Key points are not available for this paper at this time.
A theory of ballistic conduction through a constriction is developed which predicts a steplike structure with amplitude e^{2}h in the conductance as a function of Fermi energy or width. For a sharp (abrupt) constriction the steps are only quantized to 1 part in 10^3 at T=0. Disorder destroys the steps and they are modulated by novel resonant structure in certain regimes of shape and temperature.
Szafer et al. (Mon,) studied this question.