Direct 17O Isotopic Labeling of Oxides Using Mechanochemistry

While 17O NMR is increasingly being used for elucidating the structure and reactivity of complex molecular and materials systems, much effort is still required for it to become a routine analytical technique. One of the main difficulties for its development comes from the very low natural abundance of 17O (0.04%), which implies that isotopic labeling is generally needed prior to NMR analyses. However, 17O-enrichment protocols are often unattractive in terms of cost, safety, and/or practicality, even for compounds as simple as metal oxides. Here, we demonstrate how mechanochemistry can be used in a highly efficient way for the direct 17O isotopic labeling of a variety of s-, p-, and d-block oxides, which are of major interest for the preparation of functional ceramics and glasses: Li2O, CaO, Al2O3, SiO2, TiO2, and ZrO2. For each oxide, the enrichment step was performed under ambient conditions in less than 1 h and at low cost, which makes these synthetic approaches highly appealing in comparison to the existing literature. Using high-resolution solid-state 17O NMR and dynamic nuclear polarization, atomic-level insight into the enrichment process is achieved, especially for titania and alumina. Indeed, it was possible to demonstrate that enriched oxygen sites are present not only at the surface but also within the oxide particles. Moreover, information on the actual reactions occurring during the milling step could be obtained by 17O NMR, in terms of both their kinetics and the nature of the reactive species. Finally, it was demonstrated how high-resolution 17O NMR can be used for studying the reactivity at the interfaces between different oxide particles during ball-milling, especially in cases when X-ray diffraction techniques are uninformative. More generally, such investigations will be useful not only for producing 17O-enriched precursors efficiently but also for understanding better mechanisms of mechanochemical processes themselves

Role of Fibronectin in the Adhesion of Acinetobacter baumannii to Host Cells

Adhesion to host cells is an initial and important step in Acinetobacter baumannii pathogenesis. However, there is relatively little information on the mechanisms by which A. baumannii binds to and interacts with host cells. Adherence to extracellular matrix proteins, such as fibronectin, affords pathogens with a mechanism to invade epithelial cells. Here, we found that A. baumannii adheres more avidly to immobilized fibronectin than to control protein. Free fibronectin used as a competitor resulted in dose-dependent decreased binding of A. baumannii to fibronectin. Three outer membrane preparations (OMPs) were identified as fibronectin binding proteins (FBPs): OMPA, TonB-dependent copper receptor, and 34 kDa OMP. Moreover, we demonstrated that fibronectin inhibition and neutralization by specific antibody prevented significantly the adhesion of A. baumannii to human lung epithelial cells (A549 cells). Similarly, A. baumannii OMPA neutralization by specific antibody decreased significantly the adhesion of A. baumannii to A549 cells. These data indicate that FBPs are key adhesins that mediate binding of A. baumannii to human lung epithelial cells through interaction with fibronectin on the surface of these host cells

Flux de chaleur critiques (burn-out) de l’hydrogène et de l’azote liquides en convection forcée

Hydrogen and nitrogen liquids burn-out under forced convection. Experimental results obtained with a 3 mm dia. x 300 mm. Inconel tube at variable pressures and rates of flow. Occurrence of burn-out due to pronounced wall temperature instability at the tube outlet, as frequently associated with oscillating flow rates. Two burn-out values are obtained in certain cases at the same flow and different hydrodynamic conditions, depending on the stability of the flow. Burn-out ceases just below the critical pressure. Comparisons with other fluids.Les expériences ont été effectuées à l'aide d'un tube en inconel (diamètre 3 mm, longueur 300 mm) dans des conditions de débit et de pression largement variables. Le phénomène de «burn-out » est une limitation des flux de chaleur imposés. Il est peut-être dû à l'apparition de la caléfaction (titre de vapeur faible) ou à la désagrégation du film liquide adhérant à la paroi (titre élevé). La stabilité du régime hydrodynamique de l'écoulement est un facteur déterminant dans la manifestation du phénomène. Deux valeurs sensiblement différentes du flux de «burn-out » peuvent être déterminées pour un même écoulement donné : la valeur la plus faible correspondant au régime oscillatoire. Dans nos expériences, débit (G) et pression (P) sont les deux seules variables indépendantes (entrée à température constante). On discute l'influence de P et de G. Le phénomène de «burn-out» disparaît un peu en dessous de la pression critique.Perroud P., Rebière J., Weil Louis. Flux de chaleur critiques (burn-out) de l’hydrogène et de l’azote liquides en convection forcée. In: Les instabilités en hydraulique et en mécanique des fluides. Compte rendu des huitièmes journées de l'hydraulique. Lille, 8-10 juin 1964. Tome 2, 1965

LakeSST : Température de peau de la surface des plans d'eau français pour 1999-2016 à partir des archives Landsat

International audienceThe spatial and temporal coverage of the Landsat satellite imagery make it an ideal resource for the monitoring of water temperature over large territories at a moderate spatial and temporal scale at a low cost. We used Landsat 5 and Landsat 7 archive images to create the Lake Skin Surface Temperature (LakeSST) data set, which contains skin water surface temperature data for 442 French water bodies (natural lakes, reservoirs, ponds, gravel pit lakes and quarry lakes) for the period 1999-2016. We assessed the quality of the satellite temperature measurements by comparing them to in situ measurements and taking into account the cool skin and warm layer effects. To estimate these effects and to investigate the theoretical differences between the freshwater and seawater cases, we adapted the COARE 3.0 algorithm to the freshwater environment. We also estimated the warm layer effect using in situ data. At the reservoir of Bimont, the estimated cool skin effect was abou

Love wave gas sensor based on DWNTs sensitive material

International audienceThis work focuses on the application related to the detection of low moisture and environmental pollutants. A novel gas sensor with inkjet printed Double Walled Carbon Nano Tubes (DWNTs) on a Love wave sensor platform was developed for Volatile Organic Compounds (VOCs) and humidity detection application. The experiments were conducted in real-time at ambient conditions. Results demonstrate the adsorption of vapor compounds on DWNTs sensitive material and leads for example to frequency shifts of 1.97 kHz and 2.93 kHz with 120 ppm of ethanol vapor and 6.22 % RH, respectively