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