Macron vs Le Pen: a referendum on globalisation?

When French voters go to the polls on 7 May to elect their next President, they will face a choice between two candidates with radically different views on the European Union, free trade, and immigration. Guillaume Allègre previews the contest, writing that while Emmanuel Macron remains the favourite to beat Marine Le Pen, he needs to expand his coalition by offering meaningful protections to those disadvantaged by globalisation

L'enseignement en tant que supervision d'un environnement dynamique: une analyse de situations-problèmes de mathématiques

National audienceMost of current classroom observation methods view instructional settings as static (i.e., any event is the consequence of the only previous one). Here we consider instructional situations a dynamic environment supervision, the meaning of each event being grounded within the episode in which it occurs. We reanalyze in this framework a 41 mathematical problem solving situations corpus (primary school level). We used a statistical method closely related to factorial analysis, which accounts semantic similarity between two events or episodes within an instructional sequence. Results show that most of the episodes can be sorted according to their instructional goal (problem stating, searching, or correcting), without any beforehand matching between episodes and events.La plupart des méthodes classiques d'analyse de situations d'enseignement considèrent ces dernières comme des environnements statiques : un événement est la conséquence de l'événement précédent. Dans cet article, nous considérons l'enseignement comme la supervision d'un environnement dynamique, dans lequel chaque événement a une signification au sein d'un épisode. Dans ce cadre, nous ré-analysons un corpus de données d'observations de 41 situations-problèmes de mathématiques en école primaire. Nous utilisons un outil statistique d'analyse factorielle, l'analyse de la sémantique latente, permettant de rendre compte de la similarité de deux événements, ou deux épisodes dans une séance. Nous montrons que cet outil permet, sans qu'aucune correspondance entre épisode et type d'événement n'ait été établie a priori, de classer la majorité des épisodes selon leur objet (énoncé d'un problème, recherche ou correction)

Streaming potential dependence on water-content in Fontainebleau sand

The final version is available on www.blackwell-synergy.comInternational audienceThe electrokinetic potential results from the coupling between the water flow and the electrical current because of the presence of ions within water. The electrokinetic coupling is well described in fluid-saturated media, however its behaviour under unsaturated flow conditions is still discussed. We propose here an experimental approach to investigate streaming potential variations in sand at unsaturated conditions. We present for the first time continuous records of the electrokinetic coefficient as a function of water content. Two drainage experiments have been performed within a column filled with a clean sand. Streaming potential measurements are combined with water pressure and water content measurements every 10 centimeters along the column. In order to model hydrodymanics during the experiments, we solve Richards equation coupled with an inverse problem to estimate the hydraulic parameters of the constitutive relations between hydraulic conductivity, water pressure and water content. The electrokinetic coefficient $C$ shows a more complex behaviour for unsaturated conditions than it was previously reported and cannot be fitted by the existing models. The electrokinetic coefficient increases first when water saturation decreases from 100\% to about 65\% - 80\%, and then decreases as the water saturation decreases, whereas all previous works described a monotone decrease of the normalized electrokinetic coupling as water saturation decreases. We delimited two water saturation domains, and deduced two different empirical laws describing the evolution of the electrokinetic coupling for unsaturated conditions. Moreover we introduce the concept of the electrokinetic residual saturation $S_w^{r,ek}$, which allows us to propose a new model derived from the approach of the relative permeability used in hydrodynamics