Des formations à silex à la visualisation des itinéraires : vers les cartes des gîtes potentiels

In archeology, the localization of the raw material as the flint used by the prehistoric men for their tools, inform about the territory occupied by those populations. The stones, out of their original country rock, move by gravity on the field slope. This study aims to develop new cartographic methods that lead to a better understanding of the diffusion area of the stone. It is conducted in the Manaurie watershed, in Dordogne (France). From a map of primary sites and a DEM, we managed to develop a method that enables us to retrace the route of the flint between the geological formations. We suggest a representation by charts and graphs that offer a quick and efficient vision of the flint movements. For a targeted point inside the geological formation, a second method is built to identify accurately the surface where stone could come from.En archéologie, la localisation des matières premières, tel que le silex, utilisé par les hommes préhistoriques pour leurs outils, renseigne sur les territoires occupés par ces populations. Les roches, détachées de leur encaissant calcaire d’origine, se déplacent par gravité suivant les pentes. Nous proposons de développer de nouvelles méthodes cartographiques permettant de connaitre au mieux les aires de diffusion de ces nodules et de les appliquer dans le bassin versant du Manaurie, en Dordogne. Une méthode permettant de reconstituer l’itinéraire du silex entre les surfaces des formations géologiques a pu être mise en oeuvre à l’aide d’une carte des gîtes primaires du département et d’un MNT. Une représentation sous la forme de tableaux et de graphes est proposée, offrant une lecture rapide et efficace des déplacements des blocs de roches. Une seconde méthode, à l’échelle de la formation géologique elle même, est créée pour identifier les surfaces d’approvisionnement d’un endroit géographique donné (point d’intérêt) avec plus de précision

Des formations à silex à la visualisation des itinéraires : vers les cartes des gîtes potentiels

In archeology, the localization of the raw material as the flint used by the prehistoric men for their tools, inform about the territory occupied by those populations. The stones, out of their original country rock, move by gravity on the field slope. This study aims to develop new cartographic methods that lead to a better understanding of the diffusion area of the stone. It is conducted in the Manaurie watershed, in Dordogne (France). From a map of primary sites and a DEM, we managed to develop a method that enables us to retrace the route of the flint between the geological formations. We suggest a representation by charts and graphs that offer a quick and efficient vision of the flint movements. For a targeted point inside the geological formation, a second method is built to identify accurately the surface where stone could come from.En archéologie, la localisation des matières premières, tel que le silex, utilisé par les hommes préhistoriques pour leurs outils, renseigne sur les territoires occupés par ces populations. Les roches, détachées de leur encaissant calcaire d’origine, se déplacent par gravité suivant les pentes. Nous proposons de développer de nouvelles méthodes cartographiques permettant de connaitre au mieux les aires de diffusion de ces nodules et de les appliquer dans le bassin versant du Manaurie, en Dordogne. Une méthode permettant de reconstituer l’itinéraire du silex entre les surfaces des formations géologiques a pu être mise en oeuvre à l’aide d’une carte des gîtes primaires du département et d’un MNT. Une représentation sous la forme de tableaux et de graphes est proposée, offrant une lecture rapide et efficace des déplacements des blocs de roches. Une seconde méthode, à l’échelle de la formation géologique elle même, est créée pour identifier les surfaces d’approvisionnement d’un endroit géographique donné (point d’intérêt) avec plus de précision

« Vrais trous » et « fausses erreurs » : le contrôle de la numérisation de contours des formations à silex en Dordogne à l’aide d’un SIG.

International audienc

How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments

Hydrodynamics in a high-rate production reactor for microalgae cultivation affects the light history perceived by cells. The interplay between cell movement and medium turbidity leads to a complex light pattern, whose forcing effects on photosynthesis and photoacclimation dynamics are nontrivial. Hydrodynamics of high density algal ponds mixed by a paddle wheel has been studied recently, although the focus has never been on describing its impact on photosynthetic growth efficiency. In this multidisciplinary downscaling study, we first reconstructed single cell trajectories in an open raceway using an original hydrodynamical model offering a powerful discretization of the Navier-Stokes equations tailored to systems with free surfaces. The trajectory of a particular cell was selected and the associated high-frequency light pattern was computed. This light pattern was then experimentally reproduced in an Arduino-driven computer controlled cultivation system with a low density Dunaliella salina culture. The effect on growth and pigment content was recorded for various frequencies of the light pattern, by setting different paddle wheel velocities. Results show that the frequency of this realistic signal plays a decisive role in the dynamics of photosynthesis, thus revealing an unexpected photosynthetic response compared to that recorded under the on/off signals usually used in the literature. Indeed, the light received by a single cell contains signals from low to high frequencies that nonlinearly interact with the photosynthesis process and differentially stimulate the various time scales associated with photoacclimation and energy dissipation. This study highlights the need for experiments with more realistic light stimuli to better understand microalgal growth at high cell densities. An experimental protocol is also proposed, with simple, yet more realistic, step functions for light fluctuations

