61 research outputs found
An Alternative Method to Deduce Bubble Dynamics in Single Bubble Sonoluminescence Experiments
In this paper we present an experimental approach that allows to deduce the
important dynamical parameters of single sonoluminescing bubbles (pressure
amplitude, ambient radius, radius-time curve) The technique is based on a few
previously confirmed theoretical assumptions and requires the knowledge of
quantities such as the amplitude of the electric excitation and the phase of
the flashes in the acoustic period. These quantities are easily measurable by a
digital oscilloscope, avoiding the cost of expensive lasers, or ultrafast
cameras of previous methods. We show the technique on a particular example and
compare the results with conventional Mie scattering. We find that within the
experimental uncertainties these two techniques provide similar results.Comment: 8 pages, 5 figures, submitted to Phys. Rev.
Investigation of transition frequencies of two acoustically coupled bubbles using a direct numerical simulation technique
The theoretical results regarding the ``transition frequencies'' of two
acoustically interacting bubbles have been verified numerically. The theory
provided by Ida [Phys. Lett. A 297 (2002) 210] predicted the existence of three
transition frequencies per bubble, each of which has the phase difference of
between a bubble's pulsation and the external sound field, while
previous theories predicted only two natural frequencies which cause such phase
shifts. Namely, two of the three transition frequencies correspond to the
natural frequencies, while the remaining does not. In a subsequent paper [M.
Ida, Phys. Rev. E 67 (2003) 056617], it was shown theoretically that transition
frequencies other than the natural frequencies may cause the sign reversal of
the secondary Bjerknes force acting between pulsating bubbles. In the present
study, we employ a direct numerical simulation technique that uses the
compressible Navier-Stokes equations with a surface-tension term as the
governing equations to investigate the transition frequencies of two coupled
bubbles by observing their pulsation amplitudes and directions of translational
motion, both of which change as the driving frequency changes. The numerical
results reproduce the recent theoretical predictions, validating the existence
of the transition frequencies not corresponding to the natural frequency.Comment: 18 pages, 8 figures, in pres
Comparative study of non-invasive force and stress inference methods in tissue
In the course of animal development, the shape of tissue emerges in part from
mechanical and biochemical interactions between cells. Measuring stress in
tissue is essential for studying morphogenesis and its physical constraints.
Experimental measurements of stress reported thus far have been invasive,
indirect, or local. One theoretical approach is force inference from cell
shapes and connectivity, which is non-invasive, can provide a space-time map of
stress and relies on prefactors. Here, to validate force- inference methods, we
performed a comparative study of them. Three force-inference methods, which
differ in their approach of treating indefiniteness in an inverse problem
between cell shapes and forces, were tested by using two artificial and two
experimental data sets. Our results using different datasets consistently
indicate that our Bayesian force inference, by which cell-junction tensions and
cell pressures are simultaneously estimated, performs best in terms of accuracy
and robustness. Moreover, by measuring the stress anisotropy and relaxation, we
cross-validated the force inference and the global annular ablation of tissue,
each of which relies on different prefactors. A practical choice of
force-inference methods in distinct systems of interest is discussed.Comment: 12 pages, 8 figures, EPJ E: Topical issue on "Physical constraints on
morphogenesis and evolution
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