  From strain rate- and temperature-dependent deformation studies on
nanocrystalline PdAu alloys with grain sizes $\leq$ 10nm, the shear activation
volume $6b^3$, strain rate sensitivity 0.03 as well as the Helmholtz 0.9eV and
Gibbs free energy of activation 0.2eV have been extracted. The close similarity
to values found for metallic glasses indicates that grain boundary mediated
shear shuffling dominates plasticity at the low end of the nanoscale. More
fundamentally, we find that the energy barrier height exhibits universal
scaling behavior $\Delta G \propto \Delta\tau^{3/2}$, where $\Delta\tau$ is a
residual load, giving rise to a generalization of the Johnson-Samwer $T^{2/3}$
scaling law of yielding in metallic glasses.
