Fig. 3.

Dependence of the effective diffusion coefficient on the tube parameters, Eq. (3). (a) D_eff as a function of a/R at l_n/R = 0 (solid curve), l_n/R = 1 (dashed curve), and l_n/R = 10 (dashed-dotted curve). For all the curves l_w/R = 1; (b) D_eff as a function of l_n/R at a/R = 0.1, 0.3, 0.5 for l_w/R = 1 (solid curves) and l_w/R = 10 (dashed curves). One can see that non-monotonic behavior of D_eff is more pronounced at larger values of l_w/R.