An extremal model for amorphous media plasticity

An extremal model for the plasticity of amorphous materials is studied in a simple two-dimensional anti-plane geometry. The steady-state is analyzed through numerical simulations. Long-range spatial and temporal correlations in local slip events are shown to develop, leading to non-trivial and highly anisotropic scaling laws. In particular, the plastic strain is shown to statistically concentrate over a region which tends to align perpendicular to the displacement gradient. By construction, the model can be seen as giving rise to a depinning transition, the threshold of which (i.e. the macroscopic yield stress) also reveal scaling properties reflecting the localization of the activity.Comment: 4 pages, 5 figure

Elastic consequences of a single plastic event : a step towards the microscopic modeling of the flow of yield stress fluids

With the eventual aim of describing flowing elasto-plastic materials, we focus on the elementary brick of such a flow, a plastic event, and compute the long-range perturbation it elastically induces in a medium submitted to a global shear strain. We characterize the effect of a nearby wall on this perturbation, and quantify the importance of finite size effects. Although for the sake of simplicity most of our explicit formulae deal with a 2D situation, our statements hold for 3D situations as well.Comment: submitted to EPJ

Atmospheric and Galactic Production and Propagation of Light Antimatter Nuclei

The production and propagation of light antimatter nuclei has been calculated using inclusive antiproton production cross sections from a new data analysis, and coalescence models for the production of composite particles. Particles were propagated using recently proven phenomenological approaches. The atmospheric secondary flux is evaluated for the first time. The Galactic flux obtained are larger than those obtained previously in similar calculations. The non-annihilating scattering contributions of the propagated particles are introduced. The preliminary results are shown and discussed.Comment: 4 pages, Contribution to the ICRC 200

Caracterización de la fenología de la vegetación a escala global mediante series temporales SPOT VEGETATION

Revista oficial de la Asociación Española de Teledetección[EN] Land surface phenology from time series of satellite data are expected to contribute to improve the represen-tation of vegetation phenology in earth system models. We characterized the baseline phenology of the vegetation at the global scale from GEOCLIM-LAI, a global climatology of leaf area index (LAI) derived from 1-km SPOT VEGETATION time series for 1999-2010. The calibration with ground measurements showed that the start and end of season were best identified using respectively 30% and 40% threshold of LAI amplitude values. The satellite-derived phenology was spatially consistent with the global distributions of climatic drivers and biome land cover. The accuracy of the derived phenological metrics, evaluated using available ground observations for birch forests in Europe, cherry in Asia and lilac shrubs in North America showed an overall root mean square error lower than 19 days for the start, end and length of season, and good agreement between the latitudinal gradients of VEGETATION LAI phenology and ground data[ES] La teledetección debe contribuir a mejorar la representación de la fenología en los modelos climáticos. En este estudio se ha caracterizado la fenología típica de la vegetación a escala global mediante GEOCLIM-LAI, una climatología del índice de área foliar (LAI) calculada a partir de series temporales en el periodo 1999-2010 de datos SPOT VEGETATION a 1-km de resolución espacial. A partir de la calibración con observaciones in situ, el inicio y fin de la estación de crecimiento se han definido como la fecha para la cual el LAI alcanza, respectivamente, el 30% y 40% de la amplitud de su ciclo anual. Los patrones espaciales de la fenología de satélite muestran una gran consistencia con la distribución espacial de cubiertas vegetales y factores climáticos. La comparación con medidas in situ para las fe-nofases correspondientes al inicio, fin y duración de la estación de crecimiento de abedul común en Europa, cerezo en Asia y lilo en Norte América muestra errores medios menores de 19 días, y un gran acuerdo en el gradiente latitudinal de la fenología observada in situ y estimada a partir de series temporales LAI VEGETATION.Este trabajo ha sido financiado en parte por el programa Europeo de observación Copernicus Global Land, y los proyectos FP7 geoland2 (218795), GIOBIO (32-566), LONGLOVE (32-594), CGL2013-48074-P, SGR 2014-274 y IMBALANCE-P (ERC-2013-SyG-610028). A. Verger fue beneficiario de un contrato Juan de la Cierva del Ministerio de Ciencia e Innovación, Gobierno de España.Verger, A.; Filella, I.; Baret, F.; Peñuelas, J. (2016). Land surface phenology from SPOT VEGETATION time series. Revista de Teledetección. (47):1-11. https://doi.org/10.4995/raet.2016.5718SWORD1114

Land cover classification using multi-temporal MERIS vegetation indices

The spectral, spatial, and temporal resolutions of Envisat's Medium Resolution Imaging Spectrometer (MERIS) data are attractive for regional- to global-scale land cover mapping. Moreover, two novel and operational vegetation indices derived from MERIS data have considerable potential as discriminating variables in land cover classification. Here, the potential of these two vegetation indices (the MERIS global vegetation index (MGVI), MERIS terrestrial chlorophyll index (MTCI)) was evaluated for mapping eleven broad land cover classes in Wisconsin. Data acquired in the high and low chlorophyll seasons were used to increase inter-class separability. The two vegetation indices provided a higher degree of inter-class separability than data acquired in many of the individual MERIS spectral wavebands. The most accurate landcover map (73.2%) was derived from a classification of vegetation index-derived data with a support vector machine (SVM), and was more accurate than the corresponding map derived from a classification using the data acquired in the original spectral wavebands

Accelerator Testing of the General Antiparticle Spectrometer, a Novel Approach to Indirect Dark Matter Detection

We report on recent accelerator testing of a prototype general antiparticle spectrometer (GAPS). GAPS is a novel approach for indirect dark matter searches that exploits the antideuterons produced in neutralino-neutralino annihilations. GAPS captures these antideuterons into a target with the subsequent formation of exotic atoms. These exotic atoms decay with the emission of X-rays of precisely defined energy and a correlated pion signature from nuclear annihilation. This signature uniquely characterizes the antideuterons. Preliminary analysis of data from a prototype GAPS in an antiproton beam at the KEK accelerator in Japan has confirmed the multi-X-ray/pion star topology and indicated X-ray yields consistent with prior expectations. Moreover our success in utilizing solid rather than gas targets represents a significant simplification over our original approach and offers potential gains in sensitivity through reduced dead mass in the target area.Comment: 18 pages, 9 figures, submitted to JCA

Search for magnetic monopoles with ten years of the ANTARES neutrino telescope

This work presents a new search for magnetic monopoles using data taken with the ANTARES neutrino telescope over a period of 10 years (January 2008 to December 2017). Compared to previous ANTARES searches, this analysis uses a run-by-run simulation strategy, with a larger exposure as well as a new simulation of magnetic monopoles taking into account the Kasama, Yang and Goldhaber model for their interaction cross-section with matter. No signal compatible with the passage of relativistic magnetic monopoles is observed, and upper limits on the flux of magnetic monopoles with ß = v/c = 0.55, are presented. For ultra-relativistic magnetic monopoles the flux limit is ~ 7×10-18 cm-2 s -1 sr-1 .Postprint (author's final draft

The AMS-02 RICH Imager Prototype - In-Beam Tests with 20 GeV/c per Nucleon Ions -

A prototype of the AMS Cherenkov imager (RICH) has been tested at CERN by means of a low intensity 20 GeV/c per nucleon ion beam obtained by fragmentation of a primary beam of Pb ions. Data have been collected with a single beam setting, over the range of nuclear charges 2<Z<~45 in various beam conditions and using different radiators. The charge Z and velocity beta resolutions have been measured.Comment: 4 pages, contribution to the ICRC 200

The AMS-RICH velocity and charge reconstruction

The AMS detector, to be installed on the International Space Station, includes a Ring Imaging Cerenkov detector with two different radiators, silica aerogel (n=1.05) and sodium fluoride (n=1.334). This detector is designed to provide very precise measurements of velocity and electric charge in a wide range of cosmic nuclei energies and atomic numbers. The detector geometry, in particular the presence of a reflector for acceptance purposes, leads to complex Cerenkov patterns detected in a pixelized photomultiplier matrix. The results of different reconstruction methods applied to test beam data as well as to simulated samples are presented. To ensure nominal performances throughout the flight, several detector parameters have to be carefully monitored. The algorithms developed to fulfill these requirements are presented. The velocity and charge measurements provided by the RICH detector endow the AMS spectrometer with precise particle identification capabilities in a wide energy range. The expected performances on light isotope separation are discussed.Comment: Contribution to the ICRC07, Merida, Mexico (2007); Presenter: F. Bara