Neutron resonances in planar waveguides

Results of experimental investigations of a neutron resonances width in planar waveguides using the time-of-flight reflectometer REMUR of the IBR-2 pulsed reactor are reported and comparison with theoretical calculations is presented. The intensity of the neutron microbeam emitted from the waveguide edge was registered as a function of the neutron wavelength and the incident beam angular divergence. The possible applications of this method for the investigations of layered nanostructures are discussed

Wannier functions and exchange integrals: The example of LiCu2_{2}O2_{2}

Starting from a single band Hubbard model in the Wannier function basis, we revisit the problem of the ligand contribution to exchange and derive explicit formulae for the exchange integrals in metal oxide compounds in terms of atomic parameters that can be calculated with constrained LDA and LDA+U. The analysis is applied to the investigation of the isotropic exchange interactions of LiCu$_{2}$O$_{2}$, a compound where the Cu-O-Cu angle of the dominant exchange path is close to 90$^{\circ}$. Our results show that the magnetic moments are localized in Wannier orbitals which have strong contribution from oxygen atomic orbitals, leading to exchange integrals that considerably differ from the estimates based on kinetic exchange only. Using LSDA+U approach, we also perform a direct {\it ab-initio} determination of the exchange integrals LiCu$_{2}$O$_{2}$. The results agree well with those obtained from the Wannier function approach, a clear indication that this modelization captures the essential physics of exchange. A comparison with experimental results is also included, with the conclusion that a very precise determination of the Wannier function is crucial to reach quantitative estimates.Comment: 8 pages, 8 figure

First principle computation of stripes in cuprates

We present a first principle computation of vertical stripes in $La_{15/8}Sr_{1/8}CuO_4$ within the LDA+U method. We find that Cu centered stripes are unstable toward O centered stripes. The metallic core of the stripe is quite wide and shows reduced magnetic moments with suppressed antiferromagnetic (AF) interactions. The system can be pictured as alternating metallic and AF two-leg ladders the latter with strong AF interaction and a large spin gap. The Fermi surface shows warping due to interstripe hybridization. The periodicity and amplitude of the warping is in good agreement with angle resolved photoemission experiment. We discuss the connection with low-energy theories of the cuprates.Comment: 5 pages,4 figure

Equilibrium properties of the mixed state in superconducting niobium in a transverse magnetic field: Experiment and theoretical model

Equilibrium magnetic properties of the mixed state in type-II superconductors were measured with high purity bulk and film niobium samples in parallel and perpendicular magnetic fields using dc magnetometry and scanning Hall-probe microscopy. Equilibrium magnetization data for the perpendicular geometry were obtained for the first time. It was found that none of the existing theories is consistent with these new data. To address this problem, a theoretical model is developed and experimentally validated. The new model describes the mixed state in an averaged limit, i.e. %without detailing the samples' magnetic structure and therefore ignoring interactions between vortices. It is quantitatively consistent with the data obtained in a perpendicular field and provides new insights on properties of vortices. % and the entire mixed state. At low values of the Ginzburg-Landau parameter, the model converts to that of Peierls and London for the intermediate state in type-I superconductors. It is shown that description of the vortex matter in superconductors in terms of a 2D gas is more appropriate than the frequently used crystal- and glass-like scenarios.Comment: 8 pages, 9 figure

Condensation of Silica Nanoparticles on a Phospholipid Membrane

The structure of the transient layer at the interface between air and the aqueous solution of silica nanoparticles with the size distribution of particles that has been determined from small-angle scattering has been studied by the X-ray reflectometry method. The reconstructed depth profile of the polarizability of the substance indicates the presence of a structure consisting of several layers of nanoparticles with the thickness that is more than twice as large as the thickness of the previously described structure. The adsorption of 1,2-distearoyl-sn-glycero-3-phosphocholine molecules at the hydrosol/air interface is accompanied by the condensation of anion silica nanoparticles at the interface. This phenomenon can be qualitatively explained by the formation of the positive surface potential due to the penetration and accumulation of Na+ cations in the phospholipid membrane.Comment: 7 pages, 5 figure

Measurement of the energy resolution and calibration of hybrid pixel detectors with GaAs:Cr sensor and Timepix readout chip

This paper describes an iterative method of per-pixel energy calibration of hybrid pixel detectors with GaAs:Cr sensor and Timepix readout chip. A convolution of precisely measured spectra of characteristic X-rays of different metals with the resolution and the efficiency of the pixel detector is used for the calibration. The energy resolution of the detector is also measured during the calibration. The use of per-pixel calibration allows to achieve a good energy resolution of the Timepix detector with GaAs:Cr sensor: 8% and 13% at 60 keV and 20 keV, respectively

EFFECT OF IMMUNOTHERAPY ACTIVATED T-LYMPHOCYTES ON CELLULAR IMMUNITY IN DIFFERENT FORMS OF ATOPIC DERMATITIS

The article describes the results of therapy with autologous activated. T-lymphocytes in patients with atopic dermatitis. Has been shown high clinical efficacy and safety of this therapy in the treatment of patients with both allergic and nonallergic form of the disease. In the allergic form observed more rapid positive changes, but in the opposite form of the efficiency was higher. Influence on cellular immunity in different forms differed. If the allergic form there was an increase of CD8+ T-cells in the nonallergic form — increased CD8+CD25+ T-cells and changes in delayed-type hypersensitivity

Branching ratios of the decays of psi(3770) and Upsilon(10580) into light hadrons

Taking into account the new data on the full width of D^{\ast\pm}(2010) and the mass difference of the charged and neutral beauty mesons B^\pm, B^0,\bar B^0, the branching ratios of the decays psi(3770), Upsilon(10580) to pi^+pi^-, K bar K, rho(omega)pi, rho(omega)eta, rho(omega)eta^prime, K^ast bar K+ c.c, rho^+ rho^-, and K^ast bar K^ast are re-evaluated in the model in which the Okubo-Zweig-Iizuka rule is violated due to the real intermediate state D\bar D in case of psi(3770) and B\bar B in case of Upsilon(10580). The inclusive annihilation of psi(3770) and Upsilon(10580) into light hadrons is discussed.Comment: 10 page