Neste trabalho é apresentado o estudo de alguns dos principais parâmetros envolvidos na fabricação de filmes finos de brometo de tálio (TlBr) por meio da técnica de spray pyrolysis. Investigamos a possibilidade desta técnica vir a se tornar um método alternativo para fabricação de filmes finos de TlBr com qualidade adequada para a confecção de dispositivos detectores de radiação de altas energias, como raios-X e raios-γ. O tempo de fabricação e a qualidade dos filmes eram limitados pelo problema da formação de gotas d’água na parte superior da câmara de deposição, o que resultava na incidência destas gotas sobre os filmes, posteriormente. O problema foi resolvido por meio de um sistema de aquecimento extrínseco ao equipamento. A investigação dos parâmetros citados se deu pela variação dos fluxos de nitrogênio e da solução de TlBr, pelas variações da posição dos substratos no porta substrato, da temperatura e do grau de saturação das soluções. As propriedades cristalinas e estruturais dos filmes foram verificadas pela técnica de difração de raios-X e por microscopia eletrônica de varredura, respectivamente. Os resultados mostram que o pico de intensidade dos planos cristalinos preferenciais dos filmes tendem a se tornar mais intensos para soluções saturadas, fabricados com baixo fluxo de nitrogênio e a temperaturas próximas de 100oC. No entanto, dependendo da posição dos filmes sobre o porta-substrato, a intensidade dos picos, assim como a rugosidade superficial, variam significativamente. Com efeito, conseguimos estender o processo de deposição para qualquer tempo desejado, o que implica, a princípio, em filmes mais espessos e de melhor qualidade. / This work presents the results about the investigation of the importance of some of the main parameters related to the fabrication of thin films of thallium bromide (TlBr) using the spray pyrolysis technique. We evaluated the possibilities for the future use of this technique in the development of high quality TlBr thin films to be used as high-energy radiation (such as X- and gamma rays) detectors. The total deposition time as well as the quality of the films were limited due to the formation of water droplets at the inner part of the top surface of the deposition chamber. These droplets would eventually fall over the substrates damaging the sample. This problem was solved by the use of an external heating system. The investigated deposition parameters were: nitrogen and solution flows, substrate position on top of the substrate holder, deposition temperature and composition of the solution. The crystalline and structural properties of the thin films were investigated by X-ray diffraction and Scanning Electron Microscopy. According to the results obtained from the diffraction experiments, the crystalline peaks increase with the saturation of the solution, low nitrogen flow and deposition temperatures close to 100oC. Nevertheless, the substrate position can also influence the crystallinity and amount of deposited material. In summary, we optimized the deposition parameters for the development of thick and high quality films that could be used for the development of sensors in the future.

Orientador: Eric de Camargo Smidt / Resumo: O clado Ornithocephalus compreende 12 gêneros e 120 espécies e está distribuído do sul do México ao norte da Argentina, abrangendo regiões úmidas do oeste ao leste da América do sul. Embora o clado tenha sido recentemente foco de vários estudos filogenéticos, e seu monofiletismo não ser contestado, o arranjo de muitas espécies dentro do clado permanece desconhecido. Neste trabalho, investigamos o posicionamento das espécies de Centroglossa Barb.Rodr. Dunstervillea Garay e Zygostates Lindl. dentro do clado em foco, através de dados do DNA nuclear e plastidial, bem como dados morfológicos, por meio de análises de máxima verossimilhança, inferência bayesiana e máxima parcimônia. Encontramos uma relação filogenética estreita entre Dunstervillea e Eloyella P. Ortiz. sustentada por sinapomorfias morfológicas vegetativas e reprodutivas. Centroglossa e Zygostates aparecem intimamente relacionados em todas as análises, nas quais Centroglossa se mantem monofilético incluído em Zygostates. Através de análises em MEV de flores em desenvolvimento, identificamos a origem de apêndices florais, da tábula infraestigmática e do calo do labelo. Além disso, observamos em Zygostates e gêneros próximos, 26 características micromorfológicas e atividade secretora na flor em antese, que nos fornecem um maior número de caracteres e sustentam os clados gerados nas análises filogenéticas. No estado do Paraná, Zygostates possui 36 registros na Floresta Ombrófila Densa e Floresta Ombrófila Mista. Segundo ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Ornithocephalus clade comprising 12 genera and 120 species and is distributed from southern Mexico to northern Argentina, covering wetlands from west to eastern South America. Although the clade has recently been the focus of several phylogenetic studies, and its monophyly is not disproved, the arrangement of many species within the clade remains unknown. In this work, we investigate the placement of Centroglossa Barb.Rodr., Dunstervillea Garay and Zygostates Lindl. species within the clade in focus, using nuclear and plastid DNA data, as well as morphological data, through maximum likelihood, Bayesian inference and maximum parsimony analyzes. We found a close phylogenetic relationship between Dunstervillea and Eloyella P. Ortiz. supported by vegetative and reproductive morphological synapomorphies. Centroglossa and Zygostates appear closely related in all analyses, where Centroglossa remains monophyletic included in Zygostates. Based in analysis of SEM of development flowers, we identified the origin of floral appendages, tabula infrastigmatica and the lip callus. Through the same analysis, we observed in Zygostates and close genera, 26 micromorphological characteristics and secretory activity in the flower anthesis, which provide us a larger number of characters and support the clades generated in phylogenetic analyzes. In the state of Paraná, Zygostates has 36 records in Floresta Ombrófila Densa and Floresta Ombrófila Mista. According to IUCN criteria, Zygostates allen... (Complete abstract click electronic access below) / Doutor

Introduction We measured the excitation functions of natZn (p,x) reactions up to 17.6 MeV using the stacked-foils activation technique. High-purity natural zinc (and copper) foils were irradiated with proton beams from an 18MeV medical cyclotron, the predominant purpose of which is to provide a routine regional service for clinical PET radiopharmaceuticals. Thick-target integral yields were also deduced from the measured excitation functions of the produced radioisotopes. These results were compared with the literature and were found to be in good agreement with most but not all published reports. Material and Methods The excitation functions of the natZn(p,x) reactions were measured by the well-known stacked foil technique (1). High purity zinc foils (99.99%; Goodfellow Metals Ltd., UK) each thickness 0.025 ± 0.003 mm with isotopic composition 64Zn (48.6 %), 66Zn (27.9 %), 67Zn (4.1 %), 68Zn (18.8 %) and 70Zn (0.6 %) were loaded into a solid targetry system on a 300-mm external beam line utilising helium-gas and chilled water to cool the target body (2). A typical foils stack consisted of repeated units of four Zn foils interleaved with a high purity copper foil (0.025 ± 0.004 mm); the latter for monitoring beam flux using the well documented 63,65Cu(p,n)63,65Zn reactions. Foil stacks were irradiated with a primary beam of energy 17.6 MeV, accounting for beam degradation by an obligatory 0.0250 ± 0.0005 mm-thick Havar® foil beam-line vacuum window. Irradiation was for 3 min at a beam current of 5 µA. Activated foils were measured using cryo high-purity Ge γ-spectroscopy to quantify the product radionuclides 61Cu, 66Ga, 67Ga and 65Zn. Radioactivity of each isotope was corrected to end of bombardment (EOB). Results and Conclusion New cross-sectional data for natZn(p,x) reactions up to 17.6 MeV yielding 61Cu, 66Ga, 67Ga and 65Zn isotopes were measured in independent replicated (N = 3) experiments. Results were generally in good agreement with published data. These isotopes can potentially be used in clinical or preclinical studies, following appropriate chemical separations of the zinc, gallium and copper (3). The FIG. 1 shows thick-target integral yields calculated from excitation functions measured in this study. It can be calculated (for example) that useful activities of 61Cu can be produced using a 100 µm thick natZn target in a beam provided by a standard medium-energy medical cyclotron. For example, an irradiation at 40 µA for 2 hr at 17.6 MeV would produce approximately 1.7 GBq of 61Cu at EOB. Such currents are readily achievable using solid targetry in our laboratory (2).

Thèse numérisée par la Direction des bibliothèques de l’Université de Montréal / Le travail présenté dans cette thèse se concentre sur la diffusion inélastique de neutrons de 14 MeV sur les premiers niveaux excités du carbone, de l'oxygène, et du lithium. Les mesures des sections efficaces différentielles ont été réalisées à des angles compris entre 30° et 130°. Le faisceau de deutérons, d'une énergie de 170 keV provenant de l'accélérateur Cockcroft-Walton, frappe une cible de tritium, produisant ainsi des neutrons de 14 MeV par la réaction T(d,n)He4. L'énergie des neutrons diffusés est déterminée par une méthode de temps de vol, utilisant la détection de la particule associée à la production du neutron pour connaître son temps de départ. Le temps de vol est converti en une impulsion de tension, qui est mesurée par un sélecteur d'amplitude à 100 canaux. La résolution temporelle du système est de 3 nanosecondes. Pour tous les niveaux excités observés, les courbes des sections efficaces différentielles inélastiques présentent une asymétrie par rapport à 90 degrés. Les résultats sont comparés aux prédictions du modèle d'interaction directe de Glendenning, et l'accord est satisfaisant pour tous les niveaux étudiés.

The rise of cryptocurrencies has brought with it new math problems with new sets of constraints. The MEV problem entails solving for the ordering of pending trades that maximizes a block creator's profit. In decentralized finance, time is a big constraint, so an exhaustive search of all possible orderings is impossible. I propose a solution to the MEV problem that gives a near optimal result that can be solved in a reasonable amount of time. I layout the method and the formulas required for my solution. Additionally, I test my solution on synthesized data to show that it works as desired.

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Master of Science / Department of Mechanical and Nuclear Engineering / William L. Dunn / A prototype system for detecting explosives at standoff distances, using a signature based radiation scanning approach, is being developed at Kansas State University. The prototype will incorporate both a machine x-ray source and a machine neutron source to generate signatures from unknown samples of material. These signatures can be compared to templates measured or calculated from known explosive samples using a figure-of-merit. The machine neutron source uses the fusion of deuterium and tritium to create 14.1 MeV neutrons. Due to its radioactivity, the tritium must be sealed within the system. A new method of controlling the gas pressure with the DT generator was developed using a Zr-V-Fe getter supplied by a commercial firm. The shielding and collimation of the 14.1 MeV neutron source is accomplished using layers of steel, high-density polyethylene and borated high-density polyethylene. This thesis describes the development of the gas control method for the sealed neutron source, design studies for the shielding and collimation of the neutron source and modifications made to the building in which the prototype is being housed.

C’est grâce à une initiative de Revenu Québec, avec la collaboration de l’Association des restaurateurs du Québec, que le module d'enregistrement des ventes a été déployé dans le secteur de la restauration, entre le 1er septembre 2010 et le 1er novembre 2011, afin de lutter contre l’évasion fiscale. Jusqu’à ce jour, l’impact de ce projet a seulement été évalué à l’interne par Revenu Québec. Cette étude propose donc une analyse empirique, avec les données publiques canadiennes, afin d’évaluer l’impact de l’implantation du module d'enregistrement des ventes dans le secteur de la restauration au Québec, à l’aide d’un modèle en difference-in-differences et d’un modèle en Premières différences. Plus précisément, nous cherchons à déterminer si la mesure a eu un impact sur le PIB du secteur de l’hébergement et des services de restauration au Québec. Avec l’implantation du module d’enregistrement des ventes, on s’attend à ce que les possibilités d’évasion fiscale soient réduites et que les ventes déclarées augmentent. Les résultats de l’analyse suggèrent des signes potentiels d’effets de la mesure, sans toutefois avoir suffisamment de précision dans les données pour appuyer l’hypothèse avec certitude.

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