Tertiary treatment in integrated algal ponding systems
- Authors: Wells, Charles Digby
- Date: 2005
- Subjects: Sewage -- Purification -- Anaerobic treatment , Water -- Purification -- Biological treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4068 , http://hdl.handle.net/10962/d1006162 , Sewage -- Purification -- Anaerobic treatment , Water -- Purification -- Biological treatment
- Description: Inadequate sanitation is one of the leading causes of water pollution and consequently illness in many underdeveloped countries, including South Africa and, specifically, the Eastern Cape Province, where cholera has become endemic. As modern wastewater treatment processes are often energy intensive and expensive, they are not suitable for use in these areas. There is thus a need to develop more sustainable wastewater treatment technologies for application in smaller communities. The integrated algal ponding system (IAPS) was identified as a possible solution to this wastewater management problem and was investigated for adaptation to local conditions, at the Rhodes University Environmental Experimental Field Station in Grahamstown, South Africa. The system was monitored over a period of nine years, with various configuration adjustments of the high rate algal pond (HRAP) unit operation investigated. Under standard operating conditions, the system was able to achieve levels of nutrient and organic removal comparable with conventional wastewater treatment works. The mean nitrate level achieved in the effluent was below the 15mg.l-1 South African discharge standard, however, nitrate removal in the IAPS was found to be inconsistent. Although the system was unable to sustain chemical oxygen demand (COD) removal to below the 75mg.l-1 South African discharge standard, a removal rate of 87% was recorded, with the residual COD remaining in the form of algal biomass. Previous studies in the Eastern Cape Province have shown that few small wastewater treatment works produce effluent that meets the microbial count specification. Therefore, in addition to the collation of IAPS data from the entire nine year monitoring period, this study also investigated the use of the HRAP as an independent unit operation for disinfection of effluent from small sewage plants. It was demonstrated that the independent high rate algal pond (IHRAP) as a free standing unit operation could consistently produce water with Escherichia coli counts of 0cfu.100ml-1. The observed effect was related to a number of possible conditions prevailing in the system, including elevated pH, sunlight and dissolved oxygen. It was also found that the IHRAP greatly enhanced the nutrient removal capabilities of the conventional IAPS, making it possible to reliably and consistently maintain phosphate and ammonium levels in the final effluent to below 5mg.l-1 and 2mg.l-1 respectively (South African discharge standards are 10mg.l-1 and 3mg.l-1 in each case). The quality of the final effluent produced by the optimisation of the IAPS would allow it to be used for irrigation, thereby providing an alternative water source in water stressed areas. The system also proved to be exceptionally robust and data collected during periods of intensive and low management regimes were broadly comparable. Results of the 9 year study have demonstrated reliable performance of the IAPS and its use an appropriate, sustainable wastewater treatment option for small communities.
- Full Text:
- Date Issued: 2005
- Authors: Wells, Charles Digby
- Date: 2005
- Subjects: Sewage -- Purification -- Anaerobic treatment , Water -- Purification -- Biological treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4068 , http://hdl.handle.net/10962/d1006162 , Sewage -- Purification -- Anaerobic treatment , Water -- Purification -- Biological treatment
- Description: Inadequate sanitation is one of the leading causes of water pollution and consequently illness in many underdeveloped countries, including South Africa and, specifically, the Eastern Cape Province, where cholera has become endemic. As modern wastewater treatment processes are often energy intensive and expensive, they are not suitable for use in these areas. There is thus a need to develop more sustainable wastewater treatment technologies for application in smaller communities. The integrated algal ponding system (IAPS) was identified as a possible solution to this wastewater management problem and was investigated for adaptation to local conditions, at the Rhodes University Environmental Experimental Field Station in Grahamstown, South Africa. The system was monitored over a period of nine years, with various configuration adjustments of the high rate algal pond (HRAP) unit operation investigated. Under standard operating conditions, the system was able to achieve levels of nutrient and organic removal comparable with conventional wastewater treatment works. The mean nitrate level achieved in the effluent was below the 15mg.l-1 South African discharge standard, however, nitrate removal in the IAPS was found to be inconsistent. Although the system was unable to sustain chemical oxygen demand (COD) removal to below the 75mg.l-1 South African discharge standard, a removal rate of 87% was recorded, with the residual COD remaining in the form of algal biomass. Previous studies in the Eastern Cape Province have shown that few small wastewater treatment works produce effluent that meets the microbial count specification. Therefore, in addition to the collation of IAPS data from the entire nine year monitoring period, this study also investigated the use of the HRAP as an independent unit operation for disinfection of effluent from small sewage plants. It was demonstrated that the independent high rate algal pond (IHRAP) as a free standing unit operation could consistently produce water with Escherichia coli counts of 0cfu.100ml-1. The observed effect was related to a number of possible conditions prevailing in the system, including elevated pH, sunlight and dissolved oxygen. It was also found that the IHRAP greatly enhanced the nutrient removal capabilities of the conventional IAPS, making it possible to reliably and consistently maintain phosphate and ammonium levels in the final effluent to below 5mg.l-1 and 2mg.l-1 respectively (South African discharge standards are 10mg.l-1 and 3mg.l-1 in each case). The quality of the final effluent produced by the optimisation of the IAPS would allow it to be used for irrigation, thereby providing an alternative water source in water stressed areas. The system also proved to be exceptionally robust and data collected during periods of intensive and low management regimes were broadly comparable. Results of the 9 year study have demonstrated reliable performance of the IAPS and its use an appropriate, sustainable wastewater treatment option for small communities.
- Full Text:
- Date Issued: 2005
A revision of a section of the hearing and speech scale of the Griffiths Scales of Mental Development
- Authors: Kotras, Nicole
- Date: 2004
- Subjects: Griffiths scales of mental development , Psychological tests for children
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:11022 , http://hdl.handle.net/10948/350 , Griffiths scales of mental development , Psychological tests for children
- Description: Since the introduction of the Griffiths Scales of Mental Development (Griffiths Scales) in the United Kingdom (1950) and South Africa (1977) they have become widely used and researched, both at a national and international level. Studies completed in South Africa have demonstrated the invaluable role the Griffiths Scales have fulfilled in the assessment of South African children of all cultural and socio-economic groups. However, research has indicated a need for the revision of the scales specifically relating to social and cultural factors that influence performance. The aim of this study was two-fold , namely: (i) to revise the 20 small pictures and the large picture of the Hearing and Speech Scale of the Griffiths Scales, making them more culturally relevant for the children of our contemporary world, and especially in South Africa; and (ii) to describe the performance of South African children, between 60 and 83 months of age, utilizing the revised pictures. For the qualitative component of the study a questionnaire pertaining to the small and large “Experimental pictures” was completed by the participants. The participants consisted of the executive committee members of the ARICD in the United Kingdom. Additionally 17 “expert “ Griffith's users and “lay-experts” working in early childhood development throughout South Africa, were included. Their responses were content analyzed and incorporated into the Experimental pictures. This resulted in the development of the Revised Griffiths pictures. The quantitative component of the study utilized two sample pools. Sample 1 (n=204) and Sample 2 (n=180) were comprised of pre-school children aged between 60 and 83 months. Sample 1 was utilized for the 20 small revised pictures and the large revised SA picture, while sample 2 was utilized for the 20 small revised pictures and the large revised United Kingdom/ European/Australian picture. Furthermore, both samples, consisted of children from all cultural, socio-economic, language, and gender groups. x The major findings of the present study were as follows: 1. Referring to sample 1, only the White and Indian pre-schoolers correctly identified a mean number of small pictures above that which was proposed by Griffiths (1960). The Coloured pre-schoolers almost identified Griffiths (1960) proposed number. 2. Referring to sample 2, all excepting the Black pre-schoolers correctly identified Griffiths’ (1960) proposed mean of small pictures. 3. All children from sample 1 and sample 2 were able to identify more stimuli from the large revised pictures, than was proposed by Griffiths (1960). 4. All four cultural groups from samples 1 and 2, elicited a mean number of descriptive words below Griffiths’ (1960) proposed criteria. 5. White pre-schoolers from sample 1 elicited a mean number of descriptive sentences above Griffiths’ (1960) proposed criteria. 6. White and Coloured pre-schoolers from sample 2 elicited a mean number of descriptive sentences above Griffiths’ (1960) proposed criteria. 7. All four cultural groups from sample 1 and sample 2, elicited a mean number of personal or possessive pronouns below Griffith's (1960) proposed criteria. 8. A general trend noted for the four cultural groups of both samples, was that the percentage of children who passed successive age-appropriate items, did not decrease stepwise as would be expected from the placement of items in order of difficulty. In view of the latter finding, it is recommended that for South African children the placement of the items for the small and large pictures of the Hearing and Speech Scale should be revised in terms of their order of difficulty. It is furthermore recommended that separate norms for South African children be established for the Hearing and Speech Scale
- Full Text:
- Authors: Kotras, Nicole
- Date: 2004
- Subjects: Griffiths scales of mental development , Psychological tests for children
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:11022 , http://hdl.handle.net/10948/350 , Griffiths scales of mental development , Psychological tests for children
- Description: Since the introduction of the Griffiths Scales of Mental Development (Griffiths Scales) in the United Kingdom (1950) and South Africa (1977) they have become widely used and researched, both at a national and international level. Studies completed in South Africa have demonstrated the invaluable role the Griffiths Scales have fulfilled in the assessment of South African children of all cultural and socio-economic groups. However, research has indicated a need for the revision of the scales specifically relating to social and cultural factors that influence performance. The aim of this study was two-fold , namely: (i) to revise the 20 small pictures and the large picture of the Hearing and Speech Scale of the Griffiths Scales, making them more culturally relevant for the children of our contemporary world, and especially in South Africa; and (ii) to describe the performance of South African children, between 60 and 83 months of age, utilizing the revised pictures. For the qualitative component of the study a questionnaire pertaining to the small and large “Experimental pictures” was completed by the participants. The participants consisted of the executive committee members of the ARICD in the United Kingdom. Additionally 17 “expert “ Griffith's users and “lay-experts” working in early childhood development throughout South Africa, were included. Their responses were content analyzed and incorporated into the Experimental pictures. This resulted in the development of the Revised Griffiths pictures. The quantitative component of the study utilized two sample pools. Sample 1 (n=204) and Sample 2 (n=180) were comprised of pre-school children aged between 60 and 83 months. Sample 1 was utilized for the 20 small revised pictures and the large revised SA picture, while sample 2 was utilized for the 20 small revised pictures and the large revised United Kingdom/ European/Australian picture. Furthermore, both samples, consisted of children from all cultural, socio-economic, language, and gender groups. x The major findings of the present study were as follows: 1. Referring to sample 1, only the White and Indian pre-schoolers correctly identified a mean number of small pictures above that which was proposed by Griffiths (1960). The Coloured pre-schoolers almost identified Griffiths (1960) proposed number. 2. Referring to sample 2, all excepting the Black pre-schoolers correctly identified Griffiths’ (1960) proposed mean of small pictures. 3. All children from sample 1 and sample 2 were able to identify more stimuli from the large revised pictures, than was proposed by Griffiths (1960). 4. All four cultural groups from samples 1 and 2, elicited a mean number of descriptive words below Griffiths’ (1960) proposed criteria. 5. White pre-schoolers from sample 1 elicited a mean number of descriptive sentences above Griffiths’ (1960) proposed criteria. 6. White and Coloured pre-schoolers from sample 2 elicited a mean number of descriptive sentences above Griffiths’ (1960) proposed criteria. 7. All four cultural groups from sample 1 and sample 2, elicited a mean number of personal or possessive pronouns below Griffith's (1960) proposed criteria. 8. A general trend noted for the four cultural groups of both samples, was that the percentage of children who passed successive age-appropriate items, did not decrease stepwise as would be expected from the placement of items in order of difficulty. In view of the latter finding, it is recommended that for South African children the placement of the items for the small and large pictures of the Hearing and Speech Scale should be revised in terms of their order of difficulty. It is furthermore recommended that separate norms for South African children be established for the Hearing and Speech Scale
- Full Text:
Attitudes of isiXhosa-speaking students at the University of Fort Hare towards the use of isiXhosa as a language of learning and teaching (LOLT)
- Authors: Dalvit, Lorenzo
- Date: 2004
- Subjects: Native language and education -- South Africa -- Eastern Cape , Xhosa language -- Study and teaching (Higher) -- South Africa , English language -- Study and teaching (Higher) -- South Africa , Education, Bilingual , Language and education -- South Africa , Language policy -- South Africa , University of Fort Hare -- Students -- Attitudes
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2343 , http://hdl.handle.net/10962/d1002625 , Native language and education -- South Africa -- Eastern Cape , Xhosa language -- Study and teaching (Higher) -- South Africa , English language -- Study and teaching (Higher) -- South Africa , Education, Bilingual , Language and education -- South Africa , Language policy -- South Africa , University of Fort Hare -- Students -- Attitudes
- Description: The present work presents and discusses the results of a survey of a sample of isiXhosa-speaking students at the University of Fort Hare (Alice campus) and their attitudes towards the possible introduction of isiXhosa as a medium of instruction at this institution. More specifically, the research focuses on, among other things, the students’ attitudes towards English and isiXhosa and their opinions and beliefs about the introduction of dual-mediumship and its possible consequences. The survey methods used are a questionnaire survey as well as follow-up interviews, supplemented by on-campus observation. The results are first analysed as a whole, and then split into different categories according to a set of background variables (gender, year of study, subject studied etc). This analysis indicates that, while English is recognised as the dominant language in South Africa and, more specifically, in the domain of education, some categories of respondents acknowledge the usefulness of isiXhosa as an additional medium of instruction. This survey clearly shows that it makes little sense to present isiXhosa-speaking students with a rigid choice between the existing English-medium and a dual-medium (English and isiXhosa) policy. If dual-mediumship is ever to be implemented, respondents seem to consider the use of isiXhosa as a medium of instruction more appropriate in the first years of study, for selected subjects and in some domains within the academic context rather than others. This study is part of a growing set of surveys on the attitudes of university students towards the use of African languages in education, and can be fruitfully compared with similar research at other institutions. Moreover, the results of the present research can be used to inform future decisions regarding language policy at the University of Fort Hare.
- Full Text:
- Date Issued: 2004
- Authors: Dalvit, Lorenzo
- Date: 2004
- Subjects: Native language and education -- South Africa -- Eastern Cape , Xhosa language -- Study and teaching (Higher) -- South Africa , English language -- Study and teaching (Higher) -- South Africa , Education, Bilingual , Language and education -- South Africa , Language policy -- South Africa , University of Fort Hare -- Students -- Attitudes
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2343 , http://hdl.handle.net/10962/d1002625 , Native language and education -- South Africa -- Eastern Cape , Xhosa language -- Study and teaching (Higher) -- South Africa , English language -- Study and teaching (Higher) -- South Africa , Education, Bilingual , Language and education -- South Africa , Language policy -- South Africa , University of Fort Hare -- Students -- Attitudes
- Description: The present work presents and discusses the results of a survey of a sample of isiXhosa-speaking students at the University of Fort Hare (Alice campus) and their attitudes towards the possible introduction of isiXhosa as a medium of instruction at this institution. More specifically, the research focuses on, among other things, the students’ attitudes towards English and isiXhosa and their opinions and beliefs about the introduction of dual-mediumship and its possible consequences. The survey methods used are a questionnaire survey as well as follow-up interviews, supplemented by on-campus observation. The results are first analysed as a whole, and then split into different categories according to a set of background variables (gender, year of study, subject studied etc). This analysis indicates that, while English is recognised as the dominant language in South Africa and, more specifically, in the domain of education, some categories of respondents acknowledge the usefulness of isiXhosa as an additional medium of instruction. This survey clearly shows that it makes little sense to present isiXhosa-speaking students with a rigid choice between the existing English-medium and a dual-medium (English and isiXhosa) policy. If dual-mediumship is ever to be implemented, respondents seem to consider the use of isiXhosa as a medium of instruction more appropriate in the first years of study, for selected subjects and in some domains within the academic context rather than others. This study is part of a growing set of surveys on the attitudes of university students towards the use of African languages in education, and can be fruitfully compared with similar research at other institutions. Moreover, the results of the present research can be used to inform future decisions regarding language policy at the University of Fort Hare.
- Full Text:
- Date Issued: 2004
Distributed control applications using local area networks: a LAN based power control system at Rhodes University
- Authors: Sullivan, Anthony John
- Date: 2002
- Subjects: Embedded computer systems , Local area networks (Computer networks) , Linux
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5461 , http://hdl.handle.net/10962/d1005246 , Embedded computer systems , Local area networks (Computer networks) , Linux
- Description: This thesis describes the design and development of both the hardware and software of an embedded, distributed control system using a LAN infrastructure for communication between nodes. The primary application of this system is for power monitoring and control at Rhodes University. Both the hardware and software have been developed to provide a modular and scalable system capable of growing and adapting to meet the changing demands placed on it. The software includes a custom written Internet Protocol stack for use in the embedded environment, with a small code footprint and low processing overheads. There is also Linux-based control software, which includes a web-based device management interface and graphical output. Problems specific to the application are discussed as well as their solutions, with particular attention to the constraints of an embedded system.
- Full Text:
- Date Issued: 2002
- Authors: Sullivan, Anthony John
- Date: 2002
- Subjects: Embedded computer systems , Local area networks (Computer networks) , Linux
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5461 , http://hdl.handle.net/10962/d1005246 , Embedded computer systems , Local area networks (Computer networks) , Linux
- Description: This thesis describes the design and development of both the hardware and software of an embedded, distributed control system using a LAN infrastructure for communication between nodes. The primary application of this system is for power monitoring and control at Rhodes University. Both the hardware and software have been developed to provide a modular and scalable system capable of growing and adapting to meet the changing demands placed on it. The software includes a custom written Internet Protocol stack for use in the embedded environment, with a small code footprint and low processing overheads. There is also Linux-based control software, which includes a web-based device management interface and graphical output. Problems specific to the application are discussed as well as their solutions, with particular attention to the constraints of an embedded system.
- Full Text:
- Date Issued: 2002
A reconstruction of the history of land degradation in relation to land use change and land tenure in Peddie district, former Ciskei
- Authors: Kakembo, Vincent
- Date: 1997
- Subjects: Land use -- South Africa -- Eastern Cape , Land degradation -- South Africa -- Eastern Cape , Soil erosion -- South Africa -- Eastern Cape , Land tenure -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4847 , http://hdl.handle.net/10962/d1005523 , Land use -- South Africa -- Eastern Cape , Land degradation -- South Africa -- Eastern Cape , Soil erosion -- South Africa -- Eastern Cape , Land tenure -- South Africa -- Eastern Cape
- Description: A history of land degradation is reconstructed in a part of the dividing ridge between the Great Fish and Keiskamma rivers, in Peddie District, former Ciskei. The study entails a comparative investigation of the progressive changes in land use, vegetation and soil erosion in three tenure units, namely: former commercial farms, traditional and betterment villages. Analysis of the sequential aerial photography of the area for 1938,1954, 1965, 1975 and 1988 is employed. This is backed by groundtruthing exercises. Data thus obtained are quantified, and linkages between degradation, anthropogenic and physical factors are derived using PC ARC/INFO GIS. Differences in land tenure systems emerge as the main controlling factor to variations in land degradation. Confinement of vegetation diminution and erosion to traditional and betterment villages is observed at all dates. Scantily vegetated surfaces and riparian vegetation removal are a characteristic feature of both areas throughout the study period. 'Betterment,' introduced in the early 1960s to curb land degradation is, instead observed to exacerbate it, particularly soil erosion. Trends in land use change are characterised by the abandonment of cultivated land, which is noted to coincide with a sharp rise in population. Erosion intensification into severe forms particularly between 1965 and 1975, coincident with a period of extreme rainfall events, emerges as the most significant degradation trend. A close spatial correlation between abandoned cultivated land and intricate gullies is identified. So is the case between grazing land and severe sheet erosion. Within the grazing lands, an examination of erosion and categories of vegetated surfaces reveals that erosion occurs predominantly on the scanty vegetation category. Such erosion-vegetation interaction largely explains the non-recovery of the scanty vegetation category, even during periods of intense rainfall. Extensive channel degradation is evident along stream courses with scanty riparian vegetation. Physical factors are noted to have a significant bearing on erosion. The high prevalence of erosion on the Ecca group of rocks confirms its erosion-prone nature. Pockets of colluvium and alluvium accumulation in the steep bottomlands are identified as the sites of the most severe gully erosion. Field surveys at some of the sites indicate that a dolerite sill through the area forms a boundary of colluvium accumulation and the upslope limit to gully incision. That these sites are recognised as formerly cultivated land, portrays the interaction between physical and anthropogenic variables with regard to inducing degradation in the area.
- Full Text:
- Date Issued: 1997
- Authors: Kakembo, Vincent
- Date: 1997
- Subjects: Land use -- South Africa -- Eastern Cape , Land degradation -- South Africa -- Eastern Cape , Soil erosion -- South Africa -- Eastern Cape , Land tenure -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4847 , http://hdl.handle.net/10962/d1005523 , Land use -- South Africa -- Eastern Cape , Land degradation -- South Africa -- Eastern Cape , Soil erosion -- South Africa -- Eastern Cape , Land tenure -- South Africa -- Eastern Cape
- Description: A history of land degradation is reconstructed in a part of the dividing ridge between the Great Fish and Keiskamma rivers, in Peddie District, former Ciskei. The study entails a comparative investigation of the progressive changes in land use, vegetation and soil erosion in three tenure units, namely: former commercial farms, traditional and betterment villages. Analysis of the sequential aerial photography of the area for 1938,1954, 1965, 1975 and 1988 is employed. This is backed by groundtruthing exercises. Data thus obtained are quantified, and linkages between degradation, anthropogenic and physical factors are derived using PC ARC/INFO GIS. Differences in land tenure systems emerge as the main controlling factor to variations in land degradation. Confinement of vegetation diminution and erosion to traditional and betterment villages is observed at all dates. Scantily vegetated surfaces and riparian vegetation removal are a characteristic feature of both areas throughout the study period. 'Betterment,' introduced in the early 1960s to curb land degradation is, instead observed to exacerbate it, particularly soil erosion. Trends in land use change are characterised by the abandonment of cultivated land, which is noted to coincide with a sharp rise in population. Erosion intensification into severe forms particularly between 1965 and 1975, coincident with a period of extreme rainfall events, emerges as the most significant degradation trend. A close spatial correlation between abandoned cultivated land and intricate gullies is identified. So is the case between grazing land and severe sheet erosion. Within the grazing lands, an examination of erosion and categories of vegetated surfaces reveals that erosion occurs predominantly on the scanty vegetation category. Such erosion-vegetation interaction largely explains the non-recovery of the scanty vegetation category, even during periods of intense rainfall. Extensive channel degradation is evident along stream courses with scanty riparian vegetation. Physical factors are noted to have a significant bearing on erosion. The high prevalence of erosion on the Ecca group of rocks confirms its erosion-prone nature. Pockets of colluvium and alluvium accumulation in the steep bottomlands are identified as the sites of the most severe gully erosion. Field surveys at some of the sites indicate that a dolerite sill through the area forms a boundary of colluvium accumulation and the upslope limit to gully incision. That these sites are recognised as formerly cultivated land, portrays the interaction between physical and anthropogenic variables with regard to inducing degradation in the area.
- Full Text:
- Date Issued: 1997
L'image du peuple dans Le premier homme d'Albert Camus
- Heynderickx, Nathalie Marcel Madeleine
- Authors: Heynderickx, Nathalie Marcel Madeleine
- Date: 1996
- Subjects: Camus, Albert, 1913-1960. Premier homme
- Language: French
- Type: Thesis , Masters , MA
- Identifier: vital:3577 , http://hdl.handle.net/10962/d1002150 , Camus, Albert, 1913-1960. Premier homme
- Full Text:
- Date Issued: 1996
- Authors: Heynderickx, Nathalie Marcel Madeleine
- Date: 1996
- Subjects: Camus, Albert, 1913-1960. Premier homme
- Language: French
- Type: Thesis , Masters , MA
- Identifier: vital:3577 , http://hdl.handle.net/10962/d1002150 , Camus, Albert, 1913-1960. Premier homme
- Full Text:
- Date Issued: 1996
The conflict between adaptation and constraint : the case of the Siphonariid limpets
- Authors: Chambers, Richard Jonathan
- Date: 1995
- Subjects: Siphonaria -- Adaptation Limpets -- Adaptation Pulmonata
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5657 , http://hdl.handle.net/10962/d1005340
- Description: The reproductive strategies of marine invertebrates have been related to various aspects of both their ecology, and their phylogenetic history. It has been the purpose of this thesis to try and separate these components among Siphonaria, a group of marine pulmonates. The taxonomy of these species is revised and I conclude that nine species are valid. All species deposit benthic egg masses and development may be either direct (S. anneae, S. compressa, S. dayi, S. nigerrima, S. serrata and S. tenuicostulata) or planktonic (S. capensis, S.concinna and S. oculus). Data on distribution and life-history relating to mode of larval development is then presented for 26 species of Siphonaria worldwide. Fifteen species are direct developers, nine are planktonic developers and a further two appear to have a dual developmental capacity, retaining both the velar swimming apparatus of a planktonic developer and the crawling foot of a direct developer. Direct developing species hatch from larger egg capsules, and generally occur higher on the shore than planktonic developers. Worldwide, planktonic developers are more widespread than direct developers, and individual planktonic species may have a greater latitudinal range. In most S~honaria subgenera, mode of larval development appears to be constant, although two subgenera (Patel/opsis and Sacculosiphonaria) include both developmental types. Locally, the intertidal zonation of three sympatric species (S. capensis, S. concinna and S. serrata) does not support a model which predicts direct development on the high shore and planktonic development on the low shore. However, distributions do correspond to particular intertidal microhabitats, and while there may be no, direct relationship between mode of larval development and intertidal height, the physical structure of egg masses, and the microhabitats used for spawning appear adaptive with regards to desiccation in the intertidal. S. concinna (planktonic development) and S. serrata (direct development) occur in similar microhabitats and are likely to be under similar selection pressures. In having different modes of larval development, there appears to be more than one optimal solution in a particular selective regime. In addition, both species seem to apportion similar amounts of energy to reproduction for each spawning episode, and also annually suggesting an optimum allocation of resources to reproduction. Genetic investigations using PolyAcrylamide Gel Electrophoresis (PAGE) confirm the status of the southern African species initially described, and indicate greater genetic variability associated with planktonic developing species than direct developing species. The systematic relationships revealed by DNA fingerprinting support the current classification systems, and also have implications with regards the evolution of larval development: direct development may be the plesiomorphic condition in, and among, some Siphonaria groups. There are both phylogenetic and adaptive explanations for the distribution of reproductive mode among benthic marine invertebrates. An evolutionary question, however, is not just a matter of either adaptation or constraint, it is a combination of these. Both contribute to the distribution of developmental mode among Siphonaria.
- Full Text:
- Date Issued: 1995
- Authors: Chambers, Richard Jonathan
- Date: 1995
- Subjects: Siphonaria -- Adaptation Limpets -- Adaptation Pulmonata
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5657 , http://hdl.handle.net/10962/d1005340
- Description: The reproductive strategies of marine invertebrates have been related to various aspects of both their ecology, and their phylogenetic history. It has been the purpose of this thesis to try and separate these components among Siphonaria, a group of marine pulmonates. The taxonomy of these species is revised and I conclude that nine species are valid. All species deposit benthic egg masses and development may be either direct (S. anneae, S. compressa, S. dayi, S. nigerrima, S. serrata and S. tenuicostulata) or planktonic (S. capensis, S.concinna and S. oculus). Data on distribution and life-history relating to mode of larval development is then presented for 26 species of Siphonaria worldwide. Fifteen species are direct developers, nine are planktonic developers and a further two appear to have a dual developmental capacity, retaining both the velar swimming apparatus of a planktonic developer and the crawling foot of a direct developer. Direct developing species hatch from larger egg capsules, and generally occur higher on the shore than planktonic developers. Worldwide, planktonic developers are more widespread than direct developers, and individual planktonic species may have a greater latitudinal range. In most S~honaria subgenera, mode of larval development appears to be constant, although two subgenera (Patel/opsis and Sacculosiphonaria) include both developmental types. Locally, the intertidal zonation of three sympatric species (S. capensis, S. concinna and S. serrata) does not support a model which predicts direct development on the high shore and planktonic development on the low shore. However, distributions do correspond to particular intertidal microhabitats, and while there may be no, direct relationship between mode of larval development and intertidal height, the physical structure of egg masses, and the microhabitats used for spawning appear adaptive with regards to desiccation in the intertidal. S. concinna (planktonic development) and S. serrata (direct development) occur in similar microhabitats and are likely to be under similar selection pressures. In having different modes of larval development, there appears to be more than one optimal solution in a particular selective regime. In addition, both species seem to apportion similar amounts of energy to reproduction for each spawning episode, and also annually suggesting an optimum allocation of resources to reproduction. Genetic investigations using PolyAcrylamide Gel Electrophoresis (PAGE) confirm the status of the southern African species initially described, and indicate greater genetic variability associated with planktonic developing species than direct developing species. The systematic relationships revealed by DNA fingerprinting support the current classification systems, and also have implications with regards the evolution of larval development: direct development may be the plesiomorphic condition in, and among, some Siphonaria groups. There are both phylogenetic and adaptive explanations for the distribution of reproductive mode among benthic marine invertebrates. An evolutionary question, however, is not just a matter of either adaptation or constraint, it is a combination of these. Both contribute to the distribution of developmental mode among Siphonaria.
- Full Text:
- Date Issued: 1995
The geology and evaluation of the "A"-reef at No.3 shaft, Western Holdings Mine, Welkom goldfield
- Blamey, Nigel John Frederick
- Authors: Blamey, Nigel John Frederick
- Date: 1992
- Subjects: Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4957 , http://hdl.handle.net/10962/d1005569 , Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
- Description: The "A" -Reef occurs within the Aandenk Formation of the Central Rand Group, Witwatersrand Supergroup, in the Welkom Goldfield. It comprises the Witpan and Uitsig Reefs which are both oligomictic conglomerates, and are exploited for their gold content by Anglo American Corporation. The main Witpan channel complex is orientated in a NW-SE direction and occurs close to No.3 Shaft of Western Holdings Mine where it is currently being mined. The Witpan Reef varies in thickness from 7-220cm, with lateral facies changes controlling the thickness. Within the reef, gold is associated with degradation surfaces, carbonaceous material, increase in pebble sphericity, and channel edges. Two channel edges have yielded the best gold values on No.3 Shaft although the potential for further payable gold lies in the recognition of sieve conditions. The potential also exists for extensions of the "carbon"-bearing Uitsig channel currently being mined on President Steyn Mine. The palaeo-environment proposed for formation of the Witpan Reef is a braidplain that was partly reworked by a brief transgression. Ore evaluation using geostatistics was considered a valid technique as the dataset is sufficiently well structured. Semi-variograms in the channel and across-channel directions differ markedly. It was found that variograms of gold in cmg/t lacked sufficient structure for modelling, however, log semi-variogram modelling followed by simple log-kriging and back-transformation, proved to be the most successful method. Owing to the morphology and distribution of gold within the reef, a geologically based geostatistical valuation method is proposed. The potential for further exploration of "A" -Reef depends on a substantially higher gold price. In this event, exploration of Uitsig Reef to the southwest of the current mining area is recommended as well as a new exploration strategy for Witpan Reef.
- Full Text:
- Date Issued: 1992
- Authors: Blamey, Nigel John Frederick
- Date: 1992
- Subjects: Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4957 , http://hdl.handle.net/10962/d1005569 , Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
- Description: The "A" -Reef occurs within the Aandenk Formation of the Central Rand Group, Witwatersrand Supergroup, in the Welkom Goldfield. It comprises the Witpan and Uitsig Reefs which are both oligomictic conglomerates, and are exploited for their gold content by Anglo American Corporation. The main Witpan channel complex is orientated in a NW-SE direction and occurs close to No.3 Shaft of Western Holdings Mine where it is currently being mined. The Witpan Reef varies in thickness from 7-220cm, with lateral facies changes controlling the thickness. Within the reef, gold is associated with degradation surfaces, carbonaceous material, increase in pebble sphericity, and channel edges. Two channel edges have yielded the best gold values on No.3 Shaft although the potential for further payable gold lies in the recognition of sieve conditions. The potential also exists for extensions of the "carbon"-bearing Uitsig channel currently being mined on President Steyn Mine. The palaeo-environment proposed for formation of the Witpan Reef is a braidplain that was partly reworked by a brief transgression. Ore evaluation using geostatistics was considered a valid technique as the dataset is sufficiently well structured. Semi-variograms in the channel and across-channel directions differ markedly. It was found that variograms of gold in cmg/t lacked sufficient structure for modelling, however, log semi-variogram modelling followed by simple log-kriging and back-transformation, proved to be the most successful method. Owing to the morphology and distribution of gold within the reef, a geologically based geostatistical valuation method is proposed. The potential for further exploration of "A" -Reef depends on a substantially higher gold price. In this event, exploration of Uitsig Reef to the southwest of the current mining area is recommended as well as a new exploration strategy for Witpan Reef.
- Full Text:
- Date Issued: 1992
The sedimentology of the Zerrissene turbidite system, Damara Orogen, Namibia
- Authors: Swart, Roger
- Date: 1991
- Subjects: Sedimentology Sediments (Geology) -- Namibia Sedimentation and deposition Turbidites
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5000 , http://hdl.handle.net/10962/d1005613
- Description: The Zerrissene turbidite system of central-western Namibia is a late Proterozoic sequence which consists of dominantly siliciclastic turbidites interbedded with minor turbiditic and hemipelagic marbles. The basin in which these sediments were deposited is located at the junction of the coastal and intra-cratonic arms of the Pan-African Damara Orogen, and an understanding of the sedimentary evolution of this basin is therefore important to the understanding of the development of the orogen as a whole. One major and two minor phases of folding have deformed the sediments, but the grade of metamorphism is low and sedimentary structures are often well preserved. Further, the area lies entirely within the Namib Desert and the lack of vegetation cover results in good outcrops providing an unusual opportunity for examining a large Precambrian turbidite system. The system consists of five formations: three siliciclastic and two mixed carbonatesiliciclastic units. The floor of the system is not exposed, and the oldest sedimentary rocks which outcrop are siliciclastics of the Zebrapiits Formation. This is overlain successively by the Brandberg West Formation (dominantly calcareous), the Brak River Formation (siliciclastic), the Gemsbok River Formation (calcareous) and the Amis River Formation (siliciclastic). Nine silicilastic turbidite facies have been recognised in the basin. These are facies A₂ (disorganised onglomerates), B₁ (horizontally laminated to massive greyackes), C₂ ("classical" turbidites), Dl (sandstone-shale couplets with base cut-out Bouma sequences), D₂ (sandstone-shale couplets with less sand than shale and base cut-out Bouma sequences), E (coarse, discontinuous sandstone-shale couplets), F (slumped units), G (shale) and H (glacial dropstones). Four facies are associated with the carbonate horizons, and these carbonate facies are given the suffix c to distinguish them from similar siliciclastic facies. These are facies Ac (disorganised and graded marble breccias), facies Cc (graded carbonates), facies Gc (hemi-pelagic marbles) and facies G (pelagic shales). The basal Zebrapiits Formation is made up of relatively thin packages of thin- to thickbedded, laterally continuous facies D₁, D₂ and B₁ beds encased in thick envelopes of shale. This type of sequence is typical of a distal lobe-fringe, and requires an unconfined basin-floor on which it can develop. The overlying Brandberg West Formation consists of a basal portion of interbedded facies Cc and G, followed by a sequence dominanted by facies Gc. This sequence is interpreted as representing outer-apron carbonate turbidites, derived from multiple point sources (facies Cc), with background pelagic settling (facies G) overlain by hemi-pelagic deposits (facies Gc). A reversal back to siliciclastic turbidites followed with deposition of the Brak River Formation. This sequence comprises relatively thick packages of laterally continuous facies B₁, D₁, and D₂ beds sandwiched between facies G shales, a succession characteristic of a lobe to lobe-fringe environment with intermittent abandonment of lobes. An unconfined basin floor adjacent to a passive margin is required for the development of this type of sequence. Glacial dropstones (facies H) are found in the upper portions of this formation, and slumped beds are also present (facies F), but are uncommon. The facies F beds are only found in association with facies H and are therefore considered to be genetically related. Slumping of beds was possibly caused by an oversupply of sediment from ice-rafting which caused instability. The overlying Gemsbok River Formation has a sequence similar to the Brandberg West Formation in that the basal portion consists of interbedded facies Cc and G, which is overlain by a thick sequence of largely facies Gc beds. Minor facies Ac beds occur near the top of the overall sequence. This formation is interpreted as an outer-apron succession with the facies Ac beds representing distal inner-apron deposits, indicating progradation of the system. The youngest unit in the basin, the Amis River Formation, shows strong lateral variation from west to east. In the west the sequence comprises laterally continuous facies B₁, C₂, D₁ and D₂ with rare, discontinuous facies E beds. Facies G is relatively minor in the sequence. In the east the succession is dominated by facies D₁, D₂ and G, and this succession is interpreted as a sequence of distal turbidites which were deposited on a basin-plain. The system developed by aggradation rather than progradation as only minor cycles are developed. Geochemical and petrological features indicate that the entire siliciclastic system was derived from a granite-recycled orogen terrane. Palaeocurrent data are unreliable because of the deformation, but transport was initially from the south-west, moving later to the west and north-west. The provenance of the carbonates is uncertain as reliable palaeocurrent indicators are rare, but they could have been derived either from South America or from the extensive carbonate deposits developed on the north-western margins of the basin. The Zenissene siliciclastic turbidite system represents the distal portion of a major submarine turbidite system, the more proximal parts of which now lie west of the exposed basin, either under the Atlantic Ocean or in eastern South America. The calcareous deposits developed as an apron adjacent to a multiple point source, the position of which is at present unknown.
- Full Text:
- Date Issued: 1991
- Authors: Swart, Roger
- Date: 1991
- Subjects: Sedimentology Sediments (Geology) -- Namibia Sedimentation and deposition Turbidites
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5000 , http://hdl.handle.net/10962/d1005613
- Description: The Zerrissene turbidite system of central-western Namibia is a late Proterozoic sequence which consists of dominantly siliciclastic turbidites interbedded with minor turbiditic and hemipelagic marbles. The basin in which these sediments were deposited is located at the junction of the coastal and intra-cratonic arms of the Pan-African Damara Orogen, and an understanding of the sedimentary evolution of this basin is therefore important to the understanding of the development of the orogen as a whole. One major and two minor phases of folding have deformed the sediments, but the grade of metamorphism is low and sedimentary structures are often well preserved. Further, the area lies entirely within the Namib Desert and the lack of vegetation cover results in good outcrops providing an unusual opportunity for examining a large Precambrian turbidite system. The system consists of five formations: three siliciclastic and two mixed carbonatesiliciclastic units. The floor of the system is not exposed, and the oldest sedimentary rocks which outcrop are siliciclastics of the Zebrapiits Formation. This is overlain successively by the Brandberg West Formation (dominantly calcareous), the Brak River Formation (siliciclastic), the Gemsbok River Formation (calcareous) and the Amis River Formation (siliciclastic). Nine silicilastic turbidite facies have been recognised in the basin. These are facies A₂ (disorganised onglomerates), B₁ (horizontally laminated to massive greyackes), C₂ ("classical" turbidites), Dl (sandstone-shale couplets with base cut-out Bouma sequences), D₂ (sandstone-shale couplets with less sand than shale and base cut-out Bouma sequences), E (coarse, discontinuous sandstone-shale couplets), F (slumped units), G (shale) and H (glacial dropstones). Four facies are associated with the carbonate horizons, and these carbonate facies are given the suffix c to distinguish them from similar siliciclastic facies. These are facies Ac (disorganised and graded marble breccias), facies Cc (graded carbonates), facies Gc (hemi-pelagic marbles) and facies G (pelagic shales). The basal Zebrapiits Formation is made up of relatively thin packages of thin- to thickbedded, laterally continuous facies D₁, D₂ and B₁ beds encased in thick envelopes of shale. This type of sequence is typical of a distal lobe-fringe, and requires an unconfined basin-floor on which it can develop. The overlying Brandberg West Formation consists of a basal portion of interbedded facies Cc and G, followed by a sequence dominanted by facies Gc. This sequence is interpreted as representing outer-apron carbonate turbidites, derived from multiple point sources (facies Cc), with background pelagic settling (facies G) overlain by hemi-pelagic deposits (facies Gc). A reversal back to siliciclastic turbidites followed with deposition of the Brak River Formation. This sequence comprises relatively thick packages of laterally continuous facies B₁, D₁, and D₂ beds sandwiched between facies G shales, a succession characteristic of a lobe to lobe-fringe environment with intermittent abandonment of lobes. An unconfined basin floor adjacent to a passive margin is required for the development of this type of sequence. Glacial dropstones (facies H) are found in the upper portions of this formation, and slumped beds are also present (facies F), but are uncommon. The facies F beds are only found in association with facies H and are therefore considered to be genetically related. Slumping of beds was possibly caused by an oversupply of sediment from ice-rafting which caused instability. The overlying Gemsbok River Formation has a sequence similar to the Brandberg West Formation in that the basal portion consists of interbedded facies Cc and G, which is overlain by a thick sequence of largely facies Gc beds. Minor facies Ac beds occur near the top of the overall sequence. This formation is interpreted as an outer-apron succession with the facies Ac beds representing distal inner-apron deposits, indicating progradation of the system. The youngest unit in the basin, the Amis River Formation, shows strong lateral variation from west to east. In the west the sequence comprises laterally continuous facies B₁, C₂, D₁ and D₂ with rare, discontinuous facies E beds. Facies G is relatively minor in the sequence. In the east the succession is dominated by facies D₁, D₂ and G, and this succession is interpreted as a sequence of distal turbidites which were deposited on a basin-plain. The system developed by aggradation rather than progradation as only minor cycles are developed. Geochemical and petrological features indicate that the entire siliciclastic system was derived from a granite-recycled orogen terrane. Palaeocurrent data are unreliable because of the deformation, but transport was initially from the south-west, moving later to the west and north-west. The provenance of the carbonates is uncertain as reliable palaeocurrent indicators are rare, but they could have been derived either from South America or from the extensive carbonate deposits developed on the north-western margins of the basin. The Zenissene siliciclastic turbidite system represents the distal portion of a major submarine turbidite system, the more proximal parts of which now lie west of the exposed basin, either under the Atlantic Ocean or in eastern South America. The calcareous deposits developed as an apron adjacent to a multiple point source, the position of which is at present unknown.
- Full Text:
- Date Issued: 1991
A pilot study of commonly held misconceptions in secondary school genetics
- Authors: Moore, Aldyth Margaret
- Date: 1990
- Subjects: Genetics -- Study and teaching (Secondary)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1338 , http://hdl.handle.net/10962/d1001404
- Description: This pilot study was aimed at investigating with the aid of a two-tier multiple choice questionnaire, the misconceptions held by pupils in standards 8 and 10 as well as first year Biology students in the area of senior secondary school genetics. It was found that certain of the children's preconceived ideas were altered by tuition while others were unaffected by either age or tuition and consequently warranted the name misconceptions. Four misconceptions were identified in this study and these were seen to be at the root of the difficulties experienced in genetics. They involved plants being seen to be unable to reproduce sexually, an inability to relate meiosis to genetics, a tendency to cling to the Punnett square algorithm when solving genetics problems despite a lack of understanding of the underlying processes and a failure to see the role of chance in genetics. These misconceptions were seen to have arisen because of certain preconceived ideas which hamper the formation of a suitable conceptual framework. The adoption of suitable teaching strategies appears to be the most likely method of rectifying the problem. However, before this can be regarded as conclusive, further research into the concept development of specific aspects such as sexual reproduction, needs to be done. Studies to investigate the most suitable teaching strategy should also be carried out as well as an investigation into the structure of the curriculum
- Full Text:
- Date Issued: 1990
- Authors: Moore, Aldyth Margaret
- Date: 1990
- Subjects: Genetics -- Study and teaching (Secondary)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1338 , http://hdl.handle.net/10962/d1001404
- Description: This pilot study was aimed at investigating with the aid of a two-tier multiple choice questionnaire, the misconceptions held by pupils in standards 8 and 10 as well as first year Biology students in the area of senior secondary school genetics. It was found that certain of the children's preconceived ideas were altered by tuition while others were unaffected by either age or tuition and consequently warranted the name misconceptions. Four misconceptions were identified in this study and these were seen to be at the root of the difficulties experienced in genetics. They involved plants being seen to be unable to reproduce sexually, an inability to relate meiosis to genetics, a tendency to cling to the Punnett square algorithm when solving genetics problems despite a lack of understanding of the underlying processes and a failure to see the role of chance in genetics. These misconceptions were seen to have arisen because of certain preconceived ideas which hamper the formation of a suitable conceptual framework. The adoption of suitable teaching strategies appears to be the most likely method of rectifying the problem. However, before this can be regarded as conclusive, further research into the concept development of specific aspects such as sexual reproduction, needs to be done. Studies to investigate the most suitable teaching strategy should also be carried out as well as an investigation into the structure of the curriculum
- Full Text:
- Date Issued: 1990
An investigation into the need for counselling service at the Cape College of Education
- Authors: Blom, Lana-Lorraine
- Date: 1989
- Subjects: Counseling in higher education Teachers -- Training of -- South Africa -- Eastern Cape Cape College of Education Counseling
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1610 , http://hdl.handle.net/10962/d1003492
- Description: Many students find that their greatest academic step is that from high school to college or university, and that it involves a transition affecting almost all aspects of their lives. In order to offer assistance to students experiencing transitional and other personal problems, Student Counselling Services have been established and are operature at most tertiary institutions in Southern Africa. Currently no such service exists on the campus of the Cape College of Education, Fort Beaufort. This exploratory study attempts to determine whether there is a need for such a service and further, to establish factors which might encourage or discourage students from using such a service. An open-ended questionnaire was administered to 178 students at the College in order to gain insight into their ideas and feelings and what they perceive their needs to be. Through an explication of the student protocols, several major themes emerged and are discussed in detail. The research findings suggest a need for the establishment of a counselling service, and shed some light on factors which need be considered should such a service be offered. The methodological approach is discussed as well as recommendations for improvements.
- Full Text:
- Date Issued: 1989
- Authors: Blom, Lana-Lorraine
- Date: 1989
- Subjects: Counseling in higher education Teachers -- Training of -- South Africa -- Eastern Cape Cape College of Education Counseling
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1610 , http://hdl.handle.net/10962/d1003492
- Description: Many students find that their greatest academic step is that from high school to college or university, and that it involves a transition affecting almost all aspects of their lives. In order to offer assistance to students experiencing transitional and other personal problems, Student Counselling Services have been established and are operature at most tertiary institutions in Southern Africa. Currently no such service exists on the campus of the Cape College of Education, Fort Beaufort. This exploratory study attempts to determine whether there is a need for such a service and further, to establish factors which might encourage or discourage students from using such a service. An open-ended questionnaire was administered to 178 students at the College in order to gain insight into their ideas and feelings and what they perceive their needs to be. Through an explication of the student protocols, several major themes emerged and are discussed in detail. The research findings suggest a need for the establishment of a counselling service, and shed some light on factors which need be considered should such a service be offered. The methodological approach is discussed as well as recommendations for improvements.
- Full Text:
- Date Issued: 1989
A price analysis of vegetables on the East London municipal market
- Authors: Fraser, Gavin Cecil Gilbert
- Date: 1983
- Subjects: Agricultural prices -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1055 , http://hdl.handle.net/10962/d1006970 , Agricultural prices -- South Africa
- Description: [Introduction] Much of the information available on the prices of vegetables marketed through the fresh produce markets is of limited use to producers. This information contains the actual prices for individual years. This can obviously be taken as a guide to future prices but it does not necessarily mean that those prices are a true reflection of the general pattern. In this study an attempt will be made, firstly, to establish whether a general pattern exists in the prices of selected vegetables on the East London municipal market. This will be attempted by studying the prices obtained over the 1964-1979 period. Information of this nature can be used as a basis for the planning of future crops. Secondly, to determine the months which obtain the "best" prices for the selected vegetables taking into account the quantities supplied to the market.
- Full Text:
- Date Issued: 1983
- Authors: Fraser, Gavin Cecil Gilbert
- Date: 1983
- Subjects: Agricultural prices -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1055 , http://hdl.handle.net/10962/d1006970 , Agricultural prices -- South Africa
- Description: [Introduction] Much of the information available on the prices of vegetables marketed through the fresh produce markets is of limited use to producers. This information contains the actual prices for individual years. This can obviously be taken as a guide to future prices but it does not necessarily mean that those prices are a true reflection of the general pattern. In this study an attempt will be made, firstly, to establish whether a general pattern exists in the prices of selected vegetables on the East London municipal market. This will be attempted by studying the prices obtained over the 1964-1979 period. Information of this nature can be used as a basis for the planning of future crops. Secondly, to determine the months which obtain the "best" prices for the selected vegetables taking into account the quantities supplied to the market.
- Full Text:
- Date Issued: 1983
Review of carbonate hosted lead-zinc (copper) deposits and the geological factors affecting their shape, size and grade
- Authors: McDonald, B
- Date: 1981
- Subjects: Lead ores , Zinc ores , Copper ores , Sedimentology , Sedimentation and deposition
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5028 , http://hdl.handle.net/10962/d1006903
- Description: From Introduction: For at least two centuries and a corresponding number of generations of geologists and miners there has been active argument concerning the origin of certain types of carbonate hosted mineral deposit. The characterization of the type itself was and still is debatable. Objections have been raised to grouping several examples under one heading because each has its individually distinctive features. ·This is especially applicable to the carbonate hosted lead-zinc "sedimentary" deposits. The type that will be discussed in the text to follow is composed chiefly of galena, sphalerite, barite and fluorite, with pyrite , marcasite and chalcopyrite as conspicuous accessory ore minerals. Exceptions to this general copper deficient characteristic displayed by the sedimentary carbonate-hosted lead-zinc deposits are the deposits at Tsumeb and Kombat, Namibia. These deposits are hosted by the carbonate sequence of the Otavi Shelf sediments, and copper, in the form of tennantite, chalcopyrite and bornite, is the major ore constituent. Calcite, aragonite, dolomite and quartz are the commonest nonmetallic gangue minerals but siderite and silica may also be present. In contrast with other lead and zinc sulphide (volcanogenic) deposits, those to be considered here seldom carry noteworthy amounts of silver or any other precious metals. Commonly the country rock is a carbonate; limestone or dolomite, but deposits in. sandstone, shale and conglomerate are not unknown. Characteristic features are ore bodies that extend parallel or nearly so with the bedding although many such deposits are partly, or completely developed along crosscutting fissures and breccias. Some observers regard these fissure fillings as evidence for a magmatic source of the metals, whereas others regard them as an indication of remobilization of ions, metals or minerals orginally present in low-grade stratiform deposits elsewhere in the stratigraphic succession.
- Full Text:
- Date Issued: 1981
- Authors: McDonald, B
- Date: 1981
- Subjects: Lead ores , Zinc ores , Copper ores , Sedimentology , Sedimentation and deposition
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5028 , http://hdl.handle.net/10962/d1006903
- Description: From Introduction: For at least two centuries and a corresponding number of generations of geologists and miners there has been active argument concerning the origin of certain types of carbonate hosted mineral deposit. The characterization of the type itself was and still is debatable. Objections have been raised to grouping several examples under one heading because each has its individually distinctive features. ·This is especially applicable to the carbonate hosted lead-zinc "sedimentary" deposits. The type that will be discussed in the text to follow is composed chiefly of galena, sphalerite, barite and fluorite, with pyrite , marcasite and chalcopyrite as conspicuous accessory ore minerals. Exceptions to this general copper deficient characteristic displayed by the sedimentary carbonate-hosted lead-zinc deposits are the deposits at Tsumeb and Kombat, Namibia. These deposits are hosted by the carbonate sequence of the Otavi Shelf sediments, and copper, in the form of tennantite, chalcopyrite and bornite, is the major ore constituent. Calcite, aragonite, dolomite and quartz are the commonest nonmetallic gangue minerals but siderite and silica may also be present. In contrast with other lead and zinc sulphide (volcanogenic) deposits, those to be considered here seldom carry noteworthy amounts of silver or any other precious metals. Commonly the country rock is a carbonate; limestone or dolomite, but deposits in. sandstone, shale and conglomerate are not unknown. Characteristic features are ore bodies that extend parallel or nearly so with the bedding although many such deposits are partly, or completely developed along crosscutting fissures and breccias. Some observers regard these fissure fillings as evidence for a magmatic source of the metals, whereas others regard them as an indication of remobilization of ions, metals or minerals orginally present in low-grade stratiform deposits elsewhere in the stratigraphic succession.
- Full Text:
- Date Issued: 1981
A critical investigation into the methods of determining sulphur in plant material
- Authors: Smith, Anthony John Hibbert
- Date: 1962
- Subjects: Plants -- Effect of sulfur on , Plants -- Nutrition , Sulfur
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4520 , http://hdl.handle.net/10962/d1014526
- Description: Although sulphur is one of the more abundant elements present in plants, its importance as a plant nutrient has been underestimated until comparatively recently. Scientific literature over the past few years, however, shows that interest in the determination of sulphur in natural waters, soil and plant materials has been renewed. Perhaps the main reason for the non-recognition of the importance of sulphur as a plant nutrient is the fact that sulphur-deficiency seldom occurs since sufficient sulphur is usually added to the soil in rainfall (particularly near industrial towns) to supply all the sulphur requirements of plants. In addition, sulphur is frequently present in fertilizers added to soils to counteract deficiency in other elements, especially phosphorus. Superphosphates, for example contain up to 60%, gypsum. Sulphur is also added to the soil in some instances in order to reduce the soil pH, the elemental sulphur being fairly readily oxidised in the soil to sulphuric acid. The organic fraction in the soil also contains sulphur. , [From Introduction]. Although sulphur is one of the more abundant elements present in plants, its importance as a plant nutrient has been underestimated until comparatively recently. Scientific literature over the past few years, however, shows that interest in the determination of sulphur in natural waters, soil and plant materials has been renewed. Perhaps the main reason for the non-recognition of the importance of sulphur as a plant nutrient is the fact that sulphur-deficiency seldom occurs since sufficient sulphur is usually added to the soil in rainfall (particularly near industrial towns) to supply all the sulphur requirements of plants. In addition, sulphur is frequently present in fertilizers added to soils to counteract deficiency in other elements, especially phosphorus. Superphosphates, for example contain up to 60%, gypsum. Sulphur is also added to the soil in some instances in order to reduce the soil pH, the elemental sulphur being fairly readily oxidised in the soil to sulphuric acid. The organic fraction in the soil also contains sulphur.
- Full Text: false
- Date Issued: 1962
- Authors: Smith, Anthony John Hibbert
- Date: 1962
- Subjects: Plants -- Effect of sulfur on , Plants -- Nutrition , Sulfur
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4520 , http://hdl.handle.net/10962/d1014526
- Description: Although sulphur is one of the more abundant elements present in plants, its importance as a plant nutrient has been underestimated until comparatively recently. Scientific literature over the past few years, however, shows that interest in the determination of sulphur in natural waters, soil and plant materials has been renewed. Perhaps the main reason for the non-recognition of the importance of sulphur as a plant nutrient is the fact that sulphur-deficiency seldom occurs since sufficient sulphur is usually added to the soil in rainfall (particularly near industrial towns) to supply all the sulphur requirements of plants. In addition, sulphur is frequently present in fertilizers added to soils to counteract deficiency in other elements, especially phosphorus. Superphosphates, for example contain up to 60%, gypsum. Sulphur is also added to the soil in some instances in order to reduce the soil pH, the elemental sulphur being fairly readily oxidised in the soil to sulphuric acid. The organic fraction in the soil also contains sulphur. , [From Introduction]. Although sulphur is one of the more abundant elements present in plants, its importance as a plant nutrient has been underestimated until comparatively recently. Scientific literature over the past few years, however, shows that interest in the determination of sulphur in natural waters, soil and plant materials has been renewed. Perhaps the main reason for the non-recognition of the importance of sulphur as a plant nutrient is the fact that sulphur-deficiency seldom occurs since sufficient sulphur is usually added to the soil in rainfall (particularly near industrial towns) to supply all the sulphur requirements of plants. In addition, sulphur is frequently present in fertilizers added to soils to counteract deficiency in other elements, especially phosphorus. Superphosphates, for example contain up to 60%, gypsum. Sulphur is also added to the soil in some instances in order to reduce the soil pH, the elemental sulphur being fairly readily oxidised in the soil to sulphuric acid. The organic fraction in the soil also contains sulphur.
- Full Text: false
- Date Issued: 1962