Looking good can matter a lot when you are a teenager. Of course the budget(财政） matters a lot, too. Luckily, fashion trends (流行趋势) in the UK mean that getting the right image doesn't have to cost the earth. Here's a quick guide to which looks are hot this year.

    For girls, the 70s are back. Wide-legged jeans, platform shoes and skirts that reach the feet are again in fashion among UK teens, topped off with colored, shining eyeshadow. Girls can have fun mixing and matching bright shades. Colors like pink, orange and light yellow-green are all perfectly fit. Shorts and mini-skirts are still popular in cold weather. By wearing a pair of tights underneath ( 在..底下), girls can stay warm as well as fashionable in the winter.

    How about boys? To look lively, fans of skateboards and snowboards can dress in skinny jeans accompanied by a T-shirt topped off with a baseball cap or a woolen hat. Music is often an inspiration for fashion, and hip-hop music fans like to dress in baggy jeans, T-shirts, baseball caps and sneakers. For those who can afford it, designer clothing is a must, especially if the logo is showing.

    Drinking more than two alcoholic drinks daily in middle-age may raise your stroke(中风) risk more than traditional factors such as high blood pressure and diabetes（糖尿病）, according to new research in the American Heart Association journal Stroke.

    In a study of 11,644 middle-aged Swedish twins who were followed for 43 years, researchers compared the effects of an average of more than two drinks daily ("heavy drinking") to less than half a drink daily ("light drinking").

The study showed that:

·Heavy drinkers had about a 34 percent higher risk of stroke compared to light drinkers.

·Mid-life heavy drinkers (in their 50s and 60s) were likely to have a stroke five years earlier in life irrespective of genetic and early-life factors.

·Heavy drinkers had increased stroke risk in their mid-life compared to well-known risk factors like high blood pressure and diabetes.

·At around age 75, blood pressure and diabetes appeared to take over as one of the main influences on having a stroke.

Past studies have shown that alcohol affects stroke risk, but this is the first study to pinpoint differences with age. "We now have a clearer picture about these risk factors—-how they change with age and how the influence of drinking alcohol shifts as we get older," said Pavla Kadlecová, M.Sc., a statistician at St. Anne's University Hospital's International Clinical Research Center in the Czech Republic.

    Researchers analyzed results from the Swedish Twin Registry of same-sex twins who answered questionnaires in 1967-1970. All twins were under age 60 at the start. By 2010, the Registry had provided 43 years of follow-up, including hospital discharge(出院) and cause of death data.

    Researchers then sorted(整理) the data based on strokes, high blood pressure, diabetes and other cardiovascular (心血管)incidents. Almost 30 percent of participants had a stroke. They were categorized(将……分类) as light, moderate, heavy or non-drinkers based on the questionnaires. Researchers compared the risk from drinking and health risks like high blood pressure, diabetes and smoking. Among identical twin pairs, siblings(兄弟姐妹) who had a stroke drank more than their siblings who hadn't had a stroke, suggesting that mid-life drinking raises stroke risks regardless of genetics and early lifestyle.

    The study is consistent (一致)with the American Heart Association's recommended limit of two drinks a day for men and one for women. That's about 8 ounces of wine for a man and 4 ounces for a woman.

    Regular heavy drinking of any kind of alcohol can raise blood pressure and cause heart failure or irregular heartbeats over time, in addition to stroke and other risks. "For mid-aged adults, avoiding more than two drinks a day could be a way to prevent stroke in later productive age ," Kadlecová said.

    As global temperatures rise, trees around the world are experiencing longer growing seasons, sometimes as much as three extra weeks a year. All that time helps trees grow faster. For the past 100 years, trees have been experiencing fast growth in temperate regions from Maryland to Finland, to Central Europe, where the growth rate of some trees has even sped up nearly 77% since 1870. Assuming wood is just as strong today, those gains would mean more timber(木材) for building, burning, and storing carbon captured from the atmosphere. But is wood really as dense as it used to be?

    Hans Pretzsch, a forest scientist at the Technical University of Munich in Germany, and his colleagues wanted to find an answer. They carried out a study of the forests of Central Europe. They started with 41 experimental plots in southern Germany, some of which have been continuously monitored since 1870. Pretzsch and his team took core samples from the trees—which included Norway spruce, sessile oak, European beech, and Scots pine—and analyzed the tree rings using a high-frequency probe.

    They found that in all four species, wood density has decreased by 8% to 12%, they report online in Forest Ecology and Management. “We expected a trend of the wood density like this, but not such a strong and significant decrease,” Pretzsch says. Increasing temperatures, and the faster growth they spur, probably account for some of the drop. Another factor, Pretzsch says, is more nitrogen in the soil from agricultural fertilizer(化肥) and vehicle exhaust. Previous studies have linked increased fertilizer use to decreased wood density. Above all, the study suggests that the higher temperatures—combined with pollution from auto exhaust and farms—are making wood weaker, resulting in trees that break more easily and wood that is less durable.

    “I am getting worried,” says Richard Houghton, an ecologist at the Woods Hole Research Center in Falmouth, Massachusetts, who was not part of the new study. As the density of the samples dropped, so did their carbon content, by about 50%. That means forests may suffer more damage from storms and may be less efficient at soaking up the greenhouse gas carbon dioxide (CO2) than scientists had thought, Houghton says.

    Chinese researchers say they have come up with a simple way to find out a person's biological age —how much the body has aged physically – through a urine (尿) test.

    Their findings will help researchers conduct numbers of ageing studies and even predict a person's risk of age-related diseases, according to a paper published in the journal Frontiers in Ageing Neuroscience.

    Another paper by researchers at the Beijing Hospital and the West China Hospital in Chengdu, Sichuan province, said on Tuesday that people aged at different rates due to changes in their genetic make-up and their environment.

    Chronological age – which is based on one's birth date —was not an exact measure of biological age so a more exact method was needed, the team said.

    Ageing is driven by the lifelong gradual accumulation(积累) of a broad variety of molecular (分子) faults in the body's cells. The team said they had identified a matter 8-oxoGsn that indicated increases in oxidative (氧化性) damage in urine as people's bodies aged.

    Cai Jianping, a co-author at the Beijing Hospital, said: “As we age, we suffer increasing oxidative damage and so the levels of oxidative matters increase in our body.” The team tested the levels of 8-oxoGsn in urine samples from 1,228 Chinese people aged two to 90 and concluded the marker helped accurately determine the stage of biological ageing in adults.

    They had previously found that 8-oxoGsn levels also increased with age in the urine of animals such as mice.

    The team has also developed a rapid analysis technique called ultra-high-performance liquid chromatography(层析法), which can process up to 10 urine samples an hour, according to the study.

    If humans pump enough carbon dioxide (CO₂) into the atmosphere, the stratocumulus clouds(层积云) could disappear, and the earth's temperature could climb sharply to heights not predicted in current climate models. It would burn the planet. That's the conclusion of a paper published in the journal Nature Geoscience and described in detail by Natalie Wolchover for Quanta Magazine.

    As Wolchover explained, clouds have long been one of the great uncertainties of climate models. Computer models that easily capture the complexity and detail of most climate systems just aren't powerful enough to predict worldwide changes in cloud behavior. But clouds are important. They reflect sunlight away from the earth's surface. And stratocumulus clouds are those white blankets you might have seen as you looked out the window of arm airplane, rolling out below you and hiding the ground Researchers suspect that certain sudden, past jumps in temperature may have been caused by changes to clouds like these.

    For the new research, scientists modeled just a small patch of sky using a supercomputer. They found that if carbon dioxide levels reach about 1, 200 parts per million(ppm) in the atmosphere, stratocumulus clouds break up. That's a very high carbon dioxide concentration.  Right now, levels have climbed past 410 ppm--a dangerous change from 280 ppm before the Industrial Revolution.

    But humans put more and more CO₂ into the atmosphere every year. If current trends continue, the earth could reach 1, 200 ppm within 100 to 150 years. This could happen if our society doesn't follow through on any of its commitments to reduce emissions(排放), Wolchover reported. And even if it does, the result would be another 8 degrees Celsius of heat added to the global average, on top of the dangerous changes already underway due to greenhouse gases.

    That's an enormous change, and it goes beyond predictions of worldwide ice melt and catastrophic sea level rise. And, once the stratocumulus clouds are gone, Wolchover reported, they likely wouldn't reappear until atmospheric carbon dioxide levels dropped below where they are currently.

    There's still some uncertainty in the data. The 1, 200 ppm figure could change as scientists look into the issue further.

    Metal-organic frameworks(MOFs) are compounds that are set to solve some tough challenges: producing water in the desert, removing greenhouse gases from the air and storing dangerous gases more safely.

    The Arizona desert is really dry. Anyone stuck in it without water would die from dehydration (脱水) within three days. Unless, that is, they had one of Omar Yaghi's next-generation water harvesters. Although daytime humidity(湿度)is only about 10 per cent, this rises to 40 per cent at night, which means there's enough water in the atmosphere to support life — if it can be transformed into liquid form.

    That's exactly what Yaghi's device does. It's a box about the size of a small microwave oven designed to suck the humidity from the air at night and turn it into drinking water the next day using only the heat of the sun as its power source. What makes it work is a special material called a metal-organic framework (MOF), which at normal temperatures attracts water molecules (分子) onto its surface of its internal pores(细孔). Warm it up and the water is released, each harvest producing one-third of a cup of pure drinking water.

    "With further improvements, a device, the size of a washing machine, could produce enough water for the basic needs of a household," says Yaghi, a chemist at the University of California. One-third of the world's population lacks safe drinking water; for them such a device could be a lifesaver.

    These crystalline cluster(结晶群)of metals, such as aluminum or magnesium, linked by organic molecules can be made into materials with an extremely high absorption ability, attracting specific molecules to their surface. In this way, MOFs cling to a variety of liquids and gases.

MOFs work thanks to their unique structure—large quantities of nanometer-sized internal spaces. In fact one MOF has so many pores that they would cover an area as large as six football fields. MOFs are also extremely stable light and have many different uses: their molecular structure can be varied to attract specific molecules, such as water, and their pores can be designed to best store them. Adding a small amount of heat or pressure causes the MOF to release what it is holding. More than 70,000 different MOFs have been produced to date for various applications.