Portail HAL de l'Université du Littoral Côte d'Opale
Not a member yet
11255 research outputs found
Sort by
Self-assembly and ambipolar charge transport in columnar phases of polynuclear gold isocyano–triphenylene complexes
No full textInternational audienceAn uncommon approach to the synthesis of ambipolar semiconductors based on di- and tri-nuclear gold isocyano–triphenylene complexes of the formula [(AuX)n(CN–C6H4–O–(CH2)6)n–TriPh] (n = 2, 3; X = Cl, CC– Ph) is described. Although mesomorphism has only been obtained with chloro derivatives, the trialkynyl complex has turned out to be a precursor of gold nanoparticles. The chloro complexes self-assemble in lamello-columnar phases, whose supramolecular organizations were confirmed by SAXS/WAXS experiments. Both the tri(chloro-gold) and the di(chloro-gold) complexes display high ambipolar charge transport along the columnar stacking direction, either in the mesophase (trichloro derivative) or in the crystalline solid state (dichloro complex). The analysis of ambipolar charge transport in the chloro-gold compounds has been performed using the time-of-flight (ToF) technique. The dichloro compound exhibits an ambipolar charge carrier mobility of the order of 10−4 cm2 V−1 s−1, whereas the trinuclear compound displays an ambipolar charge carrier mobility of the order of 10−3 cm2 V−1 s−1, which is attributed to the addition of a supplementary peripheral –NC–Au–Cl complex unit, offering a drift field to the charge carriers and a lower optical bandgap. Quantum chemical calculations show that the introduction of an additional –NC–Au–Cl fragment to the dinuclear complex to give the trinuclear derivative promotes a cofacial stacking of the molecules, which increases the mobility of the charge carriers of the system. Due to their ambipolar charge carrier mobility, the poly-nuclear gold isocyano–triphenylene complexes demonstrate their potential for use in organic electronics and optoelectronic devices
Caractérisation et analyse de la variabilité biogéochimique des eaux côtières vietnamiennes à l'aide d'observations par satellite à haute et moyenne résolution spatiale en relation avec l'aquaculture et les forçages naturels
No full textAquaculture plays a prominent role in supporting food security, providing livelihoods, and contributing to economic growth. Given its importance, the global aquaculture sector has expanded rapidly in recent decades, particularly in Asian countries such as Vietnam. Such rapid expansion has led to numerous negative impacts on the ecosystem and the surrounding environment, particularly in the coastal area where aquaculture ponds are frequently located. One of these impacts is the degradation of the coastal water quality near the aquaculture areas. Numerous studies found that aquaculture effluent causes a surge in nutrients and organic matter in the adjacent water bodies (rivers, estuaries, coastal water) leading to eutrophication. This type of study, however, is still lacking in Vietnam where the focus is mostly on the impacts of the environment on aquaculture productivity, and the impact of aquaculture extension on the environment (i.e. mangroves, water resources). Moreover, studies on aquaculture impacts on water quality are mainly conducted over a limited tima and spatial scale using in-situ measurements due to limitations in logistical and financial resources. Therefore, this thesis aims to fill the gaps in the literature by analyzing the long-term change in the coastal water quality of Vietnam with regard to natural forcings and local aquaculture activities, represented by yearly total production and crop timetable, using satellite ocean color remote sensing. The satellite sensors used in the present thesis include OLCI on Sentinel-3A/3B series (with a medium spatial resolution of 600 meters), OLI on Landsat_8, and MSI on Sentinel-2A/B series (both with a reduces resolution of 60 meters). The bio-geochemical parameters measured using remote sensing consist of the absorption of colored dissolved organic matter (acdom), chlorophyll-a (Chl-a), and suspended particulate matter (SPM). A new empirical algorithm to estimate acdom at 412 nm (acdom(412)) has been developed and published (Nguyen et al., 2024). In contrast, the most suitable algorithms for the latter parameters were selected from the literature. In addition, methodologies for a new metric to validate remote sensing algorithms and for combining OLI and MSI observations were also developed. The bio-geochemical variabilities observed from OLCI show that the variation of SPM is due to the hydrological patterns while acdom(412) and Chl-a are not directly influenced by discharge but by the variation of organic matter and nutrients. Analysis using higher spatial resolution data (from OLI and MSI) in the Mekong River Delta reveals that a goog correlation between acdom(412) and river discharge exists only on the first-order, with acdom(412) remaining high or experiencing second peaks well into low discharge condition indicating a continuing generation and/or addition of new dissolved organic matter. At the same time, Chl-a is high during low discharge up to the peak of discharge due to a complex balance between light and nutrient variability with aquaculture ponds potentially controlling the latter. The gradient inside the rivers, which pass through coastal aquaculture areas, starts increasing for acdom(412) and Chl-a at the beginning of the recommended periods for aquaculture crops. This pattern indicates that organic matter and nutrients released in aquaculture effluents offset the natural dilution effect. Moreover, the variation in the yearly average of acdom(412) and Chl-a corresponded well with the increase in the annual total aquaculture production only at the stations after aquaculture areas while that of SPM did not, regardless of locations. In the end, the present thesis concludes that aquaculture does impact the variabilities of acdom(412) and Chl-a in Vietnamese coastal water, particularly in the Mekong River Delta, while that of SPM is primarily controlled by river discharge.L'aquaculture joue un rôle clé dans la sécurité alimentaires, les moyens de subsistance et la croissance économique. Avec son importance, le secteur mondial de l'aquaculture s'est développé rapidement au cours des dernières décennies, notamment en Asie, comme au Vietnam. Cette expansion rapide a entraîné des impacts négatifs sur l'écosystème et l'environnement, surtout dans les zones côtières où se situent les fermes aquacoles. Un des effets majeurs est la dégradation de la qualité des eaux côtières adjacentes, qui peut notamment être associée à l'augmentation des nutriments et de la matière organique dans la colonne d'eau entraînant l'eutrophisation de ces systèmes (estuaires, eaux côtières, etc.). Au Vietnam, les études se concentrent sur les impacts environnementaux sur la productivité et les effets de l'expansion aquacole (ex. mangroves, ressources en eau). Mais celles concernant l'impact de l'aquaculture sur la qualité de l'eau sont limitées, en raison de contraintes logistiques et financières. Cette thèse vise à évaluer l'impact de l'aquaculture à partir de données limitées (production annuelle et calendrier des récoltes) et de la télédétection spatiale de la couleur de l'eau. Les capteurs satellitaires incluent OLCI sur Sentinel-3A/3B (avec une résolution spatiale moyenne de 600 mètres), OLI sur Landsat-8 et MSI sur Sentinel-2A/B (tous deux avec une résolution réduite de 60 mètres). Les paramètres biogéochimiques mesurés sont l'absorption de matière organique dissoute colorée (acdom), la chlorophylle-a (Chl-a) et la matière particulaire en suspension (SPM). Un nouvel algorithme empirique pour estimer acdom(412) a été développé et publié (Nguyen et al., 2024). En revanche, les algorithmes les plus adaptés pour ces derniers paramètres ont été sélectionnés dans la littérature. De plus, des méthodologies pour une nouvelle métrique visant à valider les algorithmes de télédétection et à combiner les observations OLI et MSI ont également été développées. Les variabilités biogéochimiques observées à partir d'OLCI montrent que la variation de SPM est principalement gouvernée par les régimes hydrologiques, tandis que acdom(412) et Chl-a ne sont pas directement influencés par le débit mais par la variation de la matière organique et des nutriments. Une analyse utilisant des données à plus haute résolution spatiale (provenant d'OLI et MSI) dans le delta du Mékong révèle que si une bonne corrélation entre acdom(412) et le débit du fleuve existe au premier ordre, acdom(412) conserve de fortes valeurs également lors des faibles débits, avec l'existence de second pics (contrairement à SPM). Ceci indique une génération continue et/ou ajout de nouvelle matière organique dissoute dans le milieu. Dans le même temps, Chl-a est élevée pendant le régime de faible débit jusqu'au pic de débit en raison d'un équilibre complexe entre la variabilité de la lumière et des nutriments, les étangs d'aquaculture contrôlant potentiellement ce dernier. Le gradient à l'intérieur des rivières, qui traversent des zones aquacoles côtières, commence à augmenter pour acdom(412) et Chl-a au début des périodes recommandées pour les cultures aquacoles. Ceci indique que la matière organique et les nutriments libérés dans les effluents aquacoles compensent l'effet de dilution naturelle. De plus, la variation de la moyenne annuelle de acdom(412) et Chl-a correspond bien à l'augmentation de la production aquacole totale annuelle uniquement aux stations après les zones aquacoles alors que SPM ne montre aucune covariation avec la production et cela quelque soit la localisation. Au final, la présente thèse conclut que l'aquaculture a un impact sur les variabilités de acdom(412) et Chl-a dans les eaux côtières vietnamiennes, en particulier dans le delta du Mékong, tandis que celle de SPM est principalement contrôlée par le débit des rivières
Construction of ergodic IDLA forests in
No full textInternational audienceWe prove the existence of infinite-volume IDLA forests in , with , based on a multi-source IDLA protocol. Unlike IDLA aggregates, the laws of the IDLA forests studied here depend on the trajectories of particles, and then do not satisfy the famous Abelian property. Their existence is due to a stabilization result (Theorem 1.1, our main result) that we establish using percolation tools. Although the sources are infinitely many, we also prove that each of them play the same role in the building procedure, which results in an ergodicity property for the IDLA forests (Theorem 1.2)
La Maison des livreurs de Bordeaux : Un entrepreneur social, bastion de la résistance au capitalisme de plateformes
No full textInternational audienceFor over a decade, we have witnessed the undeniable dominance of the GAFAM (Google, Apple, Facebook, Amazon, and Microsoft) over the global economy. These five companies now rank among the top seven global market capitalizations, while Uber Technologies, another player in platform capitalism, which is also our subject of study, paradoxically, since its creation in 2000, only recorded a positive result in 2013, 13 years later. Digital platforms, one of the main vehicles of platform capitalism, currently contribute significantly to job creation. Their contribution continues on an upward trend (Forissier et al., 2020; Boutillier, 2020). Although salaried employment gradually became the dominant form of employment in the 20th century, since the beginning of the third millennium, however, we have witnessed a shift in this configuration, even if salaried employment remains dominant in industrial countries in Europe and the United States (Leriche, 2016). The wage-earning society, thanks to social struggles, has made salaried employment a stable and protected status (Castel, 1995). However, it is now being challenged by the development of the process of what is commonly called the “Uberization” of the economy (Benavant, 2016; Cette, 2017; Evans, 2017; Hill, 2015; Jacquet, Leclercq, 2016; Linhart, 2015; Veltz, 2017), in which the boundaries between salaried employment and self-employment are increasingly blurred (Forissier et al., 2020). This question of the development of digital platforms is part of a process of profound transformation of the economic and social organization, which is perceived by the respective share of salaried employment and self-employment.While the advent of the Internet and the Web had raised utopian hopes, the consolidation of platform capitalism has instead fueled a multiplicity of criticism and encouraged service providers to come together and take action to denounce their captivity to a summons. These mobilizations should lead public authorities to play a regulatory role, as illustrated in particular by the adoption of a European directive on platform workers on March 11, 2024 (consilium.europa.eu, 2024); or in reference to the fight led by digital platform workers demanding the reclassification of their service provider contract into an employment contract, which bore fruit, since the French Court of Cassation gave a favorable opinion to them in 2018. This deliberation should be seen as a strong signal of the beginning of regulation of this segment of the labor market. But nothing is less certain, even if the struggles of gig economy platform workers have become more visible due to their media coverage. The purpose of our proposed presentation is to understand and analyze the forms of resistance organized by a collective of self-employed delivery workers structured as a production cooperative. With a view to reconfiguring spatialities, we will focus on the characteristics of La Maison des Livreurs as a symbolic place, the material basis of resistance. The analysis is based on a monographic study of La Maison des Livreurs in Bordeaux. In addition to the history of the cooperative's formation, we examine its governance, organizational logic, operations, the objectives set by the members, the meaning of their cooperation forced by Uberization, the alliances formed, and their repertoires of action. La Maison des Livreurs can be understood as an unprecedented mobilization against new forms of contractual relationships in the world of work. We will seek to show the meaning and perspectives of this mobilization.Depuis plus d’une décennie, on assiste à une domination incontestable des GAFAM (Google, Apple, Facebook, Amazon et Microsoft) sur l’économie mondiale. Ces cinq compagnies figurent aujourd’hui parmi les sept premières capitalisations boursières mondiales, tandis qu’Uber Technologies, autre acteur du capitalisme de plateforme, qui par ailleurs constitue notre objet d’étude, n’a paradoxalement depuis sa création en 2000, enregistré un résultat positif qu’en 2013, soit 13 ans après.Les plateformes numériques, un des véhicules principaux du capitalisme de plateforme, participent de nos jours, très largement à la création d’emplois. Leur contribution poursuit une trajectoire tendanciellement ascendante (Forissier et al., 2020 ; Boutillier, 2020). Bien que l’emploi salarié se soit progressivement imposé au 20ème siècle comme la forme dominante de mise au travail, depuis le début du troisième millénaire cependant, on assiste à une inflexion de cette configuration, même si le salariat reste dominant dans les pays industriels en Europe comme aux États-Unis (Leriche, 2016). La société salariale, grâce aux luttes sociales, a fait de l’emploi salarié un statut stable et protégé (Castel, 1995). Cependant, il est remis en question aujourd’hui par le développement du processus de ce qu’il est convenu d’appeler l’« Uberisation » de l’économie (Benavant, 2016 ; Cette, 2017 ; Evans, 2017 ; Hill, 2015 ; Jacquet, Leclercq, 2016 ; Linhart, 2015 ; Veltz, 2017), dans laquelle les frontières entre salariat et travail indépendant sont de plus en plus floues (Forissier et al., 2020). Cette question du développement des plateformes numériques s’inscrit dans un processus de transformation profonde de l’organisation économique et sociale, que l’on perçoit par la part respective de l’emploi salarié et de l’emploi indépendant.Tandis que l’avènement d’Internet et du Web avaient suscité des espoirs utopiques, la consolidation du capitalisme de plateforme a plutôt alimenté une multiplicité de critiques et encouragé les prestataires à se réunir et à agir pour dénoncer leur captivité à une assignation. Ces mobilisations devraient amener les autorités publiques à jouer un rôle de régulation, comme l’illustre notamment l’adoption d’une directive européenne relative aux travailleurs de plateforme le 11 mars 2024 (consilium.europa.eu, 2024) ; ou en référence au combat mené par des travailleurs de plateformes numériques demandant la requalification de leur contrat de prestataire de service en contrat de travail et qui a porté ses fruits, puisque la Cour de cassation française a attribué en 2018 un avis favorable à ces derniers . Ce délibéré devrait être perçu comme le signal fort d’un début de régulation de ce segment du marché de l’emploi. Mais rien n’est moins sûr, même si les luttes des travailleurs des plateformes de l’économie à la demande sont devenues plus visibles, du fait de leur médiatisation.L’objet de notre proposition de communication est de saisir et d’analyser les formes de résistances organisées par un collectif de livreurs autoentrepreneurs structuré en coopérative de production. Dans une perspective de reconfiguration des spatialités, nous nous attarderons sur les caractéristiques de La Maison des Livreurs en tant que lieu symbolique, base matérielle de la résistance. L’analyse s’appuie sur une enquête monographique de La Maison des Livreurs de Bordeaux. Outre l’historique de la constitution de la coopérative, nous nous intéressons à sa gouvernance, ses logiques organisationnelles, son fonctionnement, les objectifs fixés par les coopérateurs, le sens de leur coopération forcée par l’Uberisation, les alliances nouées et leurs répertoires d’actions. La Maison des Livreurs peut être appréhendée comme une mobilisation inédite contre de nouvelles formes de relations contractuelles dans le monde du travail. Nous chercherons à montrer le sens et les perspectives de cette mobilisation
Angelica cultivation and mycorrhizal inoculation improve microbial diversity, functions and network complexity of trace elements-polluted soil: A three-year field study
No full textInternational audienceGrowing aromatic and medicinal plants for producing essential oils has been presented as an innovative and economically viable alternative for phytomanaging soils polluted by trace elements (TE). However, the influence of aromatic plants, particularly angelica cultivation, on the soil microbial communities has received little attention. Thus, this work is aimed at studying changes in the biomass, composition, functional diversity, and network complexity of soil bacterial and fungal communities during three years of cultivation. Although growing angelica had little effect on fungal richness and diversity, the biomass and diversity of bacterial communities increased, as did the complexity of interactions between various microorganisms in the polluted soil compared to the initial state. Saprotrophic fungi became significantly more abundant after angelica cultivation, contributing to increased soil organic carbon and organic matter content. Arbuscular mycorrhizal fungi inoculation enhanced microbial network complexity from the year 2. Finally, an improvement in the abundance of functional genes linked to the carbon cycle was demonstrated. The findings evidenced the ecological requalification of TE-polluted soil thanks to the angelica cultivation
Morpho-molecular diversity and evolutionary analyses suggest hidden life styles in Spumellaria (Radiolaria)
No full textAbstract Spumellaria (Radiolaria, Rhizaria) are holoplanktonic amoeboid protists, ubiquitous and abundant in the global ocean. Their silicified skeleton preserves very well in sediments displaying an excellent fossil record, from the early middle Cambrian (ca. 509-521 Ma), extremely valuable for paleo-environmental reconstruction studies. Spumellaria are tedious to maintain in laboratory conditions preventing an accurate perception of their extant diversity and ecology in today’s oceans, most of which being inferred from sediment records. This study represents an integrated and comprehensive classification of Spumellaria based on the combination of ribosomal taxonomic marker genes (rDNA) and morphological characteristics. In contrast to established taxonomic knowledge, we demonstrate that symmetry of the skeleton takes more importance than internal structures at high taxonomic rank classification. Such reconsideration allows gathering different morphologies with concentric structure and a spherical or radial symmetry believed to belong to other Radiolaria orders from the fossil record, as for some Entactinaria families. Results obtained in this study suggest the existence of new Spumellaria diversity at early diverging positions, in which a non-bearing skeleton organism lives within shelled ones. Using fossil calibrated molecular clock we estimated the origin of Spumellaria in the middle Cambrian (ca. 515 Ma), in agreement with the appearance of the first radiolarian representatives in the fossil record. The morpho-molecular and evolutionary framework established herein allows a direct connection between living specimens and fossil morphologies from the Cambrian, bringing both a standpoint for future molecular environmental surveys and a better understanding for paleo-environmental reconstruction studies
Poisson approximation and D(u n ) condition for extremes of transient random walks in random sceneries
No full textInternational audienceLet (S n ) n≥0 be a transient random walk in the domain of attraction of a stable law and let (ξ(s)) s∈Z be a sequence of random variables. Under suitable assumptions, we establish a Poisson approximation result for the point process of exceedances associated with (ξ(S n )) n≥0 and demonstrate that it satisfies the D(u n ) condition.</div
Entretien de Jean-Louis Bourlanges. "Grandeur et misère de l'Europe"
No full textInternational audienc
Enriching organisational design for games: the case of badminton in physical education
No full textInternational audiencePurpose:Providing students with enjoyable experiences in Physical Education (PE) is considered a key variable in research on increasing Physical Activity (PA) levels. Designing game formats in PE is relevant to achieving this aim. Coupling principles of Motor Praxeology (MP) and the Constraints Led Approach (CLA) to design three games, the aim of this study was to examine how participants’ sex, age and skill levels (organismic constraints) interacted with varied manipulations of task and environmental constraints in the organisational design of badminton games to increase their enjoyment and PA.Method:Participants were students (n = 55, Mage = 14.0, SD = 2.41, 41.8% girls, aged 11–19) enrolled in a PE unit with three distinct badminton organisational designs for games: Individual Tournament (IT), Team Score (TS) and Personal Challenge (PC). IT challenges students in a group of a homogeneous skill level with a one-on-one competition. TS consists of a series of one-on-one games amongst a group of students with a heterogeneous skill level. PC is a competition between students in a heterogenous-level group, adopting a handicap score system. Enjoyment and level of PA was measured using a pleasure scale and accelerometers.Results:Results indicated little effect of organisational design on pupils’ enjoyment but showed a difference in their PA: younger and skilled boys moved less in the PC design compared to the TS organisational design.Discussion/conclusion:Our results suggest that potential interactions between the format of the organisational design and individual differences in students could be relevant for increasing PA in PE programmes. In exploring the effects of interactions of organisational designs for games, goal tasks and students’ characteristics, a combination of MP and CLA frameworks helps to address some of the prevailing beliefs about pleasure and the commitment made by students in common physical education play and activity formats. Our study showed that there is no ideal organisational design for engaging students, but that the most fruitful formats depend on the specific interests of the students.Practical implications:These theoretical frameworks invite PE teachers to develop organisational designs by providing interaction between goal-oriented tasks and social variables (e.g. relationships between players) to provoke richer experiences in all students from different skill levels