  For systems in nonequilibrium steady states, a novel modulated Gaussian
probability distribution is derived to incorporate a new phenomenon of biased
current fluctuations, discovered by recent laboratory experiments and confirmed
by molecular dynamics simulations. Our results consistently extend
Onsager-Machlup fluctuation theory for systems in thermal equilibrium.
Connections with the principles of Statistical Mechanics due to Boltzmann and
Gibbs are discussed. At last, the modulated Gaussian distribution is of
potential interest for other statistical disciplines, which make use of the
Large Deviation theory.
