POLYDISPERSE SCATTERING-THEORY AND COMPARISONS WITH DATA FOR RED-BLOOD-CELLS

Recent results for low-frequency scattering by polydisperse distributions of correlated low-refracting particles averaged over orientation are analyzed numerically. The roles of shape and correlations (parameterized by c) and polydispersity (specified by the normalized variance d in size governed by the gamma probability density) are investigated. The key variable is the net volume fraction w occupied by the particles. The incoherent scattering is determined by DELTA = PS(c,d;w) with P as a particle population factor that is independent of w, and S as the fluctuation-correlation function of w. Earlier applications of monodisperse (d = 0) theory emphasized the influence of c on the peak DELTA = DELTA AND and its location w = w AND in order to invert ultrasonic scattering data of Shung and his associates for red blood cell suspensions under different flow conditions. For d > 0, comparable curves for DELTA(w) decrease more gradually with w increasing past w AND (because of additional scattering arising from polydispersity) and thereby provide better fits to data for the more controlled flows over broader ranges of hematocrit.