Neste trabalho descreve-se o estudo do estabelecimento de uma técnica para o crescimento e preparo de cristais de HgI2, com o intuito de utilizá-los como detectores semicondutores de radiação que operam a temperatura ambiente. Três métodos de crescimento de cristais foram estudados no desenvolvimento deste trabalho: (1) Transporte Físico de Vapor (Physical Vapor Transport PVT), (2) Solução Saturada de HgI2 empregando dois solventes distintos; Dimetil Sulfóxido (DMSO) (a) e acetona (b) e (3) método de Bridgman. A fim de avaliar os cristais de HgI2 desenvolvidos pelos três métodos, medidas sistemáticas foram realizadas para determinar a estrutura, o plano de orientação, a estequiometria, a morfologia da superfície e as impurezas do cristal. A influência destas propriedades físico-químicas sobre os cristais desenvolvidos foi avaliada em termos de desempenho como detector de radiação. Os difratogramas indicaram que os cristais estão orientados preferencialmente planos (001) e (101) com estrutura tetragonal para todos os cristais desenvolvidos. No entanto, a morfologia com menor nível de deformação foi observada para o cristal obtido pela técnica de PVT. Uma uniformidade na camada de superfície do cristal de PVT foi observada, enquanto na superfície do cristal de DMSO podem ser nitidamente encontradas incrustações de elementos distintos ao cristal. A melhor resposta de radiação foi encontrada para os cristais crescidos pela PVT. Significativa melhora no desempenho do detector de radiação de HgI2 foi encontrada, purificando o cristal por meio de dois crescimentos sucessivos, pela técnica de PVT. / In this work, the establishment of a technique for HgI growth and preparation of crystals, for use as room temperature radiation semiconductor detectors is described. Three methods of crystal growth were studied while developing this work: (1) Physical Vapor Transport (PVT); (2) Saturated Solution of HgI2, using two different solvents; (a) dimethyl sulfoxide (DMSO) and (b) acetone, and (3) the Bridgman method. In order to evaluate the obtained crystals by the three methods, systematic measurements were carried out for determining the stoichiometry, structure, orientation, surface morphology and impurity of the crystal. The influence of these physical chemical properties on the crystals development was studied, evaluating their performance as radiation detectors. The X-ray diffractograms indicated that the crystals were, preferentially, oriented in the (001) e (101) directions with tetragonal structure for all crystals. Nevertheless, morphology with a smaller deformation level was observed for the crystal obtained by the PVT technique, comparing to other methods. Uniformity on the surface layer of the PVT crystal was detected, while clear incrustations of elements distinct from the crystal could be viewed on the DMSO crystal surface. The best results as to radiation response were found for the crystal grown by physical vapor transport. Significant improvement in the HgIz2 radiation detector performance was achieved for purer crystals, growing the crystal twice by PVT technique.

Philosophiae Doctor - PhD / The organic-inorganic hybrid perovskites such as methyl ammonium lead iodide (MAPbI3) or mixed halide MAPbI3-xClx (x is usually very small) have emerged as an interesting class of semiconductor materials for their application in photovoltaic (PV) and other semiconducting devices. A fast rise in PCE of this material observed in just under a decade from 3.8% in 2009 to over 25.2% recently is highly unique compared to other established PV technologies such as c-Si, GaAs, and CdTe. The high efficiency of perovskites solar cells has been attributed to its excellent optical and electronic properties. Perovskites thin film solar cells are usually deposited via spin coating, vacuum thermal evaporation, and chemical vapour deposition (CVD).

This diploma thesis deals with the possibilities of stress resistance analysis of the Cupriavidus necator H16 and PHB-4 bacterial cells by spectroscopic methods and by testing the suitability of acridine orange as a viable dye. Based on research in literature, suitable analytical methods have been proposed, namely flow cytometer and fluorescence microscope. The first part of the experimental work was focused on the fluorescence microscope, which confirmed the basic character of acridine orange. Three stress factors, 50% and 70% ethanol, and acidic pH (pH = 1) were selected for viability monitoring. The bacteria fluoresced with green color after exposure to ethanol and red spots were found next to the cells, indicating their loss of integrity. In an acidic environment, the bacteria fluoresced red because of a partial DNA breakdown. The results were verified by the combination of propidium iodide with SYTO9 and the acridine orange suitability proved to be useful in this method. Image records were processed using image analysis. In the second part, acridine orange was used to monitor fluorescence using a flow cytometer. The result of the measurement was fluorescence expressed as histograms for individual channels, where fluorescence was characterized by median and mean intensity. By comparing the methods used, the acridine orange appears to be a more suitable fluorescent dye for the microscope than for a flow cytometer in which it was more difficult to obtain cell viability information. In the last part of the experimental work interesting photophysical properties of acridine orange were investigated.

Deep geological repositories (DGR) are considered an effective long-term solution for radioactive waste disposal. Sedimentary (argillaceous formations) and crystalline rocks are currently under investigation worldwide as potential host formations for DGR. Their low porosity (<1-2 %) and very low hydraulic conductivity result in diffusion-dominated solute transport. There is a need to investigate their diffusion properties in detail, the long-established diffusion methods do not allow an evaluation of the spatial relationship between tracers and the characteristics of the geological medium. The aim of this project was to measure diffusion coefficients in low-porosity rocks (< 2%) using X-ray radiography and iodide tracer. The method is a non-destructive technique based on the principle of X-ray attenuation; it provides temporal- and spatially-resolved information of a highly attenuating tracer diffusing in a sample. Samples from the Cobourg Formation, an Ordovician argillaceous limestone from the Michigan Basin, and from the Lac du Bonnet batholith, an Archean granitic pluton were used in this study. X-ray radiography data from the Cobourg Formation indicate tracer accumulation occurs on dark argillaceous layers in the rock characterized by clay minerals and organic matter. It is proposed that the I– tracer solution underwent photo-chemical oxidation, leading to the formation of I2, a highly reactive volatile iodine species and I3–, which readily reacted with humic substances contained in the clay- and organic rich zones in the limestone samples. In the case of the granitic samples, attempts at measuring diffusion coefficients encountered several challenges. The results indicate that tracer signal can be detected, however diffusion signal is masked by imaging errors and noise.

The ability to deliver sequences of DNA and other molecular loads across the membrane of a cell and into its nucleus is an area of interest in the medical community. One of its many applications is that of gene therapy. In contrast to other forms of treatment, gene therapy seeks to treat diseases at the cellular level. The success of these treatments depends on the technologies for cell transfection that are available. Physical methods are sometimes able to overcome poor efficiencies of chemical methods and the safety concerns of viral methods, but are usually impractical due to the limited number of cells that are able to be transfected at a time, isolation, and immobilization of the cells. Nanoinjection is capable of using millions of small lances in an array to inject hundreds of thousands of cells simultaneously with relatively high efficiencies and viabilities. The solid nature of the lances also allows them to be smaller than their hollow-needle counterparts, which results in higher cell viability. Propidium Iodide (PI), a dye whose fluorescence increases greatly when bound to nucleic acids, was used as an injection molecule for testing the efficacy of the nanoinjection process on HeLa 229 cancer cells in a portion of the experiments, with a GFP plasmid of DNA being used in the rest. After injection, flow cytometry was used to detect the concentration of PI or the expression of the GFP in the injected cells. Since PI cannot normally penetrate the membrane of living cells, those found with high concentrations of PI were either successfully injected or dead, which can be determined by the flow cytometry. Investigation of the parameters that affect the efficiency of the nanoinjection process will help improve it for further research. Some of these parameters that were investigated include the force of injection, the material used for the lances (silicon versus carbon nanotubes), and the injection speed of the lance arrays. An injection device capable of small changes in deflection was designed to ensure accurate increments in force for testing, as well as a pulsed current control injection system. Results for injections of varying forces indicate a slow rise in PI uptake from 0 to 1.8 Newtons where it reaches a maximum uptake of 4.11 when normalized to the PI uptake of the positive controls. The PI uptake then remains relatively level as the force continues to increase, averaging an uptake of approximately 3.1. The slow rise is likely due to more of the cells being punctured as the force increases until most have been punctured and the PI uptake levels off. The viability of the injected cells was close to that of the controls with no clear trend. A comparison of lance arrays made from silicon and carbon nanotubes using DNA as the molecular load shows little difference between materials. Different injection speeds tested show that only 1-5% of the cells in the injection process are lost for speeds in the range of 0.08-0.16 mm/sec, whereas 49-69% of the cells are lost using speeds between 0.6-3 mm/sec.

Delivering foreign molecules into living cells is a broad and ongoing area of research. Gene therapy, or delivering nucleic acids into cells via non-viral or viral pathways, is an especially promising area for pharmaceutics. All gene therapy methods have their respective advantages and disadvantages, including limited delivery efficiency and low viability. Nanoinjection, or delivering molecules into cells using a solid lance, has proven to be highly efficient while maintaining high viability levels. In this thesis, an array of solid silicon lances was tested by nanoinjecting tens of thousands of HeLa cancer cells simultaneously. Several molecule types were injected in different tests to understand cell uptake efficiency and cell viability. Voltage was used to determine the impact of an electric field on molecule delivery. Propidium iodide, a dye that fluoresces when bound to nucleic acids and does not fluoresce when unbound, was delivered into cells using the lance array. Results show that the lance array delivers propidium iodide into up to 78% of a nanoinjected HeLa cell culture, while maintaining 78%-91% viability. Using similar protocol as in propidium iodide experiments, plasmid DNA containing the code for a fluorescent protein was nanoinjected into HeLa cells, resulting in an average expression rate of up to 0.21%. Since gene expression only occurs in cells which have integrated DNA into the genome in the nucleus, a different DNA detection method was developed to determine total DNA count in cells following nanoinjection. DNA strands tagged with a radioactive isotope were nanoinjected into HeLa cells. Liquid scintillation was employed to quantify and discriminate between DNA delivered to cells and DNA that remained in solution around cells following nanoinjection. The largest average amount of DNA delivered to cells was 20.0 x 10^3 DNA molecules per cell. Further development of the radioactive nanoinjection process is needed to more fully understand the parameters that affect DNA delivery efficiency. In all experiments with propidium iodide and DNA molecules, low accumulation voltage, coupled with a short pulsed release voltage, resulted in the greatest molecule delivery efficiencies when compared to tests without voltage or with a constant voltage only. Lastly, an automated nanoinjection system was developed to eliminate variability in user applied nanoinjection force. The automated system was found to reduce variability in average propidium iodide uptake values by 56%. In conclusion, experimental testing of the multi-cell nanoinjection process has shown promising molecule delivery results into human cells, suggesting that further optimization of the process would have positive implications in the field of academic and clinical gene therapy.

α-Epimerisation has been found to be absent in the reactions of threo-1,2-diphenyl-1-propyltrimethylammonium ion and its -2-d₁ analogue with t-butoxide ion in t-butyl alcohol at 30ºC. The formation of trans-α-methylstilbene, cis-α-methylstilbene and threo-N,N-dimthyl-1,2-diphenyl-1-propylamine has been associated with anti-elimination, syn-elimination and with nucleophilic substitution at a N-methyl carbon atom, respectively, and interpreted in terms of structural and medium features of the reactions. The β-hydrogen isotope effects for anti- and syn-elimination have been associated with reactant-like and product-like transition states, respectively, for these reaction modes. / Thesis / Master of Science (MSc)

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