Biomedical subjects

Ruediger Toegel

Publications and source records attributed to Ruediger Toegel.

3 recordsLinked to original sources

PubMed2006

Viscosity destabilizes sonoluminescing bubbles.

In single-bubble sonoluminescence (SBSL) microbubbles are trapped in a standing sound wave, typically in water or water-glycerol mixtures. However, in viscous liquids such as glycol, methylformamide, or sulphuric acid it is not possible to trap the bubble in a stable position. This is very peculiar as larger viscosity normally stabilizes the dynamics. Suslick and co-workers call this new mysterious state of SBSL "moving-SBSL." We identify the history force (a force nonlocal in time) as the origin of this destabilization and show that the instability is parametric. A force balance model quantitatively accounts for the observed quasiperiodic bubble trajectories.

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PubMed2003

Harmonic enhancement of single-bubble sonoluminescence.

It is known from experiment that the light emission from a sonoluminescing bubble can be increased by using more than one driving frequency. In this paper, a systematic method to determine the optimal conditions of pressure amplitude and relative phase for this effect is described. As a specific application, a two-frequency system--26.5 kHz and 53 kHz--is considered. It is found that the maximum temperatures achievable can be appreciably increased with respect to single-frequency drive, still maintaining spherical stability, provided the dissolved inert gas concentration is kept extremely low in order to maintain diffusive stability.

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PubMed2002

Suppressing dissociation in sonoluminescing bubbles: the effect of excluded volume.

Recent theoretical work in single-bubble sonoluminescence has suggested that water vapor in the collapsing bubble leads to energy-consuming chemical reactions, restricting the peak temperatures to values for which hardly any light emission could occur. Analyzing the reaction thermodynamics within the dense, collapsed bubble, we demonstrate that the excluded volume of the nonideal gas results in pronounced suppression of the particle-producing endothermic reactions. Thus, sufficiently high temperatures for considerable bremsstrahlung emission can be achieved.

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