In that position, the vent is located at {HEAD ~ the interface} of {TAIL ~ the two cells} 
of
In that position , the vent is located at { HEAD ~ the interface } of { TAIL ~ the two cells }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL