On the transition from pulled to pushed monotonic fronts of the extended Fisher-Kolmogorov equation

The extended Fisher-Kolmogorov equation ut=uxx-γuxxxx+f(u) with arbitrary positive f(u), satisfying f(0)=f(1)=0, has monotonic traveling fronts for γ<112. We find a simple lower bound on the speed of the fronts which allows to determine, for a given reaction term, when will the front of minimal speed be pushed.