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Orientador: Iakov Veniaminovitch Kopelevitch / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-25T10:44:08Z (GMT). No. of bitstreams: 1 Camargo_BrunoCury_D.pdf: 12321037 bytes, checksum: 83e565ea9fa63c5cf0f9f7a0fb7be452 (MD5) Previous issue date: 2014 / Resumo: Neste trabalho serão apresentados os principais resultados obtidos peloautor no decorrer de seu doutorado. Os sistemas estudados eram compostos por grafite, grafeno, antimônio e interfaces de grafite/silício. Uma das partes do trabalho consistiu no estudo de efeitos de desordem estrutural sobre oscilações quânticas em grafite. O estudo revelou que a mosaicidade da grafite estudada, largamente utilizada para se determinar a qualidade de amostras de grafite pirolítico altamente orientado (HOPG), não apresenta correlação com a amplitude das oscilações quânticas no material. Ao invés disso, os experimentos mostraram uma clara correlação entre a rugosidade superficial, a mobilidade eletrônica média e a amplitude do efeito de Haas van Alphen no material. Os resultados indicam que deformações da superfície da grafite afetam fortemente a mobilidade eletrônica do material (reduzindo a amplitude de oscilações quânticas) sem reduzir sua anisotropia. No trabalho, também é discutida a possibilidade de que as oscilações quânticas em grafite estejam relacionadas com a existência de interfaces bem definidas na estrutura interna do material. Também foram estudadas propriedades de transporte elétrico interplanar em grafite no limite ultraquântico. Medidas de magnetorresistência interplanar para campos magnéticos de até 60 T acusaram a ocorrência de uma região de magnetorresistência positiva seguida de magnetorresistência negativa (MRN) para campos magnéticos suficientemente altos. O efeito persistia até temperatura ambiente. Ele é explicado considerando-se o tunelamento de férmions de Dirac entre níveis fundamentais de Landau de planos de grafeno adjacentes dentro da grafite. A região de MRN é mais pronunciada em grafites com menor mosaicidade, o que sugere que o alargamento de níveis de Landau seja responsável pela magnetorresistência positiva observada nas medidas ao longo do eixo c da grafite. Além disso, experimentos de magnetorresistência interplanar com campos magnéticos orientados paralelamente à direção dos planos da grafite apresentaram indícios de que o material se torna mais tridimensional com a redução da temperatura. Os resultados sugerem que a integral de overlap interplanar em grafite possui valor ?1 < 7 meV. Esse valor é muito inferior àqueles reportados na literatura considerando-se o modelo mais bem aceito para grafite, segundo o qual ?1 ? 380 meV. Nesta tese também são apresentados resultados inéditos obtidos pelo autor relacionados a efeito Hall quântico em grafeno crescido epitaxial mente sobre substratos de carbeto de silício, efeitos de desordem estrutural sobre as propriedades de transporte elétrico basal da grafite, supercondutividade em heteroestruturas de grafite e silício e supercondutividade em compósitos de antimônio-ouro / Abstract: In this thesis, experimental results obtained by the author during his PhD will be presented. The work consisted on the study of electrical and magnetic properties of Dirac semimetals and related heterostructures. Namely: graphite, graphene, graphite/silicon interfaces and antimony. Part of the work about graphite consisted on the study of the effects of structural disorder on the quantum oscillations in the material. Experimental results in the literature widely regard the mosaic spread in graphite as a good disorder parameter. However, in the present work, we report that the mosaicity of graphite samples does not correlate with their quantum oscillations¿ amplitude. Experiments have revealed a clear relation of surface roughness to the electronic mobility and the amplitude of the deHaas van Alphen effect in the material. The possibility that quantum oscillations in graphite are affected by the presence of sharp interfaces within its stacking structure is also discussed. We have also studied out-of-plane magnetoresistance properties in ultraquantum graphite. Experiments performed at magnetic fields B//c up to 60 T have shown the occurrence of positive c-axis magnetoresistance followed by a region of negative magnetoresistance (NMR). The NMR persists up to room temperature and has been explained in terms of the tunneling of electrons between zero-energy Landau levels of adjacent graphitic layers. The NMR is more evident in samples with low mosaicity, suggesting the positive c-axis magnetoresistance is induced by means of broadening of LL¿s by disorder. In addition, c-axis magnetoresistance measurements with magnetic fields perpendicular to c-axis (B?c) suggest that our samples undergo a 2D to 3D transition with the reduction of temperature. Based on our results, we estimate a value for the interplane hopping energy parameter ?1 < 7 meV. This value is at odds with the most accepted model for graphite, for which ?1 ? 380 meV. In this thesis, we also present unpublished results on the occurrence of quantum Hall effect in graphene grown epitaxially in silicon carbide substrates, on the effects of structural disorder in the basal electric properties of graphite / Doutorado / Física / Doutor em Ciências

[pt] A administração de antimoniais no tratamento da leishmaniose é uma rara oportunidade para estudar o metabolismo de antimônio e das suas espécies químicas no corpo humano. No presente trabalho, a técnica de espectrometria de massa (ICPMS), acoplada ou não à cromatografia iônica (IC) e à geração de hidretos (HG), foi utilizada para determinação das concentrações de antimônio total e de suas espécies químicas, Sb(III), Sb(V) e trimetilantimônio (TMSbV) em amostras clínicas de pacientes com leishmaniose e/ou de macacos Rhesus (Mucaca mulatta) tratados com antimoniato de meglumina (AM). Diferentes regimes terapêuticos foram avaliados, incluindo a administração de doses baixa e alta (5 mg ou 20 mg de Sb(V) por kg de massa corpórea). A concentração total de Sb foi determinada após a decomposição de amostras por HNO3/H2O2. Análises de especiação foram realizadas em amostra de plasma e urina, através do acoplamento em linha da CI ao instrumento de ICPMS. Duas colunas de troca aniônica PRP-X100 foram utilizadas para a separação de espécies empregando o EDTA (eluição isocrática: 4,7 mmol L-1, 2,5% v/v metanol, pH 4,7) ou tampão de EDTA/fosfato (eluição com variação abrupta de eluente: 1o. eluente - 20 mmol L-1 EDTA + 2 mmol L-1, pH 4,5; 2o. eluente - 50 mmol L-1 (NH4)2PO4, pH 8,3) como fase móvel. As características de desempenho de todos os métodos foram avaliadas e serão apresentadas. Testes de estabilidades mostraram que as espécies de antimônio estudadas são suficientemente estáveis permitindo análises de especiação dentro de 24 horas após a coleta. Em humanos, assim como em macacos Rhesus, as concentrações de antimônio em amostras de urina e/ou plasma coletadas após o período de administração de AM, mostraram uma rápida cinética inicial de excreção (t1/2 ~ 3 dias) da droga, seguida de duas fases mais lentas. Determinou-se concentrações de Sb significativamente maiores em frações de hemácias do que nas amostras de plasma correspondentes, com exceção da fase inicial de administração da droga (primeiras 12 horas). A bioredução de Sb(V) a Sb(III) foi observada e confirmada como um importante processo metabólico durante a fase de eliminação. Nenhuma evidência de formação de TMSb (V) foi obtida em nossos estudos. As concentrações de antimônio em amostras de tecidos de macacos Rhesus coletadas aproximadamente 60 dias após a última administração de AM foram maiores na tireóide, seguida por fígado e baço. As concentrações no fígado foram pelo menos 1000 vezes maiores que a concentração basal. Amostras de cabelos/pelos e unhas de pacientes e símios tratados com AM também apresentaram altas concentrações, as quais corresponderam ao histórico de administração da droga e também mostraram que a incorporação de Sb nestes tecidos é acumulativa, mesmo após o fim da administração de AM. Em cabelos, mesmo após mais de 300 dias do fim do tratamento as concentrações de Sb não retornaram ao nível basal. / [en] Clinical applications of antimonials in the treatment of leishmaniasis are a unique opportunity to investigate the metabolism of antimony and its species in the human body. In this work, inductively coupled plasma mass spectrometry (ICPMS), without or in combination with ion chromatography (IC) and flow injection hydride generation (FI-HG), has been used for the determination of total antimony concentrations [Sb] and three of its expected species, Sb (III), Sb (V) and trimethyl antimony (TMSbV), in clinical samples of leishmaniasis patients and/or of rhesus monkeys (Mucaca mulatta) treated with meglumine antimoniate (AM). Different drug administration schemes were evaluated, including low and high dose administration (5 mg or 20 mg of Sb5+ per kg of body mass). Total [Sb] was assayed after wet decomposition of the samples by HNO3/H2O2. Speciation analysis was performed on plasma and urine samples using IC on-line coupled to the ICPMS instrument. Two PRP-X100 anion exchange columns were used for species separation employing EDTA (isocratic elution: 4.7 mmol L-1, 2.5% v/v methanol, pH 4.7) or EDTA/phosphate buffer (step elution: 1st eluent - 20 mmol L-1 EDTA + 2 mmol L-1 KHP, at pH 4.5; 2nd eluent - 50 mmol L-1 (NH4)2HPO4 at pH 8.3) as the mobile phases. Performance characteristics of all methods were evaluated and are presented. Stability tests showed that all studied antimony species are sufficiently stable to allow speciation analysis within 24 hours after collection. In humans, as well as in rhesus monkeys, the concentrations of antimony in urine and/or plasma samples measured after the administration period of MA, showed rapid excretion kinetics (t1/2 ~ 3 days) of the drug followed by two slower ones. Significantly higher concentrations of [Sb] were measured in erythrocyte fractions than in corresponding plasma samples, excepting the very initial phase of drug administration (first 12 hours). Bio-reduction of Sb5+ to Sb3+ was observed and confirmed as an important metabolic process during the slow elimination phase. No evidence for the formation of TMSbV was so far obtained in our studies. Antimony concentrations in tissue samples of rhesus monkeys 60 d after the last AM administration were highest in thyroid, followed by liver and spleen. Liver concentrations were at least 1000 times the basal concentrations. Hair and nail samples from treated patients and monkeys had also very high Sb concentrations, which matched drug administration history and showed also that incorporation of Sb into these tissues is continuing, even after ceasing AM application. In human hair, more than 300 days are required for the return of antimony concentrations to basal levels.

Au sein de la croûte terrestre, une grande partie des processus de mobilisation et redistribution des métaux résulte de circulations de fluides à grande échelle. Par conséquent, c’est un paramètre clé dans la formation de nombreux types de gisements variés. Les zones de déformation étant les vecteurs principaux des circulations de fluides, la plupart des gisements d’or (Au) et d’antimoine (Sb) se retrouvent localisés au sein des ceintures orogéniques. Le Massif Armoricain constitue un segment de la chaîne varisque ouest-européenne et contient de nombreux gisements à Sb-Au. L’objectif de cette thèse est à la fois de fournir de nouvelles contraintes sur la genèse des minéralisations varisques à Sb-Au et d’améliorer l’état des connaissances sur les processus critiques à l’origine des circulations de fluides minéralisatrices. Ainsi, une analyse des relations spatiales et des analyses structurales, géochronologiques et géochimiques ont été réalisées sur les gisements à Sb-Au du Domaine Centre Armoricain (DCA) et sur le gisement du Semnon en particulier. Une grande partie des gisements à Sb-Au est spatialement associée à des zones denses et relativement magnétiques suggérant la présence de corps mafiques/ultramafiques en profondeur. Cela est supporté par les nombreuses occurrences de dykes et sills de dolérites à travers toute la région. Ces dykes et sills sont issus d’un important évènement magmatique mafique mis en place à 360 Ma durant un changement drastique de la dynamique de convergence, passant de la subduction continentale à l’initiation de la collision. Les minéralisations à Sb-Au du DCA sont précoces dans l’histoire Carbonifère de la chaîne varisque armoricaine. Par conséquent, la plupart des minéralisations du DCA ne sont pas associées à l’évènement hydrothermal minéralisateur tardi-Carbonifère, bien connu dans la chaîne varisque européenne, en particulier au sein des zones internes de la chaîne tel que le Massif Central français. Au-delà du fait que cet évènement hydrothemal à Sb-Au soit précoce, la mise en place d’un magmatisme mafique généralisé dans la croûte supérieure du DCA est synchrone avec les minéralisations à Sb-Au et apparait comme un paramètre essentiel dans la mobilisation de circulations de fluides minéralisateurs advectifs. A plus grande échelle, la mise en place d’un magmatisme mafique couplée à la circulation de fluides hydrothermaux à Sb-Au met en lumière et améliore nos connaissances sur les processus hydrothermaux, magmatiques et tectoniques d’échelle lithosphérique gouvernant l’hydrothermalisme porteur de métaux. Par conséquent, ces résultats ouvrent de nouvelles perspectives pour l’exploration minière, notamment dans la recherche de nouveaux gisements d'antimoine et d'or au sein de la chaîne varisque européenne. / Through the Earth’s crust, a major part of the mobilization and the redistribution processes of metals are the result of large-scale fluid flows. Consequently, it is a key factor in the formation of various types of mineral deposits. Because deformation zones are the principal vector for fluid flows, most hydrothermal antimony (Sb) and gold (Au) deposits are localized in orogenic deformed belts. As a western part of the European Variscan belt, the Armorican Massif hosts several Sb-Au deposits. The purpose of this work is to provide new constraints on the genesis of these Variscan Sb-Au mineralization and to improve our knowledge about critical processes for hydrothermal mineralizing fluid flows. For these reasons, spatial relationships, structural, geochemical and geochronological investigations were performed on the Sb-Au deposits from the Central Armorican Domain (CAD), the Le Semnon Sb-Au deposit in particular. A major part of Sb-Au deposits are spatially associated with high-density and magnetic zones reflecting the presence of mafic/ultramafic bodies at depth and that is supported by numerous occurrences of dolerite dykes and sills throughout the region. These dykes and sills are issued from an important mafic magmatic event at ca. 360 Ma emplaced during a plate dynamic shift from continental subduction to incipient collision stage. Sb-Au mineralization from the CAD belongs to the early Carboniferous history within the Variscan framework. Consequently, most of Sb-Au mineralization (at least in the CAD) is not related to the Late Carboniferous hydrothermal mineralizing event, well-identified in the Variscan southernmost internal zones and especially in the French Massif Central. Beyond that early hydrothermal event, the widespread emplacement of a mafic magmatism in the CAD upper crust is coeval with Sb-Au mineralization and appears as a major trigger for highly advective mineralizing fluid flows. At a larger scale, mafic magmatism emplacement coupled with early Carboniferous Sb-Au hydrothermal fluid flows highlights and improves our knowledge of lithospheric-scale tectonics, magmatic and hydrothermal processes governing such metal-bearing hydrothermalism. As a consequence, those results provide a new framework for future mining exploration of antimony and gold deposits in the European Variscan belt.

Nous avons identifié le rôle de la distribution solide et l’implication de facteurs (potentiel d’oxydoréduction, anions compétiteurs, activité biologique, matière organique (MO)) dans la mobilité de l’arsenic (As) et l’antimoine (Sb) dans un sol de zone humide (ZH) agricole. Pour cela, nous avons effectué i) un suivi de la physico–chimie de l’eau interstitielle de la ZH et ii) des incubations en batch du sol de surface de la ZH (0–20/30 cm). En parallèle, nous avons déterminé la distribution solide de As et Sb sur le sol de la ZH à différentes profondeurs (0–130 cm). Nous avons démontré que As est accumulé à la surface du sol avec une association préférentielle avec les oxyhydroxydes de Fe/Mn « amorphes » (59% de As total) en présence de taux élevés de MO. En conditions réductrices, As est fortement solubilisé (jusqu’à 20% de la teneur en As total) contrairement aux conditions oxydantes ce qui est associé i) à la dissolution des oxyhydroxydes de Fe/Mn catalysée par l’activité microbienne et ii) au changement de la spéciation inorganique de As sous forme de As(III) (espèce plus mobile que As(V)). Pour ce qui est de Sb, il est accumulé à la surface du sol avec i) une distribution plus étendues avec les phases solides (27% et 15% dans les oxyhydroxydes de Fe/Mn « amorphes » et « cristallins », 21% dans la MO et 32% dans la fraction résiduelle) et ii) une affinité directe pour la MO contrairement à As. La mobilisation de Sb est favorisée en conditions oxydantes (jusqu'à 5 μg.L–1) en présence de MO dissoute dans l’eau interstitielle et est limitée en conditions réductrices (<3%) (0,2 μg.L–1 dans l’eau interstitielle et 1,5 μg.L–1 dans les batch). Cette mobilité en conditions réductrices est attribuée i) à la dissolution réductrice des oxyhydroxydes de Fe/ Mn catalysée par l’activité microbienne réductrice du sol et ii) au possible changement d’état d’oxydation de Sb sous forme de Sb(III) (espèce moins mobile que Sb(V)). En conditions réductrices, l’apport de 50 mg.L–1 de nitrates et de 20 mg.L–1 de phosphates au sol a engendré une mobilisation plus importante de As et Sb (d’un facteur 2,3 et 1,6, respectivement) qui est attribuée à une possible amplification de la respiration microbienne du sol causant une production plus importante en ions hydrogénocarbonates qui en plus des ions phosphates favoriserait la mobilisation de As et Sb par des effets de compétition. / In this study, we evaluated the effect of i) solid-phase distribution and ii) biophysico–chemical factors (redox potential (Eh), competing anions, microbial activity, organic matter (OM)) on the mobility of arsenic (As) and antimony (Sb) in an agricultural wetland soil. For that, we first performed a physico–chemical monitoring of wetland porewater (field scale) then we conducted controlled batch incubations of the wetland soil (0–20/30 cm) (batch scale). The solid–phase distribution of As and Sb in wetland soil was also performed at different soil depths (0–130 cm). We showed that the highest As content was found in the upper soil layers (0–40 cm) with a preferential association to “amorphous” oxyhydroxydes (59% of total As) in presence of high levels of OM. Under reducing conditions, As was highly solubilized at both field and batch scale (up to 20% of the total As content) which was induced by i) the dissolution of Fe/Mn oxyhydroxides enhanced by soil microbial activity and ii) As(V) reduction into As(III) (very mobile specie). On the other hand, Sb mobilization was enhanced under oxidizing conditions at field scale (up to 5 μg.L–1) with the concomitant occurrence of dissolved OM (up to 93 mg.L–1) and was rather limited under reducing conditions (<3% of the total Sb content; 0.2 μg.L–1 at field scale and up to 1.5 μg.L–1 at batch scale). The mobility behavior of Sb was attributed to i) the dissolution of Fe/Mn oxyhydroxides catalyzed by microbial activity, ii) the possible occurrence of Sb in its less mobile form (Sb(III)) under reducing conditions and iii) probable DOM–induced mobilization under oxidizing conditions. Under reducing conditions, the addition of nitrate (50 mg.L–1) and phosphate (20 mg.L–1) to wetland soil, enhanced As and Sb mobilization by factors of 2.3 and 1.6 which was suggested to be caused by the combined competing effect of phosphate and hydrogenocarbonate ions; the latter one resulting from a possible enhanced microbial activity.

This work is a cooperation with Boliden Minerals AB, who recently has been interested in recovering more valuable elements from their byproducts. For this case, solvent extraction was chosen as a potential method of recovering these valuables, as it is a method considered to be ideal for separation of trace elements from large amounts of other substances. The goal for this work was to execute manual extraction experiments as a preparation for a bigger project at LTU. The objectives of this thesis included the investigation of the selectivity for extraction of tin and antimony, using different concentrations of hydrochloric acid in the feed solution, analysis of the equilibrium isotherms for Sn and Sb at 8M of HCl as well as the evaluation of the number of steps needed for future extraction experiments, using the McCabe- Thiele method. By executing manual experiments with a speiss precipitate dissolved in hydrochloric acid, the results obtained indicated that the selectivity increased with a higher content of HCl in the feed solution. Using different ratios between the aqueous and organic phase, the equilibrium curves denoted a pushback effect, causing antimony to migrate back into the aqueous phase at the saturation level of tin. By constructing a McCable-Thiele diagram according to the equilibrium curves, the number of steps could be evaluated to three.

