LES ÉLÉMENTS SUPERLOURDS

L'état actuel de la recherche des éléments superlourds est présenté. Après un bref rappel des prévisions théoriques concernant leur stabilité les problèmes rencontrés pour réaliser leur synthèse en laboratoire, et les espoirs que font naître les futurs accélérateurs d'ions lourds sont exposés. Les contraintes imposées à la fois par la physique nucléaire et l'astrophysique à leur existence dans la nature sont évoquées, et les techniques très sensibles mises au point au cours des 2 dernières années pour leur détection sont décrites. Les résultats négatifs obtenus jusqu'à maintenant ne paraissent néanmoins pas définitifs

Elaboration of complex shapes by spark plasma sintering

Spark Plasma Sintering (SPS) is an efficient powder consolidation technique that allows the production of fully dense materials with a controlled microstructure. Recently a milestone has been reached by C. Manière et al. [1] on the elaboration of parts with complex shapes using SPS. This method is based on a mobile interface placed between the powder to be sintered and a sacrificial porous material, which defines a pre-form of the part to be obtained. The mobile interface enables an easy separation of the dense part and the sacrificial material after the sintering cycle. In order to industrialize this process a thorough investigation of the sintering mechanisms and the mechanical interactions between the two materials is needed. Numerical simulation is an efficient tool to address these new challenges and allows a better understanding of the process. A fully coupled thermo-electrical and mechanical simulation of the sintering of a complex shape was developed in order to obtain a dense and near-net shape object by SPS. The model was done by finite element analysis in parallel with experimental testing to ensure the validity of the predicted results. Numerical simulation can also be used as a predictive tool in order to anticipate issues like the apparition of hot spots or local concentration of mechanical stress during SPS. [1] : C. Manière et al. / Powder Technology 320 (2017) 340–34

Posibilidades de clusterización y desconcentración de la industria de las TIC en Uruguay.

El objetivo de esta tesis fue aportar datos y elementos de análisis acerca de las posibilidades de clusterización que tienen las empresas del área de las TIC en las ciudades del interior de Uruguay, así como encontrar herramientas que permitan un análisis de los posibles emplazamientos en el territorio. La metodología de esta tesis, desde el punto de vista de su aplicación, fue de investigación aplicada ya que se centró en un problema concreto de la realidad con resultados enfocados al entendimiento del problema y las discusión de posibles soluciones, con un enfoque fundamentalmente cualitativo. Desde el punto de vista de sus objetivos, esta tesis fue principalmente descriptiva pero con un componente innovador desde el punto de vista exploratorio. Para lograr lo propuesto se llevó a cabo un relevamiento bibliográfico, se realizaron entrevistas con informantes calificados y se desarrollaron variantes de un índice para identificar los emplazamientos de clústers más promisorios. En el trabajo se describieron los factores necesarios para desarrollar un clúster exitoso, se presentaron ejemplos de clústers y trabajos relacionados, así como aspectos de la realidad uruguaya de la industria de las TIC. Como resultado de la investigación quedaron identificados las siguientes variables relevantes para la confección de un índice de emplazamientos para clústers: formación terciaria específica, nivel socioeconómico de la región, existencia de zonas francas y distancia a la capital. Se identificaron las ciudades de Maldonado, San Carlos y Rivera como ciudades con ventajas para la instalación de clústers. Por último, se hicieron recomendaciones para desarrollar la estrategia de clusterización y los aspectos asociados

The y activity from 11Li beta decay

The energies and absolute intensities of the γ-rays from the β-decay of 11Li are measured. There is no sizable β branch to the 11Be ground state. Only (5.2 ± 1.4) % of the β-decay strength does not lead to β-delayed particle emission. New β-delayed neutron branches to excited states of 10Be are observed and the total delayed neutron emission probability is deduced

Fully coupled electrothermal and mechanical simulation of the production of complex shapes by spark plasma sintering

The obtention of an accurate mechanical model of the spark plasma sintering (SPS) requires the identification of creep parameters. Those parameters are usually determined experimentally, which involves several tests and could be a source of error for the model predictions. A numerical identification, based on only one SPS experiment per material, allowed the determination of the creep parameters of Al2O3 and TiAl samples. The resulting mechanical model was then coupled with an electro-thermal model of the system to obtain a fully coupled simulation of the SPS. This model can predict the densification behavior not only of simple pellets, but also of complex shape configurations. It accurately predicts the density gradients inside the complex sintered parts as well as the interface distortion during sintering. Thus, numerical simulation can be used as an efficient predictive tool to obtain fully dense objects with the desired geometry

Helium Clustering in Neutron-Rich Be Isotopes

Measurements of the helium-cluster breakup and neutron removal cross sections for neutron-rich Be isotopes A=10-12,14 are presented. These have been studied in the 30 to 42 MeV/u energy range where reaction measurements are proposed to be sensitive to the cluster content of the ground-state wave-function. These measurements provide a comprehensive survey of the decay processes of the Be isotopes by which the valence neutrons are removed revealing the underlying alpha-alpha core-cluster structure. The measurements indicate that clustering in the Be isotopes remains important up to the drip-line nucleus 14^Be and that the dominant helium-cluster structure in the neutron-rich Be isotopes corresponds to alpha-Xn-alpha.Comment: 5 pages, 2 tables and 3 figure

Mechanical design report of the barrel liquid argon presampler

The note describes the mechanical design of the Atlas barrel presampler and its evolution since the publication of thecalorimeter TDR in December 9

Atomic mass measurements of short-lived nuclides around the doubly-magic 208Pb

Accurate atomic mass measurements of neutron-deficient and neutron-rich nuclides around the doubly-magic 208Pb and of neutron-rich cesium isotopes were performed with the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The masses of 145,147Cs, 181,183Tl, 186Tlm, 187Tl, 196Tlm, 205Tl, 197Pbm, 208Pb, 190 to 197Bi, 209,215,216Bi, 203,205,229Fr, and 214,229,230Ra were determined. The obtained relative mass uncertainty in the range of $2 \cdot 10^{-7}$ to $2 \cdot 10^{-8}$ is not only required for safe identification of isomeric states but also allows mapping the detailed structure of the mass surface. A mass adjustment procedure was carried out and the results included into the Atomic Mass Evaluation. The resulting separation energies are discussed and the mass spectrometric and laser spectroscopic data are examined for possible correlations.Comment: 40 pages, 20 figures, accept. for publication in Nucl. Phys.

Synthesis, characterisation and study of magnetocaloric effects (enhanced and reduced) in manganate perovskites

The effect of the A-site dopant ionic radii on the observed magnetocaloric effect (MCE) exhibited by three different families of manganese-based perovskites was investigated using both induction heating and SQUID magnetometry measurements. The doped perovskites La1-xSrxMnO3 (LSMO), La1-xCaxMnO3 (LCMO), and La1-xBaxMnO3 (LBMO) (x = 0.25, 0.35, 0.4) were prepared using a modified peroxide sol-gel synthesis. This method has not been previously used for the synthesis of LCMO or LBMO. Structural characterisation of the agglomerates of magnetic nanoparticles (MNP) for each material was carried out using SEM, XRD and IR spectroscopy. Magnetic heating was observed for materials with larger A-site dopant radii relative to La3+; LSMO40 and LBMO40, with average SARs obtained of 51.5 Wg-1Mn and 33.8 Wg-1Mn respectively. However, reduced magnetic heating effects were observed for smaller A-site dopant radii relative to La3+ (LCMO). In fact, the calculated Specific Absorption Rate for LCMO40 of 14.72 Wg-1Mn is half that of the blank