{HEAD ~ Sintered, translucent ceramic microbeads}, preferably alumina, titania, {TAIL ~ zirconia}, yttria, zirconium phosphate, or yttrium aluminum garnet are doped with one or more optically active species 
{ HEAD ~ Sintered , translucent ceramic microbeads } , preferably alumina , titania , { TAIL ~ zirconia } , yttria , zirconium phosphate , or yttrium aluminum garnet are doped with one or more optically active species
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