72 research outputs found

    Relativistic effects and quasipotential equations

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    We compare the scattering amplitude resulting from the several quasipotential equations for scalar particles. We consider the Blankenbecler-Sugar, Spectator, Thompson, Erkelenz-Holinde and Equal-Time equations, which were solved numerically without decomposition into partial waves. We analyze both negative-energy state components of the propagators and retardation effects. We found that the scattering solutions of the Spectator and the Equal-Time equations are very close to the nonrelativistic solution even at high energies. The overall relativistic effect increases with the energy. The width of the band for the relative uncertainty in the real part of the scattering TT matrix, due to different dynamical equations, is largest for backward-scattering angles where it can be as large as 40%.Comment: Accepted for publication in Phys. Rev.

    Postponing surgery to optimise patients with acute right-sided obstructing colon cancer - A pilot study

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    Background: Right-sided obstructing colon cancer is most often treated with acute resection. Recent studies on right-sided obstructing colon cancer report higher mortality and morbidity rates than those in patients without obstruction. The aim of this study is to retrospectively analyse whether it is possible to optimise the health condition of patients with acute right-sided obstructing colon cancer, prior to surgery, and whether this improves postoperative outcomes. Method: All consecutive patients with high suspicion of, or histologically proven, right-sided obstructing colon cancer, treated with curative intent between March 2013 and December 2019, were analysed retrospectively. Patients were divided into two groups: optimised group and non-optimised group. Pre-operative optimisation included additional nutrition, physiotherapy, and, if needed, bowel decompression. Results: In total, 54 patients were analysed in this study. Twenty-four patients received optimisation before elective surgery, and thirty patients received emergency surgery, without optimisation. Scheduled surgery was performed after a median of eight days (IQR 7–12). Postoperative complications were found in twelve (50%) patients in the optimised group, compared to twenty-three (77%) patients in the non-optimised group (p = 0.051). Major complications were diagnosed in three (13%) patients with optimisation, compared to ten (33%) patients without optimisation (p = 0.111). Postoperative in-hospital stay, 30-day mortality, as well as primary anastomosis were comparable in both groups. Conclusion: This pilot study suggests that pre-operative optimisation of patients with obstructing right sided colonic cancer may be feasible and safe but is associated with longer in-patient stay.</p

    K* nucleon hyperon form factors and nucleon strangeness

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    A crucial input for recent meson hyperon cloud model estimates of the nucleon matrix element of the strangeness current are the nucleon-hyperon-K* (NYK*) form factors which regularize some of the arising loops. Prompted by new and forthcoming information on these form factors from hyperon-nucleon potential models, we analyze the dependence of the loop model results for the strange-quark observables on the NYK* form factors and couplings. We find, in particular, that the now generally favored soft N-Lambda-K* form factors can reduce the magnitude of the K* contributions in such models by more than an order of magnitude, compared to previous results with hard form factors. We also discuss some general implications of our results for hadronic loop models.Comment: 9 pages, 8 figures, new co-author, discussion extended to the momentum dependence of the strange vector form factor

    Disentangling the effect of illness perceptions on health status in people with type 2 diabetes after an acute coronary event

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    Public Health and primary carePrevention, Population and Disease management (PrePoD

    A low-lying scalar meson nonet in a unitarized meson model

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    A unitarized nonrelativistic meson model which is successful for the description of the heavy and light vector and pseudoscalar mesons yields, in its extension to the scalar mesons but for the same model parameters, a complete nonet below 1 GeV. In the unitarization scheme, real and virtual meson-meson decay channels are coupled to the quark-antiquark confinement channels. The flavor-dependent harmonic-oscillator confining potential itself has bound states epsilon(1.3 GeV), S(1.5 GeV), delta(1.3 GeV), kappa(1.4 GeV), similar to the results of other bound-state qqbar models. However, the full coupled-channel equations show poles at epsilon(0.5 GeV), S(0.99 GeV), delta(0.97 GeV), kappa(0.73 GeV). Not only can these pole positions be calculated in our model, but also cross sections and phase shifts in the meson-scattering channels, which are in reasonable agreement with the available data for pion-pion, eta-pion and Kaon-pion in S-wave scattering.Comment: A slightly revised version of Zeitschrift fuer Physik C30, 615 (1986

    Hyperon-nucleon scattering and hyperon masses in the nuclear medium

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    We analyze low-energy hyperon-nucleon scattering using an effective field theory in next-to-leading order. By fitting experimental cross sections for laboratory hyperon momenta below 200 MeV/c and using information from the hypertriton we determine twelve contact-interaction coefficients. Based on these we discuss the low-density expansion of hyperon mass shifts in the nuclear medium.Comment: 10 pages, 2 figure

    The hyperon-nucleon interaction: conventional versus effective field theory approach

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    Hyperon-nucleon interactions are presented that are derived either in the conventional meson-exchange picture or within leading order chiral effective field theory. The chiral potential consists of one-pseudoscalar-meson exchanges and non-derivative four-baryon contact terms. With regard to meson-exchange hyperon-nucleon models we focus on the new potential of the Juelich group, whose most salient feature is that the contributions in the scalar--isoscalar (\sigma) and vector--isovector (\rho) exchange channels are constrained by a microscopic model of correlated \pi\pi and KKbar exchange.Comment: 28 pages, 8 figures, submitted to Lecture Notes in Physic
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