Orientador: Luiz Carlos Dias / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-20T22:05:16Z (GMT). No. of bitstreams: 1 Ferreira_MarcoAntonioBarbosa_D.pdf: 22008245 bytes, checksum: 306bdd05b22f9f07a0496a6e9806f940 (MD5) Previous issue date: 2012 / Resumo: SÍNTESE TOTAL DA (-)-GONIOTRIONINA: Foi desenvolvida uma rota sintética flexível, em uma abordagem modular, que permitiu a primeira síntese total da estrutura descrita para a goniotrionina (11), em 4% de rendimento global e em 17 etapas pela rota linear mais longa, a partir do glicidol quiral (R)-109. A nossa rota sintética fez uso de epóxidos quirais como blocos de construção, em uma estratégia envolvendo a abertura de epóxidos. As etapas chave incluem ciclização aeróbica de Mukaiyama para formação do anel THF-2,5-trans e reação aldólica de Mukaiyama 1,2-syn seletiva. Esta mesma abordagem sintética pode permitir a preparação de análogos e outros diastereoisômeros da (-)-goniotrionina (11). ESTUDO TEÓRICO DA INFLUÊNCIA ESTEREOELETRÔNICA NA SELETIVIDADE 1,5 EM REAÇÕES ALDÓLICAS ENVOLVENDO B-ALCOXI METILCETONAS. Nesta segunda parte do trabalho foi possível aprofundar o conhecimento sobre a origem da seletividade 1,5 em reações aldólicas envolvendo enolatos de boro de b-alcóxi metilcetonas, a partir do cálculo das estruturas eletrônicas dos estados de transição. Investigou-se a influência dos estereocentros em a, b, y e s em reações aldólicas, determinando os fatores decisivos que governam o senso de indução 1,5. Adicionalmente, foi proposto um modelo teórico que permitiu racionalizar a seletividade 1,5 em função das características estereoeletrônicas de cetonas com acentuado volume estéreo na posição beta com relação à carbonila / Abstract: TOTAL SYNTHESIS OF (-)-GONIOTRIONIN: We have accomplished the first total synthesis of the reported structure of goniotrionin (11) in 4% overall yield over a longest-linear sequence of 17 steps from glycidol (R)-109. Our synthetic route employed an epoxide-opening strategy, using chiral epoxides as building blocks. Key steps included a Mukaiyama aerobic oxidative cyclization and a 1,2-syn selective Mukaiyama aldol reaction. This synthesis employs highly flexible key couplings that allow for the preparation of analogs, including other diastereoisomers of goniotrionin (11). THEORETICAL STUDY OF THE STEREOELECTRONIC INFLUENCE IN 1,5 SELECTIVITY OF ALDOL REACTIONS INVOLVING b-ALKOXY METHYLKETONES: In the second part of this work was extended the knowledge about the origin of 1,5 selectivity in aldol reactions involving boron enolates of b-alkoxy methyl ketones, based on the calculation of electronic structures of the corresponding transition states. We investigated the influence of stereocenters at the a, b, y and s positions in aldol reactions, determining the key factors that govern the 1,5 induction. Additionally, we propose a theoretical model that racionalize the 1,5 selectivity depending on the stereoelectronic characteristics of b-bulky ketones / Doutorado / Quimica Organica / Doutor em Ciências

The growth rate of a fish is a fundamental function used in stock assessments to estimate the population size and the fishery pressure affecting the species. There has been recent debate within the stock assessment community regarding which type of growth model best represents the true growth rate of yellowfin tuna (Thunnus albacares), in the Atlantic Ocean; specifically, should assessments use a traditional von Bertalanffy growth curve or a so-called “two-stanza” growth curve, which combines one growth rate for smaller individual tuna and another for larger sizes. Using a simulated population created with the software R, both growth models were compared under different scenarios. The first part of this thesis examines the effect of different fisheries and their associated gear selectivity. Purse seine, baitboat and pelagic longline fisheries, which target yellowfin tuna in the Atlantic Ocean, were incorporated into the analysis. The second part looks at different sources of variability that occur either in nature (observation error) or in the process of analysis (process error). These include different growth variation, looking only at the fast growing young fish and using a set birth date versus a spawning period. These scenarios were used to determine if the sample, derived from a fishery-dependent sample, reflects the true population. Three populations of yellowfin tuna were created: an un-fished population, a fished population from stock assessment data, and a fished population from simulation software called ‘Population Simulator’. These populations were all analyzed for the different scenarios as well as the different fisheries. The final part of this thesis looks at three similar tuna species; skipjack (Katsuwonus pelamis), bigeye (Thunnus obesus ) and albacore (Thunnus alalunga). The same scenarios and gear selectivities were applied to these tuna species. The results of this study showed that the two-stanza growth curve was not a better fit for yellowfin tuna population in the Atlantic Ocean than the traditional von Bertalanffy growth curve. There were several scenarios that favored the two-stanza growth curve, but either it was a sample population not representative of the Atlantic Ocean population, or the two-stanza had no initial growth rate, making it the same as a traditional growth curve. Based on these results, it was evident that the traditional von Bertalanffy growth curve was the more accurate growth curve to use for yellowfin tuna in the Atlantic Ocean and it is recommended that this growth curve be used in the stock assessments going forward.

Older adults are increasingly using social networking sites such as Facebook to maintain social relationships. A growing body of literature indicates that frequent communication with family members and close friends influences successful ageing. Consequently, the purpose of this study is to establish the nature of the relationship between the impact of Facebook communication and successful ageing on older adults living in the rural municipality of Hagfors. This study defines an older adult as a person aged 55 years and above. Self-reported life-satisfaction, social engagement and social trust are used as indicators of successful ageing. Predictions about Facebook communication and successful ageing are tested by theories of socio-emotional selectivity and social capital. This is based on 15 semi-structured interviews conducted with older adults living in the municipality of Hagfors. The results indicate that having small social connections and frequently exchanging privately composed communication with family members and close friends promotes successful ageing. Facebook is found to be a potential source of social capital.

The development of new methods to make carbon-carbon bonds asymmetrically remains a challenge in organic chemistry. Indeed, the development of highly selective methods often proceeds on a trial and error basis. The way chiral information is transferred to the substrate is unclear in many reactions, limiting further development. We focus here on developing an asymmetric conjugate addition of alkylzirconium nucleophiles to Michael acceptors. The development of new phosphoramidite ligands, supported by a computer based model, allowed further development of the reaction. First, existing methods to introduce enantioselectively chirality are described. Then we discuss ligands, and modern ways to parameterise experimental data using computational methods. In chapter two, after discussing the use of alkenes as reagents, especially processes initiated by hydrometallation, we describe a new conjugate addition reaction using cyclic enones that achieves both high yields and levels of enantioselectivity. In chapter three, various applications of phosphoramidite ligands are discussed and we describe the synthesis of a variety of different phosphoramidites and identification of important structural features of these ligands. New, efficient ligands are obtained and a computer model is developed to account for the selectivity of the reaction discussed in chapter two. Chapter four describes the development of an enantioselective synthesis of quaternary centres with novel ligands used to optimise the new system. Lastly, chapter five describes the extension of the method to some linear enones, using different ligands. Overall, we have developed a variety of ligands which were used to expand the enone scope of a conjugate addition and an understanding of what factors make these ligands effective.

The search for alternatives to oil-based monomers has sparked interest for scientists to focus on the use of renewable resources for energy production, for the synthesis of polymeric materials and in other areas. With the use of renewable resources, scientists face new challenges to first isolate interesting molecules and then to process them. Enzymes are nature’s own powerful catalysts and display a variety of activities. They regulate important functions in life. They can also be used for chemical synthesis due to their efficiency, selectivity and mild reaction conditions. The selectivity of the enzyme allows specific reactions enabling the design of building blocks for polymers. In the work presented here, a lipase (Candida antarctica lipase B (CalB)) was used to produce building blocks for polymers. An efficient route was developed to selectively process epoxy-functional fatty acids into resins with a variety of functional groups (maleimide, oxetane, thiol, methacrylate). These oligoester structures, based on epoxy fatty acids from birch bark and vegetable oils, could be selectively cured to form thermosets with tailored properties. The specificity of an esterase with acyl transfer activity from Mycobacterium smegmatis (MsAcT) was altered by rational design. The produced variants increased the substrate scope and were then used to synthesize amides in water, where the wild type showed no conversion. A synthetic procedure was developed to form mixed dicarboxylic esters by selectively reacting only one side of divinyl adipate in order to introduce additional functional groups. / <p>QC 20170823</p>

Magister Commercii - MCom / This study seeks to evaluate the performance of unit trust managers based on their client affiliation classification. Worldwide, the number of investors investing in unit trusts is on the rise and increasingly they want to be able to evaluate the performance of the managers managing their funds so as to make better investment decisions. This increase in the asset size and number of unit trusts funds could be attributed but not limited to the low capital required for investment by small investors who before could not afford to invest in portfolios requiring large capital (Prather, Bertin, and Henker, 2004). In addition, the fund managers of these units are believed to have special skills such as market timing and stock selectivity which contribute to the performances they achieve. The evaluation of the performance of unit trust fund managers is a largely unexplored area in South Africa. As a result, the study focuses on South Africa fund managers and has as aim to evaluate the performance of two groups of fund managers (independent and dependent) who were classified based on their client affiliation structure. The client affiliation classification is as a result of the fund manager's clientele base. The dependent group are those who formed part of a group structure and offer other wealth management services for which their clients or investors in the unit trust services originate from within the group while the independent group are those whose clients are pulled together from diverse individuals or institutions and does not form part of a group or render other services other than fund management. Two fund types were selected namely; general equity funds and balanced funds. It has also examined the underlying skills the different groups of fund managers possess. The performance of unit trust has an effect on many parties who are related in one way or the other to the unit trust funds. The results of this study will inform individual investors, trustees and asset consultants in their decision making process of selecting a fund manager. The results of the study will be of value to the asset management industry in terms of assessing their structures and restructuring the investment service business to meet the expectations of their clients; the investors. It could also be used as a marketing tool. Publicly available historical data on the returns generated by fund managers for a five year period from 2005 to 2009 was obtained. Analyses were done using the independent sampled t-test and the Treynor Mazel model respectively for the different research questions posed. The results obtained indicated that there were no statistically significant differences between the performances of independent fund managers with those of dependent fund managers. However, dependent fund managers of equity funds performed better than their counterparts the independent fund managers. In the case of balanced funds, the independent fund managers performed better than their dependent counterparts. On average, both fund manager types possessed selectivity skills for equity funds and none for balanced funds. However for both fund types, the dependent fund manager demonstrated more selectivity skills than their independent counterparts. The results for market timing skills demonstrated that on average, both fund managers did not possess market timing skills for balanced funds while possessing these skills for equity funds. The dependent fund managers demonstrated more market timing skills for balanced funds though negative when compared to that of their counterparts. On the other hand, the equity fund independent fund managers demonstrated more market timing skills than the dependent fund managers. / South Africa

Magister Legum - LLM / Sexual violence leaves the victims psychologically traumatised and stigmatised in the eyes of its community. Used on a large scale, sexual violence can destabilise a society as a whole and when used during armed conflicts, it serves as a powerful weapon against members of a community. During armed conflicts, sexual violence is widespread and systematically used as a tool of war and this makes sexual violence amount to crimes against humanity, genocide and war crimes. This research paper critically analyses and evaluates sexual violence as an international crime, as well as its prosecution under international criminal law mainly by the International Criminal Court (hereafter ICC), International Criminal Tribunal for the Former Yugoslavia (hereafter ICTY) and International Criminal Tribunal for Rwanda (hereafter ICTR). It discusses the problem of selectivity that can be observed in prosecuting sexual violence that has in fact, left many victims of sexual violence dissatisfied. By doing so, it analyses the law as it is to determine whether the law applied during sexual violence prosecutions is sufficient. The paper also states recommendations that can contribute to the effective prosecution of sexual crimes under international criminal law. / South Africa

Philosophiae Doctor - PhD / The limited supply of fossil hydrocarbon resources and the negative impact of CO2 emission on the global environment dictate the increasing usage of renewable energy sources. Concentrating solar power (CSP) systems are the most likely candidate for providing the majority of the renewable energy. For efficient photo-thermal conversion, these systems require spectrally selective solar absorber surfaces with high solar absorbance in the solar spectrum region and low thermal emittance in the infrared region. In this thesis, a spectrally selective AlxOy/Pt/AlxOy multilayer solar absorber was designed and deposited onto copper substrate using electron beam evaporation at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit the multilayer solar absorber coatings. The optical constants measured using spectroscopic ellipsometry, showed that both AlxOy layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance ~ 0.94±0.01 and low thermal emittance ~ 0.06 ± 0.01 at 82oC.The structural and optical properties of the coatings were investigated. It was found that the stratification of the coatings consists of a semitransparent middle Pt layer sandwiched between two layers of AlxOy. The top and bottom AlxOy layers were nonstoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of AlxOy. The surface roughness of the stack was found to be comparable to the inter-particle distance. To study the thermal stability of the multilayer solar absorber coatings, the samples were annealed at different temperatures for different duration in air. The results showed changes in morphology, structure, composition, and optical properties depend on both temperature and duration of annealing. The XRD pattern showed that the intensity of Pt decreased with increasing annealing temperature and therefore, disappeared at high temperature. With increasing annealing temperature, an increase in the size of Pt particles was observed from SEM. The AlxOy/Pt/AlxOy multilayer solar absorber coatings deposited onto Cu substrate were found to be thermally stable up to 500oC in air for 2 h with good spectral selectivity of 0.951/0.09. At 600oC and 700oC, the spectral selectivity decreased to 0.92/0.10 and 0.846/0.11 respectively, which is attributed to the diffusion of Cu and formation of CuO and Cu2O phases. Long term thermal stability study showed that the coatings were thermally stable in air up to 450oC for 24 h. To elucidate the degradation mechanism beyond 500oC, HI-ERDA has been used to study depth-dependent atomic concentration profiles. These measurements revealed outward diffusion of the copper substrate towards the surface and therefore, the decrease in the constituents of the coating. Hence, to prevent copper from diffusing towards the coatings, a thin Tantalum (Ta) layer was deposited between the base AlxOy layer and the copper substrate.The effect of a thin Ta layer on the thermal stability of AlxOy/Pt/AlxOy multilayer solar absorber coatings was investigated. The Cu/Ta/AlxOy/Pt/AlxOy multilayer solar absorber coatings were found to be thermally stable up to 700oC in air for 2 h with good spectral selectivity of 0.937/0.10. At 800oC, the spectral selectivity decreased to 0.870/0.12, which is attributed to the diffusion of Cu and formation of CuO phase. The formation of CuO phase was confirmed by XRD, EDS and Raman spectroscopy. Long term thermal stability study showed that the coatings were thermally stable in air up to 550oC for 24 h. Therefore, the Cu/Ta/AlxOy/Pt/AlxOy spectrally selective solar absorber coatings can be used for high temperature solar-thermal applications.

The feeding ecology of a common saltmarsh crab, Armases cinereum (Armases), was investigated to determine how habitat (mangrove vs. ecotone, natural mangrove vs. modified mangrove fringe) influenced this species’ feeding behavior and trophic ecology in its southwestern Florida, USA, distribution. In the laboratory, Armases’ preference for mangrove material was examined using leaves of three mangrove species (Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle) and leaves of different degradation levels (fresh, senescent, and partially-decomposed). Leaf material from A. germinans was preferentially consumed over the other taxa at fresh and partially-decomposed levels of leaf decay. When Armases were offered a choice between four common upland vegetation types (Iva frutescens, Borrichia frutescens, Nephrolepis biserrata, and Stenotaphrum secundatum), the preferred mangrove from the previous experiment (A. germinans, partially-decomposed), and an animal prey item (Gryllodes sigillatus, cricket), Armases displayed greatest selectivity for the animal prey item and high selectivity for both I. frutescens and A. germinans plant taxa (Manly-Chesson α selectivity and Chesson ϵ electivity). Field-based stable isotope analysis was used to determine trophic position and reconstruct dietary proportions of Armases across three pairs of natural and heavily-modified sites within Tampa Bay to determine whether Armases feeding behavior is impacted by the presence of upland forest adjacent to mangrove forest habitat. Analysis of trophic position based on δ15N signatures of Armases from each of the six populations revealed that Armases in habitats with modified connectivity had lower trophic variability and significantly higher average trophic position compared to Armases sampled from the three sites with natural connectivity. Stable isotope diet reconstruction using the Bayesian mixing model SIMMR further established Armases preference for animal-derived food material in habitats with natural and modified connectivity. This preference is likely driven by high selectivity for sources rich in Nitrogen (i.e., animal tissue, partially-decomposed A. germinans material, and I. frutescens). I determined that the use of laboratory experiments in conjunction with stable isotope mixing models is important in accurately investigating feeding preferences of Armases in mangrove intertidal regions. Together, my results show that the diet of Armases is broadly omnivorous and populations can be influenced by the heterogeneity of their habitat. Further feeding experiments, dietary analyses and a longer sampling period are needed to more definitively identify the patterns of Armases detritivory in mangrove and ecotonal upland habitats.

No description available.