850 research outputs found

    Low-Energy Effective Action in Non-Perturbative Electrodynamics in Curved Spacetime

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    We study the heat kernel for the Laplace type partial differential operator acting on smooth sections of a complex spin-tensor bundle over a generic nn-dimensional Riemannian manifold. Assuming that the curvature of the U(1) connection (that we call the electromagnetic field) is constant we compute the first two coefficients of the non-perturbative asymptotic expansion of the heat kernel which are of zero and the first order in Riemannian curvature and of arbitrary order in the electromagnetic field. We apply these results to the study of the effective action in non-perturbative electrodynamics in four dimensions and derive a generalization of the Schwinger's result for the creation of scalar and spinor particles in electromagnetic field induced by the gravitational field. We discover a new infrared divergence in the imaginary part of the effective action due to the gravitational corrections, which seems to be a new physical effect.Comment: LaTeX, 42 page

    Pregabalin reduces cocaine self-administration and relapse to cocaine seeking in the rat

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    Pregabalin (Lyricaâ„¢) is a structural analog of g-aminobutyric acid (GABA) and is approved by the FDA for partial epilepsy, neuropathic pain and generalized anxiety disorders. Pregabalin also reduces excitatory neurotransmitter release and post-synaptic excitability. Recently, we demonstrated that pregabalin reduced alcohol intake and prevented relapse to the alcohol seeking elicited by stress or environmental stimuli associated with alcohol availability. Here, we sought to extend these findings by examining the effect of pregabalin on cocaine self-administration (0.25 mg/infusion) and on cocaine seeking elicited by both conditioned stimuli and stress, as generated by administration of yohimbine (1.25 mg/kg). The results showed that oral administration of pregabalin (0, 10 or 30 mg/kg) reduced self-administration of cocaine over an extended period (6 hours), whereas it did not modify self-administration of food. In cocaine reinstatement studies, pregabalin (10 and 30 mg/kg) abolished the cocaine seeking elicited by both the pharmacological stressor yohimbine and the cues predictive of cocaine availability. Overall, these results demonstrate that pregabalin may have potential in the treatment of some aspects of cocaine addiction

    ANALYSIS OF THE TRADITIONAL PASSIVE SYSTEMS PERFORMANCE THROUGH THE APPLICATION OF CFD SOFTWARE

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    The need to reduce energy consumption is pushing the building design research to the evaluation of passive conditioning systems, since urban buildings are one of the major energy dissipater resulting in emission of CO2. This approach is not modern, but it is historically rooted in the architectural culture of the Mediterranean area and in the Middle East. The passive systems have ancient origins: they were developed to mitigate the summer heat and the winter cold. To understand the reasons that led to the development of passive systems, it should be remembered that about One-Fifth of the emerged planet surface and One-Third of the world's population live in conditions of warm-dry or hot-humid. In addition, most continental areas, even above high values of latitude (50\ub0), are characterized by climatic conditions with summer temperatures over the limit levels of comfort. Nowadays the scientific knowledge and the modern technologies allow to understand the working of passive systems in order to apply them on buildings to improve indoor comfort. This can be obtained through a new approach that involves the elaboration of design strategies based on the development of techniques and on computational and control tools. This work will show the results of a research that aims to verify the working of natural passive cooling systems employed in existing ancient buildings throughout CFD (Computational Fluid Dynamic) software application. Particularly we will define, through computational tools, models and study cases to compare and to set proposals able to actualize the original passive systems conceived and developed in an empirical way

    Non-commutative Corrections in Spectral Matrix Gravity

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    We study a non-commutative deformation of general relativity based on spectral invariants of a partial differential operator acting on sections of a vector bundle over a smooth manifold. We compute the first non-commutative corrections to Einstein equations in the weak deformation limit and analyze the spectrum of the theory. Related topics are discussed as well.Comment: 32 Pages, LaTex. Some nonessential typos in intermediate calculations in sect. 3 and 4 are corrected. The final results are the sam

    Low-Dose Topiramate in Alcohol Dependence: A Single-Blind, Placebo-Controlled Study

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    Introduction:Topiramate (TOP) and anticonvulsants in general are considered safe and effective drugs for the treatment of alcohol dependence, even though TOP-induced adverse events are quite common, especially for high initial doses or if titration to 300 mg/d is too rapid. The aim of the present study was to assess the efficacy and tolerability profile of low-dose TOP for relapse prevention. METHODS: After detoxification, 52 patients were randomized into 2 groups as follows: 26 patients received 100 mg of TOP (oral, twice daily), titrated over 2 weeks, and 26 patients received placebo (PLA). Both groups underwent rehabilitation twice a week. RESULTS: After 6 weeks of treatment, compared with the PLA group, patients receiving TOP showed the following: (1) fewer drinking days (P < 0.05); (2) less daily alcohol consumption (P < 0.05); (3) more days of treatment (P < 0.05); (4) reduced levels of craving (Obsessive-Compulsive Drinking Scale) and withdrawal symptoms (Clinical Institute Withdrawal Assessment for Alcohol-Revised); and (5) improvement of anxiety, depression, and obsessive-compulsive symptom severity (Symptom Check List 90 Revised). CONCLUSIONS: Despite the small sample size and the short follow-up period, the present PLA-controlled study demonstrated the potential usefulness of TOP, even when administered at a dosage of 100 mg/d, for the treatment of detoxified alcohol-dependent subjects, confirming results from previous studies testing higher doses of TOP

    Performance of a deep learning algorithm for the evaluation of CAD-RADS classification with CCTA

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    Background and aims: Artificial intelligence (AI) is increasing its role in diagnosis of patients with suspicious coronary artery disease. The aim of this manuscript is to develop a deep convolutional neural network (CNN) to classify coronary computed tomography angiography (CCTA) in the correct Coronary Artery Disease Reporting and Data System (CAD-RADS) category. Methods: Two hundred eighty eight patients who underwent clinically indicated CCTA were included in this single-center retrospective study. The CCTAs were stratified by CAD-RADS scores by expert readers and considered as reference standard. A deep CNN was designed and tested on the CCTA dataset and compared to on-site reading. The deep CNN analyzed the diagnostic accuracy of the following three Models based on CAD-RADS classification: Model A (CAD-RADS 0 vs CAD-RADS 1–2 vs CAD-RADS 3,4,5), Model 1 (CAD-RADS 0 vs CAD-RADS>0), Model 2 (CAD-RADS 0–2 vs CAD-RADS 3–5). Time of analysis for both physicians and CNN were recorded. Results: Model A showed a sensitivity, specificity, negative predictive value, positive predictive value and accuracy of 47%, 74%, 77%, 46% and 60%, respectively. Model 1 showed a sensitivity, specificity, negative predictive value, positive predictive value and accuracy of 66%, 91%, 92%, 63%, 86%, respectively. Conversely, Model 2 demonstrated the following sensitivity, specificity, negative predictive value, positive predictive value and accuracy: 82%, 58%, 74%, 69%, 71%, respectively. Time of analysis was significantly lower using CNN as compared to on-site reading (530.5 ± 179.1 vs 104.3 ± 1.4 sec, p=0.01) Conclusions: Deep CNN yielded accurate automated classification of patients with CAD-RADS

    Non-perturbative Heat Kernel Asymptotics on Homogeneous Abelian Bundles

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    We study the heat kernel for a Laplace type partial differential operator acting on smooth sections of a complex vector bundle with the structure group G×U(1)G\times U(1) over a Riemannian manifold MM without boundary. The total connection on the vector bundle naturally splits into a GG-connection and a U(1)-connection, which is assumed to have a parallel curvature FF. We find a new local short time asymptotic expansion of the off-diagonal heat kernel U(t∣x,x′)U(t|x,x') close to the diagonal of M×MM\times M assuming the curvature FF to be of order t−1t^{-1}. The coefficients of this expansion are polynomial functions in the Riemann curvature tensor (and the curvature of the GG-connection) and its derivatives with universal coefficients depending in a non-polynomial but analytic way on the curvature FF, more precisely, on tFtF. These functions generate all terms quadratic and linear in the Riemann curvature and of arbitrary order in FF in the usual heat kernel coefficients. In that sense, we effectively sum up the usual short time heat kernel asymptotic expansion to all orders of the curvature FF. We compute the first three coefficients (both diagonal and off-diagonal) of this new asymptotic expansion.Comment: LaTeX, 45 pages, in version 2 a typo has been correcte
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