In this article, we study the local structure and heat transfer properties (thermal conductivity and interfacial conductance) in model semi-crystalline polyethylene (PE) by non-equilibrium molecular dynamics. We compare three different force fields with different levels of detail (all-atom, all-atom with constraints, and united-atom) and find that the structure of the model PE is significantly influenced by the choice of force field. The united-atom force field results in a reduced overall crystallinity and an over-idealized organization of the polymer chains, compared to the all-atom force fields. We find that thermal transport properties are not greatly influenced when structural effects are taken into consideration, and our results suggest that united-atom models can be used to study heat transfer properties of model PE, with decreased computational cost.

Ultraviolet-light-induced changes to the nucleobase thymine deposited onto a MoS surface were studied using photoelectron spectroscopy and first-principles calculations. These measurements suggest changes in the molecular structure indicated by changes in core electron binding energies. The experimental work has been interpreted by means of ab initio calculations using coupled cluster singles and doubles (CCSD) linear response theory. Contrary to the expected behavior, i.e., the dimerization of two thymine molecules into a pyrimidine dimer, a shift between two tautomeric forms was observed upon UV-exposure. Exposure to ionizing radiation is known to induce damage in many biological molecules, and the present work gives additional insight into its effects on thymine, the interactions of the molecules, and finally how certain UV photoproducts may be avoided.

The models of vapor-induced depolarization currents developed in the preceding paper are applied to an experimental investigation of corona-charged polypropylene electrets.The results are shown to be completely consistent with the theoretical predictions, and with the results of thermally stimulated current experiments. The influence of aging at or below room temperature is studied; it is shown that the evolution of the space charge can be easily followed by vapor-induced depolarization-current experiments.

A physical model of vapor-induced depolarization currents is presented. Various boundary conditions are considered, corresponding to various experimental conditions; the transport equations are solved analytically or numerically. It is shown that vapor-induced depolarization-current curves are very sensitive to the initial charge distribution, so that the technique should prove useful in determining the spatial charge distribution.