两边的双眼皮不对称，还没有之前的单眼皮好看，这给陈小姐带来了很大的烦恼，本来是想给出差的老公一个惊喜，这下只有惊没有喜了。

　　双眼皮手术失败修复方法：如果术后双眼皮不对称，选择其中理想的一条双眼皮，将另一侧按照这条双眼皮的模样修复。一般在术后3－6个月上睑肿胀完全消退后再次手术修复。

　　三、修复手术原则：

　　1、认真分析前次手术失败的原因。

　　2、重新设计双眼皮切开线，尽量将原切口疤痕全部切除。

　　3、去尽睑板前疤痕，充分分离肌肉与睑板前腱膜的粘连。

　　4、缝合时弧线流畅自然，睑板前腱膜固定牢靠。

　　5、前次手术眶隔脂肪去除过多时可释放内侧脂肪，或游离移植下睑眶隔脂肪，或分次注射自体脂肪。

　　6、手术时要爱护组织，轻柔微创，缩短恢复期并减少疤痕增生。

　　四、修复双眼皮手术应该按照个人双眼皮失败的表现不同而使用不同的修复方法：

　　1、双眼皮不对称：一般在术后3－6个月上睑肿胀完全消退后再次手术修复。

　　2、双眼皮过宽：术后3－6个月重新设计切口，分离第一次手术形成的粘连，其他步骤与重睑术相同。

　　3、双眼皮过低：消肿后二期手术。切口线上移作新切口，向下剥离，使新老切口成为一个整体，再做重睑缝合。

　　4、双眼皮弧度不佳：消肿后按自然皱襞重新设计重睑线，切开重做。

　　5、双眼皮消失：消肿后，埋线法者改作切开法双眼皮手术。切开法者经原切口切开，去除足够的皮下组织与眼轮匝肌，缝合时皮肤紧贴睑板或睑肌组织，术中让患者睁眼观察，达到满意的重睑即可。

　　6、三眼皮形成：消肿后经原切口切开，将过多的皮肤切除，上方的皱襞就可消失。

　　7、上睑下垂：再次手术将切断的上睑提肌腱膜与睑板缝合。

　　8、下睑外翻：轻度者可采用局部按摩或局部注射糖皮质激素以促使下睑皮肤松解，一般数月即可复原或改善；重度者可作外侧V形皮肤切除缝合，或将眼轮匝肌瓣向外上眶缘提吊固定，或利用上睑旋转皮瓣、鼻侧皮瓣、颞部皮瓣矫正外翻；严重者则需行游离植皮矫正术。

　　更多有关双眼皮的资讯，请关注>>

　　推荐阅读：

　　割双眼皮网友分享消肿心得

　　告诉你什么季节割双眼皮好

　　割双眼皮多久消肿护理很重要

39健康网(www.39.net)专稿，未经书面授权请勿转载。

（责任编辑：陈绣莹）

TAG:双眼皮术失败表现双眼皮术失败修复方法割双眼皮

2012年6月19日星期二

夏季易上火这10款去火凉茶最适合女性喝_女性

核心提示：夏天最容易上火了，喝凉茶是解决上火问题的最简单方法，但因为中药有寒性热性之分，人的体质也有寒性热性之分，因此乱选凉茶就会起到反作用。下面推荐几款适合女性的凉茶。

　　炎热夏季，人们易上火。怎样去火、预防上火呢?中医认为，喝凉茶是解决上火问题的最简单方法，却也让不少女性头痛不已，因为中药有寒性热性之分，人的体质也有寒性热性之分。如果分不清自己的体质与当前身体状况，乱选凉茶非但无法解除症状，甚至起反作用。下面介绍几种适合女性喝的去火凉茶。

　　目前市面上出售的凉茶多为属于寒性，并不太适合女性饮用。因为大多女性体质虚寒，而脾虚、脾胃两虚的人饮用后，可能会惹出肠胃不适，如腹泻、腹胀、作呕等问题。这类人的身体特征是：怕冷、怕风、多汗。尤其经期女性如果喝了寒性的凉茶，极易导致气血受寒而凝滞、经血排出不畅，引发痛经，孕妇更是忌讳喝凉茶。

　　辨体质，选凉茶

　　因为中药有寒性热性之分，人的体质也有寒性热性之分。如果分不清自己的体质与当前身体状况，乱选凉茶非但无法解除症状，甚至起反作用。因此凤凰中医提醒，女性选去火凉茶时，首先要辨清自己的体质。那么女性如何选适合自己的去火凉茶呢。

　　适合女性喝的去火凉茶

　　1、明目茶：现代人已离不开电脑，而长时间盯着电脑屏幕，眼睛容易疲劳。此时，不妨喝点用枸杞子、白菊花、生晒参等配成的药茶，可有效缓解眼睛疲劳，还可预防上火。

　　2、麦茶：麦茶中拥有与夏季匹配的成分和功效，例如维生素B族和维生素E，可以缓冲身体疲劳。钾和铁，对预防贫血和中暑非常有效。另外，麦茶还有降低体温的作用，因此被认为是最适合夏季的高营养饮品。尤其适合女性饮用。

　　3、消暑养阴茶：取枸杞、五味子各12g，甘草9g，洗净后放入锅中加水，煮沸十分钟后加薄荷9g，加盖离火，5分钟后加适量白糖搅匀，即可饮用。此茶益气养阴，治中暑内热。

　　4、三花清凉茶：该药茶由三种花组成，分别是杭白菊、野菊花和金银花，超市里即可买到这些原料。该药茶有清热解毒、平肝明目的功效，适宜女性饮用。

　　5、菊银茶：将白菊花6克，罗布麻4克，决明子2克，槐米2克，金银花2克。放进锅内，倒入清水，用大火煮沸8～10分钟，即可饮用。可消暑、清热排毒，减肥降脂。

　　6、利喉清咽茶：由西青果、射干、麦冬、黄芩组成，具有消炎止痛、利喉清咽的作用。尤其是因工作繁忙而导致"上火"的上班族，这款茶很值得推荐。

　　7、午时茶：苍术、陈皮、藿香、甘草、防风、连翘、柴胡、前胡、羌活、枳实、山楂、川穹、神曲、白芷、麦芽、桔梗、厚朴、绿茶、紫苏叶，本茶是成药，其性状为深棕色茶块。每次用1-2块，清水2~3碗煎至1碗饮用。能解暑清热，倒滞止渴，开胃进食。宜忌：本茶消积滞而行气散结，可增强肠蠕动，孕妇慎用。

　　8、养颜茶：由灵芝、玉竹、麦冬等组成，具有养阴生津、安神健胃的功效，配方在药房里可抓到。

　　9、陈皮茶：将干橘子皮10克洗净，撕成小块，放入茶杯中，用开水冲入，盖上杯盖焖10分钟左右，然后去渣，放入少量白糖。稍凉后，放入冰箱中冰镇一下更好。女性常饮此茶，既能消暑又能止咳、化痰、健胃。

　　10、葛根茶：将鲜葛根切小块，清水5~6碗煎至1碗饮用。具有解肌镇痛，散热祛烦，生津止渴的功效。宜忌：此养生凉茶需明火久煎，一般需水沸后煎1小时以上，若煎煮时间不足，则功效降低。

（责任编辑：滕小兰实习编辑：蒋蓉）

TAG:凉茶去火

生病时吃什么水果最有益_女性

核心提示：我们都知道多吃水果好，但是水果并不是谁都能随便吃，特别是在生病的时候。那么在生病时吃什么水果对身体最好呢？一起来看看。

　　在生病时吃什么水果对身体最有益呢？下面就来告诉你！

　　腹泻

　　宜吃葡萄、石榴、苹果、杨梅等具有收剑使用的水果；不宜吃香蕉、梨、西瓜等偏寒、润肠通便的水果，因吃后易致大便溏泻，加重病情。

　　便秘、痔疮

　　宜吃香蕉、梨、桃、柑橘，以利润肠通便；不宜吃柿子、山楂、苹果、莲子等，因为这些水果中含鞣酸较多，有涩肠止泻作用，吃后易引起便秘。

　　溃疡、胃酸过多

　　不宜吃酸梨、柠檬、杨梅、青梅、李子等含酸较高的水果，以防有损溃疡愈合，或因胃酸骤增而加重病症。

　　糖尿病

　　宜吃富含果胶，能改变胰岛素分泌量，具有降低血糖作用的菠萝、杨梅、樱桃水果；不宜吃含糖分较高的枣子、葡萄、香蕉、苹果、梨、无花果、荔枝、柠檬等水果，以免吃后会引起血糖升高，而加重胰腺负担，不利于治疗。

　　肝炎

　　宜吃香蕉、梨、枣子、柑橘、苹果、西瓜等富含维生素C，有保护肝脏，促进肝细胞再生功能的水果。

　　心力衰竭、严重水肿

　　不宜吃含水分多的西瓜、梨、菠萝等水果，因大量水分会使心力衰竭、水肿病情加重。

　　急性肾炎

　　如有肾功能不良或浮肿而需要忌盐者不宜吃香蕉，因香蕉中含有较多的钠盐，能加重浮肿，增加心脏和肾脏的负担。

　　高血压、动脉硬化

　　宜吃山楂、枣子、柑橘等富含维生素C，有降压、缓解血管硬化作用的水果。

　　冠心病、高血脂

　　宜吃柑橘、柚子、山楂、桃、草莓等水果，因这些水果富含维生素C和烟酸，具有降低血脂和胆固醇的作用。

　　心肌梗塞、中风

　　宜吃西瓜、香蕉、柑橘、桃子等帮助消化的水果；不宜吃柿子、苹果、莲子等水果，因含鞣酸有收敛作用，易引起便秘，会使病情加重。

　　呼吸道感染

　　尤其是伴有咽痛、咳嗽、痰多的病人，宜吃梨、枇杷、橙子、杏、罗汉果等能化痰、润肺、止咳的水果。

　　体质燥热

　　宜吃梨、香蕉、西瓜等性偏寒的水果；不宜吃葡萄、柑橘、枣子、樱桃等属温热的水果。

　　发烧

　　宜吃具有生津止渴、解热散毒功能的梨、柑橘等水果。因发烧病人出汗多，梨、柑橘等含有充足的水分和钾，对发烧病人更有益。

（责任编辑：滕小兰）

TAG:生病水果生病吃什么水果

2012年6月5日星期二

性趣金字塔：混搭5种爱爱花样最能讨好她

　　阅读提示：金字塔，食物金字塔？不不不，现在的话题是你的他的亲密金字塔。来看看加哪些新鲜元素进去能让你们变得更加健康、完美、满足。

性趣金字塔：混搭5种爱爱花样最能讨好她

　　总吃一种食物既不健康，也缺乏新鲜感。两性生活也一样。研究发现，总在同一家餐厅点同样的菜的女性不会享受生活。纽约市性和关系学家Ian Kerner博士说：在爱爱的过程中采用不同的姿势或加些花样不仅不会产生厌烦情绪，还能更好地满足身体和心理的需求。同时也能展现自己不一样的个性，让伴侣更加了解你，也让你们的关系变得更加亲密。

　　1. 亲密

　　如何亲密：

　　慢慢探索对方身体的每个部位能使两人更亲密。

　　亲密有何好处：

　　高潮固然感觉不错但是充满爱的交合才能满足我们情感上的亲密需求，只有两个人心灵深处达到共鸣才能让彼此获得更高程度的满足。

　　亲密的性爱是女性性金字塔的基础，也是金字塔的底层。感觉相通，彼此才能感受到对方浓浓的爱意，与对方产生共鸣。

　　这就需要你在开始的时候避免操之过急。两个人爱爱的游戏，是为了让彼此更加喜欢对方，并不需要有能否令对方达到高潮的压力，这样想的话无疑会产生一种暖洋洋的感觉。

　　精华：

　　无论你与伴侣在一起多久，他也不可能完全读懂你的心思。所以必要的交流会使你们的关系更进一步(他不知道你需要多久就能享受到高潮的快感——所以你需要告诉他)，而且要赞扬对方。

　　说一些肯定对方的话如：我喜欢你这样……我们再来一次！在那个时候尽量做些让彼此感觉更亲近的事情：亲吻对方、讲个笑话或开怀浅笑。无论结果如何你们都会拥有美妙的享受。

　　2. 冒险

　　什么是冒险：