考研英语阅读理解精读练习
William Illiam Morris (the wallpaper designer, rather than the carmaker) suggested that nothing should have a place that is not known to be uful or believed to be beautiful. Opals, though, might be both. A group of rearchers from the University of Southampton, in England, and the German Plastics Institute in Darmstadt, led by Jeremy Baumberg, have discovered how to create a plastic with the gemstone's iridescent properties. Their invention could be ud to make a sparkling substitute for paint, banknotes that are hard to counterfeit and chemical nsors that can act as visible ll-by dates.
Opals get their milky sheen and rainbow sparkle from the way light is scattered by the tiny crystals that form them. The crystals are stacked in what is known as a face-centred cubic structure. This means that the constituent atoms are arranged in a lattice of cubes, with one extra atom sitting at the centre of each cube's six faces. Light entering this lattice gets bounced around in ways that generate colour by reinforcing the peaks of some wavelengths and cancelling out tho of others.
For many years rearchers have been trying to develop a synthetic material with the same light-scattering properties as an opal, by etching patterns into various materials. That approach has failed. Instead, Dr Baumberg has built his opalescent material from scratch. He and his team grew tiny polystyrene spheres until they were some 200 nanometres across, before hardening them with a blast of heat. They then coated the spheres with a sticky polymer before heating them again. As the mixture was baked, the spheres moved naturally into a face-centred cubic structure.
The result is a flexible film of crystals with opalescent properties that can be ud to coat malleable surfaces, producing attractive iridescent hues. The size of the spheres can be tailored to scatter particular wavelengths of light—a uful property for curity applications in which it is important that materials can be identified precily. Moreover, when the film is warped, the spaces between the crystals change—and the colours produced change with them. The two properties make opalescent film an obvious material for currency. Banknotes containing it would produce distinctive colours when stretched, unlike counterfeits made from other materials.
To u the film to detect food spoilage, Dr Baumberg propos adding a sprinkle of carbon particles even smaller than the polystyrene spheres. The would nestle in the spaces between the spheres and cau the material to scatter light from even more angles, making it yet more iridescent. This arrangement could be “tuned” to react to specific toxic chemicals. Food packaging made from such a material would thus change colour as the rot t in.
Such packaging need not be expensive. The polymer spheres and carbon particles arrange themlves spontaneously into the correct crystal structure when encouraged by a little heat, so manufacturing opalescent film should be easy. Indeed Merck, a German chemical company that was a partner in the rearch, has already produced rolls of the stuff a metre wide and 100 metres long. Perfect for wallpaper.
金曲100首1．Which one of the following statement is NOT true of the opals according to the passage?
[A] For years, scientists’ endeavor of imitating opals’ unique characteristics has reached t
学习字母间多音字o nil.
[B] Opals could be brilliant mainly becau they have some kind of iridescent properties.
[C] Opals could be brilliant becau they have tiny crystals which could scatter light.
[D] Opals could be ud to make a sparkling substitute for paint.
2．The opalescent material that Dr Baumberg and his team have developed model itlf on _____
[A] the face-centred cubic structure of the opals.
[B] the light scattering properties of the opals.
[C] the tiny polystyrene spheres of the opals.
[D] the flexible film of crystals of the opals.
3．The flexible film of crystals Dr Baumberg has finally got is an ideal material for currenc
y becau _____
[A] it can be ud to coat malleable surfaces so that the currency could have iridescent hues.
开办小型加工厂[B] the colour change as the film is bent so that the currency could be identified precily.
[C] different colours could be produced as the film could be tailored to scatter particular wavelengths of light.
[D] certain colours could be made as the currency is distended so that it is easy to distinguish.
谦虚的名言4．The logic that food spoilage could be detected by u of the film is that _____致家长的一封信
[A] the carbon particles Dr Baumberg adds into the film could react to specific toxic chemicals.
山水美景
[B] the polystyrene spheres could scatter light from more angeles.
[C] carbon particles positioned among the spheres could be adjusted to be nsitive to addled materials.
[D] carbon particles added into the polystyrene spheres could make the film more iridescent. 复活节习俗
