Space charge behavior of XLPE/silica nanocomposites under high electric field
Space charge formation behavior is compared among crosslinked polyethylene and its two nanocomposites with silica nanofillers with and without surface treatment. By conducting a degassing treatment, we have prepared nine kinds of samples in total. As a result, it was found that the presence of cross-linking by-products suppresses space charge formation. As far as the present silica nanofillers are concerned, their addition to XLPE enhances the formation of negative space charge near the cathode.
Space charge formation in LDPE/MgO Nano-composite under high electric field at high temperature
Time dependence of space charge formation under high dc electric field at various temperatures between 30 and 60degC in nanocomposite of low density polyethylene (LDPE) mixed with nano-size filler of magnesium oxide (MgO) were studied using pulsed electro-acoustic (PEA) method. In LDPE without MgO, it is found that huge amounts of both positive and negative packet-like charges injection at all measured temperatures, and they makes a local electric field in bulk higher. On the other hand, there is almost no such huge packet-like charge was observed in LDPE/MgO with MgO content of more than 1 phr even under high electric field at high temperature, while it was observed in that with MgO content of 0.2 phr. To study the reason of such space charge suppression effect by nano-filler, we tried to calculate the potential distribution which is induced by the difference of relative permittivities between LDPE and MgO under such high electric field. By a numerical analysis, it is found that the induced potential distribution induced around the nano-filler under high electric field works as a deep trap to capture and to prevent the movement of injected carriers from electrode.
New Approaches for Positron Emission Tomography ( PET ) in Breast Carcinoma
Positron Emission Tomography (PET) is a nuclear medicine imaging technique which allows the quantitative evaluation of the distribution of several pharmaceuticals in a target area. PET therefore provides valuable information on the biochemical and biological activity inside a living subject in a noninvasive way, combining techniques applied in nuclear medicine with the precise localization achieved by computerized image reconstruction.