A General Approach for Predicting the Filtration of Soft and Permeable Colloids: The Milk Example

Membrane filtration operations (ultra-, microfiltration) are now extensively used for concentrating or separating an ever-growing variety of colloidal dispersions. However, the phenomena that determine the efficiency of these operations are not yet fully understood. This is especially the case when dealing with colloids that are soft, deformable, and permeable. In this paper, we propose a methodology for building a model that is able to predict the performance (flux, concentration profiles) of the filtration of such objects in relation with the operating conditions. This is done by focusing on the case of milk filtration, all experiments being performed with dispersions of milk casein micelles, which are sort of ″natural″ colloidal microgels. Using this example, we develop the general idea that a filtration model can always be built for a given colloidal dispersion as long as this dispersion has been characterized in terms of osmotic pressure Π and hydraulic permeability k. For soft and permeable colloids, the major issue is that the permeability k cannot be assessed in a trivial way like in the case for hard-sphere colloids. To get around this difficulty, we follow two distinct approaches to actually measure k: a direct approach, involving osmotic stress experiments, and a reverse-calculation approach, that consists of estimating k through well-controlled filtration experiments. The resulting filtration model is then validated against experimental measurements obtained from combined milk filtration/SAXS experiments. We also give precise examples of how the model can be used, as well as a brief discussion on the possible universality of the approach presented here

Le débriefing postsimulation en santé. Que nous apprend-il et comment ?

International audienceAims Debriefing is a fundamental part of simulation training in health care, but remains a complex and difficult process to put in place. The aim of this article is to define the postsimulation debriefing, to clarify objectives and identify the main principles of debriefing with regard to the current literature. Results Several definitions of postsimulation debriefing exist in the literature, and have in common the reflexive practice with respect to action performed by the participants. This guided or facilitated analysis is carried out in a context of social interaction within an experiential learning cycle. The purpose of debriefing is to understand the student’s reaction and reasoning based on observations (from actions and results of the simulation), so as to validate or rebuild them. Debriefing is typically carried out in three phases: reaction–description, analysis, and summary–transposition, all of which need to be adapted to account for multiple variables. In 2011, Raemer et al. proposed that a debriefing takes place using the 5 “W” principles: Who, What, When, Where, and Why, which forms the basis of our analysis. Conclusion Debriefing is one of the principal parts of a fullscale medical simulation. It is a complex multiple-level process. The completion of a debriefing remains a difficult exercise for trainers. Beyond the broad principles discussed in this article, many questions remain unanswered