  We study transport in a class of exactly solvable models of interacting
fermions in one dimension. We contrast these models with models of
non-interacting fermions in an Aharanov-Bohm ring to which they are
superficially similar. We introduce magnetic and non-magnetic impurities at a
site, through either a weak $\delta$-function potential or through a weak link.
Using a renormalisation group analysis, we show that the strength of the
nonmagnetic impurity is not affected by the interaction, whereas the magnetic
impurity cuts the wire at the impurity site.
