The improvement 9, wherein said at least one element capable of attenuating {HEAD ~ x rays} is selected from the group consisting of {TAIL ~ lead oxide}, bismuth oxide, tantalum oxide, and uranium oxide 
The improvement 9 , wherein said at least one element capable of attenuating { HEAD ~ x rays } is selected from the group consisting of { TAIL ~ lead oxide } , bismuth oxide , tantalum oxide , and uranium oxide
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH