Scaling Theory of Conduction Through a Normal-Superconductor Microbridge
  The length dependence is computed of the resistance of a disordered normal-metal wire attached to a superconductor. The scaling of the transmission eigenvalue distribution with length is obtained exactly in the metallic limit, by a transformation onto the isobaric flow of a two-dimensional ideal fluid. The resistance has a minimum for lengths near l/Gamma, with l the mean free path and Gamma the transmittance of the superconductor interface. 
C.W.J. Beenakker, B. Rejaei, and J.A. Melsen (Instituut-Lorentz,   Leiden, The Netherlands)