New methods to analyse fragmentation mechanisms of precipitated silicas

International audiencePrecipitated silica is traditionally used as reinforcing filler in rubber applications. In pneumatic manufacture, it offers several advantages compared to carbon black. Indeed, in tyres treads, precipitated silica can yield a lower rolling resistance and better wet grip at equal wear resistance than carbon black. The development of a new method to study the fragmentation mechanism of precipitated silica is investigated. Usually, the dispersion of granules is done in high viscous media (elastomer or oils). In this paper, the study is carried out in a friendlier medium (air or water)

Ohmic heating applied to the baking process: experimental and numerical approaches

International audienceThis work aims at studying the feasibility of ohmic heating (OH) technology applied to the baking process. The method includes proofing (fermentation) and baking and leads to the production of crustless sandwich bread without the need of cutting the crust away, in a shorter time and with theoretically lower energy costs than conventional baking. An ohmic cell was made to study the electrical conductivity (EC) of bread dough under different experimental conditions. The results showed that the EC increased linearly with the temperature, except during the starch gelatinization stage (60 – 76 °C) because of the bounding of water. The EC decreased with the porosity of the dough when fermented by yeasts, and drastically decreased with the reduction of salt content in the dough, showing the need to control the product formulation. An ohmic baking oven monitored by a PLC was developed to perform both proofing and baking in the same apparatus. The results showed that using OH to quickly reach the optimal temperature of yeast activity (35 °C) significantly reduced the lag phase and shortened the total proofing time. A numerical model was developed and validated by experimental results, taking into account heat and water (vapour and liquid water) transfers. The results confirmed the importance of temperature gradients between the surface of the electrodes and the core of the product, first observed by the underbaked aspect of the bread loaf on its sides. Different baking scenarios and their impacts on temperature and water content gradients were modelled

Internal structure and fragmentation kinetics of silica granules

International audienceTo improve the mechanical properties of tires, silica granules can be incorporated into the elastomer as well as carbon black. Ideally, the fragmentation of the granules in the elastomer must be obtained with low mechanical stresses and lead to very small fragments distributed homogeneously in the material. On the other hand, granules must present a sufficient cohesion, in order to avoid the generation of fine particles during handling operations. Thus it appears necessary to control the mechanical strength of granules and the mechanism of their fragmentation. In this experimental study, we investigated the fragmentation of silica granules of 250 microns produced by spray drying. For this, we characterized by granulometry the evolution of the Particle Size Distribution of silica powder in water. The granules were suspended in water and submitted to ultrasounds. This treatment is used to create the fragmentation that occurs by viscous shearing in industrial rubber processing. A core-shell structure, characteristic of granules obtained by atomization process, was observed by SEM. Furthermore, by varying the intensity of mechanical stress, the multi-scale structure of granules was evidenced as well as the existence of different regimes of fragmentation. The kinetics of fragmentation was experimentally followed on two grades of silica that showed significant differences in their behavior during the fragmentation process

Plateformes de coproduction et mondialisation de l’audiovisuel : espaces stratégiques de médiation au carrefour d’enjeux industriels et créatifs

Au sein du circuit international d’évènements et de rencontres professionnelles de l’industrie cinématographique et audiovisuelle, les « plateformes de coproduction » couramment associées aux festivals de séries constituent des espaces stratégiques de médiation, au carrefour d’enjeux industriels et créatifs majeurs et transnationaux. Sur la base d’une enquête menée lors du forum de coproduction de Séries Mania 2017 auprès d’un ensemble de cadres de l’industrie (producteurs, diffuseurs, distributeurs), cet article se propose d’appréhender les plateformes de coproduction comme des espaces d’observation privilégiés des dynamiques créatives et des reconfigurations socio-économiques qui traversent l’industrie cinématographique et audiovisuelle.In the international circuit of events and professional encounters of the film and audiovisual industry, ‘co-production platforms’, often associated with TV series festivals, represent strategic areas of mediation, at the crossroads of major industrial and creatives issues, on a transnational scale. Based on an investigation during the co-production forum of Series Mania 2017 among a group of executives of the industry (producers, broadcasters, distributors), this paper proposes to apprehend co-production platforms as a vantage point from which to observe creative dynamics and socio-economical reconfigurations of the film and audiovisual industry

Challenges in VGI for scientific projects

Volunteered Geographic Information (VGI) is a recent trend that has been successfully used in order to collect and share geographic information. This method is of interest for scientists who are in need of data and who want to get people involved in their cause. In this paper we discuss the challenges and opportunities that scientists may face when using the concept. An initial challenge is to find users who are willing to contribute. Second scientist must get these users to interact with the application and with each other. The final goal is to end up with high quality data that can be used for scientific research

Prospection Hydrogéologique et Géophysique du Système Aquifère du Plateau de Mbé, District de Ngabé, Congo

La prospection hydrogéologique et géophysique entreprise sur les sites des villages d’Imvouba et d’Ingah dans le plateau de Mbé a permis de déterminer la qualité des eaux souterraines et de surface ainsi que les niveaux aquifères favorables à l’implantation des forages productifs. La prospection géophysique utilisant les méthodes des résistivités électriques avec le dispositif Schlumberger est menée dans le but de déterminer les emplacements favorables à l’implantation des forages positifs avec des débits d’exploitation importants pour un approvisionnement en eau potable des populations. Cette prospection géophysique a révélé que la foration devrait se faire à des profondeurs prévisionnelles de 200 à 250 m voir plus afin d’atteindre les débits prévus par le projet. La prospection hydrogéologique des eaux souterraines et de surface a montré la dominance du faciès chimique bicarbonaté et calcique et que la bonne qualité physico-chimique des eaux de la région est remise en cause par la présence de certains éléments comme le fer total, le manganèse, les phosphates et l’aluminium à des teneurs élevées dépassant parfois les concentrations maximales admissibles pour l’eau de boisson (OMS, 2017). Les formations géologiques présentes dans le plateau de Mbé renferment un système aquifère multicouche bien alimentés par l’infiltration directe des eaux de pluie (1600 à 2500 mm/an). The hydrogeological and geophysical prospection carried out on the sites of the Imvouba and Ingah villages in theMbé plateau has made it possible to determine the quality of the groundwater and surface water as well as the aquifer levels, which is favorable to the implantation of the productive boreholes. Geophysical prospecting, based on electrical resistivity methods using the Schlumberger device, was conducted in order to determine the favorable locations for the implantation of positive boreholes with high exploitation rates for a drinking water supply of the populations. This geophysical survey revealed that the drilling should be done at predicted depths of 200 to 250 m or more in order to reach the projected flows of the project. Hydrogeological prospecting of groundwater and surface water has shown the dominance of the bicarbonated and calcic chemical facies. The good physicochemical quality of the waters of the region shows the presence of some elements such as total iron, manganese, phosphates and aluminum at high levels which sometimes exceeds the maximum permissible concentrations for drinking water (WHO, 2017). The geological formations present in the Mbé plateau contain a multilayer aquifer system well fed by the direct infiltration of rainwater (1600 to 2500 mm / year)

Elimination of HIV-1-infected cells by broadly neutralizing antibodies.

International audienceThe Fc region of HIV-1 Env-specific broadly neutralizing antibodies (bNAbs) is required for suppressing viraemia, through mechanisms which remain poorly understood. Here, we identify bNAbs that exert antibody-dependent cellular cytotoxicity (ADCC) in cell culture and kill HIV-1-infected lymphocytes through natural killer (NK) engagement. These antibodies target the CD4-binding site, the glycans/V3 and V1/V2 loops on gp120, or the gp41 moiety. The landscape of Env epitope exposure at the surface and the sensitivity of infected cells to ADCC vary considerably between viral strains. Efficient ADCC requires sustained cell surface binding of bNAbs to Env, and combining bNAbs allows a potent killing activity. Furthermore, reactivated infected cells from HIV-positive individuals expose heterogeneous Env epitope patterns, with levels that are often but not always sufficient to trigger killing by bNAbs. Our study delineates the parameters controlling ADCC activity of bNAbs, and supports the use of the most potent antibodies to clear the viral reservoir

N,N-bis-heteroaryl methylamines: Potent anti-mitotic and highly cytotoxic agents

International audienceThe synthesis and evaluation of a series of N,N-bis-heterocyclic-methylamines 1 as isoazaerianin analogues are descriebed. It was demonstrated that the replacement of the 3,4,5-trimethoxyphenyl A-ring present in CA-4, isoCA-4 and isoazaerianin by a quinoline or a quinazoline ring is possible and often beneficiary for a high level of cytotoxicity. We have also showed that a carbazole or an indole nucleus are very effective as Brings in this series, leading to anti-cancer drugs 1 having a sub-nanomolar level of cytotoxicity (1a: IC50 = 70 pM against HCT116 cells). 1a also display a high level of cytotoxicity against four other human cancer cells and inhibited tubulin assembly at a micromolar level. Moreover, at a concentration of 5 nM, 1a arrested the cellular cycle in G2/M phase of the cellular cycle and induced apoptosis of HCT116 cells. It was also showed that after few hours 1a at a concentration of 10 nM totally disrupted endothelial network formation on Matrigel

Revisiting an IgG Fc Loss-of-Function Experiment: The Role of Complement in HIV Broadly Neutralizing Antibody b12 Activity

The role of the complement system in HIV-1 immunity and pathogenesis is multifaceted, and an improved understanding of complement activities mediated by HIV-1-specific antibodies has the potential to inform and advance clinical development efforts. A seminal nonhuman primate challenge experiment suggested that complement was dispensable for the protective effect of the early broadly neutralizing antibody (bnAb) b12, but recent experiments have raised questions about the breadth of circumstances under which this conclusion may hold. Here, we reassess the original observation using Fc variants of IgG1 b12 that enhance complement activity and report that complement fixation on recombinant antigen, virions, and cells and complement-dependent viral and cellular lysis in vitro vary among bnAbs. Specifically, while the clinically significant V3 glycan-specific bnAb 10-1074 demonstrates activity, we found that b12 does not meaningfully activate the classical complement cascade. Consistent with avid engagement by C1q and its complex system of regulatory factors, these results suggest that complement-mediated antibody activities demonstrate a high degree of context dependence and motivate revisiting the role of complement in antibody-mediated prevention of HIV-1 infection by next-generation bnAbs in new translational studies in animal models. IMPORTANCE Given the suboptimal outcome of VRC01 antibody-mediated prevention of HIV-1 infection in its first field trial, means to improve diverse antiviral activities in vivo have renewed importance. This work revisits a loss-of-function experiment that investigated the mechanism of action of b12, a similar antibody, and finds that the reason why complement-mediated antiviral activities were not observed to contribute to protection may be the inherent lack of activity of wild-type b12, raising the prospect that this mechanism may contribute in the context of other HIV-specific antibodies

Mecanismes De Contamination Des Eaux Souterraines Dans Le Secteur Du Lac Mbeubeuss, Dakar, Senegal

The physicochemistry of groundwater in the immediate environment of the dump, and its surroundings, shows that the true value of the electrical conductivity of groundwater is close to 2000 μS / cm. The value of electrical conductivity that is greater than 2000 μS / cm demonstrates groundwater contamination through the Mbeubeuss Lake landfill, with chemical groundwater facies dominated by Sodium Chloride, Potassium Chloride, and Calcium Chloride. The study of the unsaturated zone of the aquifer and the relationship between the major chemical elements of groundwater, rainwater, and seawater made it possible to specify, on one hand, the sources of mineralization of the groundwater at the Mbeubeuss Lake site and its surroundings. Indeed, the situation close to the sea would suggest a considerable intake of salts by aerosols and sea spray. Based on contribution to this study, the influence of the old sediments of the dry Lake Mbeubeuss and the percolation of leachates resulting from the decomposition of garbage landfilled under the action of rainwater would be added. On the other hand, this study also made it possible to determine the main processes of controlling the mineralization of groundwater. This includes the marine inputs, the dissolution-precipitation of clay minerals present in the geological formations constituting the aquifer, the dilution- concentration, evaporation, and anthropogenic pollution