{HEAD ~ A fresh supply} of {TAIL ~ solution} to the face of the membrane is provided by a stirrer 
{ HEAD ~ A fresh supply } of { TAIL ~ solution } to the face of the membrane is provided by a stirrer
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH