Essay: Popular Modernism And The American Prose Poem: From Sherwood Anderson To Kenneth Patchen

peer reviewe

Thermocapillary flows and interface deformations produced by localized laser heating in confined environment

The deformation of a fluid-fluid interface due to the thermocapillary stress induced by a continuous Gaussian laser wave is investigated analytically. We show that the direction of deformation of the liquid interface strongly depends on the viscosities and the thicknesses of the involved liquid layers. We first investigate the case of an interface separating two different liquid layers while a second part is dedicated to a thin film squeezed by two external layers of same liquid. These results are predictive for applications fields where localized thermocapillary stresses are used to produce flows or to deform interfaces in presence of confinement, such as optofluidics

Morton Marcus, Pursuing the Dream Bone

peer reviewe

Optohydrodynamics of soft fluid interfaces : Optical and viscous nonlinear effects

Recent experimental developments showed that the use of the radiation pressure, induced by a continuous laser wave, to control fluid-fluid interface deformations at the microscale, represents a very promising alternative to electric or magnetic actuation. In this article, we solve numerically the dynamics and steady state of the fluid interface under the effects of buoyancy, capillarity, optical radiation pressure and viscous stress. A precise quantitative validation is shown by comparison with experimental data. New results due to the nonlinear dependence of the optical pressure on the angle of incidence are presented, showing different morphologies of the deformed interface going from needle-like to finger-like shapes, depending on the refractive index contrast. In the transient regime, we show that the viscosity ratio influences the time taken for the deformation to reach steady state

Pour une anthropologie symétrique entre "développeurs" et "développés"

International audienceWhen studying development projects, some anthropologists refuse to investigate symmetrically " developed " and " developers ", with the same weberian comprehensive postulate they claim for the populations they usually study. Analyzing two cases, this paper shows that this leads to non rigorous demonstration and biased interpretation. While they claim such a symmetric methodology, numbers of studies in French development anthropology tend to neglect the institutional frameworks of development projects and developers' concrete practices and representations. Important parts of what are concretely development projects, such as institutional configurations, practitioners' reflexivity, pro-jects as socio-technique processes, are thus left under analyzed, even if they give new light on the reality of development projects.Dans leurs analyses de projets de développement, certains anthropologues refusent le principe de symétrie consistant à interroger les " développeurs " avec la même posture compréhensive qu'ils accordent aux populations qu'ils étudient d'habitude. A partir de deux cas, cet article montre que cela aboutit à des démonstrations peu rigoureuses et des interprétations biaisées. Tout en affirmant un tel principe de symétrie, nombre de travaux français en anthropologie du développement tendent à négliger les dispositifs institutionnels et l'analyse des pratiques et des représentations des développeurs. Une telle omission laisse dans l'ombre des parts importantes de ce qui constitue l'intervention de développement (les configurations institutionnelles, la réflexivité des agents de développement, les projets comme dispositifs socio-techniques, etc.), dont l'analyse éclaire pourtant la réalité des interventions et de leurs effets

Groupements villageois et processus de transition

En Afrique de l'Ouest, la multiplication des groupements paysans et des associations villageoises doit désormais être perçue comme un phénomène social à part entière. Aussi éloigné de la conception utilitariste que de l'idéologie communautaire, un groupement est d'abord un problème d'action collective pour les villageois; interfaces entre technique et rapports sociaux, les groupements reflètent et cristallisent en leur sein les enjeux de pouvoir de la société globale. Ils sont à la fois révélateurs et effecteurs des dynamiques de changement social. (Résumé d'auteur

Thermocapillary valve for droplet production and sorting

Droplets are natural candidates for use as microfluidic reactors, if active control of their formation and transport can be achieved. We show here that localized heating from a laser can block the motion of a water-oil interface, acting as a microfluidic valve for two-phase flows. A theoretical model is developed to explain the forces acting on a drop due to thermocapillary flow, predicting a scaling law which favors miniaturization. Finally, we show how the laser forcing can be applied to sorting drops, thus demonstrating how it may be integrated in complex droplet microfluidic systems.Comment: Five pages, four figure