Magister Scientiae - MSc (Chemistry) / Plants have been widely used in traditional medicine for a number of ailments, among which may be included infectious diseases such as colds, influenza, chicken pox, TB, etc. as well as lifestyle diseases such as diabetes and cancer. Seaweeds have also been shown to contribute to the maintenance of health through their nutritional and medicinal properties and recently, a great deal of interest has developed towards the isolation of bioactive compounds from marine sources due to their numerous health benefits. Furthermore, marine algae are valuable sources of structurally diverse metabolites with scientifically proven therapeutic claims. Chemical constituents of red seaweed, Porphyra capensis was investigated in this present study along with subsequent brine shrimp lethality assay analysis of the crude extracts. The compounds isolated from the plant were from the hexane (6) and butanol (2) extracts. These compounds were all isolated and purified by various chromatographic techniques, namely silica gel chromatography, Sephadex LH-20 gel as well as C18 reversed phase silica gel. The structures of the isolated compounds were analysed and characterised by NMR, GC-MS, ESI MS and FTIR spectroscopy. Eight compounds were isolated and identified as phytol, desmosterol, 9-eicosenoic acid, 5,8,11,14,17-eicosapentanoic acid, palmitic acid, methyl (E)-hexadec-9-enoate, glycerol and compound 1 (novel compound). All the compounds were isolated from Porphyra capensis for the first time. The hexane, butanol and methanol extracts were found to be non-toxic with the brine shrimp test LC50 value at least two times greater than ?g/ml.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2014-09-17T17:51:04Z No. of bitstreams: 1 (Dissertação_mestrado__(03.11_)).pdf: 1756144 bytes, checksum: 6a5c8a2f486f154eba91b5aa9780dde0 (MD5) / Approved for entry into archive by Fatima Cleômenis Botelho Maria (botelho@ufba.br) on 2014-09-19T12:24:04Z (GMT) No. of bitstreams: 1 (Dissertação_mestrado__(03.11_)).pdf: 1756144 bytes, checksum: 6a5c8a2f486f154eba91b5aa9780dde0 (MD5) / Made available in DSpace on 2014-09-19T12:24:04Z (GMT). No. of bitstreams: 1 (Dissertação_mestrado__(03.11_)).pdf: 1756144 bytes, checksum: 6a5c8a2f486f154eba91b5aa9780dde0 (MD5) / CNPQ / A determinação de metais em águas naturais por Espectrometria de Emissão Óptica com Plasma Indutivamente Acoplado (ICP OES), em geral, deve envolver etapas de pré- concentração, devido os níveis de concentração dos metais em água serem muitas vezes abaixo dos limites de detecção da técnica. Dessa forma, o objetivo desse trabalho foi desenvolver um método de pré-concentração em fase sólida sensível e simples para a determinação de cobre, ferro, níquel, manganês, chumbo e zinco em amostras de água por ICP OES. As condições experimentais para pré-concentração foram otimizadas considerando os fatores: concentração do eluente, volume de eluente, volume da amostra, vazão e pH. As condições otimizadas corresponderam ao uso de 5 mL de solução de HCl 0,8 mol L-1 como eluente, volume da amostra de 50 mL, vazão de 1,9 mL min-1 e pH 9,0. Para a determinação dos metais, as amostras, após ajuste do pH, foram percoladas com o auxílio de uma bomba peristáltica em cartucho Sep-pak C18 com 1-(2-piridilazo)-2-naftol (PAN) imobilizado na sílica funcionalizada C18. A eluição dos analitos foi realizada com a passagem da solução de HCl pelo cartucho para posterior determinação por ICP OES. Nestas condições, os limites de detecção para Cu, Fe, Mn, Ni, Pb e Zn obtidos variaram entre 0,11 e 21 µg L-1 e os limites de quantificação entre 0,36-69 µg L-1, respectivamente. Os desvios padrão relativos (R.S.D.) para a determinação dos analitos não ultrapassaram 9 %. O efeito de possíveis espécies interferentes sobre a recuperação dos analitos também foram investigados. A exatidão do método foi avaliada mediante análise de material de referência certificado (SLEW-3 Estuariene Water Reference Material for Trace Metals) e o método proposto foi aplicado para análise de amostras de água subterrânea, água potável e água de rio coletadas nos municípios de Cachoeira e São Félix, Bahia, Brasil. As amostras foram analisadas por Espectrometria de Massas com Plasma Indutivamente Acoplado (ICP-MS) como método comparativo, não sendo observadas diferenças significativas entre estes resultados e os resultados obtidos pelo método proposto. / The determination of metals in natural waters by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES), in general, involves pre-concentration steps, due the concentration levels of metals in water are often below the limits of detection of this technique. In this way, the objective of this work was to develop a pre-concentration solid phase method for sensitive and simple determination of copper, iron, nickel, manganese, lead and zinc in water samples by ICP OES. The experimental conditions for pre- concentration were optimized considering the following factors: the concentration of the eluent, eluent volume, sample volume, flow-rate and pH. The optimized conditions corresponded to the use of 5 mL of HCl solution 0.8 mol L-1 as an eluent sample volume 50 ml, flow-rate 1.9 mL min-1 and pH 9.0. For the determination of metals by the procedure, the samples after pH adjustment were percolated with the aid of a peristaltic pump on Sep-Pak C18 cartridge with 1-(2-pyridylazo)-2-naphthol (PAN). The analyte elution was carried out with the passage of the HCl solution in the cartridge for subsequent determination by ICP OES. In these conditions, the detection limit for Cu, Fe, Mn, Ni, Pb and Zn varied between 0.11 to 21 μg L-1 and the limits of quantification from 0.36 to 69 μg L-1, respectively. The relative standard deviation (RSD) for the analytes of this study did not exceed 9%. The effect of possible interfering species on the recovery of the analytes was also investigated. The accuracy of the method was evaluated by analysis of certified reference material (SLEW-3 Estuariene Water Reference Material for Trace Metals) and the proposed method was applied to samples of ground water, drinking water and river water collected in Cachoeira and São Félix cities, Bahia, Brazil. The samples were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) as a comparative method do not being found significant differences among these results and the results obtained by the proposed method.

