Thesis (MScAgric)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

In 1959 Abbott Laboratories estimated (3) that every year 60 million persons go on controlled diets. Of these about 34 million have serious obesity problems, 3 million are diabetics and the rest have disorders that demand strict dietary measures.

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Enhancing satiety may be a route to overcome excess food intake, a causative agent of the obesity epidemic effecting [sic] developed and developing nations. A theory has evolved that if food processing has been a major contributor to the obesity epidemic then food processing and manipulation could be the solution to the crisis. This could be by means of the manipulation of food to target regulatory mechanisms of the food-gut-brain axis to produce satiety from fewer calories. This thesis is an investigation, using the Sprague Dawley rat model, into possible interactions between macronutrient content and food structure in the regulation of satiation and satiety, and to provide evidence for possible enhanced satiation or satiety by protein crosslinking noted in human studies. Three principle studies were performed: 1) variation in macronutrient content of a base diet presented in a solid or liquid form; 2) gavage of a single macronutrient containing solutions directly to the stomach; and 3) using protein crosslinking to change food form without changing caloric density. Overall, the study found no evidence to support an interaction between macronutrient content and diet form, nor that protein is a more effective macronutrient for inducing satiation or prolonging satiety. The analysis did identify that liquid diets can increase satiation, but can result in negative homeostatic effects and excess food consumption. Research exploring the use of protein crosslinking to promote satiation is still at an early stage but the findings presented in this thesis identify utilisation as a potential tool for enhanced satiation. These studies suggest that while protein crosslinking may enhance satiation there is no translation into longer term satiety. Nevertheless, these findings serve as a basis for further research and could provide information to the food industry for the development of food products that increase the satiation and satiety properties of food.

The diploma thesis thematically deals with the adaptation of exercises for teaching arithmetic and algebra at primary school. The aim of the thesis was to create a collection of methodically processed exercises for the second grade students. In seven parts, the collection focuses on working with fraction from introduction of it to particular operations with fractions. The thesis has following structure: the first part is dealing with theoretic adaptation of literary sources on the given topic. The second part contains practical orientation with a motivational example, an explanatory example, exercises for practising, an exercise to test the curriculum, an exercise for the quick-witted and an exercise for home preparation in every thematic unit.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O ligante asfÃltico brasileiro oriundo do Estado do EspÃrito Santo e processado na unidade de NegÃcios da Petrobras (LUBNOR) foi analisado nas suas principais caracterÃsticas utilizando-se de mÃtodos espectromÃtricos (RMN e FTIR), cromatogrÃficos (GPC), anÃlise tÃrmica (TGA) e microscÃpica (AFM). As duas principais fraÃÃes do ligante constituÃdas de maltenos e asfaltenos tambÃm foram analisadas. Da fraÃÃo maltÃnica do ligante foram extraÃdos os hidrocarbonetos policÃclicos aromÃticos (HPAs) utilizando-se de mÃtodos cromatogrÃficos, tais como: DispersÃo de matriz em fase sÃlida (DMFS), cromatografia de adsorÃÃo em coluna e cromatografia gasosa (GC). Os resultados mostraram que o ligante asfÃltico apresentou HPAs considerados tÃxicos e outros considerados mutagÃnicos e carcinogÃnicos, alÃm de outros HPAs, diferentes dos padrÃes analÃticos estudados. A estrutura molecular do coroneno foi visualizada atravÃs da imagem microscÃpica (STM). Imagens obtidas atravÃs do uso da tÃcnica de microscopia de forÃa atÃmica (AFM) do ligante mostram a coexistÃncia de uma fase rica em asfaltenos em equilÃbrio. Imagens (AFM) do ligante quando modificado por polÃmero sugerem que parte da fraÃÃo maltÃnica à absorvida pelo polÃmero. As imagens AFM dos asfaltenos quando extraÃdos do ligante mostraram-se na forma de aglomerados circulares estabilizados na presenÃa do solvente. A massa molar mÃdia dos asfaltenos foi calculada a partir de duas tÃcnicas empregadas, osmometria e cromatografia de permeaÃÃo em gel apresentando-se na faixa de 5900-6700 g/mol. A estabilidade tÃrmica do ligante e asfaltenos foram analisadas atravÃs das curvas TGA. A estabilidade oxidativa do ligante e asfaltenos, a partir do cÃlculo da energia de ativaÃÃo, mostram-se caÃticas dadas à presenÃa de compostos altamente reativos frente ao oxigÃnio. Parece ser influenciada pelas reaÃÃes secundÃrias de decomposiÃÃo e/ou oxidaÃÃo de produtos e resÃduos formados. A solubilizaÃÃo dos asfaltenos em n-hexano foi avaliada na presenÃa de aditivos e mostraram que a solubilizaÃÃo aumentou com a adiÃÃo do lÃquido da castanha de caju (LCC) e da cera de carnaÃba. / The Brazilian binder processed at Petrobras/Lubnor from a crude of the state of EspÃrito Santo was investigated using the following procedures: spectrometric methods (RMN and FTIR), chromatographic (GPC), thermal analysis (TGA) and atomic microscopy (AFM). The two main fractions of the binder, maltenes and asphaltenes, were also analyzed. Hydrocarbons polycyclic aromatics (HPAs) were extracted from the maltene portion using chromatographic methods such as: matrix dispersion in solid phase (DMFS), chromatographic adsorption in column and gas chromatographic (GC). The results indicate that the asphaltic binder present toxic HPAs as well as mutagenic and carcinogenic, and yet other HPAs different from the analytical references that were studied. The molecular structure of coroneno was visualized using image microscopy (STM). Binder images obtained from atomic microscopy (AFM) show a coexistence of a phase rich in asphaltenes in equilibrium. Images (AFM) of a polymer modified binder indicate that the maltenes are absorbed by the polymer. The AFM images of the asphaltenes extracted from the binder were perceived as circular bundles stabilized in the presence of a solvent. The average asphaltene mol mass was calculated based on two different techniques: osmometry and gel permeation chromatography in the range 5900-6700 g/mol. Thermal stability of the binder and the asphaltenes was analyzed from TGA curves. From activation energy calculation, oxidative stability of the binder and the asphaltenes was chaotic because of the high reactivity of the constituents with oxygen. Such stability seems to be affected by secondary reactions decomposition and/or product oxidation. The solubility of asphaltenes in n-hexane was evaluated in the presence of additives and it was found that it increases with the addition of cashew nut shell liquid (CNSL) and carnauba wax.

In the last decade, organic photovoltaics (OPV) have gained considerable attention with a rapid improvement of power conversion efficiency (PCE) from 5% to more than 13%. At the origin of the gradual efficiency improvements are (i) the rationalization of material design and (ii) systematic optimization of film processing condition. OPV can have a key role in markets such as building-integrated photovoltaics (BIPV). The main advantages of organic solar cells are semitransparency, low weight, good performance at low light intensity, flexibility and potential low-cost module manufacture through solution processed-based technologies. In solution processed OPV, the active layer that converts photons into electric charges is a composite of two organic compounds, a donor (D) and an acceptor (A) where the best morphology is achieved via the so-called bulk heterojunction (BHJ): an interpenetrating phase-separated D-A network. Historically, research has been focused on polymer donors and guidelines about morphology and film processing have been established. However recent studies have shown that small-molecule (SM) donors can rival their polymer counterparts in performance. The advantages of SM are a defined molecular weight, the ease of purification and a good batch-to-batch reproducibility. Using this class of material the existing guidelines have to be adjusted and refined. In this dissertation, using new SM synthesized in our laboratory, solution-processed organic solar cells are fabricated in which the morphology of the active layer is controlled by thermal annealing, the use of additive or solvent vapor annealing. In-depth analyses of the morphology are correlated to charge generation, recombination and extraction inferred from device physics. In the first part of the dissertation, using a small amount of 1,8-Diiodooctane additive that acts as a plasticizer, it is found that the D-A domains do not necessarily need to be pure and that mixed domains can also result in high performing devices. In the second part of the dissertation, the effect of solvent vapor annealing, particularly effective for SM:PCBM BHJ, is discussed where excellent control of the morphology is achieved. In the last part of the dissertation, efficient organic solar cells with open circuit voltage of >1.05V are made via fine-tuning of the morphology.