CHAPTER SEVEN 



SONIC AND OSMOTIC EFFECTS ON VIRUSES 



A sound wave is a compression-rarefaction wave which can 

 travel in any material medium. It is possible to excite high- 

 frequency sound waves very satisfactorily by using the piezo- 

 electric properties of a quartz crystal. If a high-frequency elec- 

 tric field is applied to a quartz crystal, cut so that its mechanical 

 vibration is resonant with the electric field, then mechanical 

 oscillations are set up which can be communicated to a liquid 

 and produce sound waves. Energies of up to 100 watts at one 

 megacycle per second (mc), or even up to 30 mc with less energy, 

 are possible, so that considerable power can be dissipated in the 

 sound wave. 



A consideration of ultrasonic action has been given by Fry, 

 Wulff, Tucker, and Fry (1950). Although their work has not 

 been concerned with viruses themselves, they point out the 

 various physical factors which can enter into the process of 

 sonic inactivation. It is clear that temperatures are developed 

 which are quite able to account for many inactivation data. 



Pressures Developed 



The pressure, amplitude and density are related by the 

 equation 



P2 = 2pT7 (7.1) 



where P is the pressure in dynes per square centimeter, p is 

 the density in grams per cubic centimeter, V is the velocity of 

 sound in centimeters per second, and / is the intensity in ergs 

 per square centimeter. For a case where 35 watts/cm- are de- 

 veloped, the pressure amplitude can be 10 atmospheres. Note 

 that the pressure swings to low pressure also. Actually, as pres- 



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