In 1999, twelve percent of public elementary schools in the United States required students to wear uniforms. Just three years later, the amount was almost double that.

    A study of six big-city Ohio public schools showed students who were required to wear uniforms had improved graduation, behavior and attendance rates. Academic performance was unchanged.

    Some high schools in Texas have also joined in the movement. Yet studies find mixed results from requiring uniforms. And some schools have turned away from such policies.

    Supporters believe dressing the same creates a better learning environment and safer schools. The school district in Long Beach, California, was the first in the country to require uniforms in all elementary and middle schools. The example helped build national interest in uniforms as a way to deal with school violence and improve learning.

    Findings in Long Beach suggested that the policy resulted in fewer behavior problems and better attendance. But researcher Viktoria, who has looked at those findings, says they were based only on opinions about the effects of uniforms.

    She says other steps taken at the same time to improve schools in Long Beach and statewide could have influenced the findings. The district (the area marked by government) increased punishments for misbehavior. And California passed a law to reduce class sizes.

    In Florida, for example, researcher Sharon found that uniforms seemed to improve behavior and reduce violence. In Texas, Eloise found fewer discipline problems among students required to wear uniforms, but no effect on attendance.

    Sociologist David has studied school uniform policies since1998.He collected the reports in the book. In his own study, he found that reading and mathematics performance dropped after a school in Pennsylvania（宾夕法尼亚州）required uniforms.

    Political and community pressures may persuade schools to go to uniforms to improve learning. But David and others believe there is not enough evidence of a direct relationship. In fact, he says requiring uniforms may even increase discipline problems.

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    Animals, including insects, do not have a language like ours. They do not talk to each other in words and sentences. But if we watch them, we can see that they do have ways of communicating with each other.

    Can you see the rabbits' tail? When rabbits see this white tail moving up and down, they run too. The rabbit has reminded them of potential dangers without making a sound. It has given them a signal.

    Many other animals use this kind of language. When a cobra (眼镜蛇) is angry, it raises its hood (兜帽) and makes itself look fierce. This warns other animals. When a bee has found some food, it goes back to its home. It cannot tell the other bees where the food is by speaking to them, but it does a little dance in the air. This tells the bees where the food is.

    Some animals say things by making sound. A dog barks, for example, when a stranger comes near. A cat purrs (猫的呜呜声) when pleased. Some birds make several different sounds, each with its own meaning. Sometimes we human beings speak in the same way. We make sounds like “Oh” or “Ah!” when we are frightened or pleased or when we drop something on our toes.

    But we have something that no animals have — a large number of words which have the meanings of things, actions, feeling or ideas. We are able to give each other all kinds of different information in words and sentences, which no other animals can do. No other animals have so wonderful a language as we have.

    If you are taking vitamin supplements to reduce your risk of heart disease or cancer, a group of health experts want you to know that those vitamins may actually increase your risk of cancer.

    The US Preventive Services Task Force came to this conclusion after reviewing dozens of studies.

    Nearly half of adults in the US take at least one vitamin or mineral supplement on a regular basis. These pills are advertised as a way to promote general health. In some cases, manufacturers promote them as cancer fighters and heart protectors.

    Studies in animals and in laboratory dishes suggest that oxidative(氧化性的) stress contributes to diseases like cancer and heart disease. If so, there is a reason to believe that antioxidants—including beta-carotene, vitamins A, C, and E—could be useful as preventive medicines.

    But when the Task Force examined the medical evidence on vitamins, it found “inadequate(不充分的) evidence” to support the claims that vitamin and mineral supplements benefit healthy adults.

    “Cardiovascular(心血管的) disease and cancer have a significant health impact in America, and we all want to find ways to prevent these diseases,” Dr. Virginia Moyer, who heads the Task Force, said in a statement. But so far, she added, the medical evidence does not show that taking vitamins is helpful in this regard.

    However, the Task Force did find “adequate evidence” that people with a raised risk for lung cancer actually increase their risk further by taking beta-carotene, a precursor of vitamin A.

    The Task Force recommendations of taking vitamins regularly apply to healthy adults aged 50 and older who don't have “special nutritional needs”. The advice does not apply to children, women who are pregnant or may become pregnant, people with chronic illnesses, or people who have to take supplements because they can't get all their essential nutrients from their diet.

    A team of international scientists is due to set off for the world's biggest iceberg in a mission aiming to answer fundamental questions about the impact of climate change in the polar regions. The scientists, led by the British Antarctic Survey (BAS), are trying to reach a newly revealed ecosystem that had been hidden for 120,000 years below the Larsen C ice shelf.

    Last year, part of the Larsen C ice shelf calved (崩解) away, forming a huge iceberg-A68—which is four times bigger than London, and revealing life beneath for the first time. Now scientists say it is a race against time to explore these new ecosystems before they are transformed to the light. Marine biologist Dr Katrin Linse from the BAS is leading the mission.

    "The calving of A68 provides us with a unique opportunity to study marine life as it responds to a huge environment change," she said. "It is important that we get there quickly before the undersea environment changes as sunlight enters the water."

    Professor David Vaughan, science director at the BAs, said, "We need to be bold (大胆的) on this one. Larsen C is a long way south and there's lots of sea ice in the area, but this is important science, so we will try our best to get the team where they need to be. He said climate change had already affected the sea around Antarctica and is warming some coastal waters. "Future warming may make some habitats warm. Where these habitats support unique species that are adapted to love the cold and not the warm, those species are going to either move or die."

    There is growing concern about the possible impact of climate change in the Antarctic. Earlier this month, a report revealed that melting ice sheets in Greenland and Antarctica are speeding up the already fast pace of the sea level rise. The research, published by the National Academies of Science, Engineering and Medicine, said, "At the current rate, the world's ocean will be, on average, at least 60cm higher by the end of the century." However, it found that the process is accelerating, and more than three quarters of the acceleration since 1993 is due to melting ice sheets in Greenland and Antarctica, the study shows.

    During an earthquake, you should know what to do. If the earthquake strikes while you're inside a house, you should lie on the floor under a strong table or other furniture. If there is no furniture, you can cover your head with your arms and keep still in the corner of the room. You should keep away from windows, glass walls, or anything that can fall.

    If you are in bed, hold firmly onto your bed and make use of a pillow to safeguard your head. You may use a doorway but only when it is close to you. It should also be considered whether it is strong enough to deal with the load.

    If you are running out, do not use lifts, even if they work. Electricity may go out at any time. Many injuries happen when people try to rush out. This means you ought to stay in your house or perhaps wherever you are.

    When you stay outdoors, you should stay far from buildings, power wires or lights. You should be in the open until the quake stops. Remember that many earthquake deaths outside the house come from falling-apart walls, flying glass and other falling things.

    If an earthquake strikes and you are driving, you should pull up to the side of the highway and stop as quickly as possible. You ought not to stop under trees, buildings or energy wires. Don't stop in the middle of the street as it could trouble others.

    When trapped, you shouldn't move. Your mouth should be covered with a piece of clothing or a handkerchief. This is because it is possible for you to breathe in some dust. Do not shout whenever possible. You should only shout in the end to get help from rescuers.

The editor of the Cool Camping Britain chooses some of his favorite new finds in England, Wales and Scotland.

Cleadale, Isle of Eigg, Inner Hebrides

Is this Britain's most beautiful campsite? From the grassy point looking seaward to the mountains, it's not hard for campers to see how the island inspired fantasy landscapes in The Lord of the Rings.The campsite itself is as wild and wonderful as its setting.

Open April~September, pitches from £5 per tent per night.

Swattesfield, Thornham Magna, Suffolk

Deep in the wilds of north Suffolk, this seven-acre campsite has only been open for a few years, with two fields separated by a lake and surrounded by woodland. The position is perfect. It's a great place to do nothing and get into nature.You can set up your tent in the bottom field or the woodland beyond.

Open Easter~October, pitches from £10 per tent per night.

Pleasant Streams, near St Austell, Cornwall

This site, by a lake, is all about simple pleasures. Located in the former mining village, it has a summerhouse with books and games for a rainy day, many animals including pigs, hens, goats and ducks, and a pub just a 10-minute stroll (walk) away. There's very little to do here, no bells or whistles. Campfires are encouraged.

Open Easter~September, pitches from £10 per tent per night.

Troytown Campsite, St Agnes, Isles of Scilly

Its only campsite couldn't be in a more remote position. Isolation is its greatest asst (优点)－so bring plenty of books to read and don't expect a phone signal. But at least one of life's necessities is available. Lying on the hillside overlooking the bay and near the island of the Gugh, it might just win the prize for best beer garden view in England.

Open MarchOctober, pitches from 7.50 per tent per night.