  Some cosmological consequences of first order quantum corrections to Maxwell
electrodynamics are investigated in the context of a spatially flat homogeneous
and isotropic universe driven by a magnetic field plus a cosmological term
$\Lambda$. For a vanishing $\Lambda$, we derive the general solution
corresponding to the particular one recently found by Novello et al.
[gr-qc/9806076]. We also find a general solution for the case when $\Lambda$ is
a non-vanishing constant. Both solutions describe a non-singular, bouncing
universe. However, we show that the first order correction to the
electromagnetic Lagrangean density, in which the analysis is based, fails to
describe the dynamics near $a_{min}$. The time range where the first order
approximation can be used is explicitly evaluated. These problems my be
circumvented through the use of higher order terms in the effective Lagrangean,
as numerical calculations performed by Novello et al. [gr-qc/9809080], for the
vanishing $\Lambda$ case, have indicated. A third general solution
corresponding to a constant magnetic field sustained by a time dependent
$\Lambda$ is derived. This latter solution is capable of describing the whole
cosmic history and describes a universe that, although with vanishing curvature
(K=0), has a scale factor that reaches a maximum and then contracts back to an
arbitrarilly small size. The cosmological term decays during the initial
expansion phase and increases during the late contraction phase, so as to keep
$B$ constant throughout.
