Chemical transformations and phytochemical studies of bioactive components from extracts of Rosmarinus officinalis L
- Authors: Okoh, Omobola Oluranti
- Date: 2010
- Subjects: Essences and essential oils , Rosmarinus , Lamiaceae , Solution (Chemistry) , Extractive distillation , Medicinal plants , Bioactive compounds
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11331 , http://hdl.handle.net/10353/354 , Essences and essential oils , Rosmarinus , Lamiaceae , Solution (Chemistry) , Extractive distillation , Medicinal plants , Bioactive compounds
- Description: Variations in the yield, chemical composition, antibacterial, and antioxidant properties of the essential oils of Rosmarinus officinalis L. cultivated in Alice, Eastern Cape of South Africa over a period of 12 months using the solvent-free microwave extraction and traditional hydrodistillation methods were evaluated. The GC-MS analyses of the essential oils revealed the presence of 33 compounds with 1,8-cineole, a-pinene, camphor, verbenone, bornyl acetate and camphene constituting about 80 percent of the oils throughout the period of investigation, with the solvent-free microwave extraction method generally yielding more of the major components than the hydrodistillation method. Each of the major components of the oils varied in quantity and quality of yield at different periods of the year. The method of extraction and time of harvest are of importance to the quantity and quality of essential oil of Rosmarinus officinalis. Higher amounts of oxygenated monoterpenes such as borneol, camphor, terpene- 4-ol, linalool, a-terpeneol were present in the oil of SFME in comparison with HD. However, HD oil contained more monoterpene hydrocarbons such as a-pinene, camphene, β-pinene, myrcene, a-phellanderene, 1,8-cineole, trans- β-ocimene, γ-teprinene, and cis-sabinene hydrate than SFME extracted oil. Accumulation of monoterpene alcohols and ketones was observed during maturation process of Rosmarinus leaves. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration values were determined using a serial microplate dilution method. The essential oils obtained using both methods of extraction were active against all the bacteria tested at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the SFME extracted oils ranged between 0.23 and 1.88 mg mL-1, while those of the HD extracted oils varied between 0.94 and 7.5 mg mL-1, thus suggesting that the oil obtained by solvent free microwave extraction was more active against bacteria than the oil obtained through hydrodistillation. The antioxidant and free radical scavenging activity of the obtained oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay and β- carotene bleaching test. In the DPPH+ assay, while the free radical scavenging activity of the oil obtained by SFME method showed percentage inhibitions of between 48.8 percent and 67 percent, the HD derived oil showed inhibitions of between 52.2 percent and 65.30 percent at concentrations of 0.33, 0.50 and 1.0 mg mL-1, respectively. In the β-carotene bleaching assay, the percentage inhibition increased with increasing concentration of both oils with a higher antioxidant activity of the oil obtained through the SFME than the HD method. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i. e. CEF, BEA and EMW and sprayed with vanillin-sulfuric acid. The chemical composition of the different extracts was similar with the exception of methanol and water extracts which had only one or two visible compounds after treating with vanillin-spray reagent. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against two most important nosocomial microorganisms. S. aureus (Gram positive) and E. coli (Gram negative). Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of E. coli. The hexane extract had the most lines of inhibition followed by ethyl acetate. Bioassay-guided fractionation against E. coli was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the hexane fraction. Furthermore we tried to complete the characterization by extracting and studying other biologically important plant metabolites such as phenolic compounds to evaluate the antioxidant capacity of Rosmarinus extracts.
- Full Text:
- Date Issued: 2010
- Authors: Okoh, Omobola Oluranti
- Date: 2010
- Subjects: Essences and essential oils , Rosmarinus , Lamiaceae , Solution (Chemistry) , Extractive distillation , Medicinal plants , Bioactive compounds
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11331 , http://hdl.handle.net/10353/354 , Essences and essential oils , Rosmarinus , Lamiaceae , Solution (Chemistry) , Extractive distillation , Medicinal plants , Bioactive compounds
- Description: Variations in the yield, chemical composition, antibacterial, and antioxidant properties of the essential oils of Rosmarinus officinalis L. cultivated in Alice, Eastern Cape of South Africa over a period of 12 months using the solvent-free microwave extraction and traditional hydrodistillation methods were evaluated. The GC-MS analyses of the essential oils revealed the presence of 33 compounds with 1,8-cineole, a-pinene, camphor, verbenone, bornyl acetate and camphene constituting about 80 percent of the oils throughout the period of investigation, with the solvent-free microwave extraction method generally yielding more of the major components than the hydrodistillation method. Each of the major components of the oils varied in quantity and quality of yield at different periods of the year. The method of extraction and time of harvest are of importance to the quantity and quality of essential oil of Rosmarinus officinalis. Higher amounts of oxygenated monoterpenes such as borneol, camphor, terpene- 4-ol, linalool, a-terpeneol were present in the oil of SFME in comparison with HD. However, HD oil contained more monoterpene hydrocarbons such as a-pinene, camphene, β-pinene, myrcene, a-phellanderene, 1,8-cineole, trans- β-ocimene, γ-teprinene, and cis-sabinene hydrate than SFME extracted oil. Accumulation of monoterpene alcohols and ketones was observed during maturation process of Rosmarinus leaves. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration values were determined using a serial microplate dilution method. The essential oils obtained using both methods of extraction were active against all the bacteria tested at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the SFME extracted oils ranged between 0.23 and 1.88 mg mL-1, while those of the HD extracted oils varied between 0.94 and 7.5 mg mL-1, thus suggesting that the oil obtained by solvent free microwave extraction was more active against bacteria than the oil obtained through hydrodistillation. The antioxidant and free radical scavenging activity of the obtained oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay and β- carotene bleaching test. In the DPPH+ assay, while the free radical scavenging activity of the oil obtained by SFME method showed percentage inhibitions of between 48.8 percent and 67 percent, the HD derived oil showed inhibitions of between 52.2 percent and 65.30 percent at concentrations of 0.33, 0.50 and 1.0 mg mL-1, respectively. In the β-carotene bleaching assay, the percentage inhibition increased with increasing concentration of both oils with a higher antioxidant activity of the oil obtained through the SFME than the HD method. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i. e. CEF, BEA and EMW and sprayed with vanillin-sulfuric acid. The chemical composition of the different extracts was similar with the exception of methanol and water extracts which had only one or two visible compounds after treating with vanillin-spray reagent. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against two most important nosocomial microorganisms. S. aureus (Gram positive) and E. coli (Gram negative). Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of E. coli. The hexane extract had the most lines of inhibition followed by ethyl acetate. Bioassay-guided fractionation against E. coli was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the hexane fraction. Furthermore we tried to complete the characterization by extracting and studying other biologically important plant metabolites such as phenolic compounds to evaluate the antioxidant capacity of Rosmarinus extracts.
- Full Text:
- Date Issued: 2010
Dynamic adaptive cost model for wireless Internet connectivity in African rural communities
- Authors: Sibanda, Khulumani
- Date: 2010
- Subjects: Internet , Community development -- South Africa -- Eastern Cape , Cost effectiveness , Wireless communication systems , Rural development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Computer Science)
- Identifier: vital:11389 , http://hdl.handle.net/10353/380 , Internet , Community development -- South Africa -- Eastern Cape , Cost effectiveness , Wireless communication systems , Rural development -- South Africa -- Eastern Cape
- Description: In today’s dynamic technological landscape, wireless communication networks have become an important part of economic development. The emergence of wireless technologies raises hopes to extend communication to remote areas that have not seen any tangible deployment to date. As developing nations pin their hopes to wireless technologies, cost models for wireless communication networks are becoming vital to support the emerging technologies. However, varying cost changes raise critical challenges to the estimation of both capital expenditure and operational expenditure. The network deployment process has numerous events that may cause adjustments to initially estimated project costs. These adjustments are necessary for a cost management plan and this plan includes monitoring cost performance and ensuring that only appropriate changes are made to the network project. The incidents that may cause cost changes can not be entirely predicted as their distribution tend to change dynamically from time to time. Estimating network deployment costs in such a dynamic environment necessitates cost models that can adapt to random occurrence of cost changes. Widely used cost models are usually performed by experienced personnel whose engineering experience is derived from deploying similar networks. In this approach experienced personnel add a certain percentage to the cost estimate to cater for contingency costs. Certainly such an approach depends on individual opinion, making it subjective and void of mathematical estimating relationships which are of paramount importance in ensuring that estimated deployment costs are sufficient to deal with cost uncertainties. We observe that existing approaches can only explore a limited solution space and hence can lead to cost overruns if implemented in dynamically cost changing environments. This thesis presents a wireless communication network deployment cost model that incorporates uncertainties into the final cost estimate. The model is adaptive to unpredictable cost changes since it allows adjustments of confidence levels when calculating contingency costs. This allows dynamically updating the cost changes without the cost model being reconstructed from scratch. We make use of the Poisson process in modeling the occurrence of incidents that are responsible for causing cost changes during network deployment. We also show that the occurrence of the incidents causing cost change are random and tend to follow the Poisson distribution. Using different levels of confidence we model various cost contingencies and make sensitivity analyses to identify the probability of cost overrun when given different contingencies. The dynamic adaptive cost model can be used either at the strategic level to understand the cost of a particular technique or at the operational level, as a way to show how Poisson process in network deployment can compare with engineering experience and other estimating techniques. We believe that the model is useful for remote areas where deployment costs are volatile and the distribution of incidents causing cost change to original cost estimates are diverse and dynamically changing. Further we expect that our research improves the knowledge base of information about the costs for rural communities to connect to the Internet, consequently providing useful input to future policy debates. This work is further poised to be a utility function to help those planning internet infrastructure deployments in least developed regions.
- Full Text:
- Date Issued: 2010
- Authors: Sibanda, Khulumani
- Date: 2010
- Subjects: Internet , Community development -- South Africa -- Eastern Cape , Cost effectiveness , Wireless communication systems , Rural development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Computer Science)
- Identifier: vital:11389 , http://hdl.handle.net/10353/380 , Internet , Community development -- South Africa -- Eastern Cape , Cost effectiveness , Wireless communication systems , Rural development -- South Africa -- Eastern Cape
- Description: In today’s dynamic technological landscape, wireless communication networks have become an important part of economic development. The emergence of wireless technologies raises hopes to extend communication to remote areas that have not seen any tangible deployment to date. As developing nations pin their hopes to wireless technologies, cost models for wireless communication networks are becoming vital to support the emerging technologies. However, varying cost changes raise critical challenges to the estimation of both capital expenditure and operational expenditure. The network deployment process has numerous events that may cause adjustments to initially estimated project costs. These adjustments are necessary for a cost management plan and this plan includes monitoring cost performance and ensuring that only appropriate changes are made to the network project. The incidents that may cause cost changes can not be entirely predicted as their distribution tend to change dynamically from time to time. Estimating network deployment costs in such a dynamic environment necessitates cost models that can adapt to random occurrence of cost changes. Widely used cost models are usually performed by experienced personnel whose engineering experience is derived from deploying similar networks. In this approach experienced personnel add a certain percentage to the cost estimate to cater for contingency costs. Certainly such an approach depends on individual opinion, making it subjective and void of mathematical estimating relationships which are of paramount importance in ensuring that estimated deployment costs are sufficient to deal with cost uncertainties. We observe that existing approaches can only explore a limited solution space and hence can lead to cost overruns if implemented in dynamically cost changing environments. This thesis presents a wireless communication network deployment cost model that incorporates uncertainties into the final cost estimate. The model is adaptive to unpredictable cost changes since it allows adjustments of confidence levels when calculating contingency costs. This allows dynamically updating the cost changes without the cost model being reconstructed from scratch. We make use of the Poisson process in modeling the occurrence of incidents that are responsible for causing cost changes during network deployment. We also show that the occurrence of the incidents causing cost change are random and tend to follow the Poisson distribution. Using different levels of confidence we model various cost contingencies and make sensitivity analyses to identify the probability of cost overrun when given different contingencies. The dynamic adaptive cost model can be used either at the strategic level to understand the cost of a particular technique or at the operational level, as a way to show how Poisson process in network deployment can compare with engineering experience and other estimating techniques. We believe that the model is useful for remote areas where deployment costs are volatile and the distribution of incidents causing cost change to original cost estimates are diverse and dynamically changing. Further we expect that our research improves the knowledge base of information about the costs for rural communities to connect to the Internet, consequently providing useful input to future policy debates. This work is further poised to be a utility function to help those planning internet infrastructure deployments in least developed regions.
- Full Text:
- Date Issued: 2010
Quantification of greenhouse gas fluxes from soil in agricultural fields
- Authors: Nkongolo, Nsalambi Vakanda
- Date: 2010
- Subjects: Greenhouse gases -- Environmental aspects
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10645 , http://hdl.handle.net/10948/1474 , Greenhouse gases -- Environmental aspects
- Description: Field studies were conducted at Lincoln University of Missouri (USA) and Hokkaido University (Japan) to: (i) study the relationships between greenhouse gases emissions and soil properties, (ii) assess the influence of agricultural practices on greenhouse gas fluxes and soil properties and (iii) improve the quantification of greenhouse gases from soil in agricultural fields using geospatial technologies. Results showed that besides soil temperature (T), soil thermal properties such as thermal conductivity (K), resistivity (R) and diffusivity (D) and soil pore spaces indices such as the pore tortuosity factor and the relative gas diffusion coefficient (Ds/Do) are controlling factors for greenhouse gases emissions. Soil thermal properties correlated with greenhouse gases emissions when soil temperature could not. The study has found that predicted Ds/Do and correlate with greenhouse gas fluxes even when the air-filled porosity and the total porosity from which they are predicted did not. We have also showed that Ds/Do and can be predicted quickly from routine measurements of soil water and air and existing diffusivity models found in the literature. Agricultural practices do seriously impact greenhouse gases emissions as showed by the effect of mechanized tillage operations on soil physical properties and greenhouse gas fluxes in a corn and soybean fields. In fact, our results showed that tractor compaction increased soil resistance to penetration, water, bulk density and pore tortuosity while reducing air-filled porosity, total pore space and the soil gas diffusion coefficient. Changes in soil properties resulted in increased CO2, NO and N2O emissions. Finally, our results also confirmed that greenhouse gas fluxes vary tremendously in space and time. As estimates of greenhouse gas emissions are influenced by the data processing approach, differences between the different calculation approaches leads to uncertainty. Thus, techniques for developing better estimates are needed. We have showed that Geographic Information Systems (GIS), Global Positioning System (GPS), computer mapping and geo-statistics are technologies that can be used to better understand systems containing large amounts of spatial and temporal variability. Our GIS-based approach for quantifying CO2, CH4 and N2O fluxes from soil in agricultural fields showed that estimating (extrapolating) total greenhouse gas fluxes using the “standard” approach – multiplying the average flux value by the total field area – results in biased predictions of field total greenhouse gases emissions. In contrast, the GIS-based approach we developed produces an interpolated map portraying the spatial distribution of gas fluxes across the field from point measurements and later process the interpolated map produced to determine flux zones. Furthermore, processing, classification and modeling enables the computation of field total fluxes as the sum of fluxes in different zones, therefore taking into account the spatial variability of greenhouse gas fluxes.
- Full Text:
- Date Issued: 2010
- Authors: Nkongolo, Nsalambi Vakanda
- Date: 2010
- Subjects: Greenhouse gases -- Environmental aspects
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10645 , http://hdl.handle.net/10948/1474 , Greenhouse gases -- Environmental aspects
- Description: Field studies were conducted at Lincoln University of Missouri (USA) and Hokkaido University (Japan) to: (i) study the relationships between greenhouse gases emissions and soil properties, (ii) assess the influence of agricultural practices on greenhouse gas fluxes and soil properties and (iii) improve the quantification of greenhouse gases from soil in agricultural fields using geospatial technologies. Results showed that besides soil temperature (T), soil thermal properties such as thermal conductivity (K), resistivity (R) and diffusivity (D) and soil pore spaces indices such as the pore tortuosity factor and the relative gas diffusion coefficient (Ds/Do) are controlling factors for greenhouse gases emissions. Soil thermal properties correlated with greenhouse gases emissions when soil temperature could not. The study has found that predicted Ds/Do and correlate with greenhouse gas fluxes even when the air-filled porosity and the total porosity from which they are predicted did not. We have also showed that Ds/Do and can be predicted quickly from routine measurements of soil water and air and existing diffusivity models found in the literature. Agricultural practices do seriously impact greenhouse gases emissions as showed by the effect of mechanized tillage operations on soil physical properties and greenhouse gas fluxes in a corn and soybean fields. In fact, our results showed that tractor compaction increased soil resistance to penetration, water, bulk density and pore tortuosity while reducing air-filled porosity, total pore space and the soil gas diffusion coefficient. Changes in soil properties resulted in increased CO2, NO and N2O emissions. Finally, our results also confirmed that greenhouse gas fluxes vary tremendously in space and time. As estimates of greenhouse gas emissions are influenced by the data processing approach, differences between the different calculation approaches leads to uncertainty. Thus, techniques for developing better estimates are needed. We have showed that Geographic Information Systems (GIS), Global Positioning System (GPS), computer mapping and geo-statistics are technologies that can be used to better understand systems containing large amounts of spatial and temporal variability. Our GIS-based approach for quantifying CO2, CH4 and N2O fluxes from soil in agricultural fields showed that estimating (extrapolating) total greenhouse gas fluxes using the “standard” approach – multiplying the average flux value by the total field area – results in biased predictions of field total greenhouse gases emissions. In contrast, the GIS-based approach we developed produces an interpolated map portraying the spatial distribution of gas fluxes across the field from point measurements and later process the interpolated map produced to determine flux zones. Furthermore, processing, classification and modeling enables the computation of field total fluxes as the sum of fluxes in different zones, therefore taking into account the spatial variability of greenhouse gas fluxes.
- Full Text:
- Date Issued: 2010
Integrated teaching strategies model for improved scientific literacy in second-language learners
- Villanueva, Mary Grace Flores
- Authors: Villanueva, Mary Grace Flores
- Date: 2010
- Subjects: Science -- Study and teaching (Elementary) -- South Africa , Science -- South Africa -- Methodology , Science -- Curricula
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:9514 , http://hdl.handle.net/10948/1107 , Science -- Study and teaching (Elementary) -- South Africa , Science -- South Africa -- Methodology , Science -- Curricula
- Description: The importance of a scientifically literate society is currently acknowledged both internationally and South Africa. The notion of scientific literacy in South Africa has emerged largely due to the government’s recognition of the role that science and technology plays in economic growth, employment creation, social redress and social development. However, in light of South Africa’s learner performance on international and national assessments such as TIMMS (2003) and PIRLS (2006), as well as the problems of teaching and learning in a second language, there appears to be a primary and pressing need to develop learners’ fundamental sense of scientific literacy (Norris & Phillips, 2003). Expanding learners’ ability to read, write and communicate in science may provide the necessary framework for engaging learners in the critical principles and foundations of the scientific endeavour (Hand, Prain, & Yore, 2001). As such, this study focuses on equipping and training grade six and seven science teachers to develop scientifically literate learners via professional development workshops with a strategy that supports reading, writing, talking and conducting (‘doing’) science through scientific investigations. The typology of triangulation and the mixed method research approach was supported by a fully mixed, concurrent, and equal status design (Leech & Onwuegbuzi, 2007). Quantitative data were collected from the baseline and post-intervention testing of learners’ problem solving skills, as well as their literacy skills in English and isiXhosa. Qualitative measures were generated through classroom observations, teacher interviews and learners’ science notebooks. The study was conducted in two different milieus in the Eastern Cape, South Africa. The first setting, in the rural area of Tyumie Valley near the Hogsback Mountains, was comprised of a sample of grade six and seven (multi-grade classrooms) teachers (n=7) and learners (n=168) from five experimental schools and two comparison schools. The second setting, in the urban townships area east of Port Elizabeth, was comprised of a sample of grade six teachers (n=8) and learners (n=675) from six experimental schools and two comparison schools. Mean differences between the experimental and the comparison groups were computed for the Raven’s Standard Progressive Matrices (RSPM) and the literacy tests, and the data generated were treated with an Analysis of Covariance (ANCOVA). The data suggest that the scientific literacy strategy improved the experimental learners’ problem solving skills. Both experimental groups demonstrated greater gains than that of the comparison schools. However, statistically significant improvements were only detected in Port Elizabeth. Improvements in learners’ literacy skills in isiXhosa and English varied according to each milieu. While the teachers initially identified challenges to learners’ reading and writing abilities, the analysis of learners’ science notebooks suggested that they used writings to support their investigations. Some teachers cited difficulties with certain aspects of the model, such as problems with developing an investigable question and argumentation, yet overall, teachers found the strategy useful for developing learners’ language skills, as well for strengthening their pedagogical practices in science. Teachers’ gradual improvements in the use of the model suggest that they were able to use the scientific literacy strategy to support the cognitive and linguistic development of second-language learners.
- Full Text:
- Date Issued: 2010
- Authors: Villanueva, Mary Grace Flores
- Date: 2010
- Subjects: Science -- Study and teaching (Elementary) -- South Africa , Science -- South Africa -- Methodology , Science -- Curricula
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:9514 , http://hdl.handle.net/10948/1107 , Science -- Study and teaching (Elementary) -- South Africa , Science -- South Africa -- Methodology , Science -- Curricula
- Description: The importance of a scientifically literate society is currently acknowledged both internationally and South Africa. The notion of scientific literacy in South Africa has emerged largely due to the government’s recognition of the role that science and technology plays in economic growth, employment creation, social redress and social development. However, in light of South Africa’s learner performance on international and national assessments such as TIMMS (2003) and PIRLS (2006), as well as the problems of teaching and learning in a second language, there appears to be a primary and pressing need to develop learners’ fundamental sense of scientific literacy (Norris & Phillips, 2003). Expanding learners’ ability to read, write and communicate in science may provide the necessary framework for engaging learners in the critical principles and foundations of the scientific endeavour (Hand, Prain, & Yore, 2001). As such, this study focuses on equipping and training grade six and seven science teachers to develop scientifically literate learners via professional development workshops with a strategy that supports reading, writing, talking and conducting (‘doing’) science through scientific investigations. The typology of triangulation and the mixed method research approach was supported by a fully mixed, concurrent, and equal status design (Leech & Onwuegbuzi, 2007). Quantitative data were collected from the baseline and post-intervention testing of learners’ problem solving skills, as well as their literacy skills in English and isiXhosa. Qualitative measures were generated through classroom observations, teacher interviews and learners’ science notebooks. The study was conducted in two different milieus in the Eastern Cape, South Africa. The first setting, in the rural area of Tyumie Valley near the Hogsback Mountains, was comprised of a sample of grade six and seven (multi-grade classrooms) teachers (n=7) and learners (n=168) from five experimental schools and two comparison schools. The second setting, in the urban townships area east of Port Elizabeth, was comprised of a sample of grade six teachers (n=8) and learners (n=675) from six experimental schools and two comparison schools. Mean differences between the experimental and the comparison groups were computed for the Raven’s Standard Progressive Matrices (RSPM) and the literacy tests, and the data generated were treated with an Analysis of Covariance (ANCOVA). The data suggest that the scientific literacy strategy improved the experimental learners’ problem solving skills. Both experimental groups demonstrated greater gains than that of the comparison schools. However, statistically significant improvements were only detected in Port Elizabeth. Improvements in learners’ literacy skills in isiXhosa and English varied according to each milieu. While the teachers initially identified challenges to learners’ reading and writing abilities, the analysis of learners’ science notebooks suggested that they used writings to support their investigations. Some teachers cited difficulties with certain aspects of the model, such as problems with developing an investigable question and argumentation, yet overall, teachers found the strategy useful for developing learners’ language skills, as well for strengthening their pedagogical practices in science. Teachers’ gradual improvements in the use of the model suggest that they were able to use the scientific literacy strategy to support the cognitive and linguistic development of second-language learners.
- Full Text:
- Date Issued: 2010
Beta-N-methylamino-L-alanine in South African fresh water cyanobacteria : incidence, prevalence, ecotoxicological considerations and human exposure risk
- Authors: Esterhuizen-Londt, Maranda
- Date: 2010
- Subjects: Cyanobacteria , Bioaccumulation , Chromatographic analysis , Neurotoxic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10306 , http://hdl.handle.net/10948/1473 , Cyanobacteria , Bioaccumulation , Chromatographic analysis , Neurotoxic agents
- Description: β-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid associated with human neurodegenerative disease. Due to the cosmopolitan nature of cyanobacteria, detection of BMAA in cyanobacteria has caused concerns about human exposure risk. This study was therefore based on the hypothesis that BMAA poses a health risk to humans either by direct ingestion or by indirect exposure to BMAA from a cyanobacterial source via a freshwater food chain. A validated gas chromatography-mass spectrometry (GC-MS) BMAA analysis method and a confirmatory liquid chromatography-mass spectrometry (LC-MS) method, with improved sensitivity, were developed in addition to a LC-MS/MS method for analyte confirmation. These methods were used to quantify BMAA in South African cyanobacteria, isolated from various potable water reservoirs. The majority of the isolates tested, contained BMAA. Possible human exposure by direct consumption of BMAA released from cyanobacterial blooms was investigated by the development of a robust solid phase extraction (SPE) method used for BMAA concentration and quantification in raw and treated tap water. Despite the use of the SPE method that facilitated the concentration of BMAA from large quantities of water, no free dissolved BMAA was detected in raw or processed fresh water. The fate of exogenous BMAA was therefore investigated firstly by evaluating the efficacy of standard water treatment processes employed in South Africa and secondly by investigating the possibility of BMAA bioaccumulation and biomagnification in aquatic food chains. Standard water treatment processes proved highly efficient at removing free dissolved BMAA, explaining the absence of BMAA in treated tap water. However, the cause of the BMAA absence in raw potable water remained unknown. Uptake of BMAA by model aquatic organisms was investigated in controlled experiments. BMAA uptake was documented in both Ceratophyllum demersum and Daphnia magna, however, BMAA-protein association and biomagnification were not observed in D. magna. BMAA had an inhibitory effect on the oxidative stress enzyme acitivties of both organisms tested (as well as human S9 extracts), resulting in accumulation of detrimental reactive oxygen species (ROS) in the cells. Exposure of crop plants to BMAA in controlled experiments resulted in BMAA uptake, protein association, and subsequent inhibition of the antioxidative enzyme activities. However, BMAA was detected in neither free nor protein-associated form in natural crop plants irrigated with known BMAA-containing bloom water. Post-mortem liver samples of Clarias gariepinus (Catfish) and Crocodylus niloticus (Crocodile), from a natural fresh water ecosystem that experienced frequent cyanobacterial blooms, contained both free and protein-associated BMAA. Higher BMAA concentrations were found in crocodile liver samples compared to fish liver samples, strongly suggesting biomagnification from one trophic level to the next. BMAA concentrations corresponded to crocodile age. This is the first report of bioaccumulation and biomagnification in two trophic levels in a fresh water ecosystem. These findings strongly suggest possible human exposure via aquatic food chains of cyanobacterial origin. Direct BMAA exposure via drinking water is not plausible due to the efficiency of standard water treatment processes to remove BMAA. The use of raw water for agricultural and recreational use, however, remains a problem. The development of management strategies as well as daily tolerable levels for BMAA is urgently required.
- Full Text:
- Date Issued: 2010
- Authors: Esterhuizen-Londt, Maranda
- Date: 2010
- Subjects: Cyanobacteria , Bioaccumulation , Chromatographic analysis , Neurotoxic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10306 , http://hdl.handle.net/10948/1473 , Cyanobacteria , Bioaccumulation , Chromatographic analysis , Neurotoxic agents
- Description: β-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid associated with human neurodegenerative disease. Due to the cosmopolitan nature of cyanobacteria, detection of BMAA in cyanobacteria has caused concerns about human exposure risk. This study was therefore based on the hypothesis that BMAA poses a health risk to humans either by direct ingestion or by indirect exposure to BMAA from a cyanobacterial source via a freshwater food chain. A validated gas chromatography-mass spectrometry (GC-MS) BMAA analysis method and a confirmatory liquid chromatography-mass spectrometry (LC-MS) method, with improved sensitivity, were developed in addition to a LC-MS/MS method for analyte confirmation. These methods were used to quantify BMAA in South African cyanobacteria, isolated from various potable water reservoirs. The majority of the isolates tested, contained BMAA. Possible human exposure by direct consumption of BMAA released from cyanobacterial blooms was investigated by the development of a robust solid phase extraction (SPE) method used for BMAA concentration and quantification in raw and treated tap water. Despite the use of the SPE method that facilitated the concentration of BMAA from large quantities of water, no free dissolved BMAA was detected in raw or processed fresh water. The fate of exogenous BMAA was therefore investigated firstly by evaluating the efficacy of standard water treatment processes employed in South Africa and secondly by investigating the possibility of BMAA bioaccumulation and biomagnification in aquatic food chains. Standard water treatment processes proved highly efficient at removing free dissolved BMAA, explaining the absence of BMAA in treated tap water. However, the cause of the BMAA absence in raw potable water remained unknown. Uptake of BMAA by model aquatic organisms was investigated in controlled experiments. BMAA uptake was documented in both Ceratophyllum demersum and Daphnia magna, however, BMAA-protein association and biomagnification were not observed in D. magna. BMAA had an inhibitory effect on the oxidative stress enzyme acitivties of both organisms tested (as well as human S9 extracts), resulting in accumulation of detrimental reactive oxygen species (ROS) in the cells. Exposure of crop plants to BMAA in controlled experiments resulted in BMAA uptake, protein association, and subsequent inhibition of the antioxidative enzyme activities. However, BMAA was detected in neither free nor protein-associated form in natural crop plants irrigated with known BMAA-containing bloom water. Post-mortem liver samples of Clarias gariepinus (Catfish) and Crocodylus niloticus (Crocodile), from a natural fresh water ecosystem that experienced frequent cyanobacterial blooms, contained both free and protein-associated BMAA. Higher BMAA concentrations were found in crocodile liver samples compared to fish liver samples, strongly suggesting biomagnification from one trophic level to the next. BMAA concentrations corresponded to crocodile age. This is the first report of bioaccumulation and biomagnification in two trophic levels in a fresh water ecosystem. These findings strongly suggest possible human exposure via aquatic food chains of cyanobacterial origin. Direct BMAA exposure via drinking water is not plausible due to the efficiency of standard water treatment processes to remove BMAA. The use of raw water for agricultural and recreational use, however, remains a problem. The development of management strategies as well as daily tolerable levels for BMAA is urgently required.
- Full Text:
- Date Issued: 2010
Psigobiografiese persoonlikheidsbeskrywing van Generaal Christiaan de Wet
- Authors: Henning, Riana
- Date: 2010
- Subjects: De Wet, Christiaan Rudolf, 1854-1922 Psychology -- Biographical methods Psychoanalysis Big Five model Politicians -- Psychology South Africa -- Politics and government -- 1836-1909 South Africa -- Politics and government -- 1909-1948
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2990 , http://hdl.handle.net/10962/d1002499
- Description: Hierdie is 'n psigobiografiese studie van Generaal Christiaan Rudolph de Wet. 'n Psigobiografiese studie is die bestudering van 'n persoon se volledige lewe met die doel om die persoon beter te verstaan. Psigobiografiese navorsing maak gebruik van psigologiese teorieë wat aangewend word om die biografiese data van 'n persoon se lewe te beskryf en moontlik ook te verklaar. Die individu wat bestudeer word, is gewoonlik 'n bekende, invloedryke, navolgenswaardige, interessante of modelfiguur. Daar is tans 'n oplewing in die veld van psigobiografiese studies, maar daar word nog steeds nie genoeg in die akademiese veld gedoen om psigobiografiese studies te bevorder nie. De Wet (1854-1922) is vir hierdie studie gekies omdat hy 'n interessante, dog komplekse figuur was. Hy het veral tydens die Anglo-Boereoorlog in 1899-1902 bekendheid verwerf. As 45-jarige man het De Wet in die Anglo-Boereoorlog geveg en vinnig opgang as 'n militêre leier gemaak. Sy vindingryke ontsnappingspogings het die Britse magte hoofbrekens besorg. Wat De Wet verder uniek maak, is dat hy met net drie maande skoolopleiding in die parlement gedien het, as president verkies is, die hoogste gesag in die Verdedigingsmag gehad het en 'n boek oor sy oorlogsherinneringe geskryf het. Alhoewel daar akademiese werke oor De Wet bestaan, is daar tot op hede nog geen psigobiografiese studie oor hom gedoen nie. Die doel van die studie was om die mens agter die legende na vore te bring. Daar is ook gepoog om moontlike antwoorde en verklarings op onbeantwoorde vrae te gee. Die studie het van beide kwalitatiewe en kwantitatiewe data gebruik gemaak en kan as 'n psigobiografiese gevalstudie beskryf word. Die Vyf-faktor model van Costa en McCrae (1992) is op die biografiese data van De Wet toegepas om sodoende sy persoonlikheidseienskappe te beskryf. Die bevindinge het interessante persoonlikheidseienskappe van De Wet deur middel van die Vyf-faktor model aan die lig gebring. Volgens die kwalitatiewe navorsingsbevindinge was De Wet 'n vyandige, aksie-gedrewe, bevoegde, prestasie-strewende, selfgedissiplineerde, warm, openhartige, saggeaarde en beskeie persoon. Die kwalitatiewe en kwantitatiewe data-ontledings het uiteenlopende persoonlikheidskenmerke by De Wet geïdentifiseer. Die grootste verskille het by die fasette warmte, openhartigheid en altruïsme voorgekom. Die waarde van die studie is dat 'n wetenskaplike persoonlikheidsontleding van De Wet gedoen is. Dit is ook die eerste studie waar 'n teoretiese model op De Wet se persoonlikheid toegepas is. Alhoewel die studie sekere tekortkominge toon, beklemtoon dit terselfdertyd die wenslikheid daarvan om alternatiewe modelle te gebruik tydens die ontleding van persoonlikheidskenmerke. Die studie dui ook op die behoefte aan verdere navorsing, byvoorbeeld soortgelyke ontledings en vergelykings van die persoonlikhede van ander militêre bevelvoerders (De la Rey, Smuts, Beyers, Hertzog).
- Full Text:
- Date Issued: 2010
- Authors: Henning, Riana
- Date: 2010
- Subjects: De Wet, Christiaan Rudolf, 1854-1922 Psychology -- Biographical methods Psychoanalysis Big Five model Politicians -- Psychology South Africa -- Politics and government -- 1836-1909 South Africa -- Politics and government -- 1909-1948
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2990 , http://hdl.handle.net/10962/d1002499
- Description: Hierdie is 'n psigobiografiese studie van Generaal Christiaan Rudolph de Wet. 'n Psigobiografiese studie is die bestudering van 'n persoon se volledige lewe met die doel om die persoon beter te verstaan. Psigobiografiese navorsing maak gebruik van psigologiese teorieë wat aangewend word om die biografiese data van 'n persoon se lewe te beskryf en moontlik ook te verklaar. Die individu wat bestudeer word, is gewoonlik 'n bekende, invloedryke, navolgenswaardige, interessante of modelfiguur. Daar is tans 'n oplewing in die veld van psigobiografiese studies, maar daar word nog steeds nie genoeg in die akademiese veld gedoen om psigobiografiese studies te bevorder nie. De Wet (1854-1922) is vir hierdie studie gekies omdat hy 'n interessante, dog komplekse figuur was. Hy het veral tydens die Anglo-Boereoorlog in 1899-1902 bekendheid verwerf. As 45-jarige man het De Wet in die Anglo-Boereoorlog geveg en vinnig opgang as 'n militêre leier gemaak. Sy vindingryke ontsnappingspogings het die Britse magte hoofbrekens besorg. Wat De Wet verder uniek maak, is dat hy met net drie maande skoolopleiding in die parlement gedien het, as president verkies is, die hoogste gesag in die Verdedigingsmag gehad het en 'n boek oor sy oorlogsherinneringe geskryf het. Alhoewel daar akademiese werke oor De Wet bestaan, is daar tot op hede nog geen psigobiografiese studie oor hom gedoen nie. Die doel van die studie was om die mens agter die legende na vore te bring. Daar is ook gepoog om moontlike antwoorde en verklarings op onbeantwoorde vrae te gee. Die studie het van beide kwalitatiewe en kwantitatiewe data gebruik gemaak en kan as 'n psigobiografiese gevalstudie beskryf word. Die Vyf-faktor model van Costa en McCrae (1992) is op die biografiese data van De Wet toegepas om sodoende sy persoonlikheidseienskappe te beskryf. Die bevindinge het interessante persoonlikheidseienskappe van De Wet deur middel van die Vyf-faktor model aan die lig gebring. Volgens die kwalitatiewe navorsingsbevindinge was De Wet 'n vyandige, aksie-gedrewe, bevoegde, prestasie-strewende, selfgedissiplineerde, warm, openhartige, saggeaarde en beskeie persoon. Die kwalitatiewe en kwantitatiewe data-ontledings het uiteenlopende persoonlikheidskenmerke by De Wet geïdentifiseer. Die grootste verskille het by die fasette warmte, openhartigheid en altruïsme voorgekom. Die waarde van die studie is dat 'n wetenskaplike persoonlikheidsontleding van De Wet gedoen is. Dit is ook die eerste studie waar 'n teoretiese model op De Wet se persoonlikheid toegepas is. Alhoewel die studie sekere tekortkominge toon, beklemtoon dit terselfdertyd die wenslikheid daarvan om alternatiewe modelle te gebruik tydens die ontleding van persoonlikheidskenmerke. Die studie dui ook op die behoefte aan verdere navorsing, byvoorbeeld soortgelyke ontledings en vergelykings van die persoonlikhede van ander militêre bevelvoerders (De la Rey, Smuts, Beyers, Hertzog).
- Full Text:
- Date Issued: 2010
The depiction of female characters by male writers in selected isiXhosa drama works
- Authors: Peter, Zola Welcome
- Date: 2010
- Subjects: Xhosa drama -- 20th century -- History and criticism , Women in literature , Feminism and literature , Xhosa drama -- Male authors , Gender identity in literature
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8446 , http://hdl.handle.net/10948/1482 , Xhosa drama -- 20th century -- History and criticism , Women in literature , Feminism and literature , Xhosa drama -- Male authors , Gender identity in literature
- Description: This research expresses female character portrayal in various drama works written by males. Chapter one is a general introduction that gives the key to this study, the motivation that leads to the selection of this topic; a literary review on the portrayal of female characters in literary works written by males; the scope of study, the basic composition of the ensuing chapters and the definitions of terms that are of paramount importance for this research. Various literary theories are used in Chapter two for the analysis of the research texts. These literary theories include womanism, gender and feminism which expose the social effects caused by the negative perception of females in social life and the negative portrayal of female characters in male dramatic writings. Other literary theories include onomastics as a literary theory, which exposes the relationship between the name giver of a person and the power the name gives to its bearer, as well as psychoanalysis as a theory which proved to be unavoidable, since this study analyses the personal behaviour of the individual characters within their literary environment. Chapter three depicts the general victimization of female characters in male drama works and exposes the various effects of the attitudes of male writers towards female characters in terms of gender role. Chapter four shows a general stereotypical portrayal of female characters in male written drama texts. This chapter shows the impact of stereotyping on female characters from drama works that puts them in a vulnerable position, showing that it is risky to become a victim of ill-treatment in their communities and the literary world. Chapter five deals with the psychological literary review of female characters, showing them as being suicidal and murderers who easily take their own lives and those of other people. Chapter six is a general conclusion of the works which includes observer remarks from other literary researchers of the literature.
- Full Text:
- Date Issued: 2010
- Authors: Peter, Zola Welcome
- Date: 2010
- Subjects: Xhosa drama -- 20th century -- History and criticism , Women in literature , Feminism and literature , Xhosa drama -- Male authors , Gender identity in literature
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8446 , http://hdl.handle.net/10948/1482 , Xhosa drama -- 20th century -- History and criticism , Women in literature , Feminism and literature , Xhosa drama -- Male authors , Gender identity in literature
- Description: This research expresses female character portrayal in various drama works written by males. Chapter one is a general introduction that gives the key to this study, the motivation that leads to the selection of this topic; a literary review on the portrayal of female characters in literary works written by males; the scope of study, the basic composition of the ensuing chapters and the definitions of terms that are of paramount importance for this research. Various literary theories are used in Chapter two for the analysis of the research texts. These literary theories include womanism, gender and feminism which expose the social effects caused by the negative perception of females in social life and the negative portrayal of female characters in male dramatic writings. Other literary theories include onomastics as a literary theory, which exposes the relationship between the name giver of a person and the power the name gives to its bearer, as well as psychoanalysis as a theory which proved to be unavoidable, since this study analyses the personal behaviour of the individual characters within their literary environment. Chapter three depicts the general victimization of female characters in male drama works and exposes the various effects of the attitudes of male writers towards female characters in terms of gender role. Chapter four shows a general stereotypical portrayal of female characters in male written drama texts. This chapter shows the impact of stereotyping on female characters from drama works that puts them in a vulnerable position, showing that it is risky to become a victim of ill-treatment in their communities and the literary world. Chapter five deals with the psychological literary review of female characters, showing them as being suicidal and murderers who easily take their own lives and those of other people. Chapter six is a general conclusion of the works which includes observer remarks from other literary researchers of the literature.
- Full Text:
- Date Issued: 2010
Sample preparation for pesticide analysis in water and sediments a case study of the Okavango Delta, Botswana
- Authors: Mmualefe, Lesego Cecilia
- Date: 2010
- Subjects: Water quality -- Botswana -- Okavango Delta Water -- Analysis Pesticides -- Environmental aspects -- Botswana -- Okavango Delta Water -- Pollution -- Botswana -- Okavango Delta DDT (Insecticide) -- Environmental aspects -- Botswana -- Okavango Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4344 , http://hdl.handle.net/10962/d1005006
- Description: This thesis presents a first ever extensive analysis of pesticides in water and sediments from the Okavango Delta, Botswana, employing green sample preparation techniques that require small volumes of organic solvents hence generating negligible volumes of organic solvent waste. Pesticides were extracted and pre-concentrated from water by solid phase extraction (SPE) and headspace solid phase microextraction (HS-SPME) while supercritical fluid extraction (SFE) and pressurized fluid extraction (PFE) were employed for sediments. Subsequent analysis was carried out on a gas chromatograph with electron capture detection and analytes were unequivocally confirmed by high resolution mass spectrometric detection. Hexachlorobenzene (HCB), trans-chlordane, 4,4′-DDD and 4,4′-DDE were detected after optimized HS-SPME in several water samples from the lower Delta at concentrations ranging from 2.4 to 61.4 μg L-1 that are much higher than the 0.1 μg L-1 maximum limit of individual organochlorine pesticides in drinking water set by the European Community Directive. The same samples were cleaned with ISOLUTE C18 SPE sorbent with an optimal acetone/n-hexane (1:1 v/v) mixture for the elution of analytes. No pesticides were detected after SPE clean-up and pre-concentration. HCB, aldrin and 4, 4‟-DDT were identified in sediments after SFE at concentration ranges of 1.1 - 30.3, 0.5 – 15.2 and 1.4 – 55.4 μg/g, respectively. There was an increase of pesticides concentrations in the direction of water flow from the Panhandle (point of entry) to the lower delta. DDE, fatty acids and phthalates were detected after PFE with optimized extraction solvent and temperature. The presence of DDT metabolites in the water and sediments from the Okavango Delta confirm historical exposure to the pesticide. However their cumulative concentration increase in the water-flow direction calls for further investigation of point sources for the long-term preservation of the Delta. The green sample preparation techniques and low toxicity solvents employed in this thesis are thus recommended for routine environmental monitoring exercises.
- Full Text:
- Date Issued: 2010
- Authors: Mmualefe, Lesego Cecilia
- Date: 2010
- Subjects: Water quality -- Botswana -- Okavango Delta Water -- Analysis Pesticides -- Environmental aspects -- Botswana -- Okavango Delta Water -- Pollution -- Botswana -- Okavango Delta DDT (Insecticide) -- Environmental aspects -- Botswana -- Okavango Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4344 , http://hdl.handle.net/10962/d1005006
- Description: This thesis presents a first ever extensive analysis of pesticides in water and sediments from the Okavango Delta, Botswana, employing green sample preparation techniques that require small volumes of organic solvents hence generating negligible volumes of organic solvent waste. Pesticides were extracted and pre-concentrated from water by solid phase extraction (SPE) and headspace solid phase microextraction (HS-SPME) while supercritical fluid extraction (SFE) and pressurized fluid extraction (PFE) were employed for sediments. Subsequent analysis was carried out on a gas chromatograph with electron capture detection and analytes were unequivocally confirmed by high resolution mass spectrometric detection. Hexachlorobenzene (HCB), trans-chlordane, 4,4′-DDD and 4,4′-DDE were detected after optimized HS-SPME in several water samples from the lower Delta at concentrations ranging from 2.4 to 61.4 μg L-1 that are much higher than the 0.1 μg L-1 maximum limit of individual organochlorine pesticides in drinking water set by the European Community Directive. The same samples were cleaned with ISOLUTE C18 SPE sorbent with an optimal acetone/n-hexane (1:1 v/v) mixture for the elution of analytes. No pesticides were detected after SPE clean-up and pre-concentration. HCB, aldrin and 4, 4‟-DDT were identified in sediments after SFE at concentration ranges of 1.1 - 30.3, 0.5 – 15.2 and 1.4 – 55.4 μg/g, respectively. There was an increase of pesticides concentrations in the direction of water flow from the Panhandle (point of entry) to the lower delta. DDE, fatty acids and phthalates were detected after PFE with optimized extraction solvent and temperature. The presence of DDT metabolites in the water and sediments from the Okavango Delta confirm historical exposure to the pesticide. However their cumulative concentration increase in the water-flow direction calls for further investigation of point sources for the long-term preservation of the Delta. The green sample preparation techniques and low toxicity solvents employed in this thesis are thus recommended for routine environmental monitoring exercises.
- Full Text:
- Date Issued: 2010
Studies on the nutritional value of seven accessions of cocoyam growing in South Africa
- Authors: Lewu, Muinat Nike
- Date: 2010
- Subjects: Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11305 , http://hdl.handle.net/10353/d1001054 , Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
- Description: Cocoyam [Colocasia esculenta (L.) Schott] is widely cultivated as a staple food in the tropical and subtropical regions of the world. The crop, however, remains unpopular and not well known outside KwaZulu-Natal Province of South Africa where it is cultivated mainly for subsistence. The aims of the study were to collect local landraces (accessions) of the crop from where it is found growing within the country for various studies and also to document its nutritional values as well as the safety/toxicity of the crop. The study was carried out using various methods. These included a comparative assessment of the proximate, mineral and antinutrient compositions of cooked and uncooked tubers of a typical commercially available cocoyam and potato found in South African markets. These investigations were repeated for the tubers and leaves of available landraces (seven accessions) of C. esculenta found growing in the farmers’ fields in KwaZulu-Natal Province. Also, an in vivo toxicological study on cooked accessions of the local landraces was conducted to determine possible toxicity effects after consumption using albino rats as a model. The results revealed that commercially available cocoyam and potato tubers have very close nutritional components. Analysis of the proximate composition of seven accessions (UFCe1- UFCe7) of cooked and uncooked tubers of cocoyam indicated that UFCe7 was better in ash, crude protein, crude fibre and crude lipid contents but with higher moisture which could make it more vulnerable to microbial attack. No tubers of the seven accessions appeared to be ii outstandingly better than the others based on their mineral compositions. However, in terms of antinutritional factors, UFCe1, UFCe3 and UFCe7 had the least amounts of oxalate, tannins and phytate in their cooked states. It was discovered however, that the leaves of the accessions of this vegetable contain substantial amount of minerals, and therefore, can contribute significantly to the nutrient requirements of humans and could be recommended as a cheap source of nutrients in South Africa. None of the accessions was outstandingly better than the others in terms of their mineral contents and anti-nutritional factors. Moreover, the current study has shown that boiling the leaves of cocoyam prior to consumption is an effective way of reducing the antinutrient contents of the leaves of the plant thereby making it safe for consumption. The findings also revealed that cooking C. esculenta leaves may increase the levels of protein, fibre and lipid contents while cooking may also decrease the mineral, carbohydrate and caloric contents of the leaves of the accessions. The leafy vegetable may, therefore, be recommended as a cheap source of plant protein. Cooking improved the nutritive value as a result of the reduction in antinutrient levels, thereby improving the food quality in all the tuber and leaf samples used for this study. At the same time, cooked samples also suffered loss of some nutrients with respect to the proximate and mineral compositions. However, supplementation from other food sources that are rich in these nutrients is necessary when these crops are cooked for consumption. Any of the cocoyam accessions may be recommended for consumption for improved protein and mineral nutrients while tubers of accession UFCe7 have also shown good promise in terms of protein and fibre content availability. The results of the in vivo study, using the liver and kidney functional endpoints of weanling albino rats (Rattus norvegicus) maintained on different accessions of cooked cocoyam-based iii diets (UFCe1-UFCe7) for 28 days, revealed that all the accessions produced selective alterations on the hepatorenal indices of weanling rats. The highest alterations were produced by UFCe4 while the least was from UFCe2. These alterations may have consequential effects on the normal functioning of the liver and kidney of the animals. The UFCe2 exhibited the least toxicity risk among the accessions of C. esculenta growing in KwaZulu-Natal Province of South Africa.
- Full Text:
- Date Issued: 2010
- Authors: Lewu, Muinat Nike
- Date: 2010
- Subjects: Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11305 , http://hdl.handle.net/10353/d1001054 , Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
- Description: Cocoyam [Colocasia esculenta (L.) Schott] is widely cultivated as a staple food in the tropical and subtropical regions of the world. The crop, however, remains unpopular and not well known outside KwaZulu-Natal Province of South Africa where it is cultivated mainly for subsistence. The aims of the study were to collect local landraces (accessions) of the crop from where it is found growing within the country for various studies and also to document its nutritional values as well as the safety/toxicity of the crop. The study was carried out using various methods. These included a comparative assessment of the proximate, mineral and antinutrient compositions of cooked and uncooked tubers of a typical commercially available cocoyam and potato found in South African markets. These investigations were repeated for the tubers and leaves of available landraces (seven accessions) of C. esculenta found growing in the farmers’ fields in KwaZulu-Natal Province. Also, an in vivo toxicological study on cooked accessions of the local landraces was conducted to determine possible toxicity effects after consumption using albino rats as a model. The results revealed that commercially available cocoyam and potato tubers have very close nutritional components. Analysis of the proximate composition of seven accessions (UFCe1- UFCe7) of cooked and uncooked tubers of cocoyam indicated that UFCe7 was better in ash, crude protein, crude fibre and crude lipid contents but with higher moisture which could make it more vulnerable to microbial attack. No tubers of the seven accessions appeared to be ii outstandingly better than the others based on their mineral compositions. However, in terms of antinutritional factors, UFCe1, UFCe3 and UFCe7 had the least amounts of oxalate, tannins and phytate in their cooked states. It was discovered however, that the leaves of the accessions of this vegetable contain substantial amount of minerals, and therefore, can contribute significantly to the nutrient requirements of humans and could be recommended as a cheap source of nutrients in South Africa. None of the accessions was outstandingly better than the others in terms of their mineral contents and anti-nutritional factors. Moreover, the current study has shown that boiling the leaves of cocoyam prior to consumption is an effective way of reducing the antinutrient contents of the leaves of the plant thereby making it safe for consumption. The findings also revealed that cooking C. esculenta leaves may increase the levels of protein, fibre and lipid contents while cooking may also decrease the mineral, carbohydrate and caloric contents of the leaves of the accessions. The leafy vegetable may, therefore, be recommended as a cheap source of plant protein. Cooking improved the nutritive value as a result of the reduction in antinutrient levels, thereby improving the food quality in all the tuber and leaf samples used for this study. At the same time, cooked samples also suffered loss of some nutrients with respect to the proximate and mineral compositions. However, supplementation from other food sources that are rich in these nutrients is necessary when these crops are cooked for consumption. Any of the cocoyam accessions may be recommended for consumption for improved protein and mineral nutrients while tubers of accession UFCe7 have also shown good promise in terms of protein and fibre content availability. The results of the in vivo study, using the liver and kidney functional endpoints of weanling albino rats (Rattus norvegicus) maintained on different accessions of cooked cocoyam-based iii diets (UFCe1-UFCe7) for 28 days, revealed that all the accessions produced selective alterations on the hepatorenal indices of weanling rats. The highest alterations were produced by UFCe4 while the least was from UFCe2. These alterations may have consequential effects on the normal functioning of the liver and kidney of the animals. The UFCe2 exhibited the least toxicity risk among the accessions of C. esculenta growing in KwaZulu-Natal Province of South Africa.
- Full Text:
- Date Issued: 2010
Improving sanitization and fertiliser value of dairy manure and waste paper mixtures enriched with rock phosphate through combined thermophilic composting and vermicomposting
- Authors: Mupondi, Lushian Tapiwa
- Date: 2010
- Subjects: Compost , Vermicomposting , Manures , Biodegradation , Waste paper -- South Africa -- Eastern Cape , Thermophilic bacteria , Fertilizers
- Language: English
- Type: Thesis , Doctoral , PhD (Soil Science)
- Identifier: vital:11961 , http://hdl.handle.net/10353/411 , Compost , Vermicomposting , Manures , Biodegradation , Waste paper -- South Africa -- Eastern Cape , Thermophilic bacteria , Fertilizers
- Description: Thermophilic composting (TC) and vermicomposting (V) are the two most common methods used for biological stabilization of solid organic wastes. Both have their advantages and disadvantages but the proposed method of combining composting and vermicomposting (CV) borrows pertinent attributes from each of the two methods and combines them to enhance overall process and product qualities. Dairy manure and waste paper are two wastes produced in large quantities at the University of Fort Hare. The study was carried out to address the following specific objectives, to determine (i) the effectiveness of combined thermophilic composting and vermicomposting on the biodegradation and sanitization of mixtures of dairy manure and paper waste, (ii) an optimum precomposting period for dairy manure paper waste mixtures that results in vermicomposts of good nutritional quality and whose use will not jeopardize human health, (iii) the effectiveness of phosphate rock (PR) in increasing available P and degradation and nutrient content of dairy manure-paper vermicomposts, (iv) the physicochemical properties of vermicompost substituted pine bark compost and performance of resultant growing medium on plant growth and nutrient uptake. Results of this study revealed that wastes with a C: N ratio of 30 were more suitable for both V and CV as their composts were more stabilized and with higher nutrient contents than composts made from wastes with a C: N ratio of 45. Both V and CV were effective methods for the biodegradation of dairy manure and paper waste mixtures with C: N ratio of 30 but the latter was more effective in the biodegradation of waste mixtures with a C: N ratio of 45. The combinination of composting and vermicomposting eliminated the indicator pathogen E. coli 0157 from the final composts whereas V only managed to reduce the pathogen population. iv A follow up study was done to determine the effects of precomposting on pathogen numbers so as to come up with a suitable precomposting period to use when combine composting dairy manure-waste paper mixtures. Results of this study showed that over 95% of fecal coliforms, E. coli and of E. coli 0157 were eliminated from the wastes within one week of precomposting and total elimination of these and protozoan (oo)cysts achieved after 3 weeks of precomposting. The vermicomposts pathogen content was related to the waste’s precomposting period. Final vermicomposts pathogen content was reduced and varied according to precomposting period. Vermicomposts from wastes precomposted for over two weeks were less stabilized, less humified and had less nutrient contents compared to vermicomposts from wastes that were precomposted for one week or less. The findings suggest that a precomposting period of one week is ideal for the effective vermicomposting of dairy manure-waste paper mixtures. Results of the P enrichment study indicated an increase in the inorganic phosphate and a reduction in the organic phosphate fractions of dairy manure-waste paper vermicompost that were enriched with PR. This implied an increase in mineralization of organic matter and or solubilization of PR with vermicomposting time. Applying PR to dairy manure-waste paper mixtures also enhanced degradation and had increased N and P contents of dairy manure-waste paper vermicomposts. Earthworms accumulated heavy metals in their bodies and reduced heavy metal contents of vermicomposts. A study to determine the physicochemical properties of vermicompost substituted pine bark compost and performance of resultant growing medium on plant growth and nutrient uptake was done. Results obtained revealed that increasing proportions of dairy manure vermicomposts in pine bark compost improved tomato plant height, stem girth, shoot and root dry weights. v Tomatoes grew best in the 40 to 60% CV substituted pine bark and application of Horticote (7:2:1 (22)) fertilizer significantly increased plant growth in all media. Progressive substitution pine bark with dairy manure vermicomposts resulted in a decrease in the percentage total porosity, percentage air space whilst bulk density, water holding capacity, particle density, pH, electrical conductivity and N and P levels increased. Precomposting wastes not only reduced and or eliminated pathogens but also improved the stabilisation and nutrient content of dairy manure waste paper mixtures. The application of PR to dairy manure waste paper mixtures improved the chemical and physical properties of vermicomposts. Earthworms bio-accumulated the heavy metals Cd, Cr, Cu, Pb and Zn whilst the contents of these in the vermicomposts declined. It is, therefore, recommended that dairy manure waste paper mixtures be precomposted for one week for sanitization followed by PR application and vermicomposting for stabilization and improved nutrients contents of resultant vermicomposts. Substitution of pine bark compost with 40 to 60 % PR-enriched vermicompost produced a growing medium with superior physical and chemical properties which supported good seedling growth. However, for optimum seedling growth, supplementation with mineral fertilizer was found to be necessary.
- Full Text:
- Date Issued: 2010
- Authors: Mupondi, Lushian Tapiwa
- Date: 2010
- Subjects: Compost , Vermicomposting , Manures , Biodegradation , Waste paper -- South Africa -- Eastern Cape , Thermophilic bacteria , Fertilizers
- Language: English
- Type: Thesis , Doctoral , PhD (Soil Science)
- Identifier: vital:11961 , http://hdl.handle.net/10353/411 , Compost , Vermicomposting , Manures , Biodegradation , Waste paper -- South Africa -- Eastern Cape , Thermophilic bacteria , Fertilizers
- Description: Thermophilic composting (TC) and vermicomposting (V) are the two most common methods used for biological stabilization of solid organic wastes. Both have their advantages and disadvantages but the proposed method of combining composting and vermicomposting (CV) borrows pertinent attributes from each of the two methods and combines them to enhance overall process and product qualities. Dairy manure and waste paper are two wastes produced in large quantities at the University of Fort Hare. The study was carried out to address the following specific objectives, to determine (i) the effectiveness of combined thermophilic composting and vermicomposting on the biodegradation and sanitization of mixtures of dairy manure and paper waste, (ii) an optimum precomposting period for dairy manure paper waste mixtures that results in vermicomposts of good nutritional quality and whose use will not jeopardize human health, (iii) the effectiveness of phosphate rock (PR) in increasing available P and degradation and nutrient content of dairy manure-paper vermicomposts, (iv) the physicochemical properties of vermicompost substituted pine bark compost and performance of resultant growing medium on plant growth and nutrient uptake. Results of this study revealed that wastes with a C: N ratio of 30 were more suitable for both V and CV as their composts were more stabilized and with higher nutrient contents than composts made from wastes with a C: N ratio of 45. Both V and CV were effective methods for the biodegradation of dairy manure and paper waste mixtures with C: N ratio of 30 but the latter was more effective in the biodegradation of waste mixtures with a C: N ratio of 45. The combinination of composting and vermicomposting eliminated the indicator pathogen E. coli 0157 from the final composts whereas V only managed to reduce the pathogen population. iv A follow up study was done to determine the effects of precomposting on pathogen numbers so as to come up with a suitable precomposting period to use when combine composting dairy manure-waste paper mixtures. Results of this study showed that over 95% of fecal coliforms, E. coli and of E. coli 0157 were eliminated from the wastes within one week of precomposting and total elimination of these and protozoan (oo)cysts achieved after 3 weeks of precomposting. The vermicomposts pathogen content was related to the waste’s precomposting period. Final vermicomposts pathogen content was reduced and varied according to precomposting period. Vermicomposts from wastes precomposted for over two weeks were less stabilized, less humified and had less nutrient contents compared to vermicomposts from wastes that were precomposted for one week or less. The findings suggest that a precomposting period of one week is ideal for the effective vermicomposting of dairy manure-waste paper mixtures. Results of the P enrichment study indicated an increase in the inorganic phosphate and a reduction in the organic phosphate fractions of dairy manure-waste paper vermicompost that were enriched with PR. This implied an increase in mineralization of organic matter and or solubilization of PR with vermicomposting time. Applying PR to dairy manure-waste paper mixtures also enhanced degradation and had increased N and P contents of dairy manure-waste paper vermicomposts. Earthworms accumulated heavy metals in their bodies and reduced heavy metal contents of vermicomposts. A study to determine the physicochemical properties of vermicompost substituted pine bark compost and performance of resultant growing medium on plant growth and nutrient uptake was done. Results obtained revealed that increasing proportions of dairy manure vermicomposts in pine bark compost improved tomato plant height, stem girth, shoot and root dry weights. v Tomatoes grew best in the 40 to 60% CV substituted pine bark and application of Horticote (7:2:1 (22)) fertilizer significantly increased plant growth in all media. Progressive substitution pine bark with dairy manure vermicomposts resulted in a decrease in the percentage total porosity, percentage air space whilst bulk density, water holding capacity, particle density, pH, electrical conductivity and N and P levels increased. Precomposting wastes not only reduced and or eliminated pathogens but also improved the stabilisation and nutrient content of dairy manure waste paper mixtures. The application of PR to dairy manure waste paper mixtures improved the chemical and physical properties of vermicomposts. Earthworms bio-accumulated the heavy metals Cd, Cr, Cu, Pb and Zn whilst the contents of these in the vermicomposts declined. It is, therefore, recommended that dairy manure waste paper mixtures be precomposted for one week for sanitization followed by PR application and vermicomposting for stabilization and improved nutrients contents of resultant vermicomposts. Substitution of pine bark compost with 40 to 60 % PR-enriched vermicompost produced a growing medium with superior physical and chemical properties which supported good seedling growth. However, for optimum seedling growth, supplementation with mineral fertilizer was found to be necessary.
- Full Text:
- Date Issued: 2010
Intertidal patterns and processes : tracking the effects of coastline topography and settlement choice across life stages of the mussels perna perna and mytilus galloprovincialis
- Von Der Meden, Charles Eric Otto
- Authors: Von Der Meden, Charles Eric Otto
- Date: 2010
- Subjects: Mexilhao mussel -- Behavior -- South Africa Mytilus galloprovincialis -- Behavior -- South Africa Perna -- Behavior -- South Africa Mussels -- Ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5721 , http://hdl.handle.net/10962/d1005407
- Description: Within landscapes, spatial heterogeneity is common and specific landscape features can influence propagule dispersal by wind or water, affecting population connectivity and dynamics. Coastline topographic features, such as bays and headlands, have a variety of biophysical effects on nearshore oceanography, larval transport, retention and supply, and the processes of larval settlement and recruitment. Although this has been demonstrated in several parts of the world, engendering a perception of a general ‘bay effect’, few studies have investigated this generality in a single experiment or region, by replicating at the level of ‘bay’. The Agulhas biogeographic region of the south coast of South Africa is a useful system within which to test for such generality. Using the intertidal mussels Mytilus galloprovincialis and Perna perna as model organisms, patterns of adult distribution were surveyed across four large ‘halfheart’ bays and intervening stretches of open coast, providing replication at the level of ‘bay’ and duplication of ecologically similar species. In support of a general, pervasive influence of bays on intertidal populations, mussel cover was found to be greater in bays than on the open coast for both species, although the effect was strongest for M. galloprovincialis. To explain this adult distribution, settlement, post-settlement mortality and recruitment were examined over 12mo at the same sites, with the prediction that rates of each would favour larger bay populations. Contrary to this, an interaction between month and bay-status was found, with greater settlement and recruitment on the open coast than in bays reflecting extreme settlement and recruitment events at 3 westerly open coast sites during summer. Re-analysis excluding these outliers, revealed the expected effect, of greater settlement and recruitment in bays. While this indicates the broad generality of the bay effect, it highlights exceptions and the need for replication in time and space when examining landscape effects. Measuring post-settlement mortality required testing small-scale settlement behaviour on established and newly deployed settler collectors. It was found that all settlers preferred collectors with biofilm, but that primary settlers avoided conspecific settlers, while secondary settlers were attracted to them. With discrepancies in settler attraction to new and established collectors accounted for, initial (over 2d) and longer-term (over 7d) post-settlement mortality rates were found to be substantial (ca 60 %) for both species. No topographic effect on p-s mortality was evident. Finally, recruit-settler, adult-recruit and interspecies correlations were examined at regional and local scales. Synergistic (or neutral) effects maintained the initial settlement pattern in recruit and adult populations regionally, but not at local scales; striking interspecies correlations suggested the influence of common regional transport processes. Ultimately, the results emphasize the importance of the direction of effects in different life stages and at different spatial scales, and the possibility that antagonistic effects may mask even strong patterns.
- Full Text:
- Date Issued: 2010
- Authors: Von Der Meden, Charles Eric Otto
- Date: 2010
- Subjects: Mexilhao mussel -- Behavior -- South Africa Mytilus galloprovincialis -- Behavior -- South Africa Perna -- Behavior -- South Africa Mussels -- Ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5721 , http://hdl.handle.net/10962/d1005407
- Description: Within landscapes, spatial heterogeneity is common and specific landscape features can influence propagule dispersal by wind or water, affecting population connectivity and dynamics. Coastline topographic features, such as bays and headlands, have a variety of biophysical effects on nearshore oceanography, larval transport, retention and supply, and the processes of larval settlement and recruitment. Although this has been demonstrated in several parts of the world, engendering a perception of a general ‘bay effect’, few studies have investigated this generality in a single experiment or region, by replicating at the level of ‘bay’. The Agulhas biogeographic region of the south coast of South Africa is a useful system within which to test for such generality. Using the intertidal mussels Mytilus galloprovincialis and Perna perna as model organisms, patterns of adult distribution were surveyed across four large ‘halfheart’ bays and intervening stretches of open coast, providing replication at the level of ‘bay’ and duplication of ecologically similar species. In support of a general, pervasive influence of bays on intertidal populations, mussel cover was found to be greater in bays than on the open coast for both species, although the effect was strongest for M. galloprovincialis. To explain this adult distribution, settlement, post-settlement mortality and recruitment were examined over 12mo at the same sites, with the prediction that rates of each would favour larger bay populations. Contrary to this, an interaction between month and bay-status was found, with greater settlement and recruitment on the open coast than in bays reflecting extreme settlement and recruitment events at 3 westerly open coast sites during summer. Re-analysis excluding these outliers, revealed the expected effect, of greater settlement and recruitment in bays. While this indicates the broad generality of the bay effect, it highlights exceptions and the need for replication in time and space when examining landscape effects. Measuring post-settlement mortality required testing small-scale settlement behaviour on established and newly deployed settler collectors. It was found that all settlers preferred collectors with biofilm, but that primary settlers avoided conspecific settlers, while secondary settlers were attracted to them. With discrepancies in settler attraction to new and established collectors accounted for, initial (over 2d) and longer-term (over 7d) post-settlement mortality rates were found to be substantial (ca 60 %) for both species. No topographic effect on p-s mortality was evident. Finally, recruit-settler, adult-recruit and interspecies correlations were examined at regional and local scales. Synergistic (or neutral) effects maintained the initial settlement pattern in recruit and adult populations regionally, but not at local scales; striking interspecies correlations suggested the influence of common regional transport processes. Ultimately, the results emphasize the importance of the direction of effects in different life stages and at different spatial scales, and the possibility that antagonistic effects may mask even strong patterns.
- Full Text:
- Date Issued: 2010
A chemo-enzymatic process for the production of beta-thymidine, a key intermediate in antiretrovirol manufacture
- Gordon, Gregory Ernest Robert
- Authors: Gordon, Gregory Ernest Robert
- Date: 2010
- Subjects: HIV infections -- Treatment -- South Africa , HIV infections -- South Africa -- Prevention , Antiretroviral agents
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10423 , http://hdl.handle.net/10948/d1016217
- Description: The socio-economic impact of HIV/AIDS on South Africa has resulted in lower gross domestic product, loss of skills in key sectors such as education, and increased health-care costs in providing access to treatment. Currently active pharmaceutical ingredients (API’s) such as stavudine (d4T) and azidothymidine (AZT) are imported from India and China, while formulation is conducted locally. A strategy was initiated between CSIR Biosciences and LIFElab under the auspices of Arvir Technologies to investigate the feasibility of local antiretroviral manufacture (d4T and AZT) or the manufacture of a key intermediate such as β- thymidine (dT). Several advantages associated with successful implementation of this strategy include ensuring a local supply of API’s, thus reducing reliance on procurement from foreign sources and reducing the effect of foreign exchange rate fluctuations on providing cost effective access to treatment. A local supply source would also reduce the imports and thus aid the balance of payments deficit, and in addition to this, provide stimulus in the local pharmaceutical manufacturing industry (which has been in decline for several decades), resulting in increased skills and employment opportunities. This thesis describes the development of a superior chemo-enzymatic process for the production of β-thymidine (72 percent yield, prior to isolation), a key intermediate in the preparation of anti-retrovirals. Alternative processes based purely on chemical or bioprocess transformations to prepare either 5-methyluridine (5-MU) or dT suffer from several disadvantages: lengthy transformations due to protection/deprotection strategies, low selectivties and product yields (30 percent in the chemical process) and isolation of the product from dilute process streams requiring the use of large uneconomical reactors (bioprocesss). This contributes significantly to the cost of d4T and AZT manufacture. Our novel chemoenzymatic process comprises of a biocatalytic reaction for the production of 5-MU, with subsequent chemical transformation into dT (3 steps) negating and circumventing the limitations of the chemical or bioprocess routes. During the course of this project development, the β-thymidine selling price declined from 175 $/kg (2005) to 100 $/kg (2008). However, the process described in this work is still competitive based on the current β- thymidine selling price of 100 $/kg. The process economics show that with further optimization and increasing the isolated dT yield from 70 percent to 90 percent, the variable cost decreases from 136 $/kg to 110 $/kg. The increase in isolated yield is highly probable, based on solubility data of β-thymidine. The decrease in β-thymidine selling price and technological improvement in dT manufacture should translate into lower API manufacture costs and more cost effective access to treatment. Our novel biocatalytic process producing 5-MU uses a coupled enzyme system employing PNP, Purine Nucleoside Phosphorylase and PyNP, Pyrimidine Nucleoside Phosphorylase. The overall transglycosylation reaction may be decoupled into the phosphorolysis reaction (PNP) and synthesis reaction (PyNP). During the phosphorolysis reaction, guanosine is converted into guanine and ribose-1-phosphate (R-1-P) in the presence of PNP enzyme. The reaction intermediate R-1-P is then coupled to thymine in the presence of PyNP enzyme during the synthesis reaction, producing 5-MU. The process was scaled up from lab-scale to bench-scale (10 - 20 L) and demonstrated to be robust and reproducible. This is evident from the average guanosine conversion (94.7 percent ± 2.03) and 5-MU yield (88.2 percent ± 6.21) and mole balance (104 percent ± 7.61) which were obtained at bench-scale (3 replicates, 10 L). The reaction was carried out at reactor productivities of between 7 – 11 g.L-1.h-1. The integration of the biocatalytic process and chemical processes was successfully carried out, showing that 5-MU produced using our novel biocatalytic process behaved similarly to commercially available 5- MU (ex. Dayang Chemicals, China). A PCT patent application (Ref. No. P44422PC01) on this chemo-enzymatic process has been filed and currently public private partnerships are being explored through Arvir Technologies to evaluate and validate this technology at one ton scale.
- Full Text:
- Date Issued: 2010
- Authors: Gordon, Gregory Ernest Robert
- Date: 2010
- Subjects: HIV infections -- Treatment -- South Africa , HIV infections -- South Africa -- Prevention , Antiretroviral agents
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10423 , http://hdl.handle.net/10948/d1016217
- Description: The socio-economic impact of HIV/AIDS on South Africa has resulted in lower gross domestic product, loss of skills in key sectors such as education, and increased health-care costs in providing access to treatment. Currently active pharmaceutical ingredients (API’s) such as stavudine (d4T) and azidothymidine (AZT) are imported from India and China, while formulation is conducted locally. A strategy was initiated between CSIR Biosciences and LIFElab under the auspices of Arvir Technologies to investigate the feasibility of local antiretroviral manufacture (d4T and AZT) or the manufacture of a key intermediate such as β- thymidine (dT). Several advantages associated with successful implementation of this strategy include ensuring a local supply of API’s, thus reducing reliance on procurement from foreign sources and reducing the effect of foreign exchange rate fluctuations on providing cost effective access to treatment. A local supply source would also reduce the imports and thus aid the balance of payments deficit, and in addition to this, provide stimulus in the local pharmaceutical manufacturing industry (which has been in decline for several decades), resulting in increased skills and employment opportunities. This thesis describes the development of a superior chemo-enzymatic process for the production of β-thymidine (72 percent yield, prior to isolation), a key intermediate in the preparation of anti-retrovirals. Alternative processes based purely on chemical or bioprocess transformations to prepare either 5-methyluridine (5-MU) or dT suffer from several disadvantages: lengthy transformations due to protection/deprotection strategies, low selectivties and product yields (30 percent in the chemical process) and isolation of the product from dilute process streams requiring the use of large uneconomical reactors (bioprocesss). This contributes significantly to the cost of d4T and AZT manufacture. Our novel chemoenzymatic process comprises of a biocatalytic reaction for the production of 5-MU, with subsequent chemical transformation into dT (3 steps) negating and circumventing the limitations of the chemical or bioprocess routes. During the course of this project development, the β-thymidine selling price declined from 175 $/kg (2005) to 100 $/kg (2008). However, the process described in this work is still competitive based on the current β- thymidine selling price of 100 $/kg. The process economics show that with further optimization and increasing the isolated dT yield from 70 percent to 90 percent, the variable cost decreases from 136 $/kg to 110 $/kg. The increase in isolated yield is highly probable, based on solubility data of β-thymidine. The decrease in β-thymidine selling price and technological improvement in dT manufacture should translate into lower API manufacture costs and more cost effective access to treatment. Our novel biocatalytic process producing 5-MU uses a coupled enzyme system employing PNP, Purine Nucleoside Phosphorylase and PyNP, Pyrimidine Nucleoside Phosphorylase. The overall transglycosylation reaction may be decoupled into the phosphorolysis reaction (PNP) and synthesis reaction (PyNP). During the phosphorolysis reaction, guanosine is converted into guanine and ribose-1-phosphate (R-1-P) in the presence of PNP enzyme. The reaction intermediate R-1-P is then coupled to thymine in the presence of PyNP enzyme during the synthesis reaction, producing 5-MU. The process was scaled up from lab-scale to bench-scale (10 - 20 L) and demonstrated to be robust and reproducible. This is evident from the average guanosine conversion (94.7 percent ± 2.03) and 5-MU yield (88.2 percent ± 6.21) and mole balance (104 percent ± 7.61) which were obtained at bench-scale (3 replicates, 10 L). The reaction was carried out at reactor productivities of between 7 – 11 g.L-1.h-1. The integration of the biocatalytic process and chemical processes was successfully carried out, showing that 5-MU produced using our novel biocatalytic process behaved similarly to commercially available 5- MU (ex. Dayang Chemicals, China). A PCT patent application (Ref. No. P44422PC01) on this chemo-enzymatic process has been filed and currently public private partnerships are being explored through Arvir Technologies to evaluate and validate this technology at one ton scale.
- Full Text:
- Date Issued: 2010
Ecology and degree of specialization of South African milkweeds with diverse pollination systems
- Authors: Coombs, Gareth
- Date: 2010
- Subjects: Milkweeds -- South Africa Milkweeds -- South Africa -- Ecology Milkweeds -- South Africa -- Pollination Allee effect Self-pollination Pollination by insects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4189 , http://hdl.handle.net/10962/d1003758
- Description: Like orchids, the complexity of flowers found in asclepiads (Asclepiadoideae, Apocynaceae) and the fact that pollen is presented as pollinaria, offers excellent opportunities to study various aspects of plant-pollinator interactions. In this thesis I investigated two broad themes: ecological aspects of the pollination biology of hymenopteran and fly-pollinated asclepiads as well as the degree of specialization to certain pollinators in these species. Colonizing plants often reproduce through self-pollination, or have highly generalized pollination systems, or both. These characteristics facilitate establishment in small founding populations and generates the prediction that reproductive success should be independent of population size in these species. Chapter one examines the pollination biology of Gomphocarpus physocarpus, an indigenous, weedy species and investigates the relationship between reproductive success and population size. In this species, there is no evidence of an Allee effect and reproductive success is not correlated with population size. In addition G. physocarpus is not capable of self-pollination, suggesting it is completely reliant on pollinators for seed set. The lack of a relationship between pollination success and population size is therefore likely explained by the generalized wasp pollination system of this species. Several milkweeds are invasive outside of their native ranges. Invasive species either need to co-opt native pollinators in order to reproduce or reduce their reliance on pollinators through having the ability to self-pollinate. Co-opting native pollinators is expected to be easier in species that have generalized pollination systems, alternatively species with specialized flower morphologies need to rely on similar functional groups of pollinators to be present within the invaded range. Chapter two investigates the pollination biology and pollination success of the invasive milkweed, Araujia sericifera, and finds that in South Africa, this species is visited mainly by native honeybees and nocturnal moths. Moths however contribute little to pollen removal, and deposition. Based on the apparent morphological mismatch between the flower of A. sericifera and native honeybees, I propose that the native pollinators of this species are likely to be larger Hymenoptera (e.g. Bumblebees). Data from a breeding system study, indicated that this species is not capable of automatic self-pollination, but could set fruit from geitonogamous self-pollinations pointing to the importance of native pollinators for successful reproduction. The pollinaria of milkweeds can accumulate on pollinators to form pollen masses large enough to physically interfere with the foraging behaviour of pollinating insects. In chapter three I describe the pollination biology of Cynanchum ellipticum and find that this species is mainly pollinated by honeybees although this species is visited by several other members of Hymenoptera, Lepidoptera and Diptera. Due to the structure of the pollinaria, these chain together relatively efficiently and frequently form large pollinarium loads on the mouthparts of honeybees. However there is little evidence that these pollinarium loads influence the foraging times of pollinators and only a few individual honeybees exhibited longer foraging times and most honeybees were unaffected by the presence of large pollinarium loads. Within the genus Cynanchum there is large variation in the gynostegium structure that may influence the pattern of pollinarium loading on pollinators as well as pollen reception as shown in chapter three. In Chapter four, the pollination biology of Cynanchum obtusifolium is examined, and like that of C. ellipticum, this species is visited by a wide diversity of pollinators but honeybees appear to be the primary pollinators. More importantly this species is shown to be andromonoecious and produces two morphologically different flower types, that may be distinguished based on differences in the gynostegium structure. These two types of flower could mainly be distinguished by the length of the anther wings. I found that flowers with short anther wings function as male flowers by only exporting- and rarely receiving pollinia. Flowers with longer anther wings function as hermaphrodite flowers and can both export and receive pollinia. The ratio of male to hermaphrodite flowers varied at different times during the flowering season, but preliminary data suggested that this was not related to levels of pollination success. The genera Stapelia and Ceropegia are well known for their intricate floral adaptations that mimic the brood and feeding substrates of pollinating flies. Despite several studies that have documented the various adaptations to fly pollination in different species, there is a lack of natural history studies documenting different flower visitors, pollen loads and long term levels of pollination success in these species. In Chapter six I document the pollination biology of Ceropegia ampliata by documenting different pollinators and quantifying average levels of pollination success and the nectar reward. I also experimentally manipulated the trapping hairs of this species to determine whether trapping hairs influence average levels of pollen export and receipt. I show that Ceropegia ampliata is pollinated by a generalist guild of flies (mainly Tachinidae, Sarcophagidae, Muscidae and Lauxaniidae) and produces minute quantities of relatively dilute nectar as a reward. Pollination success was generally low in this species and increases periodically suggesting that the abundance of pollinators is patchy. I found that flowers with trapping hairs that had already wilted had higher levels of pollinarium removal than flowers with erect hairs, however experimentally removing the hairs had no significant effect on pollen export and receipt. In Chapter seven, I document the pollinators, pollen loads and long term levels of pollination success in Stapelia hirsuta var. bayllissi, a rare sapromyiophilous stapeliad. I find that, in contrast to C. ampliata, this species was specialized to pollination by small flies of the family Anthomyiidae. Similar to the results from Chapter seven, I find that long term levels of pollination success were typically low but could increase periodically, although such increases were generally unpredictable. There are currently very few records documenting pollinator interactions in the Periplocoideae. Many species within this subfamily exhibit open-access flowers suggestive of pollination by short-tongued insects. I investigated the pollination biology of Chlorocyathus lobulata, a rare species with a highly localized distribution. I aimed to determine the pollinators, average levels of pollination success and demography of this species in order to determine whether this rare species is suffering from the collapse of a highly specialized pollinator mutualism. I also quantified the high incidence of flower herbivory caused by larvae of the moth, Bocchoris onychinalis. I find that C. lobulata has a highly generalized fly pollination system and average levels of pollination success suggested that a large proportion of flowers had pollen removed and deposited suggesting that this species is not experiencing pollination failure. The large numbers of juveniles present also indicated that recruitment is taking place.
- Full Text:
- Date Issued: 2010
- Authors: Coombs, Gareth
- Date: 2010
- Subjects: Milkweeds -- South Africa Milkweeds -- South Africa -- Ecology Milkweeds -- South Africa -- Pollination Allee effect Self-pollination Pollination by insects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4189 , http://hdl.handle.net/10962/d1003758
- Description: Like orchids, the complexity of flowers found in asclepiads (Asclepiadoideae, Apocynaceae) and the fact that pollen is presented as pollinaria, offers excellent opportunities to study various aspects of plant-pollinator interactions. In this thesis I investigated two broad themes: ecological aspects of the pollination biology of hymenopteran and fly-pollinated asclepiads as well as the degree of specialization to certain pollinators in these species. Colonizing plants often reproduce through self-pollination, or have highly generalized pollination systems, or both. These characteristics facilitate establishment in small founding populations and generates the prediction that reproductive success should be independent of population size in these species. Chapter one examines the pollination biology of Gomphocarpus physocarpus, an indigenous, weedy species and investigates the relationship between reproductive success and population size. In this species, there is no evidence of an Allee effect and reproductive success is not correlated with population size. In addition G. physocarpus is not capable of self-pollination, suggesting it is completely reliant on pollinators for seed set. The lack of a relationship between pollination success and population size is therefore likely explained by the generalized wasp pollination system of this species. Several milkweeds are invasive outside of their native ranges. Invasive species either need to co-opt native pollinators in order to reproduce or reduce their reliance on pollinators through having the ability to self-pollinate. Co-opting native pollinators is expected to be easier in species that have generalized pollination systems, alternatively species with specialized flower morphologies need to rely on similar functional groups of pollinators to be present within the invaded range. Chapter two investigates the pollination biology and pollination success of the invasive milkweed, Araujia sericifera, and finds that in South Africa, this species is visited mainly by native honeybees and nocturnal moths. Moths however contribute little to pollen removal, and deposition. Based on the apparent morphological mismatch between the flower of A. sericifera and native honeybees, I propose that the native pollinators of this species are likely to be larger Hymenoptera (e.g. Bumblebees). Data from a breeding system study, indicated that this species is not capable of automatic self-pollination, but could set fruit from geitonogamous self-pollinations pointing to the importance of native pollinators for successful reproduction. The pollinaria of milkweeds can accumulate on pollinators to form pollen masses large enough to physically interfere with the foraging behaviour of pollinating insects. In chapter three I describe the pollination biology of Cynanchum ellipticum and find that this species is mainly pollinated by honeybees although this species is visited by several other members of Hymenoptera, Lepidoptera and Diptera. Due to the structure of the pollinaria, these chain together relatively efficiently and frequently form large pollinarium loads on the mouthparts of honeybees. However there is little evidence that these pollinarium loads influence the foraging times of pollinators and only a few individual honeybees exhibited longer foraging times and most honeybees were unaffected by the presence of large pollinarium loads. Within the genus Cynanchum there is large variation in the gynostegium structure that may influence the pattern of pollinarium loading on pollinators as well as pollen reception as shown in chapter three. In Chapter four, the pollination biology of Cynanchum obtusifolium is examined, and like that of C. ellipticum, this species is visited by a wide diversity of pollinators but honeybees appear to be the primary pollinators. More importantly this species is shown to be andromonoecious and produces two morphologically different flower types, that may be distinguished based on differences in the gynostegium structure. These two types of flower could mainly be distinguished by the length of the anther wings. I found that flowers with short anther wings function as male flowers by only exporting- and rarely receiving pollinia. Flowers with longer anther wings function as hermaphrodite flowers and can both export and receive pollinia. The ratio of male to hermaphrodite flowers varied at different times during the flowering season, but preliminary data suggested that this was not related to levels of pollination success. The genera Stapelia and Ceropegia are well known for their intricate floral adaptations that mimic the brood and feeding substrates of pollinating flies. Despite several studies that have documented the various adaptations to fly pollination in different species, there is a lack of natural history studies documenting different flower visitors, pollen loads and long term levels of pollination success in these species. In Chapter six I document the pollination biology of Ceropegia ampliata by documenting different pollinators and quantifying average levels of pollination success and the nectar reward. I also experimentally manipulated the trapping hairs of this species to determine whether trapping hairs influence average levels of pollen export and receipt. I show that Ceropegia ampliata is pollinated by a generalist guild of flies (mainly Tachinidae, Sarcophagidae, Muscidae and Lauxaniidae) and produces minute quantities of relatively dilute nectar as a reward. Pollination success was generally low in this species and increases periodically suggesting that the abundance of pollinators is patchy. I found that flowers with trapping hairs that had already wilted had higher levels of pollinarium removal than flowers with erect hairs, however experimentally removing the hairs had no significant effect on pollen export and receipt. In Chapter seven, I document the pollinators, pollen loads and long term levels of pollination success in Stapelia hirsuta var. bayllissi, a rare sapromyiophilous stapeliad. I find that, in contrast to C. ampliata, this species was specialized to pollination by small flies of the family Anthomyiidae. Similar to the results from Chapter seven, I find that long term levels of pollination success were typically low but could increase periodically, although such increases were generally unpredictable. There are currently very few records documenting pollinator interactions in the Periplocoideae. Many species within this subfamily exhibit open-access flowers suggestive of pollination by short-tongued insects. I investigated the pollination biology of Chlorocyathus lobulata, a rare species with a highly localized distribution. I aimed to determine the pollinators, average levels of pollination success and demography of this species in order to determine whether this rare species is suffering from the collapse of a highly specialized pollinator mutualism. I also quantified the high incidence of flower herbivory caused by larvae of the moth, Bocchoris onychinalis. I find that C. lobulata has a highly generalized fly pollination system and average levels of pollination success suggested that a large proportion of flowers had pollen removed and deposited suggesting that this species is not experiencing pollination failure. The large numbers of juveniles present also indicated that recruitment is taking place.
- Full Text:
- Date Issued: 2010
A value-based approach to promoting excellence in mathematics education
- Authors: Austin, Pamela Winifred
- Date: 2010
- Subjects: Mathematics -- Study and teaching -- South Africa , Inquiry-based learning -- South Africa , Active learning -- South Africa , Effective teaching -- South Africa , Self-efficacy
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9482 , http://hdl.handle.net/10948/1656 , Mathematics -- Study and teaching -- South Africa , Inquiry-based learning -- South Africa , Active learning -- South Africa , Effective teaching -- South Africa , Self-efficacy
- Description: This research study has emerged as a result of my concern regarding the apparent low self-efficacy amongst initial teacher education students in my mathematics education classes. It also reflects a reported renewed interest in values, and the promotion of excellence in education. The effects of a values-based approach to mathematics education towards improving students’ self-efficacy and promoting excellence have been investigated, grounded within my ontology of excellence in mathematics education, which incorporates the values of respect, fairness, accountability, honesty and compassion. An inquiry-based teaching and learning approach formed the framework within which the study took place. Notions of ‘new scholarship’, premised on the view that teaching is about engagement in participatory learning, and the development of communities of creative students, provided the theoretical framework. Both quantitative and qualitative data gathering methods were used. Data-collection tools included affective-disposition statements, interviews, journal entries, as well as a video recording of a mathematics education lesson. The quantitative and qualitative data generated suggest improved levels of self-efficacy amongst the students who participated in the study. The data also suggest that a valuesbased approach to teaching can be used as an effective approach by mathematics teachers – and mathematics teacher educators – for the purpose of promoting the pursuit of excellence. As teacher education worldwide is currently characterised by a lack of vitality in teacher preparation (Grossman, 2008), the findings of this study should provide insights for teacher educators, teachers and policy makers who wish to promote mathematics self-efficacy, excellence and facilitate enhanced vitality within the teaching profession.
- Full Text:
- Date Issued: 2010
- Authors: Austin, Pamela Winifred
- Date: 2010
- Subjects: Mathematics -- Study and teaching -- South Africa , Inquiry-based learning -- South Africa , Active learning -- South Africa , Effective teaching -- South Africa , Self-efficacy
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9482 , http://hdl.handle.net/10948/1656 , Mathematics -- Study and teaching -- South Africa , Inquiry-based learning -- South Africa , Active learning -- South Africa , Effective teaching -- South Africa , Self-efficacy
- Description: This research study has emerged as a result of my concern regarding the apparent low self-efficacy amongst initial teacher education students in my mathematics education classes. It also reflects a reported renewed interest in values, and the promotion of excellence in education. The effects of a values-based approach to mathematics education towards improving students’ self-efficacy and promoting excellence have been investigated, grounded within my ontology of excellence in mathematics education, which incorporates the values of respect, fairness, accountability, honesty and compassion. An inquiry-based teaching and learning approach formed the framework within which the study took place. Notions of ‘new scholarship’, premised on the view that teaching is about engagement in participatory learning, and the development of communities of creative students, provided the theoretical framework. Both quantitative and qualitative data gathering methods were used. Data-collection tools included affective-disposition statements, interviews, journal entries, as well as a video recording of a mathematics education lesson. The quantitative and qualitative data generated suggest improved levels of self-efficacy amongst the students who participated in the study. The data also suggest that a valuesbased approach to teaching can be used as an effective approach by mathematics teachers – and mathematics teacher educators – for the purpose of promoting the pursuit of excellence. As teacher education worldwide is currently characterised by a lack of vitality in teacher preparation (Grossman, 2008), the findings of this study should provide insights for teacher educators, teachers and policy makers who wish to promote mathematics self-efficacy, excellence and facilitate enhanced vitality within the teaching profession.
- Full Text:
- Date Issued: 2010
Photophysiochemical studies of d¹⁰ metallophthalocyanines and their interaction with nanoparticles
- Chidawanyika, Wadzanai Janet Upenyu
- Authors: Chidawanyika, Wadzanai Janet Upenyu
- Date: 2010
- Subjects: Nanoparticles Phthalocyanines Photochemistry Electrochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4335 , http://hdl.handle.net/10962/d1004996
- Description: The syntheses, extensive spectroscopic characterization, photophysical and photochemical studies have been conducted for a variation of d10 metallophthaloycanines (MPcs). Comparisons have been made taking into consideration the nfluence of the central metal ion, solvent properties, substituent type and position. Coordination to heavy central metals i.e. Hg gives enhanced triplet state properties. Low symmetry metallophthalocyanine complexes were similarly haracterized and the influence of nteractions with nanoparticles on their photophysical and photochemical properties determined. The MPcs have been linked and adsorbed or mixed with nanoparticles i.e. hemically functionalized single-walled carbon nanotubes SWCNT) and mercaptocarboxylic acid capped CdTe quantum dots (QDs) and changes in the spectra accounted for with respect to the proposed conjugate structures. Distinct differences ccur for linked and adsorbed or mixed conjugates in the bsorption, infrared (IR) and Raman spectra and for thermal ravimetric decay profiles, suggesting successful formation f covalent bonds (linked) and point to structurally ifferent materials. SWCNT quench MPc fluorescence by a photoinduced electron transfer mediated process to give low fluorescence quantum yields. The QDs were used as energy transfer donors and facilitate energy transfer, through Förster resonance energy transfer (FRET) from the QDs to the MPcs. Improved FRET efficiencies were found for linked MPc-QD conjugates relative to the mixed species. Photophysicochemical properties of MPcs were, in general, improved as a result of interactions with nanoparticles.
- Full Text:
- Date Issued: 2010
- Authors: Chidawanyika, Wadzanai Janet Upenyu
- Date: 2010
- Subjects: Nanoparticles Phthalocyanines Photochemistry Electrochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4335 , http://hdl.handle.net/10962/d1004996
- Description: The syntheses, extensive spectroscopic characterization, photophysical and photochemical studies have been conducted for a variation of d10 metallophthaloycanines (MPcs). Comparisons have been made taking into consideration the nfluence of the central metal ion, solvent properties, substituent type and position. Coordination to heavy central metals i.e. Hg gives enhanced triplet state properties. Low symmetry metallophthalocyanine complexes were similarly haracterized and the influence of nteractions with nanoparticles on their photophysical and photochemical properties determined. The MPcs have been linked and adsorbed or mixed with nanoparticles i.e. hemically functionalized single-walled carbon nanotubes SWCNT) and mercaptocarboxylic acid capped CdTe quantum dots (QDs) and changes in the spectra accounted for with respect to the proposed conjugate structures. Distinct differences ccur for linked and adsorbed or mixed conjugates in the bsorption, infrared (IR) and Raman spectra and for thermal ravimetric decay profiles, suggesting successful formation f covalent bonds (linked) and point to structurally ifferent materials. SWCNT quench MPc fluorescence by a photoinduced electron transfer mediated process to give low fluorescence quantum yields. The QDs were used as energy transfer donors and facilitate energy transfer, through Förster resonance energy transfer (FRET) from the QDs to the MPcs. Improved FRET efficiencies were found for linked MPc-QD conjugates relative to the mixed species. Photophysicochemical properties of MPcs were, in general, improved as a result of interactions with nanoparticles.
- Full Text:
- Date Issued: 2010
Grade 9 second-language learners in township schools : issues of language and mathematics when solving word problems
- Authors: Sepeng, Johannes Percy
- Date: 2010
- Subjects: Mathematics -- Language , Mathematics -- Study and teaching , Language and languages -- Mathematics , Second language acquisition -- Study and teaching
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:9498 , http://hdl.handle.net/10948/1455 , Mathematics -- Language , Mathematics -- Study and teaching , Language and languages -- Mathematics , Second language acquisition -- Study and teaching
- Description: Second language (English) learning of mathematics is common in South African mathematics classrooms, including those in the Eastern Cape Province of South Africa where isiXhosa speakers are taught in the language that is not spoken at home by both teachers and learners. The purpose of this research was to investigate issues of language, both home (isiXhosa) and the language of learning and teaching (LoLT), i.e. English, when 9th grade second language learners engage in problem-solving and sense-making of wor(l)d problems in multilingual mathematics classrooms. In addition, the aim of the study was to explore whether the introduction of discussion and argumentation techniques in these classrooms can ameliorate these issues. The study used a pre-test – intervention – post-test mixed method design utilising both quantitative and qualitative data. The data collection strategies for the purpose of this study included interviews (learners [n=24] and teachers [n=4]), classroom observations, and tests (experimental [n=107] and comparison [69]) in four experimental and two comparison schools in townships of Port Elizabeth. This study is framed by socio-cultural perspective which proposes that collective and individual processes are directly related and that students‘ unrealistic responses to real world problems reflect the students‘ socio-cultural relationship to school mathematics and their willingness to employ the approaches emphasised in school. Analysis of the data generated from pre- and post-tests, interviews and classroom observation schedule suggest that the interventional strategy significantly improved the experimental learners‘ problem-solving skills and sense-making abilities in both English and isiXhosa (but more significantly in English). The statistical results illustrate that the experimental group performed statistical significantly (p < .0005) better in the English posttest compared to comparison group. The data also suggests that the interventional strategy in this study (discussion and argumentation techniques) positively influenced the participating learners‘ word problem-solving abilities. The experimental group appeared to show a tendency to consider reality marginally better than the comparison group after the intervention. In particular, learners seemed to make realistic considerations better in the isiXhosa translation post-test compared to the English post-test. A large practical significant (d = 0.86) difference between the experimental group and the comparison group was also noted in the isiXhosa translation compared to a moderate practical significance (d = 0.57) noted in the English tests after the intervention. As such, the results of the study suggest that the introduction of discussion and argumentation techniques in the teaching and learning of mathematics word problems had a positive effect on learners‘ ability to consider reality during word problem-solving in both languages. Analysis of learners‘ interviews suggests that, although English is the preferred LoLT, they would prefer dual-use/parallel-use of English and isiXhosa for teaching and learning mathematics. There was also evidence of the benefits of code-switching throughout most of the lessons observed, coupled with instances of peer translation, and/or re-voicing. Overall results in this study illustrate that number skills displayed and mathematical errors made by learners seem to be directly related to language use in the classroom.
- Full Text:
- Date Issued: 2010
- Authors: Sepeng, Johannes Percy
- Date: 2010
- Subjects: Mathematics -- Language , Mathematics -- Study and teaching , Language and languages -- Mathematics , Second language acquisition -- Study and teaching
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:9498 , http://hdl.handle.net/10948/1455 , Mathematics -- Language , Mathematics -- Study and teaching , Language and languages -- Mathematics , Second language acquisition -- Study and teaching
- Description: Second language (English) learning of mathematics is common in South African mathematics classrooms, including those in the Eastern Cape Province of South Africa where isiXhosa speakers are taught in the language that is not spoken at home by both teachers and learners. The purpose of this research was to investigate issues of language, both home (isiXhosa) and the language of learning and teaching (LoLT), i.e. English, when 9th grade second language learners engage in problem-solving and sense-making of wor(l)d problems in multilingual mathematics classrooms. In addition, the aim of the study was to explore whether the introduction of discussion and argumentation techniques in these classrooms can ameliorate these issues. The study used a pre-test – intervention – post-test mixed method design utilising both quantitative and qualitative data. The data collection strategies for the purpose of this study included interviews (learners [n=24] and teachers [n=4]), classroom observations, and tests (experimental [n=107] and comparison [69]) in four experimental and two comparison schools in townships of Port Elizabeth. This study is framed by socio-cultural perspective which proposes that collective and individual processes are directly related and that students‘ unrealistic responses to real world problems reflect the students‘ socio-cultural relationship to school mathematics and their willingness to employ the approaches emphasised in school. Analysis of the data generated from pre- and post-tests, interviews and classroom observation schedule suggest that the interventional strategy significantly improved the experimental learners‘ problem-solving skills and sense-making abilities in both English and isiXhosa (but more significantly in English). The statistical results illustrate that the experimental group performed statistical significantly (p < .0005) better in the English posttest compared to comparison group. The data also suggests that the interventional strategy in this study (discussion and argumentation techniques) positively influenced the participating learners‘ word problem-solving abilities. The experimental group appeared to show a tendency to consider reality marginally better than the comparison group after the intervention. In particular, learners seemed to make realistic considerations better in the isiXhosa translation post-test compared to the English post-test. A large practical significant (d = 0.86) difference between the experimental group and the comparison group was also noted in the isiXhosa translation compared to a moderate practical significance (d = 0.57) noted in the English tests after the intervention. As such, the results of the study suggest that the introduction of discussion and argumentation techniques in the teaching and learning of mathematics word problems had a positive effect on learners‘ ability to consider reality during word problem-solving in both languages. Analysis of learners‘ interviews suggests that, although English is the preferred LoLT, they would prefer dual-use/parallel-use of English and isiXhosa for teaching and learning mathematics. There was also evidence of the benefits of code-switching throughout most of the lessons observed, coupled with instances of peer translation, and/or re-voicing. Overall results in this study illustrate that number skills displayed and mathematical errors made by learners seem to be directly related to language use in the classroom.
- Full Text:
- Date Issued: 2010
Development of insulin resistance in a rat model and the effects of sutherlandia frutescens as treatment and prevention
- Authors: Mackenzie, Janine
- Date: 2010
- Subjects: Metabolic syndrome , Insulin resistance -- Animal models , Obesity -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10340 , http://hdl.handle.net/10948/d1016216
- Description: The global number of obese people has reached pandemic proportions. High caloric diets and reduced physical exercise are to blame for this growing epidemic. Obesity has a very complex association with several other metabolic disorders, such as insulin resistance (IR), diabetes mellitus type 2 (DMT2) and cardiovascular disease. This puts a huge burden on health care systems world wide and claims many lives. Sutherlandia frutescens is a traditionally used herb, which is known to have anti-diabetic properties. However, the direct mode of action of S. frutescens still remains to be elucidated. The aim of this study was to investigate the developmental stages of high fat diet (HFD)-induced IR, to illuminate the pathogenesis of IR with a focal point on modifications in the lipid metabolism. Furthermore, the effects of S. frutescens as a treatment or prevention drug for IR and associated metabolic changes were examined. Two sets of experiments were conducted on male Wistar rats. In the first experiment rats, one week post weaning received a low fat diet (LFD), high fat diet (HFD) or HFD supplemented with S. frutescens (50mg/kg BW/d). Rats were sacrificed at week 0, 1, 2, 4, 8 and 12 in the feeding regime. In a second experiment rats were fed with a LFD or a HFD for 12 weeks and treated thereafter with S. frutescens (50mg/kg BW/d), metformin (13mg/kg BW/d) or water (control) for 28 days. Rats in the second experiment were sacrificed at week 12 to confirm IR while concurrently run rats were sacrificed after 28 days of treatment. For all the experiments rats were anaesthetized, blood was removed and rats were dissected. Plasma samples were analyzed for insulin, glucose, blood lipid parameters and cytokines. Liver, muscle and adipose tissue were analyzed for glucose uptake, total lipid content, lipid profile and fatty acid profile. It was shown that the intake of HFD caused IR and hyperinsulinaemia. The developmental stages in experiment one confirmed that an increase in plasma free fatty acids preceeded the onset of IR. Plasma and tissue lipid parameters (free fatty acid-, triglyceride- and cholesterol concentrations) showed pathological modifications in the HFD group. An ectopic accumulation of fat was observed in muscle and liver, as well as a change in membrane fatty acid profile. The results for circulating cytokines were somewhat inconclusive. Rats supplemented with S. frutescens did not develop HFD-induced IR (study one) or IR was reversed (study two). S. frutescens treatment also resulted in positive changes in plasma and tissue lipid parameters. In summary, an animal model for HFD-induced IR was established and the detrimental effect of elevated plasma FFA on glucose and lipid metabolism was observed. A novel discovery suggests that the anti-diabetic mode of action of S. frutescens is through modulation of lipid metabolism. It was also established that S. frutescens has the potential to prevent IR in vivo.
- Full Text:
- Date Issued: 2010
- Authors: Mackenzie, Janine
- Date: 2010
- Subjects: Metabolic syndrome , Insulin resistance -- Animal models , Obesity -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10340 , http://hdl.handle.net/10948/d1016216
- Description: The global number of obese people has reached pandemic proportions. High caloric diets and reduced physical exercise are to blame for this growing epidemic. Obesity has a very complex association with several other metabolic disorders, such as insulin resistance (IR), diabetes mellitus type 2 (DMT2) and cardiovascular disease. This puts a huge burden on health care systems world wide and claims many lives. Sutherlandia frutescens is a traditionally used herb, which is known to have anti-diabetic properties. However, the direct mode of action of S. frutescens still remains to be elucidated. The aim of this study was to investigate the developmental stages of high fat diet (HFD)-induced IR, to illuminate the pathogenesis of IR with a focal point on modifications in the lipid metabolism. Furthermore, the effects of S. frutescens as a treatment or prevention drug for IR and associated metabolic changes were examined. Two sets of experiments were conducted on male Wistar rats. In the first experiment rats, one week post weaning received a low fat diet (LFD), high fat diet (HFD) or HFD supplemented with S. frutescens (50mg/kg BW/d). Rats were sacrificed at week 0, 1, 2, 4, 8 and 12 in the feeding regime. In a second experiment rats were fed with a LFD or a HFD for 12 weeks and treated thereafter with S. frutescens (50mg/kg BW/d), metformin (13mg/kg BW/d) or water (control) for 28 days. Rats in the second experiment were sacrificed at week 12 to confirm IR while concurrently run rats were sacrificed after 28 days of treatment. For all the experiments rats were anaesthetized, blood was removed and rats were dissected. Plasma samples were analyzed for insulin, glucose, blood lipid parameters and cytokines. Liver, muscle and adipose tissue were analyzed for glucose uptake, total lipid content, lipid profile and fatty acid profile. It was shown that the intake of HFD caused IR and hyperinsulinaemia. The developmental stages in experiment one confirmed that an increase in plasma free fatty acids preceeded the onset of IR. Plasma and tissue lipid parameters (free fatty acid-, triglyceride- and cholesterol concentrations) showed pathological modifications in the HFD group. An ectopic accumulation of fat was observed in muscle and liver, as well as a change in membrane fatty acid profile. The results for circulating cytokines were somewhat inconclusive. Rats supplemented with S. frutescens did not develop HFD-induced IR (study one) or IR was reversed (study two). S. frutescens treatment also resulted in positive changes in plasma and tissue lipid parameters. In summary, an animal model for HFD-induced IR was established and the detrimental effect of elevated plasma FFA on glucose and lipid metabolism was observed. A novel discovery suggests that the anti-diabetic mode of action of S. frutescens is through modulation of lipid metabolism. It was also established that S. frutescens has the potential to prevent IR in vivo.
- Full Text:
- Date Issued: 2010
The in vitro biological activities of three Hypoxis species and their active compounds
- Authors: Boukes, Gerhardt Johannes
- Date: 2010
- Subjects: Potatoes -- Africa , Potatoes -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10322 , http://hdl.handle.net/10948/1228 , Potatoes -- Africa , Potatoes -- Therapeutic use , Medicinal plants
- Description: The African potato is used as an African traditional medicine for its nutritional and medicinal properties. Most research has been carried out on H. hemerocallidea, with very little or nothing on other Hypoxis spp. The main aim of this project was to provide scientific data on the anticancer, anti-inflammatory and antioxidant properties of H. hemerocallidea, H. stellipilis and H. sobolifera chloroform extracts and their active compounds. The hypoxoside and phytosterol contents of the three Hypoxis spp. were determined using TLC, HPLC and GC. H. hemerocallidea and H. sobolifera chloroform extracts contained the highest amounts of hypoxoside and β-sitosterol, respectively. For the anticancer properties, cytotoxicity of the Hypoxis extracts and its purified compounds were determined against the HeLa, HT-29 and MCF-7 cancer cell lines (using MTT), and PBMCs (using CellTiter-Blue®). H. sobolifera had the best cytotoxicity against the three cancer cell lines, whereas H. stellipilis stimulated HeLa and HT-29 cancer cell growth. IC50 values of hypoxoside and rooperol were determined. DNA cell cycle arrest (using PI staining) occurred in the late G1/early S (confirmed by increased p21Waf1/Cip1 expression) and G2/M phases after 15 and 48 hrs, respectively, when treated with Hypoxis extracts and rooperol. H. sobolifera and rooperol activated caspase-3 and -7 (using fluorescently labelled antibodies) in HeLa and HT-29 cancer cells, and caspase-7 in MCF-7 cancer cells after 48 hrs. Annexin V binding to phosphatidylserines in rooperol treated U937 cells confirmed early apoptosis after 15 hrs. The TUNEL assay showed DNA fragmentation in the three cancer cell lines when treated with H. sobolifera and rooperol for 48 hrs. A shift pass the G2/M phase has led to the investigation of endoreduplication, which was confirmed by cell/nucleus size, and anti-apoptotic proteins (Akt, phospho-Akt, phospho-Bcl-2 and p21Waf1/Cip1). U937 cell differentiation to monocyte-macrophages was optimized using PMA and 1,25(OH)2D3, which was confirmed by morphological and biochemical changes. For the anti-inflammatory properties, Hypoxis extracts and rooperol significantly increased NO production in monocyte-macrophages (pre-loaded with DAF-2 DA) and phagocytosis of pHrodoTM E. coli BioParticles®. The treatments had no effect on COX-2 expression in monocyte-macrophages. The phytosterols significantly increased IL-1β and IL-6 secretion xv (using the FlowCytomix Multiplex human Th1/Th2 10plex Kit I) in the PBMCs of one donor. For the antioxidant properties, Hypoxis extracts and rooperol significantly increased ROS production in undifferentiated and differentiated U937 cells, which were pre-loaded with DCFH-DA. Hypoxis extracts and purified compounds had ferric reducing activities, but only rooperol had ferric reducing activities significantly greater than ascorbic acid. β-sitosterol, campesterol and cholesterol significantly increased SOD activity in Chang liver cells, while H. stellipilis, H. sobolifera and rooperol decreased SOD activity. Anticancer, anti-inflammatory and antioxidant properties of the Hypoxis extracts may be attributed to the β-sitosterol content, because Hypoxis chloroform extracts contained very little or no hypoxoside. Unidentified compounds, and synergistic and additive effects of the compounds may have contributed to the biological effects. This study confirms previous reports that rooperol is the active compound. Results provide scientific data on the medicinal properties of one of the most frequently used medicinal plants in South Africa.
- Full Text:
- Date Issued: 2010
- Authors: Boukes, Gerhardt Johannes
- Date: 2010
- Subjects: Potatoes -- Africa , Potatoes -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10322 , http://hdl.handle.net/10948/1228 , Potatoes -- Africa , Potatoes -- Therapeutic use , Medicinal plants
- Description: The African potato is used as an African traditional medicine for its nutritional and medicinal properties. Most research has been carried out on H. hemerocallidea, with very little or nothing on other Hypoxis spp. The main aim of this project was to provide scientific data on the anticancer, anti-inflammatory and antioxidant properties of H. hemerocallidea, H. stellipilis and H. sobolifera chloroform extracts and their active compounds. The hypoxoside and phytosterol contents of the three Hypoxis spp. were determined using TLC, HPLC and GC. H. hemerocallidea and H. sobolifera chloroform extracts contained the highest amounts of hypoxoside and β-sitosterol, respectively. For the anticancer properties, cytotoxicity of the Hypoxis extracts and its purified compounds were determined against the HeLa, HT-29 and MCF-7 cancer cell lines (using MTT), and PBMCs (using CellTiter-Blue®). H. sobolifera had the best cytotoxicity against the three cancer cell lines, whereas H. stellipilis stimulated HeLa and HT-29 cancer cell growth. IC50 values of hypoxoside and rooperol were determined. DNA cell cycle arrest (using PI staining) occurred in the late G1/early S (confirmed by increased p21Waf1/Cip1 expression) and G2/M phases after 15 and 48 hrs, respectively, when treated with Hypoxis extracts and rooperol. H. sobolifera and rooperol activated caspase-3 and -7 (using fluorescently labelled antibodies) in HeLa and HT-29 cancer cells, and caspase-7 in MCF-7 cancer cells after 48 hrs. Annexin V binding to phosphatidylserines in rooperol treated U937 cells confirmed early apoptosis after 15 hrs. The TUNEL assay showed DNA fragmentation in the three cancer cell lines when treated with H. sobolifera and rooperol for 48 hrs. A shift pass the G2/M phase has led to the investigation of endoreduplication, which was confirmed by cell/nucleus size, and anti-apoptotic proteins (Akt, phospho-Akt, phospho-Bcl-2 and p21Waf1/Cip1). U937 cell differentiation to monocyte-macrophages was optimized using PMA and 1,25(OH)2D3, which was confirmed by morphological and biochemical changes. For the anti-inflammatory properties, Hypoxis extracts and rooperol significantly increased NO production in monocyte-macrophages (pre-loaded with DAF-2 DA) and phagocytosis of pHrodoTM E. coli BioParticles®. The treatments had no effect on COX-2 expression in monocyte-macrophages. The phytosterols significantly increased IL-1β and IL-6 secretion xv (using the FlowCytomix Multiplex human Th1/Th2 10plex Kit I) in the PBMCs of one donor. For the antioxidant properties, Hypoxis extracts and rooperol significantly increased ROS production in undifferentiated and differentiated U937 cells, which were pre-loaded with DCFH-DA. Hypoxis extracts and purified compounds had ferric reducing activities, but only rooperol had ferric reducing activities significantly greater than ascorbic acid. β-sitosterol, campesterol and cholesterol significantly increased SOD activity in Chang liver cells, while H. stellipilis, H. sobolifera and rooperol decreased SOD activity. Anticancer, anti-inflammatory and antioxidant properties of the Hypoxis extracts may be attributed to the β-sitosterol content, because Hypoxis chloroform extracts contained very little or no hypoxoside. Unidentified compounds, and synergistic and additive effects of the compounds may have contributed to the biological effects. This study confirms previous reports that rooperol is the active compound. Results provide scientific data on the medicinal properties of one of the most frequently used medicinal plants in South Africa.
- Full Text:
- Date Issued: 2010
Characterisation of dissimilar friction stir welds between 5754 Aluminium alloy and C11000 copper
- Authors: Akinlabi, Esther Titilayo
- Date: 2010
- Subjects: Friction stir welding , Aluminum alloys , Copper alloys
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9629 , http://hdl.handle.net/10948/1536 , Friction stir welding , Aluminum alloys , Copper alloys
- Description: Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in 1991, for joining ferrous and non-ferrous materials1. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. This research work through material characterisation of the welded joints establishes a process window for the Friction Stir welding of 5754 Aluminium Alloy and C11000 Copper. Furthermore, preliminary studies83,85 on the FSW of aluminium and copper have revealed the presence of intermetallic compounds which are detrimental to the weld qualities. This research work is also aimed at establishing process parameters that will result in limited or no intermetallic formation in the weld. The joint integrity of the resulting welds will also be correlated with the input process parameters. Based on the preliminary investigations conducted, a final weld matrix consisting of twenty seven welds was produced by varying the rotational speed between 600 and 1200 rpm, and the feed rate between 50 and 300 mm/min using three different shoulder diameter tools – 15, 18 and 25 mm to compare the heat input into the welds and to achieve the best results. The welds were characterised through microstructural evaluation, tensile testing, microhardness profiling, X-Ray Diffraction analysis, electrical resistivity and statistical analysis – in order to establish the interrelationship between the process parameters and the weld qualities. viii Microstructural evaluation of the weld samples revealed that the interfacial regions are characterised by mixture layers of aluminium and copper; while 33 percent of the tensile samples are within the acceptable range (> 75 percent joint efficiency). High Vickers microhardness values were measured at the joint interfaces, which corresponded with the intermetallic compounds. The Energy Dispersive Spectroscopy analysis revealed the presence of thin layers of intermetallics in nanoscale at the interfacial regions. The diffractograms of the X-Ray Diffraction analysis showed small peaks for intermetallics in some of the welds. Low electrical resistivities were measured at the joint interfaces. The statistical analysis showed that the downward vertical force, (Fz) can significantly influence the resulting weld qualities. An overall summary of the analysis of the weld qualities - with respect to the shoulder diameter tools employed showed that the 18 mm shoulder diameter tool is most appropriate among the three shoulder diameters considered, and a process window of medium spindle speed of 950 rpm and low-to-medium feed rate between 50 and 150 mm/min is established for FSW of Aluminium and Copper. Welds produced at 1200 rpm and 300 mm/min with low heat input did not have intermetallics formed at the joint interface.
- Full Text:
- Date Issued: 2010
- Authors: Akinlabi, Esther Titilayo
- Date: 2010
- Subjects: Friction stir welding , Aluminum alloys , Copper alloys
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9629 , http://hdl.handle.net/10948/1536 , Friction stir welding , Aluminum alloys , Copper alloys
- Description: Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in 1991, for joining ferrous and non-ferrous materials1. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. This research work through material characterisation of the welded joints establishes a process window for the Friction Stir welding of 5754 Aluminium Alloy and C11000 Copper. Furthermore, preliminary studies83,85 on the FSW of aluminium and copper have revealed the presence of intermetallic compounds which are detrimental to the weld qualities. This research work is also aimed at establishing process parameters that will result in limited or no intermetallic formation in the weld. The joint integrity of the resulting welds will also be correlated with the input process parameters. Based on the preliminary investigations conducted, a final weld matrix consisting of twenty seven welds was produced by varying the rotational speed between 600 and 1200 rpm, and the feed rate between 50 and 300 mm/min using three different shoulder diameter tools – 15, 18 and 25 mm to compare the heat input into the welds and to achieve the best results. The welds were characterised through microstructural evaluation, tensile testing, microhardness profiling, X-Ray Diffraction analysis, electrical resistivity and statistical analysis – in order to establish the interrelationship between the process parameters and the weld qualities. viii Microstructural evaluation of the weld samples revealed that the interfacial regions are characterised by mixture layers of aluminium and copper; while 33 percent of the tensile samples are within the acceptable range (> 75 percent joint efficiency). High Vickers microhardness values were measured at the joint interfaces, which corresponded with the intermetallic compounds. The Energy Dispersive Spectroscopy analysis revealed the presence of thin layers of intermetallics in nanoscale at the interfacial regions. The diffractograms of the X-Ray Diffraction analysis showed small peaks for intermetallics in some of the welds. Low electrical resistivities were measured at the joint interfaces. The statistical analysis showed that the downward vertical force, (Fz) can significantly influence the resulting weld qualities. An overall summary of the analysis of the weld qualities - with respect to the shoulder diameter tools employed showed that the 18 mm shoulder diameter tool is most appropriate among the three shoulder diameters considered, and a process window of medium spindle speed of 950 rpm and low-to-medium feed rate between 50 and 150 mm/min is established for FSW of Aluminium and Copper. Welds produced at 1200 rpm and 300 mm/min with low heat input did not have intermetallics formed at the joint interface.
- Full Text:
- Date Issued: 2010
Improving Productivity of Maize-based Smallholder Irrigated Cropping Systems: A Case Study of Zanyokwe Irrigation Scheme, Eastern Cape, South Africa
- Authors: Fanadzo, Morris
- Date: 2010
- Subjects: Farms, Small -- South Africa -- Eastern Cape Crop yields -- South Africa -- Eastern Cape Agricultural productivity -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/11009 , vital:36450
- Description: Smallholder irrigation schemes (SIS) in South Africa have performed poorly and failed to achieve the development objectives of sustaining rural livelihoods by increasing crop production and income. Limited knowledge of crop production among farmers is one constraint to improved crop productivity and, yet little research has been carried out to relate agronomic practices to productivity. This study was aimed at identifying strategies to improve the productivity of maize-based smallholder irrigated cropping systems in South Africa, using Zanyokwe irrigation scheme (ZIS) in the Eastern Cape Province as a case study. The research design was emergent, developed progressively as influenced by the progressive analyses that were made. The research work involved two main phases: exploratory studies and refinement on-farm experiments for testing technologies as informed by the exploratory studies. Exploratory studies were aimed at describing farmer crop production practices in major crop enterprises and identifying and prioritizing major agronomic yield constraints. Findings indicated that the overall performance of the cropping systems was poor as evidenced by low overall yields of < 25% of the potential in maize and butternut. Poor management of weeds, soil fertility, plant populations and water, late planting and poor cultivar choice were the most important yield constraints. The average cropping intensity achieved by farmers was only 48%. New hybrids yielded 50 - 65% higher grain than the cultivars commonly grown by farmers. However, farmers favoured their traditional cultivars, as they preferred green maize production as opposed to dry grains. As a result of these findings, focused research was designed on options for iii improving green maize production, soil fertility, crop stand and weed management in crop production. On-farm trials were, therefore, designed to (1) compare the response to nitrogen (N) rate of direct seeded and transplanted maize; (2) evaluate comparative performance of direct seeded and transplanted green maize under farmer management, and to work out the economics of transplanting; (3) investigate the effects of row spacing and atrazine dosage on weed dynamics maize yield; (4) determine the effects of inter-row spacing and plant population on weed dynamics and maize yield; and (5) investigate the effects of pre-plant weed control, N rate and plant population on weed dynamics and butternut yield. Maize transplanting improved crop stand, had earlier maturity and yielded higher at lower N rates compared to direct seeding for both green and grain maize. Total costs that varied were higher by R3 565 ha-1 for transplanted maize compared to direct-seeded maize, but the net benefits from transplanting were also much higher by R8 773 ha-1. Farmers favoured transplanting, citing bigger cobs, early maturity and the absence of seedling damage by birds, when maize was transplanted. However, a follow-up survey conducted during the subsequent year indicated that five of the six farmers abandoned transplanting, citing shortage of labour and high cost of commercially produced seedlings. It was concluded that transplanting is unlikely to be adopted unless the labour intensiveness of manual transplanting can be solved. Increasing atrazine dosage from a third of the label recommended dosage (LRD) and reducing row spacing from 90 to 45 cm resulted in an increase in weed mortality. A 100% kill of annual broadleaf weeds was possible while iv perennial grasses and the annual broadleaf weed, Oxalis latifolia, could not be controlled even at the LRD. However, improved weed mortality with increase in atrazine dosage and/or narrow rows did not translate into improved maize productivity. In butternut, pre-plant weed control resulted in a six-fold decrease in weed biomass and a 100% increase in fruit yield. These findings demonstrated the possibility of incorporation of reduced herbicide dosages and narrow rows to achieve adequate weed control and optimise on maize yields in smallholder farming systems. The results also suggested that pre-plant weed control is one of the pre-requisite to successful butternut production in SIS in South Africa. Increasing maize population from 40 000 to 60 000 plants ha-1 resulted in a 30% grain yield increase, but decreased length of cobs. Row spacing had no effect on maize yield at 40 000 plants ha-1, but at 60 000 plants ha-1 45 cm rows resulted in 11% higher grain yield (12 547 kg ha-1) than 90 cm rows (11 288 kg ha-1). Butternut yield increased significantly (p < 0.01) with increase in plant population and N rate. The optimum butternut population and N rate were estimated at 25 000 plants ha-1 and 120 kg N ha-1, respectively. Pre-plant weed control in butternut resulted in a six-fold decrease in weed biomass. Increasing butternut planting density from 10 000 to 30 000 plants ha-1 decreased weed biomass by 47%. No marketable fruits were obtained when planting was done without prior weed control. This result suggest that application of non-selective herbicide before planting is one technique that can be used by farmers as part of integrated weed management to give the crop a competitive advantage in the early growth stages before the plants start to produce vines. Yield increased significantly (p < 0.01) with increase in plant density and N rate. The optimum plant density and N rate were estimated at 25 000 plants ha-1 and 120 kg N ha-1, respectively. These findings emphasise the need to take into consideration production practices by farmers as a basis to build up skills in the management of crop enterprises and the farm as a viable business in any efforts to improve on the performance of SIS in South Africa. Future research should concentrate on labour-saving sustainable production technologies for SIS in South Africa.
- Full Text:
- Date Issued: 2010
- Authors: Fanadzo, Morris
- Date: 2010
- Subjects: Farms, Small -- South Africa -- Eastern Cape Crop yields -- South Africa -- Eastern Cape Agricultural productivity -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/11009 , vital:36450
- Description: Smallholder irrigation schemes (SIS) in South Africa have performed poorly and failed to achieve the development objectives of sustaining rural livelihoods by increasing crop production and income. Limited knowledge of crop production among farmers is one constraint to improved crop productivity and, yet little research has been carried out to relate agronomic practices to productivity. This study was aimed at identifying strategies to improve the productivity of maize-based smallholder irrigated cropping systems in South Africa, using Zanyokwe irrigation scheme (ZIS) in the Eastern Cape Province as a case study. The research design was emergent, developed progressively as influenced by the progressive analyses that were made. The research work involved two main phases: exploratory studies and refinement on-farm experiments for testing technologies as informed by the exploratory studies. Exploratory studies were aimed at describing farmer crop production practices in major crop enterprises and identifying and prioritizing major agronomic yield constraints. Findings indicated that the overall performance of the cropping systems was poor as evidenced by low overall yields of < 25% of the potential in maize and butternut. Poor management of weeds, soil fertility, plant populations and water, late planting and poor cultivar choice were the most important yield constraints. The average cropping intensity achieved by farmers was only 48%. New hybrids yielded 50 - 65% higher grain than the cultivars commonly grown by farmers. However, farmers favoured their traditional cultivars, as they preferred green maize production as opposed to dry grains. As a result of these findings, focused research was designed on options for iii improving green maize production, soil fertility, crop stand and weed management in crop production. On-farm trials were, therefore, designed to (1) compare the response to nitrogen (N) rate of direct seeded and transplanted maize; (2) evaluate comparative performance of direct seeded and transplanted green maize under farmer management, and to work out the economics of transplanting; (3) investigate the effects of row spacing and atrazine dosage on weed dynamics maize yield; (4) determine the effects of inter-row spacing and plant population on weed dynamics and maize yield; and (5) investigate the effects of pre-plant weed control, N rate and plant population on weed dynamics and butternut yield. Maize transplanting improved crop stand, had earlier maturity and yielded higher at lower N rates compared to direct seeding for both green and grain maize. Total costs that varied were higher by R3 565 ha-1 for transplanted maize compared to direct-seeded maize, but the net benefits from transplanting were also much higher by R8 773 ha-1. Farmers favoured transplanting, citing bigger cobs, early maturity and the absence of seedling damage by birds, when maize was transplanted. However, a follow-up survey conducted during the subsequent year indicated that five of the six farmers abandoned transplanting, citing shortage of labour and high cost of commercially produced seedlings. It was concluded that transplanting is unlikely to be adopted unless the labour intensiveness of manual transplanting can be solved. Increasing atrazine dosage from a third of the label recommended dosage (LRD) and reducing row spacing from 90 to 45 cm resulted in an increase in weed mortality. A 100% kill of annual broadleaf weeds was possible while iv perennial grasses and the annual broadleaf weed, Oxalis latifolia, could not be controlled even at the LRD. However, improved weed mortality with increase in atrazine dosage and/or narrow rows did not translate into improved maize productivity. In butternut, pre-plant weed control resulted in a six-fold decrease in weed biomass and a 100% increase in fruit yield. These findings demonstrated the possibility of incorporation of reduced herbicide dosages and narrow rows to achieve adequate weed control and optimise on maize yields in smallholder farming systems. The results also suggested that pre-plant weed control is one of the pre-requisite to successful butternut production in SIS in South Africa. Increasing maize population from 40 000 to 60 000 plants ha-1 resulted in a 30% grain yield increase, but decreased length of cobs. Row spacing had no effect on maize yield at 40 000 plants ha-1, but at 60 000 plants ha-1 45 cm rows resulted in 11% higher grain yield (12 547 kg ha-1) than 90 cm rows (11 288 kg ha-1). Butternut yield increased significantly (p < 0.01) with increase in plant population and N rate. The optimum butternut population and N rate were estimated at 25 000 plants ha-1 and 120 kg N ha-1, respectively. Pre-plant weed control in butternut resulted in a six-fold decrease in weed biomass. Increasing butternut planting density from 10 000 to 30 000 plants ha-1 decreased weed biomass by 47%. No marketable fruits were obtained when planting was done without prior weed control. This result suggest that application of non-selective herbicide before planting is one technique that can be used by farmers as part of integrated weed management to give the crop a competitive advantage in the early growth stages before the plants start to produce vines. Yield increased significantly (p < 0.01) with increase in plant density and N rate. The optimum plant density and N rate were estimated at 25 000 plants ha-1 and 120 kg N ha-1, respectively. These findings emphasise the need to take into consideration production practices by farmers as a basis to build up skills in the management of crop enterprises and the farm as a viable business in any efforts to improve on the performance of SIS in South Africa. Future research should concentrate on labour-saving sustainable production technologies for SIS in South Africa.
- Full Text:
- Date Issued: 2010