2,652 research outputs found

    Binary trees, coproducts, and integrable systems

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    We provide a unified framework for the treatment of special integrable systems which we propose to call "generalized mean field systems". Thereby previous results on integrable classical and quantum systems are generalized. Following Ballesteros and Ragnisco, the framework consists of a unital algebra with brackets, a Casimir element, and a coproduct which can be lifted to higher tensor products. The coupling scheme of the iterated tensor product is encoded in a binary tree. The theory is exemplified by the case of a spin octahedron.Comment: 15 pages, 6 figures, v2: minor correction in theorem 1, two new appendices adde

    Numerical investigation on water exchange of shale samples

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    Interest in the hydraulic and mechanical characterization of shales has grown in recent years, because of their application in the context of energy geotechnics. In the frame of nuclear waste disposal shales are considered as host formations for the placements of nuclear waste at high depths. In the frame of hydrocarbon production they are considered as unconventional reservoirs, from which extracting natural gas. Understanding how fluids flow through shales is then a key aspect for both fields of application. This paper focuses on the analysis of the transport of water vapour through laboratory samples. After reviewing the balance and flow laws that govern the transport of fluid in unsaturated porous media, a simplified model is put forward. The model was implemented in a commercial finite element code, and it was used to reproduce the results of a literature study on wetting and drying of Opalinus Clay shale samples, imposed through the vapour equilibrium technique. Back analysis of the water content and volume strains of these specimens suggests that existing models underestimate the actual flow rate of water vapour which takes place at low suctions. The current interpretation also seems to be consistent with microstructural investigations on the interconnection between large pores of this material

    Old Age and Aerobic Microorganisms of Patients Affected by Clostridium difficile Infection are Associated Primarily with the Intestinal Presence of Clostridium difficile

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    Clostridium difficile infection in human occurs when the organism is present and germinating in the bowel. Old age of patients\u2019 and particular microorganisms in stools are identified as risk factors for the disease onset. We aimed to investigate if risk factors for C. difficile infections in a large Italian hospital were connected to C. difficile intestinal presence or to germination. Toxin B positivity was linked with age over 65 years (P=0.03), medical hospitalization (P=0.015) and growth of Enterobacteriaceae (P=0.029) and Enterococcus (P=0.05) from the same stools. The presence of tcdB was even more strictly linked with old age (P=0.005), medicine hospitalization (P=0.012) and growth of Enterobacteriaceae (P=0.003) and Enterococcus (P=0.04). Our results indicated that the presence of C. difficile in stools, irrespective of being spore or vegetative form, is reliably associated with old age of subjects and fecal presence of viable Enterobacteriaceae and Enterococcus

    ArteriolopatĂ­a calcificante (calcifilaxis). Recomendaciones para su manejo

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    Gaudin Models and Bending Flows: a Geometrical Point of View

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    In this paper we discuss the bihamiltonian formulation of the (rational XXX) Gaudin models of spin-spin interaction, generalized to the case of sl(r)-valued spins. In particular, we focus on the homogeneous models. We find a pencil of Poisson brackets that recursively define a complete set of integrals of the motion, alternative to the set of integrals associated with the 'standard' Lax representation of the Gaudin model. These integrals, in the case of su(2), coincide wih the Hamiltonians of the 'bending flows' in the moduli space of polygons in Euclidean space introduced by Kapovich and Millson. We finally address the problem of separability of these flows and explicitly find separation coordinates and separation relations for the r=2 case.Comment: 27 pages, LaTeX with amsmath and amssym

    Monitoring drying and wetting of a cement bentonite mixture with Electrical Resistivity Tomography

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    Cement bentonite slurry cutoff walls are used to encapsulate pollutants within contaminated areas, so avoiding their spreading in the environment. In both temperate and arid climates, at shallow depths, slurry walls are exposed to interaction with the atmosphere and thus to relative humidity values which might induce desaturation and significant shrinkage. This note presents the main results of a study aimed at investigating the impact of drying processes on the integrity and the hydraulic performance of cement bentonite slurry walls. Cement bentonite samples were cured under water for different times (1 months, 2 months and 4 months) and then dried naturally by exposing them to the laboratory environment (T = 21 °C, relative humidity approximately 38%). Once dried, the bottom of the samples was placed in contact with a thin layer of water to induce wetting. The distribution of the electrical conductivity within these samples was evaluated through Electrical Resistivity Tomography measurements, and electrical conductivity maps were converted then into maps of water contents on basis of a phenomenological relationship. The reconstructed water contents compared very well to the measured ones. Drying induced a limited cracking of the samples, which might affect to some extent the hydraulic performance of the barriers

    Lung transplantation from donation after controlled cardiocirculatory death: Systematic review and meta-analysis

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    Background: The interest in donation after cardiocirculatory death (DCD) donors for lung transplantation (LT) has been recently rekindled due to lung allograft shortage. Clinical outcomes following DCD have proved satisfactory. The aim of this systematic review is to provide a thorough analysis of published experience regarding outcomes of LT after controlled DCD compared with donation after brain death (DBD) donors. Methods: We performed a literature search in Cochrane Database of Systematic Reviews, PubMed and Web of Science using the items "lung transplantation" AND "donation after circulatory death" on November 1, 2018. The full text of relevant articles was evaluated by two authors independently. Quality assessment was performed using the NIH protocol for case-control and case series studies. A pooled Odds ratio (OR) and mean differences with inverse variance weighting using DerSimonian-Laird random effect models were computed to account for between-trial variance (tau 2). Results: Of the 508 articles identified with our search, 9 regarding controlled donation after cardiac death (cDCD) were included in the systematic review, including 2973 patients (403 who received graft from DCD and 2570 who had DBD). Both 1-year survival and 2 and 3-grade primary graft dysfunction (PGD) were balanced between the two cohorts (OR = 1.00 and 1.03 respectively); OR for airway complications was 2.07 against cDCD. We also report an OR = 0.57 for chronic lung allograft dysfunction (CLAD) and an OR = 0.57 for 5-year survival against cDCD. Conclusions: Our meta-analysis shows no significant difference between recipients after cDCD or DBD regarding 1-year survival, PGD and 1-year freedom from CLAD. Airway complications and long-term survival were both related with transplantation after cDCD, but these statistical associations need further research
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