A differential pressure is applied across the membrane after each step of reagent addition to the membrane in order to remove {HEAD ~ excess reagent} from {TAIL ~ the membrane} 
from
A differential pressure is applied across the membrane after each step of reagent addition to the membrane in order to remove { HEAD ~ excess reagent } from { TAIL ~ the membrane }
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 REL TAIL TAIL TAIL TAIL TAIL TAIL