Made available in DSpace on 2016-09-27T13:40:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-02-26. Added 1 bitstream(s) on 2016-09-27T13:45:19Z : No. of bitstreams: 1 000868845.pdf: 1530216 bytes, checksum: 42c21c1e0a6ab7333a7999028faa991d (MD5) / PbO possui duas fases alotrópicas principais: (i) a-PbO, com estrutura tetragonal, tipo massicote, pertencente ao grupo espacial P42/mnm (129), com célula de parâmetros a=0,3975nm e c= 0,5022nm e (ii) B-PbO, tipo litárgico, estrutura ortorrômbica pertencente ao grupo espacial Cmma (67), com constantes de célula: a= 0,5609nm, b =0,5607nm e c=0,4997nm. PbO2 possui duas fases alotrópicas principais: (i) a-PbO2, tipo columbita,com estrutura ortorrômbica que pertence ao grupo de espacial Pbcn (60), com parâmetros de rede: a= 0,497nm, b= 0,596nm e c= 0,544nm, e (ii) B-PbO2, tipo rutilo, estrutura tetragonal pertencente ao grupo espacial P42/mnm (136), com parâmetros de rede: a = 0,491 nm e c = 0,3385 nm. a-PbO e B-PbO2 são ambos considerados materiais altamente covalentes com forte hibridação entre os orbitais 2p de O e 6s e 6p doPb. Para o PbO a fase α apresenta um band gap indireto, diferentemente do B-PbO em que o band gap é direto, materiais de band-gap indireto a energia absorvida é liberada na forma não apenas de luz, mas também de calor. Analisando-se as densidades de estado, em ambas as fases, a banda de valência é formada predominantemente deorbitais do O, já a banda de condução é formada por orbitais do metal. B-PbO2 é um semicondutor com band gap estreito, que recebeu grande atenção ultimamente devido à sua potencial utilização como óxido condutor transparente (TCO). Neste trabalho, adotamos uma abordagem mecânico-quântica baseada na Teoria do Funcional de Densidade periódica, com potencial híbrido B3LYP.Assim, investigamos a estrutura eletrônica de todas as fases com o objetivo de contribuir para uma melhor compreensão do comportamento dos referidos materiais. O código computacional CRYSTAL09 foi utilizado para os cálculos. Os dados da estrutura de bandas, sugerem que a condução do B-PbO2 é uma característica intrínseca do material que surge a partir das sobreposições dos orbitais 6s da banda... / PbO has two main allotropic phases: a-PbO, massicot type tetragonal structure belonging to space group P42/mnm (129), with cell constants a = 0.3975 nm and c = 0.5022 nm and B-PbO, litharge type orthorhombic structure belonging to the space group Cmma (67), with cell constants a = 0.5609 nm, b = 0.5607 nm and c = 0.4997 nm. PbO2 has two main allotropic phases: a-PbO2, columbite type orthorhombic structure belonging to the space group Pbcn (60), with cell constants a = 0.497 nm, b = 0.596 nm and c = 0.544 nm, and B-PbO2, rutile type tetragonal structure belonging to space group P42/mnm (136), with cell constants a = 0.491 nm and c = 0.3385 nm. a-PbO and B-PbO2 are both considered highly covalent materials with strong hybridization between the 2p orbitals of O and 6s and 6p orbitals of Pb. B-PbO2 is a narrow band gap semiconducting, which has received a great deal of attention lately due to their potential use as TCO. In this work, we adopt a quantum mechanical approach based on the periodic Density Functional Theory (DFT), with B3LYP hybrid potential, to investigate the electronic structure of all phases, aiming to contribute to a better understanding of the materials behavior. The CRYSTAL09 code has been used for the calculations. From the calculations of band structures, it is suggested that the conducting behavior of B-PbO2 is an intrinsic characteristic of the material that arises from the overlaping of the 6s orbital of the conducting band of Pb and the 2p orbital of the top of valence band of O. The charge density of the Pb cations in B-PbO2 and a-PbO2 is about half the formal ionic charge. PbO2 has a small direct band gap

Orientador: João Manuel Marques Cordeiro / Banca: Victor Ciro Solano Reynoso / Banca: Osmar Vital de Oliveira / Resumo: PbO possui duas fases alotrópicas principais: (i) a-PbO, com estrutura tetragonal, tipo massicote, pertencente ao grupo espacial P42/mnm (129), com célula de parâmetros a=0,3975nm e c= 0,5022nm e (ii) B-PbO, tipo litárgico, estrutura ortorrômbica pertencente ao grupo espacial Cmma (67), com constantes de célula: a= 0,5609nm, b =0,5607nm e c=0,4997nm. PbO2 possui duas fases alotrópicas principais: (i) a-PbO2, tipo columbita,com estrutura ortorrômbica que pertence ao grupo de espacial Pbcn (60), com parâmetros de rede: a= 0,497nm, b= 0,596nm e c= 0,544nm, e (ii) B-PbO2, tipo rutilo, estrutura tetragonal pertencente ao grupo espacial P42/mnm (136), com parâmetros de rede: a = 0,491 nm e c = 0,3385 nm. a-PbO e B-PbO2 são ambos considerados materiais altamente covalentes com forte hibridação entre os orbitais 2p de O e 6s e 6p doPb. Para o PbO a fase α apresenta um band gap indireto, diferentemente do B-PbO em que o band gap é direto, materiais de band-gap indireto a energia absorvida é liberada na forma não apenas de luz, mas também de calor. Analisando-se as densidades de estado, em ambas as fases, a banda de valência é formada predominantemente deorbitais do O, já a banda de condução é formada por orbitais do metal. B-PbO2 é um semicondutor com band gap estreito, que recebeu grande atenção ultimamente devido à sua potencial utilização como óxido condutor transparente (TCO). Neste trabalho, adotamos uma abordagem mecânico-quântica baseada na Teoria do Funcional de Densidade periódica, com potencial híbrido B3LYP.Assim, investigamos a estrutura eletrônica de todas as fases com o objetivo de contribuir para uma melhor compreensão do comportamento dos referidos materiais. O código computacional CRYSTAL09 foi utilizado para os cálculos. Os dados da estrutura de bandas, sugerem que a condução do B-PbO2 é uma característica intrínseca do material que surge a partir das sobreposições dos orbitais 6s da banda... / Abstract: PbO has two main allotropic phases: a-PbO, massicot type tetragonal structure belonging to space group P42/mnm (129), with cell constants a = 0.3975 nm and c = 0.5022 nm and B-PbO, litharge type orthorhombic structure belonging to the space group Cmma (67), with cell constants a = 0.5609 nm, b = 0.5607 nm and c = 0.4997 nm. PbO2 has two main allotropic phases: a-PbO2, columbite type orthorhombic structure belonging to the space group Pbcn (60), with cell constants a = 0.497 nm, b = 0.596 nm and c = 0.544 nm, and B-PbO2, rutile type tetragonal structure belonging to space group P42/mnm (136), with cell constants a = 0.491 nm and c = 0.3385 nm. a-PbO and B-PbO2 are both considered highly covalent materials with strong hybridization between the 2p orbitals of O and 6s and 6p orbitals of Pb. B-PbO2 is a narrow band gap semiconducting, which has received a great deal of attention lately due to their potential use as TCO. In this work, we adopt a quantum mechanical approach based on the periodic Density Functional Theory (DFT), with B3LYP hybrid potential, to investigate the electronic structure of all phases, aiming to contribute to a better understanding of the materials behavior. The CRYSTAL09 code has been used for the calculations. From the calculations of band structures, it is suggested that the conducting behavior of B-PbO2 is an intrinsic characteristic of the material that arises from the overlaping of the 6s orbital of the conducting band of Pb and the 2p orbital of the top of valence band of O. The charge density of the Pb cations in B-PbO2 and a-PbO2 is about half the formal ionic charge. PbO2 has a small direct band gap / Mestre

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Made available in DSpace on 2014-10-09T12:23:48Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:52Z (GMT). No. of bitstreams: 1 00340.pdf: 2185302 bytes, checksum: 4bcbd0d784b94c5fcd08401a5972d419 (MD5) / Tese (Doutoramento) / IEA/T / Instituto de Fisica, Universidade de Sao Paulo - IF/USP

La préservation de la qualité des eaux marines et la lutte contre les pollutions liées à l'activité humaine sont devenues des enjeux mondiaux. De nombreux contaminants biologiques et polluants chimiques se retrouvent dans l’eau de mer, par conséquent dans les produits aquacoles. Ce contexte fait qu’aujourd’hui, les professionnels de la mer sont à la recherche de solutions pour préserver voire améliorer la qualité de leurs eaux. Au sein de notre biodiversité, les éponges marines sont des animaux capables de filtrer 10 000 fois leur volume en eau par jour et de retenir 80% des particules en suspension comme la matière organique, les minéraux, les bactéries et les virus. Par la même occasion, elles accumulent certains éléments traces métalliques comme le plomb, le cadmium ou le cuivre. En collaboration avec le Comité Régional de Conchyliculture de Bretagne Sud, le projet REMEDBIO dans lequel s’inscrit cette thèse se propose d'exploiter le potentiel de filtration des éponges marines du littoral breton. Les objectifs sont de contrôler le développement de bactéries pathogènes et de réduire la présence de polluants chimiques. L’éponge marine Hymeniacidon perlevis (Demospongiae) a été choisie comme modèle pour cette étude. Après avoir mis en évidence la faisabilité de la culture d’éponges marines sur l’estran, notre travail a montré, lors d’essais in vitro, une diminution de la contamination des huîtres par deux bactéries, Escherichia coli et Vibrio aestuarianus, et par le plomb, un élément trace métallique, en présence d’éponges. La dernière phase de ce travail a consisté à valoriser les résultats obtenus. Le projet d’entreprise LECOMER a débuté par le concours START’UBS (lauréat) proposé par l’Université de Bretagne Sud en 2014. Par la suite, LECOMER a été élu lauréat des Trophées de l’Innovation du Morbihan 2014. / The conservation of waters quality and the fight against pollution due to human activities havebecome global issues. Many biological contaminants and chemical pollutants are found in sea water, therefore in aquaculture products. This context fact sea professional are looking for solutions to preserve or even improve the quality of their waters. Among marine biodiversity, marine sponges filter 10 000 times their volume of water per day and retain 80 % of suspended particles such as organic matter, minerals, bacteria and viruses. In addition, sponges are therefore considered as bio-accumulators of metallic trace element such as lead, cadmium or copper. In collaboration with the Comité Régional de Conchyliculture de Bretagne Sud, REMEDBIO project proposes to exploite potential of marine sponges of the Brittany coast. One of the main priorities of this project is to reduce the impact of chemicals (heavy metals) and of biological contaminants (bacteria, viruses) on shellfish breeding. The marine sponges Hymeniacidon perlevis (Demospongiae) was chosen as the model for this study. Having demonstrated the feasibility of the culture of marine sponges on the foreshore, our work has shown, when tested in vitro, reduced contamination of oysters by two bacteria, Escherichia coli and Vibrio aestuarianus, and lead, a metal trace element, in the presence of sponges. The last phase of this work has been to enhance the results. The company LECOMER project began with the START'UBS contest (winner) proposed by the Université de Bretagne Sud in 2014. Thereafter, LECOMER was elected winner of the Innovation Awards of Morbihan in 2014.

M. Sc. / The Pering Pb-Zn deposit is hosted in the stromatolitic dolomites of the Campbellrand Subgroup of the Ghaap Group, Transvaal Supergroup. The deposit is situated 20 km northeast of the town Reivilo in the semi-arid region of the Northwest Province, South Africa. It has been classified as a Mississippi Valley type deposit and is, together with the Bushy Park Pb-Zn deposit and F-Pb-Zn deposits near Zeerust, the only known MVT deposit of Paleoproterozoic age. The Pering open cast mine has been operational since 1986, yielding 18 Mt at an average ore grade of 3.6 wt.% Zn and 0.6 wt.% Pb. The aim of this study is to devise a metallogenetic model by integrating core logging, petrography, fluid inclusion and stable C-0-S isotope studies. The mineralogy includes sphalerite, galena and minor chalcopyrite as ore minerals, with diagenetic pyrite, hydrothermal dolomite, quartz and calcite as gangue minerals. Sphalerite predominates over galena. Mineralisation occurs as (a) disseminated stratabound replacements sheets restricted mainly to stromatolitic zones of the Steekdorings Member of the Reivilo Formation, and as (b) open space infill in breccia bodies that cross-cut the stratigraphy. Three events of hydrothermal brecciation, resultant of prolonged pulses of fluid infiltration, and mineralisation are recognised. The first brecciation event is marked by the cementation of the dolomite host rock by sparry dolomite, closely associated with finegrained disseminated sphalerite and galena. The second brecciation event is of minor importance, and is marked by the formation of small amounts of the second sphalerite generation, while the third, and final, brecciation event is marked by the formation of euhedral sphalerite, galena, quartz, sparry dolomite, and calcite as open space fill.

Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 2005. / School of Health Systems and Public Health (SHSPH) / Unrestricted

No description available.

This thesis provides an introduction to the subject of Delivery Performance and its measurement. The review shows that non-price factors, especially delivery performance, have become recognised as of major importance in manufacturing business success. Attention is given to the reasons why UK manufacturing companies have such a poor delivery record and the adverse effects which result.

No description available.