Microscopic Air Bubbles Research Articles

Enhancement of parametric efficiency by saturation suppression

The energy conservation equations due to Westervelt are used to show that saturation effects in a finite amplitude wave can in principle be suppressed, if the attenuation coefficient at the second harmonic frequency of the primary wave can be selectively increased. Introduction of microscopic air bubbles which are resonant at the second harmonic frequency is proposed as a scheme for applying this idea to a parametric array operating in water. The parameter of non-linearity also increases when the bubbles are introduced; hence parametric efficiency would be enhanced by both of these effects.

A Preventive Method for Bubble Formation in Methacrylate Embedding

As a Preventive msthod for bubble formation in methacrylate embedding of tissue blocks, the authors have tried a procedure in which reduction of surrounding air pressor up to 10 to 20 mm Hg within a vaccume dessicator is applied to the tissue blocks during routine dehydration in 70 to 90% alcohol. The results of embedding with and without the above reduction procedure were compared with each other in many kinds of tissues statistically. A group of blocks with the reduction procedure before embedding showed prominent decrease of bubble formation less than half of the other group without the procedure. The effectiveness of this procedure may be mostly due to the removal of the microscopic air bubbles by the reduction of surrounding air pressor. This procedure will be useful in embedding of very important but few tissue blocks.