Pulsed laser deposition of thin YBCO films on faceted YSZ single crystal fibers

Flexible rods of single crystals of 9% Y2O 3-stabilized ZrO2 (YSZ) were used as substrates for deposition of high-critical temperature superconducting (HTS) thin films. YSZ fibers were prepared by mini-pedestal method with laser heating and had average diameter of 300 micrometers and 30 mm length. X-ray diffraction analysis demonstrated high crystalline quality of obtained fibers and also indicated the presence of 15° deviation of the fiber axis from the [001] YSZ direction. Thin YBa2Cu3O7-x films were grown by pulsed laser deposition on YSZ rods using CeO2 buffer layer. Films have shown high critical temperature of 90 K with sharp superconducting transition. Critical current density was estimated to about 3×104 A/cm 2 at 80 K. Temperature dependence of critical current density suggests granular structure of films with grain size about several microns. Our results demonstrate feasibility of flexible YSZ fibers coated by HTS thin films for practical use

Numerical approximation of the Euler-Poisson-Boltzmann model in the quasineutral limit

This paper analyzes various schemes for the Euler-Poisson-Boltzmann (EPB) model of plasma physics. This model consists of the pressureless gas dynamics equations coupled with the Poisson equation and where the Boltzmann relation relates the potential to the electron density. If the quasi-neutral assumption is made, the Poisson equation is replaced by the constraint of zero local charge and the model reduces to the Isothermal Compressible Euler (ICE) model. We compare a numerical strategy based on the EPB model to a strategy using a reformulation (called REPB formulation). The REPB scheme captures the quasi-neutral limit more accurately

Physical research of microgravity influence on physical phenomenon in cryogenic liquids and general-purpose onboard cryogenic facility for realization of this researchaboard International Space Station

The united research plan named "Boiling" is created on the basis of several cryogenic research projects developed by experts in Russia and Ukraine for International Space Station. The "Boiling" plan includes 8 first experiments aimed at investigating the influence of microgravity on boiling processes, heat transfer and hydrodynamics in liquid helium being either under normal or superfluid conditions. The experiments are supposed to be carried out with individual cells collected inside a single cryogenic onboard experimental facility. The international research program experiments are characterized by the following features: utilization of several artificially simulated microgravity levels, owing to rotation of the experimental helium cryostat; visualization of the processes that occur in liquid helium; research of boiling and hydrodynamics both in a large volume of stationary liquid, and in a liquid flow running through a channel. Upon completion of the "Boiling" research plan, the cryogenic onboard facility created for International Space Station would be able to find its application in further scientific and experimental researches with helium

The Physics of Cluster Mergers

Clusters of galaxies generally form by the gravitational merger of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. Some of the basic physical properties of mergers will be discussed, with an emphasis on simple analytic arguments rather than numerical simulations. Semi-analytic estimates of merger rates are reviewed, and a simple treatment of the kinematics of binary mergers is given. Mergers drive shocks into the intracluster medium, and these shocks heat the gas and should also accelerate nonthermal relativistic particles. X-ray observations of shocks can be used to determine the geometry and kinematics of the merger. Many clusters contain cooling flow cores; the hydrodynamical interactions of these cores with the hotter, less dense gas during mergers are discussed. As a result of particle acceleration in shocks, clusters of galaxies should contain very large populations of relativistic electrons and ions. Electrons with Lorentz factors gamma~300 (energies E = gamma m_e c^2 ~ 150 MeV) are expected to be particularly common. Observations and models for the radio, extreme ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles accelerated in these mergers are described.Comment: 38 pages with 9 embedded Postscript figures. To appear in Merging Processes in Clusters of Galaxies, edited by L. Feretti, I. M. Gioia, and G. Giovannini (Dordrecht: Kluwer), in press (2001

Features of Designing the Criterion-Based Rehabilitation Program for Patients after Arthroscopic Reconstruction of the Anterior Cruciate Ligament

The article presents an innovative criterion-based rehabilitation program for patients, who underwent arthroscopic reconstruction of the anterior cruciate ligament. The features of the program are described, methodological foundations to perform permissible exercises are presented for each periods of the program, which correspond to a specific motor mode. The degree of preparedness of the patient is determined by the criterion of performance of the test exercises that will permit him to the loads of a new, higher level of trainings. The effectiveness of the developed program is confirmed clinically