The complex interactions at the interfaces of minerals, microbes, and metals drive the cycling of iron and the fate and transport of metal(loid)s in contaminated systems. The former uranium mine near Ronneburg, Germany is one such system, where slightly acidic mine drainage crossing a steep redox gradient (groundwater outflow into a stream) forms and transforms iron (oxy)hydroxide nanoparticles. These particles interact with toxic metal(loid)s in water and sediments. Iron oxidizing and reducing bacteria also play a role in these processes. Biogeochemical reactions are influenced by nanoscale properties, and thus it is critical to probe environmental samples with appropriate techniques such as analytical transmission electron microscopy (TEM). This dissertation presents two studies on the iron (oxy)hydroxide mineral nanoparticles found in the Ronneburg mine drainage system. The first study uses TEM in conjunction with bulk analytical techniques to demonstrate the complexity of iron (oxy)hydroxide transformations at the steep redox gradient, and the partitioning of metal(loid)s within those mineral phases. An important result was the identification of Zn-bearing green rust platelets in the anoxic outflow water. Green rust minerals have only been identified in nature a handful of times, and we believe this work to be only the second to examine naturally occurring green rust using high resolution TEM (HR-TEM). Downstream of the outflow, aggregates of poorly crystalline iron oxide spheroids co-precipitated with amorphous silica formed and settled to the stream bed, where they aged to form nanoparticulate goethite and sequestered metals such as As and Zn. However, significant concentrations of Zn and Ni remained in the dissolved/nano (< 0.1 um) water fraction and continued downstream. The second study demonstrates that natural green rust nanoparticles and their synthetic analogs can be complex polycrystalline phases composed of crystallites only a few nanometers in size, and often include nano-regions of amorphous material. In addition to the typical pseudo-hexagonal platelet morphology, green rust nanorods were synthesized, which has not previously been reported. This work has important implications for the reactivity of green rust with biogeochemical interfaces in natural, anthropogenic, and industrial systems. A third study, presented in the appendix, characterizes the bacterial community at the Ronneburg mine drainage site and highlights iron oxidizers such as Gallionella sp., in particular those that form stalks of iron oxide nanoparticles. These biogenic stalks also contribute to the uptake of metal contaminants in water and sediments. The science of iron cycling is complex. It requires field-based exploration to enrich the contributions made by experimental, laboratory and modeling studies. This dissertation adds another chapter in the search for filling in missing pieces of this interconnected system. / Ph. D.

No / Solvent influences on the crystallization of polymorph and hydrate forms of the nootropic drug piracetam (2-oxo-pyrrolidineacetamide) were investigated from water, methanol, 2-propanol, isobutanol, and nitromethane. Crystal growth profiles of piracetam polymorphs were constructed using time-resolved diffraction snapshots collected for each solvent system. Measurements were performed by in situ energy dispersive X-ray diffraction recorded in Station 16.4 at the synchrotron radiation source (SRS) at Daresbury Laboratory, CCLRC UK. Crystallizations from methanol, 2-propanol, isobutanol, and nitromethane progressed in a similar fashion with the initial formation of form I which then converted relatively quickly to form II with form III being generated upon further cooling. However, considerable differences were observed for the polymorphs lifetime and both the rate and temperature of conversion using the different solvents. The thermodynamically unstable form I was kinetically favored in isobutanol and nitromethane where traces of this polymorph were observed below 10°C. In contrast, the transformation of form II and subsequent growth of form III were inhibited in 2-propanol and nitromethane solutions. Aqueous solutions produced hydrate forms of piracetam which are different from the reported monohydrate; this crystallization evolved through successive generation of transient structures which transformed upon exchange of intramolecular water between the liquid and crystalline phases

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25299号 / 工博第5258号 / 新制||工||2000(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 陰山 洋, 教授 阿部 竜, 教授 藤田 晃司 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

This project relates to the non-classical growth of inorganic crystals with interesting morphologies that are highly desirable in industry. All crystals were synthesized via hydrothermal or solvothermal methods and their growth was studied by stopping each reaction at a range of different times, extracting the particles and analysing them using a variety of characterisation techniques. The main techniques used were scanning electron microscopy and transmission electron microscopy but other techniques, such as powder X-ray diffraction and thermal gravimetric analysis, were also employed. Decorated ZnO microstadiums were studied where ZnO nanocones coat the inner and outer columnar walls of ZnO microstadiums. It was revealed that the polymer in the synthetic solution enhanced the aggregation of nanocrystallites of precursor ions on the microstadium surfaces, which then underwent recrystallization, forming ZnO nanocones. The presence of organic agents was also found to be crucial in the non-classical growth mechanisms of CaCO₃ and RHO-ZIF crystals as the presence of charged groups on the organic molecules led to the aggregation of precursor molecules/ions, preventing classical growth. The disordered aggregates underwent surface recrystallization, forming ‘core-shell' structures where a thin layer of single crystal encased a disordered core. Over time the crystallisation extended from the surface inwards, towards the core, until true single crystals were formed. Organic molecules were also shown to play a role in the non-classical growth of 8-branched Cu₂O structures. In this case, however, studies of the electronic configuration of the main terminating facets of Cu₂O crystals revealed another key factor in their non-classical growth. Terminating hydroxyl groups on the Cu₂O surfaces could have different charges depending on the number of Cu⁺ ions they were coordinated to. The terminating {111} faces were the only ones to be coated with negatively charged hydroxyl groups, which explained the rapid growth on these surfaces as they were able to attract the positively charged metal/polymer precursor clusters. This new phenomenon was also found to be the main driving force in the rapid growth of branches in snowflake-like Fe₂O₃ crystals despite no organic agent being used. In this case, the {11-20} faces of the seed crystals had positively charged hydroxyl groups that were able to rapidly attract the negatively charged [Fe(CN) ₆]³⁻ ions in the aqueous solution.

A numerical code for solving the time-dependent incompressible 3D Navier-Stokes equations with finite volumes on overlapping staggered grids in cylindrical and rectangular geometry is developed. In the code, written in FORTRAN, the momentum equation for the velocity is solved by projection method and Poisson equation for the pressure is solved by ADI implicit method in two directions combined with discrete fast Fourier transform in the third direction. A special technique for overcoming the singularity on the cylinder's axis is developed. This code, taking into account dependence upon temperature of the viscosity, density and surface tension of the liquid, is used to study the fluid motion in a cylinder with free cylindrical surface (under normal and zero-gravity conditions); and in a rectangular closed cell with a source of thermocapillary convection (bubble inside attached to one of the cell's faces). They are significant problems in crystal growth and in general experiments in fluid dynamics respectively. Nevertheless, the main study is dedicated to the liquid bridge problem.<p><p>The development of thermocapillary convection inside a cylindrical liquid bridge is investigated by using a direct numerical simulation of the 3D, time-dependent problem for a wide range of Prandtl numbers, Pr = 0.01 - 108. For Pr > 0.08 (e.g. silicon oils), above the critical value of temperature difference between the supporting disks, two counter propagating hydrothermal waves bifurcate from the 2D steady state. The existence of standing and traveling waves is discussed. The dependence of viscosity upon temperature is taken into account. For Pr = 4, 0-g conditions, and for Pr = 18.8, 1-g case with unit aspect ratio an investigation of the onset of chaos was numerically carried out. <p><p>For a Pr = 108 liquid bridge under terrestrial conditions ,the appearance and the development of thermoconvective oscillatory flows were investigated for different ambient conditions around the free surface.<p><p>Transition from 2D thermoconvective steady flow to a 3D flow is considered for low-Prandtl fluids (Pr = 0.01) in a liquid bridge with a non-cylindrical free surface. For Pr < 0.08 (e.g. liquid metals), in supercritical region of parameters 3D but non-oscillatory convective flow is observed. The computer program developed for this simulation transforms the original non-rectangular physical domain into a rectangular computational domain.<p><p>A study of how presence of a bubble in experimental rectangular cell influences the convective flow when carrying out microgravity experiments. As a model, a real experiment called TRAMP is numerically simulated. The obtained results were very different from what was expected. First, because of residual gravity taking place on board any spacecraft; second, due to presence of a bubble having appeared on the experimental cell's wall. Real data obtained from experimental observations were taken for the calculations.<p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

Le procédé de précipitation du peroxyde d'uranium en lit fluidisé breveté par AREVA est actuellement testé à l'échelle pilote sur différents sites miniers en vue d'applications industrielles à court terme. Le yellow cake formé par ce procédé a des qualités très intéressantes en termes de densité, granulométrie et morphologie pour la manipulation et le transport. De plus, le faible taux d'impuretés présents dans le peroxyde d'uranium est un atout important pour la suite du procédé de fabrication du combustible. L'objectif de ce travail est de déterminer la thermodynamique ainsi que les cinétiques de nucléation primaire et de croissance cristalline qui régissent la précipitation du peroxyde d'uranium en vue d'une modélisation globale permettant de simuler le comportement du système. Afin de déterminer la solubilité du peroxyde d'uranium sur une large gamme de conditions opératoires correspondante aux conditions du procédé industriel, un modèle de solubilité a été développé et optimisé à l'aide de mesures expérimentales. Dans le cadre de cette étude, le produit de solubilité a été identifié ce qui a permis la mise en équation et le calcul de la sursaturation, force motrice de la précipitation qu'il est indispensable de connaitre pour l'étude des cinétiques de nucléation et de croissance. Les nucléations primaires sont étudiées par une approche phénoménologique qui met en oeuvre une méthode développée par Bertrand-Andrieu basée sur l'utilisation d'un appareil permettant un micromélange très rapide (~1ms) des réactifs. La cinétique de nucléation primaire du peroxyde d'uranium suit la loi classique de Volmer et Weber. De plus il est démontré que la nucléation primaire est fonction de la concentration de sulfate, la loi correspondante intègre alors cette dépendance via le terme BN lié à la tension interfaciale et ainsi à la quantité de sulfate absorbée. La cinétique de croissance est de même déterminer par une approche phénoménologique. Au vue de la production d'ions H+ au cours de la réaction de précipitation, l'étude expérimentale de la croissance cristalline est effectuée par suivi pH-métrique. Étant indépendante de la vitesse d'agitation, la croissance est contrôlée par l'intégration au réseau cristallin selon un mécanisme en spirale. Il est démontré que la loi de croissance du peroxyde d'uranium est d'ordre un vis-à-vis de la sursaturation, le paramètre cinétique kg étant dépendant de la concentration de sulfate et du pH, une loi empirique fonction des conditions expérimentales est alors proposée pour ce paramètre / The uranium peroxide precipitation in fluidised bed patented by AREVA is currently tested on pilot scale reactor on different mine sites for industrial applications in the short term. The yellow cake produced on this way has very interesting qualities in terms of density, particle size and morphology for handing and transport. In addition, the low level of impurities present in the uranium peroxide is an important advantage for the rest of the manufacturing process fuel. The objective of this work is to determine the thermodynamics and kinetics of primary nucleation and crystal growth governing the uranium peroxide precipitation for a global modelling to stimulate the system behaviour. In order to determine the uranium peroxide solubility over a wide range of operating conditions corresponding to the industrial process conditions, a solubility model has been developed and optimized using experimental measurements. In this study, the solubility product has been identified which allows the calculation of the supersaturation, driving force of the precipitation which is an essential parameter to know in order to study the nucleation and crystal growth kinetics. The primary nucleation is investigated by a phenomenological approach which implements a method developed by Bertrand-Andrieu based on the use of a very fast reagents micromixing device (~1ms). Uranium peroxide primary nucleation kinetics follows the Volmer and Weber law. Furthermore it is shown that the primary nucleation depends on the sulphate concentration, the corresponding law incorporates this link with the BN term related to the interfacial tension and thus the quantity of sulphate absorbed. Crystal growth kinetics is also determined by a phenomenological approach. Due to the hydrogen ion production during the precipitation reaction, the crystal growth experimental study is performed by a pH-metric monitoring. Independent of the impeller speed, crystal growth is surface integration controlled with a spiral mechanism. It is shown that the uranium peroxide crystal growth law is first order with respect to the supersaturation. The kinetic parameter kg is dependent on pH and sulphate concentration, an empirical law function of the experimental conditions is then proposed for this parameter

Os peptídeos da estaterina (DR9) e da histatina 3 (RR14), que ocorrem naturalmente na película in vivo, amplificam o efeito inibitório do crescimento de cristais de hidroxiapatita, função relacionada à remineralizarão do esmalte e formação de cálculos dentários. A hipótese da duplicação/hibridação de domínios funcionais dos peptídeos DR9 da estaterina e RR14 da histatina 3 foi testada. Para isto, os peptídeos peptidomiméticos (DR9-DR9, DR9-RR14), além deles individualmente e suas proteínas intactas (DR9, RR14, estaterina e histatina 3) foram estudados em sete concentrações diferentes para avaliar o efeito da inibição do crescimento de cristais de hidroxiapatita. Foi utilizado um ensaio colorimétrico de microplaca para quantificar o crescimento de cristais de hidroxiapatita. As experiências foram feitas em triplicata e a concentração inibitória (IC50) foi estabelecida para cada grupo. A IC50 foi calculada para todos os peptídeos e proteínas testados. A histatina 3 e o RR14 não atingiram o valor de IC50. O DR9- RR14 atingiu o valor de IC50 a 3,80 M. Como esperado, DR9 e DR9-DR9 demonstraram um efeito inibitório significativo na atividade de crescimento de cristais, atingindo o valor de IC50 a 2,82 M e 1,07 M, respectivamente. A estaterina atingiu o valor de IC50 a 2,50 M. Na análise estatística, foram aplicados os testes ANOVA e Student-Newman-Keuls para comparações por pares, para comparar os valores entre os grupos. O DR9-DR9 amplificou o efeito inibitório do crescimento de cristais de hidroxiapatita quando comparado com DR9 único (p <0,05), demonstrando que a multiplicação do domínio funcional é uma forte tendência evolutiva da proteína. De forma interessante, o peptídeo híbrido DR9-RR14 demonstrou um efeito inibitório intermediário quando comparado com outros dois grupos: DR9 único e DR9-DR9. Este estudo utilizou a abordagem peptidomimética para investigar uma via potencial de evolução da proteína relacionada com a duplicação/hibridação dos constituintes peptídicos naturais da película adquirida de esmalte. O conhecimento obtido por meio dos resultados deste trabalho pode fornecer uma base para o desenvolvimento de peptídeos sintéticos para uso terapêutico, tanto contra cárie dentária, como para a doença periodontal. / The statherin and histatin 3 peptides (DR9 and RR14 respectively), which occur naturally in the film in vivo, amplify the inhibitory effect for the growth of hydroxyapatite crystals, a function related to remineralization of the enamel and formation of dental calculi. The hypothesis of duplication/hybridization of functional domains of the DR9 peptides of the statherin and RR14 of histatin 3 was tested. For this, the peptidomimetic peptides (DR9-DR9, DR9-RR14), in addition to them individually and their intact proteins (DR9, RR14, statherin and histatin 3) were studied at seven different concentrations to evaluate the effect of growth inhibition of hydroxyapatite crystals. A colorimetric assay of microplate was used to quantify the growth of hydroxyapatite crystals. The experiments were done in triplicate and the inhibitory concentration (IC50) was established for each group. The IC50 was calculated for all peptides and proteins tested. Histatin 3 and RR14 did not reach the IC50 value. DR9-RR14 reached the IC50 value at 3.80 M. As expected, DR9 and DR9-DR9 demonstrated a significant inhibitory effect on crystal growth activity, reaching the IC50 value at 2.82 M and 1.07 M, respectively. Statherin reached the IC50 value at 2.50 M. ANOVA and Student-Newman-Keuls tests for paired comparisons were applied to compare the values between the groups. DR9-DR9 amplified the inhibitory effect of hydroxyapatite crystal growth when compared to single DR9 (p <0.05), demonstrating that the multiplication of the functional domain is a strong protein evolution pathway. Interestingly, the hybrid peptide DR9-RR14 demonstrated an intermediate inhibitory effect when compared to other two groups: single DR9 and DR9-DR9. This study utilized the peptidomimetic approach to investigate a potential pathway of protein evolution related to duplication/hybridization of the natural peptidic constituents of the acquired enamel film. The knowledge obtained through the results of this work can provide a basis for the development of synthetic peptides for therapeutic use, both against dental caries and for periodontal disease.

Foram realizados estudos da síntese e do crescimento de cristais de BaY2F8:TR (TR= Nd3+; Pr3+; Er3+; Tb3+; Dy3+) simplesmente dopados e codopados (Nd3+:Dy3+ ; Nd3+:Pr3+) por meio do método de fusão por zona (FZ). Os cristais crescidos foram caracterizados quanto a sua estrutura por Difração de raios-x (DRX) e Difração de nêutrons (DN) com análise pelo método de Rietveld. Foi também estudado o comportamento na fusão deste material puro e dopado com elementos terras raras trivalentes através de: microscopia eletrônica de varredura (MEV) e espectroscopia dispersiva de raios-x (EDS). A concentração final de dopantes, bem como, sua distribuição nos cristais crescidos foi estimada e, quando possível, foi ainda calculado o coeficiente de segregação de cada dopante nesta matriz. Os cristais foram também analisados por espectroscopia de absorção e emissão no caso dos materiais duplamente dopados, sendo observada evidencias de transferência de energia Nd-Pr na região UV. Foram obtidos cristais com dimensões da ordem de 40 mm x 10mm com boa qualidade óptica e estrutural adequados para estudos espectroscópicos e testes de ação laser com bombeamento por laser de diodo. Experiências preliminares de crescimento de fibras monocristalinas desta matriz pura e dopada com Tb3+, pelo método de crescimento de micro-pulling down, foram também realizadas visando uma avaliação do método aplicado a este fluoreto. Foram obtidas apenas fibras translúcidas com diâmetro constante sendo necessária maior investigação sobre o crescimento de fibras deste material puro ou dopado. / Synthesis and Growth process of single crystals of BaY2F8:TR (TR= Nd3+; Pr3+; Er3+; Tb3+;Dy3+) single-doped and co-doped (Nd3+ :Dy3+ ; Nd3+:Pr3+) were performed by Zone Melting method (ZM). The grown crystals were characterized by X-ray diffraction (XRD) and Neutron Diffraction (ND) and analyzed by the Rietveld Method. The melting behavior of this pure and trivalent rare earth doped-fluoride was investigated also by scanning electron microscopy (MEV) and X-ray energy dispersive spectroscopy (EDS). The concentration and distribution of the dopants in the grown crystals were measured, and when feasible, the segregation coefficient was estimated. The single crystals were also analyzed by absorption spectroscopy and emission spectroscopy in the case of the co-doped crystals. Evidences of the occurrence of energy transfer process in the UV for Nd-Pr were detected. From the study of the growth process single crystals of 40mm x 10mm in size, with good optical and structural quality were obtained for spectroscopy studies and tests of laser emission. Initial experiments were also performed in the growth of single crystalline fibers of this host doped with Tb3+, by the micro-pulling down method aiming a preliminary evaluation of the use of this growth process. Only semi-transparent fibers were obtained. Additional studies are necessary to improve the growth of single crystalline fibers of this fluoride.

In dieser Arbeit wurden Segregationen, die bei der Z"uchtung einkristalliner Fasern von Oxidmischkristallsystemen mittels der Micro-Pulling-Down Methode auftreten, experimentell und theoretisch untersucht. Dazu wurden Fasern von hochschmelzenden Oxidmischkristallsystemen mit unterschiedlichen Gleichgewichtsverteilungskoeffizienten gezüchtet. Es wurde gezeigt, dass die Dotierstoffprofil von dem Gleichgewichtsverteilungskoeffizienten, der Ziehgeschwindigkeit, dem Sauerstoffpartialdruck der Züchtungsatmosphäre sowie der Meniskushöhe abhängt. Ein analytisches und ein numerisches Modell wurden erstellt um den Segregationsprozess zu beschreiben. Ein Modell basierend auf der irreversiblen Thermodynamik wurde zur Berechnung der Thermodiffusionskoeffizienten mittels Enthalpie und Entropie hergeleitet. Ausserdem wurden mechanische Spannungen, die durch die Segregationen erzeugt werden, untersucht. LiYF4 wurde erfolgreich gezüchtet. Für diesen Fall wurde die Notwendigkeit einer reinen Züchtungsatmosphäre sowie eines reinen Ausgangsmaterials in Bezug auf Wasser- und Sauerstoffverunreinigungen, gezeigt. / Within this study segregations, which occur during micro-pulling-down growth of single-crystal fibers of oxide solid solutions, have been analyzed in an experimental and theoretical manner. Single-crystal fibers of high melting point oxide solid solutions with different equilibrium distribution coefficient have been grown. It has been shown, that the dopant distribution depends on the equilibrium distribution coefficient of the dopant, the pulling speed, the oxygen partial pressure of the growth atmosphere and the meniscus height. An analytical and a numerical model have been established to describe the segregation process. A theoretical model based on irreversible thermodynamics to calculate the thermodiffusion factors using the enthalpy and entropy was derived. Also mechanical stresses induced by the segregation have been analyzed. LiYF4 has been grown successfully. In this case the necessity of a very high purity atmosphere and source material in terms of water and oxygen trace impurities has been shown.