Variations in the lateral dimensions of capillaries and ultrathin gels
along their length could lead to a distortion of the sample zone beca
use charged particles traveling near the wall must travel a longer dis
tance under a smaller field than particles traveling along the centerl
ine. The size of the effect is computed by solving Laplace's equation
for the potential everywhere in a conducting slab with a discontinuity
in the lateral dimensions and integrating the travel time along diffe
rent streamlines.