[en] We discuss results on tunneling in barriers consisting of both pure fullerene films and layered composites of fullerenes and dielectric materials. This work focuses on C₆₀ films, which ranged from 50 to 600 Angstrom in thickness and were layered with both Al₂O₃ and Ge films 10 to 40 Angstrom in thickness. These studies reveal that for the deposition conditions used here, incomplete C₆₀ coverage occurred for film thicknesses less than ∼400 Angstrom. For composites of C₆₀ with Al₂O₃ or Ge, we observed isolated clusters of C₆₀ molecules and Coulomb blockade behavior consistent with the size scale of the clusters. Interesting dynamical effects were also observed in conductance characteristics that were both dramatic and in some cases entirely reproducible. copyright 1998 The American Physical Society

[en] The technique for handling time varying problems implemented in the Monte Carlo Application tool-kit (MCATK) provides a robust approach for simulating neutral particle behavior. The tool-kit uses a time interval approach that when applied to the entire population creates opportunities for adjusting simulation parameters to account for emergent problems. The current version of the MCATK uses the time edges to apply a population adjustment. While the tracked population will still fluctuate, the PCA (Population Control Algorithm) removes the common requirement that the user have some knowledge of the systems criticality

[en] Particle population control methods are required in both dynamic and static Monte Carlo methods. If no population control is performed the particle population will die out or grow exponentially. A general particle population control method has been derived from splitting and Russian Roulette for dynamic Monte Carlo particle transport. A well-known particle population control method, known as the particle population comb, has been shown to be a special case of this general method. This general method has been incorporated in Los Alamos National Laboratory's Monte Carlo Application Tool-kit (MCATK) and it has been shown that this method is useful in the dynamic simulation of examples of super-critical and sub-critical systems

[en] The Monte Carlo Application tool-kit (MCATK) is a C++ component-based software library designed to build specialized applications and to provide new functionality for existing general purpose Monte Carlo radiation transport codes such as MCNP. We will describe MCATK and its capabilities along with presenting some verification and validations results. (authors)