The development of a concept of psychological well-being
- Authors: Bar-On, Reuven
- Date: 1988
- Subjects: Mental health -- Psychological aspects Personality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2928 , http://hdl.handle.net/10962/d1002437
- Description: This thesis focuses on the development of an operational and theoretically eclectic concept of psychological well-being. A comprehensive research strategy was employed to examine various personality factors thought to be components of psychological health (i.e., the basis of the proposed concept). The general approach involved four major phases: (1) the clustering of various variables and identification of underlying key factors purported to be related to psychological health based on the writer's clinical experience and review of the mental health literature, (2) the formulation of an ~ priori concept of psychological well-being based on the operational definition of those factors, (3) the construction of an inventory designed to examine the proposed concept, and (4) the interpretation of the results and their implications for the development of the overall concept based on the examination of the factorial structure, validity and reliability of the inventory. The"a posteriori concept" evolved out of this process. The results of the present study indicate that the most valid and reliable factorial components of psychological well-being are self regard,interpersonal relationship, independence, problem-solving, assertiveness,reality testing, stress tolerance, self-actualization and happiness; social responsibility and flexibility emerged as questionable components of the a posteriori concept. The inventory which was designed to study the concept was successful in significantly differentiating various levels of psychological health. This way of conceptualizing and assessing psychological well-being has potential applicability for mental health practitioners and researchers.
- Full Text:
- Authors: Bar-On, Reuven
- Date: 1988
- Subjects: Mental health -- Psychological aspects Personality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2928 , http://hdl.handle.net/10962/d1002437
- Description: This thesis focuses on the development of an operational and theoretically eclectic concept of psychological well-being. A comprehensive research strategy was employed to examine various personality factors thought to be components of psychological health (i.e., the basis of the proposed concept). The general approach involved four major phases: (1) the clustering of various variables and identification of underlying key factors purported to be related to psychological health based on the writer's clinical experience and review of the mental health literature, (2) the formulation of an ~ priori concept of psychological well-being based on the operational definition of those factors, (3) the construction of an inventory designed to examine the proposed concept, and (4) the interpretation of the results and their implications for the development of the overall concept based on the examination of the factorial structure, validity and reliability of the inventory. The"a posteriori concept" evolved out of this process. The results of the present study indicate that the most valid and reliable factorial components of psychological well-being are self regard,interpersonal relationship, independence, problem-solving, assertiveness,reality testing, stress tolerance, self-actualization and happiness; social responsibility and flexibility emerged as questionable components of the a posteriori concept. The inventory which was designed to study the concept was successful in significantly differentiating various levels of psychological health. This way of conceptualizing and assessing psychological well-being has potential applicability for mental health practitioners and researchers.
- Full Text:
Synthetic and physical organic studies of chromone derivatives
- Ramaite, Ipfani David Isaiah
- Authors: Ramaite, Ipfani David Isaiah
- Date: 1997
- Subjects: Benzopyrans Heterocyclic compounds -- Derivatives Coumarins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4380 , http://hdl.handle.net/10962/d1005045
- Description: A range of chromone-2-carboxylic acids has been prepared by condensing suitably substituted 2-hydroxyacetophenones with diethyl oxalate. pK₂ Studies of these acids revealed that 6- or 7-methoxy substituents decreased acidity while the 6-nitro group enhanced acidity; the strongest acid was the 3-chloro derivative, the increase in acidity being attributed to steric inhibition of acid-weakening delocalisation between the carboxyl group and the chromone system. Various chromone-2-carboxamides, derived from acid chloride precursors, were converted to polysubstituted acrylamides by nucleophilic ring-opening with selected amine nucleophiles. The main fragmentation patterns exhibited by these acrylamides were elucidated using a combination of low resolution, high resolution and meta-stable peak analysis, while the effect of substituents on the simultaneous internal rotation involving the carboxamide and enamine moieties were studied using dynamic NMR spectroscopy. Rotational barriers of ca. 67.1 kJmol ̄¹ and ca. 102 kJmol ̄¹ were found for the enamine and amide rotors, respectively. Several synthetic pathways were followed to prepare a series of 2-(N,N-dialkylamino)chromones which were subjected to detailed mass spectral analysis. In addition to substituent-specific fragmentations , the 2-aminochromones appear to fragment via 3 major pathways. The effect of substituents on the internal rotation of the amino moeity was investigated by variable temperature ¹H NMR spectroscopy and the resulting DNMR data was used to calculate the rotational barriers. Examination of the data reveals that the electron-releasing 6- and 7- substituents reduce the C-NMe₂ rotational barrier to ca. 43.5 kJmol ̄¹ , while the nitro analogue has the largest rotational barrier (ca. 46.1 kJmol ̄¹) because of the electron-withdrawing effect of this substituent.
- Full Text:
- Authors: Ramaite, Ipfani David Isaiah
- Date: 1997
- Subjects: Benzopyrans Heterocyclic compounds -- Derivatives Coumarins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4380 , http://hdl.handle.net/10962/d1005045
- Description: A range of chromone-2-carboxylic acids has been prepared by condensing suitably substituted 2-hydroxyacetophenones with diethyl oxalate. pK₂ Studies of these acids revealed that 6- or 7-methoxy substituents decreased acidity while the 6-nitro group enhanced acidity; the strongest acid was the 3-chloro derivative, the increase in acidity being attributed to steric inhibition of acid-weakening delocalisation between the carboxyl group and the chromone system. Various chromone-2-carboxamides, derived from acid chloride precursors, were converted to polysubstituted acrylamides by nucleophilic ring-opening with selected amine nucleophiles. The main fragmentation patterns exhibited by these acrylamides were elucidated using a combination of low resolution, high resolution and meta-stable peak analysis, while the effect of substituents on the simultaneous internal rotation involving the carboxamide and enamine moieties were studied using dynamic NMR spectroscopy. Rotational barriers of ca. 67.1 kJmol ̄¹ and ca. 102 kJmol ̄¹ were found for the enamine and amide rotors, respectively. Several synthetic pathways were followed to prepare a series of 2-(N,N-dialkylamino)chromones which were subjected to detailed mass spectral analysis. In addition to substituent-specific fragmentations , the 2-aminochromones appear to fragment via 3 major pathways. The effect of substituents on the internal rotation of the amino moeity was investigated by variable temperature ¹H NMR spectroscopy and the resulting DNMR data was used to calculate the rotational barriers. Examination of the data reveals that the electron-releasing 6- and 7- substituents reduce the C-NMe₂ rotational barrier to ca. 43.5 kJmol ̄¹ , while the nitro analogue has the largest rotational barrier (ca. 46.1 kJmol ̄¹) because of the electron-withdrawing effect of this substituent.
- Full Text:
An examination of the extractives of Leonotis species
- Authors: Kaplan, Errol R
- Date: 1966
- Subjects: Leonotis -- Analysis Botanical chemistry Chemistry, Analytic Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4481 , http://hdl.handle.net/10962/d1012628
- Description: Marrubiin and the other two diterpenoids, compounds X and Y, which had previously been isolated from Leonotus leonurus have been reinvestigated. Although the structure for marrubiin is well known its stereochemistry has been the subject of protracted discussion and is by no means secure except at C₅ and C₁₀ . N.M.R. spectral evidence showed that the lactone ring was cis-fused and β-orientated. Dehydration experiments carried out by previous workers were repeated, in order to resolve the residual uncertainty regarding the stereochemistry at C₉, an attempt was made to prepare iodoacetyl marrubic acid for X-ray crystallographic studies. Compound Y, C₂₀H₂₈0₃, a triply-unsaturated compound was shown by spectral studies to contain a furan ring and an α,β- unsaturated keto-group. It possesses a hydroxyl group incapable of acetylation, but readily removed by alkali and dehydrating agents to yield a tetraunsaturated compound, anhydro~Y; the hydroxyl is thus tertiary, Isolation of 1:2:5-trimethylnaphthalene on dehydrogenation indicated a relationship with the labdane diterpene group and supported the C₂₀ formula, The position of the α,β-unsaturated keto-group was resolved by interpretation of the ultraviolet spectra of degradation products and also by isolation of 1:2:3:5- trimethylnaphthalene on dehydrogenation of a suitable grignard product, The presence of a β-substituted furan was further indicated by colour reactions and confirmed by mass and n.m.r. spectra. The skeleton of compound Y is correlated with marrubiin via "iso-ambreinolide " and its stereochemistry is discussed. Further stereochemical assignments are postulated from the study of the n.m.r. spectra. Compound X, C₂₀H₂₈0₅, was shown by spectral and chemical evidence to be a diterpenoid dilactone containing an ether bridge between C₉ and C₁₃ Isolation of 1:2:5 trimethylnaphthal ene on dehydrogenation showed it to be closely related to marrubiin, This was supported by n.m.r. spectral results. A structure for compound X is proposed and the stereochemistry discussed. The aerial portions of Leonotis leonitis were also extracted and shown to contain a new compound, compound R. Preliminary investigation showed that it was a dilactone containing a furan ring, The n.m.r. spectrum of the compound is discussed.
- Full Text:
- Authors: Kaplan, Errol R
- Date: 1966
- Subjects: Leonotis -- Analysis Botanical chemistry Chemistry, Analytic Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4481 , http://hdl.handle.net/10962/d1012628
- Description: Marrubiin and the other two diterpenoids, compounds X and Y, which had previously been isolated from Leonotus leonurus have been reinvestigated. Although the structure for marrubiin is well known its stereochemistry has been the subject of protracted discussion and is by no means secure except at C₅ and C₁₀ . N.M.R. spectral evidence showed that the lactone ring was cis-fused and β-orientated. Dehydration experiments carried out by previous workers were repeated, in order to resolve the residual uncertainty regarding the stereochemistry at C₉, an attempt was made to prepare iodoacetyl marrubic acid for X-ray crystallographic studies. Compound Y, C₂₀H₂₈0₃, a triply-unsaturated compound was shown by spectral studies to contain a furan ring and an α,β- unsaturated keto-group. It possesses a hydroxyl group incapable of acetylation, but readily removed by alkali and dehydrating agents to yield a tetraunsaturated compound, anhydro~Y; the hydroxyl is thus tertiary, Isolation of 1:2:5-trimethylnaphthalene on dehydrogenation indicated a relationship with the labdane diterpene group and supported the C₂₀ formula, The position of the α,β-unsaturated keto-group was resolved by interpretation of the ultraviolet spectra of degradation products and also by isolation of 1:2:3:5- trimethylnaphthalene on dehydrogenation of a suitable grignard product, The presence of a β-substituted furan was further indicated by colour reactions and confirmed by mass and n.m.r. spectra. The skeleton of compound Y is correlated with marrubiin via "iso-ambreinolide " and its stereochemistry is discussed. Further stereochemical assignments are postulated from the study of the n.m.r. spectra. Compound X, C₂₀H₂₈0₅, was shown by spectral and chemical evidence to be a diterpenoid dilactone containing an ether bridge between C₉ and C₁₃ Isolation of 1:2:5 trimethylnaphthal ene on dehydrogenation showed it to be closely related to marrubiin, This was supported by n.m.r. spectral results. A structure for compound X is proposed and the stereochemistry discussed. The aerial portions of Leonotis leonitis were also extracted and shown to contain a new compound, compound R. Preliminary investigation showed that it was a dilactone containing a furan ring, The n.m.r. spectrum of the compound is discussed.
- Full Text:
A contribution to the limnology of Swartvlei: the effect of physico-chemical factors upon primary and secondary production in the pelagic zone
- Authors: Robarts, R D (Richard D)
- Date: 1974
- Subjects: Limnology -- South Africa -- Swartvlei
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5822 , http://hdl.handle.net/10962/d1007474
- Description: From Resumé: The effect of physico-chemical factors on the biology of the upper reaches of Swartvlei has been investigated during 1971-1972. Physico-chemical data have shown that Swartvlei was characterized by an extremely labile ectogenic meromixis. This instability was due to three factors : (1) the inflow of freshwater, (2) the inflow of sea water, and (3) wind stress. The magnitude of the effects of these factors upon the physics, chemistry and biology of the upper reaches was dependent upon whether or not the estuary mouth was open or closed. The phytoplankton of the pelagic zone of Swartvlei was dominated by nannoplankton. Three major categories were recorded: dinoflagellates, flagellates and diatoms. The major factor regulating their productivity in the upper reaches was light. As a result of humate staining and suspended detrital matter light conditions in Swartvlei were comparable to those in extremely eutrophic northern hemisphere lakes. A maximum integral primary productivity of 39.66 mg C m⁻² h⁻¹ was recorded in November 1972. The aerobic heterotrophic bacterial population in Swartvlei was usually less than 300 col. ml⁻¹ (plate counts). The activity of the total microbial population was measured with ¹⁴C techniques. Uptake of acetate was dominated by flagellates and one species of dinoflagellate when they were present. Glucose uptake was due to bacteria as was acetate uptake in the absence of heterotrophic phytoplankton. Glucose uptake was usually greatest in the anaerobic zone. This, and the presence of H₂S, suggested that a large active photosynthetic and chemosynthetic bacterial population may have been present in the monimolimnion. The possible importance of these bacterial processes in the total productivity of the pelagic zone of Swartvlei was discussed. Daytime zooplankton population size was statistically correlated with the size of the flagellate population. The zooplankton was dominated by Acartia and Halicyclops. These two animals were found in the anaerobic bottom of Swartvlei after October 1971. This corresponded to the disappearance of the flagellate population from the water column. The dominance of these animals in the zooplankton population may have been related to their ability to live in anaerobic water where the bacterial population appeared to be considerably more abundant than in the aerobic zone. Further implications of the results are discussed in reference to phytoplankton cell size and heterotrophy indicating a possible adaptive significance of these factors in Swartvlei.
- Full Text:
- Authors: Robarts, R D (Richard D)
- Date: 1974
- Subjects: Limnology -- South Africa -- Swartvlei
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5822 , http://hdl.handle.net/10962/d1007474
- Description: From Resumé: The effect of physico-chemical factors on the biology of the upper reaches of Swartvlei has been investigated during 1971-1972. Physico-chemical data have shown that Swartvlei was characterized by an extremely labile ectogenic meromixis. This instability was due to three factors : (1) the inflow of freshwater, (2) the inflow of sea water, and (3) wind stress. The magnitude of the effects of these factors upon the physics, chemistry and biology of the upper reaches was dependent upon whether or not the estuary mouth was open or closed. The phytoplankton of the pelagic zone of Swartvlei was dominated by nannoplankton. Three major categories were recorded: dinoflagellates, flagellates and diatoms. The major factor regulating their productivity in the upper reaches was light. As a result of humate staining and suspended detrital matter light conditions in Swartvlei were comparable to those in extremely eutrophic northern hemisphere lakes. A maximum integral primary productivity of 39.66 mg C m⁻² h⁻¹ was recorded in November 1972. The aerobic heterotrophic bacterial population in Swartvlei was usually less than 300 col. ml⁻¹ (plate counts). The activity of the total microbial population was measured with ¹⁴C techniques. Uptake of acetate was dominated by flagellates and one species of dinoflagellate when they were present. Glucose uptake was due to bacteria as was acetate uptake in the absence of heterotrophic phytoplankton. Glucose uptake was usually greatest in the anaerobic zone. This, and the presence of H₂S, suggested that a large active photosynthetic and chemosynthetic bacterial population may have been present in the monimolimnion. The possible importance of these bacterial processes in the total productivity of the pelagic zone of Swartvlei was discussed. Daytime zooplankton population size was statistically correlated with the size of the flagellate population. The zooplankton was dominated by Acartia and Halicyclops. These two animals were found in the anaerobic bottom of Swartvlei after October 1971. This corresponded to the disappearance of the flagellate population from the water column. The dominance of these animals in the zooplankton population may have been related to their ability to live in anaerobic water where the bacterial population appeared to be considerably more abundant than in the aerobic zone. Further implications of the results are discussed in reference to phytoplankton cell size and heterotrophy indicating a possible adaptive significance of these factors in Swartvlei.
- Full Text:
Simulation of the visuo-motor processes in the tracking and interception of a tennis ball in play
- Authors: Pappo, Harry A
- Date: 1985
- Subjects: Tennis -- Psychological aspects Motor ability -- Physiological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1365 , http://hdl.handle.net/10962/d1001431
- Description: In sports, one might wish to test new ideas regarding player movement, tactics, or strategy without subjecting the athletes to possibly wasteful or even harmful habit formations. If a method of simulation of the athlete can be devised, experiments might reasonably be conducted to evaluate the ideas independently of actual training or trial in the field. Simulation of a complex system generally begins with a long period of analysis. During this time there may be mathematical and programming explorations and constructions to sharpen and examine different approaches. Meetings are usually held by the participants to try to define the task and explore alternatives. Ideas are amplified, possibly discarded as not feasible, or incorporated into the system package. Gradually there evolves a tighter and more acceptable formulation using logical and mathematical expressions (Preface, p. vii)
- Full Text:
- Authors: Pappo, Harry A
- Date: 1985
- Subjects: Tennis -- Psychological aspects Motor ability -- Physiological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1365 , http://hdl.handle.net/10962/d1001431
- Description: In sports, one might wish to test new ideas regarding player movement, tactics, or strategy without subjecting the athletes to possibly wasteful or even harmful habit formations. If a method of simulation of the athlete can be devised, experiments might reasonably be conducted to evaluate the ideas independently of actual training or trial in the field. Simulation of a complex system generally begins with a long period of analysis. During this time there may be mathematical and programming explorations and constructions to sharpen and examine different approaches. Meetings are usually held by the participants to try to define the task and explore alternatives. Ideas are amplified, possibly discarded as not feasible, or incorporated into the system package. Gradually there evolves a tighter and more acceptable formulation using logical and mathematical expressions (Preface, p. vii)
- Full Text:
Applications of the Baylis-Hillman reaction in the synthesis of coumarin derivatives
- Authors: Musa, Musiliyu Ayodele
- Date: 2003
- Subjects: Coumarins Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4403 , http://hdl.handle.net/10962/d1006705
- Description: The reaction of specially prepared salicylaldehyde benzyl ethers with the activated alkenes, methyl acrylate or acrylonitrile, in the presence of the catalyst, DABCO, has afforded Baylis-Hillman products, which have been subjected to conjugate addition with either piperidine or benzylamine. Hydrogenolysis of these conjugate addition products in the presence of a palladium-on-carbon catalyst has been shown to afford the corresponding 3-substituted coumarins, while treatment of O-benzylated Baylis-Hillman adducts with HCl or HI afforded the corresponding 3-(halomethyl)coumarins directly, in up to 94%. The 3-(halomethyl)coumarins have also been obtained in excellent yields (up to 98%) and even more conveniently, by treating the unprotected Baylis-Hillman products with HCl in a mixture of AcOH and Ac₂O, obtained from tert-butyl acrylate and various salicylaldehydes. The generality of an established route to the synthesis of coumarins via an intramolecular Baylis-Hillman reaction, involving the use of salicylaldehyde acrylate esters in the presence of DABCO, has also been demonstrated. Reactions between the 3-(halomethyl)coumarins and various nitrogen and carbon nucleophiles have been shown to proceed with a high degree of regioselectivity at the exocyclic allylic centre to afford 3-substituted coumarin products. The electronimpact mass spectra of selected coumarin derivatives have been investigated using high-resolution and B/E linked scan data. Fragmentation pathways have been proposed and fragmentation modes associated with different coumarin-containing analogues have been compared. A series of coumarin-containing analogues of ritonavir (a clinically useful HIV-1 protease inhibitor) have been prepared and characterized. The synthetic approach has involved the coupling of coumarin derivatives with a hydroxyethylene dipeptide isostere to afford ritonavir analogues containing coumarin termini. An interactive docking procedure has been used to explore the docking of ritonavir and a coumarincontaining analogue into the enzyme active site.
- Full Text:
- Authors: Musa, Musiliyu Ayodele
- Date: 2003
- Subjects: Coumarins Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4403 , http://hdl.handle.net/10962/d1006705
- Description: The reaction of specially prepared salicylaldehyde benzyl ethers with the activated alkenes, methyl acrylate or acrylonitrile, in the presence of the catalyst, DABCO, has afforded Baylis-Hillman products, which have been subjected to conjugate addition with either piperidine or benzylamine. Hydrogenolysis of these conjugate addition products in the presence of a palladium-on-carbon catalyst has been shown to afford the corresponding 3-substituted coumarins, while treatment of O-benzylated Baylis-Hillman adducts with HCl or HI afforded the corresponding 3-(halomethyl)coumarins directly, in up to 94%. The 3-(halomethyl)coumarins have also been obtained in excellent yields (up to 98%) and even more conveniently, by treating the unprotected Baylis-Hillman products with HCl in a mixture of AcOH and Ac₂O, obtained from tert-butyl acrylate and various salicylaldehydes. The generality of an established route to the synthesis of coumarins via an intramolecular Baylis-Hillman reaction, involving the use of salicylaldehyde acrylate esters in the presence of DABCO, has also been demonstrated. Reactions between the 3-(halomethyl)coumarins and various nitrogen and carbon nucleophiles have been shown to proceed with a high degree of regioselectivity at the exocyclic allylic centre to afford 3-substituted coumarin products. The electronimpact mass spectra of selected coumarin derivatives have been investigated using high-resolution and B/E linked scan data. Fragmentation pathways have been proposed and fragmentation modes associated with different coumarin-containing analogues have been compared. A series of coumarin-containing analogues of ritonavir (a clinically useful HIV-1 protease inhibitor) have been prepared and characterized. The synthetic approach has involved the coupling of coumarin derivatives with a hydroxyethylene dipeptide isostere to afford ritonavir analogues containing coumarin termini. An interactive docking procedure has been used to explore the docking of ritonavir and a coumarincontaining analogue into the enzyme active site.
- Full Text:
Some aspects of the ecology of the citrus red mite, Panonychus citri (McGregor), in the Eastern Cape Province
- Authors: Keetch, D P
- Date: 1969
- Subjects: Citrus -- Diseases and pests -- South Africa -- Eastern Cape Plant mites -- Ecology -- South Africa Citrus red mite Citrus red mite -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5860 , http://hdl.handle.net/10962/d1012630
- Description: The citrus red mite, Panonychus citri (McGregor), is a relatively new pest to South African citriculture, the first recorded injury to citrus trees was from Rustenberg, Transvaal in 1950 (Smith 1953). In the U.S.A. the biology of this mite has been studied by Quayle (1938), Prendergast (1938), English and Turnipseed (1941), DeBach (1947), DeBach et al. (1950), Ebeling (1959) and Jeppson et al. (1957,1961). However, in South Africa little information is available concerning the ecolopy of the citrus red mite. The majority of the literature pertaining to P. citri in Republic, (Smith (1953), Mentz (1954), Stofberg (1959), Schwartz (1965) and Brodrick (1965) is of a descriptive nature, and mainly concerned with the chemical control of the mite. The only biological investigation on the development of P.citri, and the effect of insecticides and insect predators on its biology, under South African conditions, was made by van Rooyen (1966) at Zebediela, Transvaal. In the control of citrus pests, such as the citrus red mite, that need for a better understanding of their ecology has been well emphasised by DeBach (1951) and Griffiths (1951). DeBach (1951) in particular, stressed the danger of the continued reliance on insecticidal treatment as the only method of nest control, and has pointed out that persistent chemical applications may only serve to intensify the pest problem. He has suggested that a closer study of the environment of the pest species could provide a solution to the problems now encountered as a result of insecticidal control measures. Intro., p. 1-2.
- Full Text:
- Authors: Keetch, D P
- Date: 1969
- Subjects: Citrus -- Diseases and pests -- South Africa -- Eastern Cape Plant mites -- Ecology -- South Africa Citrus red mite Citrus red mite -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5860 , http://hdl.handle.net/10962/d1012630
- Description: The citrus red mite, Panonychus citri (McGregor), is a relatively new pest to South African citriculture, the first recorded injury to citrus trees was from Rustenberg, Transvaal in 1950 (Smith 1953). In the U.S.A. the biology of this mite has been studied by Quayle (1938), Prendergast (1938), English and Turnipseed (1941), DeBach (1947), DeBach et al. (1950), Ebeling (1959) and Jeppson et al. (1957,1961). However, in South Africa little information is available concerning the ecolopy of the citrus red mite. The majority of the literature pertaining to P. citri in Republic, (Smith (1953), Mentz (1954), Stofberg (1959), Schwartz (1965) and Brodrick (1965) is of a descriptive nature, and mainly concerned with the chemical control of the mite. The only biological investigation on the development of P.citri, and the effect of insecticides and insect predators on its biology, under South African conditions, was made by van Rooyen (1966) at Zebediela, Transvaal. In the control of citrus pests, such as the citrus red mite, that need for a better understanding of their ecology has been well emphasised by DeBach (1951) and Griffiths (1951). DeBach (1951) in particular, stressed the danger of the continued reliance on insecticidal treatment as the only method of nest control, and has pointed out that persistent chemical applications may only serve to intensify the pest problem. He has suggested that a closer study of the environment of the pest species could provide a solution to the problems now encountered as a result of insecticidal control measures. Intro., p. 1-2.
- Full Text:
Ellipsis in the vP domain in Mandarin and Xhosa
- Authors: Ma, Xiujie
- Date: 2017
- Subjects: Grammar, Comparative and general -- Ellipsis , Chinese lanaguage -- Ellipsis , Chinese lanaguage -- Grammar, Comparative -- Xhosa , Xhosa lanaguage -- Ellipsis , Xhosa lanaguage -- Grammar, Comparative -- Chinese
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/43105 , vital:25266
- Description: This thesis provides a unified analysis of ellipsis in the vP domain in two typologically different languages, Mandarin and Xhosa from a generative perspective. It starts with the V-stranding Verb Phrase Ellipsis (VPE) assumption and shows that Mandarin and Xhosa do not have V-stranding VPE. The evidence for this is that in both languages, the constituents that remain in vP obligatorily are not allowed to be deleted, whereas the ones that can/must move out of vP can be deleted. The deleted constituents display the characteristics of PF-deletion, i.e. they have an internal syntactic structure. Based on the parallel between movement and ellipsis of the vP-internal constituents, I propose the Ellipsis EPP Hypothesis to account for ellipsis in the vP domain. The Hypothesis predicts that there is an Ellipsis Phrase at the left periphery of vP. The EP bears an Ellipsis-EPP (EEPP) feature, which must be satisfied. Maximal phrases in the c-command domain of EP are all potential candidates for satisfying the EEPP feature by moving to [Spec, EP]. However, only the phrases that are allowed to move out of vP can move to [Spec, EP] as EP is located above vP. Moreover, the movement to [Spec, EP] is subject to the syntactic and semantic restrictions in structure-building in that ellipsis is one operation in the course of structure-building and the derivation will continue after ellipsis takes place. The EEPP feature renders an XP in the specifier phonetically empty and syntactically frozen; therefore, a constituent will be deleted as soon as it moves to [Spec, EP]. The Hypothesis is schematically represented below. The Ellipsis EPP Hypothesis adequately accounts for the ellipsis of various vP-internal constituents - NPs, DPs, infinitive complements and CP complements - in both Mandarin and Xhosa. At the same time, it reveals the reasons why vP is precluded from being elided in these two languages. In Mandarin vP moves to [Spec, AspPi] to check the uninterpretable [asp] feature and in Xhosa vP moves to [Spec, FocP] to realize the focus; consequently, vP may not move to [Spec, EP] for ellipsis.
- Full Text:
- Authors: Ma, Xiujie
- Date: 2017
- Subjects: Grammar, Comparative and general -- Ellipsis , Chinese lanaguage -- Ellipsis , Chinese lanaguage -- Grammar, Comparative -- Xhosa , Xhosa lanaguage -- Ellipsis , Xhosa lanaguage -- Grammar, Comparative -- Chinese
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/43105 , vital:25266
- Description: This thesis provides a unified analysis of ellipsis in the vP domain in two typologically different languages, Mandarin and Xhosa from a generative perspective. It starts with the V-stranding Verb Phrase Ellipsis (VPE) assumption and shows that Mandarin and Xhosa do not have V-stranding VPE. The evidence for this is that in both languages, the constituents that remain in vP obligatorily are not allowed to be deleted, whereas the ones that can/must move out of vP can be deleted. The deleted constituents display the characteristics of PF-deletion, i.e. they have an internal syntactic structure. Based on the parallel between movement and ellipsis of the vP-internal constituents, I propose the Ellipsis EPP Hypothesis to account for ellipsis in the vP domain. The Hypothesis predicts that there is an Ellipsis Phrase at the left periphery of vP. The EP bears an Ellipsis-EPP (EEPP) feature, which must be satisfied. Maximal phrases in the c-command domain of EP are all potential candidates for satisfying the EEPP feature by moving to [Spec, EP]. However, only the phrases that are allowed to move out of vP can move to [Spec, EP] as EP is located above vP. Moreover, the movement to [Spec, EP] is subject to the syntactic and semantic restrictions in structure-building in that ellipsis is one operation in the course of structure-building and the derivation will continue after ellipsis takes place. The EEPP feature renders an XP in the specifier phonetically empty and syntactically frozen; therefore, a constituent will be deleted as soon as it moves to [Spec, EP]. The Hypothesis is schematically represented below. The Ellipsis EPP Hypothesis adequately accounts for the ellipsis of various vP-internal constituents - NPs, DPs, infinitive complements and CP complements - in both Mandarin and Xhosa. At the same time, it reveals the reasons why vP is precluded from being elided in these two languages. In Mandarin vP moves to [Spec, AspPi] to check the uninterpretable [asp] feature and in Xhosa vP moves to [Spec, FocP] to realize the focus; consequently, vP may not move to [Spec, EP] for ellipsis.
- Full Text:
A study of the nature, function and availability of orders of restitutio in integrum and specific performance as remedies in South African law
- Authors: Lambiris, Michael A
- Date: 1987
- Subjects: Restitutio in integrum (Roman law) Restitutio in integrum -- South Africa Remedies (Law) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3703 , http://hdl.handle.net/10962/d1004752
- Description: This study is of two remedies that are available in South African law: orders of restitutio in integrum, and specific performance. The study demonstrates that, by treating these remedies as legal topics in their own right, a greater understanding emerges of their inherent characteristics, the role that they play in the law, and of the particular circumstances in which these remedies are available. An order of restitutio in integrum performs an important and unique function in South African law. The fundamental realisation is that it is a remedy in terms of which the courts exercise an extraordinary and discretionary power, and nullify ab initio legal transactions, or the legal consequences of events, which were previously perfectly valid and enforceable at law. Because of the extraordinary nature of this remedy, the circumstances in which it is available are limited by the requirement that iusta causa must exist to justify nullification. Further, before the remedy is available, the person seeking relief must have suffered loss or prejudice as a result of the event complained of. Finally, a mutual restoration of benefits received by the persons involved is required. The nature and effect of orders of restitutio in integrum, and the essential elements which determine the availability of the remedy, enable it to be distinguished from, and contrasted with, other remedies in South African law. An order of specific performance is available in South African law, at the option of a plaintiff, to enforce the actual performance of contractual undertakings. The remedy is appropriate to enforce positive undertakings, as well as acts of restraint. For the remedy to be available, it is firstly necessary that a contractual obligation be proved to exist. Secondly, performance of that obligation must be due. Thirdly, the performance sought must not in fact have already been rendered. These elements determine the availability of the remedy in particular factual circumstances, such as in cases involving pre-emptive rights. The nature and characteristics of the remedy are determined by principles of South African, and not English law. The remedy is available as of right in South African law, but subject to a discretionary power of a court to refuse to order specific performance. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Authors: Lambiris, Michael A
- Date: 1987
- Subjects: Restitutio in integrum (Roman law) Restitutio in integrum -- South Africa Remedies (Law) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3703 , http://hdl.handle.net/10962/d1004752
- Description: This study is of two remedies that are available in South African law: orders of restitutio in integrum, and specific performance. The study demonstrates that, by treating these remedies as legal topics in their own right, a greater understanding emerges of their inherent characteristics, the role that they play in the law, and of the particular circumstances in which these remedies are available. An order of restitutio in integrum performs an important and unique function in South African law. The fundamental realisation is that it is a remedy in terms of which the courts exercise an extraordinary and discretionary power, and nullify ab initio legal transactions, or the legal consequences of events, which were previously perfectly valid and enforceable at law. Because of the extraordinary nature of this remedy, the circumstances in which it is available are limited by the requirement that iusta causa must exist to justify nullification. Further, before the remedy is available, the person seeking relief must have suffered loss or prejudice as a result of the event complained of. Finally, a mutual restoration of benefits received by the persons involved is required. The nature and effect of orders of restitutio in integrum, and the essential elements which determine the availability of the remedy, enable it to be distinguished from, and contrasted with, other remedies in South African law. An order of specific performance is available in South African law, at the option of a plaintiff, to enforce the actual performance of contractual undertakings. The remedy is appropriate to enforce positive undertakings, as well as acts of restraint. For the remedy to be available, it is firstly necessary that a contractual obligation be proved to exist. Secondly, performance of that obligation must be due. Thirdly, the performance sought must not in fact have already been rendered. These elements determine the availability of the remedy in particular factual circumstances, such as in cases involving pre-emptive rights. The nature and characteristics of the remedy are determined by principles of South African, and not English law. The remedy is available as of right in South African law, but subject to a discretionary power of a court to refuse to order specific performance. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
A critical investigation of the semantic and morphological aspects of terminological incompetence (with special reference to the English-speaking student of Physical Science and History in the Cape Education Department high school)
- Authors: Venter, Malcolm Gordon
- Date: 1984
- Subjects: English language -- Semantics English language -- Morphology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2369 , http://hdl.handle.net/10962/d1003810
- Description: From Background to the thesis: It has been said that 'educational failure is language failure'. It can be argued here that there are many other factors which could cause educational failure and that language failure does not necessarily result in lack of academic success. However, it is no doubt true that the schoolchild who does not attain a certain type of language competence will be handicapped as regards academic performance. The underlying reason for this is the fact that our educational system is heavily reliant on language - and espacially the written language - as a medium of learning as opposed to the 'direct learning' experiences advocated by certain educationists today such as Ivan Illich in America and John Holt in Britain. Language is the basis both of learning and of communicating what has been learnt. From the moment the child steps into his first period class in the morning till he leaves the last five hours later the child is involved in what is primarily a verbal experience.
- Full Text:
- Authors: Venter, Malcolm Gordon
- Date: 1984
- Subjects: English language -- Semantics English language -- Morphology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2369 , http://hdl.handle.net/10962/d1003810
- Description: From Background to the thesis: It has been said that 'educational failure is language failure'. It can be argued here that there are many other factors which could cause educational failure and that language failure does not necessarily result in lack of academic success. However, it is no doubt true that the schoolchild who does not attain a certain type of language competence will be handicapped as regards academic performance. The underlying reason for this is the fact that our educational system is heavily reliant on language - and espacially the written language - as a medium of learning as opposed to the 'direct learning' experiences advocated by certain educationists today such as Ivan Illich in America and John Holt in Britain. Language is the basis both of learning and of communicating what has been learnt. From the moment the child steps into his first period class in the morning till he leaves the last five hours later the child is involved in what is primarily a verbal experience.
- Full Text:
Oblique incidence investigations of the ionosphere over the Southern Ocean
- Authors: Rash, Jonathan Paul Stuart
- Date: 1979
- Subjects: Ionosphere Ionosphere -- Antartctic Ocean
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5438 , http://hdl.handle.net/10962/d1001991
- Description: The region of the South Atlantic and Southern Oceans ... is of considerable interest in ionospheric and aeronomic research owing to the presence of several 'anomalies'. The most notable of these is the South Atlantic (or Brazilian) Anomaly associated with the global minimum of magnetic field intensity off the coast of Brazil (Introduction, p. 1)
- Full Text:
- Authors: Rash, Jonathan Paul Stuart
- Date: 1979
- Subjects: Ionosphere Ionosphere -- Antartctic Ocean
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5438 , http://hdl.handle.net/10962/d1001991
- Description: The region of the South Atlantic and Southern Oceans ... is of considerable interest in ionospheric and aeronomic research owing to the presence of several 'anomalies'. The most notable of these is the South Atlantic (or Brazilian) Anomaly associated with the global minimum of magnetic field intensity off the coast of Brazil (Introduction, p. 1)
- Full Text:
Analysis of the human HSP70-HSP90 organising protein (HOP) gene - characterisation of the promoter and identification of a novel isoform
- Authors: Mattison, Stacey
- Date: 2018
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62821 , vital:28296
- Description: Expected release date-April 2020
- Full Text:
- Authors: Mattison, Stacey
- Date: 2018
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62821 , vital:28296
- Description: Expected release date-April 2020
- Full Text:
Afro-communitarianism and the nature of reconciliation
- Authors: Oelofsen, Rianna
- Date: 2013
- Subjects: Ubuntu (Philosophy) Reconciliation -- South Africa Communitarianism -- Africa Philosophy, African
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2736 , http://hdl.handle.net/10962/d1006809
- Description: In this dissertation I sketch a conception of personhood as understood from within an Afrocommunitarian worldview, and argue that this understanding of personhood has implications for understanding the concept of reconciliation. Understanding ‘being human’ as a collective, communal enterprise has implications for how responsibility, justice, forgiveness and humanization (all cognate concepts of reconciliation) are conceptualized. In line with this understanding of reconciliation and its cognate concepts, I argue that the humanization of self and other (according to the Afrocommunitarian understanding of personhood) is required for addressing the ‘inferiority’ and concurrent ‘superiority’ racial complexes as diagnosed by Franz Fanon and Steve Biko. These complexes reach deeply within individual and collective psyches and political identities, and I argue that political solutions to protracted conflict (in South Africa and other racially charged contexts) which do not address these deeply entrenched pathologies will be inadequate according to an Afrocommunitarian framework.
- Full Text:
- Authors: Oelofsen, Rianna
- Date: 2013
- Subjects: Ubuntu (Philosophy) Reconciliation -- South Africa Communitarianism -- Africa Philosophy, African
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2736 , http://hdl.handle.net/10962/d1006809
- Description: In this dissertation I sketch a conception of personhood as understood from within an Afrocommunitarian worldview, and argue that this understanding of personhood has implications for understanding the concept of reconciliation. Understanding ‘being human’ as a collective, communal enterprise has implications for how responsibility, justice, forgiveness and humanization (all cognate concepts of reconciliation) are conceptualized. In line with this understanding of reconciliation and its cognate concepts, I argue that the humanization of self and other (according to the Afrocommunitarian understanding of personhood) is required for addressing the ‘inferiority’ and concurrent ‘superiority’ racial complexes as diagnosed by Franz Fanon and Steve Biko. These complexes reach deeply within individual and collective psyches and political identities, and I argue that political solutions to protracted conflict (in South Africa and other racially charged contexts) which do not address these deeply entrenched pathologies will be inadequate according to an Afrocommunitarian framework.
- Full Text:
Some problems of dialect lexicography with particular reference to the preparation of a draft of an illustrative, experientially categorised Dictionary of South African English
- Authors: Branford, Jean
- Date: 1976
- Subjects: English language -- Provincialisms -- South Africa -- Dictionaries English language -- South Africa English language -- Lexicography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3626 , http://hdl.handle.net/10962/d1009689
- Description: This dissertation consists in essence of an experiment and a commentary upon it. The text which constitutes Part II is a lexicographical experiment incorporating some features and treatments not usual in lexicography, and Part I consists of a discussion of the problems encountered, principles applied and procedures followed. Neither the matter nor the manner of the experiment, however, lends itself in the present state of our knowledge to the fully impersonal objectivity that is often claimed for the experiments in the physical sciences. At the same time every effort has been made to establish an unbiased record of the data and to maintain a certain methodological consistency. The main experimental feature of Part II is that it is an attempt to combine an orthodox, alphabetical dictionary with an experiential categorisation of the vocabulary, without repeating the entire data for each type of treatment. This has been done by means of a series of numbered, classified word-lists with a limited subject index as a guide to their use. The entries themselves, instead of being repeated in the order of their classification, are numbered according to the category or categories to which the word defined belongs. It can then, by means of its number(s), be found in its own lexical or experiential set (or sets) in the categorised section. This part of the work might be better described as lexicology rather than lexicography but does, I think, prove itself to be a useful adjunct to the A - Z lexicon proper. Apart from the detailed categorisation system the text contains three features not normally included in dictionaries of small compass: illustrative quotations, etymologies and a number of tentative parallels between South African and other varieties of English by means of cross-references to items of similar or related meaning or form in the English of Australia, Canada, the U.S.A., Hong Kong, Anglo-India and other 'overseas' English speech communities. Introduction, p. 1.
- Full Text:
- Authors: Branford, Jean
- Date: 1976
- Subjects: English language -- Provincialisms -- South Africa -- Dictionaries English language -- South Africa English language -- Lexicography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3626 , http://hdl.handle.net/10962/d1009689
- Description: This dissertation consists in essence of an experiment and a commentary upon it. The text which constitutes Part II is a lexicographical experiment incorporating some features and treatments not usual in lexicography, and Part I consists of a discussion of the problems encountered, principles applied and procedures followed. Neither the matter nor the manner of the experiment, however, lends itself in the present state of our knowledge to the fully impersonal objectivity that is often claimed for the experiments in the physical sciences. At the same time every effort has been made to establish an unbiased record of the data and to maintain a certain methodological consistency. The main experimental feature of Part II is that it is an attempt to combine an orthodox, alphabetical dictionary with an experiential categorisation of the vocabulary, without repeating the entire data for each type of treatment. This has been done by means of a series of numbered, classified word-lists with a limited subject index as a guide to their use. The entries themselves, instead of being repeated in the order of their classification, are numbered according to the category or categories to which the word defined belongs. It can then, by means of its number(s), be found in its own lexical or experiential set (or sets) in the categorised section. This part of the work might be better described as lexicology rather than lexicography but does, I think, prove itself to be a useful adjunct to the A - Z lexicon proper. Apart from the detailed categorisation system the text contains three features not normally included in dictionaries of small compass: illustrative quotations, etymologies and a number of tentative parallels between South African and other varieties of English by means of cross-references to items of similar or related meaning or form in the English of Australia, Canada, the U.S.A., Hong Kong, Anglo-India and other 'overseas' English speech communities. Introduction, p. 1.
- Full Text:
Apparent digestibility coefficients of feed ingredients and essential amino acid requirements of dusky kob (Argyrosomus japonicus)
- Authors: Adesola, Abidemi Adejoke
- Date: 2017
- Subjects: Amino acids in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/32140 , vital:24014
- Description: Important to the evaluation of potential feed ingredients for inclusion in fish diets should be their digestibility and amino acid requirement so that feeds can be formulated on a digestible basis rather than a gross nutrient basis. This thesis established techniques for faecal collection, the validity of digestibility markers, it determined apparent digestibility coefficients for various novel feed ingredients, and it established the optimal lysine requirement for Argyrosomus japonicus, which was used to estimate each of the essential amino acid requirements by using the ideal protein concept. There were no significant differences in dry matter apparent digestibility coefficients when faeces were collected by stripping (77.0 %), dissection (80.1 %) or settlement (83.5 %). Faecal collection by the settlement method produced the most reliable digestibility data. Apparent digestibility coefficients for dry matter, crude protein and energy calculated using acid-insoluble ash were higher (84.0 %, 93.2 % and 93.0 %, respectively) than those using chromic oxide (55.7 %, 79.1 % and 78.2 %) and titanium dioxide (58.6 %, 79.7 % and 80.5 %). The magnitude of variation in digestibility coefficients obtained using acid-insoluble ash was always lower than that obtained with the other markers. Therefore, acid-insoluble ash was preferred as a dietary marker. Using the above protocol, protein and amino acid digestibility of some animal and plant protein ingredients were evaluated in a series of experiments. The first trial compared the apparent digestibility coefficients of some animal products included as single protein source in the test diets. Apparent protein digestibility values were 84.5 %, 83.8 %, 85.8 % and 83.1 % for fishmeal-prime, fishmeal-standard, poultry meal and pork meal, respectively. Apparent digestibility coefficients for poultry meal were comparable to those of fishmeal, which indicate its potential as a substitute for fishmeal in the diets of A. japonicus. The second trial determined the apparent coefficients of plant and animal protein sources included at 30 % into a practical reference diet (70 %). Apparent protein digestibility ranged from 92.4 % in sunflower meal to 85.5 % in corn gluten meal. Soybean meal is a promising feed ingredient in A. japonicus due to the high apparent digestibility of its protein (92.0 %) and essential amino acid digestibility (mean average 91.4 %). A fundamental assumption in fish feed formulation is that the digestibility of nutrients is additive, i.e., digestibility of a nutrient in one ingredient does not interact with the digestibility of the same nutrient in another ingredient. In the third trial, additivity of feed ingredients was tested using pork meal and poultry meal. The results indicate that the apparent digestibility coefficient of animal protein ingredients could be calculated from compound diets to accurately determine protein and amino acid digestibility in A. japonicus, and possibly other carnivorous fish species. Dietary essential amino acid requirements were determined for juvenile A. japonicus in two trials. A dose-response study was conducted using crystalline lysine to determine the optimal requirement of dietary lysine for A. japonicus. Optimal dietary lysine was estimated at 31.7 g kg-¹ dry diet, corresponding to 73.5 g kg-¹ of dietary protein, based on specific growth rate and broken-line segmented regression analyses. Dietary requirements for other essential amino acids ranged from 22 g kg-¹ (histidine) to 71 g kg-¹ (leucine) crude protein. The results of the present study provided a research tool that could be used to assess and verify the conclusions of earlier dietary work on A. japonicus and in further studies to develop least cost diet formulations for this species. The study also adds to the knowledge of the nutritional requirements of A. japonicus by providing information on the digestibility of plants and animal protein ingredients. It also contributes to future dietary research for this species because this study determines, for the first time, the most suitable methods for investigating the digestibility of raw materials for A. japonicus.
- Full Text:
- Authors: Adesola, Abidemi Adejoke
- Date: 2017
- Subjects: Amino acids in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/32140 , vital:24014
- Description: Important to the evaluation of potential feed ingredients for inclusion in fish diets should be their digestibility and amino acid requirement so that feeds can be formulated on a digestible basis rather than a gross nutrient basis. This thesis established techniques for faecal collection, the validity of digestibility markers, it determined apparent digestibility coefficients for various novel feed ingredients, and it established the optimal lysine requirement for Argyrosomus japonicus, which was used to estimate each of the essential amino acid requirements by using the ideal protein concept. There were no significant differences in dry matter apparent digestibility coefficients when faeces were collected by stripping (77.0 %), dissection (80.1 %) or settlement (83.5 %). Faecal collection by the settlement method produced the most reliable digestibility data. Apparent digestibility coefficients for dry matter, crude protein and energy calculated using acid-insoluble ash were higher (84.0 %, 93.2 % and 93.0 %, respectively) than those using chromic oxide (55.7 %, 79.1 % and 78.2 %) and titanium dioxide (58.6 %, 79.7 % and 80.5 %). The magnitude of variation in digestibility coefficients obtained using acid-insoluble ash was always lower than that obtained with the other markers. Therefore, acid-insoluble ash was preferred as a dietary marker. Using the above protocol, protein and amino acid digestibility of some animal and plant protein ingredients were evaluated in a series of experiments. The first trial compared the apparent digestibility coefficients of some animal products included as single protein source in the test diets. Apparent protein digestibility values were 84.5 %, 83.8 %, 85.8 % and 83.1 % for fishmeal-prime, fishmeal-standard, poultry meal and pork meal, respectively. Apparent digestibility coefficients for poultry meal were comparable to those of fishmeal, which indicate its potential as a substitute for fishmeal in the diets of A. japonicus. The second trial determined the apparent coefficients of plant and animal protein sources included at 30 % into a practical reference diet (70 %). Apparent protein digestibility ranged from 92.4 % in sunflower meal to 85.5 % in corn gluten meal. Soybean meal is a promising feed ingredient in A. japonicus due to the high apparent digestibility of its protein (92.0 %) and essential amino acid digestibility (mean average 91.4 %). A fundamental assumption in fish feed formulation is that the digestibility of nutrients is additive, i.e., digestibility of a nutrient in one ingredient does not interact with the digestibility of the same nutrient in another ingredient. In the third trial, additivity of feed ingredients was tested using pork meal and poultry meal. The results indicate that the apparent digestibility coefficient of animal protein ingredients could be calculated from compound diets to accurately determine protein and amino acid digestibility in A. japonicus, and possibly other carnivorous fish species. Dietary essential amino acid requirements were determined for juvenile A. japonicus in two trials. A dose-response study was conducted using crystalline lysine to determine the optimal requirement of dietary lysine for A. japonicus. Optimal dietary lysine was estimated at 31.7 g kg-¹ dry diet, corresponding to 73.5 g kg-¹ of dietary protein, based on specific growth rate and broken-line segmented regression analyses. Dietary requirements for other essential amino acids ranged from 22 g kg-¹ (histidine) to 71 g kg-¹ (leucine) crude protein. The results of the present study provided a research tool that could be used to assess and verify the conclusions of earlier dietary work on A. japonicus and in further studies to develop least cost diet formulations for this species. The study also adds to the knowledge of the nutritional requirements of A. japonicus by providing information on the digestibility of plants and animal protein ingredients. It also contributes to future dietary research for this species because this study determines, for the first time, the most suitable methods for investigating the digestibility of raw materials for A. japonicus.
- Full Text:
Shifting identities: An exploration of the possibilities for a syncretic Afrikaans theatre by means of three case studies – Hex (2003), Lady Anne (2007), Ekspedisies (2008)
- Authors: Gehring, Heike
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2165 , http://hdl.handle.net/10962/d1021269
- Description: This thesis investigates the possibilities for syncretic Afrikaans language theatre within a post-1994 South African society. The research sets out to explore in what manner theatre can be language-specific, while at the same time being able to cross language contexts. This exploration is driven by the wish to develop strategies for creating Afrikaans theatre that is able to reflect on a society “united in diversity”. In this regard it is argued that for theatre to be able to both retain and cross language barriers, processes of bonding and bridging are necessary. The thesis sets out first to explain why these processes are required and then to suggest ways in which such processes can be implemented in practice. A triangular approach is used, in which conceptual and theoretical frameworks are developed to reflect on actual theatre practices. Three of my own productions are used as case studies, namely Hex (2000; 2003), Lady Anne (2007) and Ekspedisies (2008). These productions can be understood to be “boundary objects” in Henk Borgdorff’s (2012: 177) sense of the word, in that they fulfil a dual function: they are artistic productions that can also be reconstituted to serve a research purpose beyond the productions themselves. All three works were first created for public consumption before becoming cases for this thesis. Many of the strategies that were developed and tested in creating these productions are examples of ways in which bonding and bridging in Afrikaans language theatre can be understood. Chapter One of the thesis contextualises the political currents and events that necessitated the impulse towards “bonding and bridging”. In this case the political and ethical impetus behind the practical explorations has been related predominantly to the democratisation of South African society, in which a paradigm shift happened from viewing the Afrikaans language as one over many to one amongst many. Within a multilingual South Africa, concerns are raised about ways in which to create theatre in South African languages other than English (often understood to be the only possible bridging language) that are able to cross language divides. Following this introduction to language-related concerns, Chapter Two explains how the shift from apartheid to democracy made space for shifts in identity – on personal as well as institutional levels: a progression from essentialised notions of culture to the celebration of plurality. This progression is then related to theatre, with an explanation of how the post-1994 theatre landscape demanded a reimagining of the form and function of theatre. In this re-imagination the notion of a “third space” is important; something that is introduced in this chapter as an alternative to polarised identity constructions. The function of the “third space” as an in-between space and a meeting point for diverse people and entities is a strong underlying theme of this thesis and it serves as a reoccurring touchstone to the ideas put forward. Chapter Three discusses the South African arts festival culture and its contribution to the South African theatre landscape. Particular focus is placed on the Klein Karoo National Arts festival (KKNK) as a platform for the development of the Afrikaans language within a post-1994 context. What is emphasized in particular is the attempt by the KKNK festival to be linguistically and culturally exploratory and inclusive in the face of language protectionism. After the contextual background of the first three chapters, the thesis shifts to an analysis of theories related to “hybridity” and “syncretism”. In Chapter Four the argument is put forward that of the various inclusive performance and theatre models that represent a multicultural society, the most responsive forms are those that are syncretic and hybrid. Principles that can contribute to the unification and merging of diverse and polarized societal groups are described, and suggestions are made for possible ways to bring about bonding and bridging within cultural practices. Having introduced these principles, examples are offered of how these theories might be understood in other disciplines, namely, religious studies, anthropology, history and a range of cultural practices. Following this broad discussion, Chapter Five describes syncretism and hybridity more specifically in theatre by means of relevant examples. Taking the discussion further into the realm of application, Chapter Six offers an overview of “workshop theatre”, “translation” and “collage making” as strategies for putting theories of hybridity and syncretism into practice. This is followed (in Chapters Seven, Eight and Nine) by a discussion of the three productions (Hex, Lady Anne and Ekspedisies) as case studies that demonstrate how these theories can be understood in practice. Practical strategies for bridging language divides are foregrounded, such as code switching as an approach for enabling a “co-habitation” of languages; physical theatre as a means for crossing language divides; and the creation of more than one language version of a production as a tactic to accommodate shifting contexts. Following on from the discoveries made in the foregoing chapters, I conclude that theories and practices related to notions of “third space”, “hybridity” and “syncretism” are ideal for creating theatre forms (in the Afrikaans language in particular) that can truly reflect a South African society which is “united in diversity”. The thesis ends by offering suggestions for ways in which new, future identities, can be developed.
- Full Text:
- Authors: Gehring, Heike
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2165 , http://hdl.handle.net/10962/d1021269
- Description: This thesis investigates the possibilities for syncretic Afrikaans language theatre within a post-1994 South African society. The research sets out to explore in what manner theatre can be language-specific, while at the same time being able to cross language contexts. This exploration is driven by the wish to develop strategies for creating Afrikaans theatre that is able to reflect on a society “united in diversity”. In this regard it is argued that for theatre to be able to both retain and cross language barriers, processes of bonding and bridging are necessary. The thesis sets out first to explain why these processes are required and then to suggest ways in which such processes can be implemented in practice. A triangular approach is used, in which conceptual and theoretical frameworks are developed to reflect on actual theatre practices. Three of my own productions are used as case studies, namely Hex (2000; 2003), Lady Anne (2007) and Ekspedisies (2008). These productions can be understood to be “boundary objects” in Henk Borgdorff’s (2012: 177) sense of the word, in that they fulfil a dual function: they are artistic productions that can also be reconstituted to serve a research purpose beyond the productions themselves. All three works were first created for public consumption before becoming cases for this thesis. Many of the strategies that were developed and tested in creating these productions are examples of ways in which bonding and bridging in Afrikaans language theatre can be understood. Chapter One of the thesis contextualises the political currents and events that necessitated the impulse towards “bonding and bridging”. In this case the political and ethical impetus behind the practical explorations has been related predominantly to the democratisation of South African society, in which a paradigm shift happened from viewing the Afrikaans language as one over many to one amongst many. Within a multilingual South Africa, concerns are raised about ways in which to create theatre in South African languages other than English (often understood to be the only possible bridging language) that are able to cross language divides. Following this introduction to language-related concerns, Chapter Two explains how the shift from apartheid to democracy made space for shifts in identity – on personal as well as institutional levels: a progression from essentialised notions of culture to the celebration of plurality. This progression is then related to theatre, with an explanation of how the post-1994 theatre landscape demanded a reimagining of the form and function of theatre. In this re-imagination the notion of a “third space” is important; something that is introduced in this chapter as an alternative to polarised identity constructions. The function of the “third space” as an in-between space and a meeting point for diverse people and entities is a strong underlying theme of this thesis and it serves as a reoccurring touchstone to the ideas put forward. Chapter Three discusses the South African arts festival culture and its contribution to the South African theatre landscape. Particular focus is placed on the Klein Karoo National Arts festival (KKNK) as a platform for the development of the Afrikaans language within a post-1994 context. What is emphasized in particular is the attempt by the KKNK festival to be linguistically and culturally exploratory and inclusive in the face of language protectionism. After the contextual background of the first three chapters, the thesis shifts to an analysis of theories related to “hybridity” and “syncretism”. In Chapter Four the argument is put forward that of the various inclusive performance and theatre models that represent a multicultural society, the most responsive forms are those that are syncretic and hybrid. Principles that can contribute to the unification and merging of diverse and polarized societal groups are described, and suggestions are made for possible ways to bring about bonding and bridging within cultural practices. Having introduced these principles, examples are offered of how these theories might be understood in other disciplines, namely, religious studies, anthropology, history and a range of cultural practices. Following this broad discussion, Chapter Five describes syncretism and hybridity more specifically in theatre by means of relevant examples. Taking the discussion further into the realm of application, Chapter Six offers an overview of “workshop theatre”, “translation” and “collage making” as strategies for putting theories of hybridity and syncretism into practice. This is followed (in Chapters Seven, Eight and Nine) by a discussion of the three productions (Hex, Lady Anne and Ekspedisies) as case studies that demonstrate how these theories can be understood in practice. Practical strategies for bridging language divides are foregrounded, such as code switching as an approach for enabling a “co-habitation” of languages; physical theatre as a means for crossing language divides; and the creation of more than one language version of a production as a tactic to accommodate shifting contexts. Following on from the discoveries made in the foregoing chapters, I conclude that theories and practices related to notions of “third space”, “hybridity” and “syncretism” are ideal for creating theatre forms (in the Afrikaans language in particular) that can truly reflect a South African society which is “united in diversity”. The thesis ends by offering suggestions for ways in which new, future identities, can be developed.
- Full Text:
Effects of marine reserves on the biology of rocky intertidal limpets along the southern coast of South Africa
- Nakin, Motebang Dominic Vincent
- Authors: Nakin, Motebang Dominic Vincent
- Date: 2009
- Subjects: Limpets Marine parks and reserves -- South Africa Marine biology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5680 , http://hdl.handle.net/10962/d1005365
- Description: Limpets are harvested by people in South Africa, but are selected in terms of species and size. The effects of marine reserves on the biology of commonly exploited (Helcion concolor and Scutellastra longicosta) and rarely exploited species (Cellana capensis and Scutellastra granularis) were investigated on the southeast coast of South Africa at two reserve and two non-reserve sites. For each species, a 4-way nested ANOVA was used to test the effects of month, reserve, site (nested within reserve) and area (nested within site and reserve) on population density, size structure and recruitment of these limpets. The data were collected monthly over 20 months. The overall results indicated a gradient of exploitation among species, S. longicosta was the most heavily exploited species and S. granularis the least exploited species. However, there was also a gradient of exploitation between reserves and non-reserves. Xhora was the most heavily exploited site while Nqabara was less heavily exploited. Of the two reserve sites, Cwebe had more poachers than Dwesa. In most analyses, the month x area (reserve (site)) interaction was significant. However, this was largely an artifact due to comparisons of areas in different sites and significant differences between areas within sites occurred in relatively few months. Densities were greater inside reserves for all species except C. capensis. For S. longicosta and H. concolor this was expected but not for S. granularis and the result possibly reflects its opportunistic exploitation in the absence of the preferred species or indirect effects of reserves. Commonly exploited species and the rarely exploited C. capensis clearly showed greater mean and maximum sizes in reserves but there were month/site (reserve) interactions. Months with significant differences between reserves and nonreserves in both mean and maximum sizes generally occurred more often for commonly exploited than rarely exploited species, but C. capensis showed the strongest reserve effect on maximum size. Interview surveys showed that, although not normally exploited, C. capensis is sometimes mistaken for H. concolor and this suggests that large individuals are unintentionally harvested outside reserves. There were no significant reserve effects on recruitment for any species. Although Xhora had the lowest densities and limpet sizes, it showed the highest recruitment especially for S. longicosta, suggesting that larvae can be transported far from where they are released and settle in non-reserve sites regardless of adult densities. Reserve as a main factor was not significant for the rarely exploited species, but there was a significant month x reserve interaction, with non-reserves having greater GSI values than reserves in most months. Growth rates were examined using individual tagging and cohort analysis. The two techniques gave different results, with individual tagging giving higher growth estimates than cohort analysis. Except for the territorial species S. longicosta, growth was higher in non-reserves and inversely correlated with population density. Mortality estimates using the Cormack-Jolly-Seber model indicated that the rarely exploited species had significantly greater capture probabilities in reserves while no significant reserve effects were observed for the commonly exploited species. Reserve effects on survival probability were significant only for S. longicosta, with reserves being greater than nonreserves and no significant effects for any other species. Enhanced survival in reserves was attributed to the effects of human exploitation. In theory, marine protected areas show increases in densities, sizes and reproductive output of exploited species, but the present results revealed that the efficacy of reserves depends on the status of the species, not only whether it is exploited or non-exploited, but also whether it is territorial.
- Full Text:
- Authors: Nakin, Motebang Dominic Vincent
- Date: 2009
- Subjects: Limpets Marine parks and reserves -- South Africa Marine biology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5680 , http://hdl.handle.net/10962/d1005365
- Description: Limpets are harvested by people in South Africa, but are selected in terms of species and size. The effects of marine reserves on the biology of commonly exploited (Helcion concolor and Scutellastra longicosta) and rarely exploited species (Cellana capensis and Scutellastra granularis) were investigated on the southeast coast of South Africa at two reserve and two non-reserve sites. For each species, a 4-way nested ANOVA was used to test the effects of month, reserve, site (nested within reserve) and area (nested within site and reserve) on population density, size structure and recruitment of these limpets. The data were collected monthly over 20 months. The overall results indicated a gradient of exploitation among species, S. longicosta was the most heavily exploited species and S. granularis the least exploited species. However, there was also a gradient of exploitation between reserves and non-reserves. Xhora was the most heavily exploited site while Nqabara was less heavily exploited. Of the two reserve sites, Cwebe had more poachers than Dwesa. In most analyses, the month x area (reserve (site)) interaction was significant. However, this was largely an artifact due to comparisons of areas in different sites and significant differences between areas within sites occurred in relatively few months. Densities were greater inside reserves for all species except C. capensis. For S. longicosta and H. concolor this was expected but not for S. granularis and the result possibly reflects its opportunistic exploitation in the absence of the preferred species or indirect effects of reserves. Commonly exploited species and the rarely exploited C. capensis clearly showed greater mean and maximum sizes in reserves but there were month/site (reserve) interactions. Months with significant differences between reserves and nonreserves in both mean and maximum sizes generally occurred more often for commonly exploited than rarely exploited species, but C. capensis showed the strongest reserve effect on maximum size. Interview surveys showed that, although not normally exploited, C. capensis is sometimes mistaken for H. concolor and this suggests that large individuals are unintentionally harvested outside reserves. There were no significant reserve effects on recruitment for any species. Although Xhora had the lowest densities and limpet sizes, it showed the highest recruitment especially for S. longicosta, suggesting that larvae can be transported far from where they are released and settle in non-reserve sites regardless of adult densities. Reserve as a main factor was not significant for the rarely exploited species, but there was a significant month x reserve interaction, with non-reserves having greater GSI values than reserves in most months. Growth rates were examined using individual tagging and cohort analysis. The two techniques gave different results, with individual tagging giving higher growth estimates than cohort analysis. Except for the territorial species S. longicosta, growth was higher in non-reserves and inversely correlated with population density. Mortality estimates using the Cormack-Jolly-Seber model indicated that the rarely exploited species had significantly greater capture probabilities in reserves while no significant reserve effects were observed for the commonly exploited species. Reserve effects on survival probability were significant only for S. longicosta, with reserves being greater than nonreserves and no significant effects for any other species. Enhanced survival in reserves was attributed to the effects of human exploitation. In theory, marine protected areas show increases in densities, sizes and reproductive output of exploited species, but the present results revealed that the efficacy of reserves depends on the status of the species, not only whether it is exploited or non-exploited, but also whether it is territorial.
- Full Text:
The Influence of Clientelism on the Informal Sector in Zimbabwe : a Case Study of Glen View 8 Complex, Harare
- Authors: Tandire, Justin
- Date: 2021-04
- Subjects: Patron and client -- Zimbabwe -- Harare , Informal sector (Economics) -- Zimbabwe -- Harare , Informal sector (Economics) -- Political aspects -- Zimbabwe -- Harare , Patronage, Political -- Zimbabwe -- Harare , ZANU-PF (Organization : Zimbabwe) , Zimbabwe -- Social conditions , Glen View Complex 8 (Zimbabwe)
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/177986 , vital:42896 , 10.21504/10962/177986
- Description: This study focuses on the influence of clientelism in the informal sector of Zimbabwe in Glen View 8 (Complex). The study used the case of Glen view 8 (complex) in Harare Province. The study focused on political dynamics in the informal sector; livelihood strategies employed by informal sector operators; manifestation of “Big Men”, social networks in the informal sector; and different strategies employed by operators to overcome the problems of political manipulation, clientelism and patronage. It employs a qualitative research methodology to enable a nuanced comprehension of the clientelistic relationships that take place in the informal sector of Zimbabwe. Through in-depth interviews, focus group discussions, narratives and in-depth interviews with key informants, the study explored the clientelistic nature of the informal sector. The major findings of the study are that the informal sector in Zimbabwe is influenced by political patronage. It was established that patronage influences the informal sector in Zimbabwe in general and at Glen View Complex 8 in particular. Some of the operators revealed that patronage negatively affects their business as they are sometimes forced to attend political party meetings either at the complex or at ZANU-PF star rallies in town. The operators experience a plethora of problems such as lack of security, poor sanitation, stiff competition, poor infrastructure, lack of insurance and fire outbreaks. It has been revealed that most of the problems experienced at the complex are a result of the politicisation of the informal sector particularly by the ZANU-PF party. Operators at the complex have described the politicisation of the informal sector as a major drawback to their efforts of realising maximum benefits from their work. Therefore, the thrust of this thesis is premised on the de-politicisation of the informal sector as the starting point in the transformation of the activities of the operators. , Thesis (PhD) -- Faculty of Humanities, Sociology, 2021
- Full Text:
- Authors: Tandire, Justin
- Date: 2021-04
- Subjects: Patron and client -- Zimbabwe -- Harare , Informal sector (Economics) -- Zimbabwe -- Harare , Informal sector (Economics) -- Political aspects -- Zimbabwe -- Harare , Patronage, Political -- Zimbabwe -- Harare , ZANU-PF (Organization : Zimbabwe) , Zimbabwe -- Social conditions , Glen View Complex 8 (Zimbabwe)
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/177986 , vital:42896 , 10.21504/10962/177986
- Description: This study focuses on the influence of clientelism in the informal sector of Zimbabwe in Glen View 8 (Complex). The study used the case of Glen view 8 (complex) in Harare Province. The study focused on political dynamics in the informal sector; livelihood strategies employed by informal sector operators; manifestation of “Big Men”, social networks in the informal sector; and different strategies employed by operators to overcome the problems of political manipulation, clientelism and patronage. It employs a qualitative research methodology to enable a nuanced comprehension of the clientelistic relationships that take place in the informal sector of Zimbabwe. Through in-depth interviews, focus group discussions, narratives and in-depth interviews with key informants, the study explored the clientelistic nature of the informal sector. The major findings of the study are that the informal sector in Zimbabwe is influenced by political patronage. It was established that patronage influences the informal sector in Zimbabwe in general and at Glen View Complex 8 in particular. Some of the operators revealed that patronage negatively affects their business as they are sometimes forced to attend political party meetings either at the complex or at ZANU-PF star rallies in town. The operators experience a plethora of problems such as lack of security, poor sanitation, stiff competition, poor infrastructure, lack of insurance and fire outbreaks. It has been revealed that most of the problems experienced at the complex are a result of the politicisation of the informal sector particularly by the ZANU-PF party. Operators at the complex have described the politicisation of the informal sector as a major drawback to their efforts of realising maximum benefits from their work. Therefore, the thrust of this thesis is premised on the de-politicisation of the informal sector as the starting point in the transformation of the activities of the operators. , Thesis (PhD) -- Faculty of Humanities, Sociology, 2021
- Full Text:
In community in Christ: a study of theological setting of the sacraments in the New Testament
- Authors: Moore, Basil S
- Date: 1971
- Subjects: Sacraments Sacraments (Liturgy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1240 , http://hdl.handle.net/10962/d1007688
- Description: Introduction: Neville Clark has rightly warned against the attempt to approach the theology of the sacraments from a broad and general definition of a 'sacrament' from which we 'read off' a Christian doctrine of the sacraments without paying due regard to the biblical statements. Such an approach could not but obscure the essential differences between the sacraments, and the fact that they stem from historical roots. On the other hand, the specialist treatment of the sacraments which begins by making a detailed analysis of the biblical material fails to do justice to the wholeness of biblical theology and tends to treat the sacraments in isolation not only from each other but also from other aspects of Christian theology with which they are inalienably connected. Bearing in mind the difficulties inherent in both of these approaches, a fresh and more systematic approach is required.
- Full Text:
- Authors: Moore, Basil S
- Date: 1971
- Subjects: Sacraments Sacraments (Liturgy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1240 , http://hdl.handle.net/10962/d1007688
- Description: Introduction: Neville Clark has rightly warned against the attempt to approach the theology of the sacraments from a broad and general definition of a 'sacrament' from which we 'read off' a Christian doctrine of the sacraments without paying due regard to the biblical statements. Such an approach could not but obscure the essential differences between the sacraments, and the fact that they stem from historical roots. On the other hand, the specialist treatment of the sacraments which begins by making a detailed analysis of the biblical material fails to do justice to the wholeness of biblical theology and tends to treat the sacraments in isolation not only from each other but also from other aspects of Christian theology with which they are inalienably connected. Bearing in mind the difficulties inherent in both of these approaches, a fresh and more systematic approach is required.
- Full Text:
A combined modelling approach for simulating channel–wetland exchanges in large African river basins
- Authors: Makungu, Eunice J
- Date: 2020
- Subjects: Watersheds -- Africa , Watershed management -- Africa , Water resources development -- Africa -- International cooperation , Floodplain management -- Africa , Wetland ecology -- Simulation methods -- Africa , Wetland management -- Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/123288 , vital:35424
- Description: In Africa, many large and extensive wetlands are hydrologically connected to rivers, and their environmental integrity, as well as their influence on downstream flow regimes, depends on the prevailing channel–wetland exchange processes. These processes are inherently complex and vary spatially and temporally. Understanding channel–wetland exchanges is therefore, indispensable for the effective management of wetlands and the associated river basins. However, this information is limited in most of the river basins containing large wetlands in Africa. Furthermore, it is important to understand the links between upstream and downstream flow regimes and the wetland dynamics themselves, specifically where there are water resource developments that may affect these links (upstream developments), or be affected by them (downstream developments). Hydrological modelling of the entire basin using basin-scale models that include wetland components in their structures can be used to provide the information required to manage water resources in such basins. However, the level of detail of wetland processes included in many basin-scale models is typically very low and the lack of understanding of the wetland dynamics makes it difficult to quantify the relevant parameters. Detailed hydraulic models represent the channel-wetland exchanges in a much more explicit manner, but require relatively more data and time resources to establish than coarser scale hydrological models. The main objective of this study was, therefore, to investigate the use of a detailed hydraulic wetland model to provide a better understanding of channel–wetland exchanges and wetland dynamics, and to use the results to improve the parameterisation of a basin-scale model. The study focused on improving the water resource assessments modelling of three data-scarce African river basins that contain large wetlands: the floodplains of the Luangwa and Upper Zambezi River basins and the Usangu wetland in the Upper Great Ruaha River basin. The overall objective was achieved through a combined modelling approach that uses a detailed high-resolution LISFLOOD-FP hydraulic model to inform the structure and parameters of the GW Pitman monthly hydrological model. The results from the LISFLOOD-FP were used to improve the understanding of the channel–wetland exchange dynamics and to establish the wetland parameters required in the GW Pitman model. While some wetland parameters were directly quantified from the LISFLOOD-FP model results, others, which are highly empirical, were estimated by manually calibrating the GW Pitman wetland sub-model implemented in excel spreadsheets containing the LISFLOOD-FP model results. Finally, the GW Pitman model with the inclusion of the estimated wetland parameters was applied for each basin and the results compared to the available downstream observed flow data. The two models have been successfully applied in southern Africa, with the GW Pitman model being one of the most widely applied hydrological models in this region. To address the issue of data scarcity, during setup of these models, the study mainly relied on the global datasets which clearly adds to the overall uncertainty of the modelling approach. However, this is a typical situation for most of the data scarce regions of the continent. A number of challenges were, however, faced during the setup of the LISFLOOD-FP, mainly due to the limitations of the data inputs. Some of the LISFLOOD-FP data inputs include boundary conditions (upstream and downstream), channel cross-sections and wetland topography. In the absence of observed daily flows to quantify the wetland upstream boundary conditions, monthly flow volumes simulated using the GW Pitman monthly model (without including the wetland sub-model) were disaggregated into daily flows using a disaggregation sub-model. The simulated wetland inflows were evaluated using the observed flow data for downstream gauging stations that include the wetland effects. The results highlighted that it is important to understand the possible impacts of each wetland on the downstream flow regime during the evaluations of the model simulation results. Although the disaggregation approach cannot be validated due to a lack of observed data, it at least enables the simulated monthly flows to be used in the daily time step hydraulic model. One of the recommendations is that improvements are required in gauging station networks to provide more observed information for the main river and the larger tributary inflows into these large and important wetland systems. Even a limited amount of newly observed data would be helpful to reduce some of the uncertainties in the combined modelling approach. The SRTM 90 m DEM (used to represent wetland topography) was filtered to reduce local variations and noise effects (mainly vegetation bias), but there were some pixels that falsely affect the inundation results, and the recently released vegetation-corrected DEMs are suggested to improve the simulation results. Channel cross-section values derived from global datasets should be examined because some widths estimated from the Andreadis et al. (2013) dataset were found to be over-generalised and did not reflect widths measured using high-resolution Google Earth in many places. There is an indication that channel cross-sections digitised from Google Earth images can be successfully used in the model setup except in densely vegetated swamps where the values are difficult to estimate, and in such situations, field measured cross-section data are required. Small channels such as those found in the Usangu wetland could play major role in the exchange dynamics, but digitising them all was not straightforward and only key ones were included in the model setup. Clearly, this inevitably introduced uncertainties in the simulated results, and future studies should consider applying methods that simplify extractions of most of these channels from high-resolution images to improve the simulated results. The study demonstrated that the wetland and channel physical characteristics, as well as the seasonal flow magnitude, largely influence the channel–wetland exchanges and wetland dynamics. The inundation results indicated that the area–storage and storage–inflow relationships form hysteretic curves, but the shape of these curves vary with flood magnitude and wetland type. Anticlockwise hysteresis curves were observed in both relationships for the floodplains (Luangwa and Barotse), whereas there appears to be no dominant curve type for the Usangu wetlands. The lack of well-defined hysteretic relationships in the Usangu could be related to some of the difficulties (and resulting uncertainties) that were experienced in setting up the model for this wetland. The storage–inflow relationships in all wetlands have quite complex rising limbs due to multiple flow peaks during the main wet season. The largest inundation area and storage volume for the Barotse and Usangu wetlands occurred after the peak discharge of the wet season, a result that is clearly related to the degree of connectivity between the main channel and those areas of the wetlands that are furthest away from the channel. Hysteresis effects were found to increase with an increase in flood magnitudes and temporal variations in the wetland inflows. Overall, hysteresis behaviour is common in large wetlands and it is recommended that hysteresis curves should be reflected in basin-scale modelling of large river basins with substantial wetland areas. At a daily time scale, inflow–outflow relationships showed a significant peak reduction and a delayed time to peak of several weeks in the Barotse and Usangu wetlands, whereas the attenuation effects of the Luangwa floodplain are minimal. To a large extent, the LISFLOOD-FP results provided useful information to establish wetland parameters and assess the structure of Pitman wetland sub-model. The simple spreadsheet used to estimate wetland parameters did not account for the wetland water transfers from the upstream to the next section downstream (the condition that is included in the LISFLOOD-FP model) for the case when the wetlands were distributed across more than one sub-basin. It is recommended that a method that allows for the upstream wetland inflows and the channel inflows should be included in the spreadsheet. The same is true to the Pitman model structure, and a downstream transfer of water can be modelled through return flows to the channel. The structure of the wetland sub-model was modified to allow an option for the return flows to occur at any time during the simulation period to provide for types of wetlands (e.g. the Luangwa) where spills from the channel and drainage back to the channel occur simultaneously. The setup of the GW Pitman model with the inclusion of wetland parameters improved the simulation results. However, the results for the Usangu wetlands were not very satisfactory and the collection of additional field data related to exchange dynamics is recommended to achieve improvements. The impacts of the Luangwa floodplain on the flow regime of the Luangwa River are very small at the monthly time scale, whereas the Barotse floodplain system and the Usangu wetlands extensively regulate flows of the Zambezi River and the Great Ruaha River, respectively. The results highlighted the possibilities of regionalising some wetland parameters using an understanding of wetland physical characteristics and their water exchange dynamics. However, some parameters remain difficult to quantify in the absence of site-specific information about the water exchange dynamics. The overall conclusion is that the approach implemented in this study presents an important step towards the improvements of water resource assessments modelling for research and practical purposes in data-scarce river basins. This approach is not restricted to the two used models, as it can be applied using different model combinations to achieve similar study purpose.
- Full Text:
A combined modelling approach for simulating channel–wetland exchanges in large African river basins
- Authors: Makungu, Eunice J
- Date: 2020
- Subjects: Watersheds -- Africa , Watershed management -- Africa , Water resources development -- Africa -- International cooperation , Floodplain management -- Africa , Wetland ecology -- Simulation methods -- Africa , Wetland management -- Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/123288 , vital:35424
- Description: In Africa, many large and extensive wetlands are hydrologically connected to rivers, and their environmental integrity, as well as their influence on downstream flow regimes, depends on the prevailing channel–wetland exchange processes. These processes are inherently complex and vary spatially and temporally. Understanding channel–wetland exchanges is therefore, indispensable for the effective management of wetlands and the associated river basins. However, this information is limited in most of the river basins containing large wetlands in Africa. Furthermore, it is important to understand the links between upstream and downstream flow regimes and the wetland dynamics themselves, specifically where there are water resource developments that may affect these links (upstream developments), or be affected by them (downstream developments). Hydrological modelling of the entire basin using basin-scale models that include wetland components in their structures can be used to provide the information required to manage water resources in such basins. However, the level of detail of wetland processes included in many basin-scale models is typically very low and the lack of understanding of the wetland dynamics makes it difficult to quantify the relevant parameters. Detailed hydraulic models represent the channel-wetland exchanges in a much more explicit manner, but require relatively more data and time resources to establish than coarser scale hydrological models. The main objective of this study was, therefore, to investigate the use of a detailed hydraulic wetland model to provide a better understanding of channel–wetland exchanges and wetland dynamics, and to use the results to improve the parameterisation of a basin-scale model. The study focused on improving the water resource assessments modelling of three data-scarce African river basins that contain large wetlands: the floodplains of the Luangwa and Upper Zambezi River basins and the Usangu wetland in the Upper Great Ruaha River basin. The overall objective was achieved through a combined modelling approach that uses a detailed high-resolution LISFLOOD-FP hydraulic model to inform the structure and parameters of the GW Pitman monthly hydrological model. The results from the LISFLOOD-FP were used to improve the understanding of the channel–wetland exchange dynamics and to establish the wetland parameters required in the GW Pitman model. While some wetland parameters were directly quantified from the LISFLOOD-FP model results, others, which are highly empirical, were estimated by manually calibrating the GW Pitman wetland sub-model implemented in excel spreadsheets containing the LISFLOOD-FP model results. Finally, the GW Pitman model with the inclusion of the estimated wetland parameters was applied for each basin and the results compared to the available downstream observed flow data. The two models have been successfully applied in southern Africa, with the GW Pitman model being one of the most widely applied hydrological models in this region. To address the issue of data scarcity, during setup of these models, the study mainly relied on the global datasets which clearly adds to the overall uncertainty of the modelling approach. However, this is a typical situation for most of the data scarce regions of the continent. A number of challenges were, however, faced during the setup of the LISFLOOD-FP, mainly due to the limitations of the data inputs. Some of the LISFLOOD-FP data inputs include boundary conditions (upstream and downstream), channel cross-sections and wetland topography. In the absence of observed daily flows to quantify the wetland upstream boundary conditions, monthly flow volumes simulated using the GW Pitman monthly model (without including the wetland sub-model) were disaggregated into daily flows using a disaggregation sub-model. The simulated wetland inflows were evaluated using the observed flow data for downstream gauging stations that include the wetland effects. The results highlighted that it is important to understand the possible impacts of each wetland on the downstream flow regime during the evaluations of the model simulation results. Although the disaggregation approach cannot be validated due to a lack of observed data, it at least enables the simulated monthly flows to be used in the daily time step hydraulic model. One of the recommendations is that improvements are required in gauging station networks to provide more observed information for the main river and the larger tributary inflows into these large and important wetland systems. Even a limited amount of newly observed data would be helpful to reduce some of the uncertainties in the combined modelling approach. The SRTM 90 m DEM (used to represent wetland topography) was filtered to reduce local variations and noise effects (mainly vegetation bias), but there were some pixels that falsely affect the inundation results, and the recently released vegetation-corrected DEMs are suggested to improve the simulation results. Channel cross-section values derived from global datasets should be examined because some widths estimated from the Andreadis et al. (2013) dataset were found to be over-generalised and did not reflect widths measured using high-resolution Google Earth in many places. There is an indication that channel cross-sections digitised from Google Earth images can be successfully used in the model setup except in densely vegetated swamps where the values are difficult to estimate, and in such situations, field measured cross-section data are required. Small channels such as those found in the Usangu wetland could play major role in the exchange dynamics, but digitising them all was not straightforward and only key ones were included in the model setup. Clearly, this inevitably introduced uncertainties in the simulated results, and future studies should consider applying methods that simplify extractions of most of these channels from high-resolution images to improve the simulated results. The study demonstrated that the wetland and channel physical characteristics, as well as the seasonal flow magnitude, largely influence the channel–wetland exchanges and wetland dynamics. The inundation results indicated that the area–storage and storage–inflow relationships form hysteretic curves, but the shape of these curves vary with flood magnitude and wetland type. Anticlockwise hysteresis curves were observed in both relationships for the floodplains (Luangwa and Barotse), whereas there appears to be no dominant curve type for the Usangu wetlands. The lack of well-defined hysteretic relationships in the Usangu could be related to some of the difficulties (and resulting uncertainties) that were experienced in setting up the model for this wetland. The storage–inflow relationships in all wetlands have quite complex rising limbs due to multiple flow peaks during the main wet season. The largest inundation area and storage volume for the Barotse and Usangu wetlands occurred after the peak discharge of the wet season, a result that is clearly related to the degree of connectivity between the main channel and those areas of the wetlands that are furthest away from the channel. Hysteresis effects were found to increase with an increase in flood magnitudes and temporal variations in the wetland inflows. Overall, hysteresis behaviour is common in large wetlands and it is recommended that hysteresis curves should be reflected in basin-scale modelling of large river basins with substantial wetland areas. At a daily time scale, inflow–outflow relationships showed a significant peak reduction and a delayed time to peak of several weeks in the Barotse and Usangu wetlands, whereas the attenuation effects of the Luangwa floodplain are minimal. To a large extent, the LISFLOOD-FP results provided useful information to establish wetland parameters and assess the structure of Pitman wetland sub-model. The simple spreadsheet used to estimate wetland parameters did not account for the wetland water transfers from the upstream to the next section downstream (the condition that is included in the LISFLOOD-FP model) for the case when the wetlands were distributed across more than one sub-basin. It is recommended that a method that allows for the upstream wetland inflows and the channel inflows should be included in the spreadsheet. The same is true to the Pitman model structure, and a downstream transfer of water can be modelled through return flows to the channel. The structure of the wetland sub-model was modified to allow an option for the return flows to occur at any time during the simulation period to provide for types of wetlands (e.g. the Luangwa) where spills from the channel and drainage back to the channel occur simultaneously. The setup of the GW Pitman model with the inclusion of wetland parameters improved the simulation results. However, the results for the Usangu wetlands were not very satisfactory and the collection of additional field data related to exchange dynamics is recommended to achieve improvements. The impacts of the Luangwa floodplain on the flow regime of the Luangwa River are very small at the monthly time scale, whereas the Barotse floodplain system and the Usangu wetlands extensively regulate flows of the Zambezi River and the Great Ruaha River, respectively. The results highlighted the possibilities of regionalising some wetland parameters using an understanding of wetland physical characteristics and their water exchange dynamics. However, some parameters remain difficult to quantify in the absence of site-specific information about the water exchange dynamics. The overall conclusion is that the approach implemented in this study presents an important step towards the improvements of water resource assessments modelling for research and practical purposes in data-scarce river basins. This approach is not restricted to the two used models, as it can be applied using different model combinations to achieve similar study purpose.
- Full Text: