The authors wish to thank the US Army Research Office for their support through Grant Nos. DAAH04-95-1-0417;
DAAH04-95-2-0006 and DAAH04-94-G-0316;
and the! US Army Research Laboratory through Grant No. DAAL01-96-2-0047. We also wish to acknowledge undergraduate laboratory assistants Isaac Weingrod and Robert Mills for their help in the design;
construction;
and testing of the new high temperature compression Kolsky bar apparatus;