Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In the present work, we study the magnetic properties in the site diluted two-state Ising model on a body-centered cubic lattice. As an application of this study, we has been obtained the phase diagram for Fe-Al alloys and comparisons between theoretical model and experimental data are made by using the exchange interaction between Fe atoms in the alloy up to the third power dependence on concentration q of Al atoms. We have used the differential operator technique to expand the analytical expressions that arise from the diluted Ising model and describe such behavior by means of magnetic clusters with one and two spins. A good agreement between the theoretical model and experimental data is also obtained for both the magnetization and to the lattice parameter, r as a function of q. In this approach, it is shown as a good alternative to other analytical and computational techniques used for the study of diluted magnetic systems. The analytical results obtained for bcc lattice were compared with the Monte Carlo technique to determine the degree of applicability of the model and confirm the validity of the results obtained analytically. / Neste trabalho, aplicamos o modelo de Ising com diluição por sítios ao estudo das propriedades magnéticas de uma rede cúbica de corpo centrado (do inglês, body centered cubic, bcc), cujos sítios podem ser ocupados por spins. Como aplicação desse estudo, traçamos alguns diagramas de fase da liga Fe-Al, com comparações entre o modelo teórico utilizado e dados experimentais e propomos uma interação de troca entre os atomos de Fe, na liga, com dependência at´e terceira potência da concentração (q) de atomos de Al, possibilitando um melhor ajuste entre teoria e experimento para o diagrama T-q desta liga. Tomamos como base a t´ecnica do operador diferencial para expandir as express oes anal´ıticas que surgem do modelo de Ising dilu´ıdo e descrevemos tal comportamento magn´etico por meio de aglomerados com 1 e 2 spins. Um bom acordo entre o modelo te´orico proposto e dados experimentais tamb´em ´e obtido tanto para a magnetização como função de q quanto para o par ametro de rede, r, como função de q, sendo que esta abordagem mostra-se como uma boa alternativa a outras t´ecnicas anal´ıticas e computacionais utilizadas para o estudo de sistemas magn´eticos dilu´ıdos. Os resultados anal´ıticos obtidos para a rede bcc foram comparados com a t´ecnica de Monte Carlo para verificar o grau de aplicabilidade do modelo bem como confirmar a validade dos resultados encontrados analiticamente.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O presente trabalho mostra o estudo da influÃncia da radiaÃÃo de ultra-som sobre a eletrodeposiÃÃo de ligas de Ni-Fe. Foram avaliados a estabilidade e o desempenho eletrocatalÃtico das ligas para a ReaÃÃo de Desprendimento de HidrogÃnio (RDH) em meio alcalino. As ligas eletrodepositadas de Ni-Fe foram obtidas em soluÃÃo 0,06 mol.dm-3 de Ni2SO4.6H2O, 0,48 mol.dm-3 de Na3C3H5O7.2H2O, 0,71 mol.dm-3 de Na2CO3 e 0,16 mol.dm-3 (banho 1) e 0,04 mol.dm-3 de FeSO4.7H2O (banho 2). Foi adicionado 8,4 mL.L-1 de H2SO4 para manter o pH abaixo de 1. A eletrodeposiÃÃo foi realizada sob controle galvanostÃtico variando-se a densidade de corrente de 10 mA.cm-2 a 50 mA.cm-2, na temperatura ambiente (≡ 28ÂC) e de 55ÂC na presenÃa e na ausÃncia da radiaÃÃo de ultra-som. Todos os revestimentos foram depositados em um disco de aÃo-carbono com Ãrea geomÃtrica exposta de 0,7 cm2. A RDH foi estudada em soluÃÃo de NaOH 0,5 mol.dm-3. Foi utilizada para todos os experimentos o eletrodo auxiliar de Pt e o eletrodo de referÃncia de Hg/HgO, OH- (0,5 mol.dm-3). Os revestimentos foram caracterizados por Microscopia EletrÃnica de Varredura (MEV), Voltametria CÃclica (VC) e as propriedades eletrocatalÃticas das ligas de Ni-Fe foram avaliadas por Curva de PolarizaÃÃo de Tafel e por OperaÃÃo ContÃnua. Os resultados mostraram que o ultra-som aumentou a quantidade de Fe eletrodepositada e as ligas obtidas sob a aÃÃo da radiaÃÃo de ultra-som apresentaram o melhor desempenho para a RDH. / The present work shows the study of the ultrasound irradiation influence in the electrodeposition of Ni-Fe coatings. The electrocatalytic performance of these coatings for the hydrogen evolution reaction (her) in alkaline medium was also evaluated. The Ni-Fe coatings were obtained from plating solutions containing 0.06 mol.dm-3 Ni2SO4.6H2O, 0.48 mol.dm-3 Na3C3H5O7.2H2O, 0.71 mol.dm-3 Na2CO3 and 0.16 mol.dm-3 (bath 1) and 0.04 mol.dm-3 FeSO4.7H2O (bath 2). It was also added 8.4 mL L-1 H2SO4 to maintain the pH below 1. The electrodepositions were carried out under galvanostatic control in the range of 10 mA cm-2 to 50 mA cm-2, at room temperature (≈ 28ÂC) and at 55ÂC in the presence and in the absence of ultrasound irradiation. All coatings were deposited on disk mild steel substrate with an exposed geometric area of 0.7 cm2. The hydrogen evolution reaction was studied in 0.5 mol.dm-3 NaOH. In all electrochemical experiments Pt was the auxiliary electrode and Hg/HgO, OH- (0,5 mol.dm-3) was the reference one. The coatings ware characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and the electrocatalytic properties of the Ni-Fe coating were evaluated by Tafel polarization and long-term performance tests. The results showed that the use of the ultrasound irradiation leads to an increase of the Fe content in the electrodeposits. Additionally, the coatings obtained in presence of ultrasound also present the best performance for her.

Neste trabalho, foram estudadas a oxidação do cicloexano e a epoxidação do (Z)- cicloocteno com iodosilbenzeno (PhIO) e H2O2 como oxidantes, comparando as FeIIIclorinas pentafluorossubstituídas com as FeIIIporfirinas, [Fe(TFPCMG)]Cl, [Fe(TFPCMGCH3)]Cl2, [Fe(TFPP)]Cl e [Fe(TF4TMAPP)](CF3SO3)5 como catalisadores em meio homogêneo e suportadas via ligação iônica e/ou covalente em matrizes de sílica quimicamente modificada. No caso do substrato (Z)-cicloocteno, os metalocomplexos utilizados levaram a rendimentos elevados para formação do ciclooctenóxido, tanto em meio homogêneo quanto heterogêneo, quando PhIO foi utilizado como oxidante. A atividade catalítica foi mantida mesmo após três reciclagens sucessivas. Com o H2O2 como oxidante, os rendimentos foram menores exceto com o metanol, quando se observa um aumento nos rendimentos de epoxidação, porque favorece a formação do intermediário ativo FeIIIhidroperóxido. Já os sistemas heterogeneizados apresentam desempenho bastante inferior quando comparado aos catalisadores em solução. Os melhores rendimentos foram observados com DCE um solvente mais viscoso que aumenta o tempo de vida da gaiola do solvente favorecendo o processo biomimético. Os catalisadores imobilizados foram caracterizados por espectroscopias UV-Vis e de RPE. Estas técnicas deram informações do estado de oxidação e de spin do metal, bem como a geometria do macrociclo na superfície da matriz sólida. Os resultados catalíticos puderam ser explicados pela natureza dos grupos funcionais que ligam o metalocomplexo à sílica, bem como, pelas informações fornecidas pela técnica de RPE quanto ao estado de oxidação do ferro e à geometria dos metalocomplexos imobilizados, dando consistência aos mecanismos propostos nos processos de oxidação. / In this work, the cyclohexane oxidation and the (Z)-cyclooctene epoxidation with iodosylbenzene (PhIO) e H2O2 as oxidants were studied. A comparison between fluorinated FeIIIchlorins and FeIIIporphyrins, [Fe(TFPCMG)]Cl, [Fe(TFPCMGCH3)]Cl2, [Fe(TFPP)]Cl, [Fe(TF4TMAPP)](CF3SO3)5 as catalysts was made either in solution or supported in silica matrices via eletrostatic interaction and/or covalent bonds. In the case of (Z)-cyclooctene epoxidation by PhIO, all the studied metallocomplexes achieved high yields for the epoxide production in both homogeneous and heterogeneous systems. The catalytic activity was maintained even after three successive recyclings. On the other hand, when H2O2 was used as oxidant the yields were lower. Differently, raised yields of epoxidation were observed when using methanol as solvent due to favored formation of the active intermediate FeIIIhydroperoxide. The performance of the heterogeneous systems was significantly lower than that of the catalysts in solution. The best yields were observed with DCE, a viscous solvent that probably raises the shelf life of the solvent cage favoring the biomimetic process. The supported systems were characterized by EPR and UV-Vis spectroscopies. These techniques gave information about the oxidation state and the metal spin, as well as the macrocycle geometry on the solid matrix surface. The catalytic results were explained by the nature of the functional groups that bound the metallocomplex to the silica matrix. In addition, the information obtained by the EPR technique regarding the state of oxidation of iron and the geometry of the supported metallocomplexes gave consistence to the proposed mechanisms in the oxidation processes.

Les alliages Fe-Si sont connus pour combiner d’excellentes propriétés magnétiques avec de bonnes propriétés électriques (forte résistivité électrique). Dans ce contexte nous avons recherché à élaborer des matériaux à forte teneur en Si, souvent difficiles à obtenir et mettre en forme industriellement. Des alliages magnétiques doux de type Fe-Si avec une teneur élevée en Si (4,5%, 6,5%, 10% et 15% massique) ont été obtenus avec succès à l’état nanocristallin par broyage mécanique et recuit. La formation des alliages a été étudiée par diffraction X, spectroscopie Mössbauer et analyses thermomagnétiques. La stabilité thermique de la poudre a été analysée par DSC. Des mesures d’aimantation ont été réalisées pour caractériser les performances magnétiques. La durée de broyage nécessaire pour la formation de l’alliage a été déterminée pour chaque teneur en Si. Pour les faibles temps de broyage, le recuit conduit à la formation du composé Fe3Si. Après la formation de l’alliage par le broyage mécanique, l’effet du recuit est seulement de réduire les tensions internes du second ordre, induites dans la poudre par le broyage. L’addition de Si conduit à la diminution de la température de Curie de 770 °C pour le Fe pur, à 725 °C pour une teneur de 4,5% massique de Si et à 550 °C pour 15% massique de Si. Pour les temps faibles de broyage, l’écart entre l’aimantation de la poudre avant et après recuit est dû à la formation du composé Fe3Si pendant le recuit, lequel a une aimantation plus faible que la solution solide de Feα(Si). Pour les longs temps de broyage, le recuit à 400 °C pour 4 heures n’a pas d’effet sur la valeur de l’aimantation à saturation. En augmentant la teneur en Si, l’aimantation à saturation de l’alliage Fe-Si décroit.Les alliages Ni3Fe (aussi connus comme Permalloys) présentent de meilleures propriétés magnétiques, mais ils ont une résistivité inférieure à celles des Fe-Si. Une voie attractive semble la combinaison des propriétés des 2 classes de matériaux doux en formant un composite. Les alliages Fe-Si précédemment obtenus ont été utilisés pour l’élaboration des poudres composites de type Permalloy/Fe-Si par la mécanosynthèse. Le broyage mécanique conduit à la formation des particules composites avec un aspect stratifié. Quatre heures de broyage de l’alliage Fe-Si avec du Ni3Fe ne conduisent pas à la formation des nouvelles phases, mais la formation d’un alliage ternaire Ni-Fe-Si résulte d’un recuit ultérieur à 900 °C. L’aimantation à saturation du composite augmente avec la croissance de la teneur le d’alliage Fe-Si, mais le temps de broyage ne semble avoir aucun effet sur cela.Une étude préliminaire a été réalisée sur l’élaboration des compacts composites de type Ni3Fe/Fe-Si par frittage flash, dans le but de préserver l’état nanocristallin par de basses températures de frittage. L’influence de la température de frittage et de la durée de maintien sur la structure, et les propriétés physiques des compacts est discutée. Des températures allant jusqu'à 750 °C pour une durée de maintien minimale ou un palier de 2 minutes maximum à 700 °C ne conduisent pas à la diffusion des éléments des alliages. L'augmentation de la température ou de la durée de frittage conduit à des cristallites plus grandes, mais qui restent dans le domaine nano pour les températures étudiées. La densité des compactes augmente avec la température et le palier. En outre, la résistivité diminue en augmentant ces 2 paramètres. L'effet de la teneur en Fe-Si est de diminuer la densité et en même temps d'augmenter la résistivité des compacts. La perméabilité magnétique est réduite avec l'augmentation de la température et de la durée de frittage, ainsi que lors de la diminution du contenu de Ni3Fe. Une température élevée et un long temps de maintien à la température de frittage conduisent à l’augmentation des pertes magnétiques. Le champ coercitif est également influencé par les paramètres de frittage, via l'effet qu'ils ont sur la taille des cristallites. / Fe-Si alloys are known for combining excellent magnetic properties with good electric characteristics (high resistivity). In this context we sought to develop materials with a relatively high Si content, often difficult to obtain and shape industrially.In this thesis, soft magnetic Fe-Si alloys with high Si content (4.5, 6.5, 10 and 15 wt. %) were successfully obtained in nanocrystalline state by mechanical alloying and annealing. The formation of the alloy was studied by X-ray and neutron diffraction, Mossbauer spectroscopy and thermomagnetic analysis. DSC technique was used in order to study the powder’s thermal stability. Magnetisation measurements were also made in order to characterise their magnetic performances. The milling duration necessary for the formation of the alloy was determined for each Si content. For low milling times, annealing leads to the formation of the Fe3Si compound. Once the alloy is formed by mechanical milling, the effect of the annealing is only to reduce the second order stress induced in the powder by the milling process. Si addition leads to the decrease of the alloy’s Curie temperature from 770 °C for pure Fe to 725 °C for a 4.5 wt. % Si and down to 550 °C if the Si content increases to 15 wt. %. For low milling times, a gap between the magnetisation of the as-milled alloy and of the milled and subsequently annealed one is due to the formation of the Fe3Si compound during annealing which has a lower magnetisation than that of the αFe (Si) solid solution. For longer milling durations, annealing at 400 °C for 4 hours has no effect on the saturation magnetisation value. By increasing the Si content, the Fe-Si alloy’s saturation magnetisation decreases.Fe-Ni alloys whose composition is close to Ni3Fe (commonly known as Permalloys) have better magnetic properties, but a resistivity well inferior to that of Fe-Si alloys. Therefore, a combination of the properties of these 2 alloy classes of soft magnetic materials into a composite seems to be an attractive route. The previously obtained Fe-Si alloys were used for the preparation of Permalloy/Fe-Si composite powders by mechanical milling. Milling leads to the formation of composite powder particles with a stratified aspect. Milling of the Fe-Si and Ni3Fe alloys for 4 hours does not lead to the formation of new phases, but a subsequent annealing at 900 °C results in the formation of a Ni-Fe-Si alloy. Saturation magnetisation of the composite increases with increasing of the Fe-Si content, but milling duration seems to have no effect on it.A preliminary study was made on the elaboration of Ni3Fe/Fe-Si composite compacts obtained by spark plasma sintering, aiming to preserve the nanocrystalline state by lower sintering temperatures. The influence of the sintering temperature and temperature holding duration on the structure, density, resistivity and magnetic properties of the compacts is discussed. Temperatures of up to 750 °C for minimal holding duration or a maintain at the temperature of 700 °C for a duration of up to 2 minutes does not lead to a diffusion of the alloys’ elements. Increasing of the sintering temperature or duration leads to larger crystallite sizes, but they remain in the nano domain for the studied temperatures. The compacts’ density increases with temperature and sintering duration. Resistivity, on the other hand decreases when increasing the aforementioned parameters. The effect of the Fe-Si content is to decrease the density and at the same time increase the compacts’ resistivity. Magnetic permeability is reduced with increasing sintering temperature and duration, as well as when decreasing of the Ni3Fe content. High temperature and long maintaining duration leads to an increase of magnetic losses. Coercive field is also influenced by sintering parameters by the effect they have on the crystallite size.

Les centres fer-soufre (Fe-S) sont des cofacteurs protéiques essentiels qui participent à un nombre important de fonctions cellulaires allant du métabolisme de l’ADN à la respiration mitochondriale. L’assemblage des centres Fe-S et leur insertion dans des protéines acceptrices requièrent l’activité d’une machinerie protéique dédiée. Bien que les protéines de la biogenèse des centres Fe-S soient conservées, plusieurs aspects fonctionnels et mécanistiques restent inconnus. Notre travail de thèse a consisté à caractériser les protéines mammifères de type A, ISCA1 et ISCA2, qui sont impliquées dans la biogenèse mitochondriales des centres Fe-S. En utilisant une approche couplant l’immunoprécipitation avec une analyse protéomique par spectrométrie de masse, plusieurs interactions protéiques d’ISCA1 et ISCA2 ont pu être identifiées. En plus d’une interaction entre ISCA1 et ISCA2, nous avons ainsi montré l’existence d’interactions spécifiques à chacune de ces protéines. Une approche de knockdown dans la souris via l’injection de virus adéno-associés, a permis de montrer l’absence de redondance fonctionnelle entre ISCA1 et ISCA2 puisque seul ISCA1 se trouve être nécessaire dans la maturation d’une catégorie de protéines à centre Fe-S. / Iron-sulfur clusters (Fe-S) are essential cofactors involved in different cellular processes ranging from DNA metabolism to respiration. Assembly of Fe-S clusters and their insertion into acceptor proteins is performed by dedicated protein machineries. Despite the high conservation from bacteria to man, different functional and mechanistic aspects of the Fe-S biogenesis remain elusive. In the present work, the function of the two mammalian A-type proteins ISCA1 and ISCA2 that are implicated in Fe-S biogenesis was investigated in vivo. First, an extensive analysis coupling immunoprecipitations and mass spectrometry led to the identification of a direct binding between ISCA1 and ISCA2 as well as specific protein partners of each protein. Furthermore, knockdown experiments in the mouse using adeno-associated virus provided clear evidence of the non-redundant function of ISCA1 and ISCA2, since only ISCA1 was shown to be required for a specific subset of mitochondrial Fe-S proteins.

Les analogues du bleu de Prusse contenant du Fe et du Co (Fe/Co PBA) sont des complexes moléculaires qui présentent des propriétés physiques bistables. Par conséquent, ils sont considérés comme des candidats potentiels pour le stockage d'informations à base de molécules. Cette thèse vise à étudier la structure électronique et magnétique de Fe/Co PBA en utilisant des techniques expérimentales et théoriques avancées. Les techniques X-ray Absorption Spectroscopy (XAS) et X-ray magnetic circular dichroism (XMCD) combinées avec la théorie des multiplets en champ de ligands (LFM) sonde le changement dans les propriétés magnétiques macroscopiques de Fe/Co PBA et peuvent donner des informations locales sur les centres métalliques des complexes. Le composé tridimensionnel RbCoFe PBA, deux complexes de dinucléaire photomagnétiques et les précurseurs de Fe sont étudiés. L'étude de XMCD combinée avec la LFM a révélé une grande valeur du moment magnétique d'orbite du précurseur FeTp. Une étude détaillée a été effectuée pour vérifier les règles de somme d'orbite et de spin dans le cas des ions de Fe(III) bas spin et il a été constaté que la règle spin somme n'était pas valide à cause de l'entremélange des seuils L2 et L3. L'enquête XMCD des complexes dinucléaires photomagnétiques a confirmé le transfert d'électrons métal-métal. Cette enquête XMCD de la plus petite unité de la famille Fe / Co PBA est utile pour comprendre les propriétés magnétiques de la famille de Fe / Co PBA. L'étude XMCD sur aux seuils K du Fe et du Co d'un composé tridimensionnel RbCoFe PBA a prouvé l'existence d'une interaction antiferromagnétique entre les ions métalliques de Fe et de Co dans l'état photoinduit. / The Fe/Co Prussian Blue Analogues (PBA) are molecular complexes that exhibit externally controlled bistable physical properties. Thus, they are considered as potential candidates for photoswitchable molecule-based information storage. This thesis aims to investigate the electronic and magnetic structure of Fe/Co PBA using advanced experimental and theoretical techniques. X-ray Absorption Spectroscopy (XAS) and X-ray Magnetic Circular Dichroism (XMCD) techniques combined with Ligand Field Multiplet (LFM) theory probe the change in the macroscopic magnetic properties of PBA and can give local information about the metal centers existing in the complexes. The XAS and XMCD spectra at Fe and Co L2,3 edges are simulated using Ligand Field Multiplet (LFM) Calculations. The tridimensional RbCoFe PBA, two photomagnetic dinculear complexes and the building blocks Fe-bearing precursors are investigated. The XMCD study combined with LFM investigation revealed a large value of orbital magnetic moment in FeTp precursor of the dinuclear complex. A detailed study has been performed to check for the orbit and spin sum rules in the case of low spin FeIII ions and it was found that the spin sum rule does not hold because of intermixing between L2 and L3 edges. The XMCD investigation of the photomagnetic dinuclear complexes confirmed the metal-to-metal electron transfer. This XMCD investigation of the smallest unit of Fe/Co PBA family is helpful to understand the magnetic properties of the family of Fe/Co PBA. The XMCD study at Fe and Co K edges of a tridimensional RbCoFe PBA proved the existence of an antiferromagnetic interaction between Fe and Co metal ions in the photoinduced state.

Aus der Einleitung: "In der Produktentwicklung hat sich die numerische Simulation mittels Finite Elemente Analyse als Standardverfahren etabliert. Die Wandlung von einem Spezialistenwerkzeug zu einem generellen Ingenieurtool bringt mit sich, dass theoretisches Wissen zur FEA beim Benutzer nicht vorausgesetzt werden kann und demzufolge im Programm geeignet implementiert sein muss. Ingenieure sind im Umgang mit CAE-Tools (FEM, CFD, CAD) und theoretischen Methoden (VDI 2221, DSM, DfX) im Produktentstehungsprozess vertraut. In diesem Zusammenhang ist die aktuelle Herausforderung eine Verbindung beider etablierten Werkzeugklassen zu schaffen, die bisher nicht erfolgt ist. Es fehlt die benutzerspezifische Anpassung von computergestützten Werkzeugen an die Denkweise von Ingenieuren und deren Nutzungskontext. Methodische Wissensbasen, Retrieval-Möglichkeiten und Suchroutinen für abgeschlossene Projekte sind in CAE-Programmen nicht integriert. Ergänzt werden diese Nachteile durch die hohen Anschaffungskosten von Software in Kombination mit schlechter Usability."

The macrophytes have the ability accumulating multiple metals/metalloids species from the terrestrial and aquatic environments. The environmental-friendly phytoremediation technologies via these plant species have been applied for non-degradable pollutants removal. The macrophytes derived rhizofiltration is a major and efficient technology for metals/metalloids removal, especially in aquatic environments (e.g. wetland). Comparing with the common metals/metalloids often studied, aquatic U rhizofiltration via macrophytes has been just considered recently. In this study, the field investigation in a U tailing basin wetland showed that the rhizofiltration was crucial for aquatic U retention via Phragmites australis Trin ex Steud. (water to root bioconcentration factor (BCF): 670 to 1556). The aquatic U retention efficiency in aboveground biomass of P. australis was insufficient (BCF: 0.4 to 5.3), comparing with the rhizofiltration. However, the high productivity (1.2 to 1.9 kg•m-2 per growing season) of P. australis still resulted in a notable yearly U accumulation in the areal total aboveground biomass (0.04 to 0.35 mg•m-2 per growing season). It was potentially promoted by the enhanced aquatic U rhizofiltration. The U within aboveground biomass could be released to submerse soil with the degradable or recalcitrant fallen litters. It enhanced the organic carbon supply in rhizosphere together with the root litter, and potential water to root U translocation within mobilized organic compounds. Hence the rhizofiltration stood in the crucial position of the plant-litter-water-soil U recycling in aquatic environment. The results from field investigation and mesocosm experiment further suggested that the Fe plaque (IP) on root surface was crucial for aquatic U rhizofiltration. The IP contained most of root retained U in both environments (proportion of U within IP: 55.8 to 82.6% in field and 66.7 to 86.0% in mesocosm). However, the efficiency of IP assisted aquatic U rhizofiltration was affected by the redox state gradient (-179 to 220 mV) related redox processes. Field investigation suggested that high content of dissolved oxygen (up to 8.2 mg•l-1) was capable to rapidly oxidize soluble Fe(II) as sparingly soluble Fe(III) oxides precipitated in subhydric soil. It consequently limited the aquatic Fe availability for root uptake and precipitation as IP. However, the strong oxidation ability also relatively increased aquatic U(VI) availability incorporated with inorganics and degradable organic matters. It was adverse for controlling the aquatic U concentration (66.7 to 92.0 μg•l-1 in field). On the other hand, it also benefited the U uptake by inner root tissue and upward translocation to aboveground biomass of P. australis. The different inorganic N species also significantly influenced IP assisted aquatic U rhizofiltration. The aquatic NH4+ sustained the reduction and acidification (via nitirification) potential for Fe(III) and U(VI) bioreduction in rhizosphere (-87 to 21 mV in NH4+ cultured mesocosm pots). It improved the root uptake (mainly within IP) of Fe and U (2992.9 to 5010.7 mg•kg-1 Fe and 45.7 to 62.8 mg•kg-1 U in NH4+ cultured root). On the contrary, the NO3- depended strong oxidation ability (23 to 224 mV in NO3- cultured mesocosm pots) inhibited the IP formation and the related aquatic U rhizofiltration efficiency (1568.5 to 2569.5 mg•kg-1 Fe and 26.2 to 49.6 mg•kg-1 U in NO3- cultured root). The aquatic U availability in rhizosphere was also increased via NO3- depended oxidation processes (aquatic U concentration in mesocosm: 1.6 to 589.3 μg•L-1 (NO3-) vs. 1.4 to 58.2 μg•L-1 (NH4+)). The sufficient nitrogen supply is also a significant driving force for high biomass productivity of P. australis. The higher biomass of P. australis increased the U accumulation capacity for root and aboveground tissues. The nitrogen related high biomass accumulation of P. australis also potentially enhanced the share of organic bound U in subhydric soil via plant litters supply. The IP assisted aquatic U rhizofiltration was also affected by the co-existing metals/metalloids in rhizosphere. The field investigation indicated that high As availability (aquatic As/U ratio: 0.7 to 1.6) inhibited the U retention within IP through the competitive absorption, due to its high affinity to IP. The Ca improved the aquatic U(VI) availability by forming the soluble Ca-uranyl-carbonate compounds. The Ca also potentially competed with hydrated Fe(III) oxides within IP by incorporating with U and encourage the U retention within inner root tissue. The P was beneficial for U retention within IP possibly in form of U-Fe-phosphate complexes. However, it was still need to be proofed in further studies. Despite of the biogeochemical conditions in rhizosphere, the aboveground transpiration of P. australis also affected the IP formation and related aquatic U rhizofiltration. The higher transpiration rate (TR) of P. australis (3.3±1.2 mm•d-1 in field, 4.5±2.0 mm•d-1 (NH4+)/5.0±2.2 mm•d-1(NO3-) in mesocosm) increased the aquatic nutrient/non-essential elements availability for root uptake. For this reason, the aquatic U rhizofiltration of P. australis (21.8±3.1 mg•kg-1 in field, 62.1±1.0 mg•kg-1 (NH4+)/47.6±1.8 mg•kg-1 (NO3-) in mesocosm) was enhanced under higher TR. The higher TR also promoted the formation of IP and its U retention capacity. Furthermore, the U translocation from root to above ground biomass (mainly in leaves) of P. australis was also enhanced under higher TR. It was potentially benefited by the increased transpirational pull and root uptake of other active mediator (e.g. Ca). The effect of transpiration was also coupled with the different N species on IP assisted aquatic U rhizofiltration. The higher TR depended strong root uptake and assimilation of N increased the biomass accumulation of P. australis. Furthermore, the higher TR also potentially increased the share of root in biomass partition of P. australis. Consequently, the stronger transpiration resulted in the higher aquatic U accumulation in area related root biomass (up to 84.0±3.6 mg•m-2 (NH4+) and 86.4±5.8 mg•m-2 (NO3-) U per season in mesocosm). In conclusion, it was possible for eutrophic P. australis stands to retain the aquatic U via rhizofiltration. The IP on root surface was a crucial mediator contributing the aquatic U rhizofiltration, especially in iron rich milieu. The efficiency of IP assisted aquatic U rhizofiltration could be further improved under suitable environmental conditions. In this study, these conditions might include: i) reductive rhizosphere environment with active reducers (e.g. NH4+) encouraging Fe(II) generation for IP formation and U retention within it; ii) limited competitive elements (e.g. As and Ca) co-existed with Fe and U in rhizosphere; iii) sufficient nutrients (e.g. N) supply and related high biomass productivity of plant; iv) strong transpiration effect improved the nutrient assimilation of root and also the aquatic U/Fe availability for root uptake. By adjusting these conditions (also include other potential factors not discussed in this study), an effective rhizofiltration technology was supposed to be applied for aquatic U removal.

Cryptic trends in the trace element chemistry of Fe-Ti oxide minerals have been used to elucidate the magmatic processes responsible for the formation of Fe-Ti-V deposits in the Rivière Bell Complex layered mafic-ultramafic intrusion near Matagami, Quebec, Canada. Although metamorphism at greenschist-amphibolite facies conditions has modified the primary igneous compositions of magnetite and ilmenite, their Cr and V contents appear to have been unaffected. Chemostratigraphic variations of these elements in Fe-Ti oxides therefore remain valid tracers of magmatic differentiation, even in metamorphosed settings. Injections of compositionally evolved, Fe-Ti oxide-laden magma into a more primitive ferrogabbroic host are presumably responsible for sharp decreases in the Cr and V concentrations of Fe-Ti oxides that coincide with lithostratigraphic changes from predominantly disseminated gabbros to ultramafic sequences closely interlayered with massive oxides. These injections highlight the multistage magmatic history of the layered series of the Rivière Bell Complex and its vanadium ore horizons.

O complexo R2TP está presente em eucariotos, de leveduras a humanos, e está envolvido no correto dobramento de outras proteínas e montagem de complexos multiproteicos. R2TP é formado pelas proteínas Rvb1, Rvb2, Tah1 e Pih1/Nop17 em levedura, e direciona as chaperonas à proteínas alvo durante a montagem dos complexos. Os clusters Fe/S são sintetizados nas mitocôndrias e posteriormente transferidos para o citoplasma. Dre2 é uma proteína que contém cluster Fe/S, e está envolvida na transferência desses clusterspara outras proteínas citoplasmáticas. Nosso laboratório identificou a interação entre a subunidade Nop17 do complexo R2TP e Dre2 pelo método de duplo-híbrido, mas o papel desta interação ainda não foi elucidado. O objetivo deste trabalho foi o de estudar o papel funcional da interação entre Dre2 e Nop17 e identificar seus domínios de interação. Nossos resultados mostram que a porção N-terminal de Nop17 interage com a porção C-terminal de Dre2 e esta interação é necessária para a manutenção dos níveis de Dre2 na célula, indicando que o complexo R2TP atue na montagem do complexo CIA, de proteínas citosólicas Fe/S, do qual Dre2 faz parte. Dre2 também afeta a estabilidade de Nop17, sugerindo que Dre2 possa transferir um clusterFe/S para Nop17. Os dados mostrados aqui, portanto, indicam que a interação Nop17-Dre2 seja mutuamente importante para a estabilidade das duas proteínas / The R2TP protein complex is present in eukaryotes from yeast to humans, and is involved in the correct assembly of other protein or ribonucleoprotein complexes. R2TP is formed by proteins Rvb1, Rvb2, Tah1 and Pih1/Nop17 in yeast, and directs chaperones to target proteins during complexes assembly. Fe/S clusters are synthesized in mitochondria and later transferred to the cytoplasm. Dre2 is a Fe/S cluster protein, involved in transferring of Fe/S clusters to cytoplasmic proteins. Our laboratory has identified the interaction between the R2TP subunit Nop17 and Dre2 in the two-hybrid system. The aim of this work was to study the functional role of the interaction between Dre2 and Nop17, and to identify their domains of interaction. The results show that the N-terminal portion of Nop17 interacts with the C-terminal region of Dre2, and that this interaction is necessary for maintaining the levels of Dre2 in the cell, which suggests that the R2TP complex affects the cytosolic iron-sulfur protein assembly complex (CIA), of which Dre2 is a subunit. Dre2 also affects Nop17 stability, suggesting that Dre2 may transfer a Fe/S cluster to Nop17. The data here indicate that the interaction Nop17-Dre2 is mutually important for these proteins stabilities.