  We consider a class of systems where, due to the large mismatch of dielectric
constants, the Coulomb interaction is approximately one-dimensional. Examples
include ion channels in lipid membranes and water filled nanopores in silicon
or cellulose acetate films. Charge transport across such systems possesses the
activation behavior associated with the large electrostatic self-energy of a
charge placed inside the channel. We show here that the activation barrier
exhibits non-trivial dependence on the salt concentration in the surrounding
water solution and on the length and radius of the channel.
