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