Dissertations / Theses on the topic 'Actinidin'

Actinidin, the 23.6 kDa cysteine proteinase of Chinese gooseberry (Actinidia chinensis), is present at high concentration in fruits. A fruit-specific cDNA library was established and screened by differential hybridisation and using a synthetic oligonucleotide. Two of ten actinidin clones identified were characterised by sequence analysis. The two very similar cDNAs code for proteins with approximately 90% sequence homology to the published amino acid sequence of actinidin, as well as an additional 25 amino acids following the mature carboxyl terminus. The larger clone in addition has coding potential for 57 residues of an amino-terminal extension with considerable homology to amino-terminal sequences of other cysteine proteinases. From size determinations of both mRNA (1.4 kb) and immunoprecipitated in vitro translation product (39 kDa) it was estimated that actinidin is synthesised as a precursor approximately 15 kDa larger than the mature protein. Features of the prosegment primary sequence are considered with regard to a possible mechanism of inactivation of the proteinase, by analogy with other proteolytic zymogens. The presence of three potential glycosylation sites, one within the carboxy-terminal and two in the amino-terminal extension are consistent with subcellular location of the enzyme within membrane-bound organelles. Results from a Southern blot show that actinidin is encoded by a multigene family of up to ten members. Actinidin gene expression, both at the level of mRNA and protein, is largely restricted to the fruit of A. chinensis, where the level of actinidin mRNA accumulates early during development.

Four different actinidin gene constructions have been created, each consisting of different functional parts of the actinidin gene: (1) the mature actinidin-coding DNA, (2) the amino-terminal extension, but without the secretion signal, plus the mature actinidin-coding DNA, (3) the mature actinidin plus the carboxy-terminal extension-coding DNA, and (4) the full-length precursor actinidin-coding DNA. The first three constructions were fused to the yeast MFa1 promoter and secretion leader sequence, while the fourth was coupled to the CYC1-GAL UAS promoter. Upon expression in yeast, no protein product was detected in the culture supernatant. Analysis of intracellular proteins showed that actinidin protein was detected only from the actinidin gene constructions which have the carboxy-terminal extensions, suggesting that the carboxy-terminal extension is required for the stability of the protein. Comparison of the actinidin proteins produced in protease-proficient and protease-deficient strains suggests that the processing of the protein requires the activity of vacuolar protease(s) and indicates that the actinidin was translocated into the yeast vacuole. Examination of the amino acid sequence suggested that actinidin possesses potential vacuolar and peroxisomal targeting signals. Since the actinidin precursor was glycosylated it must have entered the secretory pathway before being translocated into a specific cellular compartment. The HSP26 gene promoter has been shown to be induced by heat-shock and upon entry into stationary phase, thus it is potentially useful for heterologous gene expression in yeast.

Research in this thesis describes the characterisation of mRNA sequences coding for actinidin, a cysteine protease found in abundance in the fruit of kiwifruit (Actinidia deliciosa). The first step in the characterisation required the isolation of mRNA from ripe kiwifruit tissue. The suitability of a number of RNA extraction procedures was investigated. The method finally adopted differed from that used for unripe fruit tissue, and was chosen as a result of the nature of the polysaccharide that contaminated nucleic acids prepared from extracts of kiwifruit fruit tissue. RNA extracted from ripe fruit was used to synthesis a partial cDNA library and clones for actinidin were isolated. A number of these cDNA clones were sequenced; three clones were almost full-length. The actinidin cDNA clones obtained fall into two broad sequence classes. The majority of them encode acidic proteins (pI˜4.7), with 97% homology to the published amino acid sequence of actinidin. The second class encode basic proteins (pI˜8.1), with 83% homology to the published amino acid sequence of actinidin. Both classes of actinidin cDNA sequence encode zymogens, which contain N- and C-terminal extensions not present in the mature form of the enzyme. The N-terminal extension of both sequence classes includes a putative signal peptide. Northern hybridization analysis was used to investigate the tissue specificity of actinidin mRNA expression, and the expression of mRNA for the two actinidin sequence classes during fruit ripening. Both actinidin sequence classes were expressed differentially during the latter stages of kiwifruit fruit development and through post-harvest fruit ripening. The expression of both sequence classes increased from just prior to fruit maturity through ripening and reached a maximum as fruit attained the stage of 'eating' ripeness. The level of expression of the sequences encoding acidic actinidin reached a plateau at this point, while the expression of the sequence encoding basic actinidin appeared to decrease slightly as fruit continued to ripen. The sequences encoding acidic actinidin were expressed during ripening at a much higher level than those encoding basic actinidin. No actinidin mRNA was detected in other tissues except for very low levels of the acidic form in kiwifruit leaf, and low levels of the basic form in senescing petals. A full-length, acidic, actinidin cDNA sequence was introduced into tobacco (Nicotiana tabacum) plants via Agrobacterium tumefaciens-mediated transformation. Using the binary vector pGA643, the sequence was introduced in both the sense and antisense orientation relative to the cauliflower mosaic virus 35S promoter and transgenic plants were obtained for both sequence orientations. The presence of the T-DNA cassette (containing the actinidin sequence) in the plant genomes was determined using PCR analysis, and confirmed by Southern hybridization. A number of the transgenic plants contained multiple insertions of the actinidin sequence, and most plants contained at least one intact copy of the T-DNA cassette. The transcription of the introduced actinidin sequence was investigated by Northern hybridization analysis. All of the plants containing actinidin in the sense orientation, and some of those incorporating the antisense construct, transcribed the actinidin sequence. Attempts to detect actinidin protein in the transgenic plants were unsuccessful. Acidic actinidin was identified as one of the most abundant bands in the total protein profile from ripe kiwifruit fruit tissue. The identity of the protein was confirmed by N-terminal sequence analysis. The electrophoretic mobility of actinidin, both in the total cell homogenate and when partially purified, suggested that the first step in post-translational processing of the zymogen may be the removal of the N-terminal extension. Actinidin was also partially purified and used to raise antibodies. Poor specificity of the antibody for actinidin led to preliminary evidence for the glycosylation of actinidin.

Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of bacterial canker disease of kiwifruit plants worldwide. The steps of the PhD project followed a logical approach, starting the study of the effect of the interactions first in pure cultures of Pseudomonas syringae pv. actinidiae at different densities, then in more complex systems in which Psa was made interact with synthetic molecules, microbial biocoenosis and the host. Intraspecific communication systems in many bacteria rely on signals synthesis and perception as function of cell density and it is often referred to as “quorum-sensing” (QS). Psa displays three QS-signal receptors, but not the signal synthase gene of N-acyl-homoserine lactones (AHLs). Gene expression by qPCR was analysed at different culture densities in order to evaluate potential effects of the intraspecific communication on pathogenicity. It was established that Psa exploited swarming, swimming and twitching motilities and that the addition of AHLs influenced motility but not the biofilm formation nor virulence in vivo. Analysis of gene expression by qPCR supported in vitro results and revealed that very little resulted density-dependent. It was also evaluated the effect of the bacterial cross-talk considering several microbial species. Those bacteria that share with Psa the same environment on kiwifruit plants primed the gene regulation and the phenotypes such as biofilm production and motility, thus indicating that interspecific signalling may occur and play a crucial role during host colonization. Moreover, Psa phenotypic bioassays and relative gene expression quantitation were characterized in Actinidia spp. plant extracts and xylem saps. In the tested conditions, plant material stimulated biofilm formation, motility and virulence, leading also to high levels of gene expression and disease when inocula grown in plant material was used for infections. Four mutants (psaR1-, psaR3-, algD-, Tr-) were also used to investigate the processes occurring during intraspecific, interspecific and interkingdom communications.

Mestrado em Bioquímica - Bioquímica Alimentar
O kiwi é o fruto de uma planta pertencente ao género botânico Actinidia, da família das Actinidiaceae. Apesar das suas propriedades bioativas, o desperdício anual associado à venda e processamento do kiwi é bastante significativo. A actinidina é uma cisteína protease que representa 50% da proteína solúvel do kiwi. O objetivo deste trabalho foi valorizar o kiwi e os seus subprodutos estudando o efeito da actinidina no glúten. A enzima foi extraída em quatro condições distintas e os extratos sujeitos a um estudo de cinética enzimática com azocaseína. A extração que resultou num extrato rico em proteína (rendimento superior a 70%) com elevada atividade enzimática específica (1,31 a 14,59 U/mg de proteína) consistiu num simples salting out da proteína presente no sumo do fruto após homogeneização e centrifugação. A zimografia realizada a pH 3, 6 e 8 mostrou ainda que a enzima é ativa numa vasta gama de pH e permitiu identificar diferentes estados de maturação da enzima (N-preactinidina e actinidina madura). Realizaram-se ensaios preliminares para avaliar o efeito da actinidina no glúten através da análise dos hidrolisados de glúten de elevado e baixo peso molecular, obtidos após incubação da enzima com glúten hidratado e com glúten liofilizado. Os hidrolisados foram analisados por FTIR, tendo-se observado alterações estruturais nas amostras tratadas com actinidina. Estas alterações estruturais foram corroboradas pela alteração do perfil eletroforético dos resíduos obtidos após hidrólise e pela presença de aminoácidos livres nos sobrenadantes. A análise dos hidrolisados obtidos por SDS-PAGE após 1, 2 e 24 horas de incubação do glúten liofilizado com actinidina (25, 50 e 75 μg/mg) mostrou a presença de péptidos com baixo peso molecular (entre 30 e 20 kDa). A incubação durante 24 horas resulta numa hidrólise mais extensa, com formação adicional de péptidos com cerca de 20 kDa. Os resultados obtidos permitiram concluir que os extratos de actinidina tem elevado potencial para aplicação industrial na produção de hidrolisados de glúten, com a vantagem de ser uma metodologia de extração simples e de baixo custo.
Kiwifruit is the fruit of a plant belonging to the genus Actinidia, the family of Actinidiaceae. Despite its bioactive properties, the annual waste associated with fruit commercialization and processing is significant. Actinidin is a cysteine protease which represents 50% of the soluble protein in kiwifruit. The goal of this work was to add value to kiwifruit and its by-products through studying actinidin effect in gluten. The enzyme was extracted in four different conditions and extracts subjected to enzyme kinetics study with azocasein. It was found that the extraction resulting in an extract rich in protein (yield greater than 70%) with high specific enzyme activity (1.31 to 14.59 U/mg protein) is obtained through a simple salting out of the protein present in the fruit juice after homogenization and centrifugation. Zymography carried out at pH 3, 6 and 8 also showed that the enzyme is active over a wide pH range and it was possible to identify the mature and N-preactinidin. Preliminary experiments were performed to evaluate the effect of actinidin on gluten by analysis of the high and low molecular weight gluten hydrolysates, obtained after incubation of the enzyme with hydrated and freeze-dried gluten. The hydrolysates were analysed by FTIR, and it was observed structural changes in the samples treated with actinidin. These structural changes were corroborated with the changes observed in the electrophoretic profile of the residues obtained after hydrolysis, and the presence of free amino acids in the supernatants. Analysis of the supernatants obtained by SDS-PAGE after 1, 2 and 24 hours of incubation of the freeze-dried gluten with actinidin (25, 50 and 75 μg/mg) showed the presence of peptides with lower molecular weight (between 30 and 20 kDa). Incubation for 24 hours results in a more extensive hydrolysis with formation of additional peptides about 20 kDa. The results showed that the actinidin extracts has high potential for industrial application in the production of hydrolysed gluten, with the advantage of a simple and low cost extracting methodology.

Mestrado em Engenharia Agronómica - Hortofruticultura e Viticultura - Instituto Superior de Agronomia - UL
Em Portugal, a cultura da actinídia está maioritariamente distribuída em zonas com invernos amenos, onde se inclui a região da Bairrada. Contudo, para a cultura abrolhar bem, necessita de pelo menos 600 a 800 horas de frio, que nem sempre ocorrem nesta região. Dada a importância da cultura e o número crescente de novas áreas, torna-se importante o estudo de soluções eficazes para a quebra da dormência. Foi então delineado um ensaio experimental, contemplando um conjunto de produtos existentes no mercado para este fim, nomeadamente o BluPrins® e BluAct (M1), o Kiplant HB15 e Kiplant Inducer (M2), o Siberio e Siberion (M3), o Syncron® e NitroActive® (M4), o W-Uniformity Superplus (M5), o Organihum Plus e Organihum B-Plus (M6) e sem aplicação de produtos (M7). No presente ano, em que se registou apenas 198 horas de frio, nenhum dos produtos contribuiu para uma taxa de abrolhamento (p > 0,05). Relativamente aos restantes parâmetros quantitativos, que culminaram na estimativa da produção, foi novamente a testemunha a destacar-se com os melhores resultados (20 t ha-1) e estatisticamente superior ao da modalidade M2 (10 t ha-1) (p <0,05). O mesmo é justificado pela evolução climatológica anormal do presente ano, que conduziu a uma má decisão da data de aplicação dos produtos. Os produtos uma vez aplicados estimularam o abrolhamento, que foi mais tarde interrompido pelas baixas temperaturas do mês de março e meados de abril, levando possivelmente ao aborto dos primórdios florais que se iam diferenciando nesta fase, sobretudo nas modalidades M1, M2, M3 e M4. Com isto, estas modalidades caracterizaram-se por um abrolhamento heterogéneo, como se pode verificar pelo registo dos estados fenológicos, onde são diferenciadas duas fases distintas na evolução do abrolhamento dos gomos
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Les propriétés physicochimiques des actinides (An) en solution restent difficiles à interpréter et plus particulièrement la différence de comportement entre An(III) et Ln(III). L'étude du comportement paramagnétique des cations actinide peut constituer une méthode « simple » et particulièrement intéressante qui permet de sonder les propriétés électroniques de ces éléments et obtenir des informations sur la nature de l'interaction ligand-actinide. L'objectif de ce travail de thèse est d'appréhender les propriétés paramagnétiques de ces éléments par des mesures de susceptibilité magnétique d'une part et l'étude des déplacements chimiques d'autre part.L'apport d'informations sur les propriétés électroniques des ions actinide pour une variété de degrés d'oxydation (+III, +IV, +V et +VI) a été réalisé par des mesures de susceptibilité magnétique en solution selon la méthode d'Evans. Contrairement aux éléments Ln(III), il n'existe aucun modèle spécifique décrivant clairement les propriétés magnétiques de ces ions en solution. L'acquisition de données de bonnes qualités étant nécessaires, l'influence des dispositifs expérimentaux et de la radioactivité de ces éléments a été analysée. Afin de décrire la structure des états électroniques de faible énergie pour ces cations, les résultats expérimentaux ont été confrontés à des calculs de chimie quantique à partir desquels l'influence du champ des ligands a été étudiée. Ces interprétations ont ensuite été appliquées à la variation des propriétés magnétiques des cations actinide lors de la complexation avec les anions chlorure et nitrate. Les informations sur les liaisons ligand-actinide peuvent être déduites de l'étude directe par RMN des déplacements chimiques de complexes d'actinide. En effet, la présence d'un ion paramagnétique au sein d'un complexe induit des modifications spectrales pouvant être séparées en deux composantes. L'une reliée au degré de covalence des liaisons de coordination et l'autre à la structure tridimensionnelle des complexes en solution. Le problème majeur de ce type d'étude réside dans la difficulté de distinguer les deux contributions. Afin de réaliser une telle étude, nous avons choisi de travailler avec les complexes d'actinide de l'acide dipicolinique (DPA). Dans un premier temps, une étude structurale (par DRX monocristal puis EXAFS) a été menée sur ces complexes formés avec les cations actinide aux degrés d'oxydation +III, +IV, +V et +VI pour caractériser avec précision leurs paramètres structuraux. Ensuite, les différentes méthodes de séparation des deux contributions mettant en jeu la spectroscopie RMN et éprouvées lors de l'étude des complexes de lanthanide (III) ont ensuite été appliquées aux éléments actinide. L'étude des déplacements paramagnétiques associée aux calculs de chimie quantique a permis de caractériser les propriétés magnétiques de ces cations. Contrairement aux études réalisées sur les ions Ln(III), une contribution de contact importante participe au déplacement paramagnétique des complexes d'An(III) et d'An(IV). A l'inverse, pour les cations actinyle, le déplacement paramagnétique des signaux RMN 1H est caractérisé par l'absence de contribution de contact. Cette particularité associée à la géométrie de ces ions a permis de caractériser précisément leurs propriétés magnétiques. Une application de ces résultats à l'étude de complexes formés avec le ligand TEDGA a pu être réalisée. Il apparait de cette étude que les informations obtenues par la description du comportement magnétique des actinides apportent une meilleure compréhension des propriétés physicochimiques de ces ions en solution
The physiochemical properties of actinide (An) solutions are still difficult to explain, particularly the behavioral differences between An(III) and Ln(III). The study of actinide paramagnetic behavior may be a “simple” method to analyze the electronic properties of actinide elements and to obtain information on the ligand-actinide interaction. The objective of this PhD thesis is to understand the paramagnetic properties of these elements by magnetic susceptibility measurements and chemical shift studies.Studies on actinide electronic properties at various oxidation states in solution were carried out by magnetic susceptibility measurements in solution according to the Evans method. Unlike Ln(III) elements, there is no specific theory describing the magnetic properties of these ions in solution. To obtain accurate data, the influence of experimental measurement technique and radioactivity of these elements was analyzed. Then, to describe the electronic structure of their low-energy states, the experimental results were complemented with quantum chemical calculations from which the influence of the ligand field was studied. Finally, these interpretations were applied to better understand the variations in the magnetic properties of actinide cations in chloride and nitrate media.Information about ligand-actinide interactions may be determined from an NMR chemical shift study of actinide complexes. Indeed, modifications induced by a paramagnetic complex can be separated into two components. The first component, a Fermi contact contribution (δc) is related to the degree of covalency in coordination bonds with the actinide ions and the second, a dipolar contribution (δpc) is related to the structure of the complex. The paramagnetic induced shift can be used only if we can isolate these two terms. To achieve this study on actinide elements, we chose to work with the complexes of dipicolinic acid (DPA).Firstly, to characterize the geometrical parameters, a structural study (by monocrystal XRD and EXAFS) was performed on these complexes with the actinide cations at various oxidation states +III, +IV, +V et +VI. Secondly, various methods for separating the two contributions involving NMR spectroscopy were checked with Ln(III) complexes and applied to actinide elements. The paramagnetic induced shift associated with quantum chemical calculations allowed us to characterize the magnetic properties of these cations. Unlike studies on Ln(III) ions, the An(III) and An(IV) paramagnetic induced shifts suggest a major Fermi contact contribution (δc). On the contrary, for actinyle cations, the paramagnetic induced shifts on 1H NMR signals show no Fermi contact contribution (δc). This characteristic, related to the geometry of these ions, allowed for their magnetic properties to be accurately described. An application of these results to the study of complexes with the TEDGA ligand has been performed.It is apparent from this study that the additional information gained on the description of actinide paramagnetic behavior has led to an improved understanding of the physiochemical properties of these ions in solution

La contamination des espèces vivantes par les éléments actinides est une source de toxicité radiologique et chimique conduisant à des séquelles graves pour l'organisme contaminé. La plupart des données disponibles sur l'interaction des actinides avec les systèmes biologiques sont basées sur des mesures macroscopiques physiologiques et fournissent très peu d'informations structurales et mécanistiques. Du fait de la complexité des systèmes impliqués dans ces processus, il est difficile de décrire la formation des complexes par des méthodes de biochimie. Notre stratégie a donc été d'approcher cette question par des systèmes biomimétiques très simplifiés que sont les peptides, en étudiant les mécanismes intramoléculaires affectés ou induits par l'interaction cation – ligand. Un pentapeptide carboxylique Ac-DDPDD-NH2 nous a servi de molécule de référence et de point de départ pour évaluer l'influence de la nature du peptide sur la topologie des complexes correspondants. Pour ce faire, différents analogues linéaires (permutations Asp/Ala, peptoïdes) et cycliques ont été synthétisés. De plus, dans le but d'incorporer des fonctions hydroxamates (très affines du Fe(III)) dans le pentapetide de référence, l'étude de la desferrioxamine et de l'acide acetohydroxamique a également été entreprise. Cependant, des difficultés de synthèse ne nous ont pas permis de tester ces dérivés. Trois cations actinides au degré d'oxydation +IV ont été sélectionnés (Th, Np, Pu) et comparés au cation Fe(III) souvent considéré comme analogue biologique du Pu(IV). L'agencement spatial du ligand autour du cation dans les complexes en solution aqueuse tamponnée a été étudié par spectrophotométrie et par Spectroscopie d'Absorption des rayons X. Les données spectroscopiques et l'ajustement des spectres EXAFS nous ont permis de rationaliser la topologie des complexes formés en fonction du peptide considéré : complexes mixtes hydroxy polynucléaires pour les séquences linéaires et cycliques, complexes mononucléaires pour la desferrioxamine. D'autre part, des différences notables sont apparues entre le Fe(III) et les actinides(IV), ce qui traduit une différence de réactivité en solution aqueuse
The contamination of living organisms by actinide elements is at the origin of both radiological and chemical toxicity that may lead to severe dysfunction. Most of the data available on the actinide interaction with biological systems are macroscopic physiological measurements and are lacking a molecular description of the systems. Because of the intricacy of these systems, classical biochemical methods are difficult to implement. Our strategy consisted in designing simplified biomimetic peptides, and describing the corresponding intramolecular interactions with actinides. A carboxylic pentapeptide of the form DDPDD has been at the starting point of this work in order to further assess the influence of the peptide sequence on the topology of the complexes. To do so, various linear (Asp/Ala permutations, peptoïds) and cyclic analogues have been synthesized. Furthermore, in order to include the hydroxamic function (with a high affinity for Fe(III)) in the peptide, both desferrioxamine and acetohydroxamic acid have been investigated. However because of difficulties in synthesis, we have not been able to test these peptides. Three actinide cations have been considered at oxidation state +IV (Th, Np, Pu) and compared to Fe(III), often considered as a biological surrogate of Pu(IV). The spatial arrangement of the peptide around the cation has been probed by spectrophotometry and X-ray Absorption Spectroscopy. The spectroscopic data and EXAFS data adjustment lead us to rationalize the topology of the complexes as a function of the peptide sequence : mix hydroxy polynuclear species for linear and cyclic peptides, mononuclear for the desferrioxamine complexes. Furthermore, significant differences have appeared between Fe(III) and actinide(IV), related to differences of reactivity in aqueous medium

Les oxydes d’actinides sont des matériaux hygroscopiques. L’adsorption de l’eau à leurs surfaces est susceptible d’entrainer des modifications quant à la nature ou à son état. Dans le cas des oxydes à fort débit de dose, vient s’ajouter les effets de radiolyse de l’eau, entrainant sa décomposition et générant du dihydrogène. Ces deux aspects, étude de surface et radiolyse de l’eau, ont été étudiés ici. L’étude de la génération de dihydrogène par radiolyse de l’eau adsorbée à la surface a montré que cette génération linéaire dans les premiers temps atteint une concentration stable au bout de plusieurs heures. Cet état stationnaire a été très peu observé, et est absent dans le cas d’humidité importante. Un conditionnement dans une atmosphère contenant du dihydrogène a permis de mettre en lumière une réaction de consommation du dihydrogène par le matériau. Ces expériences ont permis de faire émerger un modèle cinétique basé sur deux réactions de production et de consommation de dihydrogène. La première correspond à la décomposition de l’eau sous l’effet du rayonnement, et pour la seconde il est suspecté une réduction partielle de la surface avec la formation d’une phase sous-stœchiométrique en surface. Cependant, aucune technique d’analyse de surface n’a permis de mettre en évidence formellement cette phase. La chromatographie gazeuse inverse est une technique peu intrusive vis-à-vis des couches d’eau adsorbée du fait des températures et des pressions mis en jeux et de l’absence de dépôt d’énergie. Cette technique a été employée sur des oxydes de thorium et d’uranium. Sur oxyde de thorium, il en résulte un impact de la température de calcination, avec un maximum d’énergie de surface pour une calcination à 650°C. Par ailleurs, il a été montré que la préparation du dioxyde de thorium pouvait impacter l’état de sa surface. En effet, il a été observé une déshydratation de l’oxalate de thorium au fil du temps, impactant la structure de ce dernier. Cette modification se répercute sur la surface de l’oxyde final par une chute de l’énergie de surface et par une modification sur la répartition des sites d’adsorption en surface. Néanmoins un traitement chimique de l’oxalate permet de retrouver la réactivité de surface et une distribution des sites d’adsorption. L’hydratation de la surface montre une augmentation de l’énergie de surface, mais cette augmentation n’est observée que pour des hydratations de longues durées
Actinide oxides are hygroscopic materials. The adsorption of water on their surfaces is likely to cause changes in the nature or condition. In the case of oxides with a high dose rate, the effects of radiolysis of the water causes the decomposition of water and generates hydrogen. These two aspects: surface study and radiolysis of water have been studied here.The study of the generation of dihydrogen by radiolysis of water adsorbed on the surface has shown that this linear generation in the early stages reaches a stable concentration after several hours. This stationary state has been very little observed, and is absent in the case of significant humidity. Conditioning in a dihydrogen-containing atmosphere made it possible to highlight a reaction of consumption of dihydrogen by the material. These experiments led to the emergence of a kinetic model based on two reactions of production and consumption of dihydrogen. The first corresponds to the decomposition of the water under the effect of the radiation, and for the second it is suspected a partial reduction of the surface with the formation of a sub-stoichiometric phase on the surface, however no technique of analysis of surface has not formally highlighted this phase.Inverse gas chromatography is a technique that is not very intrusive with respect to the adsorbed water layers because of the temperatures and pressures involved and the absence of energy deposition. This technique has been used on oxides of thorium and uranium. On thorium oxide, this results in an impact of the calcination temperature, with a maximum of surface energy for calcination at 650 ° C. In addition, it has been shown that the preparation of thorium dioxide can impact the state of its surface. Indeed, it has been observed dehydration of thorium oxalate over time, impacting the structure of the latter. This modification affects the surface of the final oxide by a drop-in surface energy and a change in the distribution of surface adsorption sites. Nevertheless, a chemical treatment of oxalate makes it possible to recover the surface reactivity and a distribution of the adsorption sites. The hydration of the surface shows an increase in surface energy, but this increase is observed only for hydrations of long duration.Keywords: water sorption, radiolysis, plutonium, inverse gas chromatography, thorium, uranium

Le frittage est une étape clé de l’élaboration des pastilles de combustible nucléaire de type UOx et MOx (oxyde mixte (U,Pu)O2) utilisées dans les réacteurs à eau pressurisée. Le premier stade de ce procédé, qui consiste en l’élaboration de ponts entre les grains et conduit à la consolidation des matériaux, est jusqu’à présent principalement abordé par simulation numérique. Les modèles utilisés pour la description théorique de cette étape du frittage sont alors généralement constitués deux grains sphériques en contact. Afin de réaliser les premières observations expérimentales du stade initial du frittage de matériaux céramiques d’intérêt pour le cycle du combustible électronucléaire et d’en compléter les approches numériques, des poudres d’oxydes de lanthanides (CeO2) et d’actinides (ThO2 et d’UO2) de morphologie contrôlée ont été étudiées par microscopie électronique à balayage en mode environnemental lors de traitements thermiques à haute température (MEBE-HT).Dans un premier temps, des protocoles conduisant à la synthèse de microsphères d’oxydes de lanthanides ou d’actinides ont été développés, et les poudres obtenues entièrement caractérisées. Il a ainsi été possible d’obtenir pour l’ensemble des composés étudiés des systèmes similaires à ceux modélisés. Par la suite, le MEBE-HT a été utilisé comme principal outil d’investigation pour le suivi in situ de ces composés. Ainsi, l’étude de l’évolution morphologique de microsphères isolées a tout d’abord confirmé leur caractère polycristallin. Le traitement thermique conduit alors à une diminution progressive du nombre de cristallites sous l’effet de différents mécanismes (réarrangement mécanique, diffusion) dont l’énergie d’activation a été évaluée. Pour les systèmes constitués de deux microsphères de CeO2 ou de ThO2 en contact, les micrographies collectées ont permis d’observer l’évolution de paramètres tels que la taille du pont, la taille des grains et la distance entre leur centre au cours du traitement thermique. Des procédures de traitement d’images ont ensuite été appliquées pour aboutir à des données cinétiques quantitatives. Les mécanismes mis en jeu, tels que le réarrangement des plans cristallins et la diffusion de matière, ainsi que les énergies d’activation correspondantes, ont en outre été identifiés. De plus, la loi de croissance des ponts, qui permet de décrire les cinétiques d’avancement du frittage, a été utilisée pour déterminer le mécanisme de diffusion prépondérant lors du traitement thermique. L’influence de différents paramètres sur l’avancement du frittage a enfin pu être mise en évidence. A titre d’exemple, l’effet de la polycristallinité des grains sur les mécanismes et les cinétiques de frittage a été étudié en travaillant en parallèle sur des grains poly- et monocristallins, puis en comparant les données expérimentales avec celles issues de modélisation. Enfin, la méthodologie développée pour l’étude de CeO2 et ThO2 a été transposée au composé d’intérêt UO2. Dans ce cas, les données précédemment décrites ont également été complétées par une première approche de l’influence de l’atmosphère utilisée lors du traitement thermique
Sintering is a key step in the elaboration of UOx and MOx (U/Pu mixed oxide) nuclear fuels pellets used in the pressurized water reactors. The first step of this process, which consists in the elaboration of a neck between the grains and led to the consolidation of the material, is generally described through numerical simulation. The models used for the theoretical description of this step are generally constituted by two spherical grains in contact. In order to perform the first experimental observations of the initial stage of sintering of ceramics materials of interest for electronuclear fuel cycle and to complement the numerical approaches, samples of lanthanide (CeO2) and actinides (ThO2 and UO2) dioxides with controlled morphology were examined by environmental scanning electron microscopy during heat treatment at high temperature (HT-ESEM).First, the protocols leading to the synthesis of lanthanides and actinides oxides microspheres were developed, and the powders obtained characterized. It was thus possible to obtain, for all the compounds studied, systems similar to those generally modeled. HT-ESEM was then used as the main investigation tool for the in situ study of the first stage of sintering of these compounds. The study of the morphological modifications occurring in isolated microspheres first confirmed their polycristalline character. Indeed, heat treatment led to a progressive decrease of the crystallites number included inside the grains through different mechanisms (oriented attachment, diffusion), whose activation energy was evaluated. For the systems constituted by two CeO2 or ThO2 microspheres in contact, the ESEM micrographs allowed to observe the evolution of several parameters during heat treatment, such as neck size and grain size as well as distance between the grains center. Images processing methods using custom software were then applied in order to determine the quantitative kinetic data. The mechanisms involved, such as the rearrangement of crystalline planes and the matter diffusion, and the corresponding activation energies, were also identified. Furthermore, the law of neck growth, which allows one to describe the evolution of sintering degree, was used to determine the prevailing diffusion mechanism during heat treatment. The influence of various parameters on the sintering degree was also highlighted. For example, the influence of grains polycristallinity on sintering mechanisms and kinetics was particularly investigated study by working in parallel with polycristalline and single crystal grains, then by comparing the experimental results with data coming from modeling. Finally, the methodology developed for the study of CeO2 and ThO2 was transposed to the compound of interest UO2. In this case, the data previously described were complemented by a first approach of the influence of atmosphere used during the heat treatment

Actinidia chinensis, a diploid relative of kiwifruit, has valuable fruit characteristics, and varieties with superior flavour and marketable size have recently been selected in a classical breeding programme. However, the marketability of the fruit of A. chinensis and many other species of Actinidia is limited by poor fruit storage properties. Pioneering work in tomato has demonstrated that fruit ripening and senescence can be very effectively delayed by down-regulating genes required for biosynthesis of the phytohormone ethylene. The goal of this work was to isolate genes for ethylene biosynthesis in A. chinensis, characterise their expression, and to generate transgenic plants containing T-DNA constructs designed for ethylene downregulation. A small cDNA library was constructed from RNA isolated from the ripe fruit of A. chinensis. The library was screened for genes encoding each of the enzymes in the ethylene biosynthetic pathway, by probing with PCR products amplified from kiwifruit cDNA and with a cDNA clone previously isolated from kiwifruit. Three distinct cDNA clones encoding S-adenosyl-L-methionine (SAM) synthetase (ACSAM1, ACSAM2 and ACSAM3) were isolated from the library, together with two distinct 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase cDNA clones (ACAO1 and ACAO2). No ACC synthase cDNAs were detected in the library, indicating low transcript abundance. However, a partial ACC synthase cDNA (ACAS1) was amplified from ripe fruit using PCR techniques, and subsequently cloned in a plasmid vector. Phylogenetic analysis of SAM synthetase protein sequences from A. chinensis and other plant species indicates bifurcation of angiosperm SAM synthetase sequences into two main branches; ACSAM3 was assigned to a different branch from ACSAM1 and ACSAM2. The peptide sequence of ACAS1 shows higher homology to several auxin-inducible ACC synthase peptides than the product of the ethylene-inducible ACC synthase gene which is predominantly transcribed in ripening tomato fruit. RNAse protection assays were employed to estimate the relative transcript levels of each of the ethylene biosynthetic genes isolated from A. chinensis during ethylene-induced, post-harvest fruit ripening, and in immature fruit and floral samples. The response of the mature fruit to exogenous ethylene indicated a clear separation of ethylene sensitivity and ethylene production in A. chinensis. The application of exogenous ethylene correlated with increased transcript levels for all three SAM synthetase genes (ACSAM1, ACSAM2 and ACSAM3) and for the ACC oxidase gene family. Transcription of the ACC synthase gene ACAS1 was not affected by exogenous ethylene, but transcript levels increased during subsequent ethylene biosynthesis, consistent with this being a controlling step for the onset of ethylene production. One or more ACC oxidase transcripts increased significantly both prior to and during ethylene production. Only one of the SAM synthetase transcripts (ACSAM3) was induced during the late ethylene burst, and these transcripts were also abundant in floral tissues and young fruit. A role for SAM synthetase genes in the methionine salvage pathway is discussed. The expression patterns for ACAS1 and the ACC oxidase gene family arc consistent with the consensus view that the rate of ethylene biosynthesis in plant tissues is dependent on both ACC synthase and ACC oxidase activity levels. Therefore, with the aim of down-regulating ethylene biosynthesis in A. chinensis, expression cassettes containing ACAS1 and ACAO1 cDNAs, each controlled by a d35S promoter, were inserted in tandem into the Agrobacterium binary vector pCGN1549, in both the sense and antisense orientations. Leaf tissue from the ‘Earligold’ variety of A. chinensis was transformed with the resulting binary vectors, and transgenic plants were regenerated. PCR and Southern analysis indicated intact T-DNAs were integrated in at least half of the transformed plants, and Northern analysis detected mRNAs from one of the transgenes transcribed from both the sense and antisense constructs. No decrease in wound-induced ethylene biosynthesis was detected in the leaves of a small sample of these transgenic plants, and a larger number of transformants are now being grown for phenotypic screening. Down-regulation of ethylene biosynthesis may improve the storage properties and/or the shelf life of transgenic A. chinensis plants and may provide insights into the roles of ethylene in fruit ripening.
Appendix 1 restricted at the request of the author

Die Endlagerung von radioaktivem Abfall ist eine der vordringlichsten Aufgaben auf dem Gebiet der Kerntechnik. Als Teil der Sicherheitsanforderungen steht dabei der Schutz von Mensch und Umwelt vor den Gefahren der radioaktiven Stoffe selbst im Falle einer Freisetzung dieser Stoffe aus dem Endlager im Vordergrund. Als Basis für Langzeitsicherheitsanalysen dienen Modellierungen. Für diese sind umfassende Kenntnisse der chemisch-physikalischen Effekte und Einflüsse, die eine Mobilisierung und den Transport der Actiniden bewirken können, erforderlich. Diese Arbeit war ein eigenständiger Teil eines Projektes, welches sich mit der Aufklärung des Einflusses von Mikroorganismen auf die Ausbreitung von Actiniden bei einer Freisetzung dieser aus dem Endlager beschäftigt. Dabei wurde der Einfluss von mikrobiell produzierten Substanzen auf die Mobilisierung ausgewählter Actiniden untersucht. Die in diesem Projekt untersuchten mikrobiell produzierten Substanzen, sogenannte Bioliganden, wurden von Bakterien des Genus Pseudomonas unter speziellen Bedingungen produziert. Die von den Pseudomonaden freigesetzten Bioliganden, hier Siderophore vom Pyoverdin-Typ, haben ein hohes Potential, Metalle, insbesondere Eisen(III), zu komplexieren und so zu transportieren. Es wurde untersucht, in welcher Weise und unter welchen Bedingungen diese Bioliganden in der Lage sind, auch radioaktive Schadstoffe zu komplexieren und damit zu mobilisieren. Für die Untersuchungen wurden die α-strahlenden Actiniden Uran, Curium und Neptunium ausgewählt, weil diese auf Grund ihrer Langlebigkeit und Radiotoxizität von besonderem Interesse sind. Diese Arbeit beschäftigte sich mit der Wechselwirkung der Actiniden U(VI), Np(V) und Cm(III) mit Modellliganden, die die Funktionalitäten der Pyoverdine simulieren. Für die Metallbindung der Pyoverdine sind die Katecholgruppe des Chromophors und die funktionellen Gruppen der Peptidkette (Hydroxamsäuregruppen und α-Hydroxysäurereste) verantwortlich. Für die Simulation der Hydroxamsäuregruppen kamen dabei die Monohydroxamate Salicylhydroxamsäure (SHA) und Benzohydroxamsäure (BHA) und das natürliche Trihydroxamat Desferrioxamin B (DFO) zum Einsatz und für die Katecholgruppe das 6-Hydroxychinolin (6HQ) und 2,3-Dihydroxynaphthalin (NAP). Als Vergleichsligand wurde außerdem Benzoesäure (BA) untersucht. Für die Bestimmung der Stabilitätskonstanten zur Einschätzung der Stärke der gebildeten Komplexe, die Aufklärung der Struktur der Actinid-Ligand-Verbindungen und die Verfolgung der Änderung der Speziation der Actiniden vor und nach der Wechselwirkung mit den Modellliganden kamen verschiedene spektroskopische Verfahren wie Absorptionsspektroskopie, Laserfluoreszenzspektroskopie, Röntgenabsorptionsspektroskopie und Schwingungsspektroskopie zum Einsatz. Außerdem wurden erstmals theoretische Modellierungen zur Aufklärung der Struktur der Actinid-Modellligand-Komplexe durchgeführt. Die Ziele dieser Arbeit waren also die spektroskopische Charakterisierung und Bestimmung der Speziation und Komplexbildungskonstanten sowohl der ausgewählten Modellliganden als auch der gebildeten Actinid-Modellligand-Komplexe, die Aufklärung möglicher Strukturen der Komplexe sowie ein Vergleich der Ergebnisse mit denen der Pyoverdine. Der Vergleich der Stabilitätskonstanten der untersuchten Liganden mit den drei Actiniden U(VI), Cm(III) und Np(V) ergab im Wesentlichen folgende Reihenfolge der Komplexstärke: PYO ≥ DFO &gt; NAP &gt; 6HQ &gt; SHA ≥ BHA &gt; BA. Benzoesäure (hier wurde nur die Komplexbildung mit U(VI) untersucht) besitzt als einziger Ligand eine Carboxylfunktionalität und weist mit 103 die geringste Stabilitätskonstante auf. Die beiden Monohydroxamate SHA und BHA bilden mit allen drei Actiniden ähnlich starke 1:1-Komplexe. Bei den 1:2-Komplexen besitzt SHA mit Cm(III) und Np(V) etwas höhere Stabilitätskonstanten als BHA, wahrscheinlich verursacht durch einen stabilisierenden Einfluss der zusätzlichen phenolischen OH-Gruppe. Dieser Trend wurde auch in den theoretischen Modellierungen für die U(VI)-Komplexe beobachtet. Die natürlichen Siderophore DFO und PYO bilden die stärksten Komplexe mit den Actiniden (Stabilitätskonstanten von 1012 bis 1034). Dies liegt in der Struktur und der hohen Anzahl an funktionellen Gruppen begründet; DFO besitzt drei Hydroxamatgruppen, das Pyoverdinmolekül neben den Hydroxamatgruppen noch die Katecholgruppen der Chromophorfunktionalität. Die Modellliganden für die Chromophorfunktionalität, NAP und 6HQ, bilden stärkere Komplexe als die Monohydroxamate SHA und BHA, aber schwächere Komplexe als DFO und PYO. Daraus lässt sich schlussfolgern, dass die Chromophorfunktionalität eine wichtige Rolle bei der Anbindung der Actiniden an die Pyoverdine spielt. Der Vergleich der Stabilitätskonstanten der Komplexe der Liganden SHA, BHA und 6HQ mit den drei untersuchten Actiniden U(VI), Cm(III) und Np(V) untereinander zeigte, dass die Stärke der Komplexe von U(VI) über Cm(III) zu Np(V) abnimmt. Der Grund dafür liegt in den unterschiedlichen Ladungsdichten der Actinidionen. Während das UO2 2+-Ion mit einer Koordinationszahl von 5 und einem Ionenradius von ~ 0.6 eine effektive Ladung von + 3.3 besitzt, hat das Cm3+-Ion eine effektive Ladung von + 2.6 und das NpO2+-Ion von + 2.3. Damit besitzt das NpO2+-Ion die geringste Ladungsdichte der untersuchten Actinidionen und bildet damit auch die schwächsten Komplexe mit den niedrigsten Stabilitätskonstanten. Die Stärke der Komplexe der Liganden NAP, DFO und PYO nimmt von Cm(III) über U(VI) zu Np(V) ab. Obwohl Cm(III) eine geringere effektive Ladung als U(VI) hat, bildet es stärkere Komplexe als U(VI). Eventuell sind dafür strukturelle Behinderungen der Koordination durch die lineare O=U=O Einheit verantwortlich. Die Struktur der wässrigen U(VI)-Komplexe wurde mittels EXAFS-Spektroskopie und ATRFTIR-Spektroskopie untersucht. Aus den EXAFS-Spektren ließ sich schließen, dass die Koordination des Uranylions an die Hydroxamsäuregruppen der Liganden SHA, BHA und DFO eine Verkürzung des Abstandes der äquatorialen Sauerstoffatome zur Folge hat. Im Gegensatz dazu resultiert eine Koordination des Uranylions an die Carboxylgruppe des Liganden BA in einer Verlängerung des U-Oäq Abstandes. Die Ergebnisse des NAP als Modellligand für die Chromophorfunktionalität des Pyoverdins und die Ergebnisse des Pyoverdins selbst zeigten, dass das Uranylion mit großer Wahrscheinlichkeit an die katecholischen OH-Gruppen der Chromophorfunktionalität des Pyoverdinmoleküls gebunden ist. In den Spektren der ATR-FTIR-Spektroskopie ist besonders der Bereich um die Schwingungsbande des Uranylions (961 cm-1) für die Beobachtung der Komplexbildung interessant. Dabei zeigte sich im U(VI)-BHA- und U(VI)-SHA-System eine Mischung aus zwei Komplexen mit 1:1- und 1:2-Stöchiometrie, die auch durch Speziationsrechnungen nachgewiesen werden konnten. Außerdem ließ sich anhand der Schwingungsbanden des Liganden feststellen, dass die Hydroxamsäuregruppe von SHA und BHA während der Komplexierung deprotoniert und direkt an der Komplexbildung beteiligt ist. Im Falle von SHA konnte weiterhin nachgewiesen werden, dass die phenolische OH-Gruppe bei den untersuchten pH-Werten nicht deprotoniert ist. Die pH-abhängigen Spektren des U(VI)-DFOSystems zeigten bei pH 3 die Bildung eines 1:1-Komplexes ähnlich dem der Monohydroxamate, bei Erhöhung des pH-Wertes bis pH 4 dann die Bildung eines 1:1- Komplexes, bei dem das Uranylion an zwei Hydroxamsäuregruppen gebunden ist. Dies stützt die Annahme einer 112-Stöchiometrie des Komplexes, die bei den anderen verwendeten experimentellen Methoden getätigt wurde. Durch Ausfällung aus wässrigen U(VI)-SHA- und U(VI)-BHA-Lösungen wurden Feststoffe der U(VI)-Komplexe hergestellt. Die Struktur dieser ausgefällten, pulverförmigen Feststoffe wurde mittels EXAFS, XRD und FTIR untersucht. Die Untersuchung der ausgefällten Feststoffe ergab, dass die Feststoffkomplexe mit sehr hoher Wahrscheinlichkeit den in Lösung gefundenen Komplexen mit 1:2-Stöchiometrie entsprechen. Der Vergleich der Uran und Kohlenstoffgehalte der Feststoffe mit den in der Literatur beschriebenen Uranverbindungen (zur gravimetrischen Bestimmung von Urangehalten) zeigte übereinstimmende Werte. In den FTIR-Messungen wurden Banden bei 916 cm-1 beobachtet, die denen in der Lösung dem 1:2-Komplex zugeordneten Banden entsprechen. Die Ergebnisse der EXAFS-Messungen deuten auf eine unterschiedliche Nahordnung des U(VI) im Feststoff und in der Lösung hin. So ergab der Vergleich der Strukturparameter der Hydroxamat- Feststoffe mit den U(VI)-Hydroxamat-Komplexen in Lösung deutliche Unterschiede zwischen den Feststoffkomplexen und denen in Lösung. So ist in wässriger Lösung der Abstand der äquatorialen Sauerstoffatome mit 2.41 Å signifikant kürzer als der der Feststoffkomplexe mit 2.47 Å (SHA) und 2.44 Å (BHA). Die röntgendiffraktogrammischen Messungen der Festphasen ergaben reflexreiche Spektren mit signifikanten Peaks, die sich allerdings keinen bekannten U(VI)-Festphasen zuordnen ließen. In einer Kooperation mit dem Institut für Theoretische Chemie der Universität zu Köln wurden für die 1:1- und 1:2-Komplexe der wässrigen U(VI)-SHA-, U(VI)-BHA- und U(VI)-BA-Systeme erstmals theoretische Modellierungen durchgeführt. Dabei wurden die Strukturen der Komplexe sowohl in der Gasphase als auch unter Berücksichtigung der Solvatation optimiert und die relativen Stabilitäten und Anregungsspektren berechnet. Die mit DFT berechneten Bindungsenergien bestätigen die experimentell anhand der Stabilitätskonstanten log β ermittelte Reihenfolge der Komplexstabilitäten (SHA ≥ BHA &gt; BA). Außerdem zeigen die höheren Bindungsenergien der 1:2-Komplexe, dass diese stabiler sind als die 1:1-Komplexe. Dies lässt sich auch anhand der experimentell ermittelten Stabilitätskonstanten nachweisen. Die Maxima der mit TD-DFT berechneten Anregungsspektren weichen um 0.4 ± 0.2 eV von den experimentellen UV-Vis Spektren ab. Dies zeigt die gute Übereinstimmung der berechneten Anregungsspektren mit den gemessenen UV-Vis Spektren. Für den 1:1-Komplex des U(VI)-SHA-Systems konnte mit Hilfe der theoretischen Modellierung die strukturelle Anbindung des Uranylions an die Hydroxamsäuregruppe aufgeklärt werden. Der Vergleich der berechneten Strukturen, Bindungsenergien, Bindungslängen und Anregungsspektren der beiden möglichen Anbindungsmodi [O,O] und [N,O’] zeigte deutlich, dass das Uranylion bevorzugt über die beiden Sauerstoffatome der Hydroxamsäuregruppe, also den [O,O]-Modus, gebunden wird. Die Methode der DFT konnte also dazu beitragen, Defizite in der experimentellen Aufklärung der Komplexstruktur im Fall des U(VI)-SHA-Systems zu beheben. Die Modellliganden und deren Komplexe mit U(VI), Cm(III) und Np(V) wurden zum größten Teil erstmals spektroskopisch charakterisiert sowie deren bisher weitgehend unbekannten Stabilitätskonstanten bestimmt. Außerdem konnte die Struktur der U(VI)-Hydroxamat- Komplexe mit Hilfe der ATR-FTIR-Spektroskopie und der theoretischen Modellierung aufgeklärt werden. Im Vergleich der Ergebnisse der Modellliganden mit denen der Pyoverdine konnte festgestellt werden, dass die Katecholfunktionalität der Pyoverdine eine große Rolle bei der Komplexierung mit den Actiniden spielen wird. Weiterhin ließen sich aus den Ergebnissen Schlussfolgerungen zur Stärke der gebildeten Actinid-Modellligand- und Actinid-Pyoverdin-Komplexe ziehen. Die Pyoverdine bildeten mit U(VI) Komplexe mit Stabilitätskonstanten bis 1030, mit Cm(III) bis 1032 und mit Np(V) bis 1020. Die wichtigsten, in höheren Konzentrationen vorkommenden anorganischen Komplexbildner in natürlichen Wässern sind das Hydroxidion OH- sowie das Carbonation CO32-. Diese besitzen eine hohe Komplexierungsfähigkeit und bilden mit den drei Actiniden U(VI), Cm(III) und Np(V) Komplexe mit Stabilitätskonstanten von 102 bis 1020. Der Vergleich der Konstanten von OH und CO32- mit denen der organischen, mikrobiellen Pyoverdin-Liganden zeigt, dass die Pyoverdine ähnlich starke bzw. teilweise stärkere Komplexe mit den Actiniden bilden als die anorganischen Komplexbildner. Daraus lässt sich ableiten, dass die Pyoverdine selbst in niedrigeren Konzentrationen ein hohes Potential besitzen, Actiniden in natürlichen Wässern zu binden und damit zu transportieren. Die untersuchten Bioliganden sind also in der Lage, bei Anwesenheit in der Natur in bestimmten Konzentrationen im Grundwasser Actiniden, z.B. durch Herauslösen aus Festphasen, zu mobilisieren. Damit können solche Bioliganden das Verhalten der Actiniden in der Umwelt entscheidend beeinflussen. Die Ergebnisse dieser Arbeit tragen dazu bei, den Einfluss der mikrobiellen Liganden auf die Mobilisierung und Ausbreitung der Actiniden besser einschätzen zu können. Damit können die Ergebnisse zur Quantifizierung des Mobilisierungseffekts der Actiniden durch freigesetzte Bioliganden im Nahfeld genutzt werden
One of the urgent tasks in the field of nuclear technology is the final storage of radioactive substances. As a part of the safety requirements the protection of humans and the environment from the danger of radioactive substances in case of the release from the final storage is essential. For performing long-term safety calculations the detailed understanding of the physico-chemical effects and influences which cause the mobilisation and transport of actinides are necessary. The presented work was a discrete part of a project, which was focused on the clarification of the influence of microorganisms on the migration of actinides in case of the release of actinides from a final storage. The influence of microbial produced substances on the mobilisation of selected actinides was studied thereby. The microbial produced substances studied in this project were synthesized by bacteria from the Pseudomonas genus under special conditions. Fluorescent Pseudomonads secrete bacterial pyoverdin-type siderophores with a high potential to complex and transport metals, especially iron(III). The aim of the project was to determine how and under which conditions the bioligands are able to complex also radioactive substances and therefore to transport them. For this work the alpha-emitting actinides uranium, curium and neptunium were chosen because their long-life cycle and their radiotoxicity are a matter of particular interest. This work dealed with the interaction of the actinides U(VI), Np(V) and Cm(III) with model ligands simulating the functionality of the pyoverdins. The functional groups that participate in the metal binding of the pyoverdins are the catechol group of the chromophore and the ligand sites in the peptide chain, i.e. the hydroxamate groups and the α-hydroxy acid moieties. For the simulation of the hydroxamate functionality the monohydroxamates salicylhydroxamic acid (SHA) and benzohydroxamic acid (BHA) and the natural trihydroxamate desferrioxamine B (DFO) and for the simulation of the catechol groups 6-hydroxyquinoline (6HQ) and 2,3-dihydroxynaphthalene (NAP) were used. A further ligand with carboxyl functionality, benzoic acid (BA), was used as a comparison. Absorption spectroscopy, laser fluorescence spectroscopy, X-ray absorption spectroscopy and vibrational spectroscopy were applied for the determination of the stability constants to assess the strength of the formed actinide-model ligand-complexes, for the clarification of the structures of the formed complexes and to observe the variation of the speciation of the actinides during the interaction with the ligands. Furthermore, for the first time density functional theory (DFT) calculations were performed to determine the molecular structure of the actinide-modelligand-complexes. Thus, the objectives of this work were the determination of the spectroscopic properties, speciation and stability constants of the model ligands and the formed actinide-model ligand-complexes, the clarification of the complex structures and a comparison of the results with those of the pyoverdins. The comparison of the stability constants of the studied ligands with the three actinides U(VI), Cm(III) and Np(V) systems results mainly in the following order of complex strength: PYO ≥ DFO &gt; NAP &gt; 6HQ &gt; SHA ≥ BHA &gt; BA. Benzoic acid, the ligand with the carboxyl functionality, has the lowest stability constant of 103. Both monohydroxamates, SHA and BHA, form 1:1 complexes with similar stability. The stability constants of the 1:2 complexes of SHA with Cm(III) and Np(V) are slightly higher than those of BHA, which is probably caused by a stabilizing effect of the additional phenolic OH-group of SHA. This behaviour was also found in the theoretical calculations of the U(VI)-complexes. The natural siderophores DFO and PYO have the highest stability constants with U(VI) and form the strongest complexes (constants from 1012 to 1034). The reason therefore is the structure and high number of functional groups of these ligands; DFO has three hydroxamate groups, the pyoverdin molecule has the catechol groups of the chromophore functionality in addition to the hydroxamate groups. The model ligands for the chromophore functionality, NAP and 6HQ, form stronger complexes than SHA and BHA, but weaker complexes than DFO and PYO. From this it can be reasoned that the chromophore functionality probably plays an important role for the coordination of the actinides to the pyoverdins. The comparison of the stability constants of the complexes of the ligands SHA, BHA and 6HQ with the studied actinides U(VI), Cm(III) and Np(V) shows that the strength of the complex formation decreases from U(VI) via Cm(III) to Np(V). The reason therefore is the different charge density of the actinide ions. The UO22+-ion has an effective charge of + 3.3 (with a coordination number of 5 and an ionic radius of ~ 0.6), the Cm3+-ion of + 2.6 and the NpO2+-ion of + 2.3. Therefore, the neptunyl ion has the lowest charge density of the studied actinide ions and on account of this it forms the weakest complexes with the lowest stability constants. The strength of the complex formation of the ligands NAP, DFO and PYO decreases from Cm(III) via U(VI) to Np(V). Cm(III) forms stronger complexes than U(VI) although Cm(III) has a lower effective charge. The reason therefore could be a possible structural hampering of the coordination through the linear O=U=O unit. The structure of the aqueous U(VI)-complexes was studied using EXAFS spectroscopy and FTIR spectroscopy. From the results of the EXAFS spectra one can conclude that the coordination of the uranyl ion to the hydroxamic acid groups of the SHA, BHA and DFO ligands results in a shortening of the distance of the equatorial oxygen atoms. In contrast to this the coordination of the uranyl ion to the carboxyl group of BA yields in a longer U-Oeq bond length. From the findings of the EXAFS studies with NAP and pyoverdin one can conclude a strong affinity of U(VI) to the catechol functionality of the pyoverdin molecule. For the observation of the complexation in the ATR-FTIR spectra the region around the vibration band of the uranyl ion (916 cm-1) is interesting to observe. In the spectra of the U(VI)-BHA- and U(VI)-SHA-system a mixture of two complexes with 1:1 and 1:2 stoichiometry was observed, which was also existing in the speciation. Furthermore, on the basis of the vibration bands of the ligands it could be ascertained that the hydroxamate groups of SHA and BHA are deprotonated and directly involved in the complexation. Also, in case of SHA it could be verified that the phenolic OH-group is protonated at the investigated pH values. At pH 3 the pH dependent spectra of the U(VI)-DFO-system showed the formation of a 1:1 complex similar to those of the monohydroxamates. With increasing pH up to 4 the formation of a 1:1 complex was observed, in which the uranyl ion is bound to two hydroxamic acid groups. This underlines the assumption that the complex had a 112-stoichiometry, which was concluded on the basis of the other used experimental methods. Solid phases of U(VI) complexes were assembled by precipitation from the aqueous U(VI)-SHA and U(VI)-BHA solutions. The structure of these powder solids was analyzed using EXAFS, XRD and FTIR. The analysis of the solid phases showed that the solid complexes are most likely consistent with the complexes in aqueous solution with 1:2 stoichiometrie. The comparison of the uranium and carbon percentage of the solids with those of the uranium compounds described in the literature (for the gravimetric estimation of uranium contents) results in analogue values. In the FTIR spectra of the solids vibration bands at 916 cm-1 were observed according to the bands of the 1:2 complexes in aqueous solution. The results of the EXAFS measurements indicated a different short-range order of the U(VI) in solid phases and solutions. The comparison of the structural parameters of the solid phases with those of the aqueous U(VI)-hydroxamate complex species points to strong differences. Thus, in aqueous solution the distance of the equatorial oxygen atoms of 2.41 Å is significant shorter than those of the solid complexes with 2.47 Å (SHA) and 2.44 Å (BHA). The XRD measurements showed spectra high in reflexes and with significant peaks which could not be assigned to known U(VI) solid phases. In a cooperation with the Institute of Theoretical Chemistry at the University of Cologne density functional theory (DFT) calculations were performed to determine the molecular structure of 1:1 and 1:2 U(VI)-complexes with SHA, BHA and BA. The precise molecular structures of the complexes in gas phase have been calculated as well as the relative stabilities and the time-dependent DFT excitation spectra with consideration of the solvation effects. The relative stabilities calculated with DFT confirm the order of strength of the complexes determined using the stability constants log β (SHA ≥ BHA &gt; BA). Furthermore, the higher binding energies of the 1:2 complexes point to a higher complex stability of these complexes in comparison to the corresponding 1:1 complexes. This could be also demonstrated by means of the stability constants determined by the experimental studies. The peak maxima of the TD-DFT excitation spectra deviate at 0.4 ± 0.2 eV from the absorption maxima of the experimental UV-vis spectra. Thus, calculated and experimental spectra show a good qualitative agreement. For the 1:1 complex of the U(VI)-SHA-system the structurally coordination of the uranium ion to the hydroxamate group could be clarified with the help of the theoretical modelling. The comparison of the calculated structures, binding energies, bond lengths and excitation spectra of the two possible coordination modes [O,O] and [N,O’] showed clearly that the uranyl ion is bound preferable to the two oxygen atoms of the hydroxamate group ([O,O]-mode). Therefore, the method of DFT could contribute to eliminate shortcomings in the experimental determination of the complex structure in case of the U(VI)-SHA-system. The model ligands and their complexes with U(VI), Cm(III) and Np(V) were characterized spectroscopically and their widely unknown stability constants were determined for the first time. Furthermore, the structures of the U(VI)-hydroxamate-complexes were clarified using ATR-FTIR spectroscopy and theoretical calculations. The comparison of the results of the model ligands with those of the pyoverdins showed that the chromophore functionality of the pyoverdins probably plays an important role for the coordination of the actinides to the pyoverdins. Furthermore, conclusions to the strength of the formed actinide-model ligandand actinide-pyoverdin-complexes could be drawn from those results. The pyoverdins formed U(VI)-complexes with stability constants up to 1030, Cm(III)-complexes with constants up to 1032 and Np(V)-complexes with values up to 1020. The hydroxide ion OH- and the carbonato ion CO32- are the most important inorganic complexing agents in natural aquatic systems. They are highly concentrated and have great complexing ability. With the three studied actinides U(VI), Cm(III) and Np(V) complexes with stability constants from 102 to 1020 were formed. The comparison of the constants of OH- and CO3 2- with those of the organic microbial ligands showed that the pyoverdins complexes the actinides with similar and particularly higher strength than the inorganic complexing agents. Thus, it appears that the pyoverdins have a high potential to bind actinides and transport them in natural aquatic systems even though the pyoverdins exist in lower concentrations. Therefore, the studied bioligands are able to mobilize the actinides in natural aquatic systems, for example through dissolving them from solid phases, if they are present in the nature in specific concentrations. So, such bioligands can essentially influence the behaviour of actinides in the environment. The results of this work contribute to a better understanding and assessment of the influence of the microbial ligands to the mobilisation and migration of the radionuclides. The outcomes could be used to quantify the actinide-mobilising effect of the bioligands, which are released, for example, in the vicinity of a nuclear waste disposal site

The surface reactivity of thorium and uranium, and how this links to the 5f electrons, has been investigated under UHV conditions using X-ray photoelectron spectroscopy (XPS), ultra violet photoelectron spectroscopy (UPS), and inverse photoemission spectroscopy (IPES).  Water and ammonia adsorption on a polycrystalline thorium surface has been investigated at 100 and 298 K.  Water adsorbs and dissociates upon the surface, leading to the formation of oxide and hydroxide species at 298 K, and oxide, hydroxide, and physisorbed water at 100 K. The surfaces after adsorption at both temperatures proved to be unstable when exposed to the low energy electron gun utilised in IPES.  Ammonia adsorbs and dissociates upon the surface, leading to the formation of nitride and NH₂ species at 298 K, and nitride, NH₂, and physisorbed ammonia at 100 K.  Upon reaction only the mononitride ThN is formed, the metallic nature of which was confirmed by UPS and IPES.  The surface was unstable under the low energy electron gun utilised in IPES, with the ThN species being converted to the non-metallic Th₃N₄.  Water and ammonia adsorption on a polycrystalline uranium surface has also been investigated at 100 and 298 K.  Water adsorbs and dissociates upon the surface, leading to the formation of oxide and hydroxide species at 298 K, and oxide, hydroxide, and physisorbed water at 100 K.  The rate of reaction of water with uranium is substantially reduced in the presence of residual oxygen on the surface.  The small band-gap of semi-conducting UO₂ can be observed directly with UPS and IPES.  Ammonia adsorbs and dissociates upon the surface, leading to the formation of nitride and NH₂ species at 100 and 298 K.

Kiwifruit consumption is well known to have a positive impact on digestive health. Actinidin and kiwellin, two kiwifruit proteins have been characterised because of their importance in Actazin™ that is produced from kiwifruit to aid digestion. A biophysical characterisation was carried out for both proteins and the catalytic activity of actinidin was measured during the production of Actazin™ to assess if kiwifruit processing was detrimental to the catalytic rate. Actinidin, purified from A. deliciosa cultivar showed that a decrease in enzymatic activity could be from partially inactivated actinidin. Similarly actinidin from Actazin™ became inactivated when the powder was solubilised in buffer. Most of the lost activity could be recovered when a reductant was added and it is hypothesised that the catalytically important cysteine residue was becoming oxidised by a chemical species that was present in the solubilised kiwifruit powder. Freezing, thawing, and storing the processed kiwifruit pulp resulted in the largest drop of total actinidin activity of 46%. Freeze drying the frozen pulp surprisingly did not significantly affect the retention of actinidin despite incurring prolonged heat stress. Further studies that assess the effects that freezing and thawing have on the stability of actinidin is therefore suggested. Kiwellin was characterised using a number of analytical techniques and was shown to be a monomeric protein in solution that had a high melting point. It was suggested that disulfide bonds and salt bridges could be stabilising kiwellin, which was also highly dynamic in solution. Kiwellin did not show the presence of any secondary structures, which is in contrast to previous studies and small angle X-ray scattering revealed that kiwellin had an elongated shape. The dynamic nature of the protein may have implications for the interactions between kiwellin and actinidin, which has been previously shown and this could be related to the physiological function of kiwellin.

Aktinidijos (Actinidia kolomikta Maxim.) ūgliai 2013 m. buvo paimti iš Aleksandro Stulginskio Universiteto Pomologiniame sode augančių motininių augalų. Tirtos trys veislės ‘Paukštės Šakarva’, ‘Lankė’ ir ‘Landė’. Siekiant nustatyti genetinius, fiziologinius ir fizinius veiksnius, darančius įtaką margalapės aktinidijos auginių rizogenezei, tirti trijų veislių žalieji auginiai, paimti iš ūglių lignifikacijos pradžioje. Nustatyta, kad ISR augimo reguliatorius didina įsišaknijusių auginių kiekį. IAR augimo reguliatoriaus poveikis žaliesiems auginiams labai panašus kaip ir ISR. Intensyviausiai šaknis regeneravo iš ūglio viršūnės paimti auginiai, kuriems būdingas mažiausias sumedėjimo lygis. Esminę įtaką margalapės aktinidijos žaliųjų auginių rizogenezei darė auginio ilgis. Įrodyta, kad egzistuoja minimalūs auginio, turinčio potencijų rizogenezei, parametrai. Didėjant auginio ilgiui rizogenezės dažnumas didėja.
Actinidia (Actinidia kolomikta Maxim.) shoots in 2013 was cuting Aleksandras Stulginskis University Pomology garden. Were tested three varieties ‘Paukštės Šakarva’, ‘Lankė’ ir ‘Landė’. In order to evaluate genetic, physiologic and physical factors influencing rhizogenesis of soft cuttings of actinidia, cuttings from three cultivars were taken at the beginning of lignification. It was estimated, that the IBA solution, compared with the control slightly increases the yield of cuttings with roots. IAA efficiency is not significantly different from the IBA. Cuttings with the lowest lignification level, wich were taken from terminal shoot part, regenerated roots more intensively. The length of cutting is crucial from the rhizogenesis of actinidia cuttings. Minimal cutting parameters for potential rhizogenesis are shown. Rate of rhizogenesis increase in longer cuttings.

Les transitions de phases structurales observees dans les actinides sont expliquees en termes de mecanismes de deplacement atomiques. Trois types de situations sont observees dans les actinides: * transition ferroelastique transformant la structure bcc en structure fcc (deformation de bain). Cette transition est associee a une phase intermediaire quadratique. * transitions displacives dont le mecanisme conduit au collapse de certains plans atomiques. * transitions displacives par glissement de plans cristallins parallelement les uns aux autres. Les plans subissant un tel glissement sont les plans (110)#b#c#c. Ces mecanismes sont tous rattaches a un nombre restreint de direction du reseau reciproque de la structure bcc, consideree comme phase mere des autres phases. Ces mecanismes sont expliques theoriquement a l'aide d'une generalisation de la theorie de landau aux transitions reconstructives

Les isonitriles s'insèrent dans une ou deux liaisons sigma u-n des complexes cyclopentadienyles mono- ou bis-alkylaminouranium. La structure carbénoïde des composés d'insertion est établie par spectroscopie. On compare la réactivité de la liaison sigma uranium-méthylène et uranium-méthyle vis à vis des réactions d'insertion et des réactions de substitution par des composés à hydrogène "acide". La réaction d'insertion des composés carbonyles est appliquée à la synthèse chimio- et stéréosélective des alcools secondaires et tertiaires.

Tenderness, juiciness, colour and flavour are the most important meat quality attributes affecting the consumer acceptance. Maintaining the consistency of meat products by avoiding variable quality has become a major concern and great challenge to the meat industry. This in turn will also benefit meat end-users in the marketplace by having more tender meat. The present study was designed to evaluate the overall effects of pre-rigor infusion with kiwifruit juice, which contains the plant protease, actinidin, on lamb quality. A total of 18 lambs (12 months old) were divided into three treatment groups (6 lambs per each treatment). After exsanguination, lamb carcasses were infused (10% body weight) with fresh kiwifruit juice (Ac), water (W) and compared with a noninfusion treatment which acted as a control (C). Samples from different muscle/cuts (longissimus dorsi (LD) vs leg chops) at different post-mortem times (1 day post-mortem vs. 3 wks vacuum packaged storage at 2°C) and display time (0 to 6 days after the post-mortem storage) were analysed to monitor the changes on meat physical properties (e.g., tenderness, temperature, drip and cooking loss, colour), biochemical changes (pH, proteins and lipids) and volatile flavour compounds after the infusion treatments. The most tender meat (lowest shear force values) (P < 0.001) detected in the Ac carcasses post-mortem compared with C and W carcasses demonstrated that kiwifruit juice was a very powerful meat tenderizer, and could contribute to the meat tenderization process efficiently and effectively. Compared with C and W carcasses, the enhanced proteolytic activity (P = 0.002) resulting from the actinidin in kiwifruit juice in Ac carcasses caused degradation of the myofibrillar proteins and the appearance of new peptides during postmortem ageing. A slight positive effect in a*-value (redness) and decreased lipid oxidation, found in leg chops, was thought to be caused by the natural antioxidants in kiwifruit juice. Kiwifruit juice infused into the meat did not alter (P > 0.05) the volatile flavour compound profile indicating that the meat from Ac treated carcasses maintained its natural lamb flavour. No treatment differences were found for the temperature decline (P > 0.05) between the infused treatments and C. The higher rate of pH decline (P < 0.05) found in W carcasses might have contributed to the higher drip and cooking loss. The unbound water in meat might contribute to the higher L*-values (lightness) found in W carcasses. In summary, the proteolytic tenderizing infusion treatment using kiwifruit juice is a feasible approach for the commercial meat industry to increase profits, and also could satisfy the eating quality standards required by the consumers. In addition, tenderizing meat by using kiwifruit juice could also provide the kiwifruit processors an additional option for use of their product to gain a more profitable return.

Kiwifruit (genus Actinidia) is an important horticultural crop grown in the temperate regions. The four world’s largest producers are China, Italy, New Zealand and Chile. More than 50 species are recognized in the genus but the principal species in cultivation are A. deliciosa and A. chinensis. In Italy, as well as in many other countries, the kiwifruit crop has been considered to be relatively disease free and then no certification system for this species has been developed to regulate importation of propagation plant material in the European Union. During the last years a number of fungal and bacterial diseases have been recorded such as Botrytis cinerea and Pseudomonas syringae pv. actinidiae. Since 2003, several viruses and virus-like diseases have been identified and more recent studies demonstrated that Actinidia spp can be infected by a wide range of viral agents. In collaboration with the University of Auckland we have been detected thirteen different viral species on kiwifruit plants. During the three years of my PhD I worked on the characterization of Cucumber mosaic virus (CMV) and Pelargonium zonate spot virus (PZSV). The determination of causal agents has been based on host range, symptom expression in the test plant species and morphological properties of the virus particles using transmission electron microscopy (TEM) and using specific oligonucleotide primers in reverse transcription-polymerase chain reaction (RT-PCR). Both viruses induced several symptoms on kiwifruit plants. Moreover with new technologies such as high-throughput sequencing we detected additional viruses, a new member of the family Closteroviridae and a new member of the family Totiviridae. Taking together all results of my studies it is clear that, in order to minimize the risk of serious viral disease in kiwifruit, it is vital to use virus-free propagation material in order to prevent the spread of these viruses.

Die Endlagerung von radioaktivem Abfall ist eine der vordringlichsten Aufgaben auf dem Gebiet der Kerntechnik. Als Teil der Sicherheitsanforderungen steht dabei der Schutz von Mensch und Umwelt vor den Gefahren der radioaktiven Stoffe selbst im Falle einer Freisetzung dieser Stoffe aus dem Endlager im Vordergrund. Als Basis für Langzeitsicherheitsanalysen dienen Modellierungen. Für diese sind umfassende Kenntnisse der chemisch-physikalischen Effekte und Einflüsse, die eine Mobilisierung und den Transport der Actiniden bewirken können, erforderlich. Diese Arbeit war ein eigenständiger Teil eines Projektes, welches sich mit der Aufklärung des Einflusses von Mikroorganismen auf die Ausbreitung von Actiniden bei einer Freisetzung dieser aus dem Endlager beschäftigt. Dabei wurde der Einfluss von mikrobiell produzierten Substanzen auf die Mobilisierung ausgewählter Actiniden untersucht. Die in diesem Projekt untersuchten mikrobiell produzierten Substanzen, sogenannte Bioliganden, wurden von Bakterien des Genus Pseudomonas unter speziellen Bedingungen produziert. Die von den Pseudomonaden freigesetzten Bioliganden, hier Siderophore vom Pyoverdin-Typ, haben ein hohes Potential, Metalle, insbesondere Eisen(III), zu komplexieren und so zu transportieren. Es wurde untersucht, in welcher Weise und unter welchen Bedingungen diese Bioliganden in der Lage sind, auch radioaktive Schadstoffe zu komplexieren und damit zu mobilisieren. Für die Untersuchungen wurden die α-strahlenden Actiniden Uran, Curium und Neptunium ausgewählt, weil diese auf Grund ihrer Langlebigkeit und Radiotoxizität von besonderem Interesse sind. Diese Arbeit beschäftigte sich mit der Wechselwirkung der Actiniden U(VI), Np(V) und Cm(III) mit Modellliganden, die die Funktionalitäten der Pyoverdine simulieren. Für die Metallbindung der Pyoverdine sind die Katecholgruppe des Chromophors und die funktionellen Gruppen der Peptidkette (Hydroxamsäuregruppen und α-Hydroxysäurereste) verantwortlich. Für die Simulation der Hydroxamsäuregruppen kamen dabei die Monohydroxamate Salicylhydroxamsäure (SHA) und Benzohydroxamsäure (BHA) und das natürliche Trihydroxamat Desferrioxamin B (DFO) zum Einsatz und für die Katecholgruppe das 6-Hydroxychinolin (6HQ) und 2,3-Dihydroxynaphthalin (NAP). Als Vergleichsligand wurde außerdem Benzoesäure (BA) untersucht. Für die Bestimmung der Stabilitätskonstanten zur Einschätzung der Stärke der gebildeten Komplexe, die Aufklärung der Struktur der Actinid-Ligand-Verbindungen und die Verfolgung der Änderung der Speziation der Actiniden vor und nach der Wechselwirkung mit den Modellliganden kamen verschiedene spektroskopische Verfahren wie Absorptionsspektroskopie, Laserfluoreszenzspektroskopie, Röntgenabsorptionsspektroskopie und Schwingungsspektroskopie zum Einsatz. Außerdem wurden erstmals theoretische Modellierungen zur Aufklärung der Struktur der Actinid-Modellligand-Komplexe durchgeführt. Die Ziele dieser Arbeit waren also die spektroskopische Charakterisierung und Bestimmung der Speziation und Komplexbildungskonstanten sowohl der ausgewählten Modellliganden als auch der gebildeten Actinid-Modellligand-Komplexe, die Aufklärung möglicher Strukturen der Komplexe sowie ein Vergleich der Ergebnisse mit denen der Pyoverdine. Der Vergleich der Stabilitätskonstanten der untersuchten Liganden mit den drei Actiniden U(VI), Cm(III) und Np(V) ergab im Wesentlichen folgende Reihenfolge der Komplexstärke: PYO ≥ DFO &gt; NAP &gt; 6HQ &gt; SHA ≥ BHA &gt; BA. Benzoesäure (hier wurde nur die Komplexbildung mit U(VI) untersucht) besitzt als einziger Ligand eine Carboxylfunktionalität und weist mit 103 die geringste Stabilitätskonstante auf. Die beiden Monohydroxamate SHA und BHA bilden mit allen drei Actiniden ähnlich starke 1:1-Komplexe. Bei den 1:2-Komplexen besitzt SHA mit Cm(III) und Np(V) etwas höhere Stabilitätskonstanten als BHA, wahrscheinlich verursacht durch einen stabilisierenden Einfluss der zusätzlichen phenolischen OH-Gruppe. Dieser Trend wurde auch in den theoretischen Modellierungen für die U(VI)-Komplexe beobachtet. Die natürlichen Siderophore DFO und PYO bilden die stärksten Komplexe mit den Actiniden (Stabilitätskonstanten von 1012 bis 1034). Dies liegt in der Struktur und der hohen Anzahl an funktionellen Gruppen begründet; DFO besitzt drei Hydroxamatgruppen, das Pyoverdinmolekül neben den Hydroxamatgruppen noch die Katecholgruppen der Chromophorfunktionalität. Die Modellliganden für die Chromophorfunktionalität, NAP und 6HQ, bilden stärkere Komplexe als die Monohydroxamate SHA und BHA, aber schwächere Komplexe als DFO und PYO. Daraus lässt sich schlussfolgern, dass die Chromophorfunktionalität eine wichtige Rolle bei der Anbindung der Actiniden an die Pyoverdine spielt. Der Vergleich der Stabilitätskonstanten der Komplexe der Liganden SHA, BHA und 6HQ mit den drei untersuchten Actiniden U(VI), Cm(III) und Np(V) untereinander zeigte, dass die Stärke der Komplexe von U(VI) über Cm(III) zu Np(V) abnimmt. Der Grund dafür liegt in den unterschiedlichen Ladungsdichten der Actinidionen. Während das UO2 2+-Ion mit einer Koordinationszahl von 5 und einem Ionenradius von ~ 0.6 eine effektive Ladung von + 3.3 besitzt, hat das Cm3+-Ion eine effektive Ladung von + 2.6 und das NpO2+-Ion von + 2.3. Damit besitzt das NpO2+-Ion die geringste Ladungsdichte der untersuchten Actinidionen und bildet damit auch die schwächsten Komplexe mit den niedrigsten Stabilitätskonstanten. Die Stärke der Komplexe der Liganden NAP, DFO und PYO nimmt von Cm(III) über U(VI) zu Np(V) ab. Obwohl Cm(III) eine geringere effektive Ladung als U(VI) hat, bildet es stärkere Komplexe als U(VI). Eventuell sind dafür strukturelle Behinderungen der Koordination durch die lineare O=U=O Einheit verantwortlich. Die Struktur der wässrigen U(VI)-Komplexe wurde mittels EXAFS-Spektroskopie und ATRFTIR-Spektroskopie untersucht. Aus den EXAFS-Spektren ließ sich schließen, dass die Koordination des Uranylions an die Hydroxamsäuregruppen der Liganden SHA, BHA und DFO eine Verkürzung des Abstandes der äquatorialen Sauerstoffatome zur Folge hat. Im Gegensatz dazu resultiert eine Koordination des Uranylions an die Carboxylgruppe des Liganden BA in einer Verlängerung des U-Oäq Abstandes. Die Ergebnisse des NAP als Modellligand für die Chromophorfunktionalität des Pyoverdins und die Ergebnisse des Pyoverdins selbst zeigten, dass das Uranylion mit großer Wahrscheinlichkeit an die katecholischen OH-Gruppen der Chromophorfunktionalität des Pyoverdinmoleküls gebunden ist. In den Spektren der ATR-FTIR-Spektroskopie ist besonders der Bereich um die Schwingungsbande des Uranylions (961 cm-1) für die Beobachtung der Komplexbildung interessant. Dabei zeigte sich im U(VI)-BHA- und U(VI)-SHA-System eine Mischung aus zwei Komplexen mit 1:1- und 1:2-Stöchiometrie, die auch durch Speziationsrechnungen nachgewiesen werden konnten. Außerdem ließ sich anhand der Schwingungsbanden des Liganden feststellen, dass die Hydroxamsäuregruppe von SHA und BHA während der Komplexierung deprotoniert und direkt an der Komplexbildung beteiligt ist. Im Falle von SHA konnte weiterhin nachgewiesen werden, dass die phenolische OH-Gruppe bei den untersuchten pH-Werten nicht deprotoniert ist. Die pH-abhängigen Spektren des U(VI)-DFOSystems zeigten bei pH 3 die Bildung eines 1:1-Komplexes ähnlich dem der Monohydroxamate, bei Erhöhung des pH-Wertes bis pH 4 dann die Bildung eines 1:1- Komplexes, bei dem das Uranylion an zwei Hydroxamsäuregruppen gebunden ist. Dies stützt die Annahme einer 112-Stöchiometrie des Komplexes, die bei den anderen verwendeten experimentellen Methoden getätigt wurde. Durch Ausfällung aus wässrigen U(VI)-SHA- und U(VI)-BHA-Lösungen wurden Feststoffe der U(VI)-Komplexe hergestellt. Die Struktur dieser ausgefällten, pulverförmigen Feststoffe wurde mittels EXAFS, XRD und FTIR untersucht. Die Untersuchung der ausgefällten Feststoffe ergab, dass die Feststoffkomplexe mit sehr hoher Wahrscheinlichkeit den in Lösung gefundenen Komplexen mit 1:2-Stöchiometrie entsprechen. Der Vergleich der Uran und Kohlenstoffgehalte der Feststoffe mit den in der Literatur beschriebenen Uranverbindungen (zur gravimetrischen Bestimmung von Urangehalten) zeigte übereinstimmende Werte. In den FTIR-Messungen wurden Banden bei 916 cm-1 beobachtet, die denen in der Lösung dem 1:2-Komplex zugeordneten Banden entsprechen. Die Ergebnisse der EXAFS-Messungen deuten auf eine unterschiedliche Nahordnung des U(VI) im Feststoff und in der Lösung hin. So ergab der Vergleich der Strukturparameter der Hydroxamat- Feststoffe mit den U(VI)-Hydroxamat-Komplexen in Lösung deutliche Unterschiede zwischen den Feststoffkomplexen und denen in Lösung. So ist in wässriger Lösung der Abstand der äquatorialen Sauerstoffatome mit 2.41 Å signifikant kürzer als der der Feststoffkomplexe mit 2.47 Å (SHA) und 2.44 Å (BHA). Die röntgendiffraktogrammischen Messungen der Festphasen ergaben reflexreiche Spektren mit signifikanten Peaks, die sich allerdings keinen bekannten U(VI)-Festphasen zuordnen ließen. In einer Kooperation mit dem Institut für Theoretische Chemie der Universität zu Köln wurden für die 1:1- und 1:2-Komplexe der wässrigen U(VI)-SHA-, U(VI)-BHA- und U(VI)-BA-Systeme erstmals theoretische Modellierungen durchgeführt. Dabei wurden die Strukturen der Komplexe sowohl in der Gasphase als auch unter Berücksichtigung der Solvatation optimiert und die relativen Stabilitäten und Anregungsspektren berechnet. Die mit DFT berechneten Bindungsenergien bestätigen die experimentell anhand der Stabilitätskonstanten log β ermittelte Reihenfolge der Komplexstabilitäten (SHA ≥ BHA &gt; BA). Außerdem zeigen die höheren Bindungsenergien der 1:2-Komplexe, dass diese stabiler sind als die 1:1-Komplexe. Dies lässt sich auch anhand der experimentell ermittelten Stabilitätskonstanten nachweisen. Die Maxima der mit TD-DFT berechneten Anregungsspektren weichen um 0.4 ± 0.2 eV von den experimentellen UV-Vis Spektren ab. Dies zeigt die gute Übereinstimmung der berechneten Anregungsspektren mit den gemessenen UV-Vis Spektren. Für den 1:1-Komplex des U(VI)-SHA-Systems konnte mit Hilfe der theoretischen Modellierung die strukturelle Anbindung des Uranylions an die Hydroxamsäuregruppe aufgeklärt werden. Der Vergleich der berechneten Strukturen, Bindungsenergien, Bindungslängen und Anregungsspektren der beiden möglichen Anbindungsmodi [O,O] und [N,O’] zeigte deutlich, dass das Uranylion bevorzugt über die beiden Sauerstoffatome der Hydroxamsäuregruppe, also den [O,O]-Modus, gebunden wird. Die Methode der DFT konnte also dazu beitragen, Defizite in der experimentellen Aufklärung der Komplexstruktur im Fall des U(VI)-SHA-Systems zu beheben. Die Modellliganden und deren Komplexe mit U(VI), Cm(III) und Np(V) wurden zum größten Teil erstmals spektroskopisch charakterisiert sowie deren bisher weitgehend unbekannten Stabilitätskonstanten bestimmt. Außerdem konnte die Struktur der U(VI)-Hydroxamat- Komplexe mit Hilfe der ATR-FTIR-Spektroskopie und der theoretischen Modellierung aufgeklärt werden. Im Vergleich der Ergebnisse der Modellliganden mit denen der Pyoverdine konnte festgestellt werden, dass die Katecholfunktionalität der Pyoverdine eine große Rolle bei der Komplexierung mit den Actiniden spielen wird. Weiterhin ließen sich aus den Ergebnissen Schlussfolgerungen zur Stärke der gebildeten Actinid-Modellligand- und Actinid-Pyoverdin-Komplexe ziehen. Die Pyoverdine bildeten mit U(VI) Komplexe mit Stabilitätskonstanten bis 1030, mit Cm(III) bis 1032 und mit Np(V) bis 1020. Die wichtigsten, in höheren Konzentrationen vorkommenden anorganischen Komplexbildner in natürlichen Wässern sind das Hydroxidion OH- sowie das Carbonation CO32-. Diese besitzen eine hohe Komplexierungsfähigkeit und bilden mit den drei Actiniden U(VI), Cm(III) und Np(V) Komplexe mit Stabilitätskonstanten von 102 bis 1020. Der Vergleich der Konstanten von OH und CO32- mit denen der organischen, mikrobiellen Pyoverdin-Liganden zeigt, dass die Pyoverdine ähnlich starke bzw. teilweise stärkere Komplexe mit den Actiniden bilden als die anorganischen Komplexbildner. Daraus lässt sich ableiten, dass die Pyoverdine selbst in niedrigeren Konzentrationen ein hohes Potential besitzen, Actiniden in natürlichen Wässern zu binden und damit zu transportieren. Die untersuchten Bioliganden sind also in der Lage, bei Anwesenheit in der Natur in bestimmten Konzentrationen im Grundwasser Actiniden, z.B. durch Herauslösen aus Festphasen, zu mobilisieren. Damit können solche Bioliganden das Verhalten der Actiniden in der Umwelt entscheidend beeinflussen. Die Ergebnisse dieser Arbeit tragen dazu bei, den Einfluss der mikrobiellen Liganden auf die Mobilisierung und Ausbreitung der Actiniden besser einschätzen zu können. Damit können die Ergebnisse zur Quantifizierung des Mobilisierungseffekts der Actiniden durch freigesetzte Bioliganden im Nahfeld genutzt werden.
One of the urgent tasks in the field of nuclear technology is the final storage of radioactive substances. As a part of the safety requirements the protection of humans and the environment from the danger of radioactive substances in case of the release from the final storage is essential. For performing long-term safety calculations the detailed understanding of the physico-chemical effects and influences which cause the mobilisation and transport of actinides are necessary. The presented work was a discrete part of a project, which was focused on the clarification of the influence of microorganisms on the migration of actinides in case of the release of actinides from a final storage. The influence of microbial produced substances on the mobilisation of selected actinides was studied thereby. The microbial produced substances studied in this project were synthesized by bacteria from the Pseudomonas genus under special conditions. Fluorescent Pseudomonads secrete bacterial pyoverdin-type siderophores with a high potential to complex and transport metals, especially iron(III). The aim of the project was to determine how and under which conditions the bioligands are able to complex also radioactive substances and therefore to transport them. For this work the alpha-emitting actinides uranium, curium and neptunium were chosen because their long-life cycle and their radiotoxicity are a matter of particular interest. This work dealed with the interaction of the actinides U(VI), Np(V) and Cm(III) with model ligands simulating the functionality of the pyoverdins. The functional groups that participate in the metal binding of the pyoverdins are the catechol group of the chromophore and the ligand sites in the peptide chain, i.e. the hydroxamate groups and the α-hydroxy acid moieties. For the simulation of the hydroxamate functionality the monohydroxamates salicylhydroxamic acid (SHA) and benzohydroxamic acid (BHA) and the natural trihydroxamate desferrioxamine B (DFO) and for the simulation of the catechol groups 6-hydroxyquinoline (6HQ) and 2,3-dihydroxynaphthalene (NAP) were used. A further ligand with carboxyl functionality, benzoic acid (BA), was used as a comparison. Absorption spectroscopy, laser fluorescence spectroscopy, X-ray absorption spectroscopy and vibrational spectroscopy were applied for the determination of the stability constants to assess the strength of the formed actinide-model ligand-complexes, for the clarification of the structures of the formed complexes and to observe the variation of the speciation of the actinides during the interaction with the ligands. Furthermore, for the first time density functional theory (DFT) calculations were performed to determine the molecular structure of the actinide-modelligand-complexes. Thus, the objectives of this work were the determination of the spectroscopic properties, speciation and stability constants of the model ligands and the formed actinide-model ligand-complexes, the clarification of the complex structures and a comparison of the results with those of the pyoverdins. The comparison of the stability constants of the studied ligands with the three actinides U(VI), Cm(III) and Np(V) systems results mainly in the following order of complex strength: PYO ≥ DFO &gt; NAP &gt; 6HQ &gt; SHA ≥ BHA &gt; BA. Benzoic acid, the ligand with the carboxyl functionality, has the lowest stability constant of 103. Both monohydroxamates, SHA and BHA, form 1:1 complexes with similar stability. The stability constants of the 1:2 complexes of SHA with Cm(III) and Np(V) are slightly higher than those of BHA, which is probably caused by a stabilizing effect of the additional phenolic OH-group of SHA. This behaviour was also found in the theoretical calculations of the U(VI)-complexes. The natural siderophores DFO and PYO have the highest stability constants with U(VI) and form the strongest complexes (constants from 1012 to 1034). The reason therefore is the structure and high number of functional groups of these ligands; DFO has three hydroxamate groups, the pyoverdin molecule has the catechol groups of the chromophore functionality in addition to the hydroxamate groups. The model ligands for the chromophore functionality, NAP and 6HQ, form stronger complexes than SHA and BHA, but weaker complexes than DFO and PYO. From this it can be reasoned that the chromophore functionality probably plays an important role for the coordination of the actinides to the pyoverdins. The comparison of the stability constants of the complexes of the ligands SHA, BHA and 6HQ with the studied actinides U(VI), Cm(III) and Np(V) shows that the strength of the complex formation decreases from U(VI) via Cm(III) to Np(V). The reason therefore is the different charge density of the actinide ions. The UO22+-ion has an effective charge of + 3.3 (with a coordination number of 5 and an ionic radius of ~ 0.6), the Cm3+-ion of + 2.6 and the NpO2+-ion of + 2.3. Therefore, the neptunyl ion has the lowest charge density of the studied actinide ions and on account of this it forms the weakest complexes with the lowest stability constants. The strength of the complex formation of the ligands NAP, DFO and PYO decreases from Cm(III) via U(VI) to Np(V). Cm(III) forms stronger complexes than U(VI) although Cm(III) has a lower effective charge. The reason therefore could be a possible structural hampering of the coordination through the linear O=U=O unit. The structure of the aqueous U(VI)-complexes was studied using EXAFS spectroscopy and FTIR spectroscopy. From the results of the EXAFS spectra one can conclude that the coordination of the uranyl ion to the hydroxamic acid groups of the SHA, BHA and DFO ligands results in a shortening of the distance of the equatorial oxygen atoms. In contrast to this the coordination of the uranyl ion to the carboxyl group of BA yields in a longer U-Oeq bond length. From the findings of the EXAFS studies with NAP and pyoverdin one can conclude a strong affinity of U(VI) to the catechol functionality of the pyoverdin molecule. For the observation of the complexation in the ATR-FTIR spectra the region around the vibration band of the uranyl ion (916 cm-1) is interesting to observe. In the spectra of the U(VI)-BHA- and U(VI)-SHA-system a mixture of two complexes with 1:1 and 1:2 stoichiometry was observed, which was also existing in the speciation. Furthermore, on the basis of the vibration bands of the ligands it could be ascertained that the hydroxamate groups of SHA and BHA are deprotonated and directly involved in the complexation. Also, in case of SHA it could be verified that the phenolic OH-group is protonated at the investigated pH values. At pH 3 the pH dependent spectra of the U(VI)-DFO-system showed the formation of a 1:1 complex similar to those of the monohydroxamates. With increasing pH up to 4 the formation of a 1:1 complex was observed, in which the uranyl ion is bound to two hydroxamic acid groups. This underlines the assumption that the complex had a 112-stoichiometry, which was concluded on the basis of the other used experimental methods. Solid phases of U(VI) complexes were assembled by precipitation from the aqueous U(VI)-SHA and U(VI)-BHA solutions. The structure of these powder solids was analyzed using EXAFS, XRD and FTIR. The analysis of the solid phases showed that the solid complexes are most likely consistent with the complexes in aqueous solution with 1:2 stoichiometrie. The comparison of the uranium and carbon percentage of the solids with those of the uranium compounds described in the literature (for the gravimetric estimation of uranium contents) results in analogue values. In the FTIR spectra of the solids vibration bands at 916 cm-1 were observed according to the bands of the 1:2 complexes in aqueous solution. The results of the EXAFS measurements indicated a different short-range order of the U(VI) in solid phases and solutions. The comparison of the structural parameters of the solid phases with those of the aqueous U(VI)-hydroxamate complex species points to strong differences. Thus, in aqueous solution the distance of the equatorial oxygen atoms of 2.41 Å is significant shorter than those of the solid complexes with 2.47 Å (SHA) and 2.44 Å (BHA). The XRD measurements showed spectra high in reflexes and with significant peaks which could not be assigned to known U(VI) solid phases. In a cooperation with the Institute of Theoretical Chemistry at the University of Cologne density functional theory (DFT) calculations were performed to determine the molecular structure of 1:1 and 1:2 U(VI)-complexes with SHA, BHA and BA. The precise molecular structures of the complexes in gas phase have been calculated as well as the relative stabilities and the time-dependent DFT excitation spectra with consideration of the solvation effects. The relative stabilities calculated with DFT confirm the order of strength of the complexes determined using the stability constants log β (SHA ≥ BHA &gt; BA). Furthermore, the higher binding energies of the 1:2 complexes point to a higher complex stability of these complexes in comparison to the corresponding 1:1 complexes. This could be also demonstrated by means of the stability constants determined by the experimental studies. The peak maxima of the TD-DFT excitation spectra deviate at 0.4 ± 0.2 eV from the absorption maxima of the experimental UV-vis spectra. Thus, calculated and experimental spectra show a good qualitative agreement. For the 1:1 complex of the U(VI)-SHA-system the structurally coordination of the uranium ion to the hydroxamate group could be clarified with the help of the theoretical modelling. The comparison of the calculated structures, binding energies, bond lengths and excitation spectra of the two possible coordination modes [O,O] and [N,O’] showed clearly that the uranyl ion is bound preferable to the two oxygen atoms of the hydroxamate group ([O,O]-mode). Therefore, the method of DFT could contribute to eliminate shortcomings in the experimental determination of the complex structure in case of the U(VI)-SHA-system. The model ligands and their complexes with U(VI), Cm(III) and Np(V) were characterized spectroscopically and their widely unknown stability constants were determined for the first time. Furthermore, the structures of the U(VI)-hydroxamate-complexes were clarified using ATR-FTIR spectroscopy and theoretical calculations. The comparison of the results of the model ligands with those of the pyoverdins showed that the chromophore functionality of the pyoverdins probably plays an important role for the coordination of the actinides to the pyoverdins. Furthermore, conclusions to the strength of the formed actinide-model ligandand actinide-pyoverdin-complexes could be drawn from those results. The pyoverdins formed U(VI)-complexes with stability constants up to 1030, Cm(III)-complexes with constants up to 1032 and Np(V)-complexes with values up to 1020. The hydroxide ion OH- and the carbonato ion CO32- are the most important inorganic complexing agents in natural aquatic systems. They are highly concentrated and have great complexing ability. With the three studied actinides U(VI), Cm(III) and Np(V) complexes with stability constants from 102 to 1020 were formed. The comparison of the constants of OH- and CO3 2- with those of the organic microbial ligands showed that the pyoverdins complexes the actinides with similar and particularly higher strength than the inorganic complexing agents. Thus, it appears that the pyoverdins have a high potential to bind actinides and transport them in natural aquatic systems even though the pyoverdins exist in lower concentrations. Therefore, the studied bioligands are able to mobilize the actinides in natural aquatic systems, for example through dissolving them from solid phases, if they are present in the nature in specific concentrations. So, such bioligands can essentially influence the behaviour of actinides in the environment. The results of this work contribute to a better understanding and assessment of the influence of the microbial ligands to the mobilisation and migration of the radionuclides. The outcomes could be used to quantify the actinide-mobilising effect of the bioligands, which are released, for example, in the vicinity of a nuclear waste disposal site.

Dans le cadre des recherches sur l'aval du cycle du combustible et des projets de transmutation de l'américium, un procédé innovant de fabrication de Couvertures Chargées en Américium (CCAm) a été développé. Ce procédé, intitulé CRMP (Calcined Resin Microsphere Pelletization), vise la fabrication de pastilles d'oxyde mixte uranium-américium par une voie non conventionnelle de métallurgie des sphérules. Il consiste à produire des pastilles par pressage et frittage de précurseurs d'oxyde sous la forme de microsphères millimétriques obtenues par minéralisation de perles de résines échangeuses d'ions chargées en cations uranium et américium. L'avantage d'un tel procédé par rapport à la métallurgie conventionnelle des poudres est de s'affranchir de la problématique des fines particules disséminantes et contaminantes et de faciliter les opérations de transfert de matière lors de la phase de mise en forme. Le procédé a d'abord été optimisé et validé pour la production de pastilles d'oxyde de cérium. Des pastilles d'oxyde d'uranium de microstructure contrôlée, dense ou poreuse, ont ensuite été produites dans le but de répondre aux spécifications envisagées pour les CCAm. Dans une troisième phase, le procédé a été appliqué avec succès à la synthèse de microsphères d'oxydes mixtes monophasés de type U1-xCexO2±δ (0,1≤x≤0,3) qui ont servi à l'élaboration de pastilles de céramiques d'oxydes mixtes. La faisabilité technique du procédé CRMP a été finalement validée à l'échelle d'une pastille U0,9Am0,1O2±δ de microstructure homogène et de densité égale à 95 % de la densité théorique
In the framework of research on the back-end of the nuclear fuel cycle, and notably projects on transmutation of americium (Am), an innovative manufacturing process of Minor Actinides Bearing Blanket (MABB) has been developed.This process, called CRMP (Calcined Resin Microsphere Pelletization), consists in the production of mixed uranium-americium oxide pellets by a non-conventional route involving microspheres. Pellets are produced by pressing and sintering oxide precursors in the form of millimetric beads obtained by mineralization of ion exchange resin loaded with uranium and americium cations. The advantage of such a process compared to conventional powder metallurgy is to overcome the problem of the handling of very fine powders.The method was first validated and optimized for the production of ceria pellets. Then uranium dioxide pellets with tailored microstructure (dense or porous) were produced in order to reach the required specifications for MABB. In a third phase, the process has been applied to the synthesis of single-phase mixed oxide microspheres composed of U1-xCexO2±δ (0.1 ≤ x ≤ 0.3) and U0;9Am0.1O2±δ. The technical feasibility of CRMP process has been validated for the production of dense mixed oxide pellets by pressing and sintering these microspheres. A U0, 9Am0,1O2±δ pellet with homogeneous microstructure with a density equals to 95 % of theoretical density was successfully produced using CRMP process

Les polymères de coordination (PC) présentent un intérêt tant fondamental qu'appliqué de par leur structure et composition modulables ouvrant de nouvelles perspectives au niveau des propriétés chimiques (catalyse, conversion matériaux mous-durs…) et physiques (magnétisme, optique…). L'objectif principal de ces études consiste à vérifier le transfert de la structure, méso-structure et composition du PC vers la céramique obtenue par traitement thermique. Dans ce contexte, ce manuscrit décrit des études sur la conversion de polymères de coordination obtenus à partir d'un auto-assemblage entre des métaux 4f, 5f et de la 2,5-dihydroxy-1,4-benzoquinone (DHBQ). Dans un premier temps, des méthodes de synthèses, aqueuse et anhydre en atmosphère contrôlée, ont été mises au point. Ainsi, plusieurs types de PC ont été obtenus (4f, 4f-4f, 4f-5f), les composés mixtes formant des solutions solides. Après caractérisation de ces composés, leur comportement sous traitement thermique a été étudié. Les principaux résultats montrent que les précurseurs à base de DHBQ obtenus par voie aqueuse possèdent une méso-structure micrométrique, formée par l'assemblage de sous-unités monocristallines possédant la même structure cristallographique quelle que soit la morphologie observée. L'étude de l'assemblage de cette méso-structure a permis de contrôler la morphologie du grain élémentaire (cylindre, cube, disque…) avec une très bonne distribution en taille. La mise en œuvre de systèmes anhydres en atmosphère contrôlée a permis d'accéder à une plus large gamme de paramètres micro-structuraux (surface spécifique, porosité…). Pour l'ensemble des composés de type PC, la conversion thermique en céramique n'a pratiquement pas altéré la morphologie des matériaux. Les aspects microstructuraux ont pu être contrôlés via la méthode de synthèse
Coordination polymers (CP) are of great academic and industrial interest due to flexible structure and composition and offer prospects for original chemical (catalysis, soft-hard materials conversion…) and physical properties (magnetism, optics…). The major interest of these studies is to check the transfer of the structure, meso-structure and composition from the CP to the ceramic via a thermal treatment. In this context, this thesis describes studies on conversion of coordination polymers obtained by self-assembly of 4f and 5f metal ions with 2,5-dihydroxy-1,4-benzoquinone (DHBQ). Aqueous and anhydrous synthetic ways were developed, which yielded different kinds of CPs (4f, 4f-4f, 4f-5f) ; solid solutions were obtained with the mixed compounds. The products were characterized and their behaviour under thermal treatment was studied. The main results show that the DHBQ-based precursors obtained by aqueous way have a micrometric meso-structure, formed by the assembly of micro-crystalline subunits which all posses the same crystallographic structure. The study of the assembly of the meso-structure allowed controlling the morphology of the elementary grain (cylinder, cube, disk ...) with very good size distribution. The implementation of anhydrous systems in a controlled atmosphere allowed yielded a wider range of micro-structural parameters (surface area, porosity ...). For all CP-type compounds, the thermal conversion to ceramic has barely altered the morphology of the materials. The microstructural aspects could be controlled via the method of synthesis

The work described in this thesis was an investigation into the coordination chemistry of uranium(VI) and neptunium(VI). Structural determinations of comparable uranium and neptunium compounds were used to examine the actinide contraction between uranium and neptunium, the changes in metal-ligand bond length on substituting nitrogen for oxygen as the donor atom and to establish the mode of coordination of certain ligands around the actinyl(VI) ion. These areas have been explored through the determination of the crystal structures of the following compounds:- a) The 2,2'-dipyridyl complexes [CO2(NO3),C10H8N2], [NpO2(N [UOa(CH3COO)2Cl0H8N2] and [NpO2a(CH3COO)2C10H8N2]. b) The 1,10-phenanthroline complex [C02(NC3)2C12H8N2]. c) The pentan-2,4-dionate complexes [CO2(CH3COCHCOCH3)aC5H5N], [NpOa(CH3COCHCOCH3)2C 5HsN], [UO2(CH3COCHCOCH3)a.HaO] and [U0aCH3C0CHC0CH3)2H2C[UO2CH3COCHCOCH3(NO3)2 [(CH3)3C5H3N]* d) The 4,4'-dipyridyl compound [(UO2(NO3)2OH2] [C10H10N2]2* In addition the structure determination of the compound bis(nitrato)dioxo tetrakis(glycinato)uranium(VI) showed that the glycine ligands are coordinated via the oxygen atoms with two bidentate and two monodentate glycines. Other structures which have been determined are the mixed oxidation state neptunium alkali metal salt [CsTNp( v,Oa(Np( w|Oa)aClia], the organoneptunium(IV) compound [(CsHs)CI3Np(OPPh3)a] and the photo-oxidation product [L'OjfCCIjCOOICMOPPhj),] There is also an uncompleted structure of a 1,10-phenanthroline complex with uranyl(VI)acetate which is described as far as possible.

The surface reactivity of thorium, uranium, neptunium and americium has been investigated under UHV conditions using X-ray photoelectron spectroscopy (XPS) and ultra violet photoelectron spectroscopy (UPS). Oxygen, nitric oxide, nitrogen dioxide and nitrous oxide adsorption on a polycrystalline thorium surface has been investigated at 298 K. 02 dissociatively adsorbs on the surface resulting in the growth of Th02. All three of the nitrogen oxides adsorb dissociatively with both oxygen and nitrogen adsorbed on the thorium surface. The formation of thorium oxynitride (ThOxNy) is proposed. Reaction of NO, NO2 and N20 with a polycrystalline uranium surface has also been investigated at 298 K. N2O adsorbs dissociatively leaving only oxygen adsorbed on the uranium surface. NO and N2O also adsorb dissociatively but in these cases both oxygen and nitrogen remain on the surface. The formation of uranium oxynitride (UOxNy) is proposed. For exposures >350 L the rate of reaction of NO with the oxynitride surface decreases significantly. In contrast, NO2 continues to react with the surface and a further increase in surface oxygen concentration is observed. Adsorption of O2, NO and CO on thin films of neptunium metal has been studied at 80 and 300K. Following exposure to 02 at 80 and 300K, an intermediate surface oxide of Np is formed which is unstable with respect to the formation of Np02. This intermediate oxide is proposed to be associated with the chemisorption phase, NpO(chem). Dissociative adsorption of CO and NO is observed at 80 and 300K. A surface oxidic compound is formed which is not a simple neptunium oxide. NpO(chem) states are proposed to be stabilized by the presence of carbon/nitrogen as neptunium oxycarbide and oxynitride respectively. The interaction of O2 and NO with americium thin films has also been investigated. The formation of A1TI2O3 is proposed and it was found that it is not thermodynamically viable to produce a higher oxidation state of americium via gas dosing (at 300 K under UHV). Adsorption of NO on the surface results in the dissociative adsorption of N and O, and in the formation of a surface compound.

Les actinides sont des radioéléments couramment manipulés par les travailleurs de l'industrie nucléaire et font partie de la menace NRBC (nucléaire, radiologique, biologique, chimique). La contamination cutanée représente une voie d'exposition majeure de ces agents radiologiques. La décontamination de la peau est donc cruciale pour empêcher une dispersion de la contamination et l'absorption systémique du contaminant par la peau. Ce travail s'est attaché à évaluer les profils de pénétration cutanée de deux actinides : l'américium et le plutonium, sous différentes formes, dans un modèle d'étude ex vivo, la peau d'oreille de porc. L'efficacité de décontamination de différents produits usuels a également été testée sur ce modèle, mais aussi sur un modèle in vitro de poudre de couche cornée bovine. Pour compléter l'étude de la décontamination, l'efficacité d'une formulation d'hydrogel de DTPA a également été testée. La détermination de la distribution de la contamination dans la peau a été réalisée à l'aide de différentes techniques d'imagerie : l'autoradiographie par émulsion, le TASTRAK ou encore l'iQID camera. Les résultats ont montré une grande différence dans les profils de pénétration et de rétention des actinides lorsqu'ils sont en solution aqueuse modérément soluble ou en solution organique dans un mélange de solvant. De plus, cette dernière forme modifie fortement la structure cutanée, menant à une forte augmentation de la pénétration cutanée. Les résultats des protocoles de décontamination montrent une efficacité égale du savon (Trait rouge®) comparé au DTPA, qui est le traitement décorporant utilisé également en décontamination. La formulation en hydrogel présente une efficacité supérieure pour le traitement de solutions organiques et met en évidence l'intérêt de développer d'autres formulations galéniques
Actinides are alpha-emitting radioactive elements handled by nuclear industry workers and are part of the NRBC threat (nuclear, radiological, biological, and chemical). Skin contamination represents a major exposure route for these radioelements. Skin decontamination is therefore essential to prevent any dispersion of contamination and systemic absorption through the skin. This work focused the evaluation of skin penetration behavior of two actinides: americium and plutonium, in different forms, in an ex vivo model, pig ear skin. The decontamination efficacy of various products was tested on this model as well as an in vitro model of bovine hide powder. The efficacy of a new DTPA hydrogel formulation was also tested. The localization of in different skin layers was carried out using various imaging techniques: emulsion autoradiography, solid track autoradiography, TASTRAK or iQID camera. Data showed differences in penetration, retention and localization profiles of the different actinides used in moderately soluble aqueous solution or in a solvent mixture. In addition, the latter modifies skin structure that is associated with an increase in skin penetration. Radioactivity activity measurements in skin layers agreed well with distribution as shown by the different autoradiography techniques. The results of decontamination protocols showed an equal efficacy of the soap (Trait rouge®) as compared to DTPA, that is used for decorporation therapy and also for decontamination. The hydrogel formulation showed a superior efficacy for the treatment of organic solutions and demonstrates the interest for development of other pharmaceutical formulations

Innovation in kiwifruit flavour is desired. This can be achieved by affecting secondary metabolites. Here the biosynthesis of flavour-related methylsulfanyl (MeS)- volatiles in Actinidia chinensis, their genetic background and regulation by ethylene were investigated. Initially, headspace solid-phase microextraction (HS-SPME) and dynamic headspace sampling (DHS) parameters were systematically optimised to ensure highest extraction yields of MeS-volatiles from kiwifruit tissue using GC-MS. However, the qualitative and quantitative MeS-volatile profiles were improved using DHS compared with HS-SPME, making this the more sensitive and preferred method. MeS-volatile levels were then quantified during ripening and storage (1.5⁰C) of A. chinensis 'Hort16A'. The majority of MeS-compounds were specific for eating-ripe fruit and their concentrations increased in parallel with the climacteric rise in ethylene. No ethylene production was observed after long-term storage (4-6 months) and the levels of all MeS-volatiles, except methional, declined by 98-100% during that period. Transcript accumulation (RT-PCR) of six putative alcohol acyltransferase (AAT) was ripeningspecific and these levels decreased after prolonged cold storage concomitantly with (MeS)alkanoate ester production of fruit and cell-free extracts. However, ester production and gene expression was recovered by ethylene treatment after five months at 1.5⁰C, indicating that the biosynthesis of (MeS)alkanoate esters was likely to be ethyleneregulated in 'Hort16A'. The limiting steps of ethylene-dependent (MeS)alkanoate ester biosynthesis were then further investigated using closely related A. chinensis genotypes. Quantification of MeScompounds revealed little variation in their volatile composition but remarkable differences in the magnitude of their fruit volatile levels. Enzyme kinetic studies using cell-free extracts were performed to test whether this was caused by the catalytic properties of genotypespecific AATs. The substrate preferences were similar for most genotypes, thus suggesting substrate availability as the limiting factor for (MeS)alkanoate ester biosynthesis in A. chinensis. A link between precursor formation and ethylene biosynthesis in kiwifruit is proposed. Finally, ripening-specific AATs from Actinidia were characterised after recombinant expression. Striking differences in substrate preferences were found for two phylogenetically distinct AATs either exhibiting benzoyl-CoA: alcohol O-acyltransferase or acetyl-CoA: alcohol O-acyltransferase activity. An increased preference for benzoyl-CoA was associated with increased specificity for (MeS)alkanoyl-CoAs, thus suggesting a role of three likely orthologues in their production.

In a global and increasingly competitive fresh produce market, more attention is being given to fruit quality traits and consumer satisfaction. Kiwifruit occupies a niche position in the worldwide market, when compared to apples, oranges or bananas. It is a fruit with extraordinarily good nutritional traits, and its benefits to human health have been widely described. Until recently, international trade in kiwifruit was restricted to a single cultivar, but different types of kiwifruit are now becoming available in the market. Effective programmes of kiwifruit improvement start by considering the requirements of consumers, and recent surveys indicate that sweeter fruit with better flavour are generally preferred. There is a strong correlation between at-harvest dry matter and starch content, and soluble solid concentration and flavour when fruit are eating ripe. This suggests that carbon accumulation strongly influences the development of kiwifruit taste. The overall aim of the present study was to determine what factors affect carbon accumulation during Actinidia deliciosa berry development. One way of doing this is by comparing kiwifruit genotypes that differ greatly in their ability to accumulate dry matter in their fruit. Starch is the major component of dry matter content. It was hypothesized that genotypes were different in sink strength. Sink strength, by definition, is the effect of sink size and sink activity. Chapter 1 reviews fruit growth, kiwifruit growth and development and carbon metabolism. Chapter 2 describes the materials and methods used. Chapter 3, 4, 5 and 6 describes different types of experimental work. Chapter 7 contains the final discussions and the conclusions Three Actinidia deliciosa breeding populations were analysed in detail to confirm that observed differences in dry matter content were genetically determined. Fruit of the different genotypes differed in dry matter content mainly because of differences in starch concentrations and dry weight accumulation rates, irrespective of fruit size. More detailed experiments were therefore carried out on genotypes which varied most in fruit starch concentrations to determine why sink strengths were so different. The kiwifruit berry comprises three tissues which differ in dry matter content. It was initially hypothesised that observed differences in starch content could be due to a larger proportion of one or other of these tissues, for example, of the central core which is highest in dry matter content. The study results showed that this was not the case. Sink size, intended as cell number or cell size, was then investigated. The outer pericarp makes up about 60% of berry weight in ‘Hayward’ kiwifruit. The outer pericarp contains two types of parenchyma cells: large cells with low starch concentration, and small cells with high starch concentration. Large cell, small cell and total cell densities in the outer pericarp were shown to be not correlated with either dry matter content or fruit size but further investigation of volume proportion among cell types seemed justified. It was then shown that genotypes with fruit having higher dry matter contents also had a higher proportion of small cells. However, the higher proportion of small cell volume could only explain half of the observed differences in starch content. So, sink activity, intended as sucrose to starch metabolism, was investigated. In transiently starch storing sinks, such as tomato fruit and potato tubers, a pivotal role in carbon metabolism has been attributed to sucrose cleaving enzymes (mainly sucrose synthase and cell wall invertase) and to ADP-glucose pyrophosphorylase (the committed step in starch synthesis). Studies on tomato and potato genotypes differing in starch content or in final fruit soluble solid concentrations have demonstrated a strong link with either sucrose synthase or ADP-glucose pyrophosphorylase, at both enzyme activity and gene expression levels, depending on the case. Little is known about sucrose cleaving enzyme and ADP-glucose pyrophosphorylase isoforms. The HortResearch Actinidia EST database was then screened to identify sequences putatively encoding for sucrose synthase, invertase and ADP-glucose pyrophosphorylase isoforms and specific primers were designed. Sucrose synthase, invertase and ADP-glucose pyrophosphorylase isoform transcript levels were anlayzed throughout fruit development of a selection of four genotypes (two high dry matter and two low dry matter). High dry matter genotypes showed higher amounts of sucrose synthase transcripts (SUS1, SUS2 or both) and higher ADP-glucose pyrophosphorylase (AGPL4, large subunit 4) gene expression, mainly early in fruit development. SUS1- like gene expression has been linked with starch biosynthesis in several crop (tomato, potato and maize). An enhancement of its transcript level early in fruit development of high dry matter genotypes means that more activated glucose (UDP-glucose) is available for starch synthesis. This can be then correlated to the higher starch observed since soon after the onset of net starch accumulation. The higher expression level of AGPL4 observed in high dry matter genotypes suggests an involvement of this subunit in drive carbon flux into starch. Changes in both enzymes (SUSY and AGPse) are then responsible of higher starch concentrations. Low dry matter genotypes showed generally higher vacuolar invertase gene expression (and also enzyme activity), early in fruit development. This alternative cleavage strategy can possibly contribute to energy loss, in that invertases’ products are not adenylated, and further reactions and transport are needed to convert carbon into starch. Although these elements match well with observed differences in starch contents, other factors could be involved in carbon metabolism control. From the microarray experiment, in fact, several kinases and transcription factors have been found to be differentially expressed. Sink strength is known to be modified by application of regulators. In ‘Hayward’ kiwifruit, the synthetic cytokinin CPPU (N-(2-Chloro-4-Pyridyl)-N-Phenylurea) promotes a dramatic increase in fruit size, whereas dry matter content decreases. The behaviour of CPPU-treated ‘Hayward’ kiwifruit was similar to that of fruit from low dry matter genotypes: dry matter and starch concentrations were lower. However, the CPPU effect was strongly source limited, whereas in genotype variation it was not. Moreover, CPPU-treated fruit gene expression (at sucrose cleavage and AGPase levels) was similar to that in high dry matter genotypes. It was therefore concluded that CPPU promotes both sink size and sink activity, but at different “speeds” and this ends in the observed decrease in dry matter content and starch concentration. The lower “speed” in sink activity is probably due to a differential partitioning of activated glucose between starch storage and cell wall synthesis to sustain cell expansion. Starch is the main carbohydrate accumulated in growing Actinidia deliciosa fruit. Results obtained in the present study suggest that sucrose synthase and AGPase enzymes contribute to sucrose to starch conversion, and differences in their gene expression levels, mainly early in fruit development, strongly affect the rate at which starch is therefore accumulated. This results are interesting in that starch and Actinidia deliciosa fruit quality are tightly connected.

Le paramagnétisme des actinides en solution a été caractérisé par RMN selon deux approches, l'une macroscopique et l'autre moléculaire. Dans la première approche, les susceptibilités magnétiques des ions les plus stables en solution de l'uranium au californium, et ce pour différents degrés d'oxydation (U(IV)-U(VI), Np(IV)-Np(V)-Np(VI), Pu(III)-Pu(IV)-Pu(VI), Am(III), Cm(III) et Cf(III)), ont été mesurées par RMN à l'aide de la méthode d'Evans. En milieu perchlorique, l'étude ducomportement paramagnétique des cations actinide a montré des déviations significatives par rapport à celui des lanthanides, particulièrement pour les ions actinide aux degré d'oxydation +III et +IV. En milieux chlorhydrique et nitrique, il a été observé que les comportements magnétiques des actinides suivaient l'ordre M(IV) > M(VI) > M(III) > M(V), correspondant à l'ordre généralement admis concernant le pouvoir complexant des ions actinide en solution aqueuse. Il a été démontré que la présence d'ions chlorure et nitrate en solution pouvait avoir un impact important sur le comportement magnétique de ces cations. Dans la deuxième approche, les déplacements chimiques des complexes paramagnétiques actinide(IV)-dipicolinate ont été étudiés et analysés en milieu diméthylformamide. Dans ces conditions expérimentales, il a été vérifié que le degré d'oxydation +IV des actinides en solution était stable en présence ou non de ligand ainsi que sur l'échelle de temps des analyses RMN. Les déplacements chimiques paramagnétiques des complexes limites 1 : 3 ont été étudiés à différentes températures. Les méthodes de séparation des contributions de contact et dipolaire habituellement utilisées pour les complexes de lanthanide(III) se sont avérées inapplicables dans le cas des complexes d'actinide(IV)
Paramagnetism of actinides in solution was characterized by NMR according to two approaches, a macroscopic one and a molecular one. In the first approach, magnetic susceptibilities of the most stable ions in solution from uranium to californium, for various oxidation states (U(IV)-U(VI), Np(IV)-Np(V)-Np(VI), Pu(III)-Pu(IV)-Pu(VI), Am(III), Cm(III) et Cf(III)), were measured by NMR by using the Evans' method. In perchloric medium, the paramagnetic behavior of actinide cations showed significant deviations compared with lanthanides, particularly for cations at oxidation state +III and +IV. In hydrochloric and nitric media, it was observed that actinide magnetic behaviors followed the order M(IV) > M(VI) > M(III) > M(V), corresponding to the generally admitted order concerning the complexing power of actinide cations. It was demonstrated that the presence of chloride and nitrate in solution could have an large impact on the magnetic behavior of these cations. In the second approach, chemical shifts of actinide(IV)-dipicolinate paramagnetic complexes were studied and analyzed in dimethylformamide. In these experimental conditions, the only presence of the oxidation state +IV in solution as well as the stability of the latter on the NMR analysis timescale were verified, in presence or not of the ligand. Paramagneticchemical shifts of the 1 : 3 limit complex were studied at various temperatures. Themethod of separation of the contact and dipolar contributions usually used for lanthanide(III) complexes have proved not applicable in the case of actinide(IV) complexes

The chemistry of actinides in aqueous solution is important, and it is essential to build adequate conceptual models and develop methods applicable for actinide systems. The complex electronic structure makes benchmarking necessary. In the thesis a prototype reaction of the water exchange reaction for uranyl(VI), for both ground and luminescent states, described with a six-water model, was used to study the applicability of density functional methods on actinides and different solvation models. An excellent agreement between the wave function methods CCSD(T) and MP2 was obtained in the ground state, implying that near-minimal CASPT2 can be used with confidence for the reaction in the luminescent state of uranyl(VI), while density functionals are not suited to describe energetics for this type of reaction. There was an ambiguity concerning the position of the waters in the second hydration sphere. This issue was resolved by investigating a larger model, and prop- erly used the six-water model was found to adequately describe the water exchange reaction. The effect of solvation was investigated by comparing the results from conductor-like polarizable continuum models using two cavity models. Scattered numbers made it difficult to determine which solvation model to use. The final conclusion was that the water exchange reaction in the luminescent state of uranyl(VI) should be addressed with near-minimal CASPT2 and a solvation model without explicit cavities for hydrogens. Finally it was shown that no new chemistry appears in the luminescent state for this reaction. The thesis includes a methodological investigation of a multi-reference density functional method based on a range separation of the two-electron interaction. The method depends on a universal parameter, which has been determined for lighter elements. It is shown here that the same parameter could be used for actinides, a prerequisite for further development of the method. The results are in that sense promising.

This thesis is a computational study of the first members of the actinide series, thorium, protactinium, uranium, neptunium, plutonium, americium and curium. There are two general themes that occur throughout this thesis; the first is the electronic structures of the aforementioned actinides, and in particular what is the role of the 5f and 6d orbitals in the electronic structure of some early actinide complexes. The second is how covalent are the interactions between the early actinides and lighter members of the periodic table, in particular carbon, halogens and the chalcogens. The principal quantity that has been probed to assess this covalency is the electron density. Chapter 2 makes use of both time dependent density functional theory (TDDFT) and multiconfigurational self-consistent field theory (CASPT2) to assess the experimentally determined Cl K edge spectra of [AnCl6]2-; An = Th, Pa, U, Np and Pu. Particular attention is applied to the [NpCl6]2- and [PuCl6]2- spectra as an anomalous transition splitting pattern is seen. Quantum theory of atoms in molecules (QTAIM) theory has been used to probe the actinide cyclopentadienyl bond in chapter 3 and the actinide halogen bond in chapter 4. Unlike more traditional Mulliken and orbital analysis QTAIM is based on the topology of the electron density and is therefore an observable quantity. The actinide halide bond is then also probed with bond orders derived from QTAIM. The [M{N(EPPh2}2]3 ;(M = La, Ce, Eu, U, Pu, Am, Cm; E = S, Se) molecules studied in chapter 5 have been purposely synthesized so as to assess the degree of covalency between An(III) and La(III) chalcogen bonds. Natural population analysis and QTAIM is used to study these complexes.

The current UK strategy for radioactive waste management is to permanently store the waste in an underground repository. Final disposal of the radwaste may then be preceded by chemical conditioning and physical encapsulation. The objective of this work was to determine the extent of actinide immobilisation in cement. Since actinides are hazardous and costly to study directly, a chemical analogue approach to studying actinide immobilisation was adopted. Th(IV), Ce(III, IV) and Eu(III) were chosen as actinide simulants and their suitability assessed by a critical review of the literature. Ca(OH)₂ and C-S-H dominate the observed chemical properties of the aqueous phase in cement. As they are of such importance, it was these cement components which were used to investigate the reaction of the simulant elements with cement. The phases found to be predicted were ThO₂, ThSiO₄, Eu(OH)₃, Ca₂Eu₈(SiO₄)₆O₂, CeO₂, CeSiO₄ and Ca₂(SiO₄)₆O₂. CeSiO₄ and Ca₂Ce₈(SiO₄)O₂ are newly reported phases, produced by hydrothermal synthesis. Rietveld refinement confirmed CeSiO₄ to have the zircon structure, with space group 14₁/amd and cell parameters a = 6.9564(3) A, c = 6.1953 (4) A. Ca₂Ce₈(SiO₄)₆O₂ exhibits the apatite structure, with space group P6₃/m and cell parameters a = 9.4343(3) a, c = 6.8885(4) A. Preliminary solubility studies were carried out on all of the solubility-limiting phases. Phase impurity, poor crystallinity and incongruent solubility of phases hindered the generation of solubility product data. Nevertheless, these phases have naturally occurring analogues which are known to be environmentally stable and have low solubilities. On the basis of the experimental results obtained, it may be concluded that cement has the potential to be a very effective immobilisation matrix for actinide elements. Recommendations for future experiments using active elements are discussed.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.
Includes bibliographical references (p. 227-232).
Transuranic actinides dominate the long-term radiotoxity in spent LWR fuel. In an open fuel cycle, they impose a long-term burden on geologic repositories. Transmuting these materials in reactor systems is one way to ease the long-term burden on the repository. Examining the maximum possible burning of trans-uranic elements in Combined Non-Fertile and U02 (CONFU) PWR assemblies is evaluated. These assemblies are composed of a mix of standard U02 fuel pins and pins made of recycled trans-uranics (TRU) in an inert matrix, and are designed to fit in current or future PWRs. Applying appropriate limits on the neutronic and thermal safety parameters, a CONFU-Burndown (CONFU-B) assembly design is shown to attain net TRU destruction in each fuel batch through at least 9 recycles. This represents a time span of nearly 100 years of in-core residence and out-of-core storage time. In this way, when the TRU is multi-recycled, only fission products and separation/reprocessing losses are sent to the repository, and the initial inventory of TRU is reduced over time. Thus, LWRs are able to eventually operate in a fuel cycle system with an inventory of transuranic actinides much lower than that accumulated to date. Three recycling strategies are considered, all using a 4.5-year in core irradiation, followed by cooling and reprocessing. The three strategies involve a short-term cooling (6-year) after discharge, a longer-term cooling (16.5-year) after discharge, or a strategy called Remix. The Remix strategy involves partitioning the Pu/Np after 6-year cooling for immediate recycle, and partitioning the Am/Cm for an additional 10.5-year cooling before remixing it into the next CONFU-B batch. At equilibrium, the CONFU-B can burn approximately 1.5 kg to 10.0 kg of TRU per TWhe depending on the recycle strategy used.
(cont.) This represents a net burning rate of 2-8% of the TRU loaded per assembly, in addition to burning an amount equivalent to the TRU produced in the U02 pins. However, the highly heterogeneous nature of these assemblies can result in fairly high intra-assembly pin power peaking. By design, an IMF pin in the assembly carries the highest power to maximize the TRU destruction. For the initial TRU loading, the highest power peaking in an IMF pin is 1.183. This is compensated by having cooler pins in the immediate vicinity. Even so, the pin peaking distribution in the assembly can result in reduced thermal margins. The assembly mentioned above has an MDNBR of 1.43, instead of 1.62 for the all-U02 assembly, based on a core-wide radial peak-to-average assembly power peaking of 1.50. Use of neutron poisons and tailored enrichment schemes reduces the neutronic reactivity of fresh assemblies, while improving MDNBR to 1.51. In addition, RELAP was used to evaluate the fuel behavior under large break LOCA conditions. CONFU-B performance under these conditions was comparable to the standard all-UO2 assembly. Several options for spent fuel recycling in LWRs are compared economically, and all are found to be more costly than making fresh U02 fuel from mined ore. However, the CONFU-B strategy is less costly on a mills/kWhe basis than other thermal recycling strategies that recycle the full TRU vector. Given OECD estimates for the unit costs of each fuel type, and assuming 10% carrying charge factor, this cost is 12.3 mills/kWhe for the CONFU-B recycle, compared to 25.7 mills/kWhe for MOX-UE and 4.9 mills/kWhe for all UO2.
(cont.) Note that these FCCs assume the disposal fee collected during power generation of a previous cycle can be invested while the fuel is cooling and provide a credit to the cycle that uses the fuel after reprocessing. The fuel handling challenges of multirecycling TRU in CONFU-B assemblies are compared to other multi-recycling strategies. If we assume that the spent fuel from, the seventh recycle in each strategy is no longer recyclable and must be sent to the repository in its entirety. the CONFU-B strategy still places much less total burden on the repository than the once-through cycle, and even less burden than the current MOX cycle. Finally, a methodology for calculating the time integrated proliferation risk of a fuel cycle is introduced. An innovation of this methodology is the discounting of future risks to calculate an overall present value risk of a given cycle. Under this methodology, the CONFU-B presents lower risks than other multi-recycling strategies in the first 100 years. For a 10% rate of discount of risk, the CONFU-B risks are comparable to the once-through cycle. The longer term risk favors recycling due to the limited accumnulation of repository risk.
by Mark M. Visosky.
Ph.D.

Les oxydes mixtes d'uranium et de plutonium sont les matières premières privilégiées des combustibles nucléaires de nouvelles générations. Les mécanismes de leur élaboration par décomposition thermique d'oxalates mixtes, précurseurs de référence, font l'objet des présentes recherches, en vue d'une maîtrise plus aboutie des caractéristiques physico-chimiques du solide produit. La décomposition thermique de différents précurseurs oxalates en oxydes a donc été analysée expérimentalement sous atmosphères inerte et oxydante, les processus réactionnels ont été clarifiés, les paramètres thermodynamiques et cinétiques déterminés et des modèles physico-chimiques prédictifs ont été proposés. La méthodologie d'étude expérimentale de ce processus jusqu'à sa modélisation a tout d'abord été développée à l'aide de composés modèles à base de lanthanides, de complexité croissante. La conversion en oxyde des oxalates simples de Nd et Ce, comparée à celle de l'oxalate de Pu(III), a permis de cerner l'effet du redox du métal. Des oxalates doubles lanthanide-hydrazinium, par un comportement spécifique dû à leur structure cristallographique singulière, ont ensuite illustré de manière exacerbée l'importance des interactions gaz-gaz et solide-gaz en présence notamment de gaz réactifs azotés. La résolution globale des mécanismes de décomposition des oxalates mixtes d'actinides en oxydes a bénéficié ensuite d'une approche comparative des systèmes U-Ce, Th-Pu et U-Pu, compte tenu d'analogies structurales ciblées. Un mécanisme général en cinq étapes élémentaires principales a été proposé, associé à des données thermodynamiques et cinétiques. Ceci a notamment permis de simuler les diagrammes de spéciation de la phase solide suivant différentes programmations de température (linéaire ou de type double-four industriel), aussi bien pour le système simulant U-Ce utilisé dans les essais systématiques d'optimisation technologique du procédé que pour le système d'intérêt U-Pu. Enfin, une première ébauche de modèle « procédé » a été réalisée en considérant les phénomènes de transport associé à deux réactions-clés pour ces systèmes : l'étape de décomposition thermique de l'oxalate anhydre en oxyde et l'équilibre de Boudouard entre gaz carbonés. La réactivité du système et les phénomènes prépondérants concernant les flux de gaz de calcination dégagés et la formation de carbone élémentaire au sein d'un lit de poudre statique ont pu être simulés globalement
Mixed uranium-plutonium oxides are preferential raw materials for news generation nuclear fuels. The research project presented herein deals with their elaboration process by thermal decomposition of mixed oxalates, as reference precursors, in order to improve the physicochemical characteristics of the resulting product. The thermal decomposition of several oxalate precursors into oxides was thus experimentally studied under both inert and oxidizing atmospheres, the reaction mechanisms were determined, as well as the thermodynamics and kinetics, and predictive physicochemical models were proposed. The methodology of the study up to the modelling was first developed using lanthanide model compounds with increasing complexity. The conversion into oxides of simple Nd and Ce oxalates, compared with Pu(III) oxalate, allowed to understand the role of the metal cation redox properties. Double lanthanide-hydrazinium oxalates, displaying a specific behaviour due to their peculiar crystallographic structure, underlined the importance of gas-gas and solid-gas interactions. Then, the global resolution of the decomposition mechanisms of mixed actinide oxalates into oxides was carried out through a comparative approach of U-Ce, Th-Pu and U-Pu systems, given ... analogies. A general mechanism including five main steps was proposed, with the corresponding thermodynamic and kinetic parameters. This especially enabled to simulate the speciation diagrams of the solid phases according to different temperature programs (linear or double industrial oven) for the U-Ce surrogate system (used in systematic technological process optimisation tests) as well as for the U-Pu system of interest. Finally, a first attempt at process modelling was undertaken, taking into account transport phenomena associated with two key-reactions for these systems: the thermal decomposition of anhydrous oxalate into oxide and the Boudouard equilibrium between carbonaceous species. The overall system reactivity and the predominant phenomena concerning evolved gas fluxes and elemental carbon formation, within a static powder bed, were simulated

O kiwizeiro pertence ao gênero Actinidia e família Actinidiaceae. Todas as espécies deste gênero são trepadeiras perenes que se comportam de forma desordenada quando não manejadas e caracterizam-se por crescimento extremamente vigoroso. O objetivo deste trabalho foi avaliar o comportamento vegetativo e produtivo de kiwizeiros das cultivares ‘Elmwood’ (Actinidia deliciosa) e ‘MG06’ (Actinidia chinensis), enxertados sobre plantas oriundas de sementes de frutos da cultivar ‘Bruno’ (Actinidia deliciosa), conduzidos em sistema latada e submetidos a diferentes intensidades de poda de inverno, além de testar a possibilidade de utilização da técnica de ‘tip squeezing’ (“compressão do meristema apical” - CMA) para redução do vigor e do crescimento de parte aérea de kiwizeiros ‘MG06’, na região da Serra Gaúcha, RS, Brasil. O primeiro estudo foi realizado de junho de 2016 a abril de 2017 com a cultivar ‘Elmwood’. Nesse, três tratamentos com nove repetições foram utilizados no delineamento inteiramente casualizado. Os tratamentos consistiram na manutenção de diferentes níveis de cargas de gemas em cada vara: 10, 15 e 20 gemas vara-1. Avaliou-se o índice de fertilidade das gemas; o número, percentual e posição de gemas não brotadas, brotações vegetativas e brotações mistas; área, massa seca e área específica das folhas; diâmetro e comprimento de ramos; rendimento e número de frutos; e diâmetros transversal e longitudinal, massa fresca, firmeza, teor de sólidos solúveis (SS), pH, acidez total titulável (ATT) e relação SS/ATT de frutos. O segundo estudo foi realizado entre julho e dezembro de 2017 com a cultivar ‘MG06’, testando-se diferentes cargas de gemas em cada vara: 10, 15 e 20 gemas vara-1, com e sem a utilização da CMA, representando 6 diferentes tratamentos. Cada tratamento era composto de nove repetições (cada repetição correspondia a uma planta) em delineamento inteiramente casualizado. Avaliou-se o índice de fertilidade das gemas; o número, percentual e posição de gemas não brotadas, brotações vegetativas e brotações mistas; área e massa seca das folhas; diâmetro e comprimento de ramos e de entrenós; diâmetros transversal e longitudinal, massa fresca, firmeza, teor de sólidos solúveis, acidez total titulável e relação SS/ATT de frutos. A poda com diferentes cargas de gemas não influencia o índice de fertilidade real das gemas de kiwizeiros ‘Elmwood’ e ‘MG06’ em um mesmo ciclo, porém afeta o tamanho das folhas e dos ramos. A poda de kiwizeiros ‘Elmwood’ mantendo varas com 10 gemas favorece o aumento da massa de fruto e não reduz produtividade. A CMA reduz o vigor das brotações de kiwizeiros ‘MG06’ sem influir na qualidade dos frutos.
The kiwifruit belongs to Actinidia Genus and Actinidiaceae Family. All species from this kind are perennial bindweeds which behave in desordered way when not managed and are characterized by extremely vigourous growth. The objective of this work is to evaluate vegetative and productive behavior of kiwifruit trees from ‘Elmwood’ (Actinidia deliciosa) and ‘MG06’ (Actinidia chinensis) cultivars, grafted over plants originating from seeds of fruits of the ‘Bruno’ cultivar (Actinidia deliciosa), conduced in trellis system and submitted to different intensities of winter pruning, besides testing the possibility of usage of ‘tip squeezing’ technique for vigor and growth reduction of the vegetative part of ‘MG06’ kiwifruit trees, in Serra Gaucha region, RS, Brazil. The first study has been made from june of 2016 to april of 2017 with ‘Elmwood’ cultivar. In this one, three treatments with nine repetitions (each repetition corresponded to a plant) were used in the completely randomized design. The treatments consisted in maintenance of different bud loading levels in each cane: 10, 15 and 20 buds cane-1. It was evaluated the index of fertility of the buds; the number, percentage and position of not sprouted buds, vegetative buds and mixed buds; area, dry mass and specific area of the leaves; diameter and length of the branches; productivity and number of fruits; and transversal and longitudinal diameters, dry mass, firmness, soluble solids content (SS), pH, titratable total acidity, (TTA) and relation SS/TTA of the fruits. The second study has been made between july and december of 2017 with ‘MG06’ cultivar, being tested different loads of buds in each cane: 10, 15 and 20 buds cane-1, with and without the usage of the “squeezing”, representing 6 different treatments. Each treatment was compound of nine repetitions in completely randomized design. It was evaluated the index of fertility of the buds; number, percentage and position of the not sprouted buds, vegetative buds and mixed buds, area and dry mass of the leaves; diameter and length of branches and internodes; transversal and longitudinal diameters, fresh mass, firmness, SS, TTA and relation SS/TTA of the fruits. The pruning with different loads of buds doesn’t influence the index of real fertility of the buds from ‘Elmwood’ and ‘MG06’ kiwifruit trees in a same season, however it affects the size of leaves and branches. The pruning of ‘Elmwood’ kiwifruit trees maintaining canes with 10 gems favors the increase of fruit mass and it doesn’t reduce productivity. The “tip squeezing” reduces the vigor of kiwifruit trees ‘MG06’ without influencing fruits quality.

This study explores the practical value of comparative morphology as an aid to Actinidia taxonomy, using vegetative characters derived from spring and summer shoots of 20-30 taxa, selected from the “NZ D.S.I.R. Actinidia germplasm collection” at Auckland and Te Puke during 1988-1989. Data are collected from field-based observations and from samples processed for light and electron microscopy; these are supplemented with observations derived from herbarium specimens collected in China. The taxonomic potential of characters is further tested using multivariate and other statistical methods. Actinidia are morphologically variable vines which, nevertheless, express genetically-determined form in: their manner of climbing, the types and growth characteristics of shoots and in the ontogenetic expression of shoot form. There is however a strong “opportunistic component” in the realisation of plant form. Some more conservative characters include leaf venation pattern, trichome morphology, arrangement of sclerenchyma fibres and the complement of ergastic crystals associated with vascular bundles of the leaf. Microscopic examination of abaxial foliar trichomes, currently used to demarcate sections of the genus, reveal branched hair types in Maculatae and Strigosae, which are supposed to be absent (Dunn 1911, Liang 1984) from these sections of the genus. Re-examination of these groups and the characters delimiting them is recommended. Comparative morphological studies of Actinidia in the germplasm collection show that many of the characters of winter-dormant shoots are genotypic in nature. Vines of Leiocarpae and Stellatae may be identified below the species level by their bud-form characteristics. Discriminant analysis shows the value of bud height and ostiole size in separating major taxonomic and geographic groups. Detailed analysis of bud characters is justified as poor or uneven budbreak currently limits the productivity of commercial cultivars. Taxonomists need to be more aware of the spatial and temporal potential afforded by vegetative morphological characters in this genus. The discovery of “water-excreting glands” (= hydathodes) in all Actinidia seen, culminating in a combination of “water spending” characters in A. deliciosa, has important implications for water-relations in these plants. Hydathodes in A. deliciosa are well supplied by craspedodromous venation and the ultimate tracheids terminate in a spatially diffuse but metabolically active environment, in the apices of these glands. The fate and functioning of hydathodes in Actillidia needs further research. The results from this exploratory study are intended to contribute to the programme of genetic and taxonomic studies of Actinidia; currently being undertaken by D.S.I.R. Fruit and Trees, Auckland.

Le retraitement pousse du combustible nucleaire consiste en une elimination des actinides mineurs (neptunium, americium, traces du plutonium et uranium) des solutions d'effluents a tres haute activite, issues du procede purex. Parmi les procedes envisageables, l'extraction selective des actinides a leurs degres d'oxydation superieurs a trois est ici etudiee. Une premiere partie de ce travail concerne une etape prealable: l'elimination du ruthenium des solutions de produits de fission par la technique de l'electrovolatilisation du tetraoxyde de ruthenium. La deuxieme partie de ce travail comprend l'etude des reactions de complexation et d'oxydation des elements uranium, neptunium, plutonium et americium en presence d'un compose du type heteropolyanion insature: le phosphotungstate de potassium. Pour les ions actinide tetravalents complexes par l'anion phosphotungstate le mecanisme d'extraction par la dioctylamine a ete etudie et l'emploi de la technique d'extraction chromatographique a permis de realiser des separations actinides tetravalents/lanthanides trivalents. Finalement plusieurs schemas de procedes de retraitement des solutions de produits de fission sont elabores a partir des resultats obtenus