Cytochromes P450 represent a large group of proteins metabolizing variety of substrates. Many of them are responsible for metabolism of xenobiotics including drugs and chemical carcinogens. Heme-protein cytochrome b5 is a single-electron donor cooperating with a NADPH:cytochrome P450 reductase and NADH:cytochrome b5 reductase 3 enzyme. Cytochrome b5 can affect the xenobiotic metabolism via modulation of the cytochromes P450 activity. One of the goals of the Ph.D. thesis was to utilize site directed mutagenesis of cytochromes P450 family 1 to elucidate the mechanism of their nitroreductase activity. Another aim was to study the interaction between cytochrome b5 and cytochromes P450 of the 1A subfamily using site directed mutagenesis on presumed protein-protein contact interface. Another goal was to utilize the combination of theoretical and experimental approaches to explain variance in the reduction state of several human cytochromes P450 heterologously expressed in intact bacterial cells. The results found in the thesis show that nitroreductase activity of CYP1A1, CYP1A2 and CYP1B1 is mediated by the presence of a particular hydroxyl group in their active centre. Single mutation introducing a hydroxyl group to the specific part of CYP1B1 active site to the active site turned on its artificial...

Curiosity can be defined as a drive to engage in exploratory behaviors and has been associated with an increased state of arousal (Berlyne, 1954). Exploratory behaviors, such as feedback requests, are associated with an information gain and the reduction of uncertainty. Although previous research has demonstrated the effects of emotions on the value of information gain (Marvin & Shohamy, 2016), and that the manipulation of arousal affected confidence (Allen et al., 2016) suggesting uncertainty can be affected independent of task difficulty, no previous study independently manipulated arousal to test its effect on curiosity. Given the effects of curiosity on motivation and learning, understanding how arousal influence curiosity would be beneficial for applications in fields such as education. In the present study, we hypothesized that emotionally-induced arousal has an impact on curiosity by influencing uncertainty and the value of information gain. A sample of 17 students were presented with arousing supraliminal emotional cues prior to rating confidence about their answers to trivia questions and deciding on feedback choices. Feedback requests were associated with a time delay, in a way that participants were required to trade off time for information. Results showed that uncertainty levels did not reliably predict feedback choices. Further analyses failed to demonstrate an effect of arousal on feedback choices. Finally, the pupillary response to events suggested that arousal levels did not differ significantly across conditions. Results can be due to the small sample or the test sensitivity. Possible improvements to the experimental paradigm are discussed, and directions for future research are considered.

Doctor of Philosophy / Department of Curriculum and Instruction / Jacqueline D. Spears / The purpose of this study was to investigate the relationship between demographic and educational variables, epistemological beliefs as measured by Schommer’s Epistemological Questionnaire (SEQ), and learner perception of selfdirectedness as measured by Guglielmino’s Self-Directed Learning Readiness Scale (SDLRS). Participants in this study were undergraduate adult students at a private university in the Midwest region of the United States (N=394). The instruments were administered online during regularly scheduled courses. Data were analyzed at the p<.05 level of significance using Pearson product-moment correlations, factor analysis, stepwise multiple regression, and other statistical techniques. Results of this research included several significant correlations between demographic and educational variables, SEQ factors, and SDLRS total and factor scores. The educational variables of class standing, exposure to the humanities, and exposure to the social sciences significantly correlated with five SDLRS and SEQ total and factor scores. The greatest number of correlations occurred between SEQ factor 2, thinking for yourself is a waste of time, and the SDLRS factors of openness to learning opportunities, view of self as an effective and independent learner, independence and initiative in learning, responsibility for learning, and creativity. Other significant correlations with SEQ factors and SDLRS total and factor scores included age, gender, race, marital status, mother’s and father’s education level, credit earned through independent studies, cohort or non-cohort program type, grade point average, and exposure to learning contracts. Significant findings from the correlations of demographic and educational variables (p<.002) and SEQ factors (p<.05) with SDLRS total scores were entered into a stepwise multiple regression. One educational variable and three SEQ factors accounted for 25.7% of the variance in SDLRS total scores. Several suggestions for the development of expanded empirical and theoretical research initiatives and the improvement of practice were offered. This research provided a clear and compelling rationale for the establishment of adult degree programs which are grounded in the liberal arts, include both career and personal development activities, and allow for increased opportunities for learner self-direction to occur. These elements are necessary to build what Kegan (1994) called a developmental bridge for adult learners.

Die generative Fertigung stellt eine Schlüsseltechnologie der Zukunft für weite Teile der Wirtschaft dar. Der Prozess des Plasma-Pulver-Auftragschweißens soll eine Lücke im bestehenden Portfolio an generativen Prozessen schließen. Zunächst wurde der klassische Beschichtungsprozess an die Erfordernisse der generativen Fertigung angepasst. Im Ergebnis konnten Bauteile, welche aus bis zu vier verschiedenen Materialen bestehen können, prozesssicher generiert werden. Die anschließende Betrachtung des Einflusses der Systemparameter auf das Bauteil ergab, dass die Haupteinflussgrößen auf die Bauteilgeometrie die Schweißstromstärke, die Schweißgeschwindigkeit, der Pulvermassestrom sowie die Plasmagasmenge sind. Die Bauteildichte sowie der Pulverausnutzungsgrad zeigen keine signifikanten Änderungen innerhalb des hier betrachteten Bereiches. Im Mittel konnte eine relative Bauteildichte von 98,7 % und ein Materialausnutzungsgrad von 77 % bestimmt werden. In Summe ist der Prozess durch eine stabile Auftragscharakteristik mit mindestens vergleichbaren Eigenschaften zu bestehenden Systemen zu bewerten und sehr gut als generativer Prozess, insbesondere für die Herstellung von mehrkomponentigen Bauteilen, geeignet. / Additive manufacturing is one of the key technologies of the future for large parts of the economy. The process of plasma powder deposition welding is intended to close a gap in the existing portfolio of generative processes. First, the classical cladding process was adapted to the requirements of additive manufacturing. As a result, components, which can consist of up to four different materials, could be reliably generated. The subsequent consideration of the influence of the system parameters on the component showed that the main influencing variables on the part geometry are the welding current, the welding speed, the powder flow rate and the plasma gas volume. The component density as well as the powder utilization rate show no significant changes within the range considered here. On average, a relative component density of 98.7 % and a material utilization rate of 77 % could be determined. In sum, the process can be characterized by a stable application characteristic with at least comparable properties to existing systems and is very well suitable as an additive manufacturing process, especially for the production of multi material components.

Under senare år har omfattande insatser gjorts för att främja mer hållbara flygtransporter i Europa. De konventionella tillverkningsmetoderna som används inom flyg- och rymdindustrin kräver betydande mängder råmaterial, vars utvinning, bearbetning och användning har negativa miljöeffekter. Därför finns det ett starkt incitament att utveckla nya, mer material-effektiva tillverkningsmetoder. Additiv tillverkning (AM), även känd som 3D-printining, har fördelen att direkt komma nära den slutliga formen på strukturer genom att lägga till material endast där det behövs, något som minimerar spill och förbättrar materialanvändningen. Dock utgör införandet av AM komponenter i säkerhetskritiska flyg- och rymdtillämpningar en betydande utmaning på grund av komplexiteten hos processerna. Denna komplexitet kan leda till tillverkningsvariationer som i sin tur kan resultera i defekter i de tillverkade strukturerna. Därför är framsteg inom automation genom utvecklingen av lösningar för övervakning och styrning under processens gång ett nödvändigt steg för att uppnå tillräcklig pålitlighet och repeterbarhet. Denna avhandling presenterar en utveckling av multisensorövervakning och styrning av Directed Energy Deposition (DED) med en laservärmekälla (LB). DED-LB är en avancerad teknik som möjliggör tillverkning av storskaliga metallkomponenter nära den slutliga formen. I detta arbete har lösningar undersökts för övervakning av DED-LB med tillsatspulver och tråd. För fallet med tillsatstråd kan denna kompletteras med resistiv förvärmning (så kallad hotwire), vilket ger möjlighet att ytterligare finjustera värmetillförseln och förbättra smältprocessen. För övervakningsändamål undersöktes tre olika in-situtekniker för processens stabilitet och varians. Maskinseende och elektriska givare användes för DED-LB med tillsatstråd (DED-LB/w), medan optisk spektroskopi användes för övervakning både av processen med tillsatspulver (DEDLB/p) samt med tråd. Ett multisensorsystem baserat på de tre teknologierna testades för DED-LB/w. Det kamerabaserade systemet gav tydliga indikationer på avvikelser från nominella processförhållanden. Spännings-och strömgivarnas signaler korrelerade med förändringar i processparametrar och återspeglade tydligt metallöverföringen. Spektrometersystemet indikerade förändringar relaterade till värmeöverföringen. Dessutom möjliggjorde analysen av erhållna spektra en detektering av förluster av viktiga legeringselement under DED-LB/p. Slutsatsen från resultaten understryker behovet av multisensorövervakning, eftersom det inte bara möjliggör detektering och skattning av processförändringar utan även en bättre förståelse av deras grundorsaker. Den presenterade ansatsen är ett viktigt bidrag i utvecklingen av ett framtida robust och feltolerant automatiskt styrsystem. / In recent years, an extensive effort has been made to leap European aviation towards more sustainable transportation. Conventional manufacturing methods used in aerospace industry require significant amounts of raw materials, whose extraction, processing, and utilization have adverse environmental impacts. Thus, there is a strong motivation to develop novel, more material efficient fabrication methods. Additive Manufacturing (AM), also known as 3D-printing, offers the advantage of manufacturing near-net-shape structures by adding material only where it is needed, minimizing waste, and improving material efficiency. However, introducing AM fabricated structures as components in safety-critical aerospace systems poses a significant challenge due to the inherent complexity of AM processes. This complexity can result in variations that may lead to defects or inconsistencies in the fabricated structures. Thus, increasing automation by developing in-process monitoring, and control solutions is the vital step to reach the necessary reliability and repeatability. This thesis presents development towards multi-sensor monitoring and control of Directed Energy Deposition (DED) using a Laser Beam (LB). DED-LB is an advanced technology that allows to manufacture large-scale, near-net-shape metallic parts. In this work, in-process monitoring solutions for DED-LB with feedstock powder and wire were investigated. The set-up of the latter was complemented by resistive pre-heating of the feedstock wire (hot-wire) which provided means of fine-tuning the heat input and improving metal fusion. Formonitoring purposes, three different in-situ techniques were investigated to monitor process stability and variability. Machine vision and electrical sensing were utilized during DED-LB with feedstock wire (DED-LB/w) depositions,while optical emission spectroscopy was used for monitoring processes with feedstock powder (DED-LB/p) as well as wire. A multi-sensorsystem based on the three sensing technologies was tested during DED-LB/w depositions. The vision system gave clear indications of variations from nominal conditions. Voltage and current sensors indications correlated to changes in process parameters and reflected well the metal transfer (liquid bridge) condition.The spectrometer system indicated well changes related to heat input. In addition, analysis of obtained spectra allowed to detect losses of vital alloying element during DED-LB/p. The main conclusion from the results underlines the need for simultaneous multi-sensor monitoring as it allows not only to detect and estimate process changes but also to better interpret their root causes. Such setup will positively enable a future robust, fault tolerant control system. / <p>Paper 3 is under acception but included in this thesis with CC BY-license.</p>

Consumer Studies is a valuable and multifaceted subject in South African schools, requiring that teachers in the subject are well prepared. Pre-service Consumer Studies teachers need to be prepared to become lifelong learners to cope with the dynamic nature of the subject, as well as to develop various 21st century skills to be able to deal with the demands of these times. Structured guidance, however, could not be uncovered for the preparation of pre-service Consumer Studies teachers to empower them with the requirements for Consumer Studies education. Sett-directed learning is a process that supports the developn1ent of various 21st century skills, including lifelong learning, and could thus contribute to the development of preservice Consumer Studies teachers, if included in their preparation. A suitable teaching-leaming strategy that could be utilised in the preparation module for Consumer Studies teachers, as well as a vehicle to promote self-directed learning as part of such preparation, was identified in the form of project-based learning. A qualitative case study was employed to investigate how project-based learning as a teaching-learning strategy could promote self-directed learning in a pre-service Consumer Studies teacher preparation module. Project-based learning was found to foster the development of various skills as part of the process, including planning and collaboration skills. Subject content, consistent with what is required to be taught in Consumer Studies education on high school level, was developed and self-directed learning was promoted in participants using project-based learning. Recommendations were suggested for the preparation of pre-service Consumer Studies teachers, as well as for the effective structuring of projects and project-based learning in Consumer Studies. / MEd (Curriculum Development), North-West University, Potchefstroom Campus, 2015

Consumer Studies is a valuable and multifaceted subject in South African schools, requiring that teachers in the subject are well prepared. Pre-service Consumer Studies teachers need to be prepared to become lifelong learners to cope with the dynamic nature of the subject, as well as to develop various 21st century skills to be able to deal with the demands of these times. Structured guidance, however, could not be uncovered for the preparation of pre-service Consumer Studies teachers to empower them with the requirements for Consumer Studies education. Sett-directed learning is a process that supports the developn1ent of various 21st century skills, including lifelong learning, and could thus contribute to the development of preservice Consumer Studies teachers, if included in their preparation. A suitable teaching-leaming strategy that could be utilised in the preparation module for Consumer Studies teachers, as well as a vehicle to promote self-directed learning as part of such preparation, was identified in the form of project-based learning. A qualitative case study was employed to investigate how project-based learning as a teaching-learning strategy could promote self-directed learning in a pre-service Consumer Studies teacher preparation module. Project-based learning was found to foster the development of various skills as part of the process, including planning and collaboration skills. Subject content, consistent with what is required to be taught in Consumer Studies education on high school level, was developed and self-directed learning was promoted in participants using project-based learning. Recommendations were suggested for the preparation of pre-service Consumer Studies teachers, as well as for the effective structuring of projects and project-based learning in Consumer Studies. / MEd (Curriculum Development), North-West University, Potchefstroom Campus, 2015

The theory of self-leadership is gaining credibility and support in the era of globalisation and knowledge workers. As with many leadership theories, culture has been proposed to have a major impact on leadership processes. The purpose of this study was to determine the extent that self-leadership is correlated with national culture dimensions. Self-leadership was measured through the Revised Self-Leadership Questionnaire developed by Houghton and Neck (2002). The cultural values were measured through the use of Hofstede’s Value Survey Module 94 (VSM94). Hypotheses were formed regarding relationships between national culture background and Self-leadership practice. Pearson r, Chi-square test with cross tabulation and multiple regression were used to determine the associations. The results from the statistical tests showed associations between national culture values and self-leadership dimensions. PDI and UAI showed a positive relationship with visualising successful performance but a negative relationship with self-talk both aspects of constructive thought pattern strategies. MAS had a positive relationship with self-talk while negatively correlated to visualising successful performance. IDV had positive relationships with behaviour-focussed strategies, natural reward strategies and constructive thought pattern strategies. Long-term orientation had a strong negative relationship with behaviour-focussed and natural reward strategies and a very weak negative association with behaviour focussed strategies. / Graduate School of Business Leadership / M.B.L.

Note from the Library: The fulltext electronic version of this thesis has been removed due to restricted content. Please contact the Unisa Library for more details. / Industrial and Organisational Psychology / M.A. (Industrial Psychology)

Escherichia coli possède une grande plasticité génomique comme en témoigne la diversité des souches à l’intérieur de cette espèce bactérienne. Bien que la majorité des souches soient inoffensives ou à tout le moins opportunistes, plusieurs ont acquis des facteurs de virulence spécifiques leur procurant un pouvoir pathogénique. Les souches pathogènes comme E. coli O157 :H7 sont responsables de cas de morbidité, mortalité et pertes économiques importantes dans l’industrie agro-alimentaire dans le monde entier. L’évolution bactérienne est un mécanisme continuel qui se fait via l’échange d’éléments génétiques mobiles, de mutations ponctuelles et autres réarrangements génétiques. Ces changements génétiques peuvent procurer des avantages sélectifs permettant une adaptation bactérienne rapide face aux stress et changements environnementaux et favorisant le développement de pathogènes émergents. Dans la première partie de ce projet, nous avons étudié la région intergénique mutS-rpoS, qui est une des plus grandes sources de polymorphisme chromosomique chez les entérobactéries. Notre analyse génomique comparative a permis de confirmer le polymorphisme à l’intérieur même d’un ensemble de souches Escherichia spp., Salmonella spp. et Shigella spp. De plus, nous avons pu confirmer que certains types de polymorphismes dans la région mutS-rpoS étaient fortement associés à certains types de pathogènes chez E. coli. Dans notre analyse, nous avons ressorti un groupe de gènes à l’intérieur de la région mutS-rpoS qui pourraient sevir comme marqueur chromosomique intéressant pour les E. coli extra-intestinaux (ExPEC), un groupe comprennant des souches hautement pathogènes et difficiles à définir par les tests actuelllement disponibles. Dans notre analyse bio-informatique, nous avons isolé ce groupe de gènes associé aux ExPEC et nous l’avons caractérisé in sillico. Nous avons également inclus dans l’analyse deux souches hypermutables du genre Escherichia spp. de notre collection, isolées d’animaux de ferme. L’hypermutabilité ou la capacité d’acquérir des mutations plus rapidement que la normale accélère le processus d’évolution et la capacité d’adaptation de ces souches. La région mutS-rpoS est reliée au système de réparation de l’ADN bactérien (MMRS) et pourrait être impliquée dans l’apparition du phénotype d’hypermutabilité. Durant les dernières années, de plus en plus d’espèces du genre Escherichia ont été isolées de cas cliniques d’animaux et d’humains. Ces souches atypiques ont un potentiel de virulence très élevé, des combinaisons de gènes de virulence et des variants génétiques différents des souches typiques, et certaines souches ont même évolué en tant que pathogènes. Les souches de l’espèce E. albertii ont été isolées récemment et ont un grand potentiel de virulence autant chez les humains que chez les oiseaux. Ces souches sont souvent confondues avec d’autres organismes pathogènes comme E. coli dans les tests biochimiques, et le manque de connaissances sur E. albertii rend son identification difficile. Dans la deuxième partie de ce projet, nous avons identifié des gènes spécifiques aux souches d’E. albertii ainsi que des gènes de virulence présents chez E. albertii par comparaisons génomiques, ce qui a permis de développer et optimiser un test PCR (réaction en chaîne par polymérase) visant l’identification génomique rapide et fiable d’E. albertii.