The control of acoustic streaming is expected to provide a promising method in microfluidic technologies. However, there are few research reports on such acoustic systems to control streaming velocity. To confirm whether velocity is affected by sound field distribution, we carried out some experiments using a focusing ultrasound transducer that consists of two coaxially arranged concentric piezoelectric elements: i.e., one is an inner disc element and the other an outer ring element. Both the elements can be driven by electric signals at the same frequency of 3.45 MHz but different phase angles. The spheroidal beam equation (SBE) for describing finite-amplitude ultrasound beams in a viscous fluid is successfully used to predict focused sound pressure distribution. The external driving force acting on the fluid is readily calculated on the basis of sound pressure, and then streaming velocity can be theoretically predicted using the continuity equation and Navier-Stokes equation with the term of force. The profiles of speed along and across the beam axis are measured by laser Doppler velocimetry. It has been confirmed that experimental data and theoretical predictions are in good agreement. The feasibility of controlling streaming is discussed by changing the phase difference between the two signals.

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Experimental and theoretical absorptance profiles of tracks of fast heaoy ions in nuclear emulsion. M. Jensen, L. Larsson, 0.Transverse absorptance profiles of 27 tracks of cosmic ray nuclei recorded in Ilford G5 nuclear emulsion have been measured by a nuclear track photometer. Included in the study were nuclei with atomic numbers 14, 16, 20, 24 and 26 with velocities relative to that of light within the interval 0.3 GpSO.8. 'The experimental absorptance profiles have been compared with theoretical profiles calculated from the &ray theory of track formation developed by Katz and coworkers. Taking into account the rescattering of light into the cone of acceptance of the photometer, good agreement has been found between experimental and theoretical profiles within the entire charge and velocity interval. The semi-empirical formula for high aperture photometry is discussed in some detail, as well as the theory of &ray production and the transport of electrons and their energy dissipation in nuclear emulsion. ~~ ' Present address:

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Abstract. Endoscopic ultrasonography guided focused ultrasound surgery (EUS-FUS) have been developed as a less-invasive treatment for pancreatic cancer. In the present study, microbubble-enhanced heating for various parameters in EUS-FUS is investigated numerically. Mass and momentum equations for bubbly mixture are solved to reproduce the propagation of ultrasound of 4.8MHz through the gel containing microbubbles as Sonazoid®. The dynamics of bubble is governed by the equation which considers the elasticity of both shell and surrounding media. Additionally, the heat equation with the time averaged heat source is solved to obtain a temperature distribution. The basic equations are discretized by the 6 th -order finite difference method and developed based on FDTD method. The mixture and bubbles are coupled by EulerLagrange method. As the results, the temperature around the target increased due to the microbubble oscillation with increasing the initial void fraction f G0 from 10 -5 to 10 -4 %. However, at f G0 =10 -3 %, ultrasounds were too attenuated to heat the target. The heating region moved from the target to the transducer side. By comparing the results with and without shell, the shell of bubble induced the heating around focus. This is because the decrease of the attenuation due to the elasticity of the shell and the increase of the viscous dissipation rate due to the viscosity of the shell.