Made available in DSpace on 2014-10-09T12:41:30Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:49Z (GMT). No. of bitstreams: 0 / Eletrólitos sólidos de céria com adição de íons de terras raras trivalentes apresentam elevada condutividade iônica quando comparados com a zircônia estabilizada com ítria, que é um eletrólito sólido padrão. Por isso, esses condutores de íons oxigênio à base de céria têm potencial de aplicação em células a combustível de óxido sólido que operam em temperaturas intermediárias (500-700ºC). Uma das abordagens mais investigadas para otimização da condutividade elétrica e de outras propriedades destes materiais é a incorporação de um segundo aditivo. Neste trabalho, composições de céria-20% mol gadolínia com SrO, TiO2 e SrTiO3 como co-aditivos, em teores de 1; 2,5 e 5% em mol foram preparadas por reação em estado sólido. O principal objetivo foi verificar o efeito dos aditivos na densificação, na microestrutura e na condutividade elétrica da céria-gadolínia. Os compactos sinterizados foram caracterizados por medidas de densidade aparente, difração de raios X e espectroscopia Raman para determinação das fases cristalinas, microscopia eletrônica de varredura para observar as diferentes microestruturas das composições, e medida da condutividade elétrica por espectroscopia de impedância. Os resultados mostraram que os aditivos exercem influência em todas as propriedades investigadas, mas de forma diferente dependendo do tipo e do teor. De forma geral, SrO exerce efeito benéfico na condutividade elétrica intergranular, mas prejudica a densificação. O TiO2 promove um aumento na densificação da céria-gadolínia, mas aumenta também o bloqueio aos portadores de carga nos contornos de grão, além de resultar na formação da fase pirocloro Gd2Ti2O7, quando adicionado em teores acima do limite de solubilidade. O SrTiO3 não produz alterações na densificação da céria-gadolínia. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

En impesanteur réelle ou simulée, l'absence de gravité oriente les cellules souches multipotentes de la moelle osseuse à privilégier l’adipogénèse aux dépens de l’ostéogénèse. Ceci entraine une perte osseuse fréquemment rencontrée chez les astronautes lors des vols spatiaux. Parmi les traitements médicamenteux existants, le strontium possède une double action, à la fois activatrice de l'ostéogénèse et inhibitrice de l’adipogénèse. Dans ce contexte, l’objectif général de ce projet de thèse a été de démontrer que le strontium peut être un bon candidat pour contrecarrer les effets de l'impesanteur. Nous nous sommes particulièrement intéressés aux petites protéines Rho de la famille des GTPases, qui contrôlent le cytosquelette de la cellule, sa tension cellulaire ainsi que de nombreuses voies de signalisation. D'après la littérature, ces signalisations ont aussi été montrées comme étant liées aux voies du VEGF ou au statut oxydant des cellules, impliquées dans l’engagement des cellules souches multipotentes. La première partie de cette étude a permis de montrer l’effet antioxydant du strontium sur la lignée C3H10T1/2 en tant qu’activateur de la GTPase RhoA, permettant l’induction du gène clé de la réponse antioxydante, Nrf2, et par conséquent l’inhibition de l’adipogénèse. La deuxième partie a utilisé comme modèle des cultures 3D sur microbilles de polystyrène recouvertes de collagène pour la culture d'adipocytes, avec l'ajout de minéraux d’apatite pour la culture d'ostéoblastes. Ces billes ont été mises en culture dans un bioréacteur simulant l’impesanteur (Rotating Wall Vessel, RWV, NASA). Sous strontium, cette culture en RWV a favorisé l’ostéogenèse et limité l’adipogénèse, validant l'utilisation du strontium en tant que répresseur des effets délétères de l'impesanteur sur l’os. Nous avons montré que cet effet peut être expliqué d'une part par la stimulation des activités des deux GTPases RhoA et Rac1, et d'autre part par l’induction de l’isoforme matricielle du VEGF chez les ostéoblastes. En revanche, chez les adipocytes, les deux formes solubles et matricielles du VEGF étaient inhibées. De plus, le strontium a induit l'expression du récepteur Flt-1 qui favoriserait l’ostéogénèse. L’ensemble de ces données nous a permis de mieux comprendre les cinétiques de RhoA et Rac1 pendant l’ostéoblastogénèse et l’adipogénèse, ainsi que le rôle important des voies de signalisation du VEGF et du statut oxydant dans l’orientation de la différenciation des cellules multipotentes. Le strontium s’est révélé être un bon inducteur ostéogénique dont les applications fondamentales peuvent amener de nouvelles voies d’utilisation / In real or simulated microgravity, the absence of gravity directs multipotent stem cells from bone marrow to favor adipogenesis at the expense of osteogenesis. This causes a bone loss, commonly found in astronauts during spaceflight. Among existing drug therapies, strontium has a double action, both activating osteogenesis and inhibiting adipogenesis. In this context, the general objective of this project was to demonstrate that strontium may be a good candidate to counteract the microgravity effects. We were particularly interested in small proteins Rho of the GTPases family, which control cell cytoskeleton, cell tension and many signaling pathways. According to the literature, these pathways were also shown to be related to the VEGF singaling or the cell oxidative status, involved in the multipotent stem cells commitment. The first part of this study demonstrated the strontium antioxidant effect on the C3H10T1/2 line as an activator of the GTPase RhoA, allowing the induction of the key antioxidant response gene, Nrf2, and therefore inhibiting adipogenesis. The second part used a 3D cultures model on polystyrene microbeads coated with collagen for the adipocytes culture, and with mineral apatite added for osteoblasts culture. These beads were cultivated in a bioreactor simulating microgravity (Rotating Wall Vessel, RWV, NASA). With strontium, this RWV culture promoted osteogenesis and limited adipogenesis, validating the use of strontium as a repressor of the microgravity deleterious effects on bone. We have shown that this effect can be explained first by the stimulation of both GTPases RhoA and Rac1 activities, and secondly by the induction of the matrix-bound VEGF isoform in osteoblasts. In contrast, in adipocytes, both soluble and matrix-bound VEGF isoforms were inhibited. Moreover, strontium induced Flt-1 receptor expression, which would promote osteogenesis. All these data allowed us to better understand the RhoA and Rac1 kinetics during osteoblastogenesis and adipogenesis, and the important role of VEGF signaling pathways and oxidative status in directing multipotent cells differentiation. Strontium was found to be a good osteogenic inductor whose core applications can bring new ways of use

A la suite des catastrophes nucléaires d’importantes quantités de radionucléides ont été rejetés dans l’environnement. Le Strontium 90 (90Sr) fait partie de ces rejets. Du fait de sa demi-vie de 29 ans, c’est un polluant persistant qui conduit à la contamination des populations vivant autour des territoires contaminés via l’ingestion chronique de faibles quantités de ce radionucléide. Les études épidémiologiques ont mis en évidence des effets au niveau du système immunitaire, du système hématopoïétique et de la physiologie osseuse chez l’homme. Le 90Sr qui s’incorpore principalement dans l’os pourrait contribuer à l’apparition de ces effets. Le but de ce travail a été de comprendre quels sont les mécanismes d’action du 90Sr qui permettent d’expliquer de tels effets. Un premier modèle in vitro utilisant une lignée de cellules stromales murines (MS5) contaminées par le milieu de culture à 1 ou 10 kBq.ml-1 a été utilisé. Il a permis de montrer que le 90Sr était capable d’induire des cassures double-brin de l’ADN dès 30 minutes d’exposition avec une induction de la senescence et une altération de la fonction de support aux progéniteurs hématopoïétiques. Dans le deuxième modèle in vivo d’effet dose, des souris Balb/c ont été contaminées durant 24 semaines à des concentrations de 90Sr de 4, 20 et 100 kBq.l-1 dans l’eau de boisson. Cette expérience a permis d’observer une augmentation des marqueurs de la résorption osseuse en fonction de la contamination au 90Sr ainsi et une augmentation de l’expression génique des enzymes impliquées dans la défense antioxydante. Une augmentation de p21, marqueur de la senescence et une diminution d’IL-6 ont également été observées. Les implications de ces résultats sur la physiologie osseuse, le système immunitaire et hématopoïétiques sont discutées. Globalement, l’ensemble de ce travail complète les données déjà existantes sur le 90Sr et permet de mieux comprendre les mécanismes d’action du 90Sr sur les cellules stromales médullaires qui sont au centre de la régulation immuno-hématopoïétique. / Abstract : After nuclear disasters, large amounts of radionuclides were released into the environment. Strontium 90 (90Sr) is part of these wastes. Because of its half-life of 29 years, it is a persistent pollutant which leads to the contamination of surrounding populations through the chronic ingestion of low quantities of this radioelement. Epidemiologic studies have demonstrated some effects on immune system, hematopoietic system and bone physiology in humans. 90Sr accumulates mostly in bones and could contribute to the appearance of such effects. The aim of this work is to understand the action mechanisms which could explain the previous observations. In the first in vitro model, a murine stromal cell line (MS5) contaminated through the culture medium with 1 or 10 kBq.ml-1 of 90Sr was used. Thank to this model, an increased number of DNA double-strand breaks in cells after 30 minutes of exposure, a senescence induction and a modification in the support of hematopoietic progenitors were observed. In the second model, Balb/c mice were contaminated during 24 weeks through drinking water containing 90Sr at 4, 20 and 100 kBq.l-1. Both an increase in genic expression of bone resorption markers and in antioxydative enzymes were observed. An increase in p21 expression, marker of senescence, and a decrease in IL-6 were also seen. The implications of these results on bone physiology, immune and hematopoietic systems are discussed. As a whole, all this work completed the preexistent data about 90Sr and contributes to a better understanding of the action mechanisms of 90Sr on marrow stromal cells which have a pivotal function in the regulation of the immune and hematopoietic system.

Für die Behandlung von Knochendefekten überkritischer Größe stehen seit einigen Jahren zahlreiche resorbierbare Materialien zur Verfügung, die eine Defektheilung bis hin zur vollständigen knöchernen Regeneration erlauben. Im Fall systemischer Knochenerkrankungen, insbesondere im osteoporotischen Knochen, ist jedoch die Selbstheilungskapazität des Gewebes stark eingeschränkt, was neben der Defektbehandlung eine knochenanabole sowie resorptionshemmende Therapie erfordert. Diese kann beispielsweise durch die Gabe von Strontium-haltigen Präparaten erreicht werden, da der duale Wirkmechanismus der Strontium-Ionen zu vermehrter Knochenneubildung bei gleichzeitig verminderter Knochenresorption führt. Ziel der vorliegenden Arbeit war die Entwicklung eines Strontium-haltigen Knochenzements, welcher eine Freisetzung von Strontium-Ionen spezifisch im jeweiligen Knochendefekt und somit eine lokale Stimulation der Knochenneubildung ermöglicht. Basierend auf einem etablierten Calciumphosphat-Knochenzement wurden Strontium-haltige Zementvarianten hergestellt und ausgiebig charakterisiert. Im Gegensatz zu den meisten bislang verfolgten Methoden konnten Zemente mit deutlich verbesserten mechanischen Eigenschaften hergestellt werden, welche weiterhin Strontium-Ionen in physiologisch relevanten Konzentrationen freisetzen. Durch Zellkulturuntersuchungen an humanen Zellen sowohl der osteoblastären- als auch osteoklastären Linie konnte eine Stimulation der für den Knochenaufbau verantwortlichen Zellen sowie eine Hemmung der den Knochen resorbierenden Zellen durch die entwickelten Zemente nachgewiesen werden.

Das Konzept neuartiger, resistiv schaltender Langzeitspeicherzellen sieht eine enorme Erhöhung der Speicherdichte bei gleichzeitig geringem Energieverbrauch und hoher Skalierbarkeit vor. In diesem Zusammenhang sind unterschiedlichste Übergangsmetalloxide Gegenstand der aktuellen Forschung, die zwischen Metallelektroden in einer Metall-Isolator-Metall-Struktur eingebettet sind. Ein anerkanntes Modell zur Klärung der lokalen Struktur innerhalb des Schaltmechanismus beschreibt die Änderung des resistiven Zustandes in der wechselnden Ausbildung und Auflösung eines leitfähigen Pfades in der Oxidschicht, der beide Elektroden miteinander verbindet. Die vorliegende Arbeit befasst sich auf dieser Grundlage mit der Untersuchung solcher Speicherzellen, wobei anhand der gewählten Elektrodenmaterialien Speichereffekte rein auf Änderungen im Oxid zurückzuführen sind. Die sich daraus ergebende Möglichkeit der gezielten Änderung des efekthaushaltes und des resistiven Schaltverhaltens der Oxidschichten durch deren Ausheizung oder Modifikation mittels Ionenimplantation stand im Fokus der Arbeit. Dementsprechend muss für eine genaue Lokalisierung des Schaltmechanismus die gewählte Oxidstruktur nicht nur genauestens bekannt, sondern auch möglichst rein sein. Zur Vereinigung all diese Faktoren wird das Modellsystem SrO-TiO2 mit den beiden Vertretern TiO2 und SrTiO3 untersucht, da seine Eigenschaften in der Literatur bereits rege diskutiert wurden. Zur Gewährleistung der Reinheit der Schichten wird die Herstellung der Isolatorschichten durch Atomlagenabscheidung eingesetzt und deren Optimierung, sowie Schichtcharakterisierung im ersten Teil der Arbeit vorgestellt. Mittels einer Vielzahl optischer und struktureller Analysemethoden lassen sich definierte Rückschlüsse über die Eigenschaften der Oxide ziehen. Sämtliche Veröffentlichungen zur Herstellung von SrTiO3 mittels Atomlagenabscheidung beziehen sich entweder auf eigens hergestellte Anlagensysteme oder Präkursormaterialien, wodurch die Schichten industriell nicht reproduzierbar sind. Eines der Ergebnisse der vorliegenden Arbeit ermöglicht eben dies durch die erstmalige Kombination einer kommerziell erhältlichen Anlage mit kommerziellen Präkursormaterialien. Nach deren Optimierung werden die Oxidschichten zwischen den beiden Metallelektroden Au und TiN integriert und die daraus resultierenden Speicherzellen elektrisch charakterisiert. Es kann bipolares, nichtflüchtiges, resistives Schaltverhalten in amorphen und ex situ kristallisierten Oxiden nachgewiesen werden. Anhand von Struktur-Eigenschaft-Korrelationen gelingt es, die Leitungsmechanismen in den untersuchten Speicherzellen als Schottky-Emission und bei ausreichend hohen Spannungen als volumendominierte Poole-Frenkel-Emission zu charakterisieren. Bei den dafür notwendigen Defekten handelt es sich um flache Donatorzustände. Die Annahme des resistiven Schaltens über einen reversiblen leitfähigen Pfad basierend auf Defektzuständen wird durch die Änderung der Coulomb-Barrierenhöhe bei konstanter Schottky-Barrierenhöhe innerhalb derselben Mikrostruktur bestätigt. Besonders das untersuchte TiO2 amorpher Struktur mit Schalt- und Lesegeschwindigkeiten von wenigen Millisekunden, aber auch polykristallines SrTiO3 zeigen ein hohes Potential für deren zukünftige Anwendung auf dem Gebiet resistiv schaltender Speicherzellen. Durch Kr+-Ionenimplantation ändern sich nachweislich sowohl die elektrischen als auch die strukturellen Eigenschaften in TiO2 und SrTiO3. XRD-Messungen an polykristallinen TiO2-Schichten bestätigen die mittels SRIM durchgeführten Simulationsdaten und zeigen für Implantationen ausreichend hoher Fluenzen eine Amorphisierung der kristallinen Strukturen durch atomare Umverteilung im Oxid. Dadurch bilden sich zusätzlich intrinsische, tiefe Defektniveaus in den Oxidschichten, welche das resistive Schalten modifizieren. Die Implantation polykristalliner TiO2-Schichten führt nachweislich zur Umwandlung flüchtiger in nichtflüchtige Schaltkurven, die im Vergleich zu amorphen Ausgangsproben stabilere Widerstandswerte bei geringerem Energieaufwand zeigen. / The concept of novel, longterm resistive switching memories is based on an enormous increase of the storage density with a simultaneous low energy consumption and a high scalability. In this context, different transition metal oxides, which are embedded between metal electrodes in a metal-insulatormetal structure, are part of the ongoing research. A widely recognized model for an explanation of the local structure within the switching mechanism discribes the alteration of the resistive state as a result of an alternating forming and interruption of a conducting path inside an oxide layer. The presence of such a filament acts like a linkage between the electrodes. Based on that, the present study deals with the investigation of such memory storages. In the wake of this the chosen electrode materials enables the determination of memory effects due to pure modifications inside the oxide layers. Thus, a targeted manipulation of defects and the resistive switching mechanism becomes possible by annealing of the layer or its modification by ion implantation which was the central challenge. Therefore the used oxide structures have to be well reputed and, additionally, almost free of defects to be able to localize changes in the switching mechanism exactly. To combine all this facts, the model system SrO-TiO2 is investigated with the two compounds TiO2 und SrTiO3. The properties of this system are already well discussed in literature. To ensure the purity of the layers, they are created by atomic layer deposition. The optimisation of the deposition process and layer characterization is presented in the first part of this study. Using a variety of optical and structural analysis methods allows defined conclusions about the oxide properties. All publications concerning the atomic layer deposition of SrTiO3 deal with self-made devices or precursor materials foreclosing an industrial reproduction. One of the results of this thesis enables exactly that by a combination of a commerically available device and commercial precursor materials. After its optimisation, the oxide layers are integrated between the two electrode materials Au and TiN in order to characterize the electrical properties of the resulting memory cells. Bipolar, nonvolatile resistive switching can be proved for amorphous and ex situ crystallised oxides. Based on structure-property correlations the conduction mechanism within the investigated cells can be identified as Schottky emission and for sufficiently high voltage as volume-dominated Poole Frenkel emission. The necessary defects therefore are determined to be shallow donor states. The assumption of resistive switching based on a reversible conducting filament consisting of defect states is confirmed by a changing Coulomb barrier high during the high of the Schottky barrier remains contant. Especially amorphous TiO2 with switching and reading speeds up to a few milliseconds, but also polycrystalline SrTiO3 showing high potential for future implementation in resistive switching memory cells. By use of Kr+ ion implantation the electrical and structural properties of TiO2 and SrTiO3 are changed. XRD measurements at crystalline TiO2 layers verify simulation data carried out by SRIM. For high enough fluences it shows an amorphisation of the crystalline structures by atomic redistribution inside the oxids. Thus, additionally intrinsic deep defects are created inside the oxide layers which modify the resistive switching character. A special focus is on the transformation of crystalline volatile switching TiO2 layers into amorphous non-volatile memory devices which shows more stable resistance values combined with lower energy input compared to initial amorphous layers.

Les travaux réalisés dans le cadre de cette thèse ont consisté en la réalisation d'un système de détection non destructif assisté par cavité d'atomes piégés sur réseau optique pour l'amélioration de la stabilité d'une horloge optique au strontium. La caractérisation de ce système dans son fonctionnement en régime classique, dans lequel les atomes piégés diffusent suffisamment peu de photons pour ne pas être expulsés du piège durant la détection, a mis en évidence des améliorations significatives en termes de rapport signal à bruit avec un gain d'un facteur cent en comparaison avec le système précédent de détection par fluorescence. Les gains en termes de stabilité par réduction de l'effet Dick restent cependant à concrétiser.Pour la réalisation du régime quantique, dans lequel moins d'un photon est diffusé par atome durant la détection, des idées nouvelles et des changements significatifs ont du être opérés sur le système et un travail théorique conséquent a été entrepris afin de déterminer la stratégie permettant une amélioration de la stabilité par réduction du bruit de projection quantique par mesure sans démolition de la cohérence de l'état interne atomique.J'y ai également aborder l'étude des effets des collisions chaudes des atomes de strontium piégés avec les particules du fond de vide résiduel, permettant une amélioration de l'exactitude de l'horloge. Cette thèse rapporte en particulier la première mesure expérimentale du déplacement de la fréquence de transition d'horloge due à ces collisions ainsi que son étude théorique. / The work achieved in the frame of this PhD training consisted in the implementation of a cavity enhanced non destructive detection system of atoms trapped in an optical lattice aiming at improving the stability of an optical strontium clock.The characterization of the system in its classical regime, for which a sufficiently low number of photons are scattered per atom to avoid expelling them off the trap, highlighted significant improvements in term of signal to noise ratio, with gain factor around 100 compared with the previously used fluorescence scheme. Yet, gains in terms of stability via Dick effect reduction still have to be demonstrated.Regarding the quantum regime, for which less than one photon is scattered per atom over the detection, new ideas and significant changes have been carried out on the system and a theoretical study was has been undertaken to determine the strategy for the improvement of the clock stability by quantum projection noise reduction via quantum non demolition measurement.It was as well the opportunity to study the effect of the hot collisions between the trapped strontium atoms and the residual vacuum background gas particles, allowing for the improvement of the clock uncertainty. This work reports in particular on the first measurement of strontium clock hot collisions shifts as well as its theoretical study.

The low-field magnetoresistance properties in double-perovskite strontium ferromolybdate core–shell structures arise from spin-dependent tunneling through a barrier formed by the shell. It is strongly dependent on synthesis conditions. In this work, first, the resistivity behavior of granular strontium ferromolybdate ceramics comprising intergrain tunnel barriers is reviewed. Based on this generalization, the modification of the tunneling process with barrier thickness and interface conditions is demonstrated. For the first time, equations for the magnetoresistance in each special case are derived.

This thesis concerns the application of a new technique for measuring the stable isotopes of Sr, specifically pertaining to mass dependent fractionation in high temperature processes on the Earth and Moon. Processes such as mantle melting and differentiation on Earth and the formation of the Lunar Magma Ocean are investigated by the application of a double-spike TIMS method to terrestrial and lunar material to obtain high-precision ⁸⁷Sr/⁸⁶Sr, ⁸⁸Sr/⁸⁶Sr and ⁸⁴Sr/⁸⁶Sr data. Measurements of mantle-derived mafic material provide insights into the ⁸⁸Sr/⁸⁶Sr composition of the silicate mantle. Ocean Island Basalts possess restricted δ⁸⁸Sr compositions, whilst Mid-Ocean Ridge Basalts from the Pacific, Atlantic and Indian ridges reveal variations in δ⁸⁸Sr, the majority of which is seen within the FAMOUS section of the Mid-Atlantic Ridge. These variations are attributed partly due to the effects of plagioclase crystallisation and partly due to mantle source heterogeneity. Analyses of mineral separates from three different igneous systems provide an understanding of δ⁸⁸Sr fractionation at a mineral-scale. The possibility of δ⁸⁸Sr fractionation as a result of magmatic differentiation has also been assessed, and found to occur between the basalt and rhyolitic end-members of the Icelandic Hekla suite. Variations in the ⁸⁷Sr/⁸⁶Sr ratios of these rocks are also found, and considered most likely to be due to contamination. Analyses of lunar rocks indicate that the highland suite appears to be relatively uniform in δ⁸⁸Sr, whilst significant fractionation to light δ⁸⁸Sr compositions occurs in the mare basalts. Such variations are thought to be associated with the crystallisation of plagioclase during the differentiation of the lunar magma ocean. Lastly, precise ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr data yield a model age for the Moon of 4.523 ± 0.019 Ga.

A number of leaks of radioactive liquors to ground are known to have occurred from several plant buildings, vaults and disposal trenches within and around the Separation area at the Sellafield nuclear site over the past 50 years1. The most significant of these leaks have occurred from the Magnox Silo, the Caesium Extraction Plant, the Magnox Reprocessing Pump House, the Sludge Storage Tanks, the Burial Pits and the Medium Active Evaporation and Thermal Denitration Plant. The radioactive contamination will be accompanied by other components of spent fuel reprocessing, including inorganic salts from neutralised acids, solvents and other organic compounds along with the typical contaminants commonly associated with large industrial activity such as heavy metals, fuel, oils, degreasing agents etc. The research in this thesis describes the effects of common industrial contaminants on the behaviour of Cs and Sr sorption to bentonite and montmorillonite clay minerals. Batch sorption experiments of Cs and Sr uptake onto bentonite and montmorillonite in a number of complex systems were investigated as follows: 1. Initial batch sorption experiments investigating the normal behaviour of the clay minerals. 2. Introduction of anthropogenic organic ligands EDTA, NTA and picolinic acid into the system and their influence on Sr and Cs uptake. 3. Time dependent studies investigating the effect that residence time of the anthropogenic organic ligands has on the sorption properties of montmorillonite and bentonite. 4. Quaternary systems where simulant Magnox sludge equilibrated water, at a number of concentrations, was introduced to ternary systems containing anthropogenic organic ligands. 5. Time dependent studies investigating the effect of hydrocarbons TCE, toluene and naphthalene on the uptake of Cs and Sr to bentonite and montmorillonite. The batch sorption experiments show that the presence of anthropogenic organic ligands reduces the uptake of Cs and Sr by both montmorillonite and bentonite. It is also shown that the presence of simulant Magnox sludge in quaternary systems can also reduce the uptake of Cs and Sr, with significant reductions in sorption observed for Sr sorption in EDTA quaternary systems. Further, the uptake of Cs and Sr to bentonite and montmorillonite appears to decrease with increasing anthropogenic organic ligand residence time. This suggests that the ligands are altering the surface of the clay minerals reducing the number of available binding sites. The influence of hydrocarbons shows a significant decrease in sorption after 3 months for Cs and Sr sorption to montmorillonite. There were no further significant changes for all other hydrocarbon systems investigated.

published_or_final_version / abstract / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy