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科学美国人60秒 SSS Frog Spit Behaves Like Bug-Catching Ketchup

时间:2017-03-15 05:23来源:互联网 提供网友:nan   字体: [ ]
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    (单词翻译:双击或拖选)

 

You might think frogs catch insects ‘cause their tongues are sticky. "But why is the tongue sticky, and how does it actually adhere to these insects at these very high accelerations1?" 

Those are the questions Alexis Noel, a PhD candidate in mechanical engineering at Georgia Tech, wanted to answer. So she and her team got frog tongues from a dissection2 lab, and tested their consistency3. Ten times softer than human tongues. A texture4 more like brain tissue. "Their tongue is very much like a sponge. It's infused with this thick, viscous5 saliva6." 

That saliva was their next study subject. "And in order to test the saliva we had to get about a fifth of a teaspoon7 of fluid. Which is a lot of saliva, in a frog's case." They put the saliva in a rheometer, a tool that can measure viscosity8. And they found that frog saliva is what's called a 'shear9-thinning fluid'—its viscosity changes, depending on conditions. 

You might be more familiar with a different shear-thinning fluid. "Ketchup10. When you smack11 the bottom of the ketchup bottle you're actually invoking12 shear forces within the ketchup itself. And ketchup, because it's shear thinning, its viscosity actually drops and allows it to slide out of the bottle easily." 

So back to our frogs: the tongue shoots out, hits the bug13 and deforms14 around it. That impact is like a smack on a ketchup bottle—it changes the saliva from thick and sticky to more watery15, free to flow all over the bug. Then the tongue bounces back, like a bungee cord, and the saliva thickens up again. What's next is beyond weird16.

"Frogs actually take their bulbous eyeballs and bring them down into their mouth cavity and use their eyeballs to shove the insect down the throat." That force turns the saliva watery again, "and the insect slides down the gullet." The study is in the Journal of the Royal Society Interface17. [Alexis C. Noel et al., Frogs use a viscoelastic tongue and non-Newtonian saliva to catch prey]

With the case closed on this one, Noel's next inquiries18 are on grippy fingertips. The dust-collecting properties of earwax. And—wait for it—cat tongues. "Yeah, I get paid to watch cat videos all day."

—Christopher Intagliata


点击收听单词发音收听单词发音  

1 accelerations a5575285a6c8cdfce08aa0d6a138a1d2     
n.加速( acceleration的名词复数 );加速度;(车辆)加速能力;(优秀学生的)跳级
参考例句:
  • The two particles will undergo accelerations as a result of their interaction. 这两个粒子由于相互作用将获得加速度。 来自辞典例句
  • Since the cord connecting the two blocks is inextensible, the accelerations are the same. 由于连接两物块的绳子无伸缩性,因此它们的加速度相同。 来自辞典例句
2 dissection XtTxQ     
n.分析;解剖
参考例句:
  • A dissection of your argument shows several inconsistencies.对你论点作仔细分析后发现一些前后矛盾之处。
  • Researchers need a growing supply of corpses for dissection.研究人员需要更多的供解剖用的尸体。
3 consistency IY2yT     
n.一贯性,前后一致,稳定性;(液体的)浓度
参考例句:
  • Your behaviour lacks consistency.你的行为缺乏一贯性。
  • We appreciate the consistency and stability in China and in Chinese politics.我们赞赏中国及其政策的连续性和稳定性。
4 texture kpmwQ     
n.(织物)质地;(材料)构造;结构;肌理
参考例句:
  • We could feel the smooth texture of silk.我们能感觉出丝绸的光滑质地。
  • Her skin has a fine texture.她的皮肤细腻。
5 viscous KH3yL     
adj.粘滞的,粘性的
参考例句:
  • Gases are much less viscous than liquids.气体的粘滞性大大小于液体。
  • The mud is too viscous.You must have all the agitators run.泥浆太稠,你们得让所有的搅拌机都开着。
6 saliva 6Cdz0     
n.唾液,口水
参考例句:
  • He wiped a dribble of saliva from his chin.他擦掉了下巴上的几滴口水。
  • Saliva dribbled from the baby's mouth.唾液从婴儿的嘴里流了出来。
7 teaspoon SgLzim     
n.茶匙
参考例句:
  • Add one teaspoon of sugar.加一小茶匙糖。
  • I need a teaspoon to stir my tea.我需要一把茶匙搅一搅茶。
8 viscosity ehPwf     
n.粘度,粘性
参考例句:
  • The viscosity shows a rather pronounced variation with temperature.温度对粘度的影响十分明显。
  • The reciprocal of viscosity is known as fluidity.粘度的反意就是流动性。
9 shear BzhwZ     
n.修剪,剪下的东西,羊的一岁;vt.剪掉,割,剥夺;vi.修剪,切割,剥夺,穿越
参考例句:
  • Every spring they shear off the sheep's wool and sell it.每年春天他们都要剪下羊毛去卖。
  • In the Hebrides they shear their sheep later than anywhere else.在赫伯里兹,剪羊毛的时间比其他任何地方都要晚。
10 ketchup B3DxX     
n.蕃茄酱,蕃茄沙司
参考例句:
  • There's a spot of ketchup on the tablecloth.桌布上有一点番茄酱的渍斑。
  • Could I have some ketchup and napkins,please?请给我一些番茄酱和纸手巾?
11 smack XEqzV     
vt.拍,打,掴;咂嘴;vi.含有…意味;n.拍
参考例句:
  • She gave him a smack on the face.她打了他一个嘴巴。
  • I gave the fly a smack with the magazine.我用杂志拍了一下苍蝇。
12 invoking ac7bba2a53612f6fe1454f6397475d24     
v.援引( invoke的现在分词 );行使(权利等);祈求救助;恳求
参考例句:
  • You can customise the behavior of the Asynchronous Server and hence re-brand it by defining your own command set for invoking services. 通过定义自己调用服务的命令集,您可以定制自定义异步服务器的行为,通过为调用服务定义自己的命令集从而对它重新标记。 来自《简明英汉词典》
  • You can customize the behavior of the Asynchronous Server and hence re-brand it by defining your own command set for invoking services. 通过定义自己调用服务的命令集,您可以定制自定义异步服务器的行为,通过为调用服务定义自己的命令集从而对它重新标记。 来自辞典例句
13 bug 5skzf     
n.虫子;故障;窃听器;vt.纠缠;装窃听器
参考例句:
  • There is a bug in the system.系统出了故障。
  • The bird caught a bug on the fly.那鸟在飞行中捉住了一只昆虫。
14 deforms b5a4b66c680718e36b2f4eeb31547b36     
使变形,使残废,丑化( deform的第三人称单数 )
参考例句:
  • Bad rheumatoid arthritis deforms limbs. 严重的类风湿性关节炎会造成四肢变形。
  • The specimen deforms under a tensile stress applied parallel to the fibres. 试样在平行于纤维的张应力作用下发生变形。
15 watery bU5zW     
adj.有水的,水汪汪的;湿的,湿润的
参考例句:
  • In his watery eyes there is an expression of distrust.他那含泪的眼睛流露出惊惶失措的神情。
  • Her eyes became watery because of the smoke.因为烟熏,她的双眼变得泪汪汪的。
16 weird bghw8     
adj.古怪的,离奇的;怪诞的,神秘而可怕的
参考例句:
  • From his weird behaviour,he seems a bit of an oddity.从他不寻常的行为看来,他好像有点怪。
  • His weird clothes really gas me.他的怪衣裳简直笑死人。
17 interface e5Wx1     
n.接合部位,分界面;v.(使)互相联系
参考例句:
  • My computer has a network interface,which allows me to get to other computers.我的计算机有网络接口可以与其它计算机连在一起。
  • This program has perspicuous interface and extensive application. 该程序界面明了,适用范围广。
18 inquiries 86a54c7f2b27c02acf9fcb16a31c4b57     
n.调查( inquiry的名词复数 );疑问;探究;打听
参考例句:
  • He was released on bail pending further inquiries. 他获得保释,等候进一步调查。
  • I have failed to reach them by postal inquiries. 我未能通过邮政查询与他们取得联系。 来自《现代汉英综合大词典》
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TAG标签:   科学美国人60秒  英语听力  sss
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