541 research outputs found

    The Electron-Phonon Interaction of Low-Dimensional and Multi-Dimensional Materials from He Atom Scattering

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    Atom scattering is becoming recognized as a sensitive probe of the electron-phonon interaction parameter λ\lambda at metal and metal-overlayer surfaces. Here, the theory is developed linking λ\lambda to the thermal attenuation of atom scattering spectra (in particular, the Debye-Waller factor), to conducting materials of different dimensions, from quasi-one dimensional systems such as W(110):H(1×\times1) and Bi(114), to quasi-two dimensional layered chalcogenides and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ\lambda obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition the number of layers contributing to the electron-phonon interaction that is measured in an atom surface collision.Comment: 23 pages, 5 figures, 1 tabl

    Mixing of fermion fields of opposite parities and baryon resonances

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    We consider a loop mixing of two fermion fields of opposite parities whereas the parity is conserved in a Lagrangian. Such kind of mixing is specific for fermions and has no analogy in boson case. Possible applications of this effect may be related with physics of baryon resonances. The obtained matrix propagator defines a pair of unitary partial amplitudes which describe the production of resonances of spin JJ and different parity 1/2±{1/2}^{\pm} or 3/2±{3/2}^{\pm}. The use of our amplitudes for joint description of πN\pi N partial waves P13P_{13} and D13D_{13} shows that the discussed effect is clearly seen in these partial waves as the specific form of interference between resonance and background. Another interesting application of this effect may be a pair of partial waves S11S_{11} and P11P_{11} where the picture is more complicated due to presence of several resonance states.Comment: 22 pages, 6 figures, more detailed comparison with \pi N PW

    Meromorphic Approximants to Complex Cauchy Transforms with Polar Singularities

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    We study AAK-type meromorphic approximants to functions FF, where FF is a sum of a rational function RR and a Cauchy transform of a complex measure λ\lambda with compact regular support included in (1,1)(-1,1), whose argument has bounded variation on the support. The approximation is understood in LpL^p-norm of the unit circle, p2p\geq2. We obtain that the counting measures of poles of the approximants converge to the Green equilibrium distribution on the support of λ\lambda relative to the unit disk, that the approximants themselves converge in capacity to FF, and that the poles of RR attract at least as many poles of the approximants as their multiplicity and not much more.Comment: 39 pages, 4 figure

    Fractional Kinetics for Relaxation and Superdiffusion in Magnetic Field

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    We propose fractional Fokker-Planck equation for the kinetic description of relaxation and superdiffusion processes in constant magnetic and random electric fields. We assume that the random electric field acting on a test charged particle is isotropic and possesses non-Gaussian Levy stable statistics. These assumptions provide us with a straightforward possibility to consider formation of anomalous stationary states and superdiffusion processes, both properties are inherent to strongly non-equilibrium plasmas of solar systems and thermonuclear devices. We solve fractional kinetic equations, study the properties of the solution, and compare analytical results with those of numerical simulation based on the solution of the Langevin equations with the noise source having Levy stable probability density. We found, in particular, that the stationary states are essentially non-Maxwellian ones and, at the diffusion stage of relaxation, the characteristic displacement of a particle grows superdiffusively with time and is inversely proportional to the magnetic field.Comment: 15 pages, LaTeX, 5 figures PostScrip

    Understanding Anomalous Transport in Intermittent Maps: From Continuous Time Random Walks to Fractals

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    We show that the generalized diffusion coefficient of a subdiffusive intermittent map is a fractal function of control parameters. A modified continuous time random walk theory yields its coarse functional form and correctly describes a dynamical phase transition from normal to anomalous diffusion marked by strong suppression of diffusion. Similarly, the probability density of moving particles is governed by a time-fractional diffusion equation on coarse scales while exhibiting a specific fine structure. Approximations beyond stochastic theory are derived from a generalized Taylor-Green-Kubo formula.Comment: 4 pages, 3 eps figure

    HEART RATE VARIABILITY IN HEMODIALYSIS PATIENTS

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    There are a small number of works that have studied heart rhythm variability parameters in patients treated with hemodialysis. Aim. To investigate the peculiarities of heart rhythm variability parameters in patients treated with hemodialysis. Methods. The observational controlled study included 55 patients treated with hemodialysis, aged 24 to 75 years, including 29 men and 26 women. The control group consisted of 20 healthy individuals of comparable age and sex. Heart rhythm variability parameters were investigated in all patients. Results. In the study of heart rhythm variability in patients treated with hemodialysis comparatively with the control group time parameters and most of frequency indexes were decreased. Conclusions. Our study found the diminishment of the total power of neurohumoral regulation in patients treated hemodialysis, as evidenced by the low values SDNN, rNN50, CV

    RATING EVALUATION OFSPECIALIZED MEDICAL CARE BYTHEPATIENTSNEPHROLOGIC PROFILE OFTHE UKRAINEPROVINSE

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    The aim of the work was to conduct a comparative analysis of indicators of the performance of nephrological services in the regions of Ukraine by using the method of complex statistical coefficients. Materials and methods. Evaluation of the performance of the system of provision of nephrological services in the regions of Ukraine was made by studying the indicators that characterize the structure, use of health care resources, quality and efficiency of its provision submitted to National Register ofpatients with chronic kidney disease and patients with acute kidney injury (2015). Results. By using rating evaluation methodology, it was identified place of relevant region by each indicator, by each area and by all areas of provision of nephrological services in the region as a whole. Conclusions. As a result of a comprehensive study of the condition of the system of providing nephrological service in the regions, there were identified ranking places of the administrative territories
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