Today, the world's diversity (多样性) of food crops is quickly decreasing. But scientists around the world are taking action. They are building seed banks. At seed banks, scientists store the seeds of many different crops.

    There are now 1,400 seed banks around the world. However, some banks are in warm countries. If the electricity fails, the seeds will get too hot and die. Other seed banks are in countries troubled by war. Sometimes people damage the seed banks. If this happens, valuable seeds can be lost forever!

    The organization Global Crop Diversity Trust decided they wanted to deal with this problem. So, they decided to build a global seed bank. This seed bank would contain a back-up, or extra copy, of all the world's seeds. Smaller seed banks would still collect and keep local seeds. But they would also send copies of their seeds to the global bank.

    Scientists from the Global Crop Diversity Trust chose the cold, snowy mountains of Svalbard, Norway to build the global seed bank — the Svalbard Global Seed Vault (斯瓦尔巴全球种子库). Organizations, farmers, or local seed banks store their extra seeds there. And the people who place their seeds in the vault are the only people who can take them out. They pay to ship their seeds to Norway, but it does not cost them any money to store their seeds. The Global Crop Diversity Trust pays for this.

    Cary Fowler is a scientist who heads the Global Crop Diversity Trust. He said, “If the Seed Vault simply supplies seed banks with copies of seeds that those banks lost by accident, the Seed Vault will be worth more than it cost.”

    Cancer researchers urged people on Wednesday to take more vitamin D to lower risk of cancer, saying studies showed a clear link. “Our suggestion is for people to increase their intake, through diet or a vitamin supplement. ” Dr.Cedric Garland said in a telephone interview.

    Garland's research team reviewed 63 studies, including several large long-term ones, on the relationship between vitamin D and certain types of cancer worldwide between 1966 and 2004.

    “There's nothing that has this ability to prevent cancer,” he said, urging governments and public health officials to do more to fortify foods with vitamin D. Garland is part of a University of California at San Diego Moores Cancer Center team that published its findings this week online in the American Journal of Public Health. Vitamin D is found in milk, as well as in some fortified orange juice, yogurt and cheeses, usually at around 100 international units(IU) a serving. People might want to consider a vitamin supplement to raise their intake to 1000 IUs per day, Garland said, adding that it was well within the safety guidelines established by the National Academy of Sciences.

    The authors said that taking more vitamin D could be especially important for people living in northern areas, which receive less vitamin D from sunshine.

    African Americans, who don't produce as much of the vitamin because of their skin colour, could also benefit significantly from a higher intake, the authors said.

    If you see a group of people dancing and singing on the street or in the railway station, you don't need to feel surprised. They are a flash mob(快闪族), which is a group of people who come together suddenly in a public place, do something unusual for a brief period of time, and then quickly break up. They are usually organized with the help of the Internet or other digital communication network. At a predetermined(预先决定的) time, they gather and perform some distractions(消遣) such as waving their hands and exchanging books. Then, they quickly break up before the police can arrive. Using mobile phones, the flash mob can change its location if the first one has been replaced for any reason.

    Bill Lasik, senior editor of Harper's Magazine, organized the first flash mob in Manhattan in May 2003 and the first successful flash mob came together on June 3, 2003 —after the first attempt failed at Macy's department store. Lasik claimed that the activity was designed to make fun of hipsters(赶时髦的人), and call attention to the cultural atmosphere.

    Flash mob gatherings can sometimes shock people. Such an activity might seem amusing and untrue, but it also might frighten people who are not aware of what is taking place. Undoubtedly, flash mobs can serve as good political tools in any direction. They also have great economic potential, such as using flash mobs to advertise a product.

    The flash mob is now becoming more and more popular. People use it to do many things. For example, in 2009, Michael Jackson's fans took part in a flash mob to remember him. Hundreds of his fans gathered singing and dancing Michael's famous song “Beat It” together. Flash mobs give people from all walks of life an opportunity to come together to create a memory.

    The national environmental watchdog has declared that boosting efforts to cut air pollution in northern China, especially winter smog from the burning of coal, is a mission for this year.

    Burning coal for winter heating has been listed as one of the primary causes of air pollution, Chen Jining, minister of environmental protection, said on Monday at the annual meeting on environmental protection in Beijing.“As much as 60 percent of smog content is caused by coal burning in the starting phase of each smog”, said Fang Li, an official with Beijing's Environmental Protection Bureau. Therefore, Beijing has declared that it will wipe out coal use in its most rural areas by 2020.

    To start with, Beijing will replace coal-fired heating stoves with those powered by electricity or gas in 400 villages this year, before taking the campaign to the districts of Chaoyang, Haidian, Fengtai and Shijingshan by 2017,said Guo Zihua, a municipal rural development official. Beijing's downtown districts of Dongcheng and Xicheng eliminated coal burning last year, officials said.

    The capital and other places in northern China experienced several smog alerts in November and December, when peak readings were many times higher than the national safety level. Obviously, the situation is deteriorating, and will become a norm. So the government came up with a “smog subsidy (津贴)” for those who work outdoors, and 95 percent of the respondents to a survey support it.

    The Trade Union in Zhengzhou City surveyed subscribers to its official WeChat account and found that 88 percent of nearly 400 respondents said priority should be given to outdoor workers on smoggy days But 9 percent said air pollution affects everyone so it would be unfair to only address the concerns of people who work outdoors.

    Over half of the respondents think the extra subsidy, if applied, could come in the form of protective tools or cash. Twenty-two percent said money is the easiest way. To finance the proposed subsidy, 53 percent think the government and companies should jointly pay the bill, while 44 percent said central and regional governments should be responsible.

    It is commonly believed that in medieval France, New Year was celebrated on 1 April. Then in 1562, Pope Gregory introduced a new calendar for the Christian world, changing New Year to 1 January. With no modern communications, news travelled slowly and new ideas were often questioned. Many people did not hear of the change, some merely forgot, and others chose to ignore it. These people were called fools. Invitations to non-existent "New Year" parties were sent and other practical jokes were played. Over time playing tricks on 1 April became a tradition. The custom eventually spread to England and Scotland, and it was later transported across the Atlantic to the American colonies (殖民地) of the English and the French. April Fools' Day has now developed into an international festival of fun, with different nationalities celebrating the day in special ways.

    France and Italy

    In France and Italy, if someone plays a trick on you, you are the "fish of April". By the month of April fish have only just hatched and are therefore easy to catch. Children stick paper fish to their Friends' backs and chocolate fish are found in the shops.

    America and Britain

    Today, Americans and the British play small tricks on friends and strangers alike on 1 April. A common trick is to point to a friend's shoe and say "Your shoelace (鞋带) is untied." When they look down, they are laughed at. Schoolchildren might tell a friend that school has been cancelled. Sometimes the media get involved. Once, a British short film was shown on April Fools' Day about spaghetti farmers and how they harvest their crop from spaghetti trees!

    Scotland

    In Scotland, April Fools' Day lasts for two days! The second day is called "Taily Day" and tricks on this day involve the bottom (or the "tail", in informal speech). Often a sign saying ‘kick me' is stuck onto someone's back without them knowing.

    When it comes to medical care, many patients and doctors believe "more is better." But what they do not realize is that overtreatment—too many scans, too many blood tests, too many procedures—may bring harm. Sometimes a test leads you down a path to more and more testing, some of which may be invasive, or to treatment for things that should be left alone.

    Terrence Power, for example, complained that after his wife learned she had Wegener's disease, an uncommon disorder of the immune system, they found it difficult to refuse testing recommended by her doctor. The doctor insisted on office visits every three weeks, even when she was feeling well. He frequently ordered blood tests and X－rays, and repeatedly referred her to specialists for even minor complaints. Even when tests came back negative, more were ordered, and she was hospitalized as prevention when she developed a cold. She had as many as 25 doctor visits during one six－month period. The couple was spending about $30,000 a year for her care.

    After several years of physical suffering and near financial ruin from the medical costs, the couple began questioning the treatment after discussing with other patients in online support groups. "It's a really hard thing to determine when they've crossed the line," Mr. Power said. "You think she's getting the best care in the world, but after a while you start to wonder: What is the purpose?" Mr. Power then spoke with his own primary care doctor, who advised him to find a new specialist to oversee Mrs. Power's care. Under the new doctor's care, the regular testing stopped and Mrs. Power's condition stabilized. Now she sees the doctor only four or five times a year.