Self Diffusion in Cells and Tissues.

A general treatment of time-dependent transient diffusion coefficients in a system of parallel planar barriers of arbitrary permeability has been performed, with emphasis on the results expected for Nuclear Magnetic Resonance NMR pulsed-field-gradient, spin-echo measurements. This is the first such derivation for permeable barriers of any geometry. The calculated distribution functions and diffusion coefficients are in agreement with expectations in most of the limiting cases tried, except that an unexplained dependence of the diffusion coefficients on the magnitude of the field gradient was found. The application of the results to the interpretation of experimental results is discussed.