Nutrient supplementation and secondary metaolites in melanoma cells
- Authors: Stoll, Karin Elisabeth
- Date: 1994
- Subjects: Vitamin C -- Therapeutic use Cancer -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4049 , http://hdl.handle.net/10962/d1004110
- Description: Considerable interest exists with regard to the putative therapeutic role of ascorbic acid in various conditions. A condition which has received much attention is cancer, as it is reported that ascorbic acid may be a prophylactic against cancer development. However, the actual involvement of ascorbic acid, an oxidizing/reducing agent, in the development and progression of tumours is presently a subject of much speculation. This study initially addressed the effect of ascorbic acid supplementation over a nutritional concentration range (0 - 100 μg/ml) on the in vitro growth of non-malignant LLCMK and malignant B16 cells. Ascorbic acid supplementation of these two cell types resulted in an overall decrease in the growth of both types of cells. The actual inhibitory mechanism of ascorbic acid on cell growth was not clear. Further study attempted to define and explain a mechanism responsible for this effect. Ascorbic acid has a role in the maintenance of tissue integrity and host defences, thus providing a rational basis for examining its relationship to cancer. Ascorbic acid is lcnown to be essential for the structural integrity of the intercellular matrix of the cells, the latter being a complex aqueous gel containing, amongst other compounds, fats and prostaglandins. Fats and prostaglandins have diverse effects on. membrane stability, enzyme activity and secondary messengers within cells. Hence, this study investigated the effect of ascorbic acid supplementation on certain enzymes and secondary metabolites within the cells, which had the potential to be involved in the control of cell growth. Throughout this study, emphasis was placed on the Bl6 melanoma cells as ascorbic acid supplementation did not significantly affect levels of secondary metabolites within the non-malignant LLCMK cells. Ascorbic acid supplementation of the B16 cells resulted in significant increases in adenylate cyclase activity and cyclic adenosine monophosphate levels, witb a significant decrease in Bl6 cell growth in that particular experiment. As cyclic adenosine monophosphate has a regulatory role in the cell cycle, this study suggested that the inhibitory effect of ascorbic acid supplementation on cell growth was mediated tbrough a final effect provided by the second messenger, cyclic adenosine monophosphate. However, clarification of tbe mechanism of tbe effect of ascorbic acid on adenylate cyclase activity was required. Hence, a further study investigated prostaglandin E₂ levels, as tbese affect adenylate cyclase activity. Prostaglandin E₂ levels were also found to be inversely related to Bl6 cell growth with ascorbic acid supplementation. It thus appeared tbat adenylate cyclase activity was dependent on prostaglandin E₂ levels in the B16 cells, and further study showed that tbis was indeed the case. Here, higher levels of prostaglandin E₂ supplementation of the Bl6 cells inhibited cell growth significantly and also significantly increased adenylate cyclase activity. Arachidonic acid is the precursor of prostaglandin E₂. In the presence of ascorbic acid supplementation, the percentage arachidonic acid composition of the Bl6 cells was inversely correlated with cell growth. Hence, prostaglandin E₂ levels in ascorbic acid supplemented B16 cells appeared dependent on tbe amount of precursor present. This was confirmed when Bl6 cells were supplemented with arachidonic acid. The latter had an inhibitory effect on Bl6 cell growth and also stimulated prostaglandin E₂ production. The cause of tbe inverse relationship between B16 cell growth and arachidonic acid composition with ascorbic acid supplementation was furtber investigated and found to be dependent on tbe uptake of arachidonic acid and other essential fatty acids from tbe medium. The enzymes phospholipase A₂ delta-5 and delta-6-desaturase, and elongase which could influence arachidonic acid levels were not affected to any extent by ascorbic acid supplementation and therefore did not influence the inverse relationship between B16 cell growth and arachidonic acid. Hence, it can be concluded that the effect of ascorbic acid supplementation on the BI6 cells is mediated, in part at least, by cyclic adenosine monophosphate. However, this is not the result of a direct effect of ascorbic acid supplementation. The initial effect of ascorbic acid supplementation concerns fatty acid - in particular arachidonic acid - uptake from the medium, with subsequent cascade effects On secondary metabolites, ultimately affecting the cellular levels of cyclic adenosine monophosphate.
- Full Text:
- Date Issued: 1994
- Authors: Stoll, Karin Elisabeth
- Date: 1994
- Subjects: Vitamin C -- Therapeutic use Cancer -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4049 , http://hdl.handle.net/10962/d1004110
- Description: Considerable interest exists with regard to the putative therapeutic role of ascorbic acid in various conditions. A condition which has received much attention is cancer, as it is reported that ascorbic acid may be a prophylactic against cancer development. However, the actual involvement of ascorbic acid, an oxidizing/reducing agent, in the development and progression of tumours is presently a subject of much speculation. This study initially addressed the effect of ascorbic acid supplementation over a nutritional concentration range (0 - 100 μg/ml) on the in vitro growth of non-malignant LLCMK and malignant B16 cells. Ascorbic acid supplementation of these two cell types resulted in an overall decrease in the growth of both types of cells. The actual inhibitory mechanism of ascorbic acid on cell growth was not clear. Further study attempted to define and explain a mechanism responsible for this effect. Ascorbic acid has a role in the maintenance of tissue integrity and host defences, thus providing a rational basis for examining its relationship to cancer. Ascorbic acid is lcnown to be essential for the structural integrity of the intercellular matrix of the cells, the latter being a complex aqueous gel containing, amongst other compounds, fats and prostaglandins. Fats and prostaglandins have diverse effects on. membrane stability, enzyme activity and secondary messengers within cells. Hence, this study investigated the effect of ascorbic acid supplementation on certain enzymes and secondary metabolites within the cells, which had the potential to be involved in the control of cell growth. Throughout this study, emphasis was placed on the Bl6 melanoma cells as ascorbic acid supplementation did not significantly affect levels of secondary metabolites within the non-malignant LLCMK cells. Ascorbic acid supplementation of the B16 cells resulted in significant increases in adenylate cyclase activity and cyclic adenosine monophosphate levels, witb a significant decrease in Bl6 cell growth in that particular experiment. As cyclic adenosine monophosphate has a regulatory role in the cell cycle, this study suggested that the inhibitory effect of ascorbic acid supplementation on cell growth was mediated tbrough a final effect provided by the second messenger, cyclic adenosine monophosphate. However, clarification of tbe mechanism of tbe effect of ascorbic acid on adenylate cyclase activity was required. Hence, a further study investigated prostaglandin E₂ levels, as tbese affect adenylate cyclase activity. Prostaglandin E₂ levels were also found to be inversely related to Bl6 cell growth with ascorbic acid supplementation. It thus appeared tbat adenylate cyclase activity was dependent on prostaglandin E₂ levels in the B16 cells, and further study showed that tbis was indeed the case. Here, higher levels of prostaglandin E₂ supplementation of the Bl6 cells inhibited cell growth significantly and also significantly increased adenylate cyclase activity. Arachidonic acid is the precursor of prostaglandin E₂. In the presence of ascorbic acid supplementation, the percentage arachidonic acid composition of the Bl6 cells was inversely correlated with cell growth. Hence, prostaglandin E₂ levels in ascorbic acid supplemented B16 cells appeared dependent on tbe amount of precursor present. This was confirmed when Bl6 cells were supplemented with arachidonic acid. The latter had an inhibitory effect on Bl6 cell growth and also stimulated prostaglandin E₂ production. The cause of tbe inverse relationship between B16 cell growth and arachidonic acid composition with ascorbic acid supplementation was furtber investigated and found to be dependent on tbe uptake of arachidonic acid and other essential fatty acids from tbe medium. The enzymes phospholipase A₂ delta-5 and delta-6-desaturase, and elongase which could influence arachidonic acid levels were not affected to any extent by ascorbic acid supplementation and therefore did not influence the inverse relationship between B16 cell growth and arachidonic acid. Hence, it can be concluded that the effect of ascorbic acid supplementation on the BI6 cells is mediated, in part at least, by cyclic adenosine monophosphate. However, this is not the result of a direct effect of ascorbic acid supplementation. The initial effect of ascorbic acid supplementation concerns fatty acid - in particular arachidonic acid - uptake from the medium, with subsequent cascade effects On secondary metabolites, ultimately affecting the cellular levels of cyclic adenosine monophosphate.
- Full Text:
- Date Issued: 1994
Evaluation of Gratiana spadicea (Klug, 1829) and Metriona elatior (Klug, 1829) (Chrysomelidae: Cassidinae) for the biological control of sticky nightshade Solanum sisymbriifolium Lamarck (Solanaceae) in South Africa
- Authors: Hill, Martin Patrick
- Date: 1995
- Subjects: Solanaceae Solanaceae -- Biological control Chrysomelidae Chrysomelidae -- Host plants Cassida
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5688 , http://hdl.handle.net/10962/d1005374 , https://orcid.org/0000-0003-0579-5298
- Description: Solanum sisymbriifolium (sticky nightshade) is a shrubby weed of South American origin that was introduced to South Africa at the turn of the century. Despite being indicative of disturbed habitats, the weed was found to be invasive in conservation, agricultural recreational and suburban areas; this, coupled with the failure of both chemical and mechanical control attempts suggested that the weed was a good candidate for biological control. A biological control programme which followed a standard protocol was initiated. Observations suggested that S. sisymbriifolium dispersed primarily by seeds. Plants produced large quantities of fleshy fruit, favoured by frugivorous birds, which facilitated the rapid spread of the weed into new habitats. The seeds germinated quickly, especially in disturbed soil, often below the parent plant where they dropped from burst fruit, and along fences where birds roost. The pre-introductory survey of the weed revealed that S. sisymbriifolium was attacked by a relatively small number of, mainly polyphagous, herbivorous insects. These were localised and sporadic in incidence and inflicted very little observable damage. The herbivore fauna of S. sisymbriifolium was depauperate even in relation to two other exotic weeds, S. elaeaglllfolium and S. mauritianum, in South Africa. The paucity of native herbivores on S. sisymbriifoliwn was ascribed to a combination of the weed's taxonomic distinctness from South African Solanum species, and the dense covering of glandular trichomes on its leaves. Although it was shown that the exudate produced by these glandular trichomes of S. sisymbriifolium seriously impeded the movement and feeding of native herbivores, there was not enough evidence to suggest that the glandular trichomes, alone could have been responsible the lack of herbivores on the weed. Two leaf-feeding Cassidinae Gratiana spadicea and MetJ-iona elatior were screened as agents for the biological control of S. sisymbrilfolium. Favourable biological characteristics for both species included a high rate of increase, long-lived adults, many generations per year, and a high per capita feeding rate. Host range was investigated in larval survival tests and adult choice tests. The larvae of both species were reared through to the adult stage on several of the native Solanum species tested, and also on eggplant (S. melongena). However, the survival of G. spadicea on the majority of these species was very low, suggesting that the beetles would be unlikely to attack them in the field. This was supported by the adult choice tests, where G. spadicea females displayed, a strong oviposition preference for their natural host. In contrast, M. elatior larvae survived well on non-host plants, and the females selected several non-host species, including eggplant for oviposition. It was argued that the conflict of interests involving eggplant was overrated because eggplant is subjected to a stringent insecticide spray regime. Based on this evidence, permission for release was granted for G. spadicea. The impact of native parasitoid host range extensions to weed biological control agents in South Africa was investigated. Native parasitoids were recorded from nearly half of the agent species that had established on their target weed. The level of concealment and taxon influenced susceptibility of the agents to parasitoid attack Poorly concealed endophagous agents were most susceptible to attack, while exposed feeders were fairly free from attack. However, native parasitoids were reported not to strongly influence weed biological control agent populations and it was concluded that no agent should be rejected based only on its susceptibility to native parasitoid attack. Finally, several predictions are made as to the potential success of G. spadicea on S. sisymbriifolium and some of the challenges facing the biological control of weeds are discussed.
- Full Text:
- Date Issued: 1995
- Authors: Hill, Martin Patrick
- Date: 1995
- Subjects: Solanaceae Solanaceae -- Biological control Chrysomelidae Chrysomelidae -- Host plants Cassida
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5688 , http://hdl.handle.net/10962/d1005374 , https://orcid.org/0000-0003-0579-5298
- Description: Solanum sisymbriifolium (sticky nightshade) is a shrubby weed of South American origin that was introduced to South Africa at the turn of the century. Despite being indicative of disturbed habitats, the weed was found to be invasive in conservation, agricultural recreational and suburban areas; this, coupled with the failure of both chemical and mechanical control attempts suggested that the weed was a good candidate for biological control. A biological control programme which followed a standard protocol was initiated. Observations suggested that S. sisymbriifolium dispersed primarily by seeds. Plants produced large quantities of fleshy fruit, favoured by frugivorous birds, which facilitated the rapid spread of the weed into new habitats. The seeds germinated quickly, especially in disturbed soil, often below the parent plant where they dropped from burst fruit, and along fences where birds roost. The pre-introductory survey of the weed revealed that S. sisymbriifolium was attacked by a relatively small number of, mainly polyphagous, herbivorous insects. These were localised and sporadic in incidence and inflicted very little observable damage. The herbivore fauna of S. sisymbriifolium was depauperate even in relation to two other exotic weeds, S. elaeaglllfolium and S. mauritianum, in South Africa. The paucity of native herbivores on S. sisymbriifoliwn was ascribed to a combination of the weed's taxonomic distinctness from South African Solanum species, and the dense covering of glandular trichomes on its leaves. Although it was shown that the exudate produced by these glandular trichomes of S. sisymbriifolium seriously impeded the movement and feeding of native herbivores, there was not enough evidence to suggest that the glandular trichomes, alone could have been responsible the lack of herbivores on the weed. Two leaf-feeding Cassidinae Gratiana spadicea and MetJ-iona elatior were screened as agents for the biological control of S. sisymbrilfolium. Favourable biological characteristics for both species included a high rate of increase, long-lived adults, many generations per year, and a high per capita feeding rate. Host range was investigated in larval survival tests and adult choice tests. The larvae of both species were reared through to the adult stage on several of the native Solanum species tested, and also on eggplant (S. melongena). However, the survival of G. spadicea on the majority of these species was very low, suggesting that the beetles would be unlikely to attack them in the field. This was supported by the adult choice tests, where G. spadicea females displayed, a strong oviposition preference for their natural host. In contrast, M. elatior larvae survived well on non-host plants, and the females selected several non-host species, including eggplant for oviposition. It was argued that the conflict of interests involving eggplant was overrated because eggplant is subjected to a stringent insecticide spray regime. Based on this evidence, permission for release was granted for G. spadicea. The impact of native parasitoid host range extensions to weed biological control agents in South Africa was investigated. Native parasitoids were recorded from nearly half of the agent species that had established on their target weed. The level of concealment and taxon influenced susceptibility of the agents to parasitoid attack Poorly concealed endophagous agents were most susceptible to attack, while exposed feeders were fairly free from attack. However, native parasitoids were reported not to strongly influence weed biological control agent populations and it was concluded that no agent should be rejected based only on its susceptibility to native parasitoid attack. Finally, several predictions are made as to the potential success of G. spadicea on S. sisymbriifolium and some of the challenges facing the biological control of weeds are discussed.
- Full Text:
- Date Issued: 1995
Biochemical evaluation of Tulbaghia violacea harv.rhizomes in diet induced hypercholestrolemic rats
- Olorunnisola, Olubukola Sinbad
- Authors: Olorunnisola, Olubukola Sinbad
- Date: 2012
- Subjects: Violaceae , Anticoagulants (Medicine) , Antineoplastic agents , Rats , Hypercholesteremia , Cardiovascular agents , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD (Biochemistry)
- Identifier: vital:11273 , http://hdl.handle.net/10353/d1006900 , Violaceae , Anticoagulants (Medicine) , Antineoplastic agents , Rats , Hypercholesteremia , Cardiovascular agents , Medicinal plants
- Description: Discovery of cheap, nontoxic and readily available antiatherosclerotic drugs is an extraordinary challenge in this modern world. Atherosclerosis and cardiovascular diseases have been predicted to be the leading cause of death by the year 2030. Hence, this thesis was designed to search for plant (s) with anti-atherogenic properties, investigate its possible side effects and extrapolate its likely mechanism(s) of action. An ethnobotanical survey was employed in identification of locally important plants used for the management and treatment of cardiovascular diseases and its predisposing factors in Nkonkobe Municipality, Eastern Cape in South Africa. Information on the names of plants, their parts used and methods of preparation was collected through a questionnaire which was administered to herbalists, traditional healers and rural dwellers. The most frequently used plant (Rhizomes of Tulbaghia violacea Harv.) was investigated for toxicity using brine shrimp lethality (in vitro) and in vivo toxicity test (acute and subchronic) on rats to determine safety dosage. The in vitro antioxidant and free radical scavenging activity of the plant was investigated using models such as 1,1-diphenyl-2- picrylhydrazyl (DPPH), superoxide anions, hydrogen peroxide (H2O2), nitric oxide (NO), 2,2’- azinobis [3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt (ABTS), lipid peroxidation inhibition and the ferric reducing agent. Phytochemical content and the effect of oral administration of fresh methanolic extract rhizomes of Tulbaghia violacea (250, 500 mg/kg. bwt/day) on Lipid peroxidation (TBARS), serum and tissue antioxidant enzymes in normal, hypercholesterolemic and diet induced atherogenic rats were also assessed. More so, the potential of the extract (250 and 500 mg/kg. bwt) to protect against atherogenic diet (4 percentage cholesterol 1 pecentage cholic acid and 0.5 percentage thiouracil) induced fatty streaks formation, dyslipidemia, oxidative stress and endothelial dysfunction was also investigated. Ethnobotanical study revealed that 19 plant species are used for the treatment of heart related diseases in the Municipality. 53 percentage of the plants mentioned were used for the management of chest pain, 47 percentage for high blood pressure, 42 percent for heart disease, 16 percentage for stroke and 11 percentage for the treatment of hypercholesterolemia. Tulbaghia violacea was repeatedly mentioned as the plant species used for the treatment of high blood pressure and predisposing factors in the study area. The brine shrimp cytotoxicity test revealed that fresh, dried methanolic extracts and essential oil of the T. violacea exhibited a high degree of cytotoxic activity with IC50 values of 18.18 (fresh) and 19.24 (dried) μg/ml. An IC50 value of 12. 59 μg/ml was obtained for the essential oil of the plant. The low cytotoxicity values obtained, suggested that rhizome of T. violacea may serve as a potential source of antimicrobial and anticancer agents. In vivo acute study of single oral administration of 5g/kg dose does not produce mortality or significant behavioral changes during 14 days observation. In the sub-chronic study, the extract (250, 500 mg/kg/bwt/ day) administered for a period of 28 days showed no mortality or morbidity. The weekly body and organ weight of the rats showed no significant differences between the control and the rats treated with the extract. The extract at all doses does not show any effect on of biomarkers of liver or renal damage. However, a significant decrease in the activity of ƔGT was observed in the extract treated groups. Hematological evaluation revealed that oral administration of fresh methanolic extracts of rhizomes of T. violacea does not cause anaemia or leucocytosis in the animals. Furthermore, histopathology results of the internal organs revealed no detectable inflammation. These results demonstrated that the rhizome extract of T. violacea was potentially safe for consumption orally even in chronic concentration. In vitro antioxidant evaluation showed that the essential oil, fresh and dried methanolic extracts exhibited potent antioxidant activities in a concentration dependent manner. Phytochemical investigation reveals that the fresh and the dry extract of RTV are rich in flavonoid, flavonol, phenols, tannin and proanthocyanidin, while the essential oil contained dimethy disulfide, dimethyl trisulfide, (methyl methylthio) methyl, 2,4-dithiapentane (11.35 percent) and (methylthio) acetic acid, 2- (methylthio) ethanol, 3-(methylthio) - and propanenitrile (7.20 percent). The fresh extract had higher radicals scavenging activity than the essential oil or dried extract, with 50 percentage inhibition of DPPH, hydrogen peroxide and lipid peroxidation at a concentration of 35.0 ± 0.12, 19.3 ± 0.11 and 17.9 ± 0.15 μg/ml respectively. Oral administration of methanolic extract of RTV in 125, 250 and 500 mg/kg to female Wistar rats significantly inhibited reduction of glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT). The extracts also inhibited (p< 0.05) lipid peroxidation in normal, high cholesterol and diet induced atherosclerosis fed rats in a dose dependant manner. Also the extract (250 and 500 mg/kg/bwt/day) caused a significant (p<0.05) improvement in body weight of treated animals compared with untreated hypercholesterolemia control rats. The extracts also protected significantly (p<0.05) against atherogenic diet induced liver damage or fatty streaks formation in the aorta as revealed by histological examination. The anti-cholesterolemia and anti-atherosclerotic activities of the extract compared favorably well with standard drugs Gemfibrozil and Atorvastatin respectively. Conclusively, rhizomes of T. violacea possess significant anti-atherogenic activity and its mechanism of action(s) may be due to its antioxidant and anti-hypercholesterolemia properties. The results of this study also suggested that rhizome of T. violacea is relatively safe for human consumption and it may be used as an alternative to garlic.
- Full Text:
- Date Issued: 2012
- Authors: Olorunnisola, Olubukola Sinbad
- Date: 2012
- Subjects: Violaceae , Anticoagulants (Medicine) , Antineoplastic agents , Rats , Hypercholesteremia , Cardiovascular agents , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD (Biochemistry)
- Identifier: vital:11273 , http://hdl.handle.net/10353/d1006900 , Violaceae , Anticoagulants (Medicine) , Antineoplastic agents , Rats , Hypercholesteremia , Cardiovascular agents , Medicinal plants
- Description: Discovery of cheap, nontoxic and readily available antiatherosclerotic drugs is an extraordinary challenge in this modern world. Atherosclerosis and cardiovascular diseases have been predicted to be the leading cause of death by the year 2030. Hence, this thesis was designed to search for plant (s) with anti-atherogenic properties, investigate its possible side effects and extrapolate its likely mechanism(s) of action. An ethnobotanical survey was employed in identification of locally important plants used for the management and treatment of cardiovascular diseases and its predisposing factors in Nkonkobe Municipality, Eastern Cape in South Africa. Information on the names of plants, their parts used and methods of preparation was collected through a questionnaire which was administered to herbalists, traditional healers and rural dwellers. The most frequently used plant (Rhizomes of Tulbaghia violacea Harv.) was investigated for toxicity using brine shrimp lethality (in vitro) and in vivo toxicity test (acute and subchronic) on rats to determine safety dosage. The in vitro antioxidant and free radical scavenging activity of the plant was investigated using models such as 1,1-diphenyl-2- picrylhydrazyl (DPPH), superoxide anions, hydrogen peroxide (H2O2), nitric oxide (NO), 2,2’- azinobis [3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt (ABTS), lipid peroxidation inhibition and the ferric reducing agent. Phytochemical content and the effect of oral administration of fresh methanolic extract rhizomes of Tulbaghia violacea (250, 500 mg/kg. bwt/day) on Lipid peroxidation (TBARS), serum and tissue antioxidant enzymes in normal, hypercholesterolemic and diet induced atherogenic rats were also assessed. More so, the potential of the extract (250 and 500 mg/kg. bwt) to protect against atherogenic diet (4 percentage cholesterol 1 pecentage cholic acid and 0.5 percentage thiouracil) induced fatty streaks formation, dyslipidemia, oxidative stress and endothelial dysfunction was also investigated. Ethnobotanical study revealed that 19 plant species are used for the treatment of heart related diseases in the Municipality. 53 percentage of the plants mentioned were used for the management of chest pain, 47 percentage for high blood pressure, 42 percent for heart disease, 16 percentage for stroke and 11 percentage for the treatment of hypercholesterolemia. Tulbaghia violacea was repeatedly mentioned as the plant species used for the treatment of high blood pressure and predisposing factors in the study area. The brine shrimp cytotoxicity test revealed that fresh, dried methanolic extracts and essential oil of the T. violacea exhibited a high degree of cytotoxic activity with IC50 values of 18.18 (fresh) and 19.24 (dried) μg/ml. An IC50 value of 12. 59 μg/ml was obtained for the essential oil of the plant. The low cytotoxicity values obtained, suggested that rhizome of T. violacea may serve as a potential source of antimicrobial and anticancer agents. In vivo acute study of single oral administration of 5g/kg dose does not produce mortality or significant behavioral changes during 14 days observation. In the sub-chronic study, the extract (250, 500 mg/kg/bwt/ day) administered for a period of 28 days showed no mortality or morbidity. The weekly body and organ weight of the rats showed no significant differences between the control and the rats treated with the extract. The extract at all doses does not show any effect on of biomarkers of liver or renal damage. However, a significant decrease in the activity of ƔGT was observed in the extract treated groups. Hematological evaluation revealed that oral administration of fresh methanolic extracts of rhizomes of T. violacea does not cause anaemia or leucocytosis in the animals. Furthermore, histopathology results of the internal organs revealed no detectable inflammation. These results demonstrated that the rhizome extract of T. violacea was potentially safe for consumption orally even in chronic concentration. In vitro antioxidant evaluation showed that the essential oil, fresh and dried methanolic extracts exhibited potent antioxidant activities in a concentration dependent manner. Phytochemical investigation reveals that the fresh and the dry extract of RTV are rich in flavonoid, flavonol, phenols, tannin and proanthocyanidin, while the essential oil contained dimethy disulfide, dimethyl trisulfide, (methyl methylthio) methyl, 2,4-dithiapentane (11.35 percent) and (methylthio) acetic acid, 2- (methylthio) ethanol, 3-(methylthio) - and propanenitrile (7.20 percent). The fresh extract had higher radicals scavenging activity than the essential oil or dried extract, with 50 percentage inhibition of DPPH, hydrogen peroxide and lipid peroxidation at a concentration of 35.0 ± 0.12, 19.3 ± 0.11 and 17.9 ± 0.15 μg/ml respectively. Oral administration of methanolic extract of RTV in 125, 250 and 500 mg/kg to female Wistar rats significantly inhibited reduction of glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT). The extracts also inhibited (p< 0.05) lipid peroxidation in normal, high cholesterol and diet induced atherosclerosis fed rats in a dose dependant manner. Also the extract (250 and 500 mg/kg/bwt/day) caused a significant (p<0.05) improvement in body weight of treated animals compared with untreated hypercholesterolemia control rats. The extracts also protected significantly (p<0.05) against atherogenic diet induced liver damage or fatty streaks formation in the aorta as revealed by histological examination. The anti-cholesterolemia and anti-atherosclerotic activities of the extract compared favorably well with standard drugs Gemfibrozil and Atorvastatin respectively. Conclusively, rhizomes of T. violacea possess significant anti-atherogenic activity and its mechanism of action(s) may be due to its antioxidant and anti-hypercholesterolemia properties. The results of this study also suggested that rhizome of T. violacea is relatively safe for human consumption and it may be used as an alternative to garlic.
- Full Text:
- Date Issued: 2012
Morphology, patterns and processes in the Oyster Bay headland bypass dunefield, South Africa
- Authors: McConnachie, Lauren Bernyse
- Date: 2013
- Subjects: Sand dune conservation -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Coastal ecology -- South Africa -- Eastern Cape Sedimentation and deposition -- South Africa -- Eastern Cape Beach erosion -- South Africa -- Eastern Cape Coastal zone management -- South Africa -- Eastern Cape Shore protection -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4804 , http://hdl.handle.net/10962/d1001904
- Description: Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed , Maiden name: Elkington, Lauren
- Full Text:
- Date Issued: 2013
- Authors: McConnachie, Lauren Bernyse
- Date: 2013
- Subjects: Sand dune conservation -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Coastal ecology -- South Africa -- Eastern Cape Sedimentation and deposition -- South Africa -- Eastern Cape Beach erosion -- South Africa -- Eastern Cape Coastal zone management -- South Africa -- Eastern Cape Shore protection -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4804 , http://hdl.handle.net/10962/d1001904
- Description: Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed , Maiden name: Elkington, Lauren
- Full Text:
- Date Issued: 2013
Labour dispute resolution in Uganda
- Chabo, Godsent, Ndimurwimo, Leah A
- Authors: Chabo, Godsent , Ndimurwimo, Leah A
- Date: 2020
- Subjects: Dispute resolution (Law) -- Uganda , Labor disputes -- Uganda Arbitration, Industrial -- Uganda Industrial relations -- Uganda
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/48960 , vital:41566
- Description: The dissertation examines the Ugandan labour dispute resolution system by undertaking an analysis of international labour standards and a case study of South Africa’s labour dispute system. The study pronounces the legislative provisions of the Employment Act and Labour Disputes (Arbitration and Settlement) Act that exist for the effective and efficient resolution of labour disputes through an alternative dispute resolution (ADR) system. The study contends for the provision of a proactive and expeditious dispute resolution system that helps to resolve labour disputes in the most effective and efficient manner, without necessarily having to resort to the courts. The dissertation further examines the provisions of relevant international labour standards on labour dispute resolution to ascertain their adequacy as part frameworks that apply to Uganda’s obligation to provide ADR systems that respond to the needs of the labour relations community. The study contends that ratifying particular ILO conventions creates obligations upon a country to comply and apply provisions of these conventions in national legislation. It is further argued that by having ratified those international labour standards that provide for ADR, Uganda assumes specific obligations under international law, enjoining the country to provide the required ADR system of conciliation and arbitration, which is reliable and trusted by the countries citizens. A case study of South Africa is adopted with the primary focus on whether Uganda can learn from South African’s ADR system which is arguably more effective and efficient. South Africa has a labour dispute resolution system that has influenced majority of the Southern African Development Community (SADAC) law, hence prompting this study to borrow its ADR system predominantly the Commission for Conciliation Mediation and Arbitration (CCMA). Despite the differences between Uganda and South Africa, the study also indicates fundamental similarities. Preferably, disputes should be resolved at conciliation level, resulting in the minority of disputes being referred to arbitration or the Industrial Court. This is far from the reality of the situation in Uganda. The study acknowledges that the Labour Disputes (Arbitration and Settlement) Act and Employment Act have put up provisions to establish a fast and effective labour dispute system, however, the gap exists at implementing these effective provisions in the Labour Disputes (Arbitration and Settlement) Act and the Employment Act. These lacunae in implementation make the attainment of an effective and efficient labour dispute resolution difficult. For this reason, the author proposes several remedial interventions in line with international labour standards and lessons from South Africa’s system that look to the future and the continued provision of fast, effective, and user-friendly ADR services. For Uganda to solve successfully apply these remedies, a strong political will as well as concerted efforts from all role players in the labour relations community is required.
- Full Text:
- Date Issued: 2020
- Authors: Chabo, Godsent , Ndimurwimo, Leah A
- Date: 2020
- Subjects: Dispute resolution (Law) -- Uganda , Labor disputes -- Uganda Arbitration, Industrial -- Uganda Industrial relations -- Uganda
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/48960 , vital:41566
- Description: The dissertation examines the Ugandan labour dispute resolution system by undertaking an analysis of international labour standards and a case study of South Africa’s labour dispute system. The study pronounces the legislative provisions of the Employment Act and Labour Disputes (Arbitration and Settlement) Act that exist for the effective and efficient resolution of labour disputes through an alternative dispute resolution (ADR) system. The study contends for the provision of a proactive and expeditious dispute resolution system that helps to resolve labour disputes in the most effective and efficient manner, without necessarily having to resort to the courts. The dissertation further examines the provisions of relevant international labour standards on labour dispute resolution to ascertain their adequacy as part frameworks that apply to Uganda’s obligation to provide ADR systems that respond to the needs of the labour relations community. The study contends that ratifying particular ILO conventions creates obligations upon a country to comply and apply provisions of these conventions in national legislation. It is further argued that by having ratified those international labour standards that provide for ADR, Uganda assumes specific obligations under international law, enjoining the country to provide the required ADR system of conciliation and arbitration, which is reliable and trusted by the countries citizens. A case study of South Africa is adopted with the primary focus on whether Uganda can learn from South African’s ADR system which is arguably more effective and efficient. South Africa has a labour dispute resolution system that has influenced majority of the Southern African Development Community (SADAC) law, hence prompting this study to borrow its ADR system predominantly the Commission for Conciliation Mediation and Arbitration (CCMA). Despite the differences between Uganda and South Africa, the study also indicates fundamental similarities. Preferably, disputes should be resolved at conciliation level, resulting in the minority of disputes being referred to arbitration or the Industrial Court. This is far from the reality of the situation in Uganda. The study acknowledges that the Labour Disputes (Arbitration and Settlement) Act and Employment Act have put up provisions to establish a fast and effective labour dispute system, however, the gap exists at implementing these effective provisions in the Labour Disputes (Arbitration and Settlement) Act and the Employment Act. These lacunae in implementation make the attainment of an effective and efficient labour dispute resolution difficult. For this reason, the author proposes several remedial interventions in line with international labour standards and lessons from South Africa’s system that look to the future and the continued provision of fast, effective, and user-friendly ADR services. For Uganda to solve successfully apply these remedies, a strong political will as well as concerted efforts from all role players in the labour relations community is required.
- Full Text:
- Date Issued: 2020
The establishment of a Lidar facility at Rhodes University
- Grant, Richard Peter James Seton
- Authors: Grant, Richard Peter James Seton
- Date: 1988
- Subjects: Optical radar , LIDAR , Receiver , Transmitter , Photon counting electronics , Aerosol scattering , Temperature profiles , Stratosphere
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5445 , http://hdl.handle.net/10962/d1001998
- Description: LIDAR is the optical equivalent of RADAR. A LIDAR facility has been established at Rhodes University using a flashlamp-pumped dye laser as the transmitter and a photomultiplier tube at the focus of a searchlight mirror as the receiver. The setting up of the receiver and transmitter as well as the design and construction of the photon counting electronics is described. The LIDAR has been used to measure aerosol scattering ratios and temperature profiles in the stratosphere and these results are presented with the algorithms and software used to reduce the data. Finally some recommendations are made for future work
- Full Text:
- Date Issued: 1988
- Authors: Grant, Richard Peter James Seton
- Date: 1988
- Subjects: Optical radar , LIDAR , Receiver , Transmitter , Photon counting electronics , Aerosol scattering , Temperature profiles , Stratosphere
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5445 , http://hdl.handle.net/10962/d1001998
- Description: LIDAR is the optical equivalent of RADAR. A LIDAR facility has been established at Rhodes University using a flashlamp-pumped dye laser as the transmitter and a photomultiplier tube at the focus of a searchlight mirror as the receiver. The setting up of the receiver and transmitter as well as the design and construction of the photon counting electronics is described. The LIDAR has been used to measure aerosol scattering ratios and temperature profiles in the stratosphere and these results are presented with the algorithms and software used to reduce the data. Finally some recommendations are made for future work
- Full Text:
- Date Issued: 1988
The ecology and management of the fishes of the Okavango Delta, Botswana, with particular reference to the role of the seasonal floods
- Authors: Merron, Glen Steven
- Date: 1991
- Subjects: Fishes -- Ecology -- Botswana Fishes -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5268 , http://hdl.handle.net/10962/d1005112
- Description: The Okavango is a vast inland delta system in northern Botswana which receives an annual flood from the highlands of southern Angola. There are distinct communities of fish in the Okavango which can be separated from each other by the physical characteristics of the different habitat types with which they co-evolved. This thesis provides an account of the biology and ecology of selected fish species in the Okavango Delta. Their response to the annual flood regime, and the environmental factors which limit their distribution and abundance, are examined. The thesis emphasizes the importance of water fluctuations in determining the nature of the fish fauna and the reaction of the fishes in terms of community structure, movements, breeding, predator-prey interactions and feeding. Four major ecotones were studied in the Okavango Delta. In the riverine floodplain and perennial swamp ecotones a higher species diversity was recorded than in the seasonal swamp and drainage rivers ecotones where diversity was lowest and comprised mainly of smaller fish species. A greater variety of habitat types was associated with the riverine floodplain and perennial swamp relative to the seasonal swamp and drainage rivers. The variety of habitat types between ecotones is associated with the degree of flood inundation in the respective ecotones. During the course of this study, annual recruitment of fish into the drainage rivers was from refugia in the seasonal swamp whereas the greatest degree of lateral and longitudinal movement was in the riverine floodplain and perennial swamp. Movement was in response to both biological requirements, such as availability of food and spawning sites, and physical features of the environment, such as the changing water depth. The total catch per unit effort (CPUE) of fish throughout the year was more constant in the riverine floodplain and perennial swamp than in the seasonal swamp and drainage rivers where CPUE fluctutated widely. An increase in CPUE during the duration of this study was apparent and related to the magnitude of the annual flood. In contrast to most other African wetlands, the arrival of the annual flood in the Okavango Delta coincides largely with the dry winter months. This situation presented an opportunity to compare the influence of floods and water temperature on the reproductive biology of the selected fish species. The results show a definite pattern and indicate that both the flood cycle and increased water temperatures greatly influence the breeding cycles of the selected species. The tilapia Oreochromis andersonii exhibited a considerable degree of phenotypic plasticity. Fish from the seasonally inundated areas showed a smaller mean size, egg size and larger number of eggs relative to fish in the perennially flooded areas. The size at sexual maturity was also smaller. These different reproductive characteristics exhibited by O. andersonii are dependent on the degree of water retention in the different habitats. The fishes of the Okavango have adopted other reproductive strategies to survive the changing environmental conditions brought about by an annual flood cycle. These strategies include the construction of foam nests, as described for Hepsetus odoe, for guarding the young and to provide an oxygen-rich environment. Two main non-piscivorous feeding pathways were identified in the Okavango. These are a detritus pathway based on dead plant and animal material, and an epiphyte pathway, based on algae and invertebrates that are attached to plant stems. Seasonal changes in diet in relation to the annual flood were recorded. The most dramrtic change was demonstrated by the catfish Clarias gariepinus which congregates in mass aggregations in the northern regions of the Delta and hunt in packs. Pack-hunting by catfish is a regular response to the annual fluctuations in water level. It is my conclusion that the main flow of biotic and abiotic stimuli within the Okavango Delta originates from the relatively hydrologically stable riverine floodplain and perennial swamp ecotones to the widely fluctuating seasonal swamp and drainage rivers ecotones. The relatively stable ecotones allow a diverse and biotically interdependent fish community to develop, whereas the widely fluctuating seasonal swamp and drainage rivers ecotones are characterized by a less diverse and interdependent fish community. The degree of abiotic and biotic interdependence among fish in an ecotone is very important for the long term management of the Okavango Delta. Potential developers have to determine whether the effect of a given action by man is likely to result in a long term disturbance or merely in an elastic recoil to a more or less similar state. Recommendations are made on the conservation and management of Okavango fishes taking into account the ecological characteristics of the delta.
- Full Text:
- Date Issued: 1991
- Authors: Merron, Glen Steven
- Date: 1991
- Subjects: Fishes -- Ecology -- Botswana Fishes -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5268 , http://hdl.handle.net/10962/d1005112
- Description: The Okavango is a vast inland delta system in northern Botswana which receives an annual flood from the highlands of southern Angola. There are distinct communities of fish in the Okavango which can be separated from each other by the physical characteristics of the different habitat types with which they co-evolved. This thesis provides an account of the biology and ecology of selected fish species in the Okavango Delta. Their response to the annual flood regime, and the environmental factors which limit their distribution and abundance, are examined. The thesis emphasizes the importance of water fluctuations in determining the nature of the fish fauna and the reaction of the fishes in terms of community structure, movements, breeding, predator-prey interactions and feeding. Four major ecotones were studied in the Okavango Delta. In the riverine floodplain and perennial swamp ecotones a higher species diversity was recorded than in the seasonal swamp and drainage rivers ecotones where diversity was lowest and comprised mainly of smaller fish species. A greater variety of habitat types was associated with the riverine floodplain and perennial swamp relative to the seasonal swamp and drainage rivers. The variety of habitat types between ecotones is associated with the degree of flood inundation in the respective ecotones. During the course of this study, annual recruitment of fish into the drainage rivers was from refugia in the seasonal swamp whereas the greatest degree of lateral and longitudinal movement was in the riverine floodplain and perennial swamp. Movement was in response to both biological requirements, such as availability of food and spawning sites, and physical features of the environment, such as the changing water depth. The total catch per unit effort (CPUE) of fish throughout the year was more constant in the riverine floodplain and perennial swamp than in the seasonal swamp and drainage rivers where CPUE fluctutated widely. An increase in CPUE during the duration of this study was apparent and related to the magnitude of the annual flood. In contrast to most other African wetlands, the arrival of the annual flood in the Okavango Delta coincides largely with the dry winter months. This situation presented an opportunity to compare the influence of floods and water temperature on the reproductive biology of the selected fish species. The results show a definite pattern and indicate that both the flood cycle and increased water temperatures greatly influence the breeding cycles of the selected species. The tilapia Oreochromis andersonii exhibited a considerable degree of phenotypic plasticity. Fish from the seasonally inundated areas showed a smaller mean size, egg size and larger number of eggs relative to fish in the perennially flooded areas. The size at sexual maturity was also smaller. These different reproductive characteristics exhibited by O. andersonii are dependent on the degree of water retention in the different habitats. The fishes of the Okavango have adopted other reproductive strategies to survive the changing environmental conditions brought about by an annual flood cycle. These strategies include the construction of foam nests, as described for Hepsetus odoe, for guarding the young and to provide an oxygen-rich environment. Two main non-piscivorous feeding pathways were identified in the Okavango. These are a detritus pathway based on dead plant and animal material, and an epiphyte pathway, based on algae and invertebrates that are attached to plant stems. Seasonal changes in diet in relation to the annual flood were recorded. The most dramrtic change was demonstrated by the catfish Clarias gariepinus which congregates in mass aggregations in the northern regions of the Delta and hunt in packs. Pack-hunting by catfish is a regular response to the annual fluctuations in water level. It is my conclusion that the main flow of biotic and abiotic stimuli within the Okavango Delta originates from the relatively hydrologically stable riverine floodplain and perennial swamp ecotones to the widely fluctuating seasonal swamp and drainage rivers ecotones. The relatively stable ecotones allow a diverse and biotically interdependent fish community to develop, whereas the widely fluctuating seasonal swamp and drainage rivers ecotones are characterized by a less diverse and interdependent fish community. The degree of abiotic and biotic interdependence among fish in an ecotone is very important for the long term management of the Okavango Delta. Potential developers have to determine whether the effect of a given action by man is likely to result in a long term disturbance or merely in an elastic recoil to a more or less similar state. Recommendations are made on the conservation and management of Okavango fishes taking into account the ecological characteristics of the delta.
- Full Text:
- Date Issued: 1991
Gender oppression and possibilities of empowerment: images of women in African literature with specific reference to Mariama Ba's So long a letter, Buchi Emecheta's The Joys of motherhood and Tsitsi Dangarembga's Nervous conditions
- Authors: Nyanhongo, Mazvita Mollin
- Date: 2011
- Subjects: Women and literature -- Africa Women and literature -- Africa Women and literature -- Africa Women and literature -- Africa Women and literature -- Africa African literature -- Women authors Women -- Africa -- Literary collections
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10353/6411 , vital:29659
- Description: This study consists of a comparative analysis of three novels by three prominent African women writers which cast light on the ways in which women are oppressed by traditional and cultural norms in three different African countries. These three primary texts also explore the ways in which African women‟s lives are affected by other issues, such as colonialism and economic factors, and this study discusses this. An analysis of these novels reveals that the interconnectedness of racial, class and gender issues exacerbates the oppression of many African women, thereby lessening the opportunities for them to attain self-realization. This study goes on to investigate whether there are possibilities of empowerment for the women in the primary texts, and examining the reasons why some women fail to transcend their situations of oppression. The primary novels will be discussed in different chapters, which explore the problems with which various women are beset, and discuss the extent to which the various women in the novels manage to attain empowerment. In conclusion, this study compares and contrasts the ways in which the women in the primary texts are oppressed and highlights the reasons why some women are able to attain empowerment, whilst others are unable to do so. It also shows that many women are beset with comparable forms of oppression, but they may choose to react to these situations differently. Over and above these issues, the study seeks to draw attention to the fact that women need to come together and contribute to the ways in which they can attain various forms ofempowerment.
- Full Text:
- Date Issued: 2011
- Authors: Nyanhongo, Mazvita Mollin
- Date: 2011
- Subjects: Women and literature -- Africa Women and literature -- Africa Women and literature -- Africa Women and literature -- Africa Women and literature -- Africa African literature -- Women authors Women -- Africa -- Literary collections
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10353/6411 , vital:29659
- Description: This study consists of a comparative analysis of three novels by three prominent African women writers which cast light on the ways in which women are oppressed by traditional and cultural norms in three different African countries. These three primary texts also explore the ways in which African women‟s lives are affected by other issues, such as colonialism and economic factors, and this study discusses this. An analysis of these novels reveals that the interconnectedness of racial, class and gender issues exacerbates the oppression of many African women, thereby lessening the opportunities for them to attain self-realization. This study goes on to investigate whether there are possibilities of empowerment for the women in the primary texts, and examining the reasons why some women fail to transcend their situations of oppression. The primary novels will be discussed in different chapters, which explore the problems with which various women are beset, and discuss the extent to which the various women in the novels manage to attain empowerment. In conclusion, this study compares and contrasts the ways in which the women in the primary texts are oppressed and highlights the reasons why some women are able to attain empowerment, whilst others are unable to do so. It also shows that many women are beset with comparable forms of oppression, but they may choose to react to these situations differently. Over and above these issues, the study seeks to draw attention to the fact that women need to come together and contribute to the ways in which they can attain various forms ofempowerment.
- Full Text:
- Date Issued: 2011
Diversity, host plant range and ecology of Lepidoptera stem borers in South Africa
- Authors: Stemele, Mxolisi Arnold
- Date: 2019
- Subjects: Lepidoptera Host plants Stem borers
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15409 , vital:40405
- Description: The biology and ecology of Lepidopteran pests stem borers has been extensively studied because of the economic importance of pest species such as Busseola fusca (Fuller) (Noctuidae), Sesamia calamistis (Hampson) (Noctuidae), Chilo partellus (Swinhoe) (Crambidae), and Eldana saccharina (Walker) (Pyralidae). Knowledge relating to diversity, infestation dynamics, and host plant range is readily available. In natural vegetation, the variety of stem borers is higher than that found in agroecosystems. However, there is a paucity of South African studies that explain the observed differences in diversity between the two systems. Stem borers are also known to exhibit species-specific ecological requirements, which influence their distribution between African countries. South African biomes are classified based on vegetation structure and climate, which happens to be the most critical factors that affect the distribution of phytophagous insects. This makes biomes an excellent model to investigate diversity and distribution of stem borer species. In this study, we investigated diversity, distribution and species composition in four biomes. The results showed that diversity and distribution of the stem borers in natural vegetation was determined by host plant distribution. Stem borer diversity correlated with high diversity of host plants. Thirty-two stem borer species were collected from 27 host plants and another three from light traps. Widely distributed host plants supported a higher diversity of stem borers, which is consistent with the resource availability hypotheses. Non-metric dimensional scale unfolding revealed disparity in host plant preference and plant species composition between the various stem borer families (Kruskal’s Stress = 0.16). Tortricidae species and Sesamia typhae (Le rü) (Noctuidae) feed exclusively on hydrophytic Cyperaceae species. The majority of Noctuidae, Crambidae and Phycitidae species collected were oligophagous on terrestrial Poaceae, with a few polyphagous exceptions feeding on hydrophytic Cyperaceae and Typhaceae. Additionally, species composition of Poaceae host plants differed between 8 Crambidae and the Phycitidae species. Stem borer species composition between biomes revealed the presence of distinct host plants (2D stress = 0.09) and stem borer (2D stress = 0.13) communities. The stem borer abundance and diversity were strongly correlated (R2 = 0.64), but species diversity (R2 = - 0.95) and host plant diversity (R2 = - 0.85) were inversely correlated to altitude. Based on these results it was concluded that stem borer diversity and distribution in natural vegetation was influenced by host plant diversity and distribution as well as climate associated with altitudinal gradients. In the last two decades, four stem borer species previously known on wild host plants; Busseola segeta (Bowden), Busseola phaia (Bowden), Pirateolea piscator (Fletcher) and Conicofrontia sesamoides (Hampson) have invaded cultivated crops. These invasions remained undetected because of a shortage of surveys, habitat transformation and misidentifications. Misidentifications are common among stem borers due to the considerable resemblance between morphospecies. In this study, we assessed the capacity of the mitochondrial gene Cytochrome c oxidase (COI) to delineate closely related species to develop monitoring and early detection of invasive species and to assess migration patterns and gene flow between the populations. The results demonstrated that COI is an effective DNA marker for species delineation and assessment of intra- and interspecific genetic relationship. The K2P distances and phylogenetic tree defined boundaries between Noctuidae species with high resolution. No divergence distance was detected between intraspecific species, but for the congener species, divergence distance was 0.044%-0.111% with an average of 0.076%. The average interspecies K2P distance (0.57%) was 5-15 times higher than the congener species distances. Phylogenetic analysis revealed the presence of two clades. Busseola and Sesamia species were connected in a monophyletic clade with a strong (93%) bootstrap. The second monophyletic clade comprised of a cluster of Pirateolea, Acrapex and Conicofrontia species, and this was also supported with 9 a strong bootstrap (100%). The gene flow study revealed low levels of genetic differentiation between the populations of B. fusca collected from different maize producing areas in South Africa. This low genetic differentiation was consistent with high gene flow. The number of effective migrants between the populations was between 8 and 99 individuals per generation. These results indicate high connectivity between the populations.
- Full Text:
- Date Issued: 2019
- Authors: Stemele, Mxolisi Arnold
- Date: 2019
- Subjects: Lepidoptera Host plants Stem borers
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15409 , vital:40405
- Description: The biology and ecology of Lepidopteran pests stem borers has been extensively studied because of the economic importance of pest species such as Busseola fusca (Fuller) (Noctuidae), Sesamia calamistis (Hampson) (Noctuidae), Chilo partellus (Swinhoe) (Crambidae), and Eldana saccharina (Walker) (Pyralidae). Knowledge relating to diversity, infestation dynamics, and host plant range is readily available. In natural vegetation, the variety of stem borers is higher than that found in agroecosystems. However, there is a paucity of South African studies that explain the observed differences in diversity between the two systems. Stem borers are also known to exhibit species-specific ecological requirements, which influence their distribution between African countries. South African biomes are classified based on vegetation structure and climate, which happens to be the most critical factors that affect the distribution of phytophagous insects. This makes biomes an excellent model to investigate diversity and distribution of stem borer species. In this study, we investigated diversity, distribution and species composition in four biomes. The results showed that diversity and distribution of the stem borers in natural vegetation was determined by host plant distribution. Stem borer diversity correlated with high diversity of host plants. Thirty-two stem borer species were collected from 27 host plants and another three from light traps. Widely distributed host plants supported a higher diversity of stem borers, which is consistent with the resource availability hypotheses. Non-metric dimensional scale unfolding revealed disparity in host plant preference and plant species composition between the various stem borer families (Kruskal’s Stress = 0.16). Tortricidae species and Sesamia typhae (Le rü) (Noctuidae) feed exclusively on hydrophytic Cyperaceae species. The majority of Noctuidae, Crambidae and Phycitidae species collected were oligophagous on terrestrial Poaceae, with a few polyphagous exceptions feeding on hydrophytic Cyperaceae and Typhaceae. Additionally, species composition of Poaceae host plants differed between 8 Crambidae and the Phycitidae species. Stem borer species composition between biomes revealed the presence of distinct host plants (2D stress = 0.09) and stem borer (2D stress = 0.13) communities. The stem borer abundance and diversity were strongly correlated (R2 = 0.64), but species diversity (R2 = - 0.95) and host plant diversity (R2 = - 0.85) were inversely correlated to altitude. Based on these results it was concluded that stem borer diversity and distribution in natural vegetation was influenced by host plant diversity and distribution as well as climate associated with altitudinal gradients. In the last two decades, four stem borer species previously known on wild host plants; Busseola segeta (Bowden), Busseola phaia (Bowden), Pirateolea piscator (Fletcher) and Conicofrontia sesamoides (Hampson) have invaded cultivated crops. These invasions remained undetected because of a shortage of surveys, habitat transformation and misidentifications. Misidentifications are common among stem borers due to the considerable resemblance between morphospecies. In this study, we assessed the capacity of the mitochondrial gene Cytochrome c oxidase (COI) to delineate closely related species to develop monitoring and early detection of invasive species and to assess migration patterns and gene flow between the populations. The results demonstrated that COI is an effective DNA marker for species delineation and assessment of intra- and interspecific genetic relationship. The K2P distances and phylogenetic tree defined boundaries between Noctuidae species with high resolution. No divergence distance was detected between intraspecific species, but for the congener species, divergence distance was 0.044%-0.111% with an average of 0.076%. The average interspecies K2P distance (0.57%) was 5-15 times higher than the congener species distances. Phylogenetic analysis revealed the presence of two clades. Busseola and Sesamia species were connected in a monophyletic clade with a strong (93%) bootstrap. The second monophyletic clade comprised of a cluster of Pirateolea, Acrapex and Conicofrontia species, and this was also supported with 9 a strong bootstrap (100%). The gene flow study revealed low levels of genetic differentiation between the populations of B. fusca collected from different maize producing areas in South Africa. This low genetic differentiation was consistent with high gene flow. The number of effective migrants between the populations was between 8 and 99 individuals per generation. These results indicate high connectivity between the populations.
- Full Text:
- Date Issued: 2019
Assessing the physical fitness level of children with intellectual disability in the Grahamstown region of the Eastern Cape, and subsequently designing, implementing and evaluating the efficacy of an exercise intervention
- Authors: Parsons, Samantha Lee
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19723 , vital:22478
- Description: Background: Extensive research has addressed physical fitness as an agent in promoting health and well-being; however, there is little research on this topic for special populations, such as individuals with intellectual disability and even less relating to the South African context. Children with intellectual disability attending special need schools in disadvantaged communities in the Eastern Cape have lacked the opportunity to participate in structured physical education programs. Implementing a solution to this problem was seen to be a challenge, due to the lack of informative research and available data. Aims: The purpose of this research was two-fold; firstly, it aimed to identify the physical fitness levels of the intellectually disabled children in the Grahamstown region of the Eastern Cape province of South Africa; and secondly, it aimed to implement and evaluate the efficacy of an exercise intervention programme on physical fitness in a local school for children with intellectual disability. Phase 1: The descriptive study compared basic anthropometric as well as physical fitness measures from a sample of participants with intellectual disability (n=29) with a comparable sample of typically developed children (n=25). There were 15 males and 14 females in the intellectually disabled sample group, with an average age of 10.69 ± 1.26 years, and the typically developed sample had 13 males and 12 females, with an average age of 10.51 ± 0.74 years. The anthropometric measures included stature and mass; while the health-related physical fitness components included cardiorespiratory endurance, muscular endurance, strength, body composition, and flexibility; and the skill-related physical fitness components were balance, agility, speed, power, coordination and reaction time. The results revealed that the children with intellectual disability were significantly shorter in stature and lighter in mass (p <0.001) compared to their typically developed peers. Muscular endurance and strength, balance, speed, power, coordination and reaction time were poorer among those with intellectual disabilities (p <0.05). Cardiorespiratory endurance, flexibility and agility were similar between groups. Results of the correlation analyses determined significant (p <0.05) relationships between certain health-related and/or skill-related physical fitness components, which were instrumental for selecting measures for Phase 2. The physical fitness components that had the most significant (p <0.05) correlations were speed with five significant correlations, both muscular endurance and balance with six, coordination with seven, and power with eight significant correlations of the eleven physical fitness components. The comparative results, in conjunction with the correlations, determined that the most suitable physical fitness components to be implemented in the exercise intervention for Phase 2 were muscular endurance, balance, and power. Phase 2: The intervention study was a case-control study (intervention group: n = 16; control group: n = 15), whereby the intervention group was exposed to an 8-week multi-modal exercise intervention training muscular endurance, balance and power. Pre-and post-intervention measures were performed using the same eleven physical fitness tests as in Phase 1. The interaction effects and effect sizes were determined and the results showed significant improvements and large effect sizes for the intervention group’s performance of muscular endurance (p=0.026; d=0.617) and power (p<0.000; d=0.999), whereas no significant changes were found for balance. Furthermore, the exercise intervention also impacted the overall level of physical fitness, as significant changes were found for cardiorespiratory endurance (p<0.001; d=0.98), strength (p=0.021; d=0.654) and flexibility (p=0.032; d=586). In conclusion, the exercise intervention was effective for improving the intellectually disabled participants’ muscular endurance and power but not found effective for balance.
- Full Text:
- Date Issued: 2017
- Authors: Parsons, Samantha Lee
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19723 , vital:22478
- Description: Background: Extensive research has addressed physical fitness as an agent in promoting health and well-being; however, there is little research on this topic for special populations, such as individuals with intellectual disability and even less relating to the South African context. Children with intellectual disability attending special need schools in disadvantaged communities in the Eastern Cape have lacked the opportunity to participate in structured physical education programs. Implementing a solution to this problem was seen to be a challenge, due to the lack of informative research and available data. Aims: The purpose of this research was two-fold; firstly, it aimed to identify the physical fitness levels of the intellectually disabled children in the Grahamstown region of the Eastern Cape province of South Africa; and secondly, it aimed to implement and evaluate the efficacy of an exercise intervention programme on physical fitness in a local school for children with intellectual disability. Phase 1: The descriptive study compared basic anthropometric as well as physical fitness measures from a sample of participants with intellectual disability (n=29) with a comparable sample of typically developed children (n=25). There were 15 males and 14 females in the intellectually disabled sample group, with an average age of 10.69 ± 1.26 years, and the typically developed sample had 13 males and 12 females, with an average age of 10.51 ± 0.74 years. The anthropometric measures included stature and mass; while the health-related physical fitness components included cardiorespiratory endurance, muscular endurance, strength, body composition, and flexibility; and the skill-related physical fitness components were balance, agility, speed, power, coordination and reaction time. The results revealed that the children with intellectual disability were significantly shorter in stature and lighter in mass (p <0.001) compared to their typically developed peers. Muscular endurance and strength, balance, speed, power, coordination and reaction time were poorer among those with intellectual disabilities (p <0.05). Cardiorespiratory endurance, flexibility and agility were similar between groups. Results of the correlation analyses determined significant (p <0.05) relationships between certain health-related and/or skill-related physical fitness components, which were instrumental for selecting measures for Phase 2. The physical fitness components that had the most significant (p <0.05) correlations were speed with five significant correlations, both muscular endurance and balance with six, coordination with seven, and power with eight significant correlations of the eleven physical fitness components. The comparative results, in conjunction with the correlations, determined that the most suitable physical fitness components to be implemented in the exercise intervention for Phase 2 were muscular endurance, balance, and power. Phase 2: The intervention study was a case-control study (intervention group: n = 16; control group: n = 15), whereby the intervention group was exposed to an 8-week multi-modal exercise intervention training muscular endurance, balance and power. Pre-and post-intervention measures were performed using the same eleven physical fitness tests as in Phase 1. The interaction effects and effect sizes were determined and the results showed significant improvements and large effect sizes for the intervention group’s performance of muscular endurance (p=0.026; d=0.617) and power (p<0.000; d=0.999), whereas no significant changes were found for balance. Furthermore, the exercise intervention also impacted the overall level of physical fitness, as significant changes were found for cardiorespiratory endurance (p<0.001; d=0.98), strength (p=0.021; d=0.654) and flexibility (p=0.032; d=586). In conclusion, the exercise intervention was effective for improving the intellectually disabled participants’ muscular endurance and power but not found effective for balance.
- Full Text:
- Date Issued: 2017
Extraction, isolation and characterization of oleanolic acid and its analogues from Syzygium aromaticum (cloves) and evaluation of their biological activities
- Authors: khwaza, Vuyolwethu
- Date: 2019
- Subjects: Antibacterial agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19076 , vital:39882
- Description: Pathogenic microorganisms have serious impact on people's lives. Every year, millions of people around the world die of bacterial infections. Resistance to common antibacterial drugs has proven to be a challenging problem in control of bacterial infections. In an attempt to develop an effective and affordable treatment for bacterial infections, oleanolic acid isolated from syzygium aromaticum conjugates incorporating other pharmaceutical scaffolds such as chloroquine derivatives, curcumin, and ergocalciferol etc have been developed. Based on the previous successes of testing combination of antimicrobial drugs and pharmaceutical drugs which appeared to be the promising strategy to overcome treatment failure; a series of hybrid compounds containing oleanolic acid and other pharmaceutical scaffolds were synthesized. 4- Aminoquinoline derivatives were first hybridized with selected organic compounds to form a class of hybrid compounds containing either amide bond or ester bond as a linker between the precursor molecules. Analogues/hybrid compounds can overcome the disadvantages of combination therapy such as drug-drug interaction. The structural effects of this type of conjugation of oleanolic acid and other pharmaceutical scaffolds were characterised by FTIR, Mass Spec and NMR spectroscopy. These compounds were studied along with the monosubstituted oleanolic acid analogues and the organic components in order to compare the effects of the substitution on their biological response.‖ All the synthesized analogues were tested against 11 bacterial strains on both Gram-positive and Gram-negative bacteria. The synthesized compounds showed selectivity and higher activity against Enterococcus faecalis (EF), Klebsiella oxytoca (KO), Escherischia coli (EC), Staphylococcus aureous (SA), Proteus vulgaris (PV) and Bacillus subtilis (BS) with MIC values; ranging between of 1.25 mg/mL to 0.072 mg/mL
- Full Text:
- Date Issued: 2019
- Authors: khwaza, Vuyolwethu
- Date: 2019
- Subjects: Antibacterial agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19076 , vital:39882
- Description: Pathogenic microorganisms have serious impact on people's lives. Every year, millions of people around the world die of bacterial infections. Resistance to common antibacterial drugs has proven to be a challenging problem in control of bacterial infections. In an attempt to develop an effective and affordable treatment for bacterial infections, oleanolic acid isolated from syzygium aromaticum conjugates incorporating other pharmaceutical scaffolds such as chloroquine derivatives, curcumin, and ergocalciferol etc have been developed. Based on the previous successes of testing combination of antimicrobial drugs and pharmaceutical drugs which appeared to be the promising strategy to overcome treatment failure; a series of hybrid compounds containing oleanolic acid and other pharmaceutical scaffolds were synthesized. 4- Aminoquinoline derivatives were first hybridized with selected organic compounds to form a class of hybrid compounds containing either amide bond or ester bond as a linker between the precursor molecules. Analogues/hybrid compounds can overcome the disadvantages of combination therapy such as drug-drug interaction. The structural effects of this type of conjugation of oleanolic acid and other pharmaceutical scaffolds were characterised by FTIR, Mass Spec and NMR spectroscopy. These compounds were studied along with the monosubstituted oleanolic acid analogues and the organic components in order to compare the effects of the substitution on their biological response.‖ All the synthesized analogues were tested against 11 bacterial strains on both Gram-positive and Gram-negative bacteria. The synthesized compounds showed selectivity and higher activity against Enterococcus faecalis (EF), Klebsiella oxytoca (KO), Escherischia coli (EC), Staphylococcus aureous (SA), Proteus vulgaris (PV) and Bacillus subtilis (BS) with MIC values; ranging between of 1.25 mg/mL to 0.072 mg/mL
- Full Text:
- Date Issued: 2019
Mapping the Radio KC community : a case study assessing the impact of participatory research methods in assisting community radio producers to identify programming content
- Authors: Davidson, Brett Russell
- Date: 2004
- Subjects: Radio broadcasting -- South Africa -- Paarl , Radio stations -- South Africa -- Paarl , Radio journalism -- South Africa -- Paarl , Radio broadcasters -- Research -- South Africa -- Paarl , Mass media -- Political aspects -- South Africa , Mass media -- Social aspects -- South Africa , Radio in community development
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3497 , http://hdl.handle.net/10962/d1003716 , Radio broadcasting -- South Africa -- Paarl , Radio stations -- South Africa -- Paarl , Radio journalism -- South Africa -- Paarl , Radio broadcasters -- Research -- South Africa -- Paarl , Mass media -- Political aspects -- South Africa , Mass media -- Social aspects -- South Africa , Radio in community development
- Description: This thesis deals with the introduction of participatory research methods to programming staff working at Radio KC, a South African community radio station based in Paarl, in the Western Cape province. The focus is on a series of workshops conducted at the station, dealing with research tools developed to enable station workers to undertake research of their community. The aim was to determine, by means ofa case study, whether the introduction of participatory research methods could improve the ability of community broadcasters to facilitate democratic participation among the communities in which they operate. More particularly, the thesis assesses whether the application of such methods has improved the ability of the programming staff that were involved in this case study to identify a wider range of stories and voices within their target community, for inclusion in programming content. The participatory research techniques that are applied at the radio station are based on ideas in 'civic mapping' developed by Harwood and McCrehan (1996) under the auspices of The Pew Center for Civic Journalism, and supplemented by insights from Friedland (2001) and Downs and Stea (1977) about the cognitive, normative and imagined dimensions of community. All of the ideas and techniques were adapted for the South African situation. The findings of the research project illustrate that for community stations, the key concepts of 'community' and 'participation' are highly complex ones and that stations need assistance to apply these concepts in their everyday practice. The account of the intervention at Radio KC shows that the process did indeed assist the individual research participants to better deal with the application of these concepts. It did not, however, make much impact on the station as a whole. Reasons for this are believed to lie in the organisational dynamics of the station, and the fact that the model as applied in this case did not provide a means for tackling the agendas, investments and power relations that define the activities of individuals at a given community radio station - what Hochheimer (1993) talks about as the entrenchment of power and personalities. In order to address these shortcomings, an attempt is made to develop a model for future application, which places the mapping process within the context of a broader strategic planning process, focussed on a station's programming schedule.
- Full Text:
- Date Issued: 2004
- Authors: Davidson, Brett Russell
- Date: 2004
- Subjects: Radio broadcasting -- South Africa -- Paarl , Radio stations -- South Africa -- Paarl , Radio journalism -- South Africa -- Paarl , Radio broadcasters -- Research -- South Africa -- Paarl , Mass media -- Political aspects -- South Africa , Mass media -- Social aspects -- South Africa , Radio in community development
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3497 , http://hdl.handle.net/10962/d1003716 , Radio broadcasting -- South Africa -- Paarl , Radio stations -- South Africa -- Paarl , Radio journalism -- South Africa -- Paarl , Radio broadcasters -- Research -- South Africa -- Paarl , Mass media -- Political aspects -- South Africa , Mass media -- Social aspects -- South Africa , Radio in community development
- Description: This thesis deals with the introduction of participatory research methods to programming staff working at Radio KC, a South African community radio station based in Paarl, in the Western Cape province. The focus is on a series of workshops conducted at the station, dealing with research tools developed to enable station workers to undertake research of their community. The aim was to determine, by means ofa case study, whether the introduction of participatory research methods could improve the ability of community broadcasters to facilitate democratic participation among the communities in which they operate. More particularly, the thesis assesses whether the application of such methods has improved the ability of the programming staff that were involved in this case study to identify a wider range of stories and voices within their target community, for inclusion in programming content. The participatory research techniques that are applied at the radio station are based on ideas in 'civic mapping' developed by Harwood and McCrehan (1996) under the auspices of The Pew Center for Civic Journalism, and supplemented by insights from Friedland (2001) and Downs and Stea (1977) about the cognitive, normative and imagined dimensions of community. All of the ideas and techniques were adapted for the South African situation. The findings of the research project illustrate that for community stations, the key concepts of 'community' and 'participation' are highly complex ones and that stations need assistance to apply these concepts in their everyday practice. The account of the intervention at Radio KC shows that the process did indeed assist the individual research participants to better deal with the application of these concepts. It did not, however, make much impact on the station as a whole. Reasons for this are believed to lie in the organisational dynamics of the station, and the fact that the model as applied in this case did not provide a means for tackling the agendas, investments and power relations that define the activities of individuals at a given community radio station - what Hochheimer (1993) talks about as the entrenchment of power and personalities. In order to address these shortcomings, an attempt is made to develop a model for future application, which places the mapping process within the context of a broader strategic planning process, focussed on a station's programming schedule.
- Full Text:
- Date Issued: 2004
Genre analysis and the teaching of academic literacy: a case study of an academic discipline in the social sciences
- Authors: Vorwerk, Shane Paul
- Date: 1998
- Subjects: Lectures and lecturing , Lecture method in teaching , Language and culture , Discourse analysis , Language and culture -- South Africa , English language -- Discourse analysis , Intercultural communication -- South Africa , English language -- Study and teaching -- South Africa -- Foreign speakers
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2365 , http://hdl.handle.net/10962/d1002648 , Lectures and lecturing , Lecture method in teaching , Language and culture , Discourse analysis , Language and culture -- South Africa , English language -- Discourse analysis , Intercultural communication -- South Africa , English language -- Study and teaching -- South Africa -- Foreign speakers
- Description: Students in tertiary educational institutions in South Africa come from many different backgrounds and have varied educational experiences. Some students, especially those from non-English speaking backgrounds, may encounter linguistic difficulties with various academic tasks. In order for students to be successful at university, they must become academically literate. That is, they must master all the reading, writing, listening and comprehension tasks required by the disciplines in which they are studying. One such task is presented by the academic lecture which is an integral part of any course of study. Linguistically, the academic lecture can be seen as a particular genre with unique characteristics. This study investigated some linguistic characteristics of academic lectures. The discipline of Political Science, as a Social Science, was chosen because there is little research that has been done on language in the Social Sciences. The Political Science sub-disciplines of Political Philosophy, South African Politics, and International Relations were used in this research. First year lectures were recorded from each of these three sub-disciplines. The linguistic characteristics of lectures were analysed using techniques drawn from Systemic Functional linguistic theory. The analysis concentrated on the aspects mode and field as they were realised in the lectures. In addition, higher level generic structure was also analysed. The insights gained from the analysis were validated through interviews with the lecturers who gave the lectures. The aim of this research was to develop a linguistic characterisation of the lecture genre as it occurs in the three sub-disciplines of Political Science. The results of this research suggest that although there is a unified academic lecture genre, there is variation according to sub-discipline. The implications of this variation are discussed with reference to their relevance to teaching academic literacy.
- Full Text:
- Date Issued: 1998
- Authors: Vorwerk, Shane Paul
- Date: 1998
- Subjects: Lectures and lecturing , Lecture method in teaching , Language and culture , Discourse analysis , Language and culture -- South Africa , English language -- Discourse analysis , Intercultural communication -- South Africa , English language -- Study and teaching -- South Africa -- Foreign speakers
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2365 , http://hdl.handle.net/10962/d1002648 , Lectures and lecturing , Lecture method in teaching , Language and culture , Discourse analysis , Language and culture -- South Africa , English language -- Discourse analysis , Intercultural communication -- South Africa , English language -- Study and teaching -- South Africa -- Foreign speakers
- Description: Students in tertiary educational institutions in South Africa come from many different backgrounds and have varied educational experiences. Some students, especially those from non-English speaking backgrounds, may encounter linguistic difficulties with various academic tasks. In order for students to be successful at university, they must become academically literate. That is, they must master all the reading, writing, listening and comprehension tasks required by the disciplines in which they are studying. One such task is presented by the academic lecture which is an integral part of any course of study. Linguistically, the academic lecture can be seen as a particular genre with unique characteristics. This study investigated some linguistic characteristics of academic lectures. The discipline of Political Science, as a Social Science, was chosen because there is little research that has been done on language in the Social Sciences. The Political Science sub-disciplines of Political Philosophy, South African Politics, and International Relations were used in this research. First year lectures were recorded from each of these three sub-disciplines. The linguistic characteristics of lectures were analysed using techniques drawn from Systemic Functional linguistic theory. The analysis concentrated on the aspects mode and field as they were realised in the lectures. In addition, higher level generic structure was also analysed. The insights gained from the analysis were validated through interviews with the lecturers who gave the lectures. The aim of this research was to develop a linguistic characterisation of the lecture genre as it occurs in the three sub-disciplines of Political Science. The results of this research suggest that although there is a unified academic lecture genre, there is variation according to sub-discipline. The implications of this variation are discussed with reference to their relevance to teaching academic literacy.
- Full Text:
- Date Issued: 1998
Preparation and characterization of sodium alginate-based dissolvable bandages as potential wound dressings
- Authors: Ndlovu, Sindi Prescila
- Date: 2020
- Subjects: Nanostructured materials
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: http://hdl.handle.net/10353/18800 , vital:42734
- Description: Burn wounds are among the leading causes of mortality and morbidity globally. Burn wounds are painful, cause social isolation and causes post-traumatic stress disorder (PTSD) due to prolonged hospital treatment. The challenges encountered in the treatment of burn wounds are infections resulting from the use of wound dressings that do not protect the wounds from microbial invasion. Sodium alginate-based dissolvable bandages were prepared and encapsulated with various antibiotics (ampicillin and ciprofloxacin) and nanoparticles (i.e. zinc oxide and silver). The dissolvable bandages were characterized by FTIR, SEM/EDX, TEM, XRD and TGA. Furthermore, the porosity, water uptake, biodegradation, antibacterial studies, and water vapour transmittance properties of the bandages were also studied. The prepared sodium alginate-based dissolvable bandage incorporated with varied amount of drugs (such as ampicillin, ciprofloxacin, zinc oxide and silver nanoparticle) exhibited good porosity, high water uptake, excellent WVTR with sustained drug release profiles. The loading of ZnO Nps, CLP/ZnO Nps and Ag Nps/CLP into the bandages improved the antibacterial activity of the bandages against both gram-negative and gram-positive strains of bacteria. XRD confirmed the amorphous nature of the dissolvable bandage and the absence of free drugs. FTIR revealed the successful encapsulation of the antibiotics and nanoparticle into the dissolvable bandages. The dissolvable bandages exhibited high water uptake ranging from 870-4468% with good porosity suggesting that they can absorb large amount of wound exudates. The drug release for all the bandages obeyed the Korsemeyer Peppas drug release model with n values in the range 0.1-1.0. The results obtained indicate that the bandages are potential wound dressings for burns and for patients with sensitive skins.
- Full Text:
- Date Issued: 2020
- Authors: Ndlovu, Sindi Prescila
- Date: 2020
- Subjects: Nanostructured materials
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: http://hdl.handle.net/10353/18800 , vital:42734
- Description: Burn wounds are among the leading causes of mortality and morbidity globally. Burn wounds are painful, cause social isolation and causes post-traumatic stress disorder (PTSD) due to prolonged hospital treatment. The challenges encountered in the treatment of burn wounds are infections resulting from the use of wound dressings that do not protect the wounds from microbial invasion. Sodium alginate-based dissolvable bandages were prepared and encapsulated with various antibiotics (ampicillin and ciprofloxacin) and nanoparticles (i.e. zinc oxide and silver). The dissolvable bandages were characterized by FTIR, SEM/EDX, TEM, XRD and TGA. Furthermore, the porosity, water uptake, biodegradation, antibacterial studies, and water vapour transmittance properties of the bandages were also studied. The prepared sodium alginate-based dissolvable bandage incorporated with varied amount of drugs (such as ampicillin, ciprofloxacin, zinc oxide and silver nanoparticle) exhibited good porosity, high water uptake, excellent WVTR with sustained drug release profiles. The loading of ZnO Nps, CLP/ZnO Nps and Ag Nps/CLP into the bandages improved the antibacterial activity of the bandages against both gram-negative and gram-positive strains of bacteria. XRD confirmed the amorphous nature of the dissolvable bandage and the absence of free drugs. FTIR revealed the successful encapsulation of the antibiotics and nanoparticle into the dissolvable bandages. The dissolvable bandages exhibited high water uptake ranging from 870-4468% with good porosity suggesting that they can absorb large amount of wound exudates. The drug release for all the bandages obeyed the Korsemeyer Peppas drug release model with n values in the range 0.1-1.0. The results obtained indicate that the bandages are potential wound dressings for burns and for patients with sensitive skins.
- Full Text:
- Date Issued: 2020
Enrichment strategies for gifted English first language (HG) pupils at the senior secondary level : a critical evaluation of a programme implemented at Grey Boys' High School, Port Elizabeth, 1986-1988
- Authors: Cunningham, Gregory Mark
- Date: 1990
- Subjects: English language -- Study and teaching (Secondary) -- South Africa -- Eastern Cape Gifted children -- Education (Secondary) -- South Africa -- Eastern Cape Gifted children -- Education -- Research
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1510 , http://hdl.handle.net/10962/d1003392
- Description: Programmes developed specifically for the gifted and talented pupil are not a novel idea. Yet, by comparison, the history of gifted education is a brief one. Highly gifted and talented pupils often have difficulty being challenged in a conventional classroom situation. Since classroom instruction is usually designed for the benefit of pupils who function at the level of the majority of their peer age-group, this teaching, no matter how well done, may not be appropriate for the extremely gifted pupil whose abilities differ greatly from this group. Even special programmes for gifted and talented students may be designed for a broad group of gifted students and may not meet the specific needs of the gifted child, especially ones with a special intellectual talent. While it is important to bear aspects such as the characteristics of giftedness and the attributes of the talented individual in mind, the basis of this dissertation examines what enrichment and acceleration strategies may be utilised by the English First Language (HG) teacher when presented with a preselected group of pupils who are gifted in English, utilising a composite gifted educational model as a mechanism for the development of this specific programme.
- Full Text:
- Date Issued: 1990
- Authors: Cunningham, Gregory Mark
- Date: 1990
- Subjects: English language -- Study and teaching (Secondary) -- South Africa -- Eastern Cape Gifted children -- Education (Secondary) -- South Africa -- Eastern Cape Gifted children -- Education -- Research
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1510 , http://hdl.handle.net/10962/d1003392
- Description: Programmes developed specifically for the gifted and talented pupil are not a novel idea. Yet, by comparison, the history of gifted education is a brief one. Highly gifted and talented pupils often have difficulty being challenged in a conventional classroom situation. Since classroom instruction is usually designed for the benefit of pupils who function at the level of the majority of their peer age-group, this teaching, no matter how well done, may not be appropriate for the extremely gifted pupil whose abilities differ greatly from this group. Even special programmes for gifted and talented students may be designed for a broad group of gifted students and may not meet the specific needs of the gifted child, especially ones with a special intellectual talent. While it is important to bear aspects such as the characteristics of giftedness and the attributes of the talented individual in mind, the basis of this dissertation examines what enrichment and acceleration strategies may be utilised by the English First Language (HG) teacher when presented with a preselected group of pupils who are gifted in English, utilising a composite gifted educational model as a mechanism for the development of this specific programme.
- Full Text:
- Date Issued: 1990
Morphology, patterns and processes in the Oyster Bay headland bypass dunefield, South Africa
- Authors: Elkington, Lauren
- Date: 2013
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:20984 , http://hdl.handle.net/10962/5879
- Description: Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed.
- Full Text:
- Date Issued: 2013
- Authors: Elkington, Lauren
- Date: 2013
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:20984 , http://hdl.handle.net/10962/5879
- Description: Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed.
- Full Text:
- Date Issued: 2013
Critical studies of John Milton, T.S. Eliot and other writers
- Authors: Peter, John Desmond
- Date: 1973
- Subjects: Milton, John, 1608-1674 -- Paradise lost , Crashaw, Richard, 1613?-1649 -- Criticism and interpretation , Joyce, James, 1882-1941 -- Criticism and interpretation , Coleridge, Samuel Taylor, 1772-1834 -- Criticism and interpretation , Marston, John, 1575?-1634 -- Criticism and interpretation , Eliot, T. S. (Thomas Stearns), 1888-1965 -- Criticism and interpretation
- Language: English
- Type: Thesis , Doctoral , DLitt
- Identifier: vital:2329 , http://hdl.handle.net/10962/d1018265
- Full Text:
- Date Issued: 1973
- Authors: Peter, John Desmond
- Date: 1973
- Subjects: Milton, John, 1608-1674 -- Paradise lost , Crashaw, Richard, 1613?-1649 -- Criticism and interpretation , Joyce, James, 1882-1941 -- Criticism and interpretation , Coleridge, Samuel Taylor, 1772-1834 -- Criticism and interpretation , Marston, John, 1575?-1634 -- Criticism and interpretation , Eliot, T. S. (Thomas Stearns), 1888-1965 -- Criticism and interpretation
- Language: English
- Type: Thesis , Doctoral , DLitt
- Identifier: vital:2329 , http://hdl.handle.net/10962/d1018265
- Full Text:
- Date Issued: 1973
Teenage care by the Methodist church of Southern Africa :The case of Port Elizabeth North circuit (TPT 900)
- Authors: Jibiliza, Xolisa Terrance
- Date: 2020
- Subjects: Church work with teenagers Teenagers -- Pastoral counseling of Teenage pregnancy
- Language: English
- Type: Thesis , Doctoral , PhD (Theology)
- Identifier: http://hdl.handle.net/10353/17884 , vital:41973
- Description: The research study sought to acknowledge that there was a need of caring for teenagers by the Methodist Church of Southern Africa as majority of them responds to their adolescent stage with bad behaviour. This was a critical stage that challenged teenagers and required much more attention both from home, schools and church. A teenager is a young person whose age falls within the range from 13 to 19. They are called teenagers because their age number ends with "teen" (Ausubel 2002: 12). This study sought to investigate whether the impact of caring for teenagers by the Methodist Church of Southern Africa and had to achieved the intended mission statement of MCSA which is “A Methodist called to proclaim the Gospel of Jesus Christ healing and transformation” in the New Brighton and KwaZakhele areas that formed Port Elizabeth North Circuit. The study would achieve its goal by looking at the needs of a teenager such as caring which includes love, food, medication, accommodation and educational expenses required in a month. The teenage stage is a transitional stage of physical and psychological human development that generally occurs during the period from puberty to legal adulthood. The teenage years, though it’s physical, psychological and cultural expressions may begin earlier and end later (Heine, 2016: 14). This is a critical stage for a child because sometimes children change their behaviour during this period, others manage to go through this stage and behave well but others struggle and falling into substance abuse and teenage pregnancy. 2 But this stage followed a puberty stage. Gouws and Kruger (2014: 3) stresses that puberty is a period of several years in which rapid physical growth and psychological changes occur, culminating in sexual maturity. The average onset of puberty is at 10 or 11 for girls and age 11 or 12 for boys. Gouws and Kruger (2014: 3) argued that every person's individual timetable for puberty is influenced primarily by inheritance, although environmental factors, such as diet and exercise, also apply some influences. Gouws and Kruger (2014: 3) further says during puberty body growth accelerates, the reproductive organs become functional, sexual maturity is attained and secondary sexual characteristics appear. Therefore, teenagers could fall into early sex activity that leads to teenage pregnancy. Brewster (2011:183–185) stresses the consideration to the issue of the Bible as a book that contains signs in his interpretation of the theological significance of children. Moreover, the fundamental theological rationale for the notion of children is that Jesus presented child as a sign of the kingdom of God (White 2011:55). Bunge (2011: 24) argues that particular perspectives on children from the Bible should be held in creative tension. Those perspectives are comprising the notions that children are gifts of God, sources of joy, sinful creatures and moral agents, developing beings in need of instruction and guidance, are fully human and made in the likeness and image of God, they are models of faith and sources of revelation, lastly they are in need of justice. Choudhury, Blakemore & Charman (2006: 1) stated that adolescence is the transitional period between late childhood and the beginning of adulthood, and marks the beginning of the reproductive lifespan in humans. Eastman (2010: 2) argued that this phase of human development is “defined by cultural practices and 3 biological occurrences - a period by which behavioural abilities and expectations change. All societies and cultures devise means of marking and handling the realities of human existence which is Birth, Death and Procreation”. The onset of puberty is one such. The transition from dependency as children to the maturity of full adulthood is a journey common to humankind.
- Full Text:
- Date Issued: 2020
- Authors: Jibiliza, Xolisa Terrance
- Date: 2020
- Subjects: Church work with teenagers Teenagers -- Pastoral counseling of Teenage pregnancy
- Language: English
- Type: Thesis , Doctoral , PhD (Theology)
- Identifier: http://hdl.handle.net/10353/17884 , vital:41973
- Description: The research study sought to acknowledge that there was a need of caring for teenagers by the Methodist Church of Southern Africa as majority of them responds to their adolescent stage with bad behaviour. This was a critical stage that challenged teenagers and required much more attention both from home, schools and church. A teenager is a young person whose age falls within the range from 13 to 19. They are called teenagers because their age number ends with "teen" (Ausubel 2002: 12). This study sought to investigate whether the impact of caring for teenagers by the Methodist Church of Southern Africa and had to achieved the intended mission statement of MCSA which is “A Methodist called to proclaim the Gospel of Jesus Christ healing and transformation” in the New Brighton and KwaZakhele areas that formed Port Elizabeth North Circuit. The study would achieve its goal by looking at the needs of a teenager such as caring which includes love, food, medication, accommodation and educational expenses required in a month. The teenage stage is a transitional stage of physical and psychological human development that generally occurs during the period from puberty to legal adulthood. The teenage years, though it’s physical, psychological and cultural expressions may begin earlier and end later (Heine, 2016: 14). This is a critical stage for a child because sometimes children change their behaviour during this period, others manage to go through this stage and behave well but others struggle and falling into substance abuse and teenage pregnancy. 2 But this stage followed a puberty stage. Gouws and Kruger (2014: 3) stresses that puberty is a period of several years in which rapid physical growth and psychological changes occur, culminating in sexual maturity. The average onset of puberty is at 10 or 11 for girls and age 11 or 12 for boys. Gouws and Kruger (2014: 3) argued that every person's individual timetable for puberty is influenced primarily by inheritance, although environmental factors, such as diet and exercise, also apply some influences. Gouws and Kruger (2014: 3) further says during puberty body growth accelerates, the reproductive organs become functional, sexual maturity is attained and secondary sexual characteristics appear. Therefore, teenagers could fall into early sex activity that leads to teenage pregnancy. Brewster (2011:183–185) stresses the consideration to the issue of the Bible as a book that contains signs in his interpretation of the theological significance of children. Moreover, the fundamental theological rationale for the notion of children is that Jesus presented child as a sign of the kingdom of God (White 2011:55). Bunge (2011: 24) argues that particular perspectives on children from the Bible should be held in creative tension. Those perspectives are comprising the notions that children are gifts of God, sources of joy, sinful creatures and moral agents, developing beings in need of instruction and guidance, are fully human and made in the likeness and image of God, they are models of faith and sources of revelation, lastly they are in need of justice. Choudhury, Blakemore & Charman (2006: 1) stated that adolescence is the transitional period between late childhood and the beginning of adulthood, and marks the beginning of the reproductive lifespan in humans. Eastman (2010: 2) argued that this phase of human development is “defined by cultural practices and 3 biological occurrences - a period by which behavioural abilities and expectations change. All societies and cultures devise means of marking and handling the realities of human existence which is Birth, Death and Procreation”. The onset of puberty is one such. The transition from dependency as children to the maturity of full adulthood is a journey common to humankind.
- Full Text:
- Date Issued: 2020
Active Layer Dynamics at Four Borehole Sites in Western Dronning Maud Land, Antarctica
- Authors: Kotzé, Camilla
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4894 , http://hdl.handle.net/10962/d1021295
- Description: Permafrost and active layer dynamics in the Antarctic play an important role within terrestrial landscapes and ecosystems and as a climate change indicator. However, they remain less thoroughly researched than their Northern-Hemispheric counterpart. Despite advancements made by ANTPAS on the permafrost and active layer monitoring network in the Antarctic, observational gaps still exist. Western Dronning Maud Land (WDML) has been identified as one of these gaps, necessitating further research on permafrost dynamics and the influence of climate parameters thereon. Such elucidation is critical to both the cryospheric and life sciences. Variations in the surface climate of Antarctica can be seen as a result of inter-annual variations in atmospheric circulation, enhancing permafrost degradation and active layer thickening which directly affects soil processes, such as sorting and cryoturbation. Ground temperatures from four permafrost boreholes from WDML were analysed from 2007 to 2014. The study sites exhibit seasonal freezing, periglacial landforms, and altitudinal variation, ranging between ca. 450masl to ca. 1300masl. Using ground thermal regime and regional climate data, the spatial and temporal variability of the active layer in the Ahlmannryggen and Jutulsessen areas of WDML were characterised. 137 Cs tracing has revealed that the active layer and associated landforms have been active over the past half century. Further results show that active layer depths at each site vary inter-annually and are particularly influenced by snow cover, altitude and distance to the ice-shelf. Moreover, a correlation between the SAO (Semi-Annual Oscillation) and measured ground temperatures was found, principally during the transitional season of the SAO in May and September. The relationship between climate and ground thermal regimes, especially the influence of teleconnections thereon, is essential to improving the understanding of permafrost dynamics and landform morphology in continental Antarctica.
- Full Text:
- Date Issued: 2016
- Authors: Kotzé, Camilla
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4894 , http://hdl.handle.net/10962/d1021295
- Description: Permafrost and active layer dynamics in the Antarctic play an important role within terrestrial landscapes and ecosystems and as a climate change indicator. However, they remain less thoroughly researched than their Northern-Hemispheric counterpart. Despite advancements made by ANTPAS on the permafrost and active layer monitoring network in the Antarctic, observational gaps still exist. Western Dronning Maud Land (WDML) has been identified as one of these gaps, necessitating further research on permafrost dynamics and the influence of climate parameters thereon. Such elucidation is critical to both the cryospheric and life sciences. Variations in the surface climate of Antarctica can be seen as a result of inter-annual variations in atmospheric circulation, enhancing permafrost degradation and active layer thickening which directly affects soil processes, such as sorting and cryoturbation. Ground temperatures from four permafrost boreholes from WDML were analysed from 2007 to 2014. The study sites exhibit seasonal freezing, periglacial landforms, and altitudinal variation, ranging between ca. 450masl to ca. 1300masl. Using ground thermal regime and regional climate data, the spatial and temporal variability of the active layer in the Ahlmannryggen and Jutulsessen areas of WDML were characterised. 137 Cs tracing has revealed that the active layer and associated landforms have been active over the past half century. Further results show that active layer depths at each site vary inter-annually and are particularly influenced by snow cover, altitude and distance to the ice-shelf. Moreover, a correlation between the SAO (Semi-Annual Oscillation) and measured ground temperatures was found, principally during the transitional season of the SAO in May and September. The relationship between climate and ground thermal regimes, especially the influence of teleconnections thereon, is essential to improving the understanding of permafrost dynamics and landform morphology in continental Antarctica.
- Full Text:
- Date Issued: 2016
Influence of blue/green versus red and white light sources on human dark adaptation and other selected visual functions
- Authors: Hendrikse, Egbert Johannes
- Date: 1994
- Subjects: Light -- Physiological effect Lighting Vision -- Research Night vision Visual acuity Color -- Physiological effect Color vision
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5146 , http://hdl.handle.net/10962/d1009497
- Description: Red interior lighting used to preserve dark-adaptation needs to be replaced in military applications by blue/green lighting which is not detectable by 3rd-generation image intensifiers. This study investigated the influence of blue/green as compared to red and white light of equal photopic intensity on subsequent visual acuity , contrast sensitivity and dark-adaptation. Male subjects (n = 90) were assigned to one of 15 treatment conditions (n = 6) as determined by the colour (blue/green, red or white) and intensity (0.1; 0.4; 1.6; 6.4 and 25.6 cd/m²) of the pre-adaptation stimuli. A modified Goldmann/Weekers adaptometer was used to present the preadaptation stimuli, test stimuli and record visual (luminance) thresholds of each subject. Blue/green lighting had the same affect on visual (photopic) acuity and contrast sensitivity as white and red lighting. Blue/green affected visual (absolute) threshold at the start and during the process of dark-adaptation in the same manner as white but not the same as red lighting. White and red lighting did not differ significantly (p < 0.01) at low intensities (mesopic range) but did at the higher intensities (photopic range). After exposure to blue/green and white light, it will take longer to reach the same level of dark-adaptation than after exposure to red. These time differences increase with" increased intensities. The brightness ratio between red and white lights to produce the same dark-adaptation increases with an increase in intensity. At the upper mesopic region the differences between the effects of white and red lighting on subsequent dark-adaptation become irregular due to the inability to accurately equate non-monochromatic lights in the mesopic range.
- Full Text:
- Date Issued: 1994
- Authors: Hendrikse, Egbert Johannes
- Date: 1994
- Subjects: Light -- Physiological effect Lighting Vision -- Research Night vision Visual acuity Color -- Physiological effect Color vision
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5146 , http://hdl.handle.net/10962/d1009497
- Description: Red interior lighting used to preserve dark-adaptation needs to be replaced in military applications by blue/green lighting which is not detectable by 3rd-generation image intensifiers. This study investigated the influence of blue/green as compared to red and white light of equal photopic intensity on subsequent visual acuity , contrast sensitivity and dark-adaptation. Male subjects (n = 90) were assigned to one of 15 treatment conditions (n = 6) as determined by the colour (blue/green, red or white) and intensity (0.1; 0.4; 1.6; 6.4 and 25.6 cd/m²) of the pre-adaptation stimuli. A modified Goldmann/Weekers adaptometer was used to present the preadaptation stimuli, test stimuli and record visual (luminance) thresholds of each subject. Blue/green lighting had the same affect on visual (photopic) acuity and contrast sensitivity as white and red lighting. Blue/green affected visual (absolute) threshold at the start and during the process of dark-adaptation in the same manner as white but not the same as red lighting. White and red lighting did not differ significantly (p < 0.01) at low intensities (mesopic range) but did at the higher intensities (photopic range). After exposure to blue/green and white light, it will take longer to reach the same level of dark-adaptation than after exposure to red. These time differences increase with" increased intensities. The brightness ratio between red and white lights to produce the same dark-adaptation increases with an increase in intensity. At the upper mesopic region the differences between the effects of white and red lighting on subsequent dark-adaptation become irregular due to the inability to accurately equate non-monochromatic lights in the mesopic range.
- Full Text:
- Date Issued: 1994