  We present self-consistent disk models for T Tauri stars which include a
parameterized treatment of dust settling and grain growth, building on
techniques developed in a series of papers by D'Alessio etal. The models
incorporate depleted distributions of dust in upper disk layers along with
larger-sized particles near the disk midplane, as expected theoretically and as
we suggested earlier is necessary to account for mm-wave emission, SEDs,
scattered light images, and silicate emission features simultaneously. By
comparing the models with recent mid- and near-IR observations, we find that
the dust to gas mass ratio of small grains at the upper layers should be < 10 %
of the standard value. The grains that have disappeared from the upper layers
increase the dust to gas mass ratio of the disk interior; if those grains grow
to maximum sizes of the order of mm during the settling process, then both the
millimeter-wave fluxes and spectral slopes can be consistently explained.
Depletion and growth of grains can also enhance the ionization of upper layers,
enhancing the possibility of the magnetorotational instability for driving disk
accretion.
