2. 外语
  3. While chemists try to assemble molecules using a combination of theoretical principles and practical experience to mold m

While chemists try to assemble molecules using a combination of theoretical principles and practical experience to mold m

admin2011-01-17  111
问题            While chemists try to assemble molecules using a combination of theoretical
       principles and practical experience to mold molecules that have desired
       structural and chemical properties, nanotechonologists generally seek to make
Line    more than a single molecule. They build arrays of identical or complexed
(5)      molecules, sometimes on a scale that will transcend the boundaries of the
       microscopic and approach the macroscopic, using both top-down and bottom-up
       approaches. The first is exemplified by scientists who build objects and
       molecular arrays using the techniques of scanning probe microscopy, while the
       second is exemplified by investigators who design two-and three-dimensional
(10)     chemical systems that cohere according to the rules of chemical interactions.
       The top-down approach has exquisite precision, but its disadvantage is its lack
       of extensive parallelism; it requires manipulating atoms and molecules
       practically one by one, while the bottom-up approach is massively parallel. But
       in both cases, scientists are forced to use the difficult nanometer scale, i.e. the
(15)     level at which living systems tend to make their structural components, rather
       than the angstrom scale of chemistry.
The passage provides information that would answer which of the following questions?
选项 A、What are some of the structural and chemical properties that nanotechnologists strive to create when they mold molecules?
B、Why are the techniques of scanning probe microscopy necessary to the production of objects and molecule arrays in the top-down method?
C、Which is more important to the future of nanotechnology, scientists’ use of the theoretical principles or practical experience?
D、Has the nanometer scale been considered easier than the angstrom scale for nanotechnologists to work with?
E、For what reasons do bottom-up nanotechnologists prefer to work with three- dimensional chemical systems that cohere according to the rules of chemical interactions?
答案D
解析
转载请注明原文地址:https://www.kaotiyun.com/show/9hjO777K
本试题收录于： GRE VERBAL题库GRE分类
0

GRE VERBAL

GRE

相关试题推荐
随机试题
最新回复(0)