Highly viscous electron fluid in GaAs quantum wells

A fluid in which shear-stress transverse waves, being character for solids, can propagate is usually referred as a highly viscous fluid. Hydrodynamics of the fluid formed by conduction electrons has been recently discovered in graphene, ultra-pure Weyl and layered metals, and high-mobility GaAs quantum wells. Here we construct a theory of magnetotransport in a highly viscous two-dimensional (2D) electron fluid in moderate magnetic fields, accounting its viscoelastic dynamics and the memory effects in the interparticle scattering. In addition to the properties of the microwave-induced resistance oscillations (MIRO) in photoresistance explained by theories for non-interacting 2D electrons, our theory predicts an irregular shape of MIRO at certain sample sizes, a peak in photoresistance near the doubled electron cyclotron frequency, and no dependence of MIRO on the helicity of the circular polarization of radiation. These effects, which are the evidences of the excitation of the transverse magnetosonic waves, were observed in magnetotransport experiments on ultra-high-quality GaAs quantum wells. We conclude that 2D electrons in such structures in magnetic field form a highly viscous fluid.Comment: 26 pages, 10 figure

Relaxation of superflow in a network: an application to the dislocation model of supersolidity of helium crystals

We have considered the dislocation network model for the supersolid state in He-4 crystals. In difference with uniform 2D and 3D systems, the temperature of superfluid transition T_c in the network is much smaller than the degeneracy temperature T_d. It is shown that a crossover into a quasi superfluid state occurs in the temperature interval between T_c and T_d. Below the crossover temperature the time of decay of the flow increases exponentially under decrease of the temperature. The crossover has a continuous character and the crossover temperature does not depend on the density of dislocations.Comment: Corrected typo

Evaluation of the Clinical Efficacy of Prednisolone in the Treatment of Inflammatory Bowel Diseases with Different Dosage Methods

Aim: to investigate the clinical efficacy of two methods of oral dosing of prednisolone (in mg and mg/kg) for the induction of remission for patients with ulcerative colitis (UC) and Crohn's disease (CD) using the technology of constructing and evaluating the effectiveness function (dose-effect relationship).Material and methods. In this study were included 86 patients aged from 18 to 65 years with moderate or severe active inflammatory bowel disease (61 — UC, 25 — CD). All patients were treated with prednisolone at an initial daily dose from 30 to 60 mg with a subsequent tapering of dose. The clinical response to treatment was evaluated at the time of complete withdrawal of prednisolone using the generally accepted criteria. Two efficiency functions were constructed, compared and analyzed: the first — at the initial dosage of prednisolone in mg and the second calculating the dose in mg/kg of patient weight. The patients' body weight ranged from 41 to 98 kg. The “dose-effect” relationship for prednisolone was constructed with statistical transformation of the baseline clinical data and a quantitative expression of the actual doses and alternative responses into a graph of the effectiveness function. The mean value at each point was estimated based on the regression kernel scoring method.Results. Two graphs of the “dose-effect” of prednisolone in mg and mg/kg of patient weight were constructed. The optimal clinically effective dose (OCED) when calculated in mg/kg of weight was 0.70 ± 0.01 (0.68 + 0.72) mg/kg with the corresponding effect 79.25 ± 6.26 (66.62 91.88) %. When two graphs in mg and mg / kg of weight were superimposed, it is shown that when an initial dose of 40 mg is prescribed without taking into account the patient's weight, the effect of therapy will be 25 % lower. Prescribing a dose of 60 mg per day without weight will be optimal for patients with a body weight of 85-90 kg. With a lower body weight, the clinical effect will not decrease, but the likelihood of recognized side effects of prednisolone should be expected in proportion to the decrease in body weight.Conclusion. The clinical efficacy of two methods of prednisolone dosing (mg and mg/kg) for patients with IBD during the first induction course was compared.Using a new technology for constructing and evaluating the effectiveness function (dose-effect relationship) allowed us to prove a reliable relationship between the body weight of patients with the clinical effect of prednisolone in patients with UC and CD. Based on the analysis of the dose-effect relationship, the optimal clinically effective dose of prednisolone for patients with UC and CD during the first induction course was established, equal to 0.70 mg/kg, which can be recommended for use in clinical practice for calculating individual doses

Application of IT in the formation of sustainable reporting of business entities

The article deals with information technologies applied in the formation of sustainable reporting of business entites and provides a review of current information solutions and their development trends. Authors analyze the current situation in the field of non-financial reporting in the Russian Federation. To improve the competitiveness of companies and industries, strengthen the business reputation of organizations, authors proposed to develop a digital platform that is cabaple to create, publish, store of non-financial reports, go through the verification process.peer-reviewe

Methodological substantiation of the choice for optimal modes of equipment operation during the stage-wise concentrate removal in iron ores beneficiation

The urgent task of improving the quality of iron ore concentrates was studied. We propose to use the stage-wise removal of the concentrate by combining fine screening, regrinding, and magnetic-gravity separation. Exemplified by magnetite ore from the Stoilensky GOK, a scientific and methodological approach to the search for optimal separation parameters and modes was substantiated. It includes several stages: studying the particle size distribution and release of useful components in the feed product to select classification parameters; a series of experiments on grinding oversize products to diverse sizes; beneficiation of the obtained products by MG separation. To select the optimal parameters of ore preparation, an analysis of the beneficiation efficiency was used, which is calculated according to the Hancock – Luyken criterion. The results of the research are experimental dependences that connect the process parameters of beneficiation with those of fine vibratory screening. For the studied ferruginous quartzite ore processed at the Stoilensky GOK, the obtained dependences can be described by a second-order polynomial with a high accuracy of approximation. The best performance is achieved with a particle size of 0.1 mm: Fetot content in the concentrate is 69.7 %, recovery is 85 %, classification efficiency is 80.4 %. The top size of the product in this case is 0.076 mm, which corresponds to 70-73 % grinding size of –0.045 class

Morphology and Genetics of the Ciscoes (Actinopterygii: Salmoniformes: Salmonidae: Coregoninae: Coregonus) from the Solovetsky Archipelago (White Sea) as a Key to Determination of the Taxonomic Position of Ciscoes in Northeastern Europe

Background: The characteristic feature of the genus <i>Coregonus</i> is the multitude of nominal species of obscure identity. The northeastern Europe is inhabited by, inter alia—the vendace, <i>Coregonus albula</i> (Linnaeus, 1758)—considered the European cisco—and the least cisco, <i>C. sardinella</i> Valenciennes, 1848—often referred to as the Siberian species. There is a large area in where the ranges of both species overlap. Using morphological- as well as genetic tools we attempted to test the working hypothesis that the <i>Coregonus</i> fish (ciscoes) inhabiting the above-mentioned transitional zone represent a single species. Materials and methods: Within 1995–2009 we collected 344 ciscoes from five lakes in Bolshoy Solovetsky Island and determined diagnostic morphological traits for the two species. For some samples, the polymorphism of the creatine kinase isoloci (<i>CK-A1,2</i>*) and the fragment of mitochondrial DNA (mtDNA) encoding the subunit 1 of NADH-dehydrogenize complex (<i>ND-1</i> fragment) was also studied. Results: According to one of the main taxonomical characteristics—the number of vertebrae—the cisco of Solovetsky Island occupies an intermediate position between <i>C. albula</i> and <i>C. sardinella</i>. The molecular markers,however, did not reveal any differences between the ciscoes of Bolshoy Solovetsky Island and the vendace found elsewhere. All specimens had the type allele of creatine kinase <i>(CK-A*100)</i> which was considered to be typical for C. albula at other locations as well as the haplotype E of mtDNA widespread in vendace populations. Conclusion: The cisco from Solovetsky Island is more similar to typical vendace. Differences in some morphological traits between Solovetsky Island populations and the vendace from elsewhere are likely to reflect adaptation to environmental conditions. Thus it appears that morphological criteria do not allow reliable differentiation between two forms of ciscoes as well as between least cisco and vendace because they are influenced by environmental conditions. We believe that the presence of populations with intermediate features is a strong argument for combining <i>C. albula</i> and <i>C. sardinella</i> into a single species (<i>C. albula</i>)

Exclusive pp→nnπ+π+pp \to nn \pi^{+}\pi^{+} reaction at LHC and RHIC

We evaluate differential distributions for the four-body $p p \to n n \pi^+ \pi^+$ reaction. The amplitude for the process is calculated in the Regge approach including many diagrams. We make predictions for possible future experiments at RHIC and LHC energies. Very large cross sections are found which is partially due to interference of a few mechanisms. Presence of several interfering mechanisms precludes extraction of the elastic $\pi^+ \pi^+$ scattering cross section. Absorption effects are estimated. Differential distributions in pseudorapidity, rapidity, invariant two-pion mass, transverse-momentum and energy distributions of neutrons are presented for proton-proton collisions at $\sqrt{s}$ = 500 GeV (RHIC) and $\sqrt{s}$ = 0.9, 2.36 and 7 TeV (LHC). Cross sections with experimental cuts are presented.Comment: 22 pages, 18 figures, calculations have been corrected, new processes added, discussion expanded in print in Phys. Rev.

Determination of the parameters characterizing the superexchange interaction in complex ferrite-spinels

A calculation procedure is proposed here for determining the values of exchange parameters, applicable to spinels which contain three kinds of ions in tetrahedral positions and which have an arbitrary distribution of cations. The values of exchange integrals obtained here for ferrites of the manganese-zinc system provide a useful basis for a quantitative interpretation of the spread of Curie-temperature readings in experiments which involve ferrites with the same composition. © 1976 Plenum Publishing Corporation

High-pressure phase relations of Bi2_{2}Sr2_{2}CaCu2_{2}O8+δ_{8+\delta} single crystals

We have investigated the pressure dependence of the superconducting transition temperature $T_{c}$ up to 18 GPa of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ single crystals ranging from the highly underdoped through the nearly optimally doped to the highly overdoped level. For all three samples studied, $T_{c}$ is found to increase initially and then saturate at a critical pressure $P_{c}$ but decrease modestly with further compression. Oxygen doping tends to reduce the increase in $T_{c}$ and $P_{c}$. A new high-pressure phase diagram between the saturated $T_{c}$ and $P_{c}$ is then obtained. Theoretical interpretation is given by using the competition between the hole carrier density and pairing interaction strength based on the high-pressure transport data of the resistivity and Hall coefficient in this system.Comment: 8 pages, 7 figures, to appear in Physical Review