大学英语自学教程(中)（英文版）( 39页).docx

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1、大学英语自学教程（中）16-A, Heart Disease: Treat os Prevent?One of the greatest killers in the Western world is heart disease. The death rate from the disease has been increasing at an alarming speed for the past thirty years. Today in Britain, for example, about four hundred people a day die of heart disease.

2、 Western healthcare systems are spending huge sums of money on the surgical treatment of the disease.This emphasis on treatment is clearly associated with the technological advances that have taken place in the past ten to fifteen years. In this time, modern technology has enabled doctors to develop

3、 new surgical techniques and procedures. Many opeations that were considered impossible a few years ago are now performed every day in U.S. hospitals. The result has been a rapid increase in heart surgery.Although there is no doubt that a large number of people benefit from heart surgery, critics of

4、 our health-care systems point out that the emphasis on the surgical treatment of the disease has three clear disadvantages. First, it attracts interest and financial resources away from the question of prevention. Second, it causes the costs of general hospital care to rise. After hospitals buy the

5、 expensive equipment that is necessary for modern heart surgery, they must try to recover the money they have spent. To do this, they raise costs for all their patients, not just those patients whose treatment requires the equipment. The third disadvantage is that doctors are encouraged to perform s

6、urgery even on patients for whom an operation is not at all necessary because the equipment and surgical expertise is available. A federal government office recently said that major heart surgery was often per-formed even though its chances of success were low. In one type of heart surgery, for exam

7、ple, only 15 percent of patients benefited from the surgery.2. Our train decreased its speed.There are thus two possible explanations to account for the change in speed, but we dont know which one is right. Furthermore, regardless of which explanation we choose, the end result will he the same: the

8、other train will arrive at the station first. So it makes no difference whether we say that the other train increased its speed or that our train decreased its speed.Since both explanations lead to the same result, you can choose either one. Whenever two things are relative, you can choose either on

9、e of them. The converse is also true: whenever you have a choice between tw。things that are equally possible, then the things are relative.There is no reason, except convenience, for choosing one explanation over the other. The relative speed between the trains remains the same, 10 mph; and the end

10、result will be the same.Now let 祖 suppose that both trains are at the railroad station loading and unloading passengers and baggage. A half-hour passes. As we look at the other train through our window, we see that our train seems to start moving, smoothly and slowly. For a minute or so, our train s

11、eems to travel at a uniform speed. Our special speedometer shows that the relative speed between the two trains is 20 mph. But as we look out our window, we suddenly see the last coach of the other train disappear from sight and notice the motionless station behind it. So we are not moving after all

12、. The other train has been moving!This peculiar and often frustrating experience is an effect of relative motion. At the train station we cannot tell whether it was our train that changed its speed from 0 mph to 20 mph or whether it was the other train that changed its speed from 0 mph to 20 mph. On

13、ly after the other train pulled out of the station could we see that it, and not our train, was moving.Now let us again raise the question that was raised at the beginning of this article: can wc be absolutely certain that the other train did indeed Jincrease its speed, and in this case pull out of

14、the station?Tf your answer is yes, then you are wrong again. All we can be certain of is that the relative speed between the two trains changed.These examples illustrate an important principle in the special theory of relativity. If A appears to be moving at a steady speed relative to B, we cannot k

15、now for sure if it is A that is really moving. Perhaps A is standing still, and B is moving. Or perhaps both are moving. According to relativity, there is no experiment that can be devised to solve the problem. As there is no way of deciding which of the two objects is moving, we can choose either o

16、ne as the moving object. The reason is that their motion is relative, and relativity, as we have seen, means that we have a choice.This principle - that if two objects are in uniform motion relative to each other, it is impossible to decide which one is moving and which one is at rest - applies to a

17、ll objects moving uniformly in a straight line through the universe.In relativity you 11 find that whenever you have a choice among things that are equally possible, you are dealing with relative things. For example, time, which is measured with clocks and watches, is relative because it can be show

18、n that there is more than one system of time. All systems of time are equally possible and you can choose any system you wish.19-A. Animals at Risk: Who Cares?An animal species becomes extinct when it fails to produce enough young in each generation to keep pace with the death-rate. We can tell from

19、 fossil evidence in rocks that many living species have become extinct over the millions of years since life began. It is a natural process and extinction is the fate of any animal that has specialized too far to change when its environment changes, or has to compete with a better-adapted and more p

20、owerful animal. Because of remarkable technical developments during the past few centuries, man has destroyed or nearly destroyed some species by killing them at such a rate that they couldnt produce enough offspring, or by completely changing their natural environment at surprising speed.A number o

21、f examples can be given of the way in which natural environments are being rapidly changed - Amazonia, for instance. There is every likelihood that many species of animals will be made extinct because of these and similar clearances of natural vegetation. Large numbers of animals have been hunted an

22、d killed for food. The North American buffalo is a case of the near-extinction of a species through hunting. Often the numbers are so great the hunters may not realize the danger. But even when the danger is widely publicized, the financial rewards for the hunters may be so great that they choose to

23、 ignore the threat to the species. Attitudes like this have led to hunters killing animals for furs, for ivory or merely for ornaments. A slight variation on this is when tourists hunt animals for trophies. Magnificent creatures such as lions and tigers have been hunted out of existence in some part

24、s of the world. It is important to realise, though, that animals are sometimes killed out of fear. Big cats are killed in this way. And animals are sometimes killed out of a wish to reduce numbers to help the species to survive. The killing of the Canadian seals is claimed to be for this purpose, an

25、d the use of their skins for furs is only a by-product.Many people are concerned about animals and wildlife conservation. One way to preserve species under threat of extinction - whatever the cause - is to remove them to zoos and parks and breed them there. There is always the chance that enough off

26、spring will be born to return them one day to their natural environment - provided it still exists, and that hunters don*t kill them again! Another method is to protect the animals in their natural environment by creating wildlife reserves and parks and using game wardens to look after them. But the

27、 parks are large, the wardens few and the determination of hunters very great. Early in 1980 wardens and hunters clashed in East Africa. The hunters were armed with modern weapons and several people were killed.There is great pleasure in watching wildlife in natural or near-natural environments, and

28、 tourism can add to the income of countries. The animals are still resources - but in a very different form. J19-B. The Killer SmogsOn the night of December 1, 1930, a dense fog moved over the Meuse Valley, in Belgium. Many factories in the valley poured smoke and fumes into the foggy air. This crea

29、ted a dark smog of smoke and fog combined. People in the valley began to cough and strain for breath. The smog remained for four days. During that time, thou-sands of people became ill. The hospitals were filled with patients. Sixty people died. Most of them were older persons with heart and lung pr

30、oblems. Finally, a heavy rain washed away the smog. Scientists studied the causes of the disaster. They concluded that the illnesses and deaths were caused by chemicals in the smog.The first reported event of this kind in the United States happened in Donora, a factory town in a valley near Pittsbur

31、gh. In 1948, a killer smog made half of the population sick, there were 17 deaths. Again, older people with lung or heart diseases were hit hardest.London, England, has always been known for its black fags. In the winter of 1952, a milky white fog rolled into the city. It soon turned into black smog

32、 as the smoke of the city poured into the air. It was so hard to see that people had to walk in front of the buses to guide them. In this way, the most serious air pollution disaster in history began. When it was over, more than 4,000 people had been killed by the thick black smog.New York City has

33、had several London-type smogs since 1950. Each time, there were from 100 to 400 deaths caused by the smog. Although these smogs were not as deadly as London? s, New York City has the worst: air pollution problem in the United States.Tn all the killer smogs, factories and homes poured smoke and fumes

34、 into the air from the furnaces. The chemical fumes combined wittv the J water droplets in the fog to form harmful substances. These substances caused the illness of those who breathed the polluted air.Usually, such harmful fumes rise into the upper air and are blown away by the wind. Hut sometimes

35、there is an unusual weather condition called a temperature inversion. A layer of cold air remains near the ground as smoke and fumes pour into it. This is covered by an upper layer of warm air that acts like a lid. It prevents the polluted cooler air from rising. The harmful fumes pile up and make p

36、eople ill. The smog may be so thick that airports are closed and chains of collisions occur on the highways.Another type of smog occurs in Los Angeles. Here the weather may he clear and sunny. But stinging eyes and dry coughs show that harmful chemicals fill the air. The smog is due to invisible gas

37、es, mosdy from automobile exhaust. Because these chemicals are changed by the sun high up in the air, Los Angeles smog is called photochemical smog. It contains automobile exhaust fumes and nitrogen oxides changed by the sun*s rays. Added to these are sulfur dioxide and other fumes from factories an

38、d oil refineries. Photochemical smog is found in many large cities all over the world.Killer smogs dont happen very often, fortunately. Hut in many large cities, a combination of automobile exhaust fumes, home furnace smoke, and factory waste gases pours into the air. This may also happen in the sub

39、urbs, or out in the country, where large factories have been built. A number of harmful substances have been found in the air there. When these substances are breathed in day after day, the health of the population is affected.20-A, You Can t Do It Because It Hurts NobodyWho do you think breaks the

40、law in our society? If you believe that only tough guys commit crimes, you may have to think again. Answer the following questions honesdy, Has anyone you know ever driven drunk? Can you think of a friend who has used drugs? Are you aware that your parents may not always tell the truth when they go

41、through customs? Wont some of your friends admit that they have stolen an item from a store? Have any of your friends ever copied a CD onto a tape for someone else?In case you did not know, all of these acts are against the law. Now, among the people you know, how many have never broken the law? Doc

42、s that mean that most members of our society should go to jail? Unlike in the movies, wc can t divide the world into bad guys and model citizens. Real life is much more complex. Tn the same way that diseases range from the common cold to fatal forms of cancer, crimes vary in degree. For example, smo

43、king in an elevator will inconvenience people, but much less than threatening them with a gun.in addition to breaking the law themselves, people tolerate various levels of crime. Why are we tolerant of some crimes? It may be that, by seeing others do something, we accept it more easily. We may even

44、start committing that crime ourselves. For instance, most people will find it easier to speed on a highway when everybody else is driving over the speed limit. When people celebrate a sports championship, if they see someone breaking store windows, they might start breaking windows themselves or eve

45、n steal from the store. So the people around us influence how much law-breaking we can tolerate.We must also wonder whether seeing violence on television or reading about it in the newspapers every day makes us tolerate crime more than we should. We become used to seeing blood on the news on televis

46、ion, or in full color in newspapers and magazines. Because we see thousands of dead people on TV, maybe we just try to ignore the situation behind the violence.Tf so many citizens tolerate violence and crime, or even commit crimes themselves, it may simply be because of the human mind. Our minds may

47、 not care about specific laws. Instead, our minds may have a system of values that usually prevents us from hurting other people to improve our own lives. Yet, when it comes to respecting the rights of a mass of anonymous individuals, wc might not be so responsible. While most people would not steal

48、 a wallet containing $50, they may not mind cheating on taxes, because cheating on taxes does not hurt any one person. It hurts society, but society remains an abstract idea that is not as real as a neighbor or a friends friend. Perhaps this is why someone who robs a few dollars by force from a corn

49、er store will often end up with a longer jail term than a fraud artist who swindles thousands of dollars: threatening the life of an individual is not acceptable in our society.When we look at the questions in the first paragraph and realize that many people have misconceptions about law-breaking, we could think it is surprising that only about 10% of Canadians have a criminal record. How could we improve the level of honesty in our society? Would a larger police force keep everyone honest? Would severe laws he