Design and evaluation of bulk data transfer extensions for the NFComms framework
- Bradshaw, Karen L, Irwin, Barry V W, Pennefather, Sean
- Authors: Bradshaw, Karen L , Irwin, Barry V W , Pennefather, Sean
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430369 , vital:72686 , https://hdl.handle.net/10520/EJC-1d75c01e79
- Description: We present the design and implementation of an indirect messaging extension for the existing NFComms framework that provides communication between a network flow processor and host CPU. This extension addresses the bulk throughput limitations of the framework and is intended to work in conjunction with existing communication mediums. Testing of the framework extensions shows an increase in throughput performance of up to 268 that of the current direct message passing framework at the cost of increased single message latency of up to 2. This trade-off is considered acceptable as the proposed extensions are intended for bulk data transfer only while the existing message passing functionality of the framework is preserved and can be used in situations where low latency is required for small messages.
- Full Text:
- Date Issued: 2019
- Authors: Bradshaw, Karen L , Irwin, Barry V W , Pennefather, Sean
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430369 , vital:72686 , https://hdl.handle.net/10520/EJC-1d75c01e79
- Description: We present the design and implementation of an indirect messaging extension for the existing NFComms framework that provides communication between a network flow processor and host CPU. This extension addresses the bulk throughput limitations of the framework and is intended to work in conjunction with existing communication mediums. Testing of the framework extensions shows an increase in throughput performance of up to 268 that of the current direct message passing framework at the cost of increased single message latency of up to 2. This trade-off is considered acceptable as the proposed extensions are intended for bulk data transfer only while the existing message passing functionality of the framework is preserved and can be used in situations where low latency is required for small messages.
- Full Text:
- Date Issued: 2019
Design and fabrication of components of dye sensitised solar cells
- Authors: Msane, Gugu
- Date: 2019
- Subjects: Dye-sensitized solar cells
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/117106 , vital:34478
- Description: In recent decades there has been increasing global concern about the sustainability of our use of fossil fuels, which has led to increased interest in carbon–free sustainable renewable sources such as solar energy. Dye sensitized solar cells (DSSCs) are a cheap and clean technology that harnesses solar energy efficiently and convert it to electrical energy. A DSSC consists of a transparent working electrode coated with a dye-sensitized mesoporous film of nanocrystalline particles of semiconductor e.g. TiO2, an electrolyte containing a suitable redox couple and a platinized counter electrode. All the components of the DSSCs play vital roles in controlling the performance of the cell. The synergy of these components of the cells also needs to be investigated to optimise their interaction and create efficient and stable DSSCs. The information gathered from this investigation can give insight on how to improve the efficiencies of DSSCs. In this research study the semiconductor, transparent conducting layer and sensitizer were designed, optimized one at a time and their effect on the overall efficiency of the DSSCs studied. In this way it was easy to observe the effect of the individual components on the efficiency of the DSSCs. The conventional DSSCs usually use TiO2 as a semiconductor. In this research TiO2 was doped with cerium (Ce) to enhance its optical properties by reducing the band gap. A series of Ce-doped TiO2 with Ce content ranging from 0.1 to 1 mol % were successfully synthesized by an acid catalyzed sol-gel method, and their performance as the photoanodes of dye-sensitized solar cells (DSSCs) was investigated. Ce doping resulted in a red shift in the absorption of the TiO2 indicating narrowing of the band gap. The band gap first narrowed with increase in concentration of dopant up until 0.9 % dopant concentration. After this optimum doping concentration the band gap widened again. DFT calculations showed that Ce doping introduces Ce4f impurity states located just below the conduction band resulting in band gap narrowing. Ce content (0.9%) doped TiO2 photoanodes improved the performance of DSSCs with a conversion efficiency of 2.11% compared to 0,21% for the one with a pure TiO2 under 1 sun, AM1.5. Graphitised/TiO2 nanocomposites were also used a semiconductor to slow down recombination of electrons and holes in the cells. Electrophoretic deposition (EPD) was used to deposit graphitised/TiO2 nanocomposites onto an FTO electrode for application as photoelectrode in dye-sensitized solar cells (DSSCs). An enhanced power conversion efficiency (PCE) of 2.25% was observed for the 0.5 wt% graphene oxide/TiO2 (GO/TiO2) based DSSC which was higher than that of the conversion efficiency of pure TiO2 nanoparticles (i.e. 0.52%). Graphene oxide led to high migration of photoinduced electrons to the conduction band of the collection electrode and inhibition of charge carriers recombination resulting in enhanced photoconversion efficiency. A GO content above 0.5 % resulted in a reduced transparency leading to a decrease in the PCE. 0.5 wt % GO/0.9 Ce–TiO2 Ce based DSSC showed a slightly enhanced efficiency of 2.45%. 0.5 rGO/TiO2 based DSSCs had a high efficiency than 0.5 rGO/TiO2 due to improved conductivity of rGO nanosheets and suppressed recombination of charge carriers. To cut down DSSC production costs a silver wire network transparent conducting polyethylene electrodes was fabricated and used as an indium tin oxide (ITO) alternative substrates in DSSCs. The transmittance of the AgNW network was 82 % which is comparable to ITO substrates. Titanium oxide (TiO2) films on the AgWN/PET substrates were obtained using the electrophoresis method. These substrates were sensitised and used to fabricate a dye sensitised solar cell. From the measured current–voltage or I-V characteristic under AM1.5 illumination of the formed DSSC using AgWN substrates, an open circuit voltage (VOC) of 0.377 V, a short circuit current (ISC) of 0.0067 mA and a fill factor (FF) 25.7 % with an efficiency of 0.00862 % were obtained from a cell of 0.075 cm2 working area. The stability of the cell improved when a room temperature ionic liquid electrolyte was used. Gold nanofiber transparent electrodes were also prepared by the electrospinning techniques and used as an alternative to indium tin oxides substrates. Transparent conducting gold nanofiber (AuNF) transparent conducting electrodes were fabricated by using a low–cost electrospinning process and used as photoelectrodes for DSSCs. TiO2 was deposited on these electrodes by using an electrospray method. DSSC using AuNF as transparent electrodes had a power efficiency of 0.52%, compared to devices made with FTO electrodes (1.48%). DSSCs. Versatile dyes with increased spectral response, stability and suppressed recombination of holes and electrons were synthesised and used as a sensitizers for DSSCs. The boron dipyrrin (BODIPY) chromophore was combined with a carboxy coumarin moiety to create donor–acceptor (dyad) system dyes. Regenerative dyad dyes were formed through covalently linking a porphyrin chromophore to a manganese(II) ion through bridging ligands. These chromophores and also porphyrin and BODIPY dyes were used as sensitisers for DSSCs. The regenerative dye based DSSCs showed a photoconversion efficiency of 4.09% which was higher than the efficiency of the parent porphyrin (2.57%). The enhanced efficiency was attributed to the manganese bypridine cluster in the ZnTPP–Mn bpy supramolecule which acted as an electron donor to the photo-oxidized porphyrin continuously regenerating the porphyrin and preventing its decay.
- Full Text:
- Date Issued: 2019
- Authors: Msane, Gugu
- Date: 2019
- Subjects: Dye-sensitized solar cells
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/117106 , vital:34478
- Description: In recent decades there has been increasing global concern about the sustainability of our use of fossil fuels, which has led to increased interest in carbon–free sustainable renewable sources such as solar energy. Dye sensitized solar cells (DSSCs) are a cheap and clean technology that harnesses solar energy efficiently and convert it to electrical energy. A DSSC consists of a transparent working electrode coated with a dye-sensitized mesoporous film of nanocrystalline particles of semiconductor e.g. TiO2, an electrolyte containing a suitable redox couple and a platinized counter electrode. All the components of the DSSCs play vital roles in controlling the performance of the cell. The synergy of these components of the cells also needs to be investigated to optimise their interaction and create efficient and stable DSSCs. The information gathered from this investigation can give insight on how to improve the efficiencies of DSSCs. In this research study the semiconductor, transparent conducting layer and sensitizer were designed, optimized one at a time and their effect on the overall efficiency of the DSSCs studied. In this way it was easy to observe the effect of the individual components on the efficiency of the DSSCs. The conventional DSSCs usually use TiO2 as a semiconductor. In this research TiO2 was doped with cerium (Ce) to enhance its optical properties by reducing the band gap. A series of Ce-doped TiO2 with Ce content ranging from 0.1 to 1 mol % were successfully synthesized by an acid catalyzed sol-gel method, and their performance as the photoanodes of dye-sensitized solar cells (DSSCs) was investigated. Ce doping resulted in a red shift in the absorption of the TiO2 indicating narrowing of the band gap. The band gap first narrowed with increase in concentration of dopant up until 0.9 % dopant concentration. After this optimum doping concentration the band gap widened again. DFT calculations showed that Ce doping introduces Ce4f impurity states located just below the conduction band resulting in band gap narrowing. Ce content (0.9%) doped TiO2 photoanodes improved the performance of DSSCs with a conversion efficiency of 2.11% compared to 0,21% for the one with a pure TiO2 under 1 sun, AM1.5. Graphitised/TiO2 nanocomposites were also used a semiconductor to slow down recombination of electrons and holes in the cells. Electrophoretic deposition (EPD) was used to deposit graphitised/TiO2 nanocomposites onto an FTO electrode for application as photoelectrode in dye-sensitized solar cells (DSSCs). An enhanced power conversion efficiency (PCE) of 2.25% was observed for the 0.5 wt% graphene oxide/TiO2 (GO/TiO2) based DSSC which was higher than that of the conversion efficiency of pure TiO2 nanoparticles (i.e. 0.52%). Graphene oxide led to high migration of photoinduced electrons to the conduction band of the collection electrode and inhibition of charge carriers recombination resulting in enhanced photoconversion efficiency. A GO content above 0.5 % resulted in a reduced transparency leading to a decrease in the PCE. 0.5 wt % GO/0.9 Ce–TiO2 Ce based DSSC showed a slightly enhanced efficiency of 2.45%. 0.5 rGO/TiO2 based DSSCs had a high efficiency than 0.5 rGO/TiO2 due to improved conductivity of rGO nanosheets and suppressed recombination of charge carriers. To cut down DSSC production costs a silver wire network transparent conducting polyethylene electrodes was fabricated and used as an indium tin oxide (ITO) alternative substrates in DSSCs. The transmittance of the AgNW network was 82 % which is comparable to ITO substrates. Titanium oxide (TiO2) films on the AgWN/PET substrates were obtained using the electrophoresis method. These substrates were sensitised and used to fabricate a dye sensitised solar cell. From the measured current–voltage or I-V characteristic under AM1.5 illumination of the formed DSSC using AgWN substrates, an open circuit voltage (VOC) of 0.377 V, a short circuit current (ISC) of 0.0067 mA and a fill factor (FF) 25.7 % with an efficiency of 0.00862 % were obtained from a cell of 0.075 cm2 working area. The stability of the cell improved when a room temperature ionic liquid electrolyte was used. Gold nanofiber transparent electrodes were also prepared by the electrospinning techniques and used as an alternative to indium tin oxides substrates. Transparent conducting gold nanofiber (AuNF) transparent conducting electrodes were fabricated by using a low–cost electrospinning process and used as photoelectrodes for DSSCs. TiO2 was deposited on these electrodes by using an electrospray method. DSSC using AuNF as transparent electrodes had a power efficiency of 0.52%, compared to devices made with FTO electrodes (1.48%). DSSCs. Versatile dyes with increased spectral response, stability and suppressed recombination of holes and electrons were synthesised and used as a sensitizers for DSSCs. The boron dipyrrin (BODIPY) chromophore was combined with a carboxy coumarin moiety to create donor–acceptor (dyad) system dyes. Regenerative dyad dyes were formed through covalently linking a porphyrin chromophore to a manganese(II) ion through bridging ligands. These chromophores and also porphyrin and BODIPY dyes were used as sensitisers for DSSCs. The regenerative dye based DSSCs showed a photoconversion efficiency of 4.09% which was higher than the efficiency of the parent porphyrin (2.57%). The enhanced efficiency was attributed to the manganese bypridine cluster in the ZnTPP–Mn bpy supramolecule which acted as an electron donor to the photo-oxidized porphyrin continuously regenerating the porphyrin and preventing its decay.
- Full Text:
- Date Issued: 2019
Design, evaluation and optimization of taste masked clarithromycin powder
- Ntemi, Pascal V, Walker, Roderick B, Khamanga, Sandile M
- Authors: Ntemi, Pascal V , Walker, Roderick B , Khamanga, Sandile M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183503 , vital:44001 , xlink:href="https://doi.org/10.1691/ph.2019.8116"
- Description: Clarithromycin (CLA) is an extremely bitter macrolide antibiotic used to treat paediatric and adult infections. The bitter taste affects patient adherence and may compromise therapy. This research developed a taste masked CLA resinate using Indion® 234, a weak acidic cation exchange resin. The factors affecting formation of the CLA-resin complex were assessed. Design of experiments was used to optimize response while evaluating input variables such as temperature, CLA-resin ratio,stirring time and pH. CLA loading efficiency was determined spectrophotometrically and CLA release using USP Apparatus II. Differential Scanning Calorimetry (DSC), Scanning Electron Microscop (SEM), Fourier Transform Infrared (FT-IR) Spectroscopy and X-ray Diffraction (XRD) were used to confirm complex formation. A spectrophotometric method was used to assess taste evaluation. The optimum CLA-resin ratio, temperature, and stirring time were 1:4, 80 °C, 3 hours, respectively, at pH 8. Characterization techniques revealed that CLA was crystalline and the complex amorphous in nature. FT-IR spectra of resinate revealed the absence of resonance due to the tertiary amine functional group that is responsible for the bitter taste of CLA. CLA was stable in simulated salivary fluid and was released within 3 hours in gastric fluid. All CLAresin batches revealed complete taste masking. Taste analysis highlighted the improvement of taste masking properties of the resinate as the CLA to resin ratio, increased.
- Full Text:
- Date Issued: 2019
- Authors: Ntemi, Pascal V , Walker, Roderick B , Khamanga, Sandile M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183503 , vital:44001 , xlink:href="https://doi.org/10.1691/ph.2019.8116"
- Description: Clarithromycin (CLA) is an extremely bitter macrolide antibiotic used to treat paediatric and adult infections. The bitter taste affects patient adherence and may compromise therapy. This research developed a taste masked CLA resinate using Indion® 234, a weak acidic cation exchange resin. The factors affecting formation of the CLA-resin complex were assessed. Design of experiments was used to optimize response while evaluating input variables such as temperature, CLA-resin ratio,stirring time and pH. CLA loading efficiency was determined spectrophotometrically and CLA release using USP Apparatus II. Differential Scanning Calorimetry (DSC), Scanning Electron Microscop (SEM), Fourier Transform Infrared (FT-IR) Spectroscopy and X-ray Diffraction (XRD) were used to confirm complex formation. A spectrophotometric method was used to assess taste evaluation. The optimum CLA-resin ratio, temperature, and stirring time were 1:4, 80 °C, 3 hours, respectively, at pH 8. Characterization techniques revealed that CLA was crystalline and the complex amorphous in nature. FT-IR spectra of resinate revealed the absence of resonance due to the tertiary amine functional group that is responsible for the bitter taste of CLA. CLA was stable in simulated salivary fluid and was released within 3 hours in gastric fluid. All CLAresin batches revealed complete taste masking. Taste analysis highlighted the improvement of taste masking properties of the resinate as the CLA to resin ratio, increased.
- Full Text:
- Date Issued: 2019
Determining the hydrological functioning of the palmiet wetlands in the Eastern and Western Cape South Africa
- Authors: Smith, Caitlin
- Date: 2019
- Subjects: Wetlands -- South Africa -- Eastern Cape , Wetland ecology -- South Africa -- Eastern Cape , Wetland management -- South Africa -- Eastern Cape , Prioniaceae -- South Africa -- Eastern Cape , Prionium serratum -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/95956 , vital:31218
- Description: Wetlands provide a range of supporting, regulating and provisioning ecosystem services, including hydrological benefits such as flood attenuation and sustaining base flows. Despite their value, wetlands are one of the most vulnerable ecosystems in South Africa. Palmiet wetlands in the Eastern and Western Cape are particularly threatened. Palmiet (Prionium serratum) is a robust perennial plant that is endemic to wetlands and rivers located in the sandstones and quartzites of the Table Mountain Group (TMG), in the Eastern and Western Cape as well as the Natal Group sandstones in KwaZulu-Natal. Palmiet is described as an ecosystem engineer because of its ability to alter its environment and create large valley-bottom wetlands. The Krom River is an important water source for the city of Port Elizabeth and there has been a decline in palmiet wetlands along the Krom River as a result of alien vegetation invasion, agricultural activity, and gully erosion. Working for Water has been clearing alien vegetation and Working for Wetlands has been installing rehabilitation structures in the Krom River catchment for a number of years. There are, however, serious knowledge gaps in the understanding of palmiet wetland structure and function, particularly in respect of the hydrological functioning of these wetland systems. The aim of this study was to investigate the hydrology (surface and groundwater) behind these wetland systems. The investigation focussed on small-scale dynamics of the palmiet wetland system in order to increase general understanding of the surface water and groundwater processes of these wetland systems. Field work was concentrated on the Kompanjiesdrif and Krugersland palmiet wetlands in the upper K90A Krom River catchment. The investigation involved the installation of piezometers, water quality and stable isotope sampling and analysis, an Electrical Resistivity Tomography survey, and hydrological and mixing cell modelling. The results of the investigation indicate that the hydrological functioning of palmiet wetlands is closely linked with high sub-surface discharges typically associated with TMG aquifers. It is proposed that the palmiet wetlands are sustained by significant amounts of sub-surface water (both groundwater and interflow) moving through preferential flow paths in the alluvial fans and tributaries, which are in turn sustained by groundwater discharge from the surrounding sandstones and quartzites of the Nardouw Sub-group and Peninsula Formation. The palmiet wetlands clearly retain a significant amount of water, leading to the maintenance of prolonged flows, and a larger baseflow. However, it is hypothesised that the occurrence of palmiet as the dominant species in these wetlands is due to the sustained low flows related to catchment geology and high hydrological connectivity between the catchment and the wetland that is enabled by flow paths that allow the free flow of water from the catchment to the wetland. It is further proposed that palmiet is possibly more reliant on a consistent water supply for its existence and survival than it is on acidic nutrient-poor water and soils as stated by other authors.
- Full Text:
- Date Issued: 2019
- Authors: Smith, Caitlin
- Date: 2019
- Subjects: Wetlands -- South Africa -- Eastern Cape , Wetland ecology -- South Africa -- Eastern Cape , Wetland management -- South Africa -- Eastern Cape , Prioniaceae -- South Africa -- Eastern Cape , Prionium serratum -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/95956 , vital:31218
- Description: Wetlands provide a range of supporting, regulating and provisioning ecosystem services, including hydrological benefits such as flood attenuation and sustaining base flows. Despite their value, wetlands are one of the most vulnerable ecosystems in South Africa. Palmiet wetlands in the Eastern and Western Cape are particularly threatened. Palmiet (Prionium serratum) is a robust perennial plant that is endemic to wetlands and rivers located in the sandstones and quartzites of the Table Mountain Group (TMG), in the Eastern and Western Cape as well as the Natal Group sandstones in KwaZulu-Natal. Palmiet is described as an ecosystem engineer because of its ability to alter its environment and create large valley-bottom wetlands. The Krom River is an important water source for the city of Port Elizabeth and there has been a decline in palmiet wetlands along the Krom River as a result of alien vegetation invasion, agricultural activity, and gully erosion. Working for Water has been clearing alien vegetation and Working for Wetlands has been installing rehabilitation structures in the Krom River catchment for a number of years. There are, however, serious knowledge gaps in the understanding of palmiet wetland structure and function, particularly in respect of the hydrological functioning of these wetland systems. The aim of this study was to investigate the hydrology (surface and groundwater) behind these wetland systems. The investigation focussed on small-scale dynamics of the palmiet wetland system in order to increase general understanding of the surface water and groundwater processes of these wetland systems. Field work was concentrated on the Kompanjiesdrif and Krugersland palmiet wetlands in the upper K90A Krom River catchment. The investigation involved the installation of piezometers, water quality and stable isotope sampling and analysis, an Electrical Resistivity Tomography survey, and hydrological and mixing cell modelling. The results of the investigation indicate that the hydrological functioning of palmiet wetlands is closely linked with high sub-surface discharges typically associated with TMG aquifers. It is proposed that the palmiet wetlands are sustained by significant amounts of sub-surface water (both groundwater and interflow) moving through preferential flow paths in the alluvial fans and tributaries, which are in turn sustained by groundwater discharge from the surrounding sandstones and quartzites of the Nardouw Sub-group and Peninsula Formation. The palmiet wetlands clearly retain a significant amount of water, leading to the maintenance of prolonged flows, and a larger baseflow. However, it is hypothesised that the occurrence of palmiet as the dominant species in these wetlands is due to the sustained low flows related to catchment geology and high hydrological connectivity between the catchment and the wetland that is enabled by flow paths that allow the free flow of water from the catchment to the wetland. It is further proposed that palmiet is possibly more reliant on a consistent water supply for its existence and survival than it is on acidic nutrient-poor water and soils as stated by other authors.
- Full Text:
- Date Issued: 2019
Developing Mother Tongues as Academic Languages in Primary Schools in Kenya: Exploring Extent and Indispensability
- Mose, Peter N, Kaschula, Russell H
- Authors: Mose, Peter N , Kaschula, Russell H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/174793 , vital:42510 , https://doi.org/10.1080/15348458.2019.1645605
- Description: The language in education policy in Kenya recommends mother tongue education in primary school learning. The purpose of this study was to explore the development of mother tongues as academic languages at the lower primary section in which the languages are supposed to be used. The exploration was on the functions they play in classroom instruction and if they are dispensable or otherwise. Ekegusii was used as a case study. Data were obtained through classroom observations and administration of semi-structured interviews with lower primary teachers. The findings indicate that mother tongues play important pedagogical functions in grades 1 up to 3, but not exactly as contemplated in the language policy. Secondly, mother tongues are indispensable in classroom teaching in spite of negative attitude towards their use.
- Full Text:
- Date Issued: 2019
- Authors: Mose, Peter N , Kaschula, Russell H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/174793 , vital:42510 , https://doi.org/10.1080/15348458.2019.1645605
- Description: The language in education policy in Kenya recommends mother tongue education in primary school learning. The purpose of this study was to explore the development of mother tongues as academic languages at the lower primary section in which the languages are supposed to be used. The exploration was on the functions they play in classroom instruction and if they are dispensable or otherwise. Ekegusii was used as a case study. Data were obtained through classroom observations and administration of semi-structured interviews with lower primary teachers. The findings indicate that mother tongues play important pedagogical functions in grades 1 up to 3, but not exactly as contemplated in the language policy. Secondly, mother tongues are indispensable in classroom teaching in spite of negative attitude towards their use.
- Full Text:
- Date Issued: 2019
Development and Validation of a Stability-indicating RP-HPLC Method Using Quality by Design for Estimating Captopril
- Veerubhotla, Krishna, Walker, Roderick B
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183525 , vital:44003 , xlink:href="10.4172/pharmaceutical-sciences.1000478"
- Description: The applicability of a quality by design framework for the development of a sensitive, simple and selective, stability-indicating reversed-phase high-performance liquid chromatography analytical method for the analysis of captopril was investigated. Design of experiments using a central composite design approach was used for method development. Twenty experimental runs were performed with acetonitrile content ranging between 28 and 36 % v/v, pH from 2.8 to 3.6 and temperature between 22° and 32°. The experimental data obtained was used to derive a quadratic model for the retention time of captopril. The optimized method produced sharp peaks with good resolution (>2) for captopril and the internal standard with retention times of 3.1 and 6.2 min, respectively. The experimental data revealed that acetonitrile content in the mobile phase and pH are significant factors that affect the retention time and resolution of captopril. Normal probability plots revealed that the residual and predicted data fall approximately on a straight line, indicating that the experimental error for these studies was evenly distributed suggesting that the model could be used to navigate the design space. This approach is useful to expedite method development and optimization activities in analytical laboratories.
- Full Text:
- Date Issued: 2019
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183525 , vital:44003 , xlink:href="10.4172/pharmaceutical-sciences.1000478"
- Description: The applicability of a quality by design framework for the development of a sensitive, simple and selective, stability-indicating reversed-phase high-performance liquid chromatography analytical method for the analysis of captopril was investigated. Design of experiments using a central composite design approach was used for method development. Twenty experimental runs were performed with acetonitrile content ranging between 28 and 36 % v/v, pH from 2.8 to 3.6 and temperature between 22° and 32°. The experimental data obtained was used to derive a quadratic model for the retention time of captopril. The optimized method produced sharp peaks with good resolution (>2) for captopril and the internal standard with retention times of 3.1 and 6.2 min, respectively. The experimental data revealed that acetonitrile content in the mobile phase and pH are significant factors that affect the retention time and resolution of captopril. Normal probability plots revealed that the residual and predicted data fall approximately on a straight line, indicating that the experimental error for these studies was evenly distributed suggesting that the model could be used to navigate the design space. This approach is useful to expedite method development and optimization activities in analytical laboratories.
- Full Text:
- Date Issued: 2019
Development, manufacture and characterization of niosomes for the delivery for nevirapine
- Witika, Bwalya A, Walker, Roderick B
- Authors: Witika, Bwalya A , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183514 , vital:44002 , xlink:href="https://doi.org/10.1691/ph.2019.8168"
- Description: Nevirapine (NVP), used for the treatment of HIV/AIDS, exhibits unpredictable oral bioavailability, has a poor side effect profile and requires frequent dosing. Niosomes are novel drug delivery systems that have the potential to overcome these challenges. A thin layer hydration approach was used to produce niosomes and optimisation was undertaken using design of experiments (DoE) and response surface methodology (RSM) establish and identify parameters that may affect the manufacture of niosomes. The impact of cholesterol and surfactant content, hydration time and temperature on manufacture was investigated. Critical quality attributes (CQA) in respect of particle size (PS), entrapment efficiency (EE), polydispersity index (PDI) and the amount of NVP released at 48 hours was also assessed. The optimised niosome composition was identified and manufactured and the CQA characterised prior to placing the batch on stability for 12 weeks at 4±2 °C and 22±2 °C. The PS, PDI, EE and % NVP released at 48 h was 523.36±23.16 nm, 0.386±0.054, 96.8 % and 25.3 % for niosomes manufactured with Span® 20. Similarly, the parameters were 502.87±21.77 nm and 0.394±0.027, 98.0 % and 25.0 % for mean PS, PDI, EE and %NVP released at 48 h for Span® 80 niosomes. All characterisation was undertaken on the day of manufacture. In conclusion, a simple, cheap, rapid and precise method of manufacture of NVP niosomes was developed, validated and optimised using DoE and RSM and the product exhibited the target CQA.
- Full Text:
- Date Issued: 2019
- Authors: Witika, Bwalya A , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183514 , vital:44002 , xlink:href="https://doi.org/10.1691/ph.2019.8168"
- Description: Nevirapine (NVP), used for the treatment of HIV/AIDS, exhibits unpredictable oral bioavailability, has a poor side effect profile and requires frequent dosing. Niosomes are novel drug delivery systems that have the potential to overcome these challenges. A thin layer hydration approach was used to produce niosomes and optimisation was undertaken using design of experiments (DoE) and response surface methodology (RSM) establish and identify parameters that may affect the manufacture of niosomes. The impact of cholesterol and surfactant content, hydration time and temperature on manufacture was investigated. Critical quality attributes (CQA) in respect of particle size (PS), entrapment efficiency (EE), polydispersity index (PDI) and the amount of NVP released at 48 hours was also assessed. The optimised niosome composition was identified and manufactured and the CQA characterised prior to placing the batch on stability for 12 weeks at 4±2 °C and 22±2 °C. The PS, PDI, EE and % NVP released at 48 h was 523.36±23.16 nm, 0.386±0.054, 96.8 % and 25.3 % for niosomes manufactured with Span® 20. Similarly, the parameters were 502.87±21.77 nm and 0.394±0.027, 98.0 % and 25.0 % for mean PS, PDI, EE and %NVP released at 48 h for Span® 80 niosomes. All characterisation was undertaken on the day of manufacture. In conclusion, a simple, cheap, rapid and precise method of manufacture of NVP niosomes was developed, validated and optimised using DoE and RSM and the product exhibited the target CQA.
- Full Text:
- Date Issued: 2019
Digital colonialism: South Africa’s education transformation in the shadow of Silicon Valley
- Authors: Kwet, Michael
- Date: 2019
- Subjects: Operation Phakisa Education (South Africa) , Educational technology -- South Africa , Internet in education -- South Africa , Educational sociology -- South Africa , Technological innovations -- South Africa , Technological literacy -- South Africa , Education and state -- South Africa , Open source software -- South Africa , Electronic surveillance -- Social aspects -- South Africa , Privacy, Right of -- South Africa , Business and education -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/93767 , vital:30936
- Description: This dissertation investigates the social implications of technology choices for the emerging education transformation of the South African basic education sector. In October 2015, then President Jacob Zuma launched Operation Phakisa Education (OPE), an initiative designed behind closed doors to fast-track digital education into all South African public schools. This study identifies and analyses policy choices and perspectives regarding the technology considered and deployed for the national education rollout. It documents the OPE proposal, and examines how e-education policy choices relate to humanitarian objectives. Theoretically, this study draws upon libertarian socialist theory (anarchism) to examine the sociology of education technology policy. Using anarchist theory, it assesses the perspective, aims, and choices of e-education policy at the national level. It also draws on the Free Software philosophy for society as articulated by Richard Stallman and Eben Moglen. Finally, it compares classic colonialism with global power in the digital era, and posits a theory of digital colonialism. Synthesizing anarchism and the Free Software philosophy into a single theoretical framework – placed into the context of colonial relations – it is the first work to apply anarchist sociological theory to education technology policy, and the first doctoral study on digital colonialism. For its methodology, this dissertation utilizes two qualitative methods: document analysis and semi-structured interviews. Interview subjects include high-level e-education policymakers and administrators in government, key stakeholders, and experts at the intersection of technology innovation and human rights. These methods were used to both identify and interrogate e-education policy as it relates to the humanitarian objectives of education policy at the national level. The findings demonstrate that South African education policy is beholden to largely United States-based corporations and models for e-education. The study found that the types of technologies for consideration in education are rooted in surveillance capitalism, which is spreading across the world. It contends that current e-education policy choices will entrench the power and exploitation of US state-corporate power in South African education, economy, and society. It argues that an alternative set of choices, People’s Technology for People’s Power, is consistent with the spirit of South African technology policy, and should be chosen for South African schools in order to counter the power of foreign power and resist surveillance capitalism. This dissertation is the first publication to document and analyze what the new government education policy is about and how it relates to equality and human rights. It argues that present South African e-education policy constitutes a new form of digitally-driven technocratic neoliberalism which ultimately favors ruling class interests in the United States and South Africa. It also argues that OPE violates South Africa’s Free and Open Source policy and the spirit of democracy outlined in the Phakisa methodology and the Batho Pele principles. This study found that OPE replicates the latest trends in e-education implementation popular in Silicon Valley. Tech multinationals are providing both the products and models for use in South Africa. The dissertation concludes that US technological and conceptual dominance in South African education constitutes digital colonialism. It emphasizes the need for public inclusion in the policy process, and proposes alternative policies and technologies for e-education based on the idea of People’s Technology for People’s Power. It also argues that current scholarship on education technology neglects the political and sociological importance of People’s Technology to education, economy, and society, as well as the global significance of Big Tech dominance vis-a-vis digital colonialism, and that subsequent literature would be enriched by addressing these issues.
- Full Text:
- Date Issued: 2019
- Authors: Kwet, Michael
- Date: 2019
- Subjects: Operation Phakisa Education (South Africa) , Educational technology -- South Africa , Internet in education -- South Africa , Educational sociology -- South Africa , Technological innovations -- South Africa , Technological literacy -- South Africa , Education and state -- South Africa , Open source software -- South Africa , Electronic surveillance -- Social aspects -- South Africa , Privacy, Right of -- South Africa , Business and education -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/93767 , vital:30936
- Description: This dissertation investigates the social implications of technology choices for the emerging education transformation of the South African basic education sector. In October 2015, then President Jacob Zuma launched Operation Phakisa Education (OPE), an initiative designed behind closed doors to fast-track digital education into all South African public schools. This study identifies and analyses policy choices and perspectives regarding the technology considered and deployed for the national education rollout. It documents the OPE proposal, and examines how e-education policy choices relate to humanitarian objectives. Theoretically, this study draws upon libertarian socialist theory (anarchism) to examine the sociology of education technology policy. Using anarchist theory, it assesses the perspective, aims, and choices of e-education policy at the national level. It also draws on the Free Software philosophy for society as articulated by Richard Stallman and Eben Moglen. Finally, it compares classic colonialism with global power in the digital era, and posits a theory of digital colonialism. Synthesizing anarchism and the Free Software philosophy into a single theoretical framework – placed into the context of colonial relations – it is the first work to apply anarchist sociological theory to education technology policy, and the first doctoral study on digital colonialism. For its methodology, this dissertation utilizes two qualitative methods: document analysis and semi-structured interviews. Interview subjects include high-level e-education policymakers and administrators in government, key stakeholders, and experts at the intersection of technology innovation and human rights. These methods were used to both identify and interrogate e-education policy as it relates to the humanitarian objectives of education policy at the national level. The findings demonstrate that South African education policy is beholden to largely United States-based corporations and models for e-education. The study found that the types of technologies for consideration in education are rooted in surveillance capitalism, which is spreading across the world. It contends that current e-education policy choices will entrench the power and exploitation of US state-corporate power in South African education, economy, and society. It argues that an alternative set of choices, People’s Technology for People’s Power, is consistent with the spirit of South African technology policy, and should be chosen for South African schools in order to counter the power of foreign power and resist surveillance capitalism. This dissertation is the first publication to document and analyze what the new government education policy is about and how it relates to equality and human rights. It argues that present South African e-education policy constitutes a new form of digitally-driven technocratic neoliberalism which ultimately favors ruling class interests in the United States and South Africa. It also argues that OPE violates South Africa’s Free and Open Source policy and the spirit of democracy outlined in the Phakisa methodology and the Batho Pele principles. This study found that OPE replicates the latest trends in e-education implementation popular in Silicon Valley. Tech multinationals are providing both the products and models for use in South Africa. The dissertation concludes that US technological and conceptual dominance in South African education constitutes digital colonialism. It emphasizes the need for public inclusion in the policy process, and proposes alternative policies and technologies for e-education based on the idea of People’s Technology for People’s Power. It also argues that current scholarship on education technology neglects the political and sociological importance of People’s Technology to education, economy, and society, as well as the global significance of Big Tech dominance vis-a-vis digital colonialism, and that subsequent literature would be enriched by addressing these issues.
- Full Text:
- Date Issued: 2019
Discorhabdin N, a South African Natural Compound, for Hsp72 and Hsc70 Allosteric Modulation: combined study of molecular modeling and dynamic residue network analysis
- Amusengeri, Arnold, Tastan Bishop, Özlem
- Authors: Amusengeri, Arnold , Tastan Bishop, Özlem
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/162949 , vital:40999 , https://doi.org/10.3390/molecules24010188
- Description: The human heat shock proteins (Hsps), predominantly Hsp72 and Hsp90, have been strongly implicated in various critical stages of oncogenesis and progression of human cancers. While drug development has extensively focused on Hsp90 as a potential anticancer target, much less effort has been put against Hsp72. This work investigated the therapeutic potential of Hsp72 and its constitutive isoform, Hsc70, via in silico-based screening against the South African Natural Compounds Database (SANCDB). A comparative modeling approach was used to obtain nearly full-length 3D structures of the closed conformation of Hsp72 and Hsc70 proteins. Molecular docking of SANCDB compounds identified one potential allosteric modulator, Discorhabdin N, binding to the allosteric β substrate binding domain (SBDβ) back pocket, with good binding affinities in both cases.
- Full Text:
- Date Issued: 2019
- Authors: Amusengeri, Arnold , Tastan Bishop, Özlem
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/162949 , vital:40999 , https://doi.org/10.3390/molecules24010188
- Description: The human heat shock proteins (Hsps), predominantly Hsp72 and Hsp90, have been strongly implicated in various critical stages of oncogenesis and progression of human cancers. While drug development has extensively focused on Hsp90 as a potential anticancer target, much less effort has been put against Hsp72. This work investigated the therapeutic potential of Hsp72 and its constitutive isoform, Hsc70, via in silico-based screening against the South African Natural Compounds Database (SANCDB). A comparative modeling approach was used to obtain nearly full-length 3D structures of the closed conformation of Hsp72 and Hsc70 proteins. Molecular docking of SANCDB compounds identified one potential allosteric modulator, Discorhabdin N, binding to the allosteric β substrate binding domain (SBDβ) back pocket, with good binding affinities in both cases.
- Full Text:
- Date Issued: 2019
Discursive psychological analysis on the construction and performance of identity through rights talk on social media related to #FeesMustFall
- Authors: Mashaba, Tumelo Thabo
- Date: 2019
- Subjects: Identity , Right to education , Human rights , Social media -- Political aspects -- South Africa , College students -- Political activity -- South Africa , College students -- Attitudes -- South Africa , College students, Black -- Psychology -- South Africa , College students, Black -- Attitudes -- South Africa , College students -- Psychology -- South Africa , Student protestors -- Attitudes -- South Africa , Student movements -- South Africa , Internet and activisim -- South Africa , Internet in political campaigns -- South Africa , Higher education and state -- South Africa
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/96668 , vital:31306
- Description: #FeesMustFall emerged at the end of 2015 after an announcement that tuitions would increase. The student protests occurred across higher education institutions within the country in which mass shutdowns were initiated, there was the presence of violence and the use of social media. The protests occurred in 2016 but experienced a shift in tone in terms of the violence present in the protests. The research sought to unpack how identity was constructed and performed through rights talk in regards to #FeesMustFall on social media. The methodology worked from a social constructionist perspective where the research consisted of a discursive psychological analytical approach to the texts presented. The discursive repertoires that were identified were: emotions repertoire; struggle repertoire; apartheid repertoire; racial repertoire; and rights repertoire. The subject positions revealed through the repertoires indicated that protesters and supporters constructed and performed their identity in particular ways. They were positioned as black; working class; victims who are enacting a sense of agency; denied their rights; have moral authority and are a parallel to the protesters under apartheid. The repertoire of struggle, racial and apartheid all link with each other. The rights repertoire is the foundation and the emotions repertoire is the tone of the student protests.
- Full Text:
- Date Issued: 2019
- Authors: Mashaba, Tumelo Thabo
- Date: 2019
- Subjects: Identity , Right to education , Human rights , Social media -- Political aspects -- South Africa , College students -- Political activity -- South Africa , College students -- Attitudes -- South Africa , College students, Black -- Psychology -- South Africa , College students, Black -- Attitudes -- South Africa , College students -- Psychology -- South Africa , Student protestors -- Attitudes -- South Africa , Student movements -- South Africa , Internet and activisim -- South Africa , Internet in political campaigns -- South Africa , Higher education and state -- South Africa
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/96668 , vital:31306
- Description: #FeesMustFall emerged at the end of 2015 after an announcement that tuitions would increase. The student protests occurred across higher education institutions within the country in which mass shutdowns were initiated, there was the presence of violence and the use of social media. The protests occurred in 2016 but experienced a shift in tone in terms of the violence present in the protests. The research sought to unpack how identity was constructed and performed through rights talk in regards to #FeesMustFall on social media. The methodology worked from a social constructionist perspective where the research consisted of a discursive psychological analytical approach to the texts presented. The discursive repertoires that were identified were: emotions repertoire; struggle repertoire; apartheid repertoire; racial repertoire; and rights repertoire. The subject positions revealed through the repertoires indicated that protesters and supporters constructed and performed their identity in particular ways. They were positioned as black; working class; victims who are enacting a sense of agency; denied their rights; have moral authority and are a parallel to the protesters under apartheid. The repertoire of struggle, racial and apartheid all link with each other. The rights repertoire is the foundation and the emotions repertoire is the tone of the student protests.
- Full Text:
- Date Issued: 2019
Dual phototransformation of the pollutants methyl orange and Cr (VI) using phthalocyanine-cobalt ferrite based magnetic nanocomposites
- Mapukata, Sivuyisiwe, Osifeko, Olawale L, Nyokong, Tebello
- Authors: Mapukata, Sivuyisiwe , Osifeko, Olawale L , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187059 , vital:44561 , xlink:href="https://doi.org/10.1016/j.heliyon.2019.e01509"
- Description: Bifunctional nanocomposites based on zinc phthalocyanines and glutathione capped CoFe2O4 magnetic nanoparticles (GSH-CoFe2O4 MNPs) are applied in a binary system wherein simultaneous photooxidation of methyl orange (MO) and photoreduction of Cr (VI) are conducted. The photoactivity of two zinc Pcs with different functional moieties are compared based on their interactions with GSH-CoFe2O4 MNPs. Conjugation of the Pcs to the GSH-CoFe2O4 MNPs not only enhanced their singlet oxygen production but also their photocatalytic activity in both photooxidation and photoreduction experiments. Using electron paramagnetic resonance (EPR) spectroscopy, the Pc-MNP conjugates reported herein were found to exhibit superparamagnetic behaviour, giving the advantage of easy separation using an external magnetic field post application, an attractive attribute for heterogeneous catalysis. The catalysts reported herein are therefore good candidates as catalysts for real life water purification analyses as they facilitate the treatment of both organic and inorganic water pollutants.
- Full Text:
- Date Issued: 2019
- Authors: Mapukata, Sivuyisiwe , Osifeko, Olawale L , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187059 , vital:44561 , xlink:href="https://doi.org/10.1016/j.heliyon.2019.e01509"
- Description: Bifunctional nanocomposites based on zinc phthalocyanines and glutathione capped CoFe2O4 magnetic nanoparticles (GSH-CoFe2O4 MNPs) are applied in a binary system wherein simultaneous photooxidation of methyl orange (MO) and photoreduction of Cr (VI) are conducted. The photoactivity of two zinc Pcs with different functional moieties are compared based on their interactions with GSH-CoFe2O4 MNPs. Conjugation of the Pcs to the GSH-CoFe2O4 MNPs not only enhanced their singlet oxygen production but also their photocatalytic activity in both photooxidation and photoreduction experiments. Using electron paramagnetic resonance (EPR) spectroscopy, the Pc-MNP conjugates reported herein were found to exhibit superparamagnetic behaviour, giving the advantage of easy separation using an external magnetic field post application, an attractive attribute for heterogeneous catalysis. The catalysts reported herein are therefore good candidates as catalysts for real life water purification analyses as they facilitate the treatment of both organic and inorganic water pollutants.
- Full Text:
- Date Issued: 2019
Ecological connectivity between the areas beyond national jurisdiction and coastal waters: Safeguarding interests of coastal communities in developing countries
- Popova, Ekaterina, Vousden, David, Sauer, Warwick H H, Mohammed, Essam Y, Allain, Valerie, Downey-Breedt, Nicola, Fletcher, Ruth, Gjerde, Kristina M, Halpin, Patrick, Kelly, Stephen, Obura, David, Pecl, Gretta T, Roberts, Michael, Raitsos, Dionysios E, Rogers, Alex, Samoilys, Melita, Sumaila , Ussif Rashid, Tracey, Sean, Yool, Andrew
- Authors: Popova, Ekaterina , Vousden, David , Sauer, Warwick H H , Mohammed, Essam Y , Allain, Valerie , Downey-Breedt, Nicola , Fletcher, Ruth , Gjerde, Kristina M , Halpin, Patrick , Kelly, Stephen , Obura, David , Pecl, Gretta T , Roberts, Michael , Raitsos, Dionysios E , Rogers, Alex , Samoilys, Melita , Sumaila , Ussif Rashid , Tracey, Sean , Yool, Andrew
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124331 , vital:35594 , https://doi.10.1016/j.marpol.2019.02.050
- Description: The UN General Assembly has made a unanimous decision to start negotiations to establish an international, legally-binding instrument for the conservation and sustainable use of marine biological diversity within Areas Beyond National Jurisdiction (ABNJ). However, there has of yet been little discussion on the importance of this move to the ecosystem services provided by coastal zones in their downstream zone of influence. Here, we identify the ecological connectivity between ABNJ and coastal zones as critically important in the negotiation process and apply several approaches to identify some priority areas for protection from the perspective of coastal populations of Least Developed Countries (LDCs). Initially, we review the scientific evidence that demonstrates ecological connectivity between ABNJ and the coastal zones with a focus on the LDCs. We then use ocean modelling to develop a number of metrics and spatial maps that serve to quantify the connectivity of the ABNJ to the coastal zone. We find that the level of exposure to the ABNJ influences varies strongly between countries. Similarly, not all areas of the ABNJ are equal in their impacts on the coastline. Using this method, we identify the areas of the ABNJ that are in the most urgent need of protection on the grounds of the strength of their potential downstream impacts on the coastal populations of LDCs. We argue that indirect negative impacts of the ABNJ fishing, industrialisation and pollution, communicated via oceanographic, cultural and ecological connectivity to the coastal waters of the developing countries should be of concern.
- Full Text:
- Date Issued: 2019
- Authors: Popova, Ekaterina , Vousden, David , Sauer, Warwick H H , Mohammed, Essam Y , Allain, Valerie , Downey-Breedt, Nicola , Fletcher, Ruth , Gjerde, Kristina M , Halpin, Patrick , Kelly, Stephen , Obura, David , Pecl, Gretta T , Roberts, Michael , Raitsos, Dionysios E , Rogers, Alex , Samoilys, Melita , Sumaila , Ussif Rashid , Tracey, Sean , Yool, Andrew
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124331 , vital:35594 , https://doi.10.1016/j.marpol.2019.02.050
- Description: The UN General Assembly has made a unanimous decision to start negotiations to establish an international, legally-binding instrument for the conservation and sustainable use of marine biological diversity within Areas Beyond National Jurisdiction (ABNJ). However, there has of yet been little discussion on the importance of this move to the ecosystem services provided by coastal zones in their downstream zone of influence. Here, we identify the ecological connectivity between ABNJ and coastal zones as critically important in the negotiation process and apply several approaches to identify some priority areas for protection from the perspective of coastal populations of Least Developed Countries (LDCs). Initially, we review the scientific evidence that demonstrates ecological connectivity between ABNJ and the coastal zones with a focus on the LDCs. We then use ocean modelling to develop a number of metrics and spatial maps that serve to quantify the connectivity of the ABNJ to the coastal zone. We find that the level of exposure to the ABNJ influences varies strongly between countries. Similarly, not all areas of the ABNJ are equal in their impacts on the coastline. Using this method, we identify the areas of the ABNJ that are in the most urgent need of protection on the grounds of the strength of their potential downstream impacts on the coastal populations of LDCs. We argue that indirect negative impacts of the ABNJ fishing, industrialisation and pollution, communicated via oceanographic, cultural and ecological connectivity to the coastal waters of the developing countries should be of concern.
- Full Text:
- Date Issued: 2019
Econo-Language Planning and Transformation in South Africa: From Localisation to Globalisation
- Authors: Kaschula, Russell H
- Date: 2019
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/174657 , vital:42498 , ISBN 9781108425346
- Description: This chapter seeks to create an understanding of the historical, sociopolitical and economic context within which language planning has taken place in South Africa (Alexander 1992). Furthermore, the extent to which government agencies and other stakeholder bodies have taken language planning into account when developing economic and development policies within the contemporary global reality will be assessed (Edozie 2004). Policies (if one can call them policies) such as the New Partnership for Africa’s Development (NEPAD), as well as the National Development Plan (NDP) in South Africa are analysed against the backdrop of language policy planning and implementation, to see if there are linkages between opportunity language planning on the ground (Antia 2017) and economic development. In other words does language planning create work opportunities through policy creation and implementation where our languages are seen as resources to be used appropriately in the market place?.
- Full Text:
- Date Issued: 2019
- Authors: Kaschula, Russell H
- Date: 2019
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/174657 , vital:42498 , ISBN 9781108425346
- Description: This chapter seeks to create an understanding of the historical, sociopolitical and economic context within which language planning has taken place in South Africa (Alexander 1992). Furthermore, the extent to which government agencies and other stakeholder bodies have taken language planning into account when developing economic and development policies within the contemporary global reality will be assessed (Edozie 2004). Policies (if one can call them policies) such as the New Partnership for Africa’s Development (NEPAD), as well as the National Development Plan (NDP) in South Africa are analysed against the backdrop of language policy planning and implementation, to see if there are linkages between opportunity language planning on the ground (Antia 2017) and economic development. In other words does language planning create work opportunities through policy creation and implementation where our languages are seen as resources to be used appropriately in the market place?.
- Full Text:
- Date Issued: 2019
Ectomycorrhizal fungal assessment of South African Pinus patula seedlings and their biological control potential to enhance seedling growth
- FitzGerald, Véronique Chartier
- Authors: FitzGerald, Véronique Chartier
- Date: 2019
- Subjects: Ectomycorrhizal fungi , Pinus patula Diseases and pests Biological control South Africa , Fusarium , Forest nurseries , Seedlings Growth , Seedlings Diseases and pests
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/67902 , vital:29167
- 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 levels of naturally occurring ECM colonisation in South African nurseries and to determine the effects of seedling inoculation with selected ECM and bacterial isolates on plant growth and resistance to the fungal pathogen F. circiantum. Pinus patula seedlings from 10 different South African nurseries were assessed for ECM colonisation using a grid line intersect method and molecularly identified using morphological and next-generation Illumina sequencing. Explants from ECM basidiocarps, collected from Pinus stands, were plated onto MMN medium to obtain isolates which were verified using molecular techniques. Mycorrhizal helper bacteria (MHB) were also isolated from these basiocarps, tested for MHB properties, siderophore production, phospahte solubilising and IAA production. ECM and associated bacterial isolates were used to inoculate seedlings and growth was assessed over a 5 month period. Colonisation of seedlings in production nurseries was low (2-21%). Morphologically the ECM fungi T. terrestris, Suillus sibiricus, and the genera Russula, Pseudotomentella were identified. Molecularly the ECM fungi T. terrestris, Inocybe jacobi and the genera Sphaerosporella and several other ECM containing families were identified along with many saprotrophic/endophytic fungi belonging to genera such as, Penicillium, Ramasonia and Talaromyces. Inoculated seedlings showed a significant increase in growth in comparison to the un-inoculated control seedlings. ECM fungal colonisation levels of these seedlings were significantly increased and colonisation was promoted by the Suillus isolate, Salmon Suillus. Seedling growth in the presence of the pathogen F. circinatum was significantly increased and promoted by the Lactarius isolate Lactarius quieticolor. Inoculation of seedlings in the nursery would ensure the production of stronger healthy plants which may be more tolerant to fusarial infection increasing survival in the plantation. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
- Full Text:
- Date Issued: 2019
- Authors: FitzGerald, Véronique Chartier
- Date: 2019
- Subjects: Ectomycorrhizal fungi , Pinus patula Diseases and pests Biological control South Africa , Fusarium , Forest nurseries , Seedlings Growth , Seedlings Diseases and pests
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/67902 , vital:29167
- 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 levels of naturally occurring ECM colonisation in South African nurseries and to determine the effects of seedling inoculation with selected ECM and bacterial isolates on plant growth and resistance to the fungal pathogen F. circiantum. Pinus patula seedlings from 10 different South African nurseries were assessed for ECM colonisation using a grid line intersect method and molecularly identified using morphological and next-generation Illumina sequencing. Explants from ECM basidiocarps, collected from Pinus stands, were plated onto MMN medium to obtain isolates which were verified using molecular techniques. Mycorrhizal helper bacteria (MHB) were also isolated from these basiocarps, tested for MHB properties, siderophore production, phospahte solubilising and IAA production. ECM and associated bacterial isolates were used to inoculate seedlings and growth was assessed over a 5 month period. Colonisation of seedlings in production nurseries was low (2-21%). Morphologically the ECM fungi T. terrestris, Suillus sibiricus, and the genera Russula, Pseudotomentella were identified. Molecularly the ECM fungi T. terrestris, Inocybe jacobi and the genera Sphaerosporella and several other ECM containing families were identified along with many saprotrophic/endophytic fungi belonging to genera such as, Penicillium, Ramasonia and Talaromyces. Inoculated seedlings showed a significant increase in growth in comparison to the un-inoculated control seedlings. ECM fungal colonisation levels of these seedlings were significantly increased and colonisation was promoted by the Suillus isolate, Salmon Suillus. Seedling growth in the presence of the pathogen F. circinatum was significantly increased and promoted by the Lactarius isolate Lactarius quieticolor. Inoculation of seedlings in the nursery would ensure the production of stronger healthy plants which may be more tolerant to fusarial infection increasing survival in the plantation. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
- Full Text:
- Date Issued: 2019
Effect of bromination on the optical limiting properties at 532 nm of BODIPY dyes with p-benzyloxystyryl groups at the 3, 5-positions
- Ngoy, Bokolombe P, May, Aviwe K, Mack, John, Nyokong, Tebello
- Authors: Ngoy, Bokolombe P , May, Aviwe K , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187507 , vital:44665 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.08.012"
- Description: The optical limiting (OL) properties of 3,5-di-p-benzyloxystyrylBODIPY dyes that contain both protons and bromine atoms at the 2,6-positions have been investigated by using the Z-scan technique at 532 nm on the nanosecond timescale. There is relatively weak absorbance at 532 nm under ambient light conditions, because the incorporation of p-benzyloxystyryl groups at the 3,5-positions results in a ca. 140 nm red shift of the main BODIPY spectral band to the 640–670 nm range. Reverse saturable absorbance (RSA) profiles that are consistent with an excited state absorption (ESA) mechanism involving the T1 and/or S1 states are observed in CH2Cl2 solution. Second order hyperpolarizability values of ca. 8 × 10−30 esu are obtained and this demonstrates that the dyes are potentially suitable for use in OL applications at 532 nm. There is a slight enhancement of the OL properties upon bromination, due to increased intersystem crossing to the triplet manifold, but the enhancement of the OL properties is less significant than has been observed with metal phthalocyanine complexes.
- Full Text:
- Date Issued: 2019
- Authors: Ngoy, Bokolombe P , May, Aviwe K , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187507 , vital:44665 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.08.012"
- Description: The optical limiting (OL) properties of 3,5-di-p-benzyloxystyrylBODIPY dyes that contain both protons and bromine atoms at the 2,6-positions have been investigated by using the Z-scan technique at 532 nm on the nanosecond timescale. There is relatively weak absorbance at 532 nm under ambient light conditions, because the incorporation of p-benzyloxystyryl groups at the 3,5-positions results in a ca. 140 nm red shift of the main BODIPY spectral band to the 640–670 nm range. Reverse saturable absorbance (RSA) profiles that are consistent with an excited state absorption (ESA) mechanism involving the T1 and/or S1 states are observed in CH2Cl2 solution. Second order hyperpolarizability values of ca. 8 × 10−30 esu are obtained and this demonstrates that the dyes are potentially suitable for use in OL applications at 532 nm. There is a slight enhancement of the OL properties upon bromination, due to increased intersystem crossing to the triplet manifold, but the enhancement of the OL properties is less significant than has been observed with metal phthalocyanine complexes.
- Full Text:
- Date Issued: 2019
Effect of gold nanoparticle shape on the photophysicochemical properties of sulphur containing metallophthalocyanines
- Dube, Edith, Nyokong, Tebello
- Authors: Dube, Edith , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187048 , vital:44559 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.12.091"
- Description: In this work tetrakise[(thiopheneethoxy) phthalocyaninato] zinc(II) (1), tetrakise[(thiopheneethoxy) phthalocyaninato] indium (II) chloride (2), tetrakis [(benzo [d]thiazol-2-yl phenoxy) phthalocyaninato] zinc(II) (3), and tetrakis [(benzo [d]thiazol-2-yl phenoxy)phthalocyaninato] indium (II) chloride (4) were linked to both gold nanospheres (AuNSs) and gold nanotriangles (AuNTs) via Au-S and Au-N (the latter for complexes 3 and 4 only) self assembly. The photophysicochemical behaviour of complexes and their conjugates were studied. The conjugates yielded improved triplet and singlet quantum yields, with nanospheres displaying better properties than nanotriangles. The conjugates with a benzothiazole phenoxy substituent also yielded better properties than their thiophene ethoxy counterpart. These conjugates especially those with a benzothiazole phenoxy substituent have potential as photosensitisers for photodynamic therapy applications.
- Full Text:
- Date Issued: 2019
- Authors: Dube, Edith , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187048 , vital:44559 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.12.091"
- Description: In this work tetrakise[(thiopheneethoxy) phthalocyaninato] zinc(II) (1), tetrakise[(thiopheneethoxy) phthalocyaninato] indium (II) chloride (2), tetrakis [(benzo [d]thiazol-2-yl phenoxy) phthalocyaninato] zinc(II) (3), and tetrakis [(benzo [d]thiazol-2-yl phenoxy)phthalocyaninato] indium (II) chloride (4) were linked to both gold nanospheres (AuNSs) and gold nanotriangles (AuNTs) via Au-S and Au-N (the latter for complexes 3 and 4 only) self assembly. The photophysicochemical behaviour of complexes and their conjugates were studied. The conjugates yielded improved triplet and singlet quantum yields, with nanospheres displaying better properties than nanotriangles. The conjugates with a benzothiazole phenoxy substituent also yielded better properties than their thiophene ethoxy counterpart. These conjugates especially those with a benzothiazole phenoxy substituent have potential as photosensitisers for photodynamic therapy applications.
- Full Text:
- Date Issued: 2019
Effect of gold nanoparticles shape and size on the photophysicochemical behaviour of symmetric and asymmetric zinc phthalocyanines
- Dube, Edith, Nyokong, Tebello
- Authors: Dube, Edith , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187569 , vital:44672 , xlink:href="https://doi.org/10.1016/j.jlumin.2018.09.063"
- Description: Glutathione (GSH) capped Au nanotriangles (AuNTs–GSH) and nanospheres (AuNSs–GSH) are covalently linked to symmetric Zn phthalocyanine (ZnPc) substituted with phenoxy propanoic acid substituents only (complex 1) and two asymmetric ZnPc, each containing one phenoxy propanoic acid and three benzothiazole phenoxy moieties (complex 2), and one phenoxy propanoic acid and no other ligands (complex 3). The photophysicochemical behaviour of Pc complexes and their conjugates were studied. All conjugates displayed improved triplet and singlet oxygen quantum yields with decreases in fluorescence quantum yields compared to their respective Pc complexes. The conjugates of asymmetric complexes 2 and 3, afforded much higher triplet and singlet oxygen quantum yields compared to the symmetric complex 1, and could serve as good candidates for photodynamic therapy
- Full Text:
- Date Issued: 2019
- Authors: Dube, Edith , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187569 , vital:44672 , xlink:href="https://doi.org/10.1016/j.jlumin.2018.09.063"
- Description: Glutathione (GSH) capped Au nanotriangles (AuNTs–GSH) and nanospheres (AuNSs–GSH) are covalently linked to symmetric Zn phthalocyanine (ZnPc) substituted with phenoxy propanoic acid substituents only (complex 1) and two asymmetric ZnPc, each containing one phenoxy propanoic acid and three benzothiazole phenoxy moieties (complex 2), and one phenoxy propanoic acid and no other ligands (complex 3). The photophysicochemical behaviour of Pc complexes and their conjugates were studied. All conjugates displayed improved triplet and singlet oxygen quantum yields with decreases in fluorescence quantum yields compared to their respective Pc complexes. The conjugates of asymmetric complexes 2 and 3, afforded much higher triplet and singlet oxygen quantum yields compared to the symmetric complex 1, and could serve as good candidates for photodynamic therapy
- Full Text:
- Date Issued: 2019
Effect of substituents on the photophysical properties and nonlinear optical properties of asymmetrical zinc(II) phthalocyanine when conjugated to semiconductor quantum dots
- Authors: Mgidlana, Sithi
- Date: 2019
- Subjects: Nonlinear optics , Quantum dots , Phthalocyanines , Zinc
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97152 , vital:31404
- Description: Various characterization techniques have been used to characterize the synthesized asymmetrical zinc phthalocyanines (ZnPc) derivatives. Techniques include Ultraviolet-visible (UV-vis) spectrophotometry, matrix assisted laser desorption time of flight mass spectrometry (MALD-TOF MS), proton nuclear magnetic resonance (1H-NMR), elemental analysis and Fourier-transform infra-red spectroscopy (FT-IR). The complexes are covalently linked to core/shell and core/shell/shell semiconductor quantum dots (SQDs) via amide bond formation. Photophysical properties of complexes improved in the presence of semiconductor quantum dots (SQDs). SQDs contain cadmium/telluride (CdTe) as core, coated in the first shell with zinc selenide (ZnSe) or zinc sulfide (ZnS) and with zinc oxide (ZnO) in second shell. The photophysical properties of the phthalocyanine (Pc) complexes and their conjugates with SQDs are investigated in solution. Triplet quantum yields of complexes improved in the presence of semiconductor quantum dots. The optical limiting behaviour of the Pc complexes and conjugates are assessed using the open aperture Z–scan technique at laser excitation wavelength of 532 nm with 10 ns pulse. Pcs complexes showed good nonlinear optical response with higher nonlinear absorption coefficient. The conjugates afforded higher nonlinear absorption coefficient than Pc complexes alone.
- Full Text:
- Date Issued: 2019
- Authors: Mgidlana, Sithi
- Date: 2019
- Subjects: Nonlinear optics , Quantum dots , Phthalocyanines , Zinc
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97152 , vital:31404
- Description: Various characterization techniques have been used to characterize the synthesized asymmetrical zinc phthalocyanines (ZnPc) derivatives. Techniques include Ultraviolet-visible (UV-vis) spectrophotometry, matrix assisted laser desorption time of flight mass spectrometry (MALD-TOF MS), proton nuclear magnetic resonance (1H-NMR), elemental analysis and Fourier-transform infra-red spectroscopy (FT-IR). The complexes are covalently linked to core/shell and core/shell/shell semiconductor quantum dots (SQDs) via amide bond formation. Photophysical properties of complexes improved in the presence of semiconductor quantum dots (SQDs). SQDs contain cadmium/telluride (CdTe) as core, coated in the first shell with zinc selenide (ZnSe) or zinc sulfide (ZnS) and with zinc oxide (ZnO) in second shell. The photophysical properties of the phthalocyanine (Pc) complexes and their conjugates with SQDs are investigated in solution. Triplet quantum yields of complexes improved in the presence of semiconductor quantum dots. The optical limiting behaviour of the Pc complexes and conjugates are assessed using the open aperture Z–scan technique at laser excitation wavelength of 532 nm with 10 ns pulse. Pcs complexes showed good nonlinear optical response with higher nonlinear absorption coefficient. The conjugates afforded higher nonlinear absorption coefficient than Pc complexes alone.
- Full Text:
- Date Issued: 2019
Effect of symmetry and metal nanoparticles on the photophysicochemical and photodynamic therapy properties of cinnamic acid zinc phthalocyanine
- Matlou, Gauta G, Managa, Muthumuni, Nyokong, Tebello
- Authors: Matlou, Gauta G , Managa, Muthumuni , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187026 , vital:44557 , xlink:href="https://doi.org/10.1016/j.saa.2019.02.005"
- Description: In this study, a novel asymmetric cinnamic acid zinc phthalocyanine (ZnPc, 1) containing three tert-butyl substituents is reported. The asymmetric ZnPc (1) is further linked to amino functionalized magnetic nanoparticles (AMNPs) (1-AMNPs) and to cysteine functionalized silver nanoparticles (cys-AgNPs) (1-cys-AgNPs) through an amide bond. 1-AMNPs and 1-cys-AgNPs improved the triplet and singlet oxygen quantum yields of complex 1, this was also observed with the previously reported 2-AMNPs when compared to 2 while 3-AMNPs yielded an unexpected decrease in triplet quantum yield as compared to 3. The silver nanoparticles (1-cys-AgNPs) had a better effect on improving the singlet oxygen quantum yield of complex 1 than the magnetic nanoparticles (1- AMNPs). The Pcs and conjugates recorded low cell cytotoxicity in the dark and high photocytotoxicity against MCF-7 cells in-vitro. MCF-7 cell viabilities of less than 50% were recorded at 80 μg/mL making the Pcs and conjugates under study potential candidates for use as photosensitizers in cancer therapy.
- Full Text:
- Date Issued: 2019
- Authors: Matlou, Gauta G , Managa, Muthumuni , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187026 , vital:44557 , xlink:href="https://doi.org/10.1016/j.saa.2019.02.005"
- Description: In this study, a novel asymmetric cinnamic acid zinc phthalocyanine (ZnPc, 1) containing three tert-butyl substituents is reported. The asymmetric ZnPc (1) is further linked to amino functionalized magnetic nanoparticles (AMNPs) (1-AMNPs) and to cysteine functionalized silver nanoparticles (cys-AgNPs) (1-cys-AgNPs) through an amide bond. 1-AMNPs and 1-cys-AgNPs improved the triplet and singlet oxygen quantum yields of complex 1, this was also observed with the previously reported 2-AMNPs when compared to 2 while 3-AMNPs yielded an unexpected decrease in triplet quantum yield as compared to 3. The silver nanoparticles (1-cys-AgNPs) had a better effect on improving the singlet oxygen quantum yield of complex 1 than the magnetic nanoparticles (1- AMNPs). The Pcs and conjugates recorded low cell cytotoxicity in the dark and high photocytotoxicity against MCF-7 cells in-vitro. MCF-7 cell viabilities of less than 50% were recorded at 80 μg/mL making the Pcs and conjugates under study potential candidates for use as photosensitizers in cancer therapy.
- Full Text:
- Date Issued: 2019
Eight decades of invasion by Chromolaena odorata (Asteraceae) and its biological control in West Africa: the story so far
- Aigbedion-Atalor, Pascal O, Adom, Medetissi, Day, Michael D, Uyi, Osariyekemwen, Egbon, Ikponmwosa N, Idemudia, I, Igbinosa, Igho B, Paterson, Iain D, Braimah, Haruna, Wilson, David D, Zachariades, Costas
- Authors: Aigbedion-Atalor, Pascal O , Adom, Medetissi , Day, Michael D , Uyi, Osariyekemwen , Egbon, Ikponmwosa N , Idemudia, I , Igbinosa, Igho B , Paterson, Iain D , Braimah, Haruna , Wilson, David D , Zachariades, Costas
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417450 , vital:71454 , xlink:href="https://doi.org/10.1080/09583157.2019.1670782"
- Description: Chromolaena odorata (L.) R.M. King and H. Robinson (Asteraceae) is a perennial weedy shrub of neotropical origin and a serious biotic threat in its invasive range. The Asian-West Africa (AWA) biotype of C. odorata present in West Africa is both morphologically and genetically different from the southern African (SA) biotype. The AWA biotype was first introduced into Nigeria in the late 1930s and rapidly spread across West Africa. Currently, 12 of the 16 countries in West Africa have been invaded, with significant negative effects on indigenous flora and fauna. However, locals in West Africa have found several uses for the weed. As chemical, physical and other conventional methods were unsustainable, costly and largely ineffective, three biological control agents, Apion brunneonigrum (Coleoptera: Brentidae), Pareuchaetes pseudoinsulata (Lepidoptera: Erebidae) and Cecidochares connexa (Diptera: Tephritidae), have been released in West Africa between the 1970s and the early 2000s. However, only C. connexa and P. pseudoinsulata established, contributing to the control of the weed, in six and four countries in West Africa respectively. Limited research funding, the absence of post-release evaluations of the established agents, and the ‘conflict of interest’ status of C. odorata (i.e. being beneficial for local use but damaging to ecosystem services and agriculture), are serious factors deterring the overall biological control effort. Here, using historical records and field surveys, we examine the invasion history, spread, impacts, and management of C. odorata in West Africa and make recommendations for the sustainable management of C. odorata in the region.
- Full Text:
- Date Issued: 2019
- Authors: Aigbedion-Atalor, Pascal O , Adom, Medetissi , Day, Michael D , Uyi, Osariyekemwen , Egbon, Ikponmwosa N , Idemudia, I , Igbinosa, Igho B , Paterson, Iain D , Braimah, Haruna , Wilson, David D , Zachariades, Costas
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417450 , vital:71454 , xlink:href="https://doi.org/10.1080/09583157.2019.1670782"
- Description: Chromolaena odorata (L.) R.M. King and H. Robinson (Asteraceae) is a perennial weedy shrub of neotropical origin and a serious biotic threat in its invasive range. The Asian-West Africa (AWA) biotype of C. odorata present in West Africa is both morphologically and genetically different from the southern African (SA) biotype. The AWA biotype was first introduced into Nigeria in the late 1930s and rapidly spread across West Africa. Currently, 12 of the 16 countries in West Africa have been invaded, with significant negative effects on indigenous flora and fauna. However, locals in West Africa have found several uses for the weed. As chemical, physical and other conventional methods were unsustainable, costly and largely ineffective, three biological control agents, Apion brunneonigrum (Coleoptera: Brentidae), Pareuchaetes pseudoinsulata (Lepidoptera: Erebidae) and Cecidochares connexa (Diptera: Tephritidae), have been released in West Africa between the 1970s and the early 2000s. However, only C. connexa and P. pseudoinsulata established, contributing to the control of the weed, in six and four countries in West Africa respectively. Limited research funding, the absence of post-release evaluations of the established agents, and the ‘conflict of interest’ status of C. odorata (i.e. being beneficial for local use but damaging to ecosystem services and agriculture), are serious factors deterring the overall biological control effort. Here, using historical records and field surveys, we examine the invasion history, spread, impacts, and management of C. odorata in West Africa and make recommendations for the sustainable management of C. odorata in the region.
- Full Text:
- Date Issued: 2019