  The presence of bound states in a nanoscale electronic system attached to two
biased, macroscopic electrodes is shown to give rise to persistent,
non-decaying, localized current oscillations which can be much larger than the
steady part of the current. The amplitude of these oscillations depends on the
entire history of the applied potential. The bound-state contribution to the
{\em static} density is history-dependent as well. Moreover, the time-dependent
formulation leads to a natural definition of the bound-state occupations out of
equilibrium.
