The use of frequency mixing to distinguish size distributions of gas-filled micropores.
The presence of difference frequencies produced by frequency mixing from the nonlinear resonance of gas bodies has been employed to detect gas in porous hydrophobic membranes and to distinguish between gas bodies in the membranes with pore sizes. Calculations based on measured pore sizes were used to predict the range of frequencies over which resonance may be expected and also to predict that the two different nominal pore sizes in this study would have distinguishable resonance characteristics. Measurements of porous and nonporous membrane scattering characteristics before and after membrane pressurization and measurements of receiver linearity indicate that resonance of the gas bodies in the membranes is the origin of the observed difference-frequency amplitudes. Difference-frequency amplitudes in the spectra of signals scattered from the membranes with smaller pores are found to peak at excitation frequencies higher than difference-frequency amplitudes produced by membranes with larger pores and generally follow the predictions of the calculations. The results show that a two-frequency mixing technique is capable of detecting and distinguishing sizes of gas bodies that may exist in vivo and serve as cavitation nuclei.
Quain
R M
RM
Department of Biophysics, University of Rochester Medical Center, NY 14642.
Waag
R C
RC
Miller
M W
MW
D005740:Gases; D008851:Micropore Filters; D010316:Particle Size; D014463:Ultrasonography / Q000379:methods*
D005740:Gases