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Als Modellsystem für Oxide mit Perowskitstruktur ist Strontiumtitanat besonders geeignet, um generalisierbare Erkenntnisse über die Auswirkungen von Defekten zu gewinnen und ausgehend davon Struktur-Eigenschafts-Korrelationen zu diskutieren. Durch den Einsatz verschiedener oberflächensensitiver Methoden lässt sich im Ausgangszustand eine erhöhte Konzentration von Liniendefekten an der Oberfläche nachweisen, die sich durch Temperaturbehandlung verkleinert. Die Defektchemie bei hohen Temperaturen wird zur Simulation der elektrischen Leitfähigkeit in Abhängigkeit vom umgebenden Sauerstoff-Partialdruck genutzt. Die Dotierung des oxidischen Halbleitermaterials ist von Eigendefekten abhängig, wobei Sauerstoff-Leerstellen Donatorniveaus bilden und Strontium-Leerstellen Akzeptorcharakter besitzen. Neben der Diffusionsbewegung dieser Eigendefekte bei hohen Temperaturen kann bei niedrigen Temperaturen ein elektrisches Feld deren Umverteilung bewirken. Damit zeigt sich die Leitfähigkeit abhängig von externen elektrischen Feldern, aber auch weitere Eigenschaften sind auf diesem Wege modifizierbar. Im Rahmen der Arbeit werden strukturelle Änderungen, Valenz-Änderungen und veränderte mechanische Eigenschaften nachgewiesen, die jeweils abhängig vom elektrischen Feld schaltbar sind. Schließlich wird das gezielte Ausnutzen struktureller Defekte für Speicherzellen, die den schaltbaren Widerstand von Metall-SrTiO3-Kontakten zur Grundlage haben, vorgestellt. Die Anwendbarkeit des oxidischen Halbleiters als resistives Speicherelement beruht wiederum auf der Kopplung von Sauerstoff-Leerstellen an das elektrische Feld. / Being a model system for oxides with pervovskite-type of structure, strontium titanate can be used to gain generalizable insights into the consequences of defects and to discuss resulting structure-property relationships. By employing different surface sensitive methods, an increased concentration of line defects is found at the surface that reduces on temperature treatment. The defect chemistry at elevated temperatures is used to simulate the electric conductivity depending on the oxygen partial pressure during annealing. Doping of the oxidic semiconductor depends on intrinsic defects, whereby oxygen vacancies form donor states and strontium vacancies have acceptor character. Beside the diffusion movement of these intrinsic defects at elevated temperatures, at low temperatures an electric field may cause their redistribution. Hence, the conductivity becomes dependent on external electric fields but also other properties can be altered in this way. Within this work, structural changes, valence changes and changing mechanical properties are shown to be switchable by the electric field. Finally, the dedicated usage of structural defects is demonstrated on memory cells that employ the switchable resistance of metal-SrTiO3 junctions. The applicability of the oxidic semiconductor as a resistive memory element is again based on the coupling between oxygen vacancies and the electric field.

This thesis deal with three individual Pagophilus groenlandicus canin teeth from the location Asva, Estonia dating from the Late Bronze Age (here 700-900 B.C). The aim of this thesis is to find out whether the three harp seal individual was local or non-local to Asva and further if they were migrants from the Atlantic Sea. The teeth enamel are analysed for strontium isotopes using LA-ICP-MS and the result was compared against the strontium 87Sr/86Sr values in various rivers in the Baltic Sea. This is to see how the harp seal has migrated around in the Baltic Sea. By placing the 87Sr/86Sr values against the rivers, it may seem that the three harp seals were non-local and not from the Atlantic Sea.

Orientador: Elcio Marcantonio Junior / Resumo: O uso de medicamentos a base de estrôncio tem se tornado notável na prevenção e tratamento de enfermidades relacionadas ao tecido ósseo. Essa notabilidade se dá devido a sua ação conjunta em células distintas e envolvidas na neoformação óssea, osteoblastos e osteoclastos. Devido a seus resultados positivos o estrôncio passou a ser utilizado também como coadjuvante de processos de neoformação óssea, principalmente procedimentos cirúrgicos maxilo-faciais. Sendo assim, este estudo teve como objetivos a avaliação de diferentes compostos, e dosagens a base de estrôncio em procedimentos de osseointegração, enxertia óssea. Para tal, os resultados foram distribuídos em 4 artigos para melhor compreensão. No estudo 1, revisão de literatura, foram analisados estudos que utilizaram estrôncio sistêmico como terapia para processos de osseointegração e enxertia óssea em animais. No estudo 2, osseointegração, foram analisadas diferentes dosagens de ranelato de estrôncio (50 e 625mg), e carbonato/cloreto de estrôncio (30 e 365 mg), administrados sistemicamente, durante o processo de osseointegração. Semelhantemente, o estudo 3 analisou a influência dos mesmos compostos a base de estrôncio em defeitos críticos ósseos em calvarias. E por ultimo, no estudo 4, uma análise relacionada a toxicidade do suplemento foi realizada nas dosagens que obtiveram melhores resultados. Como resultados, os estudos 2 e 3 apresentaram resultados semelhantes e positivos para os suplementos a base de estrôncio nas m... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The use of strontium medications has become notable in prevention and treatment of bone tissue related diseases. This notability is related to double action in distinct cells involved in bone neoformation, osteoblasts and osteoclasts. Due to its positive results, strontium has also been used as a coadjuvant of bone neoformation processes, mainly maxillofacial surgical procedures. Thus, this study had as objectives the evaluation of different compounds, and dosages based on strontium in procedures of osseointegration and bone grafting. For this, the results were distributed in 4 studies for better understanding. In study 1, literature review, we analyzed studies that used systemic strontium as a therapy for osseointegration processes and bone grafting in animals. In study 2, osseointegration, different dosages of strontium ranelate (50 and 625mg), and strontium carbonate/strontium chloride (30 and 365mg), systemically administered during the osseointegration process, were analyzed. Similarly, study 3 analyzed the influence of the same strontium-based compounds on critical bone defects in calvarias. Finally, in study 4, an analysis related to toxicity of the supplement was performed at the dosages that obtained the best results. As results, studies 2 and 3 presented similar and positive results for the strontiumbased supplements at the highest concentrations (strontium ranelate 625 mg and strontium carbonate / 365 mg strontium). Considering these dosages, study 4 showed the abs... (Complete abstract click electronic access below) / Doutor

Orientador: Prof. Dr. Flavio Leandro de Souza / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2017. / Titanato de estrôncio é um material semicondutor interessante para aplicação em células fotoeletroquímicas. Uma via simples e de baixo custo para a preparação de fotoeletrodos de titanato de estrôncio é o método sol-gel. O método complexo polimerizado permite um controle ótimo da estequiometria e da incorporação de dopantes durante o processo. Neste trabalho, fotoanodos de titanato de estrôncio puro e dopado foram preparados usando o método sol-gel. Em primeiro lugar, fotoanodos de titanato de estrôncio puro foram produzidos e tratados termicamente a 800 °C. Em seguida, incorporaram-se os dopantes de ítrio (Y2+) e níquel (Ni2+), sendo realizado uma otimização de deposição para alcançar o melhor desempenho fotoeletroquímico. Além disso, avaliou-se a influência de um tratamento térmico em diferentes condições atmosféricas (nitrogênio e oxigênio) nas propriedades fotoeletroquímicas. Todos os fotoanodos foram analisados estruturalmente, morfologicamente e eletro/fotoeletroquimicamente. As deposições de 6 camadas e 4 tratamentos térmicos de puros e dopados, exibiram a melhor performance analisada por voltametria de varredura linear. Destacou-se os fotoanodos dopados com ítrio, apresentando a maior fotocorrente, comparado com o puro e o dopado com níquel. Adicionalmente, foram analisadas as contribuições na atividade catalítica favorecida pelo tratamento térmica adicional de 15 minutos em atmosfera rica e deficiente em oxigênio. Observou-se que o desempenho aumentou para o material puro submetido a um tratamento térmico adicional em atmosfera de oxigênio e para material dopado com ítrio e submetido a tratamento em atmosfera de nitrogênio. No entanto, fotoanodos de titanato de estrônico, nas diferentes condições de síntese e atmosfera de tratamento térmico, apresentam o desempenho fotoeletroquímico baixo. Em primeiro lugar, o intervalo de banda de titanato de estrôncio puro é muito elevado, 3,2 eV, que permite absorver uma pequena faixa do espectro da radiação solar. Por fim, sugere-se que a maior parte dos dopantes podem estar segregando nos contornos, podendo atuar como centros de recombinação, que reduz a eficiência das reações de superfície. Finalmente, os fotoanodos foram analisados eletroquimicamente através de espectroscopia impedância eletroquímica (EIS) para analisar os possíveis limitantes na performance do material. / Strontium titanate is an interesting semiconductor to be applied in photoelectrochemical cells. A simple and cost effective route to prepare strontium titanate photoelectrode is the sol-gel method. The polymerized complex method allows an optimal control of stoichiometry and the incorporation of impurities during the process. In this work, pure and doped strontium titanate photoanodes were prepared by using sol-gel method. Firstly, pure strontium titanate films were produced and heat treated at 800¿aC. Then, yttrium (Y2+) and nickel (Ni2+) dopants were incorporated. It was made a deposition optimization in order to achieve the best photoelectrochemical performance. Additionally, it was evaluated the influence of an extra heat treatment at different atmosphere (nitrogen and oxygen) on photoanodes properties. All the photoanodes were analyzed structurally, morphologically and electro/photoelectrochemically. Pure and doped strontium titanate photoanodes with 6 layer depositions and 4 time heat treatments exhibited best photocurrent than other conditions provided by linear sweep voltammetry. Yttrium-doped exhibited best photocurrent than pure and nickel-doped strontium titanate. Finally, catalytic activity of pure strontium titanate with extra heat treatment for 15 minutes in oxygen atmosphere and yttrium-doped strontium titanate with extra heat treatment for 15 minutes in nitrogen atmosphere was increased. Nevertheless, photocurrent performances of pure and modified strontium titanate films under air, nitrogen, oxygen atmosphere was very poor which can be explained by plausible hypothesis. Firstly, the band gap of pure strontium titanate is very high ¡V 3.2 eV. So, It only absorbs UV light which is only 4% of sun light. Secondly, most of the dopants may be segregated which may act as recombination centers that reduced the charge separation efficiency. Finally, polaron size of pure and doped strontium titanate under extra oxygen atmosphere decreases. Thus, resistance to charge transfer increases. Under extra nitrogen atmosphere, recombination may have increased as these films exhibited higher conductivity than films prepared under oxygen atmosphere.

abstract: This project investigates social mobility in premodern states through a contextualized program of isotopic research at the archaeological site of Teotihuacan, Mexico. Due to the lack of a concrete methodology that can be used to recover information concerning rates of social mobility from archaeological remains, many traditional archaeological models either ignore social mobility or assume that boundaries between socioeconomic strata within archaic states were largely impermeable. In this research, I develop a new methodological approach to the identification of socially mobile individuals in the archaeological record based on changes in the diet across the lifecourse that can be detected through isotopic paleodietary indicators. Drawing upon cross-cultural research surrounding the relationship between diet and socioeconomic status and established methodologies in the biogeochemical analysis of human remains, this methodological approach provides a basis for broader comparative studies evaluating the nature of social mobility within archaic states. I then test the practical application of this methodology by applying it to a mortuary sample including individuals from distinctive socioeconomic groups from the pre-Hispanic city of Teotihuacan, Mexico. The study recovers and uses the dietary isotope ratios within bone and tooth samples from 81 individuals buried throughout the city 1) to define the dietary correlates of wealth and status at Teotihuacan and 2) to identify individuals displaying lifetime dietary changes consistent with changes in socioeconomic status. In addition to supplementing our current understanding of Teotihuacan foodways and processes of geographic migration into the city, I identify an adult male individual from the La Ventilla B apartment compound who displays dietary changes throughout his life that are consistent with downward socioeconomic mobility from a high status socioeconomic group in early adolescence to an intermediate status group later in adulthood. I conclude by identifying ways to move forward with the comparative archaeology of socioeconomic mobility in premodern contexts and highlight the applicability of archaeological information to our understanding of present-day processes of social mobility. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2017

abstract: Mobility is an important aspect of the lives of religious individuals described by medieval texts in early and late medieval Ireland, and biogeochemical methods can be used to detect mobility in archaeological populations. Stories are recorded of monks and nuns traveling and founding monasteries across Ireland, Scotland, England, Wales, and other areas of Europe. However, these texts rarely address the quotidian lives of average monks and nuns who lived in monastic communities. This dissertation seeks to understand if travel was a typical part of the experiences of religious and lay people in early and late medieval Ireland. It also aims to increase understanding of how monastic communities related to the local lay communities, including addressing if the monastery was populated by those who grew up in the local area. Another methodological aim of this dissertation is to advance the field of archaeological biogeochemistry by (1) adding to the bioavailable strontium baseline in Ireland and (2) quantifying the contribution of ocean-derived strontium to coastal environments. These topics are explored through the biogeochemical analysis of 88 individuals buried at 5 early and late medieval monasteries in Ireland and the analysis of a total of 85 plant samples from four counties in Ireland. The three papers in this dissertation present: (1) a summary of the mobility of religious and lay people buried at the monasteries (Chapter 2), (2) a case study presenting evidence for fosterage of a local child at the early medieval monastery of Illaunloughan, Co. Kerry (Chapter 3), and (3) a study designed to quantify the impact of sea spray on bioavailable strontium in coastal environments (Chapter 4). The majority of lay and religious individuals studied were estimated to be local, indicating that medieval Irish Christianity was strongly rooted in the local community. The study of ocean-derived strontium in a coastal environment indicates that sea spray has a non-uniform impact on bioavailable strontium in coastal regions. These findings shed new light on medieval monastic and lay life in Ireland through the application of biogeochemical methods, contributing to the growth of the field of archaeological chemistry in Ireland. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2018

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