517 research outputs found

    Existence of solutions to a higher dimensional mean-field equation on manifolds

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    For m≄1m\geq 1 we prove an existence result for the equation (−Δg)mu+λ=λe2mu∫Me2mudÎŒg(-\Delta_g)^m u+\lambda=\lambda\frac{e^{2mu}}{\int_M e^{2mu}d\mu_g} on a closed Riemannian manifold (M,g)(M,g) of dimension 2m2m for certain values of λ\lambda.Comment: 15 Page

    A Codazzi-like equation and the singular set for C1C^{1} smooth surfaces in the Heisenberg group

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    In this paper, we study the structure of the singular set for a C1C^{1} smooth surface in the 33-dimensional Heisenberg group H1\boldsymbol{H}_{1}. We discover a Codazzi-like equation for the pp-area element along the characteristic curves on the surface. Information obtained from this ordinary differential equation helps us to analyze the local configuration of the singular set and the characteristic curves. In particular, we can estimate the size and obtain the regularity of the singular set. We understand the global structure of the singular set through a Hopf-type index theorem. We also justify that Codazzi-like equation by proving a fundamental theorem for local surfaces in H1\boldsymbol{H}_{1}.Comment: 64 pages, 17 figure

    InterjecciĂłn y extrapredicaciĂłn

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    Aquest article versa sobre la interjecciĂł i intenta analitzar el seu comportament de cara a realitzar una aproximaciĂł entre aquesta unitat i la extraprediciĂłn. Des d’un enfocament essencialment funcional, explora la interjecciĂł aixĂ­ com l’extrapredicaciĂł del seu funcionament. Acaba observant que aquesta unitat neurolingĂŒĂ­stica Ă©s eminentment extrapredicativa.Este artĂ­culo versa sobre la interjecciĂłn e intenta analizar su comportamiento con vistas a realizar una aproximaciĂłn entre esta unidad y la extrapredicaciĂłn. Desde un enfoque esencialmente funcional, explora la interjecciĂłn asĂ­ como la extraprediciĂłn de su funcionamiento. Termina observando que esta unidad neurolingĂŒĂ­stica es eminentemente extrapredicativa.Cet article traite de l’interjection et tente d’analyser son comportement afin de faire une approximation entre cette unitĂ© et l’extraprĂ©dication. D’une approche essentiellement fonctionnelle, il explore l’interjection ainsi que l’extraprĂ©diction de son fonctionnement. Il conclut en observant que cette unitĂ© neurolinguistique est Ă©minemment extra-prĂ©dictive.This paper focuses on interjection and aims to explore how it behaves, in order to make an approximation between this linguistic unit and the phenomenon called extrapredication. The perspective used here is essencially functional and, from this theory, the paper analyse the interjection and the extrapredication considering how it operates in the sentence. By the end, the constat is that this neurolinguistic unit is essencially extrapredicative

    Time representation in reinforcement learning models of the basal ganglia

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    Reinforcement learning (RL) models have been influential in understanding many aspects of basal ganglia function, from reward prediction to action selection. Time plays an important role in these models, but there is still no theoretical consensus about what kind of time representation is used by the basal ganglia. We review several theoretical accounts and their supporting evidence. We then discuss the relationship between RL models and the timing mechanisms that have been attributed to the basal ganglia. We hypothesize that a single computational system may underlie both RL and interval timing—the perception of duration in the range of seconds to hours. This hypothesis, which extends earlier models by incorporating a time-sensitive action selection mechanism, may have important implications for understanding disorders like Parkinson's disease in which both decision making and timing are impaired

    An improved geometric inequality via vanishing moments, with applications to singular Liouville equations

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    We consider a class of singular Liouville equations on compact surfaces motivated by the study of Electroweak and Self-Dual Chern-Simons theories, the Gaussian curvature prescription with conical singularities and Onsager's description of turbulence. We analyse the problem of existence variationally, and show how the angular distribution of the conformal volume near the singularities may lead to improvements in the Moser-Trudinger inequality, and in turn to lower bounds on the Euler-Lagrange functional. We then discuss existence and non-existence results.Comment: some references adde

    Simultaneous Learning of Fuzzy Sets

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    We extend a procedure based on support vector clustering and devoted to inferring the membership function of a fuzzy set to the case of a universe of discourse over which several fuzzy sets are defined. The extended approach learns simultaneously these sets without requiring as previous knowledge either their number or labels approximating membership values. This data-driven approach is completed via expert knowledge incorporation in the form of predefined shapes for the membership functions. The procedure is successfully tested on a benchmark

    Sign-changing tower of bubbles for a sinh-Poisson equation with asymmetric exponents

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    Motivated by the statistical mechanics description of stationary 2D-turbulence, for a sinh-Poisson type equation with asymmetric nonlinearity, we construct a concentrating solution sequence in the form of a tower of singular Liouville bubbles, each of which has a different degeneracy exponent. The asymmetry parameter γ∈(0,1]\gamma\in(0,1] corresponds to the ratio between the intensity of the negatively rotating vortices and the intensity of the positively rotating vortices. Our solutions correspond to a superposition of highly concentrated vortex configurations of alternating orientation; they extend in a nontrivial way some known results for γ=1\gamma=1. Thus, by analyzing the case γ≠1\gamma\neq1 we emphasize specific properties of the physically relevant parameter γ\gamma in the vortex concentration phenomena

    Mechanisms of oxygenation responses to proning and recruitment in COVID-19 pneumonia

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    Purpose: This study aimed at investigating the mechanisms underlying the oxygenation response to proning and recruitment maneuvers in coronavirus disease 2019 (COVID-19) pneumonia. Methods: Twenty-five patients with COVID-19 pneumonia, at variable times since admission (from 1 to 3 weeks), underwent computed tomography (CT) lung scans, gas-exchange and lung-mechanics measurement in supine and prone positions at 5 cmH2O and during recruiting maneuver (supine, 35 cmH2O). Within the non-aerated tissue, we differentiated the atelectatic and consolidated tissue (recruitable and non-recruitable at 35 cmH2O of airway pressure). Positive/negative response to proning/recruitment was defined as increase/decrease of PaO2/FiO2. Apparent perfusion ratio was computed as venous admixture/non aerated tissue fraction. Results: The average values of venous admixture and PaO2/FiO2 ratio were similar in supine-5 and prone-5. However, the PaO2/FiO2 changes (increasing in 65% of the patients and decreasing in 35%, from supine to prone) correlated with the balance between resolution of dorsal atelectasis and formation of ventral atelectasis (p = 0.002). Dorsal consolidated tissue determined this balance, being inversely related with dorsal recruitment (p = 0.012). From supine-5 to supine-35, the apparent perfusion ratio increased from 1.38 ± 0.71 to 2.15 ± 1.15 (p = 0.004) while PaO2/FiO2 ratio increased in 52% and decreased in 48% of patients. Non-responders had consolidated tissue fraction of 0.27 ± 0.1 vs. 0.18 ± 0.1 in the responding cohort (p = 0.04). Consolidated tissue, PaCO2 and respiratory system elastance were higher in patients assessed late (all p < 0.05), suggesting, all together, “fibrotic-like” changes of the lung over time. Conclusion: The amount of consolidated tissue was higher in patients assessed during the third week and determined the oxygenation responses following pronation and recruitment maneuvers
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