#142 text(Case 142, Parabolic, With Glass title parab=t; lithyd=100; idispa=1; coval(exit,p1,0.0,0.0) COVAL(METAL,PRPS,0.0,GLASS); difcut=0.0 The difcut setting is necessary in order to ensure that the inward flow caused by the creation of the velocity boundary layer does not, by the operation of the hybrid difference scheme (difcut = 0.5, the default setting) cut to zero north-south diffusion link.