  We present Very Large Array observations at 7 mm that trace the thermal
emission of large dust grains in the HD 169142 protoplanetary disk. Our images
show a ring of enhanced emission of radius ~25-30 AU, whose inner region is
devoid of detectable 7 mm emission. We interpret this ring as tracing the rim
of an inner cavity or gap, possibly created by a planet or a substellar
companion. The ring appears asymmetric, with the western part significantly
brighter than the eastern one. This azimuthal asymmetry is reminiscent of the
lopsided structures that are expected to be produced as a consequence of
trapping of large dust grains. Our observations also reveal an outer annular
gap at radii from ~40 to ~70 AU. Unlike other sources, the radii of the inner
cavity, the ring, and the outer gap observed in the 7 mm images, which trace
preferentially the distribution of large (mm/cm sized) dust grains, coincide
with those obtained from a previous near-infrared polarimetric image, which
traces scattered light from small (micron- sized) dust grains. We model the
broad-band spectral energy distribution and the 7 mm images to constrain the
disk physical structure. From this modeling we infer the presence of a small
(radius ~0.6 AU) residual disk inside the central cavity, indicating that the
HD 169142 disk is a pre-transitional disk. The distribution of dust in three
annuli with gaps in between them suggests that the disk in HD 169142 is being
disrupted by at least two planets or substellar objects.
