12,947 research outputs found

    SIMDET - Version 4 A Parametric Monte Carlo for a TESLA Detector

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    A new release of the parametric detector Monte Carlo program \verb+SIMDET+ (version 4.01) is now available. We describe the principles of operation and the usage of this program to simulate the response of a detector for the TESLA linear collider. The detector components are implemented according to the TESLA Technical Design Report. All detector component responses are treated in a realistic way using a parametrisation of results from the {\em ab initio} Monte Carlo program \verb+BRAHMS+. Pattern recognition is emulated using a complete cross reference between generated particles and detector response. Also, for charged particles, the covariance matrix and dE/dxdE/dx information are made available. An idealised energy flow algorithm defines the output of the program, consisting of particles generically classified as electrons, photons, muons, charged and neutral hadrons as well as unresolved clusters. The program parameters adjustable by the user are described in detail. User hooks inside the program and the output data structure are documented.Comment: 30 pages, 7 figure

    Portable linear-focused solar thermal energy collecting system

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    A solar heat collection system is provided by utilizing a line-focusing device that is effectively a cylindrically curved concentrator within a protected environment formed by a transparent inflatable casing. A target, such as a fluid or gas carrying conduit is positioned within or near the casing containing the concentrator, at the line focus of the concentrator. The casing can be inflated at the site of use by a low pressure air supply to form a unitary light weight structure. The collector, including casing, concentrator and target, is readily transportable and can be used either at ground level or on rooftops. The inflatable concentrator can be replaced with a rigid metal or other concentrator while maintaining the novel advantages of the whole solar heat collection system

    Three-dimensional tracking solar energy concentrator and method for making same

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    A three dimensional tracking solar energy concentrator, consisting of a stretched aluminized polymeric membrane supported by a hoop, was presented. The system is sturdy enough to withstand expected windage forces and precipitation. It can provide the high temperature output needed by central station power plants for power production in the multi-megawatt range

    Influence of electron-ion collisions on Coulomb crystallization of ultracold neutral plasmas

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    While ion heating by elastic electron-ion collisions may be neglected for a description of the evolution of freely expanding ultracold neutral plasmas, the situation is different in scenarios where the ions are laser-cooled during the system evolution. We show that electron-ion collisions in laser-cooled plasmas influence the ionic temperature, decreasing the degree of correlation obtainable in such systems. However, taking into account the collisions increases the ion temperature much less than what would be estimated based on static plasma clouds neglecting the plasma expansion. The latter leads to both adiabatic cooling of the ions as well as, more importantly, a rapid decrease of the collisional heating rate

    Relaxation to non-equilibrium in expanding ultracold neutral plasmas

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    We investigate the strongly correlated ion dynamics and the degree of coupling achievable in the evolution of freely expanding ultracold neutral plasmas. We demonstrate that the ionic Coulomb coupling parameter Γi\Gamma_{\rm i} increases considerably in later stages of the expansion, reaching the strongly coupled regime despite the well-known initial drop of Γi\Gamma_{\rm i} to order unity due to disorder-induced heating. Furthermore, we formulate a suitable measure of correlation and show th at Γi\Gamma_{\rm i} calculated from the ionic temperature and density reflects the degree of order in the system if it is sufficiently close to a quasisteady state. At later times, however, the expansion of the plasma cloud becomes faster than the relaxation of correlations, and the system does not reach thermodynamic equilibrium anymore

    Choledocholithiasis – Sphincterotomy and Stone Removal With an Extraction Balloon

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    AbstractAt choledocholithiasis, enlarging the papillary opening with a sphincterotomy is a prerequisite for endoscopic stone extraction. After sphincterotomy, more than 90% of common bile duct (CBD) stones can be removed with a Dormia basket or balloon catheter. Here we present a case with endoscopic management of choledocholithiasis providing step-by-step explanation of the sphincterotomy and stone extraction with a balloon catheter. This article is part of an expert video encyclopedia

    Giant Laterally Spreading Tumor of the Papilla

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    AbstractAdenomas of the papilla or ampullary adenomas have the potential to undergo malignant transformation to ampullary carcinoma and should be considered for resection. It is important to distinguish between lesions that are eligible for endoscopic resection and advanced neoplasias that require surgical resection. Detailed morphologic assessment is the key tool that informs on the risk of invasive malignancy. We present the case of a 56-year-old woman with an extensive flat adenoma that encompasses the papilla and nearly the complete duodenal circumference. Detailed macroscopic evaluation and stent placement are performed. This article is part of an expert video encyclopedia

    The electrostatic instability for realistic pair distributions in blazar/EBL cascades

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    This work revisits the electrostatic instability for blazar-induced pair beams propagating through IGM with the methods of linear analysis and PIC simulations. We study the impact of the realistic distribution function of pairs resulting from interaction of high-energy gamma-rays with the extragalactic background light. We present analytical and numerical calculations of the linear growth rate of the instability for arbitrary orientation of wave vectors. Our results explicitly demonstrate that the finite angular spread of the beam dramatically affects the growth rate of the waves, leading to fastest growth for wave vectors quasi-parallel to the beam direction and a growth rate at oblique directions that is only by a factor of 2-4 smaller compared to the maximum. To study the non-linear beam relaxation, we performed PIC simulations that take into account a realistic wide-energy distribution of beam particles. The parameters of the simulated beam-plasma system provide an adequate physical picture that can be extrapolated to realistic blazar-induced pairs. In our simulations the beam looses only 1\% percent of its energy, and we analytically estimate that the beam would lose its total energy over about 100100 simulation times. Analytical scaling is then used to extrapolate to the parameters of realistic blazar-induced pair beams. We find that they can dissipate their energy slightly faster by the electrostatic instability than through inverse-Compton scattering. The uncertainties arising from, e.g., details of the primary gamma-ray spectrum are too large to make firm statements for individual blazars, and an analysis based on their specific properties is required.Comment: Accepted for publication in ApJ (2018), in prin
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