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