Kadazans, the largest indigenous group in Sabah, northern Borneo, were surveyed for glyoxalase I, phosphoglucomutase I, red cell acid phosphatase, esterase D, adenosine deaminase, soluble glutamate pyruvate transaminase, soluble glutamate oxaloacetate transaminase, 6-phosphogluconate dehydrogenase, uridine monophosphate kinase, adenylate kinase, peptidase B and D, superoxide dismutase, C5, group specific component, haptoglobin and transferrin. Kadazans were found to be polymorphic for GLO I, PGM I, RCAP, esterase D, ADA, s-Gpt, 6PGD, UMPK, Gc, C5, haptoglobin and peptidase B. Rare variants were found for transferrin and peptidase D. No variant was found for s-Got, SOD and AK.
In-depth understanding of the pollution problems such as dry bands and the polymeric aging process requires better determination of electric field strength and its distribution over the polymeric surface. To determine the electric field distribution over the insulator surface, this research proposes utilizing a novel approach model based on nonlinear electrical characteristics derived from experimental results for polluted polymer insulators. A case study was carried out for a typical 11 kV polymeric insulator to underline the merits of this new modeling approach. The developments of the proposed pollution model and the subsequent computational works are described in detail. The study is divided into two main stages; laboratory measurements and computer simulations. In the first stage, layer conductance tests were carried out to develop nonlinear field-dependent conductivity for the pollution modeling. In the second part, equipotential and electric field distributions along the leakage were computed using the finite element method (FEM). Comparative field studies showed that the simulation using the proposed dynamic pollution model results in more detailed and realistic field profiles around insulators. This may be useful to predict the formation of dry bands and the initiation of electrical discharges on the polymeric surface.
Polymer blends have attracted significant research interest due to their potential use as power cable insulating materials. Specifically, polypropylene (PP) blends offer improved dielectric properties over conventional crosslinked polyethylene insulating materials attributable to PP's high melting temperatures, hence high rated voltages. Despite numerous promising findings have been reported regarding the potential application of PP blends as power cable insulating materials, there have been relatively less investigations into the dielectric effects of incorporating nanofillers into PP blends. The current work therefore explores the influence of calcined magnesia (MgO) nanofiller on the structure and dielectric properties of PP blended with ethylene-octene copolymer (EOC). Nanofiller-wise, calcination of MgO does not significantly affect the structure of MgO, albeit that water-related molecules are removed from MgO. Upon adding the calcined MgO to the PP/EOC blend, the breakdown performance of the PP/EOC/MgO blend nanocomposites becomes jeopardized, especially under the direct current field. This is primarily attributed to the presence of residue water molecules within the PP/EOC/MgO blend nanocomposites, even after MgO calcination. Although the addition of the calcined MgO to the PP blend does not result in favorable dielectric properties, the findings suggest that nanostructuration of PP blends could be further explored to pave the way for the development of nanostructured PP blends for use in advanced power cable insulation applications.