Nowadays, parents worry a lot because their children spend hours and hours in front of the TV screen. Because this doesn't happen to only one specific family, many experts warn us that there can be some serious effects of children watching violence on television.

    Children who become addicted(上瘾的) to TV sit down and turn on the TV as soon as they get home. Although they have lots of homework, they become absorbed in TV programs.

    Since they spend tons of time watching TV, they have less time to enjoy real life activities such as playing with friends, playing outdoor sports, or enjoying other kinds of entertainment.

    There are too many violent scenes on TV. Some experts say there are 25 acts of violence per hour on TV. In addition, there are many experiments by psychologists which show how TV violence influences children. Finally, people worry that children tend to imitate what they watch on TV and may start to behave more violently.

    What should be done? First of all, the government should regulate TV violence. It should also encourage people to invent and develop new technology which can block violent scenes from the programs children watch. For example, with a rating system(分级制度) and the V-chip, unfit scenes of violence and sex can be blocked out. Second, parents should monitor what their children watch. At the same time, they should make their children interested in real life activities. Then when the children start to spend more time playing with friends or reading books, parents can stop their monitoring.

    It is a fact that there is more violence on TV today than there was ten years ago. Moreover, violent incidents occur more frequently in real life. It's time to realize how harmful watching TV violence is, and it's time to keep our children from watching violence.

    Like people, plants experience stress. And also, like people, the response to that stress can determine success.

    Bad environmental conditions, such as drought, flood, heat and other stresses, affect yields (产量) more than crop pests and diseases. We are trying to find a way to equip plants with the ability to tolerate environmental stress and maintain high yields, said Stephen Howell, a professor of genetics and cell biology.

    Plant cells produce proteins (蛋白质) and ship them to different parts of the cell. Under normal conditions, these proteins are folded into their normal, healthy structures as they are produced. When a plant is under stress, its cells produce poorly folded or unfolded proteins. Then a built-in system senses this and “sets off an alarm in the cell,” said Howell.

    In response to the alarm, another protein (IRE1) starts working and creates a different process which activates (激活) the stress response genes whose products bring about defensive measures that help the plant survive.

    “As it turns out, responses that are activated under stress conditions actually inhibit the growth of plants,” said Howell. “This allows them to preserve their energy to survive the stress conditions.”

    For plants in the wild, this response is a help for survival, he said. In production of agriculture crops, however, this response reduces yields.

    “You don't want crop plants to stop growing,” Howell said. “You want them to continue to grow and produce even though they are under stress.”

    With the new understanding of this stress response, the next step may be to silence the alarm system, said Howell. “What may be important is to disable some of these stress responses. That may make the plant more productive under stress conditions.”

    San Francisco has long been a favorite place for travelers who are ready to learn languages. The mild (温和的) year-round climate, shops and restaurants, bars and night life, and some of the most beautiful scenery attract many visitors to this relaxing and welcoming city. Students are sure to find the San Francisco Bay Area a fun, safe and friendly place to live and study. This is the most important.

    English School in San Francisco lies in the heart of the city. It is one of the best San Francisco English language schools. You can see views of the city from your classroom! Many buses stop less than a five-minute walk from the school, which is also just a two-minute walk from the famous Union Square, San Francisco Shopping Centre, the Financial District, Yerba Buena Gardens and the Museum of Modern Art. The school is minutes away from the cable cars (缆车) to Chinatown and Fisherman's Wharf.

    San Francisco is a great place to study English and learn about American culture, offering excellent opportunities in sports, entertainment and arts. The city borders (毗邻) excellent beaches, and you can sail or surf all year round.

    San Francisco has more restaurants than any other city in the US, and is the home of many theaters, music and dance companies, as well as museums. Just walking through many areas of San Francisco, you are certain to find something wonderful.

    Two hundred years ago the English poet William Wordsworth wrote "I wander'd Lonely as a Cloud", a poem that expresses a basic spirit of early English Romanticism.

    What makes this poem an example of Romantic thinking? It isn't just that Wordsworth chooses to write about natural scene：it is the way he describes the scene as if it had human emotions. For him, nature is not only a neutral (无感情色彩的) mixture of scenery, colours, plants, rocks, soil, water and air. It is a living force that feels joy and sadness, shares human pain and even tries to educate us human beings by showing us the beauty of life.

