Aeration and hydrodynamics in submerged membrane bioreactors

Membrane bioreactor (MBR) is already a well-developed wastewater treatment process for both municipal and industrial applications. Nonetheless, membrane fouling remains a significant problem for its wider development. In the case of submerged membrane bioreactors (SMBRs), one of the most efficient strategies to limit fouling is the use of a gas/liquid two-phase flow to enhance the mass transfer. However, the effect of aeration still remains incompletely understood. The complexity of flows and of the nature of activated sludge makes a theoretical approach difficult. Aeration is the source of a large part of the operating costs in most industrial scale plants and its optimization is a necessity to make the process really efficient. This paper first deals with hydrodynamics in MBRs, then it reviews the parameters of aeration and their impact on filtration performance. Finally, the effects of aeration mechanisms on biological media are described

Submerged membrane bioreactor for waste water treatment: determination of the shear stresses produced by coarse bubbles

Submerged membrane bioreactor for waste water treatment: determination of the shear stresses produced by coarse bubble

Differential effects of parietal and frontal inactivations on reaction times distributions in a visual search task

The posterior parietal cortex participates to numerous cognitive functions, from perceptual to attentional and decisional processes. However, the same functions have also been attributed to the frontal cortex. We previously conducted a series of reversible inactivations of the lateral intraparietal area (LIP) and of the frontal eye field (FEF) in the monkey which showed impairments in covert visual search performance, characterized mainly by an increase in the mean reaction time (RT) necessary to detect a contralesional target. Only subtle differences were observed between the inactivation effects in both areas. In particular, the magnitude of the deficit was dependant of search task difficulty for LIP, but not for FEF. In the present study, we re-examine these data in order to try to dissociate the specific involvement of these two regions, by considering the entire RT distribution instead of mean RT. We use the LATER model to help us interpret the effects of the inactivations with regard to information accumulation rate and decision processes. We show that: (1) different search strategies can be used by monkeys to perform visual search, either by processing the visual scene in parallel, or by combining parallel and serial processes; (2) LIP and FEF inactivations have very different effects on the RT distributions in the two monkeys. Although our results are not conclusive with regards to the exact functional mechanisms affected by the inactivations, the effects we observe on RT distributions could be accounted by an involvement of LIP in saliency representation or decision-making, and an involvement of FEF in attentional shifts and perception. Finally, we observe that the use of the LATER model is limited in the context of a visual search as it cannot fit all the behavioral strategies encountered. We propose that the diversity in search strategies observed in our monkeys also exists in individual human subjects and should be considered in future experiments

Un dépôt révolutionnaire : des statues de Marly à Bolbec

En 1794, la petite ville normande de Bolbec, connue pour son industrie textile est administrée par un maire acquis à la Révolution, dévoué à la cause publique et au développement de sa cité et au bien-être physique et moral de ses habitants, Jacques-Dominique Ruffin. Son adhésion aux idées nouvelles et à la Révolution française est affichée et il présente lui-même son fils, François-Amable, âgé de vingt et un ans, en septembre 1792, pour signer son engagement dans l’armée de le République à l..

Validation of three satellite-derived databases of surface solar radiation using measurements performed at 42 stations in Brazil

International audienceThe SoDa website (www.soda-pro.com) is populated with numerous solar-related Web services. Among them, three satellite-derived irradiation databases can be manually or automatically accessed to retrieve radiation values within the geographical coverage of the Meteosat Second Generation (MSG) satellite: the two most advanced versions of the HelioClim-3 database (versions 4 and 5, respectively HC3v4 and HC3v5), and the CAMS radiation service. So far, these databases have been validated against measurements of several stations in Europe and North Africa only. As the quality of such databases depends on the geographical regions and the climates, this paper extends this validation campaign and proposes an extensive comparison on Brazil and global irradiation received on a horizontal surface. Eleven stations from the Brazilian Institute of Space Research (INPE) network offer 1 min observations, and thirty-one stations from the Instituto Nacional de Meteorologia (INMET) network offer hourly observations. The satellite-derived estimates have been compared to the corresponding observations on hourly, daily and monthly basis. The bias relative to the mean of the measurements for HC3v5 is mostly comprised between 1 and 3 %, and that for HC3v4 between 2 and 5 %. These are very satisfactory results and they demonstrate that HC3v5, and to a lesser extent HC3v4, may be used in studies of long-term changes in SSI in Brazil. The situation is not so good with CAMS radiation service for which the relative bias is mostly comprised between 5 and 10 %. For hourly irradiation, the relative RMSE ranges from 15 to 33 %. The correlation coefficient is very large for all stations and the three databases, with an average of 0.96. The three databases reproduce well the hour from hour changes in SSI. The errors show a tendency to increase with the viewing angle of the MSG satellite. They are greater in tropical areas where the relative humidity in the atmosphere is important. It is concluded that except for the overestimation by CAMS radiation service, the three databases are suitable for studies of the solar resources in Brazil

Comment caractériser les relations entre élevage et territoire ? Une revue de la diversité des approches existant dans la littérature.

Si les débats sur l'élevage d'herbivores sont largement posés à l'échelle planétaire (réduction des gaz à effets de serre, alimentation mondiale, biodiversité), l'élevage contribue aussi au développement durable des territoires ruraux : il s'y présente comme une activité ancrée dans des sociétés, des filières et un espace local où il fournit des produits et services multiples. Nous proposons une revue bibliographique visant à préciser comment les chercheurs abordent les relations entre élevage et territoire. Elle a été menée sur des moteurs de recherche des sciences biotechniques et sociales. Les mots-clés utilisés sont issus du champ des systèmes d'élevage et du champ du territoire, avec un accent sur ses dimensions spatiales et sociales. Trois grands domaines d'étude des liens entre " élevage " et " territoire" ressortent. Ils traitent respectivement : 1) des liens entre les activités agricoles (dont l'élevage) et le territoire réduit à sa dimension spatiale, support de ressources localisées. Par exemple, les " land use and land cover studies " développent des modèles des dynamiques spatiales des utilisations du sol sous l'effet de grands moteurs de changement (politiques agricoles, marchés). Les implications de ces dynamiques spatiales sur les processus écologiques font partie des fronts de recherche actuels. 2) de la diversité et la complémentarité des systèmes d'élevage au sein d'un territoire délimité. Sont alors mises en évidence les fonctions productives et non productives de l'élevage (sécurité alimentaire, gestion du risque), ainsi que les articulations entre activités d'élevage et autres activités (agricoles ou non). La diversité des fonctions, mais aussi les façons de produire, sont souvent vue comme un facteur de résilience. 3) des systèmes d'élevage vus comme des systèmes techniques imbriqués dans des groupes humains. Les dynamiques sont alors analysées à travers (i) les changements de normes et d'identités d'une société locale et (ii) les ressorts des actions collectives, au croisement des enjeux de filière et d'environnement. L'association de ces trois domaines demeure rare. Elle apparaît cependant comme un enjeu scientifique interdisciplinaire majeur pour produire des connaissances sur l'élevage et sur ce vers quoi il peut aller, en tant que ressource pour le développement durable des territoires. (Résumé d'auteur

Étude comparative de la mesure de l'épaisseur du buffy-coat avec les valeurs chiffrées de l'hémogramme chez le chien

Le buffy coat, obtenu après centrifugation de sang de chien recueilli sur anticoagulant selon les recommandations du National Committee for Clinical Laboratory Standards (NCCLS), est le reflet de la numération leuco-plaquettaire chez le chien. Notre étude s’intéresse à la fiabilité de la mesure de cette couche leuco-plaquettaire en vue d’un diagnostic rapide de leucopénie et leucocytose. Seules des méthodes de mesures simples (abaque, réglette et papier millimétré) ont été étudiées dans un souci de réalisation au quotidien par le praticien vétérinaire. Notre étude comparative montre que la mesure du leucocrite est un outil diagnostic supplémentaire dans le cas de leucocytoses marquées

Validation of HelioClim-3 version 4, HelioClim-3 version 5 and MACC-RAD using 14 BSRN stations

International audienceThis communication presents the results of a comparison of three satellite-derived databases covering Africa, Europe, Middle East and part of South America, against corresponding 15 min irradiations of very high quality measured by fourteen Baseline Surface Radiation Network (BSRN) stations. The three databases are accessible via the SoDa Service website, and are the two latest versions of HelioClim-3: versions 4 (HC3v4) and 5 (HC3v5), and the MACC-RAD database. The comparison was performed for durations of 15 min, 1 h, 1 day and 1 month for both the global irradiation received on a horizontal surface (GHI) and the direct irradiation received on a plane normal to sun rays (DNI). It is found that the three satellite-derived radiation databases exhibit satisfactory performances. For most of the fourteen locations, HC3v5 surpasses HC3v4 and MACC-RAD, with a bias ranging from-4 to 5% for the GHI and for all tested duration. The correlation coefficient is large for all databases and most often greater than 0.92 for 15 min and 0.98 for daily irradiation for GHI. The RMSE is fairly constant for all locations for 15 min and is approximately 20 kWh m-2 –slightly greater for MACC-RAD.-For daily irradiation, it ranges between 300 and 400 kWh m-2 for HC3v5, 300 and 500 kWh m-2 for HC3v4, and 400 and 550 kWh m-2 for MACC-RAD. Bias for the DNI is larger in absolute values than for GHI for all databases:-12 to 10% for HC3v5. The correlation coefficient is most often greater than 0.68 for 15 min and 0.84 for daily irradiation. The RMSE for 15 min ranges between 46 and 60 kWh m-2 for HC3v5, 46 and 63 kWh m-2 for HC3v4, and 48 and 66 kWh m-2 for MACC-RAD. For daily irradiation, it ranges between 1100 and 1600 kWh m-2 for HC3v5, between 1300 and 1700 kWh m-2 for HC3v4, and between 1000 and 1850 kWh m-2 for MACC-RAD. The MACC-RAD resource show promises provided the model for cloud properties is improved

Biodegradable polylactide/hydroxyapatite nanocomposite foam scaffolds for bone tissue engineering applications

Supercritical carbon dioxide processing of poly-l-lactide (PLLA)/hydroxyapatite (nHA) nanocomposites was investigated as a means to prepare foams suitable as scaffolds in bone tissue engineering applications. For given foaming parameters, addition of nHA to the PLLA gave reduced cell sizes and improved homogeneity in the size distribution, but did not significantly affect the degree of crystallinity, which remained of the order of 50wt% in all the foams. The compressive modulus and strength were primarily influenced by the porosity and there was no significant reinforcement of the matrix by the nHA. The mechanical properties of the foams were nevertheless comparable with those of trabecular bone, and by adjusting the saturation pressure and depressurization rate it was possible to generate porosities of about 85%, an interconnected morphology and cell diameters in the range 200-400μm from PLLA containing 4.17vol% nHA, satisfying established geometrical requirements for bone replacement scaffold

Biological systems: from water radiolysis to carbon ion radiotherapy

International audienceHadron therapy is an innovative cancer treatment method based on the acceleration of light ions at high energy. In addition to their interesting profile of dose deposition, which ensures accurate targeting of localized tumors, carbon ions offer biological properties that lead to an efficient treatment for radio-and chemo-resistant tumors and to provide a boost for tumors in hypoxia. This paper is a short review of the progress in theoretical, experimental, fundamental and applied research, aiming at understanding the origin of the biological benefits of light ions better. As a limit of such a vast and multidisciplinary domain, this review adopts the point of view of the physicists, leaning on results obtained in connection with CIMAP's IRRABAT platform. 1. Introduction Interaction of fast ions with biological systems constitutes one aspect of the interdisciplinary researches performed with ion-beam facilities. This domain is as rich as it is complex since it encompasses several orders of magnitude in both space and time. The shortest space and time scale corresponds to atomic collisions, which may be as short as 10 −18 s for the interaction of fast ions with individual atoms. At the opposite end of this domain, late effects – like cancer induction, chromosomal instability or organ dysfunctions – may appear or remain several years after irradiations. While irradiations may be limited to a very localized region, the whole behavior of an organ may be affected, possibly leading to human death, in particular when the irradiation dose and spatial extension are high. Between these two extreme scales, stands a great number of mechanisms, including for instance: the transport of the primary ejected electrons, the relaxation of the ionized and excited molecules, which may lead to direct damage in biological targets and to radical species and associated biochemical reactions. These early physical and chemical stages are followed by numerous and complex cell responses, such as the triggering of mechanisms to check DNA, to repair its damage, to manage the oxidative stress or to induce cell death. The numerous biological endpoints that have been studied reveal the complexity and the diversity of this biological response. These endpoints may involve particular structures of cells at the molecular scale (tracking of protein activities, damage in DNA, protein or lipid) or at the sub-cellular scale (chromosomes, nucleus, membranes, mitochondria.. .) and may concern cell organization (3D cell culture, tissues, organs, body). The domain of low dose