  Hard components of $p_t$ spectra can be identified with minimum-bias parton
fragmentation in nuclear collisions. Minimum-bias fragment distributions (FDs)
can be calculated by folding a power-law parton energy spectrum with
parametrized fragmentation functions (FFs) derived from $e^+$-$e^-$ and p-\=p
collisions. Alterations to FFs due to parton "energy loss" or "medium
modification" in Au-Au collisions are modeled by adjusting FF parametrizations
consistent with rescaling QCD splitting functions. The parton spectrum is
constrained by comparison with a p-p $p_t$ spectrum hard component. The
reference for all nuclear collisions is the FD derived from in-vacuum
$e^+$-$e^-$ FFs. Relative to that reference the hard component for p-p and
peripheral Au-Au collisions is found to be {\em strongly suppressed} for
smaller fragment momenta. At a specific point on centrality the Au-Au hard
component transitions to enhancement at smaller momenta and suppression at
larger momenta, consistent with FDs derived from medium-modified $e^+$-$e^-$
FFs.
