Time-dependent diffusion coefficient as a probe of geometry

摘要: This is a tutorial describing how the time-dependent diffusion coefficient D(t) of mobile molecules confined in pores or cells carries information about confining geometry. At early times, = D0[1 − (4/9)(S/Vp)] gives, irrespective details, pore surface to volume ratio (S/Vp), which measure microscopic length. Here D0 bulk unrestricted coefficient. long reaches limiting value D0/α at rate that depends on macroscopic length scales characteristic medium. The geometrical parameter “tortuosity” α plays an important role various transport processes porous media, such as electrical conductivity. Extensions these concepts permeable walls, fluid identification by combining with relaxation, restricted inhomogeneous magnetic fields leading edge enhancement, and fractal surfaces are briefly described. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson Part A 23A: 1–21,