A comparative analysis of Java and .NET mobile development environments for supporting mobile services
- Authors: Zhao, Xiaogeng
- Date: 2003 , 2013-05-23
- Subjects: Microsoft .NET , Java (Computer program language) , Mobile computing , Wireless communication systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4578 , http://hdl.handle.net/10962/d1003064 , Microsoft .NET , Java (Computer program language) , Mobile computing , Wireless communication systems
- Description: With the rapid development of wireless technologies, traditional mobile devices, such as pagers and cellular phones, have evolved from a purely communications and messaging-oriented medium to one that supports mobile data communication in general and acts as an application platform. As shown in a recent survey conducted by MDA, easy access to the present-day wireless Internet has resulted in mobile devices gaining more and more attention and popularity. The growth of and demand for mobile Web applications is expected to increase rapidly in the near future, as a range of software companies and mobile device manufacturers release increasingly accessible tools for creating mobile Web application and services. From a variety of possible development environments of this kind, the author has selected and examined two leading contenders, the J2ME and the Microsoft .NET mobile Web application development environments. This document reports the product life cycle of pilot mobile web applications, designed and implemented in each host environment in tum. A feature-by-feature investigation and comparison of the J2ME and .NET environments was carried out, covering the range of issues necessary for a complete mobile Web application development life cycle. The resulting analysis addresses features and efficiencies of the application development environment and the target deployment environment, the degree to which the resultant services are compatible on a variety of platforms, and the ease with which applications can be designed to be extensible. The thesis offers an objective evaluation of the J2ME and the .NET mobile development environments, which highlights their strengths and weaknesses, and suggests guidelines for designing, creating, and deploying high quality mobile Web applications. The research uncovers no clear winner across all categories assessed. J2ME currently favours situations in which bandwidth is limited and client side processing power is relatively sufficient, it exerts the processing power of mobile devices over distributed network environments. .NET requires a less constrained network throughput, but performs adequately on clients with more limited processing power, supports a more diverse target platform range, and offers a more efficient, in terms of development time, development environment. Both technologies are likely to receive significant user support for some time. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
- Authors: Zhao, Xiaogeng
- Date: 2003 , 2013-05-23
- Subjects: Microsoft .NET , Java (Computer program language) , Mobile computing , Wireless communication systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4578 , http://hdl.handle.net/10962/d1003064 , Microsoft .NET , Java (Computer program language) , Mobile computing , Wireless communication systems
- Description: With the rapid development of wireless technologies, traditional mobile devices, such as pagers and cellular phones, have evolved from a purely communications and messaging-oriented medium to one that supports mobile data communication in general and acts as an application platform. As shown in a recent survey conducted by MDA, easy access to the present-day wireless Internet has resulted in mobile devices gaining more and more attention and popularity. The growth of and demand for mobile Web applications is expected to increase rapidly in the near future, as a range of software companies and mobile device manufacturers release increasingly accessible tools for creating mobile Web application and services. From a variety of possible development environments of this kind, the author has selected and examined two leading contenders, the J2ME and the Microsoft .NET mobile Web application development environments. This document reports the product life cycle of pilot mobile web applications, designed and implemented in each host environment in tum. A feature-by-feature investigation and comparison of the J2ME and .NET environments was carried out, covering the range of issues necessary for a complete mobile Web application development life cycle. The resulting analysis addresses features and efficiencies of the application development environment and the target deployment environment, the degree to which the resultant services are compatible on a variety of platforms, and the ease with which applications can be designed to be extensible. The thesis offers an objective evaluation of the J2ME and the .NET mobile development environments, which highlights their strengths and weaknesses, and suggests guidelines for designing, creating, and deploying high quality mobile Web applications. The research uncovers no clear winner across all categories assessed. J2ME currently favours situations in which bandwidth is limited and client side processing power is relatively sufficient, it exerts the processing power of mobile devices over distributed network environments. .NET requires a less constrained network throughput, but performs adequately on clients with more limited processing power, supports a more diverse target platform range, and offers a more efficient, in terms of development time, development environment. Both technologies are likely to receive significant user support for some time. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
A review of the Kalahari group: an aid to Kimberlite exploration in this medium
- Authors: Williams, Clint
- Date: 2003 , 2013-05-23
- Subjects: Kimberlite -- Kalahari Desert , Sedimentation and deposition -- Kalahari Desert
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4916 , http://hdl.handle.net/10962/d1003216 , Kimberlite -- Kalahari Desert , Sedimentation and deposition -- Kalahari Desert
- Description: The Kalahari Group sediments cover vast portions of the Archean Kaapvaal and Congo cratons that are considered highly prospective for economic kimberlites. In southern Africa, the term Kalahari refers to a structural basin, a group of Cretaceous to recent terrestrial continental sediments and an ill-defined desert, all of which have been grouped together as the Mega Kalahari by Thomas and Shaw (1993). The Mega Kalahari grouping includes sediments stretching from South Africa in the south to the Democratic Republic of Congo in the north, and from eastern Namibia to western Zimbabwe. This sand sea, at 2.5 million km², is the largest on earth and presents significant obstacles and challenges to the kimberlite explorationist attempting to locate bedrock-hosted diamondiferous kimberlite bodies. The Mega Kalahari sediments represent an ancient depositional environment with a complex history in which the stratigraphy and age of the deposits are not particularly well constrained or understood. Low fossil content, limited exposure, poor differentiation of the dominant surficial Kalahari Sand and a limited comprehension of an extensive duricrust suite has delayed the understanding of the sedimentological and environmental history of the basin. This sequence of sediments has accumulated and evolved through fluvio-deltaic, aeolian and groundwater processes, with characteristics due to primary deposition and subsequent modification being difficult to distinguish. Deposition in the Kalahari Basin has been subject to tectonic influences, changes in drainage directions and source areas of sediments, river capture and numerous large and small climatic fluctuations both in the basin and surrounding areas. It bears the imprint of recurring cycles during which the same sediments were reworked, sometimes by different agencies, all of which exacerbate attempts to correlate sedimentary units across the sequence. The Mega Kalahari is a series of contiguous Phanerozoic sedimentary basins situated within the African Superswell. The Superswell has dominated the gross geomorphology of southern Africa and contributed significantly to the present character of the Mega Kalahari and the evolution of the drainage systems. Overall, the tectonic framework established in southern Africa by the division of Gondwanaland led to the creation of a dual drainage system, with the hingeline acting as a watershed between a coastally-orientated exoreic system and an endoreic system draining into the interior. Deposition of sediments started in the late Cretaceous. Neo-tectonic activity expressed in the rifting in central Botswana, further influenced sedimentation rates and exerted a strong control over paleo-drainage directions. This revIew presents the complexities of the Kalahari cover sequence. The most Important geomorphological and sedimentary factors to be considered when designing and implementing kimberlite exploration programs within the Mega Kalahari environment are outlined and discussed. New data from exploration drilling programs are presented on the thickness of the Kalahari within portions of northern Namibia, western Zambia and Botswana. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
- Authors: Williams, Clint
- Date: 2003 , 2013-05-23
- Subjects: Kimberlite -- Kalahari Desert , Sedimentation and deposition -- Kalahari Desert
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4916 , http://hdl.handle.net/10962/d1003216 , Kimberlite -- Kalahari Desert , Sedimentation and deposition -- Kalahari Desert
- Description: The Kalahari Group sediments cover vast portions of the Archean Kaapvaal and Congo cratons that are considered highly prospective for economic kimberlites. In southern Africa, the term Kalahari refers to a structural basin, a group of Cretaceous to recent terrestrial continental sediments and an ill-defined desert, all of which have been grouped together as the Mega Kalahari by Thomas and Shaw (1993). The Mega Kalahari grouping includes sediments stretching from South Africa in the south to the Democratic Republic of Congo in the north, and from eastern Namibia to western Zimbabwe. This sand sea, at 2.5 million km², is the largest on earth and presents significant obstacles and challenges to the kimberlite explorationist attempting to locate bedrock-hosted diamondiferous kimberlite bodies. The Mega Kalahari sediments represent an ancient depositional environment with a complex history in which the stratigraphy and age of the deposits are not particularly well constrained or understood. Low fossil content, limited exposure, poor differentiation of the dominant surficial Kalahari Sand and a limited comprehension of an extensive duricrust suite has delayed the understanding of the sedimentological and environmental history of the basin. This sequence of sediments has accumulated and evolved through fluvio-deltaic, aeolian and groundwater processes, with characteristics due to primary deposition and subsequent modification being difficult to distinguish. Deposition in the Kalahari Basin has been subject to tectonic influences, changes in drainage directions and source areas of sediments, river capture and numerous large and small climatic fluctuations both in the basin and surrounding areas. It bears the imprint of recurring cycles during which the same sediments were reworked, sometimes by different agencies, all of which exacerbate attempts to correlate sedimentary units across the sequence. The Mega Kalahari is a series of contiguous Phanerozoic sedimentary basins situated within the African Superswell. The Superswell has dominated the gross geomorphology of southern Africa and contributed significantly to the present character of the Mega Kalahari and the evolution of the drainage systems. Overall, the tectonic framework established in southern Africa by the division of Gondwanaland led to the creation of a dual drainage system, with the hingeline acting as a watershed between a coastally-orientated exoreic system and an endoreic system draining into the interior. Deposition of sediments started in the late Cretaceous. Neo-tectonic activity expressed in the rifting in central Botswana, further influenced sedimentation rates and exerted a strong control over paleo-drainage directions. This revIew presents the complexities of the Kalahari cover sequence. The most Important geomorphological and sedimentary factors to be considered when designing and implementing kimberlite exploration programs within the Mega Kalahari environment are outlined and discussed. New data from exploration drilling programs are presented on the thickness of the Kalahari within portions of northern Namibia, western Zambia and Botswana. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
A study of the structural geology of the Witteberg Group and lowermost Karoo Supergroup, Darlington Dam, Jansenville District, Eastern Cape
- Goossens, Angelique Emily Maria
- Authors: Goossens, Angelique Emily Maria
- Date: 2003
- Subjects: Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11071 , http://hdl.handle.net/10948/291 , Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Description: A number of outcrops of the Witteberg Group and lowermost Karoo Supergroup rocks were studied in the area south of the Darlington Dam, Jansenville District, with the aim of documenting structural characteristics of the area. All lithologies are folded with fold styles varying from gentle to near isoclinal (based on interlimb angle). Fold axes are either sub-horizontal or plunging at gentle to moderate angles whereas axial planes dip gently to vertically (predominantly steep to sub-vertical). Folds verge predominantly towards the north but where southward verging they are associated with faulting or strongly folded areas. Folds plunge gently to the east-southeast and west-northwest. The area consists of a large anticlinorium with both first and second order folds occurring. Eastwest striking faults occur in the study area and are classified as normal, reverse and thrust faults. A study of the joint sets shows that there are four dominant joint directions, namely 18o, 33o, 97o and 107o (in order from least to most important). An interpretation of the tectonic history is presented in which the relationships between faults and folds show that faults formed during and after folding. Folding, and reverse and thrust faulting, occurred during the compressional events that formed the Cape Fold Belt, whereas the normal faults formed during the relaxation of these compressional forces or during the break-up of Gondwana.
- Full Text:
- Date Issued: 2003
- Authors: Goossens, Angelique Emily Maria
- Date: 2003
- Subjects: Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11071 , http://hdl.handle.net/10948/291 , Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Description: A number of outcrops of the Witteberg Group and lowermost Karoo Supergroup rocks were studied in the area south of the Darlington Dam, Jansenville District, with the aim of documenting structural characteristics of the area. All lithologies are folded with fold styles varying from gentle to near isoclinal (based on interlimb angle). Fold axes are either sub-horizontal or plunging at gentle to moderate angles whereas axial planes dip gently to vertically (predominantly steep to sub-vertical). Folds verge predominantly towards the north but where southward verging they are associated with faulting or strongly folded areas. Folds plunge gently to the east-southeast and west-northwest. The area consists of a large anticlinorium with both first and second order folds occurring. Eastwest striking faults occur in the study area and are classified as normal, reverse and thrust faults. A study of the joint sets shows that there are four dominant joint directions, namely 18o, 33o, 97o and 107o (in order from least to most important). An interpretation of the tectonic history is presented in which the relationships between faults and folds show that faults formed during and after folding. Folding, and reverse and thrust faulting, occurred during the compressional events that formed the Cape Fold Belt, whereas the normal faults formed during the relaxation of these compressional forces or during the break-up of Gondwana.
- Full Text:
- Date Issued: 2003
An assessment of bait availability, utilization and management guidelines in Eastern Cape estuaries
- Authors: Jooste, Jakobus Gerrit
- Date: 2003
- Subjects: Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11073 , http://hdl.handle.net/10948/334 , Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Description: Aspects around the management of benthic soft sediment bait organisms, with special focus on the mud prawn (Upogebia africana) of eastern Cape estuaries was investigated. The recreational linefishery of the Gamtoos estuary was described, and compared to previous studies. Target fish species was identified, and a large dependency on bait sourced from estuaries needed for the capture of these species was noted, especially for spotted grunter (Pomadasys commersonnii). A comparison between bait use, success and the natural diet of target fish species was also made. The structure and distribution of sediments in the old channel mud banks was described and compared with historical data. The influence of sediments on mud prawn distribution was investigated, but no significant interactions were found at the study site. The impacts of once-off pumping and digging events, and monthly trampling on the sediments and mud prawn population was studied over a 7-month period. Initial removal rates as well as recovery time varied significantly between the two collection methods, while the largest decline in prawn numbers (to zero) with no recovery visible after seven months was caused by trampling. All disturbances caused some alteration in sediment composition, but not to such an extent that the sediments became unfavorable for mud prawns. Trampling did, however, result in the compaction of sediments to such a degree that prawns could not construct burrows. Issues around current removal quotas of bait species as well as the creation of a small-scale commercial (SSC) bait selling operation at Swartkops estuary were critically evaluated, and suggestions for the future removal rates of mud prawns based on production export calculations were made. The distribution, size, sex ratios and number of gravid females occurring along a tidal gradient as well as along horizontal gradient of the mud bank during growth (January – March) and reproductive (September – October) periods was investigated. Changes in the distribution of females between the two study periods were significant, while the distribution of reproductively active females were closely linked to the low water mark (Lower tidal levels). Females occurring in this zone were also significantly larger than females occurring towards the back of the study site. Some minor changes along the horizontal gradient were also observed. The sediment compos ition of the mud bank was found not to play a role in this distribution, leading to the suggestion that exposure to ebb and flood tide currents could influence female prawn distributions. Management recommendations based on these observations were made.
- Full Text:
- Date Issued: 2003
- Authors: Jooste, Jakobus Gerrit
- Date: 2003
- Subjects: Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11073 , http://hdl.handle.net/10948/334 , Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Description: Aspects around the management of benthic soft sediment bait organisms, with special focus on the mud prawn (Upogebia africana) of eastern Cape estuaries was investigated. The recreational linefishery of the Gamtoos estuary was described, and compared to previous studies. Target fish species was identified, and a large dependency on bait sourced from estuaries needed for the capture of these species was noted, especially for spotted grunter (Pomadasys commersonnii). A comparison between bait use, success and the natural diet of target fish species was also made. The structure and distribution of sediments in the old channel mud banks was described and compared with historical data. The influence of sediments on mud prawn distribution was investigated, but no significant interactions were found at the study site. The impacts of once-off pumping and digging events, and monthly trampling on the sediments and mud prawn population was studied over a 7-month period. Initial removal rates as well as recovery time varied significantly between the two collection methods, while the largest decline in prawn numbers (to zero) with no recovery visible after seven months was caused by trampling. All disturbances caused some alteration in sediment composition, but not to such an extent that the sediments became unfavorable for mud prawns. Trampling did, however, result in the compaction of sediments to such a degree that prawns could not construct burrows. Issues around current removal quotas of bait species as well as the creation of a small-scale commercial (SSC) bait selling operation at Swartkops estuary were critically evaluated, and suggestions for the future removal rates of mud prawns based on production export calculations were made. The distribution, size, sex ratios and number of gravid females occurring along a tidal gradient as well as along horizontal gradient of the mud bank during growth (January – March) and reproductive (September – October) periods was investigated. Changes in the distribution of females between the two study periods were significant, while the distribution of reproductively active females were closely linked to the low water mark (Lower tidal levels). Females occurring in this zone were also significantly larger than females occurring towards the back of the study site. Some minor changes along the horizontal gradient were also observed. The sediment compos ition of the mud bank was found not to play a role in this distribution, leading to the suggestion that exposure to ebb and flood tide currents could influence female prawn distributions. Management recommendations based on these observations were made.
- Full Text:
- Date Issued: 2003
An empirical, in-depth investigation into service creation in H.323 Version 4 Networks
- Authors: Penton, Jason Barry
- Date: 2003 , 2013-05-24
- Subjects: Computer programming , Computer networks , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4681 , http://hdl.handle.net/10962/d1007637 , Computer programming , Computer networks , Computer network protocols
- Description: Over the past few years there has been an increasing tendency to carry voice on IP networks as opposed to the PSTN and other switched circuit networks. Initially this trend was favoured due to reduced costs but occurred at the expense of sacrificing the quality of the voice communications. Switched circuit networks have therefore remained the preferred carrier-grade voice communication network, but this is again changing. The advancement in improved quality of service (QoS) of real-time traffic on the IP network is a contributing factor to the anticipated future of the IP network supplying carrier-grade voice communications. Another contributing factor is the possibility of creating a new range of innovative, state-of-the-art telephony and communications services that acquire leverage through the intelligence and flexibility of the IP network. The latter has yet to be fully explored. Various protocols exist that facilitate the transport of voice and other media on IP networks. The most well known and widely supported of these is H.323. This work presents and discusses H.323 version 4 service creation. The work also categorises the various H.323 services and presents the mechanisms provided by H.323 version 4 that have facilitated the development of the three services I have developed, EmailReader, Telgo323 and CANS.
- Full Text:
- Date Issued: 2003
- Authors: Penton, Jason Barry
- Date: 2003 , 2013-05-24
- Subjects: Computer programming , Computer networks , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4681 , http://hdl.handle.net/10962/d1007637 , Computer programming , Computer networks , Computer network protocols
- Description: Over the past few years there has been an increasing tendency to carry voice on IP networks as opposed to the PSTN and other switched circuit networks. Initially this trend was favoured due to reduced costs but occurred at the expense of sacrificing the quality of the voice communications. Switched circuit networks have therefore remained the preferred carrier-grade voice communication network, but this is again changing. The advancement in improved quality of service (QoS) of real-time traffic on the IP network is a contributing factor to the anticipated future of the IP network supplying carrier-grade voice communications. Another contributing factor is the possibility of creating a new range of innovative, state-of-the-art telephony and communications services that acquire leverage through the intelligence and flexibility of the IP network. The latter has yet to be fully explored. Various protocols exist that facilitate the transport of voice and other media on IP networks. The most well known and widely supported of these is H.323. This work presents and discusses H.323 version 4 service creation. The work also categorises the various H.323 services and presents the mechanisms provided by H.323 version 4 that have facilitated the development of the three services I have developed, EmailReader, Telgo323 and CANS.
- Full Text:
- Date Issued: 2003
An evaluation of the Xenopus laevis liver slice model to study the toxic effects of microcystin
- Authors: Coates, Nadya
- Date: 2003
- Subjects: Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11069 , http://hdl.handle.net/10948/307 , Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Description: Blooms of cyanobacteria have increased in occurrence in the past three decades and have been reported to cause severe problems for animals and humans, leading to death in extreme instances. The majority of poisonings that have taken place have been attributed to a hepatotoxin produced by the species Microcystis aeruginosa, namely microcystin. The appearance of a cyanobacterial bloom does not give any indication as to its toxicity and therefore, it is imperative that simple, yet sensitive, bioassays are developed to overcome this problem. This study was undertaken to evaluate the effects of microcystin-LR on the liver of Xenopus laevis both in vitro and in vivo. This animal provides an opportunity to study the long-term hepatotoxic effects of the toxin compared to in vitro studies performed with mice and rats. The use of the liver slice model system as a potential bioassay to study the effects of microcystin-LR on Xenopus laevis liver was evaluated. Liver slices were cultured in RPMI- 1640 culture medium for periods ranging from 30 hours to 10 days and the liver slices were exposed to toxin concentrations ranging from 1nM to 500nM. The use of frog liver slices to study the longer-term effects of low-dose exposure to microcystin-LR was evaluated by observing the ultrastructural changes within hepatocytes using transmission electron microscopy, the release of the enzymes alanine aminotransferase and lactate dehydrogenase into the surrounding culture medium, as well as using a 3-[4,5-dimethylthiazol-2yl]-2,5- diphenyl tetrazolium bromide assay to determine the viability of the liver slices in culture. The amount of lipid peroxidation in the liver slices after exposure to microcystin-LR was assessed using the Thiobarbituric Acid Test. Results showed the frog liver slice culture system to be an inadequate method to evaluate the hepatotoxic effects of microcystin-LR. An in vivo assessment of the effects of microcystin-LR on Xenopus laevis was carried out using a total of 9 frogs (3 groups of 3 frogs). Frogs received a single intraperitoneal dose of 120mg/kg of microcystin-LR and were sacrificed at 8 and 24 hours post exposure. Microcystin-LR caused no significant change in serum lactate dehydrogenase levels, hepatosomatic index (liver weight as a percentage body weight), glutathione peroxidase activity, glycogen or lipid peroxidation. There was, however, an increase in glutathione sii transferase activity in the liver. The presence of the toxin in the liver was confirmed by immunohistochemistry. This study suggests that Xenopus laevis has, in some way, adapted to detoxifying aquatic toxins in the environment.
- Full Text:
- Date Issued: 2003
- Authors: Coates, Nadya
- Date: 2003
- Subjects: Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11069 , http://hdl.handle.net/10948/307 , Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Description: Blooms of cyanobacteria have increased in occurrence in the past three decades and have been reported to cause severe problems for animals and humans, leading to death in extreme instances. The majority of poisonings that have taken place have been attributed to a hepatotoxin produced by the species Microcystis aeruginosa, namely microcystin. The appearance of a cyanobacterial bloom does not give any indication as to its toxicity and therefore, it is imperative that simple, yet sensitive, bioassays are developed to overcome this problem. This study was undertaken to evaluate the effects of microcystin-LR on the liver of Xenopus laevis both in vitro and in vivo. This animal provides an opportunity to study the long-term hepatotoxic effects of the toxin compared to in vitro studies performed with mice and rats. The use of the liver slice model system as a potential bioassay to study the effects of microcystin-LR on Xenopus laevis liver was evaluated. Liver slices were cultured in RPMI- 1640 culture medium for periods ranging from 30 hours to 10 days and the liver slices were exposed to toxin concentrations ranging from 1nM to 500nM. The use of frog liver slices to study the longer-term effects of low-dose exposure to microcystin-LR was evaluated by observing the ultrastructural changes within hepatocytes using transmission electron microscopy, the release of the enzymes alanine aminotransferase and lactate dehydrogenase into the surrounding culture medium, as well as using a 3-[4,5-dimethylthiazol-2yl]-2,5- diphenyl tetrazolium bromide assay to determine the viability of the liver slices in culture. The amount of lipid peroxidation in the liver slices after exposure to microcystin-LR was assessed using the Thiobarbituric Acid Test. Results showed the frog liver slice culture system to be an inadequate method to evaluate the hepatotoxic effects of microcystin-LR. An in vivo assessment of the effects of microcystin-LR on Xenopus laevis was carried out using a total of 9 frogs (3 groups of 3 frogs). Frogs received a single intraperitoneal dose of 120mg/kg of microcystin-LR and were sacrificed at 8 and 24 hours post exposure. Microcystin-LR caused no significant change in serum lactate dehydrogenase levels, hepatosomatic index (liver weight as a percentage body weight), glutathione peroxidase activity, glycogen or lipid peroxidation. There was, however, an increase in glutathione sii transferase activity in the liver. The presence of the toxin in the liver was confirmed by immunohistochemistry. This study suggests that Xenopus laevis has, in some way, adapted to detoxifying aquatic toxins in the environment.
- Full Text:
- Date Issued: 2003
An integrated economic developmental appraisal of the South African mariculture industry
- Authors: Hepburn, Bruce
- Date: 2003
- Subjects: Mariculture -- South Africa -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:941 , http://hdl.handle.net/10962/d1002674 , Mariculture -- South Africa -- Economic aspects
- Description: Current coastal legislative and institutional reformulation has effectively established new principles for the promotion of sustainable, co-ordinated integrated coastal development to be achieved through facilitatory, co-operative management mechanisms. In accordance, collaborative expansion and diversification of mariculture has been identified as a strategic mechanism for realising sustainable coastal development. Present limited foundational understanding regarding the emergent commercial contingent’s economic-institutional structure has constrained the effectiveness of current centralised broad objective formulation based planning techniques. By drawing upon findings of the 2001 National Mariculture Baseline survey, key economic development and institutional components requiring dedicated attention for further realising industry’s inherent growth potential to supply domestic and growing global aquaculture markets are examined in an inductive explorative framework. Attention is also directed towards promoting realisation of collaborative mariculture development initiatives to redress dualistic development disparities in previously marginalised coastal localities. Finally, synthesis between traditional bureaucratic centralised co-ordinated planning and regionalised decentralised implementation orientated capacity building frameworks displaying a greater relevant stakeholder participatory ethos are examined.
- Full Text:
- Date Issued: 2003
- Authors: Hepburn, Bruce
- Date: 2003
- Subjects: Mariculture -- South Africa -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:941 , http://hdl.handle.net/10962/d1002674 , Mariculture -- South Africa -- Economic aspects
- Description: Current coastal legislative and institutional reformulation has effectively established new principles for the promotion of sustainable, co-ordinated integrated coastal development to be achieved through facilitatory, co-operative management mechanisms. In accordance, collaborative expansion and diversification of mariculture has been identified as a strategic mechanism for realising sustainable coastal development. Present limited foundational understanding regarding the emergent commercial contingent’s economic-institutional structure has constrained the effectiveness of current centralised broad objective formulation based planning techniques. By drawing upon findings of the 2001 National Mariculture Baseline survey, key economic development and institutional components requiring dedicated attention for further realising industry’s inherent growth potential to supply domestic and growing global aquaculture markets are examined in an inductive explorative framework. Attention is also directed towards promoting realisation of collaborative mariculture development initiatives to redress dualistic development disparities in previously marginalised coastal localities. Finally, synthesis between traditional bureaucratic centralised co-ordinated planning and regionalised decentralised implementation orientated capacity building frameworks displaying a greater relevant stakeholder participatory ethos are examined.
- Full Text:
- Date Issued: 2003
An investigation into the application of the IEEE 1394 high performance serial bus to sound installation contro
- Authors: Klinkradt, Bradley Hugh
- Date: 2003 , 2013-05-24
- Subjects: Digital electronics , Sound -- Recording and reproducing -- Digital techniques , Music -- Data processing , Computer sound processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4612 , http://hdl.handle.net/10962/d1004899 , Digital electronics , Sound -- Recording and reproducing -- Digital techniques , Music -- Data processing , Computer sound processing
- Description: This thesis investigates the feasibility of using existing IP-based control and monitoring protocols within professional audio installations utilising IEEE 1394 technology. Current control and monitoring technologies are examined, and the characteristics common to all are extracted and compiled into an object model. This model forms the foundation for a set of evaluation criteria against which current and future control and monitoring protocols may be measured. Protocols considered include AV/C, MIDI, QSC-24, and those utilised within the UPnP architecture. As QSC-24 and the UPnP architecture are IP-based, the facilities required to transport IP datagrams over the IEEE 1394 bus are investigated and implemented. Example QSC-24 and UPnP architecture implementations are described, which permit the control and monitoring of audio devices over the IEEE 1394 network using these IP-based technologies. The way forward for the control and monitoring of professional audio devices within installations is considered, and recommendations are provided. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
- Authors: Klinkradt, Bradley Hugh
- Date: 2003 , 2013-05-24
- Subjects: Digital electronics , Sound -- Recording and reproducing -- Digital techniques , Music -- Data processing , Computer sound processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4612 , http://hdl.handle.net/10962/d1004899 , Digital electronics , Sound -- Recording and reproducing -- Digital techniques , Music -- Data processing , Computer sound processing
- Description: This thesis investigates the feasibility of using existing IP-based control and monitoring protocols within professional audio installations utilising IEEE 1394 technology. Current control and monitoring technologies are examined, and the characteristics common to all are extracted and compiled into an object model. This model forms the foundation for a set of evaluation criteria against which current and future control and monitoring protocols may be measured. Protocols considered include AV/C, MIDI, QSC-24, and those utilised within the UPnP architecture. As QSC-24 and the UPnP architecture are IP-based, the facilities required to transport IP datagrams over the IEEE 1394 bus are investigated and implemented. Example QSC-24 and UPnP architecture implementations are described, which permit the control and monitoring of audio devices over the IEEE 1394 network using these IP-based technologies. The way forward for the control and monitoring of professional audio devices within installations is considered, and recommendations are provided. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
An investigation into the feeding biology and factors influencing the population dynamics of Terebrasabella heterouncinata (Polychaeta: Sabellidae), a problematic tube-dwelling polychaete in farmed abalone in South Africa
- Authors: Chalmers, Russell
- Date: 2003
- Subjects: Polychaeta -- South Africa , Sabellidae -- South Africa , Abalones -- Feeding and feeds -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5291 , http://hdl.handle.net/10962/d1005136 , Polychaeta -- South Africa , Sabellidae -- South Africa , Abalones -- Feeding and feeds -- South Africa
- Description: Since the discovery of a new species of sabellid worm in 1993, the Californian and South African abalone industries have experienced increasing shell breakage and reduced growth rates of abalone, resulting in reduced market value of product. This polychaete worm can reach very high infestation levels. It was described as Terebrasabella heterouncinata in 1999, having originated from the South African coastline where it had been observed on several wild mollusc species. Although not a shell borer, it occupies tubes on the growing edge which are formed by deposition of nacreous shell over sabellid larvae by the host abalone. Heavy sabellid infestation levels have placed the economic viability of several South African farms under threat. Past research methods have not been successful in establishing effective means of eradication or control, partly due to the lack of knowledge of basic biological information on this species. This study forms the first part of an ongoing research project into the biology of terebrasabella heterouncinata. Abalone farms in South African utilise two main diets in abalone culture. An artificial formulated feed, Abfeed, is produced in South Africa and is used by the majority of farms as it increases abalone growth rate. Kelp, a natural diet of abalone, is harvested and also used as a feed. Farmers have observed higher sabellid infestation levels on Abfeed-fed abalone and suspect that diet may be an important factor influencing sabellid infestation. Abalone stocking density has also been identified as a potential factor influencing sabellid population growth on commercial farms. In order to better understand sabellid nutrition, the feeding behaviour of the sabellid in response to suspended solids of various particle size classes from both abalone diets were investigated. Both the effect of abalone diet and stocking density and their effects on sabellid morphometrics were quantified. The proximate composition and particle size distribution of suspended-solids present within kelp and Abfeed abalone raceways were also quantified. Results indicate that sabellid feeding follows no structured behavioural pattern for both abalone diets. The quantity of suspended solids in kelp raceways was greater than in Abfeed raceways (p<0.02) while there was no difference in particulate level between three abalone stocking densities (p>0.05). Protein (p<0.0001) and energy (p<0.0.1) levels of suspended solids were significantly greater in raceways dedicated to feeding Abfeed. The infestation level (number of tubes/centimetre on the grwoing edge) was significantly higher (p<0.001) in Abfeed-fed abalone. The morphometrics of the sabellids indicated that sabellids from Abfeed-fed abalone were larger in various body measurements: length (p<0.00001); neck width (p<0.001); base width (p<0.001); and surface area (p<0.001). This study suggests that abalone diet has an important influence on the infestation level and size of sabellids and that this is likely to be due to the fragmentation and leaching of nutrients from the artificially enriched commercial abalone diet.
- Full Text:
- Date Issued: 2003
- Authors: Chalmers, Russell
- Date: 2003
- Subjects: Polychaeta -- South Africa , Sabellidae -- South Africa , Abalones -- Feeding and feeds -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5291 , http://hdl.handle.net/10962/d1005136 , Polychaeta -- South Africa , Sabellidae -- South Africa , Abalones -- Feeding and feeds -- South Africa
- Description: Since the discovery of a new species of sabellid worm in 1993, the Californian and South African abalone industries have experienced increasing shell breakage and reduced growth rates of abalone, resulting in reduced market value of product. This polychaete worm can reach very high infestation levels. It was described as Terebrasabella heterouncinata in 1999, having originated from the South African coastline where it had been observed on several wild mollusc species. Although not a shell borer, it occupies tubes on the growing edge which are formed by deposition of nacreous shell over sabellid larvae by the host abalone. Heavy sabellid infestation levels have placed the economic viability of several South African farms under threat. Past research methods have not been successful in establishing effective means of eradication or control, partly due to the lack of knowledge of basic biological information on this species. This study forms the first part of an ongoing research project into the biology of terebrasabella heterouncinata. Abalone farms in South African utilise two main diets in abalone culture. An artificial formulated feed, Abfeed, is produced in South Africa and is used by the majority of farms as it increases abalone growth rate. Kelp, a natural diet of abalone, is harvested and also used as a feed. Farmers have observed higher sabellid infestation levels on Abfeed-fed abalone and suspect that diet may be an important factor influencing sabellid infestation. Abalone stocking density has also been identified as a potential factor influencing sabellid population growth on commercial farms. In order to better understand sabellid nutrition, the feeding behaviour of the sabellid in response to suspended solids of various particle size classes from both abalone diets were investigated. Both the effect of abalone diet and stocking density and their effects on sabellid morphometrics were quantified. The proximate composition and particle size distribution of suspended-solids present within kelp and Abfeed abalone raceways were also quantified. Results indicate that sabellid feeding follows no structured behavioural pattern for both abalone diets. The quantity of suspended solids in kelp raceways was greater than in Abfeed raceways (p<0.02) while there was no difference in particulate level between three abalone stocking densities (p>0.05). Protein (p<0.0001) and energy (p<0.0.1) levels of suspended solids were significantly greater in raceways dedicated to feeding Abfeed. The infestation level (number of tubes/centimetre on the grwoing edge) was significantly higher (p<0.001) in Abfeed-fed abalone. The morphometrics of the sabellids indicated that sabellids from Abfeed-fed abalone were larger in various body measurements: length (p<0.00001); neck width (p<0.001); base width (p<0.001); and surface area (p<0.001). This study suggests that abalone diet has an important influence on the infestation level and size of sabellids and that this is likely to be due to the fragmentation and leaching of nutrients from the artificially enriched commercial abalone diet.
- Full Text:
- Date Issued: 2003
An investigation into the induction of oxidative stress and apoptosis by microcystin-LR in the CaCo2 cell line and intestinal tract of Balb/c mice
- Authors: Botha, Nicolette
- Date: 2003
- Subjects: Microcystis aeruginosa -- Toxicology , Apoptosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11066 , http://hdl.handle.net/10948/349 , Microcystis aeruginosa -- Toxicology , Apoptosis
- Description: This study reports the findings on the effect of Microcystin-LR (MCLR) on the gastrointestinal tract cells of mice and on two different cell lines, Caco2 and MCF-7. The cyanobacterium Microcystis aeruginosa produces the potent toxin, MCLR. This toxin has been implicated in a number of cases of ill-health. It was decided to investigate whether microcystin-LR induced apoptosis in the gastrointestinal tract of mice and also which possible mechanisms were involved in the induction in vitro. Balb/c mice were given a 75% LD50 intraperitoneal dose of pure microcystin -LR and sacrificed at 8, 16, 24 and 32 hours post-exposure. The small intestinal sections were stained with haematoxylin and eosin and examined for apoptotic cells. There was a time-dependent increase in the number of apoptotic cells with most in the duodenum and the jejunum. No change in glycogen content was evident at 24 hours post exposure when PAS-stained sections were examined. To determine that microcystin was the agent responsible for the changes, fluoroscein isothiocyanate (FITC) immunostaining for the toxin was done on the sections. Apoptosis in vitro was investigated in Caco2, a cell line that behaves like normal enterocytes when the cells are differentiated at confluency, and MCF-7, a breast cancer cell line deficient in pro-caspase-3, cells by 3-[dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and by staining with DAPI and Rhodamine 123. MCLR exposure induced apoptosis, as seen in decreased cell viability and increased leakage of LDH, as well as mitochondrial damage shown by Rhodamine staining. The MCF-7 cells, deficient in pro-caspase-3, and Caco2 cells did not show cleavage of poly(ADP)ribose polymerase (PARP) after exposure to 50μM MCLR after 72 hours exposure. Both micro- and milli-calpain activity was however significantly increased in both cell lines exposed to the toxin. There was a significant increase in H2O2, one of the key reactive oxygen species, production during the first 30 minutes that the cells were exposed to 50 mM MCLR.
- Full Text:
- Date Issued: 2003
- Authors: Botha, Nicolette
- Date: 2003
- Subjects: Microcystis aeruginosa -- Toxicology , Apoptosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11066 , http://hdl.handle.net/10948/349 , Microcystis aeruginosa -- Toxicology , Apoptosis
- Description: This study reports the findings on the effect of Microcystin-LR (MCLR) on the gastrointestinal tract cells of mice and on two different cell lines, Caco2 and MCF-7. The cyanobacterium Microcystis aeruginosa produces the potent toxin, MCLR. This toxin has been implicated in a number of cases of ill-health. It was decided to investigate whether microcystin-LR induced apoptosis in the gastrointestinal tract of mice and also which possible mechanisms were involved in the induction in vitro. Balb/c mice were given a 75% LD50 intraperitoneal dose of pure microcystin -LR and sacrificed at 8, 16, 24 and 32 hours post-exposure. The small intestinal sections were stained with haematoxylin and eosin and examined for apoptotic cells. There was a time-dependent increase in the number of apoptotic cells with most in the duodenum and the jejunum. No change in glycogen content was evident at 24 hours post exposure when PAS-stained sections were examined. To determine that microcystin was the agent responsible for the changes, fluoroscein isothiocyanate (FITC) immunostaining for the toxin was done on the sections. Apoptosis in vitro was investigated in Caco2, a cell line that behaves like normal enterocytes when the cells are differentiated at confluency, and MCF-7, a breast cancer cell line deficient in pro-caspase-3, cells by 3-[dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and by staining with DAPI and Rhodamine 123. MCLR exposure induced apoptosis, as seen in decreased cell viability and increased leakage of LDH, as well as mitochondrial damage shown by Rhodamine staining. The MCF-7 cells, deficient in pro-caspase-3, and Caco2 cells did not show cleavage of poly(ADP)ribose polymerase (PARP) after exposure to 50μM MCLR after 72 hours exposure. Both micro- and milli-calpain activity was however significantly increased in both cell lines exposed to the toxin. There was a significant increase in H2O2, one of the key reactive oxygen species, production during the first 30 minutes that the cells were exposed to 50 mM MCLR.
- Full Text:
- Date Issued: 2003
An investigation into the neuroprotective properties of curcumin
- Authors: Daniel, Sheril
- Date: 2003
- Subjects: Turmeric -- Therapeutic use , Nervous system -- Degeneration -- Prevention
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3753 , http://hdl.handle.net/10962/d1003231 , Turmeric -- Therapeutic use , Nervous system -- Degeneration -- Prevention
- Description: An increasing number of studies show that nutritional antioxidants such as vitamin E and polyphenols are capable of blocking neuronal death in vitro and may have therapeutic properties in animal models of neurodegenerative diseases including Alzheimer’s and Parkinson’s diseases. In the present study, the neuroprotective ability of one such polyphenolic antioxidant, curcumin, was investigated. Curcumin is the yellow curry spice derived from turmeric, and is widely used as a dietary component and herbal medicine in India. Most neurological disorders are postulated to have an oxidative or excitototoxic basis. Thus the effects of curcumin on oxidative stress in the rat brain were investigated. Curcumin, administered to the rat in vivo and in vitro, was able to exert protective effects on oxidative damage in the brain, induced by cyanide, a mitochondrial inhibitor. Curcumin also offered protection against quinolinic acid induced lipid peroxidation, and this protection was extended to lipid peroxidation induced by metals such as lead and cadmium in the rat brain. Experiments conducted on the pineal gland revealed an increased production of the neuroprotective hormone melatonin in presence of curcumin in vivo. The hippocampus is functionally related to vital behaviour and intellectual activities and is known to be a primary target for neuronal degeneration in the brains of patients with Alzheimer’s disease. Histological studies were undertaken to assess the effects of curcumin on lead induced toxicity on the rat hippocampus, the results of which show that curcumin affords significant protection to the hippocampus of the lead treated rats. This study also sought to elucidate possible mechanisms by which curcumin exerts its neuroprotective capabilities. Curcumin was found to inhibit the action of cyanide on the mitochondrial electron transport chain, one of the most common sources of free radicals. Electrochemical, UV/VIS and Infrared spectroscopy were used to characterise interactions between curcumin and the metals lead, cadmium, iron (II) and iron (III). Curcumin was shown to directly chelate these metals with the formation and isolation of two new curcumin complexes with lead, and one complex each with cadmium and iron (III). These results suggest chelation of toxic metals as a mechanism of neuroprotection afforded by curcumin. The need for neuroprotective agents is urgent considering the rapid rise in the elderly population and the proportionate increase in neurological disorders. The findings of this study indicate that curcumin, a well-established dietary antioxidant, is capable of playing a bigger role in neuroprotection, which needs to be further explored and exploited.
- Full Text:
- Date Issued: 2003
- Authors: Daniel, Sheril
- Date: 2003
- Subjects: Turmeric -- Therapeutic use , Nervous system -- Degeneration -- Prevention
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3753 , http://hdl.handle.net/10962/d1003231 , Turmeric -- Therapeutic use , Nervous system -- Degeneration -- Prevention
- Description: An increasing number of studies show that nutritional antioxidants such as vitamin E and polyphenols are capable of blocking neuronal death in vitro and may have therapeutic properties in animal models of neurodegenerative diseases including Alzheimer’s and Parkinson’s diseases. In the present study, the neuroprotective ability of one such polyphenolic antioxidant, curcumin, was investigated. Curcumin is the yellow curry spice derived from turmeric, and is widely used as a dietary component and herbal medicine in India. Most neurological disorders are postulated to have an oxidative or excitototoxic basis. Thus the effects of curcumin on oxidative stress in the rat brain were investigated. Curcumin, administered to the rat in vivo and in vitro, was able to exert protective effects on oxidative damage in the brain, induced by cyanide, a mitochondrial inhibitor. Curcumin also offered protection against quinolinic acid induced lipid peroxidation, and this protection was extended to lipid peroxidation induced by metals such as lead and cadmium in the rat brain. Experiments conducted on the pineal gland revealed an increased production of the neuroprotective hormone melatonin in presence of curcumin in vivo. The hippocampus is functionally related to vital behaviour and intellectual activities and is known to be a primary target for neuronal degeneration in the brains of patients with Alzheimer’s disease. Histological studies were undertaken to assess the effects of curcumin on lead induced toxicity on the rat hippocampus, the results of which show that curcumin affords significant protection to the hippocampus of the lead treated rats. This study also sought to elucidate possible mechanisms by which curcumin exerts its neuroprotective capabilities. Curcumin was found to inhibit the action of cyanide on the mitochondrial electron transport chain, one of the most common sources of free radicals. Electrochemical, UV/VIS and Infrared spectroscopy were used to characterise interactions between curcumin and the metals lead, cadmium, iron (II) and iron (III). Curcumin was shown to directly chelate these metals with the formation and isolation of two new curcumin complexes with lead, and one complex each with cadmium and iron (III). These results suggest chelation of toxic metals as a mechanism of neuroprotection afforded by curcumin. The need for neuroprotective agents is urgent considering the rapid rise in the elderly population and the proportionate increase in neurological disorders. The findings of this study indicate that curcumin, a well-established dietary antioxidant, is capable of playing a bigger role in neuroprotection, which needs to be further explored and exploited.
- Full Text:
- Date Issued: 2003
An investigation of knowledge management implementation strategies
- Authors: Sunassee, Nakkiran N
- Date: 2003
- Subjects: Knowledge management , Strategic planning , Automobile industry and trade -- South Africa -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1141 , http://hdl.handle.net/10962/d1002770 , Knowledge management , Strategic planning , Automobile industry and trade -- South Africa -- Management
- Description: The world is experiencing an era which has been termed the “knowledge age” or the “knowledge economy”. In this new context, knowledge is the primary commodity, and knowledge flows are regarded as the most important factors in the economy. The management of knowledge flows within organisations has become a crucial activity because many of the activities of organisations and the broader economic and social life today are knowledge-driven. In recent years, this managerial activity has become known as Knowledge Management. Equally important are the associated Knowledge Management implementation strategies. Driven by a need expressed by the South African Motor Vehicle Industry for a knowledge management implementation strategy tailored to their needs, this research aimed to develop a knowledge management implementation strategy suited to the needs of this industry. Following an extensive literature survey and a study of the target industry using Duffy’s Knowledge Benchmarking Questionnaire, a model of knowledge management implementation is proposed that is suited to the needs of the South African Motor Vehicle Industry. The model consists of three main interlinked components: Knowledge Management of the Organisation, People, and Infrastructure and Processes. Furthermore, the model recommends a holistic approach to managing knowledge. The critical success factors of the model were tested by means of a survey of industry opinions that validated certain aspects of the model and motivated for changes in others. Additionally, despite the focus of the model on the target industry, it is considered sufficiently appropriate for use by other organisations.
- Full Text:
- Date Issued: 2003
- Authors: Sunassee, Nakkiran N
- Date: 2003
- Subjects: Knowledge management , Strategic planning , Automobile industry and trade -- South Africa -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1141 , http://hdl.handle.net/10962/d1002770 , Knowledge management , Strategic planning , Automobile industry and trade -- South Africa -- Management
- Description: The world is experiencing an era which has been termed the “knowledge age” or the “knowledge economy”. In this new context, knowledge is the primary commodity, and knowledge flows are regarded as the most important factors in the economy. The management of knowledge flows within organisations has become a crucial activity because many of the activities of organisations and the broader economic and social life today are knowledge-driven. In recent years, this managerial activity has become known as Knowledge Management. Equally important are the associated Knowledge Management implementation strategies. Driven by a need expressed by the South African Motor Vehicle Industry for a knowledge management implementation strategy tailored to their needs, this research aimed to develop a knowledge management implementation strategy suited to the needs of this industry. Following an extensive literature survey and a study of the target industry using Duffy’s Knowledge Benchmarking Questionnaire, a model of knowledge management implementation is proposed that is suited to the needs of the South African Motor Vehicle Industry. The model consists of three main interlinked components: Knowledge Management of the Organisation, People, and Infrastructure and Processes. Furthermore, the model recommends a holistic approach to managing knowledge. The critical success factors of the model were tested by means of a survey of industry opinions that validated certain aspects of the model and motivated for changes in others. Additionally, despite the focus of the model on the target industry, it is considered sufficiently appropriate for use by other organisations.
- Full Text:
- Date Issued: 2003
Applied studies of some Southern African blowflies (Diptera: Calliphoridae) of forensic importance
- Authors: Lunt, Nicola
- Date: 2003
- Subjects: Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5803 , http://hdl.handle.net/10962/d1006202 , Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Description: Three major aspects of blowfly (Diptera: Calliphoridae) research were the focus of this study. Firstly, the phylogenetic relationships of 40 oestroid species from a variety of geographical localities were investigated using Cytochrome Oxidase b subunit I (COl) gene sequences. Maximum parsimony (MP) and Jukes-Cantor neighbor-joining (NJ) analyses both extracted a paraphyletic Calliphoridae, with the Calliphorinae-Luciliinae clade being sister to the Sarcophagidae. Short branch lengths within Chrysomya indicate a recent rapid radiation of this genus. Phormia and Protophormia either formed a sister clade to Chrysomya, or were embedded in this genus. Tree topologies were comparable between MP and NJ trees, but the positions of some genera were ambiguous. Secondly, developmental parameters and behaviour were investigated for four southern African species of forensically important blowflies viz. Chrysomya chloropyga, C. putoria, C. megacephala and Lucilia sericata, and ad hoc observations were made for Calliphora croceipalpis, Chrysomya marginalis and the predatory C. albiceps. Choice of oviposition substrate differed between species, mirroring substrate preferences in the field. Sexual dimorphism and dwarfism within a cohort complicated ageing maggots using size, but the use of developmental events (e.g. ecdysis) allowed ages to be determined unambiguously. Separate species status was supported for the previously synonymised C. chloropyga and C. putoria, by differences in maggot behaviour, larval growth rates and temperature optima. The proportion of total development time assigned to each larval instar and pupariation was variable among temperatures, but similar between congeneric species. Thirdly, since a negative linear relationship was found to occur between the developmental constant (K) and developmental zero (D₀) for both Calliphoridae and Sarcophagidae, the potential for predicting physiological parameters of unstudied taxa was investigated. Species and genera of Palaearctic origin generally had high K's and low D₀'s, and the reverse was true for the tropical taxa. It was found that both K and D₀ can be estimated for "unknown" taxa using the Felsenstein's Independent Contrasts (FIC) method of PDTree (Garland et al. 200 I), provided that branch lengths are relatively short and the phylogenetic position of the estimated taxon is unambiguous.
- Full Text:
- Date Issued: 2003
- Authors: Lunt, Nicola
- Date: 2003
- Subjects: Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5803 , http://hdl.handle.net/10962/d1006202 , Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Description: Three major aspects of blowfly (Diptera: Calliphoridae) research were the focus of this study. Firstly, the phylogenetic relationships of 40 oestroid species from a variety of geographical localities were investigated using Cytochrome Oxidase b subunit I (COl) gene sequences. Maximum parsimony (MP) and Jukes-Cantor neighbor-joining (NJ) analyses both extracted a paraphyletic Calliphoridae, with the Calliphorinae-Luciliinae clade being sister to the Sarcophagidae. Short branch lengths within Chrysomya indicate a recent rapid radiation of this genus. Phormia and Protophormia either formed a sister clade to Chrysomya, or were embedded in this genus. Tree topologies were comparable between MP and NJ trees, but the positions of some genera were ambiguous. Secondly, developmental parameters and behaviour were investigated for four southern African species of forensically important blowflies viz. Chrysomya chloropyga, C. putoria, C. megacephala and Lucilia sericata, and ad hoc observations were made for Calliphora croceipalpis, Chrysomya marginalis and the predatory C. albiceps. Choice of oviposition substrate differed between species, mirroring substrate preferences in the field. Sexual dimorphism and dwarfism within a cohort complicated ageing maggots using size, but the use of developmental events (e.g. ecdysis) allowed ages to be determined unambiguously. Separate species status was supported for the previously synonymised C. chloropyga and C. putoria, by differences in maggot behaviour, larval growth rates and temperature optima. The proportion of total development time assigned to each larval instar and pupariation was variable among temperatures, but similar between congeneric species. Thirdly, since a negative linear relationship was found to occur between the developmental constant (K) and developmental zero (D₀) for both Calliphoridae and Sarcophagidae, the potential for predicting physiological parameters of unstudied taxa was investigated. Species and genera of Palaearctic origin generally had high K's and low D₀'s, and the reverse was true for the tropical taxa. It was found that both K and D₀ can be estimated for "unknown" taxa using the Felsenstein's Independent Contrasts (FIC) method of PDTree (Garland et al. 200 I), provided that branch lengths are relatively short and the phylogenetic position of the estimated taxon is unambiguous.
- Full Text:
- Date Issued: 2003
Bioaccumulation and histopathology of copper in Oreochromis mossambicus
- Authors: Naigaga, Irene
- Date: 2003
- Subjects: Mozambique tilapia , Copper , Marine toxins , Fishes -- Effect of water pollution on , Water -- Pollution -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5234 , http://hdl.handle.net/10962/d1005077 , Mozambique tilapia , Copper , Marine toxins , Fishes -- Effect of water pollution on , Water -- Pollution -- Environmental aspects
- Description: Cu is one of the most toxic elements that affect fish populations when the fish are exposed to concentrations exceeding their tolerance. To investigate the effects of elementary Cu on aspects of bioconcentration, histology and behaviour, O. mossambicus were exposed to 0 and 0.75 ± 0.20 mg/l of Cu for 96 hours (short-term study), and 0, 0.11 ± 0.02, 0.29 ± 0.02, and 0.47 ± 0.04 mg/l of Cu for 64 days (longterm study) under controlled conditions in the laboratory. For the long-term study fish were sampled for gills, liver, and kidney Cu accumulation analysis after 1, 32 and 64 days of exposure and after 1, 2, 4, 16, 32, and 64 days for gills, liver and spleen histology analysis. Cu accumulation was concentration-duration dependent with the highest accumulation capacity in the liver. A multifactor linear model was developed for the relationship between exposure dose, exposure duration and Cu accumulation in the organs with the liver model: Log L = 3.35 + 0.85W + 0.31T (r² = 0.892) giving a better fit than the gills: G = −35.09 + 10.58W + 17.58T (r² = 0.632). Where L = Cu accumulation values in the liver, G = Cu accumulation values in the gills (both in μg/g dry mass); W = exposure dose in water (mg/l); and T = exposure time (days). Using this model Cu accumulation in organs can be estimated when exposure concentration and duration is known. This model should be tested under different conditions to determine the potential of the model in monitoring Cu toxicity in the environment. Lesions were observed in the liver, gills and spleen in all Cu treatments at all exposure concentration and exposure durations. However, the incidence and the degree of alteration was related to the concentration of Cu and duration of exposure. The sequential appearance of lesions in the order of, hepatic vacuolar degeneration, fatty degeneration and necrosis indicated a gradual increase in liver damage with larger duration of exposure time and increasing Cu concentration. The initial lesions in the gills were manifested as hypertrophy and hyperplasia of the gill epithelium causing increase in the thickness of the secondary lamellae, mucous cell hypertrophy and proliferation, mucous hypersecretion, proliferation of eosinophilic granule cells and hyperplasia of interlamellar cells. With increase in exposure time, necrosis of the eosinophilic granule cells, lamellar oedema, epithelial desquamation and increase in severity of lamellar hyperplasia were observed. These lesions indicated an initial defence mechanism of the fish against Cu toxicity followed by advanced histological changes that were related to Cu concentration and duration of exposure. Changes in the spleen were haemosiderosis, increase in the white pulp and macrophage centres, reduction in the red pulp, and necrosis suggesting that fish exposed to environmentally relevant levels of Cu may be histopathologically altered leading to anaemia and immunosuppression. Regression analysis was used to quantify the relationship between the total activity of the fish, and duration of exposure. There was a gradual decline in fish activity related to Cu concentration and duration of exposure before introducing food into the tanks. There was a constant activity after introducing food in the tanks at the control and 0.11 ± 0.02 mg/l Cu exposure levels irrespective of exposure time. Analysis of covariance (ANCOVA) was used to test for the difference in slopes between treatments. There was no significant difference (p > 0.05) between slopes of the control and 0.11 ± 0.02 mg/l Cu, and between 0.29 ± 0.02 and 47 ± 0.04 mg/l Cu before and after introducing food in the tanks. The slopes of both the control and 0.11 ± 0.02 mg/l Cu were significantly different from those of 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu (p < 0.05). There were significant differences in the mean opercular movements per minute between treatments (p < 0.05). There was hyperventilation at 0.11 ± 0.02 mg/l Cu i.e. 87 ± 18 opercular movements per minute (mean ± standard deviation) and hypoventilation at 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu i.e. 37 ± 34 and 13 ± 6 opercular movements per minute compared to the control. Hypo- and hyperventilation were related to the lesser and greater gill damage, respectively. In conclusion Cu accumulation and effects on histology of the liver, gills and were related to the concentration of Cu in the water and duration of exposure showing a gradual increase in incidence and intensity with larger duration of exposure time and increasing Cu concentration. The fish were initially able to homeostatically regulate and detoxify Cu. However, as the exposure continued, the homeostatic mechanism appears to have failed to cope with the increasing metal burden causing advanced histological changes.
- Full Text:
- Date Issued: 2003
- Authors: Naigaga, Irene
- Date: 2003
- Subjects: Mozambique tilapia , Copper , Marine toxins , Fishes -- Effect of water pollution on , Water -- Pollution -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5234 , http://hdl.handle.net/10962/d1005077 , Mozambique tilapia , Copper , Marine toxins , Fishes -- Effect of water pollution on , Water -- Pollution -- Environmental aspects
- Description: Cu is one of the most toxic elements that affect fish populations when the fish are exposed to concentrations exceeding their tolerance. To investigate the effects of elementary Cu on aspects of bioconcentration, histology and behaviour, O. mossambicus were exposed to 0 and 0.75 ± 0.20 mg/l of Cu for 96 hours (short-term study), and 0, 0.11 ± 0.02, 0.29 ± 0.02, and 0.47 ± 0.04 mg/l of Cu for 64 days (longterm study) under controlled conditions in the laboratory. For the long-term study fish were sampled for gills, liver, and kidney Cu accumulation analysis after 1, 32 and 64 days of exposure and after 1, 2, 4, 16, 32, and 64 days for gills, liver and spleen histology analysis. Cu accumulation was concentration-duration dependent with the highest accumulation capacity in the liver. A multifactor linear model was developed for the relationship between exposure dose, exposure duration and Cu accumulation in the organs with the liver model: Log L = 3.35 + 0.85W + 0.31T (r² = 0.892) giving a better fit than the gills: G = −35.09 + 10.58W + 17.58T (r² = 0.632). Where L = Cu accumulation values in the liver, G = Cu accumulation values in the gills (both in μg/g dry mass); W = exposure dose in water (mg/l); and T = exposure time (days). Using this model Cu accumulation in organs can be estimated when exposure concentration and duration is known. This model should be tested under different conditions to determine the potential of the model in monitoring Cu toxicity in the environment. Lesions were observed in the liver, gills and spleen in all Cu treatments at all exposure concentration and exposure durations. However, the incidence and the degree of alteration was related to the concentration of Cu and duration of exposure. The sequential appearance of lesions in the order of, hepatic vacuolar degeneration, fatty degeneration and necrosis indicated a gradual increase in liver damage with larger duration of exposure time and increasing Cu concentration. The initial lesions in the gills were manifested as hypertrophy and hyperplasia of the gill epithelium causing increase in the thickness of the secondary lamellae, mucous cell hypertrophy and proliferation, mucous hypersecretion, proliferation of eosinophilic granule cells and hyperplasia of interlamellar cells. With increase in exposure time, necrosis of the eosinophilic granule cells, lamellar oedema, epithelial desquamation and increase in severity of lamellar hyperplasia were observed. These lesions indicated an initial defence mechanism of the fish against Cu toxicity followed by advanced histological changes that were related to Cu concentration and duration of exposure. Changes in the spleen were haemosiderosis, increase in the white pulp and macrophage centres, reduction in the red pulp, and necrosis suggesting that fish exposed to environmentally relevant levels of Cu may be histopathologically altered leading to anaemia and immunosuppression. Regression analysis was used to quantify the relationship between the total activity of the fish, and duration of exposure. There was a gradual decline in fish activity related to Cu concentration and duration of exposure before introducing food into the tanks. There was a constant activity after introducing food in the tanks at the control and 0.11 ± 0.02 mg/l Cu exposure levels irrespective of exposure time. Analysis of covariance (ANCOVA) was used to test for the difference in slopes between treatments. There was no significant difference (p > 0.05) between slopes of the control and 0.11 ± 0.02 mg/l Cu, and between 0.29 ± 0.02 and 47 ± 0.04 mg/l Cu before and after introducing food in the tanks. The slopes of both the control and 0.11 ± 0.02 mg/l Cu were significantly different from those of 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu (p < 0.05). There were significant differences in the mean opercular movements per minute between treatments (p < 0.05). There was hyperventilation at 0.11 ± 0.02 mg/l Cu i.e. 87 ± 18 opercular movements per minute (mean ± standard deviation) and hypoventilation at 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu i.e. 37 ± 34 and 13 ± 6 opercular movements per minute compared to the control. Hypo- and hyperventilation were related to the lesser and greater gill damage, respectively. In conclusion Cu accumulation and effects on histology of the liver, gills and were related to the concentration of Cu in the water and duration of exposure showing a gradual increase in incidence and intensity with larger duration of exposure time and increasing Cu concentration. The fish were initially able to homeostatically regulate and detoxify Cu. However, as the exposure continued, the homeostatic mechanism appears to have failed to cope with the increasing metal burden causing advanced histological changes.
- Full Text:
- Date Issued: 2003
Biology and demography of the spotted grunter Pomadasys commersonnii (Haemulidae) in South African waters
- Authors: Webb, Garth Anthony
- Date: 2003
- Subjects: Grunts (Fishes) -- South Africa , Grunts (Fishes) -- South Africa -- Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5201 , http://hdl.handle.net/10962/d1003727 , Grunts (Fishes) -- South Africa , Grunts (Fishes) -- South Africa -- Ecology
- Description: The spotted grunter, Pomadasys commersonnii (Haemulidae), is an Indian Ocean coastal species, extending from India to False Bay but is absent from the central Indian Ocean islands. Its taste and texture has made it one of the most important line fish species and is caught by recreational and subsistence fisherman along the entire east coast of South Africa. Because of its inshore distribution, reduced catch rates and estuarine dependence the species was de-commercialised in 1992. Since then it has been investigated as a candidate species for mariculture. All previous work on the biology of the species was undertaken on fish collected in KwaZulu-Natal in the mid 1970's. All other information has been incidental and formed part of other ecological studies. All management plans for this species have been based on these data. To develop a more comprehensive management plan that incorporates the entire population of spotted grunter, it was deemed necessary to reassess the biology (including feeding biology, age and growth and reproductive biology) as well as the demography of the population throughout its distributional range in South African waters. Analysis of the diet of spotted grunter, collected in estuaries, indicates that crustaceans form the bulk of the prey selected. Amphipods, mysids and estuarine brachyura predominate the diet of fish < 300 mm TL. At 200 mm TL fish start to prey on anomurans, which are extracted from their burrows using the 'blowing' feeding mechanism. Anomurans, in particular Upogebia africana and Callianassa krausii, become the preferred prey of fish larger than 300 mm TL. The high degree of diet flexibility that spotted grunter exhibit means that the composition and abundance of the macrobenthos of a particular environment will dictate the diet of the species. Otolith growth zones were found to be deposited annually with the opaque zones being deposited during the austral summer (November - February). The optical definition of annual otolith growth rings differed significantly between geographic regions (namely: Western Cape, South Eastern Cape and KwaZulu-Natal). Growth (sex combined) offish in the Western Cape were best described by the specialised 3 parameter Von Bertalanffy with a relative error structure in the form : Lt = 753(1- e⁻°·¹⁵⁴ ⁽t +¹·⁶¹⁵⁾) while growth in the South Eastern Cape was best described by using the Schnute model with an absolute error structure in the form: Lt=177°·⁴¹⁶ + (676.2⁻¹·²⁶⁶ - 169.2⁻¹²⁶⁶)[1-e°·⁴¹⁶⁽t-t₁⁾ / 1-e°·⁴¹⁶⁽t₂-t₁⁾]¹/¹·²⁶⁶ whereas growth was best described in KwaZulu-Natal using the specialised 3 parameter Von Bertalanffy with a relative error structure in the form: Lt = 839(1-e°·¹⁷⁽t⁺°·⁴⁹⁾) In the South Eastern Cape, length at 50% maturity was found to be 305 mm TL for males. Since females with ripe & running or spent gonads were not found in the South Eastern Cape and since histological evidence suggests that females in the South Eastern Cape have spawned, it appears that spawning does not occur in the South Eastern Cape. These results suggest that adults are resident in the estuaries of the Western and South Eastern Cape and undertake the spring/summer, northward spawning migration to KwaZulu-Natal. After joining the resident spawner stock in KwaZulu-Natal and spawning in the offshore environment of KwaZulu-Natal, adults soon return to the southern regions of their distributional range. Juveniles recruit into KwaZulu-Natal estuaries at a length of 25 - 35 mm TL. A proportion of the eggs and larvae are transported southwards along the periphery of the western boundary Agulhas Current where juveniles (25 - 30 mm TL) recruit into the estuaries as far south as the Swartvlei estuary in the Western Cape. There is evidence to suggest that the fish, which occur in the Western Cape estuaries, have migrated there once they have attained sexual maturity further east.
- Full Text:
- Date Issued: 2003
- Authors: Webb, Garth Anthony
- Date: 2003
- Subjects: Grunts (Fishes) -- South Africa , Grunts (Fishes) -- South Africa -- Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5201 , http://hdl.handle.net/10962/d1003727 , Grunts (Fishes) -- South Africa , Grunts (Fishes) -- South Africa -- Ecology
- Description: The spotted grunter, Pomadasys commersonnii (Haemulidae), is an Indian Ocean coastal species, extending from India to False Bay but is absent from the central Indian Ocean islands. Its taste and texture has made it one of the most important line fish species and is caught by recreational and subsistence fisherman along the entire east coast of South Africa. Because of its inshore distribution, reduced catch rates and estuarine dependence the species was de-commercialised in 1992. Since then it has been investigated as a candidate species for mariculture. All previous work on the biology of the species was undertaken on fish collected in KwaZulu-Natal in the mid 1970's. All other information has been incidental and formed part of other ecological studies. All management plans for this species have been based on these data. To develop a more comprehensive management plan that incorporates the entire population of spotted grunter, it was deemed necessary to reassess the biology (including feeding biology, age and growth and reproductive biology) as well as the demography of the population throughout its distributional range in South African waters. Analysis of the diet of spotted grunter, collected in estuaries, indicates that crustaceans form the bulk of the prey selected. Amphipods, mysids and estuarine brachyura predominate the diet of fish < 300 mm TL. At 200 mm TL fish start to prey on anomurans, which are extracted from their burrows using the 'blowing' feeding mechanism. Anomurans, in particular Upogebia africana and Callianassa krausii, become the preferred prey of fish larger than 300 mm TL. The high degree of diet flexibility that spotted grunter exhibit means that the composition and abundance of the macrobenthos of a particular environment will dictate the diet of the species. Otolith growth zones were found to be deposited annually with the opaque zones being deposited during the austral summer (November - February). The optical definition of annual otolith growth rings differed significantly between geographic regions (namely: Western Cape, South Eastern Cape and KwaZulu-Natal). Growth (sex combined) offish in the Western Cape were best described by the specialised 3 parameter Von Bertalanffy with a relative error structure in the form : Lt = 753(1- e⁻°·¹⁵⁴ ⁽t +¹·⁶¹⁵⁾) while growth in the South Eastern Cape was best described by using the Schnute model with an absolute error structure in the form: Lt=177°·⁴¹⁶ + (676.2⁻¹·²⁶⁶ - 169.2⁻¹²⁶⁶)[1-e°·⁴¹⁶⁽t-t₁⁾ / 1-e°·⁴¹⁶⁽t₂-t₁⁾]¹/¹·²⁶⁶ whereas growth was best described in KwaZulu-Natal using the specialised 3 parameter Von Bertalanffy with a relative error structure in the form: Lt = 839(1-e°·¹⁷⁽t⁺°·⁴⁹⁾) In the South Eastern Cape, length at 50% maturity was found to be 305 mm TL for males. Since females with ripe & running or spent gonads were not found in the South Eastern Cape and since histological evidence suggests that females in the South Eastern Cape have spawned, it appears that spawning does not occur in the South Eastern Cape. These results suggest that adults are resident in the estuaries of the Western and South Eastern Cape and undertake the spring/summer, northward spawning migration to KwaZulu-Natal. After joining the resident spawner stock in KwaZulu-Natal and spawning in the offshore environment of KwaZulu-Natal, adults soon return to the southern regions of their distributional range. Juveniles recruit into KwaZulu-Natal estuaries at a length of 25 - 35 mm TL. A proportion of the eggs and larvae are transported southwards along the periphery of the western boundary Agulhas Current where juveniles (25 - 30 mm TL) recruit into the estuaries as far south as the Swartvlei estuary in the Western Cape. There is evidence to suggest that the fish, which occur in the Western Cape estuaries, have migrated there once they have attained sexual maturity further east.
- Full Text:
- Date Issued: 2003
Botanical inventory and phenology in relation to foraging behaviour of the Cape honeybees (Apis Mellifera Capensis) at a site in the Eastern Cape, South Africa
- Authors: Merti, Admassu Addi
- Date: 2003
- Subjects: Fynbos -- South Africa -- Eastern Cape , Honeybee -- South Africa -- Eastern Cape , Honey plants -- South Africa -- Eastern Cape , Honeybee -- South Africa -- Eastern Cape -- Food , Plant ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4214 , http://hdl.handle.net/10962/d1003783 , Fynbos -- South Africa -- Eastern Cape , Honeybee -- South Africa -- Eastern Cape , Honey plants -- South Africa -- Eastern Cape , Honeybee -- South Africa -- Eastern Cape -- Food , Plant ecology -- South Africa -- Eastern Cape
- Description: From an apicultural point of view the Cape fynbos is under-utilised and our knowledge of its utilization by the Cape honeybees is incomplete. The key aim of this study was to test the hypothesis that the Cape honeybees utilize the fynbos species as the preferred source of nectar and pollen. Subsidiary aims included distinguishing vegetation communities in the area, identifying pollen and nectar sources, the relationship between brood population and seasonal pollen collection patterns, examining the effect of meteorological factors on pollen collection. The study site was on Rivendell Farm within the Eastern Cape Albany district: an area of high species richness. A checklist of vascular plant species was produced revealing 97 families, 271 genera and 448 species. A classification by two-way indicator species (TWINSPAN) recognized seven vegetation communities: Forest, Bush clumps, Acacia savanna, Grassland, Grassy fynbos, Fynbos and Shrubland. Direct field observations of the foraging of Cape honeybees identified 54 nectar and pollen source plant species. Honeybee pollen loads trapped from four colonies of hives identified 37 pollen source plants of which Metalasia muricata, Eucalyptus grandis, Eucalyptus camaldulensis, Erica chamissonis, Helichrysum odoratissimum, Helichrysum anomalum, Crassula cultrata and Acacia longifolia were the predominant pollen source plants. It was also found that 60% of pollen yield derived from fynbos vegetation. The pollen source plants came from both Cape endemic and from nonendemic species. Thus we reject the hypothesis that Cape honeybees selectively forage fynbos species as a preferred source of pollen and nectar. The examination of the effect of temperature, wind-speed and temperature on pollen collection activity of honeybees revealed that: a temperature range of between 14°C to 26°C was optimal for pollen collection; wind speeds of up to 4m/s were conducive for pollen collection; relative humidity was found to have no significant influence on pollen collection. Pollen collection and brood rearing patterns are positively correlated with flowering intensities, but we found in our Eastern Cape study site that brood rearing was not limited to the spring flowering season but did extend to the end of summer. In order to determine the available nectar yield of common plant species hourly secretion of nectar volumes was measured for 24 hours to determine the variation of available nectar during different times of the day. In all nectar producing species the nectar volume was high in the early morning and declined as the day progressed. We found that the volume of available nectar was affected by prevailing temperature and humidity around the flowers.
- Full Text:
- Date Issued: 2003
- Authors: Merti, Admassu Addi
- Date: 2003
- Subjects: Fynbos -- South Africa -- Eastern Cape , Honeybee -- South Africa -- Eastern Cape , Honey plants -- South Africa -- Eastern Cape , Honeybee -- South Africa -- Eastern Cape -- Food , Plant ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4214 , http://hdl.handle.net/10962/d1003783 , Fynbos -- South Africa -- Eastern Cape , Honeybee -- South Africa -- Eastern Cape , Honey plants -- South Africa -- Eastern Cape , Honeybee -- South Africa -- Eastern Cape -- Food , Plant ecology -- South Africa -- Eastern Cape
- Description: From an apicultural point of view the Cape fynbos is under-utilised and our knowledge of its utilization by the Cape honeybees is incomplete. The key aim of this study was to test the hypothesis that the Cape honeybees utilize the fynbos species as the preferred source of nectar and pollen. Subsidiary aims included distinguishing vegetation communities in the area, identifying pollen and nectar sources, the relationship between brood population and seasonal pollen collection patterns, examining the effect of meteorological factors on pollen collection. The study site was on Rivendell Farm within the Eastern Cape Albany district: an area of high species richness. A checklist of vascular plant species was produced revealing 97 families, 271 genera and 448 species. A classification by two-way indicator species (TWINSPAN) recognized seven vegetation communities: Forest, Bush clumps, Acacia savanna, Grassland, Grassy fynbos, Fynbos and Shrubland. Direct field observations of the foraging of Cape honeybees identified 54 nectar and pollen source plant species. Honeybee pollen loads trapped from four colonies of hives identified 37 pollen source plants of which Metalasia muricata, Eucalyptus grandis, Eucalyptus camaldulensis, Erica chamissonis, Helichrysum odoratissimum, Helichrysum anomalum, Crassula cultrata and Acacia longifolia were the predominant pollen source plants. It was also found that 60% of pollen yield derived from fynbos vegetation. The pollen source plants came from both Cape endemic and from nonendemic species. Thus we reject the hypothesis that Cape honeybees selectively forage fynbos species as a preferred source of pollen and nectar. The examination of the effect of temperature, wind-speed and temperature on pollen collection activity of honeybees revealed that: a temperature range of between 14°C to 26°C was optimal for pollen collection; wind speeds of up to 4m/s were conducive for pollen collection; relative humidity was found to have no significant influence on pollen collection. Pollen collection and brood rearing patterns are positively correlated with flowering intensities, but we found in our Eastern Cape study site that brood rearing was not limited to the spring flowering season but did extend to the end of summer. In order to determine the available nectar yield of common plant species hourly secretion of nectar volumes was measured for 24 hours to determine the variation of available nectar during different times of the day. In all nectar producing species the nectar volume was high in the early morning and declined as the day progressed. We found that the volume of available nectar was affected by prevailing temperature and humidity around the flowers.
- Full Text:
- Date Issued: 2003
Cimetidine as a free radical scavenger
- Authors: Lambat, Zaynab Yusuf
- Date: 2003
- Subjects: Cimetidine , Cimetidine -- Physiological effect , Cimetidine -- Therapeutic use , Alzheimer's disease -- Treatment , Cancer -- Treatment , Free radicals (Chemistry) -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3766 , http://hdl.handle.net/10962/d1003244 , Cimetidine , Cimetidine -- Physiological effect , Cimetidine -- Therapeutic use , Alzheimer's disease -- Treatment , Cancer -- Treatment , Free radicals (Chemistry) -- Physiological effect
- Description: The present study was undertaken to determine the effects and possible mechanism of action of cimetidine in cancer and Alzheimer’s disease (AD). Throughout this study emphasis is placed on free radical levels since the magnitude of the relationship between diseases and the levels of free radicals vary from one disease to another. Studies were carried out to examine the effect of cimetidine on free radical levels using superoxide formation and lipid peroxidation as indicators of free radical levels. The experiments revealed that addition of cimetidine, especially in high concentrations (0.5 and 1.0 x10-6 M) significantly inhibited WHCO6 cancer cell growth rather than cancer cell growth, as no normal control was available. Free radical formation as well as hydroxyl radical formation were reduced in the deoxyribose assay. In addition, cimetidine exhibits properties of binding to metals such as copper and iron. To maintain consistency in the experiments, a WHCO6 (Wits Human Carcinoma of the Oesophagus) cell line was used to investigate the effect of cimetidine in cancer. Neurodegeneration was induced in the rat brain using neurotoxins such as cyanide to investigate the relationship between cimetidine in AD. A decrease in cancer cell growth was accompanied by a concomitant decrease in the levels of free radicals and lipid peroxidation, suggesting that the growth-inhibitory effects of cimetidine on WHCO6 cancer cells in vitro may be due to free radical scavenging properties. This proposal was further strengthened by determination of free radical levels in the rat brain. After treatment with neurotoxins to induce neurodegeneration, the levels of free radicals in the rat brain suggest that addition of cimetidine reduces free radical levels in the rat brain in a dosedependent manner. Further experiments were done in an attempt to uncover the underlying mechanism by which cimetidine exhibits free radical scavenging properties. Metal binding studies were done using electrochemical, HPLC and UV/Vis studies. The results show that cimetidine binds iron and copper. These metals have been implicated in free radical production via the Fenton reaction. By binding with cimetidine the metals become unavailable to produce free radicals and hence cimetidine indirectly reduces the formation of free radicals. The final experiment was the determination of cimetidine as a hydroxyl radical scavenger in the deoxyribose assay. Cimetidine was shown to act as a potent hydroxyl radical scavenger, thereby confirming its activity as a free radical scavenger. In addition, cimetidine protects against damage to the deoxyribose sugar, a component of DNA. Whilst there are many theories that explain the therapeutic role of cimetidine in degenerative disease, the actual mechanism of the role of cimetidine is emphasized as a free radical scavenger. Regardless of the mechanism of action, cimetidine does inhibit tumour growth according to this study and also reduce free radical levels in neurodegeneration, which suggests a role for cimetidine as a possible additive in treatment of patients with such disease states. These findings have important clinical implications, and needs to be investigated further.
- Full Text:
- Date Issued: 2003
- Authors: Lambat, Zaynab Yusuf
- Date: 2003
- Subjects: Cimetidine , Cimetidine -- Physiological effect , Cimetidine -- Therapeutic use , Alzheimer's disease -- Treatment , Cancer -- Treatment , Free radicals (Chemistry) -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3766 , http://hdl.handle.net/10962/d1003244 , Cimetidine , Cimetidine -- Physiological effect , Cimetidine -- Therapeutic use , Alzheimer's disease -- Treatment , Cancer -- Treatment , Free radicals (Chemistry) -- Physiological effect
- Description: The present study was undertaken to determine the effects and possible mechanism of action of cimetidine in cancer and Alzheimer’s disease (AD). Throughout this study emphasis is placed on free radical levels since the magnitude of the relationship between diseases and the levels of free radicals vary from one disease to another. Studies were carried out to examine the effect of cimetidine on free radical levels using superoxide formation and lipid peroxidation as indicators of free radical levels. The experiments revealed that addition of cimetidine, especially in high concentrations (0.5 and 1.0 x10-6 M) significantly inhibited WHCO6 cancer cell growth rather than cancer cell growth, as no normal control was available. Free radical formation as well as hydroxyl radical formation were reduced in the deoxyribose assay. In addition, cimetidine exhibits properties of binding to metals such as copper and iron. To maintain consistency in the experiments, a WHCO6 (Wits Human Carcinoma of the Oesophagus) cell line was used to investigate the effect of cimetidine in cancer. Neurodegeneration was induced in the rat brain using neurotoxins such as cyanide to investigate the relationship between cimetidine in AD. A decrease in cancer cell growth was accompanied by a concomitant decrease in the levels of free radicals and lipid peroxidation, suggesting that the growth-inhibitory effects of cimetidine on WHCO6 cancer cells in vitro may be due to free radical scavenging properties. This proposal was further strengthened by determination of free radical levels in the rat brain. After treatment with neurotoxins to induce neurodegeneration, the levels of free radicals in the rat brain suggest that addition of cimetidine reduces free radical levels in the rat brain in a dosedependent manner. Further experiments were done in an attempt to uncover the underlying mechanism by which cimetidine exhibits free radical scavenging properties. Metal binding studies were done using electrochemical, HPLC and UV/Vis studies. The results show that cimetidine binds iron and copper. These metals have been implicated in free radical production via the Fenton reaction. By binding with cimetidine the metals become unavailable to produce free radicals and hence cimetidine indirectly reduces the formation of free radicals. The final experiment was the determination of cimetidine as a hydroxyl radical scavenger in the deoxyribose assay. Cimetidine was shown to act as a potent hydroxyl radical scavenger, thereby confirming its activity as a free radical scavenger. In addition, cimetidine protects against damage to the deoxyribose sugar, a component of DNA. Whilst there are many theories that explain the therapeutic role of cimetidine in degenerative disease, the actual mechanism of the role of cimetidine is emphasized as a free radical scavenger. Regardless of the mechanism of action, cimetidine does inhibit tumour growth according to this study and also reduce free radical levels in neurodegeneration, which suggests a role for cimetidine as a possible additive in treatment of patients with such disease states. These findings have important clinical implications, and needs to be investigated further.
- Full Text:
- Date Issued: 2003
Confirmation of a slow symplasmic loading and unloading pathway in barley (Hordeum Vulgare L.) source and sink leaves
- Authors: Buwa, Lisa Valencia
- Date: 2003
- Subjects: Phloem , Plant translocation , Barley -- Metabolism
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4253 , http://hdl.handle.net/10962/d1007804
- Description: Visualization of the transport pathway in barley (Hordeum vulgare) leaves was carried out using a combination of aniline blue and a symplasmically transported fluorochrome, 5,6 carboxyfluorescein (5,6-CF). When applied to a source leaf, basipetal movement of 5,6-CF was observed after 3 h and the fluorochrome front was observed about 3-4cm away from the point of application. The fluorochrome was taken up into the symplasm of the mesophyll and was loaded into the bundle sheath cells and then subsequently the vascular parenchyma and finally into the sieve tubes. In sink leaves, acropetal movement was observed after 3 h and the fluorochrome had moved approximately 3 cm away from the point of application. Unloading of 5,6-CF occurred from all classes of longitudinal veins. Studies on solute retrieval showed that 5,6 CF-diacetate was transferred to xylem parenchyma where it was metabolized. 5,6-CF was then transferred from the xylem parenchyma to the vascular parenchyma cells, and it would appear that thick-walled sieve tubes were the first to show 5,6-CF labeling. Counterstaining with aniline blue demonstrates the presence of plasmodesmata and this suggests a potential symplasmic pathway from the mesophyll to the sieve tubes. Application of 5,6 CF-diacetate revealed a slow symplasmic pathway, which involved transfer of 5,6-CF, which was effected via plasmodesma.
- Full Text:
- Date Issued: 2003
- Authors: Buwa, Lisa Valencia
- Date: 2003
- Subjects: Phloem , Plant translocation , Barley -- Metabolism
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4253 , http://hdl.handle.net/10962/d1007804
- Description: Visualization of the transport pathway in barley (Hordeum vulgare) leaves was carried out using a combination of aniline blue and a symplasmically transported fluorochrome, 5,6 carboxyfluorescein (5,6-CF). When applied to a source leaf, basipetal movement of 5,6-CF was observed after 3 h and the fluorochrome front was observed about 3-4cm away from the point of application. The fluorochrome was taken up into the symplasm of the mesophyll and was loaded into the bundle sheath cells and then subsequently the vascular parenchyma and finally into the sieve tubes. In sink leaves, acropetal movement was observed after 3 h and the fluorochrome had moved approximately 3 cm away from the point of application. Unloading of 5,6-CF occurred from all classes of longitudinal veins. Studies on solute retrieval showed that 5,6 CF-diacetate was transferred to xylem parenchyma where it was metabolized. 5,6-CF was then transferred from the xylem parenchyma to the vascular parenchyma cells, and it would appear that thick-walled sieve tubes were the first to show 5,6-CF labeling. Counterstaining with aniline blue demonstrates the presence of plasmodesmata and this suggests a potential symplasmic pathway from the mesophyll to the sieve tubes. Application of 5,6 CF-diacetate revealed a slow symplasmic pathway, which involved transfer of 5,6-CF, which was effected via plasmodesma.
- Full Text:
- Date Issued: 2003
Cyclodepsipeptides from a Kenyan marine cyanobacterium
- Authors: Dzeha, Thomas Mwambire
- Date: 2003
- Subjects: Cyanobacteria , Stereochemistry , Natural products -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4303 , http://hdl.handle.net/10962/d1004961 , Cyanobacteria , Stereochemistry , Natural products -- Kenya
- Description: An examination of an organic extract of the cyanobacterium Lyngbya majuscula collected from Wasini Island off the southern Kenyan coast led to the isolation of the known cyclodepsipeptide antanapeptin A (7), recently isolated from a Madagascan collection of L. majuscula, and a new bioactive cyclodepsipeptide, homodolastatin 16 (42). Although L. majuscula is a common, pantropical cyanobacterium this study represents the first investigation of the natural product chemistry of a Kenyan population of L. majuscula. The structures of the two cyclodepsipeptides were determined from 2D NMR and mass spectrometry data. The L- stereochemistry of the proline, valine, and N-methylphenylalanine amino acids in 7 and the L – proline configuration in 42, was confirmed by Marfey’s HPLC method. Chiral GC was used to determine the absolute stereochemistry of the hydroxyisovaleric acid moiety in 7 and 42, the lactate residue in 42 and tentatively propose an L-stereochemistry for the Nmethylisoleucine amino acid in 42. Homodolastatin 16, a higher homologue of the potential anti-cancer agent, dolastatin 16, exhibited moderate activity against two oesophageal cancer cell lines.
- Full Text:
- Date Issued: 2003
- Authors: Dzeha, Thomas Mwambire
- Date: 2003
- Subjects: Cyanobacteria , Stereochemistry , Natural products -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4303 , http://hdl.handle.net/10962/d1004961 , Cyanobacteria , Stereochemistry , Natural products -- Kenya
- Description: An examination of an organic extract of the cyanobacterium Lyngbya majuscula collected from Wasini Island off the southern Kenyan coast led to the isolation of the known cyclodepsipeptide antanapeptin A (7), recently isolated from a Madagascan collection of L. majuscula, and a new bioactive cyclodepsipeptide, homodolastatin 16 (42). Although L. majuscula is a common, pantropical cyanobacterium this study represents the first investigation of the natural product chemistry of a Kenyan population of L. majuscula. The structures of the two cyclodepsipeptides were determined from 2D NMR and mass spectrometry data. The L- stereochemistry of the proline, valine, and N-methylphenylalanine amino acids in 7 and the L – proline configuration in 42, was confirmed by Marfey’s HPLC method. Chiral GC was used to determine the absolute stereochemistry of the hydroxyisovaleric acid moiety in 7 and 42, the lactate residue in 42 and tentatively propose an L-stereochemistry for the Nmethylisoleucine amino acid in 42. Homodolastatin 16, a higher homologue of the potential anti-cancer agent, dolastatin 16, exhibited moderate activity against two oesophageal cancer cell lines.
- Full Text:
- Date Issued: 2003
Effects of small-scale water movement on the settlement and growth rates of the brown mussel Perna perna, on the south-east coast of South Africa
- Authors: Mathagu, Tendamudzimu Titus
- Date: 2003
- Subjects: Mussels -- South Africa , Perna -- South Africa , Perna -- Growth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5682 , http://hdl.handle.net/10962/d1005368 , Mussels -- South Africa , Perna -- South Africa , Perna -- Growth
- Description: The effects of small scale (cm) water movement on the settlement and growth rates of the brown mussel Perna perna were investigated on the south-east coast of South Africa (33°28′S, 27°10′E). L-shaped metal baffles attached to the substratum decreased the erosion rates of cement balls and it was concluded that the baffles decreased the water flow rate around cement balls. These L-shaped baffles were then used to decrease water flow rates around mussel patches and pot-scouring pads used as artificial substrata for the settlement of P.perna larvae. Anova indicated that settlement rate varied by date and site while decreased water flow rate significantly increased larval settlement (p<0.05), only on the site and day that had the overall highest number of settlers. Mussels in the low zone had significantly higher growth rates than those in the high zone. Decreased water flow rate significantly increased mussel growth rate in the lower zone (Anova, p<0.05), while it did not have a significant effect on the mussel in the high zone. Thus water flow manipulation increased growth rates in the zone, which already had high growth rate. It was concluded that small-scale (cm) water flow patterns have an effect on both Perna perna settlement and growth rates, but only under specific conditions. Larval settlement rate was significantly increased by water flow manipulation on the site and day that had the highest number of settlers. Growth rates were significantly increased by decreased water flow rate only in the low zone, where growth rates are the highest. Although water flow was manipulated in both zones its effect in the high zone was insignificant (Anova) compared to other factors affecting growth rates at this tidal level.
- Full Text:
- Date Issued: 2003
- Authors: Mathagu, Tendamudzimu Titus
- Date: 2003
- Subjects: Mussels -- South Africa , Perna -- South Africa , Perna -- Growth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5682 , http://hdl.handle.net/10962/d1005368 , Mussels -- South Africa , Perna -- South Africa , Perna -- Growth
- Description: The effects of small scale (cm) water movement on the settlement and growth rates of the brown mussel Perna perna were investigated on the south-east coast of South Africa (33°28′S, 27°10′E). L-shaped metal baffles attached to the substratum decreased the erosion rates of cement balls and it was concluded that the baffles decreased the water flow rate around cement balls. These L-shaped baffles were then used to decrease water flow rates around mussel patches and pot-scouring pads used as artificial substrata for the settlement of P.perna larvae. Anova indicated that settlement rate varied by date and site while decreased water flow rate significantly increased larval settlement (p<0.05), only on the site and day that had the overall highest number of settlers. Mussels in the low zone had significantly higher growth rates than those in the high zone. Decreased water flow rate significantly increased mussel growth rate in the lower zone (Anova, p<0.05), while it did not have a significant effect on the mussel in the high zone. Thus water flow manipulation increased growth rates in the zone, which already had high growth rate. It was concluded that small-scale (cm) water flow patterns have an effect on both Perna perna settlement and growth rates, but only under specific conditions. Larval settlement rate was significantly increased by water flow manipulation on the site and day that had the highest number of settlers. Growth rates were significantly increased by decreased water flow rate only in the low zone, where growth rates are the highest. Although water flow was manipulated in both zones its effect in the high zone was insignificant (Anova) compared to other factors affecting growth rates at this tidal level.
- Full Text:
- Date Issued: 2003