  The work in this thesis consists of two distinct parts:
  A class of models called, ``String-flip potential models,'' (SFP's) are
studied as a possible candidate for modeling nuclear matter in terms of
constituent quarks. These models are inspired from lattice
quantum-chromodynamics (QCD) and are nonperturbative in nature. It is shown
that they are viable candidates for modeling nuclear matter since they
reproduce most of the bulk properties except for nuclear binding. Their
properties are studied in nuclear and mesonic matter. A new class of models is
developed, called ``flux-bubble potential models,'' which allows for the SFP's
to be extended to include perturbative QCD interactions. Attempts to obtain
nuclear binding is not successful, but valuable insight was gained towards
possible future directions to pursue.
  The possibility of studying Superstring inspired $E_6$ phenomenology at high
energy hadron colliders is investigated. The production of heavy lepton pairs
{\it via} a gluon-gluon fusion mechanism is discussed. An enhancement in the
parton level cross-section is expected due to the heavy (s)fermion loops which
couple to the gluons.
