Monodisperse fragmentation in emulsions: Mechanisms and kinetics

How can a crude polydisperse emulsion be transformed into a monodisperse one? Mason and Bibette (Phys. Rev. Lett., 77 (1996) 3481) have experimentally discovered this phenomenon by applying a shear step on a crude emulsion. In this paper, we examine how this transformation occurs. Our strategy is to prepare calibrated emulsions and to examine the fragmentation kinetics as a function of the initial droplet size. We show that the fragmentation process involves two distinct regimes. At short time (shorter than one second), the droplet diameter decreases abruptly. The droplets deform into long threads that undergo a Rayleigh instability. The obtained diameter is mainly determined by the applied stress and weakly depends on the viscosity ratio between the dispersed and continuous phases. After this first step, the resulting droplets can, once again, break up into daughter droplets. This second mechanism is much slower with a characteristic time of several hundred seconds. Depending on the initial size, the first step can vanish and only the second slow step subsists

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The impact of the COVID-19 epidemic on primary care in South-eastern France: implementation of a real-time monitoring system based on regional health insurance system data

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L’impact de l’épidémie de COVID-19 sur les soins de premier recours en région Provence-Alpes-Côte d’Azur : retour d’expérience sur la mise en place d’un dispositif de surveillance en temps réel à partir des données régionales de l’Assurance maladie

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Scalability of transport parameters with pore sizes in isodense disordered media

6 pagesInternational audienceWe study light multiple scattering in complex disordered porous materials. High internal phase emulsion-based isodense polystyrene foams are designed. Two types of samples, exhibiting different pore size distributions, are investigated for different slab thicknesses varying from L = 1mm to 10mm. Optical measurements combining steady-state and time-resolved detection are used to characterize the photon transport parameters. Very interestingly, a clear scalability of the transport mean free path ℓt with the average size of the pores S is observed, featuring a constant velocity of the transport energy in these isodense structures. This study strongly motivates further investigations into the limits of validity of this scalability as the scattering strength of the system increases