  Several experiments in the context of ladder materials have recently shown
that the study of simple models of anisotropic ladders (i.e. with different
couplings along legs and rungs) is important for the understanding of these
compounds. In this paper Exact Diagonalization studies of the one-band Hubbard
and t-J models are reported for a variety of densities, couplings, and
anisotropy ratios. The emphasis is given to the one-particle spectral function
A(q,\omega) which presents a flat quasiparticle dispersion at the chemical
potential in some region of parameter space. This is correlated with the
existence of strong pairing fluctuations, which themselves are correlated with
an enhancement of the bulk-extrapolated value for the two-hole binding energy
as well as with the strength of the spin-gap in the hole-doped system. Part of
the results for the spectral function are explained using a simple analytical
picture valid when the hopping along the legs is small. In particular, this
picture predicts an insulating state at quarter filling in agreement with the
metal-insulator transition observed at this special filling for increasing rung
couplings. The results are compared against previous literature, and in
addition pair-pair correlations using extended operators are also here
reported.
