54,800 research outputs found

    The empirical process on Gaussian spherical harmonics

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    We establish weak convergence of the empirical process on the spherical harmonics of a Gaussian random field in the presence of an unknown angular power spectrum. This result suggests various Gaussianity tests with an asymptotic justification. The issue of testing for Gaussianity on isotropic spherical random fields has recently received strong empirical attention in the cosmological literature, in connection with the statistical analysis of cosmic microwave background radiation

    Turbulent heat transfer in spacer-filled channels: Experimental and computational study and selection of turbulence models

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    Heat transfer in spacer-filled channels of the kind used in Membrane Distillation was studied in the Reynolds number range 100–2000, encompassing both steady laminar and early-turbulent flow conditions. Experimental data, including distributions of the local heat transfer coefficient h, were obtained by Liquid Crystal Thermography and Digital Image Processing. Alternative turbulence models, both of first order (k-ε, RNG k-ε, k-ω, BSL k-ω, SST k-ω) and of second order (LRR RS, SSG RS, ω RS, BSL RS), were tested for their ability to predict measured distributions and mean values of h. The best agreement with the experimental results was provided by first-order ω-based models able to resolve the viscous/conductive sublayer, while all other models, and particularly ε-based models using wall functions, yielded disappointing predictions

    Evaporation Channel as a Tool to Study Fission Dynamics

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    The dynamics of the fission process is expected to affect the evaporation residue cross section because of the fission hindrance due to the nuclear viscosity. Systems of intermediate fissility constitute a suitable environment for testing such hypothesis, since they are characterized by evaporation residue cross sections comparable or larger than the fission ones. Observables related to emitted charged particle, due to their relatively high emission probability, can be used to put stringent constraints on models describing the excited nucleus decay and to recognize the effects of fission dynamics. In this work model simulations are compared with the experimental data collected via the ^{32}S + ^{100}Mo reaction at E_{lab}= 200 MeV. By comparing an extended set of evaporation channel observables the limits of the statistical model and the large improvement coming by using a dynamical model are evidenced. The importance of using a large angular covering apparatus to extract the observable is stressed. The opportunity to measure more sensitive observables by a new detection device in operation at LNL are also discussed.Comment: v1: 7 pages, 6 figure

    Pain-motor integration in the primary motor cortex in Parkinson's disease

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    In Parkinson's disease (PD), the influence of chronic pain on motor features has never been investigated. We have recently designed a technique that combines nociceptive system activation by laser stimuli and primary motor cortex (M1) activation through transcranial magnetic stimulation (TMS), in a laser-paired associative stimulation design (Laser-PAS). In controls, Laser-PAS induces long-term changes in motor evoked potentials reflecting M1 long-term potentiation-like plasticity, arising from pain-motor integration

    Optimization of net power density in Reverse Electrodialysis

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    Reverse Electrodialysis (RED) extracts electrical energy from the salinity difference between two solutions using selective ion exchange membranes. In RED, conditions yielding a large net power density (NPD) are generally desired, due to the still large cost of the membranes. NPD depends on a large number of physical and geometric parameters. Some of these, for example the inlet concentrations of concentrate and diluate, can be regarded as “scenario” variables, imposed by external constraints (e.g., availability) or chosen by different criteria than NPD maximization. Others, namely the thicknesses HCONC, HDIL and the velocities UCONC, UDIL in the concentrate and diluate channels, can be regarded as free design parameters and can be chosen so as to maximize NPD. In the present study, a simplified model of a RED stack was coupled with an optimization algorithm in order to determine the conditions of maximum NPD in the space of the variables HCONC, HDIL,UCONC, UDIL for different sets of “scenario” variables. The study shows that an optimal choice of the free design parameters for any given scenario, as opposed to the adoption of standard fixed values for the same parameters, may provide significant improvements in NPD

    Field distributions in heavy mesons and baryons

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    Field distributions generated by static quark-antiquark and QQQ sources are calculated analytically in the framework of the Field Correlator Method (FCM) using Gaussian (bilocal) correlator. In both cases the string consists mostly of longitudinal color electric field, while transverse electric field contributes locally less then 3%, in agreement with earlier lattice studies. In the QQQ case the profile of the Y shape was calculated for the first time and found to have a complicated structure with a deep well at the string junction position. Possible consequences of this form for the baryon structure are discussed.Comment: LaTeX2e, 11 pages, 4 Postscript figures, 2 GIF images, version to appear in Physics Letters

    Glaucoma and cigarette smoking: a review of narrative reviews

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    Background: Glaucoma is an optic neuropathy associated with visual field changes for which high intra-ocular pressure is a major risk factor. Emerging research indicates that modifiable factors, among which the cigarette smoke, besides IOP may be associated with the presence of glaucoma. Objective: The objective of the study was to perform a review of narrative reviews to examine on the relationship between cigarette smoking and glaucoma. Methods: The results of all narrative reviews in the scientific literature about glaucoma and tobacco smoking were analyzed. A quality assessment was performed according to an easy and convenient tool for the quality assessment of narrative reviews for systematic reviews (International Narrative Systematic assessment) the INSA tool. Literature searches were performed using PubMed. Results: 20 studies about relation between glaucoma and smoke were collected, no restriction language was applied. 15 of these studies have been excluded. We selected among them 5 reviews. With the INSA tool we measured the quality of the 5 selected narrative reviews. Studies that had a highest score with the INSA tool were two: A. Coleman et al. “Risk Factors for Glaucoma Needing More Attention” and R. Salowe et al. “Primary Open-Angle Glaucoma in Individuals of African Descent: A Review of Risk Factors”. Conclusion: The narrative reviews analyzed underline that there is no definitive association between cigarette smoking

    Recovery of Interdependent Networks

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    Recent network research has focused on the cascading failures in a system of interdependent networks and the necessary preconditions for system collapse. An important question that has not been addressed is how to repair a failing system before it suffers total breakdown. Here we introduce a recovery strategy of nodes and develop an analytic and numerical framework for studying the concurrent failure and recovery of a system of interdependent networks based on an efficient and practically reasonable strategy. Our strategy consists of repairing a fraction of failed nodes, with probability of recovery γ\gamma, that are neighbors of the largest connected component of each constituent network. We find that, for a given initial failure of a fraction 1p1-p of nodes, there is a critical probability of recovery above which the cascade is halted and the system fully restores to its initial state and below which the system abruptly collapses. As a consequence we find in the plane γp\gamma-p of the phase diagram three distinct phases. A phase in which the system never collapses without being restored, another phase in which the recovery strategy avoids the breakdown, and a phase in which even the repairing process cannot avoid the system collapse

    A spectroscopic analysis of a sample of narrow-line Seyfert 1 galaxies selected from the Sloan Digital Sky Survey

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    We revisited the spectroscopic characteristics of narrow-line Seyfert 1 galaxies (NLS1s) by analysing a homogeneous sample of 296 NLS1s at redshift between 0.028 and 0.345, extracted from the Sloan Digital Sky Survey (SDSS-DR7) public archive. We confirm that NLS1s are mostly characterized by Balmer lines with Lorentzian profiles, lower black hole masses and higher Eddington ratios than classic broad-line Seyfert 1 (BLS1s), but they also appear to be active galactic nuclei (AGNs) contiguous with BLS1s and sharing with them common properties. Strong Fe II emission does not seem to be a distinctive property of NLS1s, as low values of Fe II/Hβ\beta are equally observed in these AGNs. Our data indicate that Fe II and Ca II kinematics are consistent with the one of Hβ\beta. On the contrary, O I λ\lambda8446 seems to be systematically narrower and it is likely emitted by gas of the broad-line region more distant from the ionizing source and showing different physical properties. Finally, almost all NLS1s of our sample show radial motions of the narrow-line region highly-ionised gas. The mechanism responsible for this effect is not yet clear, but there are hints that very fast outflows require high continuum luminosities (> 104410^{44} erg/s) or high Eddington ratios (log(Lbol_{\rm bol}/LEdd_{\rm Edd}) > -0.1).Comment: 27 pages, 31 figures, 4 tables, accepted for publication in MNRA
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