General Abelian Orientifold Models and One Loop Amplitudes
  We construct a one loop amplitude for any Abelian orientifold point group for arbitary complex dimensions. From this we show several results for orientifolds in this general class of models as well as for low dimensional compactifications. We also discuss the importance and structure of the contribution of orientifold planes to the dynamics of D-branes, and give a physical explaination for the inconsistency of certain Z_4 models as discovered by Zwart. 
Donal O'Driscoll