This study concerned the synthesis of modified terephthalic acid monomers and branched dialcohols for the synthesis of polyesters with different properties. Monomers were prepared by esterification of terephthalic acid (TPA) and the alkylation of the ester dimethyl terephthalate (DMT). If alkylation was unsucessful, TPA was brominated using N-bromosuccinimide (NBS) and other brominating agents. However, the bromination reactions were also unsuccessful. Therefore, oxidation reactions of 2-bromoparaxylene were conducted as an attempt to obtain the desired monomers, however a mixture of products was produced that were difficult to separate. Subsequently, the brominated TPA was bought, and the alkylation reactions were performed using tetramethyltin and other alkylating agents; however the alkylation reaction was once again unsuccessful. Despite the difficulties encountered during monomer synthesis, polymerization of the obtained monomers was investigated. Polymer synthesised by the technique of condensation polymerization of branched diols and the brominated TPA. The unbranched diol monomers and unsubstituted DMT were used to synthesize reference polymers for comparison with the novel polymers produced in this study. The following diols were used: 1,2-propanediol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol. A batch reactor equipped with a mechanical stirrer connected to the vacuum pump was used as polymerization vessel. The polyesters were synthesised and they were characterised using IR and NMR. Additional polymer analysis was performed using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Gel permeation Chromatography (GPC) and Scanning Electron Microscopy (SEM). The results of the analyses indicated that the polymers became flexible and softer with an increasing number of methylene units in the main chain. Consequently, the melting point of the polymer decreased when there was branching present. SEM analyses showed that polymers were softer and had no hard edges, and the SEM also showed the catalyst inside the polymers. The decomposition temperature changed very slightly with alkyl substitution or the presence of bromide in benzene ring. It was concluded that the benzene ring did not become activated as a number of methods were attempted unsuccessfully to facilitate reaction by either alkylation or bromination. The methyl branches on the diols were not held responsible for any changes in the properties of the polyesters. Bromination of the monomers resulted in polymers that were structurally amorphous and that demonstrated a low tensile strength. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015

This thesis is a critical comparison of the <I>Macbeth</I> operas of Verdi and Bloch, with an examination of how the challenges posed by the play are dealt with by the two composers. It opens with a brief discussion of what makes the play suitable for operatic adaptation, followed by an outline of the musical techniques employed by both composers, and then a comparison of the two libretti. The main focus of this thesis is the issue of characterisation: the way in which it is altered to suit the operatic stage and how this affects the drama as a whole. There is firstly a detailed investigation of the parts played by the witches and Lady Macbeth, the way in which they are characterised through their music, and their relative importance in the downfall of Macbeth. This is followed by a brief examination of the 'good' characters, the questions raised by their presentation in play and operas, and whether the lack of any credible opposition to Macbeth contributes to the tragedy. The most substantial section of the thesis focuses on Macbeth, the problems posed by the complexity of Shakespeare's character, and the ways in which these are dealt with by Verdi and Bloch. The main issue is whether the inability of opera to present the full complexity of Macbeth's nature as verbally expressed, results in a weaker character and a lesser tragedy. Arising from the relative weakness of the operatic Macbeth is the question of how much responsibility he must bear for his downfall, and how much he is a victim of his wife, the witches, and external fates and events. Finally, taking into consideration the points raised above, conclusions are drawn regarding the success of these two operas, both as adaptations of Shakespeare and as dramatic works in their own right.

No description available.

The halophilic bacterium Vibrio parahaemolyticus is widely distributed as a natural inhabitant of marine and estuarine environments. Some strains cause gastroenteritis in humans. Clinical isolates are thought to possess virulence factors that are absent from the majority of environmental isolates. Studies were undertaken to differentiate clinical (virulent) and environmental (mainly avirulent) forms of Vibrio parahaemolyticus. Initially, identification and confirmation of a total of 55 V. parahaemolyticus isolates (23 clinical and 32 environmental) was carried out by using selective media, biochemical and nutritional tests. Identity was confirmed by specific polymerase chain reaction (PCR) targeting the toxR gene. In an attempt to differentiate between virulent and avirulent forms V. parahaemolyticus, potential virulence factors (enzyme activities), presence of plasmids and analyses of whole cell protein profiles and extracellular products (ECPs) by SDS-PAGE were performed. The results suggested that the presence of plasmids in isolates was not linked to virulence and SDS-PAGE profiles did not differentiate between virulent and avirulent forms, but a combination of enzyme activities may contribute to virulence. The ECPs of all 55 V. parahaemolyticus isolates were tested for their cytotoxicity towards two types of cell lines, the clinical isolates showed that 21 out of 23 (91%) and 2 out of 23 (8.69%) showed high and medium cytotoxicity, respectively. Amongst the environmental isolates 2 out of 32 (6.25%), 2 out of 32 (6.25%) and 28 out of 32 (87.5%) showed high, medium and low cytotoxicity, respectively. Randomly amplified polymorphic DNA (RAPD)-PCR was used to analyse the two groups of isolates. Firstly a 600 bp band was recognised in mainly clinical isolates. This DNA fragment was cloned and sequenced and found to code for an outer membrane protein (OMP). Two PCR primers were designed to specifically amplify a 200bp unique sequence from presumptive virulent strains (PCR-OMP); however, not all clinical isolates were positive (21 out of 23, 91%). A second RAPD-PCR identified a further unique band of approximately 310 bp in mostly clinical isolates. After cloning this band’s DNA, the DNA sequence revealed a hypothetical gene, htp, whose function is not known. Specific primers, VPHTP1 and VPHTP2 were developed for the detection of the htp sequence, but again not all clinical isolates were positive (19 out of 23, 82.6%). This led to the development of a multiplex M-PCR which detects all isolates of V. parahaemolyticus and differentiates them into potentially virulent and avirulent forms. The M-PCR works by targeting the toxR gene, and sequences for omp and htp. The M-PCR was performed on all V. parahaemolyticus isolates used in this study, as well as other Vibrio species and a selection of non-Vibrio species. The amplification of toxR gene 367 bp fragment was found in all V. parahaemolyticus tested; all clinical isolates (100%) showed amplification of omp and/or htp. This multiplex PCR detected 3 (9.37%) environment isolates, which may potentially be able to cause disease. No amplification was seen for the other species tested. Thus, the M-PCR could be used for identifying V. parahaemolyticus and detecting / differentiating potentially virulent and avirulent forms. This method should be

This work focuses on the design, synthesis and characterisation of novel ruthenium bipyridyl complexes and their use in dye sensitised solar cells (DSSCs). Four series of dyes have been synthesised with the general formula Ru(R-bpy)2L, where R = H, CO2Et, CO2H and L represents four different bidentate ligands; cyanodithioimidocarbonate (L1), ethyl xanthate (L2), 2,3-bis(2-cyanoethylthio)-6,7-bis(methylthio) tetrathiafulvalene (L3) and Cu(exoO2-cyclam) (L4). These have been chosen to investigate two key aims: firstly, the increase of the light-harvesting ability of the dye and secondly, the retardation of the recombination of the injected electron with the oxidised dye. Each complex was characterised using electrochemistry, absorption spectroscopy, spectroelectrochemistry and hybrid-DFT calculations. In addition the performance of the acid derivatives in a DSSC was also investigated using IPCE and IV measurements, as well as transient absorption spectroscopy. Two different S-donor ligands, L1 and L2, have been used to investigate the effect of these strongly electron-donating systems on the light-harvesting ability of the dye. Complexes utilising the di-anionic L1 were shown to exhibit significantly increased absorption range and higher extinction co-efficients, relative to the high efficiency dye N719. This dye series also showed a large degree of S-donor ligand character to the HOMO, deduced via spectroelectrochemical and computational studies. Despite these advantageous features the dye performed very poorly in a DSSC, which was attributed to fast recombination. This was a result of the cyano group of L1 coordinating to the TiO2 in addition to the acid groups of the bipyridine ligands. The complexes synthesised with the mono-anionic L2 on the other hand showed only a slightly increased lightharvesting ability relative to N719 and no significant ligand character to the HOMO. However, the performance of this dye in a DSSC was more promising, with efficiencies of up to ~ 2 % achieved. The control of the loss mechanism via recombination of the injected electron with the oxidised dye in a DSSC was investigated by incorporating redox-active ligands, L3 and L4. The series of dyes synthesised with L3 showed significant ligand character to the HOMO orbital, as deduced by spectroelectrochemical, emission and computational studies. Upon adsorption of the acid derivative to TiO2 an extremely long-lived chargeseparated state of 20 ms was observed via transient absorption spectroscopy. Despite this unique long-lived charge-separated state, the dye yielded extremely low DSSC efficiencies. This was attributed to the poor regeneration of the neutral dye by iodide, which in turn was thought to be the result of a stable intermediate formation between the dye cation and the iodide anion. The complexes synthesised with L4 showed the highest light-harvesting efficiency of all the series studied with a wide absorption range and large molar extinction co-efficients. Whilst the maximum efficiency of the dye in a DSSC was nearly 3 %, the performance was found to vary under prolonged irradiation. This was attributed to the degradation of the dye by either exchange of the counter ions with the electrolyte or loss of L4.

An efficient and flexible modelling and simulation toolset for solving spatially-resolved models of photovoltaic (PV) devices is developed, and its application towards a quantitative description of localised electrical behaviour is given. A method for the extraction of local electrical device parameters is developed as a complementary approach to the conventional characterisation techniques based on lumped models to meet the emerging demands of quantitative spatially-resolved characterisation in the PV community. It allows better understanding of the effects of inhomogeneities on performance of PV devices. The simulation tool is named PV-Oriented Nodal Analysis (PVONA). This is achieved by integrating a specifically designed sparse data structure and a graphics processing unit (GPU)-based parallel conjugate gradient algorithm into a PV-oriented numerical solver. It allows more efficient high-resolution spatially-resolved modelling and simulations of PV devices than conventional approaches based on SPICE (Simulation Program with Integrated Circuit Emphasis) tools in terms of computation time and memory usage. In tests, mega-sub-cell level test cases failed in the latest LTSpice version (v4.22) and a PSpice version (v16.6) on desktop PCs with mainstream hardware due to a memory shortage. PVONA efficiently managed to solve the models. Moreover, it required up to only 5% of the time comparing the two SPICE counterparts. This allows the investigation of inhomogeneities and fault mechanisms in PV devices with high resolution on common computing platforms. The PVONA-based spatially-resolved modelling and simulation is used in various purposes. As an example, it is utilised to evaluate the impacts of nonuniform illumination profiles in a concentrator PV unit. A joint optical and electrical modelling framework is presented. Simulation results suggest that uncertainties introduced during the manufacturing and assembly of the optical components can significantly affect the performance of the system in terms of local voltage and current distribution and global current-voltage characteristics. Significant series resistance and shunt resistance effects are found to be caused by non-uniformity irradiance profiles and design parameters of PV cells. The potential of utilising PVONA as a quality assessment tool for system design is discussed. To achieve quantitative characterisation, the PVONA toolset is then used for developing a 2-D iterative method for the extraction of local electrical parameters of spatially-resolved models of thin-film devices. The method employs PVONA to implement 2-D fitting to reproduce the lateral variations in electroluminescence (EL) images, and to match the dark current-voltage characteristic simultaneously to compensate the calibration factor in EL characterisations. It managed to separate the lateral resistance from the overall series resistance effects. The method is verified by simulations. Experimental results show that pixellation of EL images can be achieved. Effects of local shunts are accurately reproduced by a fitting algorithm. The outcomes of this thesis provide valuable tools that can be used as a complementary means of performance evaluation of PV devices. After proper optimisation, these tools can be used to assist various analysis tasks during the whole lifecycle of PV products.

Student Number : 0314958W - MSc dissertation - School of Process and Materials Engineering - Faculty of Engineering and the Built Environment / Microstructural characterisation was performed on Al-Ti-B grain refiners of different compositions prepared by aluminothermic reduction of TiO2 and B2O3 and dilution of the products in aluminium melts. The microstructure of the grain refiners showed needle-like TiAl3 particles as well as prismatic TiB2 particles. The TiB2 particles were coarser than those in conventional Al-Ti- B grain refiners. The microstructure also showed silicon particles and, in some cases, titanium carbide particles (TiC). The experimental grain refiners were subjected to rolling and reduced in thickness by 20, 40, 60 and 80%. The rolled samples were then heated at 625°C for 4 hours and allowed to cool slowly in the furnace. Significant changes in microstructure were noticed at 80% reduction. The flake-like and needle-like aluminide particles in the as cast microstructure were fragmented and aligned in the aluminium matrix, giving rise to short needle-like particles in parallel rows. These aluminide particles had rough edges which were rounded by heat treatment. The TiB2 particles were not affected in size or morphology by either the rolling or the heat treatment. The grain refining performance of the as cast materials was assessed. It was found that the experimental grain refiners had poorer performance than commercial grain refiners. The influence of mechanical and thermal treatments on the grain refining performance of the experimental Al-Ti-B grain refiners was also assessed. Cold working of the grain refiners had a positive influence on the grain refining performance promoting finer grain. Heat treatment of grain refiners after cold working was deleterious and led to a loss of grain refining capacity. The size and size distribution of TiB2 particles were determined related to grain refining performance and compared to theoretical models. A relationship was established between the size distribution of the TiB2 particles in the grain refiners and the grain size of inoculated aluminium. Grain refinement increased with decreasing proportion of coarse TiB2 particles in the grain refiners. This corresponded to a decrease in Ti and B contents and an increase in the Ti/B ratio.

<p>Nowadays, the polishing process is one of the most important steps of the manufacturing of moulds and dies. Occupying up to 40% of the total production time and cost, it is decisive for the final appearance and quality of a surface. Because of its complexity, the polishing is mainly carried out manually; and the final quality depends of the expertise of the operator. That is why an automation of the polishing process is necessary.</p><p>The purpose of this project was to find out the optimized sequence of polishing for a Mirrax ESR steel (Uddeholm Tooling AB) using the Strecon RAP-200 (robot assisted polishing equipment). Using a Design of Experiment, the machine parameters were tested in order to better understand their influences and interactions. The report starts with a description of general polishing knowledge and ends up with the results from a Design of Experiment.</p><p>The information from this test are a first step in the evaluation of the Strecon RAP-200. Even if many results have been found out, only four parameters have been tested, and to be able to optimize the polishing sequence, further studies need to be carried out.</p>

Nowadays, the polishing process is one of the most important steps of the manufacturing of moulds and dies. Occupying up to 40% of the total production time and cost, it is decisive for the final appearance and quality of a surface. Because of its complexity, the polishing is mainly carried out manually; and the final quality depends of the expertise of the operator. That is why an automation of the polishing process is necessary. The purpose of this project was to find out the optimized sequence of polishing for a Mirrax ESR steel (Uddeholm Tooling AB) using the Strecon RAP-200 (robot assisted polishing equipment). Using a Design of Experiment, the machine parameters were tested in order to better understand their influences and interactions. The report starts with a description of general polishing knowledge and ends up with the results from a Design of Experiment. The information from this test are a first step in the evaluation of the Strecon RAP-200. Even if many results have been found out, only four parameters have been tested, and to be able to optimize the polishing sequence, further studies need to be carried out.

In response to conflicting claims within the field (Fox & Thomas, 1990; Thomas, Chaigne & Fox, 1989; Jolley, 1995), a series of experiments was conducted to explore the experimental conditions under which children might alter the formal and content properties of their drawings to depict topics which have received differential topic characterisation. In Experiment 1, children produced three copies of shaded models of men, dogs and trees. All children drew a baseline drawing, and two further drawings following nice and nasty topic characterisation. It was found that nice drawings were scaled up from baseline drawings and that nasty drawings were less consistently scaled down from baseline drawing size. Topic type did not interact with-this main effect. Experiment 2 examined children's choice of colour to complete pre-drawn models of men, dogs and trees following affective topic characterisation. Children altered their colour choice for the affectively characterised topics, and colour choice was related to colour preference. Experiment 3 investigated children's use of both size and colour in spontaneous drawings, and examined which additional strategies children might use to differentiate emotional character. Children's drawings of nice figures were again found to be increased from baseline size, whilst only drawings of nasty trees were reduced in surface area from baseline figure size. Children used a wide range of strategies in response to differential topic characterisation, and it was also found that children were able to report the techniques which they had used to represent emotional character. Experiments 4-6 assessed potential effects of drawing materials, emotional terms and educational group on children's drawings of positively and negatively characterised men. More consistent evidence was found to suggest that children increase the size of positively salient figures than reduce the size of negatively salient figures. Colour choice in relation to preference was found in Experiments 4 and 5, and the same range of additional strategies was observed throughout Experiments 4-6. There were only slight variations in the use of the strategies in situations where children used different drawing materials, received different sets of emotional characterisations, and in drawings by children from different educational groups. The experiments showed that effects of topic characterisation on a range of properties of children's drawings can be measured when task demands are systematically varied.