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SSS 2011-02-17

时间:2011-03-04 05:46来源:互联网 提供网友:yw7514   字体: [ ]
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    (单词翻译:双击或拖选)

This is Scientific American’s 60-Second Science. I’m Cynthia Graber. This will just take a minute.

Usually, we trust common sense to solve problems. Is a runny mixture too thick? Add some fluid. That’ll make it runnier. Except when the fluid makes it thicker. Scientists now think they know why.

The flow of a runny mixture, technically1 a suspension, is generally controlled by the size, shape and amount of the solid particles. The researchers started out with tiny hydrophilic glass beads2 in an organic solvent3. Then they added just one percent weight of water. And like when you add water to sand and it clumps4 together, the mix turned into almost a gel. Microscopic5 analysis showed that a few beads stick tightly to each water drop.

Then the scientists made the glass beads hydrophobic. But the addition of water still made the mixture firmer. Turns out that in this case the beads form loose rings around the water droplets6, as this formation minimizes each beads contact with water. The research was published in the journal Science.

The scientists say this effect could be used to keep solids from separating out of liquids, or to fine-tune the viscosity7 of a liquid in engineering. Because sometimes, to make a mixture thicker, just add water.

Thanks for the minute. For Scientific American’s 60-Second Science, I’m Cynthia Graber.


点击收听单词发音收听单词发音  

1 technically wqYwV     
adv.专门地,技术上地
参考例句:
  • Technically it is the most advanced equipment ever.从技术上说,这是最先进的设备。
  • The tomato is technically a fruit,although it is eaten as a vegetable.严格地说,西红柿是一种水果,尽管它是当作蔬菜吃的。
2 beads 894701f6859a9d5c3c045fd6f355dbf5     
n.(空心)小珠子( bead的名词复数 );水珠;珠子项链
参考例句:
  • a necklace of wooden beads 一条木珠项链
  • Beads of perspiration stood out on his forehead. 他的前额上挂着汗珠。
3 solvent RFqz9     
n.溶剂;adj.有偿付能力的
参考例句:
  • Gasoline is a solvent liquid which removes grease spots.汽油是一种能去掉油污的有溶解力的液体。
  • A bankrupt company is not solvent.一个破产的公司是没有偿还债务的能力的。
4 clumps a9a186997b6161c6394b07405cf2f2aa     
n.(树、灌木、植物等的)丛、簇( clump的名词复数 );(土、泥等)团;块;笨重的脚步声v.(树、灌木、植物等的)丛、簇( clump的第三人称单数 );(土、泥等)团;块;笨重的脚步声
参考例句:
  • These plants quickly form dense clumps. 这些植物很快形成了浓密的树丛。 来自《简明英汉词典》
  • The bulbs were over. All that remained of them were clumps of brown leaves. 这些鳞茎死了,剩下的只是一丛丛的黃叶子。 来自《简明英汉词典》
5 microscopic nDrxq     
adj.微小的,细微的,极小的,显微的
参考例句:
  • It's impossible to read his microscopic handwriting.不可能看清他那极小的书写字迹。
  • A plant's lungs are the microscopic pores in its leaves.植物的肺就是其叶片上微细的气孔。
6 droplets 3c55b5988da2d40be7a87f6b810732d2     
n.小滴( droplet的名词复数 )
参考例句:
  • Droplets of sweat were welling up on his forehead. 他额头上冒出了滴滴汗珠。 来自辞典例句
  • In constrast, exhaled smoke contains relatively large water droplets and appears white. 相反,从人嘴里呼出的烟则包含相当大的水滴,所以呈白色。 来自辞典例句
7 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。
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