The vessel may be oriented such that the external gradient acts in {HEAD ~ opposition} to, or in {TAIL ~ conjunction} with, the influence of gravity upon the target material 
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The vessel may be oriented such that the external gradient acts in { HEAD ~ opposition } to , or in { TAIL ~ conjunction } with , the influence of gravity upon the target material
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH