  We report results of $v_1(y)$ and $dv_1/dy$ near mid-rapidity for
$\pi^{\pm}$, $K^{\pm}$, $K_s^0$, $p$, $\overline{p}$, $\Lambda$,
$\overline{\Lambda}$ and $\phi$ from Beam Energy Scan Au+Au collisions at
$\sqrt{s_{NN}} = $ 7.7 - 200 GeV using the STAR detector at RHIC. The
$dv_{1}/dy$ of $\pi^{\pm}$, $K^{\pm}$ and $K_s^0$ mesons remains negative over
all beam energies. The $dv_1/dy$ of $p$ and $\Lambda$ baryons shows a sign
change around 10 - 15 GeV, while net baryons (net p and net $\Lambda$) indicate
a double sign change. The $dv_1/dy$ of $\overline{p}$, $\overline{\Lambda}$ and
$\phi$ show a similar trend for $\sqrt{s_{NN}}>$ 14.5 GeV. For the first time,
$v_{1}$ measurements are used to test a quark coalescence hypothesis. Many
measurements are found to be consistent with the particles being formed via
coalescence of constituent quarks. The observed deviations from that
consistency offer a new approach for probing the collision process at the quark
level.
