Changes in household food security, nutrition and food waste along an agro-ecological gradient and the rural-urban continuum in mid-sized South African towns
- Authors: Chakona, Gamuchirai
- Date: 2017
- Subjects: Food security -- South Africa , Women -- South Africa -- Nutritiona , Urban women -- South Africa -- Nutrition , Rural women -- South Africa -- Nutrition , Wild foods -- South Africa , Food supply -- South Africa , Malnutrition in children -- South Africa , Grants-in-aid -- South Africa , Household ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/6484 , vital:21127
- Description: The lack of dietary diversity is a severe problem experienced by most poor households globally. Most poor communities are at high risk of inadequate intake of micronutrients resulting from diets dominated by starchy staples. The present study considered the diets, dietary diversities and food security of women of reproductive age between 15-49 years, households and communities along the rural-urban continuum in three mid-sized towns situated along an agro-ecological gradient in South Africa. A 48-hour dietary recall was performed across two seasons (twice in summer and once in winter) and focus group discussions were held to gather all information including food abundance, seasons of food scarcity as well as coping strategies which households employ during periods of food shocks. Households were further asked to quantify any type of food waste that they could have generated in the previous 48 hours. Nutritional status of children under the age of five in all three towns was also measured using height-for-age (HAZ) and mid-upper arm circumference (MUAC) as indicators of stunting and wasting respectively. The household surveys were conducted with 554 women randomly selected in rural, peri-urban and urban locations of Richards Bay, Dundee and Harrismith. For nutritional status, the sample consisted of 216 children who were randomly selected from the sampled households in rural, peri-urban and urban locations of the study sites. Household Dietary Diversity Scores (HDDS) and Women’s Dietary Diversity Scores (WDDS) were calculated from the food items consumed by each household and each woman over a two-day period, respectively. Household food access was also measured for each household using Household Food Insecurity Access Scale (HFIAS). The mean WDDS and HDDS for the wettest site of Richards Bay (3.8±0.29 and 8.44±1.72, respectively) was significantly higher than at Dundee (3.4±0.30 and 7.76±1.63, respectively) and Harrismith (3.5±0.27 and 7.83±1.59, respectively) which were not different from one another. The mean HFIAS for Dundee (9.39±7.13) was significantly higher than that in Richards Bay (5.57±6.98) and Harrismith (6.43±6.59) which were not significantly different from one another. Dietary diversity scores were also significantly higher in urban locations than in peri-urban and rural ones whilst HFIAS was significantly lower in the urban locations than peri-urban and rural locations. There was lower dependence on food purchasing in Richards Bay compared to Dundee and Harrismith where the majority of the population was purchasing most of their food. The majority of Richards Bay households were involved in subsistence agriculture and also produced a surplus for sale, as well as collecting wild foods, which improved food security, unlike Dundee and Harrismith. Food insecurity was higher in rural and peri-urban areas compared to urban areas. In all towns, food was always available throughout the year but was beyond the reach of many households. In urban areas food was readily available and only limited by access, whereas rural populations have limited access to affordable food and face higher prices. The peri-urban populations were more food insecure because of high levels of poverty, unemployment and lack of access/entitlements to land. Periurban dwellers are therefore more sensitive to changes in incomes and food prices because they lack safety nets to absorb income or price shocks as they purchase more, rather than growing their own food. Household dietary diversity was significantly negatively correlated with household food access, that is households with low HDDS had higher HFIAS scores. Due to high levels of food insecurity, a greater percentage of children under the age of five years were stunted (35 %) and wasted (18 %). There were no significant differences in stunting along the agro-ecological gradient, along the rural-urban continuum and sex of child. However, significant differences were observed in child wasting along the agro-ecological gradient with Harrismith having more wasted children than the other two towns, which were not significantly different from each other. Significant differences were also observed between MUAC and sex of child where male children had higher MUAC than females. Wasting was significantly negatively associated with HDDS, with children from households with low HDDS tending to have large MUAC thus showing an inverse association among HDDS and obesity. However, further studies are needed to confirm this finding. In general food insecurity was closely associated with low wealth, food expenditure, large household size and limited access to land. The study did not find any significant role in the use of wild foods and social grants in improving food security for those households who were consuming wild foods and those receiving social grants. Although a greater percentage of households were food insecure, significant amounts of unprepared food (495±179 g per household) were wasted in Richards Bay alone in 48 hours mainly because the food had passed the best before date or had visibly gone bad. The amount of food waste was closely significantly negatively associated with household size. In general, the prevalence of food insecurity and wasting followed the agro-ecological gradient, with households in Richards Bay where the area.
- Full Text:
- Date Issued: 2017
- Authors: Chakona, Gamuchirai
- Date: 2017
- Subjects: Food security -- South Africa , Women -- South Africa -- Nutritiona , Urban women -- South Africa -- Nutrition , Rural women -- South Africa -- Nutrition , Wild foods -- South Africa , Food supply -- South Africa , Malnutrition in children -- South Africa , Grants-in-aid -- South Africa , Household ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/6484 , vital:21127
- Description: The lack of dietary diversity is a severe problem experienced by most poor households globally. Most poor communities are at high risk of inadequate intake of micronutrients resulting from diets dominated by starchy staples. The present study considered the diets, dietary diversities and food security of women of reproductive age between 15-49 years, households and communities along the rural-urban continuum in three mid-sized towns situated along an agro-ecological gradient in South Africa. A 48-hour dietary recall was performed across two seasons (twice in summer and once in winter) and focus group discussions were held to gather all information including food abundance, seasons of food scarcity as well as coping strategies which households employ during periods of food shocks. Households were further asked to quantify any type of food waste that they could have generated in the previous 48 hours. Nutritional status of children under the age of five in all three towns was also measured using height-for-age (HAZ) and mid-upper arm circumference (MUAC) as indicators of stunting and wasting respectively. The household surveys were conducted with 554 women randomly selected in rural, peri-urban and urban locations of Richards Bay, Dundee and Harrismith. For nutritional status, the sample consisted of 216 children who were randomly selected from the sampled households in rural, peri-urban and urban locations of the study sites. Household Dietary Diversity Scores (HDDS) and Women’s Dietary Diversity Scores (WDDS) were calculated from the food items consumed by each household and each woman over a two-day period, respectively. Household food access was also measured for each household using Household Food Insecurity Access Scale (HFIAS). The mean WDDS and HDDS for the wettest site of Richards Bay (3.8±0.29 and 8.44±1.72, respectively) was significantly higher than at Dundee (3.4±0.30 and 7.76±1.63, respectively) and Harrismith (3.5±0.27 and 7.83±1.59, respectively) which were not different from one another. The mean HFIAS for Dundee (9.39±7.13) was significantly higher than that in Richards Bay (5.57±6.98) and Harrismith (6.43±6.59) which were not significantly different from one another. Dietary diversity scores were also significantly higher in urban locations than in peri-urban and rural ones whilst HFIAS was significantly lower in the urban locations than peri-urban and rural locations. There was lower dependence on food purchasing in Richards Bay compared to Dundee and Harrismith where the majority of the population was purchasing most of their food. The majority of Richards Bay households were involved in subsistence agriculture and also produced a surplus for sale, as well as collecting wild foods, which improved food security, unlike Dundee and Harrismith. Food insecurity was higher in rural and peri-urban areas compared to urban areas. In all towns, food was always available throughout the year but was beyond the reach of many households. In urban areas food was readily available and only limited by access, whereas rural populations have limited access to affordable food and face higher prices. The peri-urban populations were more food insecure because of high levels of poverty, unemployment and lack of access/entitlements to land. Periurban dwellers are therefore more sensitive to changes in incomes and food prices because they lack safety nets to absorb income or price shocks as they purchase more, rather than growing their own food. Household dietary diversity was significantly negatively correlated with household food access, that is households with low HDDS had higher HFIAS scores. Due to high levels of food insecurity, a greater percentage of children under the age of five years were stunted (35 %) and wasted (18 %). There were no significant differences in stunting along the agro-ecological gradient, along the rural-urban continuum and sex of child. However, significant differences were observed in child wasting along the agro-ecological gradient with Harrismith having more wasted children than the other two towns, which were not significantly different from each other. Significant differences were also observed between MUAC and sex of child where male children had higher MUAC than females. Wasting was significantly negatively associated with HDDS, with children from households with low HDDS tending to have large MUAC thus showing an inverse association among HDDS and obesity. However, further studies are needed to confirm this finding. In general food insecurity was closely associated with low wealth, food expenditure, large household size and limited access to land. The study did not find any significant role in the use of wild foods and social grants in improving food security for those households who were consuming wild foods and those receiving social grants. Although a greater percentage of households were food insecure, significant amounts of unprepared food (495±179 g per household) were wasted in Richards Bay alone in 48 hours mainly because the food had passed the best before date or had visibly gone bad. The amount of food waste was closely significantly negatively associated with household size. In general, the prevalence of food insecurity and wasting followed the agro-ecological gradient, with households in Richards Bay where the area.
- Full Text:
- Date Issued: 2017
Characterisation of human pathogenic vibrios and methicillin-resistant staphylococcus aureus (MRSA) from wild and tank cultured dusky kob (agyrosomus japonicus) in the Eastern Cape Province, South Africa
- Authors: Justine, Fri
- Date: 2017
- Subjects: Marine microbiology Marine microbiology--South Africa--Eastern Cape Staphylococcus aureus infections--South Africa--Eastern Cape
- Language: English
- Type: Thesis , Doctoral , Microbiology
- Identifier: http://hdl.handle.net/10353/16047 , vital:40607
- Description: Introduction: Marine finfish including dusky kob (Agyrosomus japonicus), in addition to its high protein value, is bestowed with numerous health benefits including being heart friendly due to high proportion of omega 3 fatty acids. They are therefore used as powerful preventive measures against cardiovaslcular diseases. They are also important in neurological development during gestation and infancy, thus a regular recommendation by nutritionists. However, fish and its environment may be contaminated by bacteria pathogens. Human infections caused by members of the genus Vibrio, and Staphylococcus especially Methicillin-resistant S. aureus (MRSA) are of increased concern worldwide especially with increased Vibrio disease outbreaks and rapid spread of MRSA in the community. Methicillin-resistant Staphylococcus aureus is regarded as an emerging zoonotic agent, therefore marine fish may be considered as a reservoir for infection. The emergence of multi-drug resistant organisms in both farm animals and humans has also been a challenge that hurdles chemotherapy worldwide. Methods: We enumerated the bacteria flora of skin, gill and gut of marine dusky kob (Agyrosomus japonicus) raised in a recirculatory aquaculture system using metagenomic sequencing of the 16S rRNA. We further screened 120 dusky kob fishes (skin, gill and gut) and 80 water samples from two fish farms and Kariega estuary collected over a 10 month period for human pathogenic vibrios, and MRSA using standard procedures. Vibrio species were further subjected to species specific PCRs delineating them into V. cholerae, V. parahaemolyticus, V. vulnificus, and V. fluvialis. This was followed by elucidation of the genotypic virulence determinants. The Reverse Fragment Length Polymorphism (RFLP) of the cytotoxin hemolysin (vvhA) gene of V. vulnificus strains was carried out to determine the associated biotypes. A total of 277 Vibrio strains consisting of 126 V. fluvialis, 45 Vibrio vulnificus, 30 V. parahaemolyticus and 76 vibrios belonging to other species were subjected to susceptibility testing to 15 antibiotics by the disc diffusion method and resistant strains were further evaluated for their genotypic antimicrobial resistant determinants by polymerase chain reaction followed by plasmid profiling. For MRSA screening, we evaluated the reliability of cefoxitin disc diffusion, oxacillin screen agar and BrillianceTM MRSA 2 agar tests, in detecting methicillin resistance from fish (environmental) samples using PCR detection of the mecA as the gold standard. A total of 33 mecA positive S. aureus strains (MRSA) were subjected to PCR detection of enterotoxins (Staphylococcal enterotoxin A-E) and Panton Valentine Leucocidin (PVL) encoding genes. The SCCmec types were also investigated by multiplex PCR targeting genes encoding type I-V. The antibiogram profiles of MRSA strains to 12 antibiotics by the disc diffusion method and to vancomycin by broth micro dilution method were elucidated. Polymerase chain reaction was employed to evaluate the presence of antibiotic resistant genes. The nucleotide sequences of the rpoB gene were analysed to determine mutations that could lead to rifampicin resistance. Results: A broad diversity of pathogenic and non-pathogenic bacterial species of different taxonomic groups was observed with Proteobacteria revealed as the most common bacteria phyla. Fifty one families were identified with Enterobacteriaceae the most frequently detected in all the anatomical sites and the gut showing the highest species diversity. A total of 606 (60.23 percent ) presumptive Vibrio isolates were confirmed by PCR of which V. fluvialis was the most predominant, 193 (31.85 percent ). This was followed by Vibrio vulnificus 74 (12.21 percent ), and V. parahaemolyticus 33 (5.45 percent ). No V. cholerae strain was detected. Only one of the V. parahaemolyticus strains possessed the trh virulent gene with no tdh detected. Virulence factors of V. fluvialis detected were stn (13.5 percent ), hupO (10.4 percent ), and vfpA (1.0 percent ). V. vulnificus biotype 3, formerly restricted to Isreal was identified. Generally, resistance among Vibrio isolates varied considerably with highest resistances recorded to amoxicillin (76.2 percent ), ampicillin (67.5 percent ), erythromycin (38.3 percent ), and doxycycline (35.0 percent ) while higher susceptibilities were revealed by gentamicin (100 percent ), norfloxacin (97.8 percent ), florfenicol (90.3 percent ), tetracycline (87.7 percent ), and chloramphenicol (87.4 percent ). Multiple antibiotic resistance (MAR) (resistance to ≥ 2 classes of antibiotics) was 58.5 percent . The MAR index did not vary significantly between sites (P>0.05) and values of >0.20 were recorded in 40 percent (108/277) of all the isolates. The resistant genes ampC, blaOXA, tetA, tetM, dfr1, sul1, sul2, ermB, nptII and strA were detected in two or more Vibrio isolates while the SXT intergrase was detected only in one isolate. Seven of the 18 extreme drug resistant isolates possessed 1–3 plasmids of 1.5–10 kb range. A total of 321 presumptive Staphylococcus aureus isolates were recovered by culture out of which 202 (62.9 percent ) were identified as S. aureus by PCR. Of these, 33 (16.3 percent ) strains were mecA positive while the rest, 169 (83.7 percent ) were mecA negative. The sensitivity and specificity of MRSA detection by use of cefoxitin disc (30 μg) test was 93.9 percent and 91.7 percent , that for oxacillin screen agar test (6 μg/mL) was 81.8 percent and 92.3 percent while that of BrillianceTM MRSATM 2 agar was 87.9 percent and 94.1 percent respectively. Staphylococcal enterotoxin SEE was detected in 12.1 percent (4/33) of total strains followed by SEA 3.0 percent (1/33), and SEC 3.0 percent (1/33). SEB and SED were absent. Six of the isolates had the PVL gene, giving a prevalence of 18.2 percent . The most frequently detected SCCmec type was SCCmec type III (17/33; 51.5 percent ), closely followed by SCCmec subtype IVc (10/33; 30.3 percent ) and the least were SCCmec types I and II with only 3.0 percent (1/33) each. The rest four (4/33; 12.1 percent ) did not belong to any of the above types and were therefore considered to belong to other subtypes of SCCmec type IV not tested in the study. For antibiogram patterns, 12 (36.4 percent ) strains were resistant to doxycyline, 10 (30.3 percent ) to trimethroprim-sulfamethoxazole, 9 (27.3 percent ) to tetracycline and only 1 (3.0 percent ) strain was resistant to ciprofloxacin. Nineteen (57.6 percent ) of the MRSA strains had vancomycin MIC of ≤ 2 μg/mL, 4 (12.1 percent ) with MIC range of 4-8 μg/mL, and 10 (30.3 percent ) with values ≥ 16 μg/mL. Overall, 27 (91.percent) isolates showed simultaneous resistance to 3 or more antibiotics. The resistant genes tetM, tetA, ermB, BlaZ femA were detected in two or more strains resistant to various antimicrobials. Resistance to rifampicin was not caused by mutations in the rpoB gene. Conclusions: To the best of our knowledge, this study is the first study reporting a broad, and diverse bacteria flora of skin, gill, and gut of the South African dusky kob as well as the first study on human pathogenic vibrios, and MRSA from marine finfish especially those from recirculatory aquaculture systems. Also, our study revealed that Vibrio species with pathogenic potential are present in marine dusky kob and its environs. Dusky kob is contaminated with CA- MRSA and HA- MRSA that may cause difficult to treat infections with regular antibiotics. Some of the MRSA strains contained toxins that can cause food-borne gastroeneteritis. The present study revealed that MRSA and Vibrio species are potential reservoirs for antibiotic resistant genes, which could be disseminated to other bacterial species probably through plasmids, a public health risk.
- Full Text:
- Date Issued: 2017
- Authors: Justine, Fri
- Date: 2017
- Subjects: Marine microbiology Marine microbiology--South Africa--Eastern Cape Staphylococcus aureus infections--South Africa--Eastern Cape
- Language: English
- Type: Thesis , Doctoral , Microbiology
- Identifier: http://hdl.handle.net/10353/16047 , vital:40607
- Description: Introduction: Marine finfish including dusky kob (Agyrosomus japonicus), in addition to its high protein value, is bestowed with numerous health benefits including being heart friendly due to high proportion of omega 3 fatty acids. They are therefore used as powerful preventive measures against cardiovaslcular diseases. They are also important in neurological development during gestation and infancy, thus a regular recommendation by nutritionists. However, fish and its environment may be contaminated by bacteria pathogens. Human infections caused by members of the genus Vibrio, and Staphylococcus especially Methicillin-resistant S. aureus (MRSA) are of increased concern worldwide especially with increased Vibrio disease outbreaks and rapid spread of MRSA in the community. Methicillin-resistant Staphylococcus aureus is regarded as an emerging zoonotic agent, therefore marine fish may be considered as a reservoir for infection. The emergence of multi-drug resistant organisms in both farm animals and humans has also been a challenge that hurdles chemotherapy worldwide. Methods: We enumerated the bacteria flora of skin, gill and gut of marine dusky kob (Agyrosomus japonicus) raised in a recirculatory aquaculture system using metagenomic sequencing of the 16S rRNA. We further screened 120 dusky kob fishes (skin, gill and gut) and 80 water samples from two fish farms and Kariega estuary collected over a 10 month period for human pathogenic vibrios, and MRSA using standard procedures. Vibrio species were further subjected to species specific PCRs delineating them into V. cholerae, V. parahaemolyticus, V. vulnificus, and V. fluvialis. This was followed by elucidation of the genotypic virulence determinants. The Reverse Fragment Length Polymorphism (RFLP) of the cytotoxin hemolysin (vvhA) gene of V. vulnificus strains was carried out to determine the associated biotypes. A total of 277 Vibrio strains consisting of 126 V. fluvialis, 45 Vibrio vulnificus, 30 V. parahaemolyticus and 76 vibrios belonging to other species were subjected to susceptibility testing to 15 antibiotics by the disc diffusion method and resistant strains were further evaluated for their genotypic antimicrobial resistant determinants by polymerase chain reaction followed by plasmid profiling. For MRSA screening, we evaluated the reliability of cefoxitin disc diffusion, oxacillin screen agar and BrillianceTM MRSA 2 agar tests, in detecting methicillin resistance from fish (environmental) samples using PCR detection of the mecA as the gold standard. A total of 33 mecA positive S. aureus strains (MRSA) were subjected to PCR detection of enterotoxins (Staphylococcal enterotoxin A-E) and Panton Valentine Leucocidin (PVL) encoding genes. The SCCmec types were also investigated by multiplex PCR targeting genes encoding type I-V. The antibiogram profiles of MRSA strains to 12 antibiotics by the disc diffusion method and to vancomycin by broth micro dilution method were elucidated. Polymerase chain reaction was employed to evaluate the presence of antibiotic resistant genes. The nucleotide sequences of the rpoB gene were analysed to determine mutations that could lead to rifampicin resistance. Results: A broad diversity of pathogenic and non-pathogenic bacterial species of different taxonomic groups was observed with Proteobacteria revealed as the most common bacteria phyla. Fifty one families were identified with Enterobacteriaceae the most frequently detected in all the anatomical sites and the gut showing the highest species diversity. A total of 606 (60.23 percent ) presumptive Vibrio isolates were confirmed by PCR of which V. fluvialis was the most predominant, 193 (31.85 percent ). This was followed by Vibrio vulnificus 74 (12.21 percent ), and V. parahaemolyticus 33 (5.45 percent ). No V. cholerae strain was detected. Only one of the V. parahaemolyticus strains possessed the trh virulent gene with no tdh detected. Virulence factors of V. fluvialis detected were stn (13.5 percent ), hupO (10.4 percent ), and vfpA (1.0 percent ). V. vulnificus biotype 3, formerly restricted to Isreal was identified. Generally, resistance among Vibrio isolates varied considerably with highest resistances recorded to amoxicillin (76.2 percent ), ampicillin (67.5 percent ), erythromycin (38.3 percent ), and doxycycline (35.0 percent ) while higher susceptibilities were revealed by gentamicin (100 percent ), norfloxacin (97.8 percent ), florfenicol (90.3 percent ), tetracycline (87.7 percent ), and chloramphenicol (87.4 percent ). Multiple antibiotic resistance (MAR) (resistance to ≥ 2 classes of antibiotics) was 58.5 percent . The MAR index did not vary significantly between sites (P>0.05) and values of >0.20 were recorded in 40 percent (108/277) of all the isolates. The resistant genes ampC, blaOXA, tetA, tetM, dfr1, sul1, sul2, ermB, nptII and strA were detected in two or more Vibrio isolates while the SXT intergrase was detected only in one isolate. Seven of the 18 extreme drug resistant isolates possessed 1–3 plasmids of 1.5–10 kb range. A total of 321 presumptive Staphylococcus aureus isolates were recovered by culture out of which 202 (62.9 percent ) were identified as S. aureus by PCR. Of these, 33 (16.3 percent ) strains were mecA positive while the rest, 169 (83.7 percent ) were mecA negative. The sensitivity and specificity of MRSA detection by use of cefoxitin disc (30 μg) test was 93.9 percent and 91.7 percent , that for oxacillin screen agar test (6 μg/mL) was 81.8 percent and 92.3 percent while that of BrillianceTM MRSATM 2 agar was 87.9 percent and 94.1 percent respectively. Staphylococcal enterotoxin SEE was detected in 12.1 percent (4/33) of total strains followed by SEA 3.0 percent (1/33), and SEC 3.0 percent (1/33). SEB and SED were absent. Six of the isolates had the PVL gene, giving a prevalence of 18.2 percent . The most frequently detected SCCmec type was SCCmec type III (17/33; 51.5 percent ), closely followed by SCCmec subtype IVc (10/33; 30.3 percent ) and the least were SCCmec types I and II with only 3.0 percent (1/33) each. The rest four (4/33; 12.1 percent ) did not belong to any of the above types and were therefore considered to belong to other subtypes of SCCmec type IV not tested in the study. For antibiogram patterns, 12 (36.4 percent ) strains were resistant to doxycyline, 10 (30.3 percent ) to trimethroprim-sulfamethoxazole, 9 (27.3 percent ) to tetracycline and only 1 (3.0 percent ) strain was resistant to ciprofloxacin. Nineteen (57.6 percent ) of the MRSA strains had vancomycin MIC of ≤ 2 μg/mL, 4 (12.1 percent ) with MIC range of 4-8 μg/mL, and 10 (30.3 percent ) with values ≥ 16 μg/mL. Overall, 27 (91.percent) isolates showed simultaneous resistance to 3 or more antibiotics. The resistant genes tetM, tetA, ermB, BlaZ femA were detected in two or more strains resistant to various antimicrobials. Resistance to rifampicin was not caused by mutations in the rpoB gene. Conclusions: To the best of our knowledge, this study is the first study reporting a broad, and diverse bacteria flora of skin, gill, and gut of the South African dusky kob as well as the first study on human pathogenic vibrios, and MRSA from marine finfish especially those from recirculatory aquaculture systems. Also, our study revealed that Vibrio species with pathogenic potential are present in marine dusky kob and its environs. Dusky kob is contaminated with CA- MRSA and HA- MRSA that may cause difficult to treat infections with regular antibiotics. Some of the MRSA strains contained toxins that can cause food-borne gastroeneteritis. The present study revealed that MRSA and Vibrio species are potential reservoirs for antibiotic resistant genes, which could be disseminated to other bacterial species probably through plasmids, a public health risk.
- Full Text:
- Date Issued: 2017
Characterisation of photovoltaic devices using large area light beam induced current measurements
- Okullo, Michael, Van Dyk, Ernes, Okullo, W
- Authors: Okullo, Michael , Van Dyk, Ernes , Okullo, W
- Date: 2017
- Subjects: Photovoltaic cells Photovoltaic power generation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20526 , vital:29314
- Description: Photovoltaic (PV) modules are made by connecting PV cells in series in order to generate a reasonable voltage that can be used for any productive work. Inaccuracy in cell sorting during crystalline silicon module construction, or non-uniform deposition of PV material and laser scribing during thin _lm module construction, may introduce current mismatch in the module. Current mismatch is a consequence of connecting module cells which have non-identical electrical characteristics. When current mismatch occurs in a module, it is the cell generating the lowest current that determines the module output current and this leads to a decrease in the output power and lifespan of the module. Investigation of current uniformity and the different current reducing features in PV modules, which are potential sources of current mismatch, is therefore critical in optimising the performance of PV modules. In this study, a large area light beam induced current (LA-LBIC) measurement system was developed. This non-destructive technique was used to characterise crystalline silicon PV modules (mono-crystalline and multi-crystalline), thin _lm PV modules (amorphous silicon and copper indium diselenide) and a combined concentrator photovoltaic (CPV) module. A light source mounted onto a motorised x-y scanning stage was used to illuminate a PV module, or the Fresnel lens of a CPV module, point-by-point, while measuring the module output current. The measured current was mapped as a function of position and presented as an LBIC image. The point-illuminated circuit model of a PV module was designed and used to explain the variation in current between and within module cells in the LA-LBIC maps. Application of the model to crystalline silicon modules attributes the variation in photo-generated current between cells mainly to current mismatch between series connected cells. Current variation within cells is attributed to individual cell shunts. In the thin _lm modules, the model attributes the variation in photo-generated current mainly to differences in local cell shunts and series resistances originating from the scribing procedure during cell formation in the manufacturing process. In the PV modules studied, variation in photo-generated current was found to exist both between and within cells. The variation was more pronounced between cells than within cells. Module point I-V curves at different points of the module were measured in order to extract short circuit current, to quantify the variations between and within cells. A striation ring defect, causing a drop in short circuit current of 38%, was detected in the mono-crystalline module. Investigation of the striation ring defect indicated that the defect is active in the bulk (p-type) but inactive in the top (n-type) layer. Further characterisation of the defect revealed that a higher percentage loss in short circuit current occurs at lower light intensities. In the multi-crystalline silicon module, cracks were detected and found to electrically isolate the module cells into two parts, causing them to operate in parallel and consequently introducing current mismatch in the module. The I-V curve of the module at standard test condition (STC) revealed a step below the knee, which is a manifestation of current mismatch in the module. High currents, as a consequence of diffuse reflection, leading to multiple reflections by the top glass were also observed at localised points on the bus bar and cell separations. In the a-Si module, the variation in photo-current within some cells, was found to be substantial. In the copper indium diselenide (CIS) module, an electrical disconnection across the module cells was identified. A disconnection in the form of a triangular shape was also identified in this module, which completely disconnected the front contact of this area from the module. This unique disconnection feature caused current in the module to follow in a reverse direction when the light spot was incident within the boundary of the disconnection. Scans performed under different forward voltage biases were useful in identifying severely shunted module cells. A severely shunted cell was found to generate a higher photo-current than a good cell at the same forward bias voltage. This unique observation was explored further using point-illuminated module I-V measurements, and was found to be due to the crossing over of the I-V curves of the two cells. In order to explore the relationship between cell photo-current and cell shunt resistance, a method to determine the shunt resistances of the cells in an encapsulated module was devised. The method involves measuring the I-V curves of a fully illuminated module and a partially illuminated module when one of its cells is shaded and the I-V curves used to determine the short circuit current and the shunt resistance of the shaded cell. A strong correlation was found to exist between the short circuit current of the shaded cell and the cell shunt resistance, as well as between the short circuit current of the shaded cell and dark LBIC. The LA-LBIC technique was further applied to characterise a combine CPV module. Results showed that the Fresnel lens facets close to the centre generate a higher photo-current at the receiver than those towards the edges. The reduced photo-current towards the edges was attributed to losses due to di_raction, dielectric reflection and internal re_ection. About 65% of the area of the Fresnel lenses were found to be e_ective in light collection in terms of the photo-current generated at the receiver. Abrasions and scratches on the Fresnel lenses were identi_ed as some of the current limiting features in a CPV module. The LA-LBIC technique used in this study has demonstrated the potential to investigate current mismatch, current limiting and current enhancing features in PV modules. The capacity to further characterise current limiting features in order to investigate their effects on photo-current under different wavelengths and light intensities was also demonstrated. Extending the LA-LBIC technique to characterise a combined CPV module is a great achievement of this work.
- Full Text:
- Date Issued: 2017
- Authors: Okullo, Michael , Van Dyk, Ernes , Okullo, W
- Date: 2017
- Subjects: Photovoltaic cells Photovoltaic power generation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20526 , vital:29314
- Description: Photovoltaic (PV) modules are made by connecting PV cells in series in order to generate a reasonable voltage that can be used for any productive work. Inaccuracy in cell sorting during crystalline silicon module construction, or non-uniform deposition of PV material and laser scribing during thin _lm module construction, may introduce current mismatch in the module. Current mismatch is a consequence of connecting module cells which have non-identical electrical characteristics. When current mismatch occurs in a module, it is the cell generating the lowest current that determines the module output current and this leads to a decrease in the output power and lifespan of the module. Investigation of current uniformity and the different current reducing features in PV modules, which are potential sources of current mismatch, is therefore critical in optimising the performance of PV modules. In this study, a large area light beam induced current (LA-LBIC) measurement system was developed. This non-destructive technique was used to characterise crystalline silicon PV modules (mono-crystalline and multi-crystalline), thin _lm PV modules (amorphous silicon and copper indium diselenide) and a combined concentrator photovoltaic (CPV) module. A light source mounted onto a motorised x-y scanning stage was used to illuminate a PV module, or the Fresnel lens of a CPV module, point-by-point, while measuring the module output current. The measured current was mapped as a function of position and presented as an LBIC image. The point-illuminated circuit model of a PV module was designed and used to explain the variation in current between and within module cells in the LA-LBIC maps. Application of the model to crystalline silicon modules attributes the variation in photo-generated current between cells mainly to current mismatch between series connected cells. Current variation within cells is attributed to individual cell shunts. In the thin _lm modules, the model attributes the variation in photo-generated current mainly to differences in local cell shunts and series resistances originating from the scribing procedure during cell formation in the manufacturing process. In the PV modules studied, variation in photo-generated current was found to exist both between and within cells. The variation was more pronounced between cells than within cells. Module point I-V curves at different points of the module were measured in order to extract short circuit current, to quantify the variations between and within cells. A striation ring defect, causing a drop in short circuit current of 38%, was detected in the mono-crystalline module. Investigation of the striation ring defect indicated that the defect is active in the bulk (p-type) but inactive in the top (n-type) layer. Further characterisation of the defect revealed that a higher percentage loss in short circuit current occurs at lower light intensities. In the multi-crystalline silicon module, cracks were detected and found to electrically isolate the module cells into two parts, causing them to operate in parallel and consequently introducing current mismatch in the module. The I-V curve of the module at standard test condition (STC) revealed a step below the knee, which is a manifestation of current mismatch in the module. High currents, as a consequence of diffuse reflection, leading to multiple reflections by the top glass were also observed at localised points on the bus bar and cell separations. In the a-Si module, the variation in photo-current within some cells, was found to be substantial. In the copper indium diselenide (CIS) module, an electrical disconnection across the module cells was identified. A disconnection in the form of a triangular shape was also identified in this module, which completely disconnected the front contact of this area from the module. This unique disconnection feature caused current in the module to follow in a reverse direction when the light spot was incident within the boundary of the disconnection. Scans performed under different forward voltage biases were useful in identifying severely shunted module cells. A severely shunted cell was found to generate a higher photo-current than a good cell at the same forward bias voltage. This unique observation was explored further using point-illuminated module I-V measurements, and was found to be due to the crossing over of the I-V curves of the two cells. In order to explore the relationship between cell photo-current and cell shunt resistance, a method to determine the shunt resistances of the cells in an encapsulated module was devised. The method involves measuring the I-V curves of a fully illuminated module and a partially illuminated module when one of its cells is shaded and the I-V curves used to determine the short circuit current and the shunt resistance of the shaded cell. A strong correlation was found to exist between the short circuit current of the shaded cell and the cell shunt resistance, as well as between the short circuit current of the shaded cell and dark LBIC. The LA-LBIC technique was further applied to characterise a combine CPV module. Results showed that the Fresnel lens facets close to the centre generate a higher photo-current at the receiver than those towards the edges. The reduced photo-current towards the edges was attributed to losses due to di_raction, dielectric reflection and internal re_ection. About 65% of the area of the Fresnel lenses were found to be e_ective in light collection in terms of the photo-current generated at the receiver. Abrasions and scratches on the Fresnel lenses were identi_ed as some of the current limiting features in a CPV module. The LA-LBIC technique used in this study has demonstrated the potential to investigate current mismatch, current limiting and current enhancing features in PV modules. The capacity to further characterise current limiting features in order to investigate their effects on photo-current under different wavelengths and light intensities was also demonstrated. Extending the LA-LBIC technique to characterise a combined CPV module is a great achievement of this work.
- Full Text:
- Date Issued: 2017
Chinese aid and African agency since 2000: examining the cases of Zimbabwe, Angola and Ghana
- Authors: Chipaike, Ronald
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/59151 , vital:27442
- Description: Restricted access-thesis embargoed for 2 years
- Full Text:
- Date Issued: 2017
- Authors: Chipaike, Ronald
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/59151 , vital:27442
- Description: Restricted access-thesis embargoed for 2 years
- Full Text:
- Date Issued: 2017
Colonisation and succession of fishes in Lake Liambezi, a shallow ephemeral floodplain lake in Southern Africa
- Authors: Peel, Richard Anthony
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/65211 , vital:28707
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Peel, Richard Anthony
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/65211 , vital:28707
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
Combined in silico approaches towards the identification of novel malarial cysteine protease inhibitors
- Authors: Musyoka, Thommas Mutemi
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/4488 , vital:20679
- Description: Malaria an infectious disease caused by a group of parasitic organisms of the Plasmodium genus remains a severe public health problem in Africa, South America and parts of Asia. The leading causes for the persistence of malaria are the emergence of drug resistance to common antimalarial drugs, lack of effective vaccines and the inadequate control of mosquito vectors. Worryingly, accumulating evidence shows that the parasite has developed resistant to the current first-line treatment based on artemisinin. Hence, the identification and characterization of novel drug targets and drugs with unique mode of action remains an urgent priority. The successful sequencing and assembly of genomes from several Plasmodium species has opened an opportune window for the identification of new drug targets. Cysteine proteases are one of the major drug targets to be identified so far. The use of cysteine protease inhibitors coupled with gene manipulation studies has defined specific and putative roles of cysteine proteases which include hemoglobin degradation, erythrocyte rupture, immune evasion and erythrocyte invasion, steps which are central for the completion of the Plasmodium parasite life cycle. In an aim to discover potential novel antimalarials, this thesis focussed on falcipains (FPs), a group of four papain-like cysteine proteases from Plasmodium falciparum. Two of these enzymes, FP-2 and FP-3 are the major hemoglobinases and have been validated as drug targets. For the successful elimination of malaria, drugs must be safe and target both human and wild Plasmodium infective forms. Thus, an incipient aim was to identify protein homologs of these two proteases from other Plasmodium species and the host (human). From BLASTP analysis, up to 16 FP-2 and FP-3 homologs were identified (13 plasmodial proteases and 3 human cathepsins). Using in silico characterization approaches, the intra and inter group sequence, structural, phylogenetic and physicochemical differences were determined. To extend previous work (MSc student) involving docking studies on the identified proteins using known FP-2 and FP-3 inhibitors, a South African natural compound and its ZINC analogs, molecular dynamics and binding free energy studies were performed to determine the stabilities and quantification of the strength of interactions between the different protein-ligand complexes. From the results, key structural elements that regulate the binding and selectivity of non-peptidic compounds onto the different proteins were deciphered. Interaction fingerprints and energy decomposition analysis identified key residues and energetic terms that are central for effective ligand binding. This research presents novel insight essential for the structure-based molecular drug design of more potent antimalarial drugs.
- Full Text:
- Date Issued: 2017
- Authors: Musyoka, Thommas Mutemi
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/4488 , vital:20679
- Description: Malaria an infectious disease caused by a group of parasitic organisms of the Plasmodium genus remains a severe public health problem in Africa, South America and parts of Asia. The leading causes for the persistence of malaria are the emergence of drug resistance to common antimalarial drugs, lack of effective vaccines and the inadequate control of mosquito vectors. Worryingly, accumulating evidence shows that the parasite has developed resistant to the current first-line treatment based on artemisinin. Hence, the identification and characterization of novel drug targets and drugs with unique mode of action remains an urgent priority. The successful sequencing and assembly of genomes from several Plasmodium species has opened an opportune window for the identification of new drug targets. Cysteine proteases are one of the major drug targets to be identified so far. The use of cysteine protease inhibitors coupled with gene manipulation studies has defined specific and putative roles of cysteine proteases which include hemoglobin degradation, erythrocyte rupture, immune evasion and erythrocyte invasion, steps which are central for the completion of the Plasmodium parasite life cycle. In an aim to discover potential novel antimalarials, this thesis focussed on falcipains (FPs), a group of four papain-like cysteine proteases from Plasmodium falciparum. Two of these enzymes, FP-2 and FP-3 are the major hemoglobinases and have been validated as drug targets. For the successful elimination of malaria, drugs must be safe and target both human and wild Plasmodium infective forms. Thus, an incipient aim was to identify protein homologs of these two proteases from other Plasmodium species and the host (human). From BLASTP analysis, up to 16 FP-2 and FP-3 homologs were identified (13 plasmodial proteases and 3 human cathepsins). Using in silico characterization approaches, the intra and inter group sequence, structural, phylogenetic and physicochemical differences were determined. To extend previous work (MSc student) involving docking studies on the identified proteins using known FP-2 and FP-3 inhibitors, a South African natural compound and its ZINC analogs, molecular dynamics and binding free energy studies were performed to determine the stabilities and quantification of the strength of interactions between the different protein-ligand complexes. From the results, key structural elements that regulate the binding and selectivity of non-peptidic compounds onto the different proteins were deciphered. Interaction fingerprints and energy decomposition analysis identified key residues and energetic terms that are central for effective ligand binding. This research presents novel insight essential for the structure-based molecular drug design of more potent antimalarial drugs.
- Full Text:
- Date Issued: 2017
Commerce powered by 'National culture'? : an assessment of "Wear Local" campaigns as tools for reinvigorating the textile and clothing industries in Ghana and South Africa
- Authors: Darku, Esther Naa Dodua
- Date: 2017
- Subjects: Textile industry -- Economic aspects -- Ghana Textile industry -- Economic aspects -- South Africa Sustainable development -- Ghana , Sustainable development -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2172 , vital:27619
- Description: This study examines the use of ‘cultural’ imagery and messaging as a tool to revitalise crucial national industries. Specifically, it examines the use of Wear Local campaigns in Ghana and South Africa as strategies to rejuvenate their textile industries and to make them viable in an increasingly competitive global market. Conceptualising Wear Local campaigns as possessing both cultural and economic imperatives, this study highlights how both factors contribute to making products of Buy Local campaigns marketable by showing their importance as both cultural and economic products. Using a descriptive-evaluative design, the study adopted a triangulated research approach comprising a survey, key informant interviews and document analysis. Survey questionnaires were administered to a total sample of 308 respondents in Ghana and South Africa. The qualitative phase of the study involved 10 key informant interviews (comprising textile labour unions, clothing designers, and government officials in both countries) and document/documentary research. The quantitative data were analysed using descriptive and inferential statistics, while the qualitative data were analysed using interpretive approaches, such as content analysis. The results indicate significant uses of national cultural elements in the campaign messaging in both Ghana and South Africa, as well as notable differences in the ways in which these campaigns resonated with consumers in the two countries. For instance, cultural differences accounted for high popularity of the campaign in Ghana and low popularity in South Africa. Following from these findings, the study concludes that the discourse on Buy Local and Wear Local, and the use of national culture in commerce, must go beyond the question of efficacy to examine the conditions under which these campaigns can become an effective economic/market tool. The study makes an important contribution to the existing knowledge on national culture, national economy and globalisation.
- Full Text:
- Date Issued: 2017
- Authors: Darku, Esther Naa Dodua
- Date: 2017
- Subjects: Textile industry -- Economic aspects -- Ghana Textile industry -- Economic aspects -- South Africa Sustainable development -- Ghana , Sustainable development -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2172 , vital:27619
- Description: This study examines the use of ‘cultural’ imagery and messaging as a tool to revitalise crucial national industries. Specifically, it examines the use of Wear Local campaigns in Ghana and South Africa as strategies to rejuvenate their textile industries and to make them viable in an increasingly competitive global market. Conceptualising Wear Local campaigns as possessing both cultural and economic imperatives, this study highlights how both factors contribute to making products of Buy Local campaigns marketable by showing their importance as both cultural and economic products. Using a descriptive-evaluative design, the study adopted a triangulated research approach comprising a survey, key informant interviews and document analysis. Survey questionnaires were administered to a total sample of 308 respondents in Ghana and South Africa. The qualitative phase of the study involved 10 key informant interviews (comprising textile labour unions, clothing designers, and government officials in both countries) and document/documentary research. The quantitative data were analysed using descriptive and inferential statistics, while the qualitative data were analysed using interpretive approaches, such as content analysis. The results indicate significant uses of national cultural elements in the campaign messaging in both Ghana and South Africa, as well as notable differences in the ways in which these campaigns resonated with consumers in the two countries. For instance, cultural differences accounted for high popularity of the campaign in Ghana and low popularity in South Africa. Following from these findings, the study concludes that the discourse on Buy Local and Wear Local, and the use of national culture in commerce, must go beyond the question of efficacy to examine the conditions under which these campaigns can become an effective economic/market tool. The study makes an important contribution to the existing knowledge on national culture, national economy and globalisation.
- Full Text:
- Date Issued: 2017
Community structure and trophic relations in marine tufa stromatolite pools of the Eastern Cape
- Authors: Rishworth, Gavin Midgley
- Date: 2017
- Subjects: Bioturbation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/7116 , vital:21236
- Description: Microbialites were the dominant life-form of most shallow oceans during the Precambrian. These structures are formed by the deposition of calcium carbonate by cyanobacteria as well as the binding and trapping of sediment by these and other microalgae. In modern environments they are scarce due to several factors, including grazing pressures by metazoans, altered calcium carbonate saturation states of seawater and competition with macroalgae. The recent discovery of an extensive network of actively accreting layered microbialites (stromatolites) along the South African coastline is potentially informative from this perspective. These stromatolites form within the peritidal zone, at the interface of groundwater seepage and periodic marine incursion, forming pools trapped by the accreting fabric. The aim of this thesis was to characterise the ecosystem dynamics of a representative selection of the South African locations. During a comprehensive monthly assessment over an annual cycle, as well as for additional seasonal collections, physico-chemical measurements were monitored together with biological components such as benthic and pelagic microalgae as well as the invertebrate fauna inhabiting the stromatolite pools. These components were then assessed in terms of the potential physical and biological drivers which might explain patterns of variability. Finally, to link all of the ecosystem components, a food-web analysis was conducted, to determine the trophic linkages and, importantly, the reliance by the various consumer organisms on the stromatolite material as a food resource. Results show that the stromatolite pools are driven by a regular interplay between freshwater and marine salinity states, this being determined by tidal amplitude and ocean storm cycles. Furthermore, marine incursion represents the primary source of phosphorus for the stromatolite pools, while available nitrogen is consistently provided by the freshwater inlet stream at each site. This results in an optimum zone of primary biomass within the main stromatolite pool supported by nutrient conditions, while the shifts in salinity state occurring over a weekly tidal schedule likely exclude organisms and macrophytes that are not halotolerant. This is reflected in the benthic microalgae that form the stromatolite accretions in that they are primarily driven by salinity conditions, in addition to seasonal patterns. Interestingly, the variable nutrient conditions, both between sites and temporally, did not contribute as an important driver of the benthic microalgae but did significantly relate to the pelagic microalgae (phytoplankton). This, together with the higher biomass of benthic microalgae compared to its pelagic counterpart, suggests that the stromatolite pools are a benthic-driven system. The short duration of water retention within the stromatolite pools as a result of the constant freshwater inflow, likely also precludes nutrient build-up and favours the benthic, sessile ecosystem component, especially the stromatolite-forming microalgae. In terms of the metazoan infauna, the South African stromatolite pools support a persistent assemblage. This might be surprising given the apparently destructive influence of grazing and burrowing animals on microbial mats in terms of restricting the formation of layered accretions. However, metazoans that burrow within the stromatolite fabric were observed to coexist with clear, layered accretions. This supports the observations in some other modern microbialite habitats to suggest that metazoan disruption is clearly not the only or primary factor responsible for modern microbialite scarcity. When assessing the possible drivers of the metazoan community occupying the stromatolite matrix, both salinity patterns and resource conditions in terms of nutrient supply and macroalgal cover were consistently best related to infaunal abundance and presence/absence. This further demonstrates the role of salinity conditions in terms of providing a habitat that is restrictive to most metazoan organisms, while also suggesting that the metazoans are responding to macroalgal rather than the stromatolite microalgal conditions. To further develop this observation, the results from the stable isotope work clearly reflect a dominance of pool macroalgae in the diets of invertebrate consumers, with little to no stromatolite material consumed. This suggests that there is limited apparent destructive grazing influence by the metazoans on the stromatolite matrix, in addition to the burrowing bioturbation mentioned previously. Furthermore, the metazoan grazers may be indirectly benefitting the stromatolites by restricting macroalgal biomass, which might otherwise outcompete its microalgal counterpart. This study provides a valuable understanding of benthic-driven peritidal stromatolite ecosystems, and also, from a geological perspective of past stromatolite habitats, suggests some of the mechanisms as to why metazoans may be able to coexist with layered microbialites. Given the threats to similar habitats globally, especially in terms of water resources, management measures necessary to ensure stromatolite persistence in modern environments such as these are proposed. The possible ecological role of peritidal stromatolite habitats within the broader environment, as well as recommendations for future work, is also contextualised.
- Full Text:
- Date Issued: 2017
- Authors: Rishworth, Gavin Midgley
- Date: 2017
- Subjects: Bioturbation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/7116 , vital:21236
- Description: Microbialites were the dominant life-form of most shallow oceans during the Precambrian. These structures are formed by the deposition of calcium carbonate by cyanobacteria as well as the binding and trapping of sediment by these and other microalgae. In modern environments they are scarce due to several factors, including grazing pressures by metazoans, altered calcium carbonate saturation states of seawater and competition with macroalgae. The recent discovery of an extensive network of actively accreting layered microbialites (stromatolites) along the South African coastline is potentially informative from this perspective. These stromatolites form within the peritidal zone, at the interface of groundwater seepage and periodic marine incursion, forming pools trapped by the accreting fabric. The aim of this thesis was to characterise the ecosystem dynamics of a representative selection of the South African locations. During a comprehensive monthly assessment over an annual cycle, as well as for additional seasonal collections, physico-chemical measurements were monitored together with biological components such as benthic and pelagic microalgae as well as the invertebrate fauna inhabiting the stromatolite pools. These components were then assessed in terms of the potential physical and biological drivers which might explain patterns of variability. Finally, to link all of the ecosystem components, a food-web analysis was conducted, to determine the trophic linkages and, importantly, the reliance by the various consumer organisms on the stromatolite material as a food resource. Results show that the stromatolite pools are driven by a regular interplay between freshwater and marine salinity states, this being determined by tidal amplitude and ocean storm cycles. Furthermore, marine incursion represents the primary source of phosphorus for the stromatolite pools, while available nitrogen is consistently provided by the freshwater inlet stream at each site. This results in an optimum zone of primary biomass within the main stromatolite pool supported by nutrient conditions, while the shifts in salinity state occurring over a weekly tidal schedule likely exclude organisms and macrophytes that are not halotolerant. This is reflected in the benthic microalgae that form the stromatolite accretions in that they are primarily driven by salinity conditions, in addition to seasonal patterns. Interestingly, the variable nutrient conditions, both between sites and temporally, did not contribute as an important driver of the benthic microalgae but did significantly relate to the pelagic microalgae (phytoplankton). This, together with the higher biomass of benthic microalgae compared to its pelagic counterpart, suggests that the stromatolite pools are a benthic-driven system. The short duration of water retention within the stromatolite pools as a result of the constant freshwater inflow, likely also precludes nutrient build-up and favours the benthic, sessile ecosystem component, especially the stromatolite-forming microalgae. In terms of the metazoan infauna, the South African stromatolite pools support a persistent assemblage. This might be surprising given the apparently destructive influence of grazing and burrowing animals on microbial mats in terms of restricting the formation of layered accretions. However, metazoans that burrow within the stromatolite fabric were observed to coexist with clear, layered accretions. This supports the observations in some other modern microbialite habitats to suggest that metazoan disruption is clearly not the only or primary factor responsible for modern microbialite scarcity. When assessing the possible drivers of the metazoan community occupying the stromatolite matrix, both salinity patterns and resource conditions in terms of nutrient supply and macroalgal cover were consistently best related to infaunal abundance and presence/absence. This further demonstrates the role of salinity conditions in terms of providing a habitat that is restrictive to most metazoan organisms, while also suggesting that the metazoans are responding to macroalgal rather than the stromatolite microalgal conditions. To further develop this observation, the results from the stable isotope work clearly reflect a dominance of pool macroalgae in the diets of invertebrate consumers, with little to no stromatolite material consumed. This suggests that there is limited apparent destructive grazing influence by the metazoans on the stromatolite matrix, in addition to the burrowing bioturbation mentioned previously. Furthermore, the metazoan grazers may be indirectly benefitting the stromatolites by restricting macroalgal biomass, which might otherwise outcompete its microalgal counterpart. This study provides a valuable understanding of benthic-driven peritidal stromatolite ecosystems, and also, from a geological perspective of past stromatolite habitats, suggests some of the mechanisms as to why metazoans may be able to coexist with layered microbialites. Given the threats to similar habitats globally, especially in terms of water resources, management measures necessary to ensure stromatolite persistence in modern environments such as these are proposed. The possible ecological role of peritidal stromatolite habitats within the broader environment, as well as recommendations for future work, is also contextualised.
- Full Text:
- Date Issued: 2017
Comparative performance of natural and synthetic fibre nonwoven geotextiles
- Tshifularo, Cyrus Alushavhiwi
- Authors: Tshifularo, Cyrus Alushavhiwi
- Date: 2017
- Subjects: Geotextiles Textile fabrics , Textile fibers -- Testing Textile industry -- Quality control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21362 , vital:29504
- Description: The aim of this work was to establish a range of suitable process parameters which can be utilized to produce needlepunched nonwoven fabrics for geotextile applications. Nonwoven fabrics were produced from 100% PP, a blend of 50/50% PP/kenaf and 100% kenaf fibres. The depths of needle penetration of 4, 7 and 10 mm, stroke frequencies of 250, 350 and 450 strokes/min and mass per unit area of 300, 600 and 900 g/m2 were utilized for producing the fabrics, on a Dilo loom. The effect of depth of needle penetration, stroke frequency and mass per unit area on the fabric properties, namely, tensile strength, puncture resistance, pore size, water permeability and transmissivity were analysed. In addition, the effect of chemicals, namely, 10% ammonium hydroxide (NH4OH), 10% sodium chloride (NaCl) and 3% sulphuric acid (H2SO4) solutions on degradation of the fabric was also studied. The results have shown that density, thickness and nominal weight of the needlepunched nonwoven fabrics were related to each other and they were influenced by stroke frequency, depth of needle penetration and feed rate of the needlepunching process. The increase in nominal weight of the fabrics also increases thickness and density of the fabrics. The tensile strength and puncture resistance of the fabrics increased with the increases in stroke frequency, depth of needle penetration and fabric mass per unit area. However, lower tensile strength and puncture resistance were achieved in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area. Bigger pores were resulted in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area, however, pore size decreased with increases in stroke frequency, depth of needle penetration and mass per unit area. Water permeability depends on the pore size, properties of the fibres, stroke frequency, depth of needle penetration and mass per unit area. Higher tensile strength and higher puncture resistance were achieved in the needlepunched nonwoven fabrics produced from 100% PP fibres, therefore, they are suitable for some load-bearing geotextile applications, such as reinforcement and separation. However, higher water permeability was achieved in the fabrics produced from 100% kenaf fibres, therefore, they are ideal for geotextile applications where good water permeability is required. Higher values for transmissivity were obtained in the fabrics produced from a blend of 50/50% PP/kenaf fibres, therefore they are suitable for drainage applications. The fabrics produced from a blend of 50/50% PP/kenaf fibres achieved better values of tensile strength, puncture resistance, pore size and water permeability in comparison to that produced from 100% PP and 100% kenaf fibres. However, better tensile strength and puncture resistance were achieved in the fabrics produced from 100% PP fibres and bigger pore size and higher water permeability were achieved in the fabrics produced from 100% kenaf fibres. Therefore, it can be suggested that the nonwoven fabrics produced from a blend of 50/50% PP/kenaf fibres can fulfil almost all requirements of geotextile applications, such as, filtration, separation, reinforcement and drainage. The fabrics produced from 100% PP fibres were not damaged or deteriorated when treated with all the three chemicals due to chemical inertness of polypropylene. However, the fabrics produced from a blend of 50/50% PP/kenaf and 100% kenaf fibres were damaged and deteriorated when treated with H2SO4.
- Full Text:
- Date Issued: 2017
- Authors: Tshifularo, Cyrus Alushavhiwi
- Date: 2017
- Subjects: Geotextiles Textile fabrics , Textile fibers -- Testing Textile industry -- Quality control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21362 , vital:29504
- Description: The aim of this work was to establish a range of suitable process parameters which can be utilized to produce needlepunched nonwoven fabrics for geotextile applications. Nonwoven fabrics were produced from 100% PP, a blend of 50/50% PP/kenaf and 100% kenaf fibres. The depths of needle penetration of 4, 7 and 10 mm, stroke frequencies of 250, 350 and 450 strokes/min and mass per unit area of 300, 600 and 900 g/m2 were utilized for producing the fabrics, on a Dilo loom. The effect of depth of needle penetration, stroke frequency and mass per unit area on the fabric properties, namely, tensile strength, puncture resistance, pore size, water permeability and transmissivity were analysed. In addition, the effect of chemicals, namely, 10% ammonium hydroxide (NH4OH), 10% sodium chloride (NaCl) and 3% sulphuric acid (H2SO4) solutions on degradation of the fabric was also studied. The results have shown that density, thickness and nominal weight of the needlepunched nonwoven fabrics were related to each other and they were influenced by stroke frequency, depth of needle penetration and feed rate of the needlepunching process. The increase in nominal weight of the fabrics also increases thickness and density of the fabrics. The tensile strength and puncture resistance of the fabrics increased with the increases in stroke frequency, depth of needle penetration and fabric mass per unit area. However, lower tensile strength and puncture resistance were achieved in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area. Bigger pores were resulted in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area, however, pore size decreased with increases in stroke frequency, depth of needle penetration and mass per unit area. Water permeability depends on the pore size, properties of the fibres, stroke frequency, depth of needle penetration and mass per unit area. Higher tensile strength and higher puncture resistance were achieved in the needlepunched nonwoven fabrics produced from 100% PP fibres, therefore, they are suitable for some load-bearing geotextile applications, such as reinforcement and separation. However, higher water permeability was achieved in the fabrics produced from 100% kenaf fibres, therefore, they are ideal for geotextile applications where good water permeability is required. Higher values for transmissivity were obtained in the fabrics produced from a blend of 50/50% PP/kenaf fibres, therefore they are suitable for drainage applications. The fabrics produced from a blend of 50/50% PP/kenaf fibres achieved better values of tensile strength, puncture resistance, pore size and water permeability in comparison to that produced from 100% PP and 100% kenaf fibres. However, better tensile strength and puncture resistance were achieved in the fabrics produced from 100% PP fibres and bigger pore size and higher water permeability were achieved in the fabrics produced from 100% kenaf fibres. Therefore, it can be suggested that the nonwoven fabrics produced from a blend of 50/50% PP/kenaf fibres can fulfil almost all requirements of geotextile applications, such as, filtration, separation, reinforcement and drainage. The fabrics produced from 100% PP fibres were not damaged or deteriorated when treated with all the three chemicals due to chemical inertness of polypropylene. However, the fabrics produced from a blend of 50/50% PP/kenaf and 100% kenaf fibres were damaged and deteriorated when treated with H2SO4.
- Full Text:
- Date Issued: 2017
Conflict prevention, management and resolution in Africa: a case study of the conflict in the Darfur region of Sudan (2003 – 2013)
- Authors: Chukwunaru, Charles Obinna
- Date: 2017
- Subjects: Conflict management -- Sudan -- Darfur -- 21st century Conflict management -- Africa -- Prevention , Africa -- Politics and government
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/14818 , vital:27876
- Description: Africa has witnessed some of the most horrific and devastating conflicts in the world in recent times. This study, concerned about the problem of these seemingly intractable or endemic violent conflicts ravaging the continent of Africa since decolonisation; resulting in poverty, hunger, diseases, massive killing, rape, permanent disability and underdevelopment, examined the issues relating to conflict prevention, management and resolution in Africa. In doing so, it used the conflict in the Darfur region of Sudan as a case study. It examined the role of international organisations, especially that which the African Union and the United Nations played in the prevention, management and resolution of the conflict in the Darfur region of Sudan, as well as the remote and immediate cause of the Darfur conflict and major parties to the Darfur conflict. Other issues examined by this study include the outcome of the United Nations Commission of Inquiry into the violations of international humanitarian law and human rights law, including acts of genocide in Darfur; and the Sudanese government’s response. Moreover, it analysed the implication of the Darfur conflict in the problem of preventing, managing and resolving violent conflict in Africa while drawing some lessons for the African Union, as well as the government of Sudan. However, this research, which adopted the qualitative case study methodology in data collection, presentation and analysis, posits that the protracted violent conflict, which was triggered by some rebel leaders with doubtful motives in the Darfur region of Sudan, who capitalised on the age-long problem of underdevelopment in the Darfur region, as well as low intensity disputes among the tribes over ownership of land and water resources, was avoidable. It further asserts that the African Union lacked the capacity to engage in an effective peace support operation in Africa as witnessed in the failure of its mission in Darfur, which eventually got rescued by the United Nations through the UN-AU Hybrid Mission in Darfur (UNAMID). Further, this study has contributed in narrowing the existing gaps in academic literature on the aspect of conflict prevention management and resolution especially in Africa, even as it introduced the conspiracy theory in the understanding of the issues relating to the conflict in the Darfur region while recommending the immediate operationalisation of the African Union standby force to avert the reoccurrence of the Darfur conflict in Sudan and other parts of Africa, among other strategies aimed at enhancing the capacity and capability of the African Union to prevent, manage and resolve violent conflicts in Africa with or without the intervention of foreign powers. Moreover, this study recommends good governance that will promote political, social and economic justice as well as adherence to the rule of law; against all forms marginalisation, discrimination and other forms of structural violence in Africa. Essentially, this research has made an original contribution to the conflict studies literature with the formulation of the “Violent Intrastate Conflict Model” which explains the conflict dynamics and processes in most violent intrastate conflicts or civil war.
- Full Text:
- Date Issued: 2017
- Authors: Chukwunaru, Charles Obinna
- Date: 2017
- Subjects: Conflict management -- Sudan -- Darfur -- 21st century Conflict management -- Africa -- Prevention , Africa -- Politics and government
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/14818 , vital:27876
- Description: Africa has witnessed some of the most horrific and devastating conflicts in the world in recent times. This study, concerned about the problem of these seemingly intractable or endemic violent conflicts ravaging the continent of Africa since decolonisation; resulting in poverty, hunger, diseases, massive killing, rape, permanent disability and underdevelopment, examined the issues relating to conflict prevention, management and resolution in Africa. In doing so, it used the conflict in the Darfur region of Sudan as a case study. It examined the role of international organisations, especially that which the African Union and the United Nations played in the prevention, management and resolution of the conflict in the Darfur region of Sudan, as well as the remote and immediate cause of the Darfur conflict and major parties to the Darfur conflict. Other issues examined by this study include the outcome of the United Nations Commission of Inquiry into the violations of international humanitarian law and human rights law, including acts of genocide in Darfur; and the Sudanese government’s response. Moreover, it analysed the implication of the Darfur conflict in the problem of preventing, managing and resolving violent conflict in Africa while drawing some lessons for the African Union, as well as the government of Sudan. However, this research, which adopted the qualitative case study methodology in data collection, presentation and analysis, posits that the protracted violent conflict, which was triggered by some rebel leaders with doubtful motives in the Darfur region of Sudan, who capitalised on the age-long problem of underdevelopment in the Darfur region, as well as low intensity disputes among the tribes over ownership of land and water resources, was avoidable. It further asserts that the African Union lacked the capacity to engage in an effective peace support operation in Africa as witnessed in the failure of its mission in Darfur, which eventually got rescued by the United Nations through the UN-AU Hybrid Mission in Darfur (UNAMID). Further, this study has contributed in narrowing the existing gaps in academic literature on the aspect of conflict prevention management and resolution especially in Africa, even as it introduced the conspiracy theory in the understanding of the issues relating to the conflict in the Darfur region while recommending the immediate operationalisation of the African Union standby force to avert the reoccurrence of the Darfur conflict in Sudan and other parts of Africa, among other strategies aimed at enhancing the capacity and capability of the African Union to prevent, manage and resolve violent conflicts in Africa with or without the intervention of foreign powers. Moreover, this study recommends good governance that will promote political, social and economic justice as well as adherence to the rule of law; against all forms marginalisation, discrimination and other forms of structural violence in Africa. Essentially, this research has made an original contribution to the conflict studies literature with the formulation of the “Violent Intrastate Conflict Model” which explains the conflict dynamics and processes in most violent intrastate conflicts or civil war.
- Full Text:
- Date Issued: 2017
Contextual factors influencing the use of learner-centred approaches in the teaching of home economics : a case of two universities in Zimbabwe
- Authors: Motsi, Emily
- Date: 2017
- Subjects: Home economics -- Study and teaching (Higher) -- Zimbabwe Student-centered learning -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8463 , vital:32834
- Description: This study examined contextual factors influencing the use of learner-centred approaches in the teaching of Home Economics in two universities in Zimbabwe. The sample consisted of eight students and four lecturers who were purposively sampled. The study was anchored in the interpretivist paradigm and it adopted a qualitative approach and case-study design. Data collection instruments consisted of structured in-depth interviews, observations and documents. Interviews were conducted with students and lecturers at their respective universities with observations and document analysis inter-spaced in between. Data analysis consisted of a thematic approach where common themes were identified in participants’ responses and analysed and discussed accordingly, with data from observed and documented analysis being used to buttress/refute observations made from the interviews. A number of findings emanated from the study. Students had varied conceptions of learner-centred approaches. Some viewed learner-centred approaches as methods of teaching that were participatory, while others viewed them as learning situations in which learners were actively engaged and developed specific capabilities such as problem-solving. Lecturers conceptualised learner-centred approaches as methods that led to active learner participation with the lecturer playing more of a facilitative role. The study revealed that contextual factors such as time available in each course, flexibility of content, the use of teaching methods characterised by active learner participation, the use of constructive and interactive learning activities, had facilitative as well as inhibiting influences on the use of learner-centred approaches. Social factors such as cooperativeness within the peer group, lecturer availability for consultations, technical staff support as well as structural factors such as the availability of textbooks and e-resources, provision of materials and tools, and access to the internet had a facilitative influence on use of learner-centred approaches. The main inhibitive structural factors were the absence of purpose-built facilities and limited space that caused overcrowding. University administration support for integration of learner-centred approaches was fairly evident in the two universities. To sustain the use of learner-centred approaches, lecturers required support through professional development. The study recommended that universities have well-articulated commitments to use learner-centred approaches through a Teaching and Learning Policy. Home Economics course designers should consider contextual factors in course design and course delivery to ensure effective implementation of learner-centred approaches in the teaching of the subject. Seminars and workshops should be organised by the University Teaching and Learning Centres to enhance the teacher educators’ knowledge on interactive teaching methodologies and strategies for creating student-centred learning environments.
- Full Text:
- Date Issued: 2017
- Authors: Motsi, Emily
- Date: 2017
- Subjects: Home economics -- Study and teaching (Higher) -- Zimbabwe Student-centered learning -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8463 , vital:32834
- Description: This study examined contextual factors influencing the use of learner-centred approaches in the teaching of Home Economics in two universities in Zimbabwe. The sample consisted of eight students and four lecturers who were purposively sampled. The study was anchored in the interpretivist paradigm and it adopted a qualitative approach and case-study design. Data collection instruments consisted of structured in-depth interviews, observations and documents. Interviews were conducted with students and lecturers at their respective universities with observations and document analysis inter-spaced in between. Data analysis consisted of a thematic approach where common themes were identified in participants’ responses and analysed and discussed accordingly, with data from observed and documented analysis being used to buttress/refute observations made from the interviews. A number of findings emanated from the study. Students had varied conceptions of learner-centred approaches. Some viewed learner-centred approaches as methods of teaching that were participatory, while others viewed them as learning situations in which learners were actively engaged and developed specific capabilities such as problem-solving. Lecturers conceptualised learner-centred approaches as methods that led to active learner participation with the lecturer playing more of a facilitative role. The study revealed that contextual factors such as time available in each course, flexibility of content, the use of teaching methods characterised by active learner participation, the use of constructive and interactive learning activities, had facilitative as well as inhibiting influences on the use of learner-centred approaches. Social factors such as cooperativeness within the peer group, lecturer availability for consultations, technical staff support as well as structural factors such as the availability of textbooks and e-resources, provision of materials and tools, and access to the internet had a facilitative influence on use of learner-centred approaches. The main inhibitive structural factors were the absence of purpose-built facilities and limited space that caused overcrowding. University administration support for integration of learner-centred approaches was fairly evident in the two universities. To sustain the use of learner-centred approaches, lecturers required support through professional development. The study recommended that universities have well-articulated commitments to use learner-centred approaches through a Teaching and Learning Policy. Home Economics course designers should consider contextual factors in course design and course delivery to ensure effective implementation of learner-centred approaches in the teaching of the subject. Seminars and workshops should be organised by the University Teaching and Learning Centres to enhance the teacher educators’ knowledge on interactive teaching methodologies and strategies for creating student-centred learning environments.
- Full Text:
- Date Issued: 2017
Crime and punishment Mzansi style: an exploration of the discursive production of criminality and popular justice in South Africa’s Daily Sun
- Authors: Boshoff, Priscilla
- Date: 2017
- Subjects: Daily Sun (South Africa) , Tabloid newpapers -- South Africa , Crime in mass media , Justice in mass media , Police in mass media , Newpapers -- South Africa , Newpapers -- Objectivity -- South Africa , Women -- Violence against -- South Africa -- Press coverage , Witchcraft -- South Africa -- Press coverage , Police -- South Africa -- Press coverage
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/44419 , vital:25406
- Description: The highly popular South African tabloid the Daily Sun, established post-apartheid in 2002, is known for its sensationalist and controversial reporting of black township life. Read by over five million black working class readers, much of its reporting concerns the crimes experienced by them and their struggles for justice. The extraordinarily high rate of violent crime in township areas for which South Africa became infamous during the 1980s did not decrease as much as hoped after the political transition in 1994 and crime overshadowed the first decades of the new administration, adding to the frustrations generated by the slow pace of social and economic reform. Part of the Daily Sun’s success can be attributed to how, around these linked concerns, it fashions for its readers a particular discursive world, Sunland. It is the phatic relationship that the tabloid maintains between itself and its readers which forms the foundation upon which this textual study rests. In approaching the tabloid’s representations of crime I draw on cultural criminological understandings of crime as culture and the formative relationship in this regard between crime and the media. As a preeminent site of cultural production in contemporary society, the media contribute to the ongoing definition of what constitutes crime, who is criminal and what counts as justice. This constructivist approach is congruent with Foucault’s notions of discourse and the subject, and I argue that the various competing discourses about crime and justice which appear in the paper establish a set of subjectivities with which its readers may identity. The thesis explores the rhetorical and discursive means by which such subject positions are constructed within the ‘grid of intelligibility’ created by the Daily Sun’s reportage, and using the spatial metaphor of the ‘map’ I trace the contours of the Daily Sun’s domain with regard to crime and popular justice. To this end, the approach taken is a qualitative one which draws eclectically on a variety of interpretive methods, including semiotic, narrative and discourse analysis. Using these, I map the relations between People’s Justice, the police, gender relations and witchcraft crimes, four areas chosen from a broad thematic content analysis of the complete set of editions from 2011. I show how these are not discreet but co-constructed areas within the coverage, drawing their meaning mutually from a range of conflictual relationships derived from the conditions of post-apartheid social life.
- Full Text:
- Date Issued: 2017
- Authors: Boshoff, Priscilla
- Date: 2017
- Subjects: Daily Sun (South Africa) , Tabloid newpapers -- South Africa , Crime in mass media , Justice in mass media , Police in mass media , Newpapers -- South Africa , Newpapers -- Objectivity -- South Africa , Women -- Violence against -- South Africa -- Press coverage , Witchcraft -- South Africa -- Press coverage , Police -- South Africa -- Press coverage
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/44419 , vital:25406
- Description: The highly popular South African tabloid the Daily Sun, established post-apartheid in 2002, is known for its sensationalist and controversial reporting of black township life. Read by over five million black working class readers, much of its reporting concerns the crimes experienced by them and their struggles for justice. The extraordinarily high rate of violent crime in township areas for which South Africa became infamous during the 1980s did not decrease as much as hoped after the political transition in 1994 and crime overshadowed the first decades of the new administration, adding to the frustrations generated by the slow pace of social and economic reform. Part of the Daily Sun’s success can be attributed to how, around these linked concerns, it fashions for its readers a particular discursive world, Sunland. It is the phatic relationship that the tabloid maintains between itself and its readers which forms the foundation upon which this textual study rests. In approaching the tabloid’s representations of crime I draw on cultural criminological understandings of crime as culture and the formative relationship in this regard between crime and the media. As a preeminent site of cultural production in contemporary society, the media contribute to the ongoing definition of what constitutes crime, who is criminal and what counts as justice. This constructivist approach is congruent with Foucault’s notions of discourse and the subject, and I argue that the various competing discourses about crime and justice which appear in the paper establish a set of subjectivities with which its readers may identity. The thesis explores the rhetorical and discursive means by which such subject positions are constructed within the ‘grid of intelligibility’ created by the Daily Sun’s reportage, and using the spatial metaphor of the ‘map’ I trace the contours of the Daily Sun’s domain with regard to crime and popular justice. To this end, the approach taken is a qualitative one which draws eclectically on a variety of interpretive methods, including semiotic, narrative and discourse analysis. Using these, I map the relations between People’s Justice, the police, gender relations and witchcraft crimes, four areas chosen from a broad thematic content analysis of the complete set of editions from 2011. I show how these are not discreet but co-constructed areas within the coverage, drawing their meaning mutually from a range of conflictual relationships derived from the conditions of post-apartheid social life.
- Full Text:
- Date Issued: 2017
Data compression, field of interest shaping and fast algorithms for direction-dependent deconvolution in radio interferometry
- Authors: Atemkeng, Marcellin T
- Date: 2017
- Subjects: Radio astronomy , Solar radio emission , Radio interferometers , Signal processing -- Digital techniques , Algorithms , Data compression (Computer science)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/6324 , vital:21089
- Description: In radio interferometry, observed visibilities are intrinsically sampled at some interval in time and frequency. Modern interferometers are capable of producing data at very high time and frequency resolution; practical limits on storage and computation costs require that some form of data compression be imposed. The traditional form of compression is simple averaging of the visibilities over coarser time and frequency bins. This has an undesired side effect: the resulting averaged visibilities “decorrelate”, and do so differently depending on the baseline length and averaging interval. This translates into a non-trivial signature in the image domain known as “smearing”, which manifests itself as an attenuation in amplitude towards off-centre sources. With the increasing fields of view and/or longer baselines employed in modern and future instruments, the trade-off between data rate and smearing becomes increasingly unfavourable. Averaging also results in baseline length and a position-dependent point spread function (PSF). In this work, we investigate alternative approaches to low-loss data compression. We show that averaging of the visibility data can be understood as a form of convolution by a boxcar-like window function, and that by employing alternative baseline-dependent window functions a more optimal interferometer smearing response may be induced. Specifically, we can improve amplitude response over a chosen field of interest and attenuate sources outside the field of interest. The main cost of this technique is a reduction in nominal sensitivity; we investigate the smearing vs. sensitivity trade-off and show that in certain regimes a favourable compromise can be achieved. We show the application of this technique to simulated data from the Jansky Very Large Array and the European Very Long Baseline Interferometry Network. Furthermore, we show that the position-dependent PSF shape induced by averaging can be approximated using linear algebraic properties to effectively reduce the computational complexity for evaluating the PSF at each sky position. We conclude by implementing a position-dependent PSF deconvolution in an imaging and deconvolution framework. Using the Low-Frequency Array radio interferometer, we show that deconvolution with position-dependent PSFs results in higher image fidelity compared to a simple CLEAN algorithm and its derivatives.
- Full Text:
- Date Issued: 2017
- Authors: Atemkeng, Marcellin T
- Date: 2017
- Subjects: Radio astronomy , Solar radio emission , Radio interferometers , Signal processing -- Digital techniques , Algorithms , Data compression (Computer science)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/6324 , vital:21089
- Description: In radio interferometry, observed visibilities are intrinsically sampled at some interval in time and frequency. Modern interferometers are capable of producing data at very high time and frequency resolution; practical limits on storage and computation costs require that some form of data compression be imposed. The traditional form of compression is simple averaging of the visibilities over coarser time and frequency bins. This has an undesired side effect: the resulting averaged visibilities “decorrelate”, and do so differently depending on the baseline length and averaging interval. This translates into a non-trivial signature in the image domain known as “smearing”, which manifests itself as an attenuation in amplitude towards off-centre sources. With the increasing fields of view and/or longer baselines employed in modern and future instruments, the trade-off between data rate and smearing becomes increasingly unfavourable. Averaging also results in baseline length and a position-dependent point spread function (PSF). In this work, we investigate alternative approaches to low-loss data compression. We show that averaging of the visibility data can be understood as a form of convolution by a boxcar-like window function, and that by employing alternative baseline-dependent window functions a more optimal interferometer smearing response may be induced. Specifically, we can improve amplitude response over a chosen field of interest and attenuate sources outside the field of interest. The main cost of this technique is a reduction in nominal sensitivity; we investigate the smearing vs. sensitivity trade-off and show that in certain regimes a favourable compromise can be achieved. We show the application of this technique to simulated data from the Jansky Very Large Array and the European Very Long Baseline Interferometry Network. Furthermore, we show that the position-dependent PSF shape induced by averaging can be approximated using linear algebraic properties to effectively reduce the computational complexity for evaluating the PSF at each sky position. We conclude by implementing a position-dependent PSF deconvolution in an imaging and deconvolution framework. Using the Low-Frequency Array radio interferometer, we show that deconvolution with position-dependent PSFs results in higher image fidelity compared to a simple CLEAN algorithm and its derivatives.
- Full Text:
- Date Issued: 2017
Demobilisation and the civilian reintegration of women ex-combatants in post-apartheid South Africa: the aftermath of transnational guerrilla girls, combative mothers and in- betweeners in the shadows of a late twentieth-century war
- Authors: Magadla, Siphokazi
- Date: 2017
- Subjects: South Africa. National Defence Force , Umkhonto we Sizwe (South Africa) -- Demobilization , Azanian People's Liberation Army -- Demobilization , Amabutho Self-Defence Unit -- Demobilization , South Africa. Army -- Women , Women soldiers -- South Africa , Government, Resistance to -- South Africa -- History , Women veterans -- South Africa -- History , Women veterans -- South Africa -- Interviews
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/41775 , vital:25133
- Description: This study examines the state assisted demobilisation and civilian reintegration of women excombatants in post-apartheid South Africa. The study is based on life history interviews conducted with 36 women who fought for Umkhonto we Sizwe (MK), Azanian People’s Liberation Army (APLA) and Amabutho Self-Defence Unit. There is agreement across the literature that the armed struggle against apartheid falls within the category of guerilla warfare, fought in multiple terrains, that blur conventional distinctions of civilian and combatant, homefront and battlefront, as well as the domestic and transnational. Located within feminist International Relations theory, the study argues that the formal process that led to the integration of statutory and non-statutory forces to form the South African National Defence Force, which facilitated the demobilisation process, was framed in ways that did not reflect the unconventional nature of the armed struggle against apartheid. The few women who participated in this process were the transnationally trained combatants of MK and APLA. The majority of women who participated in the multiple and overlapping sites of the domestic and international apartheid battlefront were left out of this process. It is argued that women’s roles in the armed struggle were shaped by various factors, such as age, space and period of struggle. Three categories, guerilla girls, combative mothers and the in-betweeners, are introduced in order to demonstrate the different spaces from within which women fought, and the methods they used, all of which were central to the success of the People’s War strategy. In this regard, the venerated transnationally trained woman combatant, like their male counterpart, is argued to be an exception, as the majority of women were thrust into the armed struggle without military training. Furthermore, it is argued that conservative feminist readings of black women’s relationship with nationalism in the anti-apartheid struggle have misrecognised and undermined women’s combatant contributions, by inscribing their forms of resistance as maternal, and outside the war effort. The study shows that the majority of women combatants have transitioned to civilian life without formal state recognition and assistance. The erasure of women’s role as combatants also means that they are excluded from the current legislative framework facilitated by the Department of Military Veterans to support the welfare of former combatants. As such, the study builds on Jacklyn Cock’s (1991) pioneering study on war and gender in South Africa; it is the first study that exclusively focuses on women ex-combatants’ experiences in postapartheid South Africa.
- Full Text:
- Date Issued: 2017
- Authors: Magadla, Siphokazi
- Date: 2017
- Subjects: South Africa. National Defence Force , Umkhonto we Sizwe (South Africa) -- Demobilization , Azanian People's Liberation Army -- Demobilization , Amabutho Self-Defence Unit -- Demobilization , South Africa. Army -- Women , Women soldiers -- South Africa , Government, Resistance to -- South Africa -- History , Women veterans -- South Africa -- History , Women veterans -- South Africa -- Interviews
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/41775 , vital:25133
- Description: This study examines the state assisted demobilisation and civilian reintegration of women excombatants in post-apartheid South Africa. The study is based on life history interviews conducted with 36 women who fought for Umkhonto we Sizwe (MK), Azanian People’s Liberation Army (APLA) and Amabutho Self-Defence Unit. There is agreement across the literature that the armed struggle against apartheid falls within the category of guerilla warfare, fought in multiple terrains, that blur conventional distinctions of civilian and combatant, homefront and battlefront, as well as the domestic and transnational. Located within feminist International Relations theory, the study argues that the formal process that led to the integration of statutory and non-statutory forces to form the South African National Defence Force, which facilitated the demobilisation process, was framed in ways that did not reflect the unconventional nature of the armed struggle against apartheid. The few women who participated in this process were the transnationally trained combatants of MK and APLA. The majority of women who participated in the multiple and overlapping sites of the domestic and international apartheid battlefront were left out of this process. It is argued that women’s roles in the armed struggle were shaped by various factors, such as age, space and period of struggle. Three categories, guerilla girls, combative mothers and the in-betweeners, are introduced in order to demonstrate the different spaces from within which women fought, and the methods they used, all of which were central to the success of the People’s War strategy. In this regard, the venerated transnationally trained woman combatant, like their male counterpart, is argued to be an exception, as the majority of women were thrust into the armed struggle without military training. Furthermore, it is argued that conservative feminist readings of black women’s relationship with nationalism in the anti-apartheid struggle have misrecognised and undermined women’s combatant contributions, by inscribing their forms of resistance as maternal, and outside the war effort. The study shows that the majority of women combatants have transitioned to civilian life without formal state recognition and assistance. The erasure of women’s role as combatants also means that they are excluded from the current legislative framework facilitated by the Department of Military Veterans to support the welfare of former combatants. As such, the study builds on Jacklyn Cock’s (1991) pioneering study on war and gender in South Africa; it is the first study that exclusively focuses on women ex-combatants’ experiences in postapartheid South Africa.
- Full Text:
- Date Issued: 2017
Determinants of export performance among small to medium enterprises in Zimbabwe
- Karambakuwa, Tapuwa Roseline
- Authors: Karambakuwa, Tapuwa Roseline
- Date: 2017
- Subjects: Economics -- Zimbabwe Small business -- Zimbabwe -- Management , Shipping -- Economic aspects -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/17647 , vital:28424
- Description: There is consensus that Small to Medium Enterprises (SME) exports play a critical role in the development of economies. It has been widely acknowledged in empirical research done around the world that small businesses make a significant contribution to economic development, employment, competitiveness and the reduction of regional disparities. However, empirical literature gives conflicting evidence on the determinants of export performance among SMEs. The study contributes towards the debate on SME exports by: (i) investigating the variables that determine export performance among SMEs in Zimbabwe (ii) establishing the competi-tiveness of Zimbabwe’s exports and (iii) ascertaining the major constraints faced by SME ex-porters in Zimbabwe The researcher gathered data from 120 SMEs and 10 institutions in Zimbabwe for the period 2009 to 2015. SME samples were chosen from Harare, Mashonaland Central and Mashonaland East provinces while all 10 of the institutions were chosen from Harare province. Convenient non-probability sampling method was used to select SMEs while stratified sampling technique was applied in the selection of institutions. Both qualitative and quantitative research methods were employed. For the quantitative approach, panel data ordinary least squares method was used in the form of the gravity model of trade. Export intensity (used as a measure of exports) was regressed against support institutions, business ownership, research & development, educational years, use of export processing zones, product type, export years, firm size, firm age, gender, distance from trading partner, Gross Domestic Product (GDP) of trading partner, and GDP of Zimbabwe. The random effects estimation method was used, basing on results from the Durbin-Wu-Hausman test. The null hypothesis was based on the premise that the variables under study do not determine export intensity of SMEs in Zimbabwe. Other null hypothesis were that the major constraint faced by SME exporters in Zimbabwe is not access to finance and that Zimbabwe’s exports are not competitive in the mining, agricultural and manufacturing sectors. The revealed comparative advantage index was computed to measure the competitiveness of Zimbabwe’s exports.For the qualitative approach, the study used the triangulation method which involved combining and utilising the questionnaire, interviews and focus group discussions. The results from the study indicated that following variables increased export intensity of Zimbabwean SMEs; business ownership, use of export processing zones, export years, firm size, and GDP of trading partner. The following variables have an inverse relationship with the export intensity of Zimbabwean SMEs: gender, distance from trading partner and research & development. The results also indicated that these further variables do not determine the export intensity of SMEs in Zimbabwe: support institutions, years of education, product type, firm age and GDP of Zimbabwe. The major constraint faced by exporting SMEs in Zimbabwe is limited access to finance. Zimbabwe is competitive in the agricultural and mining sector exports, but not in manufacturing sector exports The policy implication of the findings is that SME support needs to go beyond support institutions when it comes to SME export promotion. Further SMEs in the agriculture and mining sectors need to be promoted for export growth since Zimbabwe is competitive in these sectors. However the manufacturing sector cannot be ignored, since many economies have developed due to exports of manufactured products and a country needs to have balanced export growth in both primary and manufacturing sectors. In order to have motivated, career SME exporters, entrepreneurship education should begin from primary school right up to university so as to improve entrepreneurial aspirations, attitudes and behaviour in the long run.
- Full Text:
- Date Issued: 2017
- Authors: Karambakuwa, Tapuwa Roseline
- Date: 2017
- Subjects: Economics -- Zimbabwe Small business -- Zimbabwe -- Management , Shipping -- Economic aspects -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/17647 , vital:28424
- Description: There is consensus that Small to Medium Enterprises (SME) exports play a critical role in the development of economies. It has been widely acknowledged in empirical research done around the world that small businesses make a significant contribution to economic development, employment, competitiveness and the reduction of regional disparities. However, empirical literature gives conflicting evidence on the determinants of export performance among SMEs. The study contributes towards the debate on SME exports by: (i) investigating the variables that determine export performance among SMEs in Zimbabwe (ii) establishing the competi-tiveness of Zimbabwe’s exports and (iii) ascertaining the major constraints faced by SME ex-porters in Zimbabwe The researcher gathered data from 120 SMEs and 10 institutions in Zimbabwe for the period 2009 to 2015. SME samples were chosen from Harare, Mashonaland Central and Mashonaland East provinces while all 10 of the institutions were chosen from Harare province. Convenient non-probability sampling method was used to select SMEs while stratified sampling technique was applied in the selection of institutions. Both qualitative and quantitative research methods were employed. For the quantitative approach, panel data ordinary least squares method was used in the form of the gravity model of trade. Export intensity (used as a measure of exports) was regressed against support institutions, business ownership, research & development, educational years, use of export processing zones, product type, export years, firm size, firm age, gender, distance from trading partner, Gross Domestic Product (GDP) of trading partner, and GDP of Zimbabwe. The random effects estimation method was used, basing on results from the Durbin-Wu-Hausman test. The null hypothesis was based on the premise that the variables under study do not determine export intensity of SMEs in Zimbabwe. Other null hypothesis were that the major constraint faced by SME exporters in Zimbabwe is not access to finance and that Zimbabwe’s exports are not competitive in the mining, agricultural and manufacturing sectors. The revealed comparative advantage index was computed to measure the competitiveness of Zimbabwe’s exports.For the qualitative approach, the study used the triangulation method which involved combining and utilising the questionnaire, interviews and focus group discussions. The results from the study indicated that following variables increased export intensity of Zimbabwean SMEs; business ownership, use of export processing zones, export years, firm size, and GDP of trading partner. The following variables have an inverse relationship with the export intensity of Zimbabwean SMEs: gender, distance from trading partner and research & development. The results also indicated that these further variables do not determine the export intensity of SMEs in Zimbabwe: support institutions, years of education, product type, firm age and GDP of Zimbabwe. The major constraint faced by exporting SMEs in Zimbabwe is limited access to finance. Zimbabwe is competitive in the agricultural and mining sector exports, but not in manufacturing sector exports The policy implication of the findings is that SME support needs to go beyond support institutions when it comes to SME export promotion. Further SMEs in the agriculture and mining sectors need to be promoted for export growth since Zimbabwe is competitive in these sectors. However the manufacturing sector cannot be ignored, since many economies have developed due to exports of manufactured products and a country needs to have balanced export growth in both primary and manufacturing sectors. In order to have motivated, career SME exporters, entrepreneurship education should begin from primary school right up to university so as to improve entrepreneurial aspirations, attitudes and behaviour in the long run.
- Full Text:
- Date Issued: 2017
Determinants of smallholder vegetable farmers' participation on post-harvest practices and market access : evidence from Mashonaland East Province of Zimbabwe
- Authors: Mukarumbwa, Peter
- Date: 2017
- Subjects: Farms, Small -- Zimbabwe Vegetables -- Zimbabwe -- Marketing Vegetable trade -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8703 , vital:33431
- Description: Smallholder vegetable production is very vital in enhancing livelihoods in Zimbabwe’s rural areas. Vegetable production generates household income and improves household food security. Despite this, smallholder vegetable farmers in Zimbabwe suffer huge post-harvest losses which reduce their profits and market competiveness. Post-harvest losses of vegetables are a major dilemma faced by smallholder farmers. They not only represent waste of scare resources such as farm inputs but they also entail wasted investment in terms of time, human effort and food. Furthermore, there are also a myriad of other challenges which constrain smallholder vegetable farmers in Zimbabwe from accessing lucrative markets. The broad objective of the study was to assess smallholder vegetable farmers` preferred post-harvest practices for value addition as well as factors that condition their selection choices, adoption and product market access. The study was conducted in four districts: Seke, Goromonzi, Murehwa and Mutoko, in the Mashonaland East Province of Zimbabwe. A multistage sampling procedure was adopted in the selection of villages and households. A total of 385 smallholder vegetable farmers were interviewed. The survey was undertaken from August–October 2016. Descriptive statistics were employed to analyse the socio-economic and demographic characteristics of households that were sampled in Mashonaland East Province. Age of household head, gender, educational level, household size, farming experience, main sources of income, land ownership, main vegetables produced and main causes of post-harvest losses were some of the statistics that were analysed. The average age of the farmers varied significantly across districts and it was generally high (average of 50 years). Moreover, the average household size was about six (6) individuals, which is an indication of high dependency ratio. The study also revealed the major causes of post-harvest losses across all vegetables predominantly cultivated in the study area were pests and diseases, followed by decay. Most of the underlying causes of huge post-harvest losses were within the control of the farmer. Therefore, the study recommends strategies from policymakers and Non-Governmental Organisations (NGOs) which enhance post-harvest management. These can result in substantial reduction in losses which can increase farmers’ income without necessarily expanding land under cultivation. The Poisson count regression model (PCRM) was used to analyse factors influencing number of post-harvest techniques adopted by smallholder vegetable farmers in the study area. The results of the PCRM revealed that the following variables were significant in influencing number of post-harvest practices adopted by smallholder vegetable growers: gender, education level, household size, age, farming experience, distance to market, market information, group membership, credit, and hired labour. The study recommends concerted efforts through public private partnerships (PPP) to provide active extension about post-harvest education. This will promote the adoption of simple, uncomplicated and innovative low-cost technologies for post-harvest management. The binary logit model was employed to analyse factors that influence smallholder vegetable farmers’ decisions to select a specific post-harvest practice for value addition. This was based on the three major post-harvest practices which were mainly being adopted by smallholder vegetable farmers’ in the study area which were drying, grading and washing. The results of the binary model showed that nine (9) variables were significant in influencing smallholder vegetable farmers’ decisions to select post-harvest practice for value addition. These were: gender, land size, distance to market, market information, family labour, training, target market, quantity produced and storage facilities. Policymakers and other stakeholders need to provide productive resources such as inputs to improve productivity and ultimately selection of basic post-harvest management techniques along the vegetable supply chain. The multinomial logit model was used in the study to analyse factors that influence market channel choice of smallholder vegetable farmers in the study area. The results from the multinomial logistic regression model revealed that distance to market, group membership, adding value, road infrastructure and quantity produced influenced participation in informal markets. On the other hand, gender, distance to market, market information, group membership, producer price, adding value, road infrastructure, quantity produced and market infrastructure influenced farmers’ participation in formal markets. Policies aimed at assisting resources for improved productivity of vegetables should be gender sensitive. Establishment of irrigation schemes as well as provision of credit for smallholder vegetable production are vital interventions. In the same way, crafting of appropriate policies and programmes which foster collective action amongst smallholder vegetable farmers are required. This will enable them to produce larger volumes as well as participate in more lucrative markets. Finally, smallholder vegetable farmers’ transaction costs can be reduced by investment in infrastructure such as roads.
- Full Text:
- Date Issued: 2017
- Authors: Mukarumbwa, Peter
- Date: 2017
- Subjects: Farms, Small -- Zimbabwe Vegetables -- Zimbabwe -- Marketing Vegetable trade -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8703 , vital:33431
- Description: Smallholder vegetable production is very vital in enhancing livelihoods in Zimbabwe’s rural areas. Vegetable production generates household income and improves household food security. Despite this, smallholder vegetable farmers in Zimbabwe suffer huge post-harvest losses which reduce their profits and market competiveness. Post-harvest losses of vegetables are a major dilemma faced by smallholder farmers. They not only represent waste of scare resources such as farm inputs but they also entail wasted investment in terms of time, human effort and food. Furthermore, there are also a myriad of other challenges which constrain smallholder vegetable farmers in Zimbabwe from accessing lucrative markets. The broad objective of the study was to assess smallholder vegetable farmers` preferred post-harvest practices for value addition as well as factors that condition their selection choices, adoption and product market access. The study was conducted in four districts: Seke, Goromonzi, Murehwa and Mutoko, in the Mashonaland East Province of Zimbabwe. A multistage sampling procedure was adopted in the selection of villages and households. A total of 385 smallholder vegetable farmers were interviewed. The survey was undertaken from August–October 2016. Descriptive statistics were employed to analyse the socio-economic and demographic characteristics of households that were sampled in Mashonaland East Province. Age of household head, gender, educational level, household size, farming experience, main sources of income, land ownership, main vegetables produced and main causes of post-harvest losses were some of the statistics that were analysed. The average age of the farmers varied significantly across districts and it was generally high (average of 50 years). Moreover, the average household size was about six (6) individuals, which is an indication of high dependency ratio. The study also revealed the major causes of post-harvest losses across all vegetables predominantly cultivated in the study area were pests and diseases, followed by decay. Most of the underlying causes of huge post-harvest losses were within the control of the farmer. Therefore, the study recommends strategies from policymakers and Non-Governmental Organisations (NGOs) which enhance post-harvest management. These can result in substantial reduction in losses which can increase farmers’ income without necessarily expanding land under cultivation. The Poisson count regression model (PCRM) was used to analyse factors influencing number of post-harvest techniques adopted by smallholder vegetable farmers in the study area. The results of the PCRM revealed that the following variables were significant in influencing number of post-harvest practices adopted by smallholder vegetable growers: gender, education level, household size, age, farming experience, distance to market, market information, group membership, credit, and hired labour. The study recommends concerted efforts through public private partnerships (PPP) to provide active extension about post-harvest education. This will promote the adoption of simple, uncomplicated and innovative low-cost technologies for post-harvest management. The binary logit model was employed to analyse factors that influence smallholder vegetable farmers’ decisions to select a specific post-harvest practice for value addition. This was based on the three major post-harvest practices which were mainly being adopted by smallholder vegetable farmers’ in the study area which were drying, grading and washing. The results of the binary model showed that nine (9) variables were significant in influencing smallholder vegetable farmers’ decisions to select post-harvest practice for value addition. These were: gender, land size, distance to market, market information, family labour, training, target market, quantity produced and storage facilities. Policymakers and other stakeholders need to provide productive resources such as inputs to improve productivity and ultimately selection of basic post-harvest management techniques along the vegetable supply chain. The multinomial logit model was used in the study to analyse factors that influence market channel choice of smallholder vegetable farmers in the study area. The results from the multinomial logistic regression model revealed that distance to market, group membership, adding value, road infrastructure and quantity produced influenced participation in informal markets. On the other hand, gender, distance to market, market information, group membership, producer price, adding value, road infrastructure, quantity produced and market infrastructure influenced farmers’ participation in formal markets. Policies aimed at assisting resources for improved productivity of vegetables should be gender sensitive. Establishment of irrigation schemes as well as provision of credit for smallholder vegetable production are vital interventions. In the same way, crafting of appropriate policies and programmes which foster collective action amongst smallholder vegetable farmers are required. This will enable them to produce larger volumes as well as participate in more lucrative markets. Finally, smallholder vegetable farmers’ transaction costs can be reduced by investment in infrastructure such as roads.
- Full Text:
- Date Issued: 2017
Development and assessment of ketoconazole intravaginal thermosetting hydrogel formulations
- Authors: Ramanah, Ashmita
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5198 , vital:20785
- Description: Imidazole compounds are commonly used as antifungal therapies and ketoconazole was the first broad spectrum orally active azole identified and registered. However, the risks of hepatotoxicity and drug interactions following systemic delivery and absorption of ketoconazole outweigh the therapeutic benefits and ketoconazole was therefore discontinued as first line systemic antifungal therapy in many countries. Although not yet banned in South Africa, the South African Medicine Formulary has ceased to recommend the use of ketoconazole for systemic treatment. Topical use of ketoconazole is, however, regarded as safe following extensive human use as low systemic absorption occurs following topical administration. Vulvo-vaginal candidiasis is a yeast infection that affects a large number of women, some of whom present with several infections annually. The topical treatment options for vulvo-vaginal candidiasis include the use of vaginal tablets, capsules, ovules and creams administered as a single dose or one to three times daily for three to fourteen days either alone or in combination with another dosage form depending on the regimen. Administration of the dose nightly is recommended for most vaginal creams and ovule formulation due to leakage and the uncomfortable feel of the dosage form if administered during the day. A thermosetting gel that remains in the vagina following administration and prolongs the release of ketoconazole from a once daily dose would be a useful addition to the arsenal for intra-vaginal antifungal therapy. Thermosetting gels would be more comfortable to administer as the gel would set in a form similar to naturally occurring mucous in the vagina and, if formulated with a low pH, irritation of the sensitive and fissured tissue would be minimised. A further benefit would be that once set the gel would loosely take on the anatomical shape of the vagina. A simple, precise, accurate, reproducible and sensitive stability-indicating reversed phase-high performance liquid chromatographic method using ultraviolet detection for the quantitation of ketoconazole was developed and validated. The method was specific and was applied to the determination of ketoconazole in commercial and experimental formulations in addition to samples from degradation studies and in vitro release testing. Product performance characteristics of commercial products were investigated with the goal to provide a strategy for the development of a novel intra vaginal gel in the shortest possible time. Characterisation of Xolegel®, Kez® shampoo and Ketazol® cream included an evaluation of pH, viscosity and assay, in addition to spectroscopic and thermal analysis, to identify ideal characteristics of topical products that could be used as targets during formulation development of the gel. An in vitro release method was developed and validated for precision and accuracy and the in vitro release profiles of commercial ketoconazole products were compared using analysis of variance, model dependent and independent approaches. Ketoconazole release data from test gel manufactured during formulation development were investigated to obtain information about the relationship between formulation content and drug release. Poloxamers marketed as Pluronic® and Lutrol® are synthetic non-ionic tri-block copolymers that consist of hydrophobic propylene oxide and hydrophilic polyethylene oxide blocks, which in solution interact to exhibit thermo-reversible behaviour. In situ forming hydrogels consisting of poloxamers, more specifically poloxamer 407, are activated following a temperature stimulus and undergo a sol to gel transition. This approach was used to produce a thermosetting vaginal gel that would exhibit a long residence time in the vagina with an associated enhancement of therapeutic efficacy. Ketoconazole- excipient compatibility was investigated during preformulation studies using spectroscopic and thermal analysis to enable the selection of excipients best suited for the production of a novel dosage form prior to formulation development activities. No obvious interactions between ketoconazole and excipient were observed and ketoconazole was found in an amorphous form when in combination with polysorbate 80 and poloxamers. A two-level factorial design was used to produce solvent systems with different amounts of polysorbate 80, citric acid and ethanol to identify a vehicle in which ketoconazole exhibited optimum solubility and at a pH that would be least irritating to the vaginal mucosa with a low content of excipients. The optimised vehicle consisted of 4% m/v citric acid, 1.5% v/v polysorbate 80 and 9.5% v/v ethanol made up to 50 g with citrate-phosphate buffer adjusted to pH 5.0, resulted in a vehicle of pH of 3.5 in which 71.41 mg of ketoconazole was dissolved per mL. A Central Composite Design was used to evaluate compositions for the modulation of viscosity of the thermosetting dosage form such that it was a liquid at 22 °C that rapidly formed a stiff gel when heated to 37 °C (intra-vaginal temperature) using different amounts of the poloxamer grades 407, 188 and 237. Thermosetting gels containing 2% m/v ketoconazole were manufactured using specifications generated using the Central Composite Design and the viscosity at 22 °C and 37 °C, solution to gel transition time, potency and ketoconazole release at 24, 48 and 72 hours investigated. Contour and three-dimensional response surface plots and mathematical relationships with target ranges set for responses were identified and with the aid of Central Composite Design the optimisation of a desirable thermosetting gel was achieved. The optimised composition included 16% m/v poloxamer 407, 10% m/v poloxamer 188 and 6% m/v poloxamer 237 in the gel that was used as the basis for further optimisation studies. The low ketoconazole release for ketoconazole observed indicated that the poloxamers had formed a gel matrix that sustained the release of ketoconazole and would therefore ensure that once daily administration of the gel was possible. The sol-gel transition test may be used as a simple and cheap alternative to viscosity testing for thermosetting formulations when expensive viscometers and rheometers are unavailable and was successfully used for this purpose.Ketoconazole is photolabile and is prone to degradation in aqueous solutions. The hydrophobic core of micelles formed in these dosage forms are believed to shield ketoconazole molecules and improve stability in aqueous solutions and acidic gels. The thermosetting gel optimised for poloxamer content was subjected to a further Central Composite Design in which sodium metabisulphite content and vehicle pH were investigated. The length of storage was used as a numeric variable and storage condition as a categoric variable at two levels to monitor the stability of the gels. The formulations were investigated at sample times of 0, 1, 2, 4 and 8 weeks at 5 °C, 25 °C and 40 °C. The use of a Central Composite Design facilitated an understanding of the interactions between input variables and their impact on the responses analysed including ketoconazole content, release at 24, 48 and 72 hours, gel pH and viscosity at 22 °C and 37 °C. Design of Experiments may be used as a rapid cost effective tool for an overall assessment of the stability of novel topical dosage forms. However, a more thorough assessment of stability may be required for product registration. Ketoconazole was found to be unstable in the acidic thermosetting gels despite the addition of antioxidant. The gels in liquid form at 5 °C and 25 °C have a low number of micelles for ketoconazole incorporation and therefore additional optimisation studies would be required to enhance the shelf-life of this product.
- Full Text:
- Date Issued: 2017
- Authors: Ramanah, Ashmita
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5198 , vital:20785
- Description: Imidazole compounds are commonly used as antifungal therapies and ketoconazole was the first broad spectrum orally active azole identified and registered. However, the risks of hepatotoxicity and drug interactions following systemic delivery and absorption of ketoconazole outweigh the therapeutic benefits and ketoconazole was therefore discontinued as first line systemic antifungal therapy in many countries. Although not yet banned in South Africa, the South African Medicine Formulary has ceased to recommend the use of ketoconazole for systemic treatment. Topical use of ketoconazole is, however, regarded as safe following extensive human use as low systemic absorption occurs following topical administration. Vulvo-vaginal candidiasis is a yeast infection that affects a large number of women, some of whom present with several infections annually. The topical treatment options for vulvo-vaginal candidiasis include the use of vaginal tablets, capsules, ovules and creams administered as a single dose or one to three times daily for three to fourteen days either alone or in combination with another dosage form depending on the regimen. Administration of the dose nightly is recommended for most vaginal creams and ovule formulation due to leakage and the uncomfortable feel of the dosage form if administered during the day. A thermosetting gel that remains in the vagina following administration and prolongs the release of ketoconazole from a once daily dose would be a useful addition to the arsenal for intra-vaginal antifungal therapy. Thermosetting gels would be more comfortable to administer as the gel would set in a form similar to naturally occurring mucous in the vagina and, if formulated with a low pH, irritation of the sensitive and fissured tissue would be minimised. A further benefit would be that once set the gel would loosely take on the anatomical shape of the vagina. A simple, precise, accurate, reproducible and sensitive stability-indicating reversed phase-high performance liquid chromatographic method using ultraviolet detection for the quantitation of ketoconazole was developed and validated. The method was specific and was applied to the determination of ketoconazole in commercial and experimental formulations in addition to samples from degradation studies and in vitro release testing. Product performance characteristics of commercial products were investigated with the goal to provide a strategy for the development of a novel intra vaginal gel in the shortest possible time. Characterisation of Xolegel®, Kez® shampoo and Ketazol® cream included an evaluation of pH, viscosity and assay, in addition to spectroscopic and thermal analysis, to identify ideal characteristics of topical products that could be used as targets during formulation development of the gel. An in vitro release method was developed and validated for precision and accuracy and the in vitro release profiles of commercial ketoconazole products were compared using analysis of variance, model dependent and independent approaches. Ketoconazole release data from test gel manufactured during formulation development were investigated to obtain information about the relationship between formulation content and drug release. Poloxamers marketed as Pluronic® and Lutrol® are synthetic non-ionic tri-block copolymers that consist of hydrophobic propylene oxide and hydrophilic polyethylene oxide blocks, which in solution interact to exhibit thermo-reversible behaviour. In situ forming hydrogels consisting of poloxamers, more specifically poloxamer 407, are activated following a temperature stimulus and undergo a sol to gel transition. This approach was used to produce a thermosetting vaginal gel that would exhibit a long residence time in the vagina with an associated enhancement of therapeutic efficacy. Ketoconazole- excipient compatibility was investigated during preformulation studies using spectroscopic and thermal analysis to enable the selection of excipients best suited for the production of a novel dosage form prior to formulation development activities. No obvious interactions between ketoconazole and excipient were observed and ketoconazole was found in an amorphous form when in combination with polysorbate 80 and poloxamers. A two-level factorial design was used to produce solvent systems with different amounts of polysorbate 80, citric acid and ethanol to identify a vehicle in which ketoconazole exhibited optimum solubility and at a pH that would be least irritating to the vaginal mucosa with a low content of excipients. The optimised vehicle consisted of 4% m/v citric acid, 1.5% v/v polysorbate 80 and 9.5% v/v ethanol made up to 50 g with citrate-phosphate buffer adjusted to pH 5.0, resulted in a vehicle of pH of 3.5 in which 71.41 mg of ketoconazole was dissolved per mL. A Central Composite Design was used to evaluate compositions for the modulation of viscosity of the thermosetting dosage form such that it was a liquid at 22 °C that rapidly formed a stiff gel when heated to 37 °C (intra-vaginal temperature) using different amounts of the poloxamer grades 407, 188 and 237. Thermosetting gels containing 2% m/v ketoconazole were manufactured using specifications generated using the Central Composite Design and the viscosity at 22 °C and 37 °C, solution to gel transition time, potency and ketoconazole release at 24, 48 and 72 hours investigated. Contour and three-dimensional response surface plots and mathematical relationships with target ranges set for responses were identified and with the aid of Central Composite Design the optimisation of a desirable thermosetting gel was achieved. The optimised composition included 16% m/v poloxamer 407, 10% m/v poloxamer 188 and 6% m/v poloxamer 237 in the gel that was used as the basis for further optimisation studies. The low ketoconazole release for ketoconazole observed indicated that the poloxamers had formed a gel matrix that sustained the release of ketoconazole and would therefore ensure that once daily administration of the gel was possible. The sol-gel transition test may be used as a simple and cheap alternative to viscosity testing for thermosetting formulations when expensive viscometers and rheometers are unavailable and was successfully used for this purpose.Ketoconazole is photolabile and is prone to degradation in aqueous solutions. The hydrophobic core of micelles formed in these dosage forms are believed to shield ketoconazole molecules and improve stability in aqueous solutions and acidic gels. The thermosetting gel optimised for poloxamer content was subjected to a further Central Composite Design in which sodium metabisulphite content and vehicle pH were investigated. The length of storage was used as a numeric variable and storage condition as a categoric variable at two levels to monitor the stability of the gels. The formulations were investigated at sample times of 0, 1, 2, 4 and 8 weeks at 5 °C, 25 °C and 40 °C. The use of a Central Composite Design facilitated an understanding of the interactions between input variables and their impact on the responses analysed including ketoconazole content, release at 24, 48 and 72 hours, gel pH and viscosity at 22 °C and 37 °C. Design of Experiments may be used as a rapid cost effective tool for an overall assessment of the stability of novel topical dosage forms. However, a more thorough assessment of stability may be required for product registration. Ketoconazole was found to be unstable in the acidic thermosetting gels despite the addition of antioxidant. The gels in liquid form at 5 °C and 25 °C have a low number of micelles for ketoconazole incorporation and therefore additional optimisation studies would be required to enhance the shelf-life of this product.
- Full Text:
- Date Issued: 2017
Development communication for water conservation in rural and peri-urban communities : a study of three district municipalities in Eastern Cape, South Africa
- Onyenankeya, Kevin Uwaecheghi
- Authors: Onyenankeya, Kevin Uwaecheghi
- Date: 2017
- Subjects: Communication in rural development -- South Africa -- Eastern Cape Water conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8397 , vital:32562
- Description: South Africa continues to ramp up public campaigns to rein in escalating water demand amid dwindling and erratic supply. One of the objectives of the campaign is to reduce water demand in urban areas to 15 precent by 2030 through water conservation and water demand management strategies. While the water conservation drive continue to gain traction among commercial and urban water users, it does not appear to resonate with rural and peri-urban residents. Using the pragmatic convergent parallel mixed methods approach consisting of the quantitative and qualitative methods such as survey, focus groups, and indepth-interviews and observation, this study explored the water conservation attitudes, behaviour and intentions of rural and peri-urban respondents in four Eastern Cape communities in South Africa, and to determine if any factors influence their attitudes and behaviour. The study also attempted to determine whether a dialogic approach to communication about water conservation is likely to lead to positive change in attitude and behaviour. The questionnaires were distributed personally by researcher and trained assistants but respondents were left to complete the questionnaires at their convenience and in their own pace but within a negotiated period of five working days. The collected data were analysed using both parametric and non-parametric methods. The nonparametric methods used include thematic analysis. Transcripts of focus group and individual interviews were coded using Nvivo, while quantitative data was analysed in SPSS and presented in simple frequency and cross tabulation. Regression analysis was used to establish the influence of attitude, subjective norm and perceived behavioural control on water conservation intention. Results revealed respondents consider water conservation important and are favourably disposed to conserving water. Although peri-urban and rural residents considered water important and would want to make effort to conserve water in the future, not all considered water conservation an overarching social priority and, as a result, are generally passive or indifferent to water conservation. The indifference appears to be underpinned by residents’ beliefs about water. Further analysis showed that peri-urban residents have stronger positive attitude towards water conservation and greater intent and commitment towards water conservation than their rural counterpart. Attitude, subjective norm and behavioural control emerged as significant factors influencing water conservation intentions of respondents. The findings suggest that water curtailment behaviours were the prevalent water conservation activities rural and peri-urban residents engaged in, while water efficiency behaviours was very poor among the population. Factors such as cost, need, knowledge and locus of control had significant influence on residents’ water conservation behaviour and intentions, especially in purchasing or installing water efficient appliances. The study found no significant relationship between sociodemographic such as age, level of education and home tenure on resident’s water conservation behaviour or intentions. The findings indicate that many rural and peri-urban communities do not have adequate information on water conservation, what to do, how to do it and why it should be done and this affects their water conservation behaviour. It was also found that engaging residents through participatory dialogue is effective in raising awareness and stimulating interest in water saving activities. The study concludes that rural and peri-urban residents are yet to develop a social ethic of water conservation. The study highlights the need for concerted education and awareness campaign around water issues so as to build community knowledge and support for water conservation. But to encourage residents to make adjustment in deep-rooted “beliefs, habits, or practices” and change to a sustainable water use behaviour in the face of scarce water supplies and increasing demand, requires not just communication to inform and persuade, but also development communication to foster mutual understanding and collective action.
- Full Text:
- Date Issued: 2017
- Authors: Onyenankeya, Kevin Uwaecheghi
- Date: 2017
- Subjects: Communication in rural development -- South Africa -- Eastern Cape Water conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8397 , vital:32562
- Description: South Africa continues to ramp up public campaigns to rein in escalating water demand amid dwindling and erratic supply. One of the objectives of the campaign is to reduce water demand in urban areas to 15 precent by 2030 through water conservation and water demand management strategies. While the water conservation drive continue to gain traction among commercial and urban water users, it does not appear to resonate with rural and peri-urban residents. Using the pragmatic convergent parallel mixed methods approach consisting of the quantitative and qualitative methods such as survey, focus groups, and indepth-interviews and observation, this study explored the water conservation attitudes, behaviour and intentions of rural and peri-urban respondents in four Eastern Cape communities in South Africa, and to determine if any factors influence their attitudes and behaviour. The study also attempted to determine whether a dialogic approach to communication about water conservation is likely to lead to positive change in attitude and behaviour. The questionnaires were distributed personally by researcher and trained assistants but respondents were left to complete the questionnaires at their convenience and in their own pace but within a negotiated period of five working days. The collected data were analysed using both parametric and non-parametric methods. The nonparametric methods used include thematic analysis. Transcripts of focus group and individual interviews were coded using Nvivo, while quantitative data was analysed in SPSS and presented in simple frequency and cross tabulation. Regression analysis was used to establish the influence of attitude, subjective norm and perceived behavioural control on water conservation intention. Results revealed respondents consider water conservation important and are favourably disposed to conserving water. Although peri-urban and rural residents considered water important and would want to make effort to conserve water in the future, not all considered water conservation an overarching social priority and, as a result, are generally passive or indifferent to water conservation. The indifference appears to be underpinned by residents’ beliefs about water. Further analysis showed that peri-urban residents have stronger positive attitude towards water conservation and greater intent and commitment towards water conservation than their rural counterpart. Attitude, subjective norm and behavioural control emerged as significant factors influencing water conservation intentions of respondents. The findings suggest that water curtailment behaviours were the prevalent water conservation activities rural and peri-urban residents engaged in, while water efficiency behaviours was very poor among the population. Factors such as cost, need, knowledge and locus of control had significant influence on residents’ water conservation behaviour and intentions, especially in purchasing or installing water efficient appliances. The study found no significant relationship between sociodemographic such as age, level of education and home tenure on resident’s water conservation behaviour or intentions. The findings indicate that many rural and peri-urban communities do not have adequate information on water conservation, what to do, how to do it and why it should be done and this affects their water conservation behaviour. It was also found that engaging residents through participatory dialogue is effective in raising awareness and stimulating interest in water saving activities. The study concludes that rural and peri-urban residents are yet to develop a social ethic of water conservation. The study highlights the need for concerted education and awareness campaign around water issues so as to build community knowledge and support for water conservation. But to encourage residents to make adjustment in deep-rooted “beliefs, habits, or practices” and change to a sustainable water use behaviour in the face of scarce water supplies and increasing demand, requires not just communication to inform and persuade, but also development communication to foster mutual understanding and collective action.
- Full Text:
- Date Issued: 2017
Development of conservation strategies for Alepidea Amatymbica ECKL. & ZEYH. : a rare medicinal plant in the Eastern Cape, South Africa
- Mangoale, Ramatsobane Maureen
- Authors: Mangoale, Ramatsobane Maureen
- Date: 2017
- Subjects: Medicinal plants Plants, Cultivated
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/8667 , vital:33400
- Description: Conservation through cultivation has been recommended as a means to relieve overexploitation of medicinal plants. However, the medicinal plants users believe that plants collected from the wild are more potent than cultivated ones. Hence, there is a need for scientific documentation of the potency of cultivated medicinal plants to contribute to the development of a sustainable management strategy to conserve wild populations. This study was aimed at documenting cultivation techniques of a known medicinal plant, Alepidea amatymbica and to validate its medicinal efficacy. In order to identify overexploited medicinal plants in the study area and thus develop their conservation strategy, a survey on the trade of medicinal plants was conducted in selected towns of Amathole District Municipality of the Eastern Cape, South Africa. The survey revealed 67 plants belonging to 46 different families. Twenty-five medicinal plants were identified as overexploited and scarce and they were prioritized for conservation. Furthermore, 69.14 percent of the respondents were not willing to use cultivated medicinal plants. Lack of belief on the potency of cultivated plants and cultivation techniques were mentioned as the most significant constraints to conservation of medicinal plants. Also, the time for cultivated plants to reach maturity deterred herbal medicine practitioners from cultivating them. Alepidea amatymbica was mentioned as one of the most overexploited medicinal plants which has become scarce in the study area. This medicinal plant was therefore selected for this study. In order to develop sustainable conservation program for the species, various studies which include survey on the medicinal plants trade, cultivation, comparative micromorphology, elemental composition, toxicity, phytochemical and antioxidant activity of the wild and cultivated A. amatymbica were conducted. Cultivation of Alepidea amatymbica was conducted to determine the appropriate planting depth and rhizome fragment length for the growth of this plant. The experiment was laid out in a Complete Randomized Block Design (CRBD) with two factors in 6×3 factorial design. There were six levels of fragment length (1, 2, 3, 4, 5 and 6 cm) and three levels of burial depth (2.5, 5 and 7.5 cm). Emergence rate, number of leaves, leaf area, and plant height, number of florets, rhizome length gain, rhizome weight gain, shoot moisture and rhizome moisture were measured as growth parameters. The best overall yield in terms of plant height, shoot emergence, rhizome weight gain, number of florets and number of leaves was observed in 7.5 cm planting depth at 6 cm rhizome length. Four centimetre rhizome length had the highest leaf area of 111.9±3.5 cm2, 101.3±3.5 cm2, 105±3.5 cm2 at 2.5, 5, 7.5 cm planting depth respectively. Shorter fragment lengths showed high potential for vegetative propagation in terms of rhizome length gain at all burial depths. Scanning electron microscopy (SEM) was used to examine the foliar micro morphological characteristics while energy dispersive x-ray spectroscopy (EDXS) was used to determine the elemental composition in different parts of the wild and cultivated plants. The study revealed numerous differences between the wild and cultivated ones. These include deposition of epicuticular waxes, stomatal apparatus, helical thickening of the xylem walls, thickening of the epidermal cell layer and presence of starch grains in the parenchyma cells of the cortex. The EDXS analysis also revealed disproportionate quantities of C, O, Ca, K, Al, Mg, Si, Br and N as the major constituents in both cultivated and wild A. amatymbica specimens. The quantities of elements varied in the different parts of wild and cultivated plants. Toxicity of the methanol, water and acetone extracts of the fresh rhizome of the wild and cultivated A. amatymbica were evaluated using hatchability of cysts and lethality on the hatched cysts (nauplii) of Artemia salina. The highest hatching success was observed in the water extracts of the wild plant (46.16percent) with a MIC of 0.184 mg/ml while the cultivated plants had a hatching success of 40.83percent with MIC of 0.208 mg/ml. Highest mortality was observed in the acetone extract of the wild plants at the lethal dose of 0.191 mg/ml while the cultivated plant had a lethal dose of 0.270 mg/ml. Water extracts of both wild and cultivated plants showed similar lethal dose (LD50) of >1 mg/ml. Methanol extracts of both the wild and cultivated species exhibited almost the same level of toxicity (0.695 mg/ml and 0.628 mg/ml, respectively). Based on the Bastos criterion of toxicity indices of the lethality test, all the plant fractions demonstrated cytotoxicity effect, although the degree of their toxicity varied among the plants used. Standard spectrophotometry assays were used to quantify the phytochemical contents and to determine the antioxidant potentials of the cultivated and wild A. amatymbica. The results revealed different levels of phytochemicals with corresponding antioxidant activities. The wild extracts had higher phytochemical contents in most of the assays than cultivated extracts. Total phenol in the wild extracts ranged from 32.30±3.43 to 117.8±8.45 mg GAE/g with the acetone extracts having the highest content while the water extracts was the least. The range in the total phenol of the cultivated species was 66.46±5.29 to 98.44±6.08 mg GAE/g with the methanol extracts having the highest content while water extracts was the least. The flavonoids content ranged from 55.01±6.51 to 99.09±7.20 mg QE/mg and from 48.65±7.74 to 67.32±4.1 mg QE/mg for the wild and cultivated plants, respectively. The alkaloids contents ranged from 14.70±0.04 to 17.80±0.015 percent in the wild species while it ranged from 11.98±0.14 to 13.21±0.06 percent in the cultivated species. The wild species also showed higher antioxidant activities in most of the assays evaluated. The study revealed successful cultivation of the wild species of Alepidea amatymbica using fragments from the rhizome. The micromorphological study of both the wild and cultivated species showed minimal differences in the helical thickening of the walls in the xylem vessels and starch grain accumulation pattern. Although herbal medicine practitioners believe that cultivated species are not potent, however this study revealed some levels of phytochemicals contents and antioxidant activities which are comparable to the wild species. Cultivation is a major strategy in conserving nature and their resources. Hence, the successful domestication of A. amatymbica would help in reducing the pressure on the wild species while also meeting their medicinal demands purposes, utilisation and conserving for future generations.
- Full Text:
- Date Issued: 2017
- Authors: Mangoale, Ramatsobane Maureen
- Date: 2017
- Subjects: Medicinal plants Plants, Cultivated
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/8667 , vital:33400
- Description: Conservation through cultivation has been recommended as a means to relieve overexploitation of medicinal plants. However, the medicinal plants users believe that plants collected from the wild are more potent than cultivated ones. Hence, there is a need for scientific documentation of the potency of cultivated medicinal plants to contribute to the development of a sustainable management strategy to conserve wild populations. This study was aimed at documenting cultivation techniques of a known medicinal plant, Alepidea amatymbica and to validate its medicinal efficacy. In order to identify overexploited medicinal plants in the study area and thus develop their conservation strategy, a survey on the trade of medicinal plants was conducted in selected towns of Amathole District Municipality of the Eastern Cape, South Africa. The survey revealed 67 plants belonging to 46 different families. Twenty-five medicinal plants were identified as overexploited and scarce and they were prioritized for conservation. Furthermore, 69.14 percent of the respondents were not willing to use cultivated medicinal plants. Lack of belief on the potency of cultivated plants and cultivation techniques were mentioned as the most significant constraints to conservation of medicinal plants. Also, the time for cultivated plants to reach maturity deterred herbal medicine practitioners from cultivating them. Alepidea amatymbica was mentioned as one of the most overexploited medicinal plants which has become scarce in the study area. This medicinal plant was therefore selected for this study. In order to develop sustainable conservation program for the species, various studies which include survey on the medicinal plants trade, cultivation, comparative micromorphology, elemental composition, toxicity, phytochemical and antioxidant activity of the wild and cultivated A. amatymbica were conducted. Cultivation of Alepidea amatymbica was conducted to determine the appropriate planting depth and rhizome fragment length for the growth of this plant. The experiment was laid out in a Complete Randomized Block Design (CRBD) with two factors in 6×3 factorial design. There were six levels of fragment length (1, 2, 3, 4, 5 and 6 cm) and three levels of burial depth (2.5, 5 and 7.5 cm). Emergence rate, number of leaves, leaf area, and plant height, number of florets, rhizome length gain, rhizome weight gain, shoot moisture and rhizome moisture were measured as growth parameters. The best overall yield in terms of plant height, shoot emergence, rhizome weight gain, number of florets and number of leaves was observed in 7.5 cm planting depth at 6 cm rhizome length. Four centimetre rhizome length had the highest leaf area of 111.9±3.5 cm2, 101.3±3.5 cm2, 105±3.5 cm2 at 2.5, 5, 7.5 cm planting depth respectively. Shorter fragment lengths showed high potential for vegetative propagation in terms of rhizome length gain at all burial depths. Scanning electron microscopy (SEM) was used to examine the foliar micro morphological characteristics while energy dispersive x-ray spectroscopy (EDXS) was used to determine the elemental composition in different parts of the wild and cultivated plants. The study revealed numerous differences between the wild and cultivated ones. These include deposition of epicuticular waxes, stomatal apparatus, helical thickening of the xylem walls, thickening of the epidermal cell layer and presence of starch grains in the parenchyma cells of the cortex. The EDXS analysis also revealed disproportionate quantities of C, O, Ca, K, Al, Mg, Si, Br and N as the major constituents in both cultivated and wild A. amatymbica specimens. The quantities of elements varied in the different parts of wild and cultivated plants. Toxicity of the methanol, water and acetone extracts of the fresh rhizome of the wild and cultivated A. amatymbica were evaluated using hatchability of cysts and lethality on the hatched cysts (nauplii) of Artemia salina. The highest hatching success was observed in the water extracts of the wild plant (46.16percent) with a MIC of 0.184 mg/ml while the cultivated plants had a hatching success of 40.83percent with MIC of 0.208 mg/ml. Highest mortality was observed in the acetone extract of the wild plants at the lethal dose of 0.191 mg/ml while the cultivated plant had a lethal dose of 0.270 mg/ml. Water extracts of both wild and cultivated plants showed similar lethal dose (LD50) of >1 mg/ml. Methanol extracts of both the wild and cultivated species exhibited almost the same level of toxicity (0.695 mg/ml and 0.628 mg/ml, respectively). Based on the Bastos criterion of toxicity indices of the lethality test, all the plant fractions demonstrated cytotoxicity effect, although the degree of their toxicity varied among the plants used. Standard spectrophotometry assays were used to quantify the phytochemical contents and to determine the antioxidant potentials of the cultivated and wild A. amatymbica. The results revealed different levels of phytochemicals with corresponding antioxidant activities. The wild extracts had higher phytochemical contents in most of the assays than cultivated extracts. Total phenol in the wild extracts ranged from 32.30±3.43 to 117.8±8.45 mg GAE/g with the acetone extracts having the highest content while the water extracts was the least. The range in the total phenol of the cultivated species was 66.46±5.29 to 98.44±6.08 mg GAE/g with the methanol extracts having the highest content while water extracts was the least. The flavonoids content ranged from 55.01±6.51 to 99.09±7.20 mg QE/mg and from 48.65±7.74 to 67.32±4.1 mg QE/mg for the wild and cultivated plants, respectively. The alkaloids contents ranged from 14.70±0.04 to 17.80±0.015 percent in the wild species while it ranged from 11.98±0.14 to 13.21±0.06 percent in the cultivated species. The wild species also showed higher antioxidant activities in most of the assays evaluated. The study revealed successful cultivation of the wild species of Alepidea amatymbica using fragments from the rhizome. The micromorphological study of both the wild and cultivated species showed minimal differences in the helical thickening of the walls in the xylem vessels and starch grain accumulation pattern. Although herbal medicine practitioners believe that cultivated species are not potent, however this study revealed some levels of phytochemicals contents and antioxidant activities which are comparable to the wild species. Cultivation is a major strategy in conserving nature and their resources. Hence, the successful domestication of A. amatymbica would help in reducing the pressure on the wild species while also meeting their medicinal demands purposes, utilisation and conserving for future generations.
- Full Text:
- Date Issued: 2017
Differentiating engagement of opportunity identification: a grounded theory study of Chinese immigrant entreprenuers
- Ndoro, Tinashe Tsungai Raphael
- Authors: Ndoro, Tinashe Tsungai Raphael
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5568 , vital:20942
- Description: The aim of this study was to develop a substantive grounded theory describing how Chinese immigrant entrepreneurs who own and operate small retail businesses in the Eastern Cape province of South Africa identify opportunities in the business environment. The substantive grounded theory was developed using the prescripts of grounded theory proposed by Strauss and Corbin (1990). In this respect, a substantive grounded theory called differentiating engagement of opportunity identification was developed from a sample of 41 qualitative interviews conducted with Chinese immigrant entrepreneurs. The study found that Chinese immigrant entrepreneurs identified various opportunities (startup, sales, operational, relational) in the business environment through their dynamic interactions and relationships with different stakeholders. These stakeholders mainly included family members, local employees and customers. The Chinese immigrant entrepreneurs displayed two interactional processes in their interactions with stakeholders, namely engaging in and disengaging from interactions. These interactional processes enabled the Chinese immigrant entrepreneurs to identify opportunities and operate their small businesses in the business environment. Assumptions held about the interactions and relationships with stakeholders in the host community were central to the interactional processes displayed by the Chinese immigrant entrepreneurs. As they operated their small businesses, the Chinese immigrant entrepreneurs would engage in interactions with customers who were perceived as favourable (approachable). From these interactions with favourable (approachable) customers, the Chinese immigrant entrepreneurs were able to identify opportunities (gaining customer insight of opportunity), whereas they would disengage from interactions with customers perceived as unfavourable (unapproachable). In this respect, they would delegate their local employees (actions of delegation in business) with the responsibility of interacting with unfavourable and hostile customers. Additionally, the Chinese immigrant entrepreneurs would engage in interactions with local employees to gain insight into local indigenous products and identify opportunities in the host community. In order to identify other opportunities (operational, relational), the Chinese immigrant entrepreneurs would disengage from interactions with local employees and engage in interactions with other stakeholders such as family members. The varying differentiated interactions and relationships established by the Chinese immigrant entrepreneurs with different stakeholders created a relational context which enabled the identification of opportunities in the host environment. Thus, the findings of the present study and the substantive grounded theory developed (differentiating engagement of opportunity identification) are discussed from the perspective of social capital, social exchange theory and Chinese cultural values. Finally, the theory developed in the present study contributes to the understanding of the processes of how social capital and relationships contribute to the process of identifying opportunities and operating a small business by immigrant entrepreneurs within a host environment.
- Full Text:
- Date Issued: 2017
- Authors: Ndoro, Tinashe Tsungai Raphael
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5568 , vital:20942
- Description: The aim of this study was to develop a substantive grounded theory describing how Chinese immigrant entrepreneurs who own and operate small retail businesses in the Eastern Cape province of South Africa identify opportunities in the business environment. The substantive grounded theory was developed using the prescripts of grounded theory proposed by Strauss and Corbin (1990). In this respect, a substantive grounded theory called differentiating engagement of opportunity identification was developed from a sample of 41 qualitative interviews conducted with Chinese immigrant entrepreneurs. The study found that Chinese immigrant entrepreneurs identified various opportunities (startup, sales, operational, relational) in the business environment through their dynamic interactions and relationships with different stakeholders. These stakeholders mainly included family members, local employees and customers. The Chinese immigrant entrepreneurs displayed two interactional processes in their interactions with stakeholders, namely engaging in and disengaging from interactions. These interactional processes enabled the Chinese immigrant entrepreneurs to identify opportunities and operate their small businesses in the business environment. Assumptions held about the interactions and relationships with stakeholders in the host community were central to the interactional processes displayed by the Chinese immigrant entrepreneurs. As they operated their small businesses, the Chinese immigrant entrepreneurs would engage in interactions with customers who were perceived as favourable (approachable). From these interactions with favourable (approachable) customers, the Chinese immigrant entrepreneurs were able to identify opportunities (gaining customer insight of opportunity), whereas they would disengage from interactions with customers perceived as unfavourable (unapproachable). In this respect, they would delegate their local employees (actions of delegation in business) with the responsibility of interacting with unfavourable and hostile customers. Additionally, the Chinese immigrant entrepreneurs would engage in interactions with local employees to gain insight into local indigenous products and identify opportunities in the host community. In order to identify other opportunities (operational, relational), the Chinese immigrant entrepreneurs would disengage from interactions with local employees and engage in interactions with other stakeholders such as family members. The varying differentiated interactions and relationships established by the Chinese immigrant entrepreneurs with different stakeholders created a relational context which enabled the identification of opportunities in the host environment. Thus, the findings of the present study and the substantive grounded theory developed (differentiating engagement of opportunity identification) are discussed from the perspective of social capital, social exchange theory and Chinese cultural values. Finally, the theory developed in the present study contributes to the understanding of the processes of how social capital and relationships contribute to the process of identifying opportunities and operating a small business by immigrant entrepreneurs within a host environment.
- Full Text:
- Date Issued: 2017