Development and assessment of a smart thermosetting intranasal hydrogel for lamotrigine
- Authors: Melamane, Siyabonga
- Date: 2018
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62975 , vital:28349
- Description: Expected release date-April 2020
- Full Text:
- Date Issued: 2018
Development and assessment of gastroretentive sustained release captopril micro-balloons
- Authors: Oridota, Omoyosola Omolola
- Date: 2018
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63491 , vital:28419
- Description: Expected release date-April 2020
- Full Text:
- Date Issued: 2018
Development and evaluation of a web application employing artificial neural networks to facilitate the prediction of antiretroviral drug resistance in patients infected with HIV-1 subtype B
- Authors: Nabatanzi, Margaret
- Date: 2018
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63396 , vital:28406
- Description: Expected release date-April 2019
- Full Text:
- Date Issued: 2018
Development and evaluation of the coach-athlete relationship enhancement intervention
- Authors: Kuit, Wim
- Date: 2018
- Subjects: Interpersonal relations , Coaching (Athletics) -- Psychological aspects Sports -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/22508 , vital:29989
- Description: An expanding body of sport psychology theory and research has highlighted the central role of the coach-athlete relationship (CAR) in the performance, satisfaction and well-being of coaches as well as athletes. Models have been developed that identify the key dimensions of CAR quality and the interpersonal behaviour that maintains it, but there remains a need for interventions that support coaches and athletes to optimise their interpersonal skills. This can be done by harnessing recent advances in personality theory which emphasise a more holistic and developmental view of the person and provide a basis for greater mutual understanding and adaptive interpersonal behaviour change in the CAR. The aims of this study were to develop the Coach-Athlete Relationship Enhancement (CARE) intervention through an integration of the Enneagram personality typology with current models of the CAR, and then to evaluate the impact of the CARE intervention on CAR quality. Sixty-two university-level athletes and their nine coaches participated in the study. Quantitative and qualitative results indicate that the CARE intervention significantly enhanced CAR quality, including direct and meta-perceptions of closeness, commitment and complementarity, as well as co-orientation. Intervention outcomes included enhanced mutual understanding in the CAR, enhanced self-awareness, enhanced team relationships, and adaptive interpersonal behaviour change. These outcomes were associated with a shared awareness between coaches and athletes of their Enneagram personality type traits and motivations. Coach-athlete relationship quality was further enhanced by re-constructing coaches’ and athletes’ personal narratives based on self-descriptions of Enneagram type strengths, and a redefinition of individuals’ core motivations to incorporate adaptive interpersonal behaviour change.
- Full Text:
- Date Issued: 2018
Development and optimisation of a novel Plasmodium falciparum Hsp90-Hop interaction assay
- Authors: Wambua, Lynn
- Date: 2018
- Subjects: Plasmodium falciparum , Molecular chaperones , Heat shock proteins , Protein-protein interactions , Antimalarials
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62626 , vital:28216
- Description: Protein-protein interactions are involved in a range of disease processes and thus have become the focus of many drug discovery programs. Widespread drug resistance to all currently used antimalarial drugs drives the search for alternative drug targets with novel mechanisms of action that offer new therapeutic options. Molecular chaperones such as heat shock proteins facilitate protein folding, play a role in protein trafficking and prevent protein misfolding in cells under stress. Heat shock protein 90 (Hsp90) is a well-studied chaperone that has been the focus of cancer drug development with moderate success. In Plasmodium falciparum (P. falciparum), heat shock proteins are thought to play a vital role in parasite survival of the physiologically diverse habitats of the parasite lifecycle and because Hsp90 is prominently expressed in P. falciparum, the chaperone is considered a potentially ideal drug target. Hsp90 function in cells is regulated by interactions with co-chaperones, which includes Heat shock protein 70-Heat shock protein 90 organising protein (Hop). As opposed to directly inhibiting Hsp90 activity, targeting Hsp90 interaction with Hop has recently been suggested as an alternative method of Hsp90 inhibition that has not been explored in P. falciparum. The aim of this research project was to demonstrate PfHsp90 and PfHop robustly interact in vitro and to facilitate high-throughput screening of PfHsp90-PfHop inhibitors by developing and optimising a novel plate capture Hsp90-Hop interaction assay. To establish the assay, the respective domains of the proteins that mediate Hsp90-Hop interaction were used (Hsp90 C- terminal domain and Hop TPR2A domain). The human Hsp90 C-terminal domain and glutathione-S-transferase (GST) coding sequences were cloned into pET-28a(+) and murine and P. falciparum TPR2A sequences into pGEX-4T-1 plasmids to enable expression of histidine-tagged and GST fusion proteins, respectively, in Escherichia coli. The P. falciparum Hsp90 C-terminal domain sequence cloned into pET-28a(+) was supplied by GenScript. The constructs were transformed into T7 Express lysYcompetent E. coli cells and subsequent small- scale expression studies showed the recombinant proteins were expressed in a soluble form allowing for subsequent protein purification. Purification of the recombinant proteins was achieved using nickel-NTA and glutathione affinity chromatography for the His-tagged (Hsp90 C-terminal domains and GST) and GST fusion proteins (TPR2A domains), respectively. The purified proteins were used to establish and optimise mammalian and P. falciparum Hsp90- Hop interaction assays on nickel-coated plates by immobilising the His-tagged C-terminal domains on the plates and detecting the binding of the GST-TPR2A domains using a colorimetric GST enzyme assay. Z’-factor values above 0.5 were observed for both assays indicating good separation between the protein interaction signals and negative control background signals, although relatively high background signals were observed for the mammalian interaction due to non-specific binding of murine TPR2A to the plate. Designed human and P. falciparum TPR peptides were observed to be effective inhibitors of the mammalian and P. falciparum interactions, demonstrating the assay’s ability to respond to inhibitor compounds. Comparison of assay performance using GST assay kit reagents and lab- prepared reagents showed the assay was more efficient using lab-prepared reagents, however, lower GST signals were observed when comparing assay performance using a custom prepared Ni-NTA plate to a purchased Ni-NTA plate. The Hsp90-Hop interaction assays were also performed using an alternative assay format in which the GST-TPR2A fusion proteins were immobilised on glutathione-coated plates and binding of the His-tagged C-terminal domains detected with a nickel-horseradish peroxidase (HRP) conjugate and a colorimetric HRP substrate. The assay showed higher interaction signals for the P. falciparum proteins but comparatively low signals for the mammalian proteins. Z’-factor values for the assay were above 0.8 for both protein sets, suggesting this assay format is superior to the GST assay. However, further optimisation of this assay format is required. This study demonstrated direct binding of PfHsp90-PfHop in vitro and established a novel and robust PfHsp90-PfHop interaction assay format that can be used in future screening campaigns.
- Full Text:
- Date Issued: 2018
Development and validation of a health literacy measure for limited literacy public sector patients in South Africa
- Authors: Marimwe, Chipiwa
- Date: 2018
- Subjects: Health literacy -- South Africa , Patient education -- South Africa , Communication in medicine -- South Africa , Health literacy -- Social aspects -- South Africa , Poor -- Medical care -- South Africa , Analysis of variance , Multidimensional Screener of Functional Health Literacy (MSFHL)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62661 , vital:28227
- Description: The growing complexity of healthcare demands greater patient involvement and skills to navigate this complex system. It has therefore become increasingly important to identify individuals with inadequate health literacy, by using efficient, short and reliable measures for doing so. Most research on the development and validation of health literacy tests has been conducted in high-income countries, with very little reported from low-and middle-income countries (LMICs). Existing health literacy measures have come under scrutiny for their lack of cultural sensitivity, bias towards certain population groups and failure to acknowledge health literacy as a multidimensional concept. These measures usually have limited application in LMICs due to the significantly different structuring of healthcare systems, they overlook the extreme discrepancies in educational levels, and rely too heavily on the ability to read health information. No health literacy data for South Africa are available, and only a few health literacy-based research papers have been published in this country. The aim of the study was to develop and validate a health literacy measure that is contextually and culturally appropriate to measure health literacy in limited literacy public sector patients in South Africa. An Item Bank of 30 questions was developed with the input of a diverse expert consultant panel, and included skills-based and self-reported questions which ensured cultural, contextual and educational level appropriateness. The Information and Support for Health Actions Questionnaire (ISHA-Q) is a health literacy measure developed to assess health literacy for LMICs which includes 14 core scales. These were useful in ensuring coverage of a range of health literacy constructs within the Item Bank. The 30 questions were then allocated to one of three health literacy domains: Procedural knowledge, Factual knowledge and Access to healthcare, health services and social support. Ethical approval for the study was obtained. The questions were translated into isiXhosa and underwent pilot testing. Following pilot testing, 120 isiXhosa first-language speakers, at least 18 years old, who attended public sector facilities and had a maximum 12 years of education were recruited from a primary healthcare clinic in Grahamstown. An interpreter was trained and he participated in all interviews. A questionnaire was used to collect data on the 30-question Item Bank. The Multidimensional Screener of Functional Health Literacy (MSFHL) was used as the primary comparator.The second phase of the study involved the refinement of the 30 questions in the Item Bank, which involved a multi-stage process. Data were analysed statistically using t-test, correlations, chi-square and ANOVA tests at a 5% level of significance, in order to identify problematic questions. Item Response Theory was used to ascertain difficulty and discriminatory ability of the questions. Each question was further subjected to in-depth interrogation by a panel of healthcare professionals to ensure that questions were supported by the conceptual framework and the definitions of health literacy adopted for this study. The number of questions was reduced from 30 to 12, and formed the new Health Literacy Test - Limited Literacy (HELT-LL). To validate the HELT-LL, 210 patients with the same inclusion criteria as previously noted, were recruited from four primary healthcare clinics in the Eastern Cape Province. Individual interviews were conducted with the assistance of the interpreter to collect sociodemographic data as well as data from the HELT-LL, the primary comparator (MSFHL), and a secondary comparator which was a South African modified version of the Newest Vital Sign (NVS-SA). The HELT-LL was re-administered to 40 patients in a follow-up interview two weeks later. The HELT-LL categorised only 17.6% of the patients as having adequate health literacy, just over a third with inadequate health literacy, and the majority with marginal health literacy. Questions in the cognitively demanding Procedural knowledge domain were the most poorly answered, with a mean score of 48.6±24.9%. Patients had great difficulty performing the basic numeric tasks in this domain. The overall mean score for the HELT-LL was 52.8±18.4%, compared with the more cognitively demanding NVS-SA with a mean of 28.6±21.1%, and clearly illustrated the impact of the strategy to include in the HELT-LL a variety of questions with differing cognitive load. The MSFHL, which is based on demographic characteristics and perceived difficulties with reading and writing, had an overall mean score of 44.4±26.2%. Demographic characteristics including age, education and English literacy, were found to be good predictors of limited health literacy, with significant correlations being found between these variables and the mean HELT-LL score. An acceptable value for Cronbach’s alpha, excellent test-retest reliability and excellent concurrent validity show that the HELT-LL is a valid and reliable measure of health literacy in our target population. As there is a paucity of health literacy research emanating from developing countries, this study presents a significant contribution to literature. It is the first study to report the development and validation of a health literacy measure to address the dearth of available health literacy measures applicable for South Africa. If implemented for use in clinical settings and for research purposes, it could provide valuable South African health literacy data which could inform the development of interventions focusing on improving health literacy and health outcomes.
- Full Text:
- Date Issued: 2018
Development of a community pharmacy experiential learning programme in a South African context: a design research approach
- Authors: Kritiotis, Lia Costas , Thesis Advisor
- Date: 2018
- Subjects: Pharmacists -- Training of , Experintial training , Community development -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/17481 , vital:28353
- Description: Application of the design research approach to devise, develop and optimise an experiential learning programme and adaptation of the Volunteer Functions Inventory (VFI) to understand community pharmacists’ motives, are unique contributions to the global pharmacy education setting. This study generated new theory, in the form of substantive and procedural claims (design principles) regarding experiential learning programmes and preceptor and student motivation in a South African pharmacy educational context, which can be added to the existing international landscape and more importantly, plant the foundational seeds of insight that can be utilised as guiding tools by other South African pharmacy faculties.
- Full Text:
- Date Issued: 2018
Development of a computational chemistry scheme for testing the utility of synthetic bacteriochlorin in dye-sensitized solar cells
- Authors: Kota, Ntsika
- Date: 2018
- Subjects: Dye-sensitized solar cells , Computational chemistry , Density functionals , Electronic excitation , Molecular orbitals , Oscillator strengths , Bacteriochlorin
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62327 , vital:28155
- Description: A computational chemistry scheme, based on density functional theory, was developed for in silico testing of a few bacteriochlorin properties relevant to dye-sensitized solar cells. These properties included electronic excitation wavelengths, molecular orbital energy levels, and oscillator strengths among others. Comparisons were made among four species, using computational proxies for electron injection quantum yield and photo-induced current production. The proxy measures for current production (frontier orbital energy level and short circuit current) made consistent, though qualitative, predictions about the ranking of the four dyes. The proxy measures for electron injection quantum yield (change in planar dipole moment and density of states) made less categorical predictions about the ranking. Overall, the scheme singled out one dye as the worst, but made no conclusive predictions about the relative ranking of the other three. There was insufficient data for comparison of the ranking predictions with experiment.
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- Date Issued: 2018
Development of a low-cost bioprinting system for the fabrication of cell-laden sodium alginate hydrogels
- Authors: Honiball, John Robert
- Date: 2018
- Subjects: Regenerative medicine , Tissue engineering , Alginates , Colloids , Three-dimensional printing
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59204 , vital:27470
- Description: Bioprinting is a rapidly expanding technology with the ability to fabricate in vitro 3D tissues in a layer-by-layer manner to ultimately produce a living tissue which physiologically resembles native in vivo tissue functionality. Unfortunately, large costs associated with commercially available bioprinters severely limit the amount of people/research groups with access to the technology. Here, we investigated the potential for modifying a commercially available RepRap Prusa iteration 3 (i3) three-dimensional (3D) printer, by replacing the traditional plastic-based print-head with various open-source syringe-housed microextrusion print-head units, such that deposition of composite bioinks consisting of cells, biopolymer scaffolds and/or biomolecules may be achieved at a relatively low cost. Using adipose-derived human mesenchymal stromal stem cells (ad-HMSC) induced for adipogenic differentiation, as well as human umbilical vein endothelial cells (HUVEC), the potential for fabricating vascularised adipose tissue was investigated. The non-toxic, inexpensive algal polysaccharide, sodium alginate, was used to test the printability of the system, as well as for investigating the functionality unmodified sodium alginate has for use as a potential bioink in adipose tissue engineering. Cell viability assays, namely WST-1 and fluorescein diacetate (FDA)/propidium iodide (PI) live/dead cell staining, revealed that ad-HMSC were viable after 7 days of culture. However, viability of HUVEC encapsulated hydrogels revealed significantly lower cell viability. Live/dead cell staining revealed that the modified printing system was able to print ad-HMSC/HUVEC co-cocultures with a large degree of cell viability after 1 day of culture. However, after 7 days of culture, the majority of cells were revealed to be dead. Furthermore, due to the lack of mechanical integrity possessed by alginate in a liquid-like state, printing sodium alginate hydrogels in air consistently resulted in deformation of printed constructs. The newly developed 3D printing technique termed freeform reversible embedding of suspended hydrogels (FRESH) was therefore investigated as a means for achieving 3D spatial control of printed hydrogels using the modified system. Printing cell-free sodium alginate hydrogels within gelatin sacrificial support baths allowed for fabricating constructs in a spatially defined manner. However, overprinting and swelling of alginate hydrogels negatively affected the overall printing accuracy. The present study aimed to pave the way for further system modifications and refinements, such that the ultimate goal of low-cost bioprinting may be achieved. Further optimisation of printing parameters, hydrogel characteristics and sterilisation techniques may allow for fabricating viable, physiologically relevant tissues using the modified system developed.
- Full Text:
- Date Issued: 2018
Development of a paediatric-friendly formulation intended for the treatment of multi-drug resistant tuberculosis
- Authors: Nkomo, Jethro
- Date: 2018
- Subjects: Drugs -- Dosage , Pediatrics -- Formulae, receipts, prescriptions Multidrug-resistant tuberculosis -- South Africa Primary health care -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/33660 , vital:32962
- Description: Children suffering from multidrug-resistant tuberculosis (MDR-TB) are treated with at least four drugs a day for at least twenty-four months. Approximately 25 000 - 32 000 children worldwide become infected with MDR-TB each year, yet there is a lack of adequate paediatric MDR-TB options for child-friendly dosage forms for the treatment of the condition. The available options are limited to manipulating different dosage forms intended for adults by means of breaking the tablets or otherwise, to deliver the drugs to children. This challenge that is faced by both health care professionals and caregivers subsequently poses drug quality, efficacy, and safety concerns to children being treated for MDR-TB. The objective of this study was to formulate a paediatric-friendly dosage form for the treatment of MDR-TB in children below the age of eight years. A fixed-dose combination (FDC) in form of a dispersible-tablet that contains two core drugs used in treatment of MDR-TB; levofloxacin and pyrazinamide, was developed. Quality by design principles was employed in developing the product. The systematic procedure ensures that quality is built into the product throughout the manufacturing process. It allows for identification of the critical quality attributes and modification of critical process parameters to lie within desired ranges. Preformulation studies were conducted on the active ingredients to investigate potential interactions and compatibility. Some of the analytical techniques employed in the process included an HPLC assay method that was developed to simultaneously separate levofloxacin and pyrazinamide, differential scanning calorimetry (DSC), infrared spectroscopy (IR), thermogravimetric analysis (TGA), and powder density studies. A direct compression tableting process was selected as the method of choice for product formulation. Active ingredients were blended with the excipients and compressed using tableting equipment to successfully produce FDC fast-disintegrating tablets containing 150 mg of levofloxacin and 300 mg pyrazinamide. The product quality was analysed and optimised using mathematical and statistical techniques such as response surface methodology (RSM) and ANOVA, to meet the required standards recommended by the United States Pharmacopoeia. The FDC dispersible tablet containing levofloxacin and pyrazinamide in the potential treatment of MDR-TB in children was successfully formulated, manufactured and evaluated. The tablet dosage form passed all the relevant quality criteria that governed the scope of this study and disintegrate in approximately 37 seconds when placed in water. It is generally a sizeable challenge to manufacture fixed-dose combination drug products due to physicochemical differences of various drugs, however, with adequate resources researchers may still find a way to formulate more child-friendly dosage forms for MDR-TB. This may lead to improved drug efficacy, reduced safety risks and decreased burden on caregivers and healthcare workers who must administer the treatment.
- Full Text:
- Date Issued: 2018
Development of a Postharvest Cold Treatment for Cryptophlebia peltastica (Lepidoptera: Tortricidae) for Export of Litchis From South Africa
- Authors: Moore, Sean D , Kirkman, Wayne , Peyper, Mellissa , Thackeray, Sean R , Marsberg, Tamryn , Albertyn, Sonnica , Hill, Martin P
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423729 , vital:72089 , xlink:href="https://doi.org/10.1093/jee/toy287"
- Description: The litchi moth, Cryptophlebia peltastica (Meyrick) (Lepidoptera: Tortricidae), is endemic to sub-Saharan Africa and certain Indian Ocean islands. It is an important pest of litchis and to a lesser extent macadamias. Litchis are exported to certain markets that consider C. peltastica as a phytosanitary pest. Consequently, an effective postharvest phytosanitary treatment is required. This study sought to develop a cold disinfestation treatment for this purpose. First, it was established that the fifth instar was the most cold-tolerant larval stage, as it was the only instar for which there was still some survival after 12 d at 1°C. It was then determined that cold treatment trials could be conducted in artificial diet, as there was no survival of fifth instar C. peltastica in litchis after only 9 d at 1°C, whereas it took 15 d at this temperature before no survival of fifth instar C. peltastica was recorded in artificial diet. Consequently, cold susceptibility of fifth instar C. peltastica and the most cold-tolerant larval stages (fourth and fifth instar) of false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), were compared in artificial diet. There was no survival of C. peltastica after 13 d at 1°C, whereas this was only so for T. leucotreta after 16 d. Consequently, it can be concluded that any cold treatment that has been proven effective against T. leucotreta would be as effective against C. peltastica. Finally, it was confirmed that the cold susceptibility of T. leucotreta in artificial diet did not overestimate the effect of cold on T. leucotreta larvae in litchis.