Donor–acceptor complexes have been known for over a century and enjoy a long list of applications in chemistry. In this thesis, the dative interaction between phosphorus and its two heavier congeners, arsenic and antimony, are explored. Utilising peri-substitution atoms can be forced in close proximity to one another, resulting in a repulsive (nonbonding) interaction or an attractive (bonding) interaction. Hence, peri-substitution can be used to support traditionally ephemeral species. A range of phosphorus, arsenic and antimony containing peri-substituted compounds were synthesised and characterised using multi-nuclear NMR, mass spectrometry, elemental microanalysis and single crystal X-ray diffraction. The reduction of a peri-substituted dichloroarsine, led to the formation of a primary arsine, which underwent spontaneous elimination of hydrogen gas forming the first structurally characterised cyclic arsanylidene–σ⁴–phosphorane, the formation of which is essentially thermoneutral. With no sterically demanding groups shielding the arsenic atom, the reactivity and spectroscopic characteristics of this compound were explored through reactions with selected metal complexes. Reaction of the arsanylidene–phosphorane with a limited amount of oxygen reveals arsinidene–like reactivity via the formation of cycloarsines, supporting the formulation that the bonding can be described as a Lewis base–stabilised arsinidene R₃P→AsR. A series of phosphine–stibine and phosphine–stiborane peri-substituted acenaphthenes containing all permutations of pentavalent groups –SbCl[sub]nPh[sub](4-n) as well as trivalent groups –SbCl₂, –Sb(R)Cl, and –SbPh₂ (R = Ph, Mes), were synthesised and characterised by multi-nuclear NMR, MS, microanalysis and X-ray crystallography. The bonding in these species was studied by DFT computational methods. The P–Sb dative interactions range from strongly bonding to nonbonding as the Lewis acidity of the Sb acceptor is decreased. Unexpectedly, the phosphine–stiborane complexes represent the first examples of σ⁴P→σ⁶Sb structural motif. A study of unsymmetrical bis(phosphino)acenaphthenes showed the presence of a 3c–4e interaction, supported by the short P∙∙∙P distances and the large J[sub](PP) through-space couplings. Severely strained bis(sulfides) of the unsymmetrical phosphines experience pronounced displacements of the exocyclic peri-atoms. The resulting nonbonded intramolecular P∙∙∙P distances (ca. 4.05 Å) are among the largest ever reported peri-separations, independent of the heteroatoms involved. In addition, three metal complexes with square planar, tetrahedral and octahedral geometry are reported. In all three cases, the acenaphthene backbone is distorted to a greater extent than in the free bis(phosphine) but notably less than in the bis(sulfides).

