  The competing effects of slow structural relaxations (aging) and deformation
at constant strain rate on the shear yield stress $\tau^y$ of simple model
glasses are examined using molecular simulations. At long times, aging leads to
a logarithmic increase in density and $\tau^y$. The yield stress also rises
logarithmically with rate, but shows a sharp transition in slope at a rate that
decreases with increasing age. We present a simple phenomenological model that
includes both intrinsic rate dependence and the change in properties with the
total age of the system at yield. As predicted by the model, all data for each
temperature collapse onto a universal curve.
