Development and assessment of minocycline sustained release capsule formulations
- Sachikonye, Tinotenda Chipo Victoria
- Authors: Sachikonye, Tinotenda Chipo Victoria
- Date: 2010
- Subjects: Drugs -- Controlled release , Drugs -- Dosage forms , Capsules (Pharmacy) , Drugs -- Administration , Acne -- Treatment , Tetracyclines , Antibiotics -- Side effects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3854 , http://hdl.handle.net/10962/d1013127
- Description: The use of minocycline for the treatment of a broad range of systemic infections and for severe acne has been associated with vestibular side effects. The severity of side effects may lead to poor adherence to therapy by patients. The use of sustained release formulations of minocycline that display slow dissolution of minocycline following administration may be beneficial in reducing the incidence and severity of side effects. Therefore, sustained release capsule dosage forms containing 100 mg minocycline (base) were manufactured and assessed for use as sustained release oral dosage forms of minocycline. Minocycline sustained release capsules were manufactured based on matrix technologies using hydroxypropylmethyl cellulose (HPMC) and Compritol® as release retarding polymers. The rate and extent of minocycline release from the capsules was evaluated using USP Apparatus 1 and samples were analysed using a validated High Performance Liquid Chromatographic (HPLC) method with ultraviolet (UV) detection. Differences in the rate and extent of minocycline release from formulations manufactured using HPMC or Compritol® were influenced by the concentration of polymer used in the formulations. The rate and extent of minocycline release was faster and greater when low concentrations of polymer were used in formulations. The effect of different excipients on the release pattern(s) of minocycline and particularly their potential to optimise minocycline release from experimental formulations was investigated. The use of diluents such as lactose and microcrystalline cellulose (MCC) revealed that lactose facilitated minocycline release when HPMC was used as the polymer matrix. In contrast, the use of lactose as diluent resulted in slower release of minocycline from Compritol® based formulations. The addition of sodium starch glycolate to HPMC based formulations resulted in slower release of minocycline than when no sodium starch glycolate was used. Compritol® based formulations were observed to release minocycline faster following addition of sodium starch glycolate and Poloxamer 188 to experimental formulations. In vitro dissolution profiles were compared to a target or reference profile using the difference and similarity factors, ƒ1 and ƒ2 , and a one way analysis of variance (ANOVA). In addition, the mechanism of minocycline release was elucidated following fitting of dissolution data to the Korsmeyer-Peppas, Higuchi and Zero order models. Minocycline release kinetics were best described by the Korsmeyer-Peppas model and the values of the release exponent, n (italics), revealed that drug release was a result of the combined effects of minocycline diffusion through matrices and erosion of the matrices. These in vitro dissolution profiles were better fit to the Higuchi model than to the Zero order model. Two formulations that displayed a fit to the Zero order model were identified for further studies as potential dosage forms for sustained release minocycline.
- Full Text:
- Date Issued: 2010
- Authors: Sachikonye, Tinotenda Chipo Victoria
- Date: 2010
- Subjects: Drugs -- Controlled release , Drugs -- Dosage forms , Capsules (Pharmacy) , Drugs -- Administration , Acne -- Treatment , Tetracyclines , Antibiotics -- Side effects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3854 , http://hdl.handle.net/10962/d1013127
- Description: The use of minocycline for the treatment of a broad range of systemic infections and for severe acne has been associated with vestibular side effects. The severity of side effects may lead to poor adherence to therapy by patients. The use of sustained release formulations of minocycline that display slow dissolution of minocycline following administration may be beneficial in reducing the incidence and severity of side effects. Therefore, sustained release capsule dosage forms containing 100 mg minocycline (base) were manufactured and assessed for use as sustained release oral dosage forms of minocycline. Minocycline sustained release capsules were manufactured based on matrix technologies using hydroxypropylmethyl cellulose (HPMC) and Compritol® as release retarding polymers. The rate and extent of minocycline release from the capsules was evaluated using USP Apparatus 1 and samples were analysed using a validated High Performance Liquid Chromatographic (HPLC) method with ultraviolet (UV) detection. Differences in the rate and extent of minocycline release from formulations manufactured using HPMC or Compritol® were influenced by the concentration of polymer used in the formulations. The rate and extent of minocycline release was faster and greater when low concentrations of polymer were used in formulations. The effect of different excipients on the release pattern(s) of minocycline and particularly their potential to optimise minocycline release from experimental formulations was investigated. The use of diluents such as lactose and microcrystalline cellulose (MCC) revealed that lactose facilitated minocycline release when HPMC was used as the polymer matrix. In contrast, the use of lactose as diluent resulted in slower release of minocycline from Compritol® based formulations. The addition of sodium starch glycolate to HPMC based formulations resulted in slower release of minocycline than when no sodium starch glycolate was used. Compritol® based formulations were observed to release minocycline faster following addition of sodium starch glycolate and Poloxamer 188 to experimental formulations. In vitro dissolution profiles were compared to a target or reference profile using the difference and similarity factors, ƒ1 and ƒ2 , and a one way analysis of variance (ANOVA). In addition, the mechanism of minocycline release was elucidated following fitting of dissolution data to the Korsmeyer-Peppas, Higuchi and Zero order models. Minocycline release kinetics were best described by the Korsmeyer-Peppas model and the values of the release exponent, n (italics), revealed that drug release was a result of the combined effects of minocycline diffusion through matrices and erosion of the matrices. These in vitro dissolution profiles were better fit to the Higuchi model than to the Zero order model. Two formulations that displayed a fit to the Zero order model were identified for further studies as potential dosage forms for sustained release minocycline.
- Full Text:
- Date Issued: 2010
Development of a stability-indicating high performance liquid chromatographic method for the analysis of topiramate and dissolution rate testing in topiramate tablets
- Mohammadi, Ali, Rezanour, Nasrin, Ansari Dogaheh, M, Walker, Roderick B
- Authors: Mohammadi, Ali , Rezanour, Nasrin , Ansari Dogaheh, M , Walker, Roderick B
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:6412 , http://hdl.handle.net/10962/d1006507
- Description: A stability-indicating high performance liquid chromatographic(HPLC) method was developed and validated for the quantitation and dissolution determination of topiramate in tablet dosage forms. An isocratic separation was achieved using a phenyl column with a flow rate of 1 mL/min using UV detection at 264 nm. Topiramate has low UV absorbtivity and was subjected to derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl). The mobile phase for the separation consisted of acetonitrile: 50 mM sodium dihydrogen phosphate(NaH2PO4) containing 3 % v/v triethylamine (pH 2.8) in a 48:52 v/v ratio. Topiramate was subjected to oxidation, hydrolysis, photolysis and heat for the purposes of stress testing. Separation was achieved for the parent compound and all the degradation products in an overall analytical run time of approximately 15 min with the parent compound topiramate eluting at approximately 9.2 min. The method was linear over the concentration range of 1-100 μg/mL (r = 0.9996) with limits of quantitation and detection of 1 and 0.3 μg/mL, respectively.
- Full Text:
- Date Issued: 2010
- Authors: Mohammadi, Ali , Rezanour, Nasrin , Ansari Dogaheh, M , Walker, Roderick B
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:6412 , http://hdl.handle.net/10962/d1006507
- Description: A stability-indicating high performance liquid chromatographic(HPLC) method was developed and validated for the quantitation and dissolution determination of topiramate in tablet dosage forms. An isocratic separation was achieved using a phenyl column with a flow rate of 1 mL/min using UV detection at 264 nm. Topiramate has low UV absorbtivity and was subjected to derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl). The mobile phase for the separation consisted of acetonitrile: 50 mM sodium dihydrogen phosphate(NaH2PO4) containing 3 % v/v triethylamine (pH 2.8) in a 48:52 v/v ratio. Topiramate was subjected to oxidation, hydrolysis, photolysis and heat for the purposes of stress testing. Separation was achieved for the parent compound and all the degradation products in an overall analytical run time of approximately 15 min with the parent compound topiramate eluting at approximately 9.2 min. The method was linear over the concentration range of 1-100 μg/mL (r = 0.9996) with limits of quantitation and detection of 1 and 0.3 μg/mL, respectively.
- Full Text:
- Date Issued: 2010
Development of an IMS Compliant, Cross Platform Client Using the JAIN SIP Applet Phone
- Muswera, Walter T, Terzoli, Alfredo
- Authors: Muswera, Walter T , Terzoli, Alfredo
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431274 , vital:72760 , https://www.cs.ru.ac.za/research/g09M3278/Muswera.pdf
- Description: Several open source SIP/IMS Clients are currently in use in the Rhodes University Convergence Research Group. However, there is no single Client that provides researchers with all the required functionality need-ed to test the applications they have developed. Integrating advanced features into a single Client can help to speed up testing as well as pro-vide a variety of innovative communication services. In this paper we present an overview of two popular SIP/IMS Clients currently in use. We also discuss the features and design architecture of a Client called JAIN SIP Applet Phone (JSAP) which will be used as a basis for the development of a new IMS compliant Client. We then analyse what functionality JSAP lacks and propose features that need to be imple-mented.
- Full Text:
- Date Issued: 2010
- Authors: Muswera, Walter T , Terzoli, Alfredo
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431274 , vital:72760 , https://www.cs.ru.ac.za/research/g09M3278/Muswera.pdf
- Description: Several open source SIP/IMS Clients are currently in use in the Rhodes University Convergence Research Group. However, there is no single Client that provides researchers with all the required functionality need-ed to test the applications they have developed. Integrating advanced features into a single Client can help to speed up testing as well as pro-vide a variety of innovative communication services. In this paper we present an overview of two popular SIP/IMS Clients currently in use. We also discuss the features and design architecture of a Client called JAIN SIP Applet Phone (JSAP) which will be used as a basis for the development of a new IMS compliant Client. We then analyse what functionality JSAP lacks and propose features that need to be imple-mented.
- Full Text:
- Date Issued: 2010
Development of insulin resistance in a rat model and the effects of sutherlandia frutescens as treatment and prevention
- Authors: Mackenzie, Janine
- Date: 2010
- Subjects: Metabolic syndrome , Insulin resistance -- Animal models , Obesity -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10340 , http://hdl.handle.net/10948/d1016216
- Description: The global number of obese people has reached pandemic proportions. High caloric diets and reduced physical exercise are to blame for this growing epidemic. Obesity has a very complex association with several other metabolic disorders, such as insulin resistance (IR), diabetes mellitus type 2 (DMT2) and cardiovascular disease. This puts a huge burden on health care systems world wide and claims many lives. Sutherlandia frutescens is a traditionally used herb, which is known to have anti-diabetic properties. However, the direct mode of action of S. frutescens still remains to be elucidated. The aim of this study was to investigate the developmental stages of high fat diet (HFD)-induced IR, to illuminate the pathogenesis of IR with a focal point on modifications in the lipid metabolism. Furthermore, the effects of S. frutescens as a treatment or prevention drug for IR and associated metabolic changes were examined. Two sets of experiments were conducted on male Wistar rats. In the first experiment rats, one week post weaning received a low fat diet (LFD), high fat diet (HFD) or HFD supplemented with S. frutescens (50mg/kg BW/d). Rats were sacrificed at week 0, 1, 2, 4, 8 and 12 in the feeding regime. In a second experiment rats were fed with a LFD or a HFD for 12 weeks and treated thereafter with S. frutescens (50mg/kg BW/d), metformin (13mg/kg BW/d) or water (control) for 28 days. Rats in the second experiment were sacrificed at week 12 to confirm IR while concurrently run rats were sacrificed after 28 days of treatment. For all the experiments rats were anaesthetized, blood was removed and rats were dissected. Plasma samples were analyzed for insulin, glucose, blood lipid parameters and cytokines. Liver, muscle and adipose tissue were analyzed for glucose uptake, total lipid content, lipid profile and fatty acid profile. It was shown that the intake of HFD caused IR and hyperinsulinaemia. The developmental stages in experiment one confirmed that an increase in plasma free fatty acids preceeded the onset of IR. Plasma and tissue lipid parameters (free fatty acid-, triglyceride- and cholesterol concentrations) showed pathological modifications in the HFD group. An ectopic accumulation of fat was observed in muscle and liver, as well as a change in membrane fatty acid profile. The results for circulating cytokines were somewhat inconclusive. Rats supplemented with S. frutescens did not develop HFD-induced IR (study one) or IR was reversed (study two). S. frutescens treatment also resulted in positive changes in plasma and tissue lipid parameters. In summary, an animal model for HFD-induced IR was established and the detrimental effect of elevated plasma FFA on glucose and lipid metabolism was observed. A novel discovery suggests that the anti-diabetic mode of action of S. frutescens is through modulation of lipid metabolism. It was also established that S. frutescens has the potential to prevent IR in vivo.
- Full Text:
- Date Issued: 2010
- Authors: Mackenzie, Janine
- Date: 2010
- Subjects: Metabolic syndrome , Insulin resistance -- Animal models , Obesity -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10340 , http://hdl.handle.net/10948/d1016216
- Description: The global number of obese people has reached pandemic proportions. High caloric diets and reduced physical exercise are to blame for this growing epidemic. Obesity has a very complex association with several other metabolic disorders, such as insulin resistance (IR), diabetes mellitus type 2 (DMT2) and cardiovascular disease. This puts a huge burden on health care systems world wide and claims many lives. Sutherlandia frutescens is a traditionally used herb, which is known to have anti-diabetic properties. However, the direct mode of action of S. frutescens still remains to be elucidated. The aim of this study was to investigate the developmental stages of high fat diet (HFD)-induced IR, to illuminate the pathogenesis of IR with a focal point on modifications in the lipid metabolism. Furthermore, the effects of S. frutescens as a treatment or prevention drug for IR and associated metabolic changes were examined. Two sets of experiments were conducted on male Wistar rats. In the first experiment rats, one week post weaning received a low fat diet (LFD), high fat diet (HFD) or HFD supplemented with S. frutescens (50mg/kg BW/d). Rats were sacrificed at week 0, 1, 2, 4, 8 and 12 in the feeding regime. In a second experiment rats were fed with a LFD or a HFD for 12 weeks and treated thereafter with S. frutescens (50mg/kg BW/d), metformin (13mg/kg BW/d) or water (control) for 28 days. Rats in the second experiment were sacrificed at week 12 to confirm IR while concurrently run rats were sacrificed after 28 days of treatment. For all the experiments rats were anaesthetized, blood was removed and rats were dissected. Plasma samples were analyzed for insulin, glucose, blood lipid parameters and cytokines. Liver, muscle and adipose tissue were analyzed for glucose uptake, total lipid content, lipid profile and fatty acid profile. It was shown that the intake of HFD caused IR and hyperinsulinaemia. The developmental stages in experiment one confirmed that an increase in plasma free fatty acids preceeded the onset of IR. Plasma and tissue lipid parameters (free fatty acid-, triglyceride- and cholesterol concentrations) showed pathological modifications in the HFD group. An ectopic accumulation of fat was observed in muscle and liver, as well as a change in membrane fatty acid profile. The results for circulating cytokines were somewhat inconclusive. Rats supplemented with S. frutescens did not develop HFD-induced IR (study one) or IR was reversed (study two). S. frutescens treatment also resulted in positive changes in plasma and tissue lipid parameters. In summary, an animal model for HFD-induced IR was established and the detrimental effect of elevated plasma FFA on glucose and lipid metabolism was observed. A novel discovery suggests that the anti-diabetic mode of action of S. frutescens is through modulation of lipid metabolism. It was also established that S. frutescens has the potential to prevent IR in vivo.
- Full Text:
- Date Issued: 2010
Dialectics of dance and dress: the performative negotiation of Soli girl initiates (Moye) in Zambia
- Authors: Simbao, Ruth K
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147492 , vital:38643 , https://doi.org/10.1162/afar.2010.43.3.64
- Description: During a 2005 dance rehearsal in Nkomeshya Village near Lusaka, Zambia, a group of Soli girl initiates (moye) entered a clearing, slowly moving towards the drummer who beckoned them with her rhythmic eats. The girls per-formed a polite curtseying step, reflecting the meek modesty they are taught to display when they humbly greet elders or their future husbands with downcast eyes.
- Full Text:
- Date Issued: 2010
- Authors: Simbao, Ruth K
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147492 , vital:38643 , https://doi.org/10.1162/afar.2010.43.3.64
- Description: During a 2005 dance rehearsal in Nkomeshya Village near Lusaka, Zambia, a group of Soli girl initiates (moye) entered a clearing, slowly moving towards the drummer who beckoned them with her rhythmic eats. The girls per-formed a polite curtseying step, reflecting the meek modesty they are taught to display when they humbly greet elders or their future husbands with downcast eyes.
- Full Text:
- Date Issued: 2010
Die geskiedenis van Despatch, 1945-1995: 'n verkennende studie
- Authors: Steyn, Jacobus Pieter
- Date: 2010
- Subjects: Dispatch (South Africa) -- History , Afrikaners -- South Africa -- Despatch
- Language: Afrikaans
- Type: Thesis , Masters , MA
- Identifier: vital:16142 , http://hdl.handle.net/10948/1116 , Dispatch (South Africa) -- History , Afrikaners -- South Africa -- Despatch
- Description: Hierdie studie se fokus is op die wit Afrikaanssprekende-gemeenskap van Despatch. Daar word op die sosiale, politieke en godsdienstige geskiedenis van die wit Afrikaanssprekende-gemeenskap op Despatch gekonsentreer. Die studie ondersoek slegs die geskiedenis van die wit Afrikaanssprekende-gemeenskap van Despatch aangesien die dorp bekend daarvoor is dat dit oorwegend ʼn wit Afrikaanssprekende-gemeenskap is. Die ekonomie van Despatch en die bruin en swart inwoners word egter kortliks bespreek. Die tydperk van hierdie studie handel van 1945 – 1995. Dit was tydens hierdie jare wat Despatch amptelik as ʼn munisipaliteit gefunksioneer het. Uit die aard van die saak moet die studie gebeure wat aanleiding tot die nedersetting van wit mense langs die oewer van die Swartkopsrivier bespreek. Daar word ʼn kort studie gemaak van die periode 1700 (toe die eerste wit mense hulle langs die oewers van die Swartkopsrivier gevestig het) tot 1939 (wat die begin was van permanente nedersettings langs die syspoor op Despatch). Sekere gebeure word verder as 1995 bespreek. Dit word gedoen om kontinuiteit te behou wanneer belangrike gebeurtenisse, soos die oorskakeling na demokratiese regering in 1994, ondersoek word. Die doel van die studie is om ʼn verkennende ondersoek rakende die geskiedenis van die wit Afrikaanssprekende-gemeenskap van Despatch te doen. Die studie is ʼn verkennende ondersoek omrede nie al die aspekte van die geskiedenis van Despatch ondersoek sal word nie. Slegs die wit Afrikaanssprekende-gemeenskap se sosiale strukture (onderwys, godsdiens en kultuur), munisipale bestuur en politiek sal ondersoek word.
- Full Text:
- Date Issued: 2010
- Authors: Steyn, Jacobus Pieter
- Date: 2010
- Subjects: Dispatch (South Africa) -- History , Afrikaners -- South Africa -- Despatch
- Language: Afrikaans
- Type: Thesis , Masters , MA
- Identifier: vital:16142 , http://hdl.handle.net/10948/1116 , Dispatch (South Africa) -- History , Afrikaners -- South Africa -- Despatch
- Description: Hierdie studie se fokus is op die wit Afrikaanssprekende-gemeenskap van Despatch. Daar word op die sosiale, politieke en godsdienstige geskiedenis van die wit Afrikaanssprekende-gemeenskap op Despatch gekonsentreer. Die studie ondersoek slegs die geskiedenis van die wit Afrikaanssprekende-gemeenskap van Despatch aangesien die dorp bekend daarvoor is dat dit oorwegend ʼn wit Afrikaanssprekende-gemeenskap is. Die ekonomie van Despatch en die bruin en swart inwoners word egter kortliks bespreek. Die tydperk van hierdie studie handel van 1945 – 1995. Dit was tydens hierdie jare wat Despatch amptelik as ʼn munisipaliteit gefunksioneer het. Uit die aard van die saak moet die studie gebeure wat aanleiding tot die nedersetting van wit mense langs die oewer van die Swartkopsrivier bespreek. Daar word ʼn kort studie gemaak van die periode 1700 (toe die eerste wit mense hulle langs die oewers van die Swartkopsrivier gevestig het) tot 1939 (wat die begin was van permanente nedersettings langs die syspoor op Despatch). Sekere gebeure word verder as 1995 bespreek. Dit word gedoen om kontinuiteit te behou wanneer belangrike gebeurtenisse, soos die oorskakeling na demokratiese regering in 1994, ondersoek word. Die doel van die studie is om ʼn verkennende ondersoek rakende die geskiedenis van die wit Afrikaanssprekende-gemeenskap van Despatch te doen. Die studie is ʼn verkennende ondersoek omrede nie al die aspekte van die geskiedenis van Despatch ondersoek sal word nie. Slegs die wit Afrikaanssprekende-gemeenskap se sosiale strukture (onderwys, godsdiens en kultuur), munisipale bestuur en politiek sal ondersoek word.
- Full Text:
- Date Issued: 2010
Diet and population trends of warthog in the Addo Elephant National Park
- Authors: Mgqatsa, Nokubonga
- Date: 2010
- Subjects: Warthog -- South Africa -- Addo Elelphant National Park
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10693 , http://hdl.handle.net/10948/1277 , Warthog -- South Africa -- Addo Elelphant National Park
- Description: The common warthog (Phacochoerus africanus) has recently been recognised as an alien invasive species in the Eastern Cape and their population is increasing rapidly within the region. This then raises a concern as it is recorded that invasive species have negative impacts on both economic and ecological aspects of biodiversity in the receiving community. There are few studies that have documented the impacts of this species in the Eastern Cape. This study therefore seeks to determine the diet and population trends of this species in the Addo Elephant National Park (AENP) Main Camp and the results obtained can be correlated with previous studies and used to quantify the impacts of this species in the Eastern Cape. Warthogs are specialized grazers, it was therefore hypothesized that they will have potential impacts on grazing resources in the AENP Main Camp. The diet of common warthogs in the AENP Main Camp was determined through microhistological analysis of faecal material of samples collected seasonally. Population trends of common warthogs were determined in relation to the effects of predation on the population growth and population age structure of these animals within the AENP Main Camp. The results were compared with the findings for common warthog population growth and population age structure of Great Fish River Nature Reserve (GFRNR), a predator free population. It was hypothesized that the population growth rate of common warthogs in the AENP Main Camp before the introduction of lions and hyaenas in the AENP would not differ from the population growth rate of common warthogs in GFRNR. Secondly, the post-lion/hyaena common warthog population in the AENP Main Camp would differ from both the AENP Main Camp pre-lion/hyaena and GFRNR common warthog populations due to the presence of large predators in the AENP Main Camp. For population age structure it was hypothesized that the two populations, AENP Main Camp and GFRNR would differ because of predators increasing mortality. The diet of common warthogs was dominated by grass (87.4 percent), with Cynodon dactylon being the dominant grass species. Common warthogs in the AENP Main Camp should be properly managed because they have potential impact on grasses. The population growth of common warthogs in the AENP Main Camp showed no effect of predation, with population growth not differing from that of GFRNR. Predation had an effect on common warthog population age structure with AENP Main Camp and GFRNR populations differing, particularly in terms of adult structure. Thus, population growth of common warthogs in the AENP Main Camp is not determined by the presence of predators. These findings highlight the status of common warthog as an invasive species in the AENP Main Camp and potentially impacting on grass species and show little effects of top-down population regulation. These results show a need of monitoring common warthog population as well as their potential impacts in the area.
