11,224 research outputs found

    A New Look at the Schouten-Nijenhuis, Fr\"olicher-Nijenhuis and Nijenhuis-Richardson Brackets for Symplectic Spaces

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    In this paper we re-express the Schouten-Nijenhuis, the Fr\"olicher-Nijenhuis and the Nijenhuis-Richardson brackets on a symplectic space using the extended Poisson brackets structure present in the path-integral formulation of classical mechanics.Comment: 27+1 pages, Latex, no figure

    Saturated Critical Heat Flux in a Multi-Microchannel Heat Sink Fed by a Split Flow System

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    An extensive experimental campaign has been carried out for the measurement of saturated critical heat flux in a multi-microchannel copper heat sink. The heat sink was formed by 29 parallel channels that were 199 ÎŒm wide and 756 ÎŒm deep. In order to increase the critical heat flux and reduce the two-phase pressure drop, a split flow system was implemented with one central inlet at the middle of the channels and two outlets at either end. The base critical heat flux was measured using three HFC Refrigerants (R134a, R236fa and R245fa) for mass fluxes ranging from 250 to 1500 kg/m2 s, inlet subcoolings from −25 to −5 K and saturation temperatures from 20 to 50 °C. The parametric effects of mass velocity, saturation temperature and inlet subcooling were investigated. The analysis showed that significantly higher CHF was obtainable with the split flow system (one inlet–two outlets) compared to the single inlet–single outlet system, providing also a much lower pressure drop. Notably several existing predictive methods matched the experimental data quite well and quantitatively predicted the benefit of higher CHF of the split flow

    Entanglement detection in hybrid optomechanical systems

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    We study a device formed by a Bose Einstein condensate (BEC) coupled to the field of a cavity with a moving end-mirror and find a working point such that the mirror-light entanglement is reproduced by the BEC-light quantum correlations. This provides an experimentally viable tool for inferring mirror-light entanglement with only a limited set of assumptions. We prove the existence of tripartite entanglement in the hybrid device, persisting up to temperatures of a few milli-Kelvin, and discuss a scheme to detect it.Comment: 6 pages, 7 figures, published versio

    Dark Energy Dominance and Cosmic Acceleration in First Order Formalism

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    The current accelerated universe could be produced by modified gravitational dynamics as it can be seen in particular in its Palatini formulation. We analyze here a specific non-linear gravity-scalar system in the first order Palatini formalism which leads to a FRW cosmology different from the purely metric one. It is shown that the emerging FRW cosmology may lead either to an effective quintessence phase (cosmic speed-up) or to an effective phantom phase. Moreover, the already known gravity assisted dark energy dominance occurs also in the first order formalism. Finally, it is shown that a dynamical theory able to resolve the cosmological constant problem exists also in this formalism, in close parallel with the standard metric formulation.Comment: 21 pages, LaTeX file, no figures. Replaced version to be published on Phys. Rev.

    First observation of Cherenkov rings with a large area CsI-TGEM-based RICH prototype

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    We have built a RICH detector prototype consisting of a liquid C6F14 radiator and six triple Thick Gaseous Electron Multipliers (TGEMs), each of them having an active area of 10x10 cm2. One triple TGEM has been placed behind the liquid radiator in order to detect the beam particles, whereas the other five have been positioned around the central one at a distance to collect the Cherenkov photons. The upstream electrode of each of the TGEM stacks has been coated with a 0.4 micron thick CsI layer. In this paper, we will present the results from a series of laboratory tests with this prototype carried out using UV light, 6 keV photons from 55Fe and electrons from 90Sr as well as recent results of tests with a beam of charged pions where for the first time Cherenkov Ring images have been successfully recorded with TGEM photodetectors. The achieved results prove the feasibility of building a large area Cherenkov detector consisting of a matrix of TGEMs.Comment: Presented at the International Conference NDIP-11, Lyon,July201

    Studio RIFRA: il rischio fratturativo in Italia

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    L'osteoporosi \ue8 un disordine scheletrico cronico-evolutivo, caratferizzato dalla perdita dell'equilibrio del metabolismo osseo con conseguente degenerazione quantitativa e qualitativa che compromette la resistenza dell'osso e predispone ad un aumentato rischio di fratture. Colpisce soprattutto il sesso femminile,conunaprevalenza del33%nelrange tra60eT0aacheaumentaconl'avanzaredell'et\ue0. Pu\uf2 rimanere clinicamente silente e successivamente manifestarsi con fratture (vertebrali 100.000 casi/anno, di polso 85.000 casi/anno e femorali 80.000 casi/anno). Le fratture da fragilit\ue0 comportano gravi conse gse\ueeze, sia a livello clinico individuale che sociale ed economico; rappresenrano pertanto una fonte di disabilit\ue0 complessa, che in quanto tale necessita di una presa in carico globale. Lo studio RIFRA nasce da un'idea del GISMO per rispondere alla necessit\ue0 primaria di quantificare il reale rischio fratturativo in Italia attraverso una specifica scheda e di valutare l'influenza delle comorbilit\ue0 e delle terapie corelate al rischio di frattura. L'obiettivo secondario analizzare \a percentuale di pazienti sottoposti a trattamento farmacologico in relazione ai valori densitometrici e alle pregresse fratture, nonch\ue9 valutare la prevalenza di fratture da fragilit\ue0 nella popol azione in studio

    The effectiveness of intra-articular injectionc of Hyalubrix combined with exercise therapy in the tratment of hip osteoarthritis

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    Purpose. Osteoarthritis (OA) is the most common joint disorder in the elderly, causing significant pain which negatively affects mobility and quality ol liie. The aim of the study was to assess the effectiveness of ultrasound \ucdmage-guided intra-articular injections of Hyalubrix@ combined with exercise therapy in the treatment of hip osteoarthritis. Methods. This was a single site, prosp\ue8ctive, open-fabel, Investigator-initiated study. Forty patients rilere enrolled and received three ultrasound image.guided injections of Hyalubrix@, 45 days apart, combined with three sessions a week of phys\uedcal therapy (proprioceptive rehabilitation of the lower limbs; gait training; balance training) up to a total of 30 sessions (10 weeks), starting from one week after the first injection. Results. The primary obiective was to achieve a lasting reduction in OA symptoms related to pain during activity. During the course of the study the pain perceived by the patient during activity dropped from a mean value of 6.94 cm to a mean value of 1.46 cm and showed a statistically significant decrease from visit 1 compared to baseline (p < 0.05) which was confirmed at all the subsequent time points. Significant improvements were also observed in the evaluation of the secondary objectives: hip disability; OA-related pain at rest; daily functioning and NSAIDs intake. Conclusions. Results from this study including 40 patients for a total of 65 treated hips demonstrate a significant improvement in OA-related pain, hip disability, and patient's daily functioning as well as a reduction in NSAIDS intake. Patients suffering from hip OA s\ue8em to benefil from the treatment wiih Hyalubrix@ injections plus exercise therapy

    Quorum of observables for universal quantum estimation

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    Any method for estimating the ensemble average of arbitrary operator (observables or not, including the density matrix) relates the quantity of interest to a complete set of observables, i.e. a quorum}. This corresponds to an expansion on an irreducible set of operators in the Liouville space. We give two general characterizations of these sets. All the known unbiased reconstruction techniques, i.e. ``quantum tomographies'', can be described in this framework. New operatorial resolutions are given that can be used to implement novel reconstruction schemes.Comment: Latex, no figure

    YF-12 cooperative airframe/propulsion control system program, volume 1

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    Several YF-12C airplane analog control systems were converted to a digital system. Included were the air data computer, autopilot, inlet control system, and autothrottle systems. This conversion was performed to allow assessment of digital technology applications to supersonic cruise aircraft. The digital system was composed of a digital computer and specialized interface unit. A large scale mathematical simulation of the airplane was used for integration testing and software checkout
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