A New Variant of the Casimir Effect and Its Exact Evaluation
  A new version of the Casimir effect where the two plates conduct in specific, different, directions is considered. By direct functional integration the evaluation of the Casimir energy as a function of the angle between the conduction directions is reduced to quadratures. Other applications of the method and a magnetic Casimir variant are mentioned. 
Oded Kenneth and Shmuel Nussinov