Intersection homology with field coefficients: $K$-Witt spaces and   $K$-Witt bordism
  We construct geometric examples of pseudomanifolds that satisfy the Witt condition for intersection homology Poincare duality with respect to certain fields but not others. We also compute the bordism theory of $K$-Witt spaces for an arbitrary field $K$, extending results of Siegel for $K=Q$. 
Greg Friedman