Experimental data from How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments

Experimental data obtained in the Lagrangian experimen

Hydrocortisone plus fludrocortisone for community acquired pneumonia-related septic shock: a subgroup analysis of the APROCCHSS phase 3 randomised trial

International audienceBackground: Glucocorticoids probably improve outcomes in patients hospitalised for community acquired pneumonia (CAP). In this a priori planned exploratory subgroup analysis of the phase 3 randomised controlled Activated Protein C and Corticosteroids for Human Septic Shock (APROCCHSS) trial, we aimed to investigate responses to hydrocortisone plus fludrocortisone between CAP and non-CAP related septic shock.Methods: APROCCHSS was a randomised controlled trial that investigated the effects of hydrocortisone plus fludrocortisone, drotrecogin-alfa (activated), or both on mortality in septic shock in a two-by-two factorial design; after drotrecogin-alfa was withdrawn on October 2011, from the market, the trial continued on two parallel groups. It was conducted in 34 centres in France. In this subgroup study, patients with CAP were a preselected subgroup for an exploratory secondary analysis of the APROCCHSS trial of hydrocortisone plus fludrocortisone in septic shock. Adults with septic shock were randomised 1:1 to receive, in a double-blind manner, a 7-day treatment with daily administration of intravenous hydrocortisone 50 mg bolus every 6h and a tablet of 50 μg of fludrocortisone via the nasogastric tube, or their placebos. The primary outcome was 90-day all-cause mortality. Secondary outcomes included all-cause mortality at intensive care unit (ICU) and hospital discharge, 28-day and 180-day mortality, the number of days alive and free of vasopressors, mechanical ventilation, or organ failure, and ICU and hospital free-days to 90-days. Analysis was done in the intention-to-treat population. The trial was registered at ClinicalTrials.gov (NCT00625209).Findings: Of 1241 patients included in the APROCCHSS trial, CAP could not be ruled in or out in 31 patients, 562 had a diagnosis of CAP (279 in the placebo group and 283 in the corticosteroid group), and 648 patients did not have CAP (329 in the placebo group and 319 in the corticosteroid group). In patients with CAP, there were 109 (39%) deaths of 283 patients at day 90 with hydrocortisone plus fludrocortisone and 143 (51%) of 279 patients receiving placebo (odds ratio [OR] 0·60, 95% CI 0·43-0·83). In patients without CAP, there were 148 (46%) deaths of 319 patients at day 90 in the hydrocortisone and fludrocortisone group and 157 (48%) of 329 patients in the placebo group (OR 0·95, 95% CI 0·70-1·29). There was significant heterogeneity in corticosteroid effects on 90-day mortality across subgroups with CAP and without CAP (p=0·046 for both multiplicative and additive interaction tests; moderate credibility). Of 1241 patients included in the APROCCHSS trial, 648 (52%) had ARDS (328 in the placebo group and 320 in the corticosteroid group). There were 155 (48%) deaths of 320 patients at day 90 in the corticosteroid group and 186 (57%) of 328 patients in the placebo group. The OR for death at day 90 was 0·72 (95% CI 0·53-0·98) in patients with ARDS and 0·85 (0·61-1·20) in patients without ARDS (p=0·45 for multiplicative interaction and p=0·42 for additive interaction). The OR for observing at least one serious adverse event (corticosteroid group vs placebo) within 180 days post randomisation was 0·64 (95% CI 0·46-0·89) in the CAP subgroup and 1·02 (0·75-1·39) in the non-CAP subgroup (p=0·044 for multiplicative interaction and p=0·042 for additive interaction).Interpretation: In a pre-specified subgroup analysis of the APROCCHSS trial of patients with CAP and septic shock, hydrocortisone plus fludrocortisone reduced mortality as compared with placebo. Although a large proportion of patients with CAP also met criteria for ARDS, the subgroup analysis was underpowered to fully discriminate between ARDS and CAP modifying effects on mortality reduction with corticosteroids. There was no evidence of a significant treatment effect of corticosteroids in the non-CAP subgroup.Funding: Programme Hospitalier de Recherche Clinique of the French Ministry of Health, by Programme d'Investissements d'Avenir, France 2030, and IAHU-ANR-0004