Silver eel downstream migration in fragmented rivers: use of a Bayesian model to track movements triggering and duration

Obstacles in rivers are considered to be one of the main threats to diadromous fish. As a result of the recent collapse of the European eel, the European Commission introduced a Regulation, requiring to reduce all sources of anthropogenic mortality, including those caused by passing through hydropower turbines. Improving knowledge about migration triggers and processes is crucial to assess and mitigate the impact of obstacles. In our study, we tracked 97 tagged silver eels in a fragmented river situated in the Western France (the River Dronne). Using the movement ecology framework, and implementing a Bayesian state-space model, we confirmed the influence of river discharge on migration triggering and he distance travelled by fish. We also demonstrated that, in our studied area, there is a small window of opportunity for migration. Moreover, we found that obstacles have a significant impact on distance travelled. Combined with the small window, this suggests that assessment of obstacles impact on downstream migration should not be limited to quantifying mortality at hydroelectric facilities, but should also consider the delay induced by obstacles, and its effects on escapement. The study also suggests that temporary turbines shutdown may mitigate the impacts of hydropower facilities in rivers with migration process similar to those observed here

Bayesian Network Modeling and Expert Elicitation for Probabilistic Eruption Forecasting: Pilot Study for Whakaari/White Island, New Zealand

Bayesian Networks (BNs) are probabilistic graphical models that provide a robust and flexible framework for understanding complex systems. Limited case studies have demonstrated the potential of BNs in modeling multiple data streams for eruption forecasting and volcanic hazard assessment. Nevertheless, BNs are not widely employed in volcano observatories. Motivated by their need to determine eruption-related fieldwork risks, we have worked closely with the New Zealand volcano monitoring team to appraise BNs for eruption forecasting with the purpose, at this stage, of assessing the utility of the concept rather than develop a full operational framework. We adapted a previously published BN for a pilot study to forecast volcanic eruption on Whakaari/White Island. Developing the model structure provided a useful framework for the members of the volcano monitoring team to share their knowledge and interpretation of the volcanic system. We aimed to capture the conceptual understanding of the volcanic processes and represent all observables that are regularly monitored. The pilot model has a total of 30 variables, four of them describing the volcanic processes that can lead to three different types of eruptions: phreatic, magmatic explosive and magmatic effusive. The remaining 23 variables are grouped into observations related to seismicity, fluid geochemistry and surface manifestations. To estimate the model parameters, we held a workshop with 11 experts, including two from outside the monitoring team. To reduce the number of conditional probabilities that the experts needed to estimate, each variable is described by only two states. However, experts were concerned about this limitation, in particular for continuous data. Therefore, they were reluctant to define thresholds to distinguish between states. We conclude that volcano monitoring requires BN modeling techniques that can accommodate continuous variables. More work is required to link unobservable (latent) processes with observables and with eruptive patterns, and to model dynamic processes. A provisional application of the pilot model revealed several key insights. Refining the BN modeling techniques will help advance understanding of volcanoes and improve capabilities for forecasting volcanic eruptions. We consider that BNs will become essential for handling ever-burgeoning observations, and for assessing data's evidential meaning for operational eruption forecasting

Nouvelles voies de synthèse de vanadates et de niobates luminescents au départ de précurseurs moléculaires ou hybrides

This research deals with the development of two unconventional preparation routes to AVO4 vanadates and ANbO4 niobates which are luminescent materials when doped with lanthanide ions. In addition, the preparation of A3NbO7 niobates was also implemented because of the great interest of such materials in the field of ion conductivity. The two developed preparation routes are based on coordination compounds which are used as precursors to incorporate the metals A, V and/or Nb. These precursors were either implemented alone in an aqueous preparation route called molecular precursors method or blended into a cellulose derivative matrix (hybrid precursor route). In this work, the two different routes were first used for the synthesis of bulk metallates and secondly for the preparation of thin films. Finally, an adaptation of the molecular precursor method was developed for the preparation of YVO4:Eu coated submicrometric silica spheres. This research has been therefore subdivided in five main parts. The first part deals with the synthesis of stoichiometrically well-defined coordination compounds of formula (NH4)A(EDTA)(H2O)x (A = Y, La, Pr, Sm, Eu, Gd, Dy, Er, Tm, Lu), (gu)3[Nb(O2)2(EDTAO2)]•2.5H2O and (NH4)[V(O)2(EDTA)]•0,5H2O. Secondly, these complexes were involved in the molecular precursor route. The method consists in using, for the different elements to be incorporated, molecular precursors which are coordination compounds. The final compound is obtained by an appropriate thermal treatment under dry air of a solid homogeneous mixture of the different complexes. This process was implemented for the preparation of bulk AVO4, ANbO4 and A3NbO7 as well as for the synthesis of solid solutions Y1-xAxVO4 and doped vanadates AVO4:Ln and Y1-xAxVO4:Eu. Luminescent properties of these doped materials were investigated and a significant effect of the host lattice composition was put forward. The hybrid precursor route was developed in the third part of this work. This method consists in the preparation of a mixed aqueous solution containing the synthesized complexes and a cellulose derivative named HPMC (hydroxypropylmethyl cellulose). After a freeze-drying step, the obtained solid is calcined under dry air to form the final metallate. After preliminary studies on the interaction between the cellulose derivative and the complexes, this route was applied for the synthesis of bulk Y1-xBixVO4 and Y1 xLaxVO4. For the Y1-xBixVO4 system, when the cellulose derivative was used, solid solutions have been obtained for a broader composition range than when the molecular precursors route was used. In the last two parts of this thesis, we focused on to the diversification of the forms in which these materials may be prepared. This research is particularly crucial for functional materials such as luminescent compounds. The two preparation routes developed above can indeed be easily adapted for the preparation of thin films by means of a spin-coating process of precursors solutions. By this way, we successfully prepared Y2O3, V2O5, YVO4 and YVO4:Eu films. In addition, the use of HPMC in the spin coated solutions appeared to improve significantly the films homogeneity. The fifth and last part of this research was dedicated to the preparation of submicrometric silica spheres coated with a layer of luminescent YVO4:Eu material. This work was motivated by the major utility of this kind of morphology for the preparation of high-performance display screens which require a high packing density. The study of the influence of this morphology on luminescence properties has also prompted us to undertake this part of the thesis. The synthesis of these coated spheres was performed by grafting an organic ligand on silica spheres prepared by the Stöber method. Y3+, Eu3+ and V4+ ions were then added and coordinated by the grafted ligand. A last calcination step has finally allowed the formation of luminescent YVO4:Eu/SiO2 spheres.Cette recherche traite du développement de deux méthodes non conventionnelles de préparation de vanadates AVO4 et de niobates ANbO4 pouvant, lorsqu’ils sont dopés avec des ions de lanthanides, présenter des propriétés de luminescence. En outre, les niobates A3NbO7 ont également été étudiés car ils présentent un intérêt particulier dans le domaine de la conductivité ionique. Les deux méthodes développées ici consistent à utiliser des composés de coordination comme précurseurs pour l’incorporation des métaux A, V et/ou Nb. Ces précurseurs ont soit été employés comme tels dans une voie de préparation en solution aqueuse (méthode des précurseurs moléculaires), soit incorporés dans une matrice cellulosique (méthode des précurseurs hybrides). Ces deux méthodes de préparation ont été premièrement utilisées pour la préparation de matériaux massiques, puis également pour la préparation de films minces. Des matériaux « supportés » sur sphères de silice submicrométriques ont également été synthétisés en adaptant la méthode des précurseurs moléculaires. Dès lors, le travail s’est articulé en cinq grandes parties. La première partie traite de la synthèse de composés de coordination à stœchiométrie bien définie et de formulation (NH4)A(EDTA)(H2O)x (A = Y, La, Pr, Sm, Eu, Gd, Dy, Er, Tm, Lu), (gu)3[Nb(O2)2(EDTAO2)]•2,5H2O et (NH4)[V(O)2(EDTA)]•0,5H2O. Dans la deuxième partie de ce travail, ces composés de coordination ont été introduits dans la méthode des précurseurs moléculaires. Celle-ci est basée sur l’utilisation d’un mélange solide homogène des précurseurs moléculaires que sont les composés de coordination. Ce mélange homogène solide est obtenu par préparation d’une solution mixte contenant les précurseurs puis par élimination du solvant. Il est par la suite calciné afin de former le métallate désiré. Cette méthode a été appliquée ici à la synthèse des composés AVO4, ANbO4 et A3NbO7 ainsi qu’à des solutions solides Y1 xAxVO4 et des matériaux dopés YVO4 :Ln et Y1-xAxVO4 :Eu. Les propriétés de luminescence de ces derniers ont été étudiées et un impact important de la composition du réseau hôte sur celles ci a été mis en évidence. La méthode des précurseurs hybrides a été développée dans le troisième volet de cette thèse. Cette méthode se base sur la préparation d’une solution aqueuse homogène entre les complexes synthétisés et un dérivé cellulosique, l’HPMC (hydroxypropylméthyl cellulose). Après élimination du solvant, le solide obtenu est calciné pour former le composé final. Outre des études préliminaires afin notamment d’évaluer les interactions entre la matrice cellulosique et les complexes introduits, cette voie a été appliquée à la synthèse des composés Y1-xBixVO4 et Y1 xLaxVO4. Dans le cas du système Y1-xBixVO4, l’utilisation de cette méthode a clairement permis une extension de la gamme de composition dans laquelle des solutions solides peuvent être obtenues par rapport à la gamme de composition accessible par la méthode des précurseurs moléculaires. Dans les quatrième et cinquième parties de ce travail, nous nous sommes intéressés à la diversification des formes sous lesquelles ces matériaux, et en particulier les matériaux luminescents, peuvent être préparés. Les deux méthodes étudiées ici peuvent en effet donner facilement accès à la fabrication de films minces par spin-coating des solutions de précurseurs. Nous avons ainsi pu montrer dans la quatrième partie de cette thèse que des films Y2O3, V2O5, YVO4 et YVO4 :Eu peuvent être aisément obtenus que ce soit avec l’une ou l’autre des deux méthodes employées. Nous avons également mis en évidence l’influence du choix de la méthode sur l’homogénéité des films obtenus et il est apparu ainsi que l’utilisation de la voie des précurseurs hybrides permet une nette amélioration de celle-ci. La cinquième et dernière partie concerne la préparation de sphères submicrométriques de silice sur lesquelles a été déposée une couche du matériau luminescent YVO4 :Eu. Cette recherche a été particulièrement motivée par l’utilité de ce type de morphologie pour la préparation d’écrans performants qui requièrent une densité d’empaquetage élevée. La possibilité d’étudier l’influence de cette morphologie sur les propriétés d’émission nous a également poussés à entreprendre cette étude. Concrètement, la synthèse de ce type de matériau a été réalisée par greffage d’un ligand organique à la surface de particules de silice sphériques préparées par une méthode d’hydrolyse et de condensation d’un alcoxysilane (ici, le tétraéthoxysilane) appelée méthode de Stöber. Par la suite, les ions Y3+, V4+ et Eu3+ ont été introduits et « greffés » à la surface de la silice via complexation par le ligand organique lié de manière covalente aux particules de silice. Une étape de calcination a finalement permis l’obtention de sphères submicrométriques de type YVO4 :Eu/SiO2 luminescentes.(CHIM 3) -- UCL, 201

Les mécanismes d'action antidépressive de l'électroconvulsivothérapie (hypothèses neurobiologiques)

L électroconvulsivothérapie (ECT) reste le traitement le plus efficace de la dépression. Son mécanisme d action n est pas totalement élucidé. La convergence d effets neurobiologiques induis par ce traitement dans le cadre des hypothèses monoaminergiques, neurotrophiques et anticonvulsivantes permettent de progresser dans la compréhension de son efficacité antidepressive. Les modifications du système monoaminergique ne semblent pas être une voie biologique fondamentale de l action antidépressive de l ECT. En revanche, comme le suggèrent les connaissances actuelles, le mécanisme d action de l ECT relève probablement d un double mécanisme. Le premier, neurotrophique permet de compenser l atrophie cérébrale due à la dépression et aux facteurs de stress, et le second, anticonvulsivant, par le recrutement de processus inhibiteurs de l activité cérébrale détermine l efficacité antidépressive par la durée de sa période réfractaire. Sur le plan biologique, le neuropeptide Y dont la synthèse est stimulée par le brain derived neurotrophic factor pourrait expliquer cette double action et semble être une piste importante de compréhension du mécanisme d action neurobiologique de l ECT. Mais la recherche dans ce domaine reste limitée techniquement, du fait de la restriction à l étude cérébrale in vivo chez l homme. L extrapolation des résultats obtenus chez l animal doit être prudente. La recherche systématique d une corrélation de l ECT et des chimiothérapies limite la pertinence des résultats. Le développement de techniques de neuroimagerie cérébrale performantes permettra dans le futur de progresser dans la compréhension des mécanismes neurobiologiques chez l homme. D autant que le traitement de la dépression est une priorité de santé publique dans les années à venir.AMIENS-BU Santé (800212102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

An Easy Route to Pure and Luminescent Eu-Doped YVO(4) Polycrystalline Films Based on Molecular or Hybrid Precursors

An easy "soft-chemistry" method has been developed to prepare pure and luminescent Eu-doped YVO(4) films. The method is based on the spin-coating of aqueous solutions of stoichiometrically well-defined yttrium(III)- and/or dioxidovanadium(V)-edta complexes, sometimes in the presence of a cellulose derivative, namely (hydroxypropyl)methyl cellulose. Films of the corresponding binary oxides, Y(2)O(3) and V(2)O(5), were also studied for comparative purposes. XRD, Raman spectroscopy and scanning electron microscopy were used to characterize the samples at different stages of their preparation. The spin-coating rate as well as the presence of the cellulose derivative in the precursor solutions were found to influence greatly the homogeneity and morphology of the films. The preferential orientation of crystallites within some of the films was also evidenced

De la Carbonnaria à l'Arduenna. Environnement, exploitation et paysages, du haut Moyen Âge à 1300

info:eu-repo/semantics/publishe

A facile precursor route to transition metal molybdates using a polyzwitterionic matrix bearing simultaneously charged moieties and complexing groups

An unconventional but easily accessible precursor route involving the thermal treatment of hybrid precursors containing an ampholytic polymer matrix is developed to prepare multimetallic oxides of catalytic interest such as transition metal molybdates. A copolymer of diallyldimethylammonium chloride and a functionalized maleamic acid bearing an amine group suited for cation complexation was designed, synthesized and used as a matrix to stabilize inorganic species generated in solution from Ni(NO3)(2)center dot 6H(2)O, Co(NO3)(2)center dot 6H(2)O and/or Mn(NO3)(2)center dot 4H(2)O together with (NH4)(6)Mo(7)O(24)center dot 4H(2)O. UV-vis-NIR as well as C-13-NMR studies suggest that the interactions between the cations and the polymer in solution are mainly electrostatic. Only minor complexation interactions take place under certain conditions. Homogeneous hybrid blends were prepared from these solutions. The presence of a complexing amine group in addition to the charged betaine moieties in the polymer permits stabilization of more than stoichiometric amounts of the metal species in the blends. XRD measurements suggest that the homogeneity in the solid state can be kept up to about 1.5 mol of each metal that is incorporated ( anionic as well as cationic) per mol of repeat units of the copolymer. The blends were calcined under air at 600 degrees C to produce the simple as well as mixed nickel, cobalt and manganese molybdates. Characterization of the final phases by XRD and Raman spectroscopy indicates that the alpha- as well as the beta-molybdate phases can be prepared, and that the mixed structures are solid solutions of the simple NiMoO4, MnMoO4 and CoMoO4. If the precursors engaged are homogeneous, the pH of the precursor solution, the amount of metal that is incorporated in the matrix, and the nature of the polymer matrix seem to exert only a minor influence on the nature of the final phase, which demonstrates the versatility and facile applicability of the method

Nb-Ta, Nb-Mo and Nb-V oxides prepared from hybrid organic-inorganic precursors

New hybrid organic-inorganic materials based on group 5 elements and a well-defined polymeric matrix have been prepared and used as precursors for Nb-Ta and Nb-Mo mixed oxides. In this non-conventional but easily accessible route to multimetallic oxides, a copolymer of N,N-diallyl-N-hexylamine and maleic acid was synthesised and used as matrix to stabilise inorganic species generated in solution from (NH4)(6)Mo7O24-4H(2)O, NH4VO3, (gu)(3)[Nb(O-2)(4)] and (gu)(3)[Ta(O-2)(4)]. Solid-state studies indicate that the homogeneity of the blends can be kept up to about 0.5 mol Nb-v and Ta-v and 0.25 mol V-v per mol of repeat units of the copolymer. The calcination conditions of these homogeneous hybrid precursors were optimised to produce Nb-Mo, Nb-Ta and Nb-V oxides. While the thermal treatment of the Nb-V hybrid blends led only to a mixture of different phases, the characterisation of the final phases by X-ray diffraction (XRD) proved the formation of pure Nb2MO3O14 and showed that Nb-Ta oxides could be synthesised as single phases corresponding to a continuous series of solid solutions. (c) 2007 Elsevier Inc. All rights reserved