问题 单项选择题

对于自然界中的物质,无论大的还是小的,人类似乎找到了操作它们的合适方法,利用起重机可以移动成吨重的货物,使用光镊可以拨动分子和原子,等等。最近哈佛大学的科学家又有了新的发明,那就是通过模仿生物大分子的融合装配,使微米级的物体能够自己装配自己。众所周知,DNA和蛋白质等大分子都能依靠形状的互补或分子间的作用力(如氢键和疏水作用力)来进行分子间的牵引。因此,多肽能在被基因表达后自发地折叠成有功能的蛋白质,DNA也能在扭曲成双螺旋后继续缠绕成短棒形状的染色体。然而对于比生物活性分子稍大一些的物体来说,这种作用力方式同样有效吗为了得到答案,哈佛大学的怀特赛德和他的学生开始模仿蛋白质的融合装配,用被称为二甲基硅氧烷的疏水材料制作了一些六角形的小物体,这些小物体虽然只有几个微米大小,但怀特赛德却设法将它们中的数个黏结在一起,并在个别面上涂上了亲水物质,做成一些具有不同形状的模拟“蛋白分子”。把这些“蛋白分子”放入水和油的混合系统后,亲水部位结合到亲水部位,疏水部位结合到疏水部位,它们果然按照设计的意图完成了自组装。科学家认为,这项新近发明的技术可以在一些微小物体的精确安装中发挥作用,例如制造电脑芯片和微型机械。但在获得最后的成功之前,还有一个必要的步骤需要完成——把这些自组装好的小东西焊接起来。因为目前里面的黏合力是如此的小,一旦从液体中拿出,它们就会像豆腐一样地散架。

与第一段文意不符合的一项是()。

A.人类又找到了操作自然界微小物质的新的方法——微米级物体自组装

B.哈佛大学的科学家能够使微米级物体自组装

C.微米级物体自组装是通过模仿生物大分子的自组装原理来完成的

D.生物大分子的融合装配给科学家完成微米级物体自组装以启迪

答案

参考答案:B

解析:

根据最后一段的“但在获得最后的成功之前,还有一个必要的步骤需要完成”,可知微米级物体的组装没有最后成功,所以B项说的“能够”是不准确的。

单项选择题 A1/A2型题
单项选择题

When Dr. John W. Gofman, professor of medical physics at the University of California and a leading nuclear critic, speaks of "ecocide" in his adversary view of nuclear technology, he means the following. A large nuclear plant like that in Kalkar, the Netherlands, would produce about 200 pounds of plutonium each year. One pound, released into the atmosphere, could cause 9 billion cases of lung cancer. This waste product must be stored for 500,000 years before it is of no further danger to man. In the anticipated reactor economy, it is estimated that there will be 10,000 tons of this material in Western Europe, of which one table-spoonful of plutonium-239 represents the official maximum permissible body burden for 200,000 people. Rather than being biodegradable, plutonium destroys biological properties.

In 1972 the .U.S. Occupational Safety and Health Administration ruled that the asbestos level in the work place should be lowered to 2 fibers per cubic centimeter of air, but the effective date of the ruling has been delayed until now. The International Federation of Chemical and General Workers’ Unions report that the 2-fiber standard was based primarily on one study of 290 men at a British asbestos factory. But when the workers at the British factory had been reexamined by another physician, 40--70 percent had X-ray evidence of lung abnormalities. According to present medical information at the factory in question, out of a total of 29 deaths thus far, seven were caused by lung cancer. An average European or American worker comes into contact with six million fibers a day. "We are now, in fact, finding cancer deaths within the family of the asbestos worker," states Dr. Irving Selikoff, of the Mount Sinai Medical School in New York.

It is now also clear that vinyl chloride, a gas from which the most widely used plastics are made, causes a fatal cancer of the blood-vessel cells of the liver. However, the history of the research on vinyl chloride is, in some ways, more disturbing than the "Watergate cover- up. " "There has been evidence of potentially serious disease among polyvinyl chloride workers for 25 years that has been incompletely appreciated and inadequately approached by medical scientists and by regulatory authorities," summed up Dr. Selikoff in the New Scientist. At least 17 workers have been killed by vinyl chloride because research over the past 25 years was not followed up. And for over 10 years, workers have been exposed to concentrations of vinyl chloride 10 times the "safe limit" imposed by Dow Chemical Company.

By "ecocide" the author most probably means()

A. waste utilization

B. ecological balance

C. radioactive reaction

D. massive bio-destruction