incorporating into said fluid a trisubstituted cyclic compound, of which {TAIL ~ the ring} is substituted by one or two X—Am—Yn groups and wherein the remaining one or two substituents are —X Z groups, wherein the substituted ring is a 1,3,5 substituted cyclohexane, the compound being non symmetrical in that {HEAD ~ at least one of said —X Z groups} is free of an Am moiety, wherein 
incorporating into said fluid a trisubstituted cyclic compound , of which { TAIL ~ the ring } is substituted by one or two X — Am — Yn groups and wherein the remaining one or two substituents are — X Z groups , wherein the substituted ring is a 1,3,5 substituted cyclohexane , the compound being non symmetrical in that { HEAD ~ at least one of said — X Z groups } is free of an Am moiety , wherein
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH