388 research outputs found
The Role of Arctic Sea Ice and Sea Surface Temperatures on the Cold 2015 February Over North America
No full textThe cold spell of February 2015 in North America was predominantly internally generated; reduced Arctic sea ice and anomalous sea surface temperatures may have contributed in establishing and sustaining the anomalous flow.This work was funded by the EU projects EUCLEIA (607085), SPECS (308378), and PRIMAVERA (641727). The authors are supported by the following fellowships: Bellprat
(ESA Living planet, VERITAS-CCI), Massonnet and Fučkar (Juan de la Cierva), García-Serrano (Marie Currie, DPETNA, 655339), Guemas (Ramón y Cajal) The author thankfully acknowledges the computer
resources, technical expertise, and assistance provided by the Red Española de Supercomputación. We further thank constructive comments from Martin Hoerling and three anonymous reviewers.Postprint (published version
Applying differential InSAR to orbital dynamics: a new approach for estimating ERS trajectories
No full textA new approach for tuning the trajectories of the European remote sensing (ERS) satellites is developed and assessed. Differential dual-pass interferometry is applied to calculate interferograms from the phase difference of synthetic aperture radar (SAR) images acquired by the ERS satellites over the site of the 1992 earthquake in Landers, California. These interferograms contain information about orbital trajectories and geophysical deformation. Beginning with good prior estimates of the orbital trajectories, a radial and an across-track orbital adjustment is estimated at each epoch. The data are the fringe counts along distance and azimuth. Errors in the across-track and radial components of the orbit estimates produce fringes in the interferograms. The spacing between roughly parallel fringes gives the gradients in distance and azimuth coordinates. The approach eliminates these fringes from interferometric pairs spanning relatively short time intervals containing few topographic residuals or atmospheric artefacts. An optimum interferometric path with six SAR acquisitions is selected to study post- and inter-seismic deformation fields. In order to regularize the problem, it is assumed that the radial and across-track adjustments both sum to zero. Applying the adjustment approach to the prior estimates of trajectory from the Delft Institute for Earth-Orientated Space Research (DEOS), root mean squares of 7.3 cm for the acrosstrack correction components and 2.4 cm for the radial ones are found. Assuming 0.1 fringes for the a priori standard deviation of the measurement, the approach yields mean standard deviations of 2.4 cm for the across-track and 4.5 cm for the radial components. The approach allows an "interval by interval" improvement of a set of orbital estimates from which post-fit interferograms of different time intervals spanning a total 3.8-year inter-seismic time interval can be created. The interferograms calculated with the post-fit orbital estimates compare favorably with those corrected with a conventional orbital tuning approach. Using the adjustment approach, it is possible to distinguish between orbital and deformation contributions to interferometric SAR (InSAR) phase gradients. Surface deformation changes over an inter-seismic time interval longer than one year can be measured. This approach is, however, limited to well-correlated interferograms where it is possible to measure the fringe gradient
The Interferometric Cartwheel for ENVISAT
No full textCNES and DLR have investigated the possibility of a formation flight of a cluster of passive radar micro-satellites with eth Envisat earth oberservation satellite. The mission goal is to achieve a Digital Elevation Model of the solid Earth of unequalled coverage and accuracy
Les traces de pneumatiques en sciences forensiques : de l'analyse chimique à l'évaluation de la force probante
No full textThis work is focused on the development of a methodology for the use of chemical characteristic of tire traces to help answer the following question: "Is the offending tire at the origin of the trace found on the crime scene?". This methodology goes from the trace sampling on the road to statistical analysis of its chemical characteristics.
Knowledge about the composition and manufacture of tread tires as well as a review of instrumental techniques used for the analysis of polymeric materials were studied to select, as an ansi vi cal technique for this research, pyrolysis coupled to a gas Chromatograph with a mass spectrometry detector (Py-GC/MS). An analytical method was developed and optimized to obtain the lowest variability between replicates of the same sample.
Within-variability of the tread was evaluated regarding width and circumference with several samples taken from twelve tires of different brands and/or models. The variability within each of the treads (within-variability) and between the treads (between-variability) could be quantified. Different statistical methods have shown that within-variability is lower than between-variability, which helped differentiate these tires.
Ten tire traces were produced with tires of different brands and/or models by braking tests. These traces have been adequately sampled using sheets of gelatine. Particles of each trace were analysed using the same methodology as for the tires at their origin. The general chemical profile of a trace or of a tire has been characterized by eighty-six compounds. Based on a statistical comparison of the chemical profiles obtained, it has been shown that a tire trace is not differentiable from the tire at its origin but is generally differentiable from tires that are not at its origin.
Thereafter, a sample containing sixty tires was analysed to assess the discrimination potential of the developed methodology. The statistical results showed that most of the tires of different brands and models are differentiable. However, tires of the same brand and model with identical characteristics, such as country of manufacture, size and DOT number, are not differentiable.
A model, based on a likelihood ratio approach, was chosen to evaluate the results of the comparisons between the chemical profiles of the traces and tires. The methodology developed was finally blindly tested using three simulated scenarios. Each scenario involved a trace of an unknown tire as well as two tires possibly at its origin. The correct results for the three scenarios were used to validate the developed methodology.
The different steps of this work were useful to collect the required information to test and validate the underlying assumption that it is possible to help determine if an offending tire » or is not at the origin of a trace, by means of a statistical comparison of their chemical profile. This aid was formalized by a measure of the probative value of the evidence, which is represented by the chemical profile of the trace of the tire.
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Ce travail s'est proposé de développer une méthodologie pour l'exploitation des caractéristiques chimiques des traces de pneumatiques dans le but d'aider à répondre à la question suivante : «Est-ce que le pneumatique incriminé est ou n'est pas à l'origine de la trace relevée sur les lieux ? ». Cette méthodologie s'est intéressée du prélèvement de la trace de pneumatique sur la chaussée à l'exploitation statistique de ses caractéristiques chimiques.
L'acquisition de connaissances sur la composition et la fabrication de la bande de roulement des pneumatiques ainsi que la revue de techniques instrumentales utilisées pour l'analyse de matériaux polymériques ont permis de choisir, comme technique analytique pour la présente recherche, la pyrolyse couplée à un chromatographe en phase gazeuse avec un détecteur de spectrométrie de masse (Py-GC/MS). Une méthode analytique a été développée et optimisée afin d'obtenir la plus faible variabilité entre les réplicas d'un même échantillon.
L'évaluation de l'intravariabilité de la bande de roulement a été entreprise dans sa largeur et sa circonférence à l'aide de plusieurs prélèvements effectués sur douze pneumatiques de marques et/ou modèles différents. La variabilité au sein de chacune des bandes de roulement (intravariabilité) ainsi qu'entre les bandes de roulement considérées (intervariabilité) a pu être quantifiée. Les différentes méthodes statistiques appliquées ont montré que l'intravariabilité est plus faible que l'intervariabilité, ce qui a permis de différencier ces pneumatiques.
Dix traces de pneumatiques ont été produites à l'aide de pneumatiques de marques et/ou modèles différents en effectuant des tests de freinage. Ces traces ont pu être adéquatement prélevées à l'aide de feuilles de gélatine. Des particules de chaque trace ont été analysées selon la même méthodologie que pour les pneumatiques à leur origine. Le profil chimique général d'une trace de pneumatique ou d'un pneumatique a été caractérisé à l'aide de huitante-six composés. Sur la base de la comparaison statistique des profils chimiques obtenus, il a pu être montré qu'une trace de pneumatique n'est pas différenciable du pneumatique à son origine mais est, généralement, différenciable des pneumatiques qui ne sont pas à son origine.
Par la suite, un échantillonnage comprenant soixante pneumatiques a été analysé afin d'évaluer le potentiel de discrimination de la méthodologie développée. Les méthodes statistiques appliquées ont mis en évidence que des pneumatiques de marques et modèles différents sont, majoritairement, différenciables entre eux. La méthodologie développée présente ainsi un bon potentiel de discrimination. Toutefois, des pneumatiques de la même marque et du même modèle qui présentent des caractéristiques PTD (i.e. pays de fabrication, taille et numéro DOT) identiques ne sont pas différenciables.
Un modèle d'évaluation, basé sur une approche dite du likelihood ratio, a été adopté pour apporter une signification au résultat des comparaisons entre les profils chimiques des traces et des pneumatiques. La méthodologie mise en place a finalement été testée à l'aveugle à l'aide de la simulation de trois scénarios. Chaque scénario impliquait une trace de pneumatique inconnue et deux pneumatiques suspectés d'être à l'origine de cette trace. Les résultats corrects obtenus pour les trois scénarios ont permis de valider la méthodologie développée.
Les différentes étapes de ce travail ont permis d'acquérir les informations nécessaires au test et à la validation de l'hypothèse fondamentale selon laquelle il est possible d'aider à déterminer si un pneumatique incriminé est ou n'est pas à l'origine d'une trace, par le biais d'une comparaison statistique de leur profil chimique. Cette aide a été formalisée par une mesure de la force probante de l'indice, qui est représenté par le profil chimique de la trace de pneumatique
Interferometric Synthetic Aperture Radar (SAR) Missions Employing Formation Flying
No full textThis paper presents an overview of single-pass interferometric Synthetic Aperture Radar (SAR) missions employing two or more satellites flying in a close formation. The simultaneous reception of the scattered radar echoes from different viewing directions by multiple spatially distributed antennas enables the acquisition of unique Earth observation products for environmental and climate monitoring. After a short introduction to the basic principles and applications of SAR interferometry, designs for the twin satellite missions TanDEM-X and Tandem-L are presented. Primary objective of TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is the generation of a global Digital Elevation Model (DEM) with unprecedented accuracy as the basis for a wide range of scientific research, as well as for commercial DEM production. This goal is achieved by enhancing the TerraSAR-X mission with a second TerraSAR-X like satellite that will be launched in spring 2010. Both satellites act then as a large single-pass SAR interferometer with the opportunity for flexible baseline selection. Building upon the experience gathered with the TanDEM-X mission design, the fully polarimetric L-band twin satellite formation Tandem-L is proposed. Important objectives of this highly capable interferometric SAR mission are the global acquisition of 3-D forest structure and biomass inventories, large scale measurements of millimetric displacements due to tectonic shifts, and systematic observations of glacier movements. The sophisticated mission concept and the high data acquisition capacity of Tandem-L will moreover provide a unique data source to systematically observe, analyze and quantify the dynamics of a wide range of additional processes in the bio-, litho-, hydro- and cryosphere. By this, Tandem-L will be an essential step to advance our understanding of the Earth system and its intricate dynamics. Enabling technologies and techniques are described in detail and an outlook on future interferometric and tomographic concepts and developments, including multi-static SAR systems with multiple receivers, is provided
Study and tests of a discrete readout electronic system for the R7600-00-M4 photomultiplier tube used on the calorimeter in the AMS02 experiment
No full textStudy and tests of a discrete readout electronic system for the R7600-00-M4 photomultiplier tube used on the calorimeter in the AMS02 experiment
No full textStudy and tests of a discrete readout electronic system for the R7600-00-M4 photomultiplier tube used on the calorimeter in the AMS02 experiment
No full textThe genome of Vitis vinifera cv. Mgaloblishvili reveals resistance and susceptibility factors to downy mildew in the Rpv29 and Rpv31 loci
No full textMgaloblishvili, a grapevine variety from Georgia (Southern Caucasus), exhibits a unique resistance mechanism against downy mildew. Mgaloblishvili resistance mechanism, involving pathogen recognition, activation of ethylene signalling pathway, structural and chemical defences, is mediated by the resistance loci Rpv29, Rpv30, and Rpv31. Mgaloblishvili genome was sequenced using PacBio HiFi, resulting in a chromosome-scale diploid assembly of 986 Mbp, including 58,912 predicted protein-coding genes across two phased chromosome sets. Comparative analysis with the susceptible PN40024 genome allowed us to identify differences in structure, gene content, and gene expression, as well as the impact of structural variants (SVs) and single nucleotide polymorphisms (SNPs) between Mgaloblishvili and PN40024 loci. Resistance haplotypes were identified through DNA sequencing of a self-pollinated Mgaloblishvili population. Compared to orthologous regions in PN40024, the Rpv29 locus in Mgaloblishvili exhibits reduced gene content, while the Rpv31 locus has similar gene content. In both Mgaloblishvili and PN40024, most genes within these loci are associated with plant defence pathways. While genes in both genotypes perform similar functions, SVs and SNPs were identified as key determinants of the structural differences between the genomes. Defining the Rpv30 locus was challenging due to ambiguous marker localization. DNA sequencing allowed us to identify resistance haplotypes for both Rpv30 and Rpv31 on Mgaloblishvili haplotype 2, though insights into the Rpv29 locus remain limited. Our results indicate that Mgaloblishvili's resistance is driven by numerous small SVs and SNPs, which lead to the loss of susceptibility factors and unique transcriptional regulation of defence-related genes
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