2,807 research outputs found

    Identification of viable myocardium in patients with chronic coronary artery disease and left ventricular dysfunction: role of MRI.

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    Nineteen patients (16 men and 3 women, mean age 51 years) with previous anterior myocardial infarction and severe stenosis (> or = 90%) of the left anterior descending coronary artery were studied by magnetic resonance imaging (MRI) without and with contrast media to verify the capability of MRI in identifying viable myocardium in areas of severe systolic dysfunction. In corresponding left ventricular segments, a comparison was made between regional signal intensities (SI) determined on MRI images before and 4, 8, 12, and 30 minutes after administration of paramagnetic contrast media (gadolinium diethylenetriaminepentaacetic acid, 0.4 mmol/kg intravenously) and metabolic parameters determined by iodine 123 phenylpentadecanoic acid (IPPA) scintigraphy. The SI and the time of maximum postcontrast enhancement were analyzed by dividing the left ventricle into 11 segments. Each segment was classified as normal (group 1, n = 116), hibernating (group 2, n = 50), or necrotic (group 3, n = 43) on the basis of the IPPA washout rate (> 30%, 10% to 30%, and < 10%, respectively). Regional SI demonstrated significant differences in absolute values at 12 minutes (group 3: 1.62 +/- 0.58 vs group 1: 1.32 +/- 0.52, p < 0.01, and vs group 2: 1.34 +/- 0.48, p < 0.05) and at 30 minutes (group 3: 1.71 +/- 0.47 vs group 1: 1.21 +/- 0.55, p < 0.01, and vs group 2: 1.49 +/- 0.57, p < 0.05) and in temporal distribution. These results suggest that MRI has a potential role in differentiating viable from necrotic myocardium in patients with chronic severe systolic dysfunction

    Radiative corrections to polarization observables in elastic electron-deuteron scattering in leptonic variables

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    The model--independent QED radiative corrections to polarization observables in elastic scattering of unpolarized and longitudinally--polarized electron beam by the deuteron target have been calculated in leptonic variables. The experimental setup when the deuteron target is arbitrarily polarized is considered and the procedure for applying derived results to the vector or tensor polarization of the recoil deuteron is discussed. The basis of the calculations consists of the account for all essential Feynman diagrams which results in the form of the Drell-Yan representation for the cross-section and use of the covariant parametrization of the deuteron polarization state. The numerical estimates of the radiative corrections are given for the case when event selection allows the undetected particles (photons and electron-positron pairs) and the restriction on the lost invariant mass is used.Comment: 43 pages,3 figures. To be published in ZhTEF. revised 14.02.2012. arXiv admin note: text overlap with arXiv:nucl-ex/0002003 by other author

    Chiral dynamics of p-wave in K^- p and coupled states

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    We perform an evaluation of the p-wave amplitudes of meson-baryon scattering in the strangeness S=-1 sector starting from the lowest order chiral Lagrangians and introducing explicitly the Sigma^* field with couplings to the meson-baryon states obtained using SU(6) symmetry. The N/D method of unitarization is used, equivalent, in practice, to the use of the Bethe-Salpeter equation with a cut-off. The procedure leaves no freedom for the p-waves once the s-waves are fixed and thus one obtains genuine predictions for the p-wave scattering amplitudes, which are in good agreement with experimental results for differential cross sections, as well as for the width and partial decay widths of the Sigma^*(1385).Comment: LaTeX, 18 pages, 6 figure

    Comparison of Relativistic Nucleon-Nucleon Interactions

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    We investigate the difference between those relativistic models based on interpreting a realistic nucleon-nucleon interaction as a perturbation of the square of a relativistic mass operator and those models that use the method of Kamada and Gl\"ockle to construct an equivalent interaction to add to the relativistic mass operator. Although both models reproduce the phase shifts and binding energy of the corresponding non-relativistic model, they are not scattering equivalent. The example of elastic electron-deuteron scattering in the one-photon-exchange approximation is used to study the sensitivity of three-body observables to these choices. Our conclusion is that the differences in the predictions of the two models can be understood in terms of the different ways in which the relativistic and non-relativistic SS-matrices are related. We argue that the mass squared method is consistent with conventional procedures used to fit the Lorentz-invariant cross section as a function of the laboratory energy.Comment: Revtex 13 pages, 5 figures, corrected some typo

    Performance of the LHCb Vertex Detector Alignment Algorithm determined with Beam Test Data

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    LHCb is the dedicated heavy flavour experiment at the Large Hadron Collider at CERN. The partially assembled silicon vertex locator (VELO) of the LHCb experiment has been tested in a beam test. The data from this beam test have been used to determine the performance of the VELO alignment algorithm. The relative alignment of the two silicon sensors in a module and the relative alignment of the modules has been extracted. This alignment is shown to be accurate at a level of approximately 2 micron and 0.1 mrad for translations and rotations, respectively in the plane of the sensors. A single hit precision at normal track incidence of about 10 micron is obtained for the sensors. The alignment of the system is shown to be stable at better than the 10 micron level under air to vacuum pressure changes and mechanical movements of the assembled system.Comment: accepted for publication in NIM

    Spin-Momentum Correlations in Quasi-Elastic Electron Scattering from Deuterium

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    We report on a measurement of spin-momentum correlations in quasi-elastic scattering of longitudinally polarized electrons with an energy of 720 MeV from vector-polarized deuterium. The spin correlation parameter AedVA^V_{ed} was measured for the 2H⃗(e⃗,eâ€Čp)n^2 \vec{\rm H}(\vec e,e^\prime p)n reaction for missing momenta up to 350 MeV/cc at a four-momentum transfer squared of 0.21 (GeV/c)2^2. The data give detailed information about the spin structure of the deuteron, and are in good agreement with the predictions of microscopic calculations based on realistic nucleon-nucleon potentials and including various spin-dependent reaction mechanism effects. The experiment demonstrates in a most direct manner the effects of the D-state in the deuteron ground-state wave function and shows the importance of isobar configurations for this reaction.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett. for publicatio

    Point-Form Analysis of Elastic Deuteron Form Factors

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    Point-form relativistic quantum mechanics is applied to elastic electron-deuteron scattering. The deuteron is modeled using relativistic interactions that are scattering-equivalent to the nonrelativistic Argonne v18v_{18} and Reid '93 interactions. A point-form spectator approximation (PFSA) is introduced to define a conserved covariant current in terms of single-nucleon form factors. The PFSA is shown to provide an accurate description of data up to momentum transfers of 0.5 GeV2{\rm GeV}^2, but falls below the data at higher momentum transfers. Results are sensitive to the nucleon form factor parameterization chosen, particularly to the neutron electric form factor.Comment: RevTex, 31 pages, 1 table, 13 figure
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