Barriers and drivers to the implementation of renewable energy technologies in South Africa’s aquaculture industry
- Authors: Van Wyk, Nicholas Kelly
- Date: 2018
- Subjects: Renewable energy sources South Africa , Aquaculture Environmental aspects South Africa , Sustainable aquaculture Economic aspects South Africa , Renewable energy sources Economic aspects South Africa , Renewable energy sources Environmental aspects South Africa
- Language: English
- Type: text , Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10962/61969 , vital:28090
- Description: South Africa is plagued by socio-economic issues of poverty, inequality and high rates of unemployment. The government of South Africa has as such launched an ambitious plan known as operation PHAKISA which will complement the National Development Plan in addressing the countries aforementioned shortcomings. In the operations first phase, the focus is on growing South Africa’s ocean economy. Within the ocean economy, the growth of aquaculture has been identified as an industry with the potential to create jobs and aid in economic growth of South Africa. Aquaculture, the farming of any aquatic organisms, has been the fastest growing food production sector for the past 50 years. While natural capture fisheries have stagnated in production capacity, aquaculture has grown exponentially in order to feed a global population which is fast approaching nine billion people. However, South Africa’s aquaculture production lags significantly behind other third world countries. The sustainability of aquaculture has frequently been called into question due to the possibility of various detrimental environmental effects it may cause. To further complicate the matter, Climate Change is today an overarching threat to life as we know it, and must be taken into account if we plan to keep growing our populations and economies. As such, if South Africa wants to grow its aquaculture sector, it must be done so in a sustainable manner. This research thus sought to investigate one aspect which may increase the sustainability of aquaculture in South Africa, that being the implementation of renewable energy in the sector. Renewable energy has been identified by the United Nations Intergovernmental Panel on Climate Change as key to mitigating the effects of climate change. In order to aid Renewable Energy (RE) implementation in South Africa’s aquaculture sector, this research aimed to identify the barriers and the drivers to implementing renewable energy within aquaculture. To do this, a literature review was conducted to identify possible barriers and drivers to renewable energy implementation. These were then drafted into an online questionnaire and sent via Email to all the aquaculture organisations in South Africa that could be contacted (n = 195). Respondents were asked to rank the proposed barriers and drivers to renewable energy according to their perceived importance on a Likert Scale. A total of 18 responses could be analysed with descriptive statistics. Further, three structured interviews were conducted with members of South African aquaculture organisations who had implemented some form of Renewable Energy Technology (RET). These interviews provided in-depth insights into the importance of the various proposed barriers and drivers. The results revealed the most important barriers to RE implementation were: High Initial investments, Utility monopoly of production, Lack of RE experts on a governmental level, Lack of incentives/subsidies from government, Lack of legal framework for Independent Power Producers and Power Purchase Agreements, and Diseconomy of scale respectively. The most important drivers to RE implementation were ranked as: Long term cost benefits, Reduction in cost of RETs, Innovation / advancement of RETS, Incentives or subsidies to implement renewable energy, Adequate legal framework and legislation for Power Purchase Agreement and Preference for environmentally-friendly electricity generation. Importantly, it was found that barriers and drivers are dependent on the type of RE being implemented. A Photo Voltaic (Solar Power) system will not necessarily experience the same barriers or drivers that a Wave Energy Converter system would. In order to drive investment in RE and remove the barriers that may be preventing its implementation in aquaculture, policy will have to be adapted. Particularly in terms of legislation around Power Purchase Agreements. Further, by providing subsidies for RE implementation, it is possible to sustainably grow South Africa’s aquaculture industry.
- Full Text:
- Date Issued: 2018
Baseline isotopic data for Wolffia spp.: another option for tracing N-loading in freshwater systems?
- Authors: Hill, Jaclyn M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68721 , vital:29308 , https://0-doi.org.wam.seals.ac.za/10.1086/696126
- Description: δ15N values of aquatic plants can reflect anthropogenic N loading. Recent work suggests the duckweed Spirodela spp. effectively maps N loading in freshwater ecosystems, but its use may be complicated by a cyanobacterium–duckweed symbiosis that could reduce its utility in low-nutrient environments. I aimed to evaluate the potential of a 2nd duckweed species Wolffia spp., which lacks a cyanobacterial symbiosis, for use in pollution monitoring in freshwater ecosystems. I used a series of laboratory experiments to investigate δ15N equilibration rates and concentration-level effects of single-source N solutions in plant tissue over 16 d to provide baseline data for sewage-plume mapping with Wolffia spp. I also tested concentration-level effects in multisource solutions to investigate the effects of mixed-source inputs. Wolffia reflected environmental N sources with a 12- to 16-d isotopic equilibration time and showed enriched and depleted δ15N ratios for manure and KNO3 solutions, respectively, but distinguished poorly between lower concentrations of manure. Fractionations at isotopic equilibrium were opposite to expectations and decreased with increasing [N]. Wolffia showed a consistent preference for NH3 in mixed-source treatments, regardless of the proportion or concentration of NH3 or NO3– available, and a capacity for N storage, which may complicate mapping of N-loading in natural environments. Wolffia is likely to be a less useful bioindicator than the previously tested Spirodela. Future research should focus on field applications of Spirodela spp. to test its capacity for sewage-plume mapping of freshwater ecosystems in a natural environment.
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- Date Issued: 2018
Bayesian hierarchical modelling with application in spatial epidemiology
- Authors: Southey, Richard Robert
- Date: 2018
- Subjects: Bayesian statistical decision theory , Spatial analysis (Statistics) , Medical mapping , Pericarditis , Mortality Statistics
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59489 , vital:27617
- Description: Disease mapping and spatial statistics have become an important part of modern day statistics and have increased in popularity as the methods and techniques have evolved. The application of disease mapping is not only confined to the analysis of diseases as other applications of disease mapping can be found in Econometric and financial disciplines. This thesis will consider two data sets. These are the Georgia oral cancer 2004 data set and the South African acute pericarditis 2014 data set. The Georgia data set will be used to assess the hyperprior sensitivity of the precision for the uncorrelated heterogeneity and correlated heterogeneity components in a convolution model. The correlated heterogeneity will be modelled by a conditional autoregressive prior distribution and the uncorrelated heterogeneity will be modelled with a zero mean Gaussian prior distribution. The sensitivity analysis will be performed using three models with conjugate, Jeffreys' and a fixed parameter prior for the hyperprior distribution of the precision for the uncorrelated heterogeneity component. A simulation study will be done to compare four prior distributions which will be the conjugate, Jeffreys', probability matching and divergence priors. The three models will be fitted in WinBUGS® using a Bayesian approach. The results of the three models will be in the form of disease maps, figures and tables. The results show that the hyperprior of the precision for the uncorrelated heterogeneity and correlated heterogeneity components are sensitive to changes and will result in different results depending on the specification of the hyperprior distribution of the precision for the two components in the model. The South African data set will be used to examine whether there is a difference between the proper conditional autoregressive prior and intrinsic conditional autoregressive prior for the correlated heterogeneity component in a convolution model. Two models will be fitted in WinBUGS® for this comparison. Both the hyperpriors of the precision for the uncorrelated heterogeneity and correlated heterogeneity components will be modelled using a Jeffreys' prior distribution. The results show that there is no significant difference between the results of the model with a proper conditional autoregressive prior and intrinsic conditional autoregressive prior for the South African data, although there are a few disadvantages of using a proper conditional autoregressive prior for the correlated heterogeneity which will be stated in the conclusion.
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- Date Issued: 2018
Bearing Witness to ‘Irreparable Harm': Incorporating Affective Activity as Practice into Ethics
- Authors: Barker, Kim , Macleod, Catriona I
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/434185 , vital:73037 , ISBN 978-3-319-74720-0 , https://link.springer.com/chapter/10.1007/978-3-319-74721-7_12
- Description: Research with individuals who have experienced trauma requires careful consideration. In preparing the ethics protocol for an ethnographic study of an anti-rape protest, we gave careful consideration to the potential ethical challenges in accordance with the University ethics code. However, this process did not prepare the first author for the dynamic and reciprocal positioning she encountered in relationships in the field or the ‘ethically important’ moment-by-moment decision-making which this required of her. Drawing on the philosophy of Emmanuel Levinas, a feminist reading of the contemporary ‘turn to affect’, and examples from our research, we show how ethical decision-making in ethnographic research is always relational and dialogical, both in our direct interactions with participants and in the ways in which we approach our ‘data’.
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- Date Issued: 2018
Beasts we love
- Authors: Masolane, Tseliso Chrisjan
- Date: 2018
- Subjects: Creative writing (Higher education) -- South Africa , South African fiction (English) -- 21st century , Detective and mystery stories, South African (English) -- 21st century
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/63098 , vital:28363
- Description: My thesis is a novella in flash, written as political crime fiction. It is set in contemporary South Africa and tells the story of Rafau Lekopo, a teacher from a little township called Dikgohlong, whose life is changed forever after he finds his wife and the mayor in bed and shoots them both dead. The information contained within the dead mayor's notebook proves to be explosive, showing that the mayor is far more than he seems, and that he is in fact in the employ of a foreign intelligence service. After his release from prison, the embittered Lekopo sets about his revenge against powerful men who abuse their political power. He takes refuge in Lesotho, masterminds a series of heists, car-hijackings and human trafficking, and expands his syndication back in South Africa. Using the contacts and information from the mayor's notebook, he manipulates the Lesotho government into a diplomatic feud with South Africa which treatens to escalate into a military conflict.
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- Date Issued: 2018
Before you arrive We Are Here: Shuma Sopotela’s ‘Indlulamthi’
- Authors: Makandula, Sikhumbuzo
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147248 , vital:38608 , https://artthrob.co.za/2018/08/03/before-you-arrive-we-were-here-shuma-sopotelas-indlulamthi/
- Description: Chuma Sopotela’s multimedia performance ‘Indlulamthi’ at the National Arts Festival proposes a healing of the ‘Settler Frontier’ through a sonicscape. This production was realized with Lulamil Nikani, the Palestinian actor Ahmad Tobasi and Makhanda-based children from Ntsika High School and several other children groups she invited.
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- Date Issued: 2018
Beginner teachers’ leadership development opportunities: an interventionist case study in a rural combined school in the Ohangwena region, Namibia
- Authors: Ndakolonkoshi, Klaudia
- Date: 2018
- Subjects: School management and organization -- Namibia , Teacher participation in administration -- Namibia , Educational leadership -- Namibia , Teacher effectiveness -- Namibia
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/61603 , vital:28041
- Description: The emergence of distributed leadership theory encourages multiple involvement of individuals in leadership of the school, regardless of their leadership positions (Spillane, 2006). The manifestation of teacher leadership through distributed leadership theory grants opportunities to teachers to enact leadership roles. This study explored how the notion of teacher leadership is understood, the leadership roles existing for the beginner teachers, and the constraining and enabling factors to the practice of teacher leadership in a rural combined school in Ohangwena region, in Namibia. The study is a formative intervention adopting a case study approach located in a critical paradigm since it aimed to bring changes in the activity system of the beginner teachers. The data were collected from ten participants: four beginner teachers, four experienced teachers, the principal and the Head of Department. The data were generated using the following techniques: document analysis, interview, questionnaires, observation and Change Laboratory workshops. The data were analysed thematically using second generation of Cultural Historical Activity Theory (CHAT) and Grant’s (2006, 2008, 2010) Teacher Leadership Model. The findings revealed that there were different understandings of the concept of teacher leadership. It was viewed as participation, influence, motivation and mentoring. It was also revealed that beginner teachers practiced leadership roles across the four zones of Grant’s (2006, 2008, 2010) Teacher Leadership Model, but to various extents. A high participation was noted in zone one within the classroom and zone two in curricular and extra-curricular activities and minimal participation was reported in zone three within the whole school development and zone four beyond the school into the community. Teacher leadership in the case study school was constrained by several factors, including teachers’ reluctance to lead, cultural beliefs, top-down leadership structure and lack of experience. Due to the minimal participation of beginner teachers in zone three and four, the findings suggested that the school should foster a collaborative culture, establish induction and mentoring committees in the school and encourage beginner teachers to take up leadership roles by providing opportunities for them to lead through delegation. In a series of Change Laboratory workshops (CLW) the principal and the Head of Department took up the responsibility of providing leadership training to the teachers to enable them to assume leadership roles in the school. In addition, participants agreed to establish induction and mentoring committees in the school to provide guidance and assistance to teacher leaders.
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- Date Issued: 2018
Behaviour of quiet time ionospheric disturbances at African equatorial and midlatitude regions
- Authors: Orford, Nicola Diane
- Date: 2018
- Subjects: Ionospheric storms , Ionospheric storms -- Africa , Ionosphere , Plasmasphere , Q-disturbances , Total electron content (TEC)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62672 , vital:28228
- Description: Extreme ionospheric and geomagnetic disturbances affect technology adversely. Prestorm enhancements, considered a potential predictor of geomagnetic storms, occur during quiet conditions prior to geomagnetic disturbances. The ionosphere experiences general disturbances during quiet geomagnetic conditions and these Q- disturbances remain unexplored over Africa. This study used TEC data to characterize the morphology of Q-disturbances over Africa, exploring variations with solar cycle, season, time of occurrence and latitude. Observations from 10 African GPS stations in the equatorial and midlatitude regions show that Q-disturbances in the equatorial region are predominantly driven by E x B variations, while multiple mechanisms affect the midlatitude region. Q- disturbances occur more frequently during nighttime than during daytime and no seasonal trend is observed. Midlatitude Q-disturbance mechanisms are explored in depth, considering substorm activity, the plasmaspheric contribution to GPS TEC and plasma transfer between conjugate points. Substorm activity is not a dominant mechanism, although Q-disturbances occurring under elevated substorm conditions tend to have longer duration and larger amplitude than general Q-disturbances. Many observed Q-disturbances become non-significant once the plasmaspheric contribution to the TEC measurements is removed, indicating that these disturbances occur within the plasmasphere, and not the ionosphere. Transfer of plasma between conjugate points does not seem to be a mechanism driving Q-disturbances, as the corresponding nighttime behaviour expected between depletions in the summer hemisphere and enhancements in the winter hemisphere is not observed. Pre-storm enhancements occur infrequently, rendering them a poor predictor of geomagnetic disturbances. Pre-storm enhancement morphology does not differ significantly from general quiet time enhancement morphology, suggesting pre-storms are not a special case of Q-disturbances.
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- Date Issued: 2018
Beneficial effects of medicinal plants in fish diseases
- Authors: Stratev, Deyan , Zhelyazkov, Georgi , Noundou, Xavier S , Krause, Rui W M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126177 , vital:35856 , https://doi.org/10.1007/s10499-017-0219-x
- Description: Fish are constantly in contact with pathogens inhabiting water. High populationdensity as well as poor hydrodynamic conditions and feeding lead to an increased sensitivitytowards infections. In order to prevent major economic losses due to diseases, variousmedications are used for treatment and prevention of infections. The use of antimicrobialdrugs in aquacultures could lead to emergence of resistance in pathogenic microorganisms.Alternatives are being sought over the last few years to replace antibiotics, and medicinalplants are one of available options for this purpose. These plants are rich in secondarymetabolites and phytochemical compounds, which have an effect against viral, bacterial, andparasitic diseases in fish. Their main advantage is their natural origin and most of these plantsdo not represent threat for human health, the fish, and the environment. The goal of this reviewis to present information on the treatment of viral, bacterial, and parasitic diseases in fishthrough medicinal plants, with focus on the mechanisms of action of the identified secondarymetabolites, fractions, or plant extracts.
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- Date Issued: 2018
Best simultaneous approximation in normed linear spaces
- Authors: Johnson, Solomon Nathan
- Date: 2018
- Subjects: Normed linear spaces , Approximation theory , Mathematical analysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58985 , vital:27400
- Description: In this thesis we consider the problem of simultaneously approximating elements of a set B C X by a single element of a set K C X. This type of a problem arises when the element to be approximated is not known precisely but is known to belong to a set.Thus, best simultaneous approximation is a natural generalization of best approximation which has been studied extensively. The theory of best simultaneous approximation has been studied by many authors, see for example [4], [8], [25], [28], [26] and [12] to name but a few.
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- Date Issued: 2018
Between blue and light
- Authors: Campbell, Jennifer
- Date: 2018
- Subjects: South African fiction (English) -- 21st century , Short stories, South African (English) -- 21st century
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/63570 , vital:28441
- Description: My novella follows a narrator observing her life, as she struggles with what it is to live in a world that she finds simultaneously frightening and beautiful. The story touches on the limitations of human connection and with loss in various forms. Set in both Cape Town and small town South Africa, the story explores the inner life of a woman detached and adrift.
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- Date Issued: 2018
Biochemical characterisation and small molecule modulation of the interaction between two cytosolic Hsp70s from Trypanosoma brucei and potential co-chaperones
- Authors: Bentley, Stephen John
- Date: 2018
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63402 , vital:28407
- Description: Expected release date-April 2019
- Full Text:
- Date Issued: 2018
Bioinformatics tool development with a focus on structural bioinformatics and the analysis of genetic variation in humans
- Authors: Brown, David K
- Date: 2018
- Subjects: Bioinformatics , Human genetics -- Variation , High performance computing , Workflow management systems , Molecular dynamics , Next generation sequencing , Human Mutation Analysis (HUMA)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/60708 , vital:27820
- Description: This thesis is divided into three parts, united under the general theme of bioinformatics tool development and variation analysis. Part 1 describes the design and development of the Job Management System (JMS), a workflow management system for high performance computing (HPC). HPC has become an integral part of bioinformatics. Computational methods for molecular dynamics and next generation sequencing (NGS) analysis, which require complex calculations on large datasets, are not yet feasible on desktop computers. As such, powerful computer clusters have been employed to perform these calculations. However, making use of these HPC clusters requires familiarity with command line interfaces. This excludes a large number of researchers from taking advantage of these resources. JMS was developed as a tool to make it easier for researchers without a computer science background to make use of HPC. Additionally, JMS can be used to host computational tools and pipelines and generates both web-based interfaces and RESTful APIs for those tools. The web-based interfaces can be used to quickly and easily submit jobs to the underlying cluster. The RESTful web API, on the other hand, allows JMS to provided backend functionality for external tools and web servers that want to run jobs on the cluster. Numerous tools and workflows have already been added to JMS, several of which have been incorporated into external web servers. One such web server is the Human Mutation Analysis (HUMA) web server and database. HUMA, the topic of part 2 of this thesis, is a platform for the analysis of genetic variation in humans. HUMA aggregates data from various existing databases into a single, connected and related database. The advantages of this are realized in the powerful querying abilities that it provides. HUMA includes protein, gene, disease, and variation data and can be searched from the angle of any one of these categories. For example, searching for a protein will return the protein data (e.g. protein sequences, structures, domains and families, and other meta-data). However, the related nature of the database means that genes, diseases, variation, and literature related to the protein will also be returned, giving users a powerful and holistic view of all data associated with the protein. HUMA also provides links to the original sources of the data, allowing users to follow the links to find additional details. HUMA aims to be a platform for the analysis of genetic variation. As such, it also provides tools to visualize and analyse the data (several of which run on the underlying cluster, via JMS). These tools include alignment and 3D structure visualization, homology modeling, variant analysis, and the ability to upload custom variation datasets and map them to proteins, genes and diseases. HUMA also provides collaboration features, allowing users to share and discuss datasets and job results. Finally, part 3 of this thesis focused on the development of a suite of tools, MD-TASK, to analyse genetic variation at the protein structure level via network analysis of molecular dynamics simulations. The use of MD-TASK in combination with the tools developed in the previous parts of this thesis is showcased via the analysis of variation in the renin-angiotensinogen complex, a vital part of the renin-angiotensin system.
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- Date Issued: 2018
Biological activities of plant extracts from Ficus elastica and Selaginella vogelli: an antimalarial, antitrypanosomal and cytotoxity evaluation
- Authors: Meyer, Franck , Isaacs, Michelle , Noundou, Xavier S , Krause, Rui W M , Teinkela, J E M , Hoppe, Heinrich C , Mpondo, Albert E M , Azebaze, Anatole G B , Nguemfo, Edwige L , Wintjens, Rene
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126142 , vital:35853 , https://doi.org/10.1016/j.sjbs.2017.07.002
- Description: The cytotoxic, antiplasmodial, and antitrypanosomal activities of two medicinal plants traditionally used in Cameroon were evaluated. Wood of Ficus elastica Roxb. ex Hornem. aerial roots (Moraceae) and Selaginella vogelii Spring (Selaginellaceae) leaves were collected from two different sites in Cameroon. In vitro cell-growth inhibition activities were assessed on methanol extract of plant materials against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei, as well as against HeLa human cervical carcinoma cells. Criteria for activity were an IC50 value 10 μg/mL. The extract of S. vogelii did not significantly reduce the viability of P. falciparum at a concentration of 25 μg/mL but dramatically affected the trypanosome growth with an IC50 of 2.4 μg/mL. In contrast, at the same concentration, the extract of F. elastica exhibited plasmodiacidal activity (IC50 value of 9.5 μg/mL) and trypanocidal (IC50 value of 0.9 μg/mL) activity. Both extracts presented low cytotoxic effects on HeLa cancer cell line. These results indicate that the selected medicinal plants could be further investigated for identifying compounds that may be responsible for the observed activities and that may represent new leads in parasitical drug discovery.
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- Date Issued: 2018
Biological activity of plant extracts and isolated compounds from Alchornea laxiflora: Anti-HIV, antibacterial and cytotoxicity evaluation
- Authors: Ndinteh, Derek T , Olivier, D K , Noundou, Xavier S , Krause, Rui W M , Mnkandhla, D , Isaacs, Michelle , Hoppe, Heinrich C , Muganza, F M , Mbafor, J T , Van Vuuren, S F , Patnala, S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126634 , vital:35907 , https://doi.org/10.1016/j.sajb.2018.08.010
- Description: This study was designed to assess the cytotoxicity, anti-HIV and antibacterial efficacy of various solvent extracts of roots, stem and leaves of Alchornea laxiflora, as well as five compounds isolated from its methanolic stem extract viz.; ellagic acid (1); 3-O-methyl-ellagic acid (2), 3-O-β-d-glucopyranosyl-β-sitosterol (3), 3-O-acetyl-oleanolic acid (4) and 3-O-acetyl-ursolic acid (5). The tested crude extracts were prepared from several solvent polarities including: hexane (Hex), chloroform (CHCl3), ethyl acetate (EtOAc), ethanol (EtOH), methanol (MeOH) and water (H2O). The anti-HIV properties were assessed on HIV-1 subtype C integrase while the cytotoxicity was tested against Hela cells. The antibacterial activity was studied on a panel of pathogens including gastrointestinal, skin, respiratory and urinary-tract infection causing Gram positive bacteria viz.; Bacillus cereus (ATCC 11778), Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 25923) and Staphylococcus saprophyticus (ATCC 15305)] and Gram-negative bacteria, i.e., Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Moraxella catarrhalis (ATCC 23246). All the tested samples were determined to be non-toxic due to the low inhibitions observed. The most potent anti-HIV activity was observed for the methanolic extract of A. laxiflora root (ALR4) with an IC50 value of 0.21 ng/ml, which was more active than chicoric acid used as reference drug (6.82 nM). Roots, stem and leaves of A. laxiflora extracts exhibited antibacterial activities against most of the Gram-positive bacteria with the minimum inhibitory concentrations (MIC) ranging between 50 and 63 μg/ml. Compounds 1–5 displayed antibacterial activities against S. saprophyticus with MIC values as low as 4 μg/ml. The results inferred from this study demonstrate the potential of A. laxiflora root as a source for new anti-HIV drugs and scientifically validate the traditional use of A. laxiflora in the treatment of gastrointestinal, skin, respiratory and urinary tract related infections. These results reaffirm the ethnopharmacological significance of African traditional medicines.
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- Date Issued: 2018
Biological control of Salvinia molesta in South Africa revisited
- Authors: Martin, Grant D , Coetzee, Julie A , Weyl, Philip S R , Parkinson, Matthew C , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103878 , vital:32318 , https://doi.org/10.1016/j.biocontrol.2018.06.011
- Description: The aquatic weed Salvinia molesta D.S. Mitch. (Salviniaceae) was first recorded in South Africa in the early 1900s, and by the 1960s was regarded as one of South Africa’s worst aquatic weeds. Following the release of the weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) in 1985, the weed is now considered under successful biological control. However, the post-release evaluation of this biological control programme has been ad hoc, therefore, to assess the efficacy of the agent, annual quantitative surveys of South African freshwater systems have been undertaken since 2008. Over the last ten years, of the 57 S. molesta sites visited annually in South Africa, the weevil has established at all of them. Eighteen sites are under successful biological control, where the weed no longer poses a threat to the system and 19 are under substantial biological control, where biological control has reduced the impact of the weed. Since 2008, the average percentage weed cover at sites has declined significantly from 51–100% cover to 0–5% cover in 2017 (R2 = 0.78; P < 0.05). Observations of site-specific characteristics suggest that biological control is most effective at small sites and more difficult at larger and shaded sites. Our findings show that S. molesta remains under good biological control in South Africa, however, some sites require intermittent strategic management, such as augmentative releases of C. salviniae.
