Sleep is something we all do. But some people need to sleep more than others. Babies sleep most of the time. Children in school sleep about ten to twelve hours a night. Most adults sleep only seven or eight hours.{#blank#}1{#/blank#}All parts of our bodies have to rest after they work.. Our arms need a rest after we lift heavy thing, When we run fast, our legs work hard. They get tired. We have to rest them. Our brains workhard, too.{#blank#}2{#/blank#} We can sit quite still and rest our arms andlegs. But our brains aren't resting. They go right on thinking as long as weare awake.

      Our brains slow down a bit when we sleep and dream.{#blank#}3{#/blank#} Instead of thinking wide-awake thoughts, our brains make up dreams. Some dreams are very pleasing. Some are not. Most of thetime we forget them when we wake up.

      Scientists have tried to find out what would happen if people were not allowed to sleep. They asked some people not to go to bed. The people stayed up all night and all the next day. They stayed up the next night too,and the day after. They played games, but they made mistakes. They forgot things.{#blank#}4{#/blank#} The people grew rude and mean. They became angry with their friends. Finally they were too tired to stand up. When they sat down, they fell asleep.

Scientists have found that if people are not allowed to sleep and to dream, they act in an unusual way.{#blank#}5{#/blank#}But we do know that we need it to stay well. So tonight have a goodsleep. Lie down under the covers. Shut your eyes. Let your thoughts wander.Soon you'll stop thinking. You'll be asleep.

A. It was hard for their tired brains to work.

B. When we are awake, they help us pay attention to the worldaround us

C. But babies, children, and adults—all of us need to haveour sleep

D. Good sleep helps to improve one's memory

E. No one knows why sleep is so good for us

F. But even as we sleep our brains are doing some work

G. Of course you will have a good sleep

    At first, muffled (听不太清的)conversations made researchers at a San Diego aquarium puzzled, but when a diver thought he was being told to get “out” of the water they realized the conversations were coming from a white whale.

    Noc was about one year old when he was caught off the Pacific coast of Canada. He was kept in an open-ocean pen (围栏) at the US National Marine Mammal Foundation in San Diego, California. After seven years at the Foundation, he began, automatically, to make unusual sounds, a report in the latest issue of the journal, Current Biology, said.

    “We thought of the whale' s vocalizations(发出的声音) as an attempt to imitate humans. Whale vocalizations often sounded as if two people were talking just out of the range of our understanding,” the authors said. “ 'These conversations' were heard several times before we finally realized the whale was the source.” The researchers realized it was Noc when a diver surfaced and asked, “Who told me to get out?” It was then that they realized the word “out”, which was repeated several times, had come from Noc. Later, his speech-like sounds were recorded in the air and underwater.

    Noc started making the sounds after seven years in the open-ocean pen, and continued making them for another four years. He died five years ago. Researchers have now analyzed the sound recordings. It was the first time that sound recordings had shown how such sounds imitated speech and were different from the usual calls of the species.

    The speech-like sounds were lower than normal whale sounds and much closer to those of the human voice. Also, whales talk to each other by blowing air through their noses, rather than using a larynx(喉), as people do.

    “We don't claim that our whale was a good imitator compared to such well-known imitators as parrots,” the researchers said. “However, the behavior we observed is an example of vocal learning by the white whale. It seems that Noc's close association with humans played a role in how often and how well he employed his human voice.”

Excellent Smartphone Apps

    Space

    Space helps you set goals to be more mindful of your screen usage. When you install（安装）Space, you'll complete a few questions about your smartphone habits and then select a user type that is the best match. The app then sets screen unlock and time-use goals. The app will send notices as screen time increases and reward you with different badges（徽章）when you meet your goals.

    AntiSocial

    AntiSocial is one of the best-known screen-reduction apps available on Android. While it provides many of the standard functions like screen time limits and app blocking, it has an advantages. AntiSocial compares your screen usage data（数据）to other people in your age, so you'll an idea if you're using your phone more than they do.

    Off the Grid

    For those who truly have a problem staying off that phone, Off the Grid may be for you. Off the Grid completely blocks your phone for a length of time you determine. If you want to use your phone after you're turned on Off the Grid, it's going to cost you. The app will charge you $1 each time you end your off-time early.

    The city of San Francisco is a wonderful tourist attraction that offers many different things to see and do. The best way for a traveler to get a good look at the city is to take one of the many different tours there

    Walk to Tour the City

    When touring the city by walking, you aren't going to walk much. What's more, there are far more benefits. This kind of tour allows you to see as many buildings of the city as possible. A tour of the city on foot usually focuses on a more localized neighborhood level, which can be very interesting in a number of different ways.