- Full Text:
- Date Issued: 2010
- Authors: Mgqatsa, Nokubonga
- Date: 2010
- Subjects: Warthog -- South Africa -- Addo Elelphant National Park
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10693 , http://hdl.handle.net/10948/1277 , Warthog -- South Africa -- Addo Elelphant National Park
- Description: The common warthog (Phacochoerus africanus) has recently been recognised as an alien invasive species in the Eastern Cape and their population is increasing rapidly within the region. This then raises a concern as it is recorded that invasive species have negative impacts on both economic and ecological aspects of biodiversity in the receiving community. There are few studies that have documented the impacts of this species in the Eastern Cape. This study therefore seeks to determine the diet and population trends of this species in the Addo Elephant National Park (AENP) Main Camp and the results obtained can be correlated with previous studies and used to quantify the impacts of this species in the Eastern Cape. Warthogs are specialized grazers, it was therefore hypothesized that they will have potential impacts on grazing resources in the AENP Main Camp. The diet of common warthogs in the AENP Main Camp was determined through microhistological analysis of faecal material of samples collected seasonally. Population trends of common warthogs were determined in relation to the effects of predation on the population growth and population age structure of these animals within the AENP Main Camp. The results were compared with the findings for common warthog population growth and population age structure of Great Fish River Nature Reserve (GFRNR), a predator free population. It was hypothesized that the population growth rate of common warthogs in the AENP Main Camp before the introduction of lions and hyaenas in the AENP would not differ from the population growth rate of common warthogs in GFRNR. Secondly, the post-lion/hyaena common warthog population in the AENP Main Camp would differ from both the AENP Main Camp pre-lion/hyaena and GFRNR common warthog populations due to the presence of large predators in the AENP Main Camp. For population age structure it was hypothesized that the two populations, AENP Main Camp and GFRNR would differ because of predators increasing mortality. The diet of common warthogs was dominated by grass (87.4 percent), with Cynodon dactylon being the dominant grass species. Common warthogs in the AENP Main Camp should be properly managed because they have potential impact on grasses. The population growth of common warthogs in the AENP Main Camp showed no effect of predation, with population growth not differing from that of GFRNR. Predation had an effect on common warthog population age structure with AENP Main Camp and GFRNR populations differing, particularly in terms of adult structure. Thus, population growth of common warthogs in the AENP Main Camp is not determined by the presence of predators. These findings highlight the status of common warthog as an invasive species in the AENP Main Camp and potentially impacting on grass species and show little effects of top-down population regulation. These results show a need of monitoring common warthog population as well as their potential impacts in the area.
- Full Text:
- Date Issued: 2010
Differing interpretations of reconciliation in South Africa: a discussion of the home for all campaign
- Authors: Matthews, Sally
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142454 , vital:38081 , DOI:10.1353/trn.2010.0000
- Description: The theme of reconciliation remains an important one in South African politics. The issue of reconciliation was recently highlighted by South African Human Rights Commission chairperson, Jody Kollapen. According to Kollapen, in South Africa we have a problematic narrow interpretation of reconciliation, one that presents reconciliation and transformation as being in opposition to one another. This paper explores some of the debates about reconciliation as a process and then relates these to the Home for All Campaign. This Campaign was aimed at encouraging white South Africans to acknowledge the injustices of the past and to commit themselves to healing divisions and reducing inequalities in contemporary South Africa. It conceived of reconciliation as a process in which the onus is on white South Africans to take the initiative in reconciling with black South Africans. The Campaign received much publicity and provoked debate but never managed to gain the support of a significant number of white South Africans. In this paper, I explore the reasons for the Campaign's failure to meet all of its objectives, relating this to contemporary South African discourse on reconciliation. I argue that the Campaign's interpretation of reconciliation was valuable and necessary and that it remains imperative in South Africa that white South Africans critically reflect upon past and present privileges and take the initiative in processes of inter-racial reconciliation.
- Full Text:
- Date Issued: 2010
- Authors: Matthews, Sally
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142454 , vital:38081 , DOI:10.1353/trn.2010.0000
- Description: The theme of reconciliation remains an important one in South African politics. The issue of reconciliation was recently highlighted by South African Human Rights Commission chairperson, Jody Kollapen. According to Kollapen, in South Africa we have a problematic narrow interpretation of reconciliation, one that presents reconciliation and transformation as being in opposition to one another. This paper explores some of the debates about reconciliation as a process and then relates these to the Home for All Campaign. This Campaign was aimed at encouraging white South Africans to acknowledge the injustices of the past and to commit themselves to healing divisions and reducing inequalities in contemporary South Africa. It conceived of reconciliation as a process in which the onus is on white South Africans to take the initiative in reconciling with black South Africans. The Campaign received much publicity and provoked debate but never managed to gain the support of a significant number of white South Africans. In this paper, I explore the reasons for the Campaign's failure to meet all of its objectives, relating this to contemporary South African discourse on reconciliation. I argue that the Campaign's interpretation of reconciliation was valuable and necessary and that it remains imperative in South Africa that white South Africans critically reflect upon past and present privileges and take the initiative in processes of inter-racial reconciliation.
- Full Text:
- Date Issued: 2010
Digital multimedia network with hierarchical parameter control protocol
- Gurdan, Robby, Foss, Richard
- Authors: Gurdan, Robby , Foss, Richard
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427083 , vital:72413 , https://patentimages.storage.googleapis.com/21/04/39/2266c533e05a46/US20100299421A1.pdf
- Description: The present invention relates to a digital multimedia network of apparatuses each comprising a control device, wherein a device parameter of an apparatus is controlled by sending a command message (CMD) to said control device of said apparatus containing a tree-structured hierarchical parameter address (HPA) which consists of parameter grouping identifiers each corresponding to a hierarchy level of a predetermined tree-structured parameter hierarchy used for addressing device parameters throughout said digital multimedia network.
- Full Text:
- Date Issued: 2010
- Authors: Gurdan, Robby , Foss, Richard
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427083 , vital:72413 , https://patentimages.storage.googleapis.com/21/04/39/2266c533e05a46/US20100299421A1.pdf
- Description: The present invention relates to a digital multimedia network of apparatuses each comprising a control device, wherein a device parameter of an apparatus is controlled by sending a command message (CMD) to said control device of said apparatus containing a tree-structured hierarchical parameter address (HPA) which consists of parameter grouping identifiers each corresponding to a hierarchy level of a predetermined tree-structured parameter hierarchy used for addressing device parameters throughout said digital multimedia network.
- Full Text:
- Date Issued: 2010
Disjunctures within conventional knowledge of black male homosexual identity in contemporary South Africa
- Authors: Li, Xinling
- Date: 2010
- Subjects: Mead, George Herbert 1863-1931 , Foucault, Michel, 1926-1984 , Butler, Judith, 1956- , Gay men, Black -- South Africa , Lesbians -- South Africa , Gender identity -- South Africa , Homosexuality -- South Africa , Identity (Psychology) -- South Africa , Gender identity -- Social aspects
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3297 , http://hdl.handle.net/10962/d1003085 , Mead, George Herbert 1863-1931 , Foucault, Michel, 1926-1984 , Butler, Judith, 1956- , Gay men, Black -- South Africa , Lesbians -- South Africa , Gender identity -- South Africa , Homosexuality -- South Africa , Identity (Psychology) -- South Africa , Gender identity -- Social aspects
- Description: This thesis provides a sociological understanding of how conventional knowledge of sexuality negates the identity formation of black gay men in contemporary South Africa. It investigates the coming out experiences of six black gay men in order to reveal the disjunctures between being black and being gay. The theoretical formation of disjuncture is pursued through examining a number of sociological, historical, psychoanalytical, and feminist approaches to identity, sexuality, and society; featuring specifically the theories of George Herbert Mead, Michel Foucault, and Judith Butler. The chosen research paradigm is symbolic interactionism, postulating both „pragmatist‟ and „empiricist‟ trends that lead to both interactionist and structuralist forms of argumentation. The interactionist approach to sexuality is central to the deconstruction of sexual conventions. It involves conceptualising modern sexuality in the landscapes of African colonial history and the global gay and lesbian movement. The prescribed literature on homosexuality is thus reviewed in conjunction with the South African gay and lesbian struggle, so as to spawn themes and perspectives for conducting life story interviews. The use of the life story interview favours the participants‟ own view of the studied phenomenon, yet aims to depict the structural influence on homosexual identification. Following the qualitative research tradition, the data analysis is based on the interpretation of narratives. It illustrates interpersonal relationships and microscopic experiences that lead to the self-acceptance and self-actualisation of homosexuality. Within these processes, various disjunctures that exist between the cultural sanction of lifestyle and individual choice, between parents and children, between religious belief and personal desires, and between gender identity and sexual orientation are disclosed. The findings are associated with the historical transformation of masculinity in South Africa, sex role performance, and the heterosexualisation of desire. The solution to the proposed research problem is discussed through concepts of socialisation and gender conformity.
- Full Text:
- Date Issued: 2010
- Authors: Li, Xinling
- Date: 2010
- Subjects: Mead, George Herbert 1863-1931 , Foucault, Michel, 1926-1984 , Butler, Judith, 1956- , Gay men, Black -- South Africa , Lesbians -- South Africa , Gender identity -- South Africa , Homosexuality -- South Africa , Identity (Psychology) -- South Africa , Gender identity -- Social aspects
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3297 , http://hdl.handle.net/10962/d1003085 , Mead, George Herbert 1863-1931 , Foucault, Michel, 1926-1984 , Butler, Judith, 1956- , Gay men, Black -- South Africa , Lesbians -- South Africa , Gender identity -- South Africa , Homosexuality -- South Africa , Identity (Psychology) -- South Africa , Gender identity -- Social aspects
- Description: This thesis provides a sociological understanding of how conventional knowledge of sexuality negates the identity formation of black gay men in contemporary South Africa. It investigates the coming out experiences of six black gay men in order to reveal the disjunctures between being black and being gay. The theoretical formation of disjuncture is pursued through examining a number of sociological, historical, psychoanalytical, and feminist approaches to identity, sexuality, and society; featuring specifically the theories of George Herbert Mead, Michel Foucault, and Judith Butler. The chosen research paradigm is symbolic interactionism, postulating both „pragmatist‟ and „empiricist‟ trends that lead to both interactionist and structuralist forms of argumentation. The interactionist approach to sexuality is central to the deconstruction of sexual conventions. It involves conceptualising modern sexuality in the landscapes of African colonial history and the global gay and lesbian movement. The prescribed literature on homosexuality is thus reviewed in conjunction with the South African gay and lesbian struggle, so as to spawn themes and perspectives for conducting life story interviews. The use of the life story interview favours the participants‟ own view of the studied phenomenon, yet aims to depict the structural influence on homosexual identification. Following the qualitative research tradition, the data analysis is based on the interpretation of narratives. It illustrates interpersonal relationships and microscopic experiences that lead to the self-acceptance and self-actualisation of homosexuality. Within these processes, various disjunctures that exist between the cultural sanction of lifestyle and individual choice, between parents and children, between religious belief and personal desires, and between gender identity and sexual orientation are disclosed. The findings are associated with the historical transformation of masculinity in South Africa, sex role performance, and the heterosexualisation of desire. The solution to the proposed research problem is discussed through concepts of socialisation and gender conformity.
