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Detection of the in vitro modulation of Plasmodium falciparum Arf1 by Sec7 and ArfGAP domains using a colorimetric plate-based assay:

  • Authors: Swart, Tarryn , Khan, Farrah D , Ntlantsana, Apelele , Laming, Dustin , Veale, Clinton G L , Przyborski, Jude M , Edkins, Adrienne L , Hoppe, Heinrich C
  • Date: 2020
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165418 , vital:41242 , https://0-doi.org.wam.seals.ac.za/10.1038/s41598-020-61101-3
  • Description: The regulation of human Arf1 GTPase activity by ArfGEFs that stimulate GDP/GTP exchange and ArfGAPs that mediate GTP hydrolysis has attracted attention for the discovery of Arf1 inhibitors as potential anti-cancer agents. The malaria parasite Plasmodium falciparum encodes a Sec7 domain-containing protein - presumably an ArfGEF - and two putative ArfGAPs, as well as an Arf1 homologue (PfArf1) that is essential for blood-stage parasite viability. However, ArfGEF and ArfGAP-mediated activation/deactivation of PfArf1 has not been demonstrated.
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  • Date Issued: 2020

Determinants of adaptation to climate variability:A case study of crop farming households in Tyhume Valley communities Eastern Cape,South Africa.

  • Authors: Mtintsilana, Olona
  • Date: 2020
  • Subjects: Climatic changes Sustainable agriculture Climatic changes
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10353/18789 , vital:42733
  • Description: Climate variability affects rural households and agricultural productivity, yet it is just one of many stresses that vulnerable rural households have to cope with. Climate variability is not as noticeable as weather variability, because it happens over seasons and years. It is the manner in which climate fluctuates above or below a long-term average value. Without measures at local and national level to adapt to climate variability, risk of food insecurity will continue to increase at household level. The objective of the study was to determine factors affecting adaptation to climate variability. Purposive sampling was used to identify households who participated because of un-availability of sampling frame. Information was elicited from the selected households with the aid of a semi-structured questionnaire. The study utilised a cross-sectional survey of 205 farming households in Tyhume Valley communities. Data gathered was subjected to descriptive statistics, Cross tabulations and Binary logit model. The results indicate that rural households from Tyhume Valley communities practiced coping adaptation through use of the following adaptation strategies; crop rotation, planted drought resistant crops, changed planting dates and used indigenous strategies such as using ash to kill mule (intuku). Most of the households used irrigation as the coping strategy to adapt to climate variability. However, heatwave, high winds, employment status, cell phones, age and gender of the rural households’ heads have effects on households’ adaptation to climate variability in Tyhume Valley. In view of the research findings, a large number of farming households are old and are females, there is a need for development of labour saving technologies and extension services to increase the likelihood of adaptation of climate variability by vulnerable farmers such as women and elderly farmers.The study also recommends that there must be a development of infrastructure for farmers as they are negatively affect by high winds due to low infrastructural development.The study also shows that farming households who have access to cellphones are more likely to adapt to climate variability, therefore the study recommends that communication of farming households must be improved.Adapting to climate variability is an increasingly important issue in agriculture and one that is likely to persist for many years.
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  • Date Issued: 2020

Determination of nonlinear optical properties of phthalocyanine regioisomers using computational models

  • Date: 2020
  • Subjects: Electrochemistry , Phthalocyanines , Nanoparticles , Nonlinear optics , Nonlinear optical spectroscopy , Refraction
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/166197 , vital:41337
  • Description: This work investigates the effects of the nonlinear optical properties of four different constitutional isomers (C4h, C2v, Cs, and D2h) of a series of tetrasubstituted phthalocyanines (free-base 3-4-tert-butylphenoxyether phthalocyanines, free-base 4-4-tertbutylphenoxyether phthalocyanines, SnCl2 tetra substituted 3-4-tert-butylphenoxyether phthalocyanine, and SnCl2 tetra substituted 4-4-tert-butylphenoxyether phthalocyanine). The properties investigated were the real and imaginary components of the 3rd order hyperpolarizability, as well as the excited state absorption and refraction cross sections. The investigations were performed with a z-scan over a range of laser beam intensities. This work determined the imaginary component of the 3rd order hyperpolarizability for the free-base and SnCl2 3-4-tert-butylphenoxyether phthalocyanines and 4-4-tert-butylphenoxyether phthalocyanines to be highly dependent on the excited state cross sections. The refraction caused due to the real component of the 3rd order hyperpolarizability of the phthalocyanines was also investigated, however, the values found were strongly dependent on the laser beam intensity and the cause of this was investigated. A Five-level model was developed and run on GPGPU computing devices in order to isolate the absorption and refractive cross sections. Theeffects of the regio substitution on the excited state cross sections were also investigated, and the 1st singlet excited state and 1st triplet state absorption cross sections were calculated for all constitutional isomers. It was found that the symmetry of the constitutional isomers have a disproportionately large effect on the excited state absorption when compared to the ground state absorption. The nonlinear refractive properties of all constitutional isomers were also investigated, and the values of the parametric susceptibility are reported herein. The nonlinear refraction was found to have less effect than was seen in the nonlinear absorption. The 1st singlet excited state and 1st triplet state refractive cross sections of all constitutional isomer was determined. The results indicated that if more than one excited state was present and contributing to the nonlinear refraction, then more data than was collected here would be required. However, the 1st singlet excited state cross section were successfully determined for the free-base constitutional isomers. This work concluded that the region substitution affected the excited states more than the ground state.
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  • Date Issued: 2020

Determination of speaker configuration for an immersive audio content creation system

  • Authors: Lebusa, Motebang
  • Date: 2020
  • Subjects: Loudspeakers , Surround-sound systems , Algorithms , Coordinates
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/163375 , vital:41034
  • Description: Various spatialisation algorithms require the knowledge of speaker locations to accurately localise sound in 3D environments. The rendering process uses speaker coordinates to feed into their algorithms so that they can render the immersive audio content as intended by an artist. The need to measure the loudspeaker coordinates becomes necessary, especially in environments where the speaker layouts change frequently. Manually measuring the coordinates, however, tends to be a laborious task that is prone to errors. This research provides an automated solution to the problem of speaker coordinates measurement. The solution system, SDIAS, is a client-server system that uses the capabilities provided by the Ethernet Audio Video Bridging standard to measure the 3D loudspeaker coordinates for immersive sound systems. SDIAS deploys commodity hardware and readily available software to implement the solution. A server sends a short tone to each speaker in the speaker configuration, at equal intervals. A microphone attached to a mobile device picks up these transmitted tones on the client side, from different locations. The transmission and reception times from both components of the system are used to measure the time of flight for each tone sent to a loudspeaker. These are then used to determine the 3D coordinates of each loudspeaker in the available layout. Tests were performed to determine the accuracy of the determination algorithm for SDIAS, and were compared to the manually measured coordinates. , Thesis (MSc) -- Faculty of Science, Computer Science, 2020
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  • Date Issued: 2020

Determining the unbinding events and conserved motions associated with the pyrazinamide release due to resistance mutations of Mycobacterium tuberculosis pyrazinamidase:

  • Authors: Sheik Amamuddy, Olivier , Musyoka, Thommas M , Boateng, Rita A , Zabo, Sophakama , Tastan Bishop, Özlem
  • Date: 2020
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/148869 , vital:38781 , https://doi.org/10.1016/j.csbj.2020.05.0099
  • Description: Pyrazinamide (PZA) is the only first-line antitubercular drug active against latent Mycobacterium tuberculosis (Mtb). It is activated to pyrazinoic acid by the pncA-encoded pyrazinamidase enzyme (PZase). Despite the emergence of PZA drug resistance, the underlying mechanisms of resistance remain unclear. This study investigated part of these mechanisms by modelling a PZA-bound wild type and 82 mutant PZase structures before applying molecular dynamics (MD) with an accurate Fe2+ cofactor coordination geometry.
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  • Date Issued: 2020

Detonation nanodiamonds-phthalocyanine photosensitizers with enhanced photophysicochemical properties and effective photoantibacterial activity

  • Authors: Openda, Yolande I , Nyokong, Tebello
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/186012 , vital:44455 , xlink:href="https://doi.org/10.1016/j.pdpdt.2020.102072"
  • Description: The nanophotosensitizers based on acetophenoxy tetrasubstituted metallophthalocyanines (MPc) and detonation nanodiamonds (DNDs) were successfully formed and their photophysicochemical properties were determined. The zinc(II)Pc and indium(III)Pc complexes along with their nanoconjugates were found to have high singlet oxygen quantum yields (0.72 − 0.84) associated with the heavy central metal effect. The ability of the functional groups present on the DNDs to bind to the bacteria cell and the improved solubility of the nanoconjugates due to DNDs resulted in effective photodynamic antimicrobial therapy (PACT) activity against S. aureus planktonic cells, with the highest log reduction of 9.72 ± 0.02 for the conjugate of InPc conjugate with DNDs after 30 min irradiation. PACT studies were investigated at a dose of 10 μg/mL for each sample. The results suggest that the readily synthesized nanoconjugates can be used as appropriate PACT agents.
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  • Date Issued: 2020

Developing a Machine Learning Algorithm for Outdoor Scene Image Segmentation

  • Authors: Zangwa, Yamkela
  • Date: 2020
  • Subjects: Computational intelligence Computer science
  • Language: English
  • Type: Thesis , Masters , MSc (Computer Science )
  • Identifier: http://hdl.handle.net/10353/12087 , vital:39150
  • Description: Image segmentation is one of the major problems in image processing, computer vision and machine learning fields. The main reason for image segmentation existence is to reduce the gap between computer vision and human vision by training computers with different data. Outdoor image segmentation and classification has become very important in the field of computer vision with its applications in woodland-surveillance, defence and security. The task of assigning an input image to one class from a fixed set of categories seem to be a major problem in image segmentation. The main question that has been addressed in this research is how outdoor image classification algorithms can be improved using Region-based Convolutional Neural Network (R-CNN) architecture. There has been no one segmentation method that works best on any given problem. To determine the best segmentation method for a certain dataset, various tests have to be done in order to achieve the best performance. However deep learning models have often achieved increasing success due to the availability of massive datasets and the expanding model depth and parameterisation. In this research Convolutional Neural Network architecture is used in trying to improve the implementation of outdoor scene image segmentation algorithms, empirical research method was used to answer questions about existing image segmentation algorithms and the techniques used to achieve the best performance. Outdoor scene images were trained on a pre-trained region-based convolutional neural network with Visual Geometric Group-16 (VGG-16) architecture. A pre-trained R-CNN model was retrained on five different sample data, the samples had different sizes. Sample size increased from sample one to five, to increase the size on the last two samples the data was duplicated. 21 test images were used to evaluate all the models. Researchers has shown that deep learning methods perform better in image segmentation because of the increase and availability of datasets. The duplication of images did not yield the best results; however, the model performed well on the first three samples.
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  • Date Issued: 2020

Developing a service model for a successful freight forwarding organisation in South Africa

  • Authors: Kildase, Unathi
  • Date: 2020
  • Subjects: Physical distribution of goods -- South Africa
  • Language: English
  • Type: Thesis , Masters , MBA
  • Identifier: http://hdl.handle.net/10948/48664 , vital:41057
  • Description: The Freight Logistics Industry underpins the efficient movement of freight goods globally and supports the South African economy by accounting for 80% of the movement of goods. While South Africa’s formal trade with the rest of the continent and the world has increased steadily over the years, the country is yet to make significant inroads in some of its larger and fast-growing economies. This is despite having a substantially more diversified economic base and relatively higher levels of technological advance-ment (Department of Research and Information, 2018). Complex challenges relating to transport infrastructure (roads, customs processes, sea- and airports, amongst others), determine the efficiency with which business can be done and therefore has a direct impact on the growth of the Freight Logistics Pro-vider (FLP) industry (Belfreight, 2016). Changes in the global business environment have also led FLP’s to diversity strate-gies, incorporating asset ownership on a small to large scale in order to cope with the ever-changing demands of customers. However, at its core, the FLP industry exists to manage the freight transport process. This study investigated, through interviews and surveys involving senior industry pro-fessionals; whether a service model for a successful FLP could be developed; one that did not require asset ownership. The empirical evidence gathered yielded a list of the top FLP services currently being used in business; together with the support structures and enablers for these services in the form of transport modes. A model was then developed based on these param-eters that would best suit a small to medium sized FLP for success. Success in this study proved to be non-tangible due to the limited information available in company and industry figures, however, indication of an optimal market by product was included in the developed model.
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  • Date Issued: 2020

Developing an organisational culture in support of organisational capacity for change: the case of a South African bank

  • Authors: Dhoba, Howard
  • Date: 2020
  • Subjects: Corporate culture , Bank management , Organizational change
  • Language: English
  • Type: text , Thesis , Masters , MBA
  • Identifier: http://hdl.handle.net/10962/141247 , vital:37956
  • Description: Business organisations are increasingly being exposed to challenging environmental pressures. It has been widely acknowledged and observed that an organisation that crafts an effective organisational culture should be well positioned to react to these threatening changes, and to proactively seize opportunities to adapt and learn. This research study seeks to investigate how an organisational culture that supports organisational capacity for change can be developed. It analyses what a banking organisation’s espoused culture is made up of and how it was formulated. A thematic analysis of how the bank’s aspirational and innovative culture contributes to the organisation’s capacity for change is also presented. Organisational management should take a leading role in developing the values and practices that foster participation, which are then imparted to the entire organisation. The research study thus only focused on analysing the development of organisational culture from the management perspective. An interpretivist research approach was adopted, with a case study design as the research method. Data was gathered through conducting personal interviews with twelve managers from a Retail and Business Banking cluster of one of the big South African banks. Numerous interventions were employed in the organisation to develop espoused values, aspirational culture and to encourage all employees to champion innovations and constantly search for better ways to offer delighting value propositions to clients. The research findings can assist managers and organisational leaders in building their organisational capacity for change through developing an effective organisational culture that supports change initiatives. Since the research study only focused on analysing the development of organisational culture from the perspective of management, further research studies may involve employees as well, due to the fact that everyone is expected to take an active role for an organisation to display the overall capability to effectively respond to a progressively volatile environment. The research was able to reveal how key initiatives that are designed from theoretical constructs can be used to deliver on an innovative organisational culture that contributes to organisational capability for change.
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  • Date Issued: 2020

Developing macroinvertebrate trait- and taxonomically-based approaches for biomonitoring wadeable riverine systems in the Niger delta, Nigeria

  • Authors: Edegbene, Ovie Augustine
  • Date: 2020
  • Subjects: Water – Pollution -- Nigeria -- Niger River Delta , Stream health -- Nigeria -- Niger River Delta , Water -- Pollution -- Measurement , Environmental monitoring -- Nigeria -- Niger River Delta , Water quality -- Nigeria -- Niger River Delta , Water quality biological assessment -- Nigeria -- Niger River Delta , Aquatic invertebrates -- Nigeria -- Niger River Delta , Stream restoration -- Nigeria -- Niger River Delta , Urban agriculture -- Nigeria -- Niger River Delta , Stream ecology -- Nigeria -- Niger River Delta
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/140660 , vital:37907
  • Description: Riverine systems are increasingly subjected to pollution due to rapid urbanisation, industrialisation, and agricultural activities. Increasing pollution in freshwater systems impairs water quality, causes biodiversity loss and impairs aquatic ecosystem functionality and supply of ecosystem services. Rivers in the Niger Delta region of Nigeria are particularly vulnerable to urban pollution and agricultural activities as natural forests are increasingly replaced by urbanisation and agriculture. The differential effects of these pressures on the ecological processes of these river systems are poorly explored, as is the development of appropriate biomonitoring tools for routine monitoring of river health. In this study, a physico-chemically-based approach and macroinvertebrate trait- and taxonomic- approaches were developed to better understand the effects of multiple pressures on riverine systems, while developing multimetric indices to enable sustainable management of rivers within the region. Sixty-six stations in 20 river systems within the Edo and Delta States of the Niger Delta ecoregion were monitored seasonally for a period of five (2008–2012) years. The physico-chemically based approach makes apparent the extent of degradation of rivers and streams in the Niger Delta. For each dominant land use type, river stations were classified into least impacted stations (LIS), moderately impacted stations (MIS) or heavily impacted stations (HIS). Of 11 stations within urban catchments, only two were considered least impacted, suggesting that urgent measures are necessary to revise the current trajectories of urban rivers within the region. Most of the stations designated as MIS and HIS in the urban and urban-agriculture catchments were found to be significantly correlated with increased nutrients, EC and BOD5. Characteristics of most of the MIS and HIS within rivers in urban catchments evidenced the so-called urban stream syndrome, a state of persistent degradation of urban streams. The results of the traits and ecological preferences approach showed traits sensitive to urban and urban-agriculture pollution. Traits and ecological preferences that were associated with the LIS include the possession of hardshell, moderate and high sensitivities to oxygen depletion, very large body sized individuals (>20-40mm), swimmers, flattened body shape, a preference for temporary attachment, crawling, respiration with aerial/vegetation, possession of breathing tubes, possession of strap or other apparatus for respiration, streamlined body, and a high sensitivity to oxygen depletion. Permanent attachment as an ecological preference associated with LIS was also positively correlated with increasing dissolved oxygen (DO) and was deemed a pollution sensitive ecological preference. The possession of very small body size (<5mm), associated with HIS, was deemed a pollution-tolerant trait and was negatively correlated with DO, confirming the deteriorating state of the urban and urban-agricultural rivers. The impact of urban-forestry pollution on the distribution pattern of macroinvertebrate traits and ecological preferences was also explored in the selected rivers. Traits and ecological preferences such as possession of hard-shell, large body size, and grazing as a feeding preference which were significantly positively associated with the LIS, were also either significantly positively correlated with DO, or significantly negatively correlated with increasing any two of flow velocity, water temperature, BOD5 and nutrient. These traits and ecological preferences were deemed sensitive in forested rivers receiving urban pollution. Further, burrowing, the pupa aquatic stage, and predation which were significantly positively associated with HIS on the RLQ ordination, were also significantly negatively associated with DO. These traits were deemed tolerant of forested systems receiving urban pollution. Multimetric indices (MMI) were developed, validated and applied for urban, urban-agriculture and urban-forested (MMI-urban, MMI-urban-agric and urban-forest) areas. Of the 26 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban, only five metric were retained for integration into MMI-urban, they are log VeL, Hemiptera abundance, % Coleoptera + Hemiptera, % Chironomidae + Oligochaeta and Evenness index. Further, of the 18 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban-agric, only 12 metrics were retained and nine proved to be redundant. The nine metrics represent different measures; two of them were retained in addition to Chironomidae/Diptera abundance, % Odonata and Oligochaeta richness. The two metrics selected in addition to the hironomidae/Diptera abundance, % Odonata and Oligochaeta richness were the Margalef index and the logarithm of relative abundance of sprawler. For the MMI-urban-forest, 14 metrics satisfactorily discriminated between the LIS, the MIS, and the HIS, and 12 metrics were retained and 11 proved to be redundant. The non-redundant metric was Trichoptera abundance. Three metrics were further selected in addition to the Trichoptera abundance which include % Chironomidae + Oligochaeta, Coleoptera + Hemiptera richness and Shannon diversity. The MMI-urban and MMI-urban-agric indices performed better for LIS designated stations compared to the MIS and HIS deignated stations. The developed indices proved effective as biomonitoring tools for assessing the ecological health of rivers in the urban and urban-agriculture catchments within the Niger Delta. Overall, the results of the macroinvertebrate traits and ecological preferences, and taxonomic approaches showed the strength in the complementarity of both approaches in developing biomonitoring tools for assessing levels of deterioration in riverine systems. The study contributes significantly to understanding the ecology of riverine systems in the Niger Delta, particularly those subject to urban stresses, agricultural activities and urban pollution in forested systems, and thus makes an important contribution to the science and practice of biomonitoring in Nigeria where such studies are sparse.
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  • Date Issued: 2020

Developing social indicators for the evaluation of natural resource management programmes using a capability approach in the Eastern Cape, South Africa

  • Authors: Human, Johanna Susanna
  • Date: 2020
  • Subjects: Environmental education -- South Africa -- Eastern Cape , Natural resources -- Management -- Study and teaching (Continuing education) -- South Africa -- Eastern Cape , Sustainable development -- Study and teaching (Continuing education) -- South Africa -- Eastern Cape , Environmental economics -- Study and teaching (Continuing education) -- South Africa -- Eastern Cape , Subsistence farming -- South Africa -- Eastern Cape , Watersheds -- South Africa -- Eastern Cape , Capabilities approach (Social sciences) , Tsitsa River Catchment (Eastern Cape, South Africa)
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: http://hdl.handle.net/10962/147348 , vital:38628
  • Description: The dissertation investigates how the capability approach can be used to develop social indicators for a natural resource management (NRM) programme. The study aimed to develop an understanding of what the beneficiaries of the programme value being and doing to guide the development of social indicators that will take into consideration their personal development aspirations. These valued beings and doings were then overlaid with the programme goals and objectives to identify and select the final indicators. The study was situated in the Tsitsa catchment in the Eastern Cape, South Africa and was part of a natural resource management programme, focused on land restoration and avoided degradation. Methods used to collect data for this study and develop an understanding of what the residents’ valued beings and doings were, included semi-structured interviews, workshops and document analysis. The research population was non-homogenous. I tried to include voices representing different prominent groups of land users in the study. This included established commercial farmers, emerging commercial farmers, commercial forestry, residents residing in communal areas and engaged with subsistence farming and residents from these communal areas who are now residing elsewhere but continue to have connections to the catchment. Understanding the voices of these different groups who reside in the catchment was important to develop an inclusive understanding of what residents of the catchment valued beings and doings were. The research process was supported by participatory approaches. This process, and the lessons learnt during the research process, were valuable for the further development and implementation of the planned participatory monitoring evaluation reflection and learning (PMERL) framework. The research process involved learning from the research participants about their valued beings and doings and what was important for the programme implementers. Some of the research participants from the Rhodes University implementation team (RUIT) were also involved in selecting the indicators they thought the programme should monitor. Overall, using the capability approach helped me to gain insight and understanding with regard to what the valued beings and doings are for the residents of the catchment and what they would like development programmes, such as the Tsitsa Project, to address. It was surprising to find many areas of overlap between the valued beings and doings of the different residents in the catchment, as well as the similarities between these and the goals and objectives of the Tsitsa Project. In conclusion, using the capability approach was useful to learn what was important for the residents of the catchment to help develop the social indicators but also to learn how to guide and steer participatory monitoring and evaluation processes in the future.
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  • Date Issued: 2020

Developing voice and leadership amongst a group of class captains

  • Authors: Nehunga, Jacobina Taukondjele
  • Date: 2020
  • Subjects: Educational leadership -- Namibia , Transformational leadership -- Namibia , Leadership in adolescents -- Namibia , Rural schools -- Namibia , School children – Namibia -- Attitudes , School management and organization – Namibia , Cultural Historical Activity Theory
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: http://hdl.handle.net/10962/145034 , vital:38402
  • Description: The notion that leadership can be reduced to that of a formal position such as principalship has become problematic in school leadership research and practice, globally and also in Namibia. It appears that when leadership is concentrated only at the level of a principal within schools, teachers and learners within the same school experience a lack of opportunities to contribute to leadership practices, thus losing a sense of ownership. Supporting a distributed leadership perspective and embracing transformative leadership, this study investigated how learner voice and learner leadership (see for example Mitra and Gross, 2009) can be developed within a group of class captains in a combined school in rural Namibia. Cultural Historical Activity Theory (CHAT) underpinned the study which is located within a critical paradigm. Findings of the study were captured into two phases whereby phase one generated contextual profiling findings through the adoption of qualitative methods such as questionnaires, interviews, document analysis and two other participatory methods of mapping and transect walks. Phase two findings were captured through expansive learning actions in Change Laboratory Workshops. Observation notes, video recording and photographs and informal discussions were used as data sources during this phase. Both inductive and abductive analysis were employed. The findings revealed that a few enabling conditions to class captainship practice existed, but generally there was limited participation of class captains in school leadership. Class captains were seen as merely class representatives and their leadership was confined to a classroom level in the school. They performed more managerial tasks than leadership. It was also revealed that class captainship is not a documented practice in Namibia and it lacks support. Against this backdrop, during phase two of the study, seven contradictions were identified and two contradictions were prioritised for resolution during the Change Laboratory Workshops. Some of the resolutions included the development of a school based guiding document for class captains; an establishment of a class captainship club; and the promotion of a yearly election campaign of class captains. The study recommends more interventionist studies to be conducted on class captainship in order to see the practice documented in terms of policy in Namibia, perhaps in the near future.
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  • Date Issued: 2020

Development and assessment of a fixed dose combination of perindopril arginine and indapamide loaded microparticles

  • Authors: Mandava, Tavonga Tyomai
  • Date: 2020
  • Subjects: Uncatalogued
  • Language: English
  • Type: thesis , text , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/164413 , vital:41116
  • Description: Thesis (MSc)--Rhodes University, Faculty of Pharmacy, Pharmaceutics, 2020
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  • Date Issued: 2020

Development and process verification of a linear friction welding platform for small Ti6AI4V coupons

  • Authors: Mohlala, Narishe Taetso Arnold
  • Date: 2020
  • Subjects: Friction welding , Pressure welding
  • Language: English
  • Type: Thesis , Masters , MEng
  • Identifier: http://hdl.handle.net/10948/46196 , vital:39513
  • Description: This thesis reports on a study conducted to establish the feasibility of implementing linear friction welding as a joining technique for small Ti6AI4V coupons. The main of this project is to facilitate the manufacturing of high-integrity near-net-shape components for aerospace, automotive and medical appliances. LFW is a solid-state welding technique that uses frictional heat generated by the rubbing of surfaces under an axially applied load, thereby forming a weld at temperature below beta tranus. This technique is advantageous as it has the potential to reduce defeats normally associated with conventional welding of this material. The first part of the study will describe the development of an experimental platform to facilitate the evaluation of the influence of selected process parameters on joint integrity.
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  • Date Issued: 2020

Development finance institutions and sustainable economic development : a case of the idc South Africa

  • Authors: Mare, Timothy
  • Date: 2020
  • Subjects: Economic development -- South Africa
  • Language: English
  • Type: Thesis , Masters , MPhil
  • Identifier: http://hdl.handle.net/10948/48872 , vital:41166
  • Description: The purpose of this research study is to assess the extent that the Industrial Development Cooperation (IDC) of South Africa a Development Finance Institution (DFI), has contributed to the sustainable economic development of South Africa. The objective is to quantify the impact that is attributed to the IDC’s activities in South Africa in terms of socio-economic development contributing to sustainable economic development. Social development is fundamentally important in contributing to the economic development of any country. The research constituted the collection and quantitative analysis of data using reports from the IDC. The social output index modelling developed by the World Bank was used to analyse the data and make conclusive arguments regarding the impact that the IDC was having on economic development. The findings indicate that the IDC significantly lends less comparatively to lower income groups thus resulting in a negative contribution in terms of social developmental goals. Further the analysis through social output index model suggests that the IDC in as far as socio-development is concerned did not contributing positively to sustainable economic development between 2014 and 2018 reporting periods. The following recommendations are suggested: Increase awareness about the real impact of each investment across the IDC group, this will ensure that all proposals for investment are assessed with a component focusing on a socio-developmental perspective; reduce the number of mandates that the IDC currently has and establish broader frameworks for DFIs regardless of which government is in power or control.
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  • Date Issued: 2020

Development framework in the Mdantsane central business district

  • Authors: Zenani, Pumzile
  • Date: 2020
  • Subjects: Central business district -- South Africa -- East London , City planning -- South Africa -- East London Public utilities -- Management
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/47292 , vital:39840
  • Description: The study sought to investigate a development performance and management of Mdantsane CBD. The performance measurement framework may enhance the chances of economic success in the CBD. The study was conducted by means of a review of related literature and by conducting an empirical study. The empirical study was conducted using a quantitative approach by distributing research questionnaires to members falling within the sample population. The primary objective of the study was to develop a framework for perceived enhanced development for the Mdantsane CBD. A descriptive survey was conducted among the population within Mdantsane Township. The framework includes strategic factors of planning during apartheid era, reviewed strategic planning during democratic era and it provides an understanding of the current spatial and physical characteristics of the study area. Key issues such as spatial planning, infrastructure, environment, health, safety, economics and management of the CBD were also identified. Findings were based on the survey’s results from the community members. Findings suggest that the following variables: strategic factors (democratic); spatial development framework and infrastructure implementation; budget alignment; PESTEL factors (Political, Economic, Social, Technological, Ecological and Legal); environmental health and safety, transport and transport engineering, project management (body of knowledge) and the National Development Plan positively influenced the perceived enhanced development of Mdantsane CBD. All these variables were identified in the empirical framework affecting the perceived enhanced development of Mdantsane CBD. This study may contribute to the South African spatial and development planning body of knowledge by addressing factors which are faced by planners in development of the settlements.
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  • Date Issued: 2020

Development of a low-cost bioprinting system for engineering of Human Tumour Models

  • Authors: Fanucci, Sidne
  • Date: 2020
  • Subjects: Uncatalogued
  • Language: English
  • Type: thesis , text , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/163295 , vital:41026
  • Description: Thesis (MSc)--Rhodes University, Faculty of Science, Biotechnology Innovation Centre, 2020.
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  • Date Issued: 2020

Development of a protocol for extracting and quantifying the concentration of thiafentanil in blesbok (Damaliscus pygargus phillipsi) matrices 72-74 hours post administration

  • Authors: Webber, Judith Tracy
  • Date: 2020
  • Subjects: Uncatalogued
  • Language: English
  • Type: thesis , text , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/164738 , vital:41159
  • Description: Thesis (MSc)--Rhodes University, Faculty of Science, Chemistry, 2020
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  • Date Issued: 2020

Development of a UV-tolerant strain of the South African isolate of Cryptophlebia leucotreta granulovirus for use as an enhanced biopesticide for Thaumatotibia leucotreta control on citrus

  • Authors: Mwanza, Patrick
  • Date: 2020
  • Subjects: Baculoviruses -- South Africa , Ultraviolet astronomy
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/48533 , vital:40885
  • Description: Baculoviruses are pathogenic to insects in the orders Diptera, Hymenoptera, and Lepidoptera. As a result of this natural relationship with insects they provide an environmentally friendly method to combat crop and forest pests. As such, a number of baculoviruses have been formulated into biopesticides. The use of baculovirus biopesticides is gaining popularity as the use of chemical pesticides has come under stringent regulatory conditions imposed by governments and continental blocks such as the European Union. Baculoviruses have a narrow host range and therefore do not harm non-pests or humans who consume the crops. One such baculovirus is Cryptophlebia leucotreta granulovirus (CrleGV), which is pathogenic to the citrus pest Thaumatotibia leucotreta, commonly referred to as the false codling moth (FCM). CrleGV has an occlusion body (OB) that encloses a single virion. Several CrleGV biopesticides have been registered in South Africa for use on citrus, avocadoes, macadamias, grapes and other crops by two commercial producers, River Bioscience (SA) and Andermatt (Switzerland). These biopesticides are used as part of the FCM integrated pest management (IPM) programme, a multifacetted approach to controlling FCM. However, baculoviruses are susceptible to the ultraviolet (UV) radiation component of sunlight and lose their activity within hours to a few days, after exposure to UV. Several substances have been tested as UV protectants to improve the persistence of baculovirus biopesticides in the field. These include optical brighteners, UV absorbers and anti-oxidants. While very promising in the laboratory, UV-protectants have not been as successful in the field. A few published reports have reported, that UV-tolerant baculoviruses could be isolated from a population by repeatedly exposing and re-exposing the virus to UV irradiation with a propagation step in insect host fourth or fifth instars between each exposure cycle. In this study, the South African isolate of Cryptophlebia leucotreta (CrleGV-SA) was exposed to UV irradiation for 5 exposure cycles in a Q-Sun Xe-3 HC test chamber (Qlab, USA) with parameters set to mimic a typical summer day in the Sundays River Valley, Eastern Cape Province, in South Africa. In between exposures the virus survivors were allowed to multiply in FCM fifth instars. Surface dose bioassays were also conducted to determine the LC50 of the virus after each exposure cycle. Samples from exposure cycle 1 and cycle 5 (UV-tolerant) irradiated for 72 h were prepared for Next Generation Sequencing (NGS) of DNA. The resultant sequence data were analysed using the Geneious R11 software (New Zealand) and compared with the unexposed CrleGV-SA sequence. In-silico restriction enzyme analsysis (REN) with several enzymes was also carried on both the cycle 1 and cycle 5 exposed samples and the resulting digestion patterns were compared with the original CrleGV-SA digestion patterns. The same samples were also analysed by transmission electron microscopy (TEM) and Attenuated Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) to evaluate the effect of UV irradiation on the structure of the CrleGV-SA OB. In addition, three UV protectants, lignin sulphate (Sappi, SA), BREAK-THRU®OE446 (OE446) (Evonik Industries, Germany) and Uvinul Easy (BASF, Germany) were prepared with CrleGV-SA to give final protectant concentrations of 0.09 %, 0.9 % and 9 %. The protectant-virus suspensions were exposed to UV for 24 h in the Q-Sun test chamber and bioassays conducted to determine the protective effect of each protectant concentration. The most successful protectants were then combined with the UV-tolerant CrleGV-SA and exposed to UV for 24 h in the Q-Sun test chamber and surface dose bioassays conducted afterwards. Samples exposed to UV in cycle 5 had lower LC50 values compared to samples in the early cycles. With each re-exposure cycle the LC50 values moved closer to that of the unexposed control. The LC50 of virus samples decreased from 2.89 x 108 OBs/ml after 24 h UV-exposure in cycle 1 to 2.16 x 105 OBs/ml after the same duration of exposure in cycle 5; and from 2.11 x 109 OBs/ml in cycle 1 after 72 h UV-exposure to 1.73 x 106 OBs/ml after the same duration of exposure. This represented a 1338-fold difference and a 1220-fold difference, respectively. When the UV-tolerant samples were sequenced seven SNPs were identified in cycle 1, which were thought to help establish UV tolerance, while a further seven SNPs were identified in cycle 5 samples; these were thought to further establish and maintain the UV-tolerance. Additionally, REN analysis with EcoR1 for both test samples yielded digestion patterns that were different from those of the original CrleGV-SA. TEM data showed that UV damages the virion as well as the crystalline structure of the OB. This is the first time visual evidence for UV damage to baculoviruses has been published. Comparison of cycle 1 and cycle 5 UV exposed OBs revealed that the cycle 5 OBs were significantly larger than the cycle 1 OBs (P<0.05). In addition, several peaks in the fingerprint region were shown to have either appeared or disapeered from the ATR-FTIR spectra after UV irradiation. However, there was no difference in the spectra of the Cycle 1 and Cycle 5 virus samples. The tests with potential UV-protectants revealed that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy were the most effective in protecting the virus from UV. However, there was no significant difference in their protection of UV tolerant CrleGV-SA and wild type CrleGV-SA. Going forward, it is recommended that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy combinations be explored further in future studies, particulary in the field. This study therefore forms an important foundation for the development of UV-tolerant baculovirus that will last longer in the field.
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  • Date Issued: 2020

