238 research outputs found

    Polarizability of a dielectric hemisphere

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    This article presents a method for solving the polarizability of a dielectric hemispherical object as a function of its relative electric permittivity. The polarizability of a hemisphere depends on the direction of the exciting electric field. Therefore, the polarizability can be written as a dyadic consisting of two components, the axial and the transversal polarizabilities, which can be solved separately. The solution is based on an analytical approach where the electrostatic potential function is written as a series expansion. However, no closed-form solution for the coefficients of the series is found, so they must be solved from a matrix equation. This method provides very high accuracy. However, it requires construction of large matrices which consumes both time and memory. Therefore, approximative expressions for the polarizabilities with absolute error less than 10−5 are also presented.Peer reviewe

    Status of COLDDIAG: A Cold Vacuum Chamber for Diagnostics

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    One of the still open issues for the development of superconducting insertion devices is the understanding of the beam heat load. With the aim of measuring the beam heat load to a cold bore and the hope to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. The following diagnostics will be implemented: i) retarding field analyzers to measure the electron energy and flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. This will allow the installation of the cryostat in different synchrotron light sources. COLDDIAG will be built to fit in a short straight section at ANKA. A first installation at the synchrotron light source Diamond is foreseen in June 2011. Here we describe the technical design report of this device and the planned measurements with beam.Comment: Presented at First International Particle Accelerator Conference, IPAC'10, Kyoto, Japan, from 23 to 28 May 201

    Validity of the Polar V800 heart rate monitor to measure RR intervals at rest

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    Purpose To assess the validity of RR intervals and short-term heart rate variability (HRV) data obtained from the Polar V800 heart rate monitor, in comparison to an electrocardiograph (ECG). Method Twenty participants completed an active orthostatic test using the V800 and ECG. An improved method for the identification and correction of RR intervals was employed prior to HRV analysis. Agreement of the data was assessed using intra-class correlation coefficients (ICC), Bland–Altman limits of agreement (LoA), and effect size (ES). Results A small number of errors were detected between ECG and Polar RR signal, with a combined error rate of 0.086 %. The RR intervals from ECG to V800 were significantly different, but with small ES for both supine corrected and standing corrected data (ES 0.999 for both supine and standing corrected intervals. When analysed with the same HRV software no significant differences were observed in any HRV parameters, for either supine or standing; the data displayed small bias and tight LoA, strong ICC (>0.99) and small ES (≤0.029). Conclusions The V800 improves over previous Polar models, with narrower LoA, stronger ICC and smaller ES for both the RR intervals and HRV parameters. The findings support the validity of the Polar V800 and its ability to produce RR interval recordings consistent with an ECG. In addition, HRV parameters derived from these recordings are also highly comparable

    Polarizability of conducting sphere-doublets using series of images.

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    The classical electrostatic problem of two nonintersecting conducting spheres in a uniform incident electric field is considered. Starting from the basic Kelvin’s image principle, the two spheres are replaced with equivalent series of image sources, from which the polarizability is calculated. Explicit expressions for the axial and transversal components of the polarizability dyadic are found by solving the recurrence equations. Efficient numerical evaluation of the different series is also discussed.Peer reviewe

    Improved Linear Cryptanalysis of SOSEMANUK

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    Abstract. The SOSEMANUK stream cipher is one of the finalists of the eSTREAM project. In this paper, we improve the linear cryptanalysis of SOSEMANUK presented in Asiacrypt 2008. We apply the generalized linear masking technique to SOSEMANUK and derive many linear approximations holding with the correlations of up to 2 −25.5. We show that the data complexity of the linear attack on SOSEMANUK can be reduced by a factor of 2 10 if multiple linear approximations are used. Since SOSEMANUK claims 128-bit security, our attack would not be a real threat on the security of SOSEMANUK. Keywords: Stream Ciphers, Linear Cryptanalysis, SOSEMANUK, SOBER-128.

    Update on the EFFECTS study of fluoxetine for stroke recovery: a randomised controlled trial in Sweden

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    Studies have suggested that fluoxetine might improve neurological recovery after stroke, but the results remain inconclusive. The EFFECTS (Efficacy oF Fluoxetine – a randomisEd Controlled Trial in Stroke) reached its recruitment target of 1500 patients in June 2019. The purpose of this article is to present all amendments to the protocol and describe how we formed the EFFECTS trial collaboration in Sweden. Methods In this investigator-led, multicentre, parallel-group, randomised, placebo-controlled trial, we enrolled non-depressed stroke patients aged 18 years or older between 2 and 15 days after stroke onset. The patients had a clinical diagnosis of stroke (ischaemic or intracerebral haemorrhage) with persisting focal neurological deficits. Patients were randomised to fluoxetine 20 mg or matching placebo capsules once daily for 6 months. Results Seven amendments were made and included clarification of drug interaction between fluoxetine and metoprolol and the use of metoprolol for severe heart failure as an exclusion criterion, inclusion of data from central Swedish registries and the Swedish Stroke Register, changes in informed consent from patients, and clarification of design of some sub-studies. EFFECTS recruited 1500 patients at 35 centres in Sweden between 20 October 2014 and 28 June 2019. We plan to unblind the data in January 2020 and report the primary outcome in May 2020. Conclusion EFFECTS will provide data on the safety and efficacy of 6 months of treatment with fluoxetine after stroke in a Swedish health system setting. The data from EFFECTS will also contribute to an individual patient data meta-analysis

    Linear and Partly-Pseudo-Linear Cryptanalysis of Reduced-Round SPARX Cipher

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    We propose a new cryptanalytic technique and key recovery attack for the Sparx cipher, Partly-Pseudo-Linear Cryptanalysis, a meet-in-the-middle attack combining linear and pseudo-linear approximations. We observe improvements over the linear hull attacks in the literature for Sparx 128/128 and 128/256. Additionally, we generate another attack for comparison purposes, using the Cho-Pieprzyk property for a fully-linear approximation and a corresponding key recovery attack. We observe improvements on the data complexity, bias, and number of recovered key bits, over all variants of Sparx, when compared to the use of only the Cho-Pieprzyk approximation
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