- Full Text:
- Date Issued: 2018
Development of an LCT-Based MOOC Taxonomy
- Authors: Motara, Yusuf, M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428972 , vital:72550 , https://doi.org/10.1145/3289406.3289411
- Description: Codecademy is an example of a successful and disruptive player in the online education space. This work describes the structure, content, and experience of working through a Codecademy Pro Intensive module and compares it to the offline approach in a similar domain. Existing taxonomies are insufficiently general to explain its success, and a new taxonomy based on Legitimation Code Theory is developed to compensate. This taxonomy is arguably more meaningful and more general than those presently in use.
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- Date Issued: 2018
Development of health promotion guidelines for weight management among primary health care nurses in the Eastern Cape Province, South Africa
- Authors: Monakali, Sizeka
- Date: 2018
- Subjects: Health promotion Body weight -- Regulation Obesity -- prevention and control
- Language: English
- Type: Thesis , Doctoral , Nursing
- Identifier: http://hdl.handle.net/10353/10006 , vital:35285
- Description: Overweight and obesity have become significant public health threats both globally and in South Africa. PHC professional nurses are first contact to patients and the community as well as key stakeholders in the management and education of obese patients. However, anecdotal evidence seems to question their suitability as good models of the advocated healthy lifestyle behaviours and weight management, as overweight and obesity is also prevalent among the professional nurses. This study examines the prevalence and determinants of overweight and obesity among PHC professional nurses in the Eastern Cape (EC) Province of South Africa. This was a workplace, cross-sectional study involving 203 PHC professional nurses conveniently selected across 41 PHC facilities in EC, South Africa. A WHO STEP wise questionnaire was used to collect demographic and behavioural data. Anthropometric (weight, height and waist circumference [WC]) measurements were taken following a standard protocol. Overweight and obesity was defined as a BMI of 25-29.9kgm-2, and BMI ≥ 30kgm-2, respectively. Seventy six percent of the nurses were obese. An additional 18 percent were overweight. Age, gender, marital status, duration of practice, alcohol use and smoking were significantly associated with obesity. There was no association between physical activity and obesity. After adjusting for confounders, only age more than 30 years (OR=5.2, 95 percentCI=1.6-16.4) and not using alcohol (OR= 4.0 95 percentCI= 1.7-9.1) were significant and independent predictors of obesity among the nurses. In conclusion is an alarmingly high prevalence of obesity among primary healthcare professional nurses in Eastern Cape, South Africa. This shows that PHC professional nurses in EC are not good models of the healthy behaviours, judge be BMI indicator, if they do advocates for healthy weight management to patients. This constitutes a future risk for an increased prevalence of chronic diseases and a handicapped healthcare workforce. There is a need to implement measures to promote healthy lifestyle behaviour and weight management among professional nurses in this setting.
- Full Text:
- Date Issued: 2018
Development of high capacity lithium-manganese-rich cathode materials xLi2MnO3•(1-x)LiMn0.5Ni0.5O2 for lithium ion batteries
- Authors: Rapulenyane, Nomasonto
- Date: 2018
- Subjects: Lithium ion batteries , Electrochemistry Lithium cells
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/34766 , vital:33442
- Description: In this study, a facile synthesis method was developed to produce layered-layered cathode materials with the formula xLi2MnO3•(1-x)LiMO2 (M= Ni and Mn) referred to as lithium-manganese-rich materials for lithium ion batteries. The prepared materials displayed high capacity ≥200 mAh/g at a current density of 20 mA/g in the voltage range of 2.0 V to 4.8 V. In particular the cathode material prepared at pH 10.0 delivered a high initial discharge capacity of 266 mAh/g at 20 mA/g current density and maintained a discharge capacity ≥220 mAh/g at 50 mA/g after 50 cycles. The synthesis method was used to further investigate the effect of lithium ratio in the layered-layered material. Li1+xMn0.6Ni0.2O2, x= 0.2, 0.25, 0.3 and 0.4 cathode materials were produced respectively. The BET surface area analysis results showed that Li1.3Mn0.6Ni0.2O2 material had comparatively higher surface area to the other cathode materials and also delivered good electrochemical results. XPS showed that the cation distribution is affected by the increase in lithium ratio, the Mn4+ percentages decreased significantly with an increase in lithium ratio. All materials peaks deconvoluted into two peaks namely Mn4+ and Mn3+, Li1.3Mn0.6Ni0.2O2 had the highest percentages of the stable Mn4+ 70.8%. Further investigation focused on the effect of the sintering temperature on the structure and the electrochemical performance of Li1+xMn0.6Ni0.2O2, x= 0.25, 0.3 and 0.4 cathode materials. X-ray diffraction showed the same patterns for all cathode materials sintered at 700˚C, 800˚C and 900˚C. Rietveld refined results however, showed that the increase in the sintering temperature, results in a decrease in the Li2MnO3 component percentage in the layered structures. Scanning electron microscopy images further proved that the particle size increases with increasing temperature. The charge–discharge tests of coin cells demonstrated that the materials sintered at 800˚C delivered higher discharge capacities above 200 mAh/g at 20 mA/g current density when compared to the materials made at the lower temperatures. Lastly the cathode material prepared at pH 10.0 was further evaluated in a cell using lithium titanate oxide Li4Ti5O12 as anode material. The cells delivered an initial discharge capacity of 213 mAh/g at 20 mA/g within a voltage range 3.3V-0.5V. The coin cells developed in this work delivered good cycling performance.
- Full Text:
- Date Issued: 2018
Development of InSb/GaSb quantum dots by MOVPE
- Authors: Ahia, Chinedu Christian
- Date: 2018
- Subjects: Semiconductors , Quantum electronics Organometallic compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23382 , vital:30537
- Description: There has been an increasing interest in the modification of semiconductor band structures through the reduction of their dimensions, which simultaneously increases the band gap energy of the material and gives rise to flexibility in device properties. Advances in III-V antimony (Sb) based semiconductor fabrication have triggered the quest for extension of the emission/absorption wavelength range of this family of compounds for optoelectronic devices operating in the mid-infrared region of the electromagnetic spectrum. An interesting material system for mid-infrared (MIR) applications is indium antimonide (InSb) quantum dots (QDs) within a gallium antimonide (GaSb) matrix. However, its band alignment and emission wavelength has been the subject of some interest and controversy over the years. This study focuses on the development of InSb/GaSb QDs by metal organic vapour phase epitaxy (MOVPE). The samples were grown on different substrates using various growth parameters in order to vary the size, density and aspect ratio of the dots. Interfacial growth interruptions while flowing various source precursors through the reactor were investigated in order to influence the chemical termination of the surface, and hence the resulting strain in the structures. The samples were characterized using photoluminescence spectroscopy, scanning probe microscopy, scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Likewise, the band alignment, energy levels, and carrier wave functions of the samples in this work were modelled theoretically using the nextnanomat software (version 3.1.0.0). A comparison of growth on two different GaSb substrates [(100) 2° off towards <111>B ± 0.1ᵒ and (111) ± 0.1ᵒ] using similar growth conditions yielded a higher dot density on the (100) substrate compared to the (111) substrate. This was attributed to the presence of terraces/atomic steps induced by the misorientation on the (100) substrate, which invariably gives rise to increased adsorption and an enhanced sticking coefficient of adatoms. Studies on the influence of a buffer layer on the morphology of uncapped dots showed that the shape and size of the dots are sensitive to the thickness of the buffer layer. In some case a corrugated buffer surface resulted, which introduced order in the arrangement of the dots, which formed preferentially inside the troughs. An increase in the V/III ratio from 1.0 to 3.0 was found to reduce the areal density of the QDs, while an analysis of the diameter histograms showed a narrowing of the size distribution with an increase in V/III ratio. The larger size distribution at low V/III was ascribed to the increase in indium species and the increased indium adatom migration length. This leads to increased dot density and nucleation sites, and thus triggers an increase in the conversion of tiny QDs into thermodynamically more suitable larger dots via coalescence. However, as the V/III ratio increased, the number of indium adatoms available for growth on the surface reduced, which automatically led to a decrease in the migration length of indium species which is unfavourable for the production of nucleation sites and to a decrease in dot density. Low growth rates were found to be beneficial for the growth of a high density (~5×1010cm-2) of QDs. Photoluminescence (PL) analysis of the capped samples at low temperature (~10 K), using an excitation power of 2 mW, showed a PL peak at ∼732 meV. Upon an increase in laser power to 120 mW, a blue shift of ∼ 8 meV was noticed. This emission typically persisted up to 60–70 K. An increase in the number of InSb QD-layers, was observed to cause an increase in the luminescence spectral line width and a long-wavelength shift of the PL lines, together with an enhancement in the strength of the PL emission. However, high resolution transmission electron microscopy (HRTEM) of the capped dots revealed the formation of an InGaSb quantum well-like structure, ∼10 nm thick, which was responsible for the PL signal mentioned above. The absence of QDs in the capped sample was attributed to inter-diffusion of Ga and In during the deposition of the cap layer, giving rise to a quantum well (QW) instead of the intended QDs. The presence of threading dislocations and stacking faults were also observed in the TEM micrographs of the samples containing multilayers, which can account for the fast quenching of the PL emission with increasing temperature from these samples. Theoretical simulations of the band alignment, wave functions and energy levels were in good agreement with the data collected from the PL spectra of the samples.
- Full Text:
- Date Issued: 2018
Developmental and reproductive performance of a specialist herbivore depend on seasonality of, and light conditions experienced by, the host plant
- Authors: Zachariades, Uyi O O, , Heshula, Lelethu U P , Hill, Martin P
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59845 , vital:27667 , https://doi.org/10.1371/journal.pone.0190700
- Description: Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
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- Date Issued: 2018
Digital Inclusion: A model for e-Infrastructure and e-Services in Developing Countries
- Authors: Terzoli, Alfredo , Siebörger, Ingrid , Tsietsi, Mosiuoa , Gumbo, Sibukelo
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430973 , vital:72733 , https://doi.org/10.1007/978-3-319-98827-6_7
- Description: A large portion of the South African population is still not connected in a productive manner to the Internet, despite the existence of a govern-ment plan for public broadband, ‘SA Connect’. One reason for this could be the lack of an appropriate model, through which connectivity can be diffused in a meaningful way through all areas of South Africa. This paper presents the model developed over more than a decade of experimentation in real life settings in the Siyakhula Living Lab, a joint venture between the universities of Rhodes and Fort Hare, South Afri-ca. The model proposes the ‘Broadband Island’ as basic e-infrastructure unit, which clusters nearby points-of-presence hosted in schools. In each Broadband Island is located an applications integra-tion platform, TeleWeaver, which monetizes channels of access to the local community, to support the e-infrastructure while providing useful services to the population and the Government.
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- Date Issued: 2018
Digital storytelling as a teaching and learning strategy: experiences of student nurses
- Authors: Espach, Juanita
- Date: 2018
- Subjects: Nursing -- Study and teaching -- South Africa , Nursing students -- South Africa Storytelling -- South Africa -- Computer network resources College teaching -- South Africa Competency-based education
- Language: English
- Type: Thesis , Masters , MCur
- Identifier: http://hdl.handle.net/10948/21549 , vital:29552
- Description: The ever changing landscape of technology influences every aspect of modern society, also education. Within recent years, technological advancements and inventive educators have transformed traditional teaching and learning strategies to innovative technology infused strategies. These strategies could potentially meet the learning style of the millennial student. One such strategy is described as digital storytelling, during which student groups create a three to five minute multimedia video, utilizing a combination of digital elements such as a narrative voice recording, music, pictures, video and animation. After creating the digital story, the end product is shared with peers. Paucity in research regarding the use of digital storytelling in the context of nursing education in the Republic of South Africa was found. Thus the aim of the study was to explore and describe the experiences of student nurses during the use of digital storytelling as a teaching and learning strategy at a private Nursing Education Institution in Port Elizabeth. The researcher conducted an exploratory, descriptive, contextual and qualitative study which utilized a connectivism framework as the paradigm. Digital storytelling was used as a teaching and learning strategy in the researcher’s own class. A convenience sampling method was therefore employed to select participants. Data was gathered through documenting observational notes during the process of utilizing digital storytelling in the classroom. After the student nurses had utilized digital storytelling, five focus group interviews with twenty four research participants were conducted, which provided data saturation. The data was transcribed and analysed utilizing Tesch’s thematic analysis method and three themes emerged from the data. The benefits of digital storytelling were voiced by the participants since digital storytelling gave them a means to express themselves and they gained new skills while collaborating with others and improving their learning. There was a negative side to it as well, during which research participants experienced negative emotions, lacked the necessary technological skills and found peer teaching an obstacle to their own learning. The participants also provided suggestions to improve the use of digital storytelling during teaching and learning. A thick description of the data with a literature control was provided. The researcher utilized the findings of this study to develop guidelines for Nurse Educators in order to optimize the use of digital storytelling as a teaching and learning strategy. Rigour and trustworthiness were ensured by utilizing Guba and Lincoln’s four criteria. In this study the researcher adhered to the ethical principles as described by the Belmont Report and paid specific attention to the application of these ethical principles in the context of conducting research on one’s own teaching practices. The limitations of this study were that data was collected from only one group of student nurses at one private NEI, after the student nurses’ utilized digital storytelling for the first time in their training. The findings of this study can be used by Nurse Educators to optimize the use of digital storytelling as a teaching and learning strategy. The recommendations of this study include the implementation of the guidelines developed for Nurse Educators.
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- Date Issued: 2018
Dimensions of a memorable experience within a marine tourism context
- Authors: Jonas, Altouise Glowdean
- Date: 2018
- Subjects: Customer relations -- Management , Customer relations Relationship marketing Tourism -- Environmental aspects Coastal zone management -- Environmental aspects
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30540 , vital:30958
- Description: Worldwide, businesses are operating in an environment which is continuously changing, forcing them to adapt their strategies in order to remain competitive. Two changes were of particular importance to this study. Firstly, businesses are faced with an increasing demand from consumers for experiences as opposed to products and services. Secondly, consumers are demanding experiences that are not just ordinary, but are unique and memorable. As one of the largest and most diverse industries globally, tourism offers a multitude of tourist activities. Marine tourism is one of the oldest, most popular and fastest developing types of tourism globally. Marine tourism has also become popular in South Africa. This popularity might be attributed to the country’s expansive coastline and to it being home to one of the most diverse marine systems in the world. Marine tourism makes significant contributions to South Africa’s economy. More benefits can be derived from this lucrative type of tourism if attention is given to the design and provision of marine tourism experiences that go beyond average experiences, and become memorable experiences. The reason for conducting this research was to provide the South African tourism industry, and marine tourism operators in particular, with information which might assist them in designing and staging memorable experiences. Such memorable experiences could result in a competitive advantage and enable the operators to attract more customers, which in turn, will benefit the individual operators, the industry as a whole, and ultimately, the South African economy. The study focused on three marine tourism activities, namely; shark-diving, visits to marine protected areas and whale-watching. Eight dimensions, namely; Delight, Hedonism, Involvement, Knowledge, Meaningfulness, Novelty, Refreshment and Social-Interaction were identified as prospective dimensions of a memorable experience within a marine tourism context. v The study employed purposive, convenience and snowball sampling to identify potential respondents. Primary data was collected by means of an online survey and paper-based self-administered questionnaires. Four hundred and forty-four useable responses were received. The results of the empirical study showed a positive correlation between all the dimensions and memorable experience for each of the three activities and for all the activities combined. A second order factor analysis showed that the eight dimensions loaded onto two factors. The resulting factors were named as the Affective Domain (consisting of Hedonism, Refreshment, Delight and Involvement) and the Cognitive Domain (consisting of Knowledge, Social- Interaction, Meaningfulness and Novelty). A positive relationship was found between the Affective Domain and Memorable Experience and also between the Cognitive Domain and Memorable Experience. The Cognitive domain showed a stronger relationship with Memorable Experience than what the Affective Domain did, for all the activities combined. The memorability of an experience in the case of all three activities combined can, firstly, be improved by Involvement. This is closely followed by the following dimensions in the Affective Domain; Delight, Hedonism and Refreshment. Under the Cognitive Domain the factor which is most important for improving memorability of all the activities combined is Meaningfulness, followed by Knowledge, Novelty and Social-Interaction. Finally, structural equation modelling confirmed a model representing the eight experience dimensions (Delight, Hedonism, Involvement, Knowledge, Meaningfulness, Novelty, Refreshment and Social-Interaction) and identified the relationships between the dimensions and Memorable Experience. This study makes four important contributions. Firstly, it contributes to the under-researched topic of marine tourism in South Africa. Secondly, it adds to the literature on memorable tourism experiences, specifically memorable marine tourism experiences and provides a measurement instrument and framework for further research. Thirdly, the study identifies and confirms that ‘delight’ is an important dimension of a memorable marine tourism experience. vi Lastly, a model was developed which can be used by marine tourism operators to enhance their strategies, operations and facilities which will enable operators to achieve a sustainable competitive advantage.
