The method 1 wherein the step of applying alternating forward and reverse bias potentials is effected by a bipolar signal having {HEAD ~ a reverse bias potential} of significantly larger magnitude than {TAIL ~ said forward bias potential} 
than
The method 1 wherein the step of applying alternating forward and reverse bias potentials is effected by a bipolar signal having { HEAD ~ a reverse bias potential } of significantly larger magnitude than { TAIL ~ said forward bias potential }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL