Manuscript received January 30;
1997;
B;
Marchon;
510-353-4916;
fax 510-651-7316 e-mail: bmarchon@notes.seagate.com The work at LBNL was perfoniied under a Cooperative Research and Development Agreement with Seagate (BG92-177) and was supported by the Director;
Office of Energy Research;
U.S. Department of Enzrgy;
under Contract No. DE-AC03-76SF00098;