Reducing the amount of sleep affects students' performance at school. An American study asked schoolteachers to look at the effects of sleep restriction（限制） on children between six and twelve years of age. The teachers found that children who stayed up late had trouble thinking clearly and had more learning problems.

    {#blank#}1{#/blank#} Doctor Fallone now works at the Forest Institute of Professional Psychology in Springfield, Missouri. He presented the results last month at a science reporter conference in Washington, D. C. The Publication Sleep also reported the findings.

    The teachers were asked to complete weekly performance reports on seventy-four schoolchildren. The study lasted three weeks. During that period, Doctor Fallone and his team controlled the amount of sleep the children received.

    {#blank#}2{#/blank#} During another week, every child was kept awake later than normal. Each night, the youngest boys and girls had less than eight hours of sleep. The older ones were limited to six and a half hours. During the final week of the study, each child received no less than ten hours of sleep a night.

    The teachers were not told about how much sleep the students received. The study found that students who received eight hours or less had the most difficulty remembering old information. {#blank#}3{#/blank#}

    The study did not find that sleep restriction caused hyperactivity(极度活跃) in the children. {#blank#}4{#/blank#}

    Doctor Fall one said that the results provided experts and parents with a clear message: {#blank#}5{#/blank#}

    Our planet is home to about seven billion people. Since the 1990s, population experts have predicted the number would grow to nine billion before it begins to slow down and possibly decrease.

    But a new report predicts the world's population is likely to increase to almost 11 billion by 2100. Based on the most modem statistical tools, the new report makes use of government records and considers expert predictions, including death rates, birthrates and international migration, or people moving across borders. The report says during the rest of this century, Africa's population will grow from about 3.5 billion to 5.1 billion over the next 85 years.

    John is director of the United Nations Population Division. He says that in the past, researchers thought population growth in Africa would be similar to that of other areas. They expected slower growth rates as birth control use became more widespread. But he says those ideas were wrong.

    “The level of contraception use has continued to increase but slowly — more slowly than expected, and birthrate therefore has been falling less rapidly than expected, and the population therefore continues to grow somewhat more rapidly than we expected.

    The new findings are based on a joint research project of the United Nations and the University of Washington,

    The researchers believe the population of Asia will reach five billion by 2050. That is up from the current 4.4 billion. And then begin decline. The researchers also believe that North America, Europe, Latin America and the Caribbean area will have a total population of below one billion.

    John says the pressure of feeding the rising population is likely to be less than that might be expected.

    “The relatively good news is that the world has been winning the race between population growth and food production. If you look back historically over the last 50 years, certainly for the world as a whole and for many, most individual countries and regions, the increase in food production has outpaced the increase of population.”

    Ever since I was a kid I had a 6 second rule.That means that if I had something I needed to do but didn't want to, I'd count till 6 and do it anyway.My personal rule was to just never ever break that rule,that at 6,I HAD to get it going.Most of the time I'd use it to get out of bed or get out of the bath.Sometimes I'd also use it to restrict my time playing "ok in 6 seconds I'll stop playing with my dolls."

    As I grew older,I'd use it as a motivation to get it going with my homework,get off messenger,etc.It really worked well,the same rule applied;whatever happens,don't cheat the "rule of 6." Most of the time,I wouldn't even have to count till 6 because I knew it would just mean I have to do it,so I'd just do it anyway.As an adult,I've pretty much conditioned myself to do things by the rule of 6.I've pretty much mastered most usual things in my life but the rule of 6 never fails me when I start something new.Exercising,running,getting cooking,starting reading,it just works for me.

    At the time,when I was 6,6 was my favorite number.So just go ahead and pick a number from 1-10 (although Id suggest 3-10) and try it.The important thing is not just to let yourself down.Like any other trick,it only works if you allow it to.

    In Kansas City, Missouri, a computer helps firefighters. The computer, which works very fast, has information about all the 350, 000 street addresses in the city. Within two or three seconds after a call is received, the computer provides necessary information for the firefighters. The information is then sent to them by radio from the computer centre in the City Hall. The exact place of the burning building and its size, type and any other details are clear to them.

    The Kansas City computer system also has a medical record of each of the city's 900 firefighters. This kind of information is especially useful when a firefighter is injured. With the information, doctors at hospital can treat the injured firefighters more quickly and easily.

    The firefighters themselves greatly appreciate the computer's help. They know about possible danger ahead of them and can prepare for it. Many times the computer information helps to save lives and property (财产). Sometimes the lives are those of firefighters themselves.

    Mike Horan, a firefighter captain, says, "I feel as if the computer is ready to help me if I get hurt."

    Stephen Hawking is one of the most famous scientists in this century. He was born in 1942. He's world well-known on space and time. Stephen was searching some very big questions, such as "How did the universe begin? How will it end?"

    Stephen was a student at Oxford University. He studied math and science. Then, at the age of twenty, he became sick. He was so young, but the doctors said to his family, "He has only two more years to live." As a matter of fact, the doctors were wrong – he didn't die. He can't walk but he uses a wheelchair. He can't feed himself and get in or out of bed himself. But he refused to give in to the condition. He talks with the help of a computer. After Oxford, Stephen went to Cambridge University. Three years later, in 1965, he became a doctor of philosophy(哲学).

    Because of his serious health problems, it was difficult for him to draw or to write. So he started to think in pictures. With this new way of thinking, he became one of the most famous scientists in the world. In 1981, he met the Pope(教皇) in Rome. They talked about his ideas. Then in 1988, he wrote his first important book, A Brief History of Time. It sold more than 5.5 million copies in 33 different languages. He was once invited to China, he impressed us with his self-confidence, humorous and witty(风趣的) conversation.(谈话)

    Antarctica has become one of the world's most popular tourist destinations. Since 1969, the average number of visitors to the continent has increased from several hundred to over 34,000 today. All activities in Antarctica are heavily supervised by the Antarctic treaty for environmental protection purposes and the industry is largely managed by the International Association of Antarctica Tour Operators (IAATO).

    The first expedition (探险) to Antarctica with travelers was in 1966, led by Swedish explorer Lars Eric Lindblad. He wanted to give tourists first-hand experience of the ecological sensitivity of the Antarctic environment, in order to educate them and promote a greater understanding of the continent's role in the world. In 1969, Lindblad built the world's first expedition ship, the MS Lindblad Explorer, which was specifically designed to transport tourists to Antarctica.

    In 1977, both Australia and New Zealand started to offer scenic flights to Antarctica through Qantas and Air New Zealand. The flights often flew to the continent without landing and returned to the departure airport. The experience was an average 12 to 14 hours with up to 4 hours of flying directly over the continent. The flights from Australia and New Zealand stopped in 1980. It was largely due to the Air New Zealand Flight 901 accident on November 28, 1979. In 1994, flights to Antarctica continued again.

    Despite the potential dangers and risks, trips to Antarctica continued to grow. According to IAATO, 34,354 travelers visited the continent between 2012 and 2013. Americans contributed to the largest share with 10,677 visitors, or 31.1%, followed by Germans 11.1%, Australians 10.7%, and the British 10.2%. The rest of the visitors were from China, Canada, Switzerland, France and elsewhere.

    The cost of a trip to Antarctica can range from as little as $3,000-$4,000 to over $40,000, depending on the scope of transportation, housing, and activity needs. The higher end packages typically involve air transport, on-site camping, and a visit to the South Pole.