DIFFUSION IN SPARSE FIELDS OF OBSTACLES.

Diffusion of particles or polymers in nondilute solutions or suspensions is influenced by steric and hydrodynamic interactions between the diffusers. Diffusion-controlled reaction is therefore also influenced by these factors. Hydrodynamic interaction in these suspensions has been treated in the Brinkman approximation. This amounts to finding a modified Oseen tensor to account for the hydrodynamic screening. The authors' approach enabled them to resolve certain discrepancies in the literature and also to account, at least in principle, for nonrandom, correlated placement of obstacles.