Life expectancy, heavy work and return to education ; lessons for the social security reform

In most industrial countries, while the calculation of pension bene?ts is progressive, public pension systems redistribute weakly from high to low- income earners. They are close to actuarial fairness. This statement results from the following speci?city: less paid jobs are also heavier and health- damaging jobs involving losses in life expectancy. As avoiding low earnings and hard-working conditions require acquisition of skills, we study conjointly in this article the impact of social security and the work-related life ex- pectancy loss on the schooling decision. We then study macroeconomic and distributional consequences of global gain in life expectancy associated with di¤erent social security reforms, focusing particularly on spillover e¤ects pos- sibly generated by education.social security, human capital, inequality

The destabilization of an initially thick liquid sheet edge

International audienceBy forcing the sudden dewetting of a free soap film attached on one edge to a straight solid wire, we study the recession and subsequent destabilization of its free edge. The newly formed rim bordering the sheet is initially thicker than the film to which it is attached, because of the Plateau border preexisting on the wire. The initial condition is thus that of an immobile massive toroidal rim connected to a thin liquid film of thickness h. The terminal Taylor-Culick receding velocity V = sqrt(2 sigma/rho h), where sigma and rho are the liquid surface tension and density, respectively, is only reached after a transient acceleration period which promotes the rim destabilization. The selected wavelength and associated growth time coincide with those of an inertial instability driven by surface tension

Cuisiner ensemble : ethnographie de trois ateliers cuisine

L’enquête ethnographique menée auprès des ateliers cuisine de trois centres sociaux parisiens a mis en évidence deux aspects caractéristiques de cette activité, qui apparaissent à travers les dimensions culturelles et collectives de l’activité. Les origines diverses des personnes présentes favorisent de nombreuses interactions autour de « l’exotisme culinaire » et façonnent la « relation à l’Autre ». Par ailleurs, le caractère collectif de l’activité suscite des relations sociales qui se fondent moins sur les compétences culinaires que sur les positions et propriétés sociales des participantes, au sein de l’atelier, du centre, et plus généralement de leur vie sociale. Enfin, la dimension collective met en évidence la position différenciée des ateliers sur un continuum de situations, défini par des relations sociales hiérarchisées et des conceptions de l’activité culinaire qui s’étayent entre «faire ensemble » et « être ensemble ».“ateliers cuisine”, low income people, culinary exoticism, culinary habits, social integration, social work

Obésité et alimentation dans les catégories populaires : une approche du corps féminin

L'obésité touche inégalement les milieux sociaux ; les plus exposées sont les femmes des milieux populaires (16% d'obèses chez les ouvrières), qui appartiennent également aux groupes où la corpulence moyenne est la plus élevée et où l'attention au poids (désir de maigrir, fréquence des pesées, pratique sportive) est la moins forte. Pour autant, elles ne sont pas coupées des normes corporelles dominantes. Une enquête auprès de femmes obèses issues des classes populaires - anciennes ouvrières - montre que l'attention au corps et au poids augmente en même temps que la proximité aux classes moyennes et au monde du travail et décroît à mesure que la situation de ces femmes se précarise, pour se transformer en un impératif médical.

Monotonie ou diversité de l'alimentation : les effets du vieillissement

La vieillesse ne transforme pas les habitudes alimentaires incorporées tout au long de la vie. L'alimentation des personnes âgées reflète les effets de structure traditionnellement observés dans la population française : localisation régionale et appartenance sociale. L'avance en âge se traduit toutefois par nombre de modifications dans la vie quotidienne (veuvage, relogement, etc.) qui entraînent des changements au niveau de la composition du ménage et de la délégation des courses. Ces changements affectent à leur tour les pratiques alimentaires et se traduisent en particulier par une diminution de la variété des produits consommés.

Deformation upon impact of a concentrated suspension drop

We study the impact between a plate and a drop of non-colloidal solid particles suspended in a Newtonian liquid, with a specific attention to the case when the particle volume fraction, $\phi$, is close to - or even exceeds - the critical volume fraction, $\phi_c$, at which the steady effective viscosity of the suspension diverges. We use a specific concentration protocol together with an accurate determination of $\phi$ for each drop and we measure the deformation $\beta$ for different liquid viscosities, impact velocities and particle sizes. At low volume fractions, $\beta$ is found to follow closely an effective Newtonian behavior, which we determine by documenting the low deformation limit for a highly viscous Newtonian drop and characterizing the effective shear viscosity of our suspensions. By contrast, whereas the effective Newtonian approach predicts that $\beta$ vanishes at $\phi_c$, a finite deformation is observed for $\phi>\phi_c$. This finite deformation remains controlled by the suspending liquid viscosity and increases with increasing particle size, which suggests that the dilatancy of the particle phase is a key factor of the dissipation process close to and above $\phi_c$.Comment: Submitted to JF

Pinch-off of a viscous suspension thread

International audienceThe pinch-off of a capillary thread is studied at large Ohnesorge number for non-Brownian, neutrally buoyant, mono-disperse, rigid, spherical particles suspended in a Newtonian liquid with viscosity η 0 and surface tension σ. Reproducible pinch-off dynamics is obtained by letting a drop coalesce with a bath. The bridge shape and time evolution of the neck diameter, h min , are studied for varied particle size d, volume fraction φ and liquid contact angle θ. Two successive regimes are identified: (i) a first effective-viscous-fluid regime which only depends upon φ and (ii) a subsequent discrete regime, depending both on d and φ, in which the thinning localises at the neck and accelerates continuously. In the first regime, the suspension behaves as an effective viscous fluid and the dynamics is solely characterised by the effective viscosity of the suspension, η e ∼ −σ / ˙ h min , which agrees closely with the steady shear viscosity measured in a conventional rheometer and diverges as (φ c − φ) −2 at the same critical particle volume fraction, φ c. For φ 35 %, the thinning rate is found to increase by a factor of order one when the flow becomes purely extensional, suggesting non-Newtonian effects. The discrete regime is observed from a transition neck diameter, h min ≡ h * ∼ d (φ c − φ) −1/3 , down to h min ≈ d, where the thinning rate recovers the value obtained for the pure interstitial fluid, σ /η 0 , and lasts t * ∼ η e h * /σ

Drop deformation by laser-pulse impact

A free-falling absorbing liquid drop hit by a nanosecond laser-pulse experiences a strong recoil-pressure kick. As a consequence, the drop propels forward and deforms into a thin sheet which eventually fragments. We study how the drop deformation depends on the pulse shape and drop properties. We first derive the velocity field inside the drop on the timescale of the pressure pulse, when the drop is still spherical. This yields the kinetic-energy partition inside the drop, which precisely measures the deformation rate with respect to the propulsion rate, before surface tension comes into play. On the timescale where surface tension is important the drop has evolved into a thin sheet. Its expansion dynamics is described with a slender-slope model, which uses the impulsive energy-partition as an initial condition. Completed with boundary integral simulations, this two-stage model explains the entire drop dynamics and its dependance on the pulse shape: for a given propulsion, a tightly focused pulse results in a thin curved sheet which maximizes the lateral expansion, while a uniform illumination yields a smaller expansion but a flat symmetric sheet, in good agreement with experimental observations.Comment: submitted to J. Fluid Mec