The Membrane reference article from the English Wikipedia on 24-Jul-2004
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Membrane

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A membrane is a thin, typically planar structure or material that separates two environments. Because it sits between environments or phases and has a finite volume, it can be referred to as an interphase rather than an interface. Membranes selectively control mass transport between the phases or environments.

Biological membranes include:

Artificial membranes are used in: