Interpretation of experimentally-measured diffusion coefficients using mathematical model of diffusion of HIV virions from semen, through microbicide layer, to tissue compartment. (A) Schematic of mathematical model. Measured diffusion coefficients were input to the model. Plots show percent of virions in the tissue compartment, as a function of time, for various concentrations of (B) HEC and (C) MC. In (B), curves for 20% HEC, 50% HEC, and undiluted HEC appear superimposed. In (C), curves for 50% MC and undiluted MC appear superimposed.