You can tell a lot about people by looking at their hair – not just whether they brush, spray or blow-dry. Scientists have found a way to use hair to figure out where a person is from and where that person has been. The finding could help solve crimes, among other useful applications.

    Water is central to the new technique. The liquid makes up more than half an adult human's body weight. Our bodies break water down into hydrogen(氢) and oxygen. Atoms of these two elements end up in our tissues, fingernails, and hair.

    But not all water is the same. Hydrogen and oxygen atoms can vary in how much they weigh. In the case of hydrogen, for example, there are three types according to their weights. Each type is called a hydrogen isotope（同位素）. And depending on where you live, tap water contains different isotopes.

    Can hair record this information? That's what James R. Ehleringer, an environmental chemist at the University of Utah, wondered. To find it out, he and his colleagues collected hair from hair stylists in 65 cities across the United States. Even though people drink a lot of bottled water these days, the researchers have found that people's hair has the same isotopes as found in local tap water. That's probably because people usually cook their food with the local water.

    Authorities can now use the information to analyze hair samples from criminals or crime victims and narrow their search for clues. For example, one hair sample used in Ehleringer's study came from a man who had moved from San Francisco to Salt Lake City. As his hair grew, it reflected his change in location.

    All languages change over time, but some change at a faster rate than others. {#blank#}1{#/blank#} The most important factors are the number of people who speak a language, where they live and whether they move around, the importance of the language for world trade and communication, and changes in technology.

    {#blank#}2{#/blank#} However, today English is the most widely used language in the world. English is spoken by about 350 million people as a first language in countries such as Great Britain, the United States. In addition, about a billion more people speak English as a second language.

    English started to take over French as an international language during the period of British colonialism (殖民主义) when the English ruled many countries in Africa and Asia. {#blank#}3{#/blank#} The colonial period came to an end at the same time that several other changes occurred. For example, the U.S. started to play a greater part in global affairs and the international economy. New means of communication technology such as television and the Internet spread English worldwide. {#blank#}4{#/blank#} In addition, they could use the Internet for information, business, or e-mail communication, all in English. Just as the use of English spread, other languages changed English by contact or by new inventions and technology.

    In contrast, Icelandic is a language that has changed very slowly. Icelandic speakers today can understand poetry written in a slightly different dialect over 1,000 years ago! Why has Icelandic changed so slowly? The main reason is the isolated (孤立的) location of the island in the middle of the Atlantic Ocean. {#blank#}5{#/blank#} Compared to England, Iceland had no history of colonialism. Iceland's small population has not played a major role in international trade or communication. Today, most Icelanders speak English in addition to their native language. With outside influences, Icelandic is changing more rapidly now.

A. People everywhere could watch the news or sports events in English.

B. These changes have a great influence on the development of society.

C. Isolation meant that for hundreds of years, Icelanders had little contact with speakers of other languages.

D. What are some of the factors that influence how quickly a language changes?

E. The language communication brings about the communication of technology.

F. In the past, other languages such as Latin or French were more important than English.

G. English was the primary means of communication in these colonies.

    We brush our teeth daily, but do you know everything you need to know about dental care and hygiene? Believe it or not, there is a lot more than most people realize. Luckily, here are several apps that can help you.

●Brush DJ

    You should brush your teeth for full two minutes as recommended by dentists, but that time can be difficult to judge. Many recommend you listen to music, because many songs are just around two minutes in length. Brush DJ has loads of great tunes that will get you into the two­minute habit. There are both songs to listen to, and videos to watch, and you'll find a variety of awesome tunes.

●Orasphere

    It's recommended that Orasphere videos be used by dentists for their patients, so they can learn about procedures. Those who do use these videos say that the software can greatly decrease the amount of time it takes to explain procedures to patients.

●American Dental Association(ADA)

    Everything you ever wanted to know about your teeth, and then some, can be found on the American Dental Association(ADA) website. You'll find loads of great articles that have the latest news about dentistry（牙科）. Those interested in dental careers will find plenty of information to head them in the right direction, and there's even a section devoted to public dental programs, including Give Kids a Smile and Fluoride in Water.

●DDS GP

    Here is more presentation software that explains all types of dental procedures. This is helpful for dentists to have, because they can better explain procedures to their patients.

●Dentistry IQ

    You can find information for dentists, hygienists, assistants, office managers, and more at Dentistry IQ. You can also get information about new products, clinical practices, and much more. In addition, you can learn about career opportunities, the most recent practices, and a whole lot more.

    On Aug 29, 1988, the University of Wisconsin-Madison juniors Tim Keck and Christopher Johnson published the first-ever issue of The Onion. The two founders claimed it was the “finest news source” in the US. 25 years later, the news has become one of the most established media presences in the US. But don't expect accuracy and timeliness from it, because The Onion only publishes fake news or news satire (讽刺). Its aim is to make readers laugh and see things from a different angle.

    Will Tracy, The Onion's editor-in-chief, told the NPR in an interview. “The stories are presented in that sort of news voice which improves the news to a certain level of importance. The news isn't actually understandable but it has an ability to elegantly locate a problem with concise and plain words.” For example, when George W. Bush became the US president in 2001, The Onion published a satire piece predicting massive debt and a huge growth in military spending. The headline said it all—Bush: “Our long national nightmare of peace and prosperity is finally over”.

    Traditional media outlets are cautious when reporting sensitive topics such as religion and race. Tracy says/‘Nothing is off limits for The Onion, no matter how uncomfortable they may make some readers.” But editors at The Onion do stand a fine line, as Tracy explains: “What you have to be really careful about is what the target of the joke is. If the target of the joke is wrong, then it doesn't feel right and it also doesn't feel funny.” The Onion made the public outrageous when earlier this year, it tried to make fun of a 9-year-old Oscar-nominated (奥斯卡提名的) actress by using highly impolite language. It later apologized.

    Anyone who has ever played the game of Tetris (俄罗斯方块) knows the game's surreal ability to spill into real life. After you shut off the game, you still see those Tetris blocks falling in your mind. You're grocery shopping and find yourself thinking about rearranging items on grocery shelves. Your mind continues to play the game, even when you're physically not.

    Robert Stickgold, a Harvard professor, noticed something similar after a day hiking a mountain. That night, he dreamt he was still going through the motions of mountain hiking. Curious about this, he tried something: he got a group of college students of various skill levels to play Tetris and let them sleep in the Harvard sleep lab.

    Over 60% of the students, including those who suffered from amnesia (健忘症), reported dreams of images of Tetris pieces falling, rotating (旋转), and fitting together. Interestingly, half the Tetris expert students reported such Tetris dreams, while 75% of the beginners did.

    A study found that playing Tetris can grow your brain and make it more efficient. Adolescent girls played the game for an average of 1.5 hours a week over three months. The cerebral cortex (大脑皮层) of the girls grew thicker, while brain activity in other areas decreased. Richard Haier, who had found that there was a "Tetris learning effect", in which the brain consumed less energy as mastery of the game rose, concluded, "The brain is learning which areas not to use."

    Haier's study showed that as the girls practiced playing the game, nerve cells made connections, communicating through synapses (a synapse is a connection between two nerve cells). When you learn something, you change those connections. Every time you reactivate(激活) a circuit, synaptic efficiency increases, and connections become more durable and easier to reactivate. Stickgold says sleep plays a role in this memory process.

    So to sum up, whenever you do specific tasks over and over again, they take up less of your brain power over time. And that's pretty amazing.

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