Surface Active Statistique : Optimisation de la topologie d'une surface définie par interpolation linéaire sur un maillage triangulaire utilisant la minimisation de la complexité stochastique

L'algorithme présenté permet une estimation rapide de la valeur moyenne d'images fortement bruitées mettant en oeuvre une surface maillée et une technique de MCS ne nécessitant aucun paramètre à régler dans le critère à minimiser

Process economical effects of implementation of ready-to-use micro carriers in cell- based virus vaccine production

Micro-carriers are used as support for the growth of adherent cells. By providing a large cultivation surface in bioreactor cultures, micro-carriers have replaced, to a great extent, cultivation in Cell Factory™ systems or roller bottles over the last decades. At Sanofi Pasteur, one of the world leaders in human vaccines, Cytodex™ 1 microcarriers have been used in the production of viral vaccines on Vero cells for several years. In accordance with the supplier’s recommendation, the microcarriers that are delivered dry are swollen in buffer, washed, and heat-sterilized before use. Since October 2016 a ready-to-use Cytodex™ 1 alternative, delivered presterilized by gamma irradiation, is available. Before implementing the change, the presterilized alternative was first evaluated with regards to reduced preparation time and cost. With a two-year shelf-life, the presterilized alternative reduced utility cost and added flexibility to operations by decreasing the need for steam and stainless steel materials in viral production facilities, and in alignment with extended use of single-use bioreactors equipment. The second step was to compare the cell growth and viral productivity using this ready-to-use alternative with that of the prior referenced product in place. Both cell growth and viral productivity were comparable between the two products, which supported further the documentation for the implementation of this ready-to-use alternative in GMP manufacturing for new R&D vaccine projects. The qualification process covered technical, quality, and analytical aspects based on the supplier documentation, and internal analyses and justification regarding our requirements in upstream vaccine production. While the presterilized Cytodex™ 1 microcarriers are now implemented in process development for new vaccines and qualified for manufacturing of clinical batches of new vaccine products, the next step will be to evaluate the benefits and impacts of replacing the microcarrier reference product with the gamma sterilized alternative on industrial products

Active polarimetric imaging with adaptive contrast optimization (Orale)

International audienceWe propose a method for semi-automatic target detection and contrast optimization making joint use of an adaptive polarimetric imager and a statistical image segmentation algorithm. It can be used to detect targets that differ from the background by their polarimetric properties. This method illustrates the benefits of integrating digital processing algorithms in the image acquisition process, rather than using them only for post-processing

Joint contrast optimization and object segmentation in active polarimetric images

International audienceWe present a method for automatic target detection based on the iterative interplay between an active polarimetric imager with adaptive capabilities and a snake-based image segmentation algorithm. It successfully addresses the difficult situations where the target and the background differ only by their polarimetric properties. This method illustrates the benefits of integrating digital processing algorithms at the heart of the image acquisition process rather than using them only for postprocessing

Algorithme de réduction de speckle basé sur le Maximum de Vraisemblance et modélisation des niveaux de gris par un maillage triangulaire continu

- Nous présentons dans cet article une nouvelle méthode de réduction de speckle qui repose sur un algorithme de Maximum de Vraisemblance. Cette méthode a pour particularité d'utiliser un modèle global de l'image, en opposition aux fenêtres glissantes utilisées dans de nombreux algorithmes. Le modèle de l'image est construit à partir d'un maillage triangulaire continu. Une régularisation (en plus de celle introduite par le maillage lui-même) basée sur les lignes de niveaux des valeurs de gris de l'image, est introduite afin d'améliorer la réduction de speckle dans le cas de maillage fin. Une comparaison des performances avec des algorithmes connus est réalisée à l'aide d'images synthétiques. Un résultat sur une image réelle est également présenté

Généralisation du filtre adapté au cas multi-cibles en présence de brouilleurs pour une localisation radar

Nous étudions dans cet article le cas de l'estimation des paramètres de cibles (avions), qui renvoient l'impulsion émise par le radar avec un retard et une atténuation complexe (SER), ceci en présence de brouilleurs à bruit. Pour cela nous mettons en oeuvre deux estimateurs du maximum de vraisemblance qui traitent respectivement les deux cas suivants: la présence d'un seul brouilleur à bruit blanc, dont on cherche les caractéristiques (puissance, position) et la présence de plusieurs brouilleurs à bruit, corrélés temporellement, dont on connaît la matrice interspectrale (blanchiement). Nous établissons les bornes de Cramer-Rao des différents problèmes proposés et étudions les performances obtenues à l'aide de simulations

Barcoding T Cell Calcium Response Diversity with Methods for Automated and Accurate Analysis of Cell Signals (MAAACS)

International audienceWe introduce a series of experimental procedures enabling sensitive calcium monitoring in T cell populations by confocal video-microscopy. Tracking and post-acquisition analysis was performed using Methods for Automated and Accurate Analysis of Cell Signals (MAAACS), a fully customized program that associates a high throughput tracking algorithm, an intuitive reconnection routine and a statistical platform to provide, at a glance, the calcium barcode of a population of individual T-cells. Combined with a sensitive calcium probe, this method allowed us to unravel the heterogeneity in shape and intensity of the calcium response in T cell populations and especially in naive T cells, which display intracellular calcium oscillations upon stimulation by antigen presenting cells

No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere, which-given methane's lifetime of several centuries-predicts an even, well mixed distribution of methane. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally

Martian dust storm impact on atmospheric H₂O and D/H observed by ExoMars Trace Gas Orbiter

Global dust storms on Mars are rare but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere, primarily owing to solar heating of the dust. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes, as well as a decrease in the water column at low latitudes. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere

Seasonal mass transfer on the nucleus of comet 67P/Chuyumov–Gerasimenko

We collect observational evidence that supports the scheme of mass transfer on the nucleus of comet 67P/Churyumov–Gerasimenko. The obliquity of the rotation axis of 67P causes strong seasonal variations. During perihelion the southern hemisphere is four times more active than the north. Northern territories are widely covered by granular material that indicates back fall originating from the active south. Decimetre sized chunks contain water ice and their trajectories are influenced by an antisolar force instigated by sublimation. OSIRIS observations suggest that up to 20 per cent of the particles directly return to the nucleus surface taking several hours of traveltime. The back fall covered northern areas are active if illuminated but produce mainly water vapour. The decimetre chunks from the nucleus surface are too small to contain more volatile compounds such as CO₂ or CO. This causes a north–south dichotomy of the composition measurements in the coma. Active particles are trapped in the gravitational minimum of Hapi during northern winter. They are ‘shock frozen’ and only re-activated when the comet approaches the sun after its aphelion passage. The insolation of the big cavity is enhanced by self-heating, i.e. reflection and IR radiation from the walls. This, together with the pristinity of the active back fall, explains the early observed activity of the Hapi region. Sobek may be a role model for the consolidated bottom of Hapi. Mass transfer in the case of 67P strongly influences the evolution of the nucleus and the interpretation of coma measurements