The Brownian motion of nonlinear oscillators imbedded in a heat bath is studied. For the excitation of sustained oscillations, realized by van der Pol oscillators, the entropy is calculated in the limit of weak dissipation and weak noise. At fixed average energy the entropy decreases...

The entropy lowering is calculated in the laminar as well as in the turbulent regime. For the Poiseuille flow it is shown that the entropy lowering increases monotonically if while increasing the Reynolds number the energy of the flow is kept fixed. The transition from laminar to turbulent...

The influence of external fluctuations on the bifurcational behavior of two-dimensional dynamical systems exhibiting limit cycles is investigated. Studying both exactly and approximately solvable examples it is shown that the variances of the external fluctuations occur as additional bifurcation...