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根据以下材料,回答题 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 extemal 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 understandingof 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. MIT researchers carry out the study to illustrate an ancient Chinese proverb. 查看材料
A.
Right
B.
Wrong
C.
Not mentioned
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【多选题】下列叙述哪些与胆碱受体激动剂的构效关系相符
A.
季铵氮原子为活性必须
B.
乙酰基上氢原子被芳环或较大分子量的基团取代后,活性增强
C.
在季铵氮原子和乙酰基末端氢原子之间,以不超过五个原子的距离(H-C-C-O-C-C-N)为佳。当主链长度增加时,活性迅速下降
D.
季铵氮原子上以甲基取代为最好
E.
亚乙基桥上烷基取代不影响活性
【单选题】有一两砖厚墙体,长8m,高5m,开有门窗总面积为6m2,两个通风洞口各为 0.25m2,门窗洞口上的钢筋混凝土过梁总体积为0.5m。。则该段墙体的砌砖工程量为 ( )m3。
A.
16.5
B.
16.16
C.
15.92
D.
16.75
【单选题】下列哪项不是伏寒化温病邪的致病特点().
A.
邪自里发
B.
易闭窍、动风、动血
C.
易耗伤肝肾阴液
D.
致病力强,无分老幼
【单选题】有一两砖厚墙体,长8m,高5m,开有门窗总面积为6m2,两个通风洞口各为0.25m2,门窗洞口上的钢筋混凝土过梁总体积为0.5m3。则该段墙体的砌砖工程量为( )。
A.
16.5m3
B.
16.16m3
C.
15.92m3
D.
16.75m3
【多选题】(多选) 关于 Lab 模式,以下哪些说法是正确的?
A.
Lab 是一种国际色彩标准模式
B.
L 通道表示透明度, a 和 b 通道表示色相和饱和度
C.
Lab 的图像处理速度比 CMYK 快,比 RGB 慢
D.
先将 RGB 模式转成 Lab 模式,再从 Lab 模式转成 CMYK 模式,可以减少图片的色彩损失
【单选题】若有以下语句,则下面四个选项中对ttd中lab成员的正确引用方式是 。 struct example{ char lab; int num; }ttd, *p=&ttd;
A.
(*p).lab
B.
p->ttd.lab
C.
(*p).ttd.lab
D.
p.ttd.lab
【单选题】.有一两砖厚墙体,长8m,高5m,开有门窗洞口总面积为6m2,两个通风洞口各为0.25m2,门窗洞口上的钢筋混凝土过梁总体积为0.5m3,则该段墙体的砌砖工程量为( )m3。
A.
16.5
B.
16.16
C.
15.92
D.
16.75
【单选题】有一两砖厚墙体,长8M,高5M,开有门窗总面积为6m2,两个通风洞口各为0.25m2,门窗洞口上的钢筋混凝土过梁总体积为0.5 m3.则该段墙体的砌砖工程量为( ) m3。
A.
16.5
B.
16.16
C.
15.92
D.
16.75
【单选题】有一两砖厚墙体,长8 m, 高5 m, 开有门窗总面积为6 m2, 两个通风洞口各为0.25 m2, 门窗洞口上的钢筋混凝土过梁总体积为0.5M3。则该段墙体的砌筑工程量为( )M3。
A.
16.5
B.
16.16
C.
15.92
D.
16.75
【单选题】淘宝商城成立于( )年。
A.
2006
B.
2007
C.
2008
D.
2009
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