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听力原文：W: Let' s shop around because we' ve got to buy two gifts, one for our parents for their 20th wedding anniversary, and one for Sally' s 30th birthday.
M: Okay, how about this blow dryer？ It' s a real bargain. I heard the last blow dryer she bought doesn't work any more! It hasn' t even been a month yet.
W: Oh, really？ No wonder that was cheaper than mine. How about this DVD player for our parents？ They sell like hot cakes.
M: Good! But let's pay by credit card because I have no cash now.
What are they buying for their parents？
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What did the man promise to do？
Who proved that Feynman's concept, "There's Plenty of Room at the Bottom" was right？
听力原文：M: I am pleased we've reached an agreement on the amount of materials. We just have a very tight budget. Thank you for your understanding.
W: I' m glad you are happy. But please help us next time. We are not making any profit this time.
M: I know it' s not giving you a margin. I promise that we will order at least 3,000 units every year!
W: That's a deal then.
What are they doing？
The inspiration for nanotech goes back to a 1959 speech by the late physicist Richard Feynman, then a professor at the California Institute of Technology, titled "There's Plenty of Room at the Bottom. " Four decades later, Chad Mirkin, a Chemistry professor at Northwestern University's $ 34 million nanotech center, used a nanoscale device to etch most of Feynman's speech onto a surface the size of about 10 tobacco smoke particles.
What accounts for the sudden acceleration of nanotechnology？ A key breakthrough came in 1990, when researchers at IBM's Almaden Research Center succeeded in rearranging individual atoms at will. Using a device' known as a scanning probe microscope, the team slowly moved 35 atoms to spell the three-letter IBM logo, thus proving Feynman right. The entire Logo was less than three nanometers.
Soon, scientists were not only manipulating individual atoms but "spray painting" with them as well. Using a tool known as a molecular beam epitaxy, scientists have learned to create ultra fine films of specialized crystals, built up one molecular layer at a time. This is the technology used today to build read-head components for computer hard drives.
The next stage in the development of nanotechnology borrows a page from nature. Building a supercomputer no bigger than a speck of dust might seem an impossible task, until one realizes that evolution solved such problems more than a billion years ago. Living cells contain all sorts of nanoscale motors made of proteins that perform. myriad mechanical and chemical functions, from muscle contraction to photosynthesis. In some instances, such motors may be re-engineered, or imitated, to produce products and processes useful to humans.
How are these biologically inspired machines constructed？ Often, they construct themselves, manifesting a phenomenon of nature known as self assembly. The macromolecules of such biological machines have exactly the right shape and chemical binding preferences to ensure that when they combine they will snap together in predesigned ways. For example, the two strands that make up DNA's double helix match each other exactly, which means that if they are separated in a complex chemical mixture, they are still able to find each other easily.
It can be inferred that Richard Feynman has been ______ now.
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