radian 2πrad =360° 1πrad =180°
1°=π/180 rad(about 57.29578°)
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[2012.09.12]驚奇的新發明---聲波懸浮器( acoustic levitator)


美國 DOE Argonne National Laboratory 研發出利用聲波來懸浮 水滴,

的無容處理(containerless processing)
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  • News Of New Scienist :  (英文新聞轉貼)

These drops of liquid really are floating in mid-air. It's not a trick photo and they're not in the microgravity of space. But NASA does have something to do with this wizardry: an acoustic levitator that the agency originally developed is holding the droplets in place.

The levitator consists of two small speakers, one above the other, which generate sound waves at frequencies of about 22 kilohertz - slightly higher than humans can hear. When the sound waves from the top and bottom speakers are aligned they create a standing wave. At the nodes of this wave there is no net transfer of energy and pressure from the sound waves cancels the effect of gravity on light objects like these drops.

This technique has been developed at Argonne National Laboratory in Illinois as part of a search for methods of "containerless processing" for drug development. When extracting pharmaceuticals from solution in a container, the chemicals often take their crystalline form. Take away the container, though, and many drugs retain an amorphous structure, which allows the body to absorb them more efficiently. This in turn means they require smaller doses to be effective.

"One of the biggest challenges when it comes to drug development is in reducing the amount of the drug needed to attain the therapeutic benefit, whatever it is," said Chris Benmore, who led the study. The levitating liquids can also be probed in situ with high-energy X-rays so the team can watch chemical processes in the levitating liquids.

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