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Bioelectrocatalysis and surface analysis of gold coated with nickel oxide/hydroxide and glucose oxidase towards detection of glucose:

  • Authors: Njoko, Nqobile , Louzada, Marcel , Britton, Jonathan , Khene, Samson M , Nyokong, Tebello , Mashazi, Philani N
  • Date: 2020
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/150071 , vital:38937 , https://doi.org/10.1016/j.colsurfb.2020.110981
  • Description: The fabricating of metal oxide thin films onto conducting surfaces continues to grow and their potential applications as surfaces for biosensor applications is of paramount importance. The correct orientation of glucose oxidase redox enzymes yields very important biointerfaces capable of selectively detecting D-glucose as a measure of blood sugar for healthy and diabetic sick patients. The electrodeposition of redox enzymes, such as glucose oxidase enzymes, onto gold electrode surfaces pre-modified with nickel oxide was investigated in this work.
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  • Date Issued: 2020

Biogeographic patterns of endolithic cyanobacteria and their negative impacts on mussels along the South African coast

  • Authors: Ndhlovu, Aldwin
  • Date: 2020
  • Subjects: Cyanobacteria -- South Africa , Cyanobacteria -- Geographical distribution , Prokaryotes -- South Africa , Mexilhao mussel -- South Africa , Mytilus galloprovincialis -- South Africa , Coastal biology -- South Africa , Coastal ecology -- South Africa , Mussels -- Geographical distribution , Mussels -- Predators of , Mussels -- Mortality -- South Africa , Mussels -- Ecology -- South Africa , Mussels -- Growth -- South Africa , Mussels -- Fertility -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/144656 , vital:38367
  • Description: Endolithic cyanobacterial species occur in a wide range of environments including cold and hot deserts as well as marine systems where they attack biological material such as corals and the shells of molluscs including limpets, mussels and abalone. Endoliths live as parasites in mussel shells, where they erode and extract calcium carbonate leading to shell weakening, creating fracture holes that lead to shell collapse and death, but they also have positive effects when they lead to discolouration of mussel shells hence giving them the ability to reduce stressful heat gain during periods of extreme heat stress. Mussels are ecological engineers on which the abundance and diversity of associated species assemblages depend. Understanding how endolithic cyanobacteria affect mussels will not only help in predicting future patterns of mussel abundances, but also future patterns of the infauna that depend on them. Firstly, I identified endolithic species infesting mussels and assessed the prevalence of endolithic parasitism in two intertidal mussel species in South Africa, the native Perna perna and the invasive Mytilus galloprovincialis. Large-scale surveys of endolithic infestation of mussels were conducted along 2500 km of the South African coast, covering three biogeographic regions: the subtropical east coast, dominated by P. perna, the warm temperate south coast where the indigenous species coexists with M. galloprovincialis, and the cool temperate west coast which is dominated by M. galloprovincialis. The prevalence of endolithic infestation was higher in the cool temperate bioregion than in the warm temperate and subtropical bioregions which did not differ and for P. perna endolithic species assemblages revealed clear groupings by bioregion. Results for endolithic induced mortality followed the same trend, with no significant difference between the two mussel species where they coexist and these results attribute biogeography of endoliths to environmental factors rather than host identity. Secondly, I assessed energy budgets of infested and clean mussels, to evaluate the energetic cost of infestation. This involved measuring energy acquisition, expenditure, calculating scope for growth and lethal temperatures (LT50s). The results revealed that endolithic cyanobacteria have a negative effect on scope for growth due to increased metabolic rates for infested mussels, with no effect of endoliths on the rates or efficiency of energy acquisition through filtration and no effect on lethal temperatures. The effects of infestation were then examined in more detail through a qualitative and quantitative analysis of mussel gonads and byssal attachment strength to the substratum. Endolithic infestation was found to affect reproduction by affecting the size (mass) of gonads, but not the density of eggs within them. Attachment strength was affected by endolithic infestation with very infested mussels requiring much less force to detach them from the substratum compared to mussels with low or no infestation. These results show that endolithic infestation affects mussel fitness by directly affecting attachment strength and by reducing their reproductive output. Thirdly, endolithic succession within mussel shells was examined by assessing endolithic species composition in different regions of the shell and as a function of time. The results on the spatial distribution of endolith species within a shell supported those for temporal succession in shells deployed in the field. Endolithic species that were early colonists of clean shells were similar to those that were found in the distal edge, the new and growing region of the shell and species that arrived late in succession were similar to endolithic species found near the umbo, the oldest region of the shell. Overall, the study shows that endolithic cyanobacteria show the effects of biogeography on species distribution and clear patterns of succession within mussel shells. Cyanobacteria affect mussels negatively; they lead to low scope for growth and hence low growth rates, low reproductive output and reduced attachment strength for infested mussels. This, in turn is expected to have indirect consequences for other species that rely on mussels as ecological engineers for their survival.
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  • Date Issued: 2020

Bioinformatic analysis of Aminoacyl tRNA Synthetases as potential antimalarial drug targets

  • Authors: Nyamai, Dorothy Wavinya
  • Date: 2020
  • Subjects: Uncatalogued
  • Language: English
  • Type: thesis , text , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/164579 , vital:41142 , doi:10.21504/10962/164579
  • Description: Thesis (PhD)--Rhodes University, Faculty of Science, Biochemistry and Microbiology, 2020
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  • Date Issued: 2020

Biological control of Salvinia molesta (DS Mitchell) drives aquatic ecosystem recovery

  • Authors: Motitsoe, Samuel N , Coetzee, Julie A , Hill, Jaclyn M , Hill, Martin P
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/444515 , vital:74247 , https://doi.org/10.3390/d12050204
  • Description: Salvinia molesta D.S. Mitchell (Salviniaceae) is a damaging free-floating invasive alien macrophyte native to South America. The biological control programme against S. molesta by the weevil Cyrtobagous salviniae Calder and Sands (Erirhinidae) has been successful in controlling S. molesta infestations in the introduced range, however, there is some debate as to how biological control success is measured. This study measured the response of epilithic algae and aquatic macroinvertebrate communities in a S. molesta-dominated state and subsequently where the weed had been cleared by biological control, as a proxy for ecosystem recovery in a before–after control–impact mesocosm experiment.
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  • Date Issued: 2020

Biological control of water lettuce, Pistia stratiotes L., facilitates macroinvertebrate biodiversity recovery: a mesocosm study

  • Authors: Coetzee, Julie A , Langa, Susana D , Motitsoe, Samuel N , Hill, Martin P
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/423967 , vital:72112 , xlink:href="https://doi.org/10.1007/s10750-020-04369-w"
  • Description: Floating aquatic weed infestations have negative socio-economic and environmental consequences to the ecosystems they invade. Despite the long history of invasion by macrophytes, only a few studies focus on their impacts on biodiversity, while the ecological benefits of biological control programmes against these species have been poorly quantified. We investigated the process of biotic homogenization following invasion by Pistia stratiotes on aquatic biodiversity, and recovery provided by biological control of this weed. Biotic homogenization is the increased similarity of biota as a result of introductions of non-native species. The study quantified the effect of P. stratiotes, and its biological control through the introduction of the weevil, Neohydronomus affinis on recruitment of benthic macroinvertebrates to artificial substrates. Mats of P. stratiotes altered the community composition and reduced diversity of benthic macroinvertebrates in comparison to an uninvaded control. However, reduction in percentage cover of the weed through biological control resulted in a significant increase in dissolved oxygen, and recovery of the benthic macroinvertebrate community that was comparable to the uninvaded state. This highlights the process of homogenization by an invasive macrophyte, providing a justification for sustained ecological and restoration efforts in the biological control of P. stratiotes where this plant is problematic.
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  • Date Issued: 2020

Biological control potential of ectomycorrhizal fungi against Fusarium circinatum on Pinus patula seedlings

  • Authors: Chartier FitzGerald, Veronique C , Dames, Joanna F , Hawley, Grant L
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/425960 , vital:72302 , xlink:href="https://doi.org/10.1080/09583157.2020.1771542"
  • Description: The South Africa forestry industry, covering ∼1.3 million hectares, is dependent on exotic pine and Eucalyptus species. Nursery seedlings are not inoculated with ectomycorrhizal (ECM) fungi or other beneficial microbes. Fusarium circinatum is an economically important pathogen affecting seedling survival. The purpose of this investigation was to assess the effects of ectomycorrhizal fungal inoculation on Pinus patula seedling growth and resistance to the fungal pathogen F. circinatum. Explants from ECM basidiocarps, collected from Pinus stands, were plated onto MMN medium to obtain isolates that were then verified via DNA extraction and PCR amplification and sequencing of the ITS rDNA region. These isolates were identified as Boletus edulis f. reticulatus, Lactarius quieticolor, Suillus granulatus and an unknown Suillus species. P. patula growth in the presence of the pathogen F. circinatum was significantly increased and promoted by the L. quieticolor and Suillus isolates. Preventative inoculation of seedlings in the nursery using these isolates would ensure the production of stronger, healthier plants that would be more resistant to F. circinatum infection, increasing survival in the plantation.
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  • Date Issued: 2020

Biology, stock assessment and angler attitudes towards the introduction of slot size limits for a recreationally important species Sparodon durbanensis (Sparidae) in South Africa

  • Authors: Hewett, Kyle
  • Date: 2020
  • Subjects: Sparidae -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/48389 , vital:40855
  • Description: Sparodon durbanensis (white musselcracker) is an endemic fish species in the Family Sparidae found in shallow (< 20 m) coastal waters from the Western Cape to KwaZulu-Natal. It is large-growing, late-maturing, long-lived and is a popular target species in the South African marine shore-based line and spear fisheries. Management regulations for the species have remained the same for over two decades despite anecdotal information of population declines. However, since the last life history-information for S. durbanensis was collected in the late 1980s, there is a paucity of contemporary information needed to inform wise management. The aim of this study was to collect contemporary socio-ecological information on the species and its fishery in order to better inform the management of the species. In order to do this, the growth-rate of historical and contemporary samples of Sparodon durbanensis was compared, a length-based stock assessment was performed and the knowledge and attitudes of anglers towards the introduction of improved regulations were investigated. The growth-rate was compared using otolith width as a proxy for fish growth. It was found that the growth-rate had remained relatively stable between 1963 and 2010, suggesting that S. durbanensis may be resilient to the increasing levels of environmental variability observed throughout its range and that the historical growth parameters determined for this species may remain applicable for contemporary stock assessment. The batch fecundity was determined for 50 mm size classes and used to estimate the percentage cumulative population batch fecundity using historical 803 mm FL (904 mm TL) and contemporary 776 mm FL (874 mm TL) length structure, respectively. Based on these observations a suitable harvest slot limit of 600-850 mm TL was suggested. A Length-Based Spawning Potential Ratio (SPR) model was used to provide the first formal stock assessment for S. durbanensis. The input parameters of M/k=1.44, L∞=1021 mm FL, L50=350 mm FL and L95=800 mm FL and length composition data comprising of 134 lengths obtained from a collection of competitive angling catches, estimated a SPR of 41%, which is above the 40% target reference point. A total of 126 online and face– to-face, replica questionnaires were completed by spearfishermen and recreational shore anglers. Responses indicated that anglers that target S. durbanensis are generally a specialized group who are knowledgeable about the biology and ecology of the species and are passionate about the conservation of the species. Participants indicated that Marine Protected Areas are likely the most effective regulation in the current suite of regulations used to manage the fishery and suggested that poor law enforcement was the major factor inhibiting the efficacy of fishery regulations. New proposed regulations, such as a harvest slot limit (and particularly the one between 600-850 mm TL) for S. durbanensis, was well supported, however participants suggested that non-compliance was a concern. Although, the SPR remained above the 40% target reference point, further declines in the stock status should be prevented through the implementation of a 600-850 mm TL harvest slot limit. Based on the findings of this study, this limit should provide protection against both growth and recruitment overfishing by providing protection to sexually immature, fast growing fish and to large adults that contribute the greatest proportion to population replenishment.
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  • Date Issued: 2020

Biomes, geology and past climate drive speciation of laminate-toothed rats on South African mountains (Murinae: Otomys)

