Universal moduli-dependent thresholds in Z(2)xZ(2) orbifolds
  In the context of a recently proposed method for computing exactly string loop corrections regularized in the infra-red, we determine and calculate the universal moduli-dependent part of the threshold corrections to the gauge couplings for the symmetric $Z_2\times Z_2$ orbifold model. We show that these corrections decrease the unification scale of the underlying effective field theory. We also comment on the relation between this infra-red regularization scheme and other proposed methods. 
P.M. Petropoulos(CERN) and J. Rizos(SISSA)