  We consider a Brownian particle in a ``meandering'' periodic potential when
the ambient temperature is a periodically or stochastically varying function of
time. Though far from equilibrium, the linear response of the particle to an
external static force is exactly the same as in the equilibrium case, i.e. for
constant temperature. Even more surprising is the non-linear response: the
particle slows down and then even starts to move in the direction opposite to
the applied force.
