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While military scientists test lasers against satellites, surgeons use them

游客2024-08-13  38
问题     While military scientists test lasers against satellites, surgeons use them as miraculously accurate scalpels(外科用小刀). They can even be used to detonate hydrogen bombs. (81) The beam can be focused to spot one fiftieth the size of a human hair, yet its intensity is enough to kill cancer cells or drill through the most delicate bones.
    More than a decade ago, eye surgeons realized that they could use laser’s beam to seal individually, the microscopic blood vessels in the retina (视网膜). The beam is so fine that only the target is heated. Now its pinpoint blasting power has been turned to destroying cancer cells and reducing birthmarks.  For cancer treatment, the diseased cells must be killed while their healthy neighbors are left unharmed. (82) Where the cancer can be directly and accurately attacked, laser treatment does well: early cancer of the cervix (颈) and skin cancers have been widely and successfully treated. This type of cancer is not very easy to reach. (83) For cancers that are less accessible there is a new and potentially valuable technique in which the patient is injected with a chemical that then attaches itself preferentially to cancer cells. When the laser strikes the chemical, it releases a form of oxygen that kills these cells.
    Birthmarks, once almost untreatable, are a mass of blood vessels and, being red, they absorb the laser beam strongly. It seals them so that the mark becomes less conspicuous. (84) The normal cells of the skin’s surface, which don’t absorb much of the laser beam, act in the healing and help to conceal the mark. The beam can cut with a precision that no scalpel could achieve. (85) The operation can transform the lives of people who were previously doomed to a lifetime of cosmetic concealment.
    Though this application is widely used in America, there are in Britain only two hospitals offering the treatment, and one feels bound to warn patients that success is not certain. However, some 10 new centers will soon be opened. Britain, though, is one of the leaders in the laser treatment of bleeding peptic ulcers (胃溃疡) and this, combined with new medicines can mean ulcer treatment without conventional surgery. The laser is now being used to treat all kinds of illnesses in this country. [br]
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答案 皮肤表面的正常细胞不吸收很多激光束，因此在治愈胎记的过程中有助于遮掩胎记。
解析 (laser beam激光束。)  
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