Molecular Structure Modulated Trap Distribution and Carrier Migration in Fluorinated Epoxy Resin.

Surface charge accumulation on epoxy insulators is one of the most serious problems threatening the operation safety of the direct current gas-insulated transmission line (GIL), and can be efficiently inhibited by the surface modification technology. This paper investigated the mechanisms of fluorination modulated surface charge behaviors of epoxy resin through quantum chemical calculation (QCC) analysis of the molecular structure. The results show that after fluorination, the surface charge dissipation process of the epoxy sample is accelerated by the introduced shallow trap sites, which is further clarified by the carrier mobility model. The electron distribution probability of the highest occupied molecular orbitals (HOMO) under positive charging and the lowest unoccupied molecular orbitals (LUMO) under negative charging shows distinctive patterns. It is illustrated that electrons are likely to aggregate locally around benzenes for the positively charged molecular structure, while electrons tend to distribute all along the epoxy chain under negatively charging. The calculated results verify that fluorination can modulate surface charge behaviors of epoxy resin through redesigning its molecular structure, trap distribution and charging patterns.

Computational study on acetophenone in amorphous polyethylene.

Polyethylene (PE) is widely used as an electrical insulating material. Acetophenone (AP) is a major residue in PE and is considered one of the causes of insulation deterioration. However, the physicochemical explanation of the influence of AP is still unknown. Therefore, in the present study, the behavior of AP molecules in amorphous PE was investigated using molecular dynamics (MD) simulations and quantum chemical calculation. First, the basic properties of the AP molecule were evaluated from the viewpoint of molecular electrostatic potential (MEP), molecular orbitals, and energy levels. Subsequently, an amorphous PE system containing AP molecules was studied using MD simulations. The results clearly indicate that AP does not greatly change the density and radius of gyration of amorphous PE. Quantum computations were performed using a part of the structure obtained from the MD simulations, suggesting that AP acts as a trap site in amorphous PE. It was also revealed that under the external electric field, the total density of state (DOS) changes with a dependence on the applied direction. Results of these calculations help in explaining previous experimental results.

A case of meningitis due to Neisseria subflava after ventriculostomy.

Surgical site infection (SSI) is an emerging problem in all fields of surgery, as well as in neurosurgery, with numerous strategies against SSI initiated in many countries. In this report, we describe a case of SSI caused by Neisseria subflava a month after ventriculostomy placement for acute hydrocephalus. A 53-year old man was referred to our hospital, and was diagnosed with a thalamic hemorrhage with ventricular rupture. Bilateral ventriculostomies were performed on the day of presentation. After intensive care for the acute stage, an SSI at the left ventriculostomy site was recognized on the 39th hospital day. The installed reservoir and ventricular tube was removed on the 40th hospital day. The CSF cell count was 2064/3, and N. subflava was recovered from the CSF culture. N. subflava is a common inhabitant found in the human upper respiratory tract, and is reported to be a rare cause of meningitis. There is one case report of meningitis caused by N. subflava transmitted during myelography from medical staff who did not wear facemasks during the procedure. Meningitis caused by N. subflava is rare, and transmission via a medical procedure is extremely rare. Although reported to be only rarely pathogenic, we must recognize that N. subflava can indeed be pathogenic, and can in rare cases be the cause of postoperative meningitis.