3,315 research outputs found

    Dualisation of the D=7 Heterotic String

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    The dualisation and the first-order formulation of the D=7 abelian Yang-Mills supergravity which is the low energy effective limit of the D=7 fully Higssed heterotic string is discussed. The non-linear coset formulation of the scalars is enlarged to include the entire bosonic sector by introducing dual fields and by constructing the Lie superalgebra which generates the dualized coset element.Comment: 20 page

    Topology optimisation using level set methods and the discontinuous Galerkin method

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    This paper presents a topology optimisation approach that combines an adjoint-based sensitivity analysis [1] with level set methods (LSM) [2] for front propagation, and the discontinuous Galerkin (DG) symmetric interior penalty (SIP) method [3]. The problems considered in this paper will be limited to the minimum compliance design of two-dimensional linear elastic structures

    Recurrent Pericarditis in Children and Adolescents

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    Recurrent pericarditis (RP) is a clinical syndrome characterized by recurrent attacks of acute pericardial inflammation. Prognosis quoad vitam is good, although morbidity might be significant, especially in children and adolescents. Multiple potential etiologies result in RP, in the vast majority of cases through autoimmune or autoinflammatory mechanisms. Idiopathic RP is one of the most frequent diagnoses, that requires the exclusion of all known etiologies. Therapeutic advances in the last decade have been significant with the recognition of the effectiveness of anti IL1 therapy, but a correct diagnostic and therapeutic algorithm is of key importance. Unfortunately, most of evidence comes from studies in adult patients. Here we review the etiopathogenesis, diagnosis and management of RP in pediatric patients

    Dualisation of the General Scalar Coset in Supergravity Theories

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    The dualised formulation of the symmetric space sigma model is peformed for a general scalar coset G/K where G is a maximally non-compact group and K is it's maximal compact subgroup.By using the twisted self-duality condition the general form of the first-order equations are obtained.The results are applied to the example of SL(2,R)/SO(2) scalar manifold of the IIB supergravity.Comment: 22 page

    Effects of Enriched Environment (EE) on Depressive-Like Behavior and Hippocampal Structure in Rat Model of Chronic Stress

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    Chronic stress is associated with the development of depression. It can trigger structural and neurobehavioral changes in the brain and has been shown to induce depressivelike behavior in animals. An enriched environment can modulate the structure and function of the brain by altering the expression of various genes and proteins as well as affecting neurotransmitters’ activity. The hippocampus plays an important role incontrolling the networks for mood regulation and has been implicated in the course of depression. This study aimed to investigate the effect of an enriched environment on the depressive-like behavior and hippocampal structure in rats after unpredictable chronic mild stress (UCMS) exposure. Male Wistar rats (Rattus novergicus) were divided into three groups, each consisting of 6 rats including the control, UCMS and UCMS+EEgroup. Unpredictable chronic mild stress and EE were given for 21 days. Body weight gain, depressive-like behavior, and hippocampal structure were evaluated at the end of the experiment. Depressive-like behavior was assessed with Forced Swim Test (FST) and Sucrose Preference Test (SPT). Thickness of the pyramidal layer of CA1 and CA3 area were measured with histologic examination to see changes in the hippocampalstructure. Data were analyzed using One-Way ANOVA or Kruskal-Wallis followed by multiple comparison post hoc test. The enriched environment could significantly maintain body weight gain (p = 0.036) and rat’s preference to sucrose solution (p =0.001) in a stressful condition. Enriched environment reduced immobility time in FST but it was not statistically significant (p = 0.177). There was a significant difference in the thickness of CA1 and CA3 pyramidal layer of the hippocampus among groups (p=0.015 and p=0.019 respectively). Stress markedly decreased the thickness of CA1 and CA3 pyramidal layer (p=0.014 and 0.011 respectively). The enriched environment can ameliorate stress-induced depressive-like behavior and alteration in hippocampalstructure in rats. Keywords: Environmental enrichment, depression, stress, hippocampu

    U-duality and M-Theory

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    This work is intended as a pedagogical introduction to M-theory and to its maximally supersymmetric toroidal compactifications, in the frameworks of 11D supergravity, type II string theory and M(atrix) theory. U-duality is used as the main tool and guideline in uncovering the spectrum of BPS states. We review the 11D supergravity algebra and elementary 1/2-BPS solutions, discuss T-duality in the perturbative and non-perturbative sectors from an algebraic point of view, and apply the same tools to the analysis of U-duality at the level of the effective action and the BPS spectrum, with a particular emphasis on Weyl and Borel generators. We derive the U-duality multiplets of BPS particles and strings, U-duality invariant mass formulae for 1/2- and 1/4-BPS states for general toroidal compactifications on skew tori with gauge backgrounds, and U-duality multiplets of constraints for states to preserve a given fraction of supersymmetry. A number of mysterious states are encountered in D<=3, whose existence is implied by T-duality and 11D Lorentz invariance. We then move to the M(atrix) theory point of view, give an introduction to Discrete Light Cone Quantization (DLCQ) in general and DLCQ of M-theory in particular. We discuss the realization of U-duality as electric-magnetic dualities of the Matrix gauge theory, display the Matrix gauge theory BPS spectrum in detail, and discuss the conjectured extended U-duality group in this scheme.Comment: 132 pages, 37 tables, Latex2e; v3: minor corrections, text reformatted, update of refs, note added about boundaries of M-theory moduli space, final version to appear in Phys. Rep

    Lumbar epidural fentanyl: segmental spread and effect on temporal summation and muscle pain

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    Background. Despite extensive use, different aspects of the pharmacological action of epidural fentanyl have not been clarified. We applied a multi‐modal sensory test procedure to investigate the effect of epidural fentanyl on segmental spread, temporal summation (as a measure for short‐lasting central hyperexcitability) and muscle pain. Methods. Thirty patients received either placebo, 50 or 100 ”g single dose of fentanyl epidurally (L2-3), in a randomized, double‐blind fashion. Heat pain tolerance thresholds at eight dermatomes from S1 to fifth cranial nerve (assessment of segmental spread), pain threshold to transcutaneous repeated electrical stimulation of the sural nerve (assessment of temporal summation) and pain intensity after injection of hypertonic saline into the tibialis anterior muscle (assessment of muscle pain) were recorded. Results. Fentanyl 100 ”g, but not 50 ”g, produced analgesia to heat stimulation only at L2. Surprisingly, no effect at S1 was detected. Both fentanyl doses significantly increased temporal summation threshold and decreased muscle pain intensity. Conclusions. The findings suggest that a single lumbar epidural dose of fentanyl should be injected at the spinal interspace corresponding to the dermatomal site of pain. Increased effect on L2 compared with S1 suggests that drug effect on spinal nerve roots and binding to opioid receptors on the dorsal root ganglia may be more important than traditionally believed for the segmental effect of epidurally injected fentanyl. Epidural fentanyl increases temporal summation threshold and could therefore contribute to prevention and treatment of central hypersensitivity states. I.M. injection of hypertonic saline is a sensitive technique for detecting the analgesic action of epidural opioids. Br J Anaesth 2003; 90: 467-7

    ROCKFALLS: IN SITU TEST, KINEMATIC SIMULATION AND MITIGATION MEASURES &#8211; SASSO FARINACCIO CASE STUDY

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    This research deals with the analysis of rockfall motion and the importance of kinematic simulations as well as in situ tests in designing of protection measures. The study area is a talus slope located in Northern Italy (Provence of Sondrio), where rockfalls frequently occur. The positions and dimensions of fallen blocks were measured and used in the calibration process, performed through the back-analysis approach. The calibrated values of restitution coefficients were compared with those obtained from in situ tests, which were carried out on the examined slope. Looking at the resulting rock fall hazard, the bidimensional kinematic simulations were performed in order to individuate the most suitable location and dimensions of mitigation measures

    Rock Mass Rating spatial estimation by geostatistical analysis

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    This work aims to estimate the Rock Mass Rating of 200km2 area of the Italian Central Alps, along San Giacomo Valley (province of Sondrio). The regional geological setting is related to the Pennidic Nappe arrangement, which is characterized by the emplacement of sub-horizontal gneissic bodies, separated by meta-sedimentary cover units. The resulting RMR map can be a useful tool to forecast the quality of outcropping rock masses as well as to derive their geomechanical behaviour. Almost 100 geomechanical field surveys have been carried out in the research area, in order to characterize the outcropping rock masses; afterwards rock mass quality indexes have been evaluated in each surveyed site. In order to estimate the Rock Mass Rating values in un-sampled locations, different geostatistical techniques (kriging and simulations) have been applied, using both bi-dimensional and almost three-dimensional approaches. The validation process shows that kriging tends to produce smoothened distributions, while conditional simulations allow respecting local extreme values. Although geostatistical analysis reveals that geomechanical properties show spatial correlations, it is to remind that rock mass quality is strongly related to its geological and structural history

    TOWARDS THE COMPREHENSION OF ROCKFALL MOTION, WITH THE AID OF IN SITU TESTS

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    Rockfalls frequently occur in Alpine areas, creating serious risks to population and buildings; the protection measures against rockfalls cannot be adequately designed unless the comprehensive understanding of rockfall phenomenon. Some experimental rockfall tests have been performed on a talus slope in Grosina Valley (northern Italy), with the aim to check the reliability of common simulation methods and to analyse the motion of falling blocks. First, a-priori kinematic simulations have been performed, and, after the rockfall tests, the results have been compared with the real stopping positions of blocks. Afterwards, the recorded trajectories of falling blocks have been analysed, allowing the calculation of the motion parameters of falling blocks. The motion of blocks was mainly characterized by rebounds, therefore particular attention has been paid to restitution coefficients, which describe the loss of energy during the impact and greatly affect the results of rockfall simulations. Although the talus slope features are quite constant, an unexpected wide range of restitution coefficients results from the movies: the variability is greater than that one of bibliography, moreover normal restitution coefficients are extremely high (they often overpass the unit). The qualitative relationships between restitution coefficients and slope features, falling block characteristics and pre-impact motion conditions have been searched and described
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