Materiais magnetostrictivos, como o TERFENOL-D (Tb0,27-0,30Dy0,73-0,70Fe2) e o GALFENOL (Fe72-82Ga18-28), são aplicados em diversos tipos de atuadores, sensores e coletores de energia. Contudo, existe a necessidade de novos materiais que sejam mais baratos, ambientalmente amigáveis e com melhores propriedades mecânicas. Por essa razão, as ligas de Fe-Al são uma alternativa, já que o alumínio é mais abundante na natureza e é sete vezes mais barato que o gálio. O objetivo desse trabalho foi estudar a influência de dois tratamentos termomecânicos nas propriedades magnéticas das ligas (Fe1-xAlx)98,4B1,6, onde x = 0,18; 0,13 e 0,21. No primeiro processamento, as ligas foram submetidas a um tratamento térmico sob compressão para introduzir uma anisotropia magnetocristalina extrínseca. Para compressões de até 180 MPa, as ligas tratadas sob tensão obtiveram valores de magnetostricção e dos coeficientes piezomagnéticos maiores que o das ligas sem tratamento. Ou seja, este processamento aumentou a sensibilidade das ligas como atuador (d33) e sensor (d33 *). No segundo processamento termomecânico, amostras com formato de chapa foram laminadas e tratadas termicamente para induzir um crescimento anormal de grãos e consequentemente uma textura. Embora não tenha ocorrido crescimento de grão anormal durante o tratamento térmico, os valores de magnetostricção foram maiores que o das amostras como fundidas. Ambos processamentos termomecânicos foram efetivos para melhorar as propriedades magnéticas e a liga (Fe0,87Al0,13)98,4B1,6 foi a que obteve os maiores valores de magnetostricção e dos coeficientes piezomagnéticos. Em outras palavras, dentre as ligas estudadas, esta composição foi mais promissora para ser aplicada em atuadores e sensores. / Magnetostrictive materials, like TERFENOL-D (Tb0.27-0.30Dy0.73-0.70Fe2) and GALFENOL (Fe72-82Ga18-28), are applied in several types of sensors, actuators and energy harvesting. Nevertheless, there is the necessity of new materials that are cheaper, environmentally friendly and with good mechanical properties. For that reason, the Fe-Al alloys are an alternative, since the aluminum is more abundant in nature and is seven times cheaper than gallium. The goal of this work is to study the influence of two thermomechanical proceeding at magnetic properties of the (Fe1- xAlx)98.4B1.6 alloys, which x = 0.18; 0.13 e 0.21. At the first proceeding, the alloys were submitted to a stress annealing to introduce an extrinsic magnetocrystalline anisotropy. Up to 180 MPa of compression stress, stress annealed alloys have magnetostriction and piezomagnetic coefficient values higher than the alloys without annealing. In other words, this proceeding increased the alloys sensibility to be applied like actuators (d33) and sensors (d33 *). At the second thermomechanical proceeding, samples with sheet format were rolled and annealed to induce an abnormal grain growth and, consequently, a texture. Although the annealing not produced an abnormal grain growth, the magnetostriction values are higher than for the as-cast samples. Both proceedings were efficient to improve the magnetic properties and the (Fe0.87Al0.13)98.4B1.6 alloy achieved the higher values of magnetostriction and piezomagnetic coefficient. In another words, between the studied alloys, this composition was the most promising to be applied like actuators and sensors.

O excesso de Fe no organismo gera espécies reativas de oxigênio (ERO) que são potencialmente tóxicas. Entretanto, a magnitude dos efeitos da exposição à moderada sobrecarga de Fe e da sua interação com facilitadores e/ou inibidores da absorção mineral não é conhecida. O objetivo deste trabalho foi avaliar esses efeitos e a sua interação com fruta nos e/ou fitato (facilitadores e inibidores da absorção de Fe, respectivamente) nos índices séricos do estado nutricional em Fe, no perfil dos lipídeos séricos e em parâmetros do metabolismo hepático e ósseo. Para o experimento foram utilizados 34 ratos machos Wistar, pesando inicialmente 49,3 ± 3,9g, alojados individualmente em gaiolas de aço semimetabólicas por 92 dias. Uma dieta AIN-93G (Dieta 1: Grupo Controle) e quatro dietas AIN93G modificadas foram usadas para o estudo, com as seguintes características: Dieta 2: sobrecarga moderada de ferro com 550mgFe/kg de ração (Grupo SBC); Dieta 3: sobrecarga moderada de ferro + 18% de farinha de yacon (Grupo SBC+FY); Dieta 4: sobrecarga moderada de ferro + 0,6% de fitato (Grupo SBC+FIT); Dieta 5: sobrecarga moderada de ferro + 18% de farinha de yacon + 0,6 % de fitato (Grupo SBC+FY+FIT). Os resultados demonstraram que a moderada sobrecarga de Fe ou a sua interação com farinha de yacon e/ou fitato não alterou os índices séricos do estado nutricional em Fe. Ocorreu aumento na atividade sérica da AST apenas no grupo SBC (p=0,055). Nos grupos SBC e SBC+FY houve diminuição na concentração do colesterol sérico (p=0,002) e, apenas no grupo SBC+FY+FIT, diminuição da concentração sérica do VLDL. No fígado, houve aumento significativo (p=0,002) da concentração de Fe não-heme nos grupos IO (+83%) e SBC+FIT (+117%) e, em todos os grupos SBC, na atividade da enzima GPx (p=0,000). A atividade da CAT foi menor (p=0,036) apenas para o grupo SBC+FY+FIT. Em todos os grupos SBC ocorreu significativo aumento nos depósitos de hemossiderina em torno das células de Kupffer (p=0,000). Houve aumento na apoptose em todos os grupos SBC, com os grupos SBC+FY e SBC+FY +FIT apresentando o maior número de corpúsculos apoptóticos/área (+405% e +342%, respectivamente) (p=0,000). Não houve alteração nos parâmetros relacionados ao metabolismo ósseo. No grupo SBC+FY houve significativo aumento na absorção aparente de Ca (p<0,05). Conclusões: A moderada sobrecarga de Fe não alterou os índices séricos do estado nutricional em Fe, mas resultou em alterações no tecido hepático e no perfil dos lipídeos séricos. Com exceção do perfil de lipídeos séricos, no qual apenas o fitato pareceu exercer efeito protetor, nos demais parâmetros avaliados a interação com farinha de yacon rica em fruta nos e/ou fitato reverteu parcial ou totalmente as alterações induzidas pela moderada sobrecarga de Fe. / Excess Fe in the organism generates potentially toxic reactive oxygen species (ROS). However, the magnitude of the effects of a moderate Fe overload and its interaction with factors which inhibit or facilitate mineral absorption is not known. The aim of the present work was to evaluate such effects and their interaction with fructans and/or phytate (compounds which facilitate and inhibit Fe absorption, respectively) on serum iron status indices, on the profile of serum lipids and on hepatic and bone metabolism parameters. In the experiment, thirty-four male Wistar rats initially weighing 49,3 ± 3,9g were used. The rats were housed in individual stainless-steel wire-mesh cages for 92 days. An AIN-93G diet (Diet 1: Control Group) and four modified AIN-93G diets were used in the study. The modified diets presented the following formulations: Diet 2: moderate Fe overload with 550mgFe/kg diet (IO Group); Diet 3: moderate Fe overload + 18% yacon flour (IO-YF Group); Diet 4: moderate Fe verload + 0.6% phytate (IO-Phy Group); Diet 5: moderate Fe overload + 18% yacon flour + 0.6% phytate (IO-YF-Phy Group). The results demonstrated that a moderate Fe overload or its interaction with yacon flour and/or phytate did not alter the serum iron status indices. An increase in the serum AST activity was observed only in the IO group (p=0,055). In the IO and IO-YF groups, there was a reduction in the serum cholesterol concentration (p=0,002) and a reduction in the serum VLDL concentration was observed only in the IO-YF-Phy group. In the liver, there was a significant increase (p=0,002) in non-heme Fe concentration in the IO (+83%) and IO-Phy (+117%) groups. Also, GPx activity was significantly increased (p=0,000) in all IO groups. CAT activity was lower (p=0,036) only in the IO-YF-Phy group. A significant increase in hemosiderin deposition around Kupffer cells was observed in all IO groups (p=0,000). Apoptosis was increased in all IO groups, whereas the IO-YF and IO-YF-Phy groups showed the largest number of apoptotic bodies/area (+405% and +342%, respectively) (p=0,000). There was no alteration in the parameters related to bone metabolism. In the IO-YF group, there was a significant increase in Ca apparent absorption (p<0,05).Conclusions: The moderate Fe overload did not alter the serum iron status índices, but led to alterations in the hepatic tissue and in the profile of serum lipids. Except for the profile of serum lipids where only phytate seemed to have a protective effect, in the other evaluated parameters the interaction with yacon flour rich in fructans and/or phytate partially or totally reversed the alterations induced by the moderate Fe overload.

O objetivo do presente trabalho foi investigar o efeito de diferentes concentrações dietéticas de Fe em parâmetros sangüíneos (hemograma, perfil lipídico) e hepáticos (concentração de minerais, perfil de ácidos graxos, apoptose) de ratos sadios. Depósitos de Fe no baço e medula óssea também foram avaliados por análises histológicas. Ratos Wistar (n = 40), machos e com 40 dias de idade, consumiram rações controle (35 mgFe/kg) ou com sobrecarga de Fe (350, 750 e 1500 mgFe/kg). Após 90 dias de experimento, não foram observadas alterações no perfil lipídico e na atividade das transaminases séricas e no perfil de ácidos graxos no fígado. Por outro lado, o consumo das rações com sobrecarga de Fe (G750 e G1500) aumentou a concentração de hemoglobina e o VCM em relação ao controle. Além disso, observou-se maior concentração de Fe (G350, G750 e G1500 em espectofotometria de absorção atômica e no grupo G1500 em histologia) e presença de corpúsculos apoptóticos (G750 e G1500) no fígado dos animais com sobrecarga (Fe hepático x apoptose, r = 0,749, p = 0,000). Os resultados indicaram que o fígado é um compartimento responsivo à sobrecarga de Fe pela dieta. A significativa associação com o processo de apoptose sugere que as alterações provocadas pela sobrecarga do mineral devam ser avaliadas mais detalhadamente nessas condições experimentais. / The aim of the present work was to investigate the effect of different dietary Fe concentrations on blood parameters (hemogram, lipid profile) and hepatic parameters (mineral concentration, fatty-acid profile, apoptosis) in healthy rats. Fe depositions in the spleen and bone marrow were also assessed using histological analyses. Wistar young rats (n = 40) were fed control diets (35 mgFe/kg) or diets with Fe overload (350, 750 and 1500 mgFe/kg). After 90 days of experiment, no alterations in the lipid profile and serum transaminases, and fatty-acid profile in the liver were observed. On the other hand, the consumption of diets with Fe overload (G750 and G1500) led increased hemoglobin (Hb) concentration and Mean Corpuscular Volume (MCV) when compared to the control. In addition, a higher Fe concentration (G350, G750 e G1500 in Atomic Absorption Spectrophotometry and G1500 in histological sections) and presence of apoptotic bodies (G750 e G1500) were observed in the liver of animals with Fe overload (hepatic Fe x apoptosis, r = 0.749, p = 0.000). The results indicated that the liver is a compartment responsive to dietary Fe overload. The significant association with the apoptotic process suggests that the alterations caused by an overload of the mineral should be assessed in more detail under these experimental conditions.

Uma característica de destaque da Nhecolândia, uma sub-região do Pantanal Sul-Mato- Grossense, é a presença de lagoas doces (baías) e salgadas (salinas) com uma grande variabilidade química entre si. Apesar da presença de sal nas salinas ser historicamente atribuída a processos passados, estudos recentes sugerem que as águas salgadas estão sendo originadas atualmente devido à concentração por evaporação. O perfil químico das águas salinas estaria sendo originado principalmente pelo controle de elementos (Ca2+, Mg2+ e Si(OH)4) durante a concentração das águas, com o conseqüente envolvimento destes íons em dois processos: a formação de carbonatos e de silicatos magnesianos. Estudos preliminares em solos de salinas sugerem que a ocorrência de nódulos esbranquiçados e a presença de um horizonte enriquecido em argila podem evidenciar estes dois processos. Neste tipo de ambiente, carbonatos como calcita e dolomita são comumente neoformados, mas há divergências na literatura quanto ao mecanismo de origem autigênica dos silicatos magnesianos. Baseando-se no exposto acima, foram definidos os seguintes objetivos para a presente pesquisa: 1) ampliar o conhecimento sobre os solos associados às salinas através de uma caracterização baseada em dados de campo e laboratório dos solos presentes no entorno de uma lagoa salina representativa da Nhecolândia (lagoa do Meio); 2) identificar os processos envolvidos no controle do Ca2+, Mg2+ e Si(OH)4 nas águas salinas, através do estudo das relações entre as fases líquidas (águas superficiais e subsuperficiais) e sólidas (minerais) presentes nos solos do entorno da lagoa do Meio; e 3) identificar os mecanismos específicos de gênese dos minerais autigênicos possivelmente presentes nos solos do entorno da lagoa do Meio. As amostras de solo foram coletadas ao longo de uma topossequência nos arredores da lagoa do Meio e submetidas à análise granulométrica, análises químicas (ICP-MS, pH, CE, carbono total, carbonato de cálcio equivalente, bases trocáveis e testes de imersão em água, ácido e bases) e análises mineralógicas (DRX, MET-EDS). Amostras de água superficiais e subsuperficiais foram coletadas em um transecto que abarca a topossequência estudada e então encaminhadas às análises de pH, Eh, CE, temperatura, titulação com HCl, cromatografia de íons, EAA e ICP-MS. Os solos dos arredores da salina do Meio caracterizam-se pela textura areia a franco-arenosa, pela ausência de estrutura e, de maneira geral, por altos valores de pH, CE, CTC e saturação em Na+. O pH fortemente alcalino e o domínio de Na+ no complexo de troca desencadeiam a atuação do processo de solonização e dos seguintes processos específicos associados: migração de matéria orgânica perfil abaixo, precipitação de carbonatos (calcita, dolomita e nahcolita) em nódulos, solubilização/precipitação de sílica amorfa e formação autigênica de minerais de argila do grupo das esmectitas e micas. Diferentes esmectitas estão presentes ao longo da topossequência: a) na zona raramente atingida pelas variações sazonais do nível d\'água da salina, a esmectita é do tipo ferribeidelita, possui um grau de interestratificação com mica e vermiculita e apresenta teores de Fe3+ similares às micas identificadas no mesmo solo. Estas características sugerem que o mineral do tipo ferribeidelita é originado pela transformação de micas enriquecidas em Fe3+, sendo a vermiculita provavelmente uma fase intermediária nesta transformação; b) na zona de maior variação sazonal do nível d\'água da salina, as esmectitas são classificadas como do tipo saponita e estevensita. Os baixos teores de elementos terras-raras nas amostras enriquecidas nestes minerais, o controle do Mg2+ e do Si(OH)4 nas águas próximas à lagoa do Meio, a saturação das águas do entorno da lagoa em relação a saponita e estevensita e a presença destas esmectitas magnesianas nos locais onde são esperadas máximas taxas de evaporação, provam que estes minerais estão se originando por precipitação química diretamente da coluna d\'água da lagoa salina. Já as micas presentes nos solos estudados são do tipo ilita, glauconita e mica glauconítica, possuem interestratificação com camadas de esmectitas e parecem estar associadas a materiais amorfos. Experimentos de síntese disponíveis na literatura mostram que águas semelhantes às associadas à lagoa do Meio são ideais para a cristalização de micas a partir da precipitação inicial de hidróxidos amorfos. Desta forma, as evidências obtidas sugerem que estas micas são neoformadas a partir da precipitação inicial de amorfos e posterior cristalização. Os resultados obtidos certamente ampliaram o conhecimento sobre os solos presentes no entorno de lagoas salinas, uma vez os estudos disponíveis na literatura são baseados quase que exclusivamente em dados de campo. Mostrou-se que o controle do Ca2+ das águas mais salinas está sendo realizado pela formação de calcita e dolomita em nódulos, enquanto o controle do Mg2+ e do Si(OH)4 está ocorrendo pela formação de esmectitas magnesianas do tipo saponita e estevensita. Estes processos são provavelmente os responsáveis pela alta variabilidade entre as águas doces das baías/vazantes e as salgadas das salinas/arredores, conforme hipótese lançada em literatura. Assim, o presente trabalho fornece fortes evidências de que a presença de sal nas águas das lagoas salinas da Nhecolândia é atual ou, ao menos, tem contribuição de processos atuais. Por fim, mostrou-se ser possível a formação conjunta de ilita, glauconita e mica glauconítica e de esmectitas do tipo saponita e estevensita pelo mecanismo de precipitação diretamente das águas ou soluções em ambientes sujeitos a concentração evaporativa. / A distinctive feature of Nhecolândia, a sub-region of the Pantanal wetland, is the presence in close proximity of freshwater and saline lakes with a huge chemical variability. The salt has been generally attributed to Pleistocene processes, but recent studies have suggested that saline waters arise from present-day concentration of freshwater by evaporation. The chemical profile of saline waters would be originated by chemical control of Ca2+, Mg2+, and Si(OH)4 as the water becomes more saline. Two processes would be responsible for this control: formation of carbonates and formation of Mg-silicates. The presence of whitish nodules and clayey horizons in soils associated to the saline lakes would be evidences of these processes. In saline-alkaline environments, carbonates such as calcite and dolomite are commonly formed by chemical precipitation, but the mechanisms responsible for Mgsilicates genesis are still under debate. The objectives of this research are: a) increasing the general knowledge about soils associated to Pantanal saline lakes through a detailed characterization of the soils located around a representative saline lake of Nhecolândia (\"Salina do Meio\"); b) identifying the processes involved in Ca2+, Mg2+ and Si(OH)4 control from saline waters, through the study of relationships between waters and minerals present in the soils around \"Salina do Meio\"; c) identifying the specific mechanisms of authigenic genesis of the minerals possibly found around \"Salina do Meio\". Soils were sampling along a toposequence and submitted to physical (particle-size), chemical (ICP-MS, pH, EC, total carbon, inorganic carbonate, exchangeable bases, and soaking in H2O, HCl 1N, and NaOH 4M), and mineralogical analyses (XRD and TEM-EDS). Water was collected along a transect involving the lake and submitted to pH, Eh, EC, temperature, titration with HCl, ion chromatography, and ICP-MS analyses. The studied soils are sandy, structureless, and present, in general, high values of pH, CE, CEC, and Na+ saturation. Prevailing of Na+ in the waters and exchangeable sites and dominance of extremely high pH strongly suggest the general action of solonization in these soils and its influence on the following processes: organic matter translocation toward deeper horizons, precipitation of carbonates (calcite, dolomite, and nahcolite) in nodules, precipitation of amorphous silica, and authigenic formation of smectites and micas. Different authigenic smectites occur along the toposequence: a) in the zone hardly reached by the lake level variation, the smectite is classified as ferribeidellite-type, present an interstratification with mica and vermiculite, and has similar amounts of Fe3+ than the Fe-mica present in the soils. These characteristics suggest that this ferribeidellite-type mineral originates from transformation of Fe-mica and that vermiculite may be an intermediate phase in this transformation; b) in the zone of seasonal lake level variation, the smectites are classified as saponite- and stevensite-type minerals. Low REE amounts in the samples enriched in saponite and stevensite, geochemical control of Mg2+ and Si(OH)4, saturation with respect to Mg smectite in the more saline waters, and presence of Mg-smectite where the maximum of evaporation is expected, prove that saponite- and stevensite-like minerals originate by chemical precipitation from the water column of the saline lake. The micas present in the studied soils are classified as illite-, glauconite- and glauconitic mica-type minerals. They present 20% or less smectite layers and seem to be associated to amorphous materials. Synthesis of micas available in the literature shows that water conditions similar to the study area allow for dioctahedral mica crystallization from initial precipitation of amorphous hydroxides. Therefore, it suggests that micas of study area are neoformed. The results of this dissertation contributed to a better understanding about the soils associated to Nhecolândia saline lakes, since most of the published researches are based on field data. The control of Ca2+ from more saline waters occurs by formation of calcite and dolomite in nodules, while the control of Mg2+ and Si(OH)4 occur by formation of Mg-smectites classified as saponite- and stevensite-type. These processes are probably responsible for the chemical variability between freshwater and saline lakes, as supposed in a previous research. Therefore, the present work gives strong evidences about the current origin of Nhecolândia salt water. Also, it showed the possibility of genesis of illite, glauconita, glauconitic mica, saponite, and stevensite minerals through direct precipitation of waters or soil solutions under concentration by evaporation.

In this thesis, the electronic properties in superconducting LiFeAs single crystal are investigated using low temperature scanning tunneling microscopy and spectroscopy (STM/S) at various temperatures. For this purpose, the differential conductance (dI/dV) measured by STS which is directly proportional to the local density of states (LDOS) of the sample to the sub-atomic precision, is used together with the topography information. The dI/dV spectra within the ±1 V energy range reveal a characteristic feature at around -350 mV to -400 mV in stoichiometric LiFeAs. This feature seems to be a universal property among all the Fe-based high temperature superconductors, because it is also found in Fe0.965Se1.035 and NaFe0.975Co0.025As single crystals at the energy of -210 mV and -200 mV, respectively. The temperature dependent spectroscopy data averaged over a spatially fixed clean area of 2 nm × 2 nm are successfully executed between 5 K and 20 K. The two distinct superconducting phases with critical temperatures Tc = 16 K and 18 K are observed. In addition, the distance between the dip position outside the superconducting gap and the superconducting coherence peak in the spectra remains temperature independent which confirms that it is not connected to an antiferromagnetic (AFM) spin resonance. The temperature dependent spectra have been measured between 5 K and 61 K within the energy range of ±100 mV as well. The hump structure at 42 mV tends to disappear around 60 K from unknown origin. The temperature dependent quasiparticle interference (QPI) has been studied within the temperature range between 6.7 K and 25 K and analyzed by the Fourier transformation of the measured spectroscopic maps. The dispersion plots in momentum space as a function of temperature show an enhancement of QPI intensity (±5.5 mV) within the superconducting gap at the Fermi level at 6.7 K near q ~ 0. This is interpreted on the basis of Andreev bound state. In both polarities outside of this, a depletion of QPI intensity is noticed between 5.5 mV and around 9 mV. At positive energies, the QPI intensity becomes very rich above 9 mV. The size of the enhanced QPI intensity near the Fermi level, and the edge of the rich QPI intensity beyond 9 mV are found to behave like superconducting order parameter with rising of temperature. Furthermore, an energy mode peaked at around 14 mV appears in the integrated QPI intensity below superconducting Tc (6.7 K). This is consistent with the observed peak at 1st derivative of the dI/dV spectra. In both of these cases, such 14 mV peak is suppressed at normal state (25 K). This mode is therefore directly related to superconductivity in LiFeAs. The off-stoichiometric LiFeAs single crystal with superconducting Tc of 6.5 K has a 10 mV rigid band shift of the Fermi level towards electron doping. The absence of the rich QPI intensity between 9 mV and 17 mV is found compared to the stoichiometric LiFeAs, and hence the 14 mV mode is absent here. This brings us to conclude once more time that such 14 mV energy mode is relevant for superconductivity in LiFeAs.

La dénitrification autotrophe utilisant le fer Ferreux est un bioprocédé innovant pour l'élimination des nitrates, en même temps que l'oxydation du fer dans les eaux usées. Les dénitrifiants chimio-autotrophes convertissent le nitrate en azote gazeux et l'oxydation du Fe(II) conduit à la production de précipités de fer ferrique qui peuvent ensuite être enlevés et récupérés. La possibilité de maintenir une dénitrification autotrophe avec le fer ferreux en utilisant une culture mixte de Thiobacillus, un inoculum de boue activée et des cultures pures de la souche Pseudogulbenkiania 2002 et de T. denitrificans dans différentes conditions de pH et d'EDTA:Fe(II) a été initialement étudiée dans des essais biologiques par lots. Des ratios plus faibles d’EDTA:Fe(II) se traduisent par une efficacité et des taux d'élimination des nitrates plus élevés. La culture mixte de Thiobacillus présente le taux d'élimination de nitrate le plus élevé, égal à 1.18 mM•(g VSS•d)-1.Par la suite, la culture mixte de Thiobacillus a été ensemencée dans deux réacteurs à lit tassé à flux montant identiques. Les deux réacteurs (réacteur 1 et 2) ont reçu respectivement 120 et 60 mg / L de nitrate et une alimentation différente de Fe (II) afin de respecter un rapport molaire Fe(II):NO3- de 5:1. L’EDTA a été supplémenté à un rapport molaire EDTA:Fe(II) de 0,5:1. Le pH, le TRH et la température étaient de 6,5-7,0, 31 h et 22 ± 2 ° C. Dans le réacteur 1, le TRH a été raccourci de 31 à 24 h et la concentration de NO3- a été maintenue stable à 250 mg / L. Inversement, le réacteur 2 a été mis en fonctionnement avec un TRH décroissant et une concentration de NO3- en alimentation, maintenant ainsi un taux de charge de NO3- stable. Après environ 80 jours d'incubation, l'élimination des nitrates était de 88% dans le réacteur 1 pour un THR de 31 h. L'élimination de nitrates la plus élevée obtenue dans le réacteur 2 était de 80%. Une diminution du TRH de 31 à 24 h n'a pas affecté l'élimination du nitrate dans le réacteur 1, alors que dans le réacteur 2 l'élimination du nitrate a diminué à 64%.De plus, l'influence des métaux lourds (Ni, Cu, Zn) sur la dénitrification autotrophe utilisant du fer ferreux a été évaluée dans des essais biologiques discontinus, en utilisant les mêmes quatre cultures microbiennes différentes. L'efficacité et les taux d'élimination des nitrates les plus élevés ont été obtenus avec la culture mixte dominante de Thiobacillus, alors que la souche Pseudogulbenkiania de 2002 était la moins efficace. Cu s'est avéré être le métal le plus inhibiteur pour les cultures mixtes. Un impact plus faible a été observé lorsque le Zn a été ajouté. Le Ni présentait l'effet inhibiteur le plus faible. Une sensibilité plus élevée à la toxicité des métaux a été observée pour les cultures pures. Enfin, la caractérisation minérale des précipités obtenus pour les expériences avec du Cu, Ni et Zn a été étudiée. Chez les témoins abiotiques, l'oxydation chimique du Fe (II) a entraîné la formation d'hématite. Un mélange de différents (hydro)oxides de Fe(III) a été observé pour toutes les cultures microbiennes, et en particulier : i) un mélange d'hématite, d'akaganéite et / ou de ferrihydrite a été observé dans les précipités des expériences réalisées avec la culture mixte dominée par la présence de Thiobacillus; ii) en plus d'hématite, de l'akaganeite et / ou de la ferrihydrite, la maghémite a été identifiée lorsque la culture pure de T. denitrificans a été utilisée; iii) l'utilisation de la culture pure de la souche Pseudogulbenkiania 2002 a entraîné la formation d'hématite et de maghémite; enfin, l'enrichissement en boues activées a permis la production d'hématite et de magnétite en plus de la maghémite. Aucune différence concernant la minéralogie des précipités n'a été observée avec l'addition de Cu, alors que l'addition de Ni et de Zn a probablement stimulé la formation de maghémite. Une caractérisation minérale supplémentaire est cependant nécessaire / Ferrous iron mediated autotrophic denitrification is an innovative bioprocess for nitrate removal, simultaneously with iron oxidation in wastewaters. Chemoautotrophic denitrifiers convert nitrate to nitrogen gas and Fe(II) oxidation results in the production of ferric iron precipitates that can be subsequently removed and recovered. The feasibility of maintaining Fe(II)-mediated autotrophic denitrification with a Thiobacillus mixed culture, an activated sludge inoculum and pure cultures of Pseudogulbenkiania strain 2002 and T. denitrificans under different pH and EDTA:Fe(II) conditions was initially investigated in batch bioassays. Lower EDTA: Fe(II) ratios resulted in higher nitrate removal efficiency and rates. The Thiobacillus mixed culture resulted in the highest specific nitrate removal rate, equal to 1.18 mM•(g VSS•d)-1.Subsequently, the Thiobacillus mixed culture was seeded in two identical up-flow packed bed reactors. The two reactors (reactor 1 and 2) were fed with 120 and 60 mg/L of nitrate, respectively, and a different Fe(II) feed in order to respect a molar ratio Fe(II):NO3- 5:1. EDTA was supplemented at a EDTA:Fe(II) molar ratio 0.5:1. The pH, HRT and temperature were 6.5-7.0, 31 h and 22±2°C. In reactor 1, HRT was shortened from 31 to 24 h and NO3- concentration was maintained stable at 250 mg/L. Conversely, reactor 2 was operated with decreasing HRT and feed NO3- concentration, thus maintaining a stable NO3- loading rate. After approximately 80 d of incubation, nitrate removal was 88% in reactor 1 at HRT of 31 h. The highest nitrate removal achieved in reactor 2 was 80%. A HRT decrease from 31 to 24 h did not affect nitrate removal in reactor 1, whereas nitrate removal decreased to 64% in reactor 2.Moreover, the influence of heavy metals (Ni, Cu, Zn) on Fe(II)-mediated autotrophic denitrification was assessed in batch bioassays. The highest nitrate removal efficiency and rates were achieved with the Thiobacillus-dominated mixed culture, whereas Pseudogulbenkiania strain 2002 was the least effective. Cu showed to be the most inhibitory metal for mixed cultures. A lower impact was observed when Zn was supplemented. Ni showed the lowest inhibitory effect. A higher sensitivity to metal toxicity was observed for the pure cultures. Finally, the mineral characterization of the precipitates obtained in the experiments with Cu, Ni and Zn was investigated. In abiotic controls, the chemical Fe(II) oxidation resulted in hematite formation. A mixture of different Fe(III) (hydr)oxides was observed with all microbial cultures, and in particular: i) a mixture of hematite, akaganeite and/or ferrihydrite was observed in the precipitates of the experiments carried out with the Thiobacillus-dominated mixed culture; ii) on top of hematite, akaganeite and/or ferrihydrite, maghemite was identified when the T.denitrificans pure culture was used; iii) the use of the pure culture of Pseudogulbenkiania strain 2002 resulted in hematite and maghemite formation; finally, the activated sludge enrichment allowed the production of hematite and magnetite besides maghemite. No difference in the mineralogy of the precipitates was observed with the addition of Cu, whereas the addition of Ni and Zn likely stimulated the formation of maghemite. Further mineral characterization is however required

There are great energy savings to be made by recycling aluminium; as little as 5% of the energy needed for primary aluminium production may be required. Striving to produce high quality aluminium castings requires knowledge of microstructural imperfections, which is extra important when casting recycled aluminium that generally contains higher levels of imperfections compared to primary aluminium. Imperfections include amongst others Si, Fe, and Mn as well as oxides. Si is needed for castability, but it may also initiate fracture. There are different types of Fe-rich intermetallics influencing properties of castings, generally in a negative direction. Oxides constitute cracks and they are elusive because they are difficult to quantify. This thesis aims to increase knowledge about imperfections in recycled aluminium castings originating from alloying elements and the melt. Experiments were performed in advanced laboratory equipment, including X-radiographic imaging during solidification and in-situ tensile testing in a scanning electron microscope. Experiments were also performed at industrial foundry facilities. The experiments showed that the nucleation temperature of primary α-Fe intermetallics increased with higher Fe, Mn, and Cr contents. Primary α-Fe are strongly suggested to nucleate on oxides and to grow in four basic morphologies. Lower nucleation frequency of α-Fe promoted faster growth and hopper crystals while higher nucleation frequency promoted slower growth rates and massive crystals. Results also showed that a decrease in the size of the eutectic Si and plate-like β-Fe intermetallics improved tensile properties, foremost the elongation to fracture. In β-Fe containing alloys the transversely oriented intermetallics initiated macrocracks that are potential fracture initiation sites. In alloys with primary α-Fe foremost clusters of intermetallics promoted macrocracks. In fatigue testing, a transition from β-Fe to α-Fe shifted the initiation sites from oxides and pores to the α-Fe, resulting in a decrease of fatigue strength. Oxides in Al-Si alloys continue to be elusive; no correlations between efforts to quantify the oxides and tensile properties could be observed. / Genom att återvinna aluminium kan stora energibesparingar göras eftersom återvinning kan förbruka så lite som 5% av den energi som behövs för produktion av primär aluminium. Vid gjutning av högkvalitativa aluminiumprodukter krävs förståelse för defekter i mikrostrukturen och denna kunskap är extra viktig vid användning av återvunnen aluminium, som i regel innehåller mer defekter än primär aluminium. Defekterna består bland annat av Si, Fe och Mn samt oxider. Si behövs för gjutbarhet men kan också initiera brott. Järnrika intermetaller kan ha olika morfologier som generellt påverkar gjutna komponenter negativt. Oxider, som kan utgöra sprickor, är gäckande då de är svåra att kvantifiera. Denna avhandlings syfte är att öka kunskapen om defekter i gjutna komponenter av återvunnen aluminium. Experiment utfördes med avancerad laborationsutrustning så som röntgenfotografering av prover under stelning och dragprovning i svepelektronmikroskop. Experiment utfördes också i industrimiljö. Experimenten visade att kärnbildningstemperaturen steg för primära α-Fe intermetaller med ökade andelar av Fe, Mn och Cr. Resultaten tyder starkt på att primär α-Fe kärnbildas på oxider och att de växer i fyra olika morfologier. Lägre kärnbildningstäthet av α-Fe främjade snabbare tillväxt av kristaller med håligheter men högre kärnbildningstäthet främjade långsammare tillväxt av massiva kristaller. Resultaten visade också att minskad storlek av eutektiskt Si och β-Fe intermetaller ledde till förbättring av dragprovsresultaten, främst brottförlängningen. I legeringar med β-Fe ledde transversellt orienterade intermetaller till makrosprickor vilka kan initiera brott. I legeringar med primär α-Fe var det främst kluster av intermetaller som orsakade makrosprickor. I utmattningsprovning orsakade modifiering av β-Fe till α-Fe förflyttning av sprickinitieringen från oxider och porer till α-Fe, vilket resulterade i en reducerad utmattningshållfasthet. Oxiderna i Al-Si-legeringar fortsätter att gäcka; ingen korrelation mellan försök att kvantifiera oxiderna och draghållfasthet kunde påvisas.

Les protéines à centre Fe-S sont impliquées dans de nombreux processus cellulaires. In vivo, la formation des centres Fe-S est réalisée par des machineries multi-protéiques dont ISC et SUF, conservées chez les eucaryotes et les procaryotes. D’autres composants participent à la formation des centres Fe-S chez les eucaryotes, comme la frataxine (FXN). La FXN est une protéine présente chez l’homme, les plantes, la levure ou encore les bactéries à Gram négatif. Chez les eucaryotes, l’absence de FXN conduit à des phénotypes drastiques comme une accumulation de fer dans la mitochondrie, une diminution drastique de l’activité d’enzymes à centre Fe-S ou encore des dommages oxydatifs. Chez l’homme, un déficit en FXN est responsable d’une maladie neurodégénérative, l’ataxie de Friedreich. A la différence des eucaryotes, chez les procaryotes comme Escherichia coli, l’absence de CyaY, homologue bactérien de la FXN, ne conduit à aucun des phénotypes évoqués ci-dessus.Durant ma thèse, je me suis intéressée au rôle de CyaY chez E. coli. J’ai montré que, in vivo, CyaY favorise la formation des centres Fe-S via la machinerie ISC. Un lien génétique entre CyaY et IscX a également pu être établi, montrant que ces deux protéines participent à la formation des centres Fe-S in vivo. Je me suis ensuite intéressée aux bases moléculaires pouvant expliquer la différence entre les phénotypes liés à l’absence de FXN chez les eucaryotes et les procaryotes. J’ai montré que le résidu 108 de IscU joue un rôle clé pour la dépendance de CyaY. Enfin, pour mieux comprendre le rôle de CyaY chez E. coli, j’ai réalisé une approche globale en caractérisant le transcriptome du mutant ∆cyaY. / Fe-S cluster containing proteins are involved in many cellular processes such as respiration, DNA repair or gene regulation. In vivo, Fe-S cluster biogenesis is catalysed by specific protein machineries, ISC and SUF, conserved in both eukaryotes and prokaryotes. Frataxin (FXN) is a small protein found in humans, plants, yeast and Gram negative bacteria. In eukaryotes, a defect in FXN leads to drastic phenotypes such as mitochondrial iron accumulation, drastic decrease of Fe-S cluster protein activity, sensitivity to oxidants. In humans, FXN deficiency is responsible for the neurodegenerative disease, Friedreich’s ataxia. In prokaryotes like E. coli, a defect in CyaY, the bacterial FXN homolog, does not lead to significant phenotypes compared to the wild-type strain. During my thesis, I investigated the role of the bacterial FXN CyaY in E. coli. I showed that, in vivo, CyaY assisted the ISC-catalyzed Fe-S cluster biogenesis. A genetic link was also observed between cyaY and iscX, demonstrating that these proteins participate in Fe-S cluster biogenesis. In a second part, I investigated the differences between the impact of the eukaryotic versus prokaryotic FXN. I showed that the IscU 108th residue is crucial for the CyaY-dependency. Finally, I used a transcriptomic approach to test whether CyaY has a global role in E. coli.

This study focuses on the University of the Highlands and Islands (UHI) modelled on a federal, collegiate university based on a number of existing and geographically dispersed Further Education (FE) colleges and research institutions. The inclusion of FE colleges and their geographical dispersal distinguishes it from most mainstream institutions. The UHI was heralded by its advocates as a distinctively radical enterprise designed to meet the fast-moving challenges of the twenty-first century by embracing new technologies and overcoming geographical barriers. After attaining Higher Education (HE) status in 2001, the policy goal of fostering a research culture emerged as a prominent concern for the UHI. This study explores the policy drive to foster such a research culture, focusing on the period from 2003 to 2008. The study was informed by a constructivist grounded theory methodological approach and the data gathering included twenty-six semi-structured interviews to ascertain how this policy drive was received within the UHI partners. The study found that a unified research culture was not perceived to have embedded throughout the partners, with the exception of one or two research institutions where it can be said to have pre-existed. Against this backdrop, the study identified emerging discourses encapsulating how the policy drive was perceived by a wide spectrum of different actors throughout the UHI. Two different types of performativity discourses proved to be central in shaping the policy aspiration, namely a ‘RAE performativity discourse’ and a ‘Further Education (FE) performativity discourse’. Both discourses can be seen to have influenced the trajectory of research expansionist policy within the UHI by setting up a normative space privileging certain identities, subjectivities and associated actions at the expense of others. In highlighting both the structural and socio-cultural barriers to the policy of promoting research, the study aims to contribute to wider debates on institutional policies for building research capacity in a dual sector/hybrid institutional setting. In terms of offering direct benefits to the UHI, by analysing the different sort of assumptions and realities that shape the meaning of a research culture within the UHI, this study may help inform future policy making on research expansion within UHI partners. The study concludes by making a number of practical recommendations which the author believes will help move research from the periphery to a more central stage within the UHI partners.

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