Barrier effect to charge injection in polyethylene by silver nanoparticles containing plasma polymer composites investigated by conductivity measurements

International audienceMain challenge in the development of HVDC polymeric insulation is to avoid the accumulation of space charge under electrical and/or thermal stresses which can significantly reduce the component reliability. Injection mitigation in low density polyethylene (LDPE) films by plasma processed silver nanoparticles (AgNPs) containing plasma polymer composites was recently reported through space charge measurements. The barrier effect has been assigned to the creation of permanent deep traps by introducing silver nanoparticles near the polyethylene surface. To substantiate the above findings, current measurements realized on composite layers and on polyethylene films with and without silver nanoparticles have been carried out. It is shown that in the presence of AgNPs in organosilicon layer, polarization/depolarization currents are one order of magnitude lower, transient currents decay faster and are not sensitive to multiple polarization. This can be understood if the AgNPs in the layer are acting as deep traps mitigating further injection with the result to decrease the apparent conductivity of the layer and to increase its breakdown strength. Similar trend is observed in polyethylene tailored by composite layer. These results strengthen the interpretation of the barrier effect based on space charge stabilized by deep traps formed by the AgNPs

Interface tailoring for charge injection control in polyethylene

International audienceThe insulating materials used to develop HVDC technologies suffer from a major drawback, which is the accumulation of electrical charges forming internal space charge with possibly two major consequences: (i)-the out-of-control of the internal electric field distribution initiating current runaway and (ii)-cumulated molecular level damages extending or creating defects and leading ultimately to breakdown. To prevent space charge accumulation, one possible route, not examined in depth by the scientific community to date is to control the charge injection at the interfaces between the insulating material and the "electrodes" (metallic or semi-conducting). Different routes were followed in this work for tailoring the interface between electrode and polyethylene material, based on chemical modification of the insulation or layer intercalation. Depending on the process, charge injection control is achieved either for negative charges or for charges of both polarities. The process of charge injection control is discussed with reference to the chemical/physical modifications brought about by the different treatments. The results provide indication towards a strategy to control the injection in power cables and other electrical components

The mineralogical composition of calcium and calcium-magnesium carbonate pedofeatures of calcareous soils in the European prairie ecodivision in Hungary

Abstract There is little data on the mineralogy of carbonate pedofeatures in the calcareous soils in Hungary which belong to the European prairie ecodivision. The aim of the present study is to enrich these data. The mineralogical composition of the carbonate pedofeatures from characteristic profiles of the calcareous soils in Hungary was studied by X-ray diffractometry, thermal analysis, SEM combined with microanalysis, and stable isotope determination. Regarding carbonate minerals only aragonite, calcite (+ magnesian calcite) and dolomite (+proto-dolomite) were identified in carbonate grains, skeletons and pedofeatures. The values relating, respectively, to stable isotope compositions (C13, O18) of carbonates in chernozems and in salt-affected soils were in the same range as those for recent soils (latter data reported earlier). There were no considerable differences between the values for the carbonate nodules and tubules from the same horizons, nor were there significant variations between the values of the same pedofeatures from different horizons (BC-C) of the same profile. Thus it can be assumed that there were no considerable changes in conditions of formation. Tendencies were recognized in the changes of (i) carbonate mineral associations, (ii) the MgCO3 content of calcites, (iii) the corrected decomposition temperatures, and (iv) the activation energies of carbonate thermal decompositions among the various substance-regimes of soils. Differences were found in substance-regimes types of soils rather than in soil types

Detecting SARS-CoV-2 RNA in fecal specimens: The practical challenges

10.1002/jmv.27071JOURNAL OF MEDICAL VIROLOGY9395241-524

Neural correlates of the DMT experience as assessed with multivariate EEG

Studying transitions in and out of the altered state of consciousness caused by intravenous (IV) N,N-Dimethyltryptamine (DMT - a fast-acting tryptamine psychedelic) offers a safe and powerful means of advancing knowledge on the neurobiology of conscious states. Here we sought to investigate the effects of IV DMT on the power spectrum and signal diversity of human brain activity (6 female, 7 male) recorded via multivariate EEG, and plot relationships between subjective experience, brain activity and drug plasma concentrations across time. Compared with placebo, DMT markedly reduced oscillatory power in the alpha and beta bands and robustly increased spontaneous signal diversity. Time-referenced neurophenomenological analyses revealed close relationships between changes in various aspects of subjective experience and changes in brain activity. Importantly, the emergence of oscillatory activity within the delta and theta frequency bands was found to correlate with the peak of the experience - particularly its eyes-closed visual component. These findings highlight marked changes in oscillatory activity and signal diversity with DMT that parallel broad and specific components of the subjective experience, thus advancing our understanding of the neurobiological underpinnings of immersive states of consciousness

Neural correlates of the DMT experience assessed with multivariate EEG

Studying transitions in and out of the altered state of consciousness caused by intravenous (IV) N,NDimethyltryptamine (DMT - a fast-acting tryptamine psychedelic) ofers a safe and powerful means of advancing knowledge on the neurobiology of conscious states. Here we sought to investigate the efects of IV DMT on the power spectrum and signal diversity of human brain activity (6 female, 7 male) recorded via multivariate EEG, and plot relationships between subjective experience, brain activity and drug plasma concentrations across time. Compared with placebo, DMT markedly reduced oscillatory power in the alpha and beta bands and robustly increased spontaneous signal diversity. Time-referenced and neurophenomenological analyses revealed close relationships between changes in various aspects of subjective experience and changes in brain activity. Importantly, the emergence of oscillatory activity within the delta and theta frequency bands was found to correlate with the peak of the experience - particularly its eyes-closed visual component. These fndings highlight marked changes in oscillatory activity and signal diversity with DMT that parallel broad and specifc components of the subjective experience, thus advancing our understanding of the neurobiological underpinnings of immersive states of consciousness