Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 253-262).

Thesis (D. Min.)--McCormick Theological Seminary, 1997. / Includes bibliographical references.

This thesis describes the parallel implementation of a three-dimensional numerical ice flow model of the whole of the grounded part of the Antarctic Ice Sheet at a grid resolution of 20km. Numerical modelling of ice flow is computationally intensive as it requires the solution of non-linear equations over long time scales. A parallel model was developed to overcome these restrictions, and it is demonstrated that the model runs more quickly on multiple processors than on a single processor (70% efficiency on four processors). The model was successfully validated against published benchmarks and compared against other models and remote sensing work. The main ice flow features are well reproduced, including some newly observed fast flow features in East Antarctica. The optimal run-time versus efficiency was exploited to run a series of detailed sensitivity tests on parameters that may affect the resulting ice sheet volume and basal thermal regime. Compared with the effects of surface air temperature, the accumulation rate and tuning parameter m in flow parameter A., geothermal heat flux was found to have the strongest effect on basal melting. It is shown that use of different geothermal heat flux values can affect the inclusion of sub-glacial lakes in the zone of basal melting. Topographic smoothing may reduce the model’s ability to locate subglacial lakes. Fast flow features appear in the modelled ice sheet despite the lack of basal slip conditions in the model. Use of a new topography data set improved the model’s ability to locate subglacial lakes in zones of basal melting, and revealed additional fast flow features in East Antarctica.

Satellite and in-situ radiometric measurements of sea surface temperature (SST) together with conventional SST and meteorological parameters are used to provide a description of the ocean surface skin temperature deviation (skin temperature - bulk temperature, AT) for a transect made across the Atlantic ocean from 50°N 00°W to 23°S 35°W during September and October 1992. Methods of in-situ SST measurement are discussed and the errors associated with each technique are given. The principles of infra red radiometry are explained. The differences between the calibration strategies used to determine SST using infra-red radiometers from both in-situ and satellite platforms are reviewed and the errors associated with each technique are given. Differences between published in-situ infra red SST data indicate that there may be a bias in these data as a consequence of the calibration strategy adopted. The need for an inter calibration of in-situ infra red radiometer systems used for the validaion of satellite SST is highlighted. Satellite SST algorithms are discussed and the principles of atmospheric correction are explained. The difference between the radiometric 'skin' temperature of the ocean and the conventional 'bulk' temperature at depth is defined. A review of current observations of AT is given. Several theoretical treatments of AT are reviewed. The definitions of the surface fluxes of heat and momentum are given. A description of the collection of data and an analysis of the calibration of the infra-red radiometer used to measure the skin temperature is presented. Data have been processed to obtain AT and the surface fluxes of heat and momentum nave been evaluated according to the bulk aerodynamic formulae. The relationships between AT and the measurements made are presented for the entire data set and for day and night time observations separately. Four time series of observed data are presented and the local conditions during the time of measurement are used to discuss AT. AT has a mean value of 0.39°C ±0.3°C and is shown to be a persistent feature of the Atlantic ocean. Correlation analyses reveal the skin and bulk temperature fields to be correlated at length scales > 155 km. Night time correlations are consistently higher than the day time at all length scales. For this reason it is recommended that satellite validation data are only collected during the night. High sea states are shown to affect both in-situ and satellite observations of SST biasing these data warm. The regional nature of AT is presented which is related to the dominant atmosphere-ocean conditions for each region. AT is shown to be greatest at the higher latitudes and weak in the tropical regions. Several parameterisations of AT are used to obtain estimates of AT using the data collected. These are found to be inadequate to predict AT at small temporal scales. A regional dependence of AT is found in these parameterisations. The coefficient A, of the Saunders (1969) parameterisation has been evaluated and is shown to have a regional dependence on the local atmosphere ocean conditions. The coefficient Ci and Ci of the Hasse (1971) parameterisation have been evaluated using the data collected. These are Ci=4.74 and C2=1.22. A comparison between the Along Track Scanning Radiometer Average SST is presented. Satellite - in-situ bulk AT has been obtained and shown to be comparable to that observed in-situ. This comparison highlights the need to make skin SST validation measurements rather than bulk SST measurements. The ATSR ASST data are shown to return a SST accurate to better than 0.3°C.

This thesis describes the development and application of a mass balance model for Langjökull Ice Cap to enable an investigation into its state of balance. This model is then coupled to a numerical model of ice flow, also developed as part of this thesis, to allow an assessment of the sensitivity of the ice cap to future climate change. Using data collected at a field site on one of the ice cap’s outlet glaciers in the summer of 2000, an energy balance model was optimised in order to obtain the best fit between the predicted and observed ablation. Although the optimisation enabled a reasonable fit to the observed data, it was worse than could be obtained using a simpler degree-day model. This degree-day model was developed to calculated the mass balance of the whole ice cap; using 30 years of meteorological data, the results of this model suggested that the ice cap is currently in a state of expansion – the average net mass balance across the ice cap being 0.5 m w.e.yr-1. To aid the development of a numerical model of ice flow, the flow regime of Langjökull was investigated by looking at several different methods of calculating the velocities occurring there. The effects of sediment deformation were found to be important in accurately modelling the ice flow occurring at Langjökull Ice Cap, with a till viscosity of 6x109 Pa s found suitable for modelling this process. When the degree-day and the ice flow models were coupled together, the modelled ice cap was found to be strongly dependent on air temperature and, under climate change scenarios with warming rates of 0.02 and 0.04 yr-1, Langjökull is predicted to disappear within 200 year. The inclusion of sediment deformation was found to have little effect on the response of the ice cap to climate change.

The multi-response optimization (MRO) problem in response surface methodology (RSM) is quite common in industry and in many other areas of science. During the optimization stage in MRO, the desirability function method, one of the most flexible and popular MRO approaches and which has been utilized in this research, is a highly nonlinear function. Therefore, we have proposed use of a genetic algorithm (GA), a global optimization tool, to help solve the MRO problem. Although a GA is a very powerful optimization tool, it has a computational efficiency problem. To deal with this problem, we have developed an improved GA by incorporating a local directional search into a GA process. In real life, practitioners usually prefer to identify all of the near-optimal solutions, or all feasible regions, for the desirability function, not just a single or several optimal solutions, because some feasible regions may be more desirable than others based on practical considerations. We have presented a procedure using our improved GA to approximately construct all feasible regions for the desirability function. This method is not limited by the number of factors in the design space. Before the optimization stage in MRO, appropriate fitted models for each response are required. The parametric approach, a traditional RSM regression technique, which is inflexible and heavily relies on the assumption of well-estimated models for the response of interests, can lead to highly biased estimates and result in miscalculating optimal solutions when the user's model is incorrectly specified. Nonparametric methods have been suggested as an alternative, yet they often result in highly variable estimates, especially for sparse data with a small sample size which are the typical properties of traditional RSM experiments. Therefore, in this research, we have proposed use of model robust regression 2 (MRR2), a semi-parametric method, which combines parametric and nonparametric methods. This combination does combine the advantages from each of the parametric and nonparametric methods and, at the same time, reduces some of the disadvantages inherent in each. / Ph. D.

O 68Ga é um radionuclídeo promissor para a medicina nuclear, decaindo por emissão de pósitrons com abundância de 89%, apresentando tempo de meia vida física de 68 minutos, o que é compatível com a farmacocinética de muitas biomoléculas e substratos de baixo peso molecular. Outra característica importante é a sua disponibilidade por um sistema de gerador, onde o radionuclídeo pai, 68Ge (t1/2 = 270,95 dias) é adsorvido em uma coluna e o filho, 68Ga, é eluído na forma iônica 68Ga3+. O desenvolvimento dos geradores de 68Ge/68Ga teve início na década dos anos 60, mas o seu uso clínico começou a ser aceitável e relevante apenas recentemente. O método de separação do 68Ge do 68Ga mais utilizado é o sistema cromatográfico de troca iônica, devido sua praticidade de operação, mas outros sistemas de geradores já foram propostos, como de extração por solvente e técnica de evaporação. Atualmente, os geradores de 68Ge/68Ga são disponíveis comercialmente tanto com colunas utilizando matrizes inorgânicas preparadas com TiO2 ou SnO2 como também usando resina orgânica. A eficiência de eluição do 68Ga varia de 70 % a 80 %, apresentando uma queda ao longo do tempo. Os níveis de contaminação do 68Ge vão de 10-2 a 10-3 %, porém ocorre um aumento nos níveis de contaminação após longos períodos de uso. Mesmo com todos os avanços tecnológicos, ocorridos nas últimas décadas, no desenvolvimento dos geradores de 68Ge/68Ga, o eluato de 68Ga dos geradores comerciais ainda não é adequado para uso direto em seres humanos e algumas melhorias nos sistemas precisam ser feitas para diminuir os níveis de contaminação de 68Ge e impurezas químicas. O objetivo principal deste trabalho foi desenvolver um sistema de gerador de 68Ge/68Ga com o qual se pudesse eluir o 68Ga com qualidade necessária para uso clínico. O comportamento químico do Ge e do Ga foi avaliado em vários materiais adsorvedores inorgânicos. Foram desenvolvidos dois tipos de sistemas de geradores de 68Ge/68Ga utilizando o TiO2 como material adsorvedor: sistema de eluição com pressão manual e sistema de eluição a vácuo, controlado. As eficiências dos geradores foram similares às encontradas nos geradores comerciais, assim como os níveis de impurezas no eluato. Um novo método para o controle radionuclídico foi desenvolvido e apresentou resultados satisfatórios para determinação da contaminação do 68Ge no eluato do gerador. Foi proposto um protótipo de gerador capaz de fornecer 68Ga com a qualidade necessária para ser utilizado em aplicações médicas. / The 68Ga is a promising radionuclide for nuclear medicine, decaying by positron emission with an abundance of 89%, with physical half-life of 68 minutes, which is compatible with the pharmacokinetics of many biomolecules and low molecular weight substrates. Another important feature is its availability through a generator system, where the parent radionuclide, 68Ge (t1/2 = 270.95 days) is adsorbed on a column and the daughter, 68Ga, is eluted in an ionic form 68Ga3+. The development of 68Ge/68Ga generators began in the 60s, but its clinical use began to be acceptable and relevant only recently. The method of separation of 68Ge and 68Ga most used is the ion-exchange chromatographic system, due to its practical operation, but other generator systems have been proposed, such as solvent extraction and evaporation technique. Currently, 68Ge/68Ga generators are commercially available using inorganic matrices columns prepared with TiO2 or SnO2 as well using organic resin. The efficiency of 68Ga elution ranges from 70% to 80%, decreasing over time. The 68Ge breakthrough varies from 10-2 to10-3 % or lower in a fresh generator, but there is an increase in the levels of contamination after long periods of use. Even with all the technological advances in the development of 68Ge/68Ga generators in the past decades, the 68Ga eluted from commercial generators is not suitable for direct use in humans and some improvements in the systems need to be made to reduce the 68Ge breakthrough and chemical impurities levels. The main objective of this work was to develop a 68Ge/68Ga generator system is which 68Ga could be eluted with quality required for clinical use. The chemical behavior of Ge and Ga was evaluated on various inorganic adsorbents materials. Two types of 68Ge/68Ga generator systems were developed using TiO2 as adsorbent material: elution system with manual pressure and vacuum controlled. The efficiencies of the generators were similar to those found in commercial generators, as well as the impurity levels in the eluate. A new method for radionuclidic control was developed and showed good results for the determination of 68Ge breakthrough in 68Ga eluate. It was proposed a prototype 68Ga generator capable of providing the quality needed for use in medical applications.

Este trabalho teve como objetivo a investigação de novos materiais promissores para a supercondutividade presentes no sistema ternário do Zr-V-Ga. Os resultados apresentados de magnetização, resistividade e calor específico, mostram de forma inequívoca que o Zr3V2Ga4 é um novo material supercondutor com temperatura crítica de transição supercondutora nas proximidades de 14,3K. O estudo do composto ZrV2Ga4 mostrou que a supercondutividade é revelada com temperatura crítica de aproximadamente 14,2 K. Medidas de calor especifico realizadas nessas amostras evidenciam de forma clara manifestações de supercondutores multibandas. Outra investigação importante realizada foi a substituição parcial de vanádio por titânio na estequiometria do composto ZrV2Ga4 representado pela composição global ZrV2-xTixGa4, revela que a substituição parcial de vanádio por titânio suprime a supercondutividade neste composto. Isto é mais evidente quando a substituição total de V por Ti suprime totalmente o comportamento supercondutor. Estes resultados sugerem que a supercondutividade pode ser dependente da unidade aniônica [V2Ga4]4-. Finalmente, esta dissertação mostra que o sistema ternário Zr-V-Ga é bastante rico em fases supercondutoras ainda não reportadas na literatura. / This work aimed to investigate new promising materials for superconductivity present in the ternary system of Zr-V-Ga. The presented results of magnetization, resistivity and specific heat, show unequivocally that the Zr3V2Ga4 is a new superconducting material with critical temperature of superconducting transition close to 14.3K. The study of compound ZrV2Ga4 showed that superconductivity is revealed at a critical temperature of approximately 14.2K. Specific heat measurements carried out on these samples clearly demonstrate manifestations of multiband superconductors. Another important investigation carried out was the partial substitution of vanadium by titanium in the stoichiometry of the ZrV2Ga4 compound represented by the global composition ZrV2-xTixGa4, reveals that the partial substitution of vanadium by titanium suppresses the superconductivity in this compound. This is most evident when the total substitution of V for Ti totally suppresses the superconducting behavior. These results suggest that superconductivity may be dependent on the anionic unit [V2Ga4]4-. The results presented in this dissertation reveal that the ternary system Zr-V-Ga is rich in new superconducting materials not reported yet.

Eisen-Gallium-Legierungen sind aufgrund ihrer hohen Magnetostriktion und ihrer hervorragenden mechanischen Eigenschaften sehr interessant für Anwendungen sowohl in Form von Sensoren als auch Aktoren. Die fortschreitende Miniaturisierung erfordert die Herstellung von Bauteilen in eindimensionaler Struktur und komplexen Geometrien. Beide Herausforderungen sind mit templatbasierter elektrochemischer Abscheidung zugänglich. Es konnte gezeigt werden, dass dünne Fe-Ga-Schichten schon aus einfachen wässrigen Elektrolyten abgeschieden werden können. Gallium kann nur in Anwesenheit von Fe induziert reduziert werden. Gleichzeitig konnte nachgewiesen werden, dass durch die Hydrolyseneigung der Ga-Ionen immer Hydroxide gebildet und in das Deposit eingebunden werden. Durch die Einführung einer alternierenden potentiostatischen Abscheidung mit einem Reduktions- und einem Relaxationsschritt können dennoch dichte und homogene Fe80Ga20-Schichten mit wenigen Defekten und einem vernachlässigbar kleinen Sauerstoffgehalt hergestellt werden. Die Übertragung der so gefundenen Abscheideparameter zur templatbasierten Nanodrahtherstellung ist nur bis zu einem Porendurchmesser von 100nm möglich. Wird der Durchmesser der Porenkanäle weiter verringert, führt aufgrund eingeschränkter Diffusionsvorgänge die Abscheidung zu segmentierten und sauerstoffreichen Depositen. Die Modifizierung des Elektrolyten durch Komplexierung der Metallionen verhindert die Bildung und Einbindung der Hydroxide. Damit können auch für Porendurchmesser kleiner 100nm Drähte in AAO-Template abgeschieden werden. Diese sind dicht, defektfrei und weisen keinen Zusammensetzungsgradienten entlang der Wachstumsrichtung auf. Detaillierte TEM-Untersuchungen konnten zeigen, dass die Herstellung durch ein einfacheres potentiostatisches Abscheideregime zu weniger verspannten und dennoch homogenen und defektfreien Drähten führt. Für die Herstellung von magnetisch aktiven Drähten sollte daher die potentiostatische der gepulsten Abscheidung vorgezogen werden.

O 68Ga é um radionuclídeo promissor para a medicina nuclear, decaindo por emissão de pósitrons com abundância de 89%, apresentando tempo de meia vida física de 68 minutos, o que é compatível com a farmacocinética de muitas biomoléculas e substratos de baixo peso molecular. Outra característica importante é a sua disponibilidade por um sistema de gerador, onde o radionuclídeo pai, 68Ge (t1/2 = 270,95 dias) é adsorvido em uma coluna e o filho, 68Ga, é eluído na forma iônica 68Ga3+. O desenvolvimento dos geradores de 68Ge/68Ga teve início na década dos anos 60, mas o seu uso clínico começou a ser aceitável e relevante apenas recentemente. O método de separação do 68Ge do 68Ga mais utilizado é o sistema cromatográfico de troca iônica, devido sua praticidade de operação, mas outros sistemas de geradores já foram propostos, como de extração por solvente e técnica de evaporação. Atualmente, os geradores de 68Ge/68Ga são disponíveis comercialmente tanto com colunas utilizando matrizes inorgânicas preparadas com TiO2 ou SnO2 como também usando resina orgânica. A eficiência de eluição do 68Ga varia de 70 % a 80 %, apresentando uma queda ao longo do tempo. Os níveis de contaminação do 68Ge vão de 10-2 a 10-3 %, porém ocorre um aumento nos níveis de contaminação após longos períodos de uso. Mesmo com todos os avanços tecnológicos, ocorridos nas últimas décadas, no desenvolvimento dos geradores de 68Ge/68Ga, o eluato de 68Ga dos geradores comerciais ainda não é adequado para uso direto em seres humanos e algumas melhorias nos sistemas precisam ser feitas para diminuir os níveis de contaminação de 68Ge e impurezas químicas. O objetivo principal deste trabalho foi desenvolver um sistema de gerador de 68Ge/68Ga com o qual se pudesse eluir o 68Ga com qualidade necessária para uso clínico. O comportamento químico do Ge e do Ga foi avaliado em vários materiais adsorvedores inorgânicos. Foram desenvolvidos dois tipos de sistemas de geradores de 68Ge/68Ga utilizando o TiO2 como material adsorvedor: sistema de eluição com pressão manual e sistema de eluição a vácuo, controlado. As eficiências dos geradores foram similares às encontradas nos geradores comerciais, assim como os níveis de impurezas no eluato. Um novo método para o controle radionuclídico foi desenvolvido e apresentou resultados satisfatórios para determinação da contaminação do 68Ge no eluato do gerador. Foi proposto um protótipo de gerador capaz de fornecer 68Ga com a qualidade necessária para ser utilizado em aplicações médicas. / The 68Ga is a promising radionuclide for nuclear medicine, decaying by positron emission with an abundance of 89%, with physical half-life of 68 minutes, which is compatible with the pharmacokinetics of many biomolecules and low molecular weight substrates. Another important feature is its availability through a generator system, where the parent radionuclide, 68Ge (t1/2 = 270.95 days) is adsorbed on a column and the daughter, 68Ga, is eluted in an ionic form 68Ga3+. The development of 68Ge/68Ga generators began in the 60s, but its clinical use began to be acceptable and relevant only recently. The method of separation of 68Ge and 68Ga most used is the ion-exchange chromatographic system, due to its practical operation, but other generator systems have been proposed, such as solvent extraction and evaporation technique. Currently, 68Ge/68Ga generators are commercially available using inorganic matrices columns prepared with TiO2 or SnO2 as well using organic resin. The efficiency of 68Ga elution ranges from 70% to 80%, decreasing over time. The 68Ge breakthrough varies from 10-2 to10-3 % or lower in a fresh generator, but there is an increase in the levels of contamination after long periods of use. Even with all the technological advances in the development of 68Ge/68Ga generators in the past decades, the 68Ga eluted from commercial generators is not suitable for direct use in humans and some improvements in the systems need to be made to reduce the 68Ge breakthrough and chemical impurities levels. The main objective of this work was to develop a 68Ge/68Ga generator system is which 68Ga could be eluted with quality required for clinical use. The chemical behavior of Ge and Ga was evaluated on various inorganic adsorbents materials. Two types of 68Ge/68Ga generator systems were developed using TiO2 as adsorbent material: elution system with manual pressure and vacuum controlled. The efficiencies of the generators were similar to those found in commercial generators, as well as the impurity levels in the eluate. A new method for radionuclidic control was developed and showed good results for the determination of 68Ge breakthrough in 68Ga eluate. It was proposed a prototype 68Ga generator capable of providing the quality needed for use in medical applications.