Superconducting screening on different length scales in high-quality bulk MgB2 superconductor

High quality bulk MgB2 exhibit a structure of voids and agglomeration of crystals on different length-scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length-scales, of ~1 micrometre, ~10 micrometre and whole of the sample (~millimetre). Each of these screenings contributes to the measured irreversible magnetic moment (Dm). The analysis of the field dependence of Dm for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the artefact of the sample size-dependent critical current and irreversibility field. Our data analysis enables the separation of the contribution of each of the screening currents to Dm. The field dependence of each of the currents follows a stretched exponential form. The currents flowing around whole of the sample give a dominant contribution to Dm in the intermediate fields (1T < H < 4T at 20K) and they can be used to obtain the value of Jc from critical state model, which corresponds to the transport Jc

On collocation methods for Volterra integral equations with delay arguments

In this paper we construct and give an analysis of the global convergence and local superconvergence properties of polynomial collocation solution $u in Sd$ of Volterra integral equations with constant delay thus extending the existing theory for d=-1 to the general case

On collocation methods for Volterra integral equations with delay arguments

In this paper we construct and give an analysis of the global convergence and local superconvergence properties of polynomial collocation solution $u in Sd$ of Volterra integral equations with constant delay thus extending the existing theory for d=-1 to the general case

On finite--temperature and --density radiative corrections to the neutrino effective potential in the early Universe

Finite-temperature and -density radiative corrections to the neutrino effective potential in the otherwise CP-symmetric early Universe are considered in the real-time approach of Thermal Field Theory. A consistent perturbation theory endowed with the hard thermal loop resummation techniques developed by Braaten and Pisarski is applied. Special attention is focused on the question whether such corrections can generate any nonzero contribution to the CP-symmetric part of the neutrino potential, if the contact approximation for the W-propagator is used.Comment: 11 pages, revtex styl

On the Warburg Parameter of the Ag/AgI Electrode

The possible origins of frequent deviations from the calculated and experimentally obtained values of the Warburg parameter of the Ag/AgI electrode are discussed. Following the considerations of possible conditions for classical Warburg impedance to appear in solid AgI, it is suggested that the overall Warburg impedance of the Ag/AgI electrode could be considered as the sum of the Warburg impedances in series, one in the solid, and the other in the solution phase. In addition, the influence of diffusion controlled adsorption of I- ions in parallel with diffusion controlled ion-transfer on the experimentally obtained values of the Warburg parameter is discussed. A different theoretical approach to the analysis of the Warburg impedance of the Ag/AgI electrode is suggested, different from those formerly applied

Precision Drift Chambers for the Atlas Muon Spectrometer

ATLAS is a detector under construction to explore the physics at the Large Hadron Collider at CERN. It has a muon spectrometer with an excellent momentum resolution of 3-10%, provided by three layers of precision monitored-drift-tube chambers in a toroidal magnetic field. A single drift tube measures a track point with a mean resolution close to 100 micron, even at the expected high neutron and gamma background rates. The tubes are positioned within the chamber with an accuracy of 20 microns, achieved by elaborate construction and assembly monitoring procedures.Comment: 3 pages, 2 eps figures, Proceedings for poster at Physics in Collisions Conference (PIC03), Zeuthen, Germany, June 2003. FRAP1

Once More About the Analysis of the Ag/AgI Electrode Impedance

The reliability of different electrode admittance equations in the case of the Ag/Ag I electrode is critically discussed. It is shown that the admittance equation already derived for the metal amalgam/metal-Ion reversible electrode reaction coupled with reactant adsorption offers some advantages compared to the admittance equation for the reversible electrode reaction on the metal/metal-ion electrode. New results of impedance measurements of the Ag/Ag I electrode are reported

Egorov property in perturbed cat map

We study the time evolution of the quantum-classical correspondence (QCC) for the well known model of quantised perturbed cat maps on the torus in the very specific regime of semi-classically small perturbations. The quality of the QCC is measured by the overlap of classical phase-space density and corresponding Wigner function of the quantum system called quantum-classical fidelity (QCF). In the analysed regime the QCF strongly deviates from the known general behaviour in particular it decays faster then exponential. Here we study and explain the observed behavior of the QCF and the apparent violation of the QCC principle.Comment: 12 pages, 7 figure

Large-Scale Production of Monitored Drift Tube Chambers for the ATLAS Muon Spectrometer

Precision drift tube chambers with a sense wire positioning accuracy of better than 20 microns are under construction for the ATLAS muon spectrometer. 70% of the 88 large chambers for the outermost layer of the central part of the spectrometer have been assembled. Measurements during chamber construction of the positions of the sense wires and of the sensors for the optical alignment monitoring system demonstrate that the requirements for the mechanical precision of the chambers are fulfilled