Schwinger-type parametrization of open string worldsheets
  A parametrization of (super) moduli space near the corners corresponding to bosonic or Neveu-Schwarz open string degenerations is introduced for worldsheets of arbitrary topology. With this parametrization, Feynman graph polynomials arise as the $\alpha ' \to 0$ limit of objects on moduli space. Furthermore, the integration measures of string theory take on a very simple and elegant form. 
Sam Playle and Stefano Sciuto
hep-th