- Full Text:
- Date Issued: 2010
Dismissal due to excessive ill health absenteeism
- Authors: Van der Walt, Natasha
- Date: 2010
- Subjects: Employees, Dismissal of -- South Africa , Absenteeism (Labor) -- South Africa , Employees -- Health and hygiene
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:10201 , http://hdl.handle.net/10948/1286 , Employees, Dismissal of -- South Africa , Absenteeism (Labor) -- South Africa , Employees -- Health and hygiene
- Description: In a globally competitive market place companies strive to become as efficient as possible. Absenteeism is a worldwide problem as it impacts on company efficiency and cost effectiveness. A large portion of absenteeism can be attributed to ill health absences. Companies have prioritized the need to find ways of managing and reducing absenteeism. In South Africa such processes have to occur within the confines of a constitutional right to fair labour practices and other prescriptive labour legislation. The issue is somewhat complicated by the fact that employees have a right to paid time off due to illness. It is thus clear that not all ill health absenteeism can be deemed problematic. A balancing act needs to occur between the operational needs of the employer and the rights of employees. Ill health absenteeism becomes problematic once a threshold is reached at which point it becomes intolerable for the employer, thus deemed excessive. Excessive ill health absenteeism is not a difficult concept to understand, however it is not specifically defined. A universal concept of when absence is deemed to have reached the threshold of excessiveness does not exist and varies from one employer to the next. Excessive ill health absence is a multi-facetted concept (as a result of the various types of ill health absence) and thus a universal process cannot be adopted to deal with all types of excessive ill health absenteeism. In an attempt to deal with the different types of ill health absenteeism it is pertinent to categorize the issues. The author suggests various ways of dealing with ill health absenteeism, depending on the facts of each case. A misconduct process should only be applicable in instances where it can be proved that sick leave is used inappropriately or the reason for absence is unknown. Although case law suggests the prevalence of dealing with ill health absence as misconduct, especially in the case of persistent short term absence, these cases rarely prove that abuse is taking place. Suspicions regarding abuse without proper evidence to support such claims will not satisfy the substantive fairness requirements. In the event that illness is of a medium to long term nature, an ill health incapacity process may be the most appropriate process to apply, as in such instances a clearly distinguishable illness exists, which makes accommodation less problematic. Such a process is less suited to persistent short term absence as this can be the result of many illnesses or injuries. In the case of persistent short term absence, the individual may be fully capable of performing their duties upon returning to work, however their frequent absence causes unreliability and inefficiency. It is clear in this instance that accommodation cannot take place due to the unpredictable nature of the absences. The concern with persistent short term absence is less with the illness or illnesses displayed and more with the absences itself. The author suggests that it may be appropriate to deal with such absences on the basis of incapacity due to poor work performance. This assertion is based on the fact that the concern is with frequent short term absence that causes the employee to be unreliable; however the illnesses are not of such a nature that it can warrant accommodation. If it is accepted that the employee is not malingering or if the malingering cannot be proved the employee has failed to meet a performance standard (attendance standard). It is suggested that as part of any incapacity investigation consideration should be given to whether the illness or injury can be deemed a disability. This is necessary as disabled individuals are afforded special protection and treatment. A dismissal of an incapacitated individual that is actually deemed “disabled” could be held to be automatically unfair and therefore it is pertinent that this is established at the outset.
- Full Text:
- Date Issued: 2010
- Authors: Van der Walt, Natasha
- Date: 2010
- Subjects: Employees, Dismissal of -- South Africa , Absenteeism (Labor) -- South Africa , Employees -- Health and hygiene
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:10201 , http://hdl.handle.net/10948/1286 , Employees, Dismissal of -- South Africa , Absenteeism (Labor) -- South Africa , Employees -- Health and hygiene
- Description: In a globally competitive market place companies strive to become as efficient as possible. Absenteeism is a worldwide problem as it impacts on company efficiency and cost effectiveness. A large portion of absenteeism can be attributed to ill health absences. Companies have prioritized the need to find ways of managing and reducing absenteeism. In South Africa such processes have to occur within the confines of a constitutional right to fair labour practices and other prescriptive labour legislation. The issue is somewhat complicated by the fact that employees have a right to paid time off due to illness. It is thus clear that not all ill health absenteeism can be deemed problematic. A balancing act needs to occur between the operational needs of the employer and the rights of employees. Ill health absenteeism becomes problematic once a threshold is reached at which point it becomes intolerable for the employer, thus deemed excessive. Excessive ill health absenteeism is not a difficult concept to understand, however it is not specifically defined. A universal concept of when absence is deemed to have reached the threshold of excessiveness does not exist and varies from one employer to the next. Excessive ill health absence is a multi-facetted concept (as a result of the various types of ill health absence) and thus a universal process cannot be adopted to deal with all types of excessive ill health absenteeism. In an attempