There is great interest in the development of new polar dielectric ceramics and multiferroic materials with new and improved properties. A family of tetragonal tungsten bronze (TTB) relaxors of composition Ba₆M³⁺Nb₉O₃₀ (M³⁺ = Ga³⁺, Sc³⁺ and In³⁺, and also their solid solutions) were studied in an attempt to understand their dielectric properties to enable design of novel polar TTB materials. A combination of electrical measurements (dielectric and impedance spectroscopy) and powder diffraction (X-ray and neutron) studies as a function of temperature was employed for characterising the dynamic dipole response in these materials. The effect of B-site doping on fundamental dipolar relaxation parameters were investigated by independently fitting the dielectric permittivity to the Vogel-Fulcher (VF) model, and the dielectric loss to Universal Dielectric Response (UDR) and Arrhenius models. These studies showed an increase in the characteristic dipole freezing temperature (T[subscript(f)]) with increase B-cation radius. Crystallographic data indicated a corresponding maximum in tetragonal strain at T[subscript(f)], consistent with the slowing and eventual freezing of dipoles. In addition, the B1 crystallographic site was shown to be most active in terms of the dipolar response. A more in-depth analysis of the relaxor behaviour of these materials revealed that, with the stepwise increase in the ionic radius of the M³⁺ cation on the B-site within the Sc-In solid solution series, the Vogel-Fulcher curves (lnf vs. T[subscript(m)]) are displaced to higher temperatures, while the degree of relaxor behaviour (frequency dependence) increases. Unfortunately, additional features appear in the dielectric spectroscopy data, dramatically affecting the Vogel-Fulcher fitting parameters. A parametric study of the reproducibility of acquisition and analysis of dielectric data was therefore carried out. The applicability of the Vogel-Fulcher expression to fit dielectric permittivity data was investigated, from the simple unrestricted (“free”) fit to a wider range of imposed values for the VF relaxation parameters that fit with high accuracy the experimental data. The reproducibility of the dielectric data and the relaxation parameters obtained by VF fitting were shown to be highly sensitive to the thermal history of samples and also the conditions during dielectric data acquisition (i.e., heating/cooling rate). In contrast, UDR analysis of the dielectric loss data provided far more reproducible results, and to an extent was able to partially deconvolute the additional relaxation processes present in these materials. The exact nature of these additional relaxations is not yet fully understood. It was concluded application of the Vogel-Fulcher model should be undertaken with great care. The UDR model may represent a feasible alternative to the evaluation of fundamental relaxation parameters, and a step forward towards the understanding of the dielectric processes in tetragonal tungsten bronzes.

The goal of the theses is to interpret a selected work of A. Lindgren in a theological way. Methodology of the practical part is built on the broad context of early Christian inculturation (interpretation of ancient culture in the Patristic Tradition, introduced in the work of Hugo Rahner), and of the modern philosophical-theological interpretation of secular culture (interpretation of Don Juan in the work of Karel Vrána). The personality of the author A. Lindgren is then described, with emphasis on certain biographical facts which are particularly important for the goal of the theses. The work of German theologian Thomas Vogel is introduced in the Czech environment for the first time. Thomas Vogel is well-known for his Christian interpretations of A. Lindgren?s books. In the final part the author interprets the book Mio, My Son from christological, ecclesiological and eschatological point of view.

Made available in DSpace on 2014-07-29T14:52:09Z (GMT). No. of bitstreams: 1 Tese thannya nascimento.pdf: 3166640 bytes, checksum: 0a9faeb659c9594423ee5e7f8b495662 (MD5) Previous issue date: 2009-01-22 / The goal of this study was to evaluate the genetic structure and the spatial pattern of intra and interpopulational gene flow of Dipteryx alata Vogel, based on nuclear and chloroplastidial microsatellite markers. Primers were developed based on sequencing of random fragments from a shotgun genomic library for detection of microsatellite regions. 12 microsatellites regions were obtained from 688 sequences, which allowed the construction of pairs of primers. These regions are composed of motifs with two to six nucleotides, ranging from 136 to 380 base pairs. This shows that the random sequencing strategy from shotgun libraries is interesting because it allows the achievement of primers for repetitive regions with different motifs. Two of these loci (Da_E06 e Da_E12) were polymorphic with three alleles each. He estimation for these loci showed satisfactory values (0.2946 and 0.2879, respectively), considering the number of alleles. Also, we used a transferred primer from the species Phaseolus vulgaris (BM164) for D. alata. Moreover, other two chloroplastidials microsatellite primers were used for molecular analyses of georeferenced subpopulations, totalizing 775 plants distributed over the natural occurrence area of Cerrado. 210 of these plants were collected and georeferenced one by one along the margins of the Araguaia River in the states of Mato-Grosso (RAMT) and Goiás (RAGO) for spatial distribution of genetic variability in local scale analysis. The relationship between estimations of genetic diversity parameters with patterns of potential distribution of species was evaluated. This was used to test the hypothesis that the genetic variability of D. alata populations is distributed according to the central-periphery model. D. alata subpopulations showed considerable high levels of genetic variability that was significantly structured among subpopulations and well structured in space, both for nuclear and chloroplastidial data. The estimation of the apparent cross-fertilization rate (ta = 1.0575) indicates that the species is allogamous. Estimations of migration rates by pollen and by seeds were lower than one, indicating that seed dispersal contributes more effectively for total gene flow. Estimates of the genetic diversity parameters from the Araguaia River population showed similar values between both margins. The estimation of the apparent cross-fertilization rate (0.9434) indicated that the Araguaia River is not a physical barrier to effective gene flow. The effective size of the neighborhood, i.e., the mean number of individuals in an area where panmixia occurs was 85.64 and 22.99 for nuclear and chloroplastidial data, respectively, indicating that seed dispersal is more restricted. The correlogram generated with chloroplastidial data presented a cline pattern of variance more evident than with nuclear data, suggesting that the presence of spatial genetic structure is being more influenced by seed dispersal. We observed that the genetic parameters do not follow a classical central-periphery model, because peripheral population (according to geographical distribution of sampling locations) tended to demonstrate higher values for these estimations, mainly the South and Western subpopulations. The relationship found between the fixation index (f) with human impact indicated that the subpopulations evaluated can be affected by fragmentation process and land use, probably caused by the recent human colonization in Cerrado biome. / O objetivo geral deste estudo foi avaliar a estrutura genética e o padrão espacial do fluxo gênico intra e interpopulacional de Dipteryx alata Vogel, com base em marcadores microssatélites nucleares e cloroplastidiais. Foi utilizada uma estratégia de desenvolvimento de iniciadores que se baseia no seqüenciamento aleatório de fragmentos provenientes de uma biblioteca genômica shotgun para a detecção de regiões microssatélites, em barueiro. Das 668 sequências obtidas, foram encontradas 12 regiões microssatélites que possibilitaram a construção dos pares de iniciadores. Estas regiões são compostas por motivos com dois a seis nucleotídeos, que variam entre 136 a 380 pb. Isto mostra que a estratégia de sequenciamento aleatório a partir de bibliotecas shotgun é interessante por possibilitar a obtenção de iniciadores para regiões repetitivas com diferentes motivos. Dois destes locos (Da_E06 e Da_E12) foram polimórficos, apresentando três alelos cada. As estimativas de He para estes locos apresentaram valores satisfatórios, considerando o número de alelos, e foram iguais a 0,2946 e 0,2879, respectivamente. Isto indica que os iniciadores desenvolvidos e padronizados com sucesso neste trabalho podem ser utilizados para estudos genético-populacionais. Juntamente com estes dois iniciadores desenvolvidos, foi utilizado outro transferido da espécie Phaseolus vulgaris (BM164) para D. alata, além de outros dois iniciadores microssatélites cloroplastidiais para análises moleculares de 23 subpopulações georeferenciadas, totalizando 775 plantas, distribuídas ao longo da área de ocorrência natural do Cerrado. Destas plantas, 210 foram coletadas e georreferenciadas uma a uma, ao longo das margens do alto rio Araguaia nos estados de Mato-Grosso (RAMT) e Goiás (RAGO), para análises de distribuição espacial da variabilidade genética em escala local. Para testar a hipótese de que a variabilidade genética das subpopulações de D. alata se distribui conforme o modelo central-periférico, foram avaliadas as relações entre as estimativas de parâmetro genético de diversidade com os padrões de distribuição potencial da espécie. Foi observado que as subpopulações de D. alata apresentam consideráveis níveis de variabilidade genética que se encontra significativamente estruturada entre as subpopulações, tanto para os dados nucleares quanto para os cloroplastidiais, apresentando-se também estruturada no espaço. A estimativa da taxa de fecundação cruzada aparente (ta = 1,0575) indica que a espécie seja alógama. As estimativas das razões de migração via pólen e via semente foram menores do que 1, o que indica que a dispersão de sementes contribui mais efetivamente para o fluxo gênico total em escala regional. As estimativas dos parâmetros genéticos de diversidade referentes à população contígua ao Rio Araguaia mostraram valores semelhantes entre as margens do rio. A estimativa da taxa de fecundação cruzada aparente (0,9434) confirma a reprodução por alogamia no barueiro. O baixo nível de diferenciação entre as subpopulações das duas margens do rio indica que o rio Araguaia não confere uma barreira física efetiva ao fluxo gênico. O tamanho efetivo de vizinhança, ou seja, o número médio de indivíduos numa área onde ocorre panmixia, para os dados nucleares e cloroplastidiais foi igual a 85,64 e 22,99, respectivamente, indicando que a dispersão de sementes é mais restrita em escala local. O correlograma gerado a partir dos dados cloroplastidiais apresenta um padrão clinal de variação mais evidente do que o proveniente dos dados nucleares, o que sugere que a presença da estrutura genética espacial deve estar sendo mais influenciada pelo padrão de dispersão da semente. Foi observado que parâmetros genéticos estimados para D. alata não se enquadram no clássico modelo central-periférico, pois as populações tidas como periféricas (de acordo com a distribuição geográfica dos pontos de coleta) tendem a exibir maiores valores para estas estimativas, com destaque para as as subpopulações das bordas Sul e Oeste do bioma. A relação encontrada entre os valores estimados para o índice de fixação intrapopulacional (f) com o impacto humano indica que as subpopulações estudadas podem estar sofrendo as conseqüências dos processos de fragmentação e uso da terra na variabilidade genética, causado provavelmente pelo recente processo de ocupação do Cerrado.

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