Multi-particle emission from 31Ar at IDS

XXXV Bienal de la RSEF, Gijón (España), 13-17 de Julio de 2015; http://bienalrsef-gijon2015.org/web/Acknowledge the support received from the Spanish research council under project FPA2012-32443 and FPI 2013 grant BES-2013-066348.Peer Reviewe

MAGISOL plug-in Set-up Status

Presentación en Power Point de 18 diapositivas; CERN, Meyrin, Suiza, 28-29 April 2014Peer Reviewe

Automated shape optimization using a multigrid method and estimation of distribution algorithms

Topological shape optimization refers to the problem of finding the optimal shape of a mechanical structure by using a process for removing or inserting new holes or parts, it is to say, using a process which produces topological changes.This article introduces a method for automated topological optimization via an Estimation of Distribution Algorithm (EDA) with a suitable representation of the optimization variables. The optimum structure is such with the minimum weight which does not exceed a maximum von Mises stress and displacement. The contributions of this proposal resides in the definition of a candidate solution and the optimization method. The candidate solution representation is independent of the finer discretization used for analyzing candidate structures using the finite element method. Given a domain, which corresponds to the physical space where candidate structures reside, a vector φ=[φ1,φ2,...,φm] is used to define a smooth function φ(x,y) on Ω. If φ(x,y) is less than 0.5, such region does not have material, otherwise, it has.The smooth function φ(x,y) provides the advantage of having continuous regions with or without material while it depends on few optimization parameters φ, in addition, we can define an arbitrary number of parts or gaps as thinner or larger as needed. The EDA benefits from this representation, sampling random arbitrary structures and using probabilistic learning to determine whether a region must have material. The EDA is a global optimizer which can propose different topologies without the need of a priori knowledge neither initial solutions. In addition it uses a probabilistic model which smoothly evolve through generations. In consequence, at the beginning of the optimization process it arbitrarily proposes topologically different structures, while at the convergence phase it performs similar to a local search algorithm. The EDA uses few parameters which can be set in a straight forward manner. We report several study cases from the specialized literature, showing that our proposal outperforms reported results from up-to-date well performed algorithms

The anisotropy of granular materials

The effect of the anisotropy on the elastoplastic response of two dimensional packed samples of polygons is investigated here, using molecular dynamics simulation. We show a correlation between fabric coefficients, characterizing the anisotropy of the granular skeleton, and the anisotropy of the elastic response. We also study the anisotropy induced by shearing on the subnetwork of the sliding contacts. This anisotropy provides an explanation to some features of the plastic deformation of granular media.Comment: Submitted to PR

Fast-timing study of the l-forbidden 1/2+→3/2+ M1 transition in Sn129

R. Lică et al. ; 7 págs.; 5 figs.; 3 tabs. ; Open Access funded by Creative Commons Atribution Licence 3.0The levels in Sn129 populated from the β- decay of In129 isomers were investigated at the ISOLDE facility of CERN using the newly commissioned ISOLDE Decay Station (IDS). The lowest 12+ state and the 32+ ground state in Sn129 are expected to have configurations dominated by the neutron s12 (l=0) and d32 (l=2) single-particle states, respectively. Consequently, these states should be connected by a somewhat slow l-forbidden M1 transition. Using fast-timing spectroscopy we have measured the half-life of the 12+ 315.3-keV state, T12= 19(10) ps, which corresponds to a moderately fast M1 transition. Shell-model calculations using the CD-Bonn effective interaction, with standard effective charges and g factors, predict a 4-ns half-life for this level. We can reconcile the shell-model calculations to the measured T12 value by the renormalization of the M1 effective operator for neutron holes.This work was partially supported by the Spanish MINECO through Projects No. FPA2012-32443, No. FPA2013-41267-P, and CPAN Consolider (Project No. CSD-2007-00042), and by Romanian IFA Grant CERN/ISOLDE. It was also partly funded by the NuPNET network FATIMA (PRI-PIMNUP-2011-1338), by FWO-Vlaanderen (Belgium), by GOA/2010/010 (BOF KU Leuven), and by the Interuniversity Attraction Poles Programme initiated by the Belgian Science PolicyOffice (BriX network P7/12). Support from Grupo de Física Nuclear (GFN-UCM), Programmi di Ricerca Scientifica di Rilevante Interesse Nazionale (PRIN) Grant No. 2001024324 01302, German BMBF under Contracts No. 05P12PKFNE and No. 05P15PKCIA, the U.K. Science and Technology Facilities Council, and the European Union Seventh Framework through ENSAR (Contract No. 262010) is also acknowledged. Fasttiming electronics were provided by the Fast Timing Collaboration, the ISOLDE Decay Station collaboration, and MASTICON.Peer Reviewe

Mineralogical and geochemical evidence of magma mingling/mixing in the Sierra de las Cruces volcanic range, Mexican Volcanic Belt

RESUMEN En la Sierra de las Cruces (SC), Cinturón Volcánico Mexicano (CVM), se encuentran expuestos flujos de lava, principalmente de composición dacítica, del Plioceno-Pleistoceno. Las rocas volcánicas de la SC son de textura porfirítica, conteniendo plagioclasa + anfibol + ortopiroxeno ± clinopiroxeno ± cuarzo ± óxidos de Fe-Ti. La mayor parte de ellas exhiben diversas características que indican un proceso de mezcla incompleta de magmas, con una cristalización fraccionada concomitante, en la que un pequeño volumen de un magma andesítico caliente es inyectado a un magma dacítico. Es probable que ambos tipos de roca se hayan generado por fusión parcial a diferentes niveles de la corteza continental. Las evidencias de la mezcla incompleta de magmas incluyen: (a) plagioclasas con texturas normal y anubarrada en la misma muestra, cristales redondeados y corroídos, y bordes de reacción en superficies de cristal disueltas; (b) enclaves magmáticos subredondeados y vesiculares, que ocurren en dimensiones de un pocos milímetros a ~20 centímetros de diámetro, con plagioclasa + ortopiroxeno + anfíbol + cuarzo ± olivino ± óxidos de Fe-Ti; (c) química de minerales, que incluye cristales con bordes de reacción o plagioclasas de composición heterogénea (zonación inversa y oscilatoria o cristales con zonación normal e inversa) en la misma muestra; y (d) variaciones geoquímicas de elementos y relaciones de elementos traza explicables por una mezcla de magmas y por un proceso de difusión. Los enclaves andesíticos podrían considerarse como porciones de magma intermedio que no se mezcló con los líquidos dacíticos receptores, lo que confirma la importancia de los procesos de mezcla incompleta de magmas en la evolución magmática del CVM. ABSTRACT Pliocene – Pleistocene lava flows, mainly of dacitic composition, are exposed in the Sierra de las Cruces (SC) volcanic range within the Mexican Volcanic Belt (MVB). SC volcanic rocks are porphyritic, generally containing an assemblage of plagioclase + amphibole + orthopyroxene ± clinopyroxene ± quartz ± Fe-Ti oxides. Most of them exhibit diverse mineralogical and geochemical features that attest a magma mixing and mingling processes with concomitant fractional crystallization in which a small volume of hot andesite magma injects into dacitic magma. Both rock types are probably derived from partial melting of continental crust at different levels. The evidences of magma mixing and mingling include: (a) normal and sieved plagioclases in the same sample, rounded and embayed crystals, and armoured rims over the dissolved crystal surfaces; (b) subrounded, vesicular magmatic enclaves, ranging from a few millimeters to ~20 centimeters in size, with plagioclase + orthopyroxene + amphibole + quartz ± olivine ± Fe-Ti-oxides assemblage; (c) mineral chemistry evidence such as crystals with reaction rims or heterogeneous plagioclase compositions (inverse and oscillatory zoning or normally and inversely zoned crystals) in the same sample; and (d) elemental geochemical variations and trace-element ratio more akin to magma mixing and to some extent diffusion process. These andesitic enclaves could be considered as portions of the intermediate magma that did not mix completely (mingling) with the felsic host lavas, confirming the major role of magma mixing and mingling processes in the overall evolution of the MV

Characterization of the material response in the granular ratcheting

The existence of a very special ratcheting regime has recently been reported in a granular packing subjected to cyclic loading \cite{alonso04}. In this state, the system accumulates a small permanent deformation after each cycle. After a short transient regime, the value of this permanent strain accumulation becomes independent on the number of cycles. We show that a characterization of the material response in this peculiar state is possible in terms of three simple macroscopic variables. They are defined that, they can be easily measured both in the experiments and in the simulations. We have carried out a thorough investigation of the micro- and macro-mechanical factors affecting these variables, by means of Molecular Dynamics simulations of a polydisperse disk packing, as a simple model system for granular material. Biaxial test boundary conditions with a periodically cycling load were implemented. The effect on the plastic response of the confining pressure, the deviatoric stress and the number of cycles has been investigated. The stiffness of the contacts and friction has been shown to play an important role in the overall response of the system. Specially elucidating is the influence of the particular hysteretical behavior in the stress-strain space on the accumulation of permanent strain and the energy dissipation.Comment: 13 pages, 20 figures. Submitted to PR

Evidencias mineralógicas y geoquímicas de mezcla incompleta de magmas en la Sierra de las Cruces, Cinturón Volcánico Mexicano

Received: 19/05/2011 / Accepted: 12/04/2013.Pliocene – Pleistocene lava flows, mainly of dacitic composition, are exposed in the Sierra de las Cruces (SC) volcanic range within the Mexican Volcanic Belt (MVB). SC volcanic rocks are porphyritic, generally containing an assemblage of plagioclase + amphibole + orthopyroxene ± clinopyroxene ± quartz ± Fe-Ti oxides. Most of them exhibit diverse mineralogical and geochemical features that attest a magma mixing and mingling processes with concomitant fractional crystallization in which a small volume of hot andesite magma injects into dacitic magma. Both rock types are probably derived from partial melting of continental crust at different levels. The evidences of magma mixing and mingling include: (a) normal and sieved plagioclases in the same sample, rounded and embayed crystals, and armoured rims over the dissolved crystal surfaces; (b) subrounded, vesicular magmatic enclaves, ranging from a few millimeters to ~20 centimeters in size, with plagioclase + orthopyroxene + amphibole + quartz ± olivine ± Fe-Ti-oxides assemblage; (c) mineral chemistry evidence such as crystals with reaction rims or heterogeneous plagioclase compositions (inverse and oscillatory zoning or normally and inversely zoned crystals) in the same sample; and (d) elemental geochemical variations and trace-element ratio more akin to magma mixing and to some extent diffusion process. These andesitic enclaves could be considered as portions of the intermediate magma that did not mix completely (mingling) with the felsic host lavas, confirming the major role of magma mixing and mingling processes in the overall evolution of the MVB.En la Sierra de las Cruces (SC), Cinturón Volcánico Mexicano (CVM), se encuentran expuestos flujos de lava, principalmente de composición dacítica, del Plioceno-Pleistoceno. Las rocas volcánicas de la SC son de textura porfirítica, conteniendo plagioclasa + anfibol + ortopiroxeno ± clinopiroxeno ± cuarzo ± óxidos de Fe-Ti. La mayor parte de ellas exhiben diversas características que indican un proceso de mezcla incompleta de magmas, con una cristalización fraccionada concomitante, en la que un pequeño volumen de un magma andesítico caliente es inyectado a un magma dacítico. Es probable que ambos tipos de roca se hayan generado por fusión parcial a diferentes niveles de la corteza continental. Las evidencias de la mezcla incompleta de magmas incluyen: (a) plagioclasas con texturas normal y anubarrada en la misma muestra, cristales redondeados y corroídos, y bordes de reacción en superficies de cristal disueltas; (b) enclaves magmáticos subredondeados y vesiculares, que ocurren en dimensiones de un pocos milímetros a ~20 centímetros de diámetro, con plagioclasa + ortopiroxeno + anfíbol + cuarzo ± olivino ± óxidos de Fe-Ti; (c) química de minerales, que incluye cristales con bordes de reacción o plagioclasas de composición heterogénea (zonación inversa y oscilatoria o cristales con zonación normal e inversa) en la misma muestra; y (d) variaciones geoquímicas de elementos y relaciones de elementos traza explicables por una mezcla de magmas y por un proceso de difusión. Los enclaves andesíticos podrían considerarse como porciones de magma intermedio que no se mezcló con los líquidos dacíticos receptores, lo que confirma la importancia de los procesos de mezcla incompleta de magmas en la evolución magmática del CVM.Universidad Autónoma de Nuevo LeónDepto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu

Evidencias mineralógicas y geoquímicas de mezcla incompleta de magmas en la Sierra de las Cruces, Cinturón Volcánico Mexicano

Pliocene – Pleistocene lava flows, mainly of dacitic composition, are exposed in the Sierra de las Cruces (SC) volcanic range within the Mexican Volcanic Belt (MVB). SC volcanic rocks are porphyritic, generally containing an assemblage of plagioclase + amphibole + orthopyroxene ± clinopyroxene ± quartz ± Fe-Ti oxides. Most of them exhibit diverse mineralogical and geochemical features that attest a magma mixing and mingling processes with concomitant fractional crystallization in which a small volume of hot andesite magma injects into dacitic magma. Both rock types are probably derived from partial melting of continental crust at different levels. The evidences of magma mixing and mingling include: (a) normal and sieved plagioclases in the same sample, rounded and embayed crystals, and armoured rims over the dissolved crystal surfaces; (b) subrounded, vesicular magmatic enclaves, ranging from a few millimeters to ~20 centimeters in size, with plagioclase + orthopyroxene + amphibole + quartz ± olivine ± Fe-Ti-oxides assemblage; (c) mineral chemistry evidence such as crystals with reaction rims or heterogeneous plagioclase compositions (inverse and oscillatory zoning or normally and inversely zoned crystals) in the same sample; and (d) elemental geochemical variations and trace-element ratio more akin to magma mixing and to some extent diffusion process. These andesitic enclaves could be considered as portions of the intermediate magma that did not mix completely (mingling) with the felsic host lavas, confirming the major role of magma mixing and mingling processes in the overall evolution of the MVBEn la Sierra de las Cruces (SC), Cinturón Volcánico Mexicano (CVM), se encuentran expuestos flujos de lava, principalmente de composición dacítica, del Plioceno-Pleistoceno. Las rocas volcánicas de la SC son de textura porfirítica, conteniendo plagioclasa + anfibol + ortopiroxeno ± clinopiroxeno ± cuarzo ± óxidos de Fe-Ti. La mayor parte de ellas exhiben diversas características que indican un proceso de mezcla incompleta de magmas, con una cristalización fraccionada concomitante, en la que un pequeño volumen de un magma andesítico caliente es inyectado a un magma dacítico. Es probable que ambos tipos de roca se hayan generado por fusión parcial a diferentes niveles de la corteza continental. Las evidencias de la mezcla incompleta de magmas incluyen: (a) plagioclasas con texturas normal y anubarrada en la misma muestra, cristales redondeados y corroídos, y bordes de reacción en superficies de cristal disueltas; (b) enclaves magmáticos subredondeados y vesiculares, que ocurren en dimensiones de un pocos milímetros a ~20 centímetros de diámetro, con plagioclasa + ortopiroxeno + anfíbol + cuarzo ± olivino ± óxidos de Fe-Ti; (c) química de minerales, que incluye cristales con bordes de reacción o plagioclasas de composición heterogénea (zonación inversa y oscilatoria o cristales con zonación normal e inversa) en la misma muestra; y (d) variaciones geoquímicas de elementos y relaciones de elementos traza explicables por una mezcla de magmas y por un proceso de difusión. Los enclaves andesíticos podrían considerarse como porciones de magma intermedio que no se mezcló con los líquidos dacíticos receptores, lo que confirma la importancia de los procesos de mezcla incompleta de magmas en la evolución magmática del CV