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- Date Issued: 2018
Discontinuous gully erosion as a mechanism of wetland formation: a case study of the Kompanjiesdrif basin, Kromrivier, Eastern Cape, South Africa
- Authors: Lagesse, Juliette V
- Date: 2018
- Subjects: Arroyos -- South Africa -- Kromme River (Eastern Cape) , Arroyos -- Erosion -- South Africa -- Kromme River (Eastern Cape) , Climatic geomorphology -- South Africa -- Kromme River (Eastern Cape) , Sedimentation and deposition -- South Africa -- Kromme River (Eastern Cape) , Alluvial fans -- South Africa -- Kromme River (Eastern Cape) , Wetland ecology -- South Africa -- Kromme River (Eastern Cape) , Rhizophoraceae , Palmiet (Prionium serratum)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60540 , vital:27791
- Description: The Kompanjiesdrif basin is an unchannelled valley bottom palmiet wetland located near the headwaters of the Kromrivier in the Eastern Cape of South Africa. The wetland itself is underlain by Bokkeveld shales with the bordering mountain ranges comprising more resistant Table Mountain Group quarzitic sandstones. The valley is relatively planar and broad in form over a width of approximately 200 m. None of the existing controls that are considered to lead to valley widening and longitudinal slope reduction are immediately apparent. The basin lies on the Post Africa II erosion surface; with no evidence of a resistant lithology which might act as a local base level, limiting rates of vertical erosion and inducing lateral planing in upstream reaches via a meandering channel. The possible role of sagging of the basin due to long term deep chemical weathering of bedrock is discounted as the lithologies in the basin are sedimentary in origin and thus not susceptible to chemical weathering. The degree to which climate and sea level changes affected rates of incision and subsequent slope reduction is unclear, although their potential influence should be acknowledged. This study examined the geomorphic dynamics as discerned from the sedimentary record and morphology of the wetland basin, which provide a snapshot into the long-term processes which lowered the longitudinal slope and widened this valley. Coring within the wetland to depths of 1 - 3.3 m revealed that the sedimentary fill generally comprised an upward fining sequence, with sand or fine sand at the base, grading into silt and clay and organic material in the upper sections of cores. Occasional instances of multiple fine sand layers were observed in a few of the cores. An increase in the organic content of material from the north to the south side of the wetland and the occurrence of multiple thin layers of sand in the stratigraphy, highlighted the role of the northern tributary alluvial fans in influencing valley form. Sediment from north bank alluvial fans seem to periodically, partially impound the wetland basin. Surveyed transects across the wetland basin along with subsurface coring to the depth to refusal, illustrated a localised increase in longitudinal slope downstream of the nodes of tributary alluvial fan deposits, which impinge on the trunk stream basin. Coupled with the presence of deep, drowned, trench-like features (up to 8 m deep) beneath floating mats of palmiet, which were predominantly free of sedimentary fill and found opposite tributary alluvial fans; confirmed that the northern tributaries play a major role in the structure and geomorphic dynamics of the basin. The trench-like features appeared to be remnants of deep, narrow, discontinuous gullies. Dating of sediment from the base of these features (460-7040 BP) confirmed that they were formed prior to European settlement in the area. Therefore, it is suggested that the localised increase in longitudinal slope, caused by sediment deposition on the alluvial fans, transgresses a geomorphic threshold slope and that gully erosion is thus initiated. The process of repeated gully erosion leads to planing of bedrock and longitudinal slope reduction. Gully erosion forms an integral component of a cycle of deposition and incision referred to as “cut-and-fill”. During each iteration of the cycle of cutting and filling, gullies form in novel locations leading to gradual valley widening. Over geological time scales, the planing of bedrock and resultant valley widening creates a broad planar valley with a very low longitudinal slope; producing conditions suitable for unchannelled valley bottom wetland formation.
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- Date Issued: 2018