47 research outputs found

    Possibility of Turbulence from a Post-Navier-Stokes Equation

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    We introduce corrections to the Navier-Stokes equation arising from the transitions between molecular states and the injection of external energy. In the simplest application of the proposed post Navier-Stokes equation, we find a multi-valued velocity field and the immediate possibility of velocity reversal, both features of turbulence

    Divergence Measure Between Chaotic Attractors

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    We propose a measure of divergence of probability distributions for quantifying the dissimilarity of two chaotic attractors. This measure is defined in terms of a generalized entropy. We illustrate our procedure by considering the effect of additive noise in the well known H\'enon attractor. Comparison of two H\'enon attractors for slighly different parameter values, has shown that the divergence has complex scaling structure. Finally, we show how our approach allows to detect non-stationary events in a time series.Comment: 9 pages, 6 figure

    Prostaglandin E2 possesses different potencies in inducing Vascular Endothelial Growth Factor and Interleukin-8 production in COPD human lung fibroblasts

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    We studied the role of PGE2, its biosynthetic enzymes and its receptors, in regulating the functions of lung fibroblasts through the production of Vascular Endothelial Growth Factor (VEGF) and Interleukin-8 (IL-8) in COPD subjects. Lung fibroblasts from Control (C) (n=6), Smoker (HS) (n=6) and COPD patients (n=8) were cultured, and basal PGE2, VEGF, and IL-8 measured in supernatants by ELISA. COX-1/COX-2 and EP receptors expression were assessed by western blot and by RT-PCR. Release of VEGF and IL-8 by human fetal lung fibroblasts (HFL-1; lung, diploid, human) was evaluated under different conditions. PGE2, VEGF, and IL-8 levels, COX-2, EP2, and EP4 protein expression and mRNA were increased in COPD when compared to Controls. Low concentrations of synthetic PGE2 increased the release of VEGF in HFL-1, but higher concentrations were needed to induce the release of IL-8. This effect was mimicked by an EP2 agonist and modulated by an EP4 antagonist. In the airways of COPD subjects, fibroblast-derived PGE2 may regulate angiogenesis and inflammation through the production of VEGF and IL-8 respectively, suggesting that the increase in expression of COX-2, EP2 and EP4 observed in COPD fibroblasts may contribute to steering the role of PGE2 from homeostatic to pro-inflammatory

    Period doubling boundaries of a bouncing ball

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    A simple mechanical system consisting of a bouncing ball subject to repeated impacts with a vibrating table is studied in the period doubling regime. Two control parameters (the table's forcing frequency and amplitude) are varied to discover the curves in parameter space that separate periodic orbits. Experimental results for the period doubling boundaries agree with calculations from a simple model.Nous étudions, dans le régime de doublement de période, un système mécanique simple formé d'une balle rebondissante soumise à des chocs répétés par une table vibrante. Nous faisons varier deux paramètres de contrôle (la fréquence et l'amplitude des vibrations de la table) pour découvrir les courbes qui, dans l'espace des paramètres, séparent les orbites périodiques. Les résultats expérimentaux sont en accord avec les calculs faits dans le cadre d'un modèle simple

    Treating Adolescents with Social Anxiety Disorder in School: An Attention Control Trial

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    Background: Anxiety disorders are often undetected and untreated in adolescents. This study evaluates the relative efficacy of a school-based, cognitive-behavioral intervention compared to an educational-supportive treatment for adolescents with social anxiety disorder. Methods: Thirty-six students (30 females), ages 14 to 16, were randomized to a 12-week specific intervention, Skills for Social and Academic Success (SASS), or a credible attention control matched for structure and contact, conducted in school. Results: Independent evaluations and adolescent self-reports indicated significant reduction in social anxiety for SASS compared to the control group. Parent reports of their children\u27s social anxiety did not discriminate between treatments. In the specific intervention, 59%, compared to 0% in the control, no longer met criteria for social anxiety disorder following treatment. Superiority of the SASS intervention was maintained 6 months after treatment cessation. Conclusions: The study provides evidence that intervention for social anxiety disorder that emphasizes exposure and social skills is efficacious. Results indicate that clinical improvement is sustained for at least 6 months, and that, overall, adolescents with social anxiety disorder do not respond to non-specific treatment. This investigation has public health implications by demonstrating that effective interventions can be transported to nonclinical settings

    Mechanisms Of Esophageal Cancer Development In Brazilians

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    Esophageal cancer represents one of the most common and lethal cancers around the World. Some areas of South America, including parts of Brazil, present the highest incidence of the disease in the West. The main etiological factors that have been associated with the disease in Brazil are alcohol consumption, tobacco smoking and, in the South, consumption of hot maté. Nitrosamines are the only carcinogens capable of inducing tumors in the esophagus of experimental animals, with the rat being the most susceptible species, mainly due to tissue specific metabolic activation by CYP enzymes. Studies of CYP2A expression in the esophagus of rodents suggest an association between CYP2A expression and esophageal susceptibility to tumor induction. CYP2A6 and CYP2E1, the main enzymes to activate nitrosamines in humans, are the only carcinogen activating CYP enzymes to be expressed in the esophagus of Brazilians. Patients who presented high levels of CYP2A6 expression could activate nitrosamines at rates comparable to the rat. This expression profile is different from those present in French patients. We investigated 34 Brazilian patients regarding the risk associated with polymorphisms in drug metabolizing enzymes and TP53 mutations. A GSTP1 polymorphism presented a clear risk to white and non-white patients to develop esophageal cancer. GSTM1 null polymorphism also seemed to be associated with an increased risk. CYP2A6, CYP2E1, SOD2, and GSTT1 polymorphisms were not associated with an increased risk of esophageal cancer. TP53 mutations occurred mostly in exon 7, differing from the mutation profile found in the IARC database. 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