英語聽力頻道為大家整理的英語聽力mp3下載：經(jīng)濟(jì)學(xué)人之越敲越結(jié)實(shí)，供大家參考:)
Science and Technology
科學(xué)與技術(shù)
Materials science
材料科學(xué)
Stronger when stricken
越敲越結(jié)實(shí)
A new material that gets stiffer when it is stressed
一種受外力時(shí)硬度提高的新材料
ONE of the valuable properties of bone is that when it endures repeated stress it responds by becoming denser and stronger.
骨頭有一種很珍貴的屬性，那就是當(dāng)受到反復(fù)的擊打時(shí)，其質(zhì)地反而會(huì)變得更加緊密，堅(jiān)硬度變得更高。
A living material can do that.
只有活性材料具備這種特征，
A non-living one cannot.
非活性材料則不具備。
It has no way of adding the extra matter needed to provide the extra density.
用添加必要物質(zhì)來讓材料獲得更高密度的方法是不可行的，
But it would help engineers a lot if non-living stuff could at least stiffen in response to stress—and that may now be possible.
但如果非活性材料起碼可以在外力作用下變得堅(jiān)硬—目前達(dá)到這一點(diǎn)是可能的，
Brent Carey, a graduate student at Rice University in Texas, thinks he has found a way to make it happen.
那么這對(duì)工程師們來說有非常大的借鑒意義。布倫特凱利是一名德州萊斯大學(xué)的研究生，他認(rèn)為他已找到了實(shí)現(xiàn)這一設(shè)想的辦法。
Mr Carey made his discovery when he was testing the properties of a material made of carbon nanotubes and a rubbery polymer called polydimethylsiloxane.
凱利在測(cè)試一種材料的屬性時(shí)有所發(fā)現(xiàn)，該材料的成分包含碳納米管和一種名為聚二甲基硅氧烷的橡膠聚合物。
He created this composite by growing a forest of nanotubes using hot hydrocarbon gases and an iron catalyst, and then filling the space between the tubes with the polymer.
材料的合成過程是這樣：首先，他使高溫碳?xì)浠旌蠚怏w和鐵催化劑相互作用產(chǎn)生密集的碳納米管群，然后再用聚合物充填碳納米管間的空隙。
The surprise came when he discovered how his new material responded to repeated stress.
當(dāng)他注意到新材料受到連續(xù)作用力而產(chǎn)生反應(yīng)時(shí)，令他驚訝的現(xiàn)象出現(xiàn)了。
He found this did not cause any of the damaging fatigue that would be expected.
據(jù)他觀察，預(yù)期中的材料損毀性疲勞并未產(chǎn)生。
Indeed, his initial inspection suggested the stuff was actually growing stiffer.
實(shí)際上，他的初步監(jiān)測(cè)顯示材料變得更加堅(jiān)硬了。
Fascinated by this result, he took his finding to his supervisor, Pulickel Ajayan,
這個(gè)結(jié)果讓凱利喜出望外，他馬上找到了自己的導(dǎo)師普里克爾阿賈揚(yáng)，
and they assembled a team to study the new material.
隨后他們成立了一個(gè)小組，專門研究這種新型材料。
They gave the composite a real workout.
他們給這種合成材料做了次實(shí)驗(yàn)：
They compressed it five times a second for a week.
對(duì)該材料施加5.5倍的壓力，時(shí)間持續(xù)一周，
That caused its stiffness to increase by 12%. Moreover,
結(jié)果材料硬度提高了12%，并且這種狀態(tài)沒有減弱的跡象。
the effect showed no sign of abating, which led them to suspect that if it were exposed to more stress it would grow stiffer still.
研究小組由此設(shè)想，如果對(duì)其施以更大的作用力，這種材料的硬度是否會(huì)變得更高。
Why this happens is still a mystery.
產(chǎn)生這種效果的原因還是個(gè)謎。
Mr Carey and his colleagues report in the American Chemical Society's journal Nano that heating the new material did not eliminate the response.
凱利和他的同事們發(fā)表在美國(guó)化工科學(xué)院的期刊雜志《Nano》的文章中說，即使對(duì)這種新型材料加熱，也不能消除已產(chǎn)生的變化。
This suggests that the self-stiffening is not the result of chemical changes in the polymer, which can usually be undone by heat.
這說明材料強(qiáng)度提高并不是聚合物發(fā)生化學(xué)反應(yīng)造成的，一般這種變化在加熱狀態(tài)下是可逆的。
The researchers do have one lead, though.
不過研究人員已有所發(fā)現(xiàn)。
Because of the regular alignment of the nanotubes, they were able to stress the material from various directions.
由于碳納米管呈規(guī)律狀排列，他們能夠從不同的方向?qū)Σ牧鲜┘幼饔昧Α?BR> They found that when the direction of stress was at right-angles to the tubes, it stiffened by 5.9%.
當(dāng)施力方向與碳納米管成直角時(shí)，材料硬度提高5.9%；
When it was in the direction in which tubes were pointing, the increase was only 4.3%.
當(dāng)作用力與碳納米管所指方向一致時(shí)，材料硬度僅提高4.3%。
What that means is still unclear, but it may be the key to understanding the phenomenon—and thus being able to replicate it with other ingredients.
現(xiàn)在尚無法對(duì)其中的原因作出解釋，但或許對(duì)于理解材料硬度變化是非常重要的—進(jìn)而在其他原材料身上復(fù)制這類變化也有了可能。
Science and Technology
科學(xué)與技術(shù)
Materials science
材料科學(xué)
Stronger when stricken
越敲越結(jié)實(shí)
A new material that gets stiffer when it is stressed
一種受外力時(shí)硬度提高的新材料
ONE of the valuable properties of bone is that when it endures repeated stress it responds by becoming denser and stronger.
骨頭有一種很珍貴的屬性，那就是當(dāng)受到反復(fù)的擊打時(shí)，其質(zhì)地反而會(huì)變得更加緊密，堅(jiān)硬度變得更高。
A living material can do that.
只有活性材料具備這種特征，
A non-living one cannot.
非活性材料則不具備。
It has no way of adding the extra matter needed to provide the extra density.
用添加必要物質(zhì)來讓材料獲得更高密度的方法是不可行的，
But it would help engineers a lot if non-living stuff could at least stiffen in response to stress—and that may now be possible.
但如果非活性材料起碼可以在外力作用下變得堅(jiān)硬—目前達(dá)到這一點(diǎn)是可能的，
Brent Carey, a graduate student at Rice University in Texas, thinks he has found a way to make it happen.
那么這對(duì)工程師們來說有非常大的借鑒意義。布倫特凱利是一名德州萊斯大學(xué)的研究生，他認(rèn)為他已找到了實(shí)現(xiàn)這一設(shè)想的辦法。
Mr Carey made his discovery when he was testing the properties of a material made of carbon nanotubes and a rubbery polymer called polydimethylsiloxane.
凱利在測(cè)試一種材料的屬性時(shí)有所發(fā)現(xiàn)，該材料的成分包含碳納米管和一種名為聚二甲基硅氧烷的橡膠聚合物。
He created this composite by growing a forest of nanotubes using hot hydrocarbon gases and an iron catalyst, and then filling the space between the tubes with the polymer.
材料的合成過程是這樣：首先，他使高溫碳?xì)浠旌蠚怏w和鐵催化劑相互作用產(chǎn)生密集的碳納米管群，然后再用聚合物充填碳納米管間的空隙。
The surprise came when he discovered how his new material responded to repeated stress.
當(dāng)他注意到新材料受到連續(xù)作用力而產(chǎn)生反應(yīng)時(shí)，令他驚訝的現(xiàn)象出現(xiàn)了。
He found this did not cause any of the damaging fatigue that would be expected.
據(jù)他觀察，預(yù)期中的材料損毀性疲勞并未產(chǎn)生。
Indeed, his initial inspection suggested the stuff was actually growing stiffer.
實(shí)際上，他的初步監(jiān)測(cè)顯示材料變得更加堅(jiān)硬了。
Fascinated by this result, he took his finding to his supervisor, Pulickel Ajayan,
這個(gè)結(jié)果讓凱利喜出望外，他馬上找到了自己的導(dǎo)師普里克爾阿賈揚(yáng)，
and they assembled a team to study the new material.
隨后他們成立了一個(gè)小組，專門研究這種新型材料。
They gave the composite a real workout.
他們給這種合成材料做了次實(shí)驗(yàn)：
They compressed it five times a second for a week.
對(duì)該材料施加5.5倍的壓力，時(shí)間持續(xù)一周，
That caused its stiffness to increase by 12%. Moreover,
結(jié)果材料硬度提高了12%，并且這種狀態(tài)沒有減弱的跡象。
the effect showed no sign of abating, which led them to suspect that if it were exposed to more stress it would grow stiffer still.
研究小組由此設(shè)想，如果對(duì)其施以更大的作用力，這種材料的硬度是否會(huì)變得更高。
Why this happens is still a mystery.
產(chǎn)生這種效果的原因還是個(gè)謎。
Mr Carey and his colleagues report in the American Chemical Society's journal Nano that heating the new material did not eliminate the response.
凱利和他的同事們發(fā)表在美國(guó)化工科學(xué)院的期刊雜志《Nano》的文章中說，即使對(duì)這種新型材料加熱，也不能消除已產(chǎn)生的變化。
This suggests that the self-stiffening is not the result of chemical changes in the polymer, which can usually be undone by heat.
這說明材料強(qiáng)度提高并不是聚合物發(fā)生化學(xué)反應(yīng)造成的，一般這種變化在加熱狀態(tài)下是可逆的。
The researchers do have one lead, though.
不過研究人員已有所發(fā)現(xiàn)。
Because of the regular alignment of the nanotubes, they were able to stress the material from various directions.
由于碳納米管呈規(guī)律狀排列，他們能夠從不同的方向?qū)Σ牧鲜┘幼饔昧Α?BR> They found that when the direction of stress was at right-angles to the tubes, it stiffened by 5.9%.
當(dāng)施力方向與碳納米管成直角時(shí)，材料硬度提高5.9%；
When it was in the direction in which tubes were pointing, the increase was only 4.3%.
當(dāng)作用力與碳納米管所指方向一致時(shí)，材料硬度僅提高4.3%。
What that means is still unclear, but it may be the key to understanding the phenomenon—and thus being able to replicate it with other ingredients.
現(xiàn)在尚無法對(duì)其中的原因作出解釋，但或許對(duì)于理解材料硬度變化是非常重要的—進(jìn)而在其他原材料身上復(fù)制這類變化也有了可能。