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第三篇 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. The total quantity of water on Earth
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Why can’t you stop your eternal complaining
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. The phrase "wary of" in paragraph 8 could be best replaced by
第三篇 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. Most of the fresh water on Earth
Radiocarbon Dating Nowadays scientists can answer many questions about the past through a technique called radiocarbon (放射性碳), or carbon-14, dating. One key to understanding how and by something happened is to discover when it happened. Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at he University of Chicago. An atom of ordinary carbon, called carbon-12, has six protons(质子) and six neutrons (中子) in its nucleus(原子核). Carbon-14, or C-14, is a radioactive, unstable form of carbon that has two extra neutrons. It returns to a more stable form of carbon through a process called decay (衰减). This process involves the loss of he extra neutrons and energy from the nucleus. In Libby’s radiocarbon dating technique, the weak radioactive emissions (放射) from this decay process are counted by instruments such as a radiation detector and counter. The decay rate is used to determine the proportion of C-14 atoms in the sample being dated. Carbon-14 is produced in the Earth’s atmosphere when nitrogen (氮)-14, or N-14,interacts with cosmic rays (宇宙射线). Scientists believe since the Earth was formed, the mount of nitrogen in the atmosphere has remained constant. Consequently, C-14 formation is thought to occur at a constant rate. Now the ratio of C-14 to other carbon toms in the atmosphere is known. Most scientists agree that this ratio is useful for dating items back to at least 50,000 years. All life on Earth is made of organic molecules (分子) that contain carbon atoms coming from the atmosphere. So all living things have about the same ratio of C-14 atoms to other carbon atoms in their tissues (组织). Once an organism (有机体) dies it stops taking in carbon in any form, and the C-14 already present begins to decay. Over time the amount of C-14 in the material decreases, and the ratio of C-14 to other carbon atoms goes down. In terms of radiocarbon dating, the fewer C-14 atoms in a sample, the older that sample is. The C-14 in an organism begins to decay when it dies
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