3,263 research outputs found

    A microscopic model for Josephson currents

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    A microscopic model of a Josephson junction between two superconducting plates is proposed and analysed. For this model, the nonequilibrium steady state of the total system is explicitly constructed and its properties are analysed. In particular, the Josephson current is rigorously computed as a function of the phase difference of the two plates and the typical properties of the Josephson current are recovered

    Metastability in the BCS model

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    We discuss metastable states in the mean-field version of the strong coupling BCS-model and study the evolution of a superconducting equilibrium state subjected to a dynamical semi-group with Lindblad generator in detailed balance w.r.t. another equilibrium state. The intermediate states are explicitly constructed and their stability properties are derived. The notion of metastability in this genuine quantum system, is expressed by means of energy-entropy balance inequalities and canonical coordinates of observables

    Shopping centre siting and modal choice in Belgium: a destination based analysis

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    Although modal split is only one of the elements considered in decision-making on new shopping malls, it remarkably often arises in arguments of both proponents and opponents. Today, this is also the case in the debate on the planned development of three major shopping malls in Belgium. Inspired by such debates, the present study focuses on the impact of the location of shopping centres on the travel mode choice of the customers. Our hypothesis is that destination-based variables such as embeddedness in the urban fabric, accessibility and mall size influence the travel mode choice of the visitors. Based on modal split data and location characteristics of seventeen existing shopping centres in Belgium, we develop a model for a more sustainable siting policy. The results show a major influence of the location of the shopping centre in relation to the urban form, and of the size of the mall. Shopping centres that are part of a dense urban fabric, measured through population density, are less car dependent. Smaller sites will attract more cyclists and pedestrians. Interestingly, our results deviate significantly from the figures that have been put forward in public debates on the shopping mall issue in Belgium

    Equilibrium states for the Bose gas

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    The generating functional of the cyclic representation of the CCR (Canonical Commutation Relations) representation for the thermodynamic limit of the grand canonical ensemble of the free Bose gas with attractive boundary conditions is rigorously computed. We use it to study the condensate localization as a function of the homothety point for the thermodynamic limit using a sequence of growing convex containers. The Kac function is explicitly obtained proving non-equivalence of ensembles in the condensate region in spite of the condensate density being zero locally.Comment: 21 pages, no figure

    Deep sternal wound infection after open heart surgery: current treatment insights. A retrospective study of 36 cases

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    The aim of this study was to retrospectively evaluate the results of reconstructing infected post-sternotomy wounds, with either sternal plating and/or pectoralis major flap transposition or pedicled omentoplasty after previous vacuum-assisted closure (VAC) therapy. Between January 2005 and December 2010, 36 patients, suffering from deep sternal wound infection (DSWI) after coronary artery bypass grafting procedure, received (plastic) reconstructive surgery. All patients, treated in the Maastricht University Medical Centre (Departments of Plastic Surgery and Cardiothoracic Surgery), were selected for this study. For 22 patients, sternal refixation and reconstruction were obtained by sternal internal plate fixation combined with bilateral pectoralis major advancement flap. In 11 patients, a pedicled omentoplasty was performed, with or without split-skin graft and additional VAC therapy. Three patients only received a pectoralis plasty. We evaluated preoperative characteristics and post-operative course. Twenty-four patients (66.7%) had an uneventful post-operative course. Complications in the other patients included wound dehiscence, herniation of the donor site and infection of sternal plating material. Average sternal wound healing after sternal plating plus pectoralis plasty, pectoralis plasty and omentoplasty respectively accounted 7.7, 8.0 and 11.6 weeks. From our experience, we recommend VAC therapy plus delayed sternal plating and additional bilateral pectoralis major flap advancement as first repair option in case of DSWI. However, individual clinical conditions need to be taken into account when making a decision between the different available reconstructive options. Omentoplasty should be reserved for cases in which the sternum has recurrently fallen open after previous sternal plate refixation, or for cases in which the sternum defect is too extended

    Long term survivors with metastatic pancreatic adenocarcinoma treated with gemcitabine: a retrospective analysis

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    <p>Abstract</p> <p>Background</p> <p>Metastatic pancreatic adenocarcinoma has a short median overall survival (OS) of 5–6 months. However, a subgroup of patients survives more than 1 year. We analyzed the survival outcomes of this subgroup and evaluated clinical and pathological factors that might affect survival durations.</p> <p>Methods</p> <p>We identified 20 patients with metastatic or recurrent pancreatic adenocarcinoma who received single-agent gemcitabine and had an OS longer than 1 year. Baseline data available after the diagnosis of metastatic or recurrent disease was categorized as: 1) <it>clinical/demographic data </it>(age, gender, ECOG PS, number and location of metastatic sites); 2) <it>Laboratory data </it>(Hematocrit, hemoglobin, glucose, LDH, renal and liver function and CA19-9); 3) <it>Pathologic data </it>(margins, nodal status and grade); 4) <it>Outcomes data </it>(OS, Time to Treatment Failure (TTF), and 2 year-OS). The lowest CA19-9 levels during treatment with gemcitabine were also recorded. We performed a univariate analysis with OS as the outcome variable.</p> <p>Results</p> <p>Baseline logarithm of CA19-9 and total bilirubin had a significant impact on OS (HR = 1.32 and 1.31, respectively). Median OS and TTF on gemcitabine were 26.9 (95% CI = 18 to 32) and 11.5 (95% CI = 9.0 to 14.3) months, respectively. Two-year OS was 56.4%, with 7 patients alive at the time of analysis.</p> <p>Conclusion</p> <p>A subgroup of patients with metastatic pancreatic cancer has prolonged survival after treatment with gemcitabine. Only bilirubin and CA 19-9 levels were predictive of longer survival in this population. Further analysis of potential prognostic and predictive markers of response to treatment and survival are needed.</p

    Proof of Bose-Einstein Condensation for Interacting Gases with a One-Particle Spectral Gap

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    Using a specially tuned mean-field Bose gas as a reference system, we establish a positive lower bound on the condensate density for continuous Bose systems with superstable two-body interactions and a finite gap in the one-particle excitations spectrum, i.e. we prove for the first time standard homogeneous Bose-Einstein condensation for such interacting systems
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