  We study the string topology of a closed oriented Riemannian manifold M. We
describe a compact moduli space of diagrams, and show how the cellular chain
complex of this space gives algebraic operations on the singular chains of the
free loop space LM of M. These operations are well-defined on the homology of a
quotient of this moduli space, which has the homotopy type of a
compactification of the moduli space of Riemann surfaces. In particular, our
action of the 0-dimensional homology of the quotient space on the homology of
the free loop space of M recovers the Cohen-Godin positive boundary TQFT.
