{HEAD ~ The vessel} is then positioned in {TAIL ~ a holder} on the perimeter of a centrifuge rotor 
is positioned in
{ HEAD ~ The vessel } is then positioned in { TAIL ~ a holder } on the perimeter of a centrifuge rotor
HEAD HEAD HEAD HEAD HEAD HEAD REL OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH