String Inspired QCD and $E_6$ Models
  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. 
M. M. Boyce