However, {TAIL ~ some surfactant systems} have been adapted to enable {HEAD ~ a saline drive fluid} to be used 
However , { TAIL ~ some surfactant systems } have been adapted to enable { HEAD ~ a saline drive fluid } to be used
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH