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Nowadays, more than half of the world’s population lives in urban areas, air quality prediction in urban areas is therefore flagship topic. The improvement of mesoscale chemical transport models generally focused on the dynamics, physical parameterization processes, and chemical reaction mechanisms. In the first part of the study, three configurations of vertical diffusion coefficient (Kz) based on fisrt order closure K-theory are tested within CHIMERE model fed by IFS meteorology over one year. Although, all these Kz configurations are known to be efficient for mesoscale air quality simulations and the results show small differences between the three schemes, they all overestimated vertical mixing in urban areas. It is worth noting that the model used overestimates the ratio of PM2.5/PM10 by approximately 20% for all seasons. Discrepancies on emission inventories could be a relevant explanation. Many studies on the impact of physical parameterizations indicates the need of more accurate simulations of meteorological conditions for air quality modeling at urban scale. Also, for the second part of this work, the Weather Research and Forecast (WRF) model coupled with the chemistry transport model (CTM) CHIMERE has been used to understand the impact of physics parameterizations on air quality simulation during a short-term pollution episode on the Paris region. Large differences were found between different canopy schemes, showing an overall overestimation of concentrations during the pollution episode. The boundary layer schemes sensitivity tests display an underestimation of the boundary layer height which leads to a strong overestimations of pollutants concentration. The Boulac–BEP scheme had significantly better performances than the other schemes for the simulation of both the PBL height and the pollutants concentrations, indicating that both the canopy schemes and boundary layer schemes have a critical effect on air quality prediction in the urban region. The third part of this work focuses on the vertical resolution of the grid and the height of the first layer which also plays a very important role in the transport modeling. The three configurations tested demonstrate the model's ability to simulate regular days without pollution episodes. However, during a pollution episode, the refinement of the vertical resolution and of the height of the first layer leads to a clear improvement of the modeling results compared to the initial configuration of the model. The air quality predictions in urban regions are mainly influenced by the urban canopy, the boundary layer and the diffusion conditions. The land surface model had a slight impact for both meteorological and air quality simulation. In the last part of this work, the eddy diffusion of WRF from a 1.5 order diffusivity closure scheme based on the kinetic energy of turbulence is directly integrated into CHIMERE in order to represent a more realistic vertical mixing near the surface for urban pollution applications. A two weeks high resolution simulation was performed in Paris, Lyon and Bordeaux with finest horizontal and vertical resolution of 1.67km and 12m respectively. The new eddy diffusion (NED) integrated in this research improves NO2 simulations at all urban site compared to the original Kz diffusion (IKD) on board CHIMERE. The average improvements in terms of RMSE are 18.77%, 24.51% and 9.52% in Paris, Lyon and Bordeaux, respectively. PM2.5 and PM10 simulation provided similar results with NO2, 13.47% and 19.08% improvements were found in the urban area of Paris. The simulation with more realistic eddy viscosities is better than initial Kz parameterization which has been widely used in CTM. This work illuminates the user to identify the best settings of atmospheric models for appropriate operational uses to simulate the air quality during pollution episodes or for long term analyses in urban areas.; De nos jours, plus de la moitié de la population mondiale vit dans des zones urbaines. La prévision et l’analyse de la qualité de l'air dans les zones urbaines est un sujet d'actualité. L'amélioration des modèles de transport chimique à méso-échelle passe généralement par le développement de paramétrisations plus avancées en termes de dynamique et mécanismes chimiques. Dans la première partie de l'étude, trois configurations du coefficient de diffusion verticale (Kz) basées sur la théorie de fermeture de premier ordre (k-theory) sont testées avec le modèle CHIMERE alimenté par les données Européennes météorologiques IFS pendant une année. Ces configurations, bien que jugées efficaces pour les simulations de qualité de l'air à méso-échelle, montrent une surestimation significative du mélange vertical dans les zones urbaines avec des différences faibles entre les trois schémas. Il convient de noter que le modèle ainsi configuré a surestimé le rapport PM2.5/PM10 d'environ 20% quelle que soit la saison. L'étude de l'impact de la paramétrisation de la diffusion verticale confirme bien que la modélisation météorologique est d'une importance majeure pour la modélisation de la qualité de l'air. Par la suite, le modèle Weather Research and Forecast (WRF) couplé au modèle de transport de la chimie (CTM) CHIMERE a été utilisé pour comprendre l'impact des paramétrisations physiques sur la simulation de la qualité de l'air sur épisode de pollution en la région parisienne. Les différents schémas de canopée testés montrent des différences importantes avec une surestimation globale des concentrations pendant l'épisode de pollution. Les tests de sensibilité des schémas de la couche limite montrent une sous-estimation de la hauteur de la couche limite qui a pour conséquence une forte surestimation de la concentration des polluants pendant l'épisode de pollution. Le schéma de Boulac-BEP montre des performances significativement meilleures que les autres schémas pour la simulation de cette hauteur de couche limite ainsi que pour les concentrations en polluants, ce qui confirme bien que les schémas de canopée urbaine et de couche limite ont un effet critique sur la modélisation de la qualité de l'air dans la région urbaine. La troisième partie de ce travail porte sur l’impact de la résolution verticale de la grille et la hauteur de la première couche qui jouent également un rôle très important dans la modélisation du transport. Les trois configurations testées démontrent les capacités du modèle à simuler des journées normales hors épisodes de pollution. Cependant, lors d'un épisode de pollution, l'affinement de la résolution verticale et de la hauteur de la première couche entraîne une nette amélioration des résultats de modélisation en comparaison avec la configuration initiale du modèle. La simulation et la prévision de la qualité de l'air en région urbaine sont donc influencées par les caractéristiques de la canopée urbaine, la couche limite et les conditions de diffusion, le modèle de surface terrestre ayant un léger impact sur la simulation météorologique et la qualité de l'air. Dans la dernière partie de ce travail, la diffusivité turbulente de WRF issue d’un schéma de fermeture de la diffusivité d'ordre 1.5 basé sur l'énergie cinétique de la turbulence est intégrée dans CHIMERE afin de représenter un mélange vertical plus réaliste près de la surface pour les applications de pollution urbaine. Une simulation haute résolution de 15 jours en hiver a été réalisée sur Paris, Lyon et Bordeaux avec des résolutions horizontale et verticale fines de 1,67km et 12m respectivement. Il est à noter que la nouvelle diffusion verticale (NED) a amélioré la simulation du NO2 pour chaque site urbain par rapport à la diffusion Kz initiale (IKD). Les améliorations moyennes en termes de RMSE sont de 18,77%, 24,51% et 9,52% à Paris, Lyon et Bordeaux, respectivement [...]

International audience; Stream water chemistry is routinely measured over time at fixed and sparse sites, which provides a coarse image of spatial variability. Here, we measured nitrate, dissolved organic carbon (DOC) and several chemical proxies for water flowpaths, catchment residence time and biogeochemical transformations, every 50-100m along 13km of streams in six agricultural headwater catchments (1.1-3.5km2). The objective was to examine controls on longitudinal nitrate profiles at a high spatial resolution during four seasons: rewetting of the catchments in autumn, winter high-flow, spring recession and summer low-flow. Our results showed monotonic trends in longitudinal profiles for nitrate and DOC, which were opposite for the two solutes. Spatial trends in water chemistry profiles persisted across seasons, which suggests time-invariant controls on the spatial variations in concentrations. Four catchments exhibited decreasing nitrate and increasing DOC from upstream to downstream, while two catchments exhibited increasing nitrate and decreasing DOC. These smooth gradients did not reflect a longitudinal land-use gradient, but rather an increase in the proportion of groundwater inflows when moving downstream, as suggested by the chemical proxies and punctual discharge measurements. Water chemistry also changed abruptly at confluences, at a farm point source and at a localized groundwater inflow zone.

International audience; Hi-C has become a routine method for probing the 3D organization of genomes. However, when applied to prokaryotes and archaea, the current protocols are expensive and limited in their resolution. We develop a cost-effective Hi-C protocol to explore chromosome conformations of these two kingdoms at the gene or operon level. We first validate it on E. coli and V. cholera, generating sub-kilobase-resolution contact maps, and then apply it to the euryarchaeota H. volcanii, Hbt. salinarum, and T. kodakaraensis. With a resolution of up to 1 kb, we explore the diversity of chromosome folding in this phylum. In contrast to crenarchaeota, these euryarchaeota lack (active/inactive) compartment-like structures. Instead, their genomes are composed of self-interacting domains and chromatin loops. In H. volcanii, these structures are regulated by transcription and the archaeal structural maintenance of chromosomes (SMC) protein, further supporting the ubiquitous role of these processes in shaping the higher-order organization of genomes.

