Index of content:
Volume 128, Issue 1, July 2010
- NONLINEAR ACOUSTICS 
128(2010); http://dx.doi.org/10.1121/1.3436520View Description Hide Description
This paper numerically investigates the effect of mass transfer processes on spherical single bubble dynamics using the Hertz–Langmuir–Knudsen approximation for the mass flux across the interface.Bubble behavior, with and without mass transfer, is studied for different values of pressure wave amplitude and frequency, as well as initial bubble radius. Whereas mass transfer processes do not seem to play a significant role on the bubble response for pressure amplitudes smaller than 0.9 atm, they appear to have an important effect when the amplitude is greater than or equal to 1 atm. For the later case, where the minimum liquidpressure reaches values around its vapor pressure, the importance of mass transfer depends on frequency. For frequencies in the range and initial bubble radii of the order of tens of microns, bubble implosions with and with no mass transfer are significantly different; smaller radii display a lower sensitivity. In this regime, accurate model predictions must, therefore, carefully select the correct value of the accommodation coefficient. For frequencies greater than , as a first approximation mass transfer can be ignored.
Theoretical investigation of shear stress generated by a contrast microbubble on the cell membrane as a mechanism for sonoporation128(2010); http://dx.doi.org/10.1121/1.3419775View Description Hide Description
There are numerous experimental investigations on sonoporation, while the theoretical background of this phenomenon still is in its infancy. One of the suggested mechanisms of sonoporation is linked to shear stress exerted on the cell membrane by acoustic microstreaming generated by a contrast microbubble pulsating nearby a cell. Currently, the existing model of this effect is based on an equation that has been derived for a free hemispherical bubble resting on a rigid plane. Such a model is not adequate for a contrast microbubble. In this paper, an improved theory is suggested that assumes an encapsulated bubble to be detached from the cell membrane. The improved model allows one to calculate the shear stress distribution on the cell membrane at different values of the acoustic parameters. The second problem considered is how to apply the model for pairwise bubble-cell interactions to bubble-cell solutions, which one has to deal with in experiments. An approach is proposed to evaluate the number of sonoporated cells in a bubble-cell solution. It is shown that the reaction of a bubble-cell solution to the variation of the acoustic parameters can be different from what is predicted by the analysis of interactions between single bubbles and cells.