Open Strings on Plane waves and their Yang-Mills duals
  We study the plane wave limit of $AdS_5\times S^5/Z_2$ which arises as the near horizon geometry of D3-branes at an orientifold 7-plane in type I' theory. We analyze string theory in the resulting plane wave background which contains open strings. We identify gauge invariant operators in the dual $Sp(N)$ gauge theory with unoriented closed and open string states. 
D. Berenstein, E. Gava, J. Maldacena, K.S. Narain and H. Nastase