International audience; A high-resolution climate projections dataset is obtained by statistically downscaling climate projections from the CMIP5 experiment using the ERA5 reanalysis from the Copernicus Climate Change Service. This global dataset has a spatial resolution of 0.25°x 0.25°, comprises 21 climate models and includes 5 surface daily variables at monthly resolution: air temperature (mean, minimum, and maximum), precipitation, and mean near-surface wind speed. Two greenhouse gas emissions scenarios are available: one with mitigation policy (RCP4.5) and one without mitigation (RCP8.5). The downscaling method is a Quantile Mapping method (QM) called the Cumulative Distribution Function transform (CDF-t) method that was first used for wind values and is now referenced in dozens of peer-reviewed publications. The data processing includes quality control of metadata according to the climate modeling community standards and value checking for outlier detection.

International audience; PURPOSE: High-resolution free-breathing late gadolinium enhancement (HR-LGE) was shown valuable for the diagnosis of acute coronary syndromes with non-obstructed coronary arteries. The method may be useful to detect COVID-related myocardial injuries but is hampered by prolonged acquisition times. We aimed to introduce an accelerated HR-LGE technique for the diagnosis of COVID-related myocardial injuries. METHOD: An undersampled navigator-gated HR-LGE (acquired resolution of 1.25 mm(3)) sequence combined with advanced patch-based low-rank reconstruction was developed and validated in a phantom and in 23 patients with structural heart disease (test cohort; 15 men; 55 ± 16 years). Twenty patients with laboratory-confirmed COVID-19 infection associated with troponin rise (COVID cohort; 15 men; 46 ± 24 years) prospectively underwent cardiovascular magnetic resonance (CMR) with the proposed sequence in our center. Image sharpness, quality, signal intensity differences and diagnostic value of free-breathing HR-LGE were compared against conventional breath-held low-resolution LGE (LR-LGE, voxel size 1.8x1.4x6mm). RESULTS: Structures sharpness in the phantom showed no differences with the fully sampled image up to an undersampling factor of x3.8 (P > 0.5). In patients (N = 43), this acceleration allowed for acquisition times of 7min21s ± 1min12s at 1.25 mm(3) resolution. Compared with LR-LGE, HR-LGE showed higher image quality (P = 0.03) and comparable signal intensity differences (P > 0.5). In patients with structural heart disease, all LGE-positive segments on LR-LGE were also detected on HR-LGE (80/391) with 21 additional enhanced segments visible only on HR-LGE (101/391, P

We present the high-resolution spectroscopic analysis of two new extremely metal-poor stars (EMPS) candidates in the dwarf spheroidal galaxy Sextans. These targets were pre-selected from medium resolution spectra centered around the Ca II triplet in the near-infrared and followed-up at higher resolution with VLT/UVES. We confirm their low metallicities with [Fe/H]=-2.95 and [Fe/H]=-3.01, placing them among the most metal-poor stars known in Sextans. The abundances of 18 elements, including C, Na, the alpha-elements, Fe-peak, and neutron capture elements, are determined. In particular, we present the first measurements of Zn in a classical dwarf at extremely low metallicity. There has been previous hints of a large scatter in the abundance ratios of the Sextans stellar population around [Fe/H] -3 when compared to other galaxies. We took the opportunity of this work to re-analyse the full sample of EMPS and find a Milky-Way -like plateau and a normal dispersion at fixed metallicity., Accepted for publication in A&A. 14 pages, 10 figures

International audience

The intestinal microbiota is a complex community of bacteria, archaea, viruses, protists and fungi1,2. While the composition of bacterial constituents has been linked to immune homeostasis and to infectious susceptibility3–7, the role of non-bacterial constituents and of cross-kingdom microbial interactions in these processes is poorly understood2,8. Fungi represent a major cause of infectious morbidity and mortality in immune-compromised individuals, though the relationship of intestinal fungi (i.e., the mycobiota) with fungal bloodstream infections (BSI) remains undefined9. We integrated an optimized bioinformatics pipeline with high-resolution mycobiota sequencing and comparative genomic analyses of fecal and blood specimens from recipients of allogeneic hematopoietic cell transplant (allo-HCT). Patients with Candida BSI experienced a prior marked intestinal expansion of pathogenic Candida species; this expansion consisted of a complex dynamic between multiple species and subspecies with a stochastic translocation pattern into the bloodstream. The intestinal expansion of pathogenic Candida species was associated with a significant loss in bacterial burden and diversity, particularly in the anaerobes. Thus, simultaneous analysis of intestinal fungi and bacteria identifies dysbiosis states across kingdoms that may promote fungal translocation and facilitate invasive disease. These findings support microbiota-driven approaches to identify patients at risk for fungal BSI for pre-emptive therapeutic intervention.

Silica has many industrial (i.e., glass formers) and scientific applications. The understanding and prediction of the interesting properties of such materials are dependent on the knowledge of detailed atomic structures. In this work, amorphous silica subjected to an accelerated alkali silica reaction (ASR) was recorded at different time intervals so as to follow the evolution of the structure by means of high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and electron pair distribution function (e-PDF), combined with X-ray powder diffraction (XRPD). An increase in the size of the amorphous silica nanostructures and nanopores was observed by HRTEM, which was accompanied by the possible formation of Si–OH surface species. All of the studied samples were found to be amorphous, as observed by HRTEM, a fact that was also confirmed by XRPD and e-PDF analysis. A broad diffuse peak observed in the XRPD pattern showed a shift toward higher angles following the higher reaction times of the ASR-treated material. A comparison of the EELS spectra revealed varying spectral features in the peak edges with different reaction times due to the interaction evolution between oxygen and the silicon and OH ions. Solid-state nuclear magnetic resonance (NMR) was also used to elucidate the silica nanostructures. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

The benefits of high-resolution, wide-field planetary observations are as profitable as they are technically challenging. Generation after generation, the performances of such systems have improved to astonishing levels, at the cost however of galloping complexities.The trend these days is to reduce the costs, the size and the time to operations while keeping high performance yields. The work presented in this thesis addresses these concerns : it offers an optical design method for a compact telescope that offers high-resolution observation capabilities while considerably reducing the size of its detector.On the other hand, the recent developments in freeform optics design, manufacturing and testing have allowed optical engineers to implement new degrees of freedom in their designs. These increasingly efficient, compact and complex systems have opened the door to a new area of design by boosting the creativity and productivity of the engineers.This work takes advantage of the possibilities offered by freeform optics and the recent developments in CMOS TDI sensors, paving the way for the next generations of high-resolution, wide-field planetary observation missions., Si les campagnes d'observations haute résolution et grand champ depuis l'espace permettent une acquisition et une gestion de l'information sans commune mesure, elles ne sont pas dépourvues de difficultés techniques qu'il advient de surmonter. Génération après génération, les performances de ces satellites et de leurs télescopes ont atteint des niveaux impressionnants, au détriment toutefois de complexités galopantes.Les designs tendent depuis quelques années vers une réduction des coûts, de la taille de ces systèmes et vers une réduction de leur temps de mise sur le marché, tout en conservant les meilleurs niveaux de performances. Les travaux de cette thèse se penchent sur ces problématiques en proposant une méthode de conception optique pour un design de télescope novateur, permettant des observations haute résolution et grand champ tout en réduisant considérablement la taille de son détecteur.D'autre part, les progrès réalisés ces dernières années dans le domaine des optiques freeform (conception, fabrication et métrologie) permettent aux ingénieurs opticiens d'implémenter de nouveaux degrés de liberté dans leurs designs. L'accès à des systèmes de plus en plus performants, compacts et complexes laisse entrevoir de nouvelles perspectives qui n'ont pour limites que l'inventivité et la productivité des ingénieurs.Ces travaux prennent pleinement appui sur les possibilités offertes par les optiques freeform et les développements récents dans le domaine des détecteurs CMOS TDI, ouvrant une voie potentielle aux futures générations d'imageurs haute-résolution et grand champ.

WOS:000485256000001; International audience; Advancing our understanding of ocean biogeochemistry, biology, and ecosystems relies on the ability to make observations both in the ocean and at the critical boundaries between the ocean and other earth systems at relevant spatial and temporal scales. After decades of advancement in ocean observing technologies, one of the key remaining challenges is how to cost-effectively make measurements at the increased resolution necessary for illuminating complex system processes and rapidly evolving changes. In recent years, biogeochemical in situ sensors have been emerging that are threefold or more lower in cost than established technologies; the cost reduction for many biological in situ sensors has also been significant, although the absolute costs are still relatively high. Cost savings in these advancements has been driven by miniaturization, new methods of packaging, and lower-cost mass-produced components such as electronics and materials. Recently, field projects have demonstrated the potential for science-quality data collection via large-scale deployments using cost-effective sensors and deployment strategies. In the coming decade, it is envisioned that ocean biogeochemistry and biology observations will be revolutionized by continued innovation in sensors with increasingly low price points and the scale-up of deployments of these in situ sensor technologies. The goal of this study is therefore to: (1) provide a review of existing sensor technologies that are already achieving cost-effectiveness compared with traditional instrumentation, (2) present case studies of cost-effective in situ deployments that can provide insight into methods for bridging observational gaps, (3) identify key challenge areas where progress in cost reduction is lagging, and (4) present a number of potentially transformative directions for future ocean biogeochemical and biological studies using cost-effective technologies and deployment strategies.

(IF 4.64 [2018]; Q1); International audience; While numerous high-resolution studies concerning Last Glacial aeolian sequences are available for Europe, the approach of the penultimate glacial in this geographical area is still poorly developed. In order to bridge this gap, this study focuses on the Bulgarian sequence of Harletz, along the Danube River, where extremely high sedimentation rates allow the depiction of high-resolution signals during MIS 6. At Harletz in NW Bulgaria on the western bank of the Ogosta River (tributary of the Danube) a 20 m thick loess-palaeosols section was cleaned and sampled for a multi-disciplinary study and detailed pedostratigraphic approach. High-resolution continuous bulk sampling (5 cm) was carried out to characterise sedimentary grain size, magnetic properties (including magnetic susceptibility and its frequency dependence), colour reflectance (1 cm), and organic carbon. Geochronological control is based on 16 samples collected for OSL and MET-pIRIR dating. Using a cyclo-stratigraphic approach of the sequence combined with dating constraints provided by both MET-pIRIR dates and the age of a tephra layer occurring at a depth of 12 m within the main loess unit, we can demonstrate that the Harletz section exhibits a 10 m thick Late Saalian (Marine Isotope Stage 6, MIS 6) loess accumulation unique in Europe. The lower part of the main loess unit is 4 m thick and overlies a basal brown soil complex allocated to MIS 7, which includes an exceptionally thick (4 m) and detailed succession of loess and four incipient soil horizons never described in European loess until now. The closest and best-dated high-resolution palaeoenvironmental archive suitable for comparison comes from Lake Ohrid located about 400 km to the SW of Harletz. The Ohrid palynological record shows a progressive step-by-step evolution in climate and in environmental change during the transition between MIS 7 and MIS 6 from which a parallel with the Harletz pedosedimentary succession can be proposed. During the younger part of MIS 6 (160-129ka), steppe vegetation with abundant herbs (Artemisia) is dominant in the Lake Ohrid record, in good accordance with a global enhancement of aeolian dynamics, especially well recorded in sections located close to the Danube River from Serbia to Bulgaria and Romania (L2 loess). According to interpretations stemming from this study, the silts and fine sands building the Harletz loess section would have been transported from the Danube braided river system located (at that time) at about 4.5 km to the NW. Based on our data, the main loess units are characterised by a very low to a total absence of coarse sand particles. By contrast, during the Eemian interglacial (MIS 5e), and to a lesser extent throughout MIS 5 and during MIS 3 interstadials, the long distance transport of silt and fine sand particles is stopped and a weak aeolian sedimentation is likely driven by north-easterly winds transporting coarse sand grains from the proximal Ogosta River sandy banks. Finally, the weak development of Last Glacial loess (4 m max.) likely results from a rapid infilling of the sedimentary trap during the Saalian, then followed by a strong anthropogenic erosion of the topsoil and of the upper part of the loess profile since the Early Holocene (Neolithic).

Column-averaged dry-air mole fraction of CO (XCO) measurements are obtained from two ground-based Fourier transform infrared (FTIR) spectrometers networks: the Total Carbon Column Observing Network (TCCON) and the Network for the Detection of Atmospheric Composition Change (NDACC). In this study, the differences between the TCCON and NDACC XCO measurements are investigated and discussed based on six NDACC/TCCON sites using data over the period 2007–2017. The NDACC XCO measurements are about 5.5 % larger than the TCCON data at Ny-Ålesund, Bremen, and Izaña (Northern Hemisphere), and about 0.3 % larger than the TCCON data at St Denis, Wollongong and Lauder (Southern Hemisphere). The hemispheric dependence of the bias is mainly attributed to their smoothing errors. The systematic smoothing error of the TCCON XCO data varies in the range between 0.2 % (Bremen) and 7.9 % (Lauder), and the random smoothing error in the range between 2.0 % and 3.6 %. The systematic smoothing error of NDACC data is between 0.1 % and 0.8 %, and the random smoothing error of NDACC data is about 0.3 %. For TCCON data, the smoothing error can be significant in that it is much higher than the reported uncertainty for TCCON XCO. To reduce the influence from the a priori profiles and different vertical sensitivities, the scaled NDACC a priori profiles are used as the common a priori profiles for comparing TCCON and NDACC retrievals. As a result, the biases between TCCON and NDACC XCO measurements become more consistent (5.6–8.5 %) with a mean value of 6.8 % at these sites. To understand the remaining bias, regular AirCore measurements at Orleans and Sodankylä are compared to co-located TCCON measurements. It is found that TCCON XCO measurements are 6.0 ± 1.9 % and 6.9 ± 2.5 % smaller than the AirCore measurements at Orleans and Sodankylä respectively, indicating that the scaling factor of TCCON XCO data should be around 1.0000 instead of 1.0672. Further investigations should be carried out in the TCCON community to determine the correct scaling factor to be applied to the TCCON XCO data. This paper also demonstrates that the smoothing error must be taken into account when comparing FTIR XCO data, and especially TCCON XCO data, with model or satellite data. This study is supported by the EU-funded C3S_311a_Lot3 project. The TCCON site at Reunion Island is operated by the Royal Belgian Institute for Space Aeronomy with financial support in 2014, 2015, and 2016, 2017 under the EU project ICOS-Inwire and the ministerial decree for ICOS (FR/35/IC2) and local activities supported by LACy/UMR8105 - Université de La Réunion. The NDACC and TCCON stations Ny-Ålesund, Bremen, Izaña have been supported by the German Bundesministerium für Wirtschaft und Energie (BMWi) 10 via DLR under grants 50EE1711A-B. The Lauder FTIR measurements are core funded by NIWA from New Zealand’s Ministry of Business, Innovation and Employment through the Strategic Science Investment Fund. We thank the HIPPO team for making the aircraft measurements available http://hippo.ucar.edu/.

The emergence of CdTe Photon Counting Detectors (PCD) with energy discrimination capabilities, opens up new perspectives in X-ray imaging. Medical and security applications are characterized by very high X-ray fluxes and consequently require a very fast shaper in order to limit dead time losses due to pile-up. However, if the shaper is faster than the collection of the charges in the semiconductor, there is a loss of charge called ballistic deficit. Moreover, variations of the electric field profile in the detector over time cause a change in the collection time of the charges. As a result, the conversion gain of the detector will be affected by these variations. The instability of the response is visible over time as a channel shift of the spectra, resulting in a false information of the photon energy. The aim of this work is to characterize this instability in order to understand the mechanisms behind them and to develop a method to correct its effect. We proposed a correction algorithm based on the use of two Single Delay Line (SDL) shaping amplifiers. A fast SDL is used to measure the X-ray spectra at high count rates with limited count rate losses. A slow SDL is used to measure the full collected charge in order estimate a correction factor for the compensation of the ballistic deficit fluctuations of the fast SDL. An important step is to sort the processed pulses in order to reject pile-up and other undesirable effects that may degrade the measurement of the correction factor. The proposed method was implemented in an FPGA in order to correct the ballistic deficit in real-time and to give a stable response of the detector at very high fluxes. The method was tested with a 4x4 pixels detector (CdTe) of 3 mm thickness and 800 micron pitch, which is able to measure transmitted X-ray spectra in the energy range of 20-160 kV on 256 energy bins. The developed method was initially tested at low count rate with a Co-57 and an Am-241 gamma-ray sources, then at high count rates up to ~2 Mc/s with an X-ray source. With the characterization and the validation of this innovative algorithm we prove its ability in providing a stable response of the detector over time without affecting the energy resolution (~7% at 122 keV) and the dead time (~70 ns)., L'apparition des détecteurs à comptage de photons X à base de CdTe avec des capacités de discrimination de l'énergie des photons ouvre de nouvelles perspectives pour l'imagerie radiographique. Les applications médicales et en contrôle de bagages X sont caractérisées par un flux de photons X très élevé, et exigent par conséquent une mise en forme très rapide du photo-courant mesuré pour limiter les empilements. Cependant, si cette mise en forme est plus courte que le temps de transit des électrons dans le semi-conducteur, la charge mesurée devient inférieure à la charge déposée : c’est le déficit balistique. Par ailleurs, la variation dans le temps du profil du champ électrique dans le volume du détecteur entraîne une augmentation du temps de transit des électrons. En conséquence, la charge mesurée diminue dans le temps, faussant la mesure de l’énergie des photons X. L’objectif de ce travail est de caractériser cette instabilité et de développer une méthode de correction de son effet sur les spectres en énergie. Nous avons proposé un algorithme de correction basé sur l'utilisation de deux Lignes à Retard (LAR). Une LAR rapide (50ns ?) permet de mesurer les spectres X à très fort flux sans compromis sur le taux de comptage. Une LAR lente (200ns ?) est utilisée pour mesurer intégralement la charge déposée sans déficit balistique. Un facteur de correction est évalué et utilisé pour stabiliser la mesure de l’énergie des X avec la LAR rapide. Une étape importante de cet algorithme consiste à trier les impulsions traitées pour rejeter celles qui peuvent dégrader la mesure de ce facteur de correction, notamment les empilements. La méthode proposée a été implémentée dans un FPGA pour fonctionner en temps réel et a été testée avec un détecteur CdTe de 3mm d'épaisseur avec 4×4 pixels au pas de 800 microns, capable de mesurer des spectres X dans la gamme d'énergie 20-160 keV avec 256 canaux d'énergie. La méthode développée a été initialement testée à faible taux de comptage avec des sources gamma Co-57 et Am-241, puis à fort taux de comptage jusqu'à ~2 Mc/s avec un tube à rayons X. Cet algorithme innovant a montré sa capacité de fournir une réponse stable du détecteur dans le temps sans affecter la résolution d'énergie (7 % à 122 keV) et le temps mort (~70 ns).

The emergence of CdTe Photon Counting Detectors (PCD) with energy discrimination capabilities, opens up new perspectives in X-ray imaging. Medical and security applications are characterized by very high X-ray fluxes and consequently require a very fast shaper in order to limit dead time losses due to pile-up. However, if the shaper is faster than the collection of the charges in the semiconductor, there is a loss of charge called ballistic deficit. Moreover, variations of the electric field profile in the detector over time cause a change in the collection time of the charges. As a result, the conversion gain of the detector will be affected by these variations. The instability of the response is visible over time as a channel shift of the spectra, resulting in a false information of the photon energy. The aim of this work is to characterize this instability in order to understand the mechanisms behind them and to develop a method to correct its effect. We proposed a correction algorithm based on the use of two Single Delay Line (SDL) shaping amplifiers. A fast SDL is used to measure the X-ray spectra at high count rates with limited count rate losses. A slow SDL is used to measure the full collected charge in order estimate a correction factor for the compensation of the ballistic deficit fluctuations of the fast SDL. An important step is to sort the processed pulses in order to reject pile-up and other undesirable effects that may degrade the measurement of the correction factor. The proposed method was implemented in an FPGA in order to correct the ballistic deficit in real-time and to give a stable response of the detector at very high fluxes. The method was tested with a 4x4 pixels detector (CdTe) of 3 mm thickness and 800 micron pitch, which is able to measure transmitted X-ray spectra in the energy range of 20-160 kV on 256 energy bins. The developed method was initially tested at low count rate with a Co-57 and an Am-241 gamma-ray sources, then at high count rates up to ~2 Mc/s with an X-ray source. With the characterization and the validation of this innovative algorithm we prove its ability in providing a stable response of the detector over time without affecting the energy resolution (~7% at 122 keV) and the dead time (~70 ns).; L'apparition des détecteurs à comptage de photons X à base de CdTe avec des capacités de discrimination de l'énergie des photons ouvre de nouvelles perspectives pour l'imagerie radiographique. Les applications médicales et en contrôle de bagages X sont caractérisées par un flux de photons X très élevé, et exigent par conséquent une mise en forme très rapide du photo-courant mesuré pour limiter les empilements. Cependant, si cette mise en forme est plus courte que le temps de transit des électrons dans le semi-conducteur, la charge mesurée devient inférieure à la charge déposée : c’est le déficit balistique. Par ailleurs, la variation dans le temps du profil du champ électrique dans le volume du détecteur entraîne une augmentation du temps de transit des électrons. En conséquence, la charge mesurée diminue dans le temps, faussant la mesure de l’énergie des photons X. L’objectif de ce travail est de caractériser cette instabilité et de développer une méthode de correction de son effet sur les spectres en énergie. Nous avons proposé un algorithme de correction basé sur l'utilisation de deux Lignes à Retard (LAR). Une LAR rapide (50ns ?) permet de mesurer les spectres X à très fort flux sans compromis sur le taux de comptage. Une LAR lente (200ns ?) est utilisée pour mesurer intégralement la charge déposée sans déficit balistique. Un facteur de correction est évalué et utilisé pour stabiliser la mesure de l’énergie des X avec la LAR rapide. Une étape importante de cet algorithme consiste à trier les impulsions traitées pour rejeter celles qui peuvent dégrader la mesure de ce facteur de correction, notamment les empilements. La méthode proposée a été implémentée dans un FPGA pour fonctionner en temps réel et a été testée avec un détecteur CdTe de 3mm d'épaisseur avec 4×4 pixels au pas de 800 microns, capable de mesurer des spectres X dans la gamme d'énergie 20-160 keV avec 256 canaux d'énergie. La méthode développée a été initialement testée à faible taux de comptage avec des sources gamma Co-57 et Am-241, puis à fort taux de comptage jusqu'à ~2 Mc/s avec un tube à rayons X. Cet algorithme innovant a montré sa capacité de fournir une réponse stable du détecteur dans le temps sans affecter la résolution d'énergie (7 % à 122 keV) et le temps mort (~70 ns).

Coherence lifetimes in homonuclear dipolar decoupled 1 H solid-state NMR experiments are usually on the order of a few ms. We discover an oscillation that limits the lifetime of the coherences by recording spin-echo dephasing curves. We find that this oscillation can be removed by the application of a double spin-echo experiment, leading to coherence lifetimes of more than 45 ms in adamantane and more that 22 ms in β-AspAla, corresponding to refocused linewidths of less than 7 and 14 Hz respectively.

Ribosomes are ribo-nucleoprotein complexes that read mRNA to synthesize proteins. This is important to consider in the case of cancer cells, which show a global increase in protein synthesis to support their hyper-proliferative behaviour. Inhibitors of eukaryotic protein synthesis have been shown to have significant therapeutic potential to treat a wide range of human cancers. Recently we published a multidisciplinary study in which we unravel the mechanism of action of chlorolissoclimide (CL), a compound sharing chemical similarity to cycloheximide (CHX), but showing promising lower cytotoxicity. We were interested in the new types of interaction of CL with the ribosome and therefore we solved a new crystal structure of the S.cerevisiae 80S in complex with another lissoclimide compound at 3.1 Å resolution. The coupling of high-resolution structures with computationally-driven drug design and FRET analysis will further guide the design of more selective and less cytotoxic inhibitors.; Les ribosomes sont des complexes ribo-nucléoprotéiques qui lisent l'ARNm pour synthétiser les protéines. Il a été démontré que les inhibiteurs de la synthèse des protéines eucaryotes ont un potentiel thérapeutique important pour traiter un large éventail de cancers humains. Récemment, nous avons publié une étude multidisciplinaire dans laquelle nous démêlons le mécanisme d'action du chlorolissoclimide (CL), un composé qui partage la similarité chimique avec le cycloheximide (CHX), mais qui présente une cytotoxicité inférieure prometteuse. Nous nous sommes intéressés aux nouveaux types d'interactions de CL avec le ribosome et nous avons donc résolu une nouvelle structure cristalline du complexe S.cerevisiae 80S en complexe avec un autre composé de lissoclimide à une résolution de 3.1 Å. Le couplage de structures à haute résolution avec la conception de médicaments axée sur le calcul et l'analyse FRET guidera davantage la conception d'inhibiteurs plus sélectifs et moins cytotoxiques.

International audience; The use of a room-temperature gamma spectrometer is an issue in environmental radiation monitoring. To monitor radionuclides released around a nuclear power plant, suitable instruments giving fast and reliable information are required. High-pressure xenon (HPXe) chambers have range of resolution and efficiency equivalent to those of other medium resolution detectors such as those using NaI(Tl), CdZnTe, and LaBr3:Ce. An HPXe chamber could be a cost-effective alternative, assuming temperature stability and reliability. The CEA LIST actively studied and developed HPXe-based technology applied for environmental monitoring. Xenon purification and conditioning was performed. The design of a 4-L HPXe detector was performed to minimize the detector capacitance and the required power supply. Simulations were done with the MCNPX2.7 particle transport code to estimate the intrinsic efficiency of the HPXe detector. A behavioral study dealing with ballistic deficits and electronic noise will be utilized to provide perspective for further analysis.

International audience; The present study describes extraction of high-resolution structural connectome (HRSC) in 99 healthy subjects, acquired and made available by the Human Connectome Project. Single subject connectomes were then registered to the common surface space to allow assessment of inter-individual reproducibility of this novel technique using a leave-one-out approach. The anatomic relevance of the surface-based connectome was examined via a clustering algorithm, which identified anatomic subdivisions within the striatum. The connectivity of these striatal subdivisions were then mapped on the cortical and other subcortical surfaces. Findings demonstrate that HRSC analysis is robust across individuals and accurately models the actual underlying brain networks related to the striatum. This suggests that this method has the potential to model and characterize the healthy whole-brain structural network at high anatomic resolution.

International audience; A good knowledge of the cardiac microarchitecture is essential for better understanding the function of the human heart. This paper investigates the transmural 3D microstructure of the left ventricle of the human heart. An ex-vivo sample (7 x 7 x 15 mm3) extracted from the anterior wall of the myocardium is imaged using X-rays phase contrast micro-tomography. Sampling the volume at high isotropic resolution of 3.5 x 3.5 x 3.5 μm3 allows a clear reveal of the laminar structure of collagen wrapping the myocytes groups. An image processing protocol is developed to automatically extract cleavage planes and compute statistics of their thickness and distance separating them. The results show the clear presence of cleavage planes in the myocardium and their variation in terms of thickness, inter-planes distances and local orientation, which contribute to a better understanding of the human heart function.

International audience; Full-field optical coherence tomography (FF-OCT) based on white-light interference microscopy, is an emerging noninvasive imaging technique for characterizing biological tissue or optical scattering media with micrometer resolution. Tomographic images can be obtained by analyzing a sequence of interferograms acquired with a camera. This is achieved by scanning an interferometric microscope objectives along the optical axis and performing appropriate signal processing for fringe envelope extraction, leading to three-dimensional imaging over depth. However, noise contained in the images can hide some important details or induce errors in the size of these details. To firstly reduce temporal and spatial noise from the camera, it is possible to apply basic image post processing methods such as image averaging, dark frame subtraction or flat field division. It has been demonstrate that this can improve the quality of microscopy images by enhancing the signal to noise ratio. In addition, the dynamic range of images can be enhanced to improve the contrast by combining images acquired with different exposure times or light intensity. This can be made possible by applying a hybrid high dynamic range (HDR) technique, which is proposed in this paper. High resolution tomographic analysis is thus performed using a combination of the above-mentioned image processing techniques. As a result, the lateral resolution of the system can be improved so as to approach the diffraction limit of the microscope as well as to increase the power of detection, thus enabling new sub-diffraction sized structures contained in a transparent layer, initially hidden by the noise, to be detected.

National audience; Une reconstruction météorologique probabiliste à haute résolution sur la France depuis 1871 – Contribution aux services climatiques.

X-ray detectors for high spatial resolution imaging are mainly based on indirect detection. The detector consists of a converter screen (scintillator), light microscopy optics and a CCD or CMOS camera. The screen converts part of the absorbed X-rays into visible light image, which is projected onto the camera by means of the optics. The detective quantum efficiency of the detector is strongly influenced by the properties of the converter screen (X-ray absorption, spread of energy deposition, light yield and emission wavelength). To obtain detectors with micrometer and sub-micrometer spatial resolution, thin (1-20 µm) single crystal film scintillators are required. These scintillators are grown on a substrate by liquid phase epitaxy. The critical point for these layers is their weak absorption, especially at energies exceeding 20 keV. At the European Synchrotron radiation Facility (ESRF), X-ray imaging applications can exploit energies up to 120 keV. Therefore, the development of new scintillating materials is currently investigated. The aim is to improve the contradictory compromise between absorption and spatial resolution, to increase the detection efficiency while keeping a good image contrast even at high energies.The first part of this work presents a model describing high-resolution detectors which was developed to calculate the modulation transfer function (MTF) of the system as a function of the X-ray energy. The model can be used to find the optimal combination of scintillator and visible light optics for different energy ranges, and it guided the choice of the materials to be developed as SCF scintillators. In the second part, two new kinds of scintillators for high-resolution are presented: the gadolinium-lutetium aluminum perovskite (Gd0.5Lu0.5AlO3:Eu) and the lutetium oxide (Lu2O3:Eu) SCFs, Les détecteurs de rayon-X utilisés pour l'imagerie à haute résolution (micromètrique ou submicronique) utilisés aux synchrotrons sont pour la plupart basés sur un système de détection indirecte. Les rayons X ne sont pas directement convertis en signal électrique. Ils sont absorbés par un scintillateur qui est un matériau émettant de la lumière à la suite de l'absorption d'un rayonnement ionisant. L'image émise sous forme de lumière visible est ensuite projetée par des optiques de microscopie sur une camera 2D de type CCD ou CMOS. De nos jours, il existe différents types des scintillateurs. On distingue entre autres des scintillateurs en poudre compactée, micro structurés, céramique poly-cristalline et monocristalline. L’obtention d’une image de très bonne qualité avec une résolution spatiale au-dessous du micromètre requiert le choix d’une couche mince (1-20 µm) monocristalline. Ces types des scintillateurs peuvent être déposes sur un substrat par épitaxie en phase liquide. La très faible efficacité d’absorption dans une couche mince en fait sa faiblesse, surtout pour des énergies au-dessus de 20 keV. A l’ESRF (le synchrotron européen) des énergies jusqu'à 120 keV peuvent être exploitées pour l’imagerie. Des nouveaux scintillateurs sont donc toujours recherchés pour pouvoir améliorer le compromis entre l’efficacité d’absorption et la résolution spatiale. Dans la première partie de cet travail, un model qui décrit les détecteurs indirects pour la haute résolution, est présenté. Cet model permet de calculer la MTF (fonction de transfert de modulation) du système et peut être utilisé pour trouver la combinaison optimal de scintillateur et d’optique selon l’énergie des rayons X. Les simulations ont guidées le choix des scintillateurs à développer par épitaxie.Dans la deuxième partie, deux nouveaux types de scintillateurs développés et caractérisés dans le cadre de ce projet de thèse sont introduits : les couches minces basées sur des monocristaux de gadolinium lutétium aluminium pérovskite (GdLuAP:Eu) et d’oxyde de lutétium (Lu2O3:Eu)

5-Caffeoylquinic acid (chlorogenic acid), is classified in acid-phenols family and as polyphenolic compounds it possesses antioxidant activity. The oxydative modification of chlorogenic acid in foods may lead to alteration of their qualities; to counteract these degradation effects, molecular encapsulation was used to protect chlorogenic acid. Amylose can interact strongly with a number of small molecules, including lipids. In order to enable chlorogenic acid complexation by amylose, a C16 aliphatic chain was previously grafted onto the cycle of quinic acid. This work showed that for the two lipophilic derivatives of chlorogenic acid: hexadecyl chlorogenate obtained by alkylation and 3-O-palmitoyl chlorogenic acid obtained by acylation; only the 3-O-palmitoyl chlorogenic acid complexed amylose. The chlorogenic acid derivatives were studied by X-ray diffraction, differential scanning calorimetry and NMR to elucidate the interaction. By comparing the results with previous work on the complexation of amylose by 4-O-palmitoyl chlorogenic acid, the importance of the aliphatic chain position on the cycle of the quinic acid is clearly highlighted. A study in molecular modeling helped to understand the difference in behavior relative to amylose of these three derivatives of chlorogenic acid.

The end-Ordovician was an enigmatic interval in the Phanerozoic, known for massive glaciation potentially at elevated CO2 levels, biogeochemical cycle disruptions recorded as large isotope anomalies and a devastating extinction event. Ice-sheet volumes claimed to be twice those of the Last Glacial Maximum paradoxically coincided with oceans as warm as today. Here we argue that some of these remarkable claims arise from undersampling of incomplete geological sections that led to apparent temporal correlations within the relatively coarse resolution capability of Palaeozoic biochronostratigraphy. We examine exceptionally complete sedimentary records from two, low and high, palaeolatitude settings. Their correlation framework reveals a Cenozoic-style scenario including three main glacial cycles and higher-order phenomena. This necessitates revision of mechanisms for the end-Ordovician events, as the first extinction is tied to an early phase of melting, not to initial cooling, and the largest δ13C excursion occurs during final deglaciation, not at the glacial apex., Claims that the end-Ordovician Earth was characterized by giant ice sheets, yet paradoxically warm oceans and elevated CO2 levels are open to debate. Here, Ghienne et al. examine sedimentary records from low and high palaeolatitude settings and propose a revision of the mechanisms for end-Ordovician events.

This PhD thesis addresses the reconstruction of high resolution sea surface wind fields. The availability of such high resolution fields is critical for numerous issues, e.g. coastal management, offshore structures, oil spill disaster tracking, etc. Satellites, especially from Synthetic Aperture Radar (SAR) systems, can monitor the ocean surface at a spatial resolution of a few meters. SAR wind fields are operationally produced with spatial resolutions of less than 1 km. However, satellite SAR systems involve highly irregular sampling of the ocean surface and, for a given region, SAR wind fields may be delivered with a low temporal resolution, typically every 7-to-10 days for temperate zones. By contrast, numerical model predictions, such as European Center for Medium-range Weather Forecast (ECMWF) wind fields, are typically delivered with a high temporal resolution (e.g. every 6 h), but with a low spatial resolution (~50 km * 50 km). The question of the combination of numerical model predictions and SAR wind fields naturally arises to deliver high resolution wind fields at sea surface anywhere and anytime. Here, we state this issue as the statistical learning of transfer functions between low resolution model predictions and the associated high resolution SAR fields. We investigate the extent to which such regression functions can be determined from a set of co-located low resolution and high resolution fields. Both global, local and non-local information schemes as well as linear and non-linear regression methods are considered. As a case-study, we carry out numerical experiments for a coastal area off Norway, which involves complex low resolution to high resolution situations. We show that machine learning models based on non-linear Support Vector Regression (SVR) method, combined either with local or non-local information, perform better than more classical models, e.g. those based on analog method or Multiple Linear Regression (MLR). The SVR based models produce high resolution variability very close to the reference local variability observed by SAR, especially in coastal area. Furthermore, the reconstructed wind fields preserve the statistical distribution properties of SAR wind fields., Dans cette thèse, on s'intéresse à l'émulation de champs de vent de la surface de la mer à haute résolution. La disponibilité de ces champs à haute résolution est critique dans de nombreuses situations, par exemple la gestion du littoral, les structures offshore, le suivi de nappes de pétrole, etc. Les satellites, en particulier les systèmes à SAR (Synthetic Aperture Radar) peuvent observer la surface de mer à une résolution spatiale de quelques mètres. Les champs de vent SAR produits de manière opérationnelle atteignent une résolution spatiale de moins de 1 km. Cependant, les échantillonnages de la surface de l'océan par SAR sont irréguliers en temps en en espace pour une zone donnée. En revanche, les modèles numériques comme ECMWF (European Center for Medium-range Weather Forecast) peuvent fournir des champs de vent toutes les 6 heures, mais avec une résolution spatiale très basse (~50 km * 50 km). Nous combinons les données ECMWF et SAR pour produire des champs de vent à haute résolution spatio-temporelle. Pour cela, l'émulation à haute résolution est formulée comme l'apprentissage statistique d'une fonction de transfert entre la basse résolution et la haute résolution. La fonction de transfert est calibrée par des couples de données historiques co-localisées à basse et à haute résolution. On utilise alors des informations locales, non-locales ou globales associées à des méthodes de régression linéaire ou non-linéaire. L'approche est validée sur une zone côtière de Norvège, caractérisée par la complexité de sa topographie. Nous montrons que les modèles non-linéaires SVR (machine à Vecteurs de Support pour la Régression), utilisant les informations locales ou non-locales, donnent de meilleurs résultats par rapport aux modèles basés sur des méthodes plus classiques, comme analogues ou MLR (Régression Linéaire Multiple). Les champs émulés par la méthode SVR sont très proches des observations SAR. Les biais pourtant importants en zones côtières sont bien corrigés. En outre, les champs émulés préservent les propriétés statistiques des champs de vent SAR.

This PhD thesis addresses the reconstruction of high resolution sea surface wind fields. The availability of such high resolution fields is critical for numerous issues, e.g. coastal management, offshore structures, oil spill disaster tracking, etc. Satellites, especially from Synthetic Aperture Radar (SAR) systems, can monitor the ocean surface at a spatial resolution of a few meters. SAR wind fields are operationally produced with spatial resolutions of less than 1 km. However, satellite SAR systems involve highly irregular sampling of the ocean surface and, for a given region, SAR wind fields may be delivered with a low temporal resolution, typically every 7-to-10 days for temperate zones. By contrast, numerical model predictions, such as European Center for Medium-range Weather Forecast (ECMWF) wind fields, are typically delivered with a high temporal resolution (e.g. every 6 h), but with a low spatial resolution (~50 km * 50 km). The question of the combination of numerical model predictions and SAR wind fields naturally arises to deliver high resolution wind fields at sea surface anywhere and anytime. Here, we state this issue as the statistical learning of transfer functions between low resolution model predictions and the associated high resolution SAR fields. We investigate the extent to which such regression functions can be determined from a set of co-located low resolution and high resolution fields. Both global, local and non-local information schemes as well as linear and non-linear regression methods are considered. As a case-study, we carry out numerical experiments for a coastal area off Norway, which involves complex low resolution to high resolution situations. We show that machine learning models based on non-linear Support Vector Regression (SVR) method, combined either with local or non-local information, perform better than more classical models, e.g. those based on analog method or Multiple Linear Regression (MLR). The SVR based models produce high resolution variability very close to the reference local variability observed by SAR, especially in coastal area. Furthermore, the reconstructed wind fields preserve the statistical distribution properties of SAR wind fields.; Dans cette thèse, on s'intéresse à l'émulation de champs de vent de la surface de la mer à haute résolution. La disponibilité de ces champs à haute résolution est critique dans de nombreuses situations, par exemple la gestion du littoral, les structures offshore, le suivi de nappes de pétrole, etc. Les satellites, en particulier les systèmes à SAR (Synthetic Aperture Radar) peuvent observer la surface de mer à une résolution spatiale de quelques mètres. Les champs de vent SAR produits de manière opérationnelle atteignent une résolution spatiale de moins de 1 km. Cependant, les échantillonnages de la surface de l'océan par SAR sont irréguliers en temps en en espace pour une zone donnée. En revanche, les modèles numériques comme ECMWF (European Center for Medium-range Weather Forecast) peuvent fournir des champs de vent toutes les 6 heures, mais avec une résolution spatiale très basse (~50 km * 50 km). Nous combinons les données ECMWF et SAR pour produire des champs de vent à haute résolution spatio-temporelle. Pour cela, l'émulation à haute résolution est formulée comme l'apprentissage statistique d'une fonction de transfert entre la basse résolution et la haute résolution. La fonction de transfert est calibrée par des couples de données historiques co-localisées à basse et à haute résolution. On utilise alors des informations locales, non-locales ou globales associées à des méthodes de régression linéaire ou non-linéaire. L'approche est validée sur une zone côtière de Norvège, caractérisée par la complexité de sa topographie. Nous montrons que les modèles non-linéaires SVR (machine à Vecteurs de Support pour la Régression), utilisant les informations locales ou non-locales, donnent de meilleurs résultats par rapport aux modèles basés sur des méthodes plus classiques, comme analogues ou MLR (Régression Linéaire Multiple). Les champs émulés par la méthode SVR sont très proches des observations SAR. Les biais pourtant importants en zones côtières sont bien corrigés. En outre, les champs émulés préservent les propriétés statistiques des champs de vent SAR.

International audience; The use of non-pollen palynomorphs, and among them spores of coprophilous fungi, has become greatly important in palaeoecological studies. Particularly, the genus Sporormiella has been demonstrated to be the most valuable proxy for the presence of wild and domestic herbivores. This genus could also be used to determine livestock density and reconstruct pastoral pressure during the Holocene. Non-standard counting methods have been established to determine coprophilous fungal spore abundance in sediments. Moreover, these analyses are faced with the recurrent problem of setting the minimum counting sum as small as possible to save time. We researched the reliability of Sporormiella concentration estimates based on different counting sums, using low to high count samples. Box-plots indicate that the variability of inferred Sporormiella concentrations decreases progressively with increasing sums. Statistical comparisons show that the means of box-plots became stabilised after the counts have reached 300-350 exotic marker grains. Moreover, a count of 300-350 exotic marker grains is sufficient to produce a Sporormiella concentration estimate, whatever the amount. Finally, we propose that this counting limit is valid for other fungal spores as well.

International audience; Ultrasonic non destructive testing consists in emitting an acoustic wave in a material and then locating the reflected echoes produced by impedance changes, due to flaws or medium discontinuities. In some cases, echoes can overlap in the A-scan (typically for layered materials), yielding a difficult analysis: techniques such as matched filtering may fail and advanced techniques are necessary to locate the echoes. Sparse deconvolution methods have been recently applied to such problems. The challenge is to estimate a sparse sequence composed by the echoes locations (times of flight) and amplitudes. Usually, deconvolution is addressed by considering restoration at the acquisition sampling scale. This limits the precision of the spike location and may cause spike splitting. In this paper, we consider a high-resolution formulation of the deconvolution problem with a more precise restoration grid. To do so, we extend the approach proposed by Soussen et al. (IEEE Trans. Signal. Process, 2011) which minimizes a data misfit least-square criterion, penalized by a L0-norm term. The method has been tested on synthetic and experimental data. Compared to classical deconvolution algorithms, results show a better estimation of times of flight for a small increase of the computation time.

Aim To simulate the sowing dates of 11 major annual crops at the global scale at high spatial resolution, based on climatic conditions and crop-specific temperature requirements. Location Global. Methods Sowing dates under rainfed conditions are simulated deterministically based on a set of rules depending on crop-and climate-specific characteristics. We assume that farmers base their timing of sowing on experiences with past precipitation and temperature conditions, with the intra-annual variability being especially important. The start of the growing period is assumed to be dependent either on the onset of the wet season or on the exceeding of a crop-specific temperature threshold for emergence. To validate our methodology, a global data set of observed monthly growing periods (MIRCA2000) is used. Results We show simulated sowing dates for 11 major field crops world-wide and give rules for determining their sowing dates in a specific climatic region. For all simulated crops, except for rapeseed and cassava, in at least 50% of the grid cells and on at least 60% of the cultivated area, the difference between simulated and observed sowing dates is less than 1 month. Deviations of more than 5 months occur in regions characterized by multiple-cropping systems, in tropical regions which, despite seasonality, have favourable conditions throughout the year, and in countries with large climatic gradients. Main conclusions Sowing dates under rainfed conditions for various annual crops can be satisfactorily estimated from climatic conditions for large parts of the earth. Our methodology is globally applicable, and therefore suitable for simulating sowing dates as input for crop growth models applied at the global scale and taking climate change into account.

Raman imaging of plant cell walls represents a nondestructive technique that can provide insights into chemical composition in context with structure at the micrometer level (

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Background: With the increasing availability of EST databases and whole genome sequences, SNPs have become the most abundant and powerful polymorphic markers. However, SNP chip data generally suffers from ascertainment biases caused by the SNP discovery and selection process in which a small number of individuals are used as discovery panels. The ongoing International Citrus Genome Consortium sequencing project of the highly heterozygous Clementine and sweet orange genomes will soon result in the release of several hundred thousand SNPs. The primary goals of this study were: (i) to estimate the transferability within the genus Citrus of SNPs discovered from Clementine BACend sequencing (BES), (ii) to estimate bias associated with the very narrow discovery panel, and (iii) to evaluate the usefulness of the Clementine-derived SNP markers for diversity analysis and comparative mapping studies between the different cultivated Citrus species. Results: Fifty-four accessions covering the main Citrus species and 52 interspecific hybrids between pummelo and Clementine were genotyped on a GoldenGate array platform using 1,457 SNPs mined from Clementine BES and 37 SNPs identified between and within C. maxima, C. medica, C. reticulata and C. micrantha. Consistent results were obtained from 622 SNP loci. Of these markers, 116 displayed incomplete transferability primarily in C. medica, C. maxima and wild Citrus species. The two primary biases associated with the SNP mining in Clementine were an overestimation of the C. reticulata diversity and an underestimation of the interspecific differentiation. However, the genetic stratification of the gene pool was high, with very frequent significant linkage disequilibrium. Furthermore, the shared intraspecific polymorphism and accession heterozygosity were generally enough to perform interspecific comparative genetic mapping. Conclusions: A set of 622 SNP markers providing consistent results was selected. Of the markers mined from Clementine, 80.5% were successfully transferred to the whole Citrus gene pool. Despite the ascertainment biases in relation to the Clementine origin, the SNP data confirm the important stratification of the gene pools around C. maxima, C. medica and C. reticulata as well as previous hypothesis on the origin of secondary species. The implemented SNP marker set will be very useful for comparative genetic mapping in Citrus and genetic association in C. reticulata.

International audience; High-resolution record of Holocene erosion patterns in a high altitude lake (Lake Anterne, NW French Alps): a witness of environmental changes, climatic variability and human activities

ISBN: 978-0-8194-8341-6 - WOS; International audience; In monitoring vegetation change and urban planning, the measure and the mapping of the green vegetation over the Earth play an important role. The normalized difference vegetation index (NDVI) is the most popular approach to generate vegetation maps for remote sensing imagery. Unfortunately, the NDVI generates low resolution vegetation maps. Highresolution imagery, such as IKONOS imagery, can be used to overcome this weakness leading to better classification accuracy. Hence, it is important to derive a vegetation index providing the high-resolution data. Various scientific researchers have proposed methods based on high-resolution vegetation indices. These methods use image fusion to generate high-resolution vegetation maps. IKONOS produces high-resolution panchromatic (Pan) images and low-resolution multispectral (MS) images. Generally, for the image fusion purpose, the conventional linear interpolation bicubic scheme is used to resize the low-resolution images. This scheme fails around edges and consequently produces blurred edges and annoying artefacts in interpolated images. This study presents a new index that provides high-resolution vegetation maps for IKONOS imagery. This vegetation index (HRNDVI: High Resolution NDVI) is based on a new derived formula including the high-resolution information. We use an artefact free image interpolation method to upsample the MS images so that they have the same size as that of the Pan images. The HRNDVI is then computed by using the resampled MS and the Pan images. The proposed vegetation index takes the advantage of the high spatial resolution information of Pan images to generate artefact free vegetation maps. Visual analysis demonstrates that this index is promising and performs well in vegetation extraction and visualisation.

One of the major challenges is using subspace-based approaches for the determination of the parameters of one- or multidimensional signals is their practical applicability on real data containing \emph{damped} exponentials. In this paper, we present a comparison survey of low complexity subspace-based methods and we focus on 2-D nuclear magnetic resonance (NMR) spectroscopy application. We first present free search 2-D estimation approaches for damped sinusoids and we analyze their performances using simulated signals. Then, we present the results obtained on real 2-D NMR data.

La version V2 inclut les modifications proposées par les reviewers.; International audience; A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. Statistical numerical experiments are implemented to quantify the propagation of errors from line parameters to absorption coefficients or cross-sections as a function of the resolution. The method uses line parameter predictions (position and intensity) with estimated uncertainties derived from global polyad models. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high-resolution modeling is not accurate enough to meet the desired precision. As an illustration, it is applied to predict the absorption coefficient of methane at high temperature involving simultaneously well known lower energy levels (cold bands) and higher energy levels with much lower precisions (hot bands). Potential extensions are discussed in the context of atmospheric remote sensing of astrophysical objects.

International audience; In order to model the high-resolution infrared spectrum of the phosphine molecule in the 3 mu m region, a global approach involving the lower three polyads of the molecule (Dyad, Pentad and Octad) as been applied using an effective hamiltonian in the form of irreducible tensors. This model allowed to describe all the 15 vibrational states involved and to consider explicitly all relevant ro-vibrational interactions that cannot be accounted for by conventional perturbation approaches. 2245 levels (up to J=14) observed through transitions arising from 34 cold and hot bands including all available existing data as well as new experimental data have been fitted simultaneously using a unique set of effective hamiltonian parameters. The rms achieved is 0.63 10^{-3} cm^{-1} for 450 Dyad levels, 1.5 10^{-3} cm^{-1} for 1058 Pentad levels (from 3585 transitions) and 4.3 10^{-3} cm^{-1} for 737 Octad levels (from 2243 transitions). This work represents the first theoretical modeling of the 3 mu m region. It also improves the modeling of the region around 4.5 mu m by dividing the rms reported by previous works by a factor 6. A preliminary intensity analysis based on consistent sets of effective dipole moment operators for cold and hot bands has been simultaneously undertaken for direct comparison between observed and modeled absorption from 700 to 3500 cm^{-1}.

International audience; The structure of lithium borate glasses and liquids (xLi(2)O center dot(1-x)B2O3 with x=0.1, 0.20, 0.25 and 0.33) has been investigated by neutron diffraction coupled with Li isotopic substitution at temperatures up to 1173-1273 K. Both the short range order around B and Li is changed, with the conversion of BO4 to BO3 and a subsequent increase of NBOs (nonbridging oxygens) around Li as temperature increases. The quantitative boron coordination change has been assessed by a Gaussian fitting of the B-O pair contribution. ne increasing presence of NBOs results in the opening of the borate network and the disappearance of superstructural borate rings. The reorganisation of the structure above the glass transition temperature provides a structural mechanism for the modifications of the thermodynamic and configurational properties of borate liquids.

We report a 13-year (1992–2005) dataset of total column measurements of formaldehyde (HCHO) over Lauder, New Zealand, inferred from solar infrared spectra measured using a high-resolution Fourier Transform Spectrometer (FTS). Ambient HCHO concentrations at this rural location are often close to levels typical of remote marine environments (15 molecules cm−2, peaking during summer months. A simple box model of CH4 oxidation reproduces the observed broad-scale seasonal cycle, but significantly underestimates the seasonal peak HCHO ground concentrations during summer. This suggests the existence of an additional significant source of HCHO, possibly isoprene that cannot be explained by oxidation of CH4 alone. The ground-based FTS column data compare well with collocated HCHO column measurements from the Global Ozone Monitoring Experiment (GOME) satellite instrument during the operational period of GOME (1996–2001, r2=0.65, mean bias=10%, n=48).

Photoionization cross sections for the production of the doubly charged ion N2+ from N-2 have been measured by means of synchrotron radiation in the photon energy range from 50 to 110 eV. The appearance energy for N2+ has been determined as 55.2 +/- 0.2 eV, i.e., about 1.3 eV higher than the spectroscopic dissociation limit leading to the charge asymmetric dissociation channel N2+(P-2)+N(S-4) at 53.9 eV. The onset of a second threshold at 59.9 +/- 0.2 eV is detected and the energy dependence of photoion intensities near the threshold regions is interpreted in terms of the Wannier theory. The production of the N2+ dication is discussed in terms of direct and indirect mechanisms for dissociative charge asymmetric photoionization and by comparison with the potential energy curves of the intermediate N-2(2+) dication. Experimental evidences for the opening of the Coulomb explosion channel N2++N+ at high photon energies are provided by measuring the kinetic energy release spectra of N2+ fragments at selected photon energies. (c) 2007 American Institute of Physics.

AMONG THE DIFFERENT SOURCES NATURAL BIOLOGICALLY ACTIVE COMPOUNDS, REPRESENT THE VENOM, BY THE GREAT VARIETY OF THEIR COMPONENTS, A TARGET OF CHOICE FOR MEDICAL RESEARCH. THEY CONTAIN TOXINS ARE VARIOUS AND UNDERSTAND THEIR ACTIONS IN THE PURPOSE OF SIMILAR INTEREST Summarizing PHARMACOLOGICAL PASS THROUGH PRECISE DETERMINATION OF THEIR CHEMICAL STRUCTURE WITH LOW STRESS THAT THE QUANTITY OF MATERIAL GENERALLY AVAILABLE ALL MAKES PROCESS OF SEPARATION AND CHARACTERIZATION VERY DELICATE. IT IS IN THIS CONTEXT THAT THESE LIES THAT THE PURPOSE OF WHICH WAS TO DEVELOP NEW STRATEGIES FOR ANALYSIS BY MASS SPECTROMETRY FOR HIGH RESOLUTION NEW PEPTIDE TOXINS. THIS THESIS A PARTICULAR TARGET THE STUDY OF TOXIN PEPTIDE CONES (SHELLFISH POISON FOR USING A HARPOON AND ACHIEVED paralyzed! R THEIR PREY) AND SNAKES. THE FINAL MASS SPECTROMETRY OF HIGH RESOLUTION has emerged as a VERY POWERFUL TOOL FOR THE CHARACTERIZATION OF SMALL MODIFIED TOXINS BY ITS MAIN BUILDING IN TERMS OF ACCURACY ON THE MEASUREMENT OF MASS BUT ALSO IN THE STUDY OF TOXIN FOR MORE LARGE WHICH THE LATEST TECHNOLOGY OF DISSOCIATION BY ELECTRON CAPTURE OF THE MOST EFFICIENT.; PARMI LES DIFFERENTES SOURCES NATURELLES DE COMPOSES BIOLOGIQUEMENT ACTIFS, LES VENINS REPRESENTENT, DE PAR LA GRANDE VARIETE DE LEURS CONSTITUANTS, UNE CIBLE DE CHOIX POUR LA RECHERCHE MEDICALE. LES TOXINES QU'ILS CONTIENNENT SONT VARIEES ET COMPRENDRE LEUR MODE D'ACTION DANS LE BUT DE SYNTHETISER DES ANALOGUES D'INTERET PHARMACOLOGIQUE PASSE PAR UNE DETERMINATION PRECISE DE LEUR STRUCTURE CHIMIQUE AVEC LA CONTRAINTE QUE LA FAIBLE QUANTITE DE MATERIEL GENERALEMENT DISPONIBLE REND L'ENSEMBLE DES PROCESSUS DE SEPARATION ET DE CARACTERISATION TRES DELICAT. C'EST DANS CE CONTEXTE QUE SE SITUE CETTE THESE DONT L'OBJECTIF A ETE DE METTRE AU POINT DE NOUVELLES STRATEGIES D'ANALYSE PAR SPECTROMETRIE DE MASSE A HAUTE RESOLUTION DE NOUVELLES TOXINES PEPTIDIQUES. CETTE THESE A PARTICULIEREMENT CIBLE L'ETUDE DE TOXINES PEPTIDIQUES DE CONES (MOLLUSQUES UTILISANT UN HARPON VENIMEUX POUR ATTEINDRE ET PARALYSE! R LEUR PROIE) ET DE SERPENTS. AU FINAL, LA SPECTROMETRIE DE MASSE A HAUTE RESOLUTION S'EST REVELEE COMME UN OUTIL TRES PUISSANT POUR LA CARACTERISATION DE PETITES TOXINES MODIFIEES PAR SES GRANDES CAPACITES EN TERMES DE PRECISION SUR LA MESURE DE MASSE MAIS AUSSI DANS L'ETUDE DE PLUS GROSSES TOXINES POUR LESQUELLES LA RECENTE TECHNIQUE DE DISSOCIATION PAR CAPTURE D'ELECTRON S'EST MONTREE DES PLUS PERFORMANTES.

International audience; Spectra comprised of hundreds of time-components for absorption path lengths up to 130 km have been recorded around 1050 nm by combining two recent techniques, intracavity laser spectroscopy with vertical external cavity surface emitting multiple-quantum-well lasers and time-resolved Fourier transform spectroscopy. A sensitivity of 1 10^{-10} cm^{-1}.Hz^{-1/2} is achieved, for simultaneously acquired 10^4 spectral elements, three orders of magnitude better than the sensitivity obtained in previous similar experiments. Specific advantages of the method, especially for frequency and intensity metrology of weak absorption transitions, are discussed.

The purpose of this work is to build a radargrammetric chain leading to the 3-D structures from high resolution SAR (Synthetic Aperture Radar) images. High resolution 3D maps obtained by SAR imaging are interesting because of their all-weather character. The data we use, are acquired by the experimental airborne RAMSES sensor of ONERA and represent industrial areas. These images contain a lot of strong echoes and structure roofs are not always sharply marked. These phenomena make difficult the image interpretation and unsuitable the classical methods of 3-D extraction. Then we propose a radiometric and geometrical analysis of the data. This analysis leads to an adapted algorithmic chain that aims at recovering cylindrical structures and parallelepipeds, such as tanks and rectangular buildings. In the first part concerning the analysis, we present the simplified radar image interpretation on structures and study the statistics of amplitude images. The opportunity of high resolution radargrammetry is also checked theoretically then experimentally. The second part deals with the radargrammetric chain. Our approach consists into two main steps: structure extraction from strong echoes then 3D estimation. The structure extraction represents an important part in this work. We propose a method including the recognition of the best circular or rectangular pattern including the strong structure by an area-based criterion optimization. We compare it with more classical methods of image processing and study several criteria and stochastic optimization techniques. Then, we present a method for the computation of ground altitudes between structures and their height. The results show the pertinence of our approach when the structure is well detected and in the best case where a roof echo is detectable., Cette thèse concerne l'élaboration d'une chaîne de traitements radargrammétrique conduisant aux structures 3-D à partir d'images radar haute résolution. L'intérêt de la cartographie 3-D par imagerie RSO (Radar à Synthèse d'Ouverture) est que l'image radar peut être acquise par tout temps et de jour comme de nuit. Nous disposons d'images issues du capteur expérimental RAMSES de l'ONERA et représentant des scènes industrielles. Ces données contiennent de nombreux échos forts et les toits des structures sont peu visibles. Ces phénomènes rendent difficile l'interprétation des images et insuffisantes les méthodes classiques de reconstruction 3-D. Face à ces particularités, nous menons l'analyse radiométrique et géométrique des données. Cette analyse aboutit à la proposition d'une chaîne algorithmique adaptée qui vise à restituer les structures cylindriques et parallélépipédiques telles que cuves et bâtiments de forme simple. Dans la première partie concernant l'analyse, nous donnons l'interprétation simplifiée de l'image radar d'une structure et étudions les statistiques des images d'amplitude. L'opportunité de la radargrammétrie haute résolution est vérifiée théoriquement puis expérimentalement. La seconde partie présente la chaîne radargrammétrique. Notre approche comprend deux étapes principales : l'extraction des structures à partir des échos forts puis l'estimation du 3-D. L'extraction des structures fait l'objet d'un chapitre important de cette thèse. Nous proposons une méthode permettant la reconnaissance de la forme englobant la structure brillante, circulaire ou rectangulaire, par optimisation d'un critère surfacique. Nous la comparons avec des techniques plus classiques de traitement d'images et étudions plusieurs critères ainsi que l'apport de méthodes d'optimisation stochastique. Nous présentons ensuite une méthodologie pour obtenir les altitudes du sol entre les structures détectées et leur hauteur. Les résultats montrent la pertinence de l'approche lorsque la structure a été détectée et dans le cas favorable où un écho du toit est détectable.