    Wordsworth's home, Dove Cottage, is now one of the most popular destinations in the Lake District. You can go on a tour of the garden which William planted with wild flowers and which survived in his backyard even after they disappeared from the area "He always said that if he hadn't been a poet, he would have been a wonderful scenery gardener," says Allan King of the Wordsworth Trust.

    The place near Ullswater, where Wordsworth saw the daffodils(水仙花), is at the southernmost end of the lake. The lake is wide and calm at this turning point. There's a bay where the trees have had their soil eroded(侵蚀)by lake water so that their roots are shockingly exposed. You walk along from tree to tree, hardly daring to breathe, because you are walking in the footprints of William from two centuries ago. The first group of daffodils appear, but they aren't tall yellow trumpets(小号状的花)proudly swinging in the gentle wind. They're tiny wild daffodils, most of them still green and unopened, in groups of six or seven. They're grouped around individual trees rather than collecting together.

    But as you look north, from beside a huge ancient oak, you realize this is what delighted Wordsworth: group after group of the things, spread out to left and right but coming together in your sight so that they form a beautiful, pale-yellow carpet. What you're seeing at last is nature transformed by human sight and imagination.

    Alexa is a form of artificial intelligence, or AI for short. Many people start their mornings by asking Alexa for the weather forecast or the latest news. A device(设备) that houses Alexa can also play music from your favorite playlists, keep a shopping list, order takeout food, answer questions, send messages and even run “smart” home controls.

    Training AI systems to respond to problems with human-like intelligence and learn from their mistakes can take months, or even years. Consider Alexa and similar software, such as Apple's Siri. To do the tasks its human owners ask, these systems must make sense of and then respond to sentences such as, “Alexa, play my Ed Sheeran playlist” or “Siri, what is the capital of India?”

    Computers can't understand language as it is spoken by people. So AI researchers must find a way to help humans communicate with computers. The technology used to get computers to “understand” human speech or text is known as natural language processing. By natural language, computer scientists refer to the way people naturally talk or write. To teach an AI system a task like comprehending(理解) a sentence or responding to a person 's last move in a board game, scientists need to feed it lots of examples.

AlphaGo is an AI system designed by Google that has beaten a human champion, Lee Sedol, at the strategy(策略) board game Go. To train AlphaGo, Google had to show it 30 million Go moves that people had made while playing the game. Then AlphaGo used what it learned to analyze those plays as it played against different versions (版本) of itself. During this practice, the program came up with new moves—ones never seen in games between people.

    Skiing has always been a big part of Kamikaze shiffrin's life. Her dad ski raced all through college and her mom raced and coached skiing. The Siffrins taught Mikaela and her brother, Taylor. To ski at a very young age. At two and a half years old, Mikaela made her first ski run down her driveway on plastic skis.

    Mikaela loved skiing. From ages 8 to11, she did hundreds of training runs on small hills to learn the skills of slalom skiing (障碍滑雪). When Mikaela was 11, she began to learn at the Burke Mountain Academy, a Vermont boarding school for skiers. She took classes, studied, and practiced her skiing. According to Burke Mountain Academy headmaster Kirk Dwyer, "What separated Mikaela from others was the degree of her commitment (投入) to be the best. Mikacla practiced more than anyone and believed in herself then and now." At age 14, Mikaela began her international career when she raced in the world championship for13 and 14 -year-olds. And she won!

    By the time she was17, she had already won her first World Cup race. "Living away from home four and five months at a time can be difficult" Mikaela says. "But it can also be exciting. I'm getting to see the world." When Mikaela began ski racing in Europe, her mother, Eileen, stayed with her. She worked as her high school teacher while they were on the road. "She has always been a super-hard worker," says Eileen.

    For Mikaela, working hard is a full-time job. Even her off-season is work time. "If you want something, just try your best," she says. At the 2014 Winter Olympic Games in Sochi, Russia, 18-year-old Mikaela Siffrin became the youngest slalom skier ever to win an Olympic gold medal.