The applied field comprises a first, external magnetic gradient which moves {HEAD ~ magnetically responsive particles} to {TAIL ~ a region} of a collection vessel 
to
The applied field comprises a first , external magnetic gradient which moves { HEAD ~ magnetically responsive particles } to { TAIL ~ a region } of a collection vessel
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH