We report on a search for ultralow-mass axionlike dark matter by analyzing the ratio of the spin-precession frequencies of stored ultracold neutrons and Hg199 atoms for an axion-induced oscillating ...electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range 10−24≤ma≤10−17eV . Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constraints on the axion coupling to nucleons by up to a factor of 40.
The mode of continuous acceleration of electrons in pulsed nano- and subnanosecond gas discharges is of great importance for making a correct physical model of the pulsed electric breakdown of ...strongly over-volted gas gaps. 'Runaway' or 'continuously accelerated' electrons, crossing a discharge area, intensively ionize the gas along their way, which can considerably reduce the time to form breakdown. The creation of an optimum set of conditions for the transition of electrons to the mode of continuous acceleration will allow constructing new types of superfast high-pressure gas dischargers. In this research the experimental results of the registration of runaway electrons in subnanosecond discharges in high-pressure (up to 40 atm) nitrogen are given. In this experiment electrodes that provide the formation of electric field with uniform configuration in the discharge gap were used.
HCV and oxidative stress in the liver Ivanov, Alexander V; Bartosch, Birke; Smirnova, Olga A ...
Viruses,
01/2013, Letnik:
5, Številka:
2
Journal Article, Book Review
Recenzirano
Odprti dostop
Hepatitis C virus (HCV) is the etiological agent accounting for chronic liver disease in approximately 2-3% of the population worldwide. HCV infection often leads to liver fibrosis and cirrhosis, ...various metabolic alterations including steatosis, insulin and interferon resistance or iron overload, and development of hepatocellular carcinoma or non-Hodgkin lymphoma. Multiple molecular mechanisms that trigger the emergence and development of each of these pathogenic processes have been identified so far. One of these involves marked induction of a reactive oxygen species (ROS) in infected cells leading to oxidative stress. To date, markers of oxidative stress were observed both in chronic hepatitis C patients and in various in vitro systems, including replicons or stable cell lines expressing viral proteins. The search for ROS sources in HCV-infected cells revealed several mechanisms of ROS production and thus a number of cellular proteins have become targets for future studies. Furthermore, during last several years it has been shown that HCV modifies antioxidant defense mechanisms. The aim of this review is to summarize the present state of art in the field and to try to predict directions for future studies.
Tungsten oxide was electrochemically deposited from a metastable acidic solution of isopolytungstate on glassy carbon electrodes coated by the films of a conducting polymer ...poly-3,4-ethylenedioxythiophene (PEDOT). The formation of PEDOT/WO3 composite films during electrochemical deposition of tungsten oxide into the polymer matrix was gravimetrically monitored by EQCM. The morphology of WO3 deposits was studied using SEM, TEM and EDX analysis, including element mapping and depth concentration profile of main elements. SEM and TEM images of PEDOT/WO3 composites show disperse distribution of WO3 precipitates in the porous matrix of PEDOT, possessing high surface area and pore volume, effective for charge transport. Electrochemical behavior of PEDOT/WO3 was investigated in 0.5 M H2SO4 by cyclic voltammetry, galvanostatic charge-discharge method and electrochemical impedance spectroscopy. The WO3 component in the obtained PEDOT/WO3 composite electrodes exhibited high specific capacitance of 689 F g−1 in the potential range −0.3–0.0 V. The work presents a simple approach for the synthesis of PEDOT/WO3 composites with high values of specific capacitance. The obtained results indicate that PEDOT/WO3 composite could be a promising electrode material for supercapacitor applications.
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•Synthesis of PEDOT/WO3 composites with very fast pseudocapacitive response.•Monitoring of mass change during the synthesis of PEDOT/WO3 composite.•Composite electrodes exhibited high specific capacitance of 689 F g−1•High rate of charge transfer without diffusion limitations up to 0,4 V/s scan rate.
Abstract
Dielectric losses are one of the key factors limiting the coherence of superconducting qubits. The impact of materials and fabrication steps on dielectric losses can be evaluated using ...coplanar waveguide (CPW) microwave resonators. Here, we report on superconducting CPW microwave resonators with internal quality factors systematically exceeding 5 × 10
6
at high powers and 2 × 10
6
(with the best value of 4.4 × 10
6
) at low power. Such performance is demonstrated for 100-nm-thick aluminum resonators with 7–10.5 um center trace on high-resistivity silicon substrates commonly used in Josephson-junction based quantum circuit. We investigate internal quality factors of the resonators with both dry and wet aluminum etching, as well as deep and isotropic reactive ion etching of silicon substrate. Josephson junction compatible CPW resonators fabrication process with both airbridges and silicon substrate etching is proposed. Finally, we demonstrate the effect of airbridges’ positions and extra process steps on the overall dielectric losses. The best quality factors are obtained for the wet etched aluminum resonators and isotropically removed substrate with the proposed ultrasonic metal edge microcutting.
The Yakutsk Extensive Air Shower Array has been continuously operating for more than 50 years (since 1970) and up until recently it has been one of world’s largest ground-based instruments aimed at ...studying the properties of cosmic rays in the ultra-high energy domain. In this report we discuss results recently obtained at the array—on cosmic rays’ energy spectrum, mass composition and directional anisotropy—and how they fit into the world data. Special attention is paid to the measurements of muonic component of extensive air showers. Theoretical results of particle acceleration at shocks are also briefly reviewed. Future scientific and engineering plans on the array modernization are discussed.
The results of numerical 3D modeling of the development of an electron avalanche initiated by a field emission electron in a small-sized region of an amplified electric field near the ...microinhomogeneities at the cathode have been presented. The simulation has been carried out for the discharge gaps with an initially homogeneous distribution of the electric field with a reduced intensity significantly lower than that required by the electron runaway criterion. The possibility of the transition of the field emission electrons initiating avalanches and the electrons in these avalanches into runaway regime has been investigated. The microinhomogeneities in the form of a cone, metal droplets, and boundaries between pores or microcraters have been considered. The calculations were carried out for nitrogen in the pressure range from atmospheric to 40 atm. It has been shown that the initial energy obtained near the microinhomogeneity can significantly facilitate the transition of the electron into the runaway mode. And the electron will continue to run away in a discharge gap electric field weak according to the runaway criterion. It has been shown that this effect is especially noticeable at gas pressures above 10 atm. A comparative analysis of the simulation results with the experimental data obtained by us on the switching characteristics of a discharge gap filled with nitrogen when exposed to voltage pulses with subnanosecond fronts of different steepness has been carried out. This made it possible to divide the ranges of experimental conditions into those when only the amplification of the electric field near the microinhomogeneities is sufficient for the runaway of electrons and when the electric field of an avalanche of critical or close to critical size is additionally necessary for the runaway.
This paper reviews a wide range of questions in astrophysics and cosmology that can be answered by astronomical observations in the far-IR to millimeter wavelength range and which include the ...formation and evolution of stars and planets, galaxies, and the interstellar medium, the study of black holes, and the development of the cosmological model. These questions are considered in relation to the Millimetron Space Observatory (Spectrum-M project), which is equipped with a aperture cooled telescope and can operate both as a single-dish telescope and as part of a space-ground very long baseline interferometer.
Abstract
The article presents an approach to the complex analysis of electromechanical systems using specialized packages of applied simulation programs. It is shown that the choice of research ...methodology is due to the complexity and mutual influence of energy processes in electromechanical converters and the absence of verified analytical solutions.The main research stages are defined, including the construction of a geometric model of the object, determination of the problem type to be solved and relevant initial and boundary conditions, justification of defining criteria, modeling of electromagnetic, thermal and hydraulic processes and their analysis. The software packages are based on the classical equations of electrodynamics, heat transfer, energy, motion and continuity. Creation of three-dimensional solid parametric model is implemented in the T-FlexCAD system. The simulation experiment was carried out with the use of SolidWorksFlowSimulation system, that allows to process the initial array of design parameters in conditions of the multiphysics problem statement. The variables were ranked using Statistica, a statistical processing and data analysis program. Simulation results of energy exchange processes at varying geometry of defining design parameters allow to establish dependence of electromechanical system output characteristics on design and dimension relations of system elements parameters and to design high-efficiency electromechanical systems on this basis.
The mechanism of runaway electron generation at gas pressures from a few atmospheres to several tens of atmospheres is proposed. According to this mechanism, the electrons pass into the runaway mode ...in the enhanced field zone that arises between a cathode micropoint—a source of field-emission electrons—and the region of the positive ion space charge accumulated near the cathode in the tails of the developing electron avalanches. As a result, volume gas ionization by runaway electrons begins with a time delay required for the formation of the enhanced field zone. This process determines the delay time of breakdown. The influence of the gas pressure on the formation dynamics of the space charge region is analyzed. At gas pressures of a few atmospheres, the space charge arises due to the avalanche multiplication of the very first field-emission electron, whereas at pressures of several tens of atmospheres, the space charge forms as a result of superposition of many electron avalanches with a relatively small number of charge carriers in each.
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