An investigation into conditions that enable or constrain sustainable paper usage at Rhodes University
- Authors: Mfenyana, Nondumiso Gloria
- Date: 2013
- Subjects: Colleges and Universities -- Environmental aspects -- South Africa Paper Waste paper -- Recycling
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:794 , http://hdl.handle.net/10962/d1004217
- Description: The interest in this study was initiated by the rapid global transition of paper usage to digital systems in teaching and learning at tertiary institutions, particularly those that are signatories to the Talloires Declaration, which include Rhodes University (RU). It was discovered that there are two earlier studies (Leslie et al. 2009; Amutenya et al. 2009) that investigated and proposed recommendations towards sustainable paper usage at Rhodes University (RU). This study then investigated the response of RU to the proposed recommendations of the above mentioned studies and evaluated the conditions that promote and constrain sustainable paper usage in teaching and learning, and the attitudes of users thereof.
- Full Text:
- Date Issued: 2013
- Authors: Mfenyana, Nondumiso Gloria
- Date: 2013
- Subjects: Colleges and Universities -- Environmental aspects -- South Africa Paper Waste paper -- Recycling
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:794 , http://hdl.handle.net/10962/d1004217
- Description: The interest in this study was initiated by the rapid global transition of paper usage to digital systems in teaching and learning at tertiary institutions, particularly those that are signatories to the Talloires Declaration, which include Rhodes University (RU). It was discovered that there are two earlier studies (Leslie et al. 2009; Amutenya et al. 2009) that investigated and proposed recommendations towards sustainable paper usage at Rhodes University (RU). This study then investigated the response of RU to the proposed recommendations of the above mentioned studies and evaluated the conditions that promote and constrain sustainable paper usage in teaching and learning, and the attitudes of users thereof.
- Full Text:
- Date Issued: 2013
Strategic management of construction companies
- Authors: Van Rooyen, Roelof Petrus
- Date: 2013
- Subjects: Construction industry -- Planning , Business planning -- South Africa -- Eastern Cape , Corporate turnarounds -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9712 , http://hdl.handle.net/10948/d1020407
- Description: The research emanated from an investigation of GB7, GB8 and GB9 main contractors in the Eastern Cape Province of South Africa. The study was focussed on the strident economic times in the construction industry following the FIFA Soccer World Cup from August 2010 to December 2012. The research was conducted to identify the key strategy or combination of strategies keeping construction entities in operation. The study further investigates the key elements of a successful turnaround strategy as well as the most effective methods in implementing strategies within construction organizations. The research took the form of an empirical quantitative study where a descriptive survey was used to collect data. Structured interviews were held with the target population to collect data in the field. The study established that geographic diversification was the most effective method utilized by main contractors for survival during the study timeframe. The study also found that lowering of profit margins and preliminary and general amounts were most effective methods in the use of turn around strategies. The study finally concluded that effective steps were taken by main contractors in the Eastern Cape to implement corporate strategies within their organizations. Step by step guidance to all employees on new processes was the key element in successful strategic implementation of a strategy within construction organizations. The research conducted contributes to the strategic management competency within the built environment as well as the existing body of knowledge within the construction industry. All members of the construction industry in South Africa involved with strategic level planning of entities would value the study.
- Full Text:
- Date Issued: 2013
- Authors: Van Rooyen, Roelof Petrus
- Date: 2013
- Subjects: Construction industry -- Planning , Business planning -- South Africa -- Eastern Cape , Corporate turnarounds -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9712 , http://hdl.handle.net/10948/d1020407
- Description: The research emanated from an investigation of GB7, GB8 and GB9 main contractors in the Eastern Cape Province of South Africa. The study was focussed on the strident economic times in the construction industry following the FIFA Soccer World Cup from August 2010 to December 2012. The research was conducted to identify the key strategy or combination of strategies keeping construction entities in operation. The study further investigates the key elements of a successful turnaround strategy as well as the most effective methods in implementing strategies within construction organizations. The research took the form of an empirical quantitative study where a descriptive survey was used to collect data. Structured interviews were held with the target population to collect data in the field. The study established that geographic diversification was the most effective method utilized by main contractors for survival during the study timeframe. The study also found that lowering of profit margins and preliminary and general amounts were most effective methods in the use of turn around strategies. The study finally concluded that effective steps were taken by main contractors in the Eastern Cape to implement corporate strategies within their organizations. Step by step guidance to all employees on new processes was the key element in successful strategic implementation of a strategy within construction organizations. The research conducted contributes to the strategic management competency within the built environment as well as the existing body of knowledge within the construction industry. All members of the construction industry in South Africa involved with strategic level planning of entities would value the study.
- Full Text:
- Date Issued: 2013
The value of the middleman in the supply chain of South African tyre production
- Authors: Cornelius, André G
- Date: 2008
- Subjects: Tires -- Industrialists -- South Africa Tire Industry -- South Africa Commercial agents -- South Africa Business logistics -- Management -- South Africa Physical distribution of goods -- Management Commercial agents -- South Africa Marketing channels -- Management -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:770 , http://hdl.handle.net/10962/d1003891
- Description: Only a few middlemen linking chemical intermediate product supply to world tyre productions have managed to survive new direct business models. In fact, the only region, where the practice of using a middleman in the supply chain of tyre production, for a certain primary manufacturer, is in South Africa. Tyre producers in other world regions, similar in market complexity to South Africa, have experienced the elimination of the middleman. Hence the question of this research, why is the middleman in the supply chain of tyre production in South Africa still a better option than that of direct business models? To begin with, the thesis stated that the middleman in the supply chain of South African tyre producers delivers better value than that of the direct business model. To prove/disprove this thesis, the principle that value is a trade-off between what you get for what you give was the basis of this research (Zeithaml, 1998). Further, a model was developed, from secondary literature, to conceptualise this trade-off to provide evidence to prove/disprove that the middleman provides greater value than value from the direct business model. From this point, the research approach was to collect data through interviews to find out the most important aspect of value created by the middleman. Data collected were analysed, using the structure of the model as a guide, to find evidence of the trade-off. This analysis provided evidence that the relationship between the middleman and the tyre producers in South Africa and between the middleman and primary product supplier is the value that the direct business model cannot replace.
- Full Text:
- Date Issued: 2008
- Authors: Cornelius, André G
- Date: 2008
- Subjects: Tires -- Industrialists -- South Africa Tire Industry -- South Africa Commercial agents -- South Africa Business logistics -- Management -- South Africa Physical distribution of goods -- Management Commercial agents -- South Africa Marketing channels -- Management -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:770 , http://hdl.handle.net/10962/d1003891
- Description: Only a few middlemen linking chemical intermediate product supply to world tyre productions have managed to survive new direct business models. In fact, the only region, where the practice of using a middleman in the supply chain of tyre production, for a certain primary manufacturer, is in South Africa. Tyre producers in other world regions, similar in market complexity to South Africa, have experienced the elimination of the middleman. Hence the question of this research, why is the middleman in the supply chain of tyre production in South Africa still a better option than that of direct business models? To begin with, the thesis stated that the middleman in the supply chain of South African tyre producers delivers better value than that of the direct business model. To prove/disprove this thesis, the principle that value is a trade-off between what you get for what you give was the basis of this research (Zeithaml, 1998). Further, a model was developed, from secondary literature, to conceptualise this trade-off to provide evidence to prove/disprove that the middleman provides greater value than value from the direct business model. From this point, the research approach was to collect data through interviews to find out the most important aspect of value created by the middleman. Data collected were analysed, using the structure of the model as a guide, to find evidence of the trade-off. This analysis provided evidence that the relationship between the middleman and the tyre producers in South Africa and between the middleman and primary product supplier is the value that the direct business model cannot replace.
- Full Text:
- Date Issued: 2008
An investigation into school principals' experience and perceptions of participative management
- Authors: Mungunda, Charles
- Date: 2004
- Subjects: Education -- Namibia Educational change -- Namibia School management and organization -- Namibia Educational leadership -- Namibia Management -- Employee participation -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1599 , http://hdl.handle.net/10962/d1003481
- Description: The purpose of this research was to investigate three principals’ perceptions and experience of participative management and to gain insight into and understanding of the dimensions involved in participative management from the perspective of the three principals. The research was conducted within the interpretive paradigm, since I was interested in understanding the subjective experience and individual perceptions of three principals with regard to participative management and the meaning they attach to it in their natural settings: how they describe, interpret and make sense of participative management. Data were collected by means of questionnaires, interviews and observation. The findings indicate overwhelming support for the notion that participative management (collegiality) does have a positive influence with regard to creating a sense of common goals, shared vision, a sense of ownership, commitment and improved human relations. The respondents emphasized the critical role of the leader in facilitating the implementation of collegiality as well as an increasing awareness of the potential of participative management to improve human development through delegation. The responses revealed interesting paradoxes with regard to the tensions between leadership and leaderless organizations, as well as between autonomy and interdependence. Responses also reflect the sentiment that participative management should be selective, involving only those with the necessary skills and expertise in the decision-making process. While there is an appreciation of the benefits to be derived from collegiality, critical statements about participative management include the time-consuming nature of participative management, and the notion that participative management impinges on the authority of the principals.
- Full Text:
- Date Issued: 2004
- Authors: Mungunda, Charles
- Date: 2004
- Subjects: Education -- Namibia Educational change -- Namibia School management and organization -- Namibia Educational leadership -- Namibia Management -- Employee participation -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1599 , http://hdl.handle.net/10962/d1003481
- Description: The purpose of this research was to investigate three principals’ perceptions and experience of participative management and to gain insight into and understanding of the dimensions involved in participative management from the perspective of the three principals. The research was conducted within the interpretive paradigm, since I was interested in understanding the subjective experience and individual perceptions of three principals with regard to participative management and the meaning they attach to it in their natural settings: how they describe, interpret and make sense of participative management. Data were collected by means of questionnaires, interviews and observation. The findings indicate overwhelming support for the notion that participative management (collegiality) does have a positive influence with regard to creating a sense of common goals, shared vision, a sense of ownership, commitment and improved human relations. The respondents emphasized the critical role of the leader in facilitating the implementation of collegiality as well as an increasing awareness of the potential of participative management to improve human development through delegation. The responses revealed interesting paradoxes with regard to the tensions between leadership and leaderless organizations, as well as between autonomy and interdependence. Responses also reflect the sentiment that participative management should be selective, involving only those with the necessary skills and expertise in the decision-making process. While there is an appreciation of the benefits to be derived from collegiality, critical statements about participative management include the time-consuming nature of participative management, and the notion that participative management impinges on the authority of the principals.
- Full Text:
- Date Issued: 2004
The investigation of the hydrolysis reaction of m-phenylene to resorcinol
- Authors: Khaile, Thebeeapelo John
- Date: 2002
- Subjects: Resorcinol
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10961 , http://hdl.handle.net/10948/107 , Resorcinol
- Description: The purpose of this study was to characterise the resinous material formed during the acid catalysed hydrolysis of m-phenylenediamine (MPDA) to resorcinol, and to establish a reaction mechanism that could explain the formation of both resorcinol and the resinous materials in the reaction. A further objective was to determine reaction conditions that would lead to reduced formation of the resins during the hydrolysis reaction. The number of compounds present in a sample taken during the course of the hydrolysis reaction was determined by HPLC fitted with a photodiode array detector. Five main components were detected. These compounds were identified as mphenylenediamine, m-aminophenol, resorcinol, 3,3’-aminodiphenylamine and 3- amino-3’-hydroxydiphenylamine by means of GC-MS. 3,3’-Diaminodiphenylamine is formed by self-condensation of MPDA and 3-amino-3’-hydroxydiphenylamine is formed by the reaction of MPDA with resorcinol. The degree of formation of these intermediates is substantially reduced when MPDA is added dose-wise to phosphoric acid at a reaction temperature of 220oC. The reaction mechanism of the hydrolysis reaction was investigated by isotopic lable incorporation, followed by analysis by NMR. This was done by hydrolysing MPDA using deuterated phosphoric acid (D3PO4). D3PO4 was generated by dissolving phosphorus pentoxide in deuterium oxide. The resorcinol product obtained from the hydrolysis using D3PO4 was found to be deuterated on the C-2, C-4 and C-6 positions. This suggests that the hydrolysis reaction involves protonation of MPDA on these positions, and this results in the formation of an iminium ion as one of the resonance forms. Hydrolysis then occurs on the positively charged carbon of this species. Fertiliser grade phosphoric acid can be used in the hydrolysis reaction, provided sulphates are removed before the acid is used in the hydrolysis reaction. The hydrolysis reaction using either ammonium sulphate or sulphuric acid produces resorcinol in yields lower than 60% if the hydrolysis is conducted in one pass. If these catalysts are used in the hydrolysis reaction, the reaction mixture needs to be re-heated after removal of resorcinol in order to increase the yield. Hydrolysis of MPDA using zirconium phosphate as catalyst gave resorcinol yields in excess of 90% over 24 hours. These reactions were carried out at very low concentrations of MPDA (0.3%). The mode of catalysis in these reactions is unclear. There is a possibility that the reaction is catalysed by phosphoric acid that leaches out of zirconium phosphate at high temperatures. The reaction might therefore not differ mechanistically from the phosphoric acid catalysed reaction. Further studies are required to clarify this point.
- Full Text:
- Date Issued: 2002
- Authors: Khaile, Thebeeapelo John
- Date: 2002
- Subjects: Resorcinol
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10961 , http://hdl.handle.net/10948/107 , Resorcinol
- Description: The purpose of this study was to characterise the resinous material formed during the acid catalysed hydrolysis of m-phenylenediamine (MPDA) to resorcinol, and to establish a reaction mechanism that could explain the formation of both resorcinol and the resinous materials in the reaction. A further objective was to determine reaction conditions that would lead to reduced formation of the resins during the hydrolysis reaction. The number of compounds present in a sample taken during the course of the hydrolysis reaction was determined by HPLC fitted with a photodiode array detector. Five main components were detected. These compounds were identified as mphenylenediamine, m-aminophenol, resorcinol, 3,3’-aminodiphenylamine and 3- amino-3’-hydroxydiphenylamine by means of GC-MS. 3,3’-Diaminodiphenylamine is formed by self-condensation of MPDA and 3-amino-3’-hydroxydiphenylamine is formed by the reaction of MPDA with resorcinol. The degree of formation of these intermediates is substantially reduced when MPDA is added dose-wise to phosphoric acid at a reaction temperature of 220oC. The reaction mechanism of the hydrolysis reaction was investigated by isotopic lable incorporation, followed by analysis by NMR. This was done by hydrolysing MPDA using deuterated phosphoric acid (D3PO4). D3PO4 was generated by dissolving phosphorus pentoxide in deuterium oxide. The resorcinol product obtained from the hydrolysis using D3PO4 was found to be deuterated on the C-2, C-4 and C-6 positions. This suggests that the hydrolysis reaction involves protonation of MPDA on these positions, and this results in the formation of an iminium ion as one of the resonance forms. Hydrolysis then occurs on the positively charged carbon of this species. Fertiliser grade phosphoric acid can be used in the hydrolysis reaction, provided sulphates are removed before the acid is used in the hydrolysis reaction. The hydrolysis reaction using either ammonium sulphate or sulphuric acid produces resorcinol in yields lower than 60% if the hydrolysis is conducted in one pass. If these catalysts are used in the hydrolysis reaction, the reaction mixture needs to be re-heated after removal of resorcinol in order to increase the yield. Hydrolysis of MPDA using zirconium phosphate as catalyst gave resorcinol yields in excess of 90% over 24 hours. These reactions were carried out at very low concentrations of MPDA (0.3%). The mode of catalysis in these reactions is unclear. There is a possibility that the reaction is catalysed by phosphoric acid that leaches out of zirconium phosphate at high temperatures. The reaction might therefore not differ mechanistically from the phosphoric acid catalysed reaction. Further studies are required to clarify this point.
- Full Text:
- Date Issued: 2002
Organisational leaders' perceptions of the challenges and constraints of the leadership development of Blacks in South African private organisations
- Authors: Nyamuda, Paul Andrew
- Date: 2000
- Subjects: Leadership , Black people -- South Africa , Black people -- Employment -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:3033 , http://hdl.handle.net/10962/d1002542 , Leadership , Black people -- South Africa , Black people -- Employment -- South Africa
- Description: In recent years, it has become clear that a lot of corporate collapse can be traced down to poor leadership. As more and more black executives are climbing the corporate ladder, it is becoming all the more necessary to explore how their effective leadership development can occur with private organisations in South Africa. There are many challenges and constraints associated with the leadership development of these executives. This can be expected as they are entering an environment which has been largely white-dominated. As a result they find themselves facing the challenges of succeeding amidst negative perceptions they have experienced from their superiors and subtle pressures from subordinates. Therefore, it can only be expected that if organisations are to maintain a competitive advantage they need to understand how to effectively develop this new breed of leaders. Hence, the researcher has used a qualitative approach to investigate the complexities of the experiences of black executives in private organisations. In terms of the theoretical framework, the research focuses on some of the new approaches to leadership. It was discovered that leadership development is essentially a process that goes beyond mere training sessions, and largely involves the relationships one has within the organisation. This involves relationships with superiors, peers, and subordinates. The research indicates that if these relationships are managed effectively, leadership development is enhanced. Whilst the role of formal training programs appeared somewhat downplayed, it was clear that these programs had a strong role in terms of their psychological impact on participants. They certainly affected their perception of the organisation and their own self-efficacy. The research, therefore illustrates how there are a variety of individual and organisational attributes that form a basis for effective leadership development of blacks in private organisations. The researcher argues that if these are implemented, organisational well-being is enhanced.
- Full Text:
- Date Issued: 2000
- Authors: Nyamuda, Paul Andrew
- Date: 2000
- Subjects: Leadership , Black people -- South Africa , Black people -- Employment -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:3033 , http://hdl.handle.net/10962/d1002542 , Leadership , Black people -- South Africa , Black people -- Employment -- South Africa
- Description: In recent years, it has become clear that a lot of corporate collapse can be traced down to poor leadership. As more and more black executives are climbing the corporate ladder, it is becoming all the more necessary to explore how their effective leadership development can occur with private organisations in South Africa. There are many challenges and constraints associated with the leadership development of these executives. This can be expected as they are entering an environment which has been largely white-dominated. As a result they find themselves facing the challenges of succeeding amidst negative perceptions they have experienced from their superiors and subtle pressures from subordinates. Therefore, it can only be expected that if organisations are to maintain a competitive advantage they need to understand how to effectively develop this new breed of leaders. Hence, the researcher has used a qualitative approach to investigate the complexities of the experiences of black executives in private organisations. In terms of the theoretical framework, the research focuses on some of the new approaches to leadership. It was discovered that leadership development is essentially a process that goes beyond mere training sessions, and largely involves the relationships one has within the organisation. This involves relationships with superiors, peers, and subordinates. The research indicates that if these relationships are managed effectively, leadership development is enhanced. Whilst the role of formal training programs appeared somewhat downplayed, it was clear that these programs had a strong role in terms of their psychological impact on participants. They certainly affected their perception of the organisation and their own self-efficacy. The research, therefore illustrates how there are a variety of individual and organisational attributes that form a basis for effective leadership development of blacks in private organisations. The researcher argues that if these are implemented, organisational well-being is enhanced.
- Full Text:
- Date Issued: 2000
Digestible energy as a criterion for the development of diets for the African sharptooth catfish, Clarias gariepinus (Pisces: Clariidae)
- Authors: Rouhani, Q A
- Date: 1993
- Subjects: Clariidae , Catfishes -- Africa , Catfishes -- Nutrition -- Requirements -- Africa , Catfishes , Clarias
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5259 , http://hdl.handle.net/10962/d1005103
- Description: Based on a number of attributes, the African sharptooth catfish, Clarias gariepinus is an ideal aquaculture species. Much work has been undertaken on developing the technology for the commercial culture of the species inclusive of determining the nutritional requirements for cost effective feed formulation. However, digestible energy (DE) values for specific feed ingredients were unknown. As DE values are not interchangeable between species, this study set out to determine the DE values for conventional and unconventional feed-ingredients for the formulation of an optimal feed. The ultimate goal in feed formulation is to produce a diet that supports the maximum production at the least cost. The indirect method was found to be most suitable in obtaining DE values for the catfish. Feed samples were marked by adding 2% chromic oxide as an inert indicator. The fish were then force-fed and faecal samples were obtained from the hindgut by stripping the fish 10 hours after feeding as this was found to be when the hind-gut was at its fullest and the feed maximally digested. A linear based computer programme was used to formulate experimental diets using the established DE values as an additional variable. The formulated feed was tested and compared to a commercial catfish diet and a standard reference diet (H-440). All of the newly formulated feeds were found to be cheaper to manufacture (by between 5 and 10%). Statistically (ANOVA), all of the experimental diets resulted in higher specific growth rates (SGR) than the standard reference diet. The commercial diet also resulted in a lower SGR than those experimental diets with similar protein levels.
- Full Text:
- Date Issued: 1993
- Authors: Rouhani, Q A
- Date: 1993
- Subjects: Clariidae , Catfishes -- Africa , Catfishes -- Nutrition -- Requirements -- Africa , Catfishes , Clarias
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5259 , http://hdl.handle.net/10962/d1005103
- Description: Based on a number of attributes, the African sharptooth catfish, Clarias gariepinus is an ideal aquaculture species. Much work has been undertaken on developing the technology for the commercial culture of the species inclusive of determining the nutritional requirements for cost effective feed formulation. However, digestible energy (DE) values for specific feed ingredients were unknown. As DE values are not interchangeable between species, this study set out to determine the DE values for conventional and unconventional feed-ingredients for the formulation of an optimal feed. The ultimate goal in feed formulation is to produce a diet that supports the maximum production at the least cost. The indirect method was found to be most suitable in obtaining DE values for the catfish. Feed samples were marked by adding 2% chromic oxide as an inert indicator. The fish were then force-fed and faecal samples were obtained from the hindgut by stripping the fish 10 hours after feeding as this was found to be when the hind-gut was at its fullest and the feed maximally digested. A linear based computer programme was used to formulate experimental diets using the established DE values as an additional variable. The formulated feed was tested and compared to a commercial catfish diet and a standard reference diet (H-440). All of the newly formulated feeds were found to be cheaper to manufacture (by between 5 and 10%). Statistically (ANOVA), all of the experimental diets resulted in higher specific growth rates (SGR) than the standard reference diet. The commercial diet also resulted in a lower SGR than those experimental diets with similar protein levels.
- Full Text:
- Date Issued: 1993
The interactive effects of light, temperature and CO₂/O₂ ratios in photosynthesis of Coix lachryma-jobi L
- Authors: Mjwara, Jabulani Michael
- Date: 1992
- Subjects: Coix , Plants -- Effect of light on , Plants -- Effect of oxygen on , Plants -- Effect of carbon dioxide on , Photosynthesis , Plants -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4216 , http://hdl.handle.net/10962/d1003785
- Description: A portable infra red gas analyzer was used to investigate the interactive effects of light, temperature, and CO,jO, ratios under controlled environmental conditions in an attempt to model gas exchange characteristics of Coix Iachryma-jobi L. Plotting light response curves as a function of temperature (20, 25 30 and 35°C) revealed no sign of light saturation even at a photosynthetic photon flux density (PPFD) close to 2000 !Lmol m-' sol. High net assimilation rates (A) of approximately 24 !Lmol CO, m"s'! were realized at 30-35°C. Assimilation (A) versus internal CO, partial pressure (C,) curves showed a steep rise with increase in C, but saturated at approximately 150 (JLII-!) and all the results, either in the absence or presence of 0" showed a similar response under all temperature regimes. C. Iachryma-jobi exhibited low CO, compensation points cr ) between 0 and 10 JLlI-! under similar experimental temperatures and either at 0 or 21%0,. The slopes of double reciprocal plots of llA versus llCi, were nearly identical and crossed the yintercept at almost identical points under all 0, concentrations. These data indicate first; that there was no apparent 0, inhibition and second; indicated that the apparent inhIbitor constant (K,) for 0, at the site of carboxylation did not change with increase in [OJ from 0 to 21% oxygen. These observations were further confirmed by results obtained from the analysis of apparent carboxylation efficiency (CE, as defined as the slope of response of A to increasing CO,), as no inhibition of A with increase of [OJ occurred. These characteristics were consistent with typical features of C,photosynthesis. The absence of 0, inhibition and low r values indicated that an efficient CO, concentrating mechanism which eliminates photorespiration exists in C. Iachryma-jobi. At the light microscope level, leaf anatomy exhibited typical C, structure viz. bundle sheath with large chloroplasts and this sheath is further surrounded by a radiate Kranz mesophyU cells. Furthermore the anatomical features suggested that C. wchryma-jobi was an NADP-ME species. Stomatal conductance (g,) to assimilation (g,/A) indicated an increase in A with decrease in g" an essential feature of improving water use efficiency (WUE), but one which drastically reduces CO, diffusion rate. The physical lintitation (stomatal lintitation, t) to CO, diffusion under various [0,] and temperatures, but constant PPFD, did not exhibit statistically significant change in t values at either 0 or 21% a, within each temperature regime, however there was a marked decrease in t as the plant approached its optimum photosynthetic temperature.
- Full Text:
- Date Issued: 1992
- Authors: Mjwara, Jabulani Michael
- Date: 1992
- Subjects: Coix , Plants -- Effect of light on , Plants -- Effect of oxygen on , Plants -- Effect of carbon dioxide on , Photosynthesis , Plants -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4216 , http://hdl.handle.net/10962/d1003785
- Description: A portable infra red gas analyzer was used to investigate the interactive effects of light, temperature, and CO,jO, ratios under controlled environmental conditions in an attempt to model gas exchange characteristics of Coix Iachryma-jobi L. Plotting light response curves as a function of temperature (20, 25 30 and 35°C) revealed no sign of light saturation even at a photosynthetic photon flux density (PPFD) close to 2000 !Lmol m-' sol. High net assimilation rates (A) of approximately 24 !Lmol CO, m"s'! were realized at 30-35°C. Assimilation (A) versus internal CO, partial pressure (C,) curves showed a steep rise with increase in C, but saturated at approximately 150 (JLII-!) and all the results, either in the absence or presence of 0" showed a similar response under all temperature regimes. C. Iachryma-jobi exhibited low CO, compensation points cr ) between 0 and 10 JLlI-! under similar experimental temperatures and either at 0 or 21%0,. The slopes of double reciprocal plots of llA versus llCi, were nearly identical and crossed the yintercept at almost identical points under all 0, concentrations. These data indicate first; that there was no apparent 0, inhibition and second; indicated that the apparent inhIbitor constant (K,) for 0, at the site of carboxylation did not change with increase in [OJ from 0 to 21% oxygen. These observations were further confirmed by results obtained from the analysis of apparent carboxylation efficiency (CE, as defined as the slope of response of A to increasing CO,), as no inhibition of A with increase of [OJ occurred. These characteristics were consistent with typical features of C,photosynthesis. The absence of 0, inhibition and low r values indicated that an efficient CO, concentrating mechanism which eliminates photorespiration exists in C. Iachryma-jobi. At the light microscope level, leaf anatomy exhibited typical C, structure viz. bundle sheath with large chloroplasts and this sheath is further surrounded by a radiate Kranz mesophyU cells. Furthermore the anatomical features suggested that C. wchryma-jobi was an NADP-ME species. Stomatal conductance (g,) to assimilation (g,/A) indicated an increase in A with decrease in g" an essential feature of improving water use efficiency (WUE), but one which drastically reduces CO, diffusion rate. The physical lintitation (stomatal lintitation, t) to CO, diffusion under various [0,] and temperatures, but constant PPFD, did not exhibit statistically significant change in t values at either 0 or 21% a, within each temperature regime, however there was a marked decrease in t as the plant approached its optimum photosynthetic temperature.
- Full Text:
- Date Issued: 1992
Guibourtacacidin: a new Leuco-anthocyanidin from Rhodesian copalwood; (Guibourtia coleosperma)
- Authors: De Bruyn, Guustaaf Cornelis
- Date: 1962
- Subjects: Phanerogams , Angiosperms , Flavonoids , Anthocyanidins
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4459 , http://hdl.handle.net/10962/d1011043
- Description: A new leuco-anthocyanidin, (+)-7,4'dihydroxyflavan- 3:4-diol has been isolated from the heartwood of Guibourtia coleosperma. The heartwood extractives were fractionated by enrichment procedures involving fractional precipitation and Craig partitioning, to give a high RF (subscript) low molecular weight fraction containing the above leuco -anthocyanidin. This was further fractionated by "preparative" paper chromatography . The leuco-anthocyanidin was amorphous and present in low proportion (0.004%) in the wood. On boiling with alcoholic hydrochloric acid the compound gave an anthocyanidin which was identified as 3,7,4'-trihydroxyflavylium chloride. The degradation products formed by alkali fusion, on a micro-scale, were resorcinol and ♭-resorcylic acid, and also p (underscore)-hydroxybenzoic acid. This indicated resorcinol and phenol A and B nuclei respectively. The formation of amorphous dimethyl ether and tetra-acetoxy derivatives indicated two phenolic and two alcoholic hydroxyl groups. The above indicates that the compound was 7,4'-dihydroxyflavan- 3:4- diol and a molecular weight estimation showed it to be monomeric. Comparison of the infrared absorption spectra of the natural dimethyl ether with synthetic (±) dimethoxyflavan- 3:4-diol, to which a tentative 2:3- trans- 3:4-cis conformation had been assigned (Phatak and Kulkarni 94), showed close identity. Crystalline (±)-7, 4 '-dihydroxyflavan- 3:4 - diol was synthesised by catalytic hydrogenation over platinum oxide of the corresponoing (±) -7,4'-dihydroxyflavanonol. The flavanonol was synthesised by sodium hyposulphite reduction of the 7,4 ' -dihydroxyflavonol. The infrared absorption spectra of the natural and synthetic diols were similar but not identical. Chromatographic evidence showed the apparent identity of the synthetic and natural flavan- 3:4- diols, and two possible configurations were assigned for the natural flavan-3:4-diol. The new leuco-anthocyanidin was observed to form an O(underscore)-ethyl ether derivative on manipulation in ethanol. A monomeric leuco- fisetinidin from the heartwood was identified, by two dimensional paper chromatography, as (+) - mollisacacidin. The condensed tannins found also in the heartwood of G.(underscore)- coleosperma appear to be polymeric forms of leuco - fisetinidin and leuco - guibourtinidin. These polymeric tannins form a large proportion of the heartwood extractives and furnish high yields of fisetinidin and guibourtinidin chlorides on boiling with alcoholic hydrochloric acid. Examination of some other members of the Guibourtia spp . by paper chromatography showed that only G (underscore). coleosperma contained the new leuco - anthocyanidin as well as a leuco - fisetinidin. G. (underscore) tessmannii and G. (underscore) demeusii heartwoods contained only leuco-fisetinidin and the related polymers and a close chemical relationship to G.(underscore) coleosperma is thus apparent. G.(underscore) arnoldiana on the other hand is not chemically interrelated with the above members since it appeared to contain only leuco - cyanidin. (±) - 7,4 ' -Dihydroxyflavan- 4-ol was synthesised by hydrogenation of the corresponding flavanone over platinum oxide. Observations were made regarding its reddenig and ease of condensation.
- Full Text:
- Date Issued: 1962
- Authors: De Bruyn, Guustaaf Cornelis
- Date: 1962
- Subjects: Phanerogams , Angiosperms , Flavonoids , Anthocyanidins
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4459 , http://hdl.handle.net/10962/d1011043
- Description: A new leuco-anthocyanidin, (+)-7,4'dihydroxyflavan- 3:4-diol has been isolated from the heartwood of Guibourtia coleosperma. The heartwood extractives were fractionated by enrichment procedures involving fractional precipitation and Craig partitioning, to give a high RF (subscript) low molecular weight fraction containing the above leuco -anthocyanidin. This was further fractionated by "preparative" paper chromatography . The leuco-anthocyanidin was amorphous and present in low proportion (0.004%) in the wood. On boiling with alcoholic hydrochloric acid the compound gave an anthocyanidin which was identified as 3,7,4'-trihydroxyflavylium chloride. The degradation products formed by alkali fusion, on a micro-scale, were resorcinol and ♭-resorcylic acid, and also p (underscore)-hydroxybenzoic acid. This indicated resorcinol and phenol A and B nuclei respectively. The formation of amorphous dimethyl ether and tetra-acetoxy derivatives indicated two phenolic and two alcoholic hydroxyl groups. The above indicates that the compound was 7,4'-dihydroxyflavan- 3:4- diol and a molecular weight estimation showed it to be monomeric. Comparison of the infrared absorption spectra of the natural dimethyl ether with synthetic (±) dimethoxyflavan- 3:4-diol, to which a tentative 2:3- trans- 3:4-cis conformation had been assigned (Phatak and Kulkarni 94), showed close identity. Crystalline (±)-7, 4 '-dihydroxyflavan- 3:4 - diol was synthesised by catalytic hydrogenation over platinum oxide of the corresponoing (±) -7,4'-dihydroxyflavanonol. The flavanonol was synthesised by sodium hyposulphite reduction of the 7,4 ' -dihydroxyflavonol. The infrared absorption spectra of the natural and synthetic diols were similar but not identical. Chromatographic evidence showed the apparent identity of the synthetic and natural flavan- 3:4- diols, and two possible configurations were assigned for the natural flavan-3:4-diol. The new leuco-anthocyanidin was observed to form an O(underscore)-ethyl ether derivative on manipulation in ethanol. A monomeric leuco- fisetinidin from the heartwood was identified, by two dimensional paper chromatography, as (+) - mollisacacidin. The condensed tannins found also in the heartwood of G.(underscore)- coleosperma appear to be polymeric forms of leuco - fisetinidin and leuco - guibourtinidin. These polymeric tannins form a large proportion of the heartwood extractives and furnish high yields of fisetinidin and guibourtinidin chlorides on boiling with alcoholic hydrochloric acid. Examination of some other members of the Guibourtia spp . by paper chromatography showed that only G (underscore). coleosperma contained the new leuco - anthocyanidin as well as a leuco - fisetinidin. G. (underscore) tessmannii and G. (underscore) demeusii heartwoods contained only leuco-fisetinidin and the related polymers and a close chemical relationship to G.(underscore) coleosperma is thus apparent. G.(underscore) arnoldiana on the other hand is not chemically interrelated with the above members since it appeared to contain only leuco - cyanidin. (±) - 7,4 ' -Dihydroxyflavan- 4-ol was synthesised by hydrogenation of the corresponding flavanone over platinum oxide. Observations were made regarding its reddenig and ease of condensation.
- Full Text:
- Date Issued: 1962
The contribution of the Anglican church to education in the Cape
- Authors: Rawlins, G E
- Date: 1960
- Subjects: Church and education -- South Africa , Church of England -- Education -- South Africa , Education -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1978 , http://hdl.handle.net/10962/d1013055
- Description: In his "Onderwys in Kaapland, 1652 - 1939", Dr. P.S. du Toit makes special references to the educational work of the Anglican Church, indicating that there is some contribution. This attitude has as its aim to expose more of the reef of which the outcrops receive attention by Dr. du Toit ... much can happen between 1807 and 1829, and some of what did is described in these pages. One of Dr. du Toit's interests is the effect of the attempt to make English and instruction in English the basis of all education. Chap. 1, p. 1.
- Full Text:
- Date Issued: 1960
- Authors: Rawlins, G E
- Date: 1960
- Subjects: Church and education -- South Africa , Church of England -- Education -- South Africa , Education -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1978 , http://hdl.handle.net/10962/d1013055
- Description: In his "Onderwys in Kaapland, 1652 - 1939", Dr. P.S. du Toit makes special references to the educational work of the Anglican Church, indicating that there is some contribution. This attitude has as its aim to expose more of the reef of which the outcrops receive attention by Dr. du Toit ... much can happen between 1807 and 1829, and some of what did is described in these pages. One of Dr. du Toit's interests is the effect of the attempt to make English and instruction in English the basis of all education. Chap. 1, p. 1.
- Full Text:
- Date Issued: 1960