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第一篇 Light Night, Dark Stars Thousands of people around the globe step outside to gaze at their night sky. On a clear night, with no clouds, moonlight, or artificial lights to block the view, people can see more than 14,000 stars in the sky, says Dennis Ward, an astronomer (天文学家) with the University Corporation for Atmospheric Research (UCAR) in Boulder, Colo. But when people are surrounded by city lights, he says, they’re lucky to see 150 stars. If you’ve ever driven toward a big city at night and seen its glow from a great distance, you’ve witnessed light pollution. It occurs when light from streetlights, office buildings, signs, and other sources streams into space and illuminates (照亮) the night sky. This haze (薄雾) of light makes many stars invisible to people on Earth. Even at night, big cities like New York glow from light pollution, making stargazing difficult. Dust and particles of pollution from factories and industries worsen the effects of light pollution. "If one city has a lot more light pollution than another," Ward says, "that city will suffer the effects of light pollution on a much greater scale." Hazy skies also make it far more difficult for astronomers to do their jobs. Cities are getting larger. Suburbs are growing in once dark, rural areas. Light from all this new development is increasingly obscuring (使变模糊) the faint (微弱的) light given off by distant stars. And if scientists can’t locate these objects, they can’t learn more about them. Light pollution doesn’t only affect star visibility. It can harm wildlife too. It’s clear that artificial light can attract animals, making them go off course. There’s increasing evidence, for example, that migrating (迁徙) birds use sunsets and sunrises to help find their way, says Sydney Gauthreaux Jr., a scientist at Clemson University in South Carolina. "When light occurs at night," he says, "it has a very disruptive (破坏性的) influence." Sometimes birds fly into lighted towers, high-rises, and cables from radio and television towers. Experts estimate that millions of birds die this way every year. Nowadays even suburbs are becoming unsuitable for scientists to do their jobs because
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第三篇 Youth Emancipation in Spain The Spanish Government is so worried about the number of young adults still living with their parents that it has decided to help them leave the nest. Around 55 percent of people aged 18-34 in Spain still sleep in their parents’ homes, says the latest report from the country’s state-run Institute of Youth. To coax (劝诱) young people from their homes, the Institute started a "Youth Emancipation (解放)" program this month. The program offers guidance in finding rooms and jobs. Economists blame young people’s family dependence on the precarious (不稳定的) labor market and increasing housing prices. Housing prices have risen 17 percent a year since 2000. Cultural reasons also contribute to the problem, say sociologists (社会学家). Family ties in south Europe - Italy, Portugal and Greece - are stronger than those in middle and north Europe, said Spanish sociologist Almudena Moreno Minguez in her report "The Late Emancipation of Spanish Youth: Key for Understanding". "In general, young people in Spain firmly believe in the family as the main body around which their private life is organized," said Minguez. In Spain - especially in the countryside, it is not uncommon to find entire groups of aunts, uncles, cousins, nieces and nephews (外侄/侄子) all living on the same street. They regularly get together for Sunday dinner. Parents’ tolerance is another factor. Spanish parents accept late-night partying and are wary of setting bedtime rules. "A child can arrive home at whatever time he wants. If parents complain he’ll put up a fight and call the father a fascist," said Jose Antonio G6mez Yanez, a sociologist at Carlos III University in Madrid. Mothers’ willingness to do children’s household chores (家务) worsens the problem. Dionisio Masso, a 60-year-old in Madrid, has three children in their 20s. The eldest, 28, has a girlfriend and a job. But life with mum is good. "His mum does the wash and cooks for him; in the end, he lives well," Masso said. Young people’s family dependence can be attributed to all the following factors EXCEPT
第二篇 Mind-reading Machine A team of researchers in California has developed a way to predict what kinds of objects people are looking at by scanning (扫描) what’s happening in their brains. When you look at something, your eyes send a signal about that object to your brain. Different regions of the brain process the information your eyes send. Cells in your brain called neurons (神经元) are responsible for this processing. The fMRI (functional Magnetic Resonance Imaging) (功能性磁振造影) brain scans could generally match electrical activity in the brain to the basic shape of a picture that someone was looking at. Like cells anywhere else in your body, active neurons use oxygen. Blood brings oxygen to the neurons, and the more active a neuron is, the more oxygen it will consume. The more active a region of the brain, the more active its neurons, and in turn, the more blood will travel to that region. And by using fMRI, scientists can visualize (使…显现) which parts of the brain receive more oxygen-rich blood - and therefore, which parts are working to process information. An fMRI machine is a device that scans the brain and measures changes in blood flow to the brain. The technology shows researchers how brain activity changes when a person thinks, looks at something, or carries out an activity like speaking or reading. By highlighting the areas of the brain at work when a person looks at different images, fMRI may help scientists determine specific patterns of brain activity associated with different kinds of images. The California researchers tested brain activity by having two volunteers view hundreds of pictures of everyday objects, like people, animals, and fruits. The scientists used an fMRI machine to record the volunteers’ brain activity with each photograph they looked at. Different objects caused different regions of the volunteers’ brains to light up on the scan, indicating activity. The scientists used this information to build a model to predict how the brain might respond to any image the eyes see. In a second test, the scientists asked the volunteers to look at 120 new pictures. Like before, their brains were scanned every time they looked at a new image. This time, the scientists used their model to match the fMRI scans to the image. For example, if a scan in the second test showed the same pattern of brain activity that was strongly related to pictures of apples in the first test, their model would have predicted the volunteers were looking at apples. The researchers experimented on
Jack packed up all the things he had accumulated over the last ten years.
第一篇 Water The second most important constituent (构成成份) of the biosphere (生物圈) is liquid water. This can only exist in a very narrow range of temperatures, since water freezes at 0℃ and boils at 100℃. Life as we know it would only be possible on the surface of a planet which had temperatures somewhere within this narrow range. The earth’s supply of water probably remains fairly constant in quantity. The total quantity of water is not known very accurately, but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers. Most of it is in the form of the salt water of the oceans about 97 percent. The rest is fresh, but three quarters of this is in the form of ice at the Poles and on mountains, and cannot be used by living systems until melted. Of the remaining fractional which is somewhat less than one per cent of the whole, there is 10—20 times as much stored underground water as there is actually on the surface. There is also a tiny, but extremely important fraction of the water supply which is present as water vapor in the atmosphere. Water vapor in the atmosphere is the channel through which the whole water circulation (循环) of the biosphere has to pass. Water evaporated (蒸发) from the surface of the oceans, from lakes and rivers and from moist (潮湿的) earth is added to it. From it the water comes out again as rain or snow, falling on either the sea or the land. There is, as might be expected, a more intensive evaporation per unit area over the sea and oceans than over the land, but there is more rainfall over the land than over the oceans, and the balance is restored by the runoff from the land in the form of rivers. There is more of rainfall
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