573 research outputs found

    Certification of Classical Confluence Results for Left-Linear Term Rewrite Systems

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    Unaffordable Justice: The High Cost of Mandatory Employment Arbitration for the Average Worker

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    Although the use of arbitration provisions in collective bargaining agreements and executive employment contracts serve a beneficial purpose for workers and employers alike, the growing use of mandatory, pre-dispute arbitration agreements in non-unionized employment settings stands as an obstacle for employees to vindicate their statutorily prescribed civil rights. In particular, by forcing workers to share in the unique costs of arbitration, employees may be deterred from bringing otherwise meritorious claims. Given the federal policy favoring arbitration, and in the absence of legislation banning mandatory employment arbitration agreements, it is essential for arbitration service providers and drafters of arbitration clauses to provide for employer paid arbitration expenses, all remedies that would be available to the employee in court, and the selection of a neutral arbitrator to ensure fairness for the average worker

    Populating the Peephole Optimizer of a Smart Contract Compiler

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    Developing compiler optimizations, especially for new, rapidly evolving smart contract languages, can be onerous and error-prone, but is especially important for smart contracts, where deployment and execution directly translate to monetary cost and which cannot change once deployed. One common optimization technique is the use of peephole optimizations, replacement rules that are applied using pattern-matching. These rules are normally constructed using human expertise, which is both time-consuming and far from systematic in exploring opportunities for optimization. In this work we propose a pipeline to automatically populate the peephole optimizer of a smart contract compiler. We apply superoptimization to an existing code base to obtain sequences of instructions, which can be replaced by cheaper, observationally equivalent instructions. We then generate peephole optimization rules by extracting the underlying patterns of these optimizations. We provide a case study of our approach and a prototype implementation for bytecode of the Ethereum Virtual Machine, the tool ppltr, which combines the superoptimizer ebso and the rule generator sorg. Then we evaluate our approach by generating and applying nearly 1k peephole optimization rules extracted from 2k optimizations obtained from deployed bytecode

    Attosecond two-photon interferometry for doubly excited states of helium

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    We show that the correlation dynamics in coherently excited doubly excited resonances of helium can be followed in real time by two-photon interferometry. This approach promises to map the evolution of the two-electron wave packet onto experimentally easily accessible non-coincident single electron spectra. We analyze the interferometric signal in terms of a semi-analytical model which is validated by a numerical solution of the time-dependent two-electron Schr\"odinger equation in its full dimensionality.Comment: 5 pages, 4 figure

    Incidence of new brain lesions after carotid stenting with and without cerebral protection

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    CSI: New Evidence - A Progress Report

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    Probing Electron Correlation via Attosecond XUV Pulses in the Two-Photon Double Ionization of Helium

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    Recent experimental developments of high-intensity, short-pulse XUV light sources are enhancing our ability to study electron-electron correlations. We perform time-dependent calculations to investigate the so-called "sequential" regime (photon energy above 54.4 eV) in the two-photon double ionization of helium. We show that attosecond pulses allow to induce and probe angular and energy correlations of the emitted electrons. The final momentum distribution reveals regions dominated by the Wannier ridge break-up scenario and by post-collision interaction.Comment: 4 pages, 5 figure

    Universal features in sequential and nonsequential two-photon double ionization of helium

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    We analyze two-photon double ionization of helium in both the nonsequential and sequential regime. We show that the energy spacing between the two emitted electrons provides the key parameter that controls both the energy and the angular distribution and reveals the universal features present in both the nonsequential and sequential regime. This universality, i.e., independence of photon energy, is a manifestation of the continuity across the threshold for sequential double ionization. For all photon energies, the energy distribution can be described by a universal shape function that contains only the spectral and temporal information entering second-order time-dependent perturbation theory. Angular correlations and distributions are found to be more sensitive to the photon energy. In particular, shake-up interferences have a large effect on the angular distribution. Energy spectra, angular distributions parameterized by the anisotropy parameters, and total cross sections presented in this paper are obtained by fully correlated time-dependent ab initio calculations.Comment: 12 pages, 8 figure
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