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Orientador: Carlos Roque Duarte Correia / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-06T00:38:56Z (GMT). No. of bitstreams: 1 Pastre_JulioCezar_M.pdf: 2844371 bytes, checksum: 6abfb0e87d60113816e3b01d9a02d6b9 (MD5) Previous issue date: 2005 / Mestrado / Quimica Organica / Mestre em Química

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BODIPYs são compostos fluorescentes que possuem uma ampla gama de aplicações tecnológicas em diversas áreas do conhecimento, recebendo considerável destaque na literatura, tanto do ponto de vista fotoquímico, quanto sintético. Entretanto, a reatividade química desses fluorórofos ainda não é totalmente compreendida. Neste sentido, neste trabalho utilizou-se a química de sais de diazônio aplicada aos BODIPYs, explorando uma série de perspectivas para diversificação estrutural desses fluoróforos. Como estratégias para a obtenção do BODIPY funcionalizado com o grupo diazo foram testados três diferentes métodos, que envolvem a utilização de NOBF4, NaNO2/HCl e NaNO2/HBF4. O método que envolve a utilização de NOBF4 não levou a obtenção do composto diazotado, no entanto, resultou na obtenção de compostos nitrosilados. Quando utilizado NaNO2/HCl, o composto diazotado foi obtido in situ, seguido pela reação de acoplamento diazóico. Com o método que envolve o uso de NaNO2/HBF4 foi possível obter melhores rendimentos para as reações de acoplamento diazóico, e abriu a possibilidade de novas explorações química dos sais de diazônio-BODIPY / BODIPYs are fluorescent compounds which have a wide range of technological applications in different areas of knowledge. They have remarkable presence in the literature because of their synthetic and photochemical properties. However, the chemical reactivity of these fluorophores are not fully known. Considering this, our study applied the diazonium salts chemistry to BODIPYs aiming to explore the structure diversification of these fluorophores. Three different methods were used to obtain the diazo derivatives of BODIPYs: NOBF4, NaNO2/HCl and NaNO2/HBF4. The method using the NOBF4 instead of afford the diazotized compound as expected, a nitrosylated compound was obtained. When NaNO2/HCl was used, the diazotized compound was obtained in situ, followed by diazo coupling reaction. The best yields diazo coupling reactions were obtained when NaNO2/HBF4 was used. The reactions described in our work showed new possibilities of chemical tractability of BODIPY compounds.

The utilisation of minerals in Ancient Egyptian medicine from procurement through to use is examined here in a case study investigating the role of sodium salts. The sodium salts, salt and natron are two of the three most commonly used minerals in the Egyptian pharmacopeia. The results of the project are important to medical historians and archaeomineralogists alike in that they formulate a systematic understanding of the way in which minerals were used in medical and medically associated industries. Key sources of salt and natron were examined and the Wadi Natrun was identified as the probable main site of natrun exploitation. A comprehensive study conducted of this area involved examining sources of a historical geographical nature and analysis of mineralogical samples gathered from fieldwork in the Wadi Natrun. From the source of exploitation, natron and salt were sold to the Egyptians to be used in a number of everyday industries as well as for their use in medical and medically associated industries. Salt and natron were found to be used for their astringent and cleansing qualities, and are still being used in traditional medical formulations. Prescription replication showed that these substances worked effectively. Additional research into medically associated industries showed commonality between sodium salts use between all three industries investigated. The results of this research shows that a comprehensive study of the use of minerals in medicine could be established. Primary sites of exploitation of both salt and natron were identified, and minerals from theses sites were categorised and identified. The results showed that the chemical nature of these deposits had changed in the last 2000 years. The results also demonstrate reasons why the language surrounding the term natron needed to be revised. These results have implications for both archaeology and the history of medicine.

In this study, the corrosion resistance of three different stainless steels (304, 316 and 309) towards eutectic chloride salts is investigated. The performances of two materials to reduce the corrosion of the steels are examined: zirconium as sacrificial anode and an Al2O3 coating deposited by flame spraying. Samples are submitted to a 24 hours corrosion test at 700°C in air. The samples are characterised by weight analysis, SEM observations and EDX analysis of their surface and cross-section. The corrosion resistance of the stainless steels is not improved by adding Zr rods in direct contact with the steel, rather decreased in the areas where the rod laid. However, in these conditions, stainless steel 316 has the best resistance to highly corrosive chloride salts. The Al2O3 coating is too porous and penetrated by the salt, the steel underneath is corroded. Nevertheless, some alumina remains intact after the corrosion test, because of the high inertness of the ceramic. The presence of O2 most certainly accelerated the corrosion mechanism studied here.

>Magister Scientiae - MSc / The objective of this study was to determine the hydrosalinity fluxes associated with overland and subsurface (vadose zone) flow for different soils and land uses. For this purpose, the following data were collected during 2005 and 2006 in a typical small scale catchment located near the town of Riebeeck-Wes: weather data, hydrological and water quality measurements, soil water contents and chemistry, and vegetation growth. The area is characterized by a Mediterranean climate receiving winter rainfall of approximately 300 mm a catchment is conservative, with Na + and Cl- being the dominant ions.

Silicon dispersions in water are used to produce pyrotechnic time delay compositions employed in mine detonators. The delay elements are manufactured by pressing the pyrotechnic composition into aluminium tubes. The automated filling and pressing process requires powders with good free-flow behaviour. Spray drying of water-based slurries is an appropriate method for obtaining such free-flowing granules as it creates almost perfectly spherical particle agglomerates. In addition to the acceptable flow properties, this process provides well-mixed compositions at desired particle size distributions. However, a potential hazard situation arises when water reacts dissociatively with silicon to form SiO2 and hydrogen gas according to Si + 2H2O _ SiO2 + 2H2↑. The propensity of the silicon to react with water and to release hazardous hydrogen gas must thus be suppressed. To this end, the following methods were investigated as a means of diminishing the rate of hydrogen evolution: (i) controlling the slurry pH; (ii) adding organic corrosion inhibitors; (iii) controlled silicon air oxidation before slurrying; and (iv) adding suitable metal ions to provide an additional cathodic reaction to that of water. The effect of organic surface modifications and medium pH on the rate of corrosion of silicon was studied at ambient temperature. It was found that the rate of hydrogen evolution increased with increasing pH. Silanes proved to be more effective silicon corrosion inhibitors than alcohols, with vinyl tris(2-methoxyethoxy) silane producing the best results from the silanes investigated. Differential thermal analysis (DTA) studies were performed using a near-stoichiometric amount of lead chromate as oxidant. Comparable combustion behaviour was observed when both the fuel and the oxidant powders were either uncoated or silane modified. Mixtures of neat oxidant with silane-coated silicon showed poor burn behaviour and this was attributed to poor particle- particle mixing due to the mismatch in surface energies. The controlled silicon air oxidation results showed that the best hydrogen evolution inhibition was attained upon formation of a SiO2 passivating layer at 350 °C. However, Fourier transform infrared (FTIR) data also suggest that some inhibition was imparted below 350 °C and this is due mainly to the removal of silicon surface hydroxyl groups rather than an increase in the SiO2 thickness. DTA studies performed using a nearstoichiometric amount of lead chromate revealed that although heat treatment at higher temperatures provides better passivation; it reduces the reactivity of the silicon in pyrotechnic compositions. The ignition temperature increases while the energy output decreases. Water oxidises silicon via an electrochemical reaction that produces hydrogen gas. The last approach considered in this study was the introduction of a competing cathodic reaction as a means of suppressing the liberation of hydrogen. It was found that the addition of metal ions with a higher reduction potential than hydrogen ions, e.g. copper (II) ions, reduced the amount of hydrogen liberated. In the presence of copper ions the reaction with water featured three distinct stages. During the initial stage, copper is deposited on the silicon and a rapid drop in solution pH is observed. Most of the hydrogen evolved during a second active stage, with the pH showing a slight upward drift. Finally, in the third stage, hydrogen evolution stopped as the silicon surface became passive. The reduction in the total hydrogen evolved was attributed to copper deposits reducing the active surface area available for the oxidation of silicon and to the presence of copper which facilitates accelerated passivation of the uncoated silicon surface. The nature of the anions present affected both the amount of copper deposited on the silicon and the amount of hydrogen released. DTA studies showed that exposure of silicon to copper metal salt solutions also decreases the reactivity of the silicon fuel in pyrotechnic compositions. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Chemical Engineering / unrestricted

The ability of freshly prepared spinach or poke weed (Phytolacca americana) chloroplasts to photoreduce triphosphopyridine nucleotide (TPN) under anaerobic conditions decreased in the presence of ascorbate and 2,6-dichlorophenolindophenol (DPIP). On .aging the chloroplasts, however, addition of DPIP and ascorbate was required for a high rate of TPN photoreduction. Qualitatively similar results were obtained for photoreduction of DPN, indigo carmine, riboflavin-5'-phosphate and vitamin K3 . Addition of 3-(3,4-dichlorophenyl)-1,l-dimethylurea (DCMU) at 10-5 M to freshly prepared chloroplasts inhibited the photoreduction of TPN by more than 98 %, and activity was restored to 94 %o f the original value by addition of ascorbate and.DPIF. Hydroxylamine at 10-3 Mand ammonium ion at 0.17 M produced similar effects. Qualitatively similar results were obtained with .these three inhibitors for photoreduction of DPN, indigo , carmine, .riboflavin-5 1 -phosphate, vitamin K3, methyl red and tetrazolium blue. Cesium ion and orthophenanthroline produced inhibitory effects similar to those of DCMU, hydroxylamine and ammonium ion which responded analogously to the DPIP-ascorbate couple. The data substantiate the previously proposed idea that ascorbate is photooxidized in the absence of oxygen by the photochemical oxidizing equivalents produced by illuminated chloroplasts, with the dye DPIP· acting as intermediate electron carrier. With intact .chloroplasts 2 the oxidizing equivalents are utilized preferentially for oxidation of water to produce oxygen. Only after the oxygen-evolution .system becomes .inoperativec1;1.n the ascorbate-DPIP couple compete successfully for the oxidizing equivalents. ExPosure of chloroplasts . to . light for 20 minutes _prior to ,adding .a Hill oxidant resulted in a reduced photoreducin,g capacity in the Hill reaction with TPN, indigo .carmine .and tetrazoli:um blue. However, such a treatment .actually increased the photoreducing _ability of the chloroplasts in the presence of DPIP and .ascorbate. Chloroplasts were inactivated toward the Hill reaction .by a pH of 7.7 at 30°. This inactivation was .readily overcome by addition of ascorbate and DPIP, indicating that .the principal effect of this treatment was to inactivate the oxygen-evolution system. Since indigo carmine photoreduction is stabili.z-ed· much more by the presence of sucrose in the reaction mixture than the photoreduction of DPIP it is indicated that there are components in the electron transport system leading from the site of DPIP photoreduction to that of indigo carmine photoreduction which .are sensitiye to distilled water dilution. The photoreduction of TPN, PPN .and indigo carmine was stimulated by addition of cysteine, whereas reduced glutathione was without effect. Cysteine was unable to overcome the inhibitions of DCMU, hydroxylamine and ammonium ion and no stimulation was observed when cysteine was .added to the inhibited systems containing DPIP and ascorbate even though cysteine was capable of stimulating the uninhibited reaction containing the DI"IP-ascorbate couple. It was there3 fore concluded that cysteine acts by stabilizing or reacting with the oxygen-evolving system. Chloride-deficient chloroplasts .were stimulated by added chloride and cyanide in Hill reaction activities. Reaction .mixtures containing sufficient chloride to provide maximal stimulation were further stimulated by added cyanide, versene and Tris.

The Shigella species cause millions of cases of watery or bloody diarrhea each year in developing countries, with children under the age of five years most vulnerable to infection. Emerging strains of multidrug resistant Shigella emphasize the need for a comprehensive and cost-efficient vaccine; however, an effective vaccine has yet to be produced despite years of research. Several studies have demonstrated that Shigella utilizes host physiology, specifically bile salts as signals for invasion and virulence gene expression. This study aimed to build upon previous research analyzing the bile salts transcriptional profile of Shigella flexneri 2457T, in which an induction of the uncharacterized gene was demonstrated during bile salts exposure. Here, a mutant and wild-type 2457T strains were used in infection of HT-29 colonic epithelial cells to compare invasion ability and intracellular replication. The Congo red (CR) secretion assay was also used as a measure of virulence protein secretion from the type-III secretion system (T3SS), while interleukin-8 (IL-8) secretion from infected HT-29 cells was measured as a marker for the epithelial cell response to infection. Infection analyses included subculturing the strains in media with 0.4% bile salts to mimic small intestine physiology and gastrointestinal transit of S. flexneri prior to infection. The mutant strain displayed both increased invasion of and intracellular replication in HT-29 cells compared to 2457T. The presence of bile salts enhanced both invasion and intracellular replication in both strains when compared to wild-type without bile salts exposure during subculture. The CR assays revealed increased protein secretion from the mutant compared to 2457T, and that bile salts increased T3 secretion in both strains. Increased IL-8 secretion from infected HT-29 cells was detected when both strains were subcultured in bile salts; however, a decrease in IL-8 secretion was observed following infection with the mutant subcultured without bile salts. Overall, the data suggest that this bile salt-induced gene encodes a negative regulator of virulence, and that the gene product likely prevents a hypervirulence phenotype that would compromise the ability of S. flexneri to control infection and regulate the host immune response. This work has provided insights into the function of this uncharacterized gene, which could serve as a novel target for future therapeutic development. / 2027-06-30T00:00:00Z