Abstract

Los Alamos N ational Laboratory, an affi rmat ive act ion/equal opportu nity em p loyer, is operated by the U nive rsity of California fo r the U. S . D epartment of E nergy u nder cont ract W-7405-E NG-36 . B y acceptance of this article, the publisher reco g nizes that the U .S . Governm e nt retai n s a nonexclusive , royalty-f ree license to publish or reproduce the published f orm o f this contribution, or to allow others to do so, for U .S. Government purposes . Los A lamos N ational Laboratory requests that the publisher identi fy this a r ticle as work pe rfo rmed un d erthe a u spices of the U . S. De part m ent of E nergy. Los Ala m os N ational L aboratory strongly su p ports academic freedo m and a researche r's r i ght to publish ; as an institution, however, the L aboratory does not endorse the v iewpoint of a publication or guara ntee its tech nical correctness . For m 836 (8/00)