Affiliations: [a] Department of Physiology and Biophysics, University of Southern California, School of Medicine, Los Angeles, CA, USA
Note: [*] Reprint requests to: Herbert J. Meiselman, ScD, Department of Physiology and Biophysics, USC School of Medicine, 2025 Zonal Avenue, Los Angeles, CA 90033, USA; Fax: 213-342-2283; E-mail: meiselma@hsc.usc.edu.
Abstract: The sedimentation rate (SR) of non-aggregated spherical particles in suspension was determined using an ultrasonic interferometry technique (Echo-Cell); this method is based on A-mode echography and measures the rate of formation of a sediment on a solid plate during settling. The particle accumulation rate, which is related to SR, is obtained from the interference of two waves reflected by two interfaces: one between the plate and the sediment and the other between the sediment and the suspension. Studies were carried out at 25°C using latex spheres of different diameters (7 to 20 µm) and densities (1.062 to 1.190 g/cm3) suspended in distilled water at various volume fractions (1% to 5%). As anticipated by the Stokes model, linear relations were found between SR and both particle density and the square of particle radius. Experimental SR values decreased with increasing suspension particle concentration; these concentration effects were in good agreement with those predicted by the Steinour model. Our results thus serve to validate the theoretical aspects of the Echo-Cell method and suggest its usefulness as a tool for studies of RBC interaction and RBC aggregation.
