1. Polymer Research Branch, U.S. Army Research Laboratory, APG Maryland 21005-5069, and Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
2. U.S. Department of Agriculture, Eastern Regional Research Center Agricultural Regional Service, Philadelphia, Pennsylvania 19118
3. Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899