147 research outputs found

    The effect of thermal winds on the outbursts evolution of LMXB systems

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    Theoretical models of accretion discs and observational data indicate that the X-ray emission from the inner parts of an accretion disc can irradiate its outer regions and induce a thermal wind, which carries away the mass and angular momentum from the disc. Our aim is to investigate the influence of the thermal wind on the outburst light curves of black hole X-ray binary systems. We carry out numerical simulations of a non-stationary disc accretion with wind using upgraded open code freddi. We assume that the wind launches only from the ionised part of the disc and may turn off if the latter shrinks fast enough. Our estimates of the viscosity parameter α\alpha are shifted downward compared to a scenario without a wind. Generally, correction of α\alpha depends on the spectral hardness of central X-rays and the disc outer radius, but unlikely to exceed a factor of 10 in the case of a black hole low-mass X-ray binary (BH LMXB). We fit 2002 outburst of BH LMXB 4U 1543-47 taking into account the thermal wind. The mass loss in the thermal wind is of order of the accretion rate on the central object at the peak of the outburst. New estimate of the viscosity parameter α\alpha for the accretion disc in this system is about two times lower than the previous one. Additionally, we calculate evolution of the number of hydrogen atoms towards 4U 1543-47 due to the thermal wind from the hot disc.Comment: 19 pages, 22 figures, accepted for publication in MNRA

    Updated resonance photo-decay amplitudes to 2 GeV

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    We present the results of an energy-dependent and set of single-energy partial-wave analyses of single-pion photoproduction data. These analyses extend from threshold to 2 GeV in the laboratory photon energy, and update our previous analyses to 1.8 GeV. Photo-decay amplitudes are extracted for the baryon resonances within this energy range. We consider two photoproduction sum rules and the contributions of two additional resonance candidates found in our most recent analysis of πN\pi N elastic scattering data. Comparisons are made with previous analyses.Comment: Revtex, 26 pages, 3 figures. Postscript figures available from ftp://clsaid.phys.vt.edu/pub/pr or indirectly from http://clsaid.phys.vt.edu/~CAPS

    Piezoelectric, ferroelectric, optoelectronic and photo-catalytic phenomena from defect levels in hydroxyapatite by first-principles

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    The authors thank the Russian Foundation for Basic Researches (RFBR grant 19-01-00519 A) and to the Fundação para a Ciência e a Tecnologia (FCT) through project UID/CTM/50025/2013

    Measurement of the Cross Section Asymmetry of the Reaction gp-->pi0p in the Resonance Energy Region Eg = 0.5 - 1.1 GeV

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    The cross section asymmetry Sigma has been measured for the photoproduction of pi0-mesons off protons, using polarized photons in the energy range Eg = 0.5 - 1.1 GeV. The CM angular coverage is Theta = 85 - 125 deg with energy and angle steps of 25 MeV and 5 deg, respectively. The obtained Sigma data, which cover the second and third resonance regions, are compared with existing experimental data and recent phenomenological analyses. The influence of these measurements on such analyses is also considered

    Modern aproaches to diabetic macular edema diagnosticks

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    Diabetic macular edema (DME) continues to be an important problem of modern ophthalmology and endocrinology. The risk of edema is higher in patients with type 2 diabetes. Thus, this is the main cause of irreversible vision loss in these patients. DME is one of the prognostically unfavorable and difficult to treat manifestations of diabetic retinopathy. As the main cause of vision loss in diabetic patients, diabetic macular edema is often not diagnosed immediately, which causes difficulties in the treatment of pathology. Thus, early diagnosis and timely treatment of this disease is the key to successfully counteract the uncontrolled decline in the patient’s visual functions. In this article, the team of authors highlighted the possibilities of informative instrumental research methods available in the Arsenal of modern ophthalmological services. Based on the analysis of modern literature, the main principles of these diagnostic methods were indicated, their key capabilities and limitations compared to each other were highlighted. Knowledge of these characteristics is, in our opinion, an integral and most important tool in the Arsenal of a practicing ophthalmologist who supervises patients with this pathology

    The influence of the dechanneling process on the photon emission by an ultra-relativistc positron channeling in a periodically bent crystal

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    We investigate, both analytically and numerically, the influence of the dechanneling process on the parameters of undulator radiation generated by ultra-relativistic positron channelling along a crystal plane, which is periodically bent. The bending might be due either to the propagation of a transverse acoustic wave through the crystal, or due to the static strain as it occurs in superlattices. In either case the periodically bent crystal serves as an undulator which allows to generate X-ray and gamma-radiation. We propose the scheme for accurate quantitative treatment of the radiation in presence of the dechanneling. The scheme includes (i) the analytic expression for spectral-angular distribution which contains, as a parameter, the dechanneling length, (ii) the simulation procedure of the dechanneling process of a positron in periodically bent crystals. Using these we calculate the dechanneling lengths of 5 GeV positrons channeling in Si, Ge and W crystals, and the spectral-angular and spectral distributions of the undulator over broad ranges of the photons. The calculations are performed for various parameters of the channel bending.Comment: published in J. Phys. G: Nucl. Part. Phys. 27 (2001) 95-125, http://www.iop.or

    Polarization switching and piezoresponse in PVDF/P(VDF-TrFE) ferroelectric films and multifunctional G/GO composites

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    Such composites can serve as a multifunctional molecular unit. Further models are in progress. The work is supported by RFBR grants # 15-01-04924, # 16-51-53017 and RSF grant #16-19-10112

    Integrable Ladder t-J Model with Staggered Shift of the Spectral Parameter

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    The generalization of the Yang-Baxter equations (YBE) in the presence of Z_2 grading along both chain and time directions is presented and an integrable model of t-J type with staggered disposition along a chain of shifts of the spectral parameter is constructed. The Hamiltonian of the model is computed in fermionic formulation. It involves three neighbour site interactions and therefore can be considered as a zig-zag ladder model. The Algebraic Bethe Ansatz technique is applied and the eigenstates, along with eigenvalues of the transfer matrix of the model are found. In the thermodynamic limit, the lowest energy of the model is formed by the quarter filling of the states by fermions instead of usual half filling.Comment: Latex2e with amsfonts package; 16 page

    P-wave excited baryons from pion- and photo-induced hyperon production

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    We report evidence for N(1710)P11N(1710)P_{11}, N(1875)P11N(1875)P_{11}, N(1900)P13N(1900)P_{13}, Δ(1600)P33\Delta(1600)P_{33}, Δ(1910)P31\Delta(1910)P_{31}, and Δ(1920)P33\Delta(1920)P_{33}, and find indications that N(1900)P13N(1900)P_{13} might have a companion state at 1970\,MeV. The controversial Δ(1750)P31\Delta(1750)P_{31} is not seen. The evidence is derived from a study of data on pion- and photo-induced hyperon production, but other data are included as well. Most of the resonances reported here were found in the Karlsruhe-Helsinki (KH84) and the Carnegie-Mellon (CM) analyses but were challenged recently by the Data Analysis Center at GWU. Our analysis is constrained by the energy independent πN\pi N scattering amplitudes from either KH84 or GWU. The two πN\pi N amplitudes from KH84 or GWU, respectively, lead to slightly different πN\pi N branching ratios of contributing resonances but the debated resonances are required in both series of fits.Comment: 22 pages, 28 figures. Some additional sets of data are adde
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