A polarographic study : the estimation of sodium and potassium in the presence of each other
- Authors: Carter, Austin John
- Date: 1938
- Subjects: Polarographs , Polarography , Potassium , Sodium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4455 , http://hdl.handle.net/10962/d1010434
- Description: The polarographic method has been described, and an attempt made to describe the difficulty of the simultaneous deposition of sodium and potassium. Various methods have been examined, of which precipitation of potassium with magnesium dipicrylaminate seems the most promising. The quantitative results were unsatisfactory, and possible sources of error are discussed. The method, while very convenient, rapid and labour-saving, is not sufficiently standardised to be trustworthy.
- Full Text:
- Date Issued: 1938
- Authors: Carter, Austin John
- Date: 1938
- Subjects: Polarographs , Polarography , Potassium , Sodium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4455 , http://hdl.handle.net/10962/d1010434
- Description: The polarographic method has been described, and an attempt made to describe the difficulty of the simultaneous deposition of sodium and potassium. Various methods have been examined, of which precipitation of potassium with magnesium dipicrylaminate seems the most promising. The quantitative results were unsatisfactory, and possible sources of error are discussed. The method, while very convenient, rapid and labour-saving, is not sufficiently standardised to be trustworthy.
- Full Text:
- Date Issued: 1938
A possible mechanism for enzymic depilation of skins
- Authors: Brady, Dean
- Date: 1989
- Subjects: Chemistry, Technical , Tanning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3877 , http://hdl.handle.net/10962/d1001611
- Description: Streptomyces fradiae is a bacterium which has been previously found to produce extracellular enzymes which are capable of wool degradation and skin depilation. Streptomyces fradiae 3739 and other strains of Streptomyces were found in this study to be able to degrade a keratin source (wool) to a considerable degree. However according to the evidence of SEM micrographs presented here the highly keratinised spindle cells of the paracortex are fairly resistant to protease attack, and it is the cementation material which binds these cells together which is initially degraded by the proteases. A large degree of correlation was found with the strains of Streptomyces studied, between the ability of the individual strains to degrade wool and the ability of their extracellular proteases to reduce the depilation load of sheepskins. With further analysis S. fradiae 3739 was found to produce at least one amylase and four or more proteases. The proteases as a group had maximal proteolytic activity in the 8.0-9.0 pH unit range, and were considerably thermostabilised by the inclusion of calcium ions into the reaction solution. The protease group was found to cause depilation of merino sheepskins. For comparative purposes a protease produced by a strain of Proteus vulgaris isolated from a staling hide with hair slip (natural depilation) was studied. The protease activity was maximal in the alkaline region between 8.0-9.0 pH units. Tbe protease appeared to be a single enzyme with a molecular mass of approximately 44 000 daltons. The protease was maximally active at 40°C, although it was only thermostable to 30°C. The enzyme was ineffectual as a depilant except when the skin was pre-treated with a strong alkali, preferably including sodium sulphite in the protease preparation. One of the most important differences between the extracellular proteases of S. fradiae and P. vulgaris was that the former were greater in variety and caused a greater decrease in the depilation load of sheepskins than the latter. Further research with mixtures of commercial proteases provided evidence that a synergistic depilatory effect occurs when proteases of complementary bond specificities are used in conjunction in enzymic depilatory preparations. Some form of strong alkali treatment of skins was found to be necessary to produce leather of the prerequisite quality when the skin was depilated by proteases, otherwise the skin was found to be depleted and stiff. Calcium hydroxide alone was found to be inadequate for this task, probably owing to the fact that it is less alkaline than the lime-sulphide mixture. The calcium hydroxide (lime) must therefore be used in conjunction with sodium hydroxide (which makes the solution as alkaline as that of the lime-sulphide solution) to produce leather comparable to that produced by the lime sulphide treatment. A combination of the information provided by the present research and that gleaned from the relevent literature allows for the construction of a model to represent the possible mechanism of enzymic depilation of skins, in which depilation is caused by the disruption of the basement membrane at the dermal-epidermal junction by the degradation of its constituent molecular components by general proteases, resulting in the removal of the epidermis and its associated wool or hair
- Full Text:
- Date Issued: 1989
- Authors: Brady, Dean
- Date: 1989
- Subjects: Chemistry, Technical , Tanning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3877 , http://hdl.handle.net/10962/d1001611
- Description: Streptomyces fradiae is a bacterium which has been previously found to produce extracellular enzymes which are capable of wool degradation and skin depilation. Streptomyces fradiae 3739 and other strains of Streptomyces were found in this study to be able to degrade a keratin source (wool) to a considerable degree. However according to the evidence of SEM micrographs presented here the highly keratinised spindle cells of the paracortex are fairly resistant to protease attack, and it is the cementation material which binds these cells together which is initially degraded by the proteases. A large degree of correlation was found with the strains of Streptomyces studied, between the ability of the individual strains to degrade wool and the ability of their extracellular proteases to reduce the depilation load of sheepskins. With further analysis S. fradiae 3739 was found to produce at least one amylase and four or more proteases. The proteases as a group had maximal proteolytic activity in the 8.0-9.0 pH unit range, and were considerably thermostabilised by the inclusion of calcium ions into the reaction solution. The protease group was found to cause depilation of merino sheepskins. For comparative purposes a protease produced by a strain of Proteus vulgaris isolated from a staling hide with hair slip (natural depilation) was studied. The protease activity was maximal in the alkaline region between 8.0-9.0 pH units. Tbe protease appeared to be a single enzyme with a molecular mass of approximately 44 000 daltons. The protease was maximally active at 40°C, although it was only thermostable to 30°C. The enzyme was ineffectual as a depilant except when the skin was pre-treated with a strong alkali, preferably including sodium sulphite in the protease preparation. One of the most important differences between the extracellular proteases of S. fradiae and P. vulgaris was that the former were greater in variety and caused a greater decrease in the depilation load of sheepskins than the latter. Further research with mixtures of commercial proteases provided evidence that a synergistic depilatory effect occurs when proteases of complementary bond specificities are used in conjunction in enzymic depilatory preparations. Some form of strong alkali treatment of skins was found to be necessary to produce leather of the prerequisite quality when the skin was depilated by proteases, otherwise the skin was found to be depleted and stiff. Calcium hydroxide alone was found to be inadequate for this task, probably owing to the fact that it is less alkaline than the lime-sulphide mixture. The calcium hydroxide (lime) must therefore be used in conjunction with sodium hydroxide (which makes the solution as alkaline as that of the lime-sulphide solution) to produce leather comparable to that produced by the lime sulphide treatment. A combination of the information provided by the present research and that gleaned from the relevent literature allows for the construction of a model to represent the possible mechanism of enzymic depilation of skins, in which depilation is caused by the disruption of the basement membrane at the dermal-epidermal junction by the degradation of its constituent molecular components by general proteases, resulting in the removal of the epidermis and its associated wool or hair
- Full Text:
- Date Issued: 1989
A potential biological role for microcystin in photosynthesis in Microcystis Aeruginosa
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
A predictive biogeography of selected alien plant invaders in South Africa
- Authors: Youthed, Jennifer Gay
- Date: 1997
- Subjects: Alien plants -- South Africa , Biogeography -- South Africa , Acacia -- South Africa , Acacia mearnsii -- South Africa , Opuntia ficus-indica -- South Africa , Solanum -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4846 , http://hdl.handle.net/10962/d1005522 , Alien plants -- South Africa , Biogeography -- South Africa , Acacia -- South Africa , Acacia mearnsii -- South Africa , Opuntia ficus-indica -- South Africa , Solanum -- South Africa
- Description: Five techniques were used to predict the potential biogeography of the four alien plant species, Acacia longifolia, Acacia mearnsii, Opuntia ficus-indica and Solanum sisymbrifolium. Prediction was based on five environmental factors, median annual rainfall, co-efficient of variation for rainfall, mean monthly maximum temperature for January, mean monthly minimum temperature for July and elevation. A geographical information system was used to manage the data and produce the predictive maps. The models were constructed with presence and absence data and then validated by means of an independent data set and chisquared tests. Of the five models used, three (the range, principal components analysis and discriminant function analysis) were linear while the other two (artificial neural networks and fuzzy logic) were non-linear. The two non-linear techniques were chosen as a plant's response to its environment is commonly assumed to be non-linear. However, these two techniques did not offer significant advantages over the linear methods. The principal components analysis was particularly useful in ascertaining the variables that were important in determining the distribution of each species. Artifacts on the predictive maps were also proved useful for this purpose. The techniques that produced the most statistically accurate validation results were the artificial neural networks (77% correct median prediction rate) and the discriminant function analysis (71% correct median prediction rate) while the techniques that performed the worst were the range and the fuzzy classification. The artificial neural network, discriminant function analysis and principal component analysis techniques all show great potential as predictive distribution models.
- Full Text:
- Date Issued: 1997
- Authors: Youthed, Jennifer Gay
- Date: 1997
- Subjects: Alien plants -- South Africa , Biogeography -- South Africa , Acacia -- South Africa , Acacia mearnsii -- South Africa , Opuntia ficus-indica -- South Africa , Solanum -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4846 , http://hdl.handle.net/10962/d1005522 , Alien plants -- South Africa , Biogeography -- South Africa , Acacia -- South Africa , Acacia mearnsii -- South Africa , Opuntia ficus-indica -- South Africa , Solanum -- South Africa
- Description: Five techniques were used to predict the potential biogeography of the four alien plant species, Acacia longifolia, Acacia mearnsii, Opuntia ficus-indica and Solanum sisymbrifolium. Prediction was based on five environmental factors, median annual rainfall, co-efficient of variation for rainfall, mean monthly maximum temperature for January, mean monthly minimum temperature for July and elevation. A geographical information system was used to manage the data and produce the predictive maps. The models were constructed with presence and absence data and then validated by means of an independent data set and chisquared tests. Of the five models used, three (the range, principal components analysis and discriminant function analysis) were linear while the other two (artificial neural networks and fuzzy logic) were non-linear. The two non-linear techniques were chosen as a plant's response to its environment is commonly assumed to be non-linear. However, these two techniques did not offer significant advantages over the linear methods. The principal components analysis was particularly useful in ascertaining the variables that were important in determining the distribution of each species. Artifacts on the predictive maps were also proved useful for this purpose. The techniques that produced the most statistically accurate validation results were the artificial neural networks (77% correct median prediction rate) and the discriminant function analysis (71% correct median prediction rate) while the techniques that performed the worst were the range and the fuzzy classification. The artificial neural network, discriminant function analysis and principal component analysis techniques all show great potential as predictive distribution models.
- Full Text:
- Date Issued: 1997
A preliminary appraisal of the mineral potential of Venda based on a reconnaissance geochemical soil sampling survey and literature review
- Wilson, Michael George Carey
- Authors: Wilson, Michael George Carey
- Date: 1990
- Subjects: Mines and mineral resources -- South Africa -- Venda
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4994 , http://hdl.handle.net/10962/d1005606 , Mines and mineral resources -- South Africa -- Venda
- Description: A reconnaissance soil sampling survey was carried out over Venda by Cycad (Pty) Ltd and the samples were analysed for 36 elements using XRF techniques, by Anglo American Research Laboratories in Johanuesburg. The data resulting from this survey forms the basis for the present interpretive study. Initially the sample positions were co-ordinated, then the geological, soil and sample types were allocated to each point. Twelve lithological groupings were chosen which incorporated most of the available data, retained significant geological characteristics and consisted of statistically significant sample populations. Statistical manipulation was undertaken for each of the lithological groups. Using a final population of 5768 samples, means were determined and anomalous values were identified using a threshold of mean plus two standard deviations. Due to time and budgetary constraints, 24 of the 36 elements were chosen for statisical manipulation and fourteen of these, with particular economic significance, were chosen for plotting, wherever significant numbers of anomalies were present. The element overlays were plotted so as to coincide with 18 of the 25, 1:50 000 topographic sheets covering Venda , the remaining 7 having inadequate sample coverage to yield meaningful contours. In this way a total of 175 element overlay sheets were plotted, each showing contoured element levels, with selected anomalous values. The treatment of the vast body of information made available by the Cycad sampling programme has thus been selective and has continually been aimed at highlighting and concentrating attention on the areas of greatest indicated mineralization potential, rather than on specific anomalies. In this regard it is felt that the present study has been successful, in spite of limited sample coverage in some areas. Combining the results of this study with a modern tectonically-based appraisal of mineralization potential and a knowledge of the local geology and previously known mineralization gleaned from an extensive literature review, the following types of mineralization are considered to have the highest potential in Venda: i) Nickel-copper-platinum mineralization as well as magnesite, in the olivine dolerite sills which intrude the base of the Karoo Sequence in Northern Venda. ii) Coal in the basal Karoo Sequence sediments in a broad zone from Jazz 715 MS in the west, and along the Klein Tshipise fault from Amonda 159 MT to the Mutale Copper Fields then east of these to the Kruger National Park. Where intrusives invade these lower Karoo sed iments the potential exists for amorphous graphite. iii) Hydrothermal copper and possibly gold and silver concentrations, in Nzhelele and Sibasa Formation rocks, particularly those associated with faults known to have been active in post-Soutpansberg times. iv) Sediment-hosted massive sulphide deposits (Cu-Pb -Zn) close to basin margin faults, near intersections with cross cutting faults that have resulted in localized basin formation. These are most likely in the Soutpansberg sediments. v) Martle, flake-graphite and late stage skarn mineralization (including lead, zinc, gold and tungsten), in calcareous rocks of the Gumbu Formation.
- Full Text:
- Date Issued: 1990
- Authors: Wilson, Michael George Carey
- Date: 1990
- Subjects: Mines and mineral resources -- South Africa -- Venda
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4994 , http://hdl.handle.net/10962/d1005606 , Mines and mineral resources -- South Africa -- Venda
- Description: A reconnaissance soil sampling survey was carried out over Venda by Cycad (Pty) Ltd and the samples were analysed for 36 elements using XRF techniques, by Anglo American Research Laboratories in Johanuesburg. The data resulting from this survey forms the basis for the present interpretive study. Initially the sample positions were co-ordinated, then the geological, soil and sample types were allocated to each point. Twelve lithological groupings were chosen which incorporated most of the available data, retained significant geological characteristics and consisted of statistically significant sample populations. Statistical manipulation was undertaken for each of the lithological groups. Using a final population of 5768 samples, means were determined and anomalous values were identified using a threshold of mean plus two standard deviations. Due to time and budgetary constraints, 24 of the 36 elements were chosen for statisical manipulation and fourteen of these, with particular economic significance, were chosen for plotting, wherever significant numbers of anomalies were present. The element overlays were plotted so as to coincide with 18 of the 25, 1:50 000 topographic sheets covering Venda , the remaining 7 having inadequate sample coverage to yield meaningful contours. In this way a total of 175 element overlay sheets were plotted, each showing contoured element levels, with selected anomalous values. The treatment of the vast body of information made available by the Cycad sampling programme has thus been selective and has continually been aimed at highlighting and concentrating attention on the areas of greatest indicated mineralization potential, rather than on specific anomalies. In this regard it is felt that the present study has been successful, in spite of limited sample coverage in some areas. Combining the results of this study with a modern tectonically-based appraisal of mineralization potential and a knowledge of the local geology and previously known mineralization gleaned from an extensive literature review, the following types of mineralization are considered to have the highest potential in Venda: i) Nickel-copper-platinum mineralization as well as magnesite, in the olivine dolerite sills which intrude the base of the Karoo Sequence in Northern Venda. ii) Coal in the basal Karoo Sequence sediments in a broad zone from Jazz 715 MS in the west, and along the Klein Tshipise fault from Amonda 159 MT to the Mutale Copper Fields then east of these to the Kruger National Park. Where intrusives invade these lower Karoo sed iments the potential exists for amorphous graphite. iii) Hydrothermal copper and possibly gold and silver concentrations, in Nzhelele and Sibasa Formation rocks, particularly those associated with faults known to have been active in post-Soutpansberg times. iv) Sediment-hosted massive sulphide deposits (Cu-Pb -Zn) close to basin margin faults, near intersections with cross cutting faults that have resulted in localized basin formation. These are most likely in the Soutpansberg sediments. v) Martle, flake-graphite and late stage skarn mineralization (including lead, zinc, gold and tungsten), in calcareous rocks of the Gumbu Formation.
- Full Text:
- Date Issued: 1990
A preliminary assessment linking altered catchment land-cover to the health of four temporarily open/closed South African estuaries
- Authors: Masefield, Vincent Antony
- Date: 2014
- Subjects: Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4877 , http://hdl.handle.net/10962/d1013096
- Description: Estuaries worldwide are being subjected to various degrees of catchment degradation, which is having severe consequences on the integrity of these aquatic ecosystems and their ability to function properly. This thesis investigated the relationship between catchment land-cover and estuarine health in four temporarily open/closed estuarine systems (TOCEs) in South Africa, namely the Groot Brak, East Kleinemonde, Mdloti and Tongati. GIS techniques were employed to delineate catchments, lower sections of catchments, 1 km and 100 m buffer zones, and to quantify the extent of land-cover classes present within these delineations. Anthropogenic activities outlined by the Department of Water Affairs and Forestry (DWAF) Resource Directed Measures (RDM) studies and their associated land-cover classes were described. The possible links between catchment and buffer zone land-cover class composition and health of the estuaries were explored. Results indicated that there was a relationship between catchment and estuarine health within the Coastal Protection Zone (CPZ) (1 km and 100 m) buffers, but not at a broader catchment level. Out of natural, urban built-up and cultivation land-cover classes, natural land was determined to be the best predictor of estuarine health within the CPZs. A method of rapidly assessing South African TOCE condition was applied and could be used to prioritise these estuaries for rehabilitation and/or conservation.
- Full Text:
- Date Issued: 2014
- Authors: Masefield, Vincent Antony
- Date: 2014
- Subjects: Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4877 , http://hdl.handle.net/10962/d1013096
- Description: Estuaries worldwide are being subjected to various degrees of catchment degradation, which is having severe consequences on the integrity of these aquatic ecosystems and their ability to function properly. This thesis investigated the relationship between catchment land-cover and estuarine health in four temporarily open/closed estuarine systems (TOCEs) in South Africa, namely the Groot Brak, East Kleinemonde, Mdloti and Tongati. GIS techniques were employed to delineate catchments, lower sections of catchments, 1 km and 100 m buffer zones, and to quantify the extent of land-cover classes present within these delineations. Anthropogenic activities outlined by the Department of Water Affairs and Forestry (DWAF) Resource Directed Measures (RDM) studies and their associated land-cover classes were described. The possible links between catchment and buffer zone land-cover class composition and health of the estuaries were explored. Results indicated that there was a relationship between catchment and estuarine health within the Coastal Protection Zone (CPZ) (1 km and 100 m) buffers, but not at a broader catchment level. Out of natural, urban built-up and cultivation land-cover classes, natural land was determined to be the best predictor of estuarine health within the CPZs. A method of rapidly assessing South African TOCE condition was applied and could be used to prioritise these estuaries for rehabilitation and/or conservation.
- Full Text:
- Date Issued: 2014
A preliminary investigation and photographic atlas of nodules found in the Bokkelveld group (Gydo formation), Steytlerville district, South Africa
- Authors: Browning, Claire
- Date: 2009
- Subjects: Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10656 , http://hdl.handle.net/10948/927 , Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Description: Nodules within the lower Bokkeveld shales often contain well-preserved invertebrate fossil material. The aim of this study was to describe some characteristics seen at various scales (macro-, micro- and ultra -) within nodules that might contribute to an understanding of aspects of nodule formation and the reasons for the excellent preservation of the fossil material within these nodules. Detailed, high quality macro-photographs were taken of sliced and whole nodule surfaces and a catalogue was produced to tentatively identify fossils present and illustrate the variations seen within nodules. Selected nodules were then subjected to petrographic, ultra-structural (SEM) and some chemical (EDS, XRD & XRF) analysis to investigate the possible reasons for these variations. The chemical results have indicated that nodules are enriched with quartz compared to the surrounding shale. Quartz is also the dominant mineral replacing trilobite carapace material within nodules, while trilobite material within shales is replaced with equal proportions of hematite, biotite and quartz. It appears that the higher resistance of quartz to weathering is the dominant factor leading to the preservation of both nodules within the shales and trilobite material within the nodules examined. A comparison with some Western Cape nodules highlighted possible variations in overall nodule chemical composition along strike. Western Cape nodules are predominantly composed of apatite whereas the Cockscomb nodules are mainly composed of quartz. This quartz-apatite compositional variation in nodules occurring within a single formation has been reported from nodules found in the Armorican Massif of France which are very similar in a number of respects to the Bokkeveld nodules described in this study. Based on various features of the fossils present and the structure of nodules they were probably formed during early diagenesis within an epeiric marine deposit greatly affected by sea level fluctuations.
- Full Text:
- Date Issued: 2009
- Authors: Browning, Claire
- Date: 2009
- Subjects: Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10656 , http://hdl.handle.net/10948/927 , Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Description: Nodules within the lower Bokkeveld shales often contain well-preserved invertebrate fossil material. The aim of this study was to describe some characteristics seen at various scales (macro-, micro- and ultra -) within nodules that might contribute to an understanding of aspects of nodule formation and the reasons for the excellent preservation of the fossil material within these nodules. Detailed, high quality macro-photographs were taken of sliced and whole nodule surfaces and a catalogue was produced to tentatively identify fossils present and illustrate the variations seen within nodules. Selected nodules were then subjected to petrographic, ultra-structural (SEM) and some chemical (EDS, XRD & XRF) analysis to investigate the possible reasons for these variations. The chemical results have indicated that nodules are enriched with quartz compared to the surrounding shale. Quartz is also the dominant mineral replacing trilobite carapace material within nodules, while trilobite material within shales is replaced with equal proportions of hematite, biotite and quartz. It appears that the higher resistance of quartz to weathering is the dominant factor leading to the preservation of both nodules within the shales and trilobite material within the nodules examined. A comparison with some Western Cape nodules highlighted possible variations in overall nodule chemical composition along strike. Western Cape nodules are predominantly composed of apatite whereas the Cockscomb nodules are mainly composed of quartz. This quartz-apatite compositional variation in nodules occurring within a single formation has been reported from nodules found in the Armorican Massif of France which are very similar in a number of respects to the Bokkeveld nodules described in this study. Based on various features of the fossils present and the structure of nodules they were probably formed during early diagenesis within an epeiric marine deposit greatly affected by sea level fluctuations.
- Full Text:
- Date Issued: 2009
A preliminary investigation into the use of biomarkers and a fish community index to assess estuarine health in selected Eastern Cape estuaries
- Authors: Richardson, Naomi
- Date: 2008
- Subjects: Fish communities -- South Africa -- Eastern Cape Estuarine fishes -- South Africa -- Eastern Cape Estuarine health -- South Africa -- Eastern Cape Estuaries -- South Africa -- Eastern Cape -- Management Coastal zone management -- South Africa -- Eastern Cape Environmental monitoring -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5348 , http://hdl.handle.net/10962/d1007480
- Description: The aims of this study were to determine the potential use of biomarkers at multiple levels of biological organisation together with a fish community bioindicator to assess the estuarine health status of three temporarily open/closed estuaries. The estuaries investigated were the East Kleinemonde (EK), Old Woman's (OW) and Mtana (MTN), all of which are situated in the Eastern Cape Province. Three biomarkers, the acetylcholinesterase (AChE) assay, lipid peroxidation (LPx) assay, liver histopathology and a condition factor were used to determine sub-organism health and one bioindicator, the Estuarine Fish Community Index (EFCI), was used as a bioindicator of community health. The estuarine-dependent marine species Rhabdosargus holubi was selected as an indicator species for the sub-organism level analyses. The results from the community analyses indicated that the EK and OW estuaries were in 'good' condition, while the MTN was found to be in 'moderate' condition. Histological analyses revealed that R. holubi from all three estuaries showed signs of pathological changes to the liver, with the fish from the MTN eliciting the highest occurrence of these changes. The LPx assay found that R. holubi from both the OW and MTN showed signs of oxidative damage in the liver tissue, but those from the EK did not appear to be affected. The AChE assay showed that only the fish from the OW had been affected by anticholinesterase compounds. A laboratory study was undertaken using R. holubi as a positive control for the AChE and LPx assay. The fish were exposed to 3 μg/L chlorpyrifos, a known cholinesterase inhibitor, for six hours and their tissues were examined for changes to LPx levels and AChE activities. AChE activity was significantly inhibited (Mann Whitney U test, Z = 3.65, n = 38, P < 0.001) by the exposure, but LPx levels were not significantly affected. A composite index incorporating the biomarkers at different biological levels of organisation was developed. The index was designed to assist managers and scientists to determine whether the ichthyofauna of a system was being affected by environmental stressors and what management interventions could be undertaken to ameliorate the water quality in an estuary. The index was applied to the three estuaries investigated during the present study and both the OW and MTN were assessed to be in need of immediate management intervention. The fish in the OW were found to be stressed at all the sub-organism levels measured and the reason for this was hypothesised to be as a result of golf course activities in this adjacent estuary. A number of management actions are proposed to reduce the sub-organism stress observed in the fish from the OW. The livers of fish from the MTN were shown to be under stress; however the causative agent of this stress was unknown because there is no formal development in the MTN catchment. However, a possible contaminant source is proposed and management interventions to alleviate the stress on the biota of the MTN are suggested. The EK does not require immediate management intervention, however, continuous routine monitoring is recommended to ensure that conditions do not deteriorate. Shortcomings of the index were outlined and a number of suggestions were made in terms of other measures of biological health which could be incorporated into the index.
- Full Text:
- Date Issued: 2008
- Authors: Richardson, Naomi
- Date: 2008
- Subjects: Fish communities -- South Africa -- Eastern Cape Estuarine fishes -- South Africa -- Eastern Cape Estuarine health -- South Africa -- Eastern Cape Estuaries -- South Africa -- Eastern Cape -- Management Coastal zone management -- South Africa -- Eastern Cape Environmental monitoring -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5348 , http://hdl.handle.net/10962/d1007480
- Description: The aims of this study were to determine the potential use of biomarkers at multiple levels of biological organisation together with a fish community bioindicator to assess the estuarine health status of three temporarily open/closed estuaries. The estuaries investigated were the East Kleinemonde (EK), Old Woman's (OW) and Mtana (MTN), all of which are situated in the Eastern Cape Province. Three biomarkers, the acetylcholinesterase (AChE) assay, lipid peroxidation (LPx) assay, liver histopathology and a condition factor were used to determine sub-organism health and one bioindicator, the Estuarine Fish Community Index (EFCI), was used as a bioindicator of community health. The estuarine-dependent marine species Rhabdosargus holubi was selected as an indicator species for the sub-organism level analyses. The results from the community analyses indicated that the EK and OW estuaries were in 'good' condition, while the MTN was found to be in 'moderate' condition. Histological analyses revealed that R. holubi from all three estuaries showed signs of pathological changes to the liver, with the fish from the MTN eliciting the highest occurrence of these changes. The LPx assay found that R. holubi from both the OW and MTN showed signs of oxidative damage in the liver tissue, but those from the EK did not appear to be affected. The AChE assay showed that only the fish from the OW had been affected by anticholinesterase compounds. A laboratory study was undertaken using R. holubi as a positive control for the AChE and LPx assay. The fish were exposed to 3 μg/L chlorpyrifos, a known cholinesterase inhibitor, for six hours and their tissues were examined for changes to LPx levels and AChE activities. AChE activity was significantly inhibited (Mann Whitney U test, Z = 3.65, n = 38, P < 0.001) by the exposure, but LPx levels were not significantly affected. A composite index incorporating the biomarkers at different biological levels of organisation was developed. The index was designed to assist managers and scientists to determine whether the ichthyofauna of a system was being affected by environmental stressors and what management interventions could be undertaken to ameliorate the water quality in an estuary. The index was applied to the three estuaries investigated during the present study and both the OW and MTN were assessed to be in need of immediate management intervention. The fish in the OW were found to be stressed at all the sub-organism levels measured and the reason for this was hypothesised to be as a result of golf course activities in this adjacent estuary. A number of management actions are proposed to reduce the sub-organism stress observed in the fish from the OW. The livers of fish from the MTN were shown to be under stress; however the causative agent of this stress was unknown because there is no formal development in the MTN catchment. However, a possible contaminant source is proposed and management interventions to alleviate the stress on the biota of the MTN are suggested. The EK does not require immediate management intervention, however, continuous routine monitoring is recommended to ensure that conditions do not deteriorate. Shortcomings of the index were outlined and a number of suggestions were made in terms of other measures of biological health which could be incorporated into the index.
- Full Text:
- Date Issued: 2008
A preliminary investigation of the chemical nature of wattle tannin
- Authors: Corbett, John Henry
- Date: 1945
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21062 , http://hdl.handle.net/10962/6201
- Description: From Introduction: Although the tannins of wattle bark extract are generally considered to be of the class known as condensed tannins, a review of the general chemical nature of the tannins is given for the sake of completeness. This constitutes Part I of the thesis. Part II describes the preliminary investigation of the chemical nature of black wattle extract.
- Full Text:
- Date Issued: 1945
- Authors: Corbett, John Henry
- Date: 1945
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21062 , http://hdl.handle.net/10962/6201
- Description: From Introduction: Although the tannins of wattle bark extract are generally considered to be of the class known as condensed tannins, a review of the general chemical nature of the tannins is given for the sake of completeness. This constitutes Part I of the thesis. Part II describes the preliminary investigation of the chemical nature of black wattle extract.
- Full Text:
- Date Issued: 1945
A preliminary investigation of the determination of ionic mobilities by conductometric titration
- Authors: Festenstein, Gerald Norman
- Date: 1947
- Subjects: Ionic mobility , Conductometric analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4472 , http://hdl.handle.net/10962/d1011810 , Ionic mobility , Conductometric analysis
- Description: The determination of ionic mobilities by conductometric titration was first suggested by Barker, Rowler and Shuttleworth in discussing the theory of conductometric titration of acids, bases and neutral salts. Intro. p. 1.
- Full Text:
- Date Issued: 1947
- Authors: Festenstein, Gerald Norman
- Date: 1947
- Subjects: Ionic mobility , Conductometric analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4472 , http://hdl.handle.net/10962/d1011810 , Ionic mobility , Conductometric analysis
- Description: The determination of ionic mobilities by conductometric titration was first suggested by Barker, Rowler and Shuttleworth in discussing the theory of conductometric titration of acids, bases and neutral salts. Intro. p. 1.
- Full Text:
- Date Issued: 1947
A preliminary investigation of the ecology of the Larger Kleinmond River Estuary, Bathurst District
- Brown, Alexander Claude, 1931-2005
- Authors: Brown, Alexander Claude, 1931-2005
- Date: 1953
- Subjects: Kleinemonde River Estuary (South Africa) , Estuaries -- South Africa , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5904 , http://hdl.handle.net/10962/d1014611
- Description: Introduction. On the coast of the Bathurst Division, Eastern Cape Province, some 42 miles south- east of Grahamstown, lie two estuaries opening within a few yards of one another. These are known as the Kleinemonde. This paper embodies the results of an ecological survey of the fauna of the Larger Kleinmond Estuary. The chief concern has been the aquatic fauna but animals living along the banks have also been dealt with as far as possible, as have the birds. This is the second of South Africa's blind estuaries to be studied, the Klein River, Hermanus, having been investigated in 1947-49 by workers from the University of Cape Town. Though common in South Africa, blind estuaries are rare in parts of the world such as Europe, and present an almost entirely new field of research for the ecologist. It is hoped, therefore, that the investigation of the Kleinmond Estuary and a comparison with the results obtained from the Klein River, Hermanus, will add to our knowledge of this subject and be of service to future investigators. The history of the Kleimnond River is worthy of mention, for the lagoon was not always blind and shallow. The early maps of the 1820 settlers show the river as a navigable stream; sailing vessels anchored out at sea and sent lighters up what was then known as the Lydendoch River to collect fresh meat. The area at the mouth of the river was called Port Jessie. In these early days the region abounded with game. Hippo and elephant were common. the former inhabiting deep pools in the upper reaches of the river; pools which have since completely silted up. Constant ploughing of the slopes adjoining the river has caused vast amounts of soil to be washed by rains into the stream, and today what was within living memory a deep, clear stream is a shallow, blind and muddy river, a reflection of man's destructive methods of farming. These changes must have had a far-reaching effect on the fauna of the estuary; an effect about which we can, alas, only speculate. It is perhaps significant that though rich in numbers, the fauna is poor in species, tunicates and echinoderms being apparently entirely absent. The work involved in this survey was undertaken between September 1952 and November 1953, under the direction of Professor J . Omer-Cooper of Rhodes University, frequent and regular visits being made to the estuary. The entire month of February, 1953, was spent on the shore of the lagoon, so that animals could be observed over a continuous period. The starting date of the survey was particularly fortunate, as on September 28th, 1952, the river came down in flood and broke through the sand-bar separating the lagoon from the sea. The work thus began at a definite point in the estuarine cycle, the importance of which it is hoped to show.
- Full Text:
- Date Issued: 1953
- Authors: Brown, Alexander Claude, 1931-2005
- Date: 1953
- Subjects: Kleinemonde River Estuary (South Africa) , Estuaries -- South Africa , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5904 , http://hdl.handle.net/10962/d1014611
- Description: Introduction. On the coast of the Bathurst Division, Eastern Cape Province, some 42 miles south- east of Grahamstown, lie two estuaries opening within a few yards of one another. These are known as the Kleinemonde. This paper embodies the results of an ecological survey of the fauna of the Larger Kleinmond Estuary. The chief concern has been the aquatic fauna but animals living along the banks have also been dealt with as far as possible, as have the birds. This is the second of South Africa's blind estuaries to be studied, the Klein River, Hermanus, having been investigated in 1947-49 by workers from the University of Cape Town. Though common in South Africa, blind estuaries are rare in parts of the world such as Europe, and present an almost entirely new field of research for the ecologist. It is hoped, therefore, that the investigation of the Kleinmond Estuary and a comparison with the results obtained from the Klein River, Hermanus, will add to our knowledge of this subject and be of service to future investigators. The history of the Kleimnond River is worthy of mention, for the lagoon was not always blind and shallow. The early maps of the 1820 settlers show the river as a navigable stream; sailing vessels anchored out at sea and sent lighters up what was then known as the Lydendoch River to collect fresh meat. The area at the mouth of the river was called Port Jessie. In these early days the region abounded with game. Hippo and elephant were common. the former inhabiting deep pools in the upper reaches of the river; pools which have since completely silted up. Constant ploughing of the slopes adjoining the river has caused vast amounts of soil to be washed by rains into the stream, and today what was within living memory a deep, clear stream is a shallow, blind and muddy river, a reflection of man's destructive methods of farming. These changes must have had a far-reaching effect on the fauna of the estuary; an effect about which we can, alas, only speculate. It is perhaps significant that though rich in numbers, the fauna is poor in species, tunicates and echinoderms being apparently entirely absent. The work involved in this survey was undertaken between September 1952 and November 1953, under the direction of Professor J . Omer-Cooper of Rhodes University, frequent and regular visits being made to the estuary. The entire month of February, 1953, was spent on the shore of the lagoon, so that animals could be observed over a continuous period. The starting date of the survey was particularly fortunate, as on September 28th, 1952, the river came down in flood and broke through the sand-bar separating the lagoon from the sea. The work thus began at a definite point in the estuarine cycle, the importance of which it is hoped to show.
- Full Text:
- Date Issued: 1953
A preliminary investigation of the structure of green wattle tannin (acacia decurrens willd)
- Authors: Glueck, Leonard David
- Date: 1952
- Subjects: Tannins , Tannin plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4475 , http://hdl.handle.net/10962/d1011988 , Tannins , Tannin plants
- Description: Green wattle tannin extracts were separated by lead salt precipitation into a phenolic tannin fraction and a nontannin fraction. The combustion analysis of the tannin fraction corresponded to an empirical formula C₁₅H₁₄O₆. Methoxy and acetyl values showed four oxygens were hydroxy groups while the residual oxygens could either be ether linked or carbonyl groups. Diazomethane methylation produced a white product of high methoxyl value which indicated that the four hydroxyl groups were phenolic. Chromatography of the lead salt purified tannin showed an indistinct non-fluorescent trail. Ether extraction of the tannin removed the associated Phenolic bodies. The ethereal extract unlike black wattle extracts contained no fisetin and evaporation of the ethereal solutions yielded a gummy non-crystalline residue. Alkaline fusion of the purified tannin produced for the first tlme a variety of acidic and phenolic compounds i.e. resorcinol, pyrogaloll, phloroglucinol β-resorcylic acid, gallic acid and protocatechuic acid. From the high yields of resorcinol (6%) and gallic acid (3%), these units appear to predominate. These degradation productions, coupled with the analytical figures, indicate a possible C₁₅ unit with resorcinol and pyrogallol nuclei as a basis. The non-tannin fraction failed to reveal any compound which might cause the excessive redness in green wattle extracts. Chromatography of this non-tannin fraction showed the presence of sucrose.
- Full Text:
- Date Issued: 1952
- Authors: Glueck, Leonard David
- Date: 1952
- Subjects: Tannins , Tannin plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4475 , http://hdl.handle.net/10962/d1011988 , Tannins , Tannin plants
- Description: Green wattle tannin extracts were separated by lead salt precipitation into a phenolic tannin fraction and a nontannin fraction. The combustion analysis of the tannin fraction corresponded to an empirical formula C₁₅H₁₄O₆. Methoxy and acetyl values showed four oxygens were hydroxy groups while the residual oxygens could either be ether linked or carbonyl groups. Diazomethane methylation produced a white product of high methoxyl value which indicated that the four hydroxyl groups were phenolic. Chromatography of the lead salt purified tannin showed an indistinct non-fluorescent trail. Ether extraction of the tannin removed the associated Phenolic bodies. The ethereal extract unlike black wattle extracts contained no fisetin and evaporation of the ethereal solutions yielded a gummy non-crystalline residue. Alkaline fusion of the purified tannin produced for the first tlme a variety of acidic and phenolic compounds i.e. resorcinol, pyrogaloll, phloroglucinol β-resorcylic acid, gallic acid and protocatechuic acid. From the high yields of resorcinol (6%) and gallic acid (3%), these units appear to predominate. These degradation productions, coupled with the analytical figures, indicate a possible C₁₅ unit with resorcinol and pyrogallol nuclei as a basis. The non-tannin fraction failed to reveal any compound which might cause the excessive redness in green wattle extracts. Chromatography of this non-tannin fraction showed the presence of sucrose.
- Full Text:
- Date Issued: 1952
A preliminary investigation of the toxic principle of Moraea polystachya Ker
- Dry, L J
- Authors: Dry, L J
- Date: 1954
- Subjects: Iridaceae Moraea polystachya ker
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4461 , http://hdl.handle.net/10962/d1011494
- Description: A member of the Iridaceae family, the plant (also known as the Blue Tulp) ... is a monocotyledon. The blue tulp grows profusely in rainy parts of the Union, for example along much of the Cape coastal belt as far east as Grahamstown, in both the Karroos, and in parts of the Transvaal. It is a perennial plant but only appears above the ground once a year for about two months. This is at the start of the rainy season and in Grahamstown the plant appears in April and May, after which it disappears again. Chapter 1, p.1.
- Full Text:
- Date Issued: 1954
- Authors: Dry, L J
- Date: 1954
- Subjects: Iridaceae Moraea polystachya ker
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4461 , http://hdl.handle.net/10962/d1011494
- Description: A member of the Iridaceae family, the plant (also known as the Blue Tulp) ... is a monocotyledon. The blue tulp grows profusely in rainy parts of the Union, for example along much of the Cape coastal belt as far east as Grahamstown, in both the Karroos, and in parts of the Transvaal. It is a perennial plant but only appears above the ground once a year for about two months. This is at the start of the rainy season and in Grahamstown the plant appears in April and May, after which it disappears again. Chapter 1, p.1.
- Full Text:
- Date Issued: 1954
A preliminary study of adaptation and inhibition of reflex claw opening in the crab Potamon perlatus (Milne Edwards)
- Authors: Bush, Brian M H
- Date: 1956
- Subjects: Crabs , Decapoda
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5906 , http://hdl.handle.net/10962/d1014683
- Description: The only recorded experimental attempt to determine the functional, biological significance of peripheral inhibition in the Crustacea is that of Hoffmann (1914). From a series of experiments on Astacus fluviatilis L. involving transsection of the opener inhibitor and motor axons of the cheliped, he concluded that the opener inhibitor axon of the claw responded to prolonged or repeated sensory stimulation by transmitting inhibitory impulses to the opener muscle, the peripheral inhibition thus evoked causing adaptation of the reflex opening responses of the claw to the sensory stimulation. This suggests that there may be (1) a very high degree of peripheral control of (a) the reactions of the animal to external stimuli, and perhaps also to proprioceptive stimuli, and therefore (b) of the behaviour of the animal; and (2) a correspondingly high degree of independence of this behaviour from central nervous control. It is therefore of importance to discover whether, in fact, this conclusion is valid for Astacus and other Decapod Crustacea, and if so, then to what extent the adaptation is peripherally controlled. A preliminary attempt haa been made to repeat these experiments of Hoffmann, using Potamon perlatus (M.Edw.). Experiments in which mechanical sensory stimulation was used to evoke reflex claw opening indicated that this conclusion is not applicable to P.perlatus. The adaptation of the mechanical claw openining responses which occurred with repeated sensory stimulation was not affected by transsection of either the specific opener inhibitor axon or the common inhibitor axon of the claw. It was evidently mainly due to sensory adaptation when the sensory stimuli were heavy, and to centrally controlled adaptation when the sensory stimuli were light. The significance of these results is discussed. Other effects observed during the course of the work, of electrical "sensory" stimulation, and of cerebral ganglion elimination, are also described and discussed in relation to the present problem.
- Full Text:
- Date Issued: 1956
- Authors: Bush, Brian M H
- Date: 1956
- Subjects: Crabs , Decapoda
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5906 , http://hdl.handle.net/10962/d1014683
- Description: The only recorded experimental attempt to determine the functional, biological significance of peripheral inhibition in the Crustacea is that of Hoffmann (1914). From a series of experiments on Astacus fluviatilis L. involving transsection of the opener inhibitor and motor axons of the cheliped, he concluded that the opener inhibitor axon of the claw responded to prolonged or repeated sensory stimulation by transmitting inhibitory impulses to the opener muscle, the peripheral inhibition thus evoked causing adaptation of the reflex opening responses of the claw to the sensory stimulation. This suggests that there may be (1) a very high degree of peripheral control of (a) the reactions of the animal to external stimuli, and perhaps also to proprioceptive stimuli, and therefore (b) of the behaviour of the animal; and (2) a correspondingly high degree of independence of this behaviour from central nervous control. It is therefore of importance to discover whether, in fact, this conclusion is valid for Astacus and other Decapod Crustacea, and if so, then to what extent the adaptation is peripherally controlled. A preliminary attempt haa been made to repeat these experiments of Hoffmann, using Potamon perlatus (M.Edw.). Experiments in which mechanical sensory stimulation was used to evoke reflex claw opening indicated that this conclusion is not applicable to P.perlatus. The adaptation of the mechanical claw openining responses which occurred with repeated sensory stimulation was not affected by transsection of either the specific opener inhibitor axon or the common inhibitor axon of the claw. It was evidently mainly due to sensory adaptation when the sensory stimuli were heavy, and to centrally controlled adaptation when the sensory stimuli were light. The significance of these results is discussed. Other effects observed during the course of the work, of electrical "sensory" stimulation, and of cerebral ganglion elimination, are also described and discussed in relation to the present problem.
- Full Text:
- Date Issued: 1956
A probability operator
- Authors: Sinclair, Allan M
- Date: 1965
- Subjects: Mathematics , Probabilities
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5423 , http://hdl.handle.net/10962/d1007702 , Mathematics , Probabilities
- Description: From Introduction: In probability theory it is often convenient to represent laws by characteristic functions, these being particularly suited to classical analysis. Trotter has suggest ted that probability laws can also be represented by probability operators. These operators are easily handled since they are continuous, and hence bounded, positive linear operators on a normed linear space. This representation arises because distribution functions and their complete convergence correspond to probability operators and their complete convergence. Hence the relations between distribution functions and probability operators will be discussed before the introduction of probability laws.
- Full Text:
- Date Issued: 1965
- Authors: Sinclair, Allan M
- Date: 1965
- Subjects: Mathematics , Probabilities
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5423 , http://hdl.handle.net/10962/d1007702 , Mathematics , Probabilities
- Description: From Introduction: In probability theory it is often convenient to represent laws by characteristic functions, these being particularly suited to classical analysis. Trotter has suggest ted that probability laws can also be represented by probability operators. These operators are easily handled since they are continuous, and hence bounded, positive linear operators on a normed linear space. This representation arises because distribution functions and their complete convergence correspond to probability operators and their complete convergence. Hence the relations between distribution functions and probability operators will be discussed before the introduction of probability laws.
- Full Text:
- Date Issued: 1965
A process assessment framework for rural ICT projects in developing countries: an exploration of the Siyakhula Living Lab, South Africa
- Authors: Osah, Umeoniso Joshua
- Date: 2013
- Subjects: Siyakhula Living Lab Information technology -- South Africa -- Eastern Cape Rural development projects -- South Africa -- Eastern Cape Rural development projects -- Evaluation -- South Africa -- Eastern Cape Communication in economic development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1133 , http://hdl.handle.net/10962/d1001623
- Description: Rural development can be supported by information and knowledge which are key strategic resources for socio economic development. ICTs enable the facilitation and communication of information between remotely dispersed individuals or groups and more developed regions. While it has become common place that ICTs possess capabilities to potentially support rural development, the concept of ICT for development (ICT4D) is still fraught with challenges and barriers, which impede the success and sustainability of ICT4D projects. It is therefore essential to evaluate rural ICT projects, as such an analysis may aid in revealing information related to the need, effectiveness, impact, and sustainability of these projects. This research seeks to further the implementation and exploration of the Rural ICT Comprehensive Evaluation Framework (RICT-CEF), through the application of the Process Assessment domain in a real life rural ICT project environment. The RICT-CEF framework consisting of 7 evaluation domains has the primary objective of evaluating rural ICT projects from their inception stages to post implementation. A process assessment seeks to determine whether or not a rural ICT project is operating to implement its intended functions in the intended way specified in the projects plan. Such an assessment is invaluable to a comprehensive evaluation. Evaluation questions for a process assessment are centred around critical themes of project performance. Critical themes are aspects of a programme or projects implementation which must be enacted in order to achieve desired project outcomes. This research study is aimed at identifying critical themes of process assessment relevant to rural ICT4D projects. To identify critical themes, assessment approaches on social programme process assessments, evaluation of information systems in use, and rural ICT4D project evaluation case studies are comparatively analysed. Fourteen assessment approaches from these three categories are selected based on criteria. To analyse selected assessment approaches, a template is created based on the research questions, foundational literature on process assessment and identified challenges applicable to process assessments of rural ICT4D projects. Comparing and contrasting critical themes from these assessment approaches highlight critical themes essential to assess in the iterative implementation phase of rural ICT projects. Accentuated critical themes include, service utilization, organizational function and external project factors. These themes, along with suggested guiding principles from literature for conducting process assessments enable the creation of a framework for conducting process assessments of rural ICT projects. The framework is labelled "the Rural ICT Project Process Assessment Framework (RICTP-PAF)". The application of the RICTP-PAF in a real life rural ICT project through a design science case study provides lessons learned (suitability and shortcomings) from applying the framework. This essentially demonstrates the sensitivity of the RICTP-PAF to rural contexts in which it is implemented in. For instance, the implemented prototype of the RICTP-PAF reveals that the framework places a great deal of emphasis on rural beneficiary perspectives. A practice which has been lacking in such evaluation exercises. Furthermore, the guiding principles elucidated, bring to mind best practices to deal with issues such as stakeholder conflict, unreliable data elicitation and unethical assessment practices. The RICTP-PAF represents a fundamental tool for process assessments of rural ICT projects, and may be adopted and customized to various rural ICT project contexts in developing countries.
- Full Text:
- Date Issued: 2013
- Authors: Osah, Umeoniso Joshua
- Date: 2013
- Subjects: Siyakhula Living Lab Information technology -- South Africa -- Eastern Cape Rural development projects -- South Africa -- Eastern Cape Rural development projects -- Evaluation -- South Africa -- Eastern Cape Communication in economic development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1133 , http://hdl.handle.net/10962/d1001623
- Description: Rural development can be supported by information and knowledge which are key strategic resources for socio economic development. ICTs enable the facilitation and communication of information between remotely dispersed individuals or groups and more developed regions. While it has become common place that ICTs possess capabilities to potentially support rural development, the concept of ICT for development (ICT4D) is still fraught with challenges and barriers, which impede the success and sustainability of ICT4D projects. It is therefore essential to evaluate rural ICT projects, as such an analysis may aid in revealing information related to the need, effectiveness, impact, and sustainability of these projects. This research seeks to further the implementation and exploration of the Rural ICT Comprehensive Evaluation Framework (RICT-CEF), through the application of the Process Assessment domain in a real life rural ICT project environment. The RICT-CEF framework consisting of 7 evaluation domains has the primary objective of evaluating rural ICT projects from their inception stages to post implementation. A process assessment seeks to determine whether or not a rural ICT project is operating to implement its intended functions in the intended way specified in the projects plan. Such an assessment is invaluable to a comprehensive evaluation. Evaluation questions for a process assessment are centred around critical themes of project performance. Critical themes are aspects of a programme or projects implementation which must be enacted in order to achieve desired project outcomes. This research study is aimed at identifying critical themes of process assessment relevant to rural ICT4D projects. To identify critical themes, assessment approaches on social programme process assessments, evaluation of information systems in use, and rural ICT4D project evaluation case studies are comparatively analysed. Fourteen assessment approaches from these three categories are selected based on criteria. To analyse selected assessment approaches, a template is created based on the research questions, foundational literature on process assessment and identified challenges applicable to process assessments of rural ICT4D projects. Comparing and contrasting critical themes from these assessment approaches highlight critical themes essential to assess in the iterative implementation phase of rural ICT projects. Accentuated critical themes include, service utilization, organizational function and external project factors. These themes, along with suggested guiding principles from literature for conducting process assessments enable the creation of a framework for conducting process assessments of rural ICT projects. The framework is labelled "the Rural ICT Project Process Assessment Framework (RICTP-PAF)". The application of the RICTP-PAF in a real life rural ICT project through a design science case study provides lessons learned (suitability and shortcomings) from applying the framework. This essentially demonstrates the sensitivity of the RICTP-PAF to rural contexts in which it is implemented in. For instance, the implemented prototype of the RICTP-PAF reveals that the framework places a great deal of emphasis on rural beneficiary perspectives. A practice which has been lacking in such evaluation exercises. Furthermore, the guiding principles elucidated, bring to mind best practices to deal with issues such as stakeholder conflict, unreliable data elicitation and unethical assessment practices. The RICTP-PAF represents a fundamental tool for process assessments of rural ICT projects, and may be adopted and customized to various rural ICT project contexts in developing countries.
- Full Text:
- Date Issued: 2013
A process for the detanning of chrome leather wastes utilising tannery effluents
- Authors: Glaum, Deanne Melanie
- Date: 1994
- Subjects: Tanneries -- Waste disposal , Recycling (Waste, etc.) , Leather
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4029 , http://hdl.handle.net/10962/d1004089 , Tanneries -- Waste disposal , Recycling (Waste, etc.) , Leather
- Description: The considerable volume of chromium-bearing wastes generated during the process of leather tanning, exacerbated by the potential for trivalent chromium in the wastes to be oxidised to the toxic hexavalent state, has created a major waste disposal dilemma for the tanning industry. While methods are available for the safe and effective treatment of residual chrome-tanning liquors, little has been done to address the issue of the chrome-bearing solid wastes. Given the increasingly stringent environmental compliance standards facing tanneries, unless an appropriate treatment process is developed in the immediate future, the continued use of chromium as a tanning agent could be compromised. Recent investigations have demonstrated the potential of heated alkaline conditions for dechroming these solid wastes. This study expanded upon these considerations and examined the feasibility of utilising the highly alkaline tannery waste effluents as cost-effective, substitute alkaline media. The three effluents considered in this study, classed as lime sulphide liquors, were shown to be capable of dechroming wet blue shavings, with resultant separation of the solid wastes into a protein and a concentrated chromium product. The solubilised protein product contained low chromium concentrations which comply with legal discharge limits. The precipitated chromium product offers opportunity for reutilisation in the tannery. A novel industrial-scale treatment process, based on these investigations, indicated the process to be capable of treating the quantity of shavings produced on a daily basis by a medium to large scale tannery. Application of this method for the dechroming of other chrome-tanned solid wastes was also shown to be feasible.
- Full Text:
- Date Issued: 1994
- Authors: Glaum, Deanne Melanie
- Date: 1994
- Subjects: Tanneries -- Waste disposal , Recycling (Waste, etc.) , Leather
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4029 , http://hdl.handle.net/10962/d1004089 , Tanneries -- Waste disposal , Recycling (Waste, etc.) , Leather
- Description: The considerable volume of chromium-bearing wastes generated during the process of leather tanning, exacerbated by the potential for trivalent chromium in the wastes to be oxidised to the toxic hexavalent state, has created a major waste disposal dilemma for the tanning industry. While methods are available for the safe and effective treatment of residual chrome-tanning liquors, little has been done to address the issue of the chrome-bearing solid wastes. Given the increasingly stringent environmental compliance standards facing tanneries, unless an appropriate treatment process is developed in the immediate future, the continued use of chromium as a tanning agent could be compromised. Recent investigations have demonstrated the potential of heated alkaline conditions for dechroming these solid wastes. This study expanded upon these considerations and examined the feasibility of utilising the highly alkaline tannery waste effluents as cost-effective, substitute alkaline media. The three effluents considered in this study, classed as lime sulphide liquors, were shown to be capable of dechroming wet blue shavings, with resultant separation of the solid wastes into a protein and a concentrated chromium product. The solubilised protein product contained low chromium concentrations which comply with legal discharge limits. The precipitated chromium product offers opportunity for reutilisation in the tannery. A novel industrial-scale treatment process, based on these investigations, indicated the process to be capable of treating the quantity of shavings produced on a daily basis by a medium to large scale tannery. Application of this method for the dechroming of other chrome-tanned solid wastes was also shown to be feasible.
- Full Text:
- Date Issued: 1994
A profile of young sex offenders in South Africa : a pilot study
- Authors: Wood, Catherine Jane
- Date: 1998
- Subjects: Sex offenders -- Psychology , Paraphilias , Sex offenders -- South Africa -- Psychology , Teenage sex offenders -- South Africa -- Psychology , Teenage sex offenders
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3089 , http://hdl.handle.net/10962/d1002598 , Sex offenders -- Psychology , Paraphilias , Sex offenders -- South Africa -- Psychology , Teenage sex offenders -- South Africa -- Psychology , Teenage sex offenders
- Description: In-depth interviews and psychometric tests were conducted with 20 young, South African male, hands-on sex offenders, between the ages of seven and 15 years. These offenders were referred by both the legal system and the welfare and health system. The data was gathered for the purpose of drawing up a descriptive profile of salient psychological and sociological characteristics of this population group, the patterns of offenses, the circumstances under which the offenses occurred and victims selected. Results showed that half the sample had committed prior sex offenses. The majority of young sex offenders had a history of consenting sexual interactions, had committed a non-sexual offense and engaged in a range of other antisocial behaviours. Half the sample reported a history of physical or sexual abuse (under-reporting of such victimization experiences was suspected). Typically, the young sex offender w:~s sexually naive and had not received any suitable sex education. He was usually a scholar although his school attendance was often infrequent and he was likely to have failed one or more standards. His intelligence quotient was most likely to fall in or below the borderline range of functioning. He tended to be either socially isolated and socially anxious or alternatively reported having a number of friends and appeared to have adequate social skills. His home environment was typically characterized by overcrowding, alcohol abuse and domestic violence. A significant male relative of his was likely to have committed a criminal offense. In his community environment, he regularly witnessed violence and sexual activity. The sex offenses were usually carried out with a co-perpetrator in a variety of venues. The victim was usually known and younger (mean age = seven years) than the perpetrator (mean age = 12 years). The overall results suggest that young sex offenders commit an array of sexual offenses that do not represent sexual experimentation, but rather indicate a developing pattern of sexual deviance. Comparisons between the above profile and the literature findings are explored. Finally, recommendations for structural changes, assessment procedures, additional future research pessibilities and guidelines for the development of appropriate - treatment programmes are outlined.
- Full Text:
- Date Issued: 1998
- Authors: Wood, Catherine Jane
- Date: 1998
- Subjects: Sex offenders -- Psychology , Paraphilias , Sex offenders -- South Africa -- Psychology , Teenage sex offenders -- South Africa -- Psychology , Teenage sex offenders
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3089 , http://hdl.handle.net/10962/d1002598 , Sex offenders -- Psychology , Paraphilias , Sex offenders -- South Africa -- Psychology , Teenage sex offenders -- South Africa -- Psychology , Teenage sex offenders
- Description: In-depth interviews and psychometric tests were conducted with 20 young, South African male, hands-on sex offenders, between the ages of seven and 15 years. These offenders were referred by both the legal system and the welfare and health system. The data was gathered for the purpose of drawing up a descriptive profile of salient psychological and sociological characteristics of this population group, the patterns of offenses, the circumstances under which the offenses occurred and victims selected. Results showed that half the sample had committed prior sex offenses. The majority of young sex offenders had a history of consenting sexual interactions, had committed a non-sexual offense and engaged in a range of other antisocial behaviours. Half the sample reported a history of physical or sexual abuse (under-reporting of such victimization experiences was suspected). Typically, the young sex offender w:~s sexually naive and had not received any suitable sex education. He was usually a scholar although his school attendance was often infrequent and he was likely to have failed one or more standards. His intelligence quotient was most likely to fall in or below the borderline range of functioning. He tended to be either socially isolated and socially anxious or alternatively reported having a number of friends and appeared to have adequate social skills. His home environment was typically characterized by overcrowding, alcohol abuse and domestic violence. A significant male relative of his was likely to have committed a criminal offense. In his community environment, he regularly witnessed violence and sexual activity. The sex offenses were usually carried out with a co-perpetrator in a variety of venues. The victim was usually known and younger (mean age = seven years) than the perpetrator (mean age = 12 years). The overall results suggest that young sex offenders commit an array of sexual offenses that do not represent sexual experimentation, but rather indicate a developing pattern of sexual deviance. Comparisons between the above profile and the literature findings are explored. Finally, recommendations for structural changes, assessment procedures, additional future research pessibilities and guidelines for the development of appropriate - treatment programmes are outlined.
- Full Text:
- Date Issued: 1998
A proxy approach to protocol interoperability within digital audio networks
- Authors: Igumbor, Osedum Peter
- Date: 2010
- Subjects: Digital communications , Local area networks (Computer networks) , Computer sound processing , Computer networks , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4601 , http://hdl.handle.net/10962/d1004852 , Digital communications , Local area networks (Computer networks) , Computer sound processing , Computer networks , Computer network protocols
- Description: Digital audio networks are becoming the preferred solution for the interconnection of professional audio devices. Prominent amongst their advantages are: reduced noise interference, signal multiplexing, and a reduction in the number of cables connecting networked devices. In the context of professional audio, digital networks have been used to connect devices including: mixers, effects units, preamplifiers, breakout boxes, computers, monitoring controllers, and synthesizers. Such networks are governed by protocols that define the connection management rocedures, and device synchronization processes of devices that conform to the protocols. A wide range of digital audio network control protocols exist, each defining specific hardware requirements of devices that conform to them. Device parameter control is achieved by sending a protocol message that indicates the target parameter, and the action that should be performed on the parameter. Typically, a device will conform to only one protocol. By implication, only devices that conform to a specific protocol can communicate with each other, and only a controller that conforms to the protocol can control such devices. This results in the isolation of devices that conform to disparate protocols, since devices of different protocols cannot communicate with each other. This is currently a challenge in the professional music industry, particularly where digital networks are used for audio device control. This investigation seeks to resolve the issue of interoperability between professional audio devices that conform to different digital audio network protocols. This thesis proposes the use of a proxy that allows for the translation of protocol messages, as a solution to the interoperability problem. The proxy abstracts devices of one protocol in terms of another, hence allowing all the networked devices to appear as conforming to the same protocol. The proxy receives messages on behalf of the abstracted device, and then fulfills them in accordance with the protocol that the abstracted device conforms to. Any number of protocol devices can be abstracted within such a proxy. This has the added advantage of allowing a common controller to control devices that conform to the different protocols.
- Full Text:
- Date Issued: 2010
- Authors: Igumbor, Osedum Peter
- Date: 2010
- Subjects: Digital communications , Local area networks (Computer networks) , Computer sound processing , Computer networks , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4601 , http://hdl.handle.net/10962/d1004852 , Digital communications , Local area networks (Computer networks) , Computer sound processing , Computer networks , Computer network protocols
- Description: Digital audio networks are becoming the preferred solution for the interconnection of professional audio devices. Prominent amongst their advantages are: reduced noise interference, signal multiplexing, and a reduction in the number of cables connecting networked devices. In the context of professional audio, digital networks have been used to connect devices including: mixers, effects units, preamplifiers, breakout boxes, computers, monitoring controllers, and synthesizers. Such networks are governed by protocols that define the connection management rocedures, and device synchronization processes of devices that conform to the protocols. A wide range of digital audio network control protocols exist, each defining specific hardware requirements of devices that conform to them. Device parameter control is achieved by sending a protocol message that indicates the target parameter, and the action that should be performed on the parameter. Typically, a device will conform to only one protocol. By implication, only devices that conform to a specific protocol can communicate with each other, and only a controller that conforms to the protocol can control such devices. This results in the isolation of devices that conform to disparate protocols, since devices of different protocols cannot communicate with each other. This is currently a challenge in the professional music industry, particularly where digital networks are used for audio device control. This investigation seeks to resolve the issue of interoperability between professional audio devices that conform to different digital audio network protocols. This thesis proposes the use of a proxy that allows for the translation of protocol messages, as a solution to the interoperability problem. The proxy abstracts devices of one protocol in terms of another, hence allowing all the networked devices to appear as conforming to the same protocol. The proxy receives messages on behalf of the abstracted device, and then fulfills them in accordance with the protocol that the abstracted device conforms to. Any number of protocol devices can be abstracted within such a proxy. This has the added advantage of allowing a common controller to control devices that conform to the different protocols.
- Full Text:
- Date Issued: 2010
A psychobiographical study of Antwone Fisher
- Authors: Wannenburg, Nicola
- Date: 2014
- Subjects: Fisher, Antwone Quenton , Psychology -- Biographical methods , Psychoanalysis , Abused children -- Biography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3219 , http://hdl.handle.net/10962/d1012939
- Description: Psychobiographical researchers methodically formulate life histories and interpret them by means of psychological theories. The research typically focuses on exemplary and completed lives. The cases that are studied are usually of individuals who are of particular interest to society as a result of excelling in their particular fields, be they to society’s benefit or detriment. Antwone Fisher was chosen for this study using purposive sampling as he meets the psychobiographical requirement of being an extraordinary individual. Fisher grew up in the Foster Care System and faced many abusive experiences as child. Despite difficult beginnings, Fisher developed into a stable and creative adult who excels as a poet, screenwriter and film director. The primary aim of this study is to describe and interpret the life of Antwone Fisher through Erikson’s theory of psychosocial development. The data was processed and analysed using Miles and Hubermans’ general view of qualitative analyses as well as Alexander’s method of asking the data questions. This study contributes to the development of psychobiographical research in South Africa as well as to personality and developmental theory.
- Full Text:
- Date Issued: 2014
- Authors: Wannenburg, Nicola
- Date: 2014
- Subjects: Fisher, Antwone Quenton , Psychology -- Biographical methods , Psychoanalysis , Abused children -- Biography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3219 , http://hdl.handle.net/10962/d1012939
- Description: Psychobiographical researchers methodically formulate life histories and interpret them by means of psychological theories. The research typically focuses on exemplary and completed lives. The cases that are studied are usually of individuals who are of particular interest to society as a result of excelling in their particular fields, be they to society’s benefit or detriment. Antwone Fisher was chosen for this study using purposive sampling as he meets the psychobiographical requirement of being an extraordinary individual. Fisher grew up in the Foster Care System and faced many abusive experiences as child. Despite difficult beginnings, Fisher developed into a stable and creative adult who excels as a poet, screenwriter and film director. The primary aim of this study is to describe and interpret the life of Antwone Fisher through Erikson’s theory of psychosocial development. The data was processed and analysed using Miles and Hubermans’ general view of qualitative analyses as well as Alexander’s method of asking the data questions. This study contributes to the development of psychobiographical research in South Africa as well as to personality and developmental theory.
- Full Text:
- Date Issued: 2014