78 research outputs found

    Revisiting Absorbing Phase Transition in Energy Exchange Models

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    A recent study of conserved Manna model, with both discrete and continuous variable, indicates that absorbing phase transitions therein belong to the directed percolation (DP) universality class. In this context we revisit critical behaviour in energy exchange models with a threshold. Contrary to the previous claims [PRE 83, 061130 (2011), arXiv:1102.1631], our results indicate that both the maximal and minimal versions of this model belong to the DP class.Comment: 8 pages, 7 eps figure

    Comparison of coherent and weakly incoherent transport models for the interlayer magnetoresistance of layered Fermi liquids

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    The interlayer magnetoresistance of layered metals in a tilted magnetic field is calculated for two distinct models for the interlayer transport. The first model involves coherent interlayer transport and makes use of results of semi-classical or Bloch-Boltzmann transport theory. The second model involves weakly incoherent interlayer transport where the electron is scattered many times within a layer before tunneling into the next layer. The results are relevant to the interpretation of experiments on angular-dependent magnetoresistance oscillations (AMRO) in quasi-one- and quasi-two-dimensional metals. We find that the dependence of the magnetoresistance on the direction of the magnetic field is identical for both models except when the field is almost parallel to the layers. An important implication of this result is that a three-dimensional Fermi surface is not necessary for the observation of the Yamaji and Danner oscillations seen in quasi-two- and quasi-one-dimensional metals, respectively. A universal expression is given for the dependence of the resistance at AMRO maxima and minima on the magnetic field and scattering time (and thus the temperature). We point out three distinctive features of coherent interlayer transport: (i) a beat frequency in the magnetic oscillations of quasi-two-dimensional systems, (ii) a peak in the angular-dependent magnetoresistance when the field is sufficiently large and parallel to the layers, and (iii) a crossover from a linear to a quadratic field dependence for the magnetoresistance when the field is parallel to the layers. Properties (i) and (ii) are compared with published experimental data for a range of quasi-two-dimensional organic metals and for Sr2RuO4.Comment: 21 pages, RevTeX + epsf, 4 figures. Published version. Subsection added. References update

    Congenital and childhood atrioventricular blocks: pathophysiology and contemporary management

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    Atrioventricular block is classified as congeni- tal if diagnosed in utero, at birth, or within the first month of life. The pathophysiological process is believed to be due to immune-mediated injury of the conduction system, which occurs as a result of transplacental pas- sage of maternal anti-SSA/Ro-SSB/La antibodies. Childhood atrioventricular block is therefore diagnosed between the first month and the 18th year of life. Genetic variants in multiple genes have been described to date in the pathogenesis of inherited progressive car- diac conduction disorders. Indications and techniques of cardiac pacing have also evolved to allow safe perma- nent cardiac pacing in almost all patients, including those with structural heart abnormalities

    Contagion Shocks in One Dimension

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    We consider an agent-based model of emotional contagion coupled with motion in one dimension that has recently been studied in the computer science community. The model involves movement with a speed proportional to a “fear” variable that undergoes a temporal consensus averaging based on distance to other agents. We study the effect of Riemann initial data for this problem, leading to shock dynamics that are studied both within the agent-based model as well as in a continuum limit. We examine the behavior of the model under distinguished limits as the characteristic contagion interaction distance and the interaction timescale both approach zero. The limiting behavior is related to a classical model for pressureless gas dynamics with “sticky” particles. In comparison, we observe a threshold for the interaction distance vs. interaction timescale that produce qualitatively different behavior for the system - in one case particle paths do not cross and there is a natural Eulerian limit involving nonlocal interactions and in the other case particle paths can cross and one may consider only a kinetic model in the continuum limit

    Thromboembolic risk after knee endoprosthesis

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    Thromboembolic complications are the most frequent associated pathologies after knee replacement. The secondary deep vein thrombosis in the knee arthroplasty is often low symptomatic or asymptomatic and, sometime, it could lead to fatal pulmonary embolism. This is the main purpose recommending an antithrombotic prophylaxis. In this study 214 patients operated for knee arthroplasty and receiving low molecular heparin therapy were enrolled. They were clinically and echo/radiologically monitored for thromboembolic and/or hemorrhagic complications on the 2nd, 7 th, 14th and 45th day from surgery. Results showed that only 45% of the cases developed DVT (deep vein thrombosis) out of which 17% could be objectively verified by ultrasonography and phlebography. In only one case massive pulmonary embolism with fatal evolution was discovered. It was not found any major bleeding except in four cases in which local haematomas were discovered (most probably related to anticoagulant treatment). This study concluded that the administration of low molecular weight heparin after knee arthroplasty significantly reduces the risks of thromboembolism in conditions where the increase of hemorrhagic complications doesn't result statistically significant

    Our experience in Helicobacter pylori infection and gastric MALTomas

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    OBJECTIVE: A number of recent studies have expanded our understanding of Helicobacter pylori (Hp) infection and of the pathogenesis of MALT lymphoma. The purpose of this paper is to perform a retrospective analysis of the clinical characteristics of gastric MALT lymphoma and its relationship with H. pylori infection in authors' experience. MATERIALS AND METHODS: We report nineteen patients observed during 10 years, presenting with gastric MALTomas at any stage. The staging classification and the presence of H. pylori infection have been assessed, and the chosen therapy also. RESULTS: The most part of our patients underwent surgery, still now resulting the most effective therapy. None of the patients had eradicating therapy due to their poor compliance and because the most part of cases were observed before the time of clinical validation of such treatment. CONCLUSIONS: In our series, surgery was effective for treatment of gastric MALT lymphomas. Surgery and chemotherapy remain, in accord with literature data, the best treatment for gastric MALTomas. Hence, because Hp may play a role in the development of such pathology in certain patients, antibiotic treatment for Hp eradication should not be discouraged in these patients, especially in them with low grade gastric MALT lymphomas. In fact, the failure of this therapy will not modify either survival or later recourse to surgical and/or radio- and chemotherapy
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