Tidal exchanges of carbon, nitrogen and phosphorus between a Sarcocornia salt-marsh and the Kariega estuary, and the role of salt-marsh brachyura in this transfer
- Authors: Taylor, David Ian
- Date: 1988
- Subjects: Salt marsh ecology -- South Africa -- Eastern Cape Salt marsh animals -- South Africa -- Eastern Cape Kariega River
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5623 , http://hdl.handle.net/10962/d1004524
- Description: Tidal exchanges of organic carbon, nitrogen and phosphorus between a south temperate Sarcocornia marsh and its associated estuary are examined. Subterranean water flow was small, and the hydraulic exchange between the two systems largely surficial. The dominant tidal signal was semi-diurnal, and the extent of inundation of the marsh varied considerably as a consequence of interactions of semi-lunar tidal cycles with changes in daily mean sea level. Annual net fluxes of organic carbon were directed from the marsh to the estuary, but amounted to less than 2% of marsh aerial net primary productivity. This indicates the incompatibility of E.P. Odum's outwelling hypothesis to this marsh-estuarine system. The direction of net flux of organic carbon switched on a time-scale of days. These directions were largely correlated with mesoscale oceanic events, which materially altered the extent of marsh inundation, and which provided evidence of the mutual exclusivity of outwelling of DOC from the marsh and oceanic upwelling. Laboratory mesocosm experiments using intact marsh blocks of sediment from the marsh were conducted to identify the proximate processes and interactions at the marsh-water interface responsible for the variability of marsh-estuarine exchanges. Patterns of fluxes of organic carbon, total nitrogen and phosphorus were markedly different in the structurally contrasted tidal creek and Sarcocornia Zone regions of the marsh. Both regions exported these components, but the fluxes of organic carbon and total phosphorus were significantly larger from the tidal creek than from the Sarcocornia zone, and the opposite applied to nitrogen. The presence of brachyuran crabs . the most numerous macrofauna on the marsh enhanced the flux of carbon, nitrogen and phosphorus from the marsh biocoenosis, largely as a result of the effect of their bioturbation. Evidence is examined which suggests that differential mobilization of nutrients in the two zones by crabs is responsible for biogeochemical coupling of these two regions , which may account for the elevated productivity of salt- marsh systems
- Full Text:
- Date Issued: 1988
- Authors: Taylor, David Ian
- Date: 1988
- Subjects: Salt marsh ecology -- South Africa -- Eastern Cape Salt marsh animals -- South Africa -- Eastern Cape Kariega River
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5623 , http://hdl.handle.net/10962/d1004524
- Description: Tidal exchanges of organic carbon, nitrogen and phosphorus between a south temperate Sarcocornia marsh and its associated estuary are examined. Subterranean water flow was small, and the hydraulic exchange between the two systems largely surficial. The dominant tidal signal was semi-diurnal, and the extent of inundation of the marsh varied considerably as a consequence of interactions of semi-lunar tidal cycles with changes in daily mean sea level. Annual net fluxes of organic carbon were directed from the marsh to the estuary, but amounted to less than 2% of marsh aerial net primary productivity. This indicates the incompatibility of E.P. Odum's outwelling hypothesis to this marsh-estuarine system. The direction of net flux of organic carbon switched on a time-scale of days. These directions were largely correlated with mesoscale oceanic events, which materially altered the extent of marsh inundation, and which provided evidence of the mutual exclusivity of outwelling of DOC from the marsh and oceanic upwelling. Laboratory mesocosm experiments using intact marsh blocks of sediment from the marsh were conducted to identify the proximate processes and interactions at the marsh-water interface responsible for the variability of marsh-estuarine exchanges. Patterns of fluxes of organic carbon, total nitrogen and phosphorus were markedly different in the structurally contrasted tidal creek and Sarcocornia Zone regions of the marsh. Both regions exported these components, but the fluxes of organic carbon and total phosphorus were significantly larger from the tidal creek than from the Sarcocornia zone, and the opposite applied to nitrogen. The presence of brachyuran crabs . the most numerous macrofauna on the marsh enhanced the flux of carbon, nitrogen and phosphorus from the marsh biocoenosis, largely as a result of the effect of their bioturbation. Evidence is examined which suggests that differential mobilization of nutrients in the two zones by crabs is responsible for biogeochemical coupling of these two regions , which may account for the elevated productivity of salt- marsh systems
- Full Text:
- Date Issued: 1988
Three dimensional kinetic analysis of asymmetrical lifting
- Authors: Li, Jian-Chuan
- Date: 1996
- Subjects: Lifting and carrying , Human engineering , Materials handling , Manual work
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5174 , http://hdl.handle.net/10962/d1018240
- Description: Manual lifting is dynamic in nature and involves asymmetrical loading of the human body. This study investigated kinematic and kinetic characteristics of asymmetrical lifting in three dimensions, and then constructed a 3-D biomechanical force model of the lower back which is capable of quantifying torsional stress on the human spine. Eleven healthy adult male manual workers were recruited as subjects and lifted a 1 Okg load placed at the sagittal plane (0°) and at 30°, 60° and 90° lateral planes to the right, from 150mm and 500mm initial lift heights, respectively, to an 800mm high bench in the sagittal plane. Subjects' spinal motions and the trajectorial movements of the load in three-dimensional space were monitored simultaneously by a Lumbar Motion Monitor and a V-scope Motion Analyzer. Generally, the spinal motion factors increased as a function of increasing task asymmetry and differed (p < 0.05) between the lower (150mm) and higher (500mm) levels in the sagittal plane. In all asymmetrical conditions the motion factors showed a dramatic increase at the 500mm level compared to the increase at the 150mm level. The rates of increase in the horizontal and frontal planes were greater than those in the sagittal plane. Task asymmetry had a significant effect on the spinal kinematic parameters in the frontal plane at the two lift heights, and only at the high level (500mm) in the horizontal plane, with exception of average acceleration . Initial lift height exerted a significant effect on peak velocity and acceleration in both frontal and horizontal planes and on range of motion in the horizontal plane. Kinetic characteristics of the object being lifted in three-dimensions increased with an increase in task asymmetry. The increase was more dramatic in the lateral direction in the horizontal plane. However, motion factors in the vertical direction dominated the full range of the lift, irrespective of task asymmetry and lift height. The kinetic measures differed (p < 0.05) between the lower ( 1 50mm) and the higher (500mm) levels in the vertical direction except for average force. Task asymmetry had a significant effect on dynamic measures in the anterior-posterior direction. Both task asymmetry and lift height had a significant effect on dynamic motion factors in the lateral direction. From insights gained in the empirical study a three-dimensional biomechanical force model of the lower back was constructed based on a mechanism of muscle force re-orientation in the lumbar region. Acknowledging that the lower back is designed to be able to rotate around its longitudinal axis, the proposed model accounts for compression and shear forces and a torsional moment. The model has similar predictability to Schultz and Andersson's (1981) model when the human trunk exerts only a flexion-extension moment in the sagittal plane, but additionally predicts dramatic increases in shear forces, oblique muscle forces and torsional moment under asymmetrical lifting conditions which the Schultz-Andersson model does not. The increase rates in these forces and moment are not linearly related over task asymmetric angle.
- Full Text:
- Date Issued: 1996
- Authors: Li, Jian-Chuan
- Date: 1996
- Subjects: Lifting and carrying , Human engineering , Materials handling , Manual work
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5174 , http://hdl.handle.net/10962/d1018240
- Description: Manual lifting is dynamic in nature and involves asymmetrical loading of the human body. This study investigated kinematic and kinetic characteristics of asymmetrical lifting in three dimensions, and then constructed a 3-D biomechanical force model of the lower back which is capable of quantifying torsional stress on the human spine. Eleven healthy adult male manual workers were recruited as subjects and lifted a 1 Okg load placed at the sagittal plane (0°) and at 30°, 60° and 90° lateral planes to the right, from 150mm and 500mm initial lift heights, respectively, to an 800mm high bench in the sagittal plane. Subjects' spinal motions and the trajectorial movements of the load in three-dimensional space were monitored simultaneously by a Lumbar Motion Monitor and a V-scope Motion Analyzer. Generally, the spinal motion factors increased as a function of increasing task asymmetry and differed (p < 0.05) between the lower (150mm) and higher (500mm) levels in the sagittal plane. In all asymmetrical conditions the motion factors showed a dramatic increase at the 500mm level compared to the increase at the 150mm level. The rates of increase in the horizontal and frontal planes were greater than those in the sagittal plane. Task asymmetry had a significant effect on the spinal kinematic parameters in the frontal plane at the two lift heights, and only at the high level (500mm) in the horizontal plane, with exception of average acceleration . Initial lift height exerted a significant effect on peak velocity and acceleration in both frontal and horizontal planes and on range of motion in the horizontal plane. Kinetic characteristics of the object being lifted in three-dimensions increased with an increase in task asymmetry. The increase was more dramatic in the lateral direction in the horizontal plane. However, motion factors in the vertical direction dominated the full range of the lift, irrespective of task asymmetry and lift height. The kinetic measures differed (p < 0.05) between the lower ( 1 50mm) and the higher (500mm) levels in the vertical direction except for average force. Task asymmetry had a significant effect on dynamic measures in the anterior-posterior direction. Both task asymmetry and lift height had a significant effect on dynamic motion factors in the lateral direction. From insights gained in the empirical study a three-dimensional biomechanical force model of the lower back was constructed based on a mechanism of muscle force re-orientation in the lumbar region. Acknowledging that the lower back is designed to be able to rotate around its longitudinal axis, the proposed model accounts for compression and shear forces and a torsional moment. The model has similar predictability to Schultz and Andersson's (1981) model when the human trunk exerts only a flexion-extension moment in the sagittal plane, but additionally predicts dramatic increases in shear forces, oblique muscle forces and torsional moment under asymmetrical lifting conditions which the Schultz-Andersson model does not. The increase rates in these forces and moment are not linearly related over task asymmetric angle.
- Full Text:
- Date Issued: 1996
Third sector intervention and sustainable development : an evaluation of selected non-governmental organization supported projects in the Eastern Cape, South Africa
- Authors: Moyo, Thokozani Patience
- Date: 2017
- Subjects: Non-governmental organizations -- South Africa -- Eastern Cape Economic development projects -- South Africa -- Eastern Cape Sustainable development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/5774 , vital:29389
- Description: This study evaluates the impact of Third Sector- supported rural development projects in three rural communities of the Eastern Cape, South Africa. It focusses on how interventions driven by this sector – denoted by, among others, local and international non-governmental organisations (NGOs) - impact the lives and livelihoods of the rural poor. This is against the background of an established discourse that views NGOs as effective agents in the alleviation of poverty. The thesis contends that praise for the Third Sector is driven mostly by advocacy than based on systematic scientific evidence of the real impact of NGO-sponsored rural development interventions. Rural agricultural development projects supported by two Eastern Cape-based NGOs (the one a local NGO, and the other international) were selected for the study. A mini survey was conducted in the communities where the projects are located. Survey data were complemented by qualitative data obtained through focus groups, semi-structured and in-depth interviews as well as key informant interviews. The study found that whereas the projects had been established by the state later went moribund, they were resuscitated by the NGOs through a largely ‘bottom-up’ model of rural development intermediation. In other words, the interventions were resuscitated through a relatively robust prior engagement with project beneficiaries. As a result, while originally lacking a meaningful sense of local empowerment, ownership, and commitment, the projects had become revived and now played an important role in the livelihoods of some community members – even though social grants remained the primary and main source of income for those community members. Even so, the narratives of community members revealed what may be termed a ‘transformation paradox’ in the way the projects were implemented. The NGOs seemed to have replaced one kind of lop-sidedness in rural development (the exclusion of women) with another (the exclusion of men), by focussing on community projects that were ‘culturally’ deemed as ’women jobs’. In this way, the interventions appeared like a systematic attempt to do away with the ‘feminisation of rural poverty’ and entrench the ‘feminisation of rural development interventions’. The study concludes from these and other findings, that the key to understanding the significance and impact of Third Sector-supported development interventions in the rural arena – especially in the Eastern Cape context – is to go beyond the proliferation of NGOs and NGO-supported projects – and the broad sweep of advocacy that underpins it – and pay equally robust attention to systematically studying how these projects resonate at the grassroots, especially from a beneficiary perspective.
- Full Text:
- Date Issued: 2017
- Authors: Moyo, Thokozani Patience
- Date: 2017
- Subjects: Non-governmental organizations -- South Africa -- Eastern Cape Economic development projects -- South Africa -- Eastern Cape Sustainable development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/5774 , vital:29389
- Description: This study evaluates the impact of Third Sector- supported rural development projects in three rural communities of the Eastern Cape, South Africa. It focusses on how interventions driven by this sector – denoted by, among others, local and international non-governmental organisations (NGOs) - impact the lives and livelihoods of the rural poor. This is against the background of an established discourse that views NGOs as effective agents in the alleviation of poverty. The thesis contends that praise for the Third Sector is driven mostly by advocacy than based on systematic scientific evidence of the real impact of NGO-sponsored rural development interventions. Rural agricultural development projects supported by two Eastern Cape-based NGOs (the one a local NGO, and the other international) were selected for the study. A mini survey was conducted in the communities where the projects are located. Survey data were complemented by qualitative data obtained through focus groups, semi-structured and in-depth interviews as well as key informant interviews. The study found that whereas the projects had been established by the state later went moribund, they were resuscitated by the NGOs through a largely ‘bottom-up’ model of rural development intermediation. In other words, the interventions were resuscitated through a relatively robust prior engagement with project beneficiaries. As a result, while originally lacking a meaningful sense of local empowerment, ownership, and commitment, the projects had become revived and now played an important role in the livelihoods of some community members – even though social grants remained the primary and main source of income for those community members. Even so, the narratives of community members revealed what may be termed a ‘transformation paradox’ in the way the projects were implemented. The NGOs seemed to have replaced one kind of lop-sidedness in rural development (the exclusion of women) with another (the exclusion of men), by focussing on community projects that were ‘culturally’ deemed as ’women jobs’. In this way, the interventions appeared like a systematic attempt to do away with the ‘feminisation of rural poverty’ and entrench the ‘feminisation of rural development interventions’. The study concludes from these and other findings, that the key to understanding the significance and impact of Third Sector-supported development interventions in the rural arena – especially in the Eastern Cape context – is to go beyond the proliferation of NGOs and NGO-supported projects – and the broad sweep of advocacy that underpins it – and pay equally robust attention to systematically studying how these projects resonate at the grassroots, especially from a beneficiary perspective.
- Full Text:
- Date Issued: 2017
Thermoluminescence and phototransferred phermoluminescence of synthetic quartz
- Authors: Dawam, Robert Rangmou
- Date: 2020
- Subjects: Thermoluminescence , Quartz
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/145849 , vital:38472
- Description: The main aim of this investigation is on thermoluminescence and phototransferred thermoluminescence of synthetic quartz. Thermoluminescence was one of the tools used in characterising the electron traps parameters. The samples of quartz annealed at various temperatures up to 900̊C and the unannealed were used. The thermoluminescence glow curve was measured at 1̊C s~ 1 following beta irradiation to 40 Gy from the samples annealed at 500̊C and the unannealed consist of main peak at 70̊C and secondary peaks at 110, 180 and 310̊C. In comparison, the thermoluminescence glow curve for the sample annealed at 900̊C have main peak at 86̊C and the secondary ones at 170 and 310̊C. The kinetic analysis was carried out only on the main peak in each case. The activation energy was found to be decreasing with increase in annealing temperatures. The samples annealed at 500̊C and the unannealed were found to be affected by thermal quenching while sample annealed at 900̊C shows an inverse quenching for irradiation dose of 40 Gy. However, when the dose was reduce to 3 Gy the effects of thermal quenching was manifested. The activation energy of thermal quenching was also found to decrease with increase in annealing temperature. Thermally assisted optically stimulated luminescence measurement was carried out using continuous wave optical stimulated luminescence (CW-OSL). The samples studied were those annealed at 500̊C for 10 minutes, 900̊C for 10, 30, 60 minutes and 1000̊C for 10 minutes prior to use. The CW-OSL is stimulated using 470 nm blue LEDs at sample temperatures between 30 and 200̊C. It is measured after preheating to either 300 and 500̊C. When the integrated OSL intensity is plotted as a function of measurement temperature, the intensity goes through a peak. The increase in OSL intensity as a function of temperature is associated to thermal assistance and the decrease to thermal quenching. The kinetic parameters were evaluated by fitting the experimental data. The values of activation energies of thermal quenching are the same within experimental uncertainties for all the experimental conditions. This shows that annealing temperature, duration of annealing and irradiation dose have a negligible influence on the recombination site of luminescence using OSL. Phototransferred thermoluminescence (PTTL) induced from annealed samples using 470 nm blue light was also investigated. The quartz were annealed at 500 _C for 10 minutes, 900̊C for 10, 30, 60 minutes and 1000̊C for 10 minutes prior to use. The glow curves of conventional TL measured at 1 _C s1 following irradiation to 200 Gy shows six peaks in each case labelled I-VI for ease of reference whereas peaks observed under PTTL are referred to as A1 onwards. Only the first three peaks were reproduced under phototransfer for the sample annealed at 900̊C for 60 minutes and 1000̊C C for 10 minutes. Interestingly, for the intermediate duration of annealing of 30 minutes, the only peak that appears under phototransfer is the A1. For quartz annealed at 900̊C for 10 minutes, the PTTL appears as long as the preheating temperature does not exceed 560̊C. All other annealing temperatures, PTTL only appears for preheating to 450 and below. This shows that the occupancy of deep electron traps at temperatures beyond 450̊C or 560̊C is low. The activation energy for peaks A1, A2 and A3 were calculated. The PTTL peaks were studied for thermal quenching and peaks A1 and A3 were found to be affected. The activation energies for thermal quenching were determined as 0.62 ± 0.04 eV and 0.65 ± 0.02 eV for peaks A1 and A3 respectively. The experimental dependence of PTTL intensity on illumination time is modelled using sets of coupled linear differential equations based on systems of donors and acceptors whose number is determined by preheating temperature.
- Full Text:
- Date Issued: 2020
- Authors: Dawam, Robert Rangmou
- Date: 2020
- Subjects: Thermoluminescence , Quartz
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/145849 , vital:38472
- Description: The main aim of this investigation is on thermoluminescence and phototransferred thermoluminescence of synthetic quartz. Thermoluminescence was one of the tools used in characterising the electron traps parameters. The samples of quartz annealed at various temperatures up to 900̊C and the unannealed were used. The thermoluminescence glow curve was measured at 1̊C s~ 1 following beta irradiation to 40 Gy from the samples annealed at 500̊C and the unannealed consist of main peak at 70̊C and secondary peaks at 110, 180 and 310̊C. In comparison, the thermoluminescence glow curve for the sample annealed at 900̊C have main peak at 86̊C and the secondary ones at 170 and 310̊C. The kinetic analysis was carried out only on the main peak in each case. The activation energy was found to be decreasing with increase in annealing temperatures. The samples annealed at 500̊C and the unannealed were found to be affected by thermal quenching while sample annealed at 900̊C shows an inverse quenching for irradiation dose of 40 Gy. However, when the dose was reduce to 3 Gy the effects of thermal quenching was manifested. The activation energy of thermal quenching was also found to decrease with increase in annealing temperature. Thermally assisted optically stimulated luminescence measurement was carried out using continuous wave optical stimulated luminescence (CW-OSL). The samples studied were those annealed at 500̊C for 10 minutes, 900̊C for 10, 30, 60 minutes and 1000̊C for 10 minutes prior to use. The CW-OSL is stimulated using 470 nm blue LEDs at sample temperatures between 30 and 200̊C. It is measured after preheating to either 300 and 500̊C. When the integrated OSL intensity is plotted as a function of measurement temperature, the intensity goes through a peak. The increase in OSL intensity as a function of temperature is associated to thermal assistance and the decrease to thermal quenching. The kinetic parameters were evaluated by fitting the experimental data. The values of activation energies of thermal quenching are the same within experimental uncertainties for all the experimental conditions. This shows that annealing temperature, duration of annealing and irradiation dose have a negligible influence on the recombination site of luminescence using OSL. Phototransferred thermoluminescence (PTTL) induced from annealed samples using 470 nm blue light was also investigated. The quartz were annealed at 500 _C for 10 minutes, 900̊C for 10, 30, 60 minutes and 1000̊C for 10 minutes prior to use. The glow curves of conventional TL measured at 1 _C s1 following irradiation to 200 Gy shows six peaks in each case labelled I-VI for ease of reference whereas peaks observed under PTTL are referred to as A1 onwards. Only the first three peaks were reproduced under phototransfer for the sample annealed at 900̊C for 60 minutes and 1000̊C C for 10 minutes. Interestingly, for the intermediate duration of annealing of 30 minutes, the only peak that appears under phototransfer is the A1. For quartz annealed at 900̊C for 10 minutes, the PTTL appears as long as the preheating temperature does not exceed 560̊C. All other annealing temperatures, PTTL only appears for preheating to 450 and below. This shows that the occupancy of deep electron traps at temperatures beyond 450̊C or 560̊C is low. The activation energy for peaks A1, A2 and A3 were calculated. The PTTL peaks were studied for thermal quenching and peaks A1 and A3 were found to be affected. The activation energies for thermal quenching were determined as 0.62 ± 0.04 eV and 0.65 ± 0.02 eV for peaks A1 and A3 respectively. The experimental dependence of PTTL intensity on illumination time is modelled using sets of coupled linear differential equations based on systems of donors and acceptors whose number is determined by preheating temperature.
- Full Text:
- Date Issued: 2020
Thermal, spectroscopic and x-ray diffraction studies of copper(II) 1,2,4,5-Benzenetetracarboxylates and copper(II) oxalate a study of metal-organic frameworks
- Authors: Lamprecht, Emmanuel
- Date: 2008
- Subjects: Organometallic compounds Copper Oxalates -- Thermal properties Organic compounds -- Synthesis Spectrum analysis X-rays -- Diffraction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4389 , http://hdl.handle.net/10962/d1005054
- Description: Novel and known metal organic frameworks with copper(II), sodium and 1,2,4,5-benzenetetracarboxylate were prepared by ambient precipitation, solvothermal and gel-synthesis methods, and characterized by single-crystal X-ray diffraction, X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetry with FTIR evolved-gas analysis. Some of these complexes were investigated for guest inclusion properties with water (the original guest species), methanol, ethanol and pyridine. The gel-synthesis products were the most interesting. The novel threedimensional metal-organic framework complex Cu₂ Na(OH)L·7H₂O (where L=1,2,4,5-benzenetetracarboxylate) -formed by gel-synthesis- is a covalent three-dimensional metal organic framework polymer with open channels containing both guest water molecules and water molecules coordinated to sodium. The structure collapsed on dehydration, but was essentially restored to the original structure on rehydration in moist air. On exposure of the dehydrated material to methanol and ethanol vapour, significant uptake of these solvents was observed, and the resolvated structures closely resembled that of the parent material. On heating in dry nitrogen, small amounts of methanol and ethanol remained until about 280 °C, when loss of the remaining guest triggered decomposition of the framework. The related complex, Cu₂¼(OH)½ L·7½H₂O (or possibly Cu₂⅓ (OH)⅔L·8H₂O) -formed by gel-synthesis- had a different physical appearance to Cu₂Na(OH)L·7H₂O above, but had nearly identical X-ray diffraction pattern, mid-infrared spectrum and thermal behaviour. The novel complex Cu₄Na₄L₃·14H₂O -formed by gel-synthesis- is a covalent three-dimensional metal-organic framework with small channels containing both guest water molecules and water coordinated to sodium and copper. Upon dehydration the structure collapsed, but on rehydration in moist air the original structure was partly restored. The dehydrated material did not absorb methanol. Known two-dimensional polymeric complexes [Cu₂L·6H₂O]·4H₂O and [Cu₂L·4H₂O]·2H₂O were also obtained by gel-synthesis, and were characterized and investigated for guest inclusion properties. The structures of these complexes collapsed on dehydration, and were only partly restored on rehydration in saturated water vapour. The dehydrated materials did not absorb methanol. The two-dimensional polymeric mixed-ligand complex Cu₂(pyridine)₄·6H₂O -formed very slowly by gel-synthesis- was characterized by TG-FTIR, and was shown to undergo a complicated decomposition involving the loss of water and pyridine, carbon dioxide and carbon monoxide in various stages. Solvothermal synthesis did not yield materials suitable for single-crystal X-ray diffraction studies or inclusion studies, producing only an anhydrous or hemihydrate complex with the formula Cu₂L·0.65H2O. Ambient precipitation syntheses did not yield materials suitable for singlecrystal diffraction studies, forming products approximately equivalent to the complexes [Cu₂L·6H₂O]·4H₂O and Cu₂¼(OH)½L·7 ½H₂O above. During the course of the above study it was discovered that, on changing the DSC purge from nitrogen to argon, the normally exothermic carboxylate decompositions appeared to become endothermic. The effects of the supposedly inert atmospheres of argon and nitrogen on the decomposition-mechanism of copper(II) oxalate -a well-studied copper carboxylate- were therefore studied by DSC, TG, TG-FTIR and XRPD. DSC experiments were performed in nitrogen and argon at different flow-rates, in various mixtures of nitrogen and argon, and at various heating rates. Regardless of the proportions of nitrogen and argon, the DSC residues consisted mainly of copper metal, a small amount of copper(I) oxide (cuprite) and, in some circumstances, traces of copper(II) oxide (tenorite). Also, regardless of whether TG-FTIR experiments were performed under argon or nitrogen, the gaseous decomposition products consisted mainly of carbon dioxide, with traces of carbon monoxide being detected over part of the decomposition period. Various explanations for the thermal behaviour are discussed, and it is possible that small amounts of O2 or monatomic oxygen were given off during the decomposition under argon. The design and implementation of a low-cost prototype X-ray proportional counter detector system, consisting of a hybrid analog-digital computer built using commonly available electronic components, is presented. This system was designed to replace ageing discrete-transistor designs still in use in earlier X-ray diffractometers. The prototype performs the functions of pulse-shaping, pulseheight discrimination, counting and scaling, and provides both digital and scaled analog outputs.
- Full Text:
- Date Issued: 2008
- Authors: Lamprecht, Emmanuel
- Date: 2008
- Subjects: Organometallic compounds Copper Oxalates -- Thermal properties Organic compounds -- Synthesis Spectrum analysis X-rays -- Diffraction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4389 , http://hdl.handle.net/10962/d1005054
- Description: Novel and known metal organic frameworks with copper(II), sodium and 1,2,4,5-benzenetetracarboxylate were prepared by ambient precipitation, solvothermal and gel-synthesis methods, and characterized by single-crystal X-ray diffraction, X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetry with FTIR evolved-gas analysis. Some of these complexes were investigated for guest inclusion properties with water (the original guest species), methanol, ethanol and pyridine. The gel-synthesis products were the most interesting. The novel threedimensional metal-organic framework complex Cu₂ Na(OH)L·7H₂O (where L=1,2,4,5-benzenetetracarboxylate) -formed by gel-synthesis- is a covalent three-dimensional metal organic framework polymer with open channels containing both guest water molecules and water molecules coordinated to sodium. The structure collapsed on dehydration, but was essentially restored to the original structure on rehydration in moist air. On exposure of the dehydrated material to methanol and ethanol vapour, significant uptake of these solvents was observed, and the resolvated structures closely resembled that of the parent material. On heating in dry nitrogen, small amounts of methanol and ethanol remained until about 280 °C, when loss of the remaining guest triggered decomposition of the framework. The related complex, Cu₂¼(OH)½ L·7½H₂O (or possibly Cu₂⅓ (OH)⅔L·8H₂O) -formed by gel-synthesis- had a different physical appearance to Cu₂Na(OH)L·7H₂O above, but had nearly identical X-ray diffraction pattern, mid-infrared spectrum and thermal behaviour. The novel complex Cu₄Na₄L₃·14H₂O -formed by gel-synthesis- is a covalent three-dimensional metal-organic framework with small channels containing both guest water molecules and water coordinated to sodium and copper. Upon dehydration the structure collapsed, but on rehydration in moist air the original structure was partly restored. The dehydrated material did not absorb methanol. Known two-dimensional polymeric complexes [Cu₂L·6H₂O]·4H₂O and [Cu₂L·4H₂O]·2H₂O were also obtained by gel-synthesis, and were characterized and investigated for guest inclusion properties. The structures of these complexes collapsed on dehydration, and were only partly restored on rehydration in saturated water vapour. The dehydrated materials did not absorb methanol. The two-dimensional polymeric mixed-ligand complex Cu₂(pyridine)₄·6H₂O -formed very slowly by gel-synthesis- was characterized by TG-FTIR, and was shown to undergo a complicated decomposition involving the loss of water and pyridine, carbon dioxide and carbon monoxide in various stages. Solvothermal synthesis did not yield materials suitable for single-crystal X-ray diffraction studies or inclusion studies, producing only an anhydrous or hemihydrate complex with the formula Cu₂L·0.65H2O. Ambient precipitation syntheses did not yield materials suitable for singlecrystal diffraction studies, forming products approximately equivalent to the complexes [Cu₂L·6H₂O]·4H₂O and Cu₂¼(OH)½L·7 ½H₂O above. During the course of the above study it was discovered that, on changing the DSC purge from nitrogen to argon, the normally exothermic carboxylate decompositions appeared to become endothermic. The effects of the supposedly inert atmospheres of argon and nitrogen on the decomposition-mechanism of copper(II) oxalate -a well-studied copper carboxylate- were therefore studied by DSC, TG, TG-FTIR and XRPD. DSC experiments were performed in nitrogen and argon at different flow-rates, in various mixtures of nitrogen and argon, and at various heating rates. Regardless of the proportions of nitrogen and argon, the DSC residues consisted mainly of copper metal, a small amount of copper(I) oxide (cuprite) and, in some circumstances, traces of copper(II) oxide (tenorite). Also, regardless of whether TG-FTIR experiments were performed under argon or nitrogen, the gaseous decomposition products consisted mainly of carbon dioxide, with traces of carbon monoxide being detected over part of the decomposition period. Various explanations for the thermal behaviour are discussed, and it is possible that small amounts of O2 or monatomic oxygen were given off during the decomposition under argon. The design and implementation of a low-cost prototype X-ray proportional counter detector system, consisting of a hybrid analog-digital computer built using commonly available electronic components, is presented. This system was designed to replace ageing discrete-transistor designs still in use in earlier X-ray diffractometers. The prototype performs the functions of pulse-shaping, pulseheight discrimination, counting and scaling, and provides both digital and scaled analog outputs.
- Full Text:
- Date Issued: 2008
Thermal tolerance and the potential effects of climate change on coastal intertidal and estuarine organisms in the Kariega Estuary and adjacent intertitdal coastline, Eastern Cape, South Africa
- Authors: Van der Walt, Kerry-Ann
- Date: 2020
- Subjects: Ectotherms -- Climatic factors , Ectotherms -- Effect of temperature on , Fishes -- Climatic factors , Fishes -- Effect of temperature on , Climatic changes -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/148459 , vital:38741
- Description: Temperature changes due to the effects of climate change are evident on all continents and oceans. As a result, there is a growing concern over how marine ectotherms will respond to extreme or fluctuating environmental temperatures. Temperature changes have strong direct and indirect effects on individual, population, and ecosystem functioning traits. A multi-scale approach determining the thermal tolerance and performance of several marine ectotherms belonging to different coastal habitats is rarely considered in thermal physiology studies but is effective for an integrated ecosystem assessment. As such, for this thesis, I aimed to quantify and compare the thermal tolerance and performance of a range of coastal marine ectotherms (fish and macro-invertebrates) with different biogeographical distributions from estuarine, subtidal and rocky intertidal habitats to available and projected in situ temperature data. This was also undertaken to gauge the local vulnerability of each species across summer and winter in a warm-temperate region of South Africa. This was done using a multi-method physiological approach, which included the dynamic method (CTmax and CTmin), static respirometry and maximum heart rate fHmax). Results of the dynamic method on several fish and macro-invertebrate species indicated that there are differences in thermal tolerance according to taxonomy, biogeography and habitat for both summer and winter. Macro-invertebrate species generally had higher CTmax endpoints, lower CTmin endpoints, higher upper and lower breadths in tolerance, higher upper and lower thermal safety margins and higher thermal scopes than the fish species. This could be a result of the macro-invertebrate species studied being less mobile compared with fish species (which are able to move to more favourable conditions) as well as having broader geographical distributions. In addition, macro-invertebrates from the intertidal rock pool habitat (Palaemon peringueyi; Pernaperna) were more tolerant of high and low temperatures compared with the macro-invertebrates from the estuarine habitat (Clibanarius virescens; Parasesarma catenatum; Upogebia africana). Overall, macro-invertebrates, with the exception of Parechinus angulosus, investigated in this study indicated that current temperatures and projected climate change scenarios across seasons would not have a significant impact on them and that they are highly adaptable to changing temperature regimes. This sign of high tolerance was further supported by the heart rates of P. perna and P. catenatum under an acute increase in temperature (1.0 °C.h-1) which showed individuals of each species physiologically depressing their metabolism until a final Arrhenius breakpoint temperature was reached (TAB). Among the fish species investigated in this study, tropical species (Chaetodon marleyi; Kuhlia mugil) had the highest CTmax and CTmin endpoints when compared with the temperate (Diplodus capensis; Sarpa salpa), warm-water endemic (Chelon dumerili; Rhabdosargus holubi) and cool-water endemic (Chelon richardsonii) fishes. This suggests that due to their lower breadths in tolerance and thermal safety margins being small, tropical species may be less tolerant of cold temperatures and thermal variability, especially in the form of summer upwelling events which are expected to increase in intensity and frequency in this region as a result of anthropogenic climate change effects. On the other hand, however, if a temperature increase of 2.0 - 4.0 °C takes place at the end of the century as predicted by the Intergovernmental Panel on Climate Change (IPCC), it is likely that tropical species such as C. marleyi will become more common. Temperate species such as D. capensis and S. salpa were able to tolerate a wide range of temperatures (wide thermal scope) compared with the other fish species. These findings may suggest that D. capensis and S. salpa are thermally resilient and may be the least vulnerable to climate change effects and temperature variability. When evaluating the different life stages of D. capensis, however, using the dynamic method (juveniles and adults), static respirometry (juveniles) and maximum heart rate (adults), results suggested that juveniles of this temperate species will be more resilient to increases in ocean temperatures compared with the adults because they have a higher thermal tolerance (CTmax/TCRIT) and a greater metabolic scope (TOPT) at higher temperatures. For both juveniles and adults, temperatures beyond 28.0 °C (upper Tpej; Tarr) will have a significant impact on their physiology. Using a multi-scale and multi-method approach thus helped to identify which species or community may be vulnerable to the effects of climate change within shallow coastal environments in this warm-temperate climate change hotspot. Adopting this type of approach will assist policy makers in developing comprehensive climate change management frameworks for coastal ecosystems globally and around South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Van der Walt, Kerry-Ann
- Date: 2020
- Subjects: Ectotherms -- Climatic factors , Ectotherms -- Effect of temperature on , Fishes -- Climatic factors , Fishes -- Effect of temperature on , Climatic changes -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/148459 , vital:38741
- Description: Temperature changes due to the effects of climate change are evident on all continents and oceans. As a result, there is a growing concern over how marine ectotherms will respond to extreme or fluctuating environmental temperatures. Temperature changes have strong direct and indirect effects on individual, population, and ecosystem functioning traits. A multi-scale approach determining the thermal tolerance and performance of several marine ectotherms belonging to different coastal habitats is rarely considered in thermal physiology studies but is effective for an integrated ecosystem assessment. As such, for this thesis, I aimed to quantify and compare the thermal tolerance and performance of a range of coastal marine ectotherms (fish and macro-invertebrates) with different biogeographical distributions from estuarine, subtidal and rocky intertidal habitats to available and projected in situ temperature data. This was also undertaken to gauge the local vulnerability of each species across summer and winter in a warm-temperate region of South Africa. This was done using a multi-method physiological approach, which included the dynamic method (CTmax and CTmin), static respirometry and maximum heart rate fHmax). Results of the dynamic method on several fish and macro-invertebrate species indicated that there are differences in thermal tolerance according to taxonomy, biogeography and habitat for both summer and winter. Macro-invertebrate species generally had higher CTmax endpoints, lower CTmin endpoints, higher upper and lower breadths in tolerance, higher upper and lower thermal safety margins and higher thermal scopes than the fish species. This could be a result of the macro-invertebrate species studied being less mobile compared with fish species (which are able to move to more favourable conditions) as well as having broader geographical distributions. In addition, macro-invertebrates from the intertidal rock pool habitat (Palaemon peringueyi; Pernaperna) were more tolerant of high and low temperatures compared with the macro-invertebrates from the estuarine habitat (Clibanarius virescens; Parasesarma catenatum; Upogebia africana). Overall, macro-invertebrates, with the exception of Parechinus angulosus, investigated in this study indicated that current temperatures and projected climate change scenarios across seasons would not have a significant impact on them and that they are highly adaptable to changing temperature regimes. This sign of high tolerance was further supported by the heart rates of P. perna and P. catenatum under an acute increase in temperature (1.0 °C.h-1) which showed individuals of each species physiologically depressing their metabolism until a final Arrhenius breakpoint temperature was reached (TAB). Among the fish species investigated in this study, tropical species (Chaetodon marleyi; Kuhlia mugil) had the highest CTmax and CTmin endpoints when compared with the temperate (Diplodus capensis; Sarpa salpa), warm-water endemic (Chelon dumerili; Rhabdosargus holubi) and cool-water endemic (Chelon richardsonii) fishes. This suggests that due to their lower breadths in tolerance and thermal safety margins being small, tropical species may be less tolerant of cold temperatures and thermal variability, especially in the form of summer upwelling events which are expected to increase in intensity and frequency in this region as a result of anthropogenic climate change effects. On the other hand, however, if a temperature increase of 2.0 - 4.0 °C takes place at the end of the century as predicted by the Intergovernmental Panel on Climate Change (IPCC), it is likely that tropical species such as C. marleyi will become more common. Temperate species such as D. capensis and S. salpa were able to tolerate a wide range of temperatures (wide thermal scope) compared with the other fish species. These findings may suggest that D. capensis and S. salpa are thermally resilient and may be the least vulnerable to climate change effects and temperature variability. When evaluating the different life stages of D. capensis, however, using the dynamic method (juveniles and adults), static respirometry (juveniles) and maximum heart rate (adults), results suggested that juveniles of this temperate species will be more resilient to increases in ocean temperatures compared with the adults because they have a higher thermal tolerance (CTmax/TCRIT) and a greater metabolic scope (TOPT) at higher temperatures. For both juveniles and adults, temperatures beyond 28.0 °C (upper Tpej; Tarr) will have a significant impact on their physiology. Using a multi-scale and multi-method approach thus helped to identify which species or community may be vulnerable to the effects of climate change within shallow coastal environments in this warm-temperate climate change hotspot. Adopting this type of approach will assist policy makers in developing comprehensive climate change management frameworks for coastal ecosystems globally and around South Africa.
- Full Text:
- Date Issued: 2020
Thermal physiology and behavioural ecology of the white shark, carcharodon carcharias
- Authors: Gennari, Enrico
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64002 , vital:28522
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2015
- Authors: Gennari, Enrico
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64002 , vital:28522
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2015
Thermal degradation of diamond compacts: a TEM investigation
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
Thermal decomposition of ammonium metavanadate
- Authors: Stewart, Brian Victor
- Date: 1972
- Subjects: Decomposition (Chemistry) , Solids -- Thermal properties , Ammonia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4503 , http://hdl.handle.net/10962/d1013274
- Description: The isothermal, endothermic, stepwise decomposition of ammonium metavanadate (AMV) in inert (argon or nitrogen), oxidising (air or oxygen) and reducing (ammonia) atmospheres as well as under high vacuum (pressure < IOn bar) conditions has been investigated. The reverse reaction, the isothermal recombination of V₂ 0₅ with ammonia and water vapour has also been investigated. The decomposition and recombination reactions were followed by continuously recording the mass loss of the sample with time using a Cahn R.G. Automatic Electrobalance. This enabled small samples ( ~ lOmg) to be used and consequently any self cooling of the sample during the decomposition was minimized. The intermediates and final products formed have been characterized by chemical analysis, X-ray powder diffraction studies, infrared spectroscopy and the mass loss involved in their formation. The changes in the physical properties of the samples during decomposition and recombination have been investigated by surface area measurements (using the BET method and krypton adsorption) and eIectron microscopy. Values for the enthalpy changes involved in the decomposition have been obtained by differential scanning calorimetry. The stoichiometry of the isothermal decomposition of ammonium metavanadate, under the various conditions of surrounding atmosphere has been discussed. Except for the later stages of the decomposition in ammonia, the results correspond well to the gradual reduction of the ratio of "(NH₄)₂ 0" to "V₂0₅" units from the original 1:1 ratio in ammonium metavanadate to pure "V₂0₅" with ammonia and water being evolved throughout the decomposition in the mole ratio of 2:1. The final product of the decomposition in vacuum, argon and air is "V₂0₅" and in ammonia, below 360°, V0₂. The kinetic parameters for each of the stages of the decomposition of AMV in each of the atmospheres studied have been determined. The mechanism of the first stage of the decomposition under the different conditions of surrounding atmosphere has been discussed from both the kinetic and the thermodynamic points of view. The absolute reaction rate theory has been applied to the decomposition in inert atmospheres enabling the formulae of the activated complexes formed during each stage to be calculated. It has also been shown that the detailed atomic movements occurring during the first stage of the decomposition in ammonia can be predicted from a knowledge of the stoichiometry of the reaction and of the detailed crystal structures of the starting and product materials. The kinetics and mechanism of the recombination of "V₂0₅" with ammonia and water vapour to form AMV have also been discussed in detail.
- Full Text:
- Date Issued: 1972
- Authors: Stewart, Brian Victor
- Date: 1972
- Subjects: Decomposition (Chemistry) , Solids -- Thermal properties , Ammonia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4503 , http://hdl.handle.net/10962/d1013274
- Description: The isothermal, endothermic, stepwise decomposition of ammonium metavanadate (AMV) in inert (argon or nitrogen), oxidising (air or oxygen) and reducing (ammonia) atmospheres as well as under high vacuum (pressure < IOn bar) conditions has been investigated. The reverse reaction, the isothermal recombination of V₂ 0₅ with ammonia and water vapour has also been investigated. The decomposition and recombination reactions were followed by continuously recording the mass loss of the sample with time using a Cahn R.G. Automatic Electrobalance. This enabled small samples ( ~ lOmg) to be used and consequently any self cooling of the sample during the decomposition was minimized. The intermediates and final products formed have been characterized by chemical analysis, X-ray powder diffraction studies, infrared spectroscopy and the mass loss involved in their formation. The changes in the physical properties of the samples during decomposition and recombination have been investigated by surface area measurements (using the BET method and krypton adsorption) and eIectron microscopy. Values for the enthalpy changes involved in the decomposition have been obtained by differential scanning calorimetry. The stoichiometry of the isothermal decomposition of ammonium metavanadate, under the various conditions of surrounding atmosphere has been discussed. Except for the later stages of the decomposition in ammonia, the results correspond well to the gradual reduction of the ratio of "(NH₄)₂ 0" to "V₂0₅" units from the original 1:1 ratio in ammonium metavanadate to pure "V₂0₅" with ammonia and water being evolved throughout the decomposition in the mole ratio of 2:1. The final product of the decomposition in vacuum, argon and air is "V₂0₅" and in ammonia, below 360°, V0₂. The kinetic parameters for each of the stages of the decomposition of AMV in each of the atmospheres studied have been determined. The mechanism of the first stage of the decomposition under the different conditions of surrounding atmosphere has been discussed from both the kinetic and the thermodynamic points of view. The absolute reaction rate theory has been applied to the decomposition in inert atmospheres enabling the formulae of the activated complexes formed during each stage to be calculated. It has also been shown that the detailed atomic movements occurring during the first stage of the decomposition in ammonia can be predicted from a knowledge of the stoichiometry of the reaction and of the detailed crystal structures of the starting and product materials. The kinetics and mechanism of the recombination of "V₂0₅" with ammonia and water vapour to form AMV have also been discussed in detail.
- Full Text:
- Date Issued: 1972
Theories of exchange rates and the methodology of economics
- Authors: Hodge, Duncan
- Date: 1997
- Subjects: Foreign exchange rates Economics -- Methodology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1012 , http://hdl.handle.net/10962/d1002747
- Description: This thesis is an exercise in applied methodology. Ideas in the history and philosophy of science which have proved to be influential in the methodology of economics, and in shaping economists' self-image in this regard, are selected for closer analysis and criticism. The main ideas that are addressed are those of empiricism, with emphasis on the methodological falsificationism of Karl Popper and Imre Lakatos, and Laudan's problem solving model of scientific progress . The thesis examines the relationship between empirical evidence, in the form of both econometric test results and stylized facts, and the development of theories about exchange rates and the open economy. This analysis begins with Cassel's formulation of purchasing power parity theory in 1916, through the elasticities, absorption, and Mundell-Fleming models of exchange rates and the balance of payments, up to the present day monetary and asset market models. This is done with regard to the broad methodological issues examined earlier in the thesis. Some of the main empirical and methodological difficulties in testing such theories are addressed, with particular reference to the role played by the Duhem-Quine thesis and the ceteris paribus assumption. Although some of these difficulties may be regarded as a matter of degree compared to similar problems in the natural sciences, it is argued that this difference is significant for the workability of falsification in economics . Moreover, the presence of hypotheses about expectations in many economic theories appears to be a substantive difference such that the difficulties posed by the Duhem-Quine thesis apply with much greater force in a social science like economics. The main conclusions are that neither the Popperian nor Lakatosian versions of falsification are seriously practiced in the area of exchange rate economics and that, unlike the position taken by advocates of falsification such as Mark Blaug, it would be inappropriate and misguided to do so. A tentative case is made, with some reference to the theories surveyed in this thesis, for the possibly greater relevance of Laudan' s more pragmatic problem solving model for the methodology of economics, particularly as regards his analysis and emphasis on conceptual problem solving in the progress of knowledge.
- Full Text:
- Date Issued: 1997
- Authors: Hodge, Duncan
- Date: 1997
- Subjects: Foreign exchange rates Economics -- Methodology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1012 , http://hdl.handle.net/10962/d1002747
- Description: This thesis is an exercise in applied methodology. Ideas in the history and philosophy of science which have proved to be influential in the methodology of economics, and in shaping economists' self-image in this regard, are selected for closer analysis and criticism. The main ideas that are addressed are those of empiricism, with emphasis on the methodological falsificationism of Karl Popper and Imre Lakatos, and Laudan's problem solving model of scientific progress . The thesis examines the relationship between empirical evidence, in the form of both econometric test results and stylized facts, and the development of theories about exchange rates and the open economy. This analysis begins with Cassel's formulation of purchasing power parity theory in 1916, through the elasticities, absorption, and Mundell-Fleming models of exchange rates and the balance of payments, up to the present day monetary and asset market models. This is done with regard to the broad methodological issues examined earlier in the thesis. Some of the main empirical and methodological difficulties in testing such theories are addressed, with particular reference to the role played by the Duhem-Quine thesis and the ceteris paribus assumption. Although some of these difficulties may be regarded as a matter of degree compared to similar problems in the natural sciences, it is argued that this difference is significant for the workability of falsification in economics . Moreover, the presence of hypotheses about expectations in many economic theories appears to be a substantive difference such that the difficulties posed by the Duhem-Quine thesis apply with much greater force in a social science like economics. The main conclusions are that neither the Popperian nor Lakatosian versions of falsification are seriously practiced in the area of exchange rate economics and that, unlike the position taken by advocates of falsification such as Mark Blaug, it would be inappropriate and misguided to do so. A tentative case is made, with some reference to the theories surveyed in this thesis, for the possibly greater relevance of Laudan' s more pragmatic problem solving model for the methodology of economics, particularly as regards his analysis and emphasis on conceptual problem solving in the progress of knowledge.
- Full Text:
- Date Issued: 1997
Theories of economic underdevelopment: a general equilibrium analysis
- Authors: Black, Philip Andrew
- Date: 1982
- Subjects: Equilibrium (Economics) -- Mathematical models Economic development -- Mathematical models Developing countries -- Economic conditions -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1049 , http://hdl.handle.net/10962/d1006235
- Description: This thesis is mainly concerned with the question whether 'conventional' economic theory - especially the neoclassical theory of general equilibrium - is sufficiently flexible to accommodate the particular conditions prevailing in the developing countries. It is argued that most existing theories of economic underdevelopment adopt an interpretative approach which essentially amounts to relaxing some of the chief assumptions of the neoclassical theory. When applied to the two-sector model of general equilibrium, these theories generally yield predictions which are vastly different from those associated with the neoclassical assumptions of perfect competition, unlimited factor substitutability and unrestricted resource mobility. Several theories seek to explain the development problem in terms of the specific production processes used in poor countries. Myrdal's (1957) theory of cumulative causation, for example, effectively introduces increasing returns to scale in at least one sector or region of the economy; in contrast to the neoclassical theory, he thus nvisages a cumulative process of regional divergence in the output level per worker. Similarly, Richard Eckaus's (1955) explanation of the "factor-proportions problem" is based on the assumption of limited factor substitutability. This enables him to establish the existence of a so-called "unemployment equiIibrium", thus implying that developing countries may be faced with a conflict between the objective of maximizing social -welfare on the one hand, and that of full employment on the other. More recently, Leibenstein (1960) has shown that this trade-off may be complicated by the introduction of capital-biased technological inventions and innovations. The solution to the factor-proportions problem consists in the adoption of more appropriate, usually labour-biased technologies, increased capital formation and a reduction in the rate of population growth. Much of the postwar literature on economic development has focused on the imperfectly competitive structure of the product and the factor markets in developing countries. Myint (1954) has highlighted the role played by monopolies and ligopolies during the "opening-up" process of economic development. Likewise, both Lewis's (1954) dualist theory and Todaro's (1969; 1971) model of rural-urban migration attempt to explain the unemployment problem in terms of various factor price distortions. In an international context, Prebisch (1950; 1959) and Singer (1950) have again shown how prevailing differences in the structure of markets between developed and developing countries may turn the terms of trade against the latter; using a two-sector model, Bhagwati (1958) has demonstrated that such a deterioration in the terms of trade could bring about a net decrease in the welfare level of the countries concerned. Generally, the policy measures relevant to the "market imperfections" problem include the creation of job opportunities in the rural (rather than urban) sector, the encouragement of informal-sector enterprises,and the imposition of factor taxes and subsidies as a means of counteracting the adverse effect of factor price distortions on employment. A more recent approach to the unemployment problem is the plea by the International Labor Office (1970; 1972) for a redistribution of income within the developing countries. In terms of the two-sector model, such a policy may well succeed in eliminating labour unemployment caused by fixed factor proportions and/or factor price distortions. It should be realized, though, that a redistribution of income may lower the aggregate savings level, and hence also the growth rates of capital and labour employment in the economy. On the whole, it would seem that these theories do indeed adopt a modified version of the neoclassical theory in providing a fairly comprehensive explanation of the economic problems of labour unemployment, low incomes and inequality.
- Full Text:
- Date Issued: 1982
- Authors: Black, Philip Andrew
- Date: 1982
- Subjects: Equilibrium (Economics) -- Mathematical models Economic development -- Mathematical models Developing countries -- Economic conditions -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1049 , http://hdl.handle.net/10962/d1006235
- Description: This thesis is mainly concerned with the question whether 'conventional' economic theory - especially the neoclassical theory of general equilibrium - is sufficiently flexible to accommodate the particular conditions prevailing in the developing countries. It is argued that most existing theories of economic underdevelopment adopt an interpretative approach which essentially amounts to relaxing some of the chief assumptions of the neoclassical theory. When applied to the two-sector model of general equilibrium, these theories generally yield predictions which are vastly different from those associated with the neoclassical assumptions of perfect competition, unlimited factor substitutability and unrestricted resource mobility. Several theories seek to explain the development problem in terms of the specific production processes used in poor countries. Myrdal's (1957) theory of cumulative causation, for example, effectively introduces increasing returns to scale in at least one sector or region of the economy; in contrast to the neoclassical theory, he thus nvisages a cumulative process of regional divergence in the output level per worker. Similarly, Richard Eckaus's (1955) explanation of the "factor-proportions problem" is based on the assumption of limited factor substitutability. This enables him to establish the existence of a so-called "unemployment equiIibrium", thus implying that developing countries may be faced with a conflict between the objective of maximizing social -welfare on the one hand, and that of full employment on the other. More recently, Leibenstein (1960) has shown that this trade-off may be complicated by the introduction of capital-biased technological inventions and innovations. The solution to the factor-proportions problem consists in the adoption of more appropriate, usually labour-biased technologies, increased capital formation and a reduction in the rate of population growth. Much of the postwar literature on economic development has focused on the imperfectly competitive structure of the product and the factor markets in developing countries. Myint (1954) has highlighted the role played by monopolies and ligopolies during the "opening-up" process of economic development. Likewise, both Lewis's (1954) dualist theory and Todaro's (1969; 1971) model of rural-urban migration attempt to explain the unemployment problem in terms of various factor price distortions. In an international context, Prebisch (1950; 1959) and Singer (1950) have again shown how prevailing differences in the structure of markets between developed and developing countries may turn the terms of trade against the latter; using a two-sector model, Bhagwati (1958) has demonstrated that such a deterioration in the terms of trade could bring about a net decrease in the welfare level of the countries concerned. Generally, the policy measures relevant to the "market imperfections" problem include the creation of job opportunities in the rural (rather than urban) sector, the encouragement of informal-sector enterprises,and the imposition of factor taxes and subsidies as a means of counteracting the adverse effect of factor price distortions on employment. A more recent approach to the unemployment problem is the plea by the International Labor Office (1970; 1972) for a redistribution of income within the developing countries. In terms of the two-sector model, such a policy may well succeed in eliminating labour unemployment caused by fixed factor proportions and/or factor price distortions. It should be realized, though, that a redistribution of income may lower the aggregate savings level, and hence also the growth rates of capital and labour employment in the economy. On the whole, it would seem that these theories do indeed adopt a modified version of the neoclassical theory in providing a fairly comprehensive explanation of the economic problems of labour unemployment, low incomes and inequality.
- Full Text:
- Date Issued: 1982
Theoretical aspects of the reaction of zirconium compunds and vegetable tannins with the chromium-collagen complex
- Williams-Wynn, David Ernest Arthur
- Authors: Williams-Wynn, David Ernest Arthur
- Date: 1969
- Subjects: Zirconium compounds , Collagen , Chromium compounds , Tannins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4512 , http://hdl.handle.net/10962/d1013455
- Description: Studies have been made of the reactions which take place when zirconium compounds and vegetable tannins react with chromium tanned leather, in order to elucidate the mechanisms of the reactions which occur on retannage. Statistical procedures have been used in all investigations because of the variable nature of the substrate, and computer techniques have been applied to the repetitive statistical computations. Although chromium and vegetable tannages are well understood, further information on the reaction of zirconium with collagen was necessary before attempting to interpret the results of the studies of combination tannages with chromium, and this has been obtained by a comparative study of the reactions of chromium and zirconium with modified collagen. It is concluded that the mechanism of the reaction of basic zirconium sulphate with collagen is multipoint attachment of the tanning material by residual valency forces, although charge effects with basic groups may be supplementary. Zirconyl chloride reacts with carboxyl groups but does not form satisfactory, stable cross-links with collagen. Further evidence for this theory was obtained from the investigation of the reaction of zirconium compounds with chromium tanned collagen. Zirconyl sulphate does not interfere with effective chromium tannage and therefore can have little affinity for the carboxyl groups on the protein, but it displaces chromium complexes loosely held by auxiliary valencies without reducing the shrinkage temperature of the chromium leather Zirconyl chloride, although only fixed to a limited extent, apparently forms co-ordination compounds with the carboxyl groups, disrupting the chromium tannage because there is an over-all loss of hydrothermal stability. There is no evidence that zirconium co-ordinates with, or releases acid from chromium-collagen complexes, since combination chromium/zirconium tanned leathers are stable on storage. Retannage of chromium tanned leather with vegetable tanning materials generally results in loss of strength and a product which tends to deteriorate on ageing. Lower initial strength is probably due to the increased avidity of chromium tanned pelt for vegetable tannins, resulting from the liberation of internally neutralised reactive sites which are not normally available in vegetable tannage, and from the co- ordination of vegetable tannins and non-tannins to the chromium complex with the displacement of sulphate radicals. From a study of the retannage of chromium tanned modified collagen, it appears that basic groups probably play an important part in the rapid absorption of vegetable tannin. These reactions result in overloading of the fibre and an increased number of cross-links, both of which tend to produce weak leather. Deterioration with age is primarily a hydrolytic degradation of the protein which is catalysed by acid liberated from the chromium complexes by the entry of vegetable tannins, those factors which favour the formation of acid causing greater and more rapid deterioration.
- Full Text:
- Date Issued: 1969
- Authors: Williams-Wynn, David Ernest Arthur
- Date: 1969
- Subjects: Zirconium compounds , Collagen , Chromium compounds , Tannins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4512 , http://hdl.handle.net/10962/d1013455
- Description: Studies have been made of the reactions which take place when zirconium compounds and vegetable tannins react with chromium tanned leather, in order to elucidate the mechanisms of the reactions which occur on retannage. Statistical procedures have been used in all investigations because of the variable nature of the substrate, and computer techniques have been applied to the repetitive statistical computations. Although chromium and vegetable tannages are well understood, further information on the reaction of zirconium with collagen was necessary before attempting to interpret the results of the studies of combination tannages with chromium, and this has been obtained by a comparative study of the reactions of chromium and zirconium with modified collagen. It is concluded that the mechanism of the reaction of basic zirconium sulphate with collagen is multipoint attachment of the tanning material by residual valency forces, although charge effects with basic groups may be supplementary. Zirconyl chloride reacts with carboxyl groups but does not form satisfactory, stable cross-links with collagen. Further evidence for this theory was obtained from the investigation of the reaction of zirconium compounds with chromium tanned collagen. Zirconyl sulphate does not interfere with effective chromium tannage and therefore can have little affinity for the carboxyl groups on the protein, but it displaces chromium complexes loosely held by auxiliary valencies without reducing the shrinkage temperature of the chromium leather Zirconyl chloride, although only fixed to a limited extent, apparently forms co-ordination compounds with the carboxyl groups, disrupting the chromium tannage because there is an over-all loss of hydrothermal stability. There is no evidence that zirconium co-ordinates with, or releases acid from chromium-collagen complexes, since combination chromium/zirconium tanned leathers are stable on storage. Retannage of chromium tanned leather with vegetable tanning materials generally results in loss of strength and a product which tends to deteriorate on ageing. Lower initial strength is probably due to the increased avidity of chromium tanned pelt for vegetable tannins, resulting from the liberation of internally neutralised reactive sites which are not normally available in vegetable tannage, and from the co- ordination of vegetable tannins and non-tannins to the chromium complex with the displacement of sulphate radicals. From a study of the retannage of chromium tanned modified collagen, it appears that basic groups probably play an important part in the rapid absorption of vegetable tannin. These reactions result in overloading of the fibre and an increased number of cross-links, both of which tend to produce weak leather. Deterioration with age is primarily a hydrolytic degradation of the protein which is catalysed by acid liberated from the chromium complexes by the entry of vegetable tannins, those factors which favour the formation of acid causing greater and more rapid deterioration.
- Full Text:
- Date Issued: 1969
The zonation of coastal dune plants in relation to sand burial, resource availability and physiological adaptation
- Authors: Gilbert, Matthew Edmund
- Date: 2008
- Subjects: Sand dune conservation -- South Africa -- Eastern Cape Coastal ecology -- South Africa -- Eastern Cape Botany -- South Africa -- Eastern Cape Coastal biology -- South Africa -- Eastern Cape Littoral plants -- South Africa -- Eastern Cape Littoral plants Sand dune plants -- Ecophysiology Sand dune plants -- Geographical distribution
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4195 , http://hdl.handle.net/10962/d1003764
- Description: When considering the large amount of work done on dune ecology, and that a number of the classical ecological theories originate from work on dunes, it is apparent that there remains a need for physiological and mechanistic explanations of dune plant phenomena. This thesis demonstrated that in the extreme coastal environment dune plants must survive both high rates of burial (disturbance), and low nutrient availability (stress). The ability of four species to respond to these two factors corresponded with their position in a vegetation gradient on the dunes. A low stem tissue density was shown to enhance the potential stem elongation rate of buried plants, but reduced the maximum height to which a plant could grow. Such a tradeoff implies that tall light-competitive plants are able to survive only in stable areas, while burial responsive mobile-dune plants are limited to areas of low vegetation height. This stem tissue density tradeoff was suggested as the mechanism determining the zonation that species show within the dune vegetation gradient present at various sites in South Africa. Finally, detailed investigations of dune plant ecophysiology found that: 1) The resources used in the response to burial derive from external sources of carbon and nitrogen, as well as simple physiological and physical mechanisms of resource allocation. 2) The leaves of dune plants were found to be operating at one extreme of the photosynthetic continuum; viz efficient use of leaf nitrogen at the expense of water loss. 3) Contrary to other ecosystems, the environmental characteristics of dunes may allow plants to occupy a high disturbance, high stress niche, through the maintenance of lowered competition. 4) At least two mobile-dune species form steep dunes, and are able to optimise growth, on steeper dunes, such that they have to grow less in response to burial than plants that form more shallow dunes. In this thesis, it was shown that the link between the carbon and nitrogen economies of dune plants was pivotal in determining species distributions and survival under extreme environmental conditions. As vast areas of the world’s surface are covered by sand dunes these observations are not just of passing interest.
- Full Text:
- Date Issued: 2008
- Authors: Gilbert, Matthew Edmund
- Date: 2008
- Subjects: Sand dune conservation -- South Africa -- Eastern Cape Coastal ecology -- South Africa -- Eastern Cape Botany -- South Africa -- Eastern Cape Coastal biology -- South Africa -- Eastern Cape Littoral plants -- South Africa -- Eastern Cape Littoral plants Sand dune plants -- Ecophysiology Sand dune plants -- Geographical distribution
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4195 , http://hdl.handle.net/10962/d1003764
- Description: When considering the large amount of work done on dune ecology, and that a number of the classical ecological theories originate from work on dunes, it is apparent that there remains a need for physiological and mechanistic explanations of dune plant phenomena. This thesis demonstrated that in the extreme coastal environment dune plants must survive both high rates of burial (disturbance), and low nutrient availability (stress). The ability of four species to respond to these two factors corresponded with their position in a vegetation gradient on the dunes. A low stem tissue density was shown to enhance the potential stem elongation rate of buried plants, but reduced the maximum height to which a plant could grow. Such a tradeoff implies that tall light-competitive plants are able to survive only in stable areas, while burial responsive mobile-dune plants are limited to areas of low vegetation height. This stem tissue density tradeoff was suggested as the mechanism determining the zonation that species show within the dune vegetation gradient present at various sites in South Africa. Finally, detailed investigations of dune plant ecophysiology found that: 1) The resources used in the response to burial derive from external sources of carbon and nitrogen, as well as simple physiological and physical mechanisms of resource allocation. 2) The leaves of dune plants were found to be operating at one extreme of the photosynthetic continuum; viz efficient use of leaf nitrogen at the expense of water loss. 3) Contrary to other ecosystems, the environmental characteristics of dunes may allow plants to occupy a high disturbance, high stress niche, through the maintenance of lowered competition. 4) At least two mobile-dune species form steep dunes, and are able to optimise growth, on steeper dunes, such that they have to grow less in response to burial than plants that form more shallow dunes. In this thesis, it was shown that the link between the carbon and nitrogen economies of dune plants was pivotal in determining species distributions and survival under extreme environmental conditions. As vast areas of the world’s surface are covered by sand dunes these observations are not just of passing interest.
- Full Text:
- Date Issued: 2008
The work of the international criminal court in Africa and challenges for the future of international criminal justice
- Authors: Mupanga, Godfrey
- Date: 2016
- Subjects: Immunities of foreign states Jurisdiction (International law) Government liability (International law) International relations
- Language: English
- Type: Thesis , Doctoral , Law
- Identifier: http://hdl.handle.net/10353/2645 , vital:27977
- Description: Within the first decade of the ICC‟s existence, its case docket was composed of cases originating from Africa only. Relations between the African governments represented by the AU quickly deteriorated. The AU accuses the ICC of bias and unfair targeting of Africa. After the indictment of heads of states that include Omar Al Bashir of Sudan, Uhuru Kenyatta of Kenya and the late Muammar Gaddafi of Libya, the AU passed several resolutions where it reiterated its commitment to the rule of law and to combating impunity. The AU, however, instructed member states to cease all cooperation with the ICC. African states that are ICC members are now faced with conflicting obligations as a result of the AU resolutions. Moreover, the AU resolutions raise the spectre of a legitimacy crisis for the AU and a conflict between articles 27(2) and 98(1) of the Rome Statute. Based mostly on desk research coupled with my experience working on human rights and access to justice programmes in Sudan, South Sudan, Somaliland, Ethiopia, Kenya, Uganda and Zimbabwe, this thesis considers the possibility that the ICC is suffering from a legitimacy crisis as a result of the fall out and the issues of unfair selectivity that are raised by the AU. Employing the Third World Approaches to International Law as an analytical framework, the study attempts to reconcile the apparent contradictions in the new outlook and rhetoric of the AU pursuant to its Constitutive Act and the instruction to member states to withdraw cooperation with the ICC. The thesis also proposes practical ways to resolve the conflicting obligations caused by the AU resolutions and by operation of customary international law immunity of high ranking state officials referred to the ICC by way of a Security Council resolution. The current situation gives the ICC the appearance of a weak institution that is only good for low hanging fruit, which has a negative effect on the legitimacy of the ICC.
- Full Text:
- Date Issued: 2016
- Authors: Mupanga, Godfrey
- Date: 2016
- Subjects: Immunities of foreign states Jurisdiction (International law) Government liability (International law) International relations
- Language: English
- Type: Thesis , Doctoral , Law
- Identifier: http://hdl.handle.net/10353/2645 , vital:27977
- Description: Within the first decade of the ICC‟s existence, its case docket was composed of cases originating from Africa only. Relations between the African governments represented by the AU quickly deteriorated. The AU accuses the ICC of bias and unfair targeting of Africa. After the indictment of heads of states that include Omar Al Bashir of Sudan, Uhuru Kenyatta of Kenya and the late Muammar Gaddafi of Libya, the AU passed several resolutions where it reiterated its commitment to the rule of law and to combating impunity. The AU, however, instructed member states to cease all cooperation with the ICC. African states that are ICC members are now faced with conflicting obligations as a result of the AU resolutions. Moreover, the AU resolutions raise the spectre of a legitimacy crisis for the AU and a conflict between articles 27(2) and 98(1) of the Rome Statute. Based mostly on desk research coupled with my experience working on human rights and access to justice programmes in Sudan, South Sudan, Somaliland, Ethiopia, Kenya, Uganda and Zimbabwe, this thesis considers the possibility that the ICC is suffering from a legitimacy crisis as a result of the fall out and the issues of unfair selectivity that are raised by the AU. Employing the Third World Approaches to International Law as an analytical framework, the study attempts to reconcile the apparent contradictions in the new outlook and rhetoric of the AU pursuant to its Constitutive Act and the instruction to member states to withdraw cooperation with the ICC. The thesis also proposes practical ways to resolve the conflicting obligations caused by the AU resolutions and by operation of customary international law immunity of high ranking state officials referred to the ICC by way of a Security Council resolution. The current situation gives the ICC the appearance of a weak institution that is only good for low hanging fruit, which has a negative effect on the legitimacy of the ICC.
- Full Text:
- Date Issued: 2016
The Wesleyan Methodist Church in the Transvaal, 1823-1902
- Authors: Veysie, Donald Clifford
- Date: 1971
- Subjects: Methodist Church of Southern Africa Methodist Church of Southern Africa -- History Transvaal (South Africa) -- History -- To 1880 Transvaal (South Africa) -- History -- 1880-1910
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1234 , http://hdl.handle.net/10962/d1007463
- Description: From Preface: A preliminary survey of the history of the Wesleyan Methodist Church in the Transvaal revealed that the period of the early missions, before the formation of the Transvaal and Swaziland District, required research into the documents of other Districts for the purpose of writing a detailed history. It was therefore decided to confine research to the Documents of the Transvaal and Swaziland District and to write introductory chapters on the period of the early missions. The detailed research for this dissertation begins, therefore, with the creation of the Transvaal and Swaziland District in 1880. The natural point at which to finish appeared, at first, to be the beginning of the Second Transvaal War of Independence, but further research indicated that it would be more useful to conclude with the end of the war in 1902.
- Full Text:
- Date Issued: 1971
- Authors: Veysie, Donald Clifford
- Date: 1971
- Subjects: Methodist Church of Southern Africa Methodist Church of Southern Africa -- History Transvaal (South Africa) -- History -- To 1880 Transvaal (South Africa) -- History -- 1880-1910
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1234 , http://hdl.handle.net/10962/d1007463
- Description: From Preface: A preliminary survey of the history of the Wesleyan Methodist Church in the Transvaal revealed that the period of the early missions, before the formation of the Transvaal and Swaziland District, required research into the documents of other Districts for the purpose of writing a detailed history. It was therefore decided to confine research to the Documents of the Transvaal and Swaziland District and to write introductory chapters on the period of the early missions. The detailed research for this dissertation begins, therefore, with the creation of the Transvaal and Swaziland District in 1880. The natural point at which to finish appeared, at first, to be the beginning of the Second Transvaal War of Independence, but further research indicated that it would be more useful to conclude with the end of the war in 1902.
- Full Text:
- Date Issued: 1971
The voluntary welfare organisations of the Border and Transkei: a contribution to the sociology of social work
- Authors: Bettison, D G
- Date: 1956
- Subjects: Social service -- South Africa -- Transkei Social service -- South Africa -- Eastern Cape Volunteer workers in social service
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3314 , http://hdl.handle.net/10962/d1003102
- Description: This research is intended to examine the internal organisational structure of the existing [voluntary welfare] organisations to ascertain what relationship may prove effective between themselves and the [Border Local Welfare] Board. This aim introduced the need to ascertain whether a) the organisations in any town were connected with organisations in other towns or to a central administrative office either in the area of investigation or outside it; or b) the organisations of any town were simply ad hoc units unrelated to any other organisation or similar organisations elsewhere. If the latter were the case then the difficulty of co-ordination and representation on the Board could probably be no better arranged than an ad hoc system as at present. If, however, the former was the predominant pattern, then it would suggest other and more convenient means to the end in view. Fourthly, it was hoped to gain some knowledge of the fund raising methods of welfare organisations, the nature of the people controlling them, the attitudes of managing committees to social work, and what they thought a case work agency should do; and, lastly, some indication of the history of social work as practised by the voluntary agencies in the area of investigation. These latter topics were not intended to form the principal subject matter of the work. They have not been treated fully in the text, but the information gathered has been included in appropriate places throughout.
- Full Text:
- Date Issued: 1956
- Authors: Bettison, D G
- Date: 1956
- Subjects: Social service -- South Africa -- Transkei Social service -- South Africa -- Eastern Cape Volunteer workers in social service
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3314 , http://hdl.handle.net/10962/d1003102
- Description: This research is intended to examine the internal organisational structure of the existing [voluntary welfare] organisations to ascertain what relationship may prove effective between themselves and the [Border Local Welfare] Board. This aim introduced the need to ascertain whether a) the organisations in any town were connected with organisations in other towns or to a central administrative office either in the area of investigation or outside it; or b) the organisations of any town were simply ad hoc units unrelated to any other organisation or similar organisations elsewhere. If the latter were the case then the difficulty of co-ordination and representation on the Board could probably be no better arranged than an ad hoc system as at present. If, however, the former was the predominant pattern, then it would suggest other and more convenient means to the end in view. Fourthly, it was hoped to gain some knowledge of the fund raising methods of welfare organisations, the nature of the people controlling them, the attitudes of managing committees to social work, and what they thought a case work agency should do; and, lastly, some indication of the history of social work as practised by the voluntary agencies in the area of investigation. These latter topics were not intended to form the principal subject matter of the work. They have not been treated fully in the text, but the information gathered has been included in appropriate places throughout.
- Full Text:
- Date Issued: 1956
The voice of the child in parental divorce: a narrative inquiry
- Authors: Brand, Carrie
- Date: 2016
- Subjects: Conversation analysis , Children of divorced parents , Divorced parents
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/8923 , vital:26443
- Description: Parental divorce is considered one of the most stressful events in the lives of children. The adult perspective has dominated the discourse on divorce, and only recently has research started to consider the viewpoint of children. Research indicates that the nature of the divorce process as experienced by the child is the most important factor in post-divorce adjustment. It also remains a relatively unexplored area, with research on the manner in which children experience the divorce process being limited. The current study aimed to conduct a narrative inquiry into the experiences and perceptions of parental divorce, of a purposive sample of 9 to 10 year old children. The primary aim of the study was to highlight and honour the voice of the child in a parental divorce process. The current research was qualitative in nature and adopted a narrative paradigm. Five children were interviewed qualitatively using an unstructured interview. Data were analysed using thematic analysis. Seven themes were identified. The first theme explored children’s endeavours to describe and explain parental divorce. An additional six themes were developed around the types of stories children told of the divorce process. Themes included, What is a Divorcement, Stories of Loss, Stories of Gain, Stories of Change, Stories of Stability, Healing Stories, and Complicating Stories. This study endeavoured to provide divorced parents and those working with children a greater understanding of the way in which children perceive parental divorce, and insight into the factors that facilitate children’s positive adjustment to parental divorce.
- Full Text:
- Date Issued: 2016
- Authors: Brand, Carrie
- Date: 2016
- Subjects: Conversation analysis , Children of divorced parents , Divorced parents
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/8923 , vital:26443
- Description: Parental divorce is considered one of the most stressful events in the lives of children. The adult perspective has dominated the discourse on divorce, and only recently has research started to consider the viewpoint of children. Research indicates that the nature of the divorce process as experienced by the child is the most important factor in post-divorce adjustment. It also remains a relatively unexplored area, with research on the manner in which children experience the divorce process being limited. The current study aimed to conduct a narrative inquiry into the experiences and perceptions of parental divorce, of a purposive sample of 9 to 10 year old children. The primary aim of the study was to highlight and honour the voice of the child in a parental divorce process. The current research was qualitative in nature and adopted a narrative paradigm. Five children were interviewed qualitatively using an unstructured interview. Data were analysed using thematic analysis. Seven themes were identified. The first theme explored children’s endeavours to describe and explain parental divorce. An additional six themes were developed around the types of stories children told of the divorce process. Themes included, What is a Divorcement, Stories of Loss, Stories of Gain, Stories of Change, Stories of Stability, Healing Stories, and Complicating Stories. This study endeavoured to provide divorced parents and those working with children a greater understanding of the way in which children perceive parental divorce, and insight into the factors that facilitate children’s positive adjustment to parental divorce.
- Full Text:
- Date Issued: 2016
The vocal works of Olivier Messiaen
- Authors: Donkin, Deborah Jean
- Date: 1995
- Subjects: Messiaen, Olivier, 1908-1992 Vocal music -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2634 , http://hdl.handle.net/10962/d1002299
- Description: Olivier Messiaen's compositions for voice, though less widely known than his instrumental works, span some forty years and comprise a fifth of his total output. They have hitherto not been subject to much attention. A study of the elements comprising the vocal lines and accompanying instrumentation from the piano-voice song set, Trois melodies (1930), to the vast orchestral-choral La Transfiguration de Notre Seigneur Jesus-Chlist (1969) reveals, amongst other characteristic and evolving features, the emergence of a unique, simulated, plainchant style and its subsequent transformation into incantation with suitably modified accompaniment. While wide-ranging, chromatic and rhythmically free vocal lines are typical of many twentieth century compositions, Messiaen's use of such features is found to be novel, by virtue of the peculiar modal and temporal ambits within which he operated. Vocal delivery is progressively expanded from conventional bel canto production to humming, howling,and eventually speech and percussive sounds and reaches an apotheosis in the virtuoso effects of Cinq Rechants (1949). This recedes somewhat in La Transfiguration, which displays instead a wealth of hybrid plainsong-type writing. Choral works are interesting in that the emphasis shifts from standard part-writing to monody or accompanied unison singing, with an attendant absence of characterised solo parts. By constantly varying the colour of the single melodic line with different permutations of voice types, timbre assumes a new importance, particularly in La Transfiguration. The study of the texts, most of which were conceived by the composer simultaneously with the music, contributes much to the understanding of each work. Biblical symbolism in the early lyrics is progressively enriched by references to numerological, mythological and nature symbolism, mixed in an increasingly Surrealistic manner. The gradual incorporation of emotive phonemes in the texts, culminates in the invented language of Cinq Rechants. The thesis thus reveals an evolving yet persistently idiosyncratic vocal style, which establishes Messiaen as one of the most original composers of his time. It further demonstrates that his vocal works are an important component of his total oeuvre and also a significant contribution to twentieth century vocal literature.
- Full Text:
- Date Issued: 1995
- Authors: Donkin, Deborah Jean
- Date: 1995
- Subjects: Messiaen, Olivier, 1908-1992 Vocal music -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2634 , http://hdl.handle.net/10962/d1002299
- Description: Olivier Messiaen's compositions for voice, though less widely known than his instrumental works, span some forty years and comprise a fifth of his total output. They have hitherto not been subject to much attention. A study of the elements comprising the vocal lines and accompanying instrumentation from the piano-voice song set, Trois melodies (1930), to the vast orchestral-choral La Transfiguration de Notre Seigneur Jesus-Chlist (1969) reveals, amongst other characteristic and evolving features, the emergence of a unique, simulated, plainchant style and its subsequent transformation into incantation with suitably modified accompaniment. While wide-ranging, chromatic and rhythmically free vocal lines are typical of many twentieth century compositions, Messiaen's use of such features is found to be novel, by virtue of the peculiar modal and temporal ambits within which he operated. Vocal delivery is progressively expanded from conventional bel canto production to humming, howling,and eventually speech and percussive sounds and reaches an apotheosis in the virtuoso effects of Cinq Rechants (1949). This recedes somewhat in La Transfiguration, which displays instead a wealth of hybrid plainsong-type writing. Choral works are interesting in that the emphasis shifts from standard part-writing to monody or accompanied unison singing, with an attendant absence of characterised solo parts. By constantly varying the colour of the single melodic line with different permutations of voice types, timbre assumes a new importance, particularly in La Transfiguration. The study of the texts, most of which were conceived by the composer simultaneously with the music, contributes much to the understanding of each work. Biblical symbolism in the early lyrics is progressively enriched by references to numerological, mythological and nature symbolism, mixed in an increasingly Surrealistic manner. The gradual incorporation of emotive phonemes in the texts, culminates in the invented language of Cinq Rechants. The thesis thus reveals an evolving yet persistently idiosyncratic vocal style, which establishes Messiaen as one of the most original composers of his time. It further demonstrates that his vocal works are an important component of his total oeuvre and also a significant contribution to twentieth century vocal literature.
- Full Text:
- Date Issued: 1995
The vegetation potential of natural rangelands in the mid-Fish River Valley, Eastern Cape, South Africa: towards a sustainable and acceptable management system
- Birch, Natalie Vivienne Evans
- Authors: Birch, Natalie Vivienne Evans
- Date: 2001
- Subjects: Vegetation and climate -- South Africa -- Eastern Cape Vegetation dynamics -- South Africa -- Eastern Cape Vegetation surveys -- South Africa -- Eastern Cape Land -- South Africa -- Eastern Cape Rangelands -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4186 , http://hdl.handle.net/10962/d1003754
- Description: Desertification is the diminution or destruction of the biological potential of land, and can lead ultimately to desert-like conditions. The vegetation of southern Africa is claimed to have altered over the past 100 years and much of the change is attributed to pastoral practice. In recent years however there has been much debate around the issue of the deterioration and loss of productivity of the natural rangelands, specifically those under communal management. It is one thing to claim that the vegetation has changed but quite another to produce data and analyses to show this unequivocally. Furthermore it is generally difficult to determine the nature and extent of change in natural ecosystems, as one does not know what the optimal base-line conditions should be. For this reason emphasis has been placed on developing models of potential or expected vegetation. By comparing a model of potential or expected vegetation with that of the contemporary vegetation, areas that deviate from expectation can be identified, in so doing providing evidence of the direction of change in the rangelands under various management treatments. The objective of this study was to determine shifts in the vegetation under different land-use treatments, by developing a technique to predict the potential vegetation of an area. In order to explore the nature and extent of degradation at the landscape scale a study site was selected where a range of land-use and rangeland management practices could be studied in parallel. The mid-Fish River valley consists of three markedly different units of land management, namely commercial rangelands, communal rangelands and nature conservation areas. The vegetation within the mid-Fish River valley falls within the Thicket biome and consists of three main vegetation types namely, Short Succulent Thicket, Medium Succulent Thicket and Mesic Bushclump Savanna. The creation of this potential vegetation model was dependent on the direct gradient analysis approach of relating the community patterns with environmental variables. To achieve this, floristic information was collected at sites along a topographical-moisture gradient. A Canonical Correspondence Analysis (CCA) between the environmental variables and the plant communities produced a classification from which the conditions normally associated with the major plant communities were predicted. When projected as a digital map, the qualifying sites provided a testable hypothesis of the potential vegetation. The results of this study showed a definite grazing gradient, which reflects a change from a more mesic environment towards a more arid environment with an increase in utilisation pressure. The predictive vegetation model proved to be useful for predicting the occurrence of the valley thicket communities within the Eastern Cape.
- Full Text:
- Date Issued: 2001
- Authors: Birch, Natalie Vivienne Evans
- Date: 2001
- Subjects: Vegetation and climate -- South Africa -- Eastern Cape Vegetation dynamics -- South Africa -- Eastern Cape Vegetation surveys -- South Africa -- Eastern Cape Land -- South Africa -- Eastern Cape Rangelands -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4186 , http://hdl.handle.net/10962/d1003754
- Description: Desertification is the diminution or destruction of the biological potential of land, and can lead ultimately to desert-like conditions. The vegetation of southern Africa is claimed to have altered over the past 100 years and much of the change is attributed to pastoral practice. In recent years however there has been much debate around the issue of the deterioration and loss of productivity of the natural rangelands, specifically those under communal management. It is one thing to claim that the vegetation has changed but quite another to produce data and analyses to show this unequivocally. Furthermore it is generally difficult to determine the nature and extent of change in natural ecosystems, as one does not know what the optimal base-line conditions should be. For this reason emphasis has been placed on developing models of potential or expected vegetation. By comparing a model of potential or expected vegetation with that of the contemporary vegetation, areas that deviate from expectation can be identified, in so doing providing evidence of the direction of change in the rangelands under various management treatments. The objective of this study was to determine shifts in the vegetation under different land-use treatments, by developing a technique to predict the potential vegetation of an area. In order to explore the nature and extent of degradation at the landscape scale a study site was selected where a range of land-use and rangeland management practices could be studied in parallel. The mid-Fish River valley consists of three markedly different units of land management, namely commercial rangelands, communal rangelands and nature conservation areas. The vegetation within the mid-Fish River valley falls within the Thicket biome and consists of three main vegetation types namely, Short Succulent Thicket, Medium Succulent Thicket and Mesic Bushclump Savanna. The creation of this potential vegetation model was dependent on the direct gradient analysis approach of relating the community patterns with environmental variables. To achieve this, floristic information was collected at sites along a topographical-moisture gradient. A Canonical Correspondence Analysis (CCA) between the environmental variables and the plant communities produced a classification from which the conditions normally associated with the major plant communities were predicted. When projected as a digital map, the qualifying sites provided a testable hypothesis of the potential vegetation. The results of this study showed a definite grazing gradient, which reflects a change from a more mesic environment towards a more arid environment with an increase in utilisation pressure. The predictive vegetation model proved to be useful for predicting the occurrence of the valley thicket communities within the Eastern Cape.
- Full Text:
- Date Issued: 2001
The value of locally isolated freshwater micro-algae in toxicity testing for water resource management in South Africa
- Authors: Gola, Nontutuzelo Pearl
- Date: 2015
- Subjects: Microalgae -- South Africa , Toxicity testing , Water resources development -- South Africa , Aquatic habitats -- South Africa , Water -- Pollution -- Toxicology , Water quality management -- South Africa , Sewage disposal in rivers, lakes, etc. -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6049 , http://hdl.handle.net/10962/d1017873
- Description: The ecological position of micro-algae at the base of the aquatic food web makes them critical components of aquatic ecosystems. Their short generation time also makes them useful biological indicators because they respond quickly to changes in environmental condition, enabling timely identification and assessment of water quality changes. The inclusion of micro-algae as indicators in water resource regulation and management in South Africa has started recently, their more extensive use in biomonitoring and ecotoxicology programmes for water resource management would contribute to the South African policy if water resource protection. The standard algal growth inhibition assay with the species Pseudokirchneriella subcapitata is currently used for monitoring toxicity of in-stream and industrial wastewater discharges to freshwater micro-algae. The relevance of the data generated by standard toxicity bioassays has been questioned, since micro-algae in particular are extremely variable in their sensitivity to a range of contaminants and these standard species used may not occur in the local aquatic environment. As a result, international regulatory agencies, have recommended algal growth inhibition tests be changed from a single standard species to tests with a number of species. One recommendation, in addition to the use of standard toxicity tests, is the use of species isolated from the local environment which may be more relevant for assessing site specific impacts. This study investigated the value and application of locally isolated South African freshwater micro-algae in toxicity tests for water resource management and was carried out in three phases. The first phase involved isolating micro-algae from South African aquatic resources. Micro-algae suitable for toxicity testing were identified and selected using as set of criteria. Three (Scenedesmus bicaudatus, Chlorella sorokiniana and Chlorella vulgaris) out of eight successfully isolated species satisfied the prescribed selection criteria and these were selected as potential toxicity test species. The second phase focused on refining and adapting the existing algal toxicity test protocol (the algal growth inhibition assay) for use on the locally isolated algal species. The refinement of the test protocol was achieved by exposing the locally isolated species to reference toxicants in order to assess and compare their growth and sensitivity to the toxicants under the prescribed toxicity test conditions with that of the standard toxicity test species (Pseudokirchneriella subcapitata) and a commercial laboratory species (Chlorella protothecoides). During this phase, one of the three local species (Scenedesmus bicaudatus) was eliminated as a potential toxicity test species due to inconsistent growth. The third phase of the study involved assessing the sensitivity of the two remaining species (C. vulgaris and C. sorokiniana) to a range of toxicants (reference toxicants, salts, effluents and a herbicide) and comparing it to that of the standard toxicity test species P. subcapitata and C. protothecoides. The toxicants were selected based on their relative importance in the South African context, as well as the practicality of using these local micro-algae to routinely determine the impact of these toxicants on local aquatic resources. The growth of the four micro-algae was stimulated by the selected effluents. The standard toxicity test species P. subcapitata was ranked the most sensitive and of the four species to two reference toxicants and two inorganic salts. Chlorella sorokiniana was ranked the most sensitive of the three Chlorella species to two reference toxicants and two inorganic salts. The herbicide stimulated the growth of C. vulgaris while inhibiting the growth of the other species. Pseudokirchneriela subcapitata and C. sorokiniana showed high intra-specific variability in growth, which made it difficult to determine the effective concentrations of the herbicide and therefore compare the sensitivity of the species. This varied response of micro-algal species to toxicants may result in the biodiversity shifts in aquatic ecosystems, and also supports the recommendation of using a battery of different species to support more informed decisions in water resource management.
- Full Text:
- Date Issued: 2015
- Authors: Gola, Nontutuzelo Pearl
- Date: 2015
- Subjects: Microalgae -- South Africa , Toxicity testing , Water resources development -- South Africa , Aquatic habitats -- South Africa , Water -- Pollution -- Toxicology , Water quality management -- South Africa , Sewage disposal in rivers, lakes, etc. -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6049 , http://hdl.handle.net/10962/d1017873
- Description: The ecological position of micro-algae at the base of the aquatic food web makes them critical components of aquatic ecosystems. Their short generation time also makes them useful biological indicators because they respond quickly to changes in environmental condition, enabling timely identification and assessment of water quality changes. The inclusion of micro-algae as indicators in water resource regulation and management in South Africa has started recently, their more extensive use in biomonitoring and ecotoxicology programmes for water resource management would contribute to the South African policy if water resource protection. The standard algal growth inhibition assay with the species Pseudokirchneriella subcapitata is currently used for monitoring toxicity of in-stream and industrial wastewater discharges to freshwater micro-algae. The relevance of the data generated by standard toxicity bioassays has been questioned, since micro-algae in particular are extremely variable in their sensitivity to a range of contaminants and these standard species used may not occur in the local aquatic environment. As a result, international regulatory agencies, have recommended algal growth inhibition tests be changed from a single standard species to tests with a number of species. One recommendation, in addition to the use of standard toxicity tests, is the use of species isolated from the local environment which may be more relevant for assessing site specific impacts. This study investigated the value and application of locally isolated South African freshwater micro-algae in toxicity tests for water resource management and was carried out in three phases. The first phase involved isolating micro-algae from South African aquatic resources. Micro-algae suitable for toxicity testing were identified and selected using as set of criteria. Three (Scenedesmus bicaudatus, Chlorella sorokiniana and Chlorella vulgaris) out of eight successfully isolated species satisfied the prescribed selection criteria and these were selected as potential toxicity test species. The second phase focused on refining and adapting the existing algal toxicity test protocol (the algal growth inhibition assay) for use on the locally isolated algal species. The refinement of the test protocol was achieved by exposing the locally isolated species to reference toxicants in order to assess and compare their growth and sensitivity to the toxicants under the prescribed toxicity test conditions with that of the standard toxicity test species (Pseudokirchneriella subcapitata) and a commercial laboratory species (Chlorella protothecoides). During this phase, one of the three local species (Scenedesmus bicaudatus) was eliminated as a potential toxicity test species due to inconsistent growth. The third phase of the study involved assessing the sensitivity of the two remaining species (C. vulgaris and C. sorokiniana) to a range of toxicants (reference toxicants, salts, effluents and a herbicide) and comparing it to that of the standard toxicity test species P. subcapitata and C. protothecoides. The toxicants were selected based on their relative importance in the South African context, as well as the practicality of using these local micro-algae to routinely determine the impact of these toxicants on local aquatic resources. The growth of the four micro-algae was stimulated by the selected effluents. The standard toxicity test species P. subcapitata was ranked the most sensitive and of the four species to two reference toxicants and two inorganic salts. Chlorella sorokiniana was ranked the most sensitive of the three Chlorella species to two reference toxicants and two inorganic salts. The herbicide stimulated the growth of C. vulgaris while inhibiting the growth of the other species. Pseudokirchneriela subcapitata and C. sorokiniana showed high intra-specific variability in growth, which made it difficult to determine the effective concentrations of the herbicide and therefore compare the sensitivity of the species. This varied response of micro-algal species to toxicants may result in the biodiversity shifts in aquatic ecosystems, and also supports the recommendation of using a battery of different species to support more informed decisions in water resource management.
- Full Text:
- Date Issued: 2015