flow should remain isotropic in such areas therefore previous substantially equiaxial hole shapes 188 should still be employed to permit current flow in each portion 184 186 in as unrestricted a manner as possible fig5 shows a vertical portion 224 of the device of fig4 in greater detail as can be seen extended slots 242 permit relatively unrestricted current flow in a longitudinal direction 252 but significantly more restricted flow in a transverse direction 260 as compared to the prior art device of fig1 referring now to fig6 an alternate embodiment of the present invention is shown wherein every n out of m previous substantially equiaxial hole shapes where n lt m have been replaced by non equiaxial hole shapes in the form of long extended slots 344 and the remaining portion m u2212 n of the previous substantially equiaxial hole shapes have been removed entirely the effect is a larger effective conductance in a longitudinal direction due in part to the greater crowding effect of transverse current flow 360 because of this more severe penalty for transverse current flow 360 long extended slots 344 must be placed further away from disruptive features such as branch points and vias another alternate embodiment of the present invention is shown in fig7 here it is possible to utilize non equiaxial hole shapes in the form of wide and long extended slots 446 in a very wide wire 420 as used herein u2018 wide u2019 indicates a slot that is significantly wider than the narrowest enclosed opening allowed for a given technology e g.