measuring {TAIL ~ characteristics} of a subset of said plurality of {HEAD ~ processing regions}, defining measured characteristics 
measuring { TAIL ~ characteristics } of a subset of said plurality of { HEAD ~ processing regions } , defining measured characteristics
OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH