Capillary pinching in a pinched microchannel

We report a study of the capillary pinching of a gas bubble by a wetting liquid inside a pinched channel. The capillary pinching induces very reproducible bubbling, at a very well-defined frequency. There are two regimes associated with drip and jet bubbling. In the latter, we show that highly monodispersed bubbles are formed by our pinched channel. The dynamics of the bubble formation also shows two distinct regimes: a long-duration elongation of the air bubble and a rapid relaxation of the interface after interface breakup. The slow regime depends on the flux imposed and the channel geometry. The rapid deformation dynamic regime depends very weakly on the boundary conditions. Scaling arguments are proposed in the context of the lubrication approximation to describe the two regimes

Quasi-static liquid–air drainage in narrow channels with variations in the gap

This paper studies the shape of an air bubble quasi-statically flowing in the longitudinal direction of narrow channels. Two bottom topographies are treated, i.e., linear and quadratic variations of the gap along the transverse direction. This work analyses the main characteristics of the gas–liquid interface with respect to the wedge aspect ratio. From the convergence of asymptotic, numerical and experimental analyses, we found simple dependences for the finger width and total curvature as a function of channel aspect ratio. These results provide simple and general expressions for the pressure drop needed to overcome capillary forces and push the air finger inside the channel

De la notion de juridiction en droit administratif canadien

The object of this article considers the ever-evolving concept of jurisdiction in the context of judicial review of administrative action. The author examines recent jurisprudential developments from an historical perspective in an attempt to reveal those factors triggering intervention. The Supreme Court of Canada has often fashioned its tests of jurisdiction to fit the intended results. Hence, over the last decades, jurisdictional terminology has become ripe with deceptive distinctions and attempts to rationalize the various tests have in fact raised most perplexing problems

Factors affecting methylmercury biomagnification by a widespread aquatic invertebrate predator, the phantom midge larvae Chaoborus

MeHg biomagnification by the phantom midge Chaoborus in relation to MeHg concentrations in their prey and its migratory behavior was investigated in two Canadian Precambrian Shield lakes. Three Chaoborus species with contrasted migratory behavior were collected in a fishless and a fish-inhabited lake. All species accumulated MeHg through their ontogenic development. In the lake inhabited by fish, all instars of Chaoborus punctipennis displayed a marked migratory behavior and were unable to biomagnify MeHg, whereas in the fishless lake, Chaoborus americanus and Chaoborus trivittatus biomagnified MeHg. Reduced biomagnification capacity of C. trivittatus, the coexisting species living with C. americanus, was also ascribed to a progressive vertical segregation with age. Growth dilution, amount and type of prey items or trophic position could not explain the different patterns of biomagnification. Our findings demonstrate that the most common invertebrate predator of temperate planktonic food webs can biomagnify mercury, contrarily to previous reports

Comparative transcriptome investigation of global gene expression changes caused by miR156 overexpression in Medicago sativa

Nucleotide sequences alignment between (a) M. sativa SPL2/3/4 and Arabidopsis SPL3/4/5; (b) MsSPL9 and AtSPL9, respectively. (TIF 3681 kb

Une approche orientée aspect allant du modèle d'exigences au modèle de conception

National audienceDes approches orientées aspects sont aujourd'hui disponibles à chaque phase du développement d'un logiciel : analyse des exigences, conception, ou encore implémentation. Passer d'une phase à l'autre en conservant les aspects identifiés au préalable reste un défi majeur, pourtant peu étudié. Nous proposons dans un article publié à AOSD'11 une approche itérative et dirigée par les préoccupations, permettant de transformer un modèle d'exigences orienté aspect en un modèle de conception lui aussi orienté aspect, et ceci de manière automatique. Cette ap- proche est mise en œuvre en utilisant AoURN ("use case maps") pour le modèle d'exigence et Adore pour le modèle de conception (orchestrations SOA). Elle permet l'encapsula- tion continue des préoccupations identifiées lors des exigences, transformées en artefact de conception. Nous proposons de plus une boucle de rétro-action permettant de remonter dans les modèles d'exigences des défauts constatés dans le modèle de conception, supportant ainsi un processus de développement itératif