Les exigences actuelles en terme de lubrification automobile imposent des formulations extrêmement complexes. Parmi tous les additifs présents dans l’huile, on peut noter le dithiocarbamate de molybdène et le dithiophosphate de zinc, additifs à action tribologique à base de soufre et de phosphore. Pour des raisons environnementales, il est important de diminuer voir d’éliminer la présence de ces deux éléments dans les huiles. Les molécules organiques à base de carbone, oxygène et hydrogène semblent être de bons candidats. Le mécanisme de lubrification des acides gras (acides stéarique, oléique et linoléique) est revisité par une approche visant à combiner l’étude expérimentale et la modélisation moléculaire. Tout d’abord, les mécanismes d’adsorption des acides gras sur des surfaces à base de fer sont étudiés par couplage Chimie Quantique et Dynamique Moléculaire (UA-QCMD). L’adsorption des acides gras sur des surfaces à base de fer se fait par la fonction acide. Selon la nature du substrat, la densité du film et l’angle d’inclinaison de la molécule par rapport à la surface, différents mécanismes d’adsorption peuvent avoir lieu (physisorption et chimisorption). Les molécules d’acide stéarique forment une monocouche compacte et bien arrangée alors que les molécules insaturées en sont incapables à cause d’effets stériques induits par les doubles liaisons carbone-carbone. Le frottement favorise la formation de la fonction carboxylate. Ces résultats sont confirmés par des analyses de surface (XPS et PM-IRRAS). Les propriétés tribologiques des acides gras purs, dans la PAO 4 et en mélange dans la PAO 4 sont étudiées par simulation MD et par des tribotests. Un faible frottement et une absence d’usure visible ont été observés pour l’acide stéarique pur et dissous à 1%m dans la PAO 4 à haute température. La présence de molécules insaturées inhibe les propriétés réductrices de frottement de l’acide stéarique, en particulier à 150 °C. Ceci est expliqué par la diffusion des acides gras insaturés bien supérieure à celle de l’acide stéarique dans la PAO 4 à toutes les températures étudiées. / The current requirements in automotive lubrication impose complex formulation. Among all the additives present in oil, the presence of molybdenum dithiocarbamate and zinc dithiophosphate, both tribological additives containing sulfur and phosphorous is found. For environmental reasons, it is important to reduce or eliminate the presence of these two elements contained in oil. Organic molecules based on carbon, oxygen and hydrogen seems to be good candidate. The lubrication mechanism of fatty acids (e.g. stearic, oleic and linoleic acids) is revisited with a new approach combining experimental and computational chemistry studies. First, the adsorption mechanisms of fatty acids on iron-based surfaces are investigated by Ultra-Accelerated Quantum Chemistry Molecular Dynamics simulations. The adsorption of fatty acids on iron oxide surface occurred through the acid group. Depending on the nature of the substrate, on the density of the film and on the tilt angle between the molecule and the surface, different adsorption mechanisms (physisorption and chemisorption) can occur. Stearic acid molecules form a close-packed and well-arranged monolayer whereas unsaturation acids cannot because of steric effects induced by double carbon-carbon bonds. The friction process favors the formation of carboxylate function. Results are confirmed by surface analysis (XPS and PM-IRRAS). Tribological properties of pure fatty acids, blended in PAO 4 and mixture of saturated/unsaturated acids are studied by MD simulations and tribotests. Low friction coefficient with no visible wear is reported for pure stearic acid and single stearic acid blended in PAO 4 at 1%w at high temperature. This lubricating behavior is inhibited in the presence of unsaturated acids, especially at 150 °C. MD simulation results show a faster diffusion toward the surface for unsaturated fatty acids than for stearic acid at all studied temperature.

The focus is on cross-sectional dependence in panel trade flow models. We propose alternative specifications for modeling time invariant factors such as socio-cultural indicator variables, e.g., common language and currency. These are typically treated as a source of heterogeneity eliminated using fixed effects transformations, but we find evidence of cross-sectional dependence after eliminating country-specific and time-specific effects. These findings suggest use of alternative simultaneous dependence model specifications that accommodate cross-sectional dependence, which we set forth along with Bayesian estimation methods. Ignoring cross-sectional dependence implies biased estimates from panel trade flow models that rely on fixed effects. / Series: Working Papers in Regional Science

Recent technological, social, and economic trends and transformations are contributing to the production of what is usually referred to as Big Data. Big Data, which is typically defined by four dimensions -- Volume, Velocity, Veracity, and Variety -- changes the methods and tactics for using, analyzing, and interpreting data, requiring new approaches for data provenance, data processing, data analysis and modeling, and knowledge representation. The use and analysis of Big Data involves several distinct stages from "data acquisition and recording" over "information extraction" and "data integration" to "data modeling and analysis" and "interpretation", each of which introduces challenges that need to be addressed. There also are cross-cutting challenges, which are common challenges that underlie many, sometimes all, of the stages of the data analysis pipeline. These relate to "heterogeneity", "uncertainty", "scale", "timeliness", "privacy" and "human interaction". Using the Big Data analysis pipeline as a guiding framework, this paper examines the challenges arising in the use of Big Data in regional science. The paper concludes with some suggestions for future activities to realize the possibilities and potential for Big Data in regional science. / Series: Working Papers in Regional Science

The focus is on cross-sectional dependence in panel trade flow models. We propose alternative specifications for modeling time invariant factors such as socio-cultural indicator variables, e.g., common language and currency. These are typically treated as a source of heterogeneity eliminated using fixed effects transformations, but we find evidence of cross-sectional dependence after eliminating country-specific effects. These findings suggest use of alternative simultaneous dependence model specifications that accommodate cross-sectional dependence, which we set forth along with Bayesian estimation methods. Ignoring cross-sectional dependence implies biased estimates from panel trade flow models that rely on fixed effects. / Series: Working Papers in Regional Science

The focus is on cross-sectional dependence in panel trade flow models. We propose alternative specifications for modeling time invariant factors such as socio-cultural indicator variables, e.g., common language and currency. These are typically treated as a source of heterogeneity eliminated using fixed effects transformations, but we find evidence of cross-sectional dependence after eliminating country-specific effects. These findings suggest use of alternative simultaneous dependence model specifications that accommodate cross-sectional dependence, which we set forth along with Bayesian estimation methods. Ignoring cross-sectional dependence implies biased estimates from panel trade flow models that rely on fixed effects. / Series: Working Papers in Regional Science

Past focus in the panel gravity literature has been on multidimensional fixed effects specifications in an effort to accommodate heterogeneity. After introducing conventional multidimensional fixed effects, we find evidence of cross-sectional dependence in flows. We propose a simultaneous dependence gravity model that allows for network dependence in flows, along with computationally efficient Markov Chain Monte Carlo estimation methods that produce a Monte Carlo integration estimate of log-marginal likelihood useful for model comparison. Application of the model to a panel of trade flows points to network spillover effects, suggesting the presence of network dependence and biased estimates from conventional trade flow specifications. The most important sources of network dependence were found to be membership in trade organizations, historical colonial ties, common currency and spatial proximity of countries. / Series: Working Papers in Regional Science

This paper offers an empirical analysis of net job creation patterns at the firm level for the Austrian economy between 1993 and 2013 focusing on the impact of firm size and age. We propose a new estimation strategy based on a two-part model. This allows to identify the structural parameters of interest and to decompose behavioral differences between exiting and surviving firms. Our findings suggest that conditional on survival, young Austrian firms experience the largest net job creation rates. Differences in firm size are not able to explain variation in net job creation rates among the group of continuing enterprises. Job destruction induced by market exit, however, is largest among the young and small firms with this effect being even more pronounced during the times of the Great Recession. In order to formulate sensible policy recommendations, a separate treatment of continuing versus exiting firms as proposed by the new two-part model estimation approach seems crucial.(authors' abstract) / Series: Department of Economics Working Paper Series

Novel on-line methods are presented for the extraction, preconcentration and analysis of zwitterionic biomolecules using sol-gel-coated columns coupled to a conventional UV/visible detector. The presented approaches do not require any additional modification of the commercially available standard CE instrument. Extraction, stacking, and focusing techniques were used in the preconcentration procedures. The positively charged sol-gel coatings were created using N-octadecyldimethyl[3-(trimethoxysilyl) proply]ammonium chloride (C18-TMS) in the coating sol solutions. Due to the presence of a positively charged quaternary ammonium moiety in C18-TMS, the resulting sol-gel coating carried a positive charge. The negatively charged sol-gel coatings were due to the presence of sulfonate groups, which was formed from the oxidation of thiol groups in precursor mercaptopropyltrimethoxysilane (MPTMS) by hydrogen peroxide. Besides MPTMS, tetramethoxysilane (TMOS) and n-octadecyltriethoxysilane (C18-TEOS) were also used to prepare the sol solution for the creation of the negatively charged coatings. For extraction, the pH of the samples was properly adjusted to impart a net charge opposite to the sol-gel coatings. When a long plug of the sample was passed through the sol-gel-coated capillary, extraction was achieved via electrostatic interaction between the charged sol-gel coating and the charged sample molecules. The extracted analytes were then desorbed and focused via local pH change and stacking. The local pH change was accomplished by passing buffer solutions with proper pH values, while a dynamic pH junction between the sample solution and the background electrolyte was utilized to facilitate solute focusing. The developed methods showed excellent extraction and preconcentration effects on both positively and negatively charged sol-gel-coated columns. On-line preconcentration and analysis results obtained on the sol-gel coated columns were compared with those obtained on an uncoated fused silica capillary of identical dimensions using conventional sample injections. The described procedure provided a 150 000-fold enrichment effect for alanine on the positively charged sol-gel-coated column. On the negatively charged sol-gel-coated column, the presented sample preconcentration technique provided a sensitivity enhancement factor (SEF) on the order of 3 x 103 for myoglobin, and 7 x 103 for asparagines. The developed methods provided acceptable repeatability in terms of both peak height and migration time.