674 research outputs found
Enhancement of Superconductivity in Disordered Films by Parallel Magnetic Field
We show that the superconducting transition temperature T_c(H) of a very thin
highly disordered film with strong spin-orbital scattering can be increased by
parallel magnetic field H. This effect is due to polarization of magnetic
impurity spins which reduces the full exchange scattering rate of electrons;
the largest effect is predicted for spin-1/2 impurities. Moreover, for some
range of magnetic impurity concentrations the phenomenon of {\it
superconductivity induced by magnetic field} is predicted: superconducting
transition temperature T_c(H) is found to be nonzero in the range of magnetic
fields .Comment: 4 pages, 2 figure
Anomaly crust fields from MAGSAT satellite measurements:their processing and interpretation
The space distribution of the magnetic anomaly field for the Pacific Ocean is obtained from data of the satellite
MAGSAT. A number of long-wavelength magnetic anomalies of the region are identified. A spectrum analysis of a number of profiles of the anomaly field is performed disclosing typical scales of such anomalies. The wave transform of the anomaly magnetic profiles reveals and explicitly exposes the structure of the considered profile. A schematic complex cross-section is constructed, which demonstrates that the satellite data may be used in the study of the magnetic anomaly
Subexponential estimations in Shirshov's height theorem (in English)
In 1993 E. I. Zelmanov asked the following question in Dniester Notebook:
"Suppose that F_{2, m} is a 2-generated associative ring with the identity
x^m=0. Is it true, that the nilpotency degree of F_{2, m} has exponential
growth?" We show that the nilpotency degree of l-generated associative algebra
with the identity x^d=0 is smaller than Psi(d,d,l), where Psi(n,d,l)=2^{18} l
(nd)^{3 log_3 (nd)+13}d^2. We give the definitive answer to E. I. Zelmanov by
this result. It is the consequence of one fact, which is based on combinatorics
of words. Let l, n and d>n be positive integers. Then all the words over
alphabet of cardinality l which length is greater than Psi(n,d,l) are either
n-divided or contain d-th power of subword, where a word W is n-divided, if it
can be represented in the following form W=W_0 W_1...W_n such that W_1 >'
W_2>'...>'W_n. The symbol >' means lexicographical order here. A. I. Shirshov
proved that the set of non n-divided words over alphabet of cardinality l has
bounded height h over the set Y consisting of all the words of degree <n.
Original Shirshov's estimation was just recursive, in 1982 double exponent was
obtained by A.G.Kolotov and in 1993 A.Ya.Belov obtained exponential estimation.
We show, that h<Phi(n,l), where Phi(n,l) = 2^{87} n^{12 log_3 n + 48} l. Our
proof uses Latyshev idea of Dilworth theorem application.Comment: 21 pages, Russian version of the article is located at the link
arXiv:1101.4909; Sbornik: Mathematics, 203:4 (2012), 534 -- 55
Surface impedance of superconductors with magnetic impurities
Motivated by the problem of the residual surface resistance of the
superconducting radio-frequency (SRF) cavities, we develop a microscopic theory
of the surface impedance of s-wave superconductors with magnetic impurities. We
analytically calculate the current response function and surface impedance for
a sample with spatially uniform distribution of impurities, treating magnetic
impurities in the framework of the Shiba theory. The obtained general
expressions hold in a wide range of parameter values, such as temperature,
frequency, mean free path, and exchange coupling strength. This generality, on
the one hand, allows for direct numerical implementation of our results to
describe experimental systems (SRF cavities, superconducting qubits) under
various practically relevant conditions. On the other hand, explicit analytical
expressions can be obtained in a number of limiting cases, which makes possible
further theoretical investigation of certain regimes. As a feature of key
relevance to SRF cavities, we show that in the regime of "gapless
superconductivity" the surface resistance exhibits saturation at zero
temperature. Our theory thus explicitly demonstrates that magnetic impurities,
presumably contained in the oxide surface layer of the SRF cavities, provide a
microscopic mechanism for the residual resistance.Comment: 9 pages, 3 figs; v2: published versio
Neutron lifetime measurements using gravitationally trapped ultracold neutrons
Our experiment using gravitationally trapped ultracold neutrons (UCN) to
measure the neutron lifetime is reviewed. Ultracold neutrons were trapped in a
material bottle covered with perfluoropolyether. The neutron lifetime was
deduced from comparison of UCN losses in the traps with different
surface-to-volume ratios. The precise value of the neutron lifetime is of
fundamental importance to particle physics and cosmology. In this experiment,
the UCN storage time is brought closer to the neutron lifetime than in any
experiments before:the probability of UCN losses from the trap was only 1% of
that for neutron beta decay. The neutron lifetime
obtained,878.5+/-0.7stat+/-0.3sys s, is the most accurate experimental
measurement to date.Comment: 38 pages, 19 figures,changed conten
Localization of the gamma-radiation sources using the gamma-visor
The search of the main gamma-radiation sources at the site of the temporary storage of solid radioactive wastes was carried out. The relative absorbed dose rates were measured for some of the gamma-sources before and after the rehabilitation procedures. The effectiveness of the rehabilitation procedures in the years 2006-2007 was evaluated qualitatively and quantitatively. The decrease of radiation background at the site of the temporary storage of the solid radioactive wastes after the rehabilitation procedures allowed localizing the new gamma-source
UCN anomalous losses and the UCN capture cross-section on material defects
Experimental data shows anomalously large Ultra Cold Neutrons (UCN)
reflection losses and that the process of UCN reflection is not completely
coherent. UCN anomalous losses under reflection cannot be explained in the
context of neutron optics calculations. UCN losses by means of incoherent
scattering on material defects are considered and cross-section values
calculated. The UCN capture cross-section on material defects is enhanced by a
factor of 10^4 due to localization of UCN around defects. This phenomenon can
explain anomalous losses of UCN.Comment: 13 pages, 4 figure
The method of the content selection for formation of technological culture among students based on ethnological values
© 2016 by iSER, International Society of Educational Research. The aim of this article is to develop a methodology of the content selection for formation of technological culture among students based on the ethnoaesthetics and the disclosure of its values. The leading idea of the study is the methods of formation of a scientific picture of the world among students, involving the development of ideas in their consciousness of the unity of the subject-spiritual and scientific-technological world, sustainable worldview, ethnoaesthetical worldview, ethnoaesthetical consciousness, etc. In the article there is the methodological tools of the “humanized” content selection of technological, ethnoaesthetical, and professional nature; principles of the content selection are defined; ethnoaesthetical context of the system of approaches to the content selection is justified; methods of the content selection are selected; systems’ priority in the content selection is planned; and levels and criteria of the content selection are identified, the results of implementing of this methodology are shown
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