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- Date Issued: 2018
Biophysical monitoring of unphosphorylated STAT3 homodimerization
- Authors: Mtwebana, Sinethemba Siphokazi
- Date: 2018
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63957 , vital:28514
- Description: Expected release date-April 2020
- Full Text:
- Date Issued: 2018
Bioprospecting for amylases, cellulases and xylanases from ericoid associated fungi, their production and characterisation for the bio-economy
- Authors: Adeoyo, Olusegun Richard
- Date: 2018
- Subjects: Mycorrhizal fungi , Hydrolases , Ericaceae South Africa , Ericaceae Molecular aspects
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/64327 , vital:28533
- Description: South Africa is one of the most productive areas for ericaceous plants with about 850 identified species in the Cape Floral Region. The Albany Centre of Endemism where all fungi used in this study were isolated from, falls within this region. Ericaceous plants interact with some fungi via an association called the ericoid mycorrhizal (ERM) association. All fungi used in this study were isolated from roots of six ericaceous plants; Erica cerinthoides, Erica demissa, Erica chamissonis, Erica glumiflora, Erica caffra and Erica nemorosa. Fungal enzymes are known to play a significant role in the food, brewing, detergent, pharmaceutical and biofuel industries. The enzyme industry is among the major sectors of the world, and additional novel sources are being explored from time to time. This study focussed on amylases (amyloglucosidase, AMG), cellulases (endoglucanase) and xylanases (endo-1,4-P-xylanase) production from ERM fungal isolates. Out of the fifty-one (51), fungal isolates screened, ChemRU330 (Leohumicola sp.), EdRU083 and EdRU002 were among the fungi that had the highest activities of all the enzymes. They were tested for the ability to produce amylases and cellulases under different pH and nutritional conditions that included: carbon sources, nitrogen sources and metal ions, at an optimum temperature of 28°C in a modified Melin-Norkrans (MMN) liquid medium. Cellulase specific activity of 3.99, 2.18 and 4.31 (U/mg protein) for isolates EdRU083, EdRU002 and ChemRU330, respectively, was produced at an optimal pH of 5.0. For amylase, ChemRU330 had the highest specific activity of 1.11 U/mg protein while EdRU083 and EdRU02 had a specific activity of 0.80 and 0.92 U/mg protein, respectively, at the same pH with corresponding biomass yield of 113, 125 and 97 mg/50 ml, respectively. Increased enzyme activities and improved mycelial biomass production were obtained in the presence of supplements such as potassium, sodium, glucose, maltose, cellobiose, tryptone and peptone, while NaFe-EDTA and cobalt inhibited enzyme activity. ChemRU330 was selected to determine the consistency and amount of amylase, cellulase and xylanase formed after several in vitro subculturing events. AMG and endo-1,4-P-xylanase were found to have the most consistent production throughout the study period. The AMG was stable at 45oC (pH 5.0), retaining approximately 65% activity over a period of 24 h. The molecular mass of AMG and endo-1,4-P-xylanase were estimated to be 101 kDa and 72 kDa, respectively. The Km and kcat were 0.38 mg/ml and 70 s-1, respectively, using soluble starch (AMG). For endo-1,4-P-xylanase, the Km and Vmax were 0.93 mg/ml and 8.54 U/ml, respectively, using beechwood xylan (endo-1,4-P-xylanase) as substrate. Additionally, crude extracts of five root endophytes with unique morphological characteristics were screened for antibacterial properties and was followed by determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). L. incrustata (ChemRU330) and Chaetomium sp. extracts exhibited varying degrees of inhibition against two Gram-positive and Gram-negative bacteria. The crude extract of L. incrustata was the most effective which was found to inhibit Staphylococcus aureus (MIC: 1 mg/ml), Bacillus subtilis (MIC: 2 mg/ml) and Proteus vulgaris (MIC: 16 mg/ml). The L. incrustata displayed potential for antibacterial production and could be considered as an additional source of new antimicrobial agents in drug and food preservation. Also, the three isolates used for enzyme production were identified to genus and species levels, i.e., Leohumicola incrustata (ChemRU330), Leohumicola sp. (EdRU083) and Oidiodendron sp. (EdRU002) using both ITS and Cox1 DNA regions. The molecular analysis results indicated that these ERM mycorrhizal fungi were similar to those successfully described by some researchers in South Africa and Australia. Therefore, this study opens new opportunities for exploring ERM fungal biomolecules for the bio-economy. The promising physicochemical properties, starch and xylan hydrolysis end- products, and being non-pathogenic make AMG and endo-1,4-P-xylanase potential candidates for future applications as additives in the food industry for the production of glucose, glucose syrups, high-fructose corn syrups, and as well as the production of bioethanol. Finally, the findings of this study revealed that it is possible to produce hydrolytic enzymes from ERM fungi in vitro using chemically defined media. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2018
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- Date Issued: 2018
Biotic and abiotic drivers of macroinvertebrate assemblages in a South African river
