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Crystallization kinetics of Plagioclase and application to timescale of crystal mush storage
No full textAu cours des dernières décennies, la vision des réservoirs magmatiques a profondément évolué : les grandes chambres magmatiques riches en liquide ont été remplacées par un réseau complexe de dykes et de sills dominés par des mushs cristallins. Cette nouvelle conception a renforcé l’intérêt pour la quantification des échelles de temps magmatiques, essentielles pour comprendre la dynamique volcanique. Parmi les différentes méthodes existantes (datation isotopique, diffusion, modélisation thermique), l’analyse des distributions de tailles de cristaux (CSD), associée à des taux de croissance déterminés expérimentalement, constitue un outil particulièrement précieux, notamment lorsque les minéraux datables sont absents ou que les textures sont altérées.
Cette thèse vise à évaluer le potentiel des approches texturales, en particulier la méthode CSD, pour contraindre les temps caractéristiques de l’évolution magmatique, en combinant expériences contrôlées et étude d’échantillons naturels. L’approche expérimentale, comprenant 80 expériences réalisées dans un four vertical sur une andésite basaltique en conditions anhydres, poursuivait deux objectifs principaux : (i) quantifier les taux de croissance du plagioclase au cours de différents chemins de solidification ; et (ii) étudier l’impact du chemin thermique et du prétraitement (surchauffe, élimination des germes) sur la nucléation et les textures cristallines.
Les résultats montrent une évolution similaire des taux de nucléation et de croissance, avec un maximum généralement atteint à proximité du liquidus, suivi d’une diminution progressive lors du refroidissement. Les microtextures obtenues constituent un excellent marqueur du taux de refroidissement (et donc du sous-refroidissement), avec une évolution des morphologies allant de formes euédriques à des textures squelettiques puis dendritiques lorsque ce dernier augmente. Toute modification du chemin thermique, en particulier lors du prétraitement (notamment la préchauffe initiale), influence fortement la cristallisation : elle tend à inhiber la nucléation et à favoriser la croissance de grands cristaux présentant des textures de déséquilibre (dendritiques). Les taux de croissance obtenus varient de 10⁻⁹ à 10⁻⁸ cm·s⁻¹ (pour des refroidissements compris entre 1 et 125 °C/h), et atteignent des valeurs de l’ordre de 10⁻⁷ à 10⁻⁶ cm·s⁻¹ lorsque la surchauffe dépasse 15 °C au-dessus du liquidus.
Les taux de croissance ainsi établis ont ensuite été utilisés pour interpréter les CSD de 19 échantillons issus de trois stratovolcans actifs de l’arc chilien (Osorno, Calbuco et Villarrica). Ces systèmes, dépourvus de phases accessoires datables et caractérisés par des textures criblées, se prêtent particulièrement bien à cette approche. Les durées de cristallisation estimées s’étendent de quelques jours à environ trois ans, selon les vitesses de croissance retenues et les populations cristallines considérées. Ces durées reflètent trois stades distincts de l’histoire magmatique : les macrocristaux enregistrent un séjour prolongé dans le réservoir principal ; les micro-phénocristaux témoignent d’un temps de résidence dans des réservoirs intermédiaires peu profonds, crucial pour l’évaluation des risques ; les microlites, quant à eux, reflètent la cristallisation lors de l’ascension finale précédant l’éruption.
Ces durées, plus courtes que celles obtenues par diffusion ou par les séries de l’uranium, soulignent que chaque méthode chronométrique enregistre une fenêtre temporelle distincte. L’approche CSD, sensible aux taux de croissance considérés, permet d’estimer exclusivement les temps de cristallisation. Elle apparaît néanmoins comme un complément indispensable aux chronomètres géochimiques pour mieux comprendre le stockage et la dynamique du magma dans les arcs volcaniques, en reliant à la fois échelles de temps et processus magmatiques.Over the past decades, the conceptual view of magmatic reservoirs has profoundly evolved: large, liquid-rich magma chambers have been replaced by a complex network of dykes and sills dominated by crystalline mushes. This new paradigm has reinforced interest in quantifying magmatic timescales, which are essential for understanding volcanic dynamics. Among the various existing methods (isotopic dating, diffusion chronometry, thermal modelling), the analysis of crystal size distributions (CSD), combined with experimentally determined growth rates, represents a particularly valuable tool, especially when datable accessory minerals are absent or when crystal textures are altered.
This thesis aims to assess the potential of textural approaches, particularly the CSD method, to constrain the characteristic timescales of magmatic evolution by combining controlled experiments with the study of natural samples. The experimental approach, consisting of 80 experiments performed in a vertical furnace on an anhydrous basaltic andesite, pursued two main objectives: (i) to quantify plagioclase growth rates along different solidification paths; and (ii) to investigate the influence of thermal history and pre-treatment (superheating, removal of nuclei) on nucleation behaviour and crystal textures.
The results show a similar evolution of nucleation and growth rates, with a maximum generally reached near the liquidus, followed by a progressive decrease during cooling. The resulting microtextures are excellent markers of cooling rate (and thus undercooling), with morphologies evolving from euhedral forms to skeletal and then dendritic textures as undercooling increases. Any modification of the thermal path, particularly during pre-treatment (notably initial superheating), strongly influences crystallization: it tends to inhibit nucleation while promoting the growth of large crystals exhibiting disequilibrium textures (dendritic). The measured growth rates range from 10⁻⁹ to 10⁻⁸ cm·s⁻¹ for cooling rates between 1 and 125 °C/h, and reach values on the order of 10⁻⁷ to 10⁻⁶ cm·s⁻¹ when superheating exceeds 15 °C above the liquidus.
The experimentally derived growth rates were then used to interpret the CSDs of 19 samples from three active stratovolcanoes of the Chilean arc (Osorno, Calbuco and Villarrica). These systems, which lack datable accessory phases and commonly display sieve textures, are particularly well suited to this approach. The estimated crystallization durations range from a few days to roughly three years, depending on the growth rates considered and the crystal populations analysed. These timescales reflect three distinct stages of the magmatic history: macrocrysts record prolonged residence in the main reservoir; microphenocrysts correspond to residence times in shallow intermediate reservoirs, which are crucial for hazard assessment; and microlites reflect crystallization during the final ascent prior to eruption.
These timescales, shorter than those obtained from diffusion chronometry or U-series dating, highlight that each method records a different temporal window. The CSD approach, inherently sensitive to the growth rates considered, provides estimates of crystallization durations only. Nevertheless, it emerges as an essential complement to geochemical chronometers for improving our understanding of magma storage and dynamics in volcanic arcs, by linking both timescales and magmatic processes
(Im)politeness in Ancient Egypt:Norms, Wit, and Rudeness in Texts from Pharaonic Times through Late Antiquity
No full textpeer reviewed(Im)politeness in Ancient Egypt is the first book-length study of (im)politeness in ancient Egyptian texts. Leading experts in their respective corpora examine a range of textual sources spanning approximately 2,000 years, using the latest frameworks for analyzing language in usage. This edited volume asks how ancient Egyptians adapted and modified their language to persuade, complain, or mock, and how they assessed the risks and benefits of communicating with those above or below them in the social hierarchy. The papers explore whether ancient Egyptians used politeness freely and strategically, or were constrained by mandatory social rules. The documents presented, translated, and analyzed in this book include personal letters, ritual utterances, fictional stories, dialogue captions in tomb scenes, and messages to dead relatives
Physico-chemical and mineralogical characterization of clay material from the Bakotcha locality: Application to wastewater treatment
Full text linkIn the two first parts of this study, raw clays extracted from Bana, in western Cameroon, were modified with semiconductors (TiO2 and ZnO) to improve their pollution control properties by adding photocatalytic properties. Also Cu²⁺, Na+ and Zn2+ ions were added to the clay by ion exchange to increase the specific surface area, and to modify the charge of the clay surface. The results obtained from X-ray diffraction show that the clay belonged to the smectite family and was composed of different crystalline phases. Furthermore, the presence of TiO2 and ZnO was confirmed by the detection of anatase and wurtzite, respectively. Furthermore, the composite clays showed increased specific surface areas. Finally, the pollutant removal properties of the samples were evaluated using different model pollutants: fluorescein (FL), p-nitrophenol (PNP), malachite green (MG) and diamond bright violet (DBV). It was demonstrated the possibility of obtaining highly effective hybrid materials for the removal of pollutants from water using inexpensive natural clay modified with a small amount of photocatalytic material (approximately 30% by weight of TiO2 or ZnO).
The third step consisted of modifying the clay material with two silanes, tetramethoxysilane (TMOS) and [3-(2-aminoethyl)aminopropyl]trimethoxysilane (EDAS), to increase its adsorption properties. The modified clay is intended for use as an effective adsorbent for the removal of organic pollutants from water. Three Clay/TMOS samples and two Clay/EDAS samples with different [silane]/[clay] ratios were produced and characterized. Their adsorption properties were evaluated on three model organic pollutants (i.e., FL, MG, and DBV). The two types of clays modified with TMOS and TEOS, respectively, exhibit two different adsorption behaviors for the three pollutants.
In the final part of this study, the growing presence of pharmaceuticals in wastewater, such as ibuprofen, which raises serious environmental and public health concerns, was demonstrated. In this study, some photocatalytic ZnO and TiO2-doped natural Cameroonian clays were used to ensure effective degradation of ibuprofen and bacterial inhibition under UV light (365 nm). Characterization confirmed the successful dispersion of semiconductors on the clay matrix. Under UV irradiation, the composites achieved significant degradation efficiencies, with mineralization monitored by total organic carbon (TOC), and antibacterial tests revealed notable inhibition against Shigella spp., supporting the dual functionality of the materials
Design and Characterization of a Microfluidic Well Plate for Advanced Liquid Handling and Sample Preparation
No full textLes fonctions de l’imaginaire de la vie. À quoi s’oppose le vitalisme ?
No full textpeer reviewedL’article défend l’intérêt du concept d’imaginaire pour l’étude des pratiques discursives du savoir, et en particulier pour l’étude du vitalisme dans le discours de la linguistique. Il propose une typologie des fonctions de l’imaginaire de la vie dans l’histoire des sciences, pour ensuite se centrer sur le champ spécifique de la linguistique, envisagé à travers le cas d’August Schleicher et de ses liens avec les sciences du vivant. La perspective opposée est ensuite adoptée, pour montrer que les relations dynamiques entre imaginaires s’observent tout aussi bien depuis les humanités vers les sciences du vivant. Enfin, la conclusion illustre les dimensions éthico-politiques susceptibles d’être couvertes de manière positive et assumée par le concept de vitalisme.This paper advocates for the relevance of the concept of imaginary in analyzing discursive practices related to knowledge, particularly emphasizing its applicability in studying vitalism within linguistic discourse. We begin by presenting a typology of the functions of the imaginary of life in the history of sciences, then narrow our focus to the domain of linguistics, with a specific emphasis on the case of August Schleicher and his connections to life sciences. Subsequently, we adopt the opposite perspective to demonstrate that dynamic relationships between imaginaries are equally observable from the humanities towards life sciences. Finally, the conclusions highlight the ethico-political dimensions that can be positively and consciously embraced by the concept of vitalism
Ancient Egyptian Politeness throughout the Ages: Approaches, Questions, and Results
No full textpeer reviewedThis book represents a pioneering effort in the field of (im)politeness research,
focusing on ancient Egyptian texts spanning all historical periods. The study of
politeness continues to captivate scholars interested in language and society.
Our primary aim is to create an accessible and valuable resource for researchers
in ancient Egyptian history and pragmaticians working on cross-cultural com-
munication. Despite its profound potential to unveil and dissect social dynam-
ics in communication, the methods of politeness research remain largely unfa-
miliar to philologists studying ancient texts
Synergistic visible-light photocatalysis by ZnO/black phosphorus nanohybrids immobilized on activated kaolinite
Full text linkpeer reviewedThis study reports the design and synthesis of a novel composite photocatalyst based on ZnO nanoparticles immobilized onto a black phosphorus (BP)-modified activated kaolinite matrix. The fabrication strategy combines solvothermal doping and sol-gel methods to achieve a hybrid 2D/3D semiconductor system. Comprehensive characterization, including XRD, XPS, UV-Vis DRS, PL, SEM, and TEM, confirmed the successful integration of ZnO and BP within the clay structure. The resulting composites exhibited enhanced photocatalytic activity under visible light compared to pure ZnO, as evaluated by the degradation of two polyazo dyes (Direct Red 80 and Chicago Sky Blue 6B). The Activated Clay/BP/ZnO composite showed superior performance, with first-order kinetic constants up to three times higher than those of pure ZnO. This improvement is attributed to improved charge separation, defect engineering, and strong interfacial interactions within the heterostructure. These findings highlight the potential of BP-doped clay-supported ZnO composites as efficient, sustainable photocatalysts for wastewater treatment
Understanding the Interplay Between the Driver, the Vehicle, and the Environment for Adapting Driving Automation
No full textSince the invention of the automobile at the end of the 19th century, driving has continually evolved. From rudimentary vehicles consisting of little more than an engine, a seat, and wheels, today's cars have become technological marvels equipped with hundreds of sensors and intelligent algorithms. Consequently, driving has transformed into a complex activity involving multiple interacting entities: the human driver, the vehicle automation, and the driving environment.
Despite major technological progress, how to best combine driving automation and driver monitoring systems to dynamically allocate driving tasks for safety and comfort purposes remains a key research challenge. Achieving such adaptive driving automation requires a deep understanding of the interplay between the driver, the vehicle, and the environment.
Part I describes the context of this thesis, tracing the evolution of the automobile from mechanical innovation to the integration of driving automation and driver monitoring. It also reviews the state of the art in driver monitoring, with a particular focus on mental workload and distraction.
Part II presents human studies conducted in a driving simulator to examine whether drivers' cognitive distraction and the complexity of the driving environment influence reliance on Adaptive Cruise Control (ACC) and whether such reliance affects driving performance.
Furthermore, it investigates whether and how physiological and behavioral indicators reflect drivers' cognitive distraction under varying traffic conditions and ACC use. Specifically, three Electrodermal Activity (EDA)-based and three gaze-based indicators were analyzed.
Part III introduces engineering approaches for analyzing the driving environment. In particular, it presents a novel Multi-Stream Cellular Test-Time Adaptation (MSC-TTA) setup in which computer vision models adapt on the fly to a dynamic environment divided into cells. To evaluate a method derived from this setup, a new multi-stream, large-scale synthetic semantic segmentation dataset, called DADE, was released.
In addition, a probabilistic approach to domain characterization is proposed, where domains are characterized as probability distributions. A method is presented for predicting the likelihood of different weather conditions from images captured by vehicle-mounted cameras.
Part IV proposes a closed-loop framework, called DEV, for risk-aware adaptive driving automation that captures the dynamic interplay between the driver, the environment, and the vehicle. The thesis concludes with insights and future perspectives stemming from this research, aimed at fostering safer and more adaptive human–automation cooperation