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Thesis (PhD (Microbiology))--University of Stellenbosch, 2010. / Dissertation presented for the degree of Doctor of Philosophy in Microbiology at the University of Stellenbosch. / ENGLISH ABSTRACT: The interaction between a soil yeast, Cryptococcus laurentii and a medicinal plant, Agathosma betulina (Berg.) Pillans (Rutaceae), was studied. Cryptococcus laurentii CAB 578 was isolated from the rhizosphere of wild A. betulina and liquid chromatographytandem mass spectrometry analysis revealed that the yeast was capable of producing polyamines such as cadaverine and spermine. Since the exogenous application of polyamines are known to impact on root growth, these findings supported the results obtained when A. betulina seedlings grown under axenic and low nutrient conditions were inoculated with C. laurentii CAB 578 and cultivated for five months under glasshouse conditions. The presence of the yeast increased root growth by 51%. Using soil dilution plates, it was demonstrated that yeast numbers were greater in the vicinity of the roots than in the bulk soil. Furthermore, fluoromicroscopy, in combination with the fluorescent probes Calcofluor White and Fungolight revealed the presence of metabolic active yeast colonies on the rhizoplane. The first part of the study thus provided evidence for a symbiosis between A. betulina and C. laurentii CAB 578. During the second part of the investigation, the effect of this symbiosis on quantitative elemental distribution in A. betulina roots grown under axenic, nutrient-poor conditions was assessed using micro-particle-induced x-ray emission spectrometry. To aid in the interpretation of heterogeneous elemental distribution patterns, apoplastic barriers and endophytic C. laurentii CAB 578 in root tissues were located using fluorescence microscopy and transmission electron microscopy, respectively. The results showed that the average concentrations of iron, manganese and phosphorus were significantly (P < 0.05) higher within roots of yeast-inoculated plants, compared to control plants. It was shown that the yeast was not a root endophyte and that elemental enrichment in the epi/exodermal-outer cortical tissues correlated with the presence of Casparian bands in the exodermal cells of both treatments. This was the first report describing the role of a soil yeast as a plant nutrient-scavenging microsymbiont. In the final part of the investigation, the effect of C. laurentii CAB 578 on the photosynthetic nitrogen, phosphorus and water-use efficiencies, as well as the carbon economy of A. betulina was studied. Agathosma betulina plants inoculated with C. laurentii CAB 578, as well as controls, were grown under axenic conditions and the following parameters measured: Apparent photon yield, foliar nitrogen and phosphorus concentrations, leaf dark respiration, maximum photosynthetic rate, photosynthetic nitrogen-use efficiency, photosynthetic phosphorus-use efficiency, photosynthetic wateruse efficiency, root construction cost, stomatal conductance, substomatal CO2 and transpiration rate. The data showed that the higher photosynthetic resource-use efficiencies in yeast-inoculated plants were a consequence of higher maximum rates of CO2 assimilation, which was not related to foliar nitrogen and phosphorus content. We hypothesize that photosynthetic stimulation in yeast-inoculated plants was a result of the increased demand for photosynthates of the yeast-root symbiosis. In summary, the study revealed that a symbiosis exists between A. betulina and the soil yeast C. laurentii CAB 578. This interaction has a significant effect on the size of the yeast population as well as on the physiology of the plant. / AFRIKAANSE OPSOMMING: Die interaksie tussen ‘n grondgis, Cryptococcus laurentii, en ‘n medisinale plant, Agathosma betulina (Berg.) Pillans, is ondersoek. Cryptococcus laurentii CAB 578 is vanuit die risosfeer van A. betulina in sy natuurlike omgewing geisoleer en vloeistof chromatografie tandem massa spektrofotometriese analise het bewys dat die gis poliamiene insluitend kadaverien en spermien produseer. Dit is bevind dat die eksogene aanwending van poli-amiene wortelgroei bevorder. Hierdie bevinding staaf die waargenome 51% verhoging in wortelgroei van mikroob-vrye A. betulina saailinge geinokuleer met C. laurentii CAB 578 en gekweek vir vyf maande onder lae nutriënt kondisies in ‘n glashuis. Met gebruik van die grond verdunningsplaat-metode, is dit verder bewys dat gisgetalle hoër was in die teenwoordigheid van wortels as in die omliggende grond. Dit is ook bewys met die gebruik van die fluoressente peilers Calcofluor White en Fungolight, in kombinasie met fluoressensie-mikroskopie, dat metabolies aktiewe giste die wortels se oppervlak gekoloniseer het. Die eerste deel van die studie het dus bewys dat ‘n simbiose tussen A. betulina en C. laurentii CAB 578 bestaan. Tydens die tweede deel van die ondersoek is die effek van C. laurentii CAB 578 op die konsentrasie en verspreiding van elemente binne A. betulina wortels, gekweek onder lae-nutriënt, mikroob-vrye kondisies, bepaal met behulp van mikro-partikel geinduseerde X-straal emissie spektrofotometrie. Om die interpretasie van heterogene verspreidingspatrone van die onderskeie elemente te ondersteun, is daar met behulp van fluoressensie en transmissie-elektron-mikroskopie vir apoplastiese versperrings en endofitiese C. laurentii CAB 578 in die wortelweefsel getoets. Dit is bevind dat die gemiddelde konsentrasie van fosfaat, mangaan en yster beduidend (P < 0.05) hoër was in gis-geinokuleerde plante, as in kontrole plante. Die gis was nie ‘n wortel endofiet nie en elementale verryking in die epi/eksodermale-buitenste korteks weefsels het gekorreleer met Casparian bande in die eksodermale selle van beide behandelings. Hierdie was die eerste verslag wat die rol van ‘n grondgis as ‘n nutriënt-bekommende mikrosimbiont vir plante beskryf het. In die laaste gedeelte van hierdie ondersoek is die effek van C. laurentii CAB 578 op die fotosintetiese fosfaat, stikstof en water-verbruiksdoeltreffendheid, asook die koolstof ekonomie in mikroob-vrye Agathosma betulina plante geinokuleer met C. laurentii CAB 578 asook kontrole plante bestudeer. Die volgende parameters is getoets: Blaar donker respirasie, blaar fosfaat en stikstof konsentrasies, fotosintetiese fosfaatverbruiksdoeltreffendheid, fotosintetiese stikstof-verbruiksdoeltreffendheid, fotosintetiese water-verbruiksdoeltreffendheid, huidmond konduktansie, huidmond CO2 konsentrasie, klaarblyklike foton opbrengs, maksimum fotosintetiese spoed, wortel konstruksie-koste, en transpirasie spoed. Die resultate het getoon dat die hoër maksimum fotosintestiese spoed in gis-geinokuleerde plante gelei het tot ‘n hoër fotosintetiese verbruiksdoeltreffendheid van fosfaat, stikstof en water en dat dit nie verband gehou het met blaar fosfaat en stikstof konsentrasies nie. Dit word voorgestel dat die stimulasie van fotosintese in gisgeinokuleerde plante ‘n gevolg is van die verhoogde aanvraag na fotosintaat deur die giswortel simbiose. Om op te som, die bevindings van hierdie studie het bewys dat ‘n simbiose tussen A. betulina en C. laurentii CAB 578 bestaan. Hierdie simbiose het ‘n beduidende effek op die populasie grootte van die gis sowel as die fisiologie van die plant.

This study addresses methodological critiques of ethnicity research in organisations by combining intersectionality and identity work frameworks. Additionally, it extends intersectionality beyond its traditional focus on multiple disadvantage and demonstrates contextual sensitivity to ethnicity. Taking an individual constructivist stance, I examined ethnicity and its intersection with gender and seniority through an identity work lens. The research question was: How do senior black, Asian and minority ethnic women and men make meaning of episodes that raise the salience of their intersecting identities at work? The study investigated how 24 senior black, Asian and minority ethnic (BME) women and men constructed an understanding of their multiple-identified selves in response to affirming, contradictory or ambiguous identity-heightening work experiences. Respondents kept journals about episodes that raised the salience of their intersecting identities. Then, in interviews, they described the sense they made of the episodes and their responses to them. Following a template-based analysis of 101 accounts, a typology emerged of Accommodating, Refuting, Reconciling, Affirming and Exploratory identity work modes, describing senior BME individuals’ identity construction in response to identity-heightening episodes. I introduce ‘intersectional identity work’ to illustrate how individual (e.g. cognitive effort to reconcile a paradox), relational (e.g. a sense of responsibility and affinity for subordinate minority colleagues) and contextual (e.g. visibility resulting from demographic distribution in one’s immediate environment) factors influence intersecting senior, ethnic and gender constructions at work. Integrating intersectional and identity work perspectives to examine ethnicity demonstrates the dynamic interplay of multiple identity dimensions during meaning-making, the range of modes adopted and the intensity of effort expended by senior BME women and men during personal meaning-making. This approach makes a methodological contribution to ethnicity and intersectionality research. It also makes an empirical contribution to UK ethnicity and identity work research through the suggestive model of identity work modes and rich insight into senior BME individuals’ experiences at the juxtaposition of disadvantage and privilege.

The application of adaptive micro-electro-mechanical systems (MEMS) device in biologically-inspired cochlear model (cochlear biomodel) has been seen as a preferable approach to mimic closely the human cochlear response. The thesis focuses on the design and fabrication of resonant gate transistor (RGT) device applied towards the development of RGT cochlear biomodel. An array of RGT devices can mimic the cochlea by filtering the sound input signals into multiple electrical outputs. The RGT device consists of two main components; a) the MEMS bridge gate structure that transduces the sound input into mechanical vibrations and b) the channel with source/drain regions underneath the bridge gate structure that transduce the mechanical vibrations into electrical signals. The created mathematical model for RGT calculates the electrical outputs that are suited for neural spike coding. The neuromorphic auditory system is proposed by integrating the RGT devices with the spike event interface circuits. The novelty of the system lies in the adaptive characteristics of the RGT devices that can self-tune the frequency and sensitivity using the feedback control signals from the neuromorphic circuits. The bridge gates have been designed to cover the audible frequency range signals of 20 Hz - 20 kHz. Aluminium and tantalum have been studied as the material for the bridge gate structure. The fabrication of a bridge gate requires a gentle etch release technique to release the structure from a sacrificial layer. The downstream etch release technique employing oxygen/nitrogen plasma has been introduced and characterised. In the first iteration, aluminium bridge gates have been fabricated. The presence of tensile stress within aluminium had caused the aluminium bridge gates of length >1mm to collapse. In order to address this issue, tantalum bridge gates have been fabricated in the second iteration. Straight tantalum bridge gates in tensile stress and buckled tantalum bridge gates in compressive stress have been characterised. The frequency range of 550 Hz - 29.4 kHz has been achieved from the fabricated tantalum bridge gates of length 0.57mm - 5.8mm. The channel and source/drain regions have been fabricated and integrated with the aluminium or tantalum bridge gate structures to create the RGTs. In this study, the n-channel and p-channel resonant gate transistor (n-RGT and p-RGT) have been considered. In n-RGT, phosphorus ions are implanted to form the source/drain regions. High subthreshold currents have been measured from the n-RGTs. Thus, p- RGTs have been employed with considerably small subthreshold current. In p-RGT, boron ions are implanted to form the source/drain regions. The threshold voltage, transconductance and subthreshold current for both n-channel and p-channel resonant gate transistor devices have been characterised. In this work, the channel conductance of the n-RGT and p-RGT devices has been modulated successfully and the sensitivity tuning within the audible frequency range has been achieved from the tantalum bridge gates of the p-RGT devices. The characterisation and optimisation of the resonant gate transistor provide the first step towards the development of the adaptive RGT cochlear biomodel for the neuromorphic auditory system application.

The UK micro/SME (known here as SME) retail sector is very important to the economic well being of the country. Its ability to generate jobs as well as income makes it a key part of the drive towards economic growth, and as such it is supported by government through a variety of initiatives. One initiative in 2003 aimed to energise and invigorate practitioners into using internet based technologies more fully in their business practices. This supported the widely held belief that the internet can and does enhance and improve business efficiency. It also suggests that SMEs were not fully engaging with the technology and that the government felt that it was not at the desirable level. This thesis looks at the issues surrounding technology acceptance for the SME and in particular internet adoption in the retail sector. This work explains technology acceptance and the main determinants and moderators connected with this in an organisational setting providing the practitioner with insight into why some technologies are embraced and others underutilised, or not adopted at all. Previous academic work in this area has tended to focus on the larger organisation. This thesis uses the technology acceptance literature to explore the situation of the SME. Through qualitative and quantitative research the specifics of the SME situation relating to technology acceptance are explored with the determinants and moderators being evaluated and changes made where appropriate. The specific internet based technology of online procurement is used to measure levels of acceptance and the issues relating to it. The result is an adapted model that better reflects the technology acceptance situation of the SME retail organisation. In the model three of the original constructs remain, however the moderators have been changed to reflect the SME and the relationships the constructs have with the moderators are also developed. As a new addition to the field it can be seen from the developed model that the frequency of re-ordering is an important determinant not only of online procurement but technology acceptance in general. This work will benefit practitioners in SME retail and also the wider SME field when it comes to evaluating whether or not to accept a new technology and how this is best achieved.

Ingeniero Civil Eléctrico / En el presente trabajo se propone un modelo de matemático de optimización maestro-esclavo entre un despacho económico (maestro), retroalimentado con un análisis de estabilidad de pequeña señal (esclavo). El modelo propuesto determina si una solución, determinada mediante una optimización algebraica (maestro), es estable (o no) mediante el cálculo de sus valores propios (esclavo) e itera hasta encontrar una solución que es tanto económica como estable. El método consiste en definir un problema maestro como etapa de optimización económica, caracterizada por un modelo de flujo optimo convencional (OPF, por su nombre en inglés: Optimal Power Flow), mientras que el problema esclavo o etapa de estabilidad es el encargado de determinar las ganancias de control droop (de cada unidad de generación conectada mediante un conversor) para estabilizar el despacho obtenido por el problema maestro. Si dicho despacho no puede ser estabilizado, entonces se itera insertando una restricción (o corte ) de factibilidad en el maestro hasta obtener una solución de mínimo costo (de forma local) que sea estable en pequeña señal. Se proponen dos versiones del modelo dependiendo si el maestro corresponde a un DC-OPF o uno AC-OPF. Dichas formulaciones son testeadas con micro-redes de dos y tres micro-fuentes. Esta tesis demuestra que estas formulaciones resuelven exitosamente el despacho coordinado (definiendo tanto la inyección de las unidades en potencia activa y reactiva, como las ganancias de los controladores) para sistemas de dos y tres micro-fuentes. Más aún, en el problema de dos micro-fuentes, la aproximación DC-OPF resulta completamente convexa por lo que la solución encontrada corresponde a un óptimo global.

La lumière comprimée est un état du champ électromagnétique pour lequel le bruit, mesuré selon une certaine quadrature est inférieur au bruit du vide. Dans cet ouvrage, nous étudions la possibilité de générer de la lumière micro-onde à partir d’un transistor à effet de champ commercial. D’une part, nous observons le bruit de grenaille du canal drain-source à basse fréquence, ce qui suggère que le canal est cohérent. Ensuite, nous exploitons cette cohérence et procédons à une expérience standard de compression par le bruit de grenaille. D’autre part, nous prédisons, à l’aide d’un modèle simple, la possibilité de comprimer le bruit par modulation de la résistance du canal drain-source pour des mesures de bruit à hautes fréquences. Nous concluons en proposant une mise en œuvre de cette méthode.

Tesis para optar al grado de Magíster en Economía / This research describes price-setting over time and across items in Chile, an emerging market economy. The microeconomic database underlying the consumer price index (CPI) is used to characterize microeconomic pricing behavior, and to study its implications for the transmission of monetary policy to the real economy. Prices are found to be relatively flexible at a microeconomic level, in contrast to macroeconomic findings. Price changes are also mainly small and quite synchronized, and display a decreasing hazard rate. An evaluation of the relevance of microeconomic price data moments for forecasting aggregate inflation finds that the frequency of price increases and decreases, and their respective absolute magnitudes-which can only be computed from disaggregated data-can significantly improve on inflation forecasting based solely on aggregate variables.

Context. In recent years there is a rapid increase in demand for cloud services, as cloud computing has become a flexible platform for hosting micro services over the Internet.~Micro services are the core elements of service oriented architecture (SOA) that facilitate the deployment of distributed software systems.  Objectives. This thesis work aims at developing a typical service architecture to facilitate the deployment of compute and I/O intensive services. The thesis work also aims at evaluating the service times of these services when their respective sub services are deployed in heterogeneous environments with various loads. Methods. The thesis work has been carried out using an experimental test bed in order to evaluate the performance. The transport level performance metric called Response time is measured. It is the time taken by the server to serve the request sent by the client. Experiments have been conducted based on the objectives that are to be achieved. Results. The results obtained from the experimentation contain the average service times of a service when it is deployed on both virtual and non-virtual environments. The virtual environment is provided by Docker containers. They also include the variation in the position of their sub services. Conclusions. From results, it can be concluded that the total service times obtained are less in the case of non-virtual environment when compared to container environment.

At the rate the population is growing it is important to find ways to be more efficient with the energy and water we use. The increase in population increases the need for electricity and water, but the way we are using our sources will not leave us with enough for future generations. The constant use of "dirty energy", energy that emits CO2 and other chemicals into the atmosphere, will continue to harm our environment. A new system is needed to help preserve water and produce green energy that will not harm the only earth we have.