Variability in chemical sensitivity from {TAIL ~ sensor} to sensor is conveniently provided by qualitatively or quantitatively varying {HEAD ~ the composition} of the conductive and nonconductive regions 
Variability in chemical sensitivity from { TAIL ~ sensor } to sensor is conveniently provided by qualitatively or quantitatively varying { HEAD ~ the composition } of the conductive and nonconductive regions
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH