Calculations of giant magnetoresistance in Fe/Cr trilayers using layer potentials determined from {\it ab-initio} methods

The ab initio full-potential linearized augmented plane-wave method explicitly designed for the slab geometry was employed to elucidate the physical origin of the layer potentials for the trilayers nFe/3Cr/nFe(001), where n is the number of Fe monolayers. The thickness of the transition-metal ferromagnet has been ranged from $n=1$ up to n=8 while the spacer thickness was fixed to 3 monolayers. The calculated potentials were inserted in the Fuchs-Sondheimer formalism in order to calculate the giant magnetoresistance (GMR) ratio. The predicted GMR ratio was compared with the experiment and the oscillatory behavior of the GMR as a function of the ferromagnetic layer thickness was discussed in the context of the layer potentials. The reported results confirm that the interface monolayers play a dominant role in the intrinsic GMR.Comment: 17 pages, 7 figures, 3 tables. accepted in J. Phys.: Cond. Matte

Selfconsistent calculations of fission barriers in the Fm region

The fission barriers of the nuclei 254Fm, 256Fm, 258Fm, 258No and 260Rf are investigated in a fully microscopic way up to the scission point. The analysis is based on the constrained Hartree-Fock-Bogoliubov theory and Gogny's D1S force. The quadrupole, octupole and hexadecapole moments as well as the number of nucleons in the neck region are used as constraints. Two fission paths, corresponding to the bimodal fission, are found. The decrease with isotope mass of the half-life times of heavy Fm isotopes is also explained.Comment: 29 pages in LaTeX including 14 figure

Portage rhinopharyngé de Streptococcus pneumoniae chez les enfants

Le rhinopharynx de l'enfant a une flore bactérienne résidante. C'est un écosystème complexe, comportant de nombreuses espèces bactériennes qui, d'une part, protègent en partie contre l'implantation de bactéries étrangères, et d'autre part, constituent le réservoir des bactéries impliquées dans les principales infections respiratoires, notamment les otites moyennes aiguës (OMA), et d’infections graves comme les bactériémies et les méningites. La majorité des enfants sont porteurs de Streptococcus pneumoniae à un moment ou autre de leur vie, mais ce dernier est plus important à l’âge préscolaire. L’objectif de ce travail est de faire la mise au point concernant S. pneumoniae à savoir le portage rhinopharyngé chez les enfants âgés de moins de deux ans, la prévalence, les facteurs de risque et l’impact du vaccin conjugué anti-pneumococcique sur l’incidence des infections invasives et sur la transmission et la dissémination des souches résistantes.Mots clés: Streptococcus pneumoniae, portage, résistance, vaccin anti-pneumococciqu

The pygmy dipole strength, the neutron radius of 208{}^{208}Pb and the symmetry energy

The accurate characterization of the nuclear symmetry energy and its density dependence is one of the outstanding open problems in nuclear physics. A promising nuclear observable in order to constrain the density dependence of the symmetry energy at saturation is the neutron skin thickness of medium and heavy nuclei. Recently, a low-energy peak in the isovector dipole response of neutron-rich nuclei has been discovered that may be correlated with the neutron skin thickness. The existence of this correlation is currently under debate due to our limited experimental knowledge on the microscopic structure of such a peak. We present a detailed analysis of Skyrme Hartree-Fock (HF) plus random phase approximation (RPA) predictions for the dipole response in several neutron-rich nuclei and try to elucidate whether models of common use in nuclear physics confirm or dismiss its possible connection with the neutron skin thickness. Finally, we briefly present theoretical results for parity violating electron scattering on ${}^{208}$Pb at the conditions of the PREx experiment and discuss the implications for the neutron skin thickness of ${}^{208}$Pb and the slope of the symmetry energy.Comment: Contribution to the 2nd Iberian Nuclear Astrophysics Meeting on Compact Stars proceeding

The Beam Conditions Monitor of the LHCb Experiment

The LHCb experiment at the European Organization for Nuclear Research (CERN) is dedicated to precision measurements of CP violation and rare decays of B hadrons. Its most sensitive components are protected by means of a Beam Conditions Monitor (BCM), based on polycrystalline CVD diamond sensors. Its configuration, operation and decision logics to issue or remove the beam permit signal for the Large Hadron Collider (LHC) are described in this paper.Comment: Index Terms: Accelerator measurement systems, CVD, Diamond, Radiation detector

Study of the neutron skin thickness of 208{}^{208}Pb in mean field models

We study whether the neutron skin thickness $\Delta r_{np}$ of ${}^{208}$Pb originates from the bulk or from the surface of the neutron and proton density distributions in mean field models. We find that the size of the bulk contribution to $\Delta r_{np}$ of ${}^{208}$Pb strongly depends on the slope of the nuclear symmetry energy, while the surface contribution does not. We note that most mean field models predict a neutron density for ${}^{208}$Pb between the halo and skin type limits. We investigate the dependence of parity- violating electron scattering at the kinematics of the PREX experiment on the shape of the nucleon densities predicted by the mean field models for ${}^{208}$Pb. We find an approximate formula for the parity-violating asymmetry in terms of the central radius and the surface diffuseness of the nucleon densities of ${}^{208}$Pb in these models.Comment: 5 pages, 2 figures, proceedings MBC 2011 - Many body correlations from dilute to dense nuclear systems - IHP PARI

Device for electrical stimulation of the vagus nerve

A device for auricular electrical stimulation of the vagus nerve was developed. The advantage of the developed product is the possibility of changing the shape of the stimulation signal, setting the duration of the stimulation session and monitoring the impedance of the load during the stimulation procedure

Nuclear Symmetry Energy: constraints from Giant Quadrupole Resonances and Parity Violating Electron Scattering

Experimental and theoretical efforts are being devoted to the study of observables that can shed light on the properties of the nuclear symmetry energy. We present our new results on the excitation energy [X. Roca-Maza et al., Phys. Rev. C 87, 034301 (2013)] and polarizability of the Isovector Giant Quadrupole Resonance (IVGQR), which has been the object of new experimental investigation [S. S. Henshaw et al., Phys. Rev. Lett. 107, 222501 (2011)]. We also present our theoretical analysis on the parity violating asymmetry at the kinematics of the Lead Radius Experiment [S. Abrahamyan et al. (PREx Collaboration), Phys. Rev. Lett. 108, 112502 (2012)] and highlight its relation with the density dependence of the symmetry energy [X. Roca-Maza et al., Phys. Rev. Lett. 106, 252501 (2011)].Comment: Proceedings - International Nuclear Physics Conference (INPC), Firenze 2 - 7 June 201