Epithermal precious metal deposits physicochemical constraints, classification characteristics and exploration guidelines
- Authors: McIver, Donald A
- Date: 1997
- Subjects: Precious metals , Geothermal resources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4941 , http://hdl.handle.net/10962/d1005553 , Precious metals , Geothermal resources
- Description: Epithermal deposits include a broad range of precious metal, base metal, mercury, and stibnite deposits. These deposits exhibit a low temperature of formation (180-280°C) at pressures of less than a few hundred bars (equivalent to depths of 1.5 - 2.0lkm). Epithermal gold deposits are the product of large-scale hydrothermal systems which mostly occur in convergent plate margin settings. Associated volcanism is largely of andesitic arc (calcalkaline to alkaline), or rhyolitic back-arc type. Porphyry Cu-Mo-Au deposits form deeper in the same systems. Genetic processes within individual deposits take place in an extremely complex manner. The resultant mineral associations, alteration styles and metal deposition patterns are even more complicated. Many attempts have been made to classify epithermal deposits based on mineralogy and alteration, host rocks, deposit form, genetic models, and standard deposits. For the explorationist, the most useful classification schemes should be brief, simple, descriptive, observationally based, and informative. Ultimately, two distinct styles of epithermal gold deposits are readily recognised: high-sulphidation, acid sulphate and low-sulphidation, adularia-sericite types. The terms high-sulphidation (HS) and low-sulphidation (IS) are based on the sulphidation state of associated sulphide minerals, which, along with characteristic hydrothermal alteration, reflect fundamental chemical differences in the epithermal environment. Highsulphidation-type deposits form in the root zones of volcanic domes from acid waters that contain residual magmatic volatiles. The low-sulphidation-type deposits form in geothermal systems where surficial waters mix with deeper, heated saline waters in a lateral flow regime, where neutral to weakly acidic, alkali chloride waters are dominant. The HSILS classification, combined with a simple description of the form of the deposit, conveys a large amount of information on mineralogy, alteration, and spatial characteristics of the mineralisation, and allows inferences to be drawn regarding likely regional controls, and the characteristics of the ore-forming fluids. The modern understanding of these environments allows us to quite effectively identify the most probable foci of mineral deposition in any given district. Current knowledge of these deposits has been derived from studies of active geothermal systems. Through comparison with alteration zones within these systems, the exploration geologist may determine the potential distribution and types of ore in a fossil geothermal system. Alteration zoning specifically can be used as a guide towards the most prospective part of the system. Epithermal gold deposits of both HS- and LS-styles are nevertheless profoundly difficult exploration targets. Successful exploration must rely on the integration of a variety of exploration techniques, guided by an understanding of the characteristics of the deposits and the processes that form them. There are no simple formulae for success in epithermal exploration: what works best must be determined for each terrain and each prospect. On a regional scale tectonic, igneous and structural settings can be used, together with assessment of the depth of erosion, to select areas for project area scale exploration. Integrated geological-geophysical interpretation derived from airborne geophysics providesa basis of targeting potential ore environments for follow-up. Geology, geochemistry and surface geophysics localise mineral concentrations within these target areas
- Full Text:
- Date Issued: 1997
- Authors: McIver, Donald A
- Date: 1997
- Subjects: Precious metals , Geothermal resources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4941 , http://hdl.handle.net/10962/d1005553 , Precious metals , Geothermal resources
- Description: Epithermal deposits include a broad range of precious metal, base metal, mercury, and stibnite deposits. These deposits exhibit a low temperature of formation (180-280°C) at pressures of less than a few hundred bars (equivalent to depths of 1.5 - 2.0lkm). Epithermal gold deposits are the product of large-scale hydrothermal systems which mostly occur in convergent plate margin settings. Associated volcanism is largely of andesitic arc (calcalkaline to alkaline), or rhyolitic back-arc type. Porphyry Cu-Mo-Au deposits form deeper in the same systems. Genetic processes within individual deposits take place in an extremely complex manner. The resultant mineral associations, alteration styles and metal deposition patterns are even more complicated. Many attempts have been made to classify epithermal deposits based on mineralogy and alteration, host rocks, deposit form, genetic models, and standard deposits. For the explorationist, the most useful classification schemes should be brief, simple, descriptive, observationally based, and informative. Ultimately, two distinct styles of epithermal gold deposits are readily recognised: high-sulphidation, acid sulphate and low-sulphidation, adularia-sericite types. The terms high-sulphidation (HS) and low-sulphidation (IS) are based on the sulphidation state of associated sulphide minerals, which, along with characteristic hydrothermal alteration, reflect fundamental chemical differences in the epithermal environment. Highsulphidation-type deposits form in the root zones of volcanic domes from acid waters that contain residual magmatic volatiles. The low-sulphidation-type deposits form in geothermal systems where surficial waters mix with deeper, heated saline waters in a lateral flow regime, where neutral to weakly acidic, alkali chloride waters are dominant. The HSILS classification, combined with a simple description of the form of the deposit, conveys a large amount of information on mineralogy, alteration, and spatial characteristics of the mineralisation, and allows inferences to be drawn regarding likely regional controls, and the characteristics of the ore-forming fluids. The modern understanding of these environments allows us to quite effectively identify the most probable foci of mineral deposition in any given district. Current knowledge of these deposits has been derived from studies of active geothermal systems. Through comparison with alteration zones within these systems, the exploration geologist may determine the potential distribution and types of ore in a fossil geothermal system. Alteration zoning specifically can be used as a guide towards the most prospective part of the system. Epithermal gold deposits of both HS- and LS-styles are nevertheless profoundly difficult exploration targets. Successful exploration must rely on the integration of a variety of exploration techniques, guided by an understanding of the characteristics of the deposits and the processes that form them. There are no simple formulae for success in epithermal exploration: what works best must be determined for each terrain and each prospect. On a regional scale tectonic, igneous and structural settings can be used, together with assessment of the depth of erosion, to select areas for project area scale exploration. Integrated geological-geophysical interpretation derived from airborne geophysics providesa basis of targeting potential ore environments for follow-up. Geology, geochemistry and surface geophysics localise mineral concentrations within these target areas
- Full Text:
- Date Issued: 1997
Newspapers in education programmes and South African youth: a survey of the relationship between South African school-goers and newspapers in Esikhawini, Kwazulu-Natal
- Authors: McComb, Roslin Vanessa
- Date: 1997
- Subjects: Newspapers in education -- South Africa , School children -- South Africa -- KwaZulu-Natal -- esikhawini , Newspapers in education
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3465 , http://hdl.handle.net/10962/d1002920 , Newspapers in education -- South Africa , School children -- South Africa -- KwaZulu-Natal -- esikhawini , Newspapers in education
- Description: This study examines the relationship which scholars have with newspapers against the background of a Newspapers in Education (NIE) programme in two black South African primary schools. Considering the presence of newspapers in the class as a medium of instruction, a number of factors are found to influence the -relationship which scholars have with newspapers. These factors are: scholars' access to newspapers; the nature of lessons using the newspaper; the character of the newspaper used in NIE and the context of education at the particular schools, including the attitudes and organisational abilities of both teachers and the principal. A description and analysis of this relationship is conducted in terms of the knowledge, attitudes and behaviour which scholars had -in te1ation to newspapers. This research is qualitative, undertaken from a constructivist-interpretative approach, and is set within international and South African contexts. The findings are relevant to understanding NIE programmes' interface with scholars' educational performance and with newspaper marketing objectives, as well as to the theorisation of NIE practices.
- Full Text:
- Date Issued: 1997
- Authors: McComb, Roslin Vanessa
- Date: 1997
- Subjects: Newspapers in education -- South Africa , School children -- South Africa -- KwaZulu-Natal -- esikhawini , Newspapers in education
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3465 , http://hdl.handle.net/10962/d1002920 , Newspapers in education -- South Africa , School children -- South Africa -- KwaZulu-Natal -- esikhawini , Newspapers in education
- Description: This study examines the relationship which scholars have with newspapers against the background of a Newspapers in Education (NIE) programme in two black South African primary schools. Considering the presence of newspapers in the class as a medium of instruction, a number of factors are found to influence the -relationship which scholars have with newspapers. These factors are: scholars' access to newspapers; the nature of lessons using the newspaper; the character of the newspaper used in NIE and the context of education at the particular schools, including the attitudes and organisational abilities of both teachers and the principal. A description and analysis of this relationship is conducted in terms of the knowledge, attitudes and behaviour which scholars had -in te1ation to newspapers. This research is qualitative, undertaken from a constructivist-interpretative approach, and is set within international and South African contexts. The findings are relevant to understanding NIE programmes' interface with scholars' educational performance and with newspaper marketing objectives, as well as to the theorisation of NIE practices.
- Full Text:
- Date Issued: 1997
A new empirical model for the peak ionospheric electron density using neural networks
- Authors: McKinnell, L A
- Date: 1997
- Subjects: Ionospheric electron density Neural networks (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5478 , http://hdl.handle.net/10962/d1005264
- Description: This thesis describes the search for a temporal model for predicting the peak ionospheric electron density-(foF2). Existing models, such as the International Reference Ionosphere (IRI) and 8KYCOM, were used to predict the 12 noon foF2 value over Grahamstown (26°E, 33°8). An attempt was then made to find a model that would improve upon these results. The traditional method of linear regression was used as a first step towards a new model. It was found that this would involve a multi variable regression that is reliant on guessing the optimum variables to be used in the final equation. An extremely complicated modelling equation involving many terms would result. Neural networks (NNs) are introduced as a new technique for predicting foF2. They are also applied, for the first time, to the problem of determining the best predictors of foF2. This quantity depends upon day number, level of solar activity and level of magnetic activity. The optimum averaging lengths of the solar activity index and the magnetic activity index were determined by appling NNs, using the criterion that the best indices are those that give the lowest rms error between the measured and predicted foF2. The optimum index for solar activity was found to be a 2-month running mean value of the daily sunspot number and for magnetic activity a 2-day averaged A index was found to be optimum. In addition, it was found that the response of foF2 to magnetic activity changes is highly non-linear and seasonally dependent. Using these indices as inputs, the NN trained successfully to predict foF2 with an rms error of 0.946 MHz on the daily testing values. Comparison with the IRI showed an improvement of 40% on the rms error. It is also shown that the NN will predict the noon value of foF2 to the same level of accuracy for unseen data of the same type.
- Full Text:
- Date Issued: 1997
- Authors: McKinnell, L A
- Date: 1997
- Subjects: Ionospheric electron density Neural networks (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5478 , http://hdl.handle.net/10962/d1005264
- Description: This thesis describes the search for a temporal model for predicting the peak ionospheric electron density-(foF2). Existing models, such as the International Reference Ionosphere (IRI) and 8KYCOM, were used to predict the 12 noon foF2 value over Grahamstown (26°E, 33°8). An attempt was then made to find a model that would improve upon these results. The traditional method of linear regression was used as a first step towards a new model. It was found that this would involve a multi variable regression that is reliant on guessing the optimum variables to be used in the final equation. An extremely complicated modelling equation involving many terms would result. Neural networks (NNs) are introduced as a new technique for predicting foF2. They are also applied, for the first time, to the problem of determining the best predictors of foF2. This quantity depends upon day number, level of solar activity and level of magnetic activity. The optimum averaging lengths of the solar activity index and the magnetic activity index were determined by appling NNs, using the criterion that the best indices are those that give the lowest rms error between the measured and predicted foF2. The optimum index for solar activity was found to be a 2-month running mean value of the daily sunspot number and for magnetic activity a 2-day averaged A index was found to be optimum. In addition, it was found that the response of foF2 to magnetic activity changes is highly non-linear and seasonally dependent. Using these indices as inputs, the NN trained successfully to predict foF2 with an rms error of 0.946 MHz on the daily testing values. Comparison with the IRI showed an improvement of 40% on the rms error. It is also shown that the NN will predict the noon value of foF2 to the same level of accuracy for unseen data of the same type.
- Full Text:
- Date Issued: 1997
Responding to literature: empowering girls to speak with their own voices in a multicultural context
- Authors: Foster, Lesley
- Date: 1997
- Subjects: Reader-response criticism--South Africa Multicultural education
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1742 , http://hdl.handle.net/10962/d1003626
- Description: The purpose of this study was to investigate whether the space provided by a readerresponse transaction between girls and the text, Roll of Thunder, Hear My Cry (Taylor 1977) .. empowered pupils to tell their own stories. It also sought to identify ways in which the problems and possibilities perceived by these pupils might guide curriculum decisions in a transforming education system. In addition to engaging in reader-response activities around the text, drama and videos providing social context were integral to the programme. Related work in the subject areas of history and lifeskills was also undertaken. Data was drawn from pupils' reading journals, responses to specific passages, transcripts of small group discussions, and interviews. The study is ethnographic in nature and all the data qualitative. Theoretical insights were drawn from the felds of cultural studies, postmodern criticism, and postructural modes of cultural and social analysis inasfar as they illuminate and inform the relationship between language, knowledge and power. The research was conducted in an historically white, girls' school which adopted a nonracial admissions policy in January 1991. Despite the fact that existing traditions and values of the the school to a very large extent influence what is taught, the data suggests that pupils were becoming agents in their own learning and were taking up multiple identities both within and without the world of the school.
- Full Text:
- Date Issued: 1997
Responding to literature: empowering girls to speak with their own voices in a multicultural context
- Authors: Foster, Lesley
- Date: 1997
- Subjects: Reader-response criticism--South Africa Multicultural education
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1742 , http://hdl.handle.net/10962/d1003626
- Description: The purpose of this study was to investigate whether the space provided by a readerresponse transaction between girls and the text, Roll of Thunder, Hear My Cry (Taylor 1977) .. empowered pupils to tell their own stories. It also sought to identify ways in which the problems and possibilities perceived by these pupils might guide curriculum decisions in a transforming education system. In addition to engaging in reader-response activities around the text, drama and videos providing social context were integral to the programme. Related work in the subject areas of history and lifeskills was also undertaken. Data was drawn from pupils' reading journals, responses to specific passages, transcripts of small group discussions, and interviews. The study is ethnographic in nature and all the data qualitative. Theoretical insights were drawn from the felds of cultural studies, postmodern criticism, and postructural modes of cultural and social analysis inasfar as they illuminate and inform the relationship between language, knowledge and power. The research was conducted in an historically white, girls' school which adopted a nonracial admissions policy in January 1991. Despite the fact that existing traditions and values of the the school to a very large extent influence what is taught, the data suggests that pupils were becoming agents in their own learning and were taking up multiple identities both within and without the world of the school.
- Full Text:
- Date Issued: 1997
Belethe
- Hogsback festival participants, Composer not specified, Dargie, Dave
- Authors: Hogsback festival participants , Composer not specified , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/345998 , vital:63340 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC349b-02
- Description: Xhosa music at Hogsback festival
- Full Text: false
- Date Issued: 1997
- Authors: Hogsback festival participants , Composer not specified , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/345998 , vital:63340 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC349b-02
- Description: Xhosa music at Hogsback festival
- Full Text: false
- Date Issued: 1997
Title not specified
- Performer not specified, Composer not specified, Dargie, Dave
- Authors: Performer not specified , Composer not specified , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/343028 , vital:62962 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC343a-04
- Description: Traditional xhosa music accompanied by clapping, rattle and drum
- Full Text: false
- Date Issued: 1997
- Authors: Performer not specified , Composer not specified , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/343028 , vital:62962 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC343a-04
- Description: Traditional xhosa music accompanied by clapping, rattle and drum
- Full Text: false
- Date Issued: 1997
Somagwaza
- Performer not specified, Composer not specified, Dargie, Dave
- Authors: Performer not specified , Composer not specified , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/343055 , vital:62964 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC343a-06
- Description: Traditional xhosa music accompanied by clapping, rattle and drum
- Full Text: false
- Date Issued: 1997
- Authors: Performer not specified , Composer not specified , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/343055 , vital:62964 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC343a-06
- Description: Traditional xhosa music accompanied by clapping, rattle and drum
- Full Text: false
- Date Issued: 1997
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:
- Date Issued: 1997
- 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:
- Date Issued: 1997
Towards an understanding of Amayeza esiXhosa stores (African chemists): how they operate, and the services they offer in the Eastern Cape
- Authors: Cocks, Michelle L
- Date: 1997
- Subjects: Medical anthropology -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2096 , http://hdl.handle.net/10962/d1002659 , Medical anthropology -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Description: In medical anthropology there has been a tendency to dichotomize western biomedical . healtb services, on the one hand, and traditional health care practices on the other. Much attention has been focused on the comparison between these two approaches in the hope that they might be reconciled. The problem with this approach is twofold. In the first place, it has not always acknowledged the local, historic~1, political and economic contexts in which different approaches to health care have evolved and in the second place, health care services which belong to neither the western nor traditional healing spheres and which are driven by commercial interests have been almost completely neglected because they fall outside of the basic dichotomy. Amayeza stores have been a feature of South African towns and cities for many years. They mayor may not be run by Africans, but their clientele is almost exclusively African in this region. They deal in a bewildering variety of products and remedies, from untreated herbal and animal products to pharmaceuticals specially prepared for the African market, to Dutch and Indian Remedies. These stores both reflect transfonnations in indigenous perceptions of health care and, by virtue of the choices they offer, generate change. In this empirical study three stores in the Eastern Cape are selected for detailed study - two in King William's Town, the regional capital, and one in the small town of Peddie. The approach is holistic, emphasizing the social, political and economic context, the business histories and running of each shop, and, in particular, the perceptions and choices of a sample of the customers in each case. The success of the amayeza phenomenon derives from its eclecticism and syncretism. These stores impose neither a western nor a traditional model of health care on their clients, but offer them a range of choices that reflects the complex multicultural history of their own South African society.
- Full Text:
- Date Issued: 1997
- Authors: Cocks, Michelle L
- Date: 1997
- Subjects: Medical anthropology -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2096 , http://hdl.handle.net/10962/d1002659 , Medical anthropology -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Description: In medical anthropology there has been a tendency to dichotomize western biomedical . healtb services, on the one hand, and traditional health care practices on the other. Much attention has been focused on the comparison between these two approaches in the hope that they might be reconciled. The problem with this approach is twofold. In the first place, it has not always acknowledged the local, historic~1, political and economic contexts in which different approaches to health care have evolved and in the second place, health care services which belong to neither the western nor traditional healing spheres and which are driven by commercial interests have been almost completely neglected because they fall outside of the basic dichotomy. Amayeza stores have been a feature of South African towns and cities for many years. They mayor may not be run by Africans, but their clientele is almost exclusively African in this region. They deal in a bewildering variety of products and remedies, from untreated herbal and animal products to pharmaceuticals specially prepared for the African market, to Dutch and Indian Remedies. These stores both reflect transfonnations in indigenous perceptions of health care and, by virtue of the choices they offer, generate change. In this empirical study three stores in the Eastern Cape are selected for detailed study - two in King William's Town, the regional capital, and one in the small town of Peddie. The approach is holistic, emphasizing the social, political and economic context, the business histories and running of each shop, and, in particular, the perceptions and choices of a sample of the customers in each case. The success of the amayeza phenomenon derives from its eclecticism and syncretism. These stores impose neither a western nor a traditional model of health care on their clients, but offer them a range of choices that reflects the complex multicultural history of their own South African society.
- Full Text:
- Date Issued: 1997
The application of a landscape diversity index using remote sensing and geographical information systems to identify degradation patterns in the Great Fish River Valley, Eastern Cape Province, South Africa
- Authors: Tanser, Frank Courteney
- Date: 1997
- Subjects: Geographic information systems , Earth sciences -- Remote sensing , Environmental degradation -- South Africa -- Eastern Cape -- Great Fish River Valley , Forest degradation -- South Africa -- Eastern Cape -- Great Rish River Valley
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4814 , http://hdl.handle.net/10962/d1005488 , Geographic information systems , Earth sciences -- Remote sensing , Environmental degradation -- South Africa -- Eastern Cape -- Great Fish River Valley , Forest degradation -- South Africa -- Eastern Cape -- Great Rish River Valley
- Description: Using a range of satellite-derived indices I describe. monitor and predict vegetation conditions that exist in the Great Fish River Valley, Eastern Cape. The heterogeneous nature of the area necessitates that the mapping of vegetation classes be accomplished using a combination of a supervised approach, an unsupervised approach and the use of a Moving Standard Deviation Index (MSDI). Nine vegetation classes are identified and mapped at an accuracy of 84%. The vegetation classes are strongly related to land-use and the communal areas demonstrate a reduction in palatable species and a shift towards dominance by a single species. Nature reserves and commercial rangeland are by contrast dominated by good condition vegetation types. The Modified Soil Adjusted Vegetation Index (MSA VI) is used to map the vegetation production in the study area. The influence of soil reflectance is reduced using this index. The MSA VI proves to be a good predictor of vegetation condition in the higher rainfall areas but not in the more semi-arid regions. The MSA VI has a significant relationship to rainfall but no absolute relationship to biomass. However, a stratification approach (on the basis of vegetation type) reveals that the MSA VI exhibits relationships to biomass in vegetation types occurring in the higher rainfall areas and consisting of a large cover of shrubs. A technique based on an index which describes landscape spatial variability is presented to assist in the interpretation of landscape condition. The research outlines a method for degradation assessment which overcomes many of the problems associated with cost and repeatability. Indices that attempt to provide a correlation with net primary productivity, e.g. NDVI, do not consider changes in the quality of net primary productivity. Landscape variability represents a measure of ecosystem change in the landscape that underlies the degradation process. The hypothesis is that healthy/undisturbed/stable landscapes tend to be less variable and homogenous than their degraded heterogenous counterparts. The Moving Standard Deviation Index (MSDI) is calculated by performing a 3 x 3 moving standard deviation window across Landsat Thematic Mapper (TM) band 3. The result is a sensitive indicator of landscape condition which is not affected by moisture availability and vegetation type. The MSDI shows a significant negative relationship to NDVI confirming its relationship to condition. The cross-classification of MSDI with NDVI allows the identification of invasive woody weeds which exhibit strong photosynthetic signals and would therefore be categorised as good condition using NDVI. Other ecosystems are investigated to determine the relationship between NDVI and MSDI. Where increase in NDVI is disturbance-induced (such as the Kalahari Desert) the relationship is positive. Where high NDVI values are indicative of good condition rangeland (such as the Fish River Valley) the relationship is negative. The MSDI therefore always exhibits a significant positive relationship to degradation irrespective of the relationship of NDVI to condition in the ecosystem.
- Full Text:
- Date Issued: 1997
- Authors: Tanser, Frank Courteney
- Date: 1997
- Subjects: Geographic information systems , Earth sciences -- Remote sensing , Environmental degradation -- South Africa -- Eastern Cape -- Great Fish River Valley , Forest degradation -- South Africa -- Eastern Cape -- Great Rish River Valley
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4814 , http://hdl.handle.net/10962/d1005488 , Geographic information systems , Earth sciences -- Remote sensing , Environmental degradation -- South Africa -- Eastern Cape -- Great Fish River Valley , Forest degradation -- South Africa -- Eastern Cape -- Great Rish River Valley
- Description: Using a range of satellite-derived indices I describe. monitor and predict vegetation conditions that exist in the Great Fish River Valley, Eastern Cape. The heterogeneous nature of the area necessitates that the mapping of vegetation classes be accomplished using a combination of a supervised approach, an unsupervised approach and the use of a Moving Standard Deviation Index (MSDI). Nine vegetation classes are identified and mapped at an accuracy of 84%. The vegetation classes are strongly related to land-use and the communal areas demonstrate a reduction in palatable species and a shift towards dominance by a single species. Nature reserves and commercial rangeland are by contrast dominated by good condition vegetation types. The Modified Soil Adjusted Vegetation Index (MSA VI) is used to map the vegetation production in the study area. The influence of soil reflectance is reduced using this index. The MSA VI proves to be a good predictor of vegetation condition in the higher rainfall areas but not in the more semi-arid regions. The MSA VI has a significant relationship to rainfall but no absolute relationship to biomass. However, a stratification approach (on the basis of vegetation type) reveals that the MSA VI exhibits relationships to biomass in vegetation types occurring in the higher rainfall areas and consisting of a large cover of shrubs. A technique based on an index which describes landscape spatial variability is presented to assist in the interpretation of landscape condition. The research outlines a method for degradation assessment which overcomes many of the problems associated with cost and repeatability. Indices that attempt to provide a correlation with net primary productivity, e.g. NDVI, do not consider changes in the quality of net primary productivity. Landscape variability represents a measure of ecosystem change in the landscape that underlies the degradation process. The hypothesis is that healthy/undisturbed/stable landscapes tend to be less variable and homogenous than their degraded heterogenous counterparts. The Moving Standard Deviation Index (MSDI) is calculated by performing a 3 x 3 moving standard deviation window across Landsat Thematic Mapper (TM) band 3. The result is a sensitive indicator of landscape condition which is not affected by moisture availability and vegetation type. The MSDI shows a significant negative relationship to NDVI confirming its relationship to condition. The cross-classification of MSDI with NDVI allows the identification of invasive woody weeds which exhibit strong photosynthetic signals and would therefore be categorised as good condition using NDVI. Other ecosystems are investigated to determine the relationship between NDVI and MSDI. Where increase in NDVI is disturbance-induced (such as the Kalahari Desert) the relationship is positive. Where high NDVI values are indicative of good condition rangeland (such as the Fish River Valley) the relationship is negative. The MSDI therefore always exhibits a significant positive relationship to degradation irrespective of the relationship of NDVI to condition in the ecosystem.
- Full Text:
- Date Issued: 1997
Effects of sustained elevated CO₂ concentration on two cultivars of barley (Hordeum vulgare L.)
- Authors: Siphugu, Mashudu Victor
- Date: 1997
- Subjects: Barley Barley -- Growth Photosynthesis -- Research Plants -- Effect of carbon dioxide on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4226 , http://hdl.handle.net/10962/d1003795
- Description: The enormous burning of fossil fuel and deforestation have caused an increase in the atmospheric CO₂ concentration ([CO₂]) during the last century. This will invariably have profound direct and indirect effects on plant carbon metabolism. The majority of research on the effects of CO₂ enrichment on plants are short-term and are done on other crops, but very little have been done on barley. This project aimed to determine the effects of long-term CO₂ enrichment on photosynthesis, growth and grain yield on barley. Hordeum vulgare L. cvs Stirling and Schooner plants were grown from seeds in controlled environment chambers at ambient (350) and elevated (600) μmol molˉ¹ [CO₂]. Measurements of net assimilation rate (NAR), photosynthetic pigments content and growth parameters were started 7 days after germination (DAG) and continued until senescence. The anatomy of matured fully developed leaves was also monitored. Elevated [CO₂l resulted in an increase in NAR in the two cultivars from days 7 until 14, after which the stimulation of NAR of CO₂-enriched plants started to decrease. At the onset of senescence, NAR was almost equal in plants grown under both ambient and elevated [CO₂]. The response of assimilation as a function of internal [CO₂l (C₁) at the end of the experimental period showed a significant decrease in both the initial slope of the A/C₁ curves and the CO₂-saturated photosynthetic rates in the two cultivars. Stirling showed no significant changes in the content of chlorophyll α,chlorophyll б or in total carotenoids. However, Schooner showed a stimulation in chlorophyll α content at day 7, but decreased at day 28. Chlorophyll б and total carotenoids content were not affected by CO₂ enrichment. While total above-ground biomass was not affected by elevated [CO₂] in the two cultivars, total plant height decreased significantly after 14 days in Stirling whereas no significant change occurred in Schooner throughout the experimental period. Leaf area was not significantly affected by CO₂ enrichment in the two cultivars although the leaves in CO₂ enriched plants were slightly shorter. Anatomical studies reveal that leaf thickness was significantly increased by CO₂ enrichment in Stirling, but the increase was not significant in Schooner. Both cultivars did not show any significant effect on chloroplast morphology and ultrastructure as a consequence of elevated CO₂ exposure. No signs of starch accumulation were evident in variety Schooner, but Stirling showed some form of starch accumulation, under increased atmospheric [CO₂]. Elevated CO₂ resulted in a significant reduction by more than 50 % in the number of grain yield per plant in both Stirling and Schooner. Results from this study therefore indicate that CO₂ enrichment will not be beneficial in terms of growth and yield in this important crop.
- Full Text:
- Date Issued: 1997
- Authors: Siphugu, Mashudu Victor
- Date: 1997
- Subjects: Barley Barley -- Growth Photosynthesis -- Research Plants -- Effect of carbon dioxide on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4226 , http://hdl.handle.net/10962/d1003795
- Description: The enormous burning of fossil fuel and deforestation have caused an increase in the atmospheric CO₂ concentration ([CO₂]) during the last century. This will invariably have profound direct and indirect effects on plant carbon metabolism. The majority of research on the effects of CO₂ enrichment on plants are short-term and are done on other crops, but very little have been done on barley. This project aimed to determine the effects of long-term CO₂ enrichment on photosynthesis, growth and grain yield on barley. Hordeum vulgare L. cvs Stirling and Schooner plants were grown from seeds in controlled environment chambers at ambient (350) and elevated (600) μmol molˉ¹ [CO₂]. Measurements of net assimilation rate (NAR), photosynthetic pigments content and growth parameters were started 7 days after germination (DAG) and continued until senescence. The anatomy of matured fully developed leaves was also monitored. Elevated [CO₂l resulted in an increase in NAR in the two cultivars from days 7 until 14, after which the stimulation of NAR of CO₂-enriched plants started to decrease. At the onset of senescence, NAR was almost equal in plants grown under both ambient and elevated [CO₂]. The response of assimilation as a function of internal [CO₂l (C₁) at the end of the experimental period showed a significant decrease in both the initial slope of the A/C₁ curves and the CO₂-saturated photosynthetic rates in the two cultivars. Stirling showed no significant changes in the content of chlorophyll α,chlorophyll б or in total carotenoids. However, Schooner showed a stimulation in chlorophyll α content at day 7, but decreased at day 28. Chlorophyll б and total carotenoids content were not affected by CO₂ enrichment. While total above-ground biomass was not affected by elevated [CO₂] in the two cultivars, total plant height decreased significantly after 14 days in Stirling whereas no significant change occurred in Schooner throughout the experimental period. Leaf area was not significantly affected by CO₂ enrichment in the two cultivars although the leaves in CO₂ enriched plants were slightly shorter. Anatomical studies reveal that leaf thickness was significantly increased by CO₂ enrichment in Stirling, but the increase was not significant in Schooner. Both cultivars did not show any significant effect on chloroplast morphology and ultrastructure as a consequence of elevated CO₂ exposure. No signs of starch accumulation were evident in variety Schooner, but Stirling showed some form of starch accumulation, under increased atmospheric [CO₂]. Elevated CO₂ resulted in a significant reduction by more than 50 % in the number of grain yield per plant in both Stirling and Schooner. Results from this study therefore indicate that CO₂ enrichment will not be beneficial in terms of growth and yield in this important crop.
- Full Text:
- Date Issued: 1997
Xa ungena emzin' wam
- Group performance, Group Composition, Dargie, Dave
- Authors: Group performance , Group Composition , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/343456 , vital:63011 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC346a-01
- Description: Church music
- Full Text: false
- Date Issued: 1997
- Authors: Group performance , Group Composition , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/343456 , vital:63011 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC346a-01
- Description: Church music
- Full Text: false
- Date Issued: 1997
The use of remote sensing and Geographic Information System (GIS) techniques, to interpret savanna ecosystem patterns in the Sabi Sand Game Reserve, Mpumalanga province
- Fortescue, Alexander Kenneth John
- Authors: Fortescue, Alexander Kenneth John
- Date: 1997
- Subjects: Sabi-Sand Game Reserve (South Africa) , Savanna ecology -- South Africa -- Mpumalanga , Geographic information systems , Savanna ecology -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4857 , http://hdl.handle.net/10962/d1005533 , Sabi-Sand Game Reserve (South Africa) , Savanna ecology -- South Africa -- Mpumalanga , Geographic information systems , Savanna ecology -- Remote sensing
- Description: This thesis explores techniques which ultimately strive to optimize production systems in rangeland areas of southern Africa. By linking spatially significant, satellite derived data to practical measurements of vegetation structure, valuable insight has been derived on processes of ecosystem function, in the Sabi Sand Game Reserve. A broad ecosystem response mechanism has been established from a conventional Normalized Differentiation Vegetation Index (NDVI). By responding to increases in production, which are driven by disturbance, this index has allowed quantitative systems theory in savanna to be tested and refined. Methods of biomass and production estimation which are specifically designed to reduce the cost and time involved with the more conventional method of destructive harvesting have been tested in the savanna at the Sabi Sand Game Reserve. Results from these estimates relate well with data derived through destructive harvesting in structurally similar savanna. Moreover, by relating the above-ground woody production estimates to remere sensing indices, it was possible to demonstrate that the problem of extrapolation, universal to most biomass and production studies can be overcome. Since remote sensing encompasses an array of tools fundamental to rangeland inventory, monitoring and management, valuable spatially significant information pertaining to ecosystem structure and function has been provided for managers in the Sabi Sand Game Reserve.
- Full Text:
- Date Issued: 1997
- Authors: Fortescue, Alexander Kenneth John
- Date: 1997
- Subjects: Sabi-Sand Game Reserve (South Africa) , Savanna ecology -- South Africa -- Mpumalanga , Geographic information systems , Savanna ecology -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4857 , http://hdl.handle.net/10962/d1005533 , Sabi-Sand Game Reserve (South Africa) , Savanna ecology -- South Africa -- Mpumalanga , Geographic information systems , Savanna ecology -- Remote sensing
- Description: This thesis explores techniques which ultimately strive to optimize production systems in rangeland areas of southern Africa. By linking spatially significant, satellite derived data to practical measurements of vegetation structure, valuable insight has been derived on processes of ecosystem function, in the Sabi Sand Game Reserve. A broad ecosystem response mechanism has been established from a conventional Normalized Differentiation Vegetation Index (NDVI). By responding to increases in production, which are driven by disturbance, this index has allowed quantitative systems theory in savanna to be tested and refined. Methods of biomass and production estimation which are specifically designed to reduce the cost and time involved with the more conventional method of destructive harvesting have been tested in the savanna at the Sabi Sand Game Reserve. Results from these estimates relate well with data derived through destructive harvesting in structurally similar savanna. Moreover, by relating the above-ground woody production estimates to remere sensing indices, it was possible to demonstrate that the problem of extrapolation, universal to most biomass and production studies can be overcome. Since remote sensing encompasses an array of tools fundamental to rangeland inventory, monitoring and management, valuable spatially significant information pertaining to ecosystem structure and function has been provided for managers in the Sabi Sand Game Reserve.
- Full Text:
- Date Issued: 1997
Chemical studies of necic acid analogues
- Guthrie-Strachan, Jeffry James
- Authors: Guthrie-Strachan, Jeffry James
- Date: 1997
- Subjects: Organic acids , Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4425 , http://hdl.handle.net/10962/d1006909 , Organic acids , Chemistry, Organic
- Description: Various aldehydes have been reacted with methyl acrylate under Baylis-Hillman conditions, using DABCO as a catalyst, to afford a range of α-substituted acrylic esters containing an allylic hydroxy group. Selected Baylis-Hillman products have been brominated, hydrolysed and acetylated to afford substrates for the synthesis of necic acid analogues. The diastereo- and regioselectivity of nucleophilic attack, using sodium methylmercaptan, on the Baylis-Hillman products and selected brominated derivatives was investigated. The allylic hydroxy compounds favour conjugate addition with the generation of a new chiral centre, while the allylic bromo derivatives favour substitution (SN and SN') (S[subscript N] and S[subscript N]') with consequent loss of chirality. (E)-2-Isopropylcrotonic acid, a vital precursor in the synthesis of all stereoisomers of trachelanthic and viridifloric acid, was synthesised in an attempt to obtain the necic acid components required for total alkaloid synthesis of lycopsamine and its derivatives. This precursor and salicylic acid were then used to prepare esters of retronecine, a dihydroxy necine base obtained via extraction and consequent hydrolysis of retrorsine.
- Full Text:
- Date Issued: 1997
- Authors: Guthrie-Strachan, Jeffry James
- Date: 1997
- Subjects: Organic acids , Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4425 , http://hdl.handle.net/10962/d1006909 , Organic acids , Chemistry, Organic
- Description: Various aldehydes have been reacted with methyl acrylate under Baylis-Hillman conditions, using DABCO as a catalyst, to afford a range of α-substituted acrylic esters containing an allylic hydroxy group. Selected Baylis-Hillman products have been brominated, hydrolysed and acetylated to afford substrates for the synthesis of necic acid analogues. The diastereo- and regioselectivity of nucleophilic attack, using sodium methylmercaptan, on the Baylis-Hillman products and selected brominated derivatives was investigated. The allylic hydroxy compounds favour conjugate addition with the generation of a new chiral centre, while the allylic bromo derivatives favour substitution (SN and SN') (S[subscript N] and S[subscript N]') with consequent loss of chirality. (E)-2-Isopropylcrotonic acid, a vital precursor in the synthesis of all stereoisomers of trachelanthic and viridifloric acid, was synthesised in an attempt to obtain the necic acid components required for total alkaloid synthesis of lycopsamine and its derivatives. This precursor and salicylic acid were then used to prepare esters of retronecine, a dihydroxy necine base obtained via extraction and consequent hydrolysis of retrorsine.
- Full Text:
- Date Issued: 1997
Solid state thermal decomposition of amide complexes of nickel(II) chloride
- Nelwamondo, Aubrey Ndifelani
- Authors: Nelwamondo, Aubrey Ndifelani
- Date: 1997
- Subjects: Decomposition (Chemistry) Materials -- Thermal properties Amides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4345 , http://hdl.handle.net/10962/d1005008
- Description: The thermal decompositions of a series of amide complexes of nickel(II) chloride have been studied. Thermochemical, kinetic, structure and solid-state stability correlations have been investigated. Complexes containing homologous amide ligands (L) of the form NiLCℓ₂, Ni₃L₂Cℓ₆, Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ (where M = Ni(II), Co(II) or Cu(II)) have been prepared. Chemical analysis, spectral and thermogravimetric measurements were used to characterize the complexes and their decomposition stoichiometries. Three sets of reactions were identified as yielding stable products in a single step: (i) NiLCℓ₂ (s) → NiCℓ₂ (s) + L (g) (ii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + 2L (g) (iii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + L (g) Characterization of the processes in the ML₂Cℓ₂ and NiL₂Cℓ₂(2H₂0) complexes was not straightforward. Reaction enthalpies (ΔH) were determined using DSC. The orders of the reaction onset temperatures (Tc), peak temperatures (Tmax) and ΔHL values for the NiCℓ₂ system were: N-methylacetamide < acetamide < N-methylformamide, suggesting the importance of steric hindrance of the methyl-substituent groups in the amide skeleton. In the Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ systems no simple orders could be deduced. The Te and Tmax sequences obtained from analogous metal(II) chloride complexes indicated that the copper(II) complexes were the least stable. The kinetics of the loss of L from NiLCℓ₂ complexes were investigated using isothermal TG, non-isothermal TG and DSC measurements. The contracting geometry models described the course of the decompositions in the most satisfactory manner. Apparent activation energies ( Ea) were estimated from Arrhenius plots of rate coefficients from: (i) an approximate zero-order relationship, (ii) the contracting-area (R2) and contracting-volume (R3) equations, (iii) a new empirical (B2) expression, (iv) the half-life ( 1/t₀.₅) and (v) the characteristic feature of the rate-time curve ( 1/tmax/2 ). The non-dependence of Ea on the rate equation used supports the reliability of the kinetic parameters. Non-isothermal experiments were analyzed by the Coats-Redfern, the modified BorchardtDaniels and the Kissinger methods. Arrhenius parameters were in keeping with results from the isothermal kinetic measurements. The values of Ea obtained for the NiLCℓ₂ system increased with an increase in basicity of the amide ligands. No straightforward correlation was found between Ea and Te, Tmax, ΔHL or spectral properties.
- Full Text:
- Date Issued: 1997
- Authors: Nelwamondo, Aubrey Ndifelani
- Date: 1997
- Subjects: Decomposition (Chemistry) Materials -- Thermal properties Amides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4345 , http://hdl.handle.net/10962/d1005008
- Description: The thermal decompositions of a series of amide complexes of nickel(II) chloride have been studied. Thermochemical, kinetic, structure and solid-state stability correlations have been investigated. Complexes containing homologous amide ligands (L) of the form NiLCℓ₂, Ni₃L₂Cℓ₆, Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ (where M = Ni(II), Co(II) or Cu(II)) have been prepared. Chemical analysis, spectral and thermogravimetric measurements were used to characterize the complexes and their decomposition stoichiometries. Three sets of reactions were identified as yielding stable products in a single step: (i) NiLCℓ₂ (s) → NiCℓ₂ (s) + L (g) (ii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + 2L (g) (iii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + L (g) Characterization of the processes in the ML₂Cℓ₂ and NiL₂Cℓ₂(2H₂0) complexes was not straightforward. Reaction enthalpies (ΔH) were determined using DSC. The orders of the reaction onset temperatures (Tc), peak temperatures (Tmax) and ΔHL values for the NiCℓ₂ system were: N-methylacetamide < acetamide < N-methylformamide, suggesting the importance of steric hindrance of the methyl-substituent groups in the amide skeleton. In the Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ systems no simple orders could be deduced. The Te and Tmax sequences obtained from analogous metal(II) chloride complexes indicated that the copper(II) complexes were the least stable. The kinetics of the loss of L from NiLCℓ₂ complexes were investigated using isothermal TG, non-isothermal TG and DSC measurements. The contracting geometry models described the course of the decompositions in the most satisfactory manner. Apparent activation energies ( Ea) were estimated from Arrhenius plots of rate coefficients from: (i) an approximate zero-order relationship, (ii) the contracting-area (R2) and contracting-volume (R3) equations, (iii) a new empirical (B2) expression, (iv) the half-life ( 1/t₀.₅) and (v) the characteristic feature of the rate-time curve ( 1/tmax/2 ). The non-dependence of Ea on the rate equation used supports the reliability of the kinetic parameters. Non-isothermal experiments were analyzed by the Coats-Redfern, the modified BorchardtDaniels and the Kissinger methods. Arrhenius parameters were in keeping with results from the isothermal kinetic measurements. The values of Ea obtained for the NiLCℓ₂ system increased with an increase in basicity of the amide ligands. No straightforward correlation was found between Ea and Te, Tmax, ΔHL or spectral properties.
- Full Text:
- Date Issued: 1997
Title not specified
- Performer not specified, Composer not specified, Group Composition, Dargie, Dave
- Authors: Performer not specified , Composer not specified , Group Composition , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/342821 , vital:62935 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC342b-04
- Description: Xhosa music accompanied by clapping, drum and rattle
- Full Text: false
- Date Issued: 1997
- Authors: Performer not specified , Composer not specified , Group Composition , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/342821 , vital:62935 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC342b-04
- Description: Xhosa music accompanied by clapping, drum and rattle
- Full Text: false
- Date Issued: 1997
The African National Congress' foreign policy in transition: change or continuity, 1989-1994
- Machesa, Aubrey Mpho John Refiloe
- Authors: Machesa, Aubrey Mpho John Refiloe
- Date: 1997
- Subjects: African National Congress -- Foreign relations
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2797 , http://hdl.handle.net/10962/d1003007 , African National Congress -- Foreign relations
- Description: But the central focus will be to explore the foreign policy transition by reflecting the theory that even though international and regional political developments had an impact on the foreign policy transition of the ANC, the internal and domestic political struggles that had evolved during the same time-frame as both the international and regional political developments also had major contributions to the foreign policy transition of the movement. Within this context, the study will also explore the preliminary contours of a post-apartheid foreign policy as perceived by the ANC as to how the country will be reintegrated into the political and economic world order.
- Full Text:
- Date Issued: 1997
- Authors: Machesa, Aubrey Mpho John Refiloe
- Date: 1997
- Subjects: African National Congress -- Foreign relations
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2797 , http://hdl.handle.net/10962/d1003007 , African National Congress -- Foreign relations
- Description: But the central focus will be to explore the foreign policy transition by reflecting the theory that even though international and regional political developments had an impact on the foreign policy transition of the ANC, the internal and domestic political struggles that had evolved during the same time-frame as both the international and regional political developments also had major contributions to the foreign policy transition of the movement. Within this context, the study will also explore the preliminary contours of a post-apartheid foreign policy as perceived by the ANC as to how the country will be reintegrated into the political and economic world order.
- Full Text:
- Date Issued: 1997
Icamagu livumile
- Hogsback festival participants, Ntsikana, Dargie, Dave
- Authors: Hogsback festival participants , Ntsikana , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/345905 , vital:63330 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC349a-01
- Description: Xhosa music at Hogsback festival
- Full Text: false
- Date Issued: 1997
- Authors: Hogsback festival participants , Ntsikana , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/345905 , vital:63330 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC349a-01
- Description: Xhosa music at Hogsback festival
- Full Text: false
- Date Issued: 1997
Maguqela lendawo
- Performer not specified, Composer not specified, Dargie, Dave
- Authors: Performer not specified , Composer not specified , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/343005 , vital:62956 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC343a-01
- Description: Traditional xhosa music accompanied by uhadi
- Full Text: false
- Date Issued: 1997
- Authors: Performer not specified , Composer not specified , Dargie, Dave
- Date: 1997
- Subjects: Folk music , Sacred music , Field recordings , Africa, Sub-Saharan , Africa South Africa Hogsback sa
- Language: IsiXhosa
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/343005 , vital:62956 , International Library of African Music, Rhodes University, Makhanda, South Africa , Dave Dargie Field Tapes, Rhodes University, Makhanda, South Africa , DDC343a-01
- Description: Traditional xhosa music accompanied by uhadi
- Full Text: false
- Date Issued: 1997
The effect of work-hardening on the physical work capacity of manual labourers within South African industry
- Authors: Jacka, Karen-Louise
- Date: 1997
- Subjects: Human engineering , Industrial accidents -- South Africa , Industrial safety -- South Africa , Musculoskeletal system -- Wounds and injuries
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5165 , http://hdl.handle.net/10962/d1016237
- Description: South Africa is a labour-intensive industrially developing country. As a result, in excess of 200 000 workers suffer from musculoskeletal injuries in a year. Research is thus essential to develop more effective strategies in the reduction and rehabilitation of occupational musculoskeletal disorders within industry. It was the hypothesis of this study that by improving the physical work capacity of manual labourers, through participation in an occupation specific work-hardening programme, that the ergonomic stress index and therefore the occurrence of musculoskeletal injuries within industry, may be reduced. Twenty-five male Black and Coloured manual labourers volunteered to participate in this study. In addition to in situ task analyses, the subjects participated in cardiovascular and strength assessments in the laboratory, both pre- and post-participation in the ten-week work-hardening programme. The data were statistically analyzed in order to identify any significant • improvements in the workers' physical work capacity, as measured by cardiovascular, strength and perceptual responses, following the period of work-hardening. Two significant reductions were noted in measures of working heart rate together with significant improvements in grip strength and trunk strength tested at a velocity of 60°.sec·1 at the post-conditioning assessments. In conclusion, the ten-week work-hardening programme resulted in nominal improvements in all the cardiovascular measures and significant improvements in the subjects' strength performance. However, industrialists must recognise that this study dealt with only one aspect of reducing the ergonomic stress index at the workplace and realise that, in addition to this focus, it remains essential to design the task to fit the human operator.
- Full Text:
- Date Issued: 1997
- Authors: Jacka, Karen-Louise
- Date: 1997
- Subjects: Human engineering , Industrial accidents -- South Africa , Industrial safety -- South Africa , Musculoskeletal system -- Wounds and injuries
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5165 , http://hdl.handle.net/10962/d1016237
- Description: South Africa is a labour-intensive industrially developing country. As a result, in excess of 200 000 workers suffer from musculoskeletal injuries in a year. Research is thus essential to develop more effective strategies in the reduction and rehabilitation of occupational musculoskeletal disorders within industry. It was the hypothesis of this study that by improving the physical work capacity of manual labourers, through participation in an occupation specific work-hardening programme, that the ergonomic stress index and therefore the occurrence of musculoskeletal injuries within industry, may be reduced. Twenty-five male Black and Coloured manual labourers volunteered to participate in this study. In addition to in situ task analyses, the subjects participated in cardiovascular and strength assessments in the laboratory, both pre- and post-participation in the ten-week work-hardening programme. The data were statistically analyzed in order to identify any significant • improvements in the workers' physical work capacity, as measured by cardiovascular, strength and perceptual responses, following the period of work-hardening. Two significant reductions were noted in measures of working heart rate together with significant improvements in grip strength and trunk strength tested at a velocity of 60°.sec·1 at the post-conditioning assessments. In conclusion, the ten-week work-hardening programme resulted in nominal improvements in all the cardiovascular measures and significant improvements in the subjects' strength performance. However, industrialists must recognise that this study dealt with only one aspect of reducing the ergonomic stress index at the workplace and realise that, in addition to this focus, it remains essential to design the task to fit the human operator.
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- Date Issued: 1997