Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within
  the VLBA-BU-BLAZAR Program
  We analyze the parsec-scale jet kinematics from 2007 June to 2013 January of
a sample of $\gamma$-ray bright blazars monitored roughly monthly with the Very
Long Baseline Array at 43~GHz. In a total of 1929 images, we measure apparent
speeds of 252 emission knots in 21 quasars, 12 BL~Lacertae objects (BLLacs),
and 3 radio galaxies, ranging from 0.02$c$ to 78$c$; 21\% of the knots are
quasi-stationary. Approximately 1/3 of the moving knots execute non-ballistic
motions, with the quasars exhibiting acceleration along the jet within 5~pc
(projected) of the core, and knots in the BLLacs tending to decelerate near the
core. Using apparent speeds of components and timescales of variability from
their light curves, we derive physical parameters of 120 superluminal knots,
including variability Doppler factors, Lorentz factors, and viewing angles. We
estimate the half-opening angle of each jet based on the projected opening
angle and scatter of intrinsic viewing angles of knots. We determine
characteristic values of physical parameters for each jet and AGN class based
on the range of values obtained for individual features. We calculate intrinsic
brightness temperatures of the cores, $T_{\rm b,int}^{\rm core}$, at all
epochs, finding that the radio galaxies usually maintain equipartition
conditions in the cores, while $\sim$30\% of $T_{\rm b,int}^{\rm core}$
measurements in the quasars and BLLacs deviate from equipartition values by a
factor $>$10. This probably occurs during transient events connected with
active states. In the Appendix we briefly describe the behavior of each blazar
during the period analyzed.
