  We study cosmological scenarios resulting from effective actions in four
dimensions which are, under some assumptions, connected with multidimensional,
supergravity and string theories. These effective actions are labeled by the
parameters $\omega$, the dilaton coupling constant, and $n$ which establishes
the coupling between the dilaton and a scalar field originated from the gauge
field existing in the original theories. There is a large class of bouncing as
well as Friedmann-like solutions. We investigate under which conditions
bouncing regular solutions can be obtained. In the case of the string effective
action, regularity is obtained through the inclusion of contributions from the
Ramond-Ramond sector of superstring.
