850 research outputs found

    Nuclear Spin Relaxation for Higher Spin

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    We study the relaxation of a spin I that is weakly coupled to a quantum mechanical environment. Starting from the microscopic description, we derive a system of coupled relaxation equations within the adiabatic approximation. These are valid for arbitrary I and also for a general stationary non--equilibrium state of the environment. In the case of equilibrium, the stationary solution of the equations becomes the correct Boltzmannian equilibrium distribution for given spin I. The relaxation towards the stationary solution is characterized by a set of relaxation times, the longest of which can be shorter, by a factor of up to 2I, than the relaxation time in the corresponding Bloch equations calculated in the standard perturbative way.Comment: 4 pages, Latex, 2 figure

    Phase diagram of Regge quantum gravity coupled to SU(2) gauge theory

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    We analyze Regge quantum gravity coupled to SU(2) gauge theory on 43×24^3\times 2, 63×46^{3}\times 4 and 83×48^{3}\times 4 simplicial lattices. It turns out that the window of the well-defined phase of the gravity sector where geometrical expectation values are stable extends to negative gravitational couplings as well as to gauge couplings across the deconfinement phase transition. We study the string tension from Polyakov loops, compare with the β\beta-function of pure gauge theory and conclude that a physical limit through scaling is possible.Comment: RevTeX, 14 pages, 5 figures (2 eps, 3 tex), 2 table

    Fluid structure interaction analysis: vortex shedding induced vibrations

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    Abstract Fluid Structure Interaction (FSI) numerical modelling requires an efficient workflow to properly capture the physics involved. Computational Structural Mechanics (CSM) and Computation Fluid Dynamics (CFD) have to be coupled and at the moment there is a lack of monolithic solvers capable to tackle industrial applications that involves high fidelity models which mesh can be comprised of hundred millions of cells. This paper shows an efficient approach based on standard commercial tools. The FEM solver ANSYS® Mechanical™ is used to extract a given number of eigenmodes. Then the modal shapes are imported in the CFD solver Fluent® using the Add On RBF Morph™. Updating the modal coordinates it is possible to adapt the shape of the model by taking into account the elasticity of the CFD model. Transient analysis is faced using a time marching solution by updating the shape of the mesh at each time step (weak coupling, evaluated as single DOF systems and integrating modal forces over the CFD grid). Numerical performances and solution accuracy of this approach are analyzed on a practical application (NACA0009 Hydrofoil) for which experimental data are available. A comparison between proposed method and experiment is provided. Transient coupled solver is used for the computation of eigenvalues in water by post processing the free vibration response in calm fluid

    QT Variability and Other Electrocardiographic Predictors of Sudden Cardiac Death

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    This thesis investigates sudden cardiac death, focusing of QT variability, heart-rate variability and other electrocardiographic markers. Topics include: - Normal values for heart-rate variability - Normal values for QT variability - The association of QT variability with sudden cardiac death - The association of QT variability with Heart Failure - The association of thyroid function and Sudden cardiac death - The association of thyroid function with QT variability - The association of COPD with sudden cardiac deat

    Pharmacogenetics of Drug-Induced QT Interval Prolongation: An Update

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    A prolonged QT interval is an important risk factor for ventricular arrhythmias and sudden cardiac death. QT prolongation can be caused by drugs. There are multiple risk factors for drug-induced QT prolongation, including genetic variation. QT prolongation is one of the most common reasons for withdrawal of

    Inactive and sedentary lifestyles amongst ambulatory adolescents and young adults with cerebral palsy

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    Background: To assess physical behaviour, including physical activity and sedentary behaviour, of ambulatory adolescents and young adults with cerebral palsy (CP). We compared participant physical behaviour to that of able-bodied persons and assessed differences related to Gross Motor Functioning Classification System (GMFCS) level and CP distribution (unilateral/bilateral). Methods. In 48 ambulatory persons aged 16 to 24 years with spastic CP and in 32 able-bodied controls, physical behaviour was objectively determined with an accelerometer-based activity monitor. Total duration, intensity and type of physical activity were assessed and sedentary time was determined (lying and sitting). Furthermore, distribution of walking bouts and sitting bouts was specified. Results: Adolescents and young adults with CP spent 8.6% of 24 hours physically active and 79.5% sedentary, corresponding with respectively 123 minutes and 1147 minutes per 24 hours. Compared to able-bodie

    Properties of Interfaces in the two and three dimensional Ising Model

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    To investigate order-order interfaces, we perform multimagnetical Monte Carlo simulations of the 2D2D and 3D3D Ising model. Following Binder we extract the interfacial free energy from the infinite volume limit of the magnetic probability density. Stringent tests of the numerical methods are performed by reproducing with high precision exact 2D2D results. In the physically more interesting 3D3D case we estimate the amplitude F0sF^s_0 of the critical interfacial tension Fs=F0stμF^s = F^s_0 t^\mu to be F0s=1.52±0.05F^s_0 = 1.52 \pm 0.05. This result is in good agreement with a previous MC calculation by Mon, as well as with experimental results for related amplitude ratios. In addition, we study in some details the shape of the magnetic probability density for temperatures below the Curie point.Comment: 25 pages; sorry no figures include
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