Development of bio-based xylan composites for food packaging applications

  • Authors: Naidu, Darrel Sarvesh
  • Date: 2020
  • Subjects: Xylanases
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/48544 , vital:40886
  • Description: Currently a large number of chemicals and plastics are produced from petroleum-based resources. However, due to the concerns surrounding the depletion of petroleum resources and growing carbon emissions, there is a desire to produce chemicals and plastics from renewable and carbon natural sources. Lignocellulosic biomass (biomass consisting of cellulose, lignin and hemicellulose) is the most common biomass on earth and is renewable and carbon neutral. Of the three main constituents of lignocellulosic biomass, hemicellulose is composed of a mixture of sugars which can be converted into chemicals and plastics. The most common form of hemicellulose found in nature is xylan. This study is aimed at extracting xylan from maize stalk waste residues and the development of xylan films with properties that are suitable for food packaging applications. Xylan was extracted from maize stalk waste residues using an alkaline pre-treatment method. The effects of bleaching conditions (time, temperature and bleach concentration) prior to alkaline treatment on the yield and purity of xylan extracted was studied using a Box-Behnken experimental design. It was observed that the experimental conditions tested had no effect on the yield of the xylan extracted but the bleach concentration had a significant effect on the purity of the xylan extracted. The samples with the lowest lignin content were found to be the samples treated with 3wt% bleach prior to alkaline pre-treatment. One of the main disadvantages of xylan is that it has poor film forming properties, a method of overcoming this is to combine it with another abundantly available biopolymer that has good film forming properties, such as alginate. The effect of xylan, alginate and glycerol content on the mechanical, thermal, moisture uptake and water barrier properties of the films were investigated. It was observed that with an increase in the alginate content there was an increase in the tensile strength and Young’s modulus of the films, whereas the water vapour permeability (WVP) of the films decreased. This was attributed to the greater cohesion between alginate polymer chains compared to the cohesion between xylan polymer chains. The xylanalginate films exhibited better optical and water sorption properties at higher xylan content. In order to improve the inherently poor mechanical and barrier properties of the xylan-alginate films, bentonite and halloysite were incorporated into the films. It was found that 5wt% incorporation of either bentonite or halloysite resulted in a 49% decrease of the WVP, which was attributed to water vapour impermeable nature of the silicate layers that make up both clays. The incorporation of the clays into the xylan-alginate matrix resulted in a significant
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  • Date Issued: 2020
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