  We evaluate the low-lying oscillation modes and the ballistic expansion
properties of a harmonically trapped gas of fermionic K40 atoms containing
thermal Rb87 impurities as functions of the anisotropy of the trap. Numerical
results are obtained by solving the Vlasov-Landau equations for the one-body
phase-space distribution functions and are used to test simple scaling
Ansatzes. Starting from the gas in a weak impurity-scattering regime inside a
spherical trap, the time scales associated to motions in the axial and
azimuthal directions enter into competition as the trap is deformed to an
elongated cigar-like shape. This competition gives rise to coexistence of
collisionless and hydrodynamic behaviors in the low-lying surface modes of the
gas as well as to a dependence of the aspect ratio of the expanding cloud on
the collision time.
