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Thesis advisor: Zhifeng Ren / Solid-state cooling and power generation based on thermoelectric effects are attractive for a wide range of applications in power generation, waste heat recovery, air-conditioning, and refrigeration. There have been persistent efforts on improving the figure of merit (ZT) since the 1950's; only incremental gains were achieved in increasing ZT, with the (Bi1-xSbx)2(Se1-yTey)3 alloy family remaining the best commercial material with ZT ~ 1. To improve ZT to a higher value, we have been pursuing an approach based on random nanostructures and the idea that the thermal conductivity reduction that is responsible for ZT enhancement in superlattices structures can be realized in such nanostructures. The synthesis and characterization of various nanopowders prepared by wet chemical as well as high energy ball milling methods will be discussed in this dissertation. The solid dense samples from nanopowders were prepared by direct current induced hot press (DC hot press) technique. The thermoelectric properties of the hot pressed samples have been studied in detail. By ball milling ingots of bulk alloy crystals and hot pressing the nanopowders, we had demonstrated a high figure-of-merit in nanostructured bulk bismuth antimony telluride. In this dissertation, we use the same ball milling and hot press technique, but start with elemental chunks of bismuth, antimony, and tellurium to avoid the ingot formation step. We show that a peak ZT of about 1.3 can be achieved. Our material also exhibits a ZT of 0.7 at 250 °C, close to the value reached when ingot was used. This process is more economical and environmentally friendly than starting from bulk alloy crystals. The ZT improvement is caused mostly by the low thermal conductivity, similar to the case using ingot. Transmission electron microscopy observations of the microstructures suggest that the lower thermal conductivity is mainly due to the increased phonon scattering from the high density grain boundaries and defects. The performance of thermoelectric materials is determined by its dimensionless figure-of-merit (ZT) which needs to be optimized within a specific temperature range for a desired device performance. Hence, we show that by varying the Bi/Sb ratio, the peak ZT can be shifted to a higher or lower temperature for power generation applications or a cooling mode operation. A peak ZT of about 1.3 is achieved from a Bi0.4Sb1.6Te3 composition which is highest among the different compositions. These nanostructured bulk samples have a significantly low lattice thermal conductivity compared to the bulk samples due to the increased phonon scattering in the grain boundaries and defects. This study shows that Bi0.5Sb1.5Te3 may potentially perform better for cooling devices, while Bi0.3Sb1.7Te3 should be able to show better power generation efficiency. Several issues related to accurate measurement of thermoelectric properties were identified and many of them were solved during my studies and these are discussed in this thesis. With the data we obtained, it is clear that nanopowder-based thermoelectric materials hold significant promise. Therefore, a review of synthesis of nanostructured materials by solution-based methods, including a hydrothermal process for the Bi2Te3, Bi2Se3, and Bi2Te2.25Se0.75 nanoparticles, a solvothermal route for Sb2Te3 nanostructures, and a polyol process for the preparation of Bi nanostructures is presented in this dissertation. These new nanostructures may find applications in enhancing the thermoelectric performance. Although small sized and well dispersed nanopowders of various thermoelectric materials could be prepared by a solution method in large scale, contamination and partial oxidation are always big challenges in a chemical approach. Hence, a high energy ball milling technique to prepare thermoelectric nanopowders in large scale and without major contamination is still found to be more efficient and preferred. / Thesis (PhD) — Boston College, 2009. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

[pt] A administração de antimoniais no tratamento da leishmaniose é uma rara oportunidade para estudar o metabolismo de antimônio e das suas espécies químicas. Tais estudos são de grande relevância, uma vez que não se tem conhecimento sobre os metabólitos formados no corpo humano e da sua possível importância na erradicação dos parasitas causadoras da doença, assim como sobre os mecanismos de eliminação deste elemento tóxico. Ao contrário do arsênio, existem poucas metodologias reportadas para a análise de especiação de antimônio em amostras clínicas. O presente trabalho é uma continuação de pesquisas realizadas e publicadas anteriormente, nas quais a técnica de espectrometria de massas (ICPMS) acoplada à cromatografia iônica de alta eficiência IC-(HPLC) foi utilizada para separação e quantificação, em linha, de antimoniato de N-metil glucamina, Sb(V) e Sb(III) em amostras de plasma e urina. Assim, serão apresentados resultados recentes obtidos com o emprego de uma coluna com melhor resolução (Metrosep - A Supp5; 250 mm x 4,0 mm; Metrohm, Suíça) na separação de trimetil antimônio (TMSb), Sb(V) e Sb(III). Testes de otimização mostraram que uma solução de EDTA (0,006 mol L-1, pH 4,7) é adequada como fase móvel para a separação das três espécies. Os tempos de retenção para TMSb, Sb(V) e Sb(III) foram de 44,2 s, 150,6 s e 548,4 s, respectivamente, permitindo uma perfeita e repetitiva (DPR <3 por cento) separação dessas espécies. Repetitividades melhores que 4 por cento foram também obtidas na quantificação das áreas dos três picos cromatográficos correspondentes. Curvas analíticas, construídas a partir de soluções padrão das espécies em solução aquosa e em amostras de urina fortificadas, apresentaram ótima linearidade com coeficientes de correlação maiores que 0,999. Para volumes de amostra de 100 uL, injetados na coluna e utilizando-se o espectrômetro ELAN 5000 (PE-Sciex, EUA) como detector multielementar, em combinação com o nebulizador concêntrico tipo Meinhard e uma câmara ciclônica, limites absolutos de quantificação de 0,02 ng de antimônio foram obtidas para as três espécies estudadas. Testes de estabilidade mostraram que Sb(V) sofre alterações químicas já em intervalos de tempo relativamente curtos (maiores que 8h em água, e que 4h em urina fortificada) enquanto que TMSb e Sb(III) evidenciaram estabilidades consideravelmente maiores em ambos os meios. / [en] Clinical applications of antimonials in the treatment of leishmaniasis are a unique opportunity to study the metabolism of antimony and its species in the human body. As little is known about antimony metabolism, studies are required to improve the knowledge about the excretion mechanism of this toxic element; in particular, those which deal with antimony metabolites and the action of antimonials for the eradication of leishmaniasis causing parasites. In contrast with its chemical analogue arsenic, only a few methods concerning antimony speciation in clinical samples have been described in the literature. The aim of the present work was to improve a method previously developed to separate and quantify N-methyl meglumine antimoniate, Sb(V) and Sb(III) in blood plasma and urine samples by using anion exchange high performance liquid chromatography (IC-HPLC) coupled with inductively-coupled plasma mass spectrometry (ICPMS). Results on the application of an ion chromatography column (Metrosep - A Supp5; 250 mm x 4.0 mm; Metrohm, Swiss) with better resolution for the separation of TMSb, Sb(V) and Sb(III) are presented. The optimum conditions for the separation of the three species were established with 0.006 mol L-1 EDTA at pH 4.7 as the mobile phase. The retention times for TMSb, Sb(V) and Sb(III) were 44,2 s, 151,6 s and 548,4 s, respectively. A robust linear relationship between concentration and peak area was obtained for the three species, both, in aqueous standard solutions and spiked urine samples, with an associated correlation factor higher than 0,999. Relative standard deviations below 4 percent have been obtained in the peak area quantification mode. When using the ELAN 5000 (PerkinElmer-Sciex, EUA) equipped with a concentric Meinhard nebulizer in combination with a cyclonic spray chamber as detector, and employing a 100-uL injection loop in the HPLC system, typical absolute limits of quantification were 0.02 ng of Sb for each of the three antimony species studied. Stability tests showed that Sb(V) suffers chemical alterations within a short time period (>8h in aqueous solutions and >4h in spiked urine), whereas TMSb and Sb(III) presented better stability conditions in both solutions.

O presente trabalho tem como objetivo estudar propriedades ópticas e estruturais de vidros e filmes de fosfato de antimônio dopados. Os vidros foram produzidos pela fusão a 900 °C, em cadinhos de carbono vítreo, dos precursores [Sb(PO3)3]n + Sb2O3 utilizando como dopantes o PbO e Cr2O3, sendo em seguida vertidos e resfriados rapidamente em moldes de aço inox. As composições vítreas em questão são: 20% [Sb(PO3)3]n 77% Sb2O3 3%PbO, 20 %[Sb(PO3)3]n 77% Sb2O3 3%Cr2O3 e 20 %[Sb(PO3)3]n 74% Sb2O3 6%Cr2O3 (mol%). A caracterização das amostras teve início com medidas de EDX para micro - análise composicional. Em seguida para os vidros na forma de bulk foram medidos os espectros de absorção e luminescência. As medidas de luminescência foram realizadas utilizando-se o laser de Kr+ nas linhas MLUV (350 nm) e MLVI (41 5nm). Medidas de EPR foram realizadas para os vidros dopados com Cr por estes possuírem elétrons desemparelhados. Os filmes finos foram depositados em substratos de soda lime pela técnica de evaporação de feixe de elétrons. A partir do espectro de absorção, o valor do bandgap (por volta de 3 eV) foi calculado, verificando que a melhor fonte para irradiação das amostras era o laser de Kr+ em MLUV. Apenas filmes de [Sb(PO3)3]n: 3% Pb2+ apresentaram efeito fotoestrutural. Com isso um estudo variando parâmetros, como tempo de irradiação, densidade de potência e espessura dos filmes, foi realizado a fim de observar a otimização do efeito. Acompanhado das variações fotoestruturais, ocorreram variações fotocrômicas, no caso fotoclareamento, as quais se caracterizaram por um deslocamento da borda de absorção para maiores energias, observado nos espectros de absorção das áreas irradiadas. Com os resultados observados do estudo e caracterização das amostras, algumas aplicações tecnológicas foram discutidas, como no caso dos efeitos observados nos filmes que podem ser utilizados para gravação de redes de difração. / The present work is about the study of the optical and structure properties of doped antimony phosphate glasses and thin films. The glasses were produced by the melting of precursors [Sb(PO3)3]n + Sb2O3 using PbO and Cr2O3 as dopant at 900 °C in vitreous carbon crucibles, then poured and quickly cooled into steel molds. The vitreous composition are: 20% [Sb(PO3)3]n 77% Sb2O3 3%PbO, 20 %[Sb(PO3)3]n 77% Sb2O3 3%Cr2O3 e 20 %[Sb(PO3)3]n 74% Sb2O3 6%Cr2O3 (mol%). The samples characterization started with EDX measurements for compositional micro-analysis. Then for the glasses in bulks form the absorption and luminescence spectra were measured. The luminescence measurements were done using MLUV (350 nm) and MLVI (415 nm) of a Kr+ laser. EPR measurements were taken for the Cr doped glasses because they present unpaired electrons. The thin films were deposited on soda lime substrates by the electron beam evaporation technique. From absorption spectra, the bandgap value around 3 eV was evaluated, noting that the best irradiation source of the samples was using a MLUV of a Kr+ laser. Only [Sb(PO3)3]n: 3% Pb2+ films presented photostructural effects. Therefore a systematic study varying several parameters, like irradiation time, power density and film thickness was conducted to observe the effect optimization. Following the photostructural variation, occurred photocchromic effects, in this case, photobleaching effects, which were characterized by a displacement of absorption edge to lower energies, observed in the absorption spectra of the irradiated areas. With the observed results from the study and characterization of the samples, some technologies applications were discussed, like in the case of the observed films effects that can be used for recording diffraction gratings.

Submitted by Filipe dos Santos (fsantos@pucsp.br) on 2016-08-08T14:32:24Z No. of bitstreams: 1 Marina Vieira de Figueiredo.pdf: 2377233 bytes, checksum: f182fd72c61743bfa8c84d497dc3f29f (MD5) / Made available in DSpace on 2016-08-08T14:32:24Z (GMT). No. of bitstreams: 1 Marina Vieira de Figueiredo.pdf: 2377233 bytes, checksum: f182fd72c61743bfa8c84d497dc3f29f (MD5) Previous issue date: 2016-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The legal standards must not be confused with the prescriptive texts. The first are built from such texts, which allow different interpretations and the creation of conflicting rules. Therefore, the conflict between standards is an embedded problem in the legal system. Among the conflicts which are relevant, those verified among standards derived from a single precedent of the Superior Courts stand out. Current legislation confers special attention to decisions issued by these bodies, imposing their applicability to similar cases. There is no point, however, in granting a binding effect to the precedents if there is no uniformity in their application. It is true, however, that the commonly chosen criteria for rule conflict resolution are not enough to solve this kind of contradiction, since the rules derived from the same precedent: (i) hold the same hierarchy; (ii) are equally general; and (iii) are contemporaneous. This, however, does not mean that there are no criteria liable to resolve such antinomies. Analyzing our legal system, we see that any act of implementing rules (judicial decision there included) always has the same configuration: the norm is created for means of specific concrete application, there is an assessment in order to identify if the facts are comprised by what the aforementioned legal standards set forth, and only then a legal relationship between certain individuals is constituted. Therefore, the construction of a rule based on a precedent will, necessarily, observe these aspects: applicable provision, facts taken into consideration upon decision issuance and how the dispute was settled. The latter, in its turn, will be the first step towards the resolution of conflicts upon its application. Once the ratio decidendi, i.e. the rule of the precedent, is determined then it is time to check whether the jurisdiction for which it provides (power to apply the precedent for similar cases) was legally exerted. If an illegality is identified – resulting from a controversial precedent interpretation – this allows for the application of the penalty provided in the standard of competence: invalidity declaration of the illegally created standard / a partir deste suporte físico, o qual admite interpretações divergentes e, portanto, a construção de normas conflitantes. O conflito entre normas é, portanto, é um problema inerente ao sistema jurídico. Dentre os conflitos que interessam ao direito, destacam-se aqueles verificados entre normas construídas a partir de um mesmo precedente dos Tribunais Superiores. O ordenamento jurídico, atualmente, dá especial relevo às decisões proferidas por estes órgãos, impondo a sua aplicação aos casos análogos. De nada adianta, contudo, conferir eficácia vinculante aos precedentes se não há uniformidade na sua aplicação. É certo, por outro lado, que os critérios comumente eleitos para a solução de conflitos entre normas não são suficientes para solucionar esta espécie de antinomia, já que as normas construídas a partir de um mesmo precedente: (i) ocupam a mesma hierarquia; (ii) são igualmente gerais; e (iii) são contemporâneas. Isso, no entanto, não quer dizer que não existam critérios para resolver tais antinomias. Analisando nosso ordenamento, verificamos que qualquer ato de aplicação de normas (aí incluídas as decisões judiciais) tem sempre a mesma configuração: constrói-se a norma a aplicar no caso concreto, verifica-se se há subsunção entre os fatos e aquilo que prescreve referida norma para, então, constituir uma relação jurídica entre certos indivíduos. Portanto, a construção da norma instituída por um precedente passará, necessariamente, por estes pontos: norma a aplicar, fatos considerados na decisão e modo como a lide foi solucionada. Este, por sua vez, será o primeiro passo para a resolução de conflitos na sua aplicação. Definido a ratio decidendi, ou seja, a norma do precedente, é então o momento de verificar se a competência nela prevista (competência para aplicar o precedente a casos análogos) foi licitamente exercida. Constatada a ilicitude – decorrente da interpretação controvertida do precedente – abre-se espaço para a aplicação da sanção prevista na norma de competência: nulidade da norma criada ilicitamente

Este trabalho teve como objetivo a síntese e caracterização de novos complexos de Cu2+ com &#945;-hidroxicarboxilatos fluorados, como forma de aumentar a lipofilicidade dos mesmos e, conseqüentemente, a sua biodisponibilidade. Os sólidos de coloração azul obtidos foram caracterizados por análise elementar e métodos espectroscópicos (eletrônico e infra-vermelho), confirmando a coordenação do metal a dois equivalentes dos ligantes, que se coordenam através da carboxila e da &#945;-hidroxila. Testes de partição em vesículas multi-camadas de lecitina indicaram que o complexo derivado do ácido trifluorolático é o mais lipossolúvel. A capacidade dos complexos catalisarem a reação de formação de espécies reativas de oxigênio pela reação com peróxido foi estudada por um método fluorimétrico (oxidação da 1,2,3- dihidrorodamina), sendo que os complexos fluorados em geral apresentaram menor taxa de formação de espécies oxidantes. A atividade anti-leishmânica dos compostos foi estudada em promastigotas de Leishmania amazonensis, tendo o complexo bis(trifluorolactato) de cobre(II) apresentado a maior atividade, que foi entretanto menor que o íon livre Cu(II), o que sugere que o ligante sirva como um transportador de metal para o alvo. Todos os complexos foram menos tóxicos a células de mamífero (HeLa). Nossos dados indicam que o aumento de lipofilicidade e/ou da taxa de formação de radicais livres pode ser uma estratégia interessante para o desenvolvimento de metalofármacos anti-leishmânicos a base de cobre / In this work we synthesized and characterized new Cu(II) complexes with fluorinated a-hydroxycarboxilates as a means of increase its lipophilicity and bioavailability. The blue solids were characterized by means of elemental analysis and spectroscopic methods (electronic and infrared), confirming the 2:1 ligand to metal stoichiometry and coordination through both the carboxylate and &#945;-hydroxyl moieties. Partition tests in multi-lamellar lecitin vesicles showed that the trifluorolactate derivative is the most lipossoluble. The ability of the complexes to catalyze the formation of reactive oxygen species under reaction with peroxide has been studied by a fluorimetric method (oxidation of 1,2,3-dihydrorhodamine); the fluorinated complexes showed decreased probe oxidation rate. Antileishmanial activities were studied on Leishmania amazonensis promastigotes, and the bis(trifluorolactate)copper(II) displayed the highest activity among the complexes, but smaller than that of free Cu(II), suggesting that ligand may ferry the metal to its biological target. All the complexes were less toxic to mammal (HeLa) cells. Our data suggest that increase of lipophilicity and/or free radicals generation rate may be an interesting strategy to develop antileishmanial metallodrugs based on copper

Este trabalho teve como objetivo a síntese e caracterização de novos complexos de Cu2+ com &#945;-hidroxicarboxilatos fluorados, como forma de aumentar a lipofilicidade dos mesmos e, conseqüentemente, a sua biodisponibilidade. Os sólidos de coloração azul obtidos foram caracterizados por análise elementar e métodos espectroscópicos (eletrônico e infra-vermelho), confirmando a coordenação do metal a dois equivalentes dos ligantes, que se coordenam através da carboxila e da &#945;-hidroxila. Testes de partição em vesículas multi-camadas de lecitina indicaram que o complexo derivado do ácido trifluorolático é o mais lipossolúvel. A capacidade dos complexos catalisarem a reação de formação de espécies reativas de oxigênio pela reação com peróxido foi estudada por um método fluorimétrico (oxidação da 1,2,3- dihidrorodamina), sendo que os complexos fluorados em geral apresentaram menor taxa de formação de espécies oxidantes. A atividade anti-leishmânica dos compostos foi estudada em promastigotas de Leishmania amazonensis, tendo o complexo bis(trifluorolactato) de cobre(II) apresentado a maior atividade, que foi entretanto menor que o íon livre Cu(II), o que sugere que o ligante sirva como um transportador de metal para o alvo. Todos os complexos foram menos tóxicos a células de mamífero (HeLa). Nossos dados indicam que o aumento de lipofilicidade e/ou da taxa de formação de radicais livres pode ser uma estratégia interessante para o desenvolvimento de metalofármacos anti-leishmânicos a base de cobre / In this work we synthesized and characterized new Cu(II) complexes with fluorinated a-hydroxycarboxilates as a means of increase its lipophilicity and bioavailability. The blue solids were characterized by means of elemental analysis and spectroscopic methods (electronic and infrared), confirming the 2:1 ligand to metal stoichiometry and coordination through both the carboxylate and &#945;-hydroxyl moieties. Partition tests in multi-lamellar lecitin vesicles showed that the trifluorolactate derivative is the most lipossoluble. The ability of the complexes to catalyze the formation of reactive oxygen species under reaction with peroxide has been studied by a fluorimetric method (oxidation of 1,2,3-dihydrorhodamine); the fluorinated complexes showed decreased probe oxidation rate. Antileishmanial activities were studied on Leishmania amazonensis promastigotes, and the bis(trifluorolactate)copper(II) displayed the highest activity among the complexes, but smaller than that of free Cu(II), suggesting that ligand may ferry the metal to its biological target. All the complexes were less toxic to mammal (HeLa) cells. Our data suggest that increase of lipophilicity and/or free radicals generation rate may be an interesting strategy to develop antileishmanial metallodrugs based on copper

Thesis (M.Sc. (Biochemistry)) --University of Limpopo, 2005 / Refer to document

The emerging field of spintronics relies on the manipulation of electron spin in order to use it in spin-based electronics. Such a paradigm change has to tackle several challenges including finding materials with sufficiently long spin lifetimes and materials which are efficient in generating pure spin currents. This thesis predicts that two types of material families could be a solution to the aforementioned challenges: complex oxides and bismuth based materials. We derived a general approach for constructing an effective spin-orbit Hamiltonian which is applicable to all nonmagnetic materials. This formalism is useful for calculating spin-dependent properties near an arbitrary point in momentum space. We also verified this formalism through comparisons with other approaches for III-V semiconductors, and its general applicability is illustrated by deriving the spin-orbit interaction and predicting spin lifetimes for strained SrTiO3 and a two-dimensional electron gas in SrTiO3 (such as at the LaAIO3/SrTiO3 interface). Our results suggest robust spin coherence and spin transport properties in SrTiO3 related materials even at room temperature. In the second part of the study we calculated intrinsic spin Hall conductivities for bismuth-antimony Bi1-xSbx semimetals with strong spin-orbit couplings, from the Kubo formula and using Berry curvatures evaluated throughout the Brillouin zone from a tight-binding Hamiltonian. Nearly crossing bands with strong spin-orbit interaction generate giant spin Hall conductivities in these materials, ranging from 474 ((ћ/e)Ω-1cm-1) for bismuth to 96((ћ/e)Ω-1cm-1) for antimony; the value for bismuth is more than twice that of platinum. The large spin Hall conductivities persist for alloy compositions corresponding to a three-dimensional topological insulator state, such as Bi0.83Sb0.17. The spin Hall conductivity could be changed by a factor of 5 for doped Bi, or for Bi0.83Sb0.17, by changing the chemical potential by 0.5 eV, suggesting the potential for doping or voltage tuned spin Hall current. We have also calculated intrinsic spin Hall conductivities of Bi2Se3 and Bi2Te3 topological insulators from an effective tight-binding Hamiltonian including two nearest-neighbor interactions. We showed that both materials exhibit giant spin Hall conductivities calculated from the Kubo formula in linear response theory and the clean static limit. We conclude that bismuth-antimony alloys and bismuth chalcogenides are primary candidates for efficiently generating spin currents through the spin Hall effect.

Fungal contamination of buildings poses numerous challenges to researchers, building owners and occupants. Public health agencies promote prevention and remediation of mold and water damage, but lack sensitive methods to detect hidden mold growth and a complete understanding of the biological mechanisms that make occupying moldy buildings a hazard. The wide spread use of the fire retardant antimony trioxide (Sb2O3) on building materials and furnishings makes it inevitable that mold growth on treated materials will occur in some buildings with water damage. Several authors have speculation that microbial growth on materials treated with antimony trioxide could mobilize antimony through a volatile intermediate, trimethylstibine. The purpose of this study was to determine if fungal growth on a commonly used building material that contains antimony trioxide, fiberglass ductboard, results in the mobilization and release of antimony compounds. Additionally, CO2 generation rates were determined during fungal growth on fiberglass ductboard and gypsum wallboard. Results demonstrated a significant reduction of antimony concentration in fiberglass ductboard after fungal growth had occurred. Antimony emission rates and resulting concentrations of antimony oxide aerosols were estimated using an indoor mass balance mathematical model. Concentrations of CO2 were also modeled within a wall cavity and static HVAC ducts to determine if fungal growth could elevate CO2 levels above ambient concentrations. Although volatile phase antimony was not detected in chamber experiments, probably due to rapid oxidation and high humidity, mobilization of antimony trioxide from fiberglass ductboard components was demonstrated in several experiments. Indoor Air modeling of a residence suggest that concentrations of antimony could, under worst case conditions, exceed the reference concentration (RfC) of antimony trioxide by 10 to 1,000 times. These results suggest that biomethylation and mobilization of antimony by mold growth on building materials could result in elevated occupant exposures to antimony compounds. Antimony is a known respiratory irritant that can be similar to arsenic in its toxicity. Modeling results also suggest that elevated carbon dioxide concentrations due to fungal metabolic respiration are variable and dependent on environmental conditions. Measuring elevated carbon dioxide concentrations to detect hidden fungal growth was determined to not be a predictive assessment tool.