  We discuss several closely related concepts in the NSR formulation of
superstring theory. We demonstrated that recently proposed NSR model for
superstrings on $AdS_5 \times S^5$ is described by the world-sheet logarithmic
conformal field theory (LCFT). The origin of LCFT on a world-sheet is closely
connected to the matter-ghost mixing in the structure of a brane-like vortex
operators. We suggest a dynamical origin of M theory as a string theory with an
extra dimension given by bosonised superconformal ghosts.
