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Battered and Bewildered Crinolines: Dress as Empowerment in Mary Eyre's Travel Writing
No full textInternational audienc
Groundwater and Subsurface Fluid Dynamics: Tracing Equilibrium and Fractionation with Noble Gases
No full textInternational audienceThe inertness and scarcity of noble gases in geological fluids make them ideal tracers of subsurface fluid origins and processes. The noble gas composition of subsurface water [1] and its equilibrium interaction with other fluids are well-established. However, non-equilibrium conditions in natural systems deeper than 1 km challenge our understanding of fluid behaviour. In particular, fluid density, temperature, and noble gas concentration influence molecular movement through kinetic diffusion, thermodiffusion, gravitational segregation [2] within layers, and solubility-driven fractionation at fluid interfaces [3]. This study bridges the gap between fractionation and equilibrium states by examining six gas, oil, and water samples from a 4 km deep reservoir. Results reveal unsteady conditions, with fractionation factors (F) for atmosphere-derived (20Ne/36Ar) and crustal-produced (4He/40Ar) noble gases evolving differently and varying based on phase characteristics. The samples' vertical location and proximity to fluid interfaces affect the type and intensity of fractionation. By reviewing decades of noble gas data from subsurface gases and groundwater, we provide new insights into the physical constraints shaping fractionation. We show that gas phases reach equilibrium one or two orders of magnitude faster than water, revealing dualities in fractionation patterns, even within interconnected reservoirs. Natural gas systems often show covariation in F(4He/40Ar)* and F(20Ne/36Ar), providing insight into mixing processes and timing [4]. This is less common in denser fluids. In deep groundwater, the fractionation of crustal noble gases correlates with salinity and residence time, varying according to in-reservoir or external processes. We also demonstrate how argon isotope fractionation [5] relates to fluid equilibrium states, specifically 40Ar, 38Ar and 36Ar, and can be used to determine water contact depth. This research emphasises the significance of aquifer characterisation in establishing baselines for subsurface fluid dynamics interpretation and CO2 storage operations
Algorithmic system in the workplace, the challenges of human oversight
No full textInternational audienceThis contribution aims to explore the human oversight over algorithmic system in the workplace, from a legal perspective mainly based on three European instruments, the General Data Protection Regulation (GDPR), the Artificial Intelligence Act (OJEU 12 July 2024) and the Directive of the European Parliament and of the Council on improving working conditions in platform work (OJEU 11 November 2024). It examines the applicable legal framework to highlight the challenges associated with implementing effective human oversight
Alkali-promoted FeCo/TiO<sub>2</sub> catalysts for carbon dioxide hydrogenation to fuels
No full textInternational audienceA titania support has been modified in order to prepare alkali promoted cobalt-iron catalysts for the hydrogenation of carbon dioxide into long-chain hydrocarbons (C5+). Under mild reaction temperatures (220-250-270 °C), the partial substitution of cobalt by iron decreased the catalytic activity (CO2 conversion) but increased the selectivity into C5+, since iron is less active within this temperature range, but more selective for the reverse water-gas shift reaction. Alkali promotion (Na or K) further decreased the catalytic activity of cobalt-iron catalysts, albeit, strongly increasing the selectivity into CO and C5+ by decreasing CH4 production. This could be attributed to the high basicity of alkali promoted catalysts, their beneficial effect on CO2 dissociative adsorption, and their ability to limit H2 adsorption
Conservation Genetics of the Reintroduced Giant Tortoises (Aldabrachelys gigantea) in Madagascar
No full textInternational audienceThe Aldabra giant tortoise is the only surviving lineage of the Malagasy megafauna, which went extinct due to human activitiesover the last millennium. In 2018, the first rewilding project was launched at the Anjajavy Reserve (NW Madagascar), using 12founders of unknown origin. They started to mate in 2019, but genetic proximity between individuals and their reproductive output remains to be determined for optimal management of the newly established population. Here, we used 29 microsatellite loci toanalyze the genetic diversity of native populations from Aldabra, a coral atoll 420km from Madagascar, to assign Anjajavy founders to specific genetic groups and assess how well they represent the overall genetic diversity in the native range. Additionally,five of these loci allowed us to investigate the diversity of the genomic region containing the Major Histocompatibility Complex(MHC) genes. The non-MHC microsatellite data were also used to investigate the past demography of the species using a stepwise mutation model (VarEff). Finally, we evaluated the contribution of Anjajavy founders to the offspring. First, the clusteringanalysis identified two main genetic groups in Aldabra, and demographic inferences then support that population size fluctuations were strongly shaped by climatic shifts and sea-level changes on the atoll. Both genetic groups are represented among theAnjajavy founders, who most likely originated from the southern island of Aldabra. However, the founders contributed unequallyto the offspring, as most juveniles analyzed were the result of mating between individuals from the two groups, leading to a significant global increase in heterozygosity in the offspring. We propose measures to minimize inbreeding and maintain geneticdiversity within the Anjajavy population, thereby enhancing its potential for long-term viability
A sequential approach for multiphase reactive transport: coupling PHREEQC with hydrological modeling
No full textInternational audienceThis work addresses the challenges associated with reactive transport modeling in environmental applications, such as nuclear waste disposal and geological sequestration of CO 2 . Due to limited experimental studies in long-term scenarios, numerical simulation is crucial. A thorough survey of existing codes reveals mainly two types of numerical approaches for reactive flows: global implicit and sequential or operator splitting approaches. Sequential approaches allow specific programming for hydrological and chemical processes. The objective is to develop a reactive transport package that couples PHREEQC for chemical aspects and DuMuX for hydrological aspects. The operator splitting method is implemented in a non-iterative sequential approach and a comprehensive description of the mathematical formulation is presented. The spatial discretization employs a cell-centered finite volume method with an implicit Euler scheme for time discretization. The model has been developed and implemented for both single-phase and two-phase flows. Its efficiency and robustness have been validated through a series of numerical experiments, ranging from single-phase benchmarks to complex two-phase flow scenarios. The methodology has been tested notably in two- and three-dimensional configurations,including high-performance computing, thereby demonstrating its relevance for realistic applications
Droit des obligations et transfert de compétences : des engagés qualifiés français sous contrat aux États-Unis mexicains avant « la guerre des pâtisseries ».Les effets juridiques de la géopolitique sécessionniste sur les non-nationaux (années 1830)
No full textL’article s’intéresse en particulier au transfert de compétences professionnelles en vue de développer certaines industries aux États-Unis mexicains, indépendants depuis 1821, à travers les clauses contractuelles des engagements signés par des artisans et des entrepreneurs français avec le consul général du commerce du nouvel État américain à Paris. L’étude se penche sur ce cas d’espèce du droit des contrats qui assure la transmission des savoir-faire techniques en vue de former une main d’œuvre à l’étranger, ainsi que le transfert des actifs corporels et incorporels. Elle interroge les liens possibles avec la situation des colons français de Coatzacoalcos et de Jicaltepec (État de Veracruz), dans un contexte de remise en cause des droits des résidents étrangers durant la période qui suit la reconnaissance par la France de l’Indépendance du Mexique (années 1830). La décennie est en effet marquée par des tournants juridico-politiques majeurs pour le pays (instabilités constitutionnelles) et des exactions nombreuses contre les Français présents à ce moment. La fin du premier fédéralisme (1824-1835) et le régime des Sept Lois (1835/36-1846), l‘abolition de l’esclavage (1829), les coups d’État de Santa Anna et la fin de la Guerre civile (1841) sont la toile de fond qui encadre la présence française aux États-Unis mexicains naissants. On interrogera ainsi les conditions d’exécution du contrat dans un contexte de violences et de guerres civiles où les Français sont particulièrement ciblés et ne bénéficient d’aucun soutien par les autorités du pays. Le Secrétaire des Relations Extérieures du Mexique, Gutiérrez de Estrada, déclare ainsi « les guerres civiles sont tellement fréquentes au Mexique, que s’il fallait indemniser toutes les victimes possibles de ces guerres, le Trésor public n’y suffirait pas ». Et de conclure : « dans cet état de choses, l’administration mexicaine ne pouvant pas et par conséquent ne devant pas indemniser tout le monde, les étrangers ne sauraient être en droit d’élever sous ce rapport des prétentions exceptionnelles (…). Dans quelque pays que ce soit, les étrangers doivent s’estimer satisfaits de se voir traités absolument de la même manière que les indigènes et ne peuvent être en droit d’exiger des faveurs refusées à ceux-ci ». Pourtant le même représentant du gouvernement avait argué auparavant : « quand il s’agit de stricte justice, et de mesures qui intéressent la sûreté des personnes, ou l’inviolabilité des propriétés, les étrangers conservent incontestablement le droit de réclamer contre les violations à leur égard, des principes en pareilles matières, sans s’inquiéter si ces principes sont ou non observés envers les citoyens du pays. Le droit et l’équité sont choses invariables et imprescriptibles de leur nature et contre lesquelles aucun exemple ni aucun fait ne saurait rien prouver ». Malgré cette considération sur les droits des étrangers au Mexique, les expulsions des résidents français et les violations de propriété, les extorsions de fonds, les meurtres et les violences physiques « aux cris de meurent les étrangers ! meurent les Juifs ! » accompagnent allégrement cette aventure française dans un nouveau pays qui se cherche après la conquête de l’Indépendance. Dès lors, l’interrogation porte aussi sur « un droit du plus fort », un Far West juridique, dénoncé sur place. Celui-ci semble laisser peu de place à l’application du droit international pourtant convoqué comme garant des sujets étrangers aussi bien qu'au droit des contractants français engagés par les autorités publiques, dans un contexte d’insécurité et d’instabilité
Normalized solutions to a Choquard equation involving mixed local and nonlocal operators
No full textInternational audienc
Solutions of Hypersingular Integral Equations in Two Disjoint Intervals in terms of Elliptic Integrals
No full textThis paper presents novel analytical solutions for a Hypersingular Integral Equation (HIE) over two disjoint intervals. The solution is derived for cases where the input function is a Chebyshev polynomial of the first or second kind, and is expressed as a finite series of elliptic integrals, which is amenable to efficient and accurate computation via recurrence relations. Furthermore, we derive the asymptotic form of the solution as the gap between the intervals vanishes, formally demonstrating its convergence to the well-established solution on a single continuous domain. The validity of the proposed framework is confirmed through extensive numerical experiments, which show excellent agreement with direct numerical quadrature. Finally, these new solutions are leveraged to propose a spectral method framework for the generalized HIE on disjoint intervals
