Search

The causes of U-Pb isotopic discordance documented by Paquette et al. (2004) in monazite grains from the ultra-high temperature (UHT) granulite of the Andriamena unit of Madagascar are re-evaluated in the light of nanoscale crystal-chemical characterization utilising Atom Probe Tomography (APT) and state-of-the-art Scanning Transmission Electron Microscopy (STEM). APT provides isotopic (208Pb/232Th) dating and information on the chemical segregation of trace elements (e.g., Pb) in monazite at nanoscale. Latest generation of STEM allows complementary high-resolution chemical and structural characterization at nanoscale. In situ isotopic U–Pb dating with Secondary Ion Mass Spectrometry (SIMS) on 25 monazite grains and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) on zircon have been employed to refine the age spectra. Monazite and zircon grains located in quartz and garnet formed with the peak UHT metamorphic assemblage, which is partially overprinted by retrograde coronitic textures. Zircon grains hosted in garnet and in quartz yield concordant U–Pb ages at 2758 ± 28 Ma and 2609 ± 51 Ma, respectively whereas monazite grains hosted in quartz and garnet show a discordant Pb* loss trend on the Concordia diagram recording disturbance at 1053 ± 246 Ma that is not seen by the zircon, underlining the importance of combining the use of monazite and zircon to understand the history of polymetamorphic rocks. The Pb*-loss trend of monazite is related to petrographic position, with less Pb* lost from monazite hosted in quartz and garnet than monazite hosted in the coronitic reaction texture domains. STEM shows that the garnet- and quartz-hosted monazite grains contain more Pb-bearing nanophases than monazite grains located in the coronitic textures. An inverse correlation between the number of Pb-bearing nanophases and the percentage of Pb*-loss in monazite grains demonstrates that Pb* is retained in the grain in the form of nanophases. The formation of Pb-bearing nanophases limits Pb*-loss at the grain scale and therefore allows the preservation of early events. 208Pb/232Th ratios obtained with APT in monazite located in quartz and garnet and excluding Pb*-bearing nanophases indicate a mean age of 1059 ± 129 Ma corresponding to a disturbance event hitherto undetected in the geochronological record of the Andriamena unit. Thus, geochronology with APT allows access to information and the definition of events that may be blurred or obscured when examined at lower spatial resolution.

At the heart of Western history, Caribbean and African-American thinkers identified the inaugural relationship between race and capitalism early in societies where this articulation is particularly sensitive. By the end of the 18th century, racial capitalism in North America had become intertwined with the promise of democracy. From then on, the history of the Americas bears witness to the paradoxical interweaving of capitalism and racial violence on the one hand and democracy on the other. This double – or even triple – origin lies at the heart of Americanist Sylvie Laurent’s latest book, Capital et race (2024). Drawing on the central intellectual myths on which the United States, and more broadly the modern West, is founded, she focuses on the other side of the liberal emancipation narrative: the erasure of a far-reaching operation of capitalist and racial violence. This mechanism makes the modern “origin of inequality” an impossible narrative.

The term "school form" has become something of a commonplace, and should be questioned in terms of its heuristic scope for understanding teaching practices. Even if the socio-historical form identified by Guy Vincent is clearly evolving in the operation of many contemporary establishments through the development of pedagogical innovations, this concept still appears relevant for questioning pedagogical practices in the various singular dimensions characteristic of school situations. Based on an analysis of the different dimensions at play in the practices presented in the contributions to this issue, and drawing on research into "different pedagogies" (Flexible Classrooms, Freinet Pedagogy), this article seeks to put into perspective a model of contemporary developments based on a reflection on the registers and degrees of rupture with the determinants of the initial "school form" that we can identify in school practices.

Delaying the date of the first hedge-trimming (or ‘tip-pruning’) is of limited technical value in vineyard canopy management. The impact of the delay on lateral shoot growth and must composition remains marginal within the context of the La Côte vineyard in Switzerland.

This article is less the narrative of a collection of filmed testimonies than a narrative, according to the meaning of Bourdieu, of the objectification of an objectification. By favouring an inductive and reflexive perspective, this article aims to analyse the concrete conditions of possibility of a memory type of objectification and the resulting epistemological stakes. Behind the updating of the encoding operations, it seeks to show the random part inherent to every memorial seizure. In doing so, the article also seeks to be interested in a rural area situated in the department of Cher, le Val d’Aubois, understudied by the academical world and whose history carries with it an important industrial past.

The result of work of an interdisciplinary group of researchers of the French Workshop Zone Network (Réseau des Zones Ateliers, CNRS), this article focuses on the implementation of restoration projects aiming to restore ecological connectivity of rivers. These projects are at the center of an important controversy taking place in the French public space since several years. Thus certain actors put into question the pertinence of the public policy aiming at removal of hydraulic structures contributing to connectivity interruption. Here, we first synthesize the currently known effects of the connectivity interruption in its longitudinal, lateral and vertical dimensions on a row of biophysical and socio-economic processes. Spotlighting the complexity of processes linked to river connectivity, the variablity of territorial contexts and the associated uncertainties, our analysis reveals the necessity of inscribing restoration projects within a larger project of water ressource management conducted at the scale of a territory and rooted in a participatory decision process. The decision to restore or not restore connectivity cannot be based exclusively on science and technical expertise. With this in mind, we propose an action strategy to address challenges related to river connectivity restoration. We identify ten critical points to take into account for implementing restoration projects that would be both supported by different stakeholders, and efficient in regard to their defined objectives.

The goal of the paper is to assess the temperature effect of a large (40 ha) pond with a surface weir, damming a confluence zone of four streams in Limousin (French Massif Central). The research is based on 536,552 water temperature measurements, upstream, downstream and inside the pond. Compared to the most frequent calculation method, which consists in measuring the difference between the inlet and the outlet, two new methods are used. The first consists in weighting the temperature values of each of the four tributaries, in order to construct an overall inlet temperature. The second considers the distance existing between the inlets and the outlet. After reconstitution of the former hydrographic network, the method applies a temperature gradient from upstream to downstream mixing temperatures to each confluence. According to the method of weighting the inlets, the Great Pond Cieux warms the watercourse by 1.8°C for a full year and by more than 4°C from June to September. It also modifies the thermal regime of the watercourse, by reducing its diurnal temperature variation. According to the temperature gradient method, the significant warming during the summer months would be due one third to the natural evolution of the streams from upstream to downstream and two thirds to the pond. During some weather types, in particular periods of forced convection by stormy winds, the responsibility of the pond would even be much less.

While most catalytic fixed bed gas-liquid reactors of the petrol industry work at quite high pressures, the academic scientific work in this field concerned itself almost exclusively with the domain of approximatively atmospheric pressures. The authors present the results of some years of experimental investigations on the hydrodynamic characteristics of trickle bed reactors and lately of cocurrent upflow reactors. During the last years, results were also obtained under pressures up to 8 MPa. The measurements were made in a small scale cold flow equipment (diameter 23 mm). Different aqueous and organic more or less viscous, eventually coalescence inhibiting liquids, four gases and a number of non porous more or less wettable particles were used. The liquid holdup was determined in all cases by measuring liquid phase residence time distribution by different tracers. The following conclusions may be drawn:(a) In the high interaction regime, it is the inertia of the gas and the liquid phases which is the main cause of the dissipation of mechanical energy. In this regime, results obtained in cocurrent upflow and downflow are approximately equal. (b) Most correlations of literature are unable to predict the effect of pressure on the pressure drop or the liquid holdup. (c) The gas viscosity has no influence on the hydrodynamics. It is therefore possible to simulate for example hydrogen under high pressure conditions by another gas of the same density (at a much lower pressures). A critical evaluation of the correlations and/or models of literature is presented, concerning their ability to represent the different characteristics as a function of pressure. Tandis que la plupart des réacteurs industriels gaz-liquide à lit de catalyseur fixe fonctionnent à assez hautes pressions, les travaux scientifiques académiques sont, dans ce domaine, presque exclusivement consacrés aux pressions avoisinant la pression atmosphérique. Les auteurs présentent les résultats de quelques années de recherches expérimentales sur les caractéristiques hydrodynamiques des réacteurs à écoulement cocourant ruisselant et enfin de réacteurs en cocourant montant. Au cours des dernières années, des résultats ont également pu être obtenus sous des pressions pouvant aller jusqu'à 8 MPa, les mesures étant faites à petite échelle (23 mm de diamètre) dans une maquette froide. Différents liquides aqueux et organiques plus ou moins visqueux, éventuellement inhibiteurs de coalescence, 4 gaz et un certain nombre de particules plus ou moins mouillables non poreuses ont été utilisés. La rétention liquide a, dans tous les cas, été déterminée en mesurant la distribution des temps de séjour de la phase liquide, à l'aide de différents traceurs. Les conclusions suivantes ont pu être tirées : - Pour le régime à forte interaction, c'est l'inertie du gaz et des phases liquides qui constitue la cause principale de la dissipation d'énergie mécanique. Dans ce régime, les résultats obtenus en cocourant montant et descendant sont à peu près identiques. - La plupart des corrélations relevées dans la littérature ne permettent pas de prévoir l'influence de la pression sur la chute de pression ou la retenue liquide. - La viscosité du gaz n'influence pas l'hydrodynamique. Il est donc possible de simuler, par exemple, l'hydrogène sous forte pression par un autre gaz de même densité (à pression beaucoup plus basse). Une étude critique des corrélations et/ou des modèles de la littérature est présentée du point de vue de leur aptitude à représenter les différentes caractéristiques en fonction de la pression.

This article reports on the initial results of an exploratory research aimed at mapping the informal use of English by French secondary school pupils. The research was carried out as part of a PhD in language sciences and involved 482 young teenagers attending the Esplanade international secondary school in Strasbourg. The results show that these activities are highly developed from the first year onwards, and that they increase throughout the years of secondary school. In particular, viewing and reading activities increase steadily over the years. Over and above the distribution of these activities by age group, the results also show that they vary widely depending on the personal background of each individual. The notion of pleasure experienced during these activities, which is partly linked to the high desirability of English-language contents, as well as its status of a lingua franca in pupils' minds, is the main reason given by respondents. However, these parameters cannot be approached in isolation from other aspects such as the need to communicate with and make friends, the desire to learn, etc., which all operate according to a systemic approach specific to each user-learner.

Pharmacokinetic variability in drug levels represent for some drugs a major determinant of treatment success, since sub-therapeutic concentrations might lead to toxic reactions, treatment discontinuation or inefficacy. This is true for most antiretroviral drugs, which exhibit high inter-patient variability in their pharmacokinetics that has been partially explained by some genetic and non-genetic factors. The population pharmacokinetic approach represents a very useful tool for the description of the dose-concentration relationship, the quantification of variability in the target population of patients and the identification of influencing factors. It can thus be used to make predictions and dosage adjustment optimization based on Bayesian therapeutic drug monitoring (TDM). This approach has been used to characterize the pharmacokinetics of nevirapine (NVP) in 137 HIV-positive patients followed within the frame of a TDM program. Among tested covariates, body weight, co-administration of a cytochrome (CYP) 3A4 inducer or boosted atazanavir as well as elevated aspartate transaminases showed an effect on NVP elimination. In addition, genetic polymorphism in the CYP2B6 was associated with reduced NVP clearance. Altogether, these factors could explain 26% in NVP variability. Model-based simulations were used to compare the adequacy of different dosage regimens in relation to the therapeutic target associated with treatment efficacy. In conclusion, the population approach is very useful to characterize the pharmacokinetic profile of drugs in a population of interest. The quantification and the identification of the sources of variability is a rational approach to making optimal dosage decision for certain drugs administered chronically.