Chemical composition and structural changes of porous templates obtained by anodising aluminium in phosphoric acid electrolyte

Ordered anodic aluminium oxide (AAO) filmswere first prepared by anodising in a phosphoric acid electrolyte and then studied extensively and characterised by field emission gun-scanning electron microscopy (FEG-SEM), X-ray diffraction, Raman and infrared spectroscopy at a macroscopic scale. These analyses showed that the as-prepared AAO film is in fact amorphous, partially hydrated and that its initial global chemical composition can be described, in agreement with previous works, as: Al2O3, 0.186AlPO4 · 0.005H2O. Additional analyses (thermogravimetric analysis, differential thermal analysis and FEG-SEM) showed geometrical changes of the film structure at different scales, explained by various steps of dehydration and allotropic transformations of the resulting crystallised alumina. However, because their structure remains unchanged up to 900 ◦C, the phosphoric templates appear to be particularly suitable for applications or processes atmedium or high temperatures, such as the preparation of carbon nanotubes or oxide rods

Influence of cover cropping on water uptake dynamics in an irrigated Mediterranean vineyard

As a result of its physiological characteristics, vine's yield and quality responses are greatly affected by water availability in the soil. Knowledge about water uptake of grapevines in high water availability pedoclimatic conditions is essential when considering the increasing use of irrigation in a previously rainfed crop. We studied the water uptake of irrigated grapevines under different soil covers. The study was carried out over two years in southern Portugal, a Mediterranean climate region, in 'Aragonez' grapevines installed in Vertisols. A cover crop was sown in half the area while maintaining the permanent resident vegetation in the remaining area. Five levels of annual irrigation supply were applied: 200 mm; 150 mm; 100 mm; 50 mm; no irrigation. Soil moisture was monitored every two or three weeks, and weekly after the irrigation start. Results show that water uptake in the interrows did not cease after the beginning of irrigation. Water uptake by the vines occurred to depths of approximately 3.00 m, hence 7.5 times greater than the cover crop root system depth. Results suggest that over time, the presence of the cover crop forces the vine root system, mainly its thinner roots, to seek water at increasingly deeper soil compartments

Sedimentological imprint on subseafloor microbial communities in Western Mediterranean Sea Quaternary sediments

An interdisciplinary study was conducted to evaluate the relationship between geological and paleoenvironmental parameters and the bacterial and archaeal community structure of two contrasting subseafloor sites in the Western Mediterranean Sea (Ligurian Sea and Gulf of Lion). Both depositional environments in this area are well-documented from paleoclimatic and paleooceanographic point of views. Available data sets allowed us to calibrate the investigated cores with reference and dated cores previously collected in the same area, and notably correlated to Quaternary climate variations. DNA-based fingerprints showed that the archaeal diversity was composed by one group, Miscellaneous Crenarchaeotic Group (MCG), within the Gulf of Lion sediments and of nine different lineages (dominated by MCG, South African Gold Mine Euryarchaeotal Group (SAGMEG) and <i>Halobacteria</i>) within the Ligurian Sea sediments. Bacterial molecular diversity at both sites revealed mostly the presence of the classes <i>Alphaproteobacteria</i>, <i>Betaproteobacteria</i> and <i>Gammaproteobacteria</i> within <i>Proteobacteria</i> phylum, and also members of <i>Bacteroidetes</i> phylum. The second most abundant lineages were <i>Actinobacteria</i> and <i>Firmicutes</i> at the Gulf of Lion site and <i>Chloroflexi</i> at the Ligurian Sea site. Various substrates and cultivation conditions allowed us to isolate 75 strains belonging to four lineages: <i>Alpha-</i>, <i>Gammaproteobacteria</i>, <i>Firmicutes</i> and <i>Actinobacteria</i>. In molecular surveys, the <i>Betaproteobacteria</i> group was consistently detected in the Ligurian Sea sediments, characterized by a heterolithic facies with numerous turbidites from a deep-sea <i>levee</i>. Analysis of relative betaproteobacterial abundances and turbidite frequency suggested that the microbial diversity was a result of main climatic changes occurring during the last 20 ka. Statistical direct multivariate canonical correspondence analyses (CCA) showed that the availability of electron acceptors and the quality of electron donors (indicated by age) strongly influenced the community structure. In contrast, within the Gulf of Lion core, characterized by a homogeneous lithological structure of upper-slope environment, most detected groups were <i>Bacteroidetes</i> and, to a lesser extent, <i>Betaproteobacteria</i>. At both site, the detection of <i>Betaproteobacteria</i> coincided with increased terrestrial inputs, as confirmed by the geochemical measurements (Si, Sr, Ti and Ca). In the Gulf of Lion, geochemical parameters were also found to drive microbial community composition. Taken together, our data suggest that the palaeoenvironmental history of erosion and deposition recorded in the Western Mediterranean Sea sediments has left its imprint on the sedimentological context for microbial habitability, and then indirectly on structure and composition of the microbial communities during the late Quaternary

Ecophysiological modeling of grapevine water stress in Burgundy terroirs by a machine-learning approach.

13 pagesInternational audienceIn a climate change scenario, successful modeling of the relationships between plant-soil-meteorology is crucial for a sustainable agricultural production, especially for perennial crops. Grapevines (Vitis vinifera L. cv Chardonnay) located in eight experimental plots (Burgundy, France) along a hillslope were monitored weekly for 3 years for leaf water potentials, both at predawn (Ψpd) and at midday (Ψstem). The water stress experienced by grapevine was modeled as a function of meteorological data (minimum and maximum temperature, rainfall) and soil characteristics (soil texture, gravel content, slope) by a gradient boosting machine. Model performance was assessed by comparison with carbon isotope discrimination (δ13C) of grape sugars at harvest and by the use of a test-set. The developed models reached outstanding prediction performance (RMSE < 0.08 MPa for Ψstem and < 0.06 MPa for Ψpd), comparable to measurement accuracy. Model predictions at a daily time step improved correlation with δ13C data, respect to the observed trend at a weekly time scale. The role of each predictor in these models was described in order to understand how temperature, rainfall, soil texture, gravel content and slope affect the grapevine water status in the studied context. This work proposes a straight-forward strategy to simulate plant water stress in field condition, at a local scale; to investigate ecological relationships in the vineyard and adapt cultural practices to future conditions

Computational Fluid Dynamics Applied to Chemical Reaction Engineering

Computational Fluid Dynamics (CFD) and its applications have developed quite rapidly during the last ten years. This fast growing hybrid branch of Mechanics and Mathematics is certainly to be considered as a potentially useful and efficient tool in the field of Chemical Engineering and more specifically in the area of Chemical Reaction Engineering (CRE). The difficulties in this new approach stems from the consequence of the complexity of the mechanims to be simulated simultaneously : fluid dynamics, chemical reactions and physical aspects of each system considered. Another difficulty comes from the numerical treatment of the equations for the final model, resulting in very sophisticated and diversified mathematical treatments. The types of chemical reactors to be considered for potential performance improvements when applying CFD as a new tool for their design are numerous ; two broad classes of problem have be identified as relevant to this new approach :(a) Systems involving fast chemical reactions, with characteristic times of the same order of magnitude as the characteristic time scales of turbulence. In-line mixing equipment should preferably be studied for this type of reactions. (b) Multiphase systems, whose scaling-up still has to be performed with great difficulty and, more often than not, according to empirical procedures based on very simplified models. When looking at the various types of systems found in practice, it appears that gas-liquid and fluid-solid systems should be considered first. However, basic knowledge is still missing concerning the physical behaviour of these systems, especially for the coalescence of bubbles and the momentum transfer between gas and solid. Specific research should be done in order to get this missing information. Presently there are a certain number of existing CFD software packages available commercially or developed by various research laboratories. This is certainly an interesting starting point, but we can never be sure that the numerical results given by any of these software packages are applicable to a practical industrial case, without checking these results in one way or another. There is quite general agreement on the necessity of obtaining experimental data concerning problem examples, in order to check and compare the computation results of the various software packages proposed for dealing with these specific problems. On the experimental side, there are a great deal of measurement methods able to give local values of temperature, pressure, velocities, concentrations of chemical species, phases ratio, size of bubbles, drops or particles, as well as to produce an overall visualization of flows. We have mentioned the difficulties linked to the mathematical treatment of the equations written for simulating reactive flows. As usually done in CFD, for most problems encountered, a first useful solution can be obtained by limitingthe modelto oneortwospace dimensions (1D or 2D). However, very often it will be necessary not only to solve the 3D simulation set of equations, but also to achieve the unstationary solution of the same equations in order to really represent the true behaviour of the physical system. This last objective means much more complicated research, especially from the mathematical point of view

Distillation principes de calcul et de contrôle

Cet article présente les principes de base utilisés lors de la conception et de la conduite des colonnes à distiller continues ou discontinues. Dans cet exposé d'initiation le cas des mélanges binaires est seul considéré de manière à ne pas compliquer inutilement la présentation. Par contre pour conserver à cette étude un aspect pratique, la dernière partie est consacrée aux problèmes technologiques et aux principales solutions mises en oeuvre