When {HEAD ~ the vent} is moved to {TAIL ~ a nonequilibrium position}, it is located within one of the two cells and is not in direct relation to the vent follower 
When { HEAD ~ the vent } is moved to { TAIL ~ a nonequilibrium position } , it is located within one of the two cells and is not in direct relation to the vent follower
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH