题目内容
The human ear contains the organ for hearing and the organ for balance. Both organs involve fluid-filled channels containing hair cells that produce electrochemical impulses when the hairs are stimulated by moving fluid. The ear can be divided into three regions: outer, middle, and inner. The outer ear collects sound waves and directs them to the eardrum separating the outer ear from the middle ear. The middle ear conducts sound vibrations through three small bones to the inner ear. The inner ear is a network of channels containing fluid that moves in response to sound or movement. To perform the function of hearing, the ear converts the energy of pressure waves moving through the air into nerve impulses that me brain perceives as sound. Vibrating objects, such as the vocal cords of a speaking person, create waves in me surrounding air. These waves cause the eardrum to vibrate with the same frequency. The three bones of the middle ear amplify and transmit the vibrations to the oval window, a membrane on the surface of the cochlea, the organ of hearing. Vibrations of me oval window produce pressure waves in the fluid inside me cochlea. Hair cells in the cochlea convert the energy of the vibrating fluid into impulses that travel along the auditory nerve to the brain. The organ for balance is also located in the inner ear. Sensations related to body position are generated much like sensations of sound. Hair cells in the inner ear respond to changes in head position with respect to gravity and movement. Gravity is always pulling down on the hairs, sending a constant series of impulses to the brain. When the position of the head changes—as when the head bends forward—the force on the hair cells changes its output of nerve impulses. The brain then interprets these changes to determine the head’s new position. What can be inferred about the organs for hearing and balance
查看答案
搜索结果不匹配？点我反馈
更多问题
Pity those who aspire to put the initials PhD after their names. After 16 years of closely supervised education, prospective doctors of philosophy are left more or less alone to write the equivalent of a large book. Most social-science postgraduates have still not completed their theses by the time their grant runs out after three years. They must then get a job and finish in their spare time, which can often take a further three years. By then, most new doctors are sick to death of the narrowly defined subject which has blighted their holidays and ruined their evenings. The Economic and Social Research Council, which gives grants to postgraduate social scientists, wants to get better value for money by cutting short this agony. It would like to see faster completion rates; until recently, only about 25% of PhD candidates were finishing within four years. The ESRC’s response has been to stop PhD grants to all institutions where the proportion taking less than four years is below 10% ; in the first year of this policy the national average shot up to 39%. The ESRC feels vindicated in its toughness, and will progressively raise the threshold to 40% in two years. Unless completion rates improve further, this would exclude 55 out of 73 universities and polytechnics — including Oxford University, the London School of Economics and the London Business School. Predictably, howls of protest have come from the universities, who view the blacklisting of whole institutions as arbitrary and negative. They point out that many of the best students go quickly into jobs where they can apply their research skills, but consequently take longer to finis their theses. Polytechnics with as few as two PhD candidates complain that they are penalized by random fluctuations in student performance. The colleges say there is no hard evidence to prove that faster completion rates result from greater efficiency rather than lower standards or less ambitious doctoral topics. The ESRC thinks it might not be a bad thing if PhD students were more modest in their aims. It would prefer to see more systematic teaching of research skills and fewer unrealistic expectations placed on young men and women who are undertaking their first piece of serious research. So in future its grants will be given only where it is convinced that students are being trained as researchers, rather than carrying out purely knowledge-based studies. The ESRC can not dictate the standard of thesis required by external examiners, or force departments to give graduates more teaching time. The most it can do is to try to persuade universities to change their ways. Recalcitrant professors should note that students want more research training and a less elaborate style of thesis, too. By time new doctors get a job and try to finish their theses in spare time, ______.
Scientists have long understood that supermassive black holes weighing millions or billions of suns can tear apart stars that come too close. The black hotels gravity pulls harder on the nearest part of the star, an imbalance that pulls the star apart over a period of minutes or hours, once it gets close enough. Scientists say this uneven pulling is not the only hazard facing the star. The strain of these unbalanced forces can also trigger a nuclear explosion powerful enough to destroy the star from within. Matthieu Brassart and Jean-Pierre Luminet of the Observatoire de Paris in Meudon, France, carried out computer simulations of the final moments of such an unfortunate star’s life, as it veered towards a supermassive black hole. When the star gets close enough, the uneven forces flatten it into a pancake shape. Some previous studies had suggested this flattening would increase the density and temperature inside the star enough to trigger intense nuclear reactions that would tear it apart. But other studies had suggested that the picture would be complicated by shock waves generated during the flattening process and that no nuclear explosion should occur. The new simulations investigated the effects of shock waves in detail, and found that even when their effects are included, the conditions favor a nuclear explosion. " There will be an explosion of the star — it will be completely destroyed," Brassart says. Although the explosion obliterates the star, it saves some of the star’s matter from being devoured by the black hole. The explosion is powerful enough to hurl much of the star’s matter out of the black hole’s reach, he says. The devouring of stars by black holes may already have been observed, although at a much later stage. It is thought mat several months after the event that rips the star apart, its matter starts swirling into the hole itself. It heats up as it does so, releasing ultraviolet light and X-rays. If stars disrupted near black holes really do explode, then they could in principle allow these events to be detected at a much earlier stage, says Jules Hatpern of Columbia University in New York, US2. "It may make it possible to see the disruption of that star immediately if it gets hot enough," he says. Brassart agrees. "Perhaps it can be observed in the X-rays and gamma rays, but it’s something that needs to be more studied," he says. Supernova researcher Chris Fryer of the Los Alamos National Laboratory in Los Alamos, New Mexico, US3, says the deaths of these stars are difficult to simulate, and he is not sure whether the researchers have proven their case that they explode in the process. According to the third paragraph, researchers differed from each other in the problem of ______.
Historians have only recently begun to note the increase in demand for luxury goods and services that took place in 18th-century England. McKendrick has explored the Wedgwood firm’s remarkable success in marketing luxury pottery; Plumb has written about the proliferation of provincial theaters, musical festivals, and children’s toys and books. While the fact of this consumer revolution is hardly in doubt, three key questions remain: Who were the consumers What were their motives And what were the effects of the new demand for luxuries An answer to the first of these has been difficult to obtain. Although it has been possible to infer from the goods and services actually produced what manufactures and servicing trades thought their customers wanted, only a study of relevant personal documents written by actual consumers will provide a precise picture of who wanted what. We still need to know how large this consumer market was and how far down the social scale the consumer demand for luxury goods penetrated. With regard to this last question, we might note in passing that Thompson, while rightly restoring laboring people to the stage of 18th-century English history, has probably exaggerated the opposition of these people to the inroads of capitalist consumerism in general; for example, laboring people in eighteenth-century England readily shifted from home-brewed beer to standardized beer produced by huge, heavily capitalized urban breweries. To answer the question of why consumers became so eager to buy, some historians have pointed to the ability of manufacturers to advertise in a relatively uncensored press. This, however, hardly seems a sufficient answer. McKendrick favors a Veblen model of conspicuous consumption stimulated by competition for status. The "middling sort" bought goods and services because they wanted to follow fashions set by the rich. Again, we may wonder whether this explanation is sufficient. Do not people enjoy buying things as a form of self-gratification If so, consumerism could be seen as a product of the rise of new concepts of individualism and materialism(a preoccupation with or stress upon material rather than intellectual or spiritual things), but not necessarily of the frenzy for conspicuous competition. Finally, what were the consequences of this consumer demand for luxuries McKendrick claims that it goes a long way toward explaining the coming of the Industrial Revolution. But does it What, for example, does the production of high-quality pottery and toys have to do with the development of iron manufacture or textile mills It is perfectly possible to have the psychology and reality of a consumer society without a heavy industrial sector. That future exploration of these key questions is undoubtedly necessary should not, however, diminish the force of the conclusion of recent studies: the insatiable demand in eighteenth-century England for frivolous as well as useful goods and services foreshadows our own world. In the first paragraph, the author mentions McKendrick and Plumb most probably in order to ______.
发展中国家的人们若为移民问题操心，往往是想到硅谷或发达国家的医院和大学去创造自己最辉煌的未来。英国、加拿大和澳大利亚等国给大学毕业生提供的优惠移民政策，就是为了吸引这部分人群。诸多研究表明，发展中国家受过良好教育的人才往往可能有移民倾向。2004年，曾针对印度家庭进行过一次大型调查，结果发现，近40％有移民倾向的人受过中学以上教育，而25岁以上的印度人只有约3．3％受过中学以上教育。“人才流失”问题长期以来一直让发展中国家的决策者很苦恼，他们担心这种情况会危及其经济发展，夺去他们紧缺的技术人才，而这些人才本该在他们自己的大学任教，在他们自己的医院工作，为他们自己的工厂研发新产品。
微信支付 
支付宝支付