Comparative photosensitised transformation of polychlorophenols with different sulphonated metallophthalocyanine complexes in aqueous medium
- Ozoemena, Kenneth, Kuznetsova, Nina, Nyokong, Tebello
- Authors: Ozoemena, Kenneth , Kuznetsova, Nina , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/291520 , vital:56883 , xlink:href="https://doi.org/10.1016/S1381-1169(01)00243-6"
- Description: The relative efficiencies for the oxidation of trichlorophenol (TCP) and pentachlorophenol (PCP), sensitised by sulphonated phthalocyanine complexes containing Zn, Al, Sn and Si as central metals, were studied in aqueous solutions. For the first time, sulphonated silicon and tin phthalocyanines were synthesised and their activity towards photosensitisation of singlet oxygen and photo-oxidation of polychlorophenols was examined. The efficiency of the sensitised photo-oxidative degradation of polychlorophenols depends not only on singlet oxygen quantum yield of sensitiser, but also on its stability. The influence of substrate structure and the pH of the solution on the photo-oxidation efficiency, as well as on the sensitiser photodegradation were studied. It was found that the contribution of the Type II (singlet oxygen-mediated) mechanism to the relative efficiency of the photosensitised photo-oxidation of the phenol, decreased from phenol to p-chlorophenol, TCP and PCP, whereas Type I radical pathway increased. The results obtained for PCP give evidence that electron transfer from the excited sensitiser to the substrate in its unionised form is responsible for enhanced sensitiser photodegradation.
- Full Text:
- Date Issued: 2001
- Authors: Ozoemena, Kenneth , Kuznetsova, Nina , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/291520 , vital:56883 , xlink:href="https://doi.org/10.1016/S1381-1169(01)00243-6"
- Description: The relative efficiencies for the oxidation of trichlorophenol (TCP) and pentachlorophenol (PCP), sensitised by sulphonated phthalocyanine complexes containing Zn, Al, Sn and Si as central metals, were studied in aqueous solutions. For the first time, sulphonated silicon and tin phthalocyanines were synthesised and their activity towards photosensitisation of singlet oxygen and photo-oxidation of polychlorophenols was examined. The efficiency of the sensitised photo-oxidative degradation of polychlorophenols depends not only on singlet oxygen quantum yield of sensitiser, but also on its stability. The influence of substrate structure and the pH of the solution on the photo-oxidation efficiency, as well as on the sensitiser photodegradation were studied. It was found that the contribution of the Type II (singlet oxygen-mediated) mechanism to the relative efficiency of the photosensitised photo-oxidation of the phenol, decreased from phenol to p-chlorophenol, TCP and PCP, whereas Type I radical pathway increased. The results obtained for PCP give evidence that electron transfer from the excited sensitiser to the substrate in its unionised form is responsible for enhanced sensitiser photodegradation.
- Full Text:
- Date Issued: 2001
Comparison of extent and transformation of South Africa’s woodland biome from two national databases
- Thompson, M W, Vink, E R, Fairbanks, D H K, Ballance, A, Shackleton, Charlie M
- Authors: Thompson, M W , Vink, E R , Fairbanks, D H K , Ballance, A , Shackleton, Charlie M
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6661 , http://hdl.handle.net/10962/d1007085
- Description: [From introduction] The recent completion of the South African National Land-Cover Database and the Vegetation Map of South Africa, Swaziland and Lesotho, allows for the first time a comparison to be made on a national scale between the current and potential distribution of ‘natural’ vegetation resources. This article compares the distribution and location of woodland-type vegetation categories defined within the National Land-Cover data and the equivalent ‘Savanna-thicket Biomes’ class defined within the Vegetation Mapdata. Significant differences were found, both in terms of the total areal extent, as well as the actual spatial distribution of these two data sets. These differences are a measure of the inherent mapping accuracies of each source, but rather an illustration of boundary delineation distinctions that are a result of different data sources, mapping objectives and information classes, that must be noted when comparing two essentially similar information sets.
- Full Text:
- Date Issued: 2001
Comparison of extent and transformation of South Africa’s woodland biome from two national databases
- Authors: Thompson, M W , Vink, E R , Fairbanks, D H K , Ballance, A , Shackleton, Charlie M
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6661 , http://hdl.handle.net/10962/d1007085
- Description: [From introduction] The recent completion of the South African National Land-Cover Database and the Vegetation Map of South Africa, Swaziland and Lesotho, allows for the first time a comparison to be made on a national scale between the current and potential distribution of ‘natural’ vegetation resources. This article compares the distribution and location of woodland-type vegetation categories defined within the National Land-Cover data and the equivalent ‘Savanna-thicket Biomes’ class defined within the Vegetation Mapdata. Significant differences were found, both in terms of the total areal extent, as well as the actual spatial distribution of these two data sets. These differences are a measure of the inherent mapping accuracies of each source, but rather an illustration of boundary delineation distinctions that are a result of different data sources, mapping objectives and information classes, that must be noted when comparing two essentially similar information sets.
- Full Text:
- Date Issued: 2001
Configuring convergence : southern African websites looking at American experience
- Authors: Berger, Guy
- Date: 2001
- Language: English
- Type: text
- Identifier: vital:535 , http://hdl.handle.net/10962/d1008553 , ISBN 0-86810-379-9
- Description: I want the Web to win. Africa’s news sites on the Internet need to succeed and survive. They’re a small guarantee against global marginalisation, and a critical intersection across our continent’s domestic divides. But the outlook is not good. At a conference I went to in Berkeley in April 2001, a venture capitalist had this to say: "If I were to make a speech on when there’ll be investment in new media again, it would be a rather short topic." The alarming closures and retrenchments at news websites in the USA are sending scary signals to our fledgling efforts back here. Starting and growing media enterprises of any sort in African conditions has never been easy. Long starved of investment, our cyberpublishing now faces even greater pressures as old media – newspapers, radio and TV – try to make ends meet under mounting threats. Advertising is shrinking, local costs are rising and currency falls are fuelling the price of imported production factors. Consumers have less cash to spend. Governments are giving even greater problems in some cases. Will we still be here in the morning, and in what condition? This booklet suggests the way forward is for new media to converge with selected partners, old media and new.
- Full Text:
- Date Issued: 2001
- Authors: Berger, Guy
- Date: 2001
- Language: English
- Type: text
- Identifier: vital:535 , http://hdl.handle.net/10962/d1008553 , ISBN 0-86810-379-9
- Description: I want the Web to win. Africa’s news sites on the Internet need to succeed and survive. They’re a small guarantee against global marginalisation, and a critical intersection across our continent’s domestic divides. But the outlook is not good. At a conference I went to in Berkeley in April 2001, a venture capitalist had this to say: "If I were to make a speech on when there’ll be investment in new media again, it would be a rather short topic." The alarming closures and retrenchments at news websites in the USA are sending scary signals to our fledgling efforts back here. Starting and growing media enterprises of any sort in African conditions has never been easy. Long starved of investment, our cyberpublishing now faces even greater pressures as old media – newspapers, radio and TV – try to make ends meet under mounting threats. Advertising is shrinking, local costs are rising and currency falls are fuelling the price of imported production factors. Consumers have less cash to spend. Governments are giving even greater problems in some cases. Will we still be here in the morning, and in what condition? This booklet suggests the way forward is for new media to converge with selected partners, old media and new.
- Full Text:
- Date Issued: 2001
Confronting the African nightmare: Yael Farber’s SeZaR (theatre review)
- Authors: Wright, Laurence
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:7046 , http://hdl.handle.net/10962/d1007388
- Description: Yael Farber’s adaptation of Julius Caesar marks something of a breakthrough in South African Shakespeare productions. The key achievement is that the play is no longer about Rome or Renaissance England, nor is it about processes of cultural translation or trendy theatrical Africanisation, largely cosmetic. This production is, in a generous way, squarely and pointedly about Africa.
- Full Text:
- Date Issued: 2001
- Authors: Wright, Laurence
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:7046 , http://hdl.handle.net/10962/d1007388
- Description: Yael Farber’s adaptation of Julius Caesar marks something of a breakthrough in South African Shakespeare productions. The key achievement is that the play is no longer about Rome or Renaissance England, nor is it about processes of cultural translation or trendy theatrical Africanisation, largely cosmetic. This production is, in a generous way, squarely and pointedly about Africa.
- Full Text:
- Date Issued: 2001
Consideration of the effect of nutritional status and disease patterns on the work output amongst Black South African workers involved in manual materials handling (MMH) tasks
- Authors: Christie, Candice J
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6746 , http://hdl.handle.net/10962/d1009315
- Description: The prevalence of malnutrition amongst low-income earning South Africans has been well documented and is reported to be particularly high amongst Black South African males. This, combined with poor living conditions associated with their poor socio-economic status, results in an increased prevalence of infectious diseases amongst this sector of the population. Additionally, Black South African males are most often employed by companies requiring them to carry out heavy manual materials handling tasks. It would appear that limited research has focused on the relationship between inadequate dietary intake combined with poor health status and the impact this may have on the performance of manual workers. Energy intake is in all probability considerably less than energy expenditure.
- Full Text:
- Date Issued: 2001
- Authors: Christie, Candice J
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6746 , http://hdl.handle.net/10962/d1009315
- Description: The prevalence of malnutrition amongst low-income earning South Africans has been well documented and is reported to be particularly high amongst Black South African males. This, combined with poor living conditions associated with their poor socio-economic status, results in an increased prevalence of infectious diseases amongst this sector of the population. Additionally, Black South African males are most often employed by companies requiring them to carry out heavy manual materials handling tasks. It would appear that limited research has focused on the relationship between inadequate dietary intake combined with poor health status and the impact this may have on the performance of manual workers. Energy intake is in all probability considerably less than energy expenditure.
- Full Text:
- Date Issued: 2001
Construction and characterization of carbon paste ultra-microelectrodes
- Oni, Joshua, Westbroek, Philippe, Nyokong, Tebello
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/291531 , vital:56884 , xlink:href="https://doi.org/10.1016/S1388-2481(01)00212-0"
- Description: The construction and characterization of carbon paste ultra-microelectrodes is reported. Besides a disc-shaped electrode, a carbon paste band electrode is studied. It was found that for both electrode configurations steady-state currents were obtained but that with the type of electrode material used for the band electrode, the upper limit of ultra-microelectrode dimensions, which could be used was 100–150 μm. Smaller dimensions for the band electrodes resulted in a high resistance due to the limited conductivity of the carbon paste, when using the optimal paste composition. With cyclic voltammetry, the oxidation of [Fe(CN)6]4− was studied at individual constructed electrodes and at ensembles of individual electrodes. Detection limits of less than 10−6moll−1 were obtained. Using the data of the same curves it was possible to test if the electrodes have errors and about 20% of the constructed electrodes did not pass this test. Finally it was found that these electrodes show good stability.
- Full Text:
- Date Issued: 2001
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/291531 , vital:56884 , xlink:href="https://doi.org/10.1016/S1388-2481(01)00212-0"
- Description: The construction and characterization of carbon paste ultra-microelectrodes is reported. Besides a disc-shaped electrode, a carbon paste band electrode is studied. It was found that for both electrode configurations steady-state currents were obtained but that with the type of electrode material used for the band electrode, the upper limit of ultra-microelectrode dimensions, which could be used was 100–150 μm. Smaller dimensions for the band electrodes resulted in a high resistance due to the limited conductivity of the carbon paste, when using the optimal paste composition. With cyclic voltammetry, the oxidation of [Fe(CN)6]4− was studied at individual constructed electrodes and at ensembles of individual electrodes. Detection limits of less than 10−6moll−1 were obtained. Using the data of the same curves it was possible to test if the electrodes have errors and about 20% of the constructed electrodes did not pass this test. Finally it was found that these electrodes show good stability.
- Full Text:
- Date Issued: 2001
Continuity and change in Xhosa historiography during the nineteenth century : an exploration through textual analysis
- Tisani, Nomathamsanqa Cynthia
- Authors: Tisani, Nomathamsanqa Cynthia
- Date: 2001
- Subjects: Xhosa (African people) -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2563 , http://hdl.handle.net/10962/d1002416
- Description: This study is an exploration of the making of Xhosa historiography from the end of the eighteenth century to the close of the nineteenth century. Continuity and change are key features that are identifiable in the writing of Xhosa history over the period. Selected documents provide evidence on how different writers built on the works of their predecessors. At the same time, over a period of hundred years, due to changing socio-political contexts, new ideas and perceptions crept into Xhosa history. European writers, who dominated the writing of Xhosa history, were made up of colonial officials, missionaries, and travellers. Sharing a common European Christian background these writers brought along their particular understanding of history, and held assumptions about the indigenous people and their past. However such assumptions were always in a state of flux. South-east Africans were also major contributors to the making of Xhosa history. Their oral traditions were important sources from which Xhosa history was produced. The African and European encounter in the making of Xhosa history meanHhat historioracy and historiography came together in the production of Xhosa history. At the end of the eighteenth century there were a handful of European travellers who explored the interior of southern Africa and recorded their observations of indigenous communities. These observations of south-east Africans, whom they divided into three racial groups, formed the basis of later writings about the indigenous communiti~s. The beginning of the nineteenth century brought the establishment of British rule at the C,ppe. This introduced new players into the African-European drama that was being acted out on the frontier. Colonial officials set out to inform themselves about the indigenous people, and this meant writing up their history. From the 1820s missionaries were a main source of information on amaXhosa. Xhosa history produced under the missionary influence included works by African converts, among whom Noyi was the most noteworthy. As British imperialism gained ground from the middle of the nineteenth century, history was increasingly used by British officials as a tool to justify their colonial expansion. Under Governor Grey there was a deliberate production of a Xhosa history that depicted amaXhosa as having a barbaric past and in need of civilisation. Theal who consulted Dutch and British archives as well as oral tradition made a major contribution to the writing of Xhosa history. But Theal later began to select evidence to show that amaXhosa were recent immigrants into southeast Africa. During the last quarter ofthe nineteenth century a band of literate Africans, using newspapers like Isigidimi and later Imvo Zabantsundu, embarked on writing African history. This study highlights the development of certain themes in Xhosa history, themes which remained central in later years. The royal theme became pivotal and in the process displaced other histories in African communities, like clan histories. This study has also traced the roots of some historical myths. For example claims by early travellers about an empty land fed into the migration theme which sought to explain amaXhosa as recent immigrants into south-east Africa. Xhosa historiography, just like its European counterpart, marginalised ordinary people, especially women, and became primarily an account of the lives and activities of ruling men.
- Full Text:
- Date Issued: 2001
- Authors: Tisani, Nomathamsanqa Cynthia
- Date: 2001
- Subjects: Xhosa (African people) -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2563 , http://hdl.handle.net/10962/d1002416
- Description: This study is an exploration of the making of Xhosa historiography from the end of the eighteenth century to the close of the nineteenth century. Continuity and change are key features that are identifiable in the writing of Xhosa history over the period. Selected documents provide evidence on how different writers built on the works of their predecessors. At the same time, over a period of hundred years, due to changing socio-political contexts, new ideas and perceptions crept into Xhosa history. European writers, who dominated the writing of Xhosa history, were made up of colonial officials, missionaries, and travellers. Sharing a common European Christian background these writers brought along their particular understanding of history, and held assumptions about the indigenous people and their past. However such assumptions were always in a state of flux. South-east Africans were also major contributors to the making of Xhosa history. Their oral traditions were important sources from which Xhosa history was produced. The African and European encounter in the making of Xhosa history meanHhat historioracy and historiography came together in the production of Xhosa history. At the end of the eighteenth century there were a handful of European travellers who explored the interior of southern Africa and recorded their observations of indigenous communities. These observations of south-east Africans, whom they divided into three racial groups, formed the basis of later writings about the indigenous communiti~s. The beginning of the nineteenth century brought the establishment of British rule at the C,ppe. This introduced new players into the African-European drama that was being acted out on the frontier. Colonial officials set out to inform themselves about the indigenous people, and this meant writing up their history. From the 1820s missionaries were a main source of information on amaXhosa. Xhosa history produced under the missionary influence included works by African converts, among whom Noyi was the most noteworthy. As British imperialism gained ground from the middle of the nineteenth century, history was increasingly used by British officials as a tool to justify their colonial expansion. Under Governor Grey there was a deliberate production of a Xhosa history that depicted amaXhosa as having a barbaric past and in need of civilisation. Theal who consulted Dutch and British archives as well as oral tradition made a major contribution to the writing of Xhosa history. But Theal later began to select evidence to show that amaXhosa were recent immigrants into southeast Africa. During the last quarter ofthe nineteenth century a band of literate Africans, using newspapers like Isigidimi and later Imvo Zabantsundu, embarked on writing African history. This study highlights the development of certain themes in Xhosa history, themes which remained central in later years. The royal theme became pivotal and in the process displaced other histories in African communities, like clan histories. This study has also traced the roots of some historical myths. For example claims by early travellers about an empty land fed into the migration theme which sought to explain amaXhosa as recent immigrants into south-east Africa. Xhosa historiography, just like its European counterpart, marginalised ordinary people, especially women, and became primarily an account of the lives and activities of ruling men.
- Full Text:
- Date Issued: 2001
Credit accessibility and rural development in the former Ciskei: an overview of Keiskammahoek
- Authors: Kimemia, Peter Njau
- Date: 2001
- Subjects: Credit -- Research -- South Africa -- Ciskei , Rural development -- South Africa -- Ciskei , Poor -- South Africa -- Ciskei , Poor -- Developing countries
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3312 , http://hdl.handle.net/10962/d1003100 , Credit -- Research -- South Africa -- Ciskei , Rural development -- South Africa -- Ciskei , Poor -- South Africa -- Ciskei , Poor -- Developing countries
- Description: This study focuses on the issue of credit accessibility for the rural poor. Taking cognisance of the critical role played by innovative micro-lending mechanisms in the sphere of rural development, the study reaffirms the need to enhance access to financial services by rural communities. However, it also reveals the fact that there are numerous impediments to access to credit for the people living in parts of the Keiskammahoek District of the former Ciskei. Key among the impediments has been lack of awareness about the existence and the activities of micro-lending institutions. This has, in a large measure been blamed for many of the rural poor people's failure to approach such institutions for funding. As a result, the affected people's efforts to fully actualize themselves economically have to a certain extent been hampered. Consequently, as its core argument, this study views as crucial the need to tackle all the attendant impediments. It also suggests that as the first step, the government, NGOs as well as formal and informal lending institutions should endeavour to disseminate the requisite information on micro-financing and in enhancing the affected people's institutional capacity to effectively use credit obtained for commercially productive ventures. Without sorting out the basics first, credit extension even when easily availed may not have the desired impact. At worst, it may actually complicate the poverty situation as the people grapple with piling debts.
- Full Text:
- Date Issued: 2001
- Authors: Kimemia, Peter Njau
- Date: 2001
- Subjects: Credit -- Research -- South Africa -- Ciskei , Rural development -- South Africa -- Ciskei , Poor -- South Africa -- Ciskei , Poor -- Developing countries
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3312 , http://hdl.handle.net/10962/d1003100 , Credit -- Research -- South Africa -- Ciskei , Rural development -- South Africa -- Ciskei , Poor -- South Africa -- Ciskei , Poor -- Developing countries
- Description: This study focuses on the issue of credit accessibility for the rural poor. Taking cognisance of the critical role played by innovative micro-lending mechanisms in the sphere of rural development, the study reaffirms the need to enhance access to financial services by rural communities. However, it also reveals the fact that there are numerous impediments to access to credit for the people living in parts of the Keiskammahoek District of the former Ciskei. Key among the impediments has been lack of awareness about the existence and the activities of micro-lending institutions. This has, in a large measure been blamed for many of the rural poor people's failure to approach such institutions for funding. As a result, the affected people's efforts to fully actualize themselves economically have to a certain extent been hampered. Consequently, as its core argument, this study views as crucial the need to tackle all the attendant impediments. It also suggests that as the first step, the government, NGOs as well as formal and informal lending institutions should endeavour to disseminate the requisite information on micro-financing and in enhancing the affected people's institutional capacity to effectively use credit obtained for commercially productive ventures. Without sorting out the basics first, credit extension even when easily availed may not have the desired impact. At worst, it may actually complicate the poverty situation as the people grapple with piling debts.
- Full Text:
- Date Issued: 2001
Cumulative mild head injury in rugby: a comparison of cognitive deficit and postconcussive symptomatology between schoolboy rugby players and non-contact sport controls
- Authors: Beilinsohn, Taryn
- Date: 2001
- Subjects: Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2931 , http://hdl.handle.net/10962/d1002440 , Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Description: This study investigates the cumulative effects of concussive and subconcussive mild head injury on the cognitive functioning of schoolboy rugby players. A comprehensive battery of neuropsychological tests and a self-report postconcussive questionnaire were administered to top level schoolboy rugby players (n=47), and a non-contact sport control group of top level schoolboy hockey players (n=34). Group comparisons of the percentage of individuals with cognitive deficit were carried out between i) the schoolboy rugby and the schoolboy hockey players, ii) the rugby forward and the rugby backline players; iii) the rugby forward and the schoolboy hockey players and, iv) the rugby backline and the schoolboy hockey players. Results on the neuropsychological test battery did not provide any substantial evidence of a higher level of neuropsychological impairment in the rugby players relative to the control group, or in the rugby forward players relative to the rugby backline players. Results obtained on the postconcussive symptom questionnaire provided tentative indications that the rugby players do report a greater frequency of postconcussive symptomatology. The symptoms most frequently reported were being easily angered, memory problems, clumsy speech and sleep difficulties. It was hypothesized that the absence of cognitive impairment in the schoolboy rugby players compared with that noted for professional players was due to their younger age, relatively high IQ and education level and a less intensive level of physical participation in the sport, and hence less accumulated exposure to the game, thereby decreasing their exposure to mild head injuries. From a theoretical perspective, these pre-existing conditions were considered to act as protective factors against reductions in brain reserve capacity and concomitant susceptibility to the onset of neuropsychological dysfunction.
- Full Text:
- Date Issued: 2001
- Authors: Beilinsohn, Taryn
- Date: 2001
- Subjects: Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2931 , http://hdl.handle.net/10962/d1002440 , Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Description: This study investigates the cumulative effects of concussive and subconcussive mild head injury on the cognitive functioning of schoolboy rugby players. A comprehensive battery of neuropsychological tests and a self-report postconcussive questionnaire were administered to top level schoolboy rugby players (n=47), and a non-contact sport control group of top level schoolboy hockey players (n=34). Group comparisons of the percentage of individuals with cognitive deficit were carried out between i) the schoolboy rugby and the schoolboy hockey players, ii) the rugby forward and the rugby backline players; iii) the rugby forward and the schoolboy hockey players and, iv) the rugby backline and the schoolboy hockey players. Results on the neuropsychological test battery did not provide any substantial evidence of a higher level of neuropsychological impairment in the rugby players relative to the control group, or in the rugby forward players relative to the rugby backline players. Results obtained on the postconcussive symptom questionnaire provided tentative indications that the rugby players do report a greater frequency of postconcussive symptomatology. The symptoms most frequently reported were being easily angered, memory problems, clumsy speech and sleep difficulties. It was hypothesized that the absence of cognitive impairment in the schoolboy rugby players compared with that noted for professional players was due to their younger age, relatively high IQ and education level and a less intensive level of physical participation in the sport, and hence less accumulated exposure to the game, thereby decreasing their exposure to mild head injuries. From a theoretical perspective, these pre-existing conditions were considered to act as protective factors against reductions in brain reserve capacity and concomitant susceptibility to the onset of neuropsychological dysfunction.
- Full Text:
- Date Issued: 2001
Deconstructing the Transvaal Supergroup, South Africa: implications for Palaeoproterozoic palaeoclimate models
- Moore, John M, Tsikos, Harilaos, Polteau, S
- Authors: Moore, John M , Tsikos, Harilaos , Polteau, S
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6078 , http://hdl.handle.net/10962/d1006122
- Description: Current correlations between the Pretoria and Postmasburg Groups of the Transvaal Supergroup are shown to be invalid. The Postmasburg Group is also demonstrated to be broadly conformable with the underlying Ghaap Group and therefore considerably older (~2.4 Ga) than previously supposed. The new stratigraphy documents an extensive (100 Ma) and continuous cold-climate episode with a glacial maximum at the Makganyene Formation diamictite. Iron formations of the underlying Asbesheuwels and Koegas Subgroups and overlying Hotazel Formation have similar origins, related, respectively, to the onset and cessation of the glacial event. This interpretation of the Transvaal Supergroup stratigraphy has significant implications for various Palaeoproterozoic environmental models and for the timing of the development of an oxygenated atmosphere.
- Full Text:
- Date Issued: 2001
- Authors: Moore, John M , Tsikos, Harilaos , Polteau, S
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6078 , http://hdl.handle.net/10962/d1006122
- Description: Current correlations between the Pretoria and Postmasburg Groups of the Transvaal Supergroup are shown to be invalid. The Postmasburg Group is also demonstrated to be broadly conformable with the underlying Ghaap Group and therefore considerably older (~2.4 Ga) than previously supposed. The new stratigraphy documents an extensive (100 Ma) and continuous cold-climate episode with a glacial maximum at the Makganyene Formation diamictite. Iron formations of the underlying Asbesheuwels and Koegas Subgroups and overlying Hotazel Formation have similar origins, related, respectively, to the onset and cessation of the glacial event. This interpretation of the Transvaal Supergroup stratigraphy has significant implications for various Palaeoproterozoic environmental models and for the timing of the development of an oxygenated atmosphere.
- Full Text:
- Date Issued: 2001
Design and positioning of controls : the old and the new industrial approaches
- Authors: Dirkse van Schalkwyk, C J
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6750 , http://hdl.handle.net/10962/d1009330
- Description: While copious amounts of research exist with regard to positioning of controls, very little research covers the design shape of the controls. This paper demonstrates the importance of control positioning and design within industrial settings. Furthermore it aims to highlight the changes in industries with regard to control design and positioning. This paper is a review paper and thus much is based on findings by other authors. However, the changes in the industrial practices referred to by the author are from knowledge gained while visiting numerous industries in South Africa.
- Full Text:
- Date Issued: 2001
- Authors: Dirkse van Schalkwyk, C J
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6750 , http://hdl.handle.net/10962/d1009330
- Description: While copious amounts of research exist with regard to positioning of controls, very little research covers the design shape of the controls. This paper demonstrates the importance of control positioning and design within industrial settings. Furthermore it aims to highlight the changes in industries with regard to control design and positioning. This paper is a review paper and thus much is based on findings by other authors. However, the changes in the industrial practices referred to by the author are from knowledge gained while visiting numerous industries in South Africa.
- Full Text:
- Date Issued: 2001
Design, synthesis and characterization of novel rhenium(V) and technetium(V) complexes as potential radiopharmaceuticals
- Authors: Hlabela, Patrick Simon
- Date: 2001
- Subjects: Radiopharmaceuticals , Rhenium , Technetium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4306 , http://hdl.handle.net/10962/d1004964 , Radiopharmaceuticals , Rhenium , Technetium
- Description: A number of bidentate N, N-diethyl-N' -(R ')benzoylthiourea ligands (where R' = H,CH₃,CI,OCH₃ and N0₂) have been synthesized, as well as the three Re(V) precursor complexes, ReOCl₃(PPh₃)₂,[ReO₂(py)₄]CI and [n-Bu₄N] [ReOCI₄J. The reaction of N,N-diethyl-N'-benzoylthiourea (LH) with these three metal precursor complexes in methanol in the presence of a base gave a novel mixed-ligand complex bis(N,N-diethyl-N'-benzoylthioureato)methoxyoxorhenium(V), [ReO(L)₂(OMe)] (1). In the absence of a base and under an inert atmosphere, the reaction between [n-Bu₄N][ReOCI₄] and LH yielded bis(N,N-diethyl-N'-benzoylthioureato)chlorooxorhenium(V), [ReO(L)₂CI] (lb). The reaction of LH with [ReO₂(py)₄]CI in ethanol and iso-propanol in the presence of sodium acetate gave the novel mixed ligand complexes bis(N,N-diethyl-N'benzoylthioureato) ethoxyoxorhenium(V), [ReO(L)₂(OEt)] (6) and bis(N,N-diethyl-N'benzoylthioureato)(iso-propoxy)oxorhenium(V), [ReO(L)₂(OiPr)] (7), respectively. An oxygen bridged dirhenium complex, [(L)₂0Re-O-ReO(L)₂] (15) was obtained when the reaction was carried out in acetonitrile. A series of mixed ligand Re(V)-oxo complexes using N, N-diethyl-Nʾ-(R' )benzoylthiourea (LR'),N,N-morpholino-N' -(R')benzoylthiourea (morph-LR') and 8-(N-(R')benzoylthiocarbamoyl)-1,4-dioxa-8-azaspiro[4.5]decane ligands (spiro-LR') (where R' = H,CH₃,CI, OCH₃ and N0₂) ((1)(14) have been prepared by the reaction of [ReO₂(py)₄]CI and the ligand in the presence of sodium acetate in methanol. The solution state chemistry of these complexes has shown that complexes(1)-(14) (with the exception of (1b)) undergo dimerization in solution to give complex (15) in the presence of water. Preliminary ¹H NMR kinetics studies of the dimerization of (1), (6) and (7) to (15) have shown that the rate of dimerization decreases in the order (7) > (6) > (1). The rate of dimerization has also been compared for complexes (1), [ReO(morph-L)₂(OMe)] (8) and [ReO(spiro-L)₂(OMe)] (13) and the rate of dimerization was found to be fastest for (13). The crystal structures of (1), [ReO(LN0₂)₂(OMe)] (4), (6) and (15) have been determined. The Re(V)-oxo complexes (1), (4) and (6) have a slightly distorted octahedral geometry with the two acylthiourea ligands binding in a cis arrangement in the equatorial plane of the octahedron. The alkoxy and oxo ligands occupy the axial positions and are situated trans to each other. The crystal and molecular structure of complex (15), consist of two slightly distorted octahedral [ReO(L)₂] moieties bridged by an oxygen atom with a Re-O-Re bond angle of 175.2(2)°. The preliminary studies done in the present study have indicated that the complexation chemistry of technetium(V) with the N,N-diethyl-benzoylthiourea is different to that of rhenium (V). The reaction between [n-BuN₄][TcOCl₄] and N,N-diethyl-N'-benzoylthiourea yielded the square pyramidal cationic complex [TcO(L)₂]Cl. By contrast the octahedral methoxy complex [ReO(L )₂( OMe)] was obtained when the analogous Re(V)-oxo precursor, [n-Bu₄N] [ReOCI₄], was reacted with N,N-diethyl-N'-benzoylthiourea under the same reaction conditions.
- Full Text:
- Date Issued: 2001
- Authors: Hlabela, Patrick Simon
- Date: 2001
- Subjects: Radiopharmaceuticals , Rhenium , Technetium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4306 , http://hdl.handle.net/10962/d1004964 , Radiopharmaceuticals , Rhenium , Technetium
- Description: A number of bidentate N, N-diethyl-N' -(R ')benzoylthiourea ligands (where R' = H,CH₃,CI,OCH₃ and N0₂) have been synthesized, as well as the three Re(V) precursor complexes, ReOCl₃(PPh₃)₂,[ReO₂(py)₄]CI and [n-Bu₄N] [ReOCI₄J. The reaction of N,N-diethyl-N'-benzoylthiourea (LH) with these three metal precursor complexes in methanol in the presence of a base gave a novel mixed-ligand complex bis(N,N-diethyl-N'-benzoylthioureato)methoxyoxorhenium(V), [ReO(L)₂(OMe)] (1). In the absence of a base and under an inert atmosphere, the reaction between [n-Bu₄N][ReOCI₄] and LH yielded bis(N,N-diethyl-N'-benzoylthioureato)chlorooxorhenium(V), [ReO(L)₂CI] (lb). The reaction of LH with [ReO₂(py)₄]CI in ethanol and iso-propanol in the presence of sodium acetate gave the novel mixed ligand complexes bis(N,N-diethyl-N'benzoylthioureato) ethoxyoxorhenium(V), [ReO(L)₂(OEt)] (6) and bis(N,N-diethyl-N'benzoylthioureato)(iso-propoxy)oxorhenium(V), [ReO(L)₂(OiPr)] (7), respectively. An oxygen bridged dirhenium complex, [(L)₂0Re-O-ReO(L)₂] (15) was obtained when the reaction was carried out in acetonitrile. A series of mixed ligand Re(V)-oxo complexes using N, N-diethyl-Nʾ-(R' )benzoylthiourea (LR'),N,N-morpholino-N' -(R')benzoylthiourea (morph-LR') and 8-(N-(R')benzoylthiocarbamoyl)-1,4-dioxa-8-azaspiro[4.5]decane ligands (spiro-LR') (where R' = H,CH₃,CI, OCH₃ and N0₂) ((1)(14) have been prepared by the reaction of [ReO₂(py)₄]CI and the ligand in the presence of sodium acetate in methanol. The solution state chemistry of these complexes has shown that complexes(1)-(14) (with the exception of (1b)) undergo dimerization in solution to give complex (15) in the presence of water. Preliminary ¹H NMR kinetics studies of the dimerization of (1), (6) and (7) to (15) have shown that the rate of dimerization decreases in the order (7) > (6) > (1). The rate of dimerization has also been compared for complexes (1), [ReO(morph-L)₂(OMe)] (8) and [ReO(spiro-L)₂(OMe)] (13) and the rate of dimerization was found to be fastest for (13). The crystal structures of (1), [ReO(LN0₂)₂(OMe)] (4), (6) and (15) have been determined. The Re(V)-oxo complexes (1), (4) and (6) have a slightly distorted octahedral geometry with the two acylthiourea ligands binding in a cis arrangement in the equatorial plane of the octahedron. The alkoxy and oxo ligands occupy the axial positions and are situated trans to each other. The crystal and molecular structure of complex (15), consist of two slightly distorted octahedral [ReO(L)₂] moieties bridged by an oxygen atom with a Re-O-Re bond angle of 175.2(2)°. The preliminary studies done in the present study have indicated that the complexation chemistry of technetium(V) with the N,N-diethyl-benzoylthiourea is different to that of rhenium (V). The reaction between [n-BuN₄][TcOCl₄] and N,N-diethyl-N'-benzoylthiourea yielded the square pyramidal cationic complex [TcO(L)₂]Cl. By contrast the octahedral methoxy complex [ReO(L )₂( OMe)] was obtained when the analogous Re(V)-oxo precursor, [n-Bu₄N] [ReOCI₄], was reacted with N,N-diethyl-N'-benzoylthiourea under the same reaction conditions.
- Full Text:
- Date Issued: 2001
Design, synthesis and evaluation of silver-specific ligands
- Authors: Daubinet, André
- Date: 2001
- Subjects: Ligands Ligands -- Design Ligands -- Analysis Ligands -- Evaluation Silver -- Metallurgy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4308 , http://hdl.handle.net/10962/d1004966
- Description: Several series of ligands, designed to chelate silver(I) specifically in the presence of base metals, have been synthesised. The ligands include: - dithiodiamide compounds, prepared by the condensation of acetanilide derivatives with 1,2-dibromoethane; propanenitrile and propanoic ester derivatives prepared from pyridine-2-carbaldehyde via the Morita-Baylis-Hillman reaction; and novel malonamide ligands from the reaction of diethyl malonate with a range of primary amines. The malonamide derivatives were prepared under both conventional thermal and microwave-assisted conditions, the latter proving to be highly efficient. The ligands were all characterised using a combination of spectroscopic and, where appropriate, elemental analysis; in one case, the structural assignment was confirmed by single-crystal X-ray analysis. The fragmentation patterns in the electron-impact mass spectra of the malonamide derivatives have been explored using high-resolution and meta-stable peak scanning techniques. Complexes of the malonamide ligands with copper(II) and silver(I) have been synthesised, and examination of these complexes has revealed distinct differences in their co-ordination preferences towards silver(I) and copper(II). Tentative, computer-modelled structures for the complexes have been proposed using the available spectroscopic and elemental analysis data. Computer modelling, at the Molecular Mechanics level, has also been used to assess the capacity of the ligand systems to adopt conformations suitable for the chelation of tetrahedral silver(I). Solvent extraction studies have been undertaken using aqueous metal ion solutions and various organic solvents. The dithiodiamide derivatives typically presented solubility problems, but one of the ligands, N,N´-bis(3-chlorophenyl)-3,6-dithiaoctanediamide, exhibited significant but slow extraction of silver(I) into toluene. The malonamide derivatives, however, proved to be readily soluble in ethyl acetate and, in some cases, exhibited good to excellent selectivity for silver(I) in the presence of the base metals copper and lead. Atomic absorption analysis revealed rapid equilibration times (<15 min) and high extraction efficiencies over a wide pH range (2.78 - 9.0). Metal selectivity has been determined by ICP-MS analysis of the residual silver, copper and lead present in the aqueous phase after 15 min, and one of the ligands, N,N´-bis(2-benzylsulfanylethyl)malonamide, exhibits excellent (≥ 96 %) silver(I) specificity.
- Full Text:
- Date Issued: 2001
- Authors: Daubinet, André
- Date: 2001
- Subjects: Ligands Ligands -- Design Ligands -- Analysis Ligands -- Evaluation Silver -- Metallurgy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4308 , http://hdl.handle.net/10962/d1004966
- Description: Several series of ligands, designed to chelate silver(I) specifically in the presence of base metals, have been synthesised. The ligands include: - dithiodiamide compounds, prepared by the condensation of acetanilide derivatives with 1,2-dibromoethane; propanenitrile and propanoic ester derivatives prepared from pyridine-2-carbaldehyde via the Morita-Baylis-Hillman reaction; and novel malonamide ligands from the reaction of diethyl malonate with a range of primary amines. The malonamide derivatives were prepared under both conventional thermal and microwave-assisted conditions, the latter proving to be highly efficient. The ligands were all characterised using a combination of spectroscopic and, where appropriate, elemental analysis; in one case, the structural assignment was confirmed by single-crystal X-ray analysis. The fragmentation patterns in the electron-impact mass spectra of the malonamide derivatives have been explored using high-resolution and meta-stable peak scanning techniques. Complexes of the malonamide ligands with copper(II) and silver(I) have been synthesised, and examination of these complexes has revealed distinct differences in their co-ordination preferences towards silver(I) and copper(II). Tentative, computer-modelled structures for the complexes have been proposed using the available spectroscopic and elemental analysis data. Computer modelling, at the Molecular Mechanics level, has also been used to assess the capacity of the ligand systems to adopt conformations suitable for the chelation of tetrahedral silver(I). Solvent extraction studies have been undertaken using aqueous metal ion solutions and various organic solvents. The dithiodiamide derivatives typically presented solubility problems, but one of the ligands, N,N´-bis(3-chlorophenyl)-3,6-dithiaoctanediamide, exhibited significant but slow extraction of silver(I) into toluene. The malonamide derivatives, however, proved to be readily soluble in ethyl acetate and, in some cases, exhibited good to excellent selectivity for silver(I) in the presence of the base metals copper and lead. Atomic absorption analysis revealed rapid equilibration times (<15 min) and high extraction efficiencies over a wide pH range (2.78 - 9.0). Metal selectivity has been determined by ICP-MS analysis of the residual silver, copper and lead present in the aqueous phase after 15 min, and one of the ligands, N,N´-bis(2-benzylsulfanylethyl)malonamide, exhibits excellent (≥ 96 %) silver(I) specificity.
- Full Text:
- Date Issued: 2001
Determining the use of human capital to achieve a competitive advantage in the National Ports Authority of South Africa
- Authors: Du Preez, Ian Justus
- Date: 2001
- Subjects: Portnet (South Africa) , Human capital -- South Africa , Personnel management -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10848 , http://hdl.handle.net/10948/50 , Portnet (South Africa) , Human capital -- South Africa , Personnel management -- South Africa
- Description: A new business world is emerging, which every organisation must appreciate and know how to exploit. The concepts of strategy do not need to be rewritten, but must be adapted to this new era. Utilisation of the Internet and human capital to its fullest is transforming the way that business is conducted in achieving its objectives. The key to an organisation’s competitive advantage, is to invest in training, skills enhancement and the personal development of its staff. A requirement of the National Ports Authority is to be committed to basic adult education and preparing employees for re-skilling from the shop floor to the boardroom to ensure it is seen as an equal opportunity employer. The research problem addressed in this study was to determine the factors necessary to achieve strategic advantage using human capital. Relevant literature was used to develop a new model to address some of the issues facing the organisation, as well as ensuring that the National Ports Authority can leverage itself into a competitive advantage. To manage and measure knowledge-based resources is one of the most important challenges for a modern company. This challenge is incorporated in the new model developed by the study. The theoretical model consisted of various factors, which were analysed and formed into principles which were identifiable from the literature study. This model was then used to compile a questionnaire to test the responsiveness of the role players concurring. The empirical results analysed indicated that the respondents concurred with the theoretical study and factors of the new model that was developed.
- Full Text:
- Date Issued: 2001
- Authors: Du Preez, Ian Justus
- Date: 2001
- Subjects: Portnet (South Africa) , Human capital -- South Africa , Personnel management -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10848 , http://hdl.handle.net/10948/50 , Portnet (South Africa) , Human capital -- South Africa , Personnel management -- South Africa
- Description: A new business world is emerging, which every organisation must appreciate and know how to exploit. The concepts of strategy do not need to be rewritten, but must be adapted to this new era. Utilisation of the Internet and human capital to its fullest is transforming the way that business is conducted in achieving its objectives. The key to an organisation’s competitive advantage, is to invest in training, skills enhancement and the personal development of its staff. A requirement of the National Ports Authority is to be committed to basic adult education and preparing employees for re-skilling from the shop floor to the boardroom to ensure it is seen as an equal opportunity employer. The research problem addressed in this study was to determine the factors necessary to achieve strategic advantage using human capital. Relevant literature was used to develop a new model to address some of the issues facing the organisation, as well as ensuring that the National Ports Authority can leverage itself into a competitive advantage. To manage and measure knowledge-based resources is one of the most important challenges for a modern company. This challenge is incorporated in the new model developed by the study. The theoretical model consisted of various factors, which were analysed and formed into principles which were identifiable from the literature study. This model was then used to compile a questionnaire to test the responsiveness of the role players concurring. The empirical results analysed indicated that the respondents concurred with the theoretical study and factors of the new model that was developed.
- Full Text:
- Date Issued: 2001
Development of effective solutions for the implementation and management of owner-driver schemes in the Province of the Eastern Cape
- Authors: Ranchod, Sanjiv
- Date: 2001
- Subjects: Transportation, Automotive -- Dispatching , Small business -- Management Case studies , Storage and removal trade -- Subcontracting -- South Africa , Trucking -- South Africa , Contracting out -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10891 , http://hdl.handle.net/10948/55 , Transportation, Automotive -- Dispatching , Small business -- Management Case studies , Storage and removal trade -- Subcontracting -- South Africa , Trucking -- South Africa , Contracting out -- South Africa
- Description: Introduction: During the past decade, companies have examined their core business, and anything that was not related to this, or did not add value to their product, was outsourced. One of the functions which fell into this category was the distribution operation, or more commonly known as transportation (in and out bound). In many instances, the distribution function was given up for tender, and specialised transport businesses, called third party logistic providers, whose core business was transport, were given the opportunity of taking over the distribution function. Some progressive companies went a little beyond the traditional approach and created opportunities for their own employees to be involved in the newly created, outsourced distribution network. This was largely an empowerment opportunity, with the aim of creating SME’s (Small-Medium-Enterprises), and providing people from a previously disadvantaged background (black people and other ethnic minorities) the opportunity to go into a business enterprise for themselves. The latter, although, politically the correct thing to do, simultaneously created opportunities and problems. Many of the companies that empowered their own employees, through Owner-Driver schemes, used the driving competency levels as the main criteria for the transition process. The other required skills were often overlooked or ignored. This empowerment process was driven to promote “Black Economic Empowerment”, an important national imperative. Although this process was an honorable gesture on the part of many companies, the process often took place without much foresight The viability and long-term continuity of the business were not taken into account. It is the researchers personal view, based on interviews with O-D’s and companies operating O-D schemes that the O-D’s which were empowered to operate their own business ventures, had limited or insufficient business skills and the very businesses that were given to them to improve their lifestyle were at risk of becoming unviable enterprises. This is clearly evident in some of the schemes being operated by companies such as Autonet and South African Breweries (hereinafter referred to as SAB). Other Eastern Cape companies that operate Owner-Driver schemes include Italtile, Shatterprufe and Ready Mix Materials (hereinafter referred to as RMM), and according to Management consultants spoken to, have obtained mixed levels of success with their schemes. The above schemes were confirmed with the various companies mentioned.
- Full Text:
- Date Issued: 2001
- Authors: Ranchod, Sanjiv
- Date: 2001
- Subjects: Transportation, Automotive -- Dispatching , Small business -- Management Case studies , Storage and removal trade -- Subcontracting -- South Africa , Trucking -- South Africa , Contracting out -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10891 , http://hdl.handle.net/10948/55 , Transportation, Automotive -- Dispatching , Small business -- Management Case studies , Storage and removal trade -- Subcontracting -- South Africa , Trucking -- South Africa , Contracting out -- South Africa
- Description: Introduction: During the past decade, companies have examined their core business, and anything that was not related to this, or did not add value to their product, was outsourced. One of the functions which fell into this category was the distribution operation, or more commonly known as transportation (in and out bound). In many instances, the distribution function was given up for tender, and specialised transport businesses, called third party logistic providers, whose core business was transport, were given the opportunity of taking over the distribution function. Some progressive companies went a little beyond the traditional approach and created opportunities for their own employees to be involved in the newly created, outsourced distribution network. This was largely an empowerment opportunity, with the aim of creating SME’s (Small-Medium-Enterprises), and providing people from a previously disadvantaged background (black people and other ethnic minorities) the opportunity to go into a business enterprise for themselves. The latter, although, politically the correct thing to do, simultaneously created opportunities and problems. Many of the companies that empowered their own employees, through Owner-Driver schemes, used the driving competency levels as the main criteria for the transition process. The other required skills were often overlooked or ignored. This empowerment process was driven to promote “Black Economic Empowerment”, an important national imperative. Although this process was an honorable gesture on the part of many companies, the process often took place without much foresight The viability and long-term continuity of the business were not taken into account. It is the researchers personal view, based on interviews with O-D’s and companies operating O-D schemes that the O-D’s which were empowered to operate their own business ventures, had limited or insufficient business skills and the very businesses that were given to them to improve their lifestyle were at risk of becoming unviable enterprises. This is clearly evident in some of the schemes being operated by companies such as Autonet and South African Breweries (hereinafter referred to as SAB). Other Eastern Cape companies that operate Owner-Driver schemes include Italtile, Shatterprufe and Ready Mix Materials (hereinafter referred to as RMM), and according to Management consultants spoken to, have obtained mixed levels of success with their schemes. The above schemes were confirmed with the various companies mentioned.
- Full Text:
- Date Issued: 2001
Ecology and breeding biology of Lanner Falcons in the Eastern Cape Province, South Africa
- Authors: Stephenson, Alan
- Date: 2001
- Subjects: Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5667 , http://hdl.handle.net/10962/d1005352 , Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Description: Lanner Falcons Falco biarmicus are the commonest large falcons in Africa and this study in the coastal area of the Eastern Cape Province, South Africa investigated their ecology from 1984 to 2000. Lanners have recently been categorised as near-threatened and this study was initiated to ascertain if the population was stable. Breeding success of a small population, in different habitat types, was monitored intensively from 1997 to 2000, and the factors that inhibited breeding were investigated. The earliest onset of incubation was 17 July and the latest 16 August, with 2.2 young fledged per breeding pair over the four-year period. Incubation lasted 32 days and young fledged after 42-45 days. All nest sites were on cliffs with a mean height of 114 m, a mean vertical face of 53 m; 45% of the nests were in ravens’ nests. The aspect of cliff sites also influenced breeding success. Radio tracking was used to determine home range, habitat use and hunting methods, with prey species identified. Home ranges were between 66 km² and 249 km². Preferred prey was domestic chickens, pigeons and small birds during the breeding season. Foraging ranges were smaller in intensively cultivated areas with seed crops. Data obtained from ringing returns showed that no long distance movements occurred in this region, but two juveniles dispersed 152 km and 127 km. Conservation aspects with possible threats to Lanner Falcons such as poisons, electrocutions and direct persecution are discussed with some recommendations made for future research. Evidence from this study indicates that Lanner breeding success is not limited by nest site availability, but by rainfall timing and prey availability. Lanners foraged more in open areas than areas with tall vegetation, and benefited from intensive agriculture. This population appeared to be healthy and in no danger of declining in the near future.
- Full Text:
- Date Issued: 2001
- Authors: Stephenson, Alan
- Date: 2001
- Subjects: Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5667 , http://hdl.handle.net/10962/d1005352 , Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Description: Lanner Falcons Falco biarmicus are the commonest large falcons in Africa and this study in the coastal area of the Eastern Cape Province, South Africa investigated their ecology from 1984 to 2000. Lanners have recently been categorised as near-threatened and this study was initiated to ascertain if the population was stable. Breeding success of a small population, in different habitat types, was monitored intensively from 1997 to 2000, and the factors that inhibited breeding were investigated. The earliest onset of incubation was 17 July and the latest 16 August, with 2.2 young fledged per breeding pair over the four-year period. Incubation lasted 32 days and young fledged after 42-45 days. All nest sites were on cliffs with a mean height of 114 m, a mean vertical face of 53 m; 45% of the nests were in ravens’ nests. The aspect of cliff sites also influenced breeding success. Radio tracking was used to determine home range, habitat use and hunting methods, with prey species identified. Home ranges were between 66 km² and 249 km². Preferred prey was domestic chickens, pigeons and small birds during the breeding season. Foraging ranges were smaller in intensively cultivated areas with seed crops. Data obtained from ringing returns showed that no long distance movements occurred in this region, but two juveniles dispersed 152 km and 127 km. Conservation aspects with possible threats to Lanner Falcons such as poisons, electrocutions and direct persecution are discussed with some recommendations made for future research. Evidence from this study indicates that Lanner breeding success is not limited by nest site availability, but by rainfall timing and prey availability. Lanners foraged more in open areas than areas with tall vegetation, and benefited from intensive agriculture. This population appeared to be healthy and in no danger of declining in the near future.
- Full Text:
- Date Issued: 2001
Economic review 2001
- DITSELA
- Authors: DITSELA
- Date: 2001
- Subjects: Development Institute for Training,Support and Education for Labour (DITSELA)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/178602 , vital:42958
- Description: This volume of Bargaining Indicators for 2002 comes in the context of the September 11 attacks on the World Trade Center in New York, the United States’ war on Afghanistan, the collapse of the economy of Argentina and with it the biggest sovereign bankruptcy in history. All these historic events are unfolding within the first synchronised global recession since the 1970s, and have in turn deepened this recession. Within South Africa, this edition of Bargaining Indicators comes in the context of the first anti-government national strike by organised labour since the 1994 elections, and a deepening of the economic slowdown that we noted in the last edition of Bargaining Indicators. In this review of economic developments during 2001 we shine the spotlight on the global recession and its dynamics, and we look in particular at the slide of the world’s largest economy - that of the United States - into its first serious economic crisis since the end of the cold war, and we take a look at the significance of the attacks of September 11 and their aftermath on the dynamics of the global recession. We conclude our discussion of the global recession by discussing the responses of the Bush government and its allies, and at the meaning of these responses for neoliberal economic orthodoxy. We continue our analysis by looking at developments within the South African economy. In particular, we look at the implications of the global recession on the South African economy, and at how the currency crisis that has unfolded since the last quarter of 2001 forms an important moment in the dynamics of the unfolding global recession. Within this context we look at the main economic indicators (GDP; GDE; fixed capital formation, operating surpluses, wages, employment, savings and so on). Lastly, we look at the year ahead, and in particular at the implications of the global and domestic economic developments for the 2002 bargaining season.
- Full Text:
- Date Issued: 2001
- Authors: DITSELA
- Date: 2001
- Subjects: Development Institute for Training,Support and Education for Labour (DITSELA)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/178602 , vital:42958
- Description: This volume of Bargaining Indicators for 2002 comes in the context of the September 11 attacks on the World Trade Center in New York, the United States’ war on Afghanistan, the collapse of the economy of Argentina and with it the biggest sovereign bankruptcy in history. All these historic events are unfolding within the first synchronised global recession since the 1970s, and have in turn deepened this recession. Within South Africa, this edition of Bargaining Indicators comes in the context of the first anti-government national strike by organised labour since the 1994 elections, and a deepening of the economic slowdown that we noted in the last edition of Bargaining Indicators. In this review of economic developments during 2001 we shine the spotlight on the global recession and its dynamics, and we look in particular at the slide of the world’s largest economy - that of the United States - into its first serious economic crisis since the end of the cold war, and we take a look at the significance of the attacks of September 11 and their aftermath on the dynamics of the global recession. We conclude our discussion of the global recession by discussing the responses of the Bush government and its allies, and at the meaning of these responses for neoliberal economic orthodoxy. We continue our analysis by looking at developments within the South African economy. In particular, we look at the implications of the global recession on the South African economy, and at how the currency crisis that has unfolded since the last quarter of 2001 forms an important moment in the dynamics of the unfolding global recession. Within this context we look at the main economic indicators (GDP; GDE; fixed capital formation, operating surpluses, wages, employment, savings and so on). Lastly, we look at the year ahead, and in particular at the implications of the global and domestic economic developments for the 2002 bargaining season.
- Full Text:
- Date Issued: 2001
Effect of feeding regimen, temperature and stocking density on growth and survival of juvenile clownfish (Amphiprion percula)
- Authors: Johnston, Gavin
- Date: 2001
- Subjects: Anemonefishes , Fishes -- Feeding and feeds , Fishes -- Growth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5274 , http://hdl.handle.net/10962/d1005118 , Anemonefishes , Fishes -- Feeding and feeds , Fishes -- Growth
- Description: In aquaculture, a thorough knowledge of the specific environmental requirements of a species is needed in order to maximize growth rate and survival. There is a paucity of data regarding the fundamental environmental requirements for the ongrowing phase of clownfish juveniles. This prompted the design of three experiments to determine the best feeding regimen, temperature and stocking density that maximize growth and survival of Amphiprion percula. Ration size and feeding frequency are important factors for optimizing fish growth during the juvenile grow-out phase. A factorial growth trial was conducted to determine the effect of feeding frequency and ration size on the growth of juvenile clownfish (Amphiprion percula).Three feeding frequencies (1, 2 and 3 times daily) and six rations (2,4,6,8, 10 and 12 % body weight per day (BW.day⁻¹)) were used to test the growth response over a twelve week period. Non-linear regression analysis on the effect of ration, independent of feeding frequency, on growth resulted in a significant (n = 36; r² = 68.7) parabolic model: In y = -0.0302x² + 0.5159x + -4.4377. Maximum growth corresponded to a ration of 8.5% BW.day⁻¹. Survival as a function of ration was significantly lower at 2% BW.day⁻¹. Data were further examined with Analysis of CoVariance (ANCOVA) to determine the effect of ration on growth at each feeding frequency. The combination revealed a maximum growth rate when the fish were fed a ration of 10% BW.day⁻¹ divided into two equal meals. The required ration per meal to maintain maximum growth was also found to decrease as feeding frequency increased. The determination of the best temperature for growth is of great importance due to the direct relationship between fish metabolism and temperature. The thermal preferendum of A. percula has already been estimated at 26 ± 0.7°C but it is not known whether this closely approximates the temperature for maximum growth. Sixteen tanks were set to different temperatures ranging between 21.5 and 30.2 °C. Ten juvenile A. percula were placed in each tank and growth was measured fortnightly over the course of the 10 week experiment. Non-linear regression analysis resulted in significant models for fish length (y = -0.0005x² + 0.00267x - 0.0338; r² = 56.7, n = 11) and weight (y= -0.00016x² + 0.0084x - 0.1073; r² = 61.6, n = 11). These models predict that maximum growth would be at 27.7 and 27.1 °C for length and weight, respectively. Temperature, over the range tested, had no apparent effect on survival. There was no significant difference between the temperatures for maximum growth and the preferred temperature. The effect of stocking densities ranging from 0.2 fish.L¹ to 4.0 fish.L⁻¹ on growth were used in the third experiment. The fish were fed to satiation twice daily and growth was measured fortnightly throughout the 8 week experiment. No effects on growth, survival or coefficient of variation were found within the range of stocking densities tested.
- Full Text:
- Date Issued: 2001
- Authors: Johnston, Gavin
- Date: 2001
- Subjects: Anemonefishes , Fishes -- Feeding and feeds , Fishes -- Growth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5274 , http://hdl.handle.net/10962/d1005118 , Anemonefishes , Fishes -- Feeding and feeds , Fishes -- Growth
- Description: In aquaculture, a thorough knowledge of the specific environmental requirements of a species is needed in order to maximize growth rate and survival. There is a paucity of data regarding the fundamental environmental requirements for the ongrowing phase of clownfish juveniles. This prompted the design of three experiments to determine the best feeding regimen, temperature and stocking density that maximize growth and survival of Amphiprion percula. Ration size and feeding frequency are important factors for optimizing fish growth during the juvenile grow-out phase. A factorial growth trial was conducted to determine the effect of feeding frequency and ration size on the growth of juvenile clownfish (Amphiprion percula).Three feeding frequencies (1, 2 and 3 times daily) and six rations (2,4,6,8, 10 and 12 % body weight per day (BW.day⁻¹)) were used to test the growth response over a twelve week period. Non-linear regression analysis on the effect of ration, independent of feeding frequency, on growth resulted in a significant (n = 36; r² = 68.7) parabolic model: In y = -0.0302x² + 0.5159x + -4.4377. Maximum growth corresponded to a ration of 8.5% BW.day⁻¹. Survival as a function of ration was significantly lower at 2% BW.day⁻¹. Data were further examined with Analysis of CoVariance (ANCOVA) to determine the effect of ration on growth at each feeding frequency. The combination revealed a maximum growth rate when the fish were fed a ration of 10% BW.day⁻¹ divided into two equal meals. The required ration per meal to maintain maximum growth was also found to decrease as feeding frequency increased. The determination of the best temperature for growth is of great importance due to the direct relationship between fish metabolism and temperature. The thermal preferendum of A. percula has already been estimated at 26 ± 0.7°C but it is not known whether this closely approximates the temperature for maximum growth. Sixteen tanks were set to different temperatures ranging between 21.5 and 30.2 °C. Ten juvenile A. percula were placed in each tank and growth was measured fortnightly over the course of the 10 week experiment. Non-linear regression analysis resulted in significant models for fish length (y = -0.0005x² + 0.00267x - 0.0338; r² = 56.7, n = 11) and weight (y= -0.00016x² + 0.0084x - 0.1073; r² = 61.6, n = 11). These models predict that maximum growth would be at 27.7 and 27.1 °C for length and weight, respectively. Temperature, over the range tested, had no apparent effect on survival. There was no significant difference between the temperatures for maximum growth and the preferred temperature. The effect of stocking densities ranging from 0.2 fish.L¹ to 4.0 fish.L⁻¹ on growth were used in the third experiment. The fish were fed to satiation twice daily and growth was measured fortnightly throughout the 8 week experiment. No effects on growth, survival or coefficient of variation were found within the range of stocking densities tested.
- Full Text:
- Date Issued: 2001
Effect of high energy diets on the productive and reproductive characteristics of young Bonsmara bulls
- Labuschagné, Hermanus Stefanus
- Authors: Labuschagné, Hermanus Stefanus
- Date: 2001
- Subjects: Bonsmara cattle
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10956 , http://hdl.handle.net/10948/58 , Bonsmara cattle
- Description: A study to evaluate the effect of feeding a high energy diet on the productive and reproductive characteristics of young bulls was carried out at two different locations in the Free State Province. Two trials were conducted with the aim of evaluating the effect of level of dietary energy and age of the bulls on their productive performance and reproductive characteristics. In the first trial, two levels of energy were fed to two groups of young (343 ± days) Bonsmara bulls. The high energy group HE (n=36) bulls were Phase-C performance tested in an official performance testing center and received a high energy diet for 112 days (28 days adaptation and 84 days testing). The medium energy group ME (n=18) bulls were phase-D performance tested and received a medium-energy diet for 140 days (28 days adaptation and 112 days testing). At the end of both performance testing periods, the productive performances and reproductive characteristics of the two groups were compared. The productive parameters compared included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA) and body condition score (BCS). The reproductive parameters compared between groups included scrotal circumference (SC), semen volume (Vol) and concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), as well as percentage of total abnormalities: major (MD) and minor (MinD). The results of this trial indicated that in general, bulls from the HE group showed a significant (p<0.01) higher FLW, BCS, ADG and ADA, but a significant (p<0.01) lower volume and concentration of the ejaculate, lower mass movement and linear motility, lower percentage of live sperm and higher percentage of major defects and significantly (p<0.05) higher percentage of minor defects than the bulls from the ME group. In the second trial, 36 young Bonsmara bulls were divided into two groups according to their age at the arrival at an official Phase-C performance testing center. Older bulls (OB) (n=19) and younger bulls (YB) (n=17) all received a high energy diet for 112 days (28 days adaptation and 84 days testing). At the end of the Phase-C test the productive performances and reproductive characteristics of the two groups were compared. The animals from both groups that did not pass the Phase-C test, either due to poor performance or not meeting the breed standards, were slaughtered at an official abattoir and their scrotums and carcass characteristics were also compared. The productive parameters compared between the two groups included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA), body condition score (BCS), feed conversion ratio (FCR), carcass weight both warm (CWW) and cold (CWC), as well as dressing percentage (CDP) and fat grade (CFG). The reproductive parameters compared between the two groups included scrotal circumference (SC), total scrotal weight (TSW), scrotal fat (SF), scrotal skin weight (SSW), paired testes weight (PTW), scrotal skin thickness (SST), total testes circumference (TTC), total testicle volume (TTV), weight of epididimis / spermatic cord (WESC), volume of epididymis / spermatic cord (VESC) and the percentage of bulls with depressed spermatogenesis (PBDS), semen concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), percentage of total abnormalities: major (MD) and minor(MinD) as well as the percentage of bulls with depressed spermatogenesis (PBDS). The results of this trial indicated that in general, the younger bulls showed a significant (p<0.05) higher ADG, but a significant (p<0.05) lower ADA than the older bulls. Regarding the reproductive organs compared, the younger bulls showed a significantly (p<0.01) higher total scrotal weight, scrotal fat and scrotal skin weight and thickness. No significant differences were observed on the testicular parameters measured between the two groups. In addition, both weight (WECS) and volume (VECS) of the epididymis / spermatic cord were significantly (P<0.05) higher in the older bulls. In general, the younger group showed poorer semen characteristics. A significantly (p<0.01) lower sperm concentration and linear movement and a significantly (p<0.05) higher percentage of major defects were recorded on the younger bulls, when compared to the older bulls. About half of the bulls in each group showed clear signs of depressed spermatogenesis in their seminiferous tubules, during the histological examination of testicular tissue. The results of this study indicates that high energy diets are beneficial for the productive performance of young bulls (growth rate, BCS and carcass characteristics), but have a detrimental effect on the reproductive characteristics of young bulls. The effect of high energy diets on both the productive and reproductive performances of young beef bulls are more pronounced at a younger age. High energy diets resulted in heavier scrotums in the younger bulls when compared to the older bulls, as a direct result of a higher fat deposition in this region without any relevant effect on testicular size. No intra-testicular fat deposition was observed. The scrotal fat observed in high energy fed young bulls accumulated mainly in the neck of the scrotum, although subcutaneously. These fat deposits may impair testicular thermoregulation and negatively affect the spermatogenesis in the seminiferous tubules, reducing both sperm quantity and quality. Further studies on the effect of high energy diets on bull fertility (as well as on rams and buck) are recommended, to evaluate the extension and duration of its detrimental effects on subsequent fertility.
- Full Text:
- Date Issued: 2001
- Authors: Labuschagné, Hermanus Stefanus
- Date: 2001
- Subjects: Bonsmara cattle
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10956 , http://hdl.handle.net/10948/58 , Bonsmara cattle
- Description: A study to evaluate the effect of feeding a high energy diet on the productive and reproductive characteristics of young bulls was carried out at two different locations in the Free State Province. Two trials were conducted with the aim of evaluating the effect of level of dietary energy and age of the bulls on their productive performance and reproductive characteristics. In the first trial, two levels of energy were fed to two groups of young (343 ± days) Bonsmara bulls. The high energy group HE (n=36) bulls were Phase-C performance tested in an official performance testing center and received a high energy diet for 112 days (28 days adaptation and 84 days testing). The medium energy group ME (n=18) bulls were phase-D performance tested and received a medium-energy diet for 140 days (28 days adaptation and 112 days testing). At the end of both performance testing periods, the productive performances and reproductive characteristics of the two groups were compared. The productive parameters compared included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA) and body condition score (BCS). The reproductive parameters compared between groups included scrotal circumference (SC), semen volume (Vol) and concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), as well as percentage of total abnormalities: major (MD) and minor (MinD). The results of this trial indicated that in general, bulls from the HE group showed a significant (p<0.01) higher FLW, BCS, ADG and ADA, but a significant (p<0.01) lower volume and concentration of the ejaculate, lower mass movement and linear motility, lower percentage of live sperm and higher percentage of major defects and significantly (p<0.05) higher percentage of minor defects than the bulls from the ME group. In the second trial, 36 young Bonsmara bulls were divided into two groups according to their age at the arrival at an official Phase-C performance testing center. Older bulls (OB) (n=19) and younger bulls (YB) (n=17) all received a high energy diet for 112 days (28 days adaptation and 84 days testing). At the end of the Phase-C test the productive performances and reproductive characteristics of the two groups were compared. The animals from both groups that did not pass the Phase-C test, either due to poor performance or not meeting the breed standards, were slaughtered at an official abattoir and their scrotums and carcass characteristics were also compared. The productive parameters compared between the two groups included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA), body condition score (BCS), feed conversion ratio (FCR), carcass weight both warm (CWW) and cold (CWC), as well as dressing percentage (CDP) and fat grade (CFG). The reproductive parameters compared between the two groups included scrotal circumference (SC), total scrotal weight (TSW), scrotal fat (SF), scrotal skin weight (SSW), paired testes weight (PTW), scrotal skin thickness (SST), total testes circumference (TTC), total testicle volume (TTV), weight of epididimis / spermatic cord (WESC), volume of epididymis / spermatic cord (VESC) and the percentage of bulls with depressed spermatogenesis (PBDS), semen concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), percentage of total abnormalities: major (MD) and minor(MinD) as well as the percentage of bulls with depressed spermatogenesis (PBDS). The results of this trial indicated that in general, the younger bulls showed a significant (p<0.05) higher ADG, but a significant (p<0.05) lower ADA than the older bulls. Regarding the reproductive organs compared, the younger bulls showed a significantly (p<0.01) higher total scrotal weight, scrotal fat and scrotal skin weight and thickness. No significant differences were observed on the testicular parameters measured between the two groups. In addition, both weight (WECS) and volume (VECS) of the epididymis / spermatic cord were significantly (P<0.05) higher in the older bulls. In general, the younger group showed poorer semen characteristics. A significantly (p<0.01) lower sperm concentration and linear movement and a significantly (p<0.05) higher percentage of major defects were recorded on the younger bulls, when compared to the older bulls. About half of the bulls in each group showed clear signs of depressed spermatogenesis in their seminiferous tubules, during the histological examination of testicular tissue. The results of this study indicates that high energy diets are beneficial for the productive performance of young bulls (growth rate, BCS and carcass characteristics), but have a detrimental effect on the reproductive characteristics of young bulls. The effect of high energy diets on both the productive and reproductive performances of young beef bulls are more pronounced at a younger age. High energy diets resulted in heavier scrotums in the younger bulls when compared to the older bulls, as a direct result of a higher fat deposition in this region without any relevant effect on testicular size. No intra-testicular fat deposition was observed. The scrotal fat observed in high energy fed young bulls accumulated mainly in the neck of the scrotum, although subcutaneously. These fat deposits may impair testicular thermoregulation and negatively affect the spermatogenesis in the seminiferous tubules, reducing both sperm quantity and quality. Further studies on the effect of high energy diets on bull fertility (as well as on rams and buck) are recommended, to evaluate the extension and duration of its detrimental effects on subsequent fertility.
- Full Text:
- Date Issued: 2001
Effect of oligomerization on the photochemical properties of silicon octaphenoxyphthalocyanine
- Maree, M David, Nyokong, Tebello
- Authors: Maree, M David , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/291542 , vital:56885 , xlink:href="https://doi.org/10.1016/S1010-6030(01)00485-3"
- Description: The photochemical properties of silicon octaphenoxyphthalocyanines (SiOPPc) oligomerized were studied in dimethylsulfoxide (DMSO) solutions. Oligomers containing 2–5 and 9 SiOPPc rings linked with terephthalate linkages were synthesized. Singlet oxygen quantum yields were found to be in the range 0.11–0.34, and increased with the number of rings up to five rings, a decrease in the quantum yield was observed for nine rings. This is explained in terms of the high aggregation of the oligomer containing nine rings.
- Full Text:
- Date Issued: 2001
- Authors: Maree, M David , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/291542 , vital:56885 , xlink:href="https://doi.org/10.1016/S1010-6030(01)00485-3"
- Description: The photochemical properties of silicon octaphenoxyphthalocyanines (SiOPPc) oligomerized were studied in dimethylsulfoxide (DMSO) solutions. Oligomers containing 2–5 and 9 SiOPPc rings linked with terephthalate linkages were synthesized. Singlet oxygen quantum yields were found to be in the range 0.11–0.34, and increased with the number of rings up to five rings, a decrease in the quantum yield was observed for nine rings. This is explained in terms of the high aggregation of the oligomer containing nine rings.
- Full Text:
- Date Issued: 2001