  • Authors: Taylor, Peter J , Kearney, Theresa , Dalton, Desire L , Chakona, Gamuchirai , Kelly, Christopher M R , Barker, Nigel P
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/453158 , vital:75227 , xlink:href="https://doi.org/10.1093/zoolinnean/zlz134"
  • Description: Mitochondrial DNA sequences (1137 bp) of the cytochrome b gene and craniodental and craniometric data were used to investigate the evolutionary relationships of six putative rodent taxa of Otomys (family Muridae: subfamily Murinae: tribe Otomyini) co-occurring in the Western Cape and Eastern Cape provinces of South Africa. Phylogenetic analysis of 20 new sequences together with craniodental and craniometric characters of 94 adult skulls reveal the existence of a unique lineage of Otomys cf. karoensis (named herein Otomys willani sp. nov.) from the Sneeuberg Centre of Floristic Endemism in the southern Drakensberg Mountain Range. Craniometric analysis distinguished O. karoensis from O. willani and identified a further four localities in the range of the latter species. We document southern range extensions of both Sloggett’s ice rat, Otomys sloggetti, and the vlei rat Otomys auratus to the Sneeuberg Mountain Range, in addition to appreciable genetic divergence between Sneeuberg and southern and central Drakensberg populations of O. sloggetti. Our results demonstrate parallel patterns of cryptic speciation in two co-occurring species complexes (Otomys irroratus s.l. and O. karoensis s.l.) associated closely with the boundaries of biomes (fynbos vs. grassland biomes) and geological formations (Cape Fold Belt vs. Great Escarpment).
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  • Date Issued: 2020

Biomes, geology and past climate drive speciation of laminate-toothed rats on South African mountains (Murinae: Otomys)

  • Authors: Taylor, Peter J , Kearney, Theresa , Dalton, Desire L , Chakona, Gamuchirai , Kelly, Christopher M R , Barker, Nigel P
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/425481 , vital:72249 , xlink:href="https://doi.org/10.1093/zoolinnean/zlz134"
  • Description: Mitochondrial DNA sequences (1137 bp) of the cytochrome b gene and craniodental and craniometric data were used to investigate the evolutionary relationships of six putative rodent taxa of Otomys (family Muridae: subfamily Murinae: tribe Otomyini) co-occurring in the Western Cape and Eastern Cape provinces of South Africa. Phylogenetic analysis of 20 new sequences together with craniodental and craniometric characters of 94 adult skulls reveal the existence of a unique lineage of Otomys cf. karoensis (named herein Otomys willani sp. nov.) from the Sneeuberg Centre of Floristic Endemism in the southern Drakensberg Mountain Range. Craniometric analysis distinguished O. karoensis from O. willani and identified a further four localities in the range of the latter species. We document southern range extensions of both Sloggett’s ice rat, Otomys sloggetti, and the vlei rat Otomys auratus to the Sneeuberg Mountain Range, in addition to appreciable genetic divergence between Sneeuberg and southern and central Drakensberg populations of O. sloggetti. Our results demonstrate parallel patterns of cryptic speciation in two co-occurring species complexes (Otomys irroratus s.l. and O. karoensis s.l.) associated closely with the boundaries of biomes (fynbos vs. grassland biomes) and geological formations (Cape Fold Belt vs. Great Escarpment).
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  • Date Issued: 2020

Blockchain readiness for countries towards 2030- the barriers and benefits of adopting blockchain technology

  • Authors: Moonsamy, Devakumaran
  • Date: 2020
  • Subjects: Blockchains (Databases) Financial institutions -- Technological innovations
  • Language: English
  • Type: Thesis , Masters , MBA
  • Identifier: http://hdl.handle.net/10948/49725 , vital:41783
  • Description: This study investigates the factors of blockchain that will promote sustainable business towards the year 2030. The study provides an outlook to areas where business might be vulnerable in the event of blockchain implementation. The findings of this study were identified by means of an online questionnaire that targeted specialists in the arena of blockchain and business management. By a thematic analysis, the outcome of the study guides, precautions, and prepares organisations for what may come in the future of blockchain.
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  • Date Issued: 2020

BODIPY dyes for application in the photo-oxidation of pollutants, photodynamic antimicrobial chemotherapy, and nonlinear optics

  • Authors: Kelechi, Lebechi Augustus
  • Date: 2020
  • Subjects: Dyes and dyeing -- Chemistry , Fluorescent probes , Fluorescence spectroscopy
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/140298 , vital:37859
  • Description: The synthesis and structural characterization of a series of BODIPY dyes to analyze both the effects of halogenations at the 2,6-positions and the introduction of styryl groups at the 3,5-positions. The photophysical properties of these dyes were investigated to determine their suitability as singlet oxygen-generating photosensitiser dyes for application in photocatalytic degradation of azo dyes and in photodynamic antimicrobial chemotherapy (PACT). Upon halogenation, the dyes showed high to moderate singlet oxygen quantum yields. The potential utility of electrospun polystyrene (PS) nanofibres embedded with halogenated BODIPY dyes for the photocatalytic degradation of Orange G and Methyl Orange from textile industry effluents were investigated. A comparison of the singlet oxygen quantum yield of the BODIPY dyes in solution and when embedded in the PS nanofibres support demonstrates that its photosensitiser properties are maintained in the nanofibre mats. The photocatalytic degradation properties of the PS nanofibres for Orange G and Methyl Orange were determined by using a 530 nm and 660 nm light-emitting diodes. The rate of photodegradation increases with both the Orange G and Methyl Orange concentrations and follows pseudo-first-order kinetics. The PACT activities of brominated BODIPYs on Escherichia coli and Staphylococcus aureus were investigated. Log reduction values of over 9 were obtained during the photoinactivation of Staphylococcus aureus. To be able to red-shift the main spectral band of the BODIPY dyes into the therapeutic window, styryl groups were introduced at the 3,5-positions through a modified Knoevenagel condensation reaction. Because the red-shifted spectral band lies above 532 nm, the second harmonic of the Nd:YAG laser, there is very minute absorption at this wavelength. One of the novel brominated BODIPY dyes was investigated for its potential utility as optical limiting materials in nonlinear optics (NLO), and the dyes demonstrated typical nonlinear absorption behaviour characterised by reverse saturable absorption (RSA) in Z-scan measurements. Excellent optical limiting parameters were obtained for third-order susceptibility and hyperpolarisability.
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  • Date Issued: 2020

BODIPY dyes for use in nonlinear optics and optical sensing

  • Authors: Kubheka, Gugu Patience
  • Date: 2020
  • Subjects: Uncatalogued
  • Language: English
  • Type: thesis , text , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/163352 , vital:41032 , doi:10.21504/10962/163352
  • Description: Thesis (PhD)--Rhodes University, Faculty of Science, Department of Chemistry, 2020.
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  • Date Issued: 2020

Body mass and condition of a fynbos bird community investigating impacts of time, weather and raptor abundance from long-term citizen-science datasets

  • Authors: Lee, Alan T K , Barnard, Phoebe , Fraser, Mike , Lennard, Chris , Smit, Ben , Oschadleus, Hans-Dieter
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/441546 , vital:73897 , https://doi.org/10.2989/00306525.2019.1683093
  • Description: Variation in body size, especially mass, is a function of local environmental conditions for any given species. Recent recorded decreases in body size of endotherms have been attributed to climate change in some cases. This prediction is based on the trend of smaller body size of endotherms in warmer climates (Bergmann’s rule) and it implies genetic responses rather than phenotypic flexibility. Alternatively, selection for smaller body size or lower mass could be explained by the starvation-predation hypothesis, where lighter individuals have a higher probability of escaping pursuing predators, such as raptors. Evidence that climate warming is driving patterns of size selection in birds in recent times has been mixed. We inspected data on 40 bird species contributed by bird ringers to the South African Ringing Scheme (SAFRING) for changes in body mass and condition as a function of time (year), minimum temperature of the day of capture, maximum temperature of the previous day, and rainfall data in the south-western Cape Floristic Region (fynbos) around Cape Town, South Africa, for the period 1988–2015. The region shows a warming trend over the study period (0.035 °C yr−1). Interannual body mass and condition change were poorly explained by year or temperature. High daily minimum temperature explained loss of body condition for four species, whereas evidence from recaptured birds indicated negative effects of increasing maximum daily temperature, as well as rain. For the alternative hypothesis, because raptor abundance is stable or only weakly declining, there is little evidence to suggest these as a driver influencing mass trends. Any decrease in body mass over the study period that we observed for birds appear more likely to be plastic responses to stress associated with temperature or rainfall at this time, rather than systematic selection for smaller body size, as predicted by Bergmann’s Rule.
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  • Date Issued: 2020

Body mass and condition of a fynbos bird community investigating impacts of time, weather and raptor abundance from long-term citizen-science datasets

  • Authors: Lee, Alan T K , Barnard, Phoebe , Fraser, Mike , Lennard, Chris , Smit, Ben , Oschadleus, Hans-Dieter
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/448383 , vital:74726 , https://doi.org/10.2989/00306525.2019.1683093
  • Description: Variation in body size, especially mass, is a function of local environmental conditions for any given species. Recent recorded decreases in body size of endotherms have been attributed to climate change in some cases. This prediction is based on the trend of smaller body size of endotherms in warmer climates (Bergmann’s rule) and it implies genetic responses rather than phenotypic flexibility. Alternatively, selection for smaller body size or lower mass could be explained by the starvation-predation hypothesis, where lighter individuals have a higher probability of escaping pursuing predators, such as raptors. Evidence that climate warming is driving patterns of size selection in birds in recent times has been mixed. We inspected data on 40 bird species contributed by bird ringers to the South African Ringing Scheme (SAFRING) for changes in body mass and condition as a function of time (year), minimum temperature of the day of capture, maximum temperature of the previous day, and rainfall data in the south-western Cape Floristic Region (fynbos) around Cape Town, South Africa, for the period 1988–2015.
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  • Date Issued: 2020

BTC price volatility: fundamentals versus information

  • Authors: Gbadebo, Adedeji Daniel , Adekunle, Ahmed Oluwatobi , Adebayo-Oke Abdulrauf Lukman , Adedokun, Wole , Akande, Joseph
  • Date: 2020
  • Subjects: Bitcoin price volatility , Bitcoin market fundamentals , Autoregressive Distributed Lag (ARDL)
  • Language: English
  • Type: article , text
  • Identifier: http://hdl.handle.net/11260/6978 , vital:52630 , https://doi.org/10.1080/23311975.2021.1984624
  • Description: This paper offers a plausible response to “what explains the sporadic volatility in the price of Bitcoin?” We hypothesized that market “fundamentals” and “information demands” are key drivers of Bitcoin’s unpredictable price fluctuation. We adopt the transfer-function [Autoregressive Distributed Lag, ARDL] model and its Bounds testing approach to verify how the volatility of the price of Bitcoin responds to its transaction volume, cryptocurrency market capitalisation, world market equity index and Google search. We found the existence of long-run cointegration relation and observed that all the variables except the equity index positively explain the volatility of Bitcoin price. The result established evidence that market fundamentals drive erratic swing in Bitcoin price than information.
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  • Date Issued: 2020

Budget Deficits, the Savings Gap and Current Account Deficits in the Southern African Development Community

  • Authors: Kopeledi, Alyssa
  • Date: 2020
  • Subjects: Budget deficits -- South Africa Accounts current
  • Language: English
  • Type: Thesis , Masters , MCom (Economics)
  • Identifier: http://hdl.handle.net/10353/12392 , vital:39259
  • Description: This study examines the validity of the triple deficit hypothesis for a selected number of SADC countries, utilising secondary annual data for the period 1996-2018. Based on previous studies and theory, current account deficit was chosen as the dependent variable and budget deficit and the savings gap as the independent variables. The study makes use of both first generation and second-generation unit root tests to examine the time series properties of the data. The empirical results show that the data is integrated of different orders. Kao, Pedroni and Westerlund cointegration tests were carried out to examine the long-term relationship between the variables of interest. The empirical results revealed that there is a long-term relationship between current account deficit, budget deficit s and the savings gap. The long-run model under the Autoregressive Distributed Lag test revealed that, a positive and significant relationship exists between budget deficit and current account deficit at a significance level of 10% and a negative and insignificant relationship exists between savings gap and current account deficit in the long run. This suggests that an improvement in the current account balance in SADC countries requires fiscal stringency
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  • Date Issued: 2020

Building a flexible and inexpensive multi-layer switch for software-defined networks

  • Authors: Magwenzi, Tinashe
  • Date: 2020
  • Subjects: Software-defined networking (Computer network technology) , Telecommunication -- Switching systems , OpenFlow (Computer network protocol) , Local area networks (Computer networks)
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/142841 , vital:38122
  • Description: Software-Defined Networking (SDN) is a paradigm which enables the realisation of programmable network through the separation of the control logic from the forwarding functions. This separation is a departure from the traditional architecture. Much of the work done in SDN enabled devices has concentrated on higher end, high speed networks (10s GBit/s 100s GBit/s), rather than the relatively low bandwidth links (10s MBit/s to a few GBit/s) which are seen, for example, in South Africa. As SDN is increasingly becoming more accepted, due to its advantages over the traditional networks, it has been adopted for industrial purposes such as networking in data centres and network providers. The demand for programmable networks is increasing but is limited by the ability of providers to upgrade their infrastructure. In addition, as access to the Internet has become less expensive, the use of Internet is increasing in academic institutions, NGOs, and small to medium enterprises. This thesis details a means of building and managing a small scale Software-Defined Network using commodity hardware and open source tools. Core to the SDN Network illustrated in this thesis is the prototype of a multi-layer SDN switch. The proposed device is targeted to serve lower bandwidth communication (in relation to commercially produced high speed SDN-enabled devices). The performance of the prototype multilayer switch had shown to achieve: data-rates of up to 99.998%, average latencies that are under 40µs during forwarding/switching and under 100µs during routing while using packet sizes between 64 bytes and 1518 bytes, and a jitter of less than 15µs during all tests. This research explores in detail the design, development, and management of a multi-layer switch and its placement and integration in small scale SDN network. This includes testing of Layer 2 forwarding and Layer 3 routing, OpenFlow compliance testing, the management of the switch using created SDN applications, and real life network functionality such as forwarding, routing and VLAN networking to demonstrate its real world applicability.
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  • Date Issued: 2020

Building knowledge with theory: Unpacking complexity in doctoral writing

  • Authors: Wilmot, Kirsten
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/439480 , vital:73600 , https://www.ajol.info/index.php/cristal/article/view/203971
  • Description: The use of theory to analyse and interpret empirical data is a valued practice in much social science doctoral research. A crucial aspect of this practice involves generating sophisticated theoretical understandings and critiques of phenomena in our social world. Despite the importance of theory, however, few concrete explanations of how to ‘theorise’exist in literature. This paper addresses this gap by demonstrating how a set of conceptual tools can be used to unpack what the craft of theorising looks like in explicit terms, and to reveal how this ability develops over time during the drafting process of dissertation writing. It does this by drawing on select texts from a successful doctoral dissertation, as well as an earlier draft version. In doing so, the paper provides an in-depth explanation of an essential process of doctoral research that is inherently known by many supervisors, yet seldom unpacked in explicit terms.
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  • Date Issued: 2020

Calling rhythm as a predictor of the outcome of vocal interactions: flight departure in pale-winged starling pairs

  • Authors: Hausberger, Martine , Giacalone, Aline , Harmand, Mariane , Craig, Adrian J F K , Henry, Laurence
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/449283 , vital:74808 , https://doi.org/10.1007/s00114-019-1658-1
  • Description: Vocal communication plays an important role in the regulation of social interactions and the coordination of activities in many animal species. Synchrony is an essential part of the establishment and maintenance of pair bonds, but few reports have investigated decision-making at the pair level. We investigated temporal characteristics of call exchanges in pale-winged starlings (Onychognathus nabouroup) that could predict whether one, two, or neither members of a pair would take off. Our analysis of these interactions revealed that the overall rhythm of a call exchange, as well as the acceleration towards the end of an interaction, were significantly associated with the type of behavioural outcome. Faster rhythms were associated with higher probabilities that both birds would fly away. Our results confirm the findings of previous studies showing that higher rates of alarm calls indicate imminent departure and highlight the relationship between temporal features of vocal interactions and their outcome.
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  • Date Issued: 2020

Can fishing tourism contribute to conservation and sustainability via ecotourism?: a case study of the Fishery for Giant African Threadfin Polydactylus quadrifilis on the Kwanza Estuary, Angola

  • Authors: Butler, Edward C , Childs, Amber-Robyn , Saayman, Andrea , Potts, Warren M
  • Date: 2020
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/149253 , vital:38819 , https://doi.org/10.3390/su12104221
  • Description: It has been suggested that tourism fisheries can raise the value of landed catch, provide alternative livelihoods for local artisanal fishers and, because recreationally caught fishes are often released, simultaneously conserve stocks. However, for fishing tourism to meet ecotourism standards, sustainable, local economic benefit is imperative. This study aimed to assess the direct economic contribution of the recreational fishery for Polydactylus quadrifilis on the Kwanza Estuary, Angola. The recreational fishery contributed significantly to economic productivity in an otherwise rural area, generating a total revenue (TR) of $236,826 per four-month fishing season.
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  • Date Issued: 2020
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