This study was directed at the pyrotechnic time delay compositions that are used in detonator assemblies. The objectives were to: --Investigate effective alternatives for the barium and lead-based oxidants currently used, maintaining the use of silicon as fuel --Develop easy to use, realistic measurement techniques for burn rates and shock tube ignitability --Determine the variables that affect burn rate, and --Evaluate alternative processing routes to facilitate intimate mixing of the component powders. Lead chromate and copper antimonite were found to be suitable oxidants for silicon in time delay compositions. They were ignitable by shock tubing, a relatively weak ignition source. The measured burn speeds for these systems showed a bimodal dependence on stoichiometry. Measured burn rates varied between 6-28 mm/s. Lead chromate is potentially a suitable alternative to the oxidant currently used in the medium burn rate commercial composition. It burns faster than copper antimonite. The latter is potentially a suitable replacement oxidant for the slow and medium compositions. Antimony trioxide-based compositions exhibited unreliable performance with respect to ignition with shock tubing. The addition of aluminium powder or fumed silica was found to reduce the burn rate. Increasing the silicon particle size (<3,5<font face="symbol">m</font>m) also decreased the burn speed for copper antimonite and lead chromate compositions. Addition of fumed silica improved the flow properties of the lead chromate, copper antimonite and antimony trioxide powders allowing for easier mixing. The silicon powder was found to react violently with water in alkaline solutions. This makes particle dispersion in a wet-mixing process problematic. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

This study considered bismuth (III) oxide (Bi2O3) and antimony hexitatridecoxide (Sb6O13) as potential substitutes for the red lead (Pb3O4) and barium sulphate (BaSO4) oxidants currently used in time delay compositions for detonator assemblies. Fine silicon powders with a specific surface area of 2 - 10 m2/g were used as fuels. Some experiments were also done with a coarse manganese powder as fuel. Bi2O3 was synthesised by the thermal decomposition of (BiO) 2CO3 by heating at 460°C for 15 hours. The yield was near quantitative, ie. close to the 91,4% expected based on the complete conversion of the carbonate to the oxide. Sb6O13 was obtained by heating colloidal antimony pentoxide (Sb2O5) for 8 hours at 315°C. This resulted in a ca. 20 % mass loss and yielded a reactive black powder. In the Si-Bi2O3 system, compositions in the range 5 - 40% by mass Si were ignitable with shock tubing. Burn rates measured in lead tubes varied between 15 and 155 mm/s. This highest burn rate was obtained with 20% silicon. Addition of additives such as KMnO4 and boric oxide had little effect on the burn rate. The fast burning Si-Bi2O3 system is a potential replacement for the commercial Si - red lead system. The burning rate decreased with increasing compaction of the samples. Burn rate also decreased when the aluminium instead of lead tubes were used. This is attributed to a greater heat loss with the former. The combustion products were characterised using DTA, FT-IR, XRD and SEM. The results show that the combustion reactions led to reduction of the oxidant to the corresponding metal form. The Sb6O13-Si system requires an initiating composition such as Bi2O3-50%Si (Type 4). It is slow burning and thus a possible replacement for the commercial BaS04-Si system. The lowest sustainable and reproducible burn rate, in the absence of additives, was 4,8 mm/s. It was achieved using 10% silicon Type 4. Adding small amounts of fumed silica <2%) increased the burn rate. This is attributed to better mixing and compaction. However, lower burn rates (~2 mm/s) are possible if more fumed silica is added as inert diluent. Replacing the silicon fuel with manganese powder gave more exothermic and even slower burning compositions. / Dissertation (MSc)--University of Pretoria, 2008. / Graduate School of Technology Management (GSTM) / unrestricted

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Visceral leishmaniasis (VL) is a serious infectious disease that if left untreated can lead to death. Chemotherapy is the main form of treatment and antimony are the drugs of first choice. Treatment efficacy is a consequence of the immunological profile of the patient, the pharmacokinetic properties of the drug and the inherent differences in each strain. The resistance of parasites to the antimonial and resistance to treatment is emerging worldwide. Few studies using clinical isolates of patients refractory to treatment seeking to understand the machinery of resistance. Thus, the present study aimed to characterize phenotypic components of clinical isolates of Leishmania (L.) infantum obtained from patients with LV refractory to treatment with Glucantime®. changes were evaluated ultrastructural front of the trivalent antimony (SbIII) and Action transport pumps related to drug efflux. In total, four strains were used: Two isolates treatment refractory patients and two isolates from patients responsive to treatment with antimony. The susceptibility of these strains was evaluated in vitro exposure to increasing concentrations of promastigotes SbIII and determination of median inhibitory concentration (IC50). In comparison, the IC50s of separate refractory patients are significantly greater than the IC50 of patients responsive isolated, showing an in vitro drug resistance profile. From these results, the concentration of 615 μM of SbIII was chosen to perform the experiments. This concentration proved to be toxic, but fully compatible with survival in all isolates. Then the isolates were subjected to transmission electron microscopy (TEM) after being exposed to 615 μM of SbIII for 48 hours. The two isolates from patients responsive to treatment demonstrated significant ultrastructural changes, with the presence of vacuolization, disorganization and cytoplasmic compression with increased eletrodensidade, and the strong presence of cells with intense loss eletrodense the cytoplasm, indicating incompatibility with life. While the two isolates from treatment refractory patients had preserved ultrastructure, with the presence of morphologically altered, compressed and electrodense cells, indicating the stress response. Finally, to assess the presence of transmembrane transport mechanisms related to drug efflux, the isolates were subjected to two protocols: using the fluorescent probe Rhodamine 123 with the channel blocker, verapamil hydrochloride, and the exposure to SbIII plus verapamil hydrochloride The results showed that MDR-1 type pumps are not related to the different in vitro resistance profiles to antimony in isolates from antimony-refractory patients. Together, the results of this study show that clinical refractory patients isolates have phenotypic characteristics that make her different behavior of isolates from patients responsive when exposed to antimony in vitro. / A leishmaniose visceral (LV) é uma doença infecciosa grave que se não tratada pode levar a morte. A quimioterapia é a principal forma de tratamento e os antimoniais são as drogas de primeira escolha. A eficácia do tratamento é uma consequência do perfil imunológico do paciente, das propriedades farmacocinéticas da droga e das diferenças intrínsecas de cada cepa. A resistência dos parasitos aos antimoniais e a refratariedade ao tratamento é mundialmente emergente. Poucos estudos utilizam isolados clínicos de pacientes refratários ao tratamento buscando compreender as maquinarias de resistência. Dessa forma o presente estudo teve como objetivo caracterizar componentes fenotípicos de isolados clínicos de Leishmania (L.) infantum obtidos de pacientes com LV refratários ao tratamento com Glucantime®. Foram avaliadas alterações ultraestruturais frente ao antimonial trivalente (SbIII) e ação de bombas de transporte relacionadas ao efluxo de droga. No total, foram utilizados quatro isolados: dois isolados de pacientes refratários ao tratamento e dois isolados de pacientes responsivos ao tratamento com antimonial. A susceptibilidade desses isolados foi avaliada in vitro com a exposição de promastigotas a concentrações crescentes de SbIII e determinação da concentração inibitória média (IC50). Quando comparadas, as IC50s dos isolados de pacientes refratários são significativamente maiores que as IC50s dos isolados de pacientes responsivos, mostrando um perfil de resistência a droga in vitro. A partir desses resultados, a concentração de 615 μM de SbIII foi escolhida para a execução dos experimentos. Essa concentração demonstrou ser tóxica, mas compatível com a sobrevivência em todos os isolados. Em seguida, os isolados foram submetidos a microscopia eletrônica de transmissão (MET) após serem expostos a 615 μM de SbIII por 48h. Os dois isolados de pacientes responsivos ao tratamento demonstraram alterações ultraestruturais significativas, com a presença de vacuolização, desorganização e compactação citoplasmática, com aumento da eletrodensidade, e a presença marcante de células com intensa perda de conteúdo eletrodenso do citoplasma, indicando incompatibilidade com a vida. Enquanto os dois isolados obtidos de pacientes refratários ao tratamento apresentaram algumas células morfologicamente alteradas, compactadas e eletrodensas, indicando resposta ao estresse. Por fim, para avaliar a presença de mecanismos de transporte transmembrana relacionados ao efluxo de droga, os isolados foram submetidos a dois protocolos: o uso da sonda fluorescente Rodamina 123 junto ao bloqueador de canais, cloridrato de verapamil, além do uso direto do verapamil na reversão da resistência durante a exposição ao SbIII in vitro. Os resultados obtidos demonstraram que bombas do tipo MDR-1 não estão relacionados aos diferentes perfis de resistência in vitro ao antimonial nos isolados de pacientes refratários. Juntos, os resultados encontrados no presente trabalho demonstram que isolados clínicos de pacientes refratários possuem características fenotípicas que tornam seu comportamento diferenciado dos isolados de pacientes responsivos quando expostos ao antimonial in vitro. / São Cristóvão, SE