第2部分：閱讀判斷(第16~22題，每題1分，共7分)

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New Understanding of Natural Silk’s Mysteries

Natural silk, as we all know, has a strength that manmade materials have long struggled to match. In a discovery that sounds more like an ancient Chinese proverb than a materials science breakthrough, MIT researchers have discovered that silk gets its strength from its weakness. Or, more specifically, its many weaknesses. Silk gets its extraordinary durability and ductility from an unusual arrangement of hydrogen bonds that are inherently very weak but that work together to create a strong, flexible structure.

Most materials -- especially the ones we engineer for strength -- get their toughness from brittleness. As such, natural silks like those produced by spiders have long fascinated both biologists and engineers because of their light weight, ductility and high strength (pound for pound, silk is stronger than steel and far less brittle). But on its face, it doesn't seem that silks should be as strong as they are; molecularly, they are held together by hydrogen bonds, which are far weaker than the covalent bonds found in other molecules.

To get a better understanding of how silk manages to produce such strength through such weak bonds, the MIT team created a set of computer models that allowed them to observe the way silk behaves at the atomic level. They found that the arrangement of the tiny silk nanocrystals is such that the hydrogen bonds are able to work cooperatively, reinforcing one another against external forces and failing slowly when they do fail, so as not so allow a sudden fracture to spread across a silk structure.

The result is natural silks that can stretch and bend while retaining a high degree of strength. But while that's all well and good for spiders, bees and the like, this understanding of silk geometry could lead to new materials that are stronger and more ductile than those we can currently manufacture. Our best and strongest materials are generally expensive and difficult to produce (requiring high temperature treatments or energy-intensive processes).

By looking to silk as a model, researchers could potentially devise new manufacturing methods that rely on inexpensive materials and weak bonds to create less rigid, more forgiving materials that are nonetheless stronger than anything currently on offer. And if you thought you were going to get out of this materials science story without hearing about carbon nanotubes, think again. The MIT team is already in the lab looking into ways of synthesizing silk-like structures out of materials that are stronger than natural silk -- like carbon nanotubes. Super-silks are on the horizon.

參考譯文：

我們都知道，蠶絲具有的韌性是人造織物長期奮力追求的目標(biāo)。在一項(xiàng)研究中(該項(xiàng)研究成果聽起來更像一則古代中國諺語，而不是材料科學(xué)的突破)，麻省理工學(xué)院的研究人員發(fā)現(xiàn)，蠶絲的力量源于其脆弱，或者，更具體地說，是它的多方面的脆弱。蠶絲的異常耐久性和延展性來自一種特別的氫鍵結(jié)構(gòu)，這些氫鍵本質(zhì)上非常脆弱，但它們共同創(chuàng)造了一種強(qiáng)壯而富有彈性的結(jié)構(gòu)。

大多數(shù)材料(特別是那些要求硬度很高的材料)的韌性來自脆性。因此，和蜘蛛制造的蛛絲類似的蠶絲，因其重量輕，延展性強(qiáng)和韌性高，長期以來引起了生物學(xué)家和工程師的興趣(同樣重量，蠶絲比鋼要壯，也不那么脆)。但表面上，蠶絲看起來卻不那么強(qiáng)壯;從分子結(jié)構(gòu)上看，它們是由氫鍵組成的，氫鍵比其他分子中發(fā)現(xiàn)的共價(jià)鍵要脆弱得多。

為了更好地了解蠶絲如何以如此脆弱的化學(xué)鍵產(chǎn)生這么強(qiáng)壯的力，麻省理工學(xué)院的研究小組創(chuàng)造了一套計(jì)算機(jī)模型，這種模型能夠讓他們在原子層次上觀察蠶絲的活動(dòng)方式。他們發(fā)現(xiàn)，微小蠶絲納米晶體的結(jié)構(gòu)使氫鍵能夠齊心協(xié)力地合作，相互增援，對抗外力，同時(shí)，當(dāng)外力減弱時(shí)也隨之慢慢減弱，這樣就不至于在蠶絲的整體結(jié)構(gòu)上出現(xiàn)突然的斷裂。

這樣，天然絲能夠既伸縮和彎曲，又能夠保持極高的韌力。對于蜘蛛和蜜蜂之類的昆蟲來說這也沒什么，但對于蠶絲幾何形狀的這種了解，可能幫助人們制造出比我們面前能夠制造的材料更結(jié)實(shí)而又更柔軟的新材料。最好和最結(jié)實(shí)的材料通常是很昂貴而又難以制造的(需要高溫處理，或者高能耗處理)。

通過研究蠶絲作為一個(gè)例子，研究人員有可能設(shè)計(jì)出制造材料的一種新方法，即用廉價(jià)材料和弱鍵，制造不那么堅(jiān)硬而又柔軟，但比目前所用的任何材料都結(jié)實(shí)的材料。如果你認(rèn)為不研究碳納米管的理論，就能從這一則材料學(xué)信息中獲取制造方法，那請三思。麻省理工學(xué)院研究小組已經(jīng)在實(shí)驗(yàn)室利用比蠶絲還結(jié)實(shí)的材料(比如碳納米管)研究合成類似蠶絲一樣的結(jié)構(gòu)。超級蠶絲即將出現(xiàn)。

16. MIT researchers carry out the study to illustrate an ancient Chinese proverb.

A. Right B. Wrong C. Not mentioned

17. Silk’s strength comes from its weak hydrogen bonds working together.

A. Right B. Wrong C. Not mentioned

18. Biologist and engineer are interested in understanding natural silks because they are very light and brittle.

A. Right B. Wrong C. Not mentioned

19. If the hydrogen bonds break due to external forces, they break fast.

A. Right B. Wrong C. Not mentioned

20. The MIT team had tried different materials before they studied natural silk in their research.

A. Right B. Wrong C. Not mentioned

21. Carbon nanotubes are currently the most popular topic in material science.

A. Right B. Wrong C. Not mentioned

22. It is indicated that materials stronger than natural silk can be expected in the future.

A. Right B. Wrong C. Not mentioned

參考答案：BABBCCA

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