1,417 research outputs found

    Nuclear binding energies: Global collective structure and local shell-model correlations

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    Nuclear binding energies and two-neutron separation energies are analyzed starting from the liquid-drop model and the nuclear shell model in order to describe the global trends of the above observables. We subsequently concentrate on the Interacting Boson Model (IBM) and discuss a new method in order to provide a consistent description of both, ground-state and excited-state properties. We address the artefacts that appear when crossing mid-shell using the IBM formulation and perform detailed numerical calculations for nuclei situated in the 50-82 shell. We also concentrate on local deviations from the above global trends in binding energy and two-neutron separation energies that appear in the neutron-deficient Pb region. We address possible effects on the binding energy, caused by mixing of low-lying 0+0^{+} intruder states into the ground state, using configuration mixing in the IBM framework. We also study ground-state properties using a deformed mean-field approach. Detailed comparisons with recent experimental data in the Pb region are amply discussed.Comment: 69 pages, TeX (ReVTeX). 23 eps figures. 1 table. Modified version. Accepted in Nucl. Phys.

    Multiple bounded variation solutions for a prescribed mean curvature equation with Neumann boundary conditions

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    We prove the existence of multiple positive BV-solutions of the Neumann problem \begin{cases} \displaystyle -\left(\frac{u'}{\sqrt{1+u'^2}}\right)'=a(x)f(u)\quad&\mbox{in }(0,1), u'(0)=u'(1)=0,& {cases} where a(x)>0a(x) > 0 and ff belongs to a class of nonlinear functions whose prototype example is given by f(u)=−λu+upf(u) = -\lambda u + u^p, for λ>0\lambda > 0 and p>1p > 1. In particular, f(0)=0f(0)=0 and ff has a unique positive zero, denoted by u0u_0. Solutions are distinguished by the number of intersections (in a generalized sense) with the constant solution u=u0u = u_0. We further prove that the solutions found have continuous energy and we also give sufficient conditions on the nonlinearity to get classical solutions. The analysis is performed using an approximation of the mean curvature operator and the shooting method.Comment: 28 pages, 1 figur

    Fear of exercise and health-related quality of life in patients with an implantable cardioverter defibrillator

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    Several studies have reported improved survival rates thanks to the use of an implantable cardioverter defibrillator (ICD) in the treatment of patients with life-threatening arrhythmia. However, the effects of the ICD on health-related quality of life (HR-QoL) of these patients are not clear. The aim of this study is to describe HR-QoL and fear of exercise in ICD patients. Eighty-nine ICD patients from the University Hospital in Groningen, the Netherlands, participated in this study. HR-QoL was measured using the Rand-36 and the Quality of Life After Myocardial Infarction Dutch language version questionnaires. Fear of exercise was measured using the Tampa Scale for Kinesiophobia, Dutch version and the Fear Avoidance Beliefs Questionnaire, Dutch version. Association between outcome variables was analysed by linear regression analyses. Study results show that the HR-QoL of patients with ICDs in our study population is significantly worse than that of normal healthy people. Furthermore, fear of exercise is negatively associated with HR-QoL corrected for sex, age and number of years living with an ICD. After implantation of the ICD, patients with a clear fear of exercise should be identified and interventions should be considered in order to increase their HR-QoL

    SU(4) symmetry in the extended proton-neutron interacting boson model: multiplets and symmetry breaking

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    The manifestation of SU(4)SU(4) symmetry within an interacting boson model including particle-like and hole-like π\pi- and Îœ\nu-bosons is shown for light nuclei around the Z=N=8 shell. We also present a consistent description of the particle-hole (intruder spin or II spin) multiplets in the Extended Interacting Boson Model (EIBM) and of π\pi-Îœ\nu (FF spin) multiplets in the IBM-2 as a breaking of this SU(4)SU(4) symmetry

    New particle-hole symmetries and the extended interacting boson model

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    We describe shape coexistence and intruder many-particle-hole (mp-nh)excitations in the extended interacting boson model EIBM and EIBM-2,combining both the particle-hole and the charge degree of freedom.Besides the concept of I-spin multiplets and subsequently SU(4)SU(4) multiplets, we touch upon the existence of particle-hole mixed symmetry states. We furthermore describe regular and intrudermany-particle-hole excitations in one nucleus on an equal footing, creating (annihilating) particle-hole pairs using the K-spin operatorand studying possible mixing between these states. As a limiting case,we treat the coupling of two IBM-1 Hamiltonians, each decribing the regular and intruder excitations respectively, in particular lookingat the U(5)U(5)-SU(3)SU(3) dynamical symmetry coupling. We apply such coupling scheme to the Po isotopes

    The Responses of the University of Iowa Charged Particle Detectors on Explorer 12 Graphic Summary

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    Graphs of charged particle detectors responses on Explorer XII satellit

    Shape coexistence in atomic nuclei and its spectroscopic fingerprints

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    In the present discussion we concentrate on shape coexistence asobtained within a deformed single-particle field as well as startingfrom the spherical shell-model, incorporating deformationeffects via the residual proton-neutron quadrupole interaction. Wediscuss in particular the appearance of shape coexisting phenomena inthe Pb region. In a second part then, we present a number ofexperimental fingerprints that allow to recognize the appearance ofshape coexisting phenomena or of shape mixing through the use ofselective experiments (e.g. band structure, spectroscopic factors,static moments, E0 properties and alpha-decay)

    Electric monopole transitions from low energy excitations in nuclei

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    Electric monopole (E0) properties are studied across the entire nuclear mass surface. Besides an introductory discussion of various model results (shell model, geometric vibrational and rotational models, algebraic models), we point out that many of the largest E0 transition strengths, ρ2\rho^2(E0), are associated with shape mixing. We discuss in detail the manifestation of E0 transitions and present extensive data for~: single-closed shell nuclei, vibrational nuclei, well-deformed nuclei, nuclei that exhibit sudden ground-state changes, and nuclei that exhibit shape coexistence and intruder states. We also give attention to light nuclei, odd-A nuclei, and illustrate a suggested relation between ρ2\rho^2(E0) and isotopic shifts
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