Stochastic thermodynamics provides a framework for describing small 
systems embedded in a heat bath and externally driven to non-equilibrium
[1]. Examples are colloidal particles in time-dependent optical traps, 
single biomolecules manipulated by optical tweezers or AFM tips, and 
motor proteins driven by ATP excess. A first-law like energy balance 
allows to identify applied work, dissipated heat and entropy production
on the level of an individual stochastic trajectory. 

For non-equilibrium steady states (NESSs), total entropy production obeys 
a detailed fluctuation theorem even for finite times [2]. As an 
alternative to the phenomenological approach of introducing an effective 
temperature in order to adjust the equilibrium form of the fluctuation-
dissipation theorem (FDT) to a NESS, we have derived a transparent 
general form of the FDT in a NESS [3]. Finally, generalized Green-Kubo 
relations hold true in NESSs under the weak assumption of local detailed 
balance [4]. Where available, these theoretical results will be 
illustrated using data from experimental model systems.


[1] U.S., Eur. Phys. J. B,  64, 423, 2008. 
[2] U.S., Phys. Rev. Lett. 95, 040602, 2005. 
[3] U.S. and T. Speck, EPL 89, 10007, 2010. 
[4] U.S., Phys. Rev. Lett. 104, 138101, 2010.