Systematics of parton fragmentation in $e^{+}$-$e^{-}$ and nuclear collisions

Parametrizations of fragmentation functions (FFs) from $e^{+}$-$e^{-}$ and p-=p collisions are combined with a parton spectrum model in a pQCD folding integral to produce minimum-bias {\em fragment distributions}. A model of in-medium FF modification is included. Calculated fragment distributions are compared with {\em hard components} from p-p and Au-Au $p_t$ spectra. Data are well described by pQCD over a large kinematic region for a range of Au-Au centralities.