单选题Biologists have made a lot of progress in understanding ageing. They have not, however, been able to do much about slowing it down. A piece of work reported in this week's Nature by Darren Baker, though, describes an extraordinary result that points to a way the process might be improved. Dr Baker has shown— in mice, at least—that ageing body cells not only suffer themselves, but also have adverse effects on otherwise healthy cells around them. If such ageing cells are selectively destroyed, these adverse effects go away. The story starts with an observation that senescent cells often produce a molecule called P16INK4A. Dr Baker genetically engineered a group of mice that were already quite unusual. They had a condition called progeria, meaning that they aged much more rapidly than normal mice. The extra tweak he added to the DNA of these mice was a way of killing cells that produce P16INK4A. He did this by inserting into the animals' DNA, near the gene for P 16INK4A, a second gene that was, because of this proximity, controlled by the same genetic switch. This second gene, activated whenever the gene for P16INK4A was active, produced a protein that was harmless in itself, but which could kill the senescent cells by the presence of a particular drug. The results were spectacular. Mice given the drug every three days from birth suffered far less age-related body-wasting than those which were not. Their muscles remained plump and effective. And they did not suffer cataracts of the eye. They did, though, continue to experience age-related problems in tissues that do not produce P16INK4A as they get old. In particular, their hearts and blood vessels aged normally. For that reason, since heart failure is the main cause of death in such mice, their lifespans were not extended. Regardless of the biochemical details, the most intriguing thing Dr Baker's result provides is a new way of thinking about how to slow the process of ageing—and one that works with the grain of nature, rather than against it. Actually eliminating senescent cells may be a logical extension of the process of shutting them down, and thus may not have adverse consequences. It is not an elixir of life, for eventually the body will run out of cells, as more and more of them reach their Hayflick limits. But it could be a way of providing a healthier and more robust old age than people currently enjoy. Genetically engineering people in the way that Dr Baker engineered his mice is obviously out of the question for the foreseeable fixture. But if some other means of clearing cells rich in P 16INK4A from the body could be found, it might have the desired effect. The wasting and weakening of the tissues that accompanies senescence would be a thing of the past, and old age could then truly become ripe.

单选题The year 2000 will bring big changes in communication. Cell phones will be small enough to carry in your pocket. Videophones will let you see the person you are talking to on the phone. Tiny hand size computers will know your favorite subjects. The Internet and email will be everywhere. Technologists believe 2000 will be the year of video messaging. You will be able to see whom you’re talking to. Also in the near future small wireless boxes will pick up information from satellites. In 5 years, computers won’t need to be connected through wires. All of this will be good for rural areas and countries that don’t have cable or telephone now. In 20 years you may only need to think about something and the computer will do it. Constance Hale is the author of Sin and Syntax, "I believe that email has been an incredible boon to communication. People are writing today where they would have been telephoning yesterday. So people are engaging with words more than they have for the last couple generations." If people use email and the Internet more, it could make people better readers and writers. Some people think the most important part of communication is to make people understand each other better. Will technology make that easier? The translator also comes in handy in medical emergencies. Tam Dinh says, "Where people are injured it’s always important to get as much information as quickly as possible." Bob Parks is an Associate Editor of Wired Magazine, "Bob’s morning begins at about 6:45 am. and Bob is kind of mad, because Bob usually gets up at around 7:15 and likes to cut it close with his morning commute, but I look at my radio and it says that there’s a traffic jam on 101 South and I’m gonna need an extra 1/2 hour. And so my radio has got a net connection, wireless net connection as well as a good old power cord to the wall and it has received notice that there’s a traffic jam and it has calculated an extra 1/2 hour commute time." Some day everything may be connected to the Internet. Your refrigerator will add milk to your Internet grocery list when the date on the carton has passed. Light bulbs will be ordered before they bum out. It’s fun to try to guess the future. Usually the predictions are wrong. The one thing we know for sure is that we can’t imagine how technology will change.

单选题A study of practices of financial institutions with no discrimination against self-employed women would tend to contradict

单选题The role of American women______significantly from the time the nation was born, to the modern era of the 1950s and 1960s.

单选题The book gives a brief______off the course of his research up till now.

单选题Woman: Professor Smith, I really need the credits to graduate this summer.Man: Here in this school: the credits are earned, not given.Question: What do we learn from the conversation?

单选题The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, but this is largely because,【C1】______animals, we stand upright. This means that our noses are【C2】______to perceiving those smells which float through the air, missing the majority of smells which stick to surfaces. In fact, though, we are extremely sensitive to smells, even if we do not generally realize it. Our noses are capable of【C3】______human smells even when these are【C4】______to far below one part in one million. Strangely, some people find that they can smell one type of flower but not another, whereas others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate【C5】______smell receptors in the nose. These receptors are the cells which sense smells and send【C6】______to the brain. However, it has been found that even people insensitive to a certain smell at first can suddenly become sensitive to it when【C7】______to it often enough. The explanation for insensitivity to smell seems to be that brain finds it inefficient to keep all smell receptors working all the time but can【C8】______new receptors if necessary. This may also explain why we are not usually sensitive to our own smells we simply do not need to be. We are not【C9】______of the usual smell of our own house but we notice new smells when we visit someone else's. The brain finds it best to keep smell receptors【C10】______for unfamiliar and emergency signals such as the smell of smoke, which might indicate the danger of fire.

单选题Modern linguistics began from the Swiss linguist______, who is often described as " father of modern linguistics".

单选题{{B}}Passage Three{{/B}} Mr. Smith gave his wife ten pound for her birthday —ten pretty pound notes. So the day after her birthday, Mrs Smith went shopping. She queued for a bus, got on and sat down next to an old lady. After a while, she noticed that the old lady’s handbag was open. Inside it she saw a wad of pound notes exactly like the one her husband had given her. So she quickly looked into her own bag — the notes were gone! Mrs Smith was sure that the old lady who was sitting next to her had stolen them. She thought she would have to call the police; but, as she disliked making a fuss and getting people into trouble, she decide to take back the money from the old lady’s handbag and say nothing more about it. She looked round the bus to make sure nobody was watching, then she carefully put her hand into the old lady’s bag, took the notes and put them in her own bag. When she got home that evening, she showed her husband the beautiful hat she had bought. "With the money you gave me for my birthday, of course." she said proudly. "Oh? What’s that, then?" he asked, as he pointed to a wad often pound notes on the table.

单选题Though not the ideal shape for a Christmas stocking, this slim little volume could nevertheless make a welcome seasonal gift. Launched in Britain at the end of October, and covering just under 100 pages, it is not much more than an extended essay. But it presents an interesting idea eloquently and clearly, offering digestible brain food in the middle of excessive turkey and television. The author of Hierarchy Is Not the Only Way, Gerard Fairtlough, was a senior executive with Shell for many years before he left in 1980 to found a new biotechnology company called Celltech—recently bought by UCB, a Belgian group, for over $2 billion. He knows how businesses are run—both well-established organisations, such as Shell, in which it can be hard to see an alternative to the "way things are done around here", and new firms, where the founders" enthusiasm can evaporate if it has to be organized into an organogram. The author"s thesis is that we are all addicted to hierarchy—partly because that is how we are hardwired, as are our simian cousins, but also because we do not realise there are other ways to run organisations. "The powerful status of hierarchy," writes Mr. Fairtlough, "makes us think the only alternative is disorganisation...we only compare hierarchy with anarchy or chaos." There are, he says, two alternatives to hierarchy. One is heterarchy; the other, "responsible autonomy." Heterarchy is the form of structure commonly found in professional-service firms, the partnerships of accountants or lawyers in which key decisions are taken by all the partners jointly. With responsible autonomy "an individual or a group has autonomy to decide what to do, but is accountable for the outcome of the decision." "Accountability," says Mr. Fairtlough, "is what makes responsible autonomy different from anarchy." The author says that hierarchy is so deeply rooted that it will take years before there is any significant change. But he perhaps gives too little credit to the many companies that have moved along the spectrum from hierarchy to responsible autonomy. BP, for example, a huge multinational, has managed to split authority into much smaller units in recent years and has reduced the staff in its headquarters. Toyota, likewise, evolved towards greater autonomy as it discovered that the only effective way to carry out its famous "just-in-time" system of stock control was by delegating responsibility for ordering stock to the person closest to the coal face. The fact that these are among the most successful companies in the world today strengthens Mr. Fairtlough"s case.

单选题Visitors ______ not to touch the exhibits. A．will request B．request C．are requesting D．are requested

单选题 Human needs seem endless. When a hungry man gets a meal, he begins to think about an overcoat, When a manager gets a new sports car, a big house and pleasure boats dance into view. The many needs of mankind might be regarded as making up several levels. When there is money enough to satisfy one level of needs, another level appears. The first and most basic level needs involves food. Once this level is satisfied, the second level of needs, clothing and some sort of shelter, appears. By the end of World War Ⅱ, these needs were satisfied for a great majority of Americans. Then a third level appeared. It included such items as automobiles and new houses. By 1957 or 1958 this third level of needs was fairly well satisfied. Then, in the late 1950s, a fourth level of needs appeared, the "life-enriching" level. While the other levels involve physical satisfaction, that is, the need in comfort, safety, and transportation, this level stresses mental needs for recognition, achievement, and happiness. It includes a variety of goods and services, many of which could be called "luxury" items. Among them are vacation trips, the best medical and dental care, and recreation. Also included here are fancy goods and the latest styles in clothing. On the fourth level, a lot of money is spent on services, while on the first three levels more is spent on goods. Will consumers raise their sights to a fifth level of needs as their income increases, or will they continue to demand luxuries and personal services on the fourth level? A fifth level would probably involve needs that can be achieved best by community action. Consumers may be spending more on taxes to pay for government action against disease, ignorance, crime, and prejudice. After filling our stomachs, our clothes closets, our garages, our teeth, and our minds, we now may seek to ensure the health, safety, and leisure to enjoy more fully the good things on the first four levels.

单选题Historians have only recently begun to note the increase in demand for luxury goods and services that took place in eighteenth-century England. MeKendrick has explored the Wedgewood 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 feat 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 service actually produced what manufacturers 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 eighteenth-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. MeKendriek favors a Viable 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, but not necessarily of the frenzy for conspicuous competition. Finally, what were the consequences of this consumer demand for luxuries? MeKendriek 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 potteries and toys have to do with the development of iron manufacture or textile mills? I t is perfectly possiMe Go have the psychology and reality of 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 the tenth-century England for frivolous as well as useful goods and services foreshadows our own world.

单选题 Valvular heart diseases are quite common, essentially resulting in impaired blood flow and were very difficult to treat. Some 30 years ago, it became possible to replace .diseased valves with prostheses to impose a greater control over blood flow. Early devices were of the mechanical variety, in which devices like ball-in-a-cage or tilting disc would be used to allow blood to flow under near-normal conditions. Although a few mechanical problems were encountered in the early days, the major difficulty lay with the tendency for any foreign material to initiate a blood clot. So, all valve recipients have to be given anticoagulant therapy. This is not particularly desirable for the patients, who may develop bleeding problems, and in any case is not always successful. Although good results are achieved with these valves, it was considered necessary to develop alternatives and the direction was that of natural tissues. It's not possible to transplant heart valves untreated because of rejection phenomena, but it became apparent that collagenous tissue could be cross-linked by glutaraldehyde and prepared in the form of a heart valve. Two sources of tissue were considered for this purpose, bovine pericardium ( collagenous tissue derived from the wall of a cow's heart) and porcine valves (heart valves taken from pigs) and the resulting "bioprosthetic valve" appeared to be very promising. It was particularly important that these patients didn't need anticoagulation. Unfortunately, these valves have not proved very durable, the cross-linked collagen suffering from slow calcification and deterioration so most of the replacement valves themselves need to be replaced within a decade. This would tend to suggest that the mechanical valves give superior performance, notwithstanding the anticoagulation problem, and a move back towards their use might have been expected. However, most of the valves in current use incorporate an alloy'( usually Stellite) forthe housing, and a carbon coated occuluder. The complex shapes of some of the housing have required combinations of casting and welding technologies to be used in their construction and serious problems have arisen with a valve design from one manufacturer, where a small number of catastrophic fractures have occurred within the housing. In patients where this valve has been used to treat aortic valve disease, this fracture is usually fatal and although the risks are small, the problem is important to the industry. Also, at a time when this dichotomy is exercising the minds of surgeons, scientists and regulatory bodies alike, the emergence of the disease BSE in cattle has placed even further restrictions on the use of animal tissue for this type of application and the whole question of prosthetic heart valves has been turned from a reasonable successful example of reconstructive implant surgery to a very confused area. This serves to highlight some of the very varied problems of facing the use of biomaterials.

单选题Speaker A: Look, it's going to storm. Take my umbrella. Speaker B: ______

单选题The two police officers rushed to the scene of the crime ______ they received the report from the old couple.