Search results for " shell"
showing 7 items of 307 documents
Raman Investigations to Identify Corallium rubrum in Iron Age Jewelry and Ornaments
2016
International audience; During the Central European Iron Age, more specifically between 600 and 100 BC, red precious corals (Corallium rubrum) became very popular in many regions, often associated with the so-called (early) Celts. Red corals are ideally suited to investigate several key questions of Iron Age research, like trade patterns or social and economic structures. While it is fairly easy to distinguish modern C. rubrum from bone, ivory or shells, archaeologists are confronted with ancient, hence altered, artifacts. Due to ageing processes, archaeological corals lose their intensive red color and shiny surface and can easily be confused with these other light colored materials. We pr…
Testing refined shell-model interactions in the sd shell: Coulomb excitation of 26Na
2015
Background: Shell-model calculations crucially depend on the residual interaction used to approximate the nucleon-nucleon interaction. Recent improvements to the empirical universal sd interaction (USD) describing nuclei within the sd shell yielded two new interactions—USDA and USDB—causing changes in the theoretical description of these nuclei. Purpose: Transitionmatrix elements between excited states provide an excellent probe to examine the underlying shell structure. These observables provide a stringent test for the newly derived interactions. The nucleus 26Na with 7 valence neutrons and 3 valence protons outside the doubly-magic 16O core is used as a test case. Method: A radioactive b…
Shell-model computed cross sections for charged-current scattering of astrophysical neutrinos off 40Ar
2018
Charged-current (anti)neutrino-$^{40}\mathrm{Ar}$ cross sections for astrophysical neutrinos have been calculated. The initial and final nuclear states were calculated using the nuclear shell model. The folded solar-neutrino scattering cross section was found to be $1.78(23)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}42}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}$, which is higher than what the previous papers have reported. The contributions from the ${1}^{\ensuremath{-}}$ and ${2}^{\ensuremath{-}}$ multipoles were found to be significant at supernova-neutrino energies, confirming the random-phase approximation (RPA) result of a previous study. The effects of neutrino flavor conve…
In-gas laser ionization and spectroscopy of actinium isotopes near the N=126 closed shell
2017
The in-gas laser ionization and spectroscopy (IGLIS) techniquewas applied on the $^{212–215}$Ac isotopes, produced at the Leuven Isotope Separator On-Line (LISOL) facility by using the in-gas-cell and the in-gas-jet methods. The first application under on-line conditions of the in-gas-jet laser spectroscopy method showed a superior performance in terms of selectivity, spectral resolution, and efficiency in comparison with the in-gas-cell method. Following the analysis of both experiments, the magnetic-dipole moments for the $^{212–215}$Ac isotopes, electric-quadrupole moments and nuclear spins for the $^{214,215}$Ac isotopes are presented and discussed. A good agreement is obtained with lar…
gA-driven shapes of electron spectra of forbidden β decays in the nuclear shell model
2017
The evolution of the shape of the electron spectra of 16 forbidden β− decays as a function of gA was studied using the nuclear shell model in appropriate single-particle model spaces with established, well-tested nuclear Hamiltonians. The β spectra of 94Nb(6+)→94Mo(4+) and 98Tc(6+)→98Ru(4+) were found to depend strongly on gA, which makes them excellent candidates for the determination of the effective value of gA with the spectrum-shape method (SSM). A strong gA dependence is also seen in the spectrum of 96Zr(0+)→96Nb(6+). This decay could be used for determining the quenching of gA in sixth-forbidden decays in the future, when the measurement of the spectrum becomes experimentally feasibl…
Multi-scale modelling of heterogeneous shell structures
2011
International audience; This paper reviews multi-scale computational homogenisation frameworks for the non-linear behaviour of heterogeneous thin planar shells. Based on a review of some of the currently available methods, a computational homogenisation scheme for shells is applied on to representative volume elements for plain weave composites. The effect of flexural loading on the potential failure modes of such materials is analysed, focusing on the reinforcement-matrix delamination mechanism. The attention is next shifted toward failure localisation in masonry unit cells. Subsequently, a recently developed computational FE2 solution scheme accounting for damage localisation at structura…
Variation in Sr uptake in the shell of the freshwater gastropod Bithynia tentaculata from Lake Arreo (northern Spain) and culture experiments
2010
The Sr uptake features in Bithynia tentaculata aragonite shells from monthly collections in Lake Arreo (northern Spain) over a two-year period are compared with those from the same species grown in culture experiments with similar waters under controlled temperature. The shell aragonite of B. tentaculata from Lake Arreo formed in isotopic equilibrium with the lake water. A comparison of the stable oxygen isotope values (δ18O) from the shells and waters allowed the selection of suitable shells for Sr uptake studies. The Sr/Ca molar ratio in B. tentaculata shells (Sr/Cashell) from the lake and from the culture experiments positively correlate with some chemical parameters like conductivity an…