Renormalization of the Planck mass for type II superstrings on symmetric   orbifolds
  We compute the one-loop renormalization of the Planck mass for type II string theories compactified to four dimensions on symmetric orbifolds that preserve ${\cal N}=2$ supersymmetry. Depending on the orbifold, the effect can be as large as to compete with the standard tree-level value. 
Emmanuel Kohlprath