Giant dispersion of critical currents in superconductor with fractal clusters of a normal phase

The influence of fractal clusters of a normal phase on the dynamics of a magnetic flux trapped in a percolative superconductor is considered. The critical current distribution and the current-voltage characteristics of fractal superconducting structures in the resistive state are obtained for an arbitrary fractal dimension of the cluster boundaries. The range of fractal dimensions, where the dispersion of critical currents becomes infinite, is found. It is revealed that the fractality of clusters depresses of the electric field caused by the magnetic flux motion thus increasing the critical current value. It is expected that the maximum current-carrying capability of a superconductor can be achieved in the region of giant dispersion of critical currents.Comment: 7 pages with 3 figure

The reproduction trajectories of institutions in relation to social isolation of individual population groups in regions of Russia

This article deals with spatial socio-demographic isolation as a factor of the existing settlement system in Russian regions. Theoretically, the phenomena of solitude and social isolation have their own demographic, socio-economic, and psychological origin. Conceptually, they are reflected in theories of nucleation of society’s family structure, families losing its core functions, and the deprivation of personality (friends and family) in the context of the second demographic transition. In fact, the trending reluctance to having children, increases in cohabitation and divorces, men’s premature deaths resulting in widowhood are supplemented and accompanied by institutional factors that enhance a singular lifestyle, including various forms of personal isolation from social environment in post-industrial society. We examine the increasingly higher number of private households with single individuals ranging from young to old, the incidence of widowhood institution (effects of death rate risks on marriage and family), effects of labor, academic, survival, and consumer migration (both reversible and irreversible) on replacement levels as the major reasons of socio-demographic isolation. Psychological, demographic isolation of any given local communities favors the feel of solitude as the controller of communication and interaction intensity between individuals. In socio-economic terms, isolation of local communities is related to the factor of families’ living away from communication centers and real markets, to new Russian and global logistics, deprivation of traditional sources of income of households as specific forms of survival on the vast living space of Russian society.The article has been prepared with the support of the Russian Foundation for Basic Research Grant 13-06-00008a “Creation and Enhancement of Quality of Life as a Priority for Socio-Economic Development of Russian Regions.

Resistive state of superconducting structures with fractal clusters of a normal phase

The effect of morphologic factors on magnetic flux dynamics and critical currents in percolative superconducting structures is considered. The superconductor contains the fractal clusters of a normal phase, which act as pinning centers. The properties of these clusters are analyzed in the general case of gamma-distribution of their areas. The statistical characteristics of the normal phase clusters are studied, the critical current distribution is derived, and the dependencies of the main statistical parameters on the fractal dimension are found. The effect of fractal clusters of a normal phase on the electric field induced by the motion of the magnetic flux after the vortices have been broken away from pinning centers is considered. The voltage-current characteristics of fractal superconducting structures in a resistive state for an arbitrary fractal dimension are obtained. It is found that the fractality of the boundaries of normal phase clusters intensifies magnetic flux trapping and thereby increases the current-carrying capability of the superconductor.Comment: 15 pages with 8 figures, revtex3, alternative e-mail of author is [email protected]

Decoherence induced by squeezing control errors in optical and ion trap holonomic quantum computations

We study decoherence induced by stochastic squeezing control errors considering the particular implementation of Hadamard gate on optical and ion trap holonomic quantum computers. We find the fidelity for Hadamard gate and compute the purity of the final state when the control noise is modeled by Ornstein-Uhlenbeck stochastic process. We demonstrate that in contradiction to the case of the systematic control errors the stochastic ones lead to decoherence of the final state. In the small errors limit we derive a simple formulae connecting the gate fidelity and the purity of the final state.Comment: RevTex, 5 pages, few typos correcte

Synthesis and research of polyfunctional silicon-containing amines – new promoters of adhesion

Currently, in order to obtain high-tech hybrid products, modern adhesives have high requirements for creating strong joints between dissimilar materials. It is known that adhesion depends on the compatibility of the adhesives with the surfaces of the materials. Amine compounds are the main hardeners for epoxy compositions. That is why, in this article, we synthesized silicon-containing amines based on polyfunctional aminoalkoxysiloxanes for epoxy compositions. Aminoalkoxysiloxanes were prepared by the interaction of 3-aminopropyltriethoxysilane with monoethanolamine in nitrogen at atmospheric pressure in the presence of a binary antioxidant and catalytic amounts of an alkali metal alcoholate. During the reaction in a homogeneous phase, the reaction mixture was heated to a temperature of 100-110 °C and distilled off to 90% of ethanol from the theoretically calculated amount. Further, the reaction was carried out at a reduced temperature of 10-20 mmHg pressure until the release of alcohol stops. At the same time, gravimetric control was carried out and the refractive index of the reaction mixture was measured. As a result, aminoalkoxysilanes were obtained in the form of light-yellow oily liquids. The structure of the obtained compounds was investigated by IR spectroscopy on an FSM-1202 Fourier spectrophotometer and 1H NMR spectroscopy on a high-resolution BrukerWM-250 NMR spectrometer. It was found that under the selected synthesis conditions, aminopropyltri-(2-aminoethoxy)silane is obtained with the highest yield of 97.6% at a molar ratio of 3-aminopropyltriethoxysilane AGM-9 with monoethanolamine 1:3

Neutron - Mirror Neutron Oscillations: How Fast Might They Be?

We discuss the phenomenological implications of the neutron (n) oscillation into the mirror neutron (n'), a hypothetical particle exactly degenerate in mass with the neutron but sterile to normal matter. We show that the present experimental data allow a maximal n-n' oscillation in vacuum with a characteristic time $\tau$ much shorter than the neutron lifetime, in fact as small as 1 sec. This phenomenon may manifest in neutron disappearance and regeneration experiments perfectly accessible to present experimental capabilities and may also have interesting astrophysical consequences, in particular for the propagation of ultra high energy cosmic rays.Comment: 4 pages, 1 figure; revtex; matches paper published by P.R.

Proximity effect model of ultra-narrow NbN strips

We show that narrow superconducting strips in superconducting (S) and normal (N) states are universally described by the model presenting them as lateral NSN proximity systems in which the superconducting central band is sandwiched between damaged edge-bands with suppressed superconductivity.The width of the superconducting band was experimentally determined from the value of magnetic field at which the band transits from the Meissner state to the static vortex state. Systematic experimental study of 4.9 nm thick NbN strips with widths in the interval from 50 nm to 20 ${\mu}$m, which are all smaller than the Pearl's length, demonstrates gradual evolution of the temperature dependence of the critical current with the change of the strip width

Dynamics of the magnetic flux trapped in fractal clusters of normal phase in a superconductor

The influence of geometry and morphology of superconducting structure on critical currents and magnetic flux trapping in percolative type-II superconductor is considered. The superconductor contains the clusters of a normal phase, which act as pinning centers. It is found that such clusters have significant fractal properties. The main features of these clusters are studied in detail: the cluster statistics is analyzed; the fractal dimension of their boundary is estimated; the distribution of critical currents is obtained, and its peculiarities are explored. It is examined thoroughly how the finite resolution capacity of the cluster geometrical size measurement affects the estimated value of fractal dimension. The effect of fractal properties of the normal phase clusters on the electric field arising from magnetic flux motion is investigated in the case of an exponential distribution of cluster areas. The voltage-current characteristics of superconductors in the resistive state for an arbitrary fractal dimension are obtained. It is revealed that the fractality of the boundaries of the normal phase clusters intensifies the magnetic flux trapping and thereby raises the critical current of a superconductor.Comment: revtex, 16 pages with 1 table and 5 figures; text and figures are improved; more detailed version with geometric probability analisys of the distribution of entry points into weak links over the perimeter of a normal phase clusters and one additional figure is published in Phys.Rev.B; alternative e-mail of author is [email protected]

Detection of Giant Radio Pulses from the Pulsar PSR B0656+14

Giant pulses (GPs) have been detected from the pulsar PSR B0656+14. A pulse that is more intense than the average pulse by a factor of 120 is encountered approximately once in 3000 observed periods of the pulsar. The peak flux density of the strongest pulse, 120 Jy, is a factor of 630 higher than that of the average pulse. The GP energy exceeds the energy of the average pulse by up to a factor of 110, which is comparable to that for other known pulsars with GPs, including the Crab pulsar and the millisecond pulsar PSR B1937+21. The giant pulses are a factor of 6 narrower than the average pulse and are clustered at the head of the average pulse. PSR B0656+14 along with PSR B0031-07, PSR B1112+50, and PSR J1752+2359 belong to a group of pulsars that differ from previously known ones in which GPs have been detected without any extremely strong magnetic field on the light cylinder.Comment: 10 pages, 3 figures, 1 table; originally published in Russian in Pis'ma Astron. Zh., 2006, v.32, 650; translated by George Rudnitskii; the English version will be appear in Astronomy Letter