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Bacterial leaching utilises bacteria, ubiquitous to sulphide mining environments to oxidise sulphide ores. The sulphide mineral chalcopyrite is the most common copper mineral in the world, comprising the bulk of the known copper reserves. Chalcopyrite is resistant to bacterial leaching and despite research over the last 20-30 years, has not yet been economically bioleached. Attempts have been made to use silver to catalyse the bacterial leaching of chalcopyrite since the early seventies. The majority of reported testwork had been performed on finely ground ore and concentrates in agitated batch reactors. This project used silver to catalyse the bioleaching of chalcopyrite in shake flasks, small columns and large columns. The catalytic effect was extensively studied and experimental parameters were varied to maximise copper recovery. Silver was also used to catalyse the ferric leaching of chalcopyrite at elevated temperatures. It was noted that the leaching performance of chalcopyrite in shake flasks compared to columns was markedly different. The specific differences between shake flasks and columns were qualified and separately tested to determine which parameter(s) affected the bioleaching of chalcopyrite. It was found that the ore to solution ratio, aeration, addition of carbon dioxide, solution distribution and small variations in the leaching temperature did not significantly effect the bioleaching of chalcopyrite ore in columns. The method of silver addition to columns did significantly affect the overall copper extraction. The ore in shake flasks was subjected to abrasion between ore particles and with the base of the flask. A test was designed to mimic the shake flask conditions, without the abrasion. The low abrasion test performed similarly to a column, operated with optimum silver addition. This indicated that the inherent equipment difference between shake flask and column operation largely accounted for the difference in leaching performance. Chalcopyrite ore was biologically leached in large columns. The ore crush size and other conditions were typical of those used in the field. The biological leach achieved 65% copper extraction in 160 days. This level of copper extraction is significantly higher than any previously reported results (typically /10% copper extraction) and represents a significant advance in the bacterial leaching of chalcopyrite ore. Due to the inherent high temperature within underground stopes, it was decided to investigate the possibility of separating the leaching and the bacterial oxidation stages. The concept of separate bacterial and ferric leaching has been previously suggested, however the application to a stope, and heat exchange between the process streams was a novel approach. Large column ferric leaches at 70 oC illustrated the technical feasibility of this process. Copper extraction was rapid and high (70% in 100 days of leaching), even when a reduced level of silver catalysis was used. After leaching in large columns, samples of ore were taken for analysis by optical mineralogy. The analysis gave valuable insights into the nature of reaction passivation on chalcopyrite ore. In particular, it was discovered that the precipitation of goethite was a major limiting factor in the bioleaching and ferric leaching of chalcopyrite in columns. In addition, reduced sulphide species were detected on the surface of residual chalcopyrite, giving an indication of the sequential nature of the chalcopyrite reaction chemistry. The bacterial population was characterised using DNA techniques developed during the project. Qualitative speciation was carried out and compared between the columns, down the columns and over time in a column. Comparison of these populations enabled greater mechanistic understanding of the role of bacteria in the leaching of chalcopyrite. This work was the most comprehensive attempt to date made to delineate the complex microbiological/mineral actions using analysis of population dynamics from a mixed inoculum. It was found that the iron oxidiser Thiobacillus ferrooxidans dominated within the columns and leach solutions. The sulphur oxidiser Sulfobacillus thermosulfidooxidans was also prevalent in the columns, particularly during the period of rapid chalcopyrite oxidation. The high temperature, ferric leaching of chalcopyrite was unexpectedly poor in the first round of large columns. The reason for the low extraction was attributed to an increase in pH down the column, resulting in excessive goethite precipitation. The solution flowrate (velocity) was increased by ten times in subsequent columns. There were no operational problems (e.g. break-up of ore agglomerates). The increase in flowrate resulted in a high yield of copper. The kinetics of extraction were faster than a corresponding bacterial leach, confirming the potential advantage of a high temperature leach. The small column studies highlighted that it was important to get an even distribution of silver down the stope to enable maximum catalytic effect. If the ore were agglomerated, silver would be added with acid at that point. However, it may not always be possible to agglomerate the ore. For example, the process may be used in-situ on a fractured ore body, or on an ore that has a low fines content, and hence does not require agglomeration. Various complexing agents were tested for their ability to distribute silver at the start of the leach and to recover silver at the end of the leach. For instance when silver was complexed with thiourea and then trickled through the ore, an even distribution of silver was achieved. After leaching was completed, a thiourea wash recovered a significant amount of the silver. These two techniques minimised the amount of silver required and thus significantly added to the economic viability of the process. The success of the technical work has led to an evaluation of the process in the field. A flowsheet was developed for the high temperature, in-stope ferric leach of chalcopyrite. An economic analysis was performed that illustrated the process would be viable in certain situations. An engineering study considered issues such as acid consumption, aeration, silver distribution, silver recovery and a heat balance of the stope.

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Humans have dramatically increased the amount of reactive nitrogen cycling through the biosphere. In coastal systems, excess nitrogen can lead to negative impacts. Thus, it is crucial to understand how nitrogen is cycled within, and eventually removed from, marine systems and the variables that regulate these processes. Sediment denitrification (the microbial conversion of nitrate (NO3^-) to dinitrogen (N2) gas) and water column nitrification (the two step oxidation of ammonium (NH4^+) to nitrite (NO2^-) and then nitrate (NO3^-)) rates were quantified along an in situ gradient of environmental conditions from an estuary to the continental shelf off Rhode Island, USA. Sediment net denitrification rates were directly measured over multiple seasonal cycles using the N2/Ar technique. Denitrification rates ranged from 20-75 μmol m^-2 hr^-1 (mean 44±4), indicating that this process removes ~5% of total reactive nitrogen entering the North Atlantic shelf region per year. Based on model results, these rates also represented a three-fold decrease in sediment nitrogen removal in New England continental shelf sediments over the past century. A literature review of marine water column nitrification observations were compiled to evaluate how ammonium, nitrite, and total oxidation rates vary worldwide. Rates of ammonium, nitrite, and total oxidation differed among estuary, continental shelf, and open ocean environments (p<0.05). This review highlights that as we continue to study marine "nitrification," it is necessary to consider both individual oxidation processes and environment type. Water column ammonium and nitrite oxidation rates were measured using stable isotope tracers off Rhode Island. At all study sites, nitrite oxidation rates (0-99 nM d^-1) outpaced ammonium oxidation rates (0-20 nM d^-1). These oxidation processes responded in dissimilar ways to in situ water column conditions (depth, salinity, dissolved oxygen, and pH), and these relationships varied with location. Nitrous oxide (N2O) production rates up to 10 times higher than ammonium oxidation indicated that ammonium oxidation may be underestimated if this byproduct is not measured. For the first time, the link between sediment metabolism and water column nitrification was also examined, and the results highlight the importance of benthic-pelagic coupling as controlling factor of water column ammonium and nitrite oxidation. / 2019-04-30T00:00:00Z

The current airspace configuration is highly structured, fixed and is less responsive to changes causing the overall system to lack the flexibility, adaptability, and responsibility needed to handle the increasing air traffic demands in the near future. The work presented in this thesis aims at improving the flexibility and adaptability of today's airspace management in Europe in a pretactical context. We focus on the development of a method to support a process of automatic generation of a sequence of sector configurations composed of predefined sectors. Airspace configurations should be dynamically adjusted to provide maximum efficiency and flexibility in response to demand fluctuations. We dynamically build configurations by combining existing elementary sectors. In this step, any sector combination which forms controllable airspace blocks is eligible and may be used during the day of operation. In this work, we developed efficient methods to solve DAC problem. We formulated and study the sectorization problem from an algorithmic point of view. We proposed methods based on a mathematical modeling and heuristic optimization techniques. We also introduced here an approach to evaluate the workload inside sectors.

Made available in DSpace on 2014-10-09T12:52:13Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:55Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The thesis deals with the comic aspect of the first decade of Jan Neruda's vast column work. The main goal of the thesis is to define and clearly arrange the vague terms in the comic area as well as delimit the column within the author's entire journalist work. The first part of the thesis summarizes the research efforts made so far into Neruda's column journalism focusing on its comic component. The main part of the thesis is dedicated to the two basic forms of literary comic in Neruda's columns, satire and humour, specifically their foundations, means, forms, goals and topics. The incidence, stability and/or variability of the given comic tools are also discussed. In addition, the thesis describes the interrelating factors that significantly affected the form of the author's column comic in the decade observed: the then social and political climate, Neruda's model reader and (self) censorship. KEY WORDS Neruda, column, comic, satire, humour

abstract: In situ remediation of contaminated aquifers, specifically in situ bioremediation (ISB), has gained popularity over pump-and-treat operations. It represents a more sustainable approach that can also achieve complete mineralization of contaminants in the subsurface. However, the subsurface reality is very complex, characterized by hydrodynamic groundwater movement, geological heterogeneity, and mass-transfer phenomena governing contaminant transport and bioavailability. These phenomena cannot be properly studied using commonly conducted laboratory batch microcosms lacking realistic representation of the processes named above. Instead, relevant processes are better understood by using flow-through systems (sediment columns). However, flow-through column studies are typically conducted without replicates. Due to additional sources of variability (e.g., flow rate variation between columns and over time), column studies are expected to be less reproducible than simple batch microcosms. This was assessed through a comprehensive statistical analysis of results from multiple batch and column studies. Anaerobic microbial biotransformations of trichloroethene and of perchlorate were chosen as case studies. Results revealed that no statistically significant differences were found between reproducibility of batch and column studies. It has further been recognized that laboratory studies cannot accurately reproduce many phenomena encountered in the field. To overcome this limitation, a down-hole diagnostic device (in situ microcosm array - ISMA) was developed, that enables the autonomous operation of replicate flow-through sediment columns in a realistic aquifer setting. Computer-aided design (CAD), rapid prototyping, and computer numerical control (CNC) machining were used to create a tubular device enabling practitioners to conduct conventional sediment column studies in situ. A case study where two remediation strategies, monitored natural attenuation and bioaugmentation with concomitant biostimulation, were evaluated in the laboratory and in situ at a perchlorate-contaminated site. Findings demonstrate the feasibility of evaluating anaerobic bioremediation in a moderately aerobic aquifer. They further highlight the possibility of mimicking in situ remediation strategies on the small-scale in situ. The ISMA is the first device offering autonomous in situ operation of conventional flow-through sediment microcosms and producing statistically significant data through the use of multiple replicates. With its sustainable approach to treatability testing and data gathering, the ISMA represents a versatile addition to the toolbox of scientists and engineers. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2013

L'opération de précipitation oxalique du plutonium dans les usines de retraitement du combustible nucléaire est délicate à mettre en œuvre en raison de la nature collante du précipité. Dans l'idée de pallier ce problème gênant vis à vis d'une production industrielle, le Laboratoire de génie chimique et d'instrumentation du CEA Marcoule propose de réaliser cette opération en colonne pulsée à garnissage. Le précipité est alors confiné à l’intérieur des gouttes de l’émulsion et suffisamment loin des surfaces de l'appareil.Cependant si les surfaces en contact son en acier inoxydable, l'appareil s'encrasse invariablement. La thèse s'insère alors dans une démarche de compréhension fine de ces mécanismes d'encrassement. Bien que les travaux réalisés balayent l'ensemble du problème posé, la thèse est essentiellement centrée sur l’analyse du rebond des gouttes de l’émulsion avec les parois de l'appareil. Les résultats acquis permettent d’enrichir la base de données de la littérature dans une configuration peu usitée tout en ciblant les paramètres clés de ce type d'interaction. Les résultats montrent qu'utiliser en première approche, une colonne pulsée non optimisée et conçue intégralement en acier inox ne peut convenir pour réaliser l'opération de précipitation de radionucléides. Cette précipitation peut cependant être menée en s'orientant vers une technologie différente et brevetée à l'issue de cette thèse. Ce dernier point doit cependant être nuancé car l'exploration à des débits industriels de production n'est pas encore acquise. D'un autre coté, cela peut constituer un enjeu intéressant de génie des procédés. / The process dedicated to the oxalic precipitation of plutonium is very sensitive to the high sticking behavior of the produced precipitates. Therefore, the laboratory of génie chimique et instrumentation based in Marcoule in France puts forward the idea of carrying out the process in a pulsed column. In this way, the precipitates is confined inside in the droplets of the emulsion, far from the surfaces of the apparatus. Nevertheless if those surfaces are made of stainless steal the fouling of the column is inevitably observed. The thesis also introduces the concept and tools dedicated to a fine understanding of the fouling issue. Though the work carried out scans the whole issue, the thesis mainly focuses on drop bouncing. the results provide experimental data in a low-studied configuration and target the key parameters driving th bounce. The application of the these results point out that using an unoptimized stainless steal pulsed column for the precipitation of radionucleides does not prevent from the fouling. The process could still be carried out using another technology patented during the PhD. This last poitn needs more investigations. Especially, the CEA has work on the scale-up steps to design an apparatus wich could be able to porcess industrial flow rates. Bsides ths might be an interessing issue in process engineering.