- Authors: Bellingan, Terence Andrew
- Date: 2018
- Subjects: Aquatic insects -- South Africa -- Eastern Cape , Stream ecology -- South Africa -- Eastern Cape , Freshwater ecology -- South Africa -- Eastern Cape , Riparian areas -- Management , Ecosystem management -- South Africa -- Eastern Cape , Mayflies -- South Africa -- Eastern Cape , Stoneflies -- South Africa -- Eastern Cape , Keiskamma River
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61839 , vital:28067
- Description: Aquatic insects are the most numerically abundant and diverse group of organisms found in lotic ecosystems in South Africa and the world over. They play vital roles in freshwater ecosystem functioning, processing nutrients and in turn forming integral links in stream food-webs. This thesis focussed on examining the macroinvertebrate fauna within three reaches of headwater streams of the Keiskamma River system: reaches that were considered to be fishless; reaches that were invaded by non-native salmonid species; and reaches that were dominated by native fish. I described the effects of predatory fish presence through detailed examination of macroinvertebrate assemblage composition; macroinvertebrate drift timing and density; and through niche utilisation determined from stable isotope data. Patterns in the macroinvertebrate assemblages of the headwaters of the Keiskamma River appear to be driven more strongly by flow rate and seasonal influences, but fish presence and biotope availability were also significant drivers. Niche shifts due to predator presence were not easy to detect and, while patterns of influence may have been evident, they were not found to be significant. However, I demonstrated that salmonids selectively feed on native fish species when the opportunity is presented, occupying significantly higher trophic levels when co-occurring with native fish than in invaded reaches where native fish are absent. Drift timing and density were demonstrated to be significantly different between reach for specific macroinvertebrate species from the Ephemeroptera and Plecoptera, under differing fish predation regimes, in agreement with what has been observed from studies in rivers elsewhere. In freshwater ecosystems of South Africa and worldwide, mitigation of negative effects of alien fishes through their removal using piscicides may also affect non-target organisms. To better understand the effects of just such a removal operation, employed for the first time in the history of freshwater conservation in South Africa, macroinvertebrate communities were assessed for non-target effects of rotenone. The fish eradication operations were demonstrated to have a short-term negative effect on the macroinvertebrate assemblage, through water quality index measurements and alteration of densities of macroinvertebrate taxa collected from stone surfaces. However, no long-term detrimental impact was observed as macroinvertebrate faunas returned to a comparable pre-treatment state within a year of each rotenone application.
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- Date Issued: 2018
Black university students’ experiences of negotiating their social identity in a historically white university
- Authors: Mogotsi, Opelo Petunia
- Date: 2018
- Subjects: Corporate culture -- South Africa , Social integration -- South Africa , Race discrimination -- South Africa , Segregation in higher education -- South Africa , Group identity -- South Africa , College students, Black -- South Africa , Biko, Steve, 1946-1977 , Fanon, Frantz, 1925-1961
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/62416 , vital:28174
- Description: This thesis seeks to explore the social identity of black students in a historically white university. Since 1994, South African government has been promulgating pieces of legislation aimed at ensuring racial integration, and indirectly enforcing acculturation in historically white universities. Studies have proven that institutional cultures in historically white universities alienate and exclude black students’ identities. These students’ sense of social identity, which includes amongst others; culture, heritage, language and traditions, and consequently self-esteem and self-concept is altered in these institutions. Research has been scant regarding the shape and form that black students’ identity assume when they get to these spaces. Face to face interviews were used to collect data and thematic analysis was used for data analysis. The Social Identity and the Acculturation models were used to explore the experiences of black students in negotiating their social identities in a historically white university. Evoking Steve Biko’s analysis of ‘artificial integration’, it was illustrated how the ‘integration’ narrative sought to discard the identity of black students and psychologically enforce a simulation of black students into white established identities. The main themes discussed indicated that black students in this study had social identity and identity challenges in a historically white university. This study has implications for policy development as I hope to theoretically sensitize historically white universities to (apart from mere opening of spaces of learning) understand the social identity challenges of black students.
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- Date Issued: 2018