Passage One (Words: 479 Time: 5′)

　　At a distance of five feet, it can warn of a tumor no bigger than a pinprick deep within the breast. It can look at the wall of a house and spot where faulty insulation is letting the heat out. It can scan the wall of a fiery industrial furnace and indicate dangerous weak spots. It can examine a human leg and show a malfunctioning blood vessel that is causing varicose veins(静脉曲张). Incredibly, it can even take a photograph of a past event.

　　This remarkable technique is called thermography, and it has given human beings a new way of seeing. Thermography depends upon the fact that all objects give off infrared (红外线) energy. The strength of these infrared emissions depends on the temperature of the body from which they come. Although scientists have long been able to measure the strength of infrared emissions the problems was to turn these measurements into some sort of "picture".

　　Attempts were not notably successful until 1965, when Dr. Ray Lawson, of Montreal, made the first thermograms of the human body. Progress in the science has been rapid ever since, as industrial companies in Europe and the United States have come up with new developments.

　　Today's thermograph looks, for the most part, like a small television camera. You point it at the subject, make a few fairly simple adjustments and on an accompanying screen appears a black-and-white thermal picture of the subject. Normally the warm areas are light, the cold areas dark, and the picture looks something like an ordinary photograph negative. However, in some systems, black and white are reversed, and in still others the picture comes out in brilliant colors, with the various tones representing given temperatures.

　　Using one of these systems, experiments were made to create a picture of the past. Focusing on an empty chair after someone had been sitting in it for a few minutes, they were able to see the heat pattern left by the body, still emanating from the chair's fabric. The picture was so clear that they could detect that the sister's legs had been crossed.

　　Thermography's most valuable use has been in the field of medicine. Already it has helped to save lives, and added to doctors' skills in treating disease. It has proved especially helpful in detecting breast tumors.

　　The standard examinations for breast cancer are mammography (X-ray of the breast) and clinical examination. However, Dr. Harold Isard, of Albert Einstein Medical Center in Philadelphia, who has used thermography to examine some 20,000 women for breast cancer, says,"The two methods do not catch everything. Thermography can indicate the possibility of some small cancers that have been missed. And it's safe and cheap. We can do a thermogram in a couple of minutes, and although the machines cost around $30,000 each, the price of operating them is only a matter of pennies."

　　The American Cancer Society, working with the federal government, has begun pilot programs to screen for breast cancer 270,000 women in the over-35 age range during the next six years, via 27 centers around the country. The women will be checked by mammography, thermography and clinical examination. Says Dr. Isard, "With the addition of thermography to the other two methods, we can get about 92 percent accuracy in detecting breast cancer."

　　1. Thermography depends on________.

　　A. television cameras

　　B. infrared energy

　　C. photograph negatives

　　D. temperatures

　　2. The most valuable use of thermography has been in the field of________.

　　A. medicineB. industry

　　C. scienceD. energy conservation

　　3. The advantage in using thermography to detect cancer is that it________.

　　A. is helpful in detecting breast cancer

　　B. can indicate very small cancers

　　C. adds to doctors' skills in treating disease

　　D. saves lives

　　4. The word "emanating"in paragraph 5 means ________.

　　A. coming forthB. belonging to

　　C. flowing D. starting

　　5. The main idea of this article is about ________.

　　A. a new way of detecting cancer

　　B. the history of thermography

　　C. the value of thermography

　　D. how to interpret a thermogram

　　Passage Two (Words: 354 Time: 4′)

　　The very high temperatures attained in a nuclear explosion result in the formation of an extremely hot, intense mass of gas called a fireball. For a 10-kiloton explosion in the air, the fireball will attain a maximum diameter of about 300m; for a 10-megaton weapon the fireball may be 4.8km across. A flash of heat radiation is emitted from the fireball and spreads out over a large area, but with steadily decreasing intensity. The amount of heat energy received a certain distance from the nuclear explosion depends on the power of the weapon and the state of atmosphere. If the visibility is poor or the explosion takes place above clouds, the effectiveness of heat flash will decrease. The heat radiation falling on exposed skin can cause what are called flash burns. A 10-kiloton explosion in the air can produce moderate (second-degree) flash burns, which require some medical attention, as far as 2.4km from ground zero; for a 10-megaton bomb, the corresponding distance would be more than 32km. Harsher burns occur when bare skin is directly exposed, or if clothing is too thin to absorb the heat radiation.

　　The heat radiation can start fires in dry, flammable materials, for example, paper and some fabrics, and such fires may spread if conditions are suitable. The evidence from the A-bomb explosion over Japan indicates that many fires, especially in the area near ground zero, originated from secondary causes, such as electrical short circuits, broken gas lines, and upset furnaces and boilers in industrial plants. The blast damage produced wreckage that helped to maintain the fires and denied access to fire-fighting equipment. Thus much of the fire damage in Japan was a secondary effect of the blast wave.

　　Under some conditions, such as existed at Hiroshima (广岛) but not at Nagasaki (长崎), many individual fires can combine to produce a fire storm similar to those that accompany some large forest fires. The heat of the fire causes a strong updraft, which produces strong winds drawn in toward the center of the burning area. These winds fan the flame and convert the area into a disaster in which everything flammable is destroyed.

　　6. It can be inferred that the amount of radiation________.

　　A. is greatest when an atomic bomb is dropped from the air

　　B. is greatest when an atomic bomb goes off on the ground

　　C. is weakest when it spreads over a large area

　　D. becomes increasingly weak as it travels further out

　　7. All the following conditions affect the power of the atomic bomb EXCEPT________.

　　A. fog

　　B. clouds

　　C. the size of the bomb

　　D. land features

　　8. Which of the following is true according to the passage?

　　A. Any amount of the radiation is deadly to a person.

　　B. Any kind of opaque cloth can protect a person from an atomic bomb.

　　C. A second-degree flash burn may not be as dangerous to life.

　　D. Thin cloth usually catches fire easily from heat radiation.

　　9. It is clear from paragraph 2 that the greatest danger with an atomic bomb often comes from________.

　　A. direct exposure to heat radiation

　　B. indirect damage

　　C. the fireball

　　D. fire-fighting equipment

　　10. The example of Hiroshima is given in the last paragraph to illustrate________.

　　A. the power of an atomic bomb

　　B. the effect of weather conditions on the nuclear power

　　C. the secondary effect of an atomic bomb

　　D. the damage caused by an atomic bomb

　　参考答案: 1-5 B A B A C 6-10 D C C B C

　　(文/王新华; 英语通大学英语六级考试版2004年第7期;版权归英语辅导报社所有，独家网络合作伙伴新浪教育，未经许可，不得以任何形式进行转载。)