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"I have great confidence that by the end of the decade we’ll know in vast detail how cancer cells arise," says microbiologist Robert Weinberg, an expert on cancer, "But," he cautions, "some people have the idea that once one understands the causes, the cure will rapidly follow. Consider Pasteur. He discovered the causes of many kinds of infections, but it was fifty or sixty years before cures were available." This year, 50 percent of the 910 000 people who suffer from cancer will survive at least five years. In the year 2000, the National Cancer Institute estimates, that figure will be 75 percent. For some skin cancers, the five-year survival rate is as high as 90 percent. But other survival statistic(统计)rate still discouraging-13 percent for lung cancer, and 2 percent for cancer of the pancreas(胰腺). With as many as 120 varieties in existence, discovering how cancer works is not easy. The researchers made great progress in the early 1970s, when they discovered that oncogenes, which are cancer-causing genes(基因), are inactive in normal ceils. Anything from cosmic rays to radiation to diet may activate a dormant oncogene, but how remains unknown. If several oncogenes are driven into action, the cell, unable to turn them off, becomes cancerous. The exact mechanisms involved are still mysterious, but the likelihood that many cancers are initiated at the level of genes suggest that we will never prevent all cancers. "Changes are a normal part of the evolutionary process," says oneologist William Hayward. Environmental factors can never be totally eliminated; as Hayward points out, "We can’t prepare a medicine against cosmic rays." The prospects for cure, though still distant, are brighter. "First, we need to understand how the normal cell controls itself. Second, we have to determine whether there are a limited number of genes in cells, which are always responsible for at least part of the trouble. If we can understand how cancer works, we can counteract its action.\ The word "dormant" in the third paragraph most probably means ______.
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1. Humans not only love eating ice cream, they enjoy feeding it to their pets(宠物). Market studies show that two thirds of all dog owners give ice cream ot their dogs. Unfortunately, says William Tyznik, an expert on animal nutrition(营养)at Ohio State University, ice cream is not good for dogs. "It has milk sugar in it, "he says," which dogs cannot digest very well." 2. Bothered by that knowledge but aware of the desire of dog owners to please their companions, Tyznik invented a new frozen treat for dogs that, he says, is more nutritious than ice cream--and as much fun to eat. The product, called Frosty Paws, is made of a liquid by-product(副产品)of cheese and milk with the sugar removed. Frosty Paws also contains refined soy flour, water, vegetable oil, vitamins and minerals. It took Tyznik, who has also invented a horse feed (called Tizwhiz) and another dog food (named Tizbits), three years to perfect the Frosty Paws formulas, and two attempts to commercialise it. After losing ＄ 25,000 trying to market the invention himself, Tyznik sold the rights to Associated Ice Cream of Westerville, Ohio, which makes the product and packages it in cups. 3. Tyznik claims that Frosty Paws has been tested extensively and that "dogs love it". Of 1,400 dogs that have been offered the product, he says, 89 percent took it on the first try. Three out of four preferred it to Milk-Bone or sausages. The product, which will be available in the ice-cream section of supermarkets, comes in packs of three or four cups, costing between ＄ 1.79. 4. What would happen if a human should mistake Frosty Paws for real ice cream Nothing, says Tyznik. It’s harmless, but frankly, he says, it won’t taste very good. Para 3 ______.
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"Much of the sickness and death attributed to the major communicable diseases is in fact caused by malnutrition which makes the body less able to withstand infections when they strike," said Dr Hiroshi Nakajima, Director-General of the World Health Organization (WHO). "At the same time," he added, "in developing countries today, malnutrition is the cause of 174 million children under five years of age being (51) , and 230 million being stunted(阻碍)in their growth. Such (52) represent deprivation, suffering and wasted human potential (53) a scale that is unacceptable from every point of view. Whether we think in (54) of humanitarian concern, common justice or development needs, they demand a (55) , both from national governments and from the international community." It is now (56) that 6.6 million out of the estimated 12.2 million deaths (57) among children under-five--or 54% of young child mortality in developing countries-is associated with malnutrition, In some (58) , such as sub-Saha-ran Africa and south Asia, stagnation(停滞)of nutritional improvement (59) with a rapid rise in population has resulted in an (60) increase in the total number of malnourished children. (61) , over two-thirds of the world’s malnourished children live in Asia (especially south Asia), followed by Africa and Latin America. As Dr Nakajima noted, "The globalization of industry, trade, travel and communication has brought (62) it unprecedented possibilities for mutual cooperation in (63) hunger and malnutrition. At the same time, however, the acceptability of certain foods, and the cultural aspects of their production, distribution and preparation, are now recognized as (64) in the promotion of good nutrition. Without the attention (65) them, little progress can be made towards household food security, appropriate diets, the control of micronutrient(微量元素)deficiencies, the promotion of breast-feeding, and other strategies listed in the Plan of Action adopted in 1992 (at the International Conference on Nutrition in Rome).\
国家提出要建设一个针对特定灾害的防灾预警系统，以减少灾害损失。共有三个互斥的建设方案，寿命期均为20年。根据统计资料分析及专家论证，如果不建造该预警系统，预期未来每年灾害经济损失为120亿元；如果建造该防灾预警系统，除需要初始投资外，每年还需要支付系统维护费用，但可降低每年预期灾害损失。各方案的初始投资、每年运营维护费用及预期年损失等资料见表3-3。设定基准收益率为8%。 复利系数表见表3-4所列。 表3-3 各方案投资、费用及预期损失 单位：亿元 方案 初始投资 年运营维护费用 预期年损失 1 120 12 70 2 210 20 90 3 250 30 30 【问题】
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