Drying of a model soil

International audienceDrying experiments have been carried out with model soils made of different pastes filling granular packings. A detailed information concerning the time evolution of the water density distribution inside the sample was obtained from MRI measurements. This study makes it possible to understand the physical origin of the drying characteristics of these materials. The drying curves exhibit a CRP (constant-rate period) and a FRP (falling-rate period) but the relative durations of these periods depend on the paste structure. With a kaolin suspension the CRP lasts down to very low water densities and is associated with a homogeneous drying of the paste throughout the sample. With a bentonite suspension the CRP is shorter and the drying in the FRP results from a complex process involving fractures progressing downwards through the pasty matrix. With a gel the CRP period is even shorter and the drying in the FRP results from the progression of a dry front through the packing as a result of the shrinkage of the gel matrix. This provides an overview of the main possible processes at work when drying a soil as a function of its components, along with some practical means for slowing down drying from soils

Multi-metal contamination of a calcic cambisol by fallout from a lead-recycling plant

The present study deals with the impact of a lead-recycling plant on metal accumulation in soils, evaluated by a global pedological analysis. This general approach can be used on various contaminated sites to evaluate impact of an anthropogenic activity and inform on metal origin and behavior. A soil profile collected in the vicinity of a lead-recycling plant in operation for 40 years was studied. Correlations between major and trace elements highlighted different patterns of metals according to their origins. Two groups of metals were identified: (i) Pb, Sb, Sn, As, Cu and Zn of anthropogenic origin and (ii) Ni and Cr of natural origin. The results showed that Pb, Sb and Sn presented the highest relative contamination followed by Cu, As and Zn. Moreover, Pb and Sb migrated most along the profile at an estimated rate of 1.5 cm y−1, followed by Sn, then Zn, Cu and finally As. Sequential extractions showed that all metals were mainly solubilized by reduction and therefore estimated to be bound to iron oxides, except lead which was rather in the acid-soluble fraction in the contaminated horizons. Furthermore, high levels of lead were found in water-soluble and exchangeable fractions (4.2 mg kg−1) suggesting the occurrence of lead transfer towards the trophic chain

Introduction

Il y a douze ans paraissait le livre de Jean Delumeau, Rassurer et protéger (Paris, Fayard, 1989). Il correspondait au second volet d’une vaste enquête dont la première partie avait été consacrée au sentiment de la peur en Occident. Jean Delumeau se référait alors à Lucien Febvre, auteur d’un article pionnier, « Pour l’histoire d’un sentiment : le besoin de sécurité » (Annales, XI, 1956), qui mentionnait le thème de la « sécurité spirituelle », c’est-à-dire de « la sécurité dans l’Au-delà […]..

The latest developments in cutaneous homeostasis

Background: The skin is a major actor of human homeostasis mainly due to its important role in body temperature regulation but also through its role of barrier against any external aggression, and as a transmitter of a lot of information to the brain. It is very important that this vital organ can regulate its own homeostasis to be able to assume its role for the rest of human body. It is commonly admitted that cutaneous homeostasis is more or less the barrier effect but the last discovery for the last decade opens new interesting fields of investigation. Degradation of tight junctions with age are well-known. In rosacea, the water permeation in epidermis sever the cells and break the junctions, it is an open door for microbial infections and dramatic dryness. On atopic mice skin model, Yokushi and al. showed in 2015 that tight junctions of atopic skin are more permeable and this is correlated with the filaggrin protein depletion. If junctions still stop microbials and big molecules penetration, they let small molecules under 30 KDalton to penetrate the epidermis. This could be one of the causes of the inflammatory status of atopic skins and of dryness as water permeation is increased as well. Conclusions: In conclusion, skin homeostasis becomes more and more complex with the last discoveries about skin microbiota. Interactions between sebum, epidermal lipids, epidermal peptides and microbiota are huge. We have an open field to innovate in new treatment taking into account the capability of billions of living cells on our skin surface which talk with our cells all the time and work together to help our skin assume its defense role of the human body

Dominique Rigaux, Le Christ du dimanche. Histoire d’une image médiévale

Ce livre est issu du mémoire d’habilitation à diriger des recherches soutenu par Dominique Rigaux en 1998. L’auteur, professeur d’histoire du Moyen Âge à l’université Pierre Mendès-France (Grenoble II), est spécialiste de la fresque dans le domaine alpin. La formule consacrée dans l’espace francophone « Christ du dimanche » désigne une figure du Christ en pied, entouré d’outils agricoles et de symboles des activités artisanales et commerciales dont la pratique était interdite le jour du Seign..

Mary Carruthers, Le livre de la mémoire. Une étude de la mémoire dans la culture médiévale

Il convient de saluer la traduction en français, par Diane Meur, de cet ouvrage fondamental de Mary Carruthers paru à Cambridge en 1990 sous le titre The book of Memory. A Study of Memory in Medieval Culture. Dans le sillon ouvert par le travail pionnier de Frances Yates, L’art de la mémoire (Gallimard, 1975, pour la traduction française), M. Carruthers, aujourd’hui professeur à l’Université de New York, examine le problème du statut et du rôle de la mémoire dans la culture savante au Moyen Â..

Les cieux ouverts - les anges et leurs images dans le christianisme médiéval (xie-xiiie siècles)

L'ange est une figure majeure de l'expérience religieuse au sein des religions du Livre, dans lesquelles angélologie et Révélation sont intimement liées. Historiens et philosophes des religions ont mis en évidence l'importance de l'ange comme figure médiatrice, entre le divin et l'humain. Étudiant le vaste domaine de l'islam iranien, Henry Corbin a montré combien l'angélologie fondait et mettait en mouvement la mystique, la philosophie spirituelle, la cosmologie et l'anthropologie. L'ange est..

Mary Carruthers, Le livre de la mémoire. Une étude de la mémoire dans la culture médiévale

Il convient de saluer la traduction en français, par Diane Meur, de cet ouvrage fondamental de Mary Carruthers paru à Cambridge en 1990 sous le titre The book of Memory. A Study of Memory in Medieval Culture. Dans le sillon ouvert par le travail pionnier de Frances Yates, L’art de la mémoire (Gallimard, 1975, pour la traduction française), M. Carruthers, aujourd’hui professeur à l’Université de New York, examine le problème du statut et du rôle de la mémoire dans la culture savante au Moyen Â..