A systematic research study was carried out in order to characterize the rheology of concentrated slurries prepared from eight nickel laterites. The experiments were carried out using a rotational viscometer, and the behavior of the laterites was evaluated in terms of the apparent viscosity and yield stress obtained through flow curve modeling. An attempt was made to correlate the results obtained for the laterite samples with data obtained for model single mineral systems as well as for model mixed mineral systems. In combination with detailed mineralogical characterization of the laterite samples, all the rheological results allowed a rheology-based laterite classification system to be proposed. Accordingly, the laterite samples gave the following responses: the SAPSIL samples (high-quartz) generally producedl ow yield stress values, the SAPFE samples (high-iron) were characterized by intermediate to high yield stress values, while the SAP samples (saprolite) gave the highest yield stress values. Interestingly, these dominant rheological responses of laterites could actually be predicted based on rheological tests carried out on model mineral suspensions (particularly goethite and quartz). Since the rheology of fine mineral suspensions is largely determined by the surface properties (surface charge) of the particles, a series of electro-acoustic measurements were also performed on model minerals and laterite samples to analyze the surface charge characteristics of the tested samples. It was demonstrated that the current electro-acoustic theory developed for single mineral systems can readily be used for modeling the behavior of mixed mineral systems. The modeling and experimental data agreed exceptionally well when constituent minerals were of the same surface charge under given pH. Clear but rather small deviations between experiment and theory were observed under conditions when the minerals were oppositely charged. This observation strongly suggested that inter-particle aggregation was most likely responsible for the observed discrepancies. Overall, the results of this thesis show that laterite slurries exhibit a wide range of rheological responses due to highly variable mineralogy, differences in particle size distributions, and difference in the surface properties of the many constituent minerals. It also shows that the surface properties of the minerals relates to rheology.

Australian film has engaged social issues since its earliest days, often within the genre of comedy. Writers and filmmakers have treated a wide range of issues with varying degrees of success in engaging their audience in a level of social discourse. This success has been independent of the specific issue addressed, the government funding policy, cultural policy, the national and international political climate, and available technologies. Rather it can be attributed to the filmmaker's approach to both characterization and narrative. Of the films chosen for examination it appeared that a positively portrayed protagonist in combination with a narrative that provided a clear but balanced opinion on the issue addressed was more successful in engaging its audience in a level of social discourse. The ability of the films to engage their respective audiences was based on criteria such as box office success, critical reception, and media and public discussion of the film around the time of its release as well as more recently. The findings of this investigation arose from the production of a feature length screenplay, The Last of the Wombats, which dealt with the issue of national security. The screenplay follows the Ruddocks along on their journey from personal insecurity, through issues of perceived threat, to the initial response of increasing the physical security measures around their house. These actions produce more problems than they solve, and this state of imbalance forces the main characters (Amber, Brian and Karen) to address their own insecurities and eventually to move beyond them.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Hemicellulose, a plant cell wall polysaccharide composed amongst other 6-carbon sugars of xylose, a 5-carbon fermentable sugar, has various side-chains which hinder breakdown by the hydrolytic enzyme xylanase. We executed a screen of a metagenomic library established from heat treated saw dust to isolate novel genes for plant cell wall esterases and isolated two clones that potentially could be utilised as acetyl xylan esterases: HEL12 and HEL37 from Citrobacter farmeri and Bacillus vallismortis respectively are confirmed short-chain acetyl xylan esterases (C2-C4) with an optimal temperature of 30°C and 35°C and pH 8.0. HEL12 (33kDa) and HEL37 (25kDa) are small, dextrous acetyl xylan esterases with HEL37: Km of 1.621mM for p-nitrophenyl acetate and Km of 3.571mM for the substrate p-nitrophenyl palmitate with a Vmax of 2.462 mMol/min/mg protein and Vmax of 0.4363 mMol/min/mg protein respectively. In addition HEL12 was active on other substrates with a Km of 1.321mM protein for p-nitrophenyl acetate and Km of 1.692mM for the substrate p-nitrophenyl butyrate with a Vmax of 3.812 and Vmax of 1.523 mMol/min/mg protein respectively. Both enzymes were assayed on various acetylated polymers including acetylated xylan to indicate their ability to hydrolyse plant lignocellulosic polymers. / AFRIKAANSE OPSOMMING: Met die herwinde interisering in die energie krisis, is “herwinbare energie” vinnig besig om die nuwe modewoord te raak tussen verskeie industriële bedrywighede. Hemicellulose, ‘n plant sel wand polisakkaride opgemaak uit xilose, ‘n 5-koolstof fermenteerbare suiker, het verskillende sykettings wat ‘n hindernis veroorsaak in die hidrolase van die komponent deur xilanase ensieme. HEL12 en HEL37 van bakterieë Citrobacter farmeri en Bacillus vallismortis afsonderlik, is deel van die hidrolitiese groep van ensieme wat die hidrolisasie van ester sy-bindings op die xilaan suikerstring kataliseer. Die ensieme was primêr geassesseer vir aktiwiteit deur middel van sintetiese substraat 4-nitrofeniel asetaat. HEL12 en HEL37 was gevind om kort-ketting asetiel xilaan esterase (C2-C4) te wees, met ‘n optimale temperatuur van 30°C en 35°C afsonderlik, beide met ‘n optimale pH van 8.0. Met ‘n geskatte gewig van omtrent +- 30kDa is beide die ensieme van die kleiner meer behendige asetiel xilaan esterase, met HEL37: Km = 1.621 op 4-nitrofeniel asetaat en Km = 3.571 op substraat 4-nitrofeniel palmetaat, en Vmax = 2.462 met ‘n Vmax = 0.4363 afsonderlik, en HEL12: Km = 1.321 op 4-nitrofeniel asetaat en Km = 1.692 op sustraat 4-nitrofeniel buteraat met ‘n Vmax = 3.812 en Vmax = 1.523 afsonderlik.

abstract: Semiconductor nanowires (NWs) are one dimensional materials and have size quantization effect when the diameter is sufficiently small. They can serve as optical wave guides along the length direction and contain optically active gain at the same time. Due to these unique properties, NWs are now very promising and extensively studied for nanoscale optoelectronic applications. A systematic and comprehensive optical and microstructural study of several important infrared semiconductor NWs is presented in this thesis, which includes InAs, PbS, InGaAs, erbium chloride silicate and erbium silicate. Micro-photoluminescence (PL) and transmission electron microscope (TEM) were utilized in conjunction to characterize the optical and microstructure of these wires. The focus of this thesis is on optical study of semiconductor NWs in the mid-infrared wavelengths. First, differently structured InAs NWs grown using various methods were characterized and compared. Three main PL peaks which are below, near and above InAs bandgap, respectively, were observed. The octadecylthiol self-assembled monolayer was employed to passivate the surface of InAs NWs to eliminate or reduce the effects of the surface states. The band-edge emission from wurtzite-structured NWs was completely recovered after passivatoin. The passivated NWs showed very good stability in air and under heat. In the second part, mid-infrared optical study was conducted on PbS wires of subwavelength diameter and lasing was demonstrated under optical pumping. The PbS wires were grown on Si substrate using chemical vapor deposition and have a rock-salt cubic structure. Single-mode lasing at the wavelength of ~3000-4000 nm was obtained from single as-grown PbS wire up to the temperature of 115 K. PL characterization was also utilized to demonstrate the highest crystallinity of the vertical arrays of InP and InGaAs/InP composition-graded heterostructure NWs made by a top-down fabrication method. TEM-related measurements were performed to study the crystal structures and elemental compositions of the Er-compound core-shell NWs. The core-shell NWs consist of an orthorhombic-structured erbium chloride silicate shell and a cubic-structured silicon core. These NWs provide unique Si-compatible materials with emission at 1530 nm for optical communications and solid state lasers. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

La taille du transistor MOS ne cesse de diminuer pour des questions de performance et de rentabilité de fabrication. Les procédés de fabrication évoluent, l'architecture se complexifie et les méthodologies d'extraction de paramètres électriques doivent être adaptées. C'est ainsi que dans un premier temps, les effets d'un recuit haute pression sous atmosphère hydrogène (HPH2) ou deutérium (HPD2) sur le transistor MOS sont étudiés en détail dans cette thèse. La comparaison des performances apportées en termes de transport électronique et de dégradations engendrées en fiabilité a permis de montrer que le HPD2 présente un meilleur compromis. Une étude des effets d'un canal silicium-germanium (SiGe) sur les performances des transistors MOS est ensuite réalisée. L'incorporation du SiGe a permis d'atténuer l'impact négatif sur les performances des charges contenues dans l'empilement de grille. La présence de ces charges est d'ailleurs confirmée par l'analyse des effets néfastes d'un oxyde de grille à haute permittivité, utilisé entre autre pour faciliter la miniaturisation. Dans un deuxième temps, la « fonction Y » a été étendue en régime de saturation afin d'extraire la vitesse de saturation qui est un indicateur de performance obtenu dans les mêmes conditions que le courant ION. En outre, la problématique liée à l'extraction de la charge d'inversion sur des transistors courts et à forte tension de drain VD a été résolue grâce à des mesures à hautes fréquences réalisées sur une structure deux ports. Ceci a rendu possible l'obtention de la mobilité effective, de la vitesse moyenne et de la vitesse limitante sur des transistors déca-nanométriques. / The MOS gate length is continuously downscaling because of the need of higher performance and cost-effectiveness. In addition to the fabrication process, the device architecture is being more and more complex and parameters extraction need to be adapted. First in this thesis, the effects of high pressure final anneal with hydrogen (HPH2) or deuterium (HPD2) on MOSFET properties is investigated. The transport performances and reliability degradation comparison allow to consider HPD2 as a good compromise. The effect of a silicon-germanium (SiGe) channel is also studied. It is demonstrated that SiGe channel decreases defects located in the high-κ gate stack. The presence of these defects is confirmed by the study of the negative effects of a high-k as a gate oxide. Secondly, the “Y function” method is extended to the saturation regime to reliably extract saturation velocity, obtained in the same conditions as ION current. The problematic due to inversion charge estimation in short devices is solved using high frequency measurements with a two ports structure. Then, effective mobility, average velocity and limiting velocity are obtained in ultra-scaled devices.

Microbial actions on coal have long been identified as a source of methane in coalbeds. Andrew Scott (1995) was the first to propose imitating the natural process of biogenic gasification, possibly leading to recharging coalbed methane (CBM) reservoirs, or setting up natural gas reservoirs in non-producing coalbeds. This study was aimed at identifying the changes in coal properties that affect gas deliverability in coal-gas reservoirs, when treated with microbial consortia to generate/enhance gas production. The experimental work tested the sorption and diffusion properties for the coal treated and, more importantly, the variation in the relevant parameters with continued bio-conversion since these are the first two phenomena in CBM production. During the first phase, single component sorption-diffusion experiments were carried out using pure methane and CO2 on virgin/baseline coals, retrieved from the Illinois basin. Coals were then treated with nutrient amended microbial consortia for different periods. Gas production was monitored at the end of thirty and sixty days of treatment, after which, sorption-diffusion experiments were repeated on treated coals, thus establishing a trend over the sixty-day period. The sorption data was characterized using Langmuir pressure and volume constants, obtained by fitting it over the Langmuir isotherm. The diffusion coefficient, D, was estimated by establishing the variation trend as a function of pore pressure. The pressure parameter was considered critical since, with continued production of methane, the produced gas diffuses into the coal matrix, where it gets adsorbed with increasing pressure. During production, the pressure decreases and the process is reversed, gas diffusing out of the coal matrix and arriving at the cleat system. The results indicated an increase in the sorption capacity of coal as a result of bioconversion. This was attributed to increased pore surface areas as a result of microbial actions. However, significant hysteresis was observed during desorption of methane and was attributed to preferential desorption from sorption sites in the pathways leading to pore cavities. This is corroborated by the increased rates of diffusion, especially for methane, which exhibited rates higher than that for CO2. This contradicted the results for untreated/baseline coal, which were in agreement with previous studies. Effort was made to explain this anomaly by the non-monotonic dependence of effective diffusion coefficient on the size of the diffusing particles, where in coalbed environments, CO2 has smaller kinetic diameter than methane.

Passenger vehicle disk brakes produce large amounts of wear debris that needs to be analyzed to verify its environmental and health impact because its effects are amplified by the massive extent of vehicular transportation around the world. An efficient and thorough method for wear debris analysis should be derived from this research to assist brake manufacturers and researchers in understanding the characteristics of wear particulates being released from current brake materials. In addition, a test method allowing inspection of brake formulations in development phase should be provided and several model "environmentally friendly" brake lining materials should be developed. The most hazardous constituents in a known brake lining formula should be replaced with non-hazardous materials that will obtain performance specifications comparable to the original formula. The brake manufacturing industry and general public should be notified of important findings from this research. Model brake linings fabricated on-site with known constituents were run through an AO4D performance dynamometer test to collect airborne and non-airborne wear debris that is comparable to wear debris produced by an average passenger vehicle. Based on previous experience with analysis of brake linings, this wear debris will be analyzed with scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX), transmission electron microscopy with EDX (TEM-EDX), X-ray diffraction (XRD), polarized light microscopy (PLM), X-ray fluorescence (XRF), and laser scattering particle size distribution analyzer (LSPSDA). Research presented in this report indicates clearly that the previous work published by several groups is lacking sufficient information and the findings should be corrected. For instance the particle size distribution detected by particle size analyzers and impactors (recommended by EPA) is not accurate and TEM as well as SEM studies allowing direct observation of wear particles revealed considerable differences between sizes detected by these analyzers and realistic particle size. EDX in combination with XRF and XRD allows for reliable identification of chemical species and crystalline phases present in wear debris. True airborne wear debris should be sampled from brake exhaust from an appropriate distance. Degummed hemp shows promising results as a copper replacement in low-metallic friction material.

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Byron Jones / Contamination of aircraft bleed air with engine oil and/or hydraulic fluid results in a “fume event” in the aircraft cabin. Exposure to contaminated bleed air may have acute and/or chronic adverse health effects based on the intensity of various chemicals which are released during such a fume event. ASHRAE Standard 161, Air Quality within Commercial Aircraft, includes a requirement for bleed air sensors to detect contamination from lubricating oil. One potential approach to meeting this requirement is through particle detection. In the research reported here, the end goal is to provide data needed to develop an automated detection apparatus for contaminated bleed air through oil particle detection. Consequently, the type and concentration of different chemicals as well as the number and size distribution of particles were determined for bleed air with different rates of contamination under various turbine engine operating conditions. Multiple fume events were simulated by using a four-part experimental program to develop a detailed characterization of particles that result when bleed air is contaminated with lubricating oil. Test results show that oil contamination in the compressor will result in a fog of very fine droplets in the bleed air under most operating conditions. With moderately high contamination rates at elevated power levels (high bleed air temperature) the concentration distribution and particle size does not vary much with power (temperature) and generally depends on the rate of contamination. Moreover, at elevated power levels, the peak particle concentration takes place in the range of 50 to 70 nanometers and the bulk of the particles form at less than 150 nanometers. At very low contamination rates very ultrafine particles can be generated in the size of 10 nanometers or less. As a result, detection is needed for a range of sizes ranging from about 100 nanometers to 10 nanometers.

Made available in DSpace on 2014-06-11T19:34:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-09-10Bitstream added on 2014-06-13T19:24:02Z : No. of bitstreams: 1 anazawa_rm_dr_guara.pdf: 10651017 bytes, checksum: 16ae1ffa0b957dba762c69ee5a3bb352 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os aços multifásicos são de grande interesse comercial e têm atraído a atenção, principalmente, da indústria automobilística devido a combinação de alta resistência e ductilidade. A fase austenita retida, presente nestes aços, tem sido objeto de especial interesse devido ao efeito TRIP, que contribui para a melhoria da tenacidade. Neste trabalho é utilizado o aço aeronáutico 300M e, com o objetivo de estudar a influência das fases sobre as propriedades mecânicas são realizadas as seguintes etapas: a otimização de rotas de tratamentos térmicos para a obtenção de uma microestrutura multifásica; caracterização microestrutural por microscopia óptica, microscopia eletrônica de varredura e microscopia de força atômica e avaliação do envelhecimento de deformação à temperatura ambiente. A principal contribuição é a determinação da fração volumétrica da austenita retida por meio de medidas de saturação magnética através de curvas de histerese magnética. As frações volumétricas de austenita retida obtidas por medidas de magnetização são comparadas com as obtidas por difratometria de raios X e microscopia óptica após ataques químicos de metabissulfito de sódio. Os resultados obtidos por microscopia óptica e pelo método magnético apresentam boa concordância com os valores encontrados na literatura. A alteração microestrutural devido aos tratamentos térmicos aplicados permite melhorias no limite de escoamento e resistência. Analisa-se, ainda, o efeito do envelhecimento por deformação à temperatura ambiente. Os resultados são surpreendentes, ocorrendo um aumento no limite de escoamento em até 87%, devido à associação do envelhecimento por deformação com o efeito TRIP. / The multiphase steels are of great commercial interest and have attracted attention mainly of the automobile industry due to the combination of their high strength and ductility. The retained austenite phase present in these steels has been object of special interest due to TRIP effect contribution for the improvement of the toughness. In this work the influence of the phases of the aircraft 300M steel is carried out by the optimization of heat treatments routes to obtain multiphase microstructure. Microestructural characterization is evaluated by optical microscopy, scanning electronic microscopy, atomic force microscopy and analysis of the deformation ageing at room temperature. The main contribution is the determination of retained austenite volume fractions from magnetic hysteresis curves. These values are compared with x-ray diffraction data and optical microscopy after sodium metabisulfite etching, presenting good agreement with the literature. The microstructural alterations due the applied heat treatments also affect the yield strength and strength. The association of the deformation ageing and the TRIP effect resulted in a surprising increase of up to 87% in the yield strength.

abstract: The ability of microalgae to be mass cultivated and harvested for production of pharmaceuticals, nutraceuticals, and biofuels has made microalgae a focal point of scientific investigation. However, negative impacts on production are essentially inevitable due to the open design of many microalgae mass culture systems. This challenge generates a need for the consistent monitoring of microalgae cultures for health and the presence of contaminants, predators, and competitors. The techniques for monitoring microalgae cultures are generally time-intensive, labor-intensive, and expensive. The scope of this work was to evaluate the use of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) as a viable alternative for the characterization of microalgae cultures. The studies presented here evaluated whether MALDI-TOF MS can be used to: 1) differentiate microalgae at the species and strain levels, 2) characterize simple mixtures of microalgae, 3) detect changes in a single microalgae culture over time, and 4) characterize growth phases of microalgae cultures. This research required the development of a MALDI-TOF MS microalgae analysis protocol for organism characterization. The results yielded in this research showed that MALDI-TOF MS was just as accurate, if not more so, than molecular techniques for the identification of microalgae at the species and strain levels during its logarithmic growth phase. Additionally, results suggest that MALDI-TOF MS is sensitive enough to characterize simple mixtures and detect changes in cultures over time. The data presented here suggests the next logical step is the development of protocols for the near-real time health monitoring of microalgae cultures and detection of contaminants using MALDI-TOF MS. / Dissertation/Thesis / Masters Thesis Biology 2016