Physiological winners and losers in an ocean warming hotspot: a Case study on argyrosomus off the Namibian coast, with implications for their future management
- Authors: Pringle, Brett Andrew
- Date: 2021-10
- Subjects: Argyrosomus Benguela Current , Ocean temperature Benguela Current , Sciaenidae Benguela Current , Argyrosomus Physiology Benguela Current , Argyrosomus Geographical distribution Climatic factors Benguela Current , Argyrosomus Effect of temperature on Benguela Current , Sciaenidae fisheries Namibia , Fishery management Namibia , Sustainable fisheries Namibia
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188987 , vital:44804
- Description: Anthropogenic-induced climate change is having a profound impact on aquatic ecosystems, and the resilience of fish populations will be determined by how they respond to these impacts. Changes in ocean water temperature is regarded as the most pervasive change, and affects the biological, physiological and distribution response of species, particularly ectotherms. The increasingly variable biological responses to a changing environment suggest that some species and populations will likely prove to be more tolerant than others. The northern Namibian coast is an ocean warming hotspot, with temperatures rising at approximately ten times the global average. These rapid changes are predicted to have a considerable impact on the marine fauna. One recently documented change in distribution is a southern extension of the sciaenid, Argyrosomus coronus, from southern Angola into northern Namibian waters, where it now overlaps with the closely related Namibian species, Argyrosomus inodorus. Understanding how these species perform at current and future temperatures and where they overlap is vital to optimise any adaptive management for the Argyrosomus species, which forms a large component of Namibia’s coastal commercial, recreational and subsistence fisheries. The aim of this study was to quantify the aerobic scope of both species (A. coronus and A. inodorus), to determine which Argyrosomus species will be a winner at the current and future climate predictions and to provide recommendations for the sustainable management of the Namibian Argyrosomus fishery. Intermittent flow-through respirometry was used to quantify standard and maximum metabolic rates for both species across a range of temperatures. Results showed that metabolic rates scaled positively with temperature. It appears that the aerobic scope of A. inodorus was notably higher at most temperatures (12, 15, 18 and 21˚C), while that of A. coronus was only higher at the warmest test temperature of 24˚C. This corresponded with the contemporary biogeographic patterns of each species. Based on these findings, it is likely that the warming ocean conditions in northern Namibia and the cold Lüdertiz upwelling cell south of Walvis Bay will constrain these fish to central Namibia. While both species demonstrated signs of resilience to high temperatures, it is likely that the warming conditions will increasingly favour A. coronus, and that the leading edge of their distribution will shift southward in Namibia. The distribution of A. inodorus is likely to contract, as the energy budget of those on the northern trailing edge will be compromised. To promote the sustainable utilisation of the complex Argyrosomus fishery, adaptive management strategies need to be implemented. This will only be possible with a comprehensive monitoring program, including the collection of genetic data to inform the changing proportions of the two species. To maintain the A. coronus population, the current regulations need to be re-assessed, and harvest slots should be introduced to protect juvenile A. coronus and the fecund large females of both species. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries, 2021
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- Date Issued: 2021-10
Potential Synergism between Entomopathogenic Fungi and Entomopathogenic Nematodes for the control of false codling moth (Thaumatotibia leucotreta)
- Authors: Prinsloo, Samantha Lee
- Date: 2021-10
- Subjects: Cryptophlebia leucotreta , Entomopathogenic fungi , Insect nematodes , Citrus Diseases and pests , Cryptophlebia leucotreta Biological control , Pests Integrated control , Biological pest control agents
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188832 , vital:44790
- Description: False codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) (FCM), is a major phytosanitary pest of citrus in South Africa. Sufficient control measures for the soil-dwelling life stages of FCM have yet to be identified and owing to restrictions on the use of insecticides, non-chemical control options have been investigated including the use of entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPN). Laboratory and field trials on an indigenous EPF, Metarhizium anisopliae FCM Ar 23 B3, have shown that this isolate is capable of inducing mortality in FCM soil-dwelling life stages. Other agents that have been highlighted as potential controls for soil-dwelling FCM life stages are the EPN species Steinernema yirgalemense 157-C, S. jeffreyense J194 and H. noenieputensis 158-C. This study conducted laboratory bioassays to assess the virulence of these four control agents on fifth instar FCM, in 24-well plates. These results reaffirmed the virulence of the four microbial control agents at their recommended doses of 50 IJs (EPN) and 1×107 conidia/ml (EPF) against fifth instar FCM with 80 to 96% larval mortality recorded. The EPF isolate exhibited the lowest mortality whilst S. yirgalemense induced the greatest mortality. In addition, the lethal concentration (LC) values for each isolate were determined using dose response bioassays. These values were previously unknown for all EPN species and for the EPF isolate based on the methodology used in this study. The LC50 results in order from lowest to highest EPN IJ concentration requirements were 4.38 IJs (S. yirgalemense), 4.47 IJs (S. jeffreyense) and 7.11 IJs (H. noenieputensis). The EPF isolate exhibited an LC50 of 3.42×105 conidia/ml. Lastly, research has shown that the combination of two control agents may increase control of late instar lepidopteran and coleopteran larvae, through synergistic interactions. Thus, the interactions that occurred between the combination of these EPN species with the EPF isolate were determined. This study found that when all three EPN species were combined simultaneously and sequentially with the EPF isolate M. anisopliae FCM AR 23 B3, additive interactions took place with exception of the simultaneous application of S. yirgalemense and H. noenieputensis, with the EPF and S. jeffreyense applied 24 h post EPF application. For the former, a synergistic interaction was found, whilst for the latter two, an antagonistic interaction. Although no strongly synergistic interactions were observed, additive interactions have been shown to reach a synergistic level when certain parameters are changed. Moving forward, a uniform methodology for conducting EPF/EPN interaction experiments has been suggested. It has also been recommended that due to the additive interactions observed in this study, laboratory soil-bioassays and field trials should be carried out for all three EPN species in combination with the EPF isolate. This research will inevitably facilitate the constant knowledge into management strategies for the phytosanitary pest, FCM in South African citrus. , Thesis (MSc) -- Science, Zoology and Entomology, 2021
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- Date Issued: 2021-10
Quantifying the ecological and socioeconomic implications of a recovery/collapse of South Africa’s West Coast rock lobster fishery
- Authors: Eggers, Jessica Marguerite
- Date: 2021-10
- Subjects: Jasus lalandii South Africa , Lobster fisheries South Africa , Lobster fisheries Catch effort South Africa , Fishery management South Africa , Small-scale fisheries South Africa , Economics Sociological aspects , Value chain analysis
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188854 , vital:44792
- Description: The West Coast rock lobster (WCRL) Jasus lalandii fishery is South Africa’s third most valuable fishery, but the stock is currently at less than 2% of its pristine biomass. Scientists are warning that if no measures are taken, the WCRL could face commercial extinction. The necessary reductions in the global Total allowable Catch (TAC) seen in past years have had large economic implications for the WCRL value chain, but research into the socio-economic aspects of this fishery is limited. This study, therefore, aims to establish an overview of the economic revenue over the seasons 2016/17 – 2018/19 by exploring changes and trends in the net seasonal income (NSI) for the fishery, sectors within the fishery and different stakeholders. It also investigates the prospects for the sectors and different actors in this fishery over the seasons 2019/2020 - 2030/31 through analysis of the net present value (NPV) under three proposed global TAC management scenarios (global TAC of 640 tonnes, 1084 tonnes and 1280 tonnes). Data concerning costs and incomes as well as dynamics, mechanisms and concerns surrounding the fishery were collected from stakeholders in the different sectors through interviews and surveys. Further, official records from DEFF (catches, actors, vessels and quotas) and projections made by the Marine Resource Assessment (MARAM) team at the University of Cape Town (rates of recovery of the resource and future catches under the different TAC scenarios) were obtained and analysed. Cost and income data were summarised and models characterising the economic flows within the fishery were created. Calculations regarding the NSI and NPV were made using Monte Carlo simulations to account for the uncertainty surrounding many of the input variables. Results show that while the fishery as a whole made economic profits for the three seasons, the decreasing quotas in 2018/19 had a disproportionately negative impact on some of the representative individuals examined within the different sectors. The projections indicate that while each of the sectors as a whole would continue to make profits largely proportional to their allocation under the different TAC scenarios, many vessel owners in the fishery are likely to face economic losses or very marginal gains under the lower quota options, while the NPV for quota holders who outsource the catching of their quota are likely to be proportionally less affected by the changes in global TAC. This dynamic is important to consider for the future of this fishery. If the resource is to recover, and fishing activity is to continue equitably under the decreased quotas that the recovery of the biomass necessitates, the socio-economic context and the dynamics within which the fishers operate must be considered and studied more extensively and socio-economic consequences of a lower global TAC mitigated while improving the ecological status of the resource. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
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- Date Issued: 2021-10
Scaffolding argumentative writing through Reading to Learn (RtL) pedagogy: a case study of three grade 11 English second language teachers in Namibia
- Authors: Matengu, Ernest Samubu
- Date: 2021-10
- Subjects: Rose, David, 1955- , Reading (Secondary) , Persuasion (Rhetoric) Study and teaching (Secondary) Namibia , English language Writing Study and teaching (Secondary) Namibia , English language Rhetoric Study and teaching (Secondary) Namibia , English language Study and teaching (Secondary) Foreign speakers Case studies , Reading to Learn , Scaffolding Interaction Cycle
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191148 , vital:45065
- Description: The central aim of this study was to investigate the positive impact of Reading to Learn (RtL) pedagogy in enhancing Grade 11 learners’ argumentative writing skills. This was a case study of one school in Otjozondjupa region in Namibia. The pedagogy, RtL, was designed to address learning inequalities with marginalised communities in Australia. Coupled with challenges in literacy development in learners, current methods have not successfully addressed the teaching and learning of argumentative writing amidst learning inequalities. This study employed the six stages of Scaffolding Interaction Cycle of RtL in order to teach argumentative writing. As is evidenced in recent research, the scaffolding cycle of RtL provides equal opportunities to learners from diverse backgrounds to attain epistemological access at the same pace. RtL’s theoretical and conceptual framework is derived from Bernstein’s theory of education as pedagogic discourse (a device for maintaining inequality in society), Vygotsky’s theory of learning as a social process and Halliday’s model of language as text in social context. The two research questions for this study were: (1) What role does Reading to Learn (RtL) pedagogy play in developing Grade 11 learners’ ability to write argumentative essays? And (2) How can the implementation of RtL pedagogy through scaffolding impact on/improve learners’ literacy skills development for argumentative essay writing? This qualitative case study generated data through observation of three teachers’ lessons, a Stimulated Recall Interview (SRI) conducted with the three teachers and learners’ pre and posttest of argumentative essays. The findings of this study revealed that teachers found RtL as a comprehensive pedagogy that makes teaching and learning of argumentative writing successful through systematic scaffolding of learning. Learners’ written pre and posttest also showed a narrowing of the gap between weak and strong learners in that weak learners recorded an upward trend similar to that of strong learners in their posttest. Given the design of RtL and studies conducted globally, the findings of this study can be comparable. , Thesis (MEd) -- Faculty of Education, Education, 2021
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- Date Issued: 2021-10
Self-inquiry: Comparing Plato and Patanjali
- Authors: Coughlan, Daniel Michael
- Date: 2021-10
- Subjects: Plato , Patañjali , Self , Identity (Philosophical concept) , Comparison (Philosophy) , Justification (Theory of knowledge)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190066 , vital:44960
- Description: At its most effective my research hopes to re-affirm the central value and importance of self-inquiry. That is, I hope to echo the familiar call of the wise to know thyself. Of the many mouths and temple walls that have lent authority to this precept there is perhaps no mouth more important than one’s own. To know thyself is the task and responsibility of the individual. In order to arrive at the point where I can re-affirm its value I explore the nature of self-inquiry with the help of Plato, Patanjali and a comparison between them. I propose two general senses in which we might understand self-inquiry and seek to bring out the core problems faced by each. We find an account of these two senses and the relationship between them in both Plato and Patanjali, so too, though less obviously, in the comparison between them. The comparison provides the opportunity for reflecting on the ground that it moves from and depends on, the common ground we assume between the two compared philosophers/ies. I contend that this ground is ultimately the comparer, one’s self. The consequence is that the comparative project and the project of self-inquiry both meet and are mutually beneficial. The three together; Plato, Patanjali, and the comparison between them help us account for nature of self-inquiry in helping us to better understand the relationship between the two senses in which we can come to understand and think about it. In the first sense, self-inquiry is cast as the examination of one’s life. In the second sense, we are invited to consider the possibility of an unmediated knowing of the examiner, an unmediated self-knowing. With a better understanding of what self-inquiry is I stand to conclude by re-affirming its value. , Thesis (MPhil) -- Faculty of Humanities, Philosophy, 2021
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- Date Issued: 2021-10
The factors to be considered by the competition authorities when a fine may cause the firm to exit
- Authors: Quilliam, Layne Edwin
- Date: 2021-10
- Subjects: South Africa. Competition Act, 1998 , Competition Tribunal (South Africa) , Business enterprises Law and legislation South Africa , Debt-to-equity ratio South Africa , Bankruptcy Prevention , Causation , Competition
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188408 , vital:44751
- Description: The Competition Act empowers the Competition Tribunal to levy fines against a firm for certain contraventions of the Act. Such fines are statutorily capped to prevent the fine from causing the firm’s exit. This maximum is based on the overarching principle of fairness which precludes a fine, on its own, from destroying a firm’s business. However, the Competition Appeal Court acknowledged in 2013 that fines below this cap may still cause a firm to exit. The purpose of this paper is to propose the factors that should be considered when determining a firm’s ability to pay such a below-cap fine. These factors are the calculation of the fine, probable exit, causation of exit and the competitive effect of the firm’s exit. The fining provisions of the Act are initially explored to provide context for the discussion and are then compared to equivalent provisions in Europe. Liquidation and business rescue proceedings are then described as the most common forms of a firm’s exit from the market. Methods for determining the causal relationship between the fine and the firm’s exit are explored through delictual law’s factual and legal causation. The competitive effects of the firm’s exit are premised on the purpose of the Competition Act and are evaluated through the Competition Act’s merger provisions, specifically, the failing firm factor. These proposed factors are then tested through hypothetical facts to analyse their possible interactions and efficacy. , Thesis (LLM) -- Faculty of Law, Law, 2021
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- Date Issued: 2021-10
The impact of the BBB-EE policy instrument on wealth inequality : A case study on the banking sector of South Africa
- Authors: Moshikaro, Kei Kgaogelo Felia
- Date: 2021-10
- Subjects: Black Economic Empowerment (Program : South Africa) , Income distribution South Africa , South Africa Economic policy , South Africa Economic conditions 1991- , Banks and banking South Africa , South Africa. Financial Sector Regulation Act, 2017
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191035 , vital:45052
- Description: It has been recognised that, whether measured in terms of income or wealth, South Africa remains as one of the most unequal societies in the world. Reducing these high levels of inequalities has been an important area of focus through the formulation of policy instruments by South African policy makers. Within a specific focus on the South African banking sector, the objective of this research is to ascertaining the extent to which addressing inequalities was in fact achieved through the changing of wealth ownerships under the Broad Based Black Economic Empowerment policy instrument. To contextualise, the thesis surveys literature on two stylised economic hypotheses on both income and wealth to understand the potential causes of their respective inequalities. An exploration of both income, wealth measurements and their distributions in South Africa are presented, in addition to policy instruments designed to ameliorate income and wealth inequalities in South Africa. The thesis further presents brief case studies from the literature on Brazil’s success in reducing its high income inequality and the Malaysian National Economic Policy empowerment program to effect wealth economic transformation, as comparatives to the South African experience. The thesis findings indicate that contrary to the objectives of the BBB-EE instrument and wealth transfers, the program within the banking sector resulted in highly unequal wealth shares and equally high concentration levels. The richest top one per cent of individuals participating in the BEE transactions in the banking sector captured 79 per cent of the total wealth transfers, this providing indications of extremely high concentrations of wealth. Further, wealth meaningfully cumulates at only the 50 percentage level of the wealth distribution, this additionally suggesting that wealth transfers featured less in the bottom half of the wealth distribution. The banking BBB-EE wealth Gini coefficient of 0.88 is evidence of the extremely high levels of inequality that resulted from the BBB-EE program within the banking sector. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2021
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- Date Issued: 2021-10
The physical activity status and the impact of lifestyle behaviours on workplace productivity and absenteeism of Transnet employees
- Authors: Zimmermann, Sharnae Vanessa
- Date: 2021-10
- Subjects: Transnet (Firm : South Africa) Employees , Absenteeism (Labor) South Africa Durban , Labor productivity South Africa Durban , Exercise , Sedentary behavior , Lifestyles
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190077 , vital:44961
- Description: Increased sitting time, insufficient physical activity and sub-optimal body composition are all contributing to the global disease burden. This is made evident by increases in obesity, type II diabetes, cardiovascular diseases (i.e. hypertension and strokes), cancer and other non-communicable diseases resulting in absenteeism and reduced productivity in the workplace. The global rise in sitting time and physical inactivity is caused, in part, by changes in transport convenience, work roles and technological advancements. Employees working in office environments or driving trains sit for prolonged periods; something which is evident in the industry that Transnet operates in. Sitting time and physical inactivity are independent risk factors for non-communicable diseases with poor nutrition, smoking, alcohol consumption and psychological wellbeing, being separate constructs. The purpose of the study is to determine the levels of sedentary behaviour, physical inactivity, obesity, nutrition, alcohol consumption, smoking, non-communicable disease risk, mental wellbeing and their association with productivity and absenteeism in office workers and train drivers at Transnet Freight Rail, Durban. A cross-sectional study was done with 40 participants, 20 office workers and 20 train drivers. Stature (175.80 ± 9.43 ±cm) and body mass (83.85 ± 20.31 kg) were measured; and body mass index calculated (26.98 ± 5.37 kg.m2). Physical activity levels, sedentary behaviour, body mass index and other lifestyle factors were explored using an amended version of The Health and Wellbeing survey, a self-report measure. The results revealed that there was a high prevalence of sedentary behaviour (train drivers = 7.85 ± 2.21 and office workers = 8.3 ± 1.03), particularly among office workers. Most of the participants had a relatively high body mass index, placing in the overweight and obese category, particularly among train drivers. The prevalence of physical inactivity was marginally higher for office workers compared to train drivers. There were significantly (p<0.05) higher levels of physical activity within train drivers with a moderate effect size. There were limited associations found between lifestyle factors and sickness absenteeism and worker productivity. Obesity had the most prominent relationship with noncommunicable diseases, followed by high levels of sedentary behaviour, not meeting physical activity guidelines, obesity, overweight, and prolonged sitting time at work. A significant and moderate correlation was found between obesity and absenteeism (train drivers: r = 0.32 and office workers: r= 0.46), however, no associations were found between sedentary behaviour, physical activity and fruit and vegetable intake and absenteeism. Lastly, the association between physical activity and productivity among the train drivers was low negative (r=-0.15) which was not significant (p>0.05). The associations between physical activity and productivity among office workers, however, was both significant (p<0.05) and moderate positive (r=0.39). The vegetable intake among the office workers showed a significant (p<0.05) moderate positive association with productivity (r=0.49). The association between vegetable intake and productivity among the train drivers was not significant (p>0.05) and low positive (r=0.16). There was a significant (p<0.05) and moderate positive association between fruit intake and productivity among both train drivers (r=0.43) and office workers (r=0.47). No significant associations between sedentary behaviour and obesity and productivity were found. The current study provided new insight into the risks associated with lifestyle factors of office workers and train drivers in the transportation sector. The poor lifestyle factors, together with the high prevalence of sedentary behaviour and physical inactivity, provide ideal opportunities for future interventions to focus on workers productivity and overall wellbeing. The job design of train drivers and office workers does not place significant importance on employee health and wellness. Essentially they are not “healthy” but they work productively, giving reason as to why employee wellness is not a priority for employers. The current findings of the study suggest that adopting regular physical activity, healthy dietary patterns and reduced sitting time should be promoted as key components of lifestyle interventions for the prevention of non-communicable diseases in office workers and train drivers. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2021
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- Date Issued: 2021-10
The synthesis and characterisation of Sn(IV) porphyrin derivatives and their potential application in anti-cancer and antimicrobial photodynamic therapy
- Authors: Dingiswayo, Somila
- Date: 2021-10
- Subjects: Porphyrins , Photochemotherapy , Cancer Photochemotherapy , Active oxygen Physiological effect , Aromaticity (Chemistry) , Tetrapyrroles , Magnetic circular dichroism , Corroles , Chlorins , Photodynamic antimicrobial chemotherapy (PACT)
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188843 , vital:44791
- Description: In photodynamic therapy (PDT), the activation of light-sensitive drugs in tumour cells produces reactive singlet oxygen species, which cause tumour destruction through a cascade of biochemical reactions. Over the years, the wavelength of activation has been shown to be a critical factor in the penetration of light. Hence the properties of photosensitiser dyes in this context shape their ability to treat deep-seated tumours. In this study, the synthesis, structural characterisation and photophysicochemical properties of a series of Sn(IV) porphyrins with meso-methylthiophenyl rings that have been prepared to study their PDT and photodynamic antimicrobial chemotherapy (PACT) activity properties are reported. The series of Sn(IV) complexes is comprised of a porphyrin (1-Sn), a corrole (2-Sn), a chlorin (3-Sn) and an N-confused porphyrin (4-Sn). Herein, the low symmetry Sn(IV) porphyrin derivatives are shown to have excellent singlet oxygen generation capabilities, and lifetimes of the triplet excited states were in the microsecond range. For example, 4-Sn had a singlet oxygen quantum yield (ФΔ) and an excited triplet state lifetime (τT) of 0.88 and 27 μs, respectively. The complexes were studied using UV-visible and magnetic circular dichroism (MCD) spectroscopies. Interestingly, the positive-to-negative sign sequences of the Faraday B0 terms of 2-Sn and 3-Sn reveal that the structural modifications involved break the degeneracy of the MOs derived from the 1eg* LUMO of the porphyrin 1-Sn. In contrast, a conventional negative-to-positive sign sequence is observed for 4-Sn, since the confusion of a pyrrole moiety also results in a large separation of the 1a1u and 1a2u MOs of the porphyrin 1-Sn that are derived from the HOMO of a C16H162−parent hydrocarbon perimeter. The trends in the electronic structures of the Sn(IV) complexes were further investigated through a series of time-dependent density functional theory calculations, so that the suitability of the different types of complex for use in singlet oxygen applications could be further explored. During in vitro photodynamic antimicrobial chemotherapy (PACT) studies, chlorin derivative 3-Sn had the highest activity towards S. aureus and E. coli with log10 reductions of 10.5 and 8.74, respectively. The unusually high activity of 3-Sn against E.coli suggests that the interaction of neutral photosensitisers with gram-negativebacteria is more complex than previously understood. Anti-cancer PDT studies demonstrated that the photosensitisers had negligible dark cytotoxicity. Upon photoirradiation, the Sn(IV) complexes consistently exhibited IC50 values lower than 15 μM against MCF-7 adenocarcinoma cells. An IC50 value of 1.4 μM for 4-Sn after activation at the deep-red region of the spectrum demonstrates that complexes of this type merit further in-depth investigation. The results provide evidence that the low-symmetry Sn(IV) chlorins and N-confused porphyrins merit further in-depth study for use in singlet oxygen applications. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
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- Date Issued: 2021-10
The tuber-feeding weevil Listronotus frontalis as a candidate biological control agent for the invasive semi-aquatic plant Sagittaria platyphylla within South Africa
- Authors: Rogers, Daniel James
- Date: 2021-10
- Subjects: Listronotus South Africa , Arrowhead (Plants) South Africa , Arrowhead (Plants) Biological control South Africa , Invasive plants Biological control South Africa , Insects as biological pest control agents South Africa , Plant populations South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190731 , vital:45023
- Description: Sagittaria platyphylla (Engelm.) J.G.Sm. (Alismataceae) is an invasive, aquatic macrophyte originating in the southern United States of America. In South Africa, the plant was first detected in Krantzkloof Nature Reserve, KwaZulu-Natal Province in 2008, and due to its known impact in other countries, it was listed as a Category 1a invader species under the National Environmental Management: Biodiversity Act 2004 (NEM:BA). This invasive plant has proved difficult to manage due to its varied growth forms and reproductive strategies, such as prolific seed and below ground tuber production. Due to the limitations of conventional control mechanisms, biological control is currently being considered as a potential control option. The tuber feeding weevil Listronotus frontalis LeConte (Coleoptera: Curculionidae) has been identified as a candidate biological control agent for this invasive species. The aims of this study were twofold; to firstly determine the importance of tubers to S. platyphylla populations growing in South Africa; and secondly, to determine the biology and suitability of L. frontalis, a tuber feeder, as a candidate biological control agent. Surveys of S. platyphylla populations in South Africa showed that tubers were found in all sampled sites, except for Krantzkloof Nature reserve in KwaZulu-Natal Province. The highest number of tubers was 97.75 ± 10.62 (SE) m-2 recorded at Jonkershoek in the Western Cape Province. Monthly sampling from two sites in the Eastern Cape Province, the Makana Botanical Gardens and Maden Dam showed that neither season nor water depth affected tuber production. However, the mean number of tubers as well as mass of tubers sampled, were consistently higher (F(1,179) = 20.9542, P < 0.0001) and heavier (F(1, 857) = 585.7293, P < 0.0001) at the Botanical Gardens than at Maden Dam, respectively. The study showed that tubers are an important life stage of S. platyphylla populations and may vary in size and abundance between and within sites. The tuber feeding weevil was shown to develop from egg to ovipositing adult within just over 40 days. Females were recorded to lay up to 48 eggs within a period of one week. Impact studies showed that adult feeding led to a reduction in all but one of the 11 measured plant growth and developmental measurements, including a reduction in the mean mass of the above-ground plant material (F(2,2743) = 12.05, P = 0.002) as well as a reduction in size and abundance of tubers (F(2,58.47) = 9.756, P = 0.0006) and stolons(F(14.943) = 8.7577, P = 0.003). These results are encouraging and suggest that if the insect is released in South Africa, it may prove to be a valuable biocontrol agent. It is concluded that, until suitable biological control options become available in South Africa, the chemical and mechanical control measures currently implemented should continue, however, controlling tubers should be considered during the planning and implementation of these strategies. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2021
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- Date Issued: 2021-10
Towards Reconfiguring the Agricultural Expert System (AES) for Black Small to Medium Farmer Development for Commercialization: A progressively focused policy literature review and social learning dialogue in the Eastern Cape Raymond Mhlaba Local Municipality
- Authors: Maqwelane, Lwanda
- Date: 2021-10
- Subjects: Farms, Small South Africa Amathole District Municipality , Minority farmers , Public-private sector cooperation South Africa Amathole District Municipality , Social learning South Africa Amathole District Municipality , Agricultural expert system (AES) , Black small to medium farmers (BSMF)
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188876 , vital:44794
- Description: This study focuses on the agricultural expert system (AES), its inherited and potential reframing capabilities for the development, growth and transition of black small to medium farmers (BSMF) into the commercial sector. The study was conducted as a critical analytical policy review of implemented policies pre-and post 1994 that subsequently highlighted the thematic continuities and discontinuities of policy reform and the subsequent impact on BSMFs using the AES as a conceptual lens. The study aimed working with stakeholders in the AES in the Raymond Mhlaba Local Municipality as a case study to critically engage and question the AES and its contemporary framing and potential reframing and continued impact on the BSMFs development. This was conducted through a dialogical social learning process in partnership with diverse voices that cut across the contemporary agrarian landscape that included “universities, think tanks, vocational training providers, standards-setting agencies, trade associations that provide specialized training, education, information, research and technical support” (Porter, 2000, p.17). The data for the social learning dialogue process was generated through an iterative analysis of dialogical social learning workshops, focus groups and semi-structured interviews. The analysis focused on the framing (Chapters 2, 3, and 5) and reframing of the AES (Chapter 6). Through dynamic engagement within the knowledge hub (contextual social learning and literature), the study surfaces a potential alternative discourse that actively includes the BSMFs as a crucial component of the commercial sector AES as the analysis shows these are largely excluded. This alternative discourse occurred through dialogical interactions with all participants via a pro-actively constituted social learning process, enriched and deepened by literature as indicated above. Main recommendations of the study are: 1. The AES must be framed to address the holistic value chain of BSMFs to help address underlying policy dualism, 2. Public Private Partnerships are needed to support BSMFs development and these should adopt a social learning approach that is reflective of complex realities 3. There is need for better understanding of roles and contributions of stakeholders in the AES to avoid duplications. , Thesis (MEd) -- Faculty of Education, Education, 2021
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- Date Issued: 2021-10