HAWLEY protons exchange with rates which are influenced by the net molecular charge of bacitracin and the steric environment of each individual proton. Oxidized bacitracin exchanges 10, NO.

The absorption of sound in emulsions and suspensions is due to viscous and thermal transport processes occurring at the interface of the nonhomogeneities, as well as to the intrinsic absorption in the materials comprising the system. A complete description of these processes for systems of fluid particles suspended in fluid media was given by Epstein and Carhart [J. Acoust. Soc. Amer. 25, 553 (1953)]. However, subsequent investigators of liquid systems have generally neglected the thermal transport process. We show in this work that the Epstein-Carhart results provide a good description of our experimental attenuation data in emulsions, and that the thermal transport process can be the major factor in the attenuation. We have here also extended the theory further to include the attenuation in suspensions of solid particles, and good agreement is found between our theory and experimental results for aqueous suspensions of polystyrene spheres.

Data for ultrasonic absorption and sound speed are given for water, methyl alcohol, ethyl alcohol, n-propyl alcohol, n-butyl alcohol, eugenol, carbon tetrachloride, n-hexane, and toluene, for pressures ranging up to about 5000 kg/cm2.

SynopsisThe effect of pressure on the melting temperature of DNA (Cl. perfringens) has been examined in several concentrations of neutral salt by measurement of uv absorbance.The results indicate that the apparent transition volume increases as the salt concentration, and hence the melting temperature, is raised, and suggest that the transition occurs without a change in volume at a T , of 59°C. Additional experiments were conducted in an effort to determine whether transition behavior can be found in other regions of pressure and temperature; no additional transition behavior was observed in experiments conducted with temperatures as low as -21.85OC at 2000 atm and pressures in excess of 9000 atm a t 58°C.

The absorption of sound in suspensions and emulsions, which can be several orders of magnitude greater than that in the pure substances, usually has been attributed to viscous dissipation processes including relative motion, the relaxing bulk modulus of the suspended material, or scattering. A description of these processes is contained in a more general theoretical treatment, which, in addition, indicates that thermal conduction in the vicinity of the interfaces results in substantial sound attenuation. The theoretical results will be discussed for viscous, compressible, thermal-conducting media and compared to observed experimental ultrasonic absorption behavior in a number of aqueous emulsions and suspensions. [This research was supported in part by the U. S. Office of Naval Research and the National Institutes of Health.]