    Hit the Waters of San Francisco Bay

    The waters of San Francisco Bay have played an important role in the city's development over the last century. Touring San Francisco from the water is completely unique way for you to see this wonderful city.

    Take a Bus Tour

    If you want to see a wide variety of attractions from all over the city, one of the best things you could do is to book a tour through our company that offers services here. A bus tour of San Francisco is one of the most complete ways to experience the city

    Tour San Francisco From the Air

    While it is one of the most expensive ways to see San Francisco, touring the city from the air is one of the most unique and exciting ways to see the city. Seeing the city from high above allows you to get a full view of the city as tour guides point out attractions from high above. If you do decide to tour San Francisco by air, you'll be creating memories that you won't forget forever.

    We are a travel agency providing high-quality services and discounts. For more information, please click here.

    In the U.S. state of Washington, a road called ^Interstate 90^ cuts through a wild, mountainous area to reach the city of Seattle. For the area's many kinds of animals, the busy highway greatly limits their movements. Crossing 1-90—as the road is called—is a risky but sometimes necessary act. But soon, animals will have a safer choice for crossing the road. They will be able to go above it.

    To help the animals, the state is finishing work on its largest-ever wildlife bridge. The 11-meter-tall, 20-meter-wide structure begins in the forest. It forms two arches above the highway, one for each direction of traffic. Workers are adding fencing and plants to help guide the animals across the bridge. Two-meter-thick walls will help block noise from vehicles below.

    The 1-90 Bridge is part of a growing number of wildlife crossings across the United States. Some are fences, some are overland bridges, and some are underpasses. They all aim to keep drivers and animals away from each other. Collisions between animals and drivers are rarely deadly to people. But they are often deadly to wildlife. In Canada's Banff National Park, studies have found that wildlife crossings reduce the area's animal-driver collisions by 80 percent.

    Most of the wildlife bridges are in western states. But experts have noted many other areas that have a need for such paths. Jen Watkins, whose organization has helped campaign for animal crossings, says finding for more crossings is "the number-one barrier."

    Patty Garvey-Darda of the U.S. Forest Service has worked on the 1-90 crossing from the start of the project. She says the $6- million bridge will one day pay for itself because the highway will not have to be fully or partly closed each time a large animal is struck. She said, ^"If you shut down Interstate 90, you shut down interstate commerce."

    Everything about nuclear energy seems terrifically big: the cost, construction and decommissioning—and the fears of something going badly wrong.

    The future, however may well be much smaller. Dozens of companies are working on a new generation of reactors that, they promise, can deliver nuclear power at lower cost and reduced risk.

    These small-scale plants will on average generate between 50MW and 300MW of power compared with the 1,000MW-plus from a conventional reactor. They will draw on modular manufacturing techniques that will reduce construction risk, which has plagued larger-scale projects. Supporters believe these advanced modular reactors (AMRs)—most of which will not be commercial until the 2030s—are critical if atomic power is to compete against the rapidly falling costs of solar and wind.

    "The physics hasn't changed. It's about much cleverer design that offers much-needed flexibility in terms of operation," said Tim Stone, long-term industry adviser and chairman of Nuclear risk Insurers, which insures nuclear sites in the UK.

    Since the Fukushima meltdown in Japan in 2011, safety fears have threatened nuclear power. But the biggest obstacle today is economic. In western Europe, just three plants are under construction: in the UK at Hinkley point in Somerset; at Flamanville in France; and at Olkiluoto in Finland. All involve the European Pressurized Reactor technology of EDF that will be used at Hinkley Point. All are running years late and over budget. In the US, the first two nuclear projects under way for the past 30 years are also blowing through cost estimates.

    The UK, which opened the world's first commercial nuclear reactor in 1956, is one of the few western nations committed to renewing its ageing fleet to ensure energy security and meet tough carbon reduction targets. It is seen as a proving ground, by many in the industry, of nuclear power's ability to restore confidence.

    However, the country's agreement with EDF to build two units at Hinkley Point—which together will generate 3.2GW of electricity—has come under severe criticism over its cost. The government is looking at different funding models but said it still sees nuclear power as vital to the country's future energy mix. Small reactors, it believes, have the potential to generate much-needed power from the 2030s.

    A nuclear sector deal, unveiled last month, promised up to ￡56m in funding for research and development into AMRs and attracted interest of start-ups from around the world. The government hopes the funding will give the UK a lead in the global race to develop these technologies, helping to provide energy security while also creating a multibillion-dollar export market for British engineering companies.