Asymmetric Diffusion
Abstract
Diffusion rates through a membrane can be asymmetric, if the diffusing particles are spatially extended and the pores in the membrane have asymmetric structure. This phenomenon is demonstrated here via a deterministic simulation of a two-species hard-disk gas, and via simulations of two species in Brownian motion, diffusing through a membrane that is permeable to one species but not the other. In its extreme form, this effect will rapidly seal off flow in one direction through a membrane, while allowing free flow in the other direction. The system thus relaxes to disequilibrium, with very different densities of the permeable species on each side of the membrane. A single species of appropriately shaped particles will exhibit the same effect when diffusing through appropriately shaped pores. We hypothesize that purely geometric effects discussed here may play a role in common biological contexts such as membrane ion channels.
- Publication:
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arXiv e-prints
- Pub Date:
- December 2004
- DOI:
- arXiv:
- arXiv:cond-mat/0412626
- Bibcode:
- 2004cond.mat.12626P
- Keywords:
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- Condensed Matter - Statistical Mechanics
- E-Print:
- 17 pages, 8 figures v3: one additional figure, several additional references, conceptually unchanged