Interaction between local hydrodynamics and algal community in epilithic biofilm

Interactions between epilithic biofilm and local hydrodynamics were investigated in an experimental flume. Epilithic biofilm from a natural river was grown over a 41 day period in three sections with different flow velocities (0.10, 0.25 and 0.40 m s-¹ noted LV, IV and HV respectively). Friction velocities u* and boundary layer parameters were inferred from PIV measurement in the three sections and related to the biofilm structure. The results show that there were no significant differences in Dry Mass and Ash-Free Dry Mass (g m-²) at the end of experiment, but velocity is a selective factor in algal composition and the biofilms' morphology differed according to differences in water velocity. A hierarchical agglomerative cluster analysis (BrayeCurtis distances) and an Indicator Species Analysis (IndVal) showed that the indicator taxa were Fragilaria capucina var. mesolepta in the lowvelocity (u* = ¼ 0.010e0.012 m s-¹), Navicula atomus, Navicula capitatoradiata and Nitzschia frustulum in the intermediate velocity (u* = ¼ 0.023e0.030 m s-¹) and Amphora pediculus, Cymbella proxima, Fragilaria capucina var. vaucheriae and Surirella angusta in the high-velocity (u* = ¼ 0.033e0.050m s-¹) sections. A sloughing test was performed on 40-day-old biofilms in order to study the resistance of epilithic biofilms to higher hydrodynamic regimes. The results showed an inverse relationship between the proportion of detached biomass and the average value of friction velocity during growth. Therefore, water velocity during epilithic biofilm growth conditioned the structure and algal composition of biofilm, as well as its response (ability to resist) to higher shear stresses. This result should be considered in modelling epilithic biofilm dynamics in streams subject to a variable hydrodynamics regime

Modélisation expérimentale et numérique de l’essai de flexion 3 points

L’essai de flexion 3 points a été développé par Roche dans les années 80 [1]. La particularité de cet essai est qu’il ne consiste pas en un assemblage sandwich comme il est de coutume dans les essais d’adhérence des assemblages collés. Il consiste en un plot d’adhésif collé sur le substrat. Cet essai a été choisi, car il permet d’obtenir une rupture adhésive en mode I et de visualiser la zone d’initiation de la rupture, pour la géométrie spécifiée dans la norme. Le travail présenté s’inscrit dans le contexte de la prédiction de la ruine des assemblages collés

La compétence de contextualisation au coeur de la situation d'enseignement-apprentissage

International audienceThe notion of «professional situation,» as we propose to examine it, entails questioning simultaneously the place of contexts and the role of actors in teaching-learning situations. We propose to examine the contextualization of the teaching process in light of the groups welcomed and the conditions in which the teacher’s profession is practiced. Defining contextualization as «an art of doing» in line with a professional competency thus means postulating the legitimacy of the «context(s)» as an explanatory medium or media. The conceptual model here developed follows in the tradition of Anthony Giddens’ (1987) theory of structuration and is complemented by the ecological model of human development advanced by Bronfenbrenner (1986).La notion de « situation professionnelle », telle que nous proposons de la visiter, suppose de questionner, dans un même mouvement, la place des contextes et le rôle des acteurs au sein des situations d’enseignement-apprentissage. Il s’agit pour nous d’interroger la contextualisation de la démarche d’enseignement engagée au regard des publics accueillis et des conditions d’exercice de la profession d’enseignant. Définir la contextualisation comme « un art de faire » qui relève d’une compétence professionnelle suppose alors de poser la légitimité du/des « contexte(s) » comme vecteur(s) explicatif(s). Le modèle conceptuel développé s’inscrit dans la lignée de la théorie de la structuration d’Anthony Giddens (1987). Il est complété par le modèle écologique du développement humain proposé par Bronfenbrenner (1986)

k.p theory beyond standard 8-band theory parametrization strategies and its applicability in electronic and optoelectronic devices design

International audienc

Experimental Study of the Interaction Bewteen a Turbulent Flow and a River Biofilm Growing on Macrorugosities

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Butyronitrile-based electrolyte for dye-sensitized solar cells

We elaborated a new electrolyte composition, based on butyronitrile solvent, that exhibits low volatility for use in dye-sensitized solar cells. The strong point of this new class of electrolyte is that it combines high efficiency and excellent stability properties, while having all the physical characteristics needed to pass the IEC 61646 stability test protocol. In this work, we also reveal a successful approach to control, in a sub-Nernstian way, the energetics of the distribution of the trap states without harming cell stability by means of incorporating NaI in the electrolyte, which shows good compatibility with butyronitrile. These excellent features, in conjunction with the recently developed thiophene-based C106 sensitizer, have enabled us to achieve a champion cell exhibiting 10.0% and even 10.2% power conversion efficiency (PCE) under 100 and 51.2 mW cm-2 incident solar radiation intensity, respectively. We reached >95% retention of PCE while displaying as high as 9.1% PCE after 1000 h of 100 mW cm-2 light-soaking exposure at 60 °C

Evolutionary Advantage Conferred by an Eukaryote-to-Eukaryote Gene Transfer Event in Wine Yeasts

Although an increasing number of horizontal gene transfers have been reported in eukaryotes, experimental evidence for their adaptive value is lacking. Here, we report the recent transfer of a 158-kb genomic region between Torulaspora microellipsoides and Saccharomyces cerevisiae wine yeasts or closely related strains. This genomic region has undergone several rearrangements in S. cerevisiae strains, including gene loss and gene conversion between two tandemly duplicated FOT genes encoding oligopeptide transporters. We show that FOT genes confer a strong competitive advantage during grape must fermentation by increasing the number and diversity of oligopeptides that yeast can utilize as a source of nitrogen, thereby improving biomass formation, fermentation efficiency, and cell viability. Thus, the acquisition of FOT genes has favored yeast adaptation to the nitrogen-limited wine fermentation environment. This finding indicates that anthropic environments offer substantial ecological opportunity for evolutionary diversification through gene exchange between distant yeast species

Simulation of massively separated flows using hybrid turbulence models ans mesh adaptation

International audienc

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions