2,124 research outputs found
Tidal wave in 102Pd: Rotating condensate of up to seven d-bosons
The yrast states of even even vibrational and transitional nuclei are inter-
preted as a rotating condensate of interacting d-bosons and the corresponding
semi-classical tidal wave concept. A simple experimental manifestation of the
anharmonicity caused by the boson interaction is found. The interpretation is
substantiated by calculations based on the Collective Model and the Cranking
Model.Comment: Proceedings of CGS1
Equilibrium properties of the lattice system with SALR interaction potential on a square lattice: quasi-chemical approximation versus Monte Carlo simulation
The lattice system with competing interactions that models biological objects
(colloids, ensembles of protein molecules, etc.) is considered. This system is
the lattice fluid on a square lattice with attractive interaction between
nearest neighbours and repulsive interaction between next-next-nearest
neighbours. The geometric order parameter is introduced for describing the
ordered phases in this system. The critical value of the order parameter is
estimated and the phase diagram of the system is constructed. The simple
quasi-chemical approximation (QChA) is proposed for the system under
consideration. The data of Monte Carlo simulation of equilibrium properties of
the model are compared with the results of QChA. It is shown that QChA provides
reasonable semiquantitative results for the systems studied and can be used as
the basis for next order approximations.Comment: 10 pages, 8 figure
Spontaneous polarisation of the neutral interface for valence asymmetric coulombic systems
In this paper, we discuss the phenomenon of a spontaneous polarisation of a
neutral hard planar interface for valence asymmetric coulombic systems. Within
a field theoretical description, we account for the existence of non trivial
charge density and electric potential profiles. The analysis of the phenomenon
shows that the effect is related to combinatorics in relation with the
existence of the two independent species cations and anions. This simple and
basic feature is related to the quantum mechanical properties of the system.
The theoretical results are compared with numerical simulations data and are
shown to be in very good agreement, which a fortiori justifies our physical
interpretation.Comment: 12 pages, 11 figure
Assessment of poststress left ventricular ejection fraction by gated SPECT: comparison with equilibrium radionuclide angiocardiography
PURPOSE: We compared left ventricular (LV) ejection fraction obtained by gated SPECT with that obtained by equilibrium radionuclide angiocardiography in a large cohort of patients.
METHODS: Within 1 week, 514 subjects with suspected or known coronary artery disease underwent same-day stress-rest (99m)Tc-sestamibi gated SPECT and radionuclide angiocardiography. For both studies, data were acquired 30 min after completion of exercise and after 3 h rest.
RESULTS: In the overall study population, a good correlation between ejection fraction measured by gated SPECT and by radionuclide angiocardiography was observed at rest (r=0.82, p<0.0001) and after stress (r=0.83, p<0.0001). In Bland-Altman analysis, the mean differences in ejection fraction (radionuclide angiocardiography minus gated SPECT) were -0.6% at rest and 1.7% after stress. In subjects with normal perfusion (n=362), a good correlation between ejection fraction measured by gated SPECT and by radionuclide angiocardiography was observed at rest (r=0.72, p<0.0001) and after stress (r=0.70, p<0.0001) and the mean differences in ejection fraction were -0.9% at rest and 1.4% after stress. Also in patients with abnormal perfusion (n=152), a good correlation between the two techniques was observed both at rest (r=0.89, p<0.0001) and after stress (r=0.90, p<0.0001) and the mean differences in ejection fraction were 0.1% at rest and 2.5% after stress.
CONCLUSION: In a large study population, a good agreement was observed in the evaluation of LV ejection fraction between gated SPECT and radionuclide angiocardiography. However, in patients with perfusion abnormalities, a slight underestimation in poststress LV ejection fraction was observed using gated SPECT as compared to equilibrium radionuclide angiocardiography
A formally exact field theory for classical systems at equilibrium
We propose a formally exact statistical field theory for describing classical
fluids with ingredients similar to those introduced in quantum field theory. We
consider the following essential and related problems : i) how to find the
correct field functional (Hamiltonian) which determines the partition function,
ii) how to introduce in a field theory the equivalent of the indiscernibility
of particles, iii) how to test the validity of this approach. We can use a
simple Hamiltonian in which a local functional transposes, in terms of fields,
the equivalent of the indiscernibility of particles. The diagrammatic expansion
and the renormalization of this term is presented. This corresponds to a non
standard problem in Feynman expansion and requires a careful investigation.
Then a non-local term associated with an interaction pair potential is
introduced in the Hamiltonian. It has been shown that there exists a mapping
between this approach and the standard statistical mechanics given in terms of
Mayer function expansion. We show on three properties (the chemical potential,
the so-called contact theorem and the interfacial properties) that in the field
theory the correlations are shifted on non usual quantities. Some perspectives
of the theory are given.Comment: 20 pages, 8 figure
First order shape transition and critical point nuclei in Sm isotopes from relativistic mean field approach
The critical point nuclei in Sm isotopes, which marks the first order phase
transition between spherical U(5) and axially deformed shapes SU(3), have been
investigated in the microscopic quadrupole constrained relativistic mean field
(RMF) model plus BCS method with all the most used interactions, i.e., NL1,
NL3, NLSH and TM1. The calculated potential energy surfaces show a clear shape
transition for the even-even Sm isotopes with and the critical
point nuclei are found to be Sm, Sm and Sm. Similar
conclusions can also be drawn from the microscopic neutron and proton single
particle spectra.Comment: 6 figure
Consequences of wall stiffness for a beta-soft potential
Modifications of the infinite square well E(5) and X(5) descriptions of
transitional nuclear structure are considered. The eigenproblem for a potential
with linear sloped walls is solved. The consequences of the introduction of
sloped walls and of a quadratic transition operator are investigated.Comment: RevTeX 4, 8 pages, as published in Phys. Rev.
Dynamic pulse buckling of composite stanchions in the sub-cargo floor area of a civil regional aircraft
This work is focused on the investigation of the structural behavior of a composite floor beam, located in the cargo zone of a civil aircraft, subjected to cyclical low-frequency compressive loads with different amplitudes. In the first stage, the numerical models able to correctly simulate the investigated phenomenon have been defined. Different analyses have been performed, aimed to an exhaustive evaluation of the structural behavior of the test article. In particular, implicit and explicit analyses have been considered to preliminary assess the capabilities of the numerical model. Then, explicit non-linear analyses under time-dependent loads have been considered, to predict the behavior of the composite structure under cyclic loading conditions. According to the present investigation, low-frequency cyclic loads with peak values lower than the static buckling load value are not capable of triggering significant instability
A sensitivity analysis of the damage behavior of a leading-edge subject to bird strike
This paper aims to investigate the crashworthiness capability of a commercial aircraft metallic sandwich leading edge, subjected to bird strike events. A sensitivity analysis is presented, aimed to assess the influence of the skin parameters (inner and outer faces and core thicknesses) on the leading-edge crashworthiness and to determine, among the configurations able to withstand a bird strike event, the best compromise in terms of weight and structural performances. In order to easily manage the design parameters and the output data, the ModeFrontier code was used in conjunction with the FE code Abaqus/Explicit. A dedicated python routine was developed to define a fully parametric simplified leading-edge model. To fulfill the aerodynamic requirements, the external surfaces were considered fixed during the sensitivity analysis, and, thus, only the internal leading edge’s components were modified to study their influence on the structural response. The total mass of the model, the maximum deformation and the energy dissipated due to material failure and the plastic deformations were monitored and used to compare and assess the behavior of each configuration
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