  We develop a technique using dual mixed-volumes to study the isotropic
constants of some classes of spaces. In particular, we recover, strengthen and
generalize results of Ball and Junge concerning the isotropic constants of
subspaces and quotients of L_p and related spaces. An extension of these
results to negative values of p is also obtained, using generalized
intersection-bodies. In particular, we show that the isotropic constant of a
convex body which is contained in an intersection-body is bounded (up to a
constant) by the ratio between the latter's mean-radius and the former's
volume-radius. We also show how type or cotype 2 may be used to easily prove
inequalities on any isotropic measure.
