The influence of heat generation on the contact interaction in a “cylinder – wearing circular layer” joint

The mathematical model of contact interaction in joint as “cylinder – wearing circular layer” with take into consideration wear and heat development are proposed. Being based on analytical solution of tribocontact problem contact stresses and layer wear are explore. The results of numerical analysis are presented and influence of heat development on contact stresses and wear are investigated too

A phenomenological theory of nonphotochemical laser induced nucleation

Our analysis of the experimental data related to nonphotochemical laser induced nucleation in solutions leads to the inevitable conclusion that the phase transformation is initiated by particles that are metallic in nature. This conclusion appears paradoxical because the final products are dielectric crystals. We show that the experimental results are well accounted for by the theory of electric field induced nucleation of metallic particles that are elongated in the direction of the field. However, new physical and chemical insights are required to understand the structure of the metallic precursor particles and the kinetics of subsequent dielectric crystallization.Comment: 5 pages 4 figure

Binding energy of a Cooper pairs with non-zero center of mass momentum in d-wave superconductors

The binding energy of Cooper pairs has been calculated for the case of d-wave symmetry of the superconducting gap in layered cuprate superconductors. We assume that Cooper pairs are formed by the short range potential and then derive the binding energy in the form Δkq = Δx (q) cos kx a + Δy (q) cos ky a + Ωx (q) sin kx a + Ωy (q) sin ky a, where q is a total momentum of the pair. Numerical solutions of the self-consistent system of the integral equations for quantities Δx (q), Δy (q) and Ωx (q), Ωy (q) along different lines in qx, qy planes have been obtained. Anisotropy of the depairing total momentum (or depairing current) has been calculated. © 2007 Elsevier B.V. All rights reserved

Effect of Replacement of As by Ge and Sb on the Photo-Response under Near Infrared Femtosecond Laser Irradiation in As-based Sulfide Glasses

Bulk glasses having the compositions As42S58, As36Sb6S58, and As36Ge6S58 have been irradiated at 800 nm using a femtosecond-pulsed laser to determine the relationship between composition and photo-response. Localized variation in the glass volume (photo-expansion) has been determined through interferometric measurements of surface exposures, whereas induced refractive index change (photo-darkening) was determined from the diffraction efficiency of subsurface direct-written phase gratings. To understand the compositional dependence of the photo-response, the linear and nonlinear optical properties and structure of the unexposed glasses have been compared. The ablation threshold is shown to be controlled by variation of the nonlinear absorption, related to shifts of the absorption band gap with exchange of As by Ge or Sb. Changes in the unexposed network structure show that partial replacement of As by Ge or Sb induces an increased number of As–As bonding defects in the glass, particularly in the form of As4S4 molecular units which become polymerized into the network, impacting the photo-modification process. The Ge was found to induce an increase in the ablation threshold, and enhance both photo-darkening and photo-expansion effects, whereas Sb was shown to decrease ablation threshold and inhibit photo-darkening while enhancing photo-expansion

Optical tweezers study of red blood cell aggregation and disaggregation in plasma and protein solutions

Kinetics of optical tweezers (OT)-induced spontaneous aggregation and disaggregation of red blood cells (RBCs) were studied at the level of cell doublets to assess RBC interaction mechanics. Measurements were performed under in vitro conditions in plasma and fibrinogen and fibrinogen + albumin solutions. The RBC spontaneous aggregation kinetics was found to exhibit different behavior depending on the cell environment. In contrast, the RBC disaggregation kinetics was similar in all solutions qualitatively and quantitatively, demonstrating a significant contribution of the studied proteins to the process. The impact of the study on assessing RBC interaction mechanics and the protein contribution to the reversible RBC aggregation process is discussed

Stimulated Brillouin scattering amplification in centimeter-long directly written chalcogenide waveguides

Brillouin scattering (SBS) amplification is obtained in directly written As 2 S 3 channel waveguides. Centimeter-long waveguides were written using a Ti:sapphire femtosecond laser, operating at a central wavelength of 810 nm. The cross-section of the waveguides was of 4 μm × 1 μm. A Brillouin frequency shift of 7.5 GHz is observed, in general agreement with corresponding previous studies. The SBS gain spectrum in the short waveguides is comparatively broad, with a full width at half-maximum of 200 MHz. We attribute the broad linewidth to the spatial evolution of the electromagnetic field profile along the waveguide. Herein we report the SBS amplification of probe waves in 1 cm long waveguides that are directly written in As 2 S 3 films. The results provide an independent verification of the previous works in similar devices, fabricated using RIE Films of As 2 S 3 glass were deposited by thermal evaporation of crushed glassy material from a quartz crucible, in vacuum 5112 OPTICS LETTERS / Vol. 37, No. 24 / December 15, 2012 0146-9592/12/245112-03$15.00/

London penetration depth in the tight binding approximation: Orthorhombic distortion and oxygen isotope effects in cuprates

We present a simple derivation of an expression for the superfluid density $n_s \propto 1/\lambda^2$ in superconductors with the tight binding energy dispersion. The derived expression is discussed in detail because of its distinction from the known expressions for ordinary superconductors with parabolic energy dispersion. We apply this expression for the experimental data analysis of the isotope effect in London penetration depth parameter $\lambda$ in the BiSrCuO and YBaCuO family compounds near optimal doping, taking into account the orthorhombic distortion of crystal structure, and estimate the isotopic change of hopping parameters from the experimental data. We point out that $1/\lambda^2$ temperature behaviour is very sensitive to the ratio $2\Delta_m(T=0)/ k_B T_c$ and estimate this quantity for a number of compounds.Comment: 10 pages, 4 figure