  We analyze the probability distribution for entropy production rates of
trajectories evolving on a class of out-of-equilibrium kinetic networks. These
networks can serve as simple models for driven dynamical systems, which are of
particular importance in biological processes, where energy fluxes typically
result in non-equilibrium dynamics. By analyzing the fluctuations in the
entropy production, we demonstrate the emergence, in a large system size limit,
of a dynamic phase transition between two distinct dynamical regimes.
