THE EFFECT OF LEAF ORIENTATION ON SPRAY RETENTION ON BLACKGRASS

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop trajectory and the variability of the leaf orientation. As the effect of impact angle on retention is still poorly documented, laboratory studies were conducted to highlight the effect of leaf orientation on drop impact outcomes. Measurements were performed with a high-speed camera coupled with a retro-LED lighting. Size and velocity of the drop were extracted by image analysis. Drop impact types were determined by the operator. Drops were produced with a flat-fan nozzle mounted on a movable ramp. Excised blackgrass [Alopecurus myosuroides HUDS. (ALOMY)] leaves were stretched between two parts of a U-shaped support. A surfactant (Break-Thru® S240) was sprayed to highlight the effect of mixture surface tension. The whole device was tilted from 0 to 90°. Relative volume proportions were computed within of an energy scale divided into 11 classes. These proportions have been weighted by an average volume distribution and the results were summed for all energy classes to obtain the total volume proportions for each impact outcomes and for all leaf angles. For distilled water (high surface tension) the increase of rebound proportion with the increase of drop impact angle is highlighted. For surfactant (lower surface tension), it results in an increase of drop fragmentation in Cassie-Baxter wetting regime. To be statistically representative, bigger drop samples should be used

Respiratory-deficient mutants of the unicellular green alga Chlamydomonas: A review.

Genetic manipulation of the unicellular green alga Chlamydomonas reinhardtii is straightforward. Nuclear genes can be interrupted by insertional mutagenesis or targeted by RNA interference whereas random or site-directed mutagenesis allows the introduction of mutations in the mitochondrial genome. This, combined with a screen that easily allows discriminating respiratory-deficient mutants, makes Chlamydomonas a model system of choice to study mitochondria biology in photosynthetic organisms. Since the first description of Chlamydomonas respiratory-deficient mutants in 1977 by random mutagenesis, many other mutants affected in mitochondrial components have been characterized. These respiratory-deficient mutants increased our knowledge on function and assembly of the respiratory enzyme complexes. More recently some of these mutants allowed the study of mitochondrial gene expression processes poorly understood in Chlamydomonas. In this review, we update the data concerning the respiratory components with a special focus on the assembly factors identified on other organisms. In addition, we make an inventory of different mitochondrial respiratory mutants that are inactivated either on mitochondrial or nuclear genes

Effective dynamic properties of random complex media with spherical particles

The effective dynamic bulk modulus and density are presented for random media consisting of particles in a viscous host fluid, using a core-shell, self-consistent effective medium model, under the large compressional wavelength assumption. These properties are relevant to acoustic or dynamic processes in nano- and microparticle fluids including particle density determination, resonant acoustic mixing and acoustic characterisation. Analytical expressions are obtained for the effective bulk modulus and mass density, incorporating the viscous nature of the fluid host into the core-shell model through wave mode conversion phenomena. The effective density is derived in terms of particle concentration, particle and host densities, particle size, and the acoustic and shear wavenumbers of the liquid host. The analytical expressions obtained agree with prior known results in the limit of both static and inviscid cases; the ratio of the effective bulk modulus to that of the fluid is found to be quasi-static. Numerical calculations demonstrate the dependence of the effective mass density on frequency, particle size (from nano- to micro-regime) and concentration. Herein it is demonstrated both theoretically and numerically that the viscosity, often neglected in the literature, indeed plays a significant role in the effective properties of nanofluids

The coherent shear wave in suspensions

We consider a disordered suspension of spherical silica particles in water. For a particle size of a few hundred nanometres and concentration (volume fraction) around 0.15 to 0.2, experiments conducted in the MHz range have shown that the non ideal nature of water must be taken into account for the "longitudinal" coherent wave attenuation to be understood, because of wave conversions, from longitudinal to shear and then back to longitudinal, occurring at each pair of scattering events. We are interested here in the properties of the "shear" coherent wave that are given by the expansion of its squared wavenumber, around that in the absence of particles, in powers of the concentration. At 1 MHz and a particle radius of 0.05 m, we show that convergence of the modal series involved in that expansion may be reached after three terms: we use ten terms subsequently. We study the evolution of both the effective shear velocity and attenuation with concentration, as well as that of the effective shear viscosity deduced therefrom

Evaluation of coastal and marine ecosystem services of Mayotte:indirect use values of coral reefs and associated ecosystems

Coral reefs of Mayotte (342 km2), seagrass beds (7.6 km2) and mangroves (8.5 km2) provide important ecosystem services of which the most important are the coastal protection, fish biomass production, carbon sequestration and water purification. The quantity and quality of these services have been decreasing steadily for several years and should continue to do so if no action is taken to contain anthropogenic pressures. The coral cover of the fringing reefs and the barrier reef has thus declined, respectively, by 60% in 15 years and 15% in 8 years. The pioneer front of Sonneratia for mangroves has declined by 13% in 6 years, and for seagrass beds, the water quality suggests a degraded state. The estimated annual value of these services amounts to EUR 124 million. It would be EUR 162 million if the ecosystems were in pristine conditions. The article shows that the preservation of coastal ecosystems is essential from an economic point of view.EDITED BY Sebastian Villasant

La commande publique par enchère électronique inversée

La récente réforme du Code des marchés publics prévoit l’usage de procédures d’enchères électroniques inversées. Sur la base des résultats récents de la littérature économique, cet article présente les avantages et inconvénients d’une telle réforme, en terme de prix de passation, d’efficacité allocative et de sensibilité à la collusion. En analysant à la fois le contexte d’une attribution d’un seul lot ou de plusieurs, selon le critère du prix ou de l’offre économiquement la plus avantageuse, cet article met en lumière l’importance d’une définition préalable rigoureuse des règles de l’enchère électronique inversée.The last reform of the French procurement regulation has introduced the possibility of awarding the contracts by means of electronic reverse auctions. According to recent literature, this article presents the benefits and drawbacks of electronic reverse auctions, in terms of expected costs and efficiency as well as the vulnerability to collusion. We consider different environments, single or multi-unit auctions and multi-attribute auctions. This article shows that the optimal design of electronic reverse auctions is very sensitive to details. This emphasizes the necessity to carefully design these auctions

Assessment of indirect use values ​​of coral reefs and associated ecosystems in Mayotte

Les récifs coralliens de Mayotte (342 km2), ainsi que ses mangroves (8,46 km2) et ses herbiers (7,60 km2) procurent des services écosystémiques dont les plus importants sont la protection côtière, la séquestration de carbone, le traitement des eaux et la production de biomasse halieutique. La quantité et la qualité de ces services diminuent de manière régulière depuis plusieurs années et elles devraient continuer de la sorte si aucune mesure n’est prise pour contenir les pressions anthropiques. La couverture corallienne des récifs frangeants a ainsi diminué de 60 % en 15 ans et celle du récif barrière de 15 % en 8 ans, alors que les fronts pionniers de Sonneratia des mangroves ont régressé de 13 % en 6 ans. La qualité écologique des masses d’eaux suggère quant à elle un état dégradé des herbiers. La valeur monétaire annuelle de l’ensemble de ces services est actuellement estimée à 151 millions d’euros. Si les écosystèmes étaient en parfait état écologique, elle s’élèverait alors à 188 millions d’euros. Cet article montre ainsi que la préservation des écosystèmes côtiers est primordiale d’un point de vue économique.Mayotte’s coral reefs (342 km2), mangroves (8, 46 km2) and seagrass beds (7,60 km2) provide important ecosystem services of which the most important are the coastal protection, carbon sequestration, water purification and fish biomass production. The quantity and quality of these services have been decreasing steadily for several years and should continue to do so if no action is taken to contain anthropogenic pressures. The coral cover of the fringing reefs and the barrier reef has thus declined respectively by 60 % in 15 years and 15 % in 8 years, while the pioneer front of Sonneratia for mangroves has declined by 13 % in 6 years. As for the water quality, it suggests a degraded state of seagrass beds. The estimated annual value of these services amounts to EUR 151 million. This value would then rise to EUR 188 million if the ecosystems were in pristine conditions. This article shows that the preservation of coastal ecosystems is essential from an economic point of view

Détection de bulles en mouvement dans une préforme fibreuse par méthode ultrasonore

La détection de bulles lors de l'élaboration de matériaux composites de type Resin Transfer Molding (RTM) répond à une problématique actuelle. Nous proposons une méthode pour observer les tailles et vitesses de bulles d'air moyennant un transducteur multi-éléments. La méthode est testée dans un flux d'huile silicone seule et ensuite dans un échantillon de préforme fibreuse plongé dans l'écoulement visqueux. Au moyen de ces mesures, l'évolution des bulles est reliée aux processus qui les génèrent afin d'envisager des améliorations à la technique de mise en forme