Les acides phosphoriques chiraux sont des organocatalyseurs très efficaces qui permettent de catalyser une grande variété de réactions asymétriques. Depuis leur développement en 2004, de nombreux acides phosphoriques à chiralité axiale ou à chiralité centrale ont vu le jour. Cependant, aucun exemple d’acides phosphoriques à chiralité planaire n’avait été reporté.Deux nouvelles familles d’acides phosphoriques à chiralité planaire, possédant un motif paracyclophane et un espaceur ferrocénique ou biphénylène, ont été développées au laboratoire. Les propriétés catalytiques de ces nouvelles familles ont été étudiées, notamment dans la réaction de réduction de quinoléines par les esters de Hantzsch. Une bonne activité et des excès énantiomériques allant jusqu’à 92% ont été obtenus. Ces squelettes à motif paracyclophane ont également été exploités pour développer de nouveaux catalyseurs organométalliques chiraux, qui ont été testés dans des réactions de catalyses organométalliques avec des complexes d’or et de rhodium. / Chiral phosphoric acids as organocatalysts have shown high efficiency and versatility in order to catalyze a lot of reactions. Since their development in 2004, a number of chiral phosphoric acids displaying an axial or a central chirality have been synthesized. Nevertheless, there was no example of planar chiral phosphoric acids.We have developed two new families of planar chiral phosphoric acids, based on a paracyclophane scaffold and displaying a ferrocenic or a biphenylene linker. These phosphoric acids have been evaluated, as organocatalysts, in an organocatalytic reaction of quinolines reduction using Hantzsch esters. Good yields and enantiomeric excess up to 92% have been obtained. These new paracyclophane scaffolds have been used to develop chiral organomelallic catalysts, which have been engaged in gold and rhodium complexes catalysis reactions.

Activated carbon is a highly adsorbing material and has various scopes of uses depending on needs. It is used in many industries and applications e.g. to clean industrial wastewater, in medicine, discolor sugar and so on. What makes AC such a good adsorbent is its porous structure which gives it a high surface area.  This report consists of three parts; general information about Activated Carbon (AC) and its characteristics, to give the reader a sufficient background about AC for continuous understanding throughout the report, an experimental investigation in chemical activation of carbon with phosphoric acid as the chemical reagent and sawdust from both Cuban and Swedish Pine tree as precursors, and a second experimental investigation in chemical activation of carbon with Zinc Sulfate as the chemical reagent and sawdust from Cuban Pine tree as the precursor. For the first experimental part as well as for the second the objective is how to best combine the three parameters; acid concentration, impregnation ratio and activation temperature in order to get the best adsorption performance when preparing activated carbon with different precursor specimens and chemical reagents. The experiments with phosphoric acid activation show that treatment with 40% acid concentration at 400 °C produce an activated carbon with good properties for ammonia adsorption and good iodine number. If a 30% phosphoric acid is used for activation, an activation temperature of 500 °C is recommended. With an impregnation ratio of 1, good adsorption was obtained in the activated carbon produced from Swedish pine while using Cuban pine a higher adsorption was obtained with an impregnation ratio of 2. The experiments with Zinc Sulfate activation show that influence of the sulfate concentration (between 10 % and 40 %) and temperature (between 400 °C and 500°C) on the properties for ammonia adsorption in the produced activated carbon was considerable for low impregnation ratio (0.5 and 1). In general, activation conditions of 20% zinc sulfate concentration, 400 °C and impregnation ratio: 1 are enough to produce an activated carbon with good properties for ammonia adsorption. The adsorption of carbon tetrachloride was lower. Activated carbons produced with 10 % zinc sulfate concentration, 0.5 impregnation ratio and 400 °C activation temperature (the mildest studied conditions) show already good iodine number and BET surface area.  The main conclusion from the thesis work is that the optimal conditions vary widely with wanted results. Therefore a suggestion for future work is to narrow the research to fewer variables and more repetition of the samples.

The main purpose for this project was to, by varying the parameters temperature (400 ˚C and 500 ˚C), acid concentration (10%, 25% and 40%), relative impregnation (0.75, 1.35 and 2.0) and impregnation time (1 h, 2 h and 3 h), evaluate which parameters that affect the product. Also, an investigation was made to determine the interaction of the different parameters. This was done by analysing the properties of the AC with gas adsorption of gasoline and ammonia. Liquid adsorption was analysed with iodine number and the yield of the AC was calculated with two different methods. In general an increasing of the temperature and the impregnation time results in a higher iodine number and higher capacity to absorb gasoline in the produced activated carbon. When the conditions were too strong the iodine number and the capacity to absorb gasoline decreased. The pore structure of the activated carbon is destroyed by too strong conditions. The results were also analysed with a computer program to establish statistical evidence of influence from the parameters indicating that temperature has strong effect on iodine number of the produced activated carbon. If the AC from Caribbean Pine would be commercially produced the recommended design is to keep all parameters low. This is both cost effective and energy efficient. Based on the experimental results it was determined that the AC from Caribbean Pine is better suited for adsorbing gasoline compared with ammonia. Furthermore, the adsorption of gasoline is increasing with an increasing temperature. An industrial manufactured AC was compared with the AC produced from Caribbean Pine and it had a better liquid and gas adsorption showing that more research and optimization of AC from Caribbean Pine must be done before commercializing the product. A suggestion for further research is to use the time in the oven as a parameter to be varied in the experimental setup. This could be valuable in order to determine the influence of the time in the oven both concerning the yield but also the adsorption ability of the AC.

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<p>Electropolishing is a commonly used method of mitigating surface roughness and yielding a polished appearance. One of the first described and most studied of electropolishing systems is the anodization of copper in phosphoric acid. Under normal conditions this reduces copper surface roughness substantially; however deviating from optimal electropolishing conditions can promote the development of semi-ordered surface roughness. Anodizing copper substrates in 98-100% H₃PO₄ solutions generated feature heights ranging from 0.5 - 2µm and surface area increases in excess of 30% were obtained. The samples demonstrated a macroscopic optical dullness characteristic of this type of surface roughening. Investigations as to their applicability in surface enhanced Raman spectroscopy and electron field emission were conducted. And while their formation mechanism is still speculated on, it is believed that oxygen evolution and subsequent bubble formation plays a key role. Electrochemical and microscopic imaging techniques were the primary methodologies used to probe the optical dulling phenomenon. With data obtained from experiments utilizing these techniques and others a qualitative mechanism is proposed.</p> / Master of Science (MSc)

Made available in DSpace on 2017-07-24T19:22:00Z (GMT). No. of bitstreams: 1 Andres Felipe M Cardenas.pdf: 5280325 bytes, checksum: 04a1911a6a06b35dcfc2a254330c8113 (MD5) Previous issue date: 2016-05-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study evaluated the effect of application the different pHs (0.5, 1 and 2) of meta-phosphoric acid 40% (MPA) with ortho-phosphoric acid 37% (OPA) in different application times with three laboratory studies in vitro. For all experiments, the teeth were distributed into 12 experimental conditions according to the combination of independent variables: acid [37% orthophosphoric acid (OPA), 40% metaphosphoric acid (MPA) pH - 0.5, 1 and 2] and application time [7, 15 and 30 seconds]. For experiment 1, the acids were applied on 72 human molars for microtensile bond strength (μTBS), and nanoleakage (NL). After acid conditioning the adhesive system was applied (Ambar) and restoration in composite resin was performed. Then, the teeth were sectioned to obtain specimens and tested immediately. The Etching Pattern (PC) was evaluated after acid application in dentin. For experiment 2, 93 human molars were used. After acid application in dentin, the adhesive system was applied and composite resin restoration was made. They were then sectioned, half sticks were tested immediately and the other half after 6 months of storage in water for μTBS and NL analysis. The analysis of chemical composition was performed by micro-Raman spectrometry. For experiment 3, 60 human molars were distributed according to the similar independent variables as the experiment 1 and 2. The enamel surfaces were stored in water (37 °C / 24 h) and tested for (μSBS). The PC and qualitative analysis composition of chemical enamel by micro-Raman test was evaluated. For the experiment 1 and 3, acid vs time of application the μTBS and NL data were submitted to 2-way ANOVA and Tukey's test (α = 0.05). For the experiment 2, acid vs application time vs storage time the μTBS data and NL were submitted to 3-way ANOVA and Tukey's test (α = 0.05). For experiment 1, MPA pH 0.5 showed μTBS similar to OPA, independent of the application time (p> 0.05) and statistically higher NL was observed for OPA compared with MPA (p <0, 03). For experiment 2, a significant decrease μTBS value was observed only OPA after 6 months (p = 0.001) and higher values of NL were found when compared to MPA (p = 0.003). For the experiment 3, OPA and MPA pH 0.5 produced statistically higher μSBS when compared to MPA pH 1 and 2 independent of the application times (p <0.001). The MPA acid is an alternative agent for the simultaneous conditioning of enamel and dentin, increasing the μTBS, reducing the NL immediate and after 6 months of storage when compared to the conventional ortho-phosphoric acid. The sum of the properties evaluated, MPA pH 0.5 showed high μSBS, showing be promissory. / O objetivo desse trabalho foi avaliar o efeito de diferentes pHs (0,5, 1 e 2) do ácido metafosfórico 40% (AMF) com o ácido ortofosfórico 37% (AOF) sob diferentes tempos de aplicação por meio de três estudos laboratoriais in vitro. Em cada estudo, os dentes foram distribuídos aleatoriamente em 12 condições de acordo com a combinação das variáveis independentes: Ácido [ácido ortofosfórico a 37% (AOF), ácido metafosfórico a 40% (AMF) pH - 0,5, 1 e 2] e tempos de aplicação [7, 15 e 30 s]. Para o experimento 1, os ácidos foram utilizadas e aplicados sobre 72 molares para resistência de união (RU) e nanoinfiltração (NI). Após condicionamento ácido aplicou-se o sistema adesivo (Ambar) e realizou-se a restauração em resina composta (Opallis). Depois de 24 h foram seccionados e testados. O padrão de condicionamento (PC) foi avaliado após aplicação dos ácidos em dentina. Para o experimento 2, foram utilizados 93 molares, após aplicação dos ácidos em dentina, aplicou-se o sistema adesivo e a restauração em resina composta. Logo após, foram seccionados e metade dos palitos foram testados imediatamente e a outra metade após 6 meses de armazenamento em água para análise da RU e NI. A análise da composição química foi realizada por espectroscopia micro-Raman. Para o experimento 3, 60 molares foram utilizados e distribuídos em função das variáveis já citadas. As superfícies de esmaltes foram armazenadas em água (37 °C / 24 h) e testadas para resistência de união no esmalte por microcisalhamento. O PC e análise de composição da química qualitativa do esmalte por teste micro-Raman foram avaliados. Para o experimento 1 e 3, ácido vs tempo de aplicação os dados de RU e NI foram submetidos a ANOVA 2 fatores e teste de Tukey (α = 0,05). Para o experimento 2, ácido vs tempos de aplicação vs tempo de armazenamento os dados de RU e NI foram submetidos a ANOVA 3 fatores e teste de Tukey (α = 0,05). Para o experimento 1, o AMF pH 0,5 mostrou RU significativamente semelhante ao AOF, independentemente do tempo de aplicação (p>0,05) e uma NI estatisticamente mais elevada foi observada para AOF em comparação com AMF, (p<0,03). Para o experimento 2, diminuições significativas nos valores de RU foram observados somente para AOF após 6 meses (p = 0,001) e valores de NI mais elevados foram encontrados quando comparado com AMF (p = 0,003). Para o experimento 3, o AOF e AMF pH 0,5 produziram valores RU estatisticamente mais elevados, quando comparados com AMF pH 1 e 2 independentemente dos tempos de aplicação (p<0,001). O AMF é um ácido que pode ser utilizado simultaneamente em esmalte e dentina, demonstrando uma alta RU, diminuição da nanoinfiltração imediata e após 6 meses de armazenamento quando comparado com o AOF. No somatório das propriedades avaliadas, o pH 0,5 apresentou alta RU em esmalte em relação ao AOF, mostrando-se promissor.

This thesis concerns the development of the first BINOL phosphoric acid (BPA) catalysed enantioselective N-acyliminium cyclisation reactions and their incorporation into domino sequences that allow for the construction of architecturally complex enantioenriched polycycles in a single step from easily accessible starting materials. More specifically, this thesis deals with the discovery of a BPA-catalysed enantioselective N-acyliminium cyclisation cascade of enol lactones and tryptamines. Its extension to a doubly catalysed process involving gold(I) to cycloisomerise alkynoic acids and a BPA to effect the enantioselective N-acyliminium cyclisation is presented. In addition, the exploitation of this method in highly diastereo- and enantioselective N-acyliminium cyclisations of oxoacids and tryptamines and in a site isolated base-catalysed Michael addition / acid-catalysed N-acyliminium cyclisation cascade is described. A study on the proposed mechanism and model for the origin of enantioselectivity is discussed, based on experimental data and a computational study. As a separate part of our programme, the development of a new class of stronger Brønsted acids, chiral benzenesulphonic acids, is described. The optimisation of the synthetic routes as well as the synthesis of a library of acids is presented and their assessment in precedented reactions is discussed.

The research presented in this thesis was carried out as part of a collaboration between the groups of Dr Tanja van Mourik at the School of Chemistry, University of St Andrews and Professor Jonathan Tennyson at the Department of Physics and Astronomy at University College London. This thesis presents State-Averaged Complete Active Space Self Consistent Field (SA-CASSCF) calculations on nucleic acid bases, deoxyribose and phosphoric acid H₃PO₄). In the case of uracil, for comparison, Multireference Configuration Interaction calculations were also performed. The SA-CASSCF orbitals were subsequently used in R-matrix electron scattering calculations using the close-coupling model. Of major importance for obtaining accurate SA-CASSCF results is the choice of the active space and the number of calculated states. Properties such as the electronic energy, number of configurations, excitation energy and dipole moment were considered in the choice of active space. Electron-collision calculations were performed on two of the most stable isomers of phosphoric acid, a weakly dipolar form with all OH groups pointing up and a strongly dipolar form where one OH group points down. A broad shape resonance at about 7 eV was found for both isomers. Ten-state close-coupling calculations suggest the presence of narrow, Feshbach resonances in a similar energy region. Elastic and electronically inelastic cross sections were calculated for both isomers. The R-matrix calculations on uracil were done by the group from UCL. R-matrix calculations are currently being done on guanine. Scattering calculations on the other DNA bases will be performed in the near future.

Thesis (M. Tech. Engineering: Electrical)--Vaal University of Technology / Fuel cells are electrochemical devices that convert chemical energy of a fuel cell into electricity at high efficiency without combustion. They are viewed as viable power sources for many applications including automobiles, distributed power generation and portable electronics. This dissertation presents the design and development of a phosphoric acid fuel cell. It deals with the experimental studies on phosphoric acid fuel cells and possible integration in replacing the conventional sources of electrical energy in stand-by power supply systems, particularly for use in the telecommunications industry. The design of a DC-DC converter system is also incorporated into the system. The first objective was to establish performance parameters and past studies on phosphoric acid fuel cells and this research revealed that parameters that affect the system's performance include: reactant gas pressures, mass flow rates as well as the operating temperature. Mathematical models in the literature were studied and verified against the simulation models acquired. The second objective was to design and assemble a single cell in order to analyze the cell's performances as well as the operating parameters in order to obtain a model for predicting and simulating the performance of larger fuel cell stacks. The next objective was to analyse from a set of design equations and construct a small DC-DC converter. The converter was used to boost a small fuel cell voltage and regulate it at a higher voltage level. Finally, the performance characteristics of the developed fuel cell, mathematical and simulation models were evaluated and compared. Simulation results for the models and the converter showing a regulated output voltage are presented. Some recommendations for improved system performance and for further studies are suggested.