The first and second electrodes are formed of {TAIL ~ a conductive material} forming ohmic junction with the variable resistor and {HEAD ~ a conductive material} forming non ohmic junction with the variable resistor, respectively 
The first and second electrodes are formed of { TAIL ~ a conductive material } forming ohmic junction with the variable resistor and { HEAD ~ a conductive material } forming non ohmic junction with the variable resistor , respectively
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH