Photodynamic antimicrobial chemotherapy activities of porphyrin- and phthalocyanine-platinum nanoparticle conjugates
- Authors: Managa, Muthumuni Elizabeth
- Date: 2015
- Subjects: Photochemotherapy , Anti-infective agents , Porphyrins , Phthalocyanines , Platinum , Nanoparticles , Bioconjugates , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4539 , http://hdl.handle.net/10962/d1017919
- Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (1) as well as chloro - (5,10,15,20-tetrakis (4- (4- carboxy phenycarbonoimidoyl) phenyl) porphyrinato) gallium(III) (2) The work also reports on platination of dihydroxosilicon octacarboxyphthalocyanine (OH)₂SiOCPc (3) to give dihydroxosilicontris(diaquaplatinum)octacarboxyphthalocyanine (OH)₂SiOCPc(Pt)₃ (4). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against S. aureus, E. coli and C. albicans. The degree of photo-inactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for 1 when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99 percent of the bacteria have been killed), which is much higher than 3.94 log unit for 1-hexagonal PtNPs and 3.31 log units for 1-unshaped PtNPs. Complex 2 conjugated to hexagonal PtNPs showed 18 nm red shift in the Soret band when compared to 2 alone. Complex 2 and 2-hexagonal PtNPs as well showed promising photodynamic antimicrobial chemotherapy (PACT) activity against S. aureus, E. coli and C. albicans in solution where the log reduction obtained was 4.92, 3.76, and 3.95 respectively for 2-hexagonal PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 2-hexagonl PtNPs in DMF while that of 2 was 0.52 in the same solvent. This resulted in improved PACT activity for 2-hexagonal PtNPs compared to 2. Complex 4 showed slight blue shifting of the absorption spectrum when compared to complex 3 The antimicrobial activity of 4 were promising as the highest log reduction value was observed when compared to the porphyrin conjugates.
- Full Text:
- Date Issued: 2015
- Authors: Managa, Muthumuni Elizabeth
- Date: 2015
- Subjects: Photochemotherapy , Anti-infective agents , Porphyrins , Phthalocyanines , Platinum , Nanoparticles , Bioconjugates , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4539 , http://hdl.handle.net/10962/d1017919
- Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (1) as well as chloro - (5,10,15,20-tetrakis (4- (4- carboxy phenycarbonoimidoyl) phenyl) porphyrinato) gallium(III) (2) The work also reports on platination of dihydroxosilicon octacarboxyphthalocyanine (OH)₂SiOCPc (3) to give dihydroxosilicontris(diaquaplatinum)octacarboxyphthalocyanine (OH)₂SiOCPc(Pt)₃ (4). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against S. aureus, E. coli and C. albicans. The degree of photo-inactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for 1 when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99 percent of the bacteria have been killed), which is much higher than 3.94 log unit for 1-hexagonal PtNPs and 3.31 log units for 1-unshaped PtNPs. Complex 2 conjugated to hexagonal PtNPs showed 18 nm red shift in the Soret band when compared to 2 alone. Complex 2 and 2-hexagonal PtNPs as well showed promising photodynamic antimicrobial chemotherapy (PACT) activity against S. aureus, E. coli and C. albicans in solution where the log reduction obtained was 4.92, 3.76, and 3.95 respectively for 2-hexagonal PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 2-hexagonl PtNPs in DMF while that of 2 was 0.52 in the same solvent. This resulted in improved PACT activity for 2-hexagonal PtNPs compared to 2. Complex 4 showed slight blue shifting of the absorption spectrum when compared to complex 3 The antimicrobial activity of 4 were promising as the highest log reduction value was observed when compared to the porphyrin conjugates.
- Full Text:
- Date Issued: 2015
Effects of treatment on Lantana camara (L.) and the restoration potential of riparian seed banks in cleared areas of the Victoria Falls World Heritage Site, Livingstone, Zambia
- Nang'alelwa, Michael Mubitelela
- Authors: Nang'alelwa, Michael Mubitelela
- Date: 2010
- Subjects: Lantana camara -- Victoria Falls (Zambia and Zimbabwe) , Lantana camara -- Biological control -- Victoria Falls (Zambia and Zimbabwe) , Invasive plants -- Biological control -- Victoria Falls (Zambia and Zimbabwe) , Riparian restoration -- Victoria Falls (Zambia and Zimbabwe) , Riparian ecology -- Victoria Falls (Zambia and Zimbabwe)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4217 , http://hdl.handle.net/10962/d1003786 , Lantana camara -- Victoria Falls (Zambia and Zimbabwe) , Lantana camara -- Biological control -- Victoria Falls (Zambia and Zimbabwe) , Invasive plants -- Biological control -- Victoria Falls (Zambia and Zimbabwe) , Riparian restoration -- Victoria Falls (Zambia and Zimbabwe) , Riparian ecology -- Victoria Falls (Zambia and Zimbabwe)
- Description: The exotic plant Lantana camara L. has invaded the riparian areas of the Victoria Falls World Heritage Site in Livingstone, southern Zambia, threatening native plant communities which support populations of species of special concern. I trialled the mechanical control method of manual uprooting and 3 different herbicides applied through paint brushing of an imazapyr concentrate at 250g. l¯¹, spraying on cut stumps with metsulfron methyl at 600g.l¯¹, and foliar spraying on re-emergent lantana foliage with glyphosate at a dosage of 166g. l¯¹ in July 2008 in 20 100m2 treatment plots, 5 invaded control plots and 5 uninvaded controls. Follow-up treatments for re-sprouting lantana stumps and emerging seedlings were undertaken in June 2009. I measured effectiveness of the methods using adult lantana mortality in June 2009 and lantana seedling density in the different treatment plots during the follow-up exercise. The cost of the various methods and human labour applied were compared across the four treatments at initial clear and at follow-up. All treatments recorded a high adult lantana mortality rate, though there were no significant differences in lantana adult mortality amongst the treatments. Overall, uprooting had the highest adult mortality, followed by imazapyr, metsulfron and lastly glyphosate. Germination of lantana seedlings after clearing was high for all treatments but with no significant differences occurring between the treatments. Both adult lantana mortality and seedling density were however significantly different from the control. With labour included, chemical costs were far higher relative to uprooting, though uprooting costs were the highest when it came to the follow-up because of the emerging seedlings and some resprouting stumps. The effects of mechanical and chemical treatments on vegetation composition in the cleared areas were also assessed in order to detect any non-target and medium term effects of treatments. Contrary to expectation, none of the chemicals showed any significant effects on vegetation composition in the short and medium-term and no significant differences were found in plant species richness, diversity and seedling density between invaded and uninvaded plots at baseline, in October 2008 and in September 2009. In order to determine potential for unaided vegetation recovery in the riparian areas of the study site after lantana clearing, I conducted an investigation of soil seed banks and seed rain using 60 seed bank samples measuring 1800m³ collected from 30 invaded and uninvaded plots. Using the seedling emergence method, 1, 991 seedlings belonging to 66 species representing 27 families germinated from the seed bank. Sedges (Cyperaceae family) were the most abundant taxa in the seed banks from invaded areas, followed by Ageratum conyzoides, lantana, Triumfetta annua and Achyranthes aspera which also occurred in the uninvaded soil seed banks. The seed banks from uninvaded plots were dominated by the grass Oplismenus hirtellus. Overall, species richness, diversity and seedling density from seed banks in invaded areas did not differ significantly from seed bank in uninvaded areas and there was a low similarity in species composition when above ground vegetation was compared to seed banks from invaded and uninvaded areas. It would appear if natural regeneration occured from the current seed bank in disturbed areas, future vegetation would largely comprise of short lived, early successional species in the short term as the seed bank is dominated by non-native herbaceous weedy species. From the seed traps investigating seed rain, a total of 27 species numbering 623 individual seeds were found in the thirty 1m² seedtraps distributed in invaded and uninvaded areas at the five sites, over an intermittent period of three months. Lantana had the highest monthly arrival rate in the seed traps followed by Phoenix reclinata and Ricinus communis. The number of species with invasive potential found in the seed traps located in invaded areas was more than that found in seed traps under native vegetation cover by far. Considerable forest remnants still occur around the invaded sites, and these could serve as an important source for long-term natural re-establishment of native vegetation if seed availability by animals and wind dispersal continues, while the re-invasion of lantana is prevented by ongoing follow-ups and futher clearing of lantana invaded areas. It is concluded that while uprooting and other treatments are effective in the control of lantana, its successful control in the Victoria Falls World Heritage Site will require extensive clearing to keep it from reinvading infested areas after clearing as shown by the seed rain data. The high seedling density of lantana in the seed banks and in the cleared areas shows the need for ongoing follow-up in order to deplete soil stored seed banks. There is need for longer term research to establish what the exact follow-up requirements are in order to contain lantana re-infestation and create favourable micro-sites for native species to establish. It is predicted that ongoing lantana control in the cleared plots will most likely initiate long-term community recovery.
- Full Text:
- Date Issued: 2010
- Authors: Nang'alelwa, Michael Mubitelela
- Date: 2010
- Subjects: Lantana camara -- Victoria Falls (Zambia and Zimbabwe) , Lantana camara -- Biological control -- Victoria Falls (Zambia and Zimbabwe) , Invasive plants -- Biological control -- Victoria Falls (Zambia and Zimbabwe) , Riparian restoration -- Victoria Falls (Zambia and Zimbabwe) , Riparian ecology -- Victoria Falls (Zambia and Zimbabwe)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4217 , http://hdl.handle.net/10962/d1003786 , Lantana camara -- Victoria Falls (Zambia and Zimbabwe) , Lantana camara -- Biological control -- Victoria Falls (Zambia and Zimbabwe) , Invasive plants -- Biological control -- Victoria Falls (Zambia and Zimbabwe) , Riparian restoration -- Victoria Falls (Zambia and Zimbabwe) , Riparian ecology -- Victoria Falls (Zambia and Zimbabwe)
- Description: The exotic plant Lantana camara L. has invaded the riparian areas of the Victoria Falls World Heritage Site in Livingstone, southern Zambia, threatening native plant communities which support populations of species of special concern. I trialled the mechanical control method of manual uprooting and 3 different herbicides applied through paint brushing of an imazapyr concentrate at 250g. l¯¹, spraying on cut stumps with metsulfron methyl at 600g.l¯¹, and foliar spraying on re-emergent lantana foliage with glyphosate at a dosage of 166g. l¯¹ in July 2008 in 20 100m2 treatment plots, 5 invaded control plots and 5 uninvaded controls. Follow-up treatments for re-sprouting lantana stumps and emerging seedlings were undertaken in June 2009. I measured effectiveness of the methods using adult lantana mortality in June 2009 and lantana seedling density in the different treatment plots during the follow-up exercise. The cost of the various methods and human labour applied were compared across the four treatments at initial clear and at follow-up. All treatments recorded a high adult lantana mortality rate, though there were no significant differences in lantana adult mortality amongst the treatments. Overall, uprooting had the highest adult mortality, followed by imazapyr, metsulfron and lastly glyphosate. Germination of lantana seedlings after clearing was high for all treatments but with no significant differences occurring between the treatments. Both adult lantana mortality and seedling density were however significantly different from the control. With labour included, chemical costs were far higher relative to uprooting, though uprooting costs were the highest when it came to the follow-up because of the emerging seedlings and some resprouting stumps. The effects of mechanical and chemical treatments on vegetation composition in the cleared areas were also assessed in order to detect any non-target and medium term effects of treatments. Contrary to expectation, none of the chemicals showed any significant effects on vegetation composition in the short and medium-term and no significant differences were found in plant species richness, diversity and seedling density between invaded and uninvaded plots at baseline, in October 2008 and in September 2009. In order to determine potential for unaided vegetation recovery in the riparian areas of the study site after lantana clearing, I conducted an investigation of soil seed banks and seed rain using 60 seed bank samples measuring 1800m³ collected from 30 invaded and uninvaded plots. Using the seedling emergence method, 1, 991 seedlings belonging to 66 species representing 27 families germinated from the seed bank. Sedges (Cyperaceae family) were the most abundant taxa in the seed banks from invaded areas, followed by Ageratum conyzoides, lantana, Triumfetta annua and Achyranthes aspera which also occurred in the uninvaded soil seed banks. The seed banks from uninvaded plots were dominated by the grass Oplismenus hirtellus. Overall, species richness, diversity and seedling density from seed banks in invaded areas did not differ significantly from seed bank in uninvaded areas and there was a low similarity in species composition when above ground vegetation was compared to seed banks from invaded and uninvaded areas. It would appear if natural regeneration occured from the current seed bank in disturbed areas, future vegetation would largely comprise of short lived, early successional species in the short term as the seed bank is dominated by non-native herbaceous weedy species. From the seed traps investigating seed rain, a total of 27 species numbering 623 individual seeds were found in the thirty 1m² seedtraps distributed in invaded and uninvaded areas at the five sites, over an intermittent period of three months. Lantana had the highest monthly arrival rate in the seed traps followed by Phoenix reclinata and Ricinus communis. The number of species with invasive potential found in the seed traps located in invaded areas was more than that found in seed traps under native vegetation cover by far. Considerable forest remnants still occur around the invaded sites, and these could serve as an important source for long-term natural re-establishment of native vegetation if seed availability by animals and wind dispersal continues, while the re-invasion of lantana is prevented by ongoing follow-ups and futher clearing of lantana invaded areas. It is concluded that while uprooting and other treatments are effective in the control of lantana, its successful control in the Victoria Falls World Heritage Site will require extensive clearing to keep it from reinvading infested areas after clearing as shown by the seed rain data. The high seedling density of lantana in the seed banks and in the cleared areas shows the need for ongoing follow-up in order to deplete soil stored seed banks. There is need for longer term research to establish what the exact follow-up requirements are in order to contain lantana re-infestation and create favourable micro-sites for native species to establish. It is predicted that ongoing lantana control in the cleared plots will most likely initiate long-term community recovery.
- Full Text:
- Date Issued: 2010
Deploying DNSSEC in islands of security
- Authors: Murisa, Wesley Vengayi
- Date: 2013 , 2013-03-31
- Subjects: Internet domain names , Computer security , Computer network protocols , Computer security -- Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4577 , http://hdl.handle.net/10962/d1003053 , Internet domain names , Computer security , Computer network protocols , Computer security -- Africa
- Description: The Domain Name System (DNS), a name resolution protocol is one of the vulnerable network protocols that has been subjected to many security attacks such as cache poisoning, denial of service and the 'Kaminsky' spoofing attack. When DNS was designed, security was not incorporated into its design. The DNS Security Extensions (DNSSEC) provides security to the name resolution process by using public key cryptosystems. Although DNSSEC has backward compatibility with unsecured zones, it only offers security to clients when communicating with security aware zones. Widespread deployment of DNSSEC is therefore necessary to secure the name resolution process and provide security to the Internet. Only a few Top Level Domains (TLD's) have deployed DNSSEC, this inherently makes it difficult for their sub-domains to implement the security extensions to the DNS. This study analyses mechanisms that can be used by domains in islands of security to deploy DNSSEC so that the name resolution process can be secured in two specific cases where either the TLD is not signed or the domain registrar is not able to support signed domains. The DNS client side mechanisms evaluated in this study include web browser plug-ins, local validating resolvers and domain look-aside validation. The results of the study show that web browser plug-ins cannot work on their own without local validating resolvers. The web browser validators, however, proved to be useful in indicating to the user whether a domain has been validated or not. Local resolvers present a more secure option for Internet users who cannot trust the communication channel between their stub resolvers and remote name servers. However, they do not provide a way of showing the user whether a domain name has been correctly validated or not. Based on the results of the tests conducted, it is recommended that local validators be used with browser validators for visibility and improved security. On the DNS server side, Domain Look-aside Validation (DLV) presents a viable alternative for organizations in islands of security like most countries in Africa where only two country code Top Level Domains (ccTLD) have deployed DNSSEC. This research recommends use of DLV by corporates to provide DNS security to both internal and external users accessing their web based services. , LaTeX with hyperref package , pdfTeX-1.40.10
- Full Text:
- Date Issued: 2013
- Authors: Murisa, Wesley Vengayi
- Date: 2013 , 2013-03-31
- Subjects: Internet domain names , Computer security , Computer network protocols , Computer security -- Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4577 , http://hdl.handle.net/10962/d1003053 , Internet domain names , Computer security , Computer network protocols , Computer security -- Africa
- Description: The Domain Name System (DNS), a name resolution protocol is one of the vulnerable network protocols that has been subjected to many security attacks such as cache poisoning, denial of service and the 'Kaminsky' spoofing attack. When DNS was designed, security was not incorporated into its design. The DNS Security Extensions (DNSSEC) provides security to the name resolution process by using public key cryptosystems. Although DNSSEC has backward compatibility with unsecured zones, it only offers security to clients when communicating with security aware zones. Widespread deployment of DNSSEC is therefore necessary to secure the name resolution process and provide security to the Internet. Only a few Top Level Domains (TLD's) have deployed DNSSEC, this inherently makes it difficult for their sub-domains to implement the security extensions to the DNS. This study analyses mechanisms that can be used by domains in islands of security to deploy DNSSEC so that the name resolution process can be secured in two specific cases where either the TLD is not signed or the domain registrar is not able to support signed domains. The DNS client side mechanisms evaluated in this study include web browser plug-ins, local validating resolvers and domain look-aside validation. The results of the study show that web browser plug-ins cannot work on their own without local validating resolvers. The web browser validators, however, proved to be useful in indicating to the user whether a domain has been validated or not. Local resolvers present a more secure option for Internet users who cannot trust the communication channel between their stub resolvers and remote name servers. However, they do not provide a way of showing the user whether a domain name has been correctly validated or not. Based on the results of the tests conducted, it is recommended that local validators be used with browser validators for visibility and improved security. On the DNS server side, Domain Look-aside Validation (DLV) presents a viable alternative for organizations in islands of security like most countries in Africa where only two country code Top Level Domains (ccTLD) have deployed DNSSEC. This research recommends use of DLV by corporates to provide DNS security to both internal and external users accessing their web based services. , LaTeX with hyperref package , pdfTeX-1.40.10
- Full Text:
- Date Issued: 2013
An investigation of the polarization of solar radio noise
- Authors: Verschuur, Gerrit L.,1937-
- Date: 1961
- Subjects: Solar radio emission , Polarimetry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5547 , http://hdl.handle.net/10962/d1013441
- Description: CHAPTER I A description of the sun and the type of radio radiation it emits is given. The relation that exists between this and other events occurring on the sun's surface is studied. CHAPTER II The literature dealing with the origin of solar radio noise is reviewed. CHAPTER III The method of specifying polarized radiation and the effect of a magneto- ionic medium on such radiation is discussed. The possible origin of the polarization of solar radio noise is examined and the literature relating to this and to the observations of polarization of solar noise is reviewed. A short outline of the methods used in measuring polarization is given. CHAPTER IV A detailed outline of the construction of a polarimeter is given together with full circuit diagrams and illustrative photographs. CHAPTER V A brief discussion of the operation of the polarimeter, the results obtained and suggestions for its future operation is given.
- Full Text:
- Date Issued: 1961
- Authors: Verschuur, Gerrit L.,1937-
- Date: 1961
- Subjects: Solar radio emission , Polarimetry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5547 , http://hdl.handle.net/10962/d1013441
- Description: CHAPTER I A description of the sun and the type of radio radiation it emits is given. The relation that exists between this and other events occurring on the sun's surface is studied. CHAPTER II The literature dealing with the origin of solar radio noise is reviewed. CHAPTER III The method of specifying polarized radiation and the effect of a magneto- ionic medium on such radiation is discussed. The possible origin of the polarization of solar radio noise is examined and the literature relating to this and to the observations of polarization of solar noise is reviewed. A short outline of the methods used in measuring polarization is given. CHAPTER IV A detailed outline of the construction of a polarimeter is given together with full circuit diagrams and illustrative photographs. CHAPTER V A brief discussion of the operation of the polarimeter, the results obtained and suggestions for its future operation is given.
- Full Text:
- Date Issued: 1961
The mode of action of the acyl-diethylamide molluscicides
- Authors: Solomon, Keith Ross
- Date: 1971
- Subjects: Pesticides , Molluscicides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5821 , http://hdl.handle.net/10962/d1007406
- Description: From Introduction: That bilharziasis an important public health, social and economic problem in the tropical and subtropical countries of the world is well appreciated. (WHO, 1965) Bilharsiasis is the disease caused by parasitic worms of the genus Schistosoma having certain fresh water snails as the intermediate host. In South Africa the more important snails are Bulinus africanus and B. globosus, the secondary hosts of Schistosom haematobium. (WHO, 1965) One method of controling the disease is to reduce the numbers of the intermediate host snails to such a low level that transmission cannot occur (WHO, 1965 and Macdonald, 1965) This has led to a strong interest in those substances that kill snails. The first recorded use of a molluscicide, copper sulphate, was during the first world War in Egypt. (De Villiers, 1965) More recently, the more or less random testing of large numbers of compounds led to the discovery of a large number of molluscicides. These were the heavy metal compounds such as the salts of mercury and arsenic, the substituted phenols such as pentachlorophenol (PCP) and the 2-substituted 4:6-dinitrophenols. (De Villiers, 1965) These compounds are good molluscicides but suffer from a number of disadvantages. The use of copper compounds in hard waters is impractical as the copper precipitates out as the less effective carbonate. The heavy metal salts are expensive and biocidal thus making the treated water unsuitable for human or agricultural use. The phenolic compounds are unpleasant and dangerous to handle and the hydrolysis of PCP is catalysed by sunlight in clear waters. High concentrations of these compounds are required, thus increasing transport and handling costs, particularly in inaccessible areas.
- Full Text:
- Date Issued: 1971
- Authors: Solomon, Keith Ross
- Date: 1971
- Subjects: Pesticides , Molluscicides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5821 , http://hdl.handle.net/10962/d1007406
- Description: From Introduction: That bilharziasis an important public health, social and economic problem in the tropical and subtropical countries of the world is well appreciated. (WHO, 1965) Bilharsiasis is the disease caused by parasitic worms of the genus Schistosoma having certain fresh water snails as the intermediate host. In South Africa the more important snails are Bulinus africanus and B. globosus, the secondary hosts of Schistosom haematobium. (WHO, 1965) One method of controling the disease is to reduce the numbers of the intermediate host snails to such a low level that transmission cannot occur (WHO, 1965 and Macdonald, 1965) This has led to a strong interest in those substances that kill snails. The first recorded use of a molluscicide, copper sulphate, was during the first world War in Egypt. (De Villiers, 1965) More recently, the more or less random testing of large numbers of compounds led to the discovery of a large number of molluscicides. These were the heavy metal compounds such as the salts of mercury and arsenic, the substituted phenols such as pentachlorophenol (PCP) and the 2-substituted 4:6-dinitrophenols. (De Villiers, 1965) These compounds are good molluscicides but suffer from a number of disadvantages. The use of copper compounds in hard waters is impractical as the copper precipitates out as the less effective carbonate. The heavy metal salts are expensive and biocidal thus making the treated water unsuitable for human or agricultural use. The phenolic compounds are unpleasant and dangerous to handle and the hydrolysis of PCP is catalysed by sunlight in clear waters. High concentrations of these compounds are required, thus increasing transport and handling costs, particularly in inaccessible areas.
- Full Text:
- Date Issued: 1971
Photosynthetic and growth responses of C3 and C4 grasses to short- duration sunflecks and resultant consequences for their performance in understory environments
- Authors: Adams, Claire Elizabeth
- Date: 2017
- Subjects: Understory plants -- Effect of light on , Grasses -- Effect of light on -- South Africa , Erharta -- Effect of light on , Brachiara -- Effect of light on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5016 , vital:20753
- Description: Low C4 grass species abundance in understory environments is thought to be as a result of their high-light requirements, lack of photosynthetic advantage relative to C3 species in cooler environments, and an inability to adequately utilise sunflecks. This study sets out to investigate this theory, hypothesizing that C3 grass species outperform C4 grass species under the canopy, not as a result of quantum efficiency temperature effects, but as a result of C4 species inability to utilize short-duration sunflecks. Short sunflecks could result in a breakdown in assimilate movement between the mesophyll (MSC) and bundle sheath (BSC) cells. The role of BSC leakiness, stomata and PSII efficiency on the ability of C3 and C4 Alloteropsis semialata to utilize short-duration sunflecks was investigated using gaseous exchange and chlorophyll fluorescence techniques, while the growth of both subspecies under a simulated flecking-light environment tested whether these measured responses translated into effects on growth. As C3 grasses are known to possess higher levels of stomatal conductance in relation to C4 species, results showed that C3 A. semialata was able to utilize short-duration sunflecks as a result of increased stomatal conductance and an ability to induce photosynthesis under various light flecking conditions. In contrast, C4 A. semialata was unable to utilize sunflecks possibly as a result of energetic limitations of the carboxylation mechanism (PSII) and not because of increased bundle sheath leakiness. These photosynthetic responses translated into growth differences when both types were grown in an artificially flecking light environment. The photosynthetic differences noted for C3 and C4 A.semialata were also evident in shade adapted understory grasses; Erharta erecta (C3), Dactylotenium australe (C4) and Brachiaria chusqueoides (C4). As photosynthetic induction was marginally more rapid in all species relative to A. semialata it suggests some degree of adaptation in shade grasses, however the inability of the C4 species to utilise short sunflecks remained. As a result, it was hypothesized that C3 shade adapted E. erecta and C4 B. chusqueoides, co-inhabiting the same forest understory, are able to do so because of differences in light micro-environments associated with each species. However, canopy openness and light profiles determined for theses micro-climates showed no differences and that both species have persisted within a relatively stable understory environment. The coexistence was possible as the understory was supplied with a significant proportion of its daily light in flecks sufficiently long as to not compromise C4 productivity. A survey of 10 species of grasses under various canopy densities and in the open showed a strong negative linear relationship between canopy openness and the rate at which photosynthesis was induced by flecking light, which has not been shown before. This did not result from the phylogenetic relationship between species and could be shown for a single species (E. erecta) growing in a range of light environments. This demonstrates that C4 grasses, despite adaptation, would be limited from sunfleck environments if a significant proportion of the daily light available consists of flecks of short-duration. The generation of such environments may occur as a result of woody thickening and could help explain the observed decline in C4 grasses under these conditions.
- Full Text:
- Date Issued: 2017
- Authors: Adams, Claire Elizabeth
- Date: 2017
- Subjects: Understory plants -- Effect of light on , Grasses -- Effect of light on -- South Africa , Erharta -- Effect of light on , Brachiara -- Effect of light on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5016 , vital:20753
- Description: Low C4 grass species abundance in understory environments is thought to be as a result of their high-light requirements, lack of photosynthetic advantage relative to C3 species in cooler environments, and an inability to adequately utilise sunflecks. This study sets out to investigate this theory, hypothesizing that C3 grass species outperform C4 grass species under the canopy, not as a result of quantum efficiency temperature effects, but as a result of C4 species inability to utilize short-duration sunflecks. Short sunflecks could result in a breakdown in assimilate movement between the mesophyll (MSC) and bundle sheath (BSC) cells. The role of BSC leakiness, stomata and PSII efficiency on the ability of C3 and C4 Alloteropsis semialata to utilize short-duration sunflecks was investigated using gaseous exchange and chlorophyll fluorescence techniques, while the growth of both subspecies under a simulated flecking-light environment tested whether these measured responses translated into effects on growth. As C3 grasses are known to possess higher levels of stomatal conductance in relation to C4 species, results showed that C3 A. semialata was able to utilize short-duration sunflecks as a result of increased stomatal conductance and an ability to induce photosynthesis under various light flecking conditions. In contrast, C4 A. semialata was unable to utilize sunflecks possibly as a result of energetic limitations of the carboxylation mechanism (PSII) and not because of increased bundle sheath leakiness. These photosynthetic responses translated into growth differences when both types were grown in an artificially flecking light environment. The photosynthetic differences noted for C3 and C4 A.semialata were also evident in shade adapted understory grasses; Erharta erecta (C3), Dactylotenium australe (C4) and Brachiaria chusqueoides (C4). As photosynthetic induction was marginally more rapid in all species relative to A. semialata it suggests some degree of adaptation in shade grasses, however the inability of the C4 species to utilise short sunflecks remained. As a result, it was hypothesized that C3 shade adapted E. erecta and C4 B. chusqueoides, co-inhabiting the same forest understory, are able to do so because of differences in light micro-environments associated with each species. However, canopy openness and light profiles determined for theses micro-climates showed no differences and that both species have persisted within a relatively stable understory environment. The coexistence was possible as the understory was supplied with a significant proportion of its daily light in flecks sufficiently long as to not compromise C4 productivity. A survey of 10 species of grasses under various canopy densities and in the open showed a strong negative linear relationship between canopy openness and the rate at which photosynthesis was induced by flecking light, which has not been shown before. This did not result from the phylogenetic relationship between species and could be shown for a single species (E. erecta) growing in a range of light environments. This demonstrates that C4 grasses, despite adaptation, would be limited from sunfleck environments if a significant proportion of the daily light available consists of flecks of short-duration. The generation of such environments may occur as a result of woody thickening and could help explain the observed decline in C4 grasses under these conditions.
- Full Text:
- Date Issued: 2017
The effect of appetite suppressants on pineal function
- Authors: Mchunu, Bongani Isaac
- Date: 1994
- Subjects: Pineal gland -- Research , Pineal gland -- Secretions , Appetite depressants -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4038 , http://hdl.handle.net/10962/d1004098 , Pineal gland -- Research , Pineal gland -- Secretions , Appetite depressants -- Physiological effect
- Description: The pineal gland has become the subject of considerable investigation as it provides a productive experimental model for studying circadian rhythms and regulation of end organs. In the rat, the pineal gland provides a convenient model for investigating the noradrenergic receptor system and the effects of various drugs on this system. The effect of appetite suppressants on the rat pineal gland function is described. Appetite suppressants increase melatonin synthesis in organ cultures of rat pineal glands. This effect appears to be mediated by noradrenaline acting on β-adrenoceptors on the pinealocyte membrane. When β-adrenoceptors are blocked, the appetite suppressant-induced rise in melatonin synthesis is prevented. Depletion of noradrenaline in sympathetic nerve terminals also prevented the appetite suppressant-induced rise in melatonin synthesis. Activation of β-adrenoceptors is followed by a rise in N-acetyltransferase activity via a cyclic adenosine monophosphate second messenger system. The effect of appetite suppressants on the activity of liver tryptophan pyrrolase was also investigated. The activity of this enzyme is an important determinant of tryptophan availability to the brain and consequently of brain serotonin levels. The results show that appetite suppressants inhibit both holoenzyme and total enzyme activities of tryptophan pyrrolase. This finding suggests that appetite suppressants may act by inhibiting tryptophan pyrrolase activity thereby increasing brain serotonin, a phenomenon known to be associated with anorexia. There are two possible mechanisms by which appetite suppressants inhibit tryptophan pyrrolase activity. Firstly, these agents, being drugs of dependence, may increase liver NADPH concentrations which inhibit pyrrolase activity. Secondly, appetite suppressants may act on the pineal gland to stimulate melatonin synthesis. Melatonin inhibits pyrrolase activity in a dose-dependent manner. This inhibition will elevate plasma tryptophan levels which result in a rise in brain serotonin synthesis. The present study suggests a possible relationship between the pineal gland and appetite centres in the hypothalamus. Melatonin may have a direct effect on appetite centres since food restriction is associated with an increased melatonin binding in the hypothalamus. If this possible relationship can be extended, melatonin can open new possibilities for the control of food intake and consequently, of pathological obesity.
- Full Text:
- Date Issued: 1994
- Authors: Mchunu, Bongani Isaac
- Date: 1994
- Subjects: Pineal gland -- Research , Pineal gland -- Secretions , Appetite depressants -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4038 , http://hdl.handle.net/10962/d1004098 , Pineal gland -- Research , Pineal gland -- Secretions , Appetite depressants -- Physiological effect
- Description: The pineal gland has become the subject of considerable investigation as it provides a productive experimental model for studying circadian rhythms and regulation of end organs. In the rat, the pineal gland provides a convenient model for investigating the noradrenergic receptor system and the effects of various drugs on this system. The effect of appetite suppressants on the rat pineal gland function is described. Appetite suppressants increase melatonin synthesis in organ cultures of rat pineal glands. This effect appears to be mediated by noradrenaline acting on β-adrenoceptors on the pinealocyte membrane. When β-adrenoceptors are blocked, the appetite suppressant-induced rise in melatonin synthesis is prevented. Depletion of noradrenaline in sympathetic nerve terminals also prevented the appetite suppressant-induced rise in melatonin synthesis. Activation of β-adrenoceptors is followed by a rise in N-acetyltransferase activity via a cyclic adenosine monophosphate second messenger system. The effect of appetite suppressants on the activity of liver tryptophan pyrrolase was also investigated. The activity of this enzyme is an important determinant of tryptophan availability to the brain and consequently of brain serotonin levels. The results show that appetite suppressants inhibit both holoenzyme and total enzyme activities of tryptophan pyrrolase. This finding suggests that appetite suppressants may act by inhibiting tryptophan pyrrolase activity thereby increasing brain serotonin, a phenomenon known to be associated with anorexia. There are two possible mechanisms by which appetite suppressants inhibit tryptophan pyrrolase activity. Firstly, these agents, being drugs of dependence, may increase liver NADPH concentrations which inhibit pyrrolase activity. Secondly, appetite suppressants may act on the pineal gland to stimulate melatonin synthesis. Melatonin inhibits pyrrolase activity in a dose-dependent manner. This inhibition will elevate plasma tryptophan levels which result in a rise in brain serotonin synthesis. The present study suggests a possible relationship between the pineal gland and appetite centres in the hypothalamus. Melatonin may have a direct effect on appetite centres since food restriction is associated with an increased melatonin binding in the hypothalamus. If this possible relationship can be extended, melatonin can open new possibilities for the control of food intake and consequently, of pathological obesity.
- Full Text:
- Date Issued: 1994
The exploration for and possible genesis of, some Archaean granite/gneiss-hosted gold deposits in the Pietersburg granite-greenstone terrane
- Linklater, Michael Anthony Leonard Flanders
- Authors: Linklater, Michael Anthony Leonard Flanders
- Date: 1992
- Subjects: Gold ores -- Geology -- South Africa , Gneiss , Granite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4945 , http://hdl.handle.net/10962/d1005557 , Gold ores -- Geology -- South Africa , Gneiss , Granite
- Description: Abstract The gold mineralization event within Archaean granite-greenstone terranes occurred during the late Archaean, and followed the intrusion of syn- to late-tectonic granitic plutons into previously deformed greenstone belts. An Archaean granite/gneiss-hosted gold deposit, in terms of this project, is classified as having a gold-assay cutoff of 1g/metric ton over widths of at least several metres, or higher grades over narrower widths and/or verbal descriptions that indicate such values. Fluid inclusion studies and isotopic data identify two possible origins for the auriferous fluids; namely magmatic and metamorphic. The exploration target according to the magmatic model, is a late-Archaean, hydrothermally altered, mineralized and fractured granitic intrusion preferably with a granodioritic or quartz-dioritic composition. The exploration target according to the metamorphic replacement model is a granitic stock that has intruded a zone of crustal weakness such as a shear zone, active during the late Archaean. Alternatively, the granitic intrusion should be affected by regionally extensive late-Archaean shearing. It should be hydrothermally altered, deformed and mineralized. Five areas within the Pietersburg granite-greenstone terrane were selected for the 'Regional Area Selection' phase of exploration for Archaean granite/gneiss-hosted gold deposits; namely Roodepoort, Waterval, Ramagoep, Moletsie and Matlala. Roodepoort contains a known granodiorite-hosted gold deposit; the Knight's Pluton, and served as an orientation survey for this project. The use and interpretation of LANDSAT images formed an integral part of exploration techniques; to assess their usefulness in the exploration of Archaean granite/gneiss-hosted gold deposits. Area selection criteria for granite/gneiss-hosted gold mineralization at Roodepoort are the major ENE-trending shear zone, the NNW-trending lineament and hydrothermal alteration, shearing, quartz-stockworks and sulphide mineralization within the Knight's Pluton. The origin of the gold within the Knight's Pluton is uncertain; both magmatic and metamorphic models are possibilities. Ongoing exploration is in progress at Roodepoort. The only area selection criterion for granite/gneiss-hosted gold mineralization at Waterval is the sericitized, subcropping granites located within trenches. Gold mineralization is insignificant. No area selection criteria for Archaean granite/gneiss-hosted gold mineralization were located at Ramagoep, Matlala and Moletsie. No further exploration is recommended for all these areas. The MES image interpretations were successful in identifying lineaments, granitic outcrops, greenstones, vegetation and soil cover. The Clay-iron images adequately differentiated betweeen iron-rich and clay-bearing areas. However, not all clay-bearing areas were associated with hydrothermal alteratian; field checks were necessary to discriminate between weathered granites and hydrothermally altered granites. The Wallis images served to locally enhance the contrasts of the MES and Clay-iron images.
- Full Text:
- Date Issued: 1992
- Authors: Linklater, Michael Anthony Leonard Flanders
- Date: 1992
- Subjects: Gold ores -- Geology -- South Africa , Gneiss , Granite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4945 , http://hdl.handle.net/10962/d1005557 , Gold ores -- Geology -- South Africa , Gneiss , Granite
- Description: Abstract The gold mineralization event within Archaean granite-greenstone terranes occurred during the late Archaean, and followed the intrusion of syn- to late-tectonic granitic plutons into previously deformed greenstone belts. An Archaean granite/gneiss-hosted gold deposit, in terms of this project, is classified as having a gold-assay cutoff of 1g/metric ton over widths of at least several metres, or higher grades over narrower widths and/or verbal descriptions that indicate such values. Fluid inclusion studies and isotopic data identify two possible origins for the auriferous fluids; namely magmatic and metamorphic. The exploration target according to the magmatic model, is a late-Archaean, hydrothermally altered, mineralized and fractured granitic intrusion preferably with a granodioritic or quartz-dioritic composition. The exploration target according to the metamorphic replacement model is a granitic stock that has intruded a zone of crustal weakness such as a shear zone, active during the late Archaean. Alternatively, the granitic intrusion should be affected by regionally extensive late-Archaean shearing. It should be hydrothermally altered, deformed and mineralized. Five areas within the Pietersburg granite-greenstone terrane were selected for the 'Regional Area Selection' phase of exploration for Archaean granite/gneiss-hosted gold deposits; namely Roodepoort, Waterval, Ramagoep, Moletsie and Matlala. Roodepoort contains a known granodiorite-hosted gold deposit; the Knight's Pluton, and served as an orientation survey for this project. The use and interpretation of LANDSAT images formed an integral part of exploration techniques; to assess their usefulness in the exploration of Archaean granite/gneiss-hosted gold deposits. Area selection criteria for granite/gneiss-hosted gold mineralization at Roodepoort are the major ENE-trending shear zone, the NNW-trending lineament and hydrothermal alteration, shearing, quartz-stockworks and sulphide mineralization within the Knight's Pluton. The origin of the gold within the Knight's Pluton is uncertain; both magmatic and metamorphic models are possibilities. Ongoing exploration is in progress at Roodepoort. The only area selection criterion for granite/gneiss-hosted gold mineralization at Waterval is the sericitized, subcropping granites located within trenches. Gold mineralization is insignificant. No area selection criteria for Archaean granite/gneiss-hosted gold mineralization were located at Ramagoep, Matlala and Moletsie. No further exploration is recommended for all these areas. The MES image interpretations were successful in identifying lineaments, granitic outcrops, greenstones, vegetation and soil cover. The Clay-iron images adequately differentiated betweeen iron-rich and clay-bearing areas. However, not all clay-bearing areas were associated with hydrothermal alteratian; field checks were necessary to discriminate between weathered granites and hydrothermally altered granites. The Wallis images served to locally enhance the contrasts of the MES and Clay-iron images.
- Full Text:
- Date Issued: 1992
The digestive mechanisms of an intertidal grazer, the sea urchin Parechinus angulosus
- Authors: Sweijd, Neville Anthony
- Date: 1991
- Subjects: Sea urchins -- Nutrition , Sea urchins , Echinoida
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5662 , http://hdl.handle.net/10962/d1005346 , Sea urchins -- Nutrition , Sea urchins , Echinoida
- Description: Echinoids are important grazers in the near-shore ecosystem and can significantly effect their ecology. The sea urchin Parechinus angulosus occurs inter- and subtidally along the southern African coast. Within this range it consumes an extremely wide variety of algae. Since algal cell walls have an almost species specific chemical composition, the question arises as to how it can digest the algae that it consumes. In order to investigate the digestive mechanisms employed by P. angulosus, an ultrastructural study of the gut was undertaken to characterize the tissue and identify functional regions in the gut. Ten structural and storage polysaccharides commonly found in macroalgae were used as substrates to assay the digestive polysaccharidases of the sea urchin. The enteric bacteria of the sea urchin were isolated and tested separately for polysaccharidase activity using the same substrates. The results shown that the gut of Parechinus angulosus is regionally specialized, with the foregut primarily responsible for the production of hydrolytic enzymes, while the hindgut is primarily absorptive. The occurrence of lamellar bodies, heterolysosomes, cytoplasmic blebs and paddle cilia among other characteristic features of the digestive epithelium are described and discussed. Two levels of enzyme activity are apparent. Generally the urchin could hydrolyze the reserve polysaccharides, but only partially hydrolyze the structural polysaccharides, of red and green algae. P.angulosus was unable to digest alginic acid, the main structural polysaccharide of brown algae. Mixed cultures of bacteria utilized only the reserve polysaccharides of red and green algae. Significantly, the bacteria were able to hydrolyze alginic acid. Enteric bacteria also showed agarolytic activity. Parechinus angulosus has the ability to digest red and green algae. No lysozyme activity was detected. The enteric bacteria can digest the same algal reserve polysaccharides and so may compete for carbon in the gut. However, in the case of brown algae, bacteria have a potentially important endosymbiotic role as agents of digestion. These results correspond with food preference studies which have shown that, although P.angulosus consumes the kelp Ecklonia maxima, in the western Cape, it is amongst its least preferred food species. The reasons for this are its unpalatability and the urchin's inability to digest brown algae. The digestibility of algal material can be an important factor in determining algal-herbivore interactions.
- Full Text:
- Date Issued: 1991
- Authors: Sweijd, Neville Anthony
- Date: 1991
- Subjects: Sea urchins -- Nutrition , Sea urchins , Echinoida
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5662 , http://hdl.handle.net/10962/d1005346 , Sea urchins -- Nutrition , Sea urchins , Echinoida
- Description: Echinoids are important grazers in the near-shore ecosystem and can significantly effect their ecology. The sea urchin Parechinus angulosus occurs inter- and subtidally along the southern African coast. Within this range it consumes an extremely wide variety of algae. Since algal cell walls have an almost species specific chemical composition, the question arises as to how it can digest the algae that it consumes. In order to investigate the digestive mechanisms employed by P. angulosus, an ultrastructural study of the gut was undertaken to characterize the tissue and identify functional regions in the gut. Ten structural and storage polysaccharides commonly found in macroalgae were used as substrates to assay the digestive polysaccharidases of the sea urchin. The enteric bacteria of the sea urchin were isolated and tested separately for polysaccharidase activity using the same substrates. The results shown that the gut of Parechinus angulosus is regionally specialized, with the foregut primarily responsible for the production of hydrolytic enzymes, while the hindgut is primarily absorptive. The occurrence of lamellar bodies, heterolysosomes, cytoplasmic blebs and paddle cilia among other characteristic features of the digestive epithelium are described and discussed. Two levels of enzyme activity are apparent. Generally the urchin could hydrolyze the reserve polysaccharides, but only partially hydrolyze the structural polysaccharides, of red and green algae. P.angulosus was unable to digest alginic acid, the main structural polysaccharide of brown algae. Mixed cultures of bacteria utilized only the reserve polysaccharides of red and green algae. Significantly, the bacteria were able to hydrolyze alginic acid. Enteric bacteria also showed agarolytic activity. Parechinus angulosus has the ability to digest red and green algae. No lysozyme activity was detected. The enteric bacteria can digest the same algal reserve polysaccharides and so may compete for carbon in the gut. However, in the case of brown algae, bacteria have a potentially important endosymbiotic role as agents of digestion. These results correspond with food preference studies which have shown that, although P.angulosus consumes the kelp Ecklonia maxima, in the western Cape, it is amongst its least preferred food species. The reasons for this are its unpalatability and the urchin's inability to digest brown algae. The digestibility of algal material can be an important factor in determining algal-herbivore interactions.
- Full Text:
- Date Issued: 1991
An investigation of the role of mitochondrial STAT3 and modulation of Reactive Oxygen Species in adipocyte differentiation
- Authors: Kramer, Adam Hildyard
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54632 , vital:26595
- Description: Stem cells have the ability to differentiate into a myriad of different cell types. The understanding of the differentiation process is of paramount importance if we are to use these cells in the lab as well as in therapeutics. Here, the levels and localization of the signal transducer and activator of transcription 3 (STAT3), with particular attention focused on the mitochondrial serine 727 phosphorylated form of STAT3 (pSTAT3S727) during differentiation, was investigated. Using the murine preadipocyte progenitor cell line 3T3-L1, as well as adipose derived human mesenchymal stem cells (HMSC-ad) as differentiation models, the relative levels of Reactive Oxygen Species (ROS) and the levels and localization of STAT3 were investigated during the differentiation process. ROS is known to play an important signalling role during differentiation and is well reported during the events of adipogenesis. ROS are generated as a by-product in the Electron Transport Chain (ETC), and it has recently been reported that pSTAT3S727 plays an important role at complex I of the ETC. Various techniques including fluorescence confocal microscopy, flow cytometry and Western blots were utilized to investigate the non-canonical role STAT3 plays during adipogenesis. Mitochondrial isolations were performed to investigate the levels of STAT3 in the mitochondria during differentiation. Further to this, an impedance based real time differentiation assay was developed using the xCELLigence Real Time Cell Analyser to monitor differentiation and the affects various compounds, including a STAT3 inhibitor, have on differentiation. Results indicate that upon induction of differentiation, levels of mitochondrial pSTAT3S727 dramatically decrease and leave the mitochondria. This corresponds to increasing levels of ROS. The canonical active form of STAT3 following phosphorylation on tyrosine 705 (pSTAT3Y705) was found to decrease and lose its nuclear localization. These initial results indicate that STAT3 plays an important non-canonical role in the mitochondria during differentiation.
- Full Text:
- Date Issued: 2014
- Authors: Kramer, Adam Hildyard
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54632 , vital:26595
- Description: Stem cells have the ability to differentiate into a myriad of different cell types. The understanding of the differentiation process is of paramount importance if we are to use these cells in the lab as well as in therapeutics. Here, the levels and localization of the signal transducer and activator of transcription 3 (STAT3), with particular attention focused on the mitochondrial serine 727 phosphorylated form of STAT3 (pSTAT3S727) during differentiation, was investigated. Using the murine preadipocyte progenitor cell line 3T3-L1, as well as adipose derived human mesenchymal stem cells (HMSC-ad) as differentiation models, the relative levels of Reactive Oxygen Species (ROS) and the levels and localization of STAT3 were investigated during the differentiation process. ROS is known to play an important signalling role during differentiation and is well reported during the events of adipogenesis. ROS are generated as a by-product in the Electron Transport Chain (ETC), and it has recently been reported that pSTAT3S727 plays an important role at complex I of the ETC. Various techniques including fluorescence confocal microscopy, flow cytometry and Western blots were utilized to investigate the non-canonical role STAT3 plays during adipogenesis. Mitochondrial isolations were performed to investigate the levels of STAT3 in the mitochondria during differentiation. Further to this, an impedance based real time differentiation assay was developed using the xCELLigence Real Time Cell Analyser to monitor differentiation and the affects various compounds, including a STAT3 inhibitor, have on differentiation. Results indicate that upon induction of differentiation, levels of mitochondrial pSTAT3S727 dramatically decrease and leave the mitochondria. This corresponds to increasing levels of ROS. The canonical active form of STAT3 following phosphorylation on tyrosine 705 (pSTAT3Y705) was found to decrease and lose its nuclear localization. These initial results indicate that STAT3 plays an important non-canonical role in the mitochondria during differentiation.
- Full Text:
- Date Issued: 2014
The genetic integrity of Labeo capensis and L. umbratus (Cyprinidae) in South Africa in relation to inter-basin water transfer schemes
- Authors: Ramoejane, Mpho
- Date: 2011
- Subjects: Cyprinidae -- South Africa -- Darlington Dam , Cyprinidae -- Namibia -- Hardap Dam , Labeo -- South Africa -- Darlington Dam , Labeo -- Namibia -- Hardap Dam , Fishes -- Hybridisation -- South Africa -- Darlington Dam , Fishes -- Hybridisation -- Namibia -- Hardap Dam , Fishes -- Anatomy -- South Africa -- Darlington Dam , Fishes -- Anatomy -- Namibia -- Hardap Dam , Water transfer -- South Africa-- Darlington Dam , Water transfer -- Namibia -- Hardap Dam
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5367 , http://hdl.handle.net/10962/d1013049
- Description: The Orange-Fish and Cookhouse tunnels that are part of a major inter-basin water transfer scheme (IBT) act as a pathway for several fish species from the Orange River system to enter the Great Fish and Sundays River systems in South Africa. These include Labeo capensis and L. umbratus. Labeo capensis was restricted to the Orange River system before the inter-basin water transfer scheme. Labeo umbratus occurred naturally in the Orange River and in southern flowing river systems. Previous studies showed that the two species hybridise in Hardap Dam, located in a tributary of the Orange River system in Namibia. There are also unconfirmed reports of hybrids from Darlington Dam on the Sundays River system. The aim of the thesis was to confirm hybridisation in Hardap Dam, assess whether hybridisation between L. capensis and L. umbratus has occurred in Darlington Dam and to gain a better understanding of the diversity of these two species. Morphology (morphometrics and meristics), a nuclear S7 intron and the mitochondrial cytochrome ♭ gene were used to assess for hybridisation. A total of 275 specimens were analysed from across the geographical range of the two species. The two species could be distinguished using morphometrics (dorsal fin base, interorbital width and operculum to eye distance) and meristics (lateral line, origin of the dorsal fin to lateral line, origin of the pelvic fin to lateral line and caudal peduncle scale counts) characters. Hybrids from Hardap and Darlington dams were placed between the two species clusters. Labeo umbratus from the Orange River and southern flowing rivers formed a single cluster. The two species could also be distinguished from each other with six nuclear DNA mutations and hybrids were heterozygous at such sites in both dams. Labeo umbratus populations from the Orange River and southern flowing rivers (Gouritz, Gamtoos, Sundays, Bushmans, Great Fish and Nahoon) formed a single lineage. Analysis of mitochondrial DNA, however, revealed that L. umbratus populations from the Orange River and southern flowing rivers were two lineages that differ from each other by 5 mutations. Labeo capensis could be differentiated from both these lineages. Being maternally inherited, mitochondrial DNA did not reveal hybridisation, but ten specimens with L. capensis haplotypes were found in the Darlington Dam. In Hardap Dam, however, it appears that only L. capensis mitochondrial DNA haplotypes persist, despite morphological and nuclear DNA analysis suggesting that both morphs and hybrids of the two species occur. The genetic integrity of these Labeo species has therefore been compromised in at least Hardap and Darlington dams. The Great Fish and Sundays populations are considered to be under threat of complete introgression. The Kat River and Slagboom Dam populations that were isolated before the IBTs have to remain isolated to protect the genetic integrity of the southern lineage of L. umbratus in these two systems.
- Full Text:
- Date Issued: 2011
- Authors: Ramoejane, Mpho
- Date: 2011
- Subjects: Cyprinidae -- South Africa -- Darlington Dam , Cyprinidae -- Namibia -- Hardap Dam , Labeo -- South Africa -- Darlington Dam , Labeo -- Namibia -- Hardap Dam , Fishes -- Hybridisation -- South Africa -- Darlington Dam , Fishes -- Hybridisation -- Namibia -- Hardap Dam , Fishes -- Anatomy -- South Africa -- Darlington Dam , Fishes -- Anatomy -- Namibia -- Hardap Dam , Water transfer -- South Africa-- Darlington Dam , Water transfer -- Namibia -- Hardap Dam
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5367 , http://hdl.handle.net/10962/d1013049
- Description: The Orange-Fish and Cookhouse tunnels that are part of a major inter-basin water transfer scheme (IBT) act as a pathway for several fish species from the Orange River system to enter the Great Fish and Sundays River systems in South Africa. These include Labeo capensis and L. umbratus. Labeo capensis was restricted to the Orange River system before the inter-basin water transfer scheme. Labeo umbratus occurred naturally in the Orange River and in southern flowing river systems. Previous studies showed that the two species hybridise in Hardap Dam, located in a tributary of the Orange River system in Namibia. There are also unconfirmed reports of hybrids from Darlington Dam on the Sundays River system. The aim of the thesis was to confirm hybridisation in Hardap Dam, assess whether hybridisation between L. capensis and L. umbratus has occurred in Darlington Dam and to gain a better understanding of the diversity of these two species. Morphology (morphometrics and meristics), a nuclear S7 intron and the mitochondrial cytochrome ♭ gene were used to assess for hybridisation. A total of 275 specimens were analysed from across the geographical range of the two species. The two species could be distinguished using morphometrics (dorsal fin base, interorbital width and operculum to eye distance) and meristics (lateral line, origin of the dorsal fin to lateral line, origin of the pelvic fin to lateral line and caudal peduncle scale counts) characters. Hybrids from Hardap and Darlington dams were placed between the two species clusters. Labeo umbratus from the Orange River and southern flowing rivers formed a single cluster. The two species could also be distinguished from each other with six nuclear DNA mutations and hybrids were heterozygous at such sites in both dams. Labeo umbratus populations from the Orange River and southern flowing rivers (Gouritz, Gamtoos, Sundays, Bushmans, Great Fish and Nahoon) formed a single lineage. Analysis of mitochondrial DNA, however, revealed that L. umbratus populations from the Orange River and southern flowing rivers were two lineages that differ from each other by 5 mutations. Labeo capensis could be differentiated from both these lineages. Being maternally inherited, mitochondrial DNA did not reveal hybridisation, but ten specimens with L. capensis haplotypes were found in the Darlington Dam. In Hardap Dam, however, it appears that only L. capensis mitochondrial DNA haplotypes persist, despite morphological and nuclear DNA analysis suggesting that both morphs and hybrids of the two species occur. The genetic integrity of these Labeo species has therefore been compromised in at least Hardap and Darlington dams. The Great Fish and Sundays populations are considered to be under threat of complete introgression. The Kat River and Slagboom Dam populations that were isolated before the IBTs have to remain isolated to protect the genetic integrity of the southern lineage of L. umbratus in these two systems.
- Full Text:
- Date Issued: 2011
Predation by alien largemouth bass, Micropterus salmoides Lacepéde 1802 (Centrarchidae: Perciformes), on indigenous marine fish species in the Kowie System, South Africa
- Authors: Magoro, Mandla Leon
- Date: 2014
- Subjects: Largemouth bass -- South Africa -- Port Alfred , Largemouth bass -- Food -- South Africa -- Port Alfred , Estuarine fishes -- South Africa -- Port Alfred , Estuarine fishes -- Predators of , Centrarchidae , Fishes -- Effect of human beings on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5851 , http://hdl.handle.net/10962/d1011939 , Largemouth bass -- South Africa -- Port Alfred , Largemouth bass -- Food -- South Africa -- Port Alfred , Estuarine fishes -- South Africa -- Port Alfred , Estuarine fishes -- Predators of , Centrarchidae , Fishes -- Effect of human beings on
- Description: Estuaries serve as nursery areas for a large number of estuary-associated fish species. Some of these taxa also use river catchments as nursery areas. During the upstream migration of this latter group, the juveniles are prone to predation by native and alien predatory fish inhabiting the system. The rate of invasion of ecosystems by alien organisms can be directly linked to anthropogenic influences, including both intentional and unintentional introductions by alien organisms into new regions. The largemouth bass, Micropterus salmoides, is a facultative piscivorous fish that has been successfully introduced worldwide for the main purpose of sport fishing. Where introduced, it has been found to negatively impact native fish and invertebrate species through predation, competitive exclusion and displacement of indigenous fish species. The aim of this thesis was to investigate the predatory impact of largemouth bass on the estuary-associated Cape moony Monodactylus falciformis, Cape stumpnose Rhabdosargus holubi and freshwater mullet Myxus capensis in the lower Kowie River of the Eastern Cape Province, South Africa. A combination of approaches was employed during this study. Stomach contents, stable isotopes and fatty acid analyses were employed for the reconstruction of the diet of largemouth bass. Acoustic telemetry was used to elucidate largemouth bass movements, particularly their ability to enter the upper reaches of the Kowie Estuary. Stomach contents and stable isotopes analyses showed that M. salmoides exhibit an ontogenic shift in diet, with small and medium sized individuals consuming the higher proportion of fish prey, while large sized individuals mostly consumed invertebrates such as crabs (Potamonautes sidneyi) and Odonata larvae, while consuming only a small proportion of estuary-associated fish. Fatty acid analysis only showed a direct connection between the fatty acid profiles of largemouth bass and those of M. capensis and M. falciformis. The acoustic telemetry results indicated that some M. salmoides individuals periodically move into the upper reaches of the estuary following river flood events. The results obtained from all these approaches highlight the risk posed by largemouth bass introductions on indigenous fish species, particularly those that enter the areas occupied by these top predators.
- Full Text:
- Date Issued: 2014
- Authors: Magoro, Mandla Leon
- Date: 2014
- Subjects: Largemouth bass -- South Africa -- Port Alfred , Largemouth bass -- Food -- South Africa -- Port Alfred , Estuarine fishes -- South Africa -- Port Alfred , Estuarine fishes -- Predators of , Centrarchidae , Fishes -- Effect of human beings on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5851 , http://hdl.handle.net/10962/d1011939 , Largemouth bass -- South Africa -- Port Alfred , Largemouth bass -- Food -- South Africa -- Port Alfred , Estuarine fishes -- South Africa -- Port Alfred , Estuarine fishes -- Predators of , Centrarchidae , Fishes -- Effect of human beings on
- Description: Estuaries serve as nursery areas for a large number of estuary-associated fish species. Some of these taxa also use river catchments as nursery areas. During the upstream migration of this latter group, the juveniles are prone to predation by native and alien predatory fish inhabiting the system. The rate of invasion of ecosystems by alien organisms can be directly linked to anthropogenic influences, including both intentional and unintentional introductions by alien organisms into new regions. The largemouth bass, Micropterus salmoides, is a facultative piscivorous fish that has been successfully introduced worldwide for the main purpose of sport fishing. Where introduced, it has been found to negatively impact native fish and invertebrate species through predation, competitive exclusion and displacement of indigenous fish species. The aim of this thesis was to investigate the predatory impact of largemouth bass on the estuary-associated Cape moony Monodactylus falciformis, Cape stumpnose Rhabdosargus holubi and freshwater mullet Myxus capensis in the lower Kowie River of the Eastern Cape Province, South Africa. A combination of approaches was employed during this study. Stomach contents, stable isotopes and fatty acid analyses were employed for the reconstruction of the diet of largemouth bass. Acoustic telemetry was used to elucidate largemouth bass movements, particularly their ability to enter the upper reaches of the Kowie Estuary. Stomach contents and stable isotopes analyses showed that M. salmoides exhibit an ontogenic shift in diet, with small and medium sized individuals consuming the higher proportion of fish prey, while large sized individuals mostly consumed invertebrates such as crabs (Potamonautes sidneyi) and Odonata larvae, while consuming only a small proportion of estuary-associated fish. Fatty acid analysis only showed a direct connection between the fatty acid profiles of largemouth bass and those of M. capensis and M. falciformis. The acoustic telemetry results indicated that some M. salmoides individuals periodically move into the upper reaches of the estuary following river flood events. The results obtained from all these approaches highlight the risk posed by largemouth bass introductions on indigenous fish species, particularly those that enter the areas occupied by these top predators.
- Full Text:
- Date Issued: 2014
The thermal physiology of Stenopelmus rufinasus and Neohydronomus affinis (Coleoptera: Curculionidae), biological control agents for the invasive alien aquatic weeds Azolla filiculoides and Pistia stratiotes respectively
- Authors: Mvandaba, Sisanda F
- Date: 2018
- Subjects: Beetles -- South Africa , Curculionidae -- South Africa , Azolla filiculoides -- South Africa , Water lettuce -- South Africa , Aquatic weeds -- Biological control -- South Africa , Stenopelmus rufinasus , Neohydronomus affinis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62362 , vital:28158
- Description: Water lettuce, Pistia stratiotes L. (Araceae), and red water fern, Azolla filiculoides Lam. (Azollaceae), are floating aquatic macrophytes that have become problematic invaders in numerous South African waterbodies. Two weevils, Neohydronomus affinis Hustache 1926 (Coleoptera: Curculionidae) and Stenopelmus rufinasus Gyllenhal 1936 (Coleoptera: Curculionidae), are successful biological control agents of these two species, respectively, in South Africa. However, nothing is known about the thermal physiology of these two species Therefore, the aim of this study was to investigate the thermal physiologies of these two species to explain their establishment, distribution and impact in the field. Laboratory based thermal physiology trials showed that both weevils were widely tolerant of cold and warm temperatures. The CTmin of N. affinis was determined to be 5.5 ± 0.312°C and the CTmax was 44 ± 0.697°C, while the CTmin of S. rufinasus was 5.4 ± 0.333°C and the CTmax was 44.5 ± 0.168°C. In addition, the lower lethal temperatures were -9.8 ± 0.053°C and -7.2 ± 0.19°C, and the upper lethal temperatures were 42.8 ± 0.053°C and 41.9 ± 0.19°C respectively. These results suggest that both species should not be limited by cold winter temperatures, as previously thought. This is evident in the field, where S. rufinasus has established widely on A. filiculoides, despite local cold climates in some areas of the plant’s distribution. Even though N. affinis has a similar thermal range, and should therefore theoretically reflect a similar distribution to S. rufinasus throughout South Africa, its distribution is limited by the range of its host, which is restricted to the warmer regions of the country, as is its biocontrol agent. Using the reduced major axis regression method, the development for N. affinis was described using the formulay=12.976x+435.24, while the development of S. rufinasus was described by y=13.6x+222.45. These results showed that S. rufinasus develops much faster, in fact almost twice as quickly, than N. affinis. Using these formulae and temperature data obtained from the South African Weather Service, N. affinis was predicted to complete between 4 and 9 generations per year in South Africa, while S. rufinasus was predicted to complete between 5 and 14 generations per year around the country. This study showed that although the native range of these two species is warm temperate to tropical, they possess sufficient thermal plasticity to not only establish, but also damage their respective host plants in far cooler climates. Thus, in South Africa N. affinis and S. rufinasus are limited by the distribution of their target weeds and not climate.
- Full Text:
- Date Issued: 2018
- Authors: Mvandaba, Sisanda F
- Date: 2018
- Subjects: Beetles -- South Africa , Curculionidae -- South Africa , Azolla filiculoides -- South Africa , Water lettuce -- South Africa , Aquatic weeds -- Biological control -- South Africa , Stenopelmus rufinasus , Neohydronomus affinis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62362 , vital:28158
- Description: Water lettuce, Pistia stratiotes L. (Araceae), and red water fern, Azolla filiculoides Lam. (Azollaceae), are floating aquatic macrophytes that have become problematic invaders in numerous South African waterbodies. Two weevils, Neohydronomus affinis Hustache 1926 (Coleoptera: Curculionidae) and Stenopelmus rufinasus Gyllenhal 1936 (Coleoptera: Curculionidae), are successful biological control agents of these two species, respectively, in South Africa. However, nothing is known about the thermal physiology of these two species Therefore, the aim of this study was to investigate the thermal physiologies of these two species to explain their establishment, distribution and impact in the field. Laboratory based thermal physiology trials showed that both weevils were widely tolerant of cold and warm temperatures. The CTmin of N. affinis was determined to be 5.5 ± 0.312°C and the CTmax was 44 ± 0.697°C, while the CTmin of S. rufinasus was 5.4 ± 0.333°C and the CTmax was 44.5 ± 0.168°C. In addition, the lower lethal temperatures were -9.8 ± 0.053°C and -7.2 ± 0.19°C, and the upper lethal temperatures were 42.8 ± 0.053°C and 41.9 ± 0.19°C respectively. These results suggest that both species should not be limited by cold winter temperatures, as previously thought. This is evident in the field, where S. rufinasus has established widely on A. filiculoides, despite local cold climates in some areas of the plant’s distribution. Even though N. affinis has a similar thermal range, and should therefore theoretically reflect a similar distribution to S. rufinasus throughout South Africa, its distribution is limited by the range of its host, which is restricted to the warmer regions of the country, as is its biocontrol agent. Using the reduced major axis regression method, the development for N. affinis was described using the formulay=12.976x+435.24, while the development of S. rufinasus was described by y=13.6x+222.45. These results showed that S. rufinasus develops much faster, in fact almost twice as quickly, than N. affinis. Using these formulae and temperature data obtained from the South African Weather Service, N. affinis was predicted to complete between 4 and 9 generations per year in South Africa, while S. rufinasus was predicted to complete between 5 and 14 generations per year around the country. This study showed that although the native range of these two species is warm temperate to tropical, they possess sufficient thermal plasticity to not only establish, but also damage their respective host plants in far cooler climates. Thus, in South Africa N. affinis and S. rufinasus are limited by the distribution of their target weeds and not climate.
- Full Text:
- Date Issued: 2018
Seasonal changes in the physiological and hormonal aspects of reproduction in the male long-fingered bat, Miniopterus schreibersii (Mammalia : Chiroptera)
- Authors: Paton, Joy Carol
- Date: 1989
- Subjects: Bats -- Reproduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5590 , http://hdl.handle.net/10962/d1002040
- Description: The reproductive cycle of Miniopterus schreibersii is modified as a consequence of a period of torpor/hibernation over the winter months. This bat is one of three genera which employ the reproductive strategy of delayed implantation in which the blastocyst remains free in the uterine lumen during the winter months. Spermatogenesis is initiated in February, with spermiogenesis occuring in March. Copulation, ovulation and fertilization takes place between March and May after which the testes regress and remain in an inactive condition until the following summer. Activity in the accessory gland complex is initiated in March and continues until early June. Plasma testosterone concentrations reach a peak in May, decline over the winter months and reach a second, unexplainable peak in October. Leydig cells are secretorily active in February/early March after which they undergo vacuolation and final degeneration. The question of the life cyle of Leydig cells is addressed and an increase in a certain cell after Leydig cell activity suggests that this cell type may be the precursor of Leydig cells.
- Full Text:
- Date Issued: 1989
- Authors: Paton, Joy Carol
- Date: 1989
- Subjects: Bats -- Reproduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5590 , http://hdl.handle.net/10962/d1002040
- Description: The reproductive cycle of Miniopterus schreibersii is modified as a consequence of a period of torpor/hibernation over the winter months. This bat is one of three genera which employ the reproductive strategy of delayed implantation in which the blastocyst remains free in the uterine lumen during the winter months. Spermatogenesis is initiated in February, with spermiogenesis occuring in March. Copulation, ovulation and fertilization takes place between March and May after which the testes regress and remain in an inactive condition until the following summer. Activity in the accessory gland complex is initiated in March and continues until early June. Plasma testosterone concentrations reach a peak in May, decline over the winter months and reach a second, unexplainable peak in October. Leydig cells are secretorily active in February/early March after which they undergo vacuolation and final degeneration. The question of the life cyle of Leydig cells is addressed and an increase in a certain cell after Leydig cell activity suggests that this cell type may be the precursor of Leydig cells.
- Full Text:
- Date Issued: 1989
Modernisation and extension of InetVis: a network security data visualisation tool
- Authors: Johnson, Yestin
- Date: 2019
- Subjects: Data visualization , InetVis (Application software)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/69223 , vital:29447
- Description: This research undertook an investigation in digital archaeology, modernisation, and revitalisation of the InetVis software application, developed at Rhodes University in 2007. InetVis allows users to visualise network traffic in an interactive 3D scatter plot. This software is based on the idea of the Spinning Cube of Potential Doom, introduced by Stephen Lau. The original InetVis research project aimed to extend this concept and implementation, specifically for use in analysing network telescope traffic. The InetVis source code was examined and ported to run on modern operating systems. The porting process involved updating the UI framework, Qt, from version 3 to 5, as well as adding support for 64-bit compilation. This research extended its usefulness with the implementation of new, high-value, features and improvements. The most notable new features include the addition of a general settings framework, improved screenshot generation, automated visualisation modes, new keyboard shortcuts, and support for building and running InetVis on macOS. Additional features and improvements were identified for future work. These consist of support for a plug-in architecture and an extended heads-up display. A user survey was then conducted, determining that respondents found InetVis to be easy to use and useful. The user survey also allowed the identification of new and proposed features that the respondents found to be most useful. At this point, no other tool offers the simplicity and user-friendliness of InetVis when it comes to the analysis of network packet captures, especially those from network telescopes.
- Full Text:
- Date Issued: 2019
- Authors: Johnson, Yestin
- Date: 2019
- Subjects: Data visualization , InetVis (Application software)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/69223 , vital:29447
- Description: This research undertook an investigation in digital archaeology, modernisation, and revitalisation of the InetVis software application, developed at Rhodes University in 2007. InetVis allows users to visualise network traffic in an interactive 3D scatter plot. This software is based on the idea of the Spinning Cube of Potential Doom, introduced by Stephen Lau. The original InetVis research project aimed to extend this concept and implementation, specifically for use in analysing network telescope traffic. The InetVis source code was examined and ported to run on modern operating systems. The porting process involved updating the UI framework, Qt, from version 3 to 5, as well as adding support for 64-bit compilation. This research extended its usefulness with the implementation of new, high-value, features and improvements. The most notable new features include the addition of a general settings framework, improved screenshot generation, automated visualisation modes, new keyboard shortcuts, and support for building and running InetVis on macOS. Additional features and improvements were identified for future work. These consist of support for a plug-in architecture and an extended heads-up display. A user survey was then conducted, determining that respondents found InetVis to be easy to use and useful. The user survey also allowed the identification of new and proposed features that the respondents found to be most useful. At this point, no other tool offers the simplicity and user-friendliness of InetVis when it comes to the analysis of network packet captures, especially those from network telescopes.
- Full Text:
- Date Issued: 2019
A study of barred preferential arrangements with applications to numerical approximation in electric circuits
- Authors: Nkonkobe, Sithembele
- Date: 2015
- Subjects: Electric circuits , Numerical calculations , Sequences (Mathematics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5433 , http://hdl.handle.net/10962/d1020394
- Description: In 1854 Cayley proposed an interesting sequence 1,1,3,13,75,541,... in connection with analytical forms called trees. Since then there has been various combinatorial interpretations of the sequence. The sequence has been interpreted as the number of preferential arrangements of members of a set with n elements. Alternatively the sequence has been interpreted as the number of ordered partitions; the outcomes in races in which ties are allowed or geometrically the number of vertices, edges and faces of simplicial objects. An interesting application of the sequence is found in combination locks. The idea of a preferential arrangement has been extended to a wider combinatorial object called barred preferential arrangement with multiple bars. In this thesis we study barred preferential arrangements combinatorially with application to resistance of certain electrical circuits. In the process we derive some results on cyclic properties of the last digit of the number of barred preferential arrangements. An algorithm in python has been developed to find the number of barred preferential arrangements.
- Full Text:
- Date Issued: 2015
- Authors: Nkonkobe, Sithembele
- Date: 2015
- Subjects: Electric circuits , Numerical calculations , Sequences (Mathematics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5433 , http://hdl.handle.net/10962/d1020394
- Description: In 1854 Cayley proposed an interesting sequence 1,1,3,13,75,541,... in connection with analytical forms called trees. Since then there has been various combinatorial interpretations of the sequence. The sequence has been interpreted as the number of preferential arrangements of members of a set with n elements. Alternatively the sequence has been interpreted as the number of ordered partitions; the outcomes in races in which ties are allowed or geometrically the number of vertices, edges and faces of simplicial objects. An interesting application of the sequence is found in combination locks. The idea of a preferential arrangement has been extended to a wider combinatorial object called barred preferential arrangement with multiple bars. In this thesis we study barred preferential arrangements combinatorially with application to resistance of certain electrical circuits. In the process we derive some results on cyclic properties of the last digit of the number of barred preferential arrangements. An algorithm in python has been developed to find the number of barred preferential arrangements.
- Full Text:
- Date Issued: 2015
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
Towards an evaluation and protection strategy for critical infrastructure
- Authors: Gottschalk, Jason Howard
- Date: 2015
- Subjects: Computer crimes -- Prevention , Computer networks -- Security measures , Computer crimes -- Law and legislation -- South Africa , Public works -- Security measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4721 , http://hdl.handle.net/10962/d1018793
- Description: Critical Infrastructure is often overlooked from an Information Security perspective as being of high importance to protect which may result in Critical Infrastructure being at risk to Cyber related attacks with potential dire consequences. Furthermore, what is considered Critical Infrastructure is often a complex discussion, with varying opinions across audiences. Traditional Critical Infrastructure included power stations, water, sewage pump stations, gas pipe lines, power grids and a new entrant, the “internet of things”. This list is not complete and a constant challenge exists in identifying Critical Infrastructure and its interdependencies. The purpose of this research is to highlight the importance of protecting Critical Infrastructure as well as proposing a high level framework aiding in the identification and securing of Critical Infrastructure. To achieve this, key case studies involving Cyber crime and Cyber warfare, as well as the identification of attack vectors and impact on against Critical Infrastructure (as applicable to Critical Infrastructure where possible), were identified and discussed. Furthermore industry related material was researched as to identify key controls that would aid in protecting Critical Infrastructure. The identification of initiatives that countries were pursuing, that would aid in the protection of Critical Infrastructure, were identified and discussed. Research was conducted into the various standards, frameworks and methodologies available to aid in the identification, remediation and ultimately the protection of Critical Infrastructure. A key output of the research was the development of a hybrid approach to identifying Critical Infrastructure, associated vulnerabilities and an approach for remediation with specific metrics (based on the research performed). The conclusion based on the research is that there is often a need and a requirement to identify and protect Critical Infrastructure however this is usually initiated or driven by non-owners of Critical Infrastructure (Governments, governing bodies, standards bodies and security consultants). Furthermore where there are active initiative by owners very often the suggested approaches are very high level in nature with little direct guidance available for very immature environments.
- Full Text:
- Date Issued: 2015
- Authors: Gottschalk, Jason Howard
- Date: 2015
- Subjects: Computer crimes -- Prevention , Computer networks -- Security measures , Computer crimes -- Law and legislation -- South Africa , Public works -- Security measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4721 , http://hdl.handle.net/10962/d1018793
- Description: Critical Infrastructure is often overlooked from an Information Security perspective as being of high importance to protect which may result in Critical Infrastructure being at risk to Cyber related attacks with potential dire consequences. Furthermore, what is considered Critical Infrastructure is often a complex discussion, with varying opinions across audiences. Traditional Critical Infrastructure included power stations, water, sewage pump stations, gas pipe lines, power grids and a new entrant, the “internet of things”. This list is not complete and a constant challenge exists in identifying Critical Infrastructure and its interdependencies. The purpose of this research is to highlight the importance of protecting Critical Infrastructure as well as proposing a high level framework aiding in the identification and securing of Critical Infrastructure. To achieve this, key case studies involving Cyber crime and Cyber warfare, as well as the identification of attack vectors and impact on against Critical Infrastructure (as applicable to Critical Infrastructure where possible), were identified and discussed. Furthermore industry related material was researched as to identify key controls that would aid in protecting Critical Infrastructure. The identification of initiatives that countries were pursuing, that would aid in the protection of Critical Infrastructure, were identified and discussed. Research was conducted into the various standards, frameworks and methodologies available to aid in the identification, remediation and ultimately the protection of Critical Infrastructure. A key output of the research was the development of a hybrid approach to identifying Critical Infrastructure, associated vulnerabilities and an approach for remediation with specific metrics (based on the research performed). The conclusion based on the research is that there is often a need and a requirement to identify and protect Critical Infrastructure however this is usually initiated or driven by non-owners of Critical Infrastructure (Governments, governing bodies, standards bodies and security consultants). Furthermore where there are active initiative by owners very often the suggested approaches are very high level in nature with little direct guidance available for very immature environments.
- Full Text:
- Date Issued: 2015
Progress towards the development and implementation of an unambiguous copper wire fingerprinting system
- Authors: Poole, Martin
- Date: 2003
- Subjects: Electroplating , Copper , Telecommunication , Theft -- Prevention
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5484 , http://hdl.handle.net/10962/d1005270 , Electroplating , Copper , Telecommunication , Theft -- Prevention
- Description: The Telecommunications industry in Southern Africa is faced with the problem of theft of the signal carrying copper wire, both from the ground and from telephone poles. In many cases, if the offenders are caught, the prosecuting party has no way of proving that the wire is the property of any one Telecommunication company, as any inked markings on the insulating sheaths have been burned off along with the insulation and protective coatings themselves. Through this work we * describe the problem, * specify the necessary and preferred technical properties of a viable solution, * report the preliminary investigations into the devising of an unambiguous "fingerprinting" of the 0.5 mm wires, including some of those solutions that, upon investigation, appear non-viable, * describe the development and implementation of an electrochemical marker with detection mechanism which has shown in proof-of-principle to work, * outline the road-map of necessary future work.
- Full Text:
- Date Issued: 2003
- Authors: Poole, Martin
- Date: 2003
- Subjects: Electroplating , Copper , Telecommunication , Theft -- Prevention
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5484 , http://hdl.handle.net/10962/d1005270 , Electroplating , Copper , Telecommunication , Theft -- Prevention
- Description: The Telecommunications industry in Southern Africa is faced with the problem of theft of the signal carrying copper wire, both from the ground and from telephone poles. In many cases, if the offenders are caught, the prosecuting party has no way of proving that the wire is the property of any one Telecommunication company, as any inked markings on the insulating sheaths have been burned off along with the insulation and protective coatings themselves. Through this work we * describe the problem, * specify the necessary and preferred technical properties of a viable solution, * report the preliminary investigations into the devising of an unambiguous "fingerprinting" of the 0.5 mm wires, including some of those solutions that, upon investigation, appear non-viable, * describe the development and implementation of an electrochemical marker with detection mechanism which has shown in proof-of-principle to work, * outline the road-map of necessary future work.
- Full Text:
- Date Issued: 2003
Population dynamics of selected ichthyofaunal components in the temperate, temporarily open/closed Kasouga Estuary, South Africa
- Authors: Tweddle, Gavin Paul
- Date: 2005
- Subjects: Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5742 , http://hdl.handle.net/10962/d1005428 , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
- Description: The spatial and temporal pattern of ichthyofaunal community composition in relation to selected physico-chemical (temperature and salinity) and biological variables (chlorophyll-a and zooplankton) was investigated at ten stations in the temperate temporarily open/closed Kasouga estuary. In addition, the food web structure in the estuary was investigated using stable carbon isotope analysis. Results of the 5 metre seine net survey indicated that ichthyofaunal composition and biomass in the Kasouga estuary was largely determined by seasonality and mouth condition. Maximum abundance and biomass of ichthyofauna was recorded during summer or during those periods when overtopping occurred. Overtopping coincided with the recruitment of marine estuarine dependant species, which dominated the catches both numerically and in biomass. The recruitment of these species resulted in an increase in diversity of the ichthyofaunal community. There were no significant spatial patterns in the distribution of smaller ichthyofauna (<50mm SL) identified in Bray-Curtis similarity matrices using cluster analysis (Primer 5 v5.2.4). Spearman’s correlation analysis revealed that there were no significant correlations between abundance and biomass of ichthyofauna and selected physico-chemical and biological variables other than salinity (P>0.05 in all other cases). There were two distinct spatial patterns in the distribution of the larger ichthyofauna (>50mm SL). These corresponded to a grouping associated with the mouth region and a grouping associated with the remaining regions of the estuary. Stable isotope analysis indicated that the primary source of carbon utilised by the ichthyofauna of the Kasouga estuary was derived from the channel, most likely microphytobenthic algae. The contributions of the riparian and salt marsh vegetation to the total carbon flow appear to be minimal.
- Full Text:
- Date Issued: 2005
- Authors: Tweddle, Gavin Paul
- Date: 2005
- Subjects: Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5742 , http://hdl.handle.net/10962/d1005428 , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
- Description: The spatial and temporal pattern of ichthyofaunal community composition in relation to selected physico-chemical (temperature and salinity) and biological variables (chlorophyll-a and zooplankton) was investigated at ten stations in the temperate temporarily open/closed Kasouga estuary. In addition, the food web structure in the estuary was investigated using stable carbon isotope analysis. Results of the 5 metre seine net survey indicated that ichthyofaunal composition and biomass in the Kasouga estuary was largely determined by seasonality and mouth condition. Maximum abundance and biomass of ichthyofauna was recorded during summer or during those periods when overtopping occurred. Overtopping coincided with the recruitment of marine estuarine dependant species, which dominated the catches both numerically and in biomass. The recruitment of these species resulted in an increase in diversity of the ichthyofaunal community. There were no significant spatial patterns in the distribution of smaller ichthyofauna (<50mm SL) identified in Bray-Curtis similarity matrices using cluster analysis (Primer 5 v5.2.4). Spearman’s correlation analysis revealed that there were no significant correlations between abundance and biomass of ichthyofauna and selected physico-chemical and biological variables other than salinity (P>0.05 in all other cases). There were two distinct spatial patterns in the distribution of the larger ichthyofauna (>50mm SL). These corresponded to a grouping associated with the mouth region and a grouping associated with the remaining regions of the estuary. Stable isotope analysis indicated that the primary source of carbon utilised by the ichthyofauna of the Kasouga estuary was derived from the channel, most likely microphytobenthic algae. The contributions of the riparian and salt marsh vegetation to the total carbon flow appear to be minimal.
- Full Text:
- Date Issued: 2005