Analysis of Arc Processes in Multi-chamber Arrester for Lightning Protection at High-voltage Overhead Power Lines

Nowadays multi-chamber arresters are widely distributed as devices of lightning protection of overhead power lines. A mathematical modelling of processes in the discharge chamber of multichamber arrester is necessary to carry out in order to improve its breaking capacity. A three-dimensional mathematical transient model of thermal, gas-dynamic and electromagnetic processes taking place in the discharge chamber of multi-chamber arrester is presented in the article. Basic assumptions, model equations, a computational domain and the boundary conditions are described. Plasma turbulence is taken into account. The results of the calculation i.e. distributions of plasma temperature and overpressure in the discharge chamber at different time points are shown. The analysis of the results was carried out. It is shown that the presence of cavities in the electrodes design promotes electric arc extinction in the discharge chamber of multi-chamber arrester

Development of a Momentum Determined Electron Beam in the 1 -45 GeV Range

A beam line for electrons with energies in the range of 1 to 45 GeV, low contamination of hadrons and muons and high intensity up to 10^6 per accelerator spill at 27 GeV was setup at U70 accelerator in Protvino, Russia. A beam tagging system based on drift chambers with 160 micron resolution was able to measure relative electron beam momentum precisely. The resolution sigma_p p was 0.13% at 45 GeV where multiple scattering is negligible. This test beam setup provided the possibility to study properties of lead tungstate crystals (PbWO_4) for the BTeV experiment at Fermilab.Comment: 12 pages, 8 figures; work done by the BTeV Electromagnetic Calorimeter grou

Study of Radiation Damage in Lead Tungstate Crystals Using Intense High Energy Beams

We report on the effects of radiation on the light output of lead tungstate crystals. The crystals were irradiated by pure, intense high energy electron and hadron beams as well as by a mixture of hadrons, neutrons and gammas. The crystals were manufactured in Bogoroditsk, Apatity (both Russia), and Shanghai (China). These studies were carried out at the 70-GeV proton accelerator in Protvino

Double spin asymmetry in exclusive rho^0 muoproduction at COMPASS

The longitudinal double spin asymmetry A_1^rho for exclusive leptoproduction of rho^0 mesons, mu + N -> mu + N + rho, is studied using the COMPASS 2002 and 2003 data. The measured reaction is incoherent exclusive rho^0 production on polarised deuterons. The Q^2 and x dependence of A_1^rho is presented in a wide kinematical range: 3x10^-3 < Q^2 < 7 (GeV/c)^2 and 5x10^-5 < x < 0.05. The presented results are the first measurements of A_1^rho at small Q2 (Q2 < 0.1 (GeV/c)^2) and small x (x < 3x10^-3). The asymmetry is in general compatible with zero in the whole kinematical range.Comment: 6 Figures, 15 pages, version 2 with updated author list, technical latex problem fixe

Hunting down the X17 boson at the CERN SPS

Indexación ScopusRecently, the ATOMKI experiment has reported new evidence for the excess of e+e- events with a mass ∼ 17 MeV in the nuclear transitions of 4He, that they previously observed in measurements with 8Be. These observations could be explained by the existence of a new vector X17 boson. So far, the search for the decay X17 → e+e- with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining X17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the X17 decay with the proposed method. To reach this goal an optimization of the X17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [1], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate show that the goal of the proposed search is feasible. © 2020, The Author(s).https://link-springer-com.recursosbiblioteca.unab.cl/article/10.1140%2Fepjc%2Fs10052-020-08725-

Oxidation and combustion of fuel-rich N-butane-oxygen mixture in a standard 20-liter explosion vessel

Experiments on forced ignition of extremely fuel-rich n-butane-oxygen mixture with the equivalence ratio of 23 in the standard 20-liter spherical vessel at elevated initial pressure (4.1 bar) and temperature (500 K) reveal the nonmonotonic influence of the forced ignition delay time on the maximum explosion pressure and the maximum rate of pressure rise. The objective of the study reported herein is better understanding of test mixture oxidation and combustion in the 20-liter explosion vessel by means of mathematical modeling of the accompanying phenomena. It is shown that several temporally and spatially coupled phenomena could take place simultaneously in the experiments. These are mixing caused by oxygen injection to n-butane, forced ignition, flame propagation, preflame oxidation, heat transfer, and natural convection. Based on the CFD simulations of the mixing process and natural convection of the ignition kernel, as well as on the analysis of the detailed reaction mechanism of n-butane oxidation, laminar flame propagation, and self-ignition, possible explanations for the phenomena observed in the experiments have been suggested. The results of the study indicate that apparently inflammable mixtures can nevertheless become hazardous depending on the mixture preparation procedure and forced ignition timing.Multi Scale PhysicsApplied Science

Thrombotic thrombocytopenic purpura (Moschcowitz disease): Literature review and clinical observation of the disease in a 7-year-old child

Thrombotic thrombocytopenic purpura (TTP) is a rare clinical form of thrombotic microangiopathy (TMA) characterized by a triad of symptoms including non-immune hemolytic anemia, thrombocytopenia and polyorganic disorders (kidneys, central nervous system, lung, heart, gastrointestinal tract). Vital organs functions disorder caused by microthrombosis and tissue ischemia. This is the only form of TMA that has 100% laboratory confirmation. The cause of TTP is the absolute deficit or decrease in ADAMTS13 metalloprotease activity, which lead to an increase of concentration in blood stream of ultra-large von Willebrand factor multimers with high adhesive and aggregation activity. ADAMTS13 level less than 10% indicates a pronounced deficiency of metalloprotease, which predetermines severe thrombotic complications development. TTP diagnostics is based on the algorithm for detecting and confirming TMA symptom complex and excluding other variants of primary and secondary TMA, which are typical and atypical hemolyticuremic syndrome and a variety of secondary TMA. The article presents a clinical observation of TTP in a 7-year-old boy. The child entered the hospital for emergency indications with complaints of body temperature in crease to 40,7 0C, headache, wet cough, jaundice, petechial elements on the skin, urine darkening. General blood test revealed severe anemia (Hb 46 g/L), absence of platelets; ADAMTS13 level was 4%. The clinical picture represented by symptom complex of polyorganic disorders, including, besides the typical kidney and brain lesions, lung and eye lesions; laboratory data allowed to diagnose TTP. The patient underwent pathogenetic therapy followed by TTP remission, but severe ischemic nephron damage with clinical laboratory complex of complete nephrotic syndrome for 8 months from the TTP's debut has no complete laboratory remission. The article presents new data on disease pathogenesis, diagnostics and treatment of TTP. © 2017, Pediatria Ltd. All Rights Reserved

Thrombotic thrombocytopenic purpura (Moschcowitz disease): Literature review and clinical observation of the disease in a 7-year-old child

Thrombotic thrombocytopenic purpura (TTP) is a rare clinical form of thrombotic microangiopathy (TMA) characterized by a triad of symptoms including non-immune hemolytic anemia, thrombocytopenia and polyorganic disorders (kidneys, central nervous system, lung, heart, gastrointestinal tract). Vital organs functions disorder caused by microthrombosis and tissue ischemia. This is the only form of TMA that has 100% laboratory confirmation. The cause of TTP is the absolute deficit or decrease in ADAMTS13 metalloprotease activity, which lead to an increase of concentration in blood stream of ultra-large von Willebrand factor multimers with high adhesive and aggregation activity. ADAMTS13 level less than 10% indicates a pronounced deficiency of metalloprotease, which predetermines severe thrombotic complications development. TTP diagnostics is based on the algorithm for detecting and confirming TMA symptom complex and excluding other variants of primary and secondary TMA, which are typical and atypical hemolyticuremic syndrome and a variety of secondary TMA. The article presents a clinical observation of TTP in a 7-year-old boy. The child entered the hospital for emergency indications with complaints of body temperature in crease to 40,7 0C, headache, wet cough, jaundice, petechial elements on the skin, urine darkening. General blood test revealed severe anemia (Hb 46 g/L), absence of platelets; ADAMTS13 level was 4%. The clinical picture represented by symptom complex of polyorganic disorders, including, besides the typical kidney and brain lesions, lung and eye lesions; laboratory data allowed to diagnose TTP. The patient underwent pathogenetic therapy followed by TTP remission, but severe ischemic nephron damage with clinical laboratory complex of complete nephrotic syndrome for 8 months from the TTP's debut has no complete laboratory remission. The article presents new data on disease pathogenesis, diagnostics and treatment of TTP. © 2017, Pediatria Ltd. All Rights Reserved