This report was prepared as an account of work sponsoredby an agency of the United States Government. Neither the United StatesGovernment nor any agencythereof,nor any of their P.C. Miles, R.M. Green and P.O. Witze employees, makesany warranty,express or implied,or assumes any legalliability or responsi-Sandia National Laboratories bility for the accuracy, completeness, or usefulness of any information, apparatus, product,or Livermore, California processdisclosed, or representsthat its usewould not infringeprivatelyowned rights.Refer-¢ncehereinto any specificcommercialproduct,process, or serviceby tradename,trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. " Numbers in brackets desi_ ate references at end of paper. scavenging methods. A comparison of this _sQ_[l_vides iASTER Dt,TRIBUTION OF THIS DOCUMENT IS UN__-_ ,' " ' 1