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Influence of corona on the voltages induced by nearby lightning on overhead distribution lines
No full textSummary form only given as follows. A model for the calculation of lightning-induced voltages is presented with the aim of assessing the effect of corona when power distribution lines are illuminated by lightning electromagnetic fields. Corona is taken into account by means of dynamic capacitance describing a charge-voltage diagram. Such an equivalent capacitance is then introduced in a model which describes a line illuminated by a lightning electromagnetic field. It is first concluded that the influence of corona on lightning induced overvoltages is of importance only for particularly severe strokes. It is also found that corona acts to increase the magnitude of these overvoltages, contrary to the case of voltages due to direct strokes, which are attenuated by corona. A theoretical explanation of such an amplitude increase is presented. The effect of the ground resistivity is also taken into account in the calculations. The results show that such an effect is in general as important as the effect of corona. This is different from the direct-strike behavior, where corona, when present, affects the surge propagation more than the ground resistivity. This is due to the fact that for the case of induced-voltages, the ground resistivity may affect more strongly the lightning-radiated fields rather than the surge propagation along the line, while corona affects only surge propagation. The need for experimental results to test the theoretical finding of the paper is stressed and some indication is given. Finally, a sensitivity analysis of the induced voltages as a function of the charge-voltage diagram adopted to model corona is also performedLRESCI-STI-F
Neurochemical profile of the developing mouse cortex determined by in vivo1H NMR spectroscopy at 14.1 T and the effect of recurrent anaesthesia
No full textP>The neurochemical profile of the cortex develops in a region and time specific manner, which can be distorted by psychiatric and other neurological pathologies. Pre-clinical studies often involve experimental mouse models. In this study, we determined the neurochemical profile of C57BL/6 mice in a longitudinal study design to provide a reference frame for the normal developing mouse cortex. Using in vivo proton NMR spectroscopy at 14 T, we measured the concentrations of 18 metabolites in the anterior and posterior cortex on postnatal days (P) 10, 20, 30, 60 and 90. Cortical development was marked by alterations of highly concentrated metabolites, such as N-acetylaspartate, glutamate, taurine and creatine. Regional specificity was represented by early variations in the concentration of glutamine, aspartate and choline. In adult animals, regional concentration differences were found for N-acetylaspartate, creatine and myo-inositol. In this study, animals were exposed to recurrent isoflurane anaesthesia. Additional experiments showed that the latter was devoid of major effects on behaviour or cortical neurochemical profile. In conclusion, the high sensitivity and reproducibility of the measurements achieved at 14 T allowed us to identify developmental variations of cortical areas within the mouse cortex.CIBMLIFME
First results from the ESCA microscopy beamline on ELETTRA
No full textThe results of the first experiments with test samples, tool steel and polycrystalline Sn carried out with the scanning photoemission microscope built on the ELETTRA storage ring in Trieste are presented and discussed. The scanning photoemission microscope uses a zone plate optical system for demagnification of the photon beam to submicron dimensions. The present performance of the microscope in photoemission allows elemental and chemical mapping and small-spot photoelectron spectroscopy with lateral resolution better than 200 nm. The reported results show how photoemission microscopy can distinguish the spatial distribution of carbide phases with different Fe content at the surface of a tool steel and the correlation between inhomogeneous oxidation of a polycrystalline Sn sample and its grain structure. (C) 1977 by John Wiley & Sons, Ltd.LSELPRXSincrotrone trieste,i-34012 trieste,italy. univ nova lisboa,fct,dept mat sci,p-2825 monte de caparica,portugal. univ london kings coll,dept phys,strand,london wc2r 2ls,england.ISI Document Delivery No.: XC50
Demagnetization factors and field of hemispherical objects
No full textDemagnetization factors play an important role in micromagnetics modeling but exact solutions only exist for a limited number of particle shapes. Here we use a Fourier space based approach coupled to the concept of magnetic charges to derive analytically the demagnetization factors for shapes that are subsets of a sphere: spherical sectors and spherical caps. For the uniformly magnetized hemisphere, which is a special case of both geometries, the exact demagnetization factors are shown to be Nx=Ny=7/(9π) parallel to the bottom plane and Nz=1−14/(9π) in the direction of the dome. Additionally, we provide expressions for shape amplitudes and demagnetization fields of these objects in terms of rapidly converging series. Our work demonstrates the potential of evaluating shape amplitudes to determine demagnetization factors in certain geometries and our results may facilitate numerical simulations of, for example, ferromagnetic droplets.LQ
Urban energy simulation of the EPFL Campus in Fribourg using a new paradigm: the CITYGML application domain extension energy
No full textLESO-P
A two-compartment mathematical model of neuroglial metabolism using [1-C-11] acetate
No full textThe purpose of this study was to develop a two-compartment metabolic model of brain metabolism to assess oxidative metabolism from [1-C-11] acetate radiotracer experiments, using an approach previously applied in C-13 magnetic resonance spectroscopy (MRS), and compared with an one-tissue compartment model previously used in brain [1-C-11] acetate studies. Compared with C-13 MRS studies, C-11 radiotracer measurements provide a single uptake curve representing the sum of all labeled metabolites, without chemical differentiation, but with higher temporal resolution. The reliability of the adjusted metabolic fluxes was analyzed with Monte-Carlo simulations using synthetic C-11 uptake curves, based on a typical arterial input function and previously published values of the neuroglial fluxes V-tca(g), V-x, V-nt, and V-tca(n) measured in dynamic C-13 MRS experiments. Assuming V-x(g)=10xV(tca)(g) and V-x(n)=V-tca(n), it was possible to assess the composite glial tricarboxylic acid (TCA) cycle flux V-gt(g) (Vgtg = V(x)(g)xV(tca)(g)/(V-x(g) + V-tca(g))) and the neurotransmission flux V-nt from C-11 tissue-activity curves obtained within 30 minutes in the rat cortex with a beta-probe after a bolus infusion of [1-C-11] acetate (n = 9), resulting in V-gt(g) = 0.136 +/- 0.042 and V-nt = 0.170 +/- 0.103 mu mol/g per minute (mean +/- s.d. of the group), in good agreement with 13C MRS measurements. Journal of Cerebral Blood Flow & Metabolism (2012) 32, 548-559; doi: 10.1038/jcbfm.2011.162; published online 30 November 2011LIFMETCIB
Measurement of Antiproton Production in p-He Collisions at root S-NN=110 GeV
No full textThe cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set corresponding to an integrated luminosity of 0.5 nb(-1). The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and 110 GeV/c, represent the first direct determination of the antiproton production cross section in p-He collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.LPHEThis is an open access article under the terms of the Creative Commons Attribution Licens
Modulation of perovskite crystallization processes towards highly efficient and stable perovskite solar cells with MXene quantum dot-modified SnO2
No full textNanocrystalline tin (iv) oxide (SnO2) electron-transport layers (ETL) have shown great potential for achieving highly efficient, stable perovskite solar cells (PSCs), in particular low-temperature-processed flexible PSCs. Recently, studies have further shown that a modified SnO2 bottom layer facilitates the deposition of highly crystalline perovskite films, boosting the photovoltaic performance of the PSCs. The modulation of perovskite crystallization processes is a key to obtain highly crystalline and stable perovskite films; however, a fundamental understanding is still missing. Herein, we report an in situ synchrotron-based two-dimensional grazing-incidence X-ray diffraction technique to explore the SnO2 ETL-modulated perovskite crystallization kinetics for the first time. The titanium carbide (Ti3C2Tx)-MXene quantum dot-modified SnO2 (MQDs-SnO2) ETL was found to be able to rapidly induce perovskite nucleation from the precursor solution, forming an intermediate perovskite phase upon anti-solvent treatment. This substantially improves the crystal quality and phase stability of the as-fabricated perovskite film. Benefiting in addition from the superior charge extraction properties of the MQDs-SnO2 layer, a steady-state power conversion efficiency of up to 23.3%, as well as outstanding stability against humidity and light soaking was achieved for the corresponding PSCs.LPILSP
Integrated modelling of neon impact on JET H-mode core plasmas
No full textNuclear fusion reactor plasmas will need to exhaust a significant proportion of energy flux through radiative processes, to enable acceptable divertor loads. This can be obtained by line radiation from impurities, injected from the plasma edge. There are however limitations on the sustainable impurity content, since radiation from the core can lead to a deleterious electron heat sink. Moreover, dilution of the main ions reduces the available fuel. Simultaneously, impurities have an impact on the turbulent transport, both by dilution and by changes in the effective charge. Recent experiments at JET point towards an improvement in plasma confinement in neon seeded discharges with respect to purer equivalent plasmas. In this paper the impact of the impurities on the confinement is studied, isolating various effects. First-principle-based integrated modelling with the QuaLiKiz quasilinear turbulent transport model explains the improvement by a combination of higher pedestal temperature, increased rotation shear, and impurity-induced microturbulence stabilization. These results are optimistic with respect to the maximum impurity levels allowed in ITER and future reactors. Comparison between QuaLiKiz and higher fidelity gyrokinetics has exposed issues with QuaLiKiz impurity peaking predictions with rotation.SP
Effects of crab burrows on pore water flows in salt marshes
No full textMacro-pores such as crab burrows are found commonly distributed in salt marsh sediments. Their disturbance on the soil structure is likely to influence both pore water flows and solute transport in salt marshes; however, the effects of crab burrows are not well understood. Here, a three-dimensional model simulated tidally driven pore water flows subject to the influence of crab burrows in a marsh system. The model, based on Richards’ equation, considered variably saturated flow in the marsh with a two-layer soil configuration, as observed at the Chongming Dongtan wetland (Shanghai, China). The simulation results showed that crab burrows distributed in the upper low- permeability soil layer, acting as preferential flow paths, affected pore water flows in the marsh particularly when the contrast of hydraulic conductivity between the lower high-permeability soil layer and the overlying low- permeability soils was high. The burrows were found to increase the volume of tidally driven water exchange between the marsh soil and the tidal creek. The simulations also showed improvement of soil aeration conditions in the presence of crab burrows. These effects may lead to increased productivity of the marsh ecosystem and enhancement of its material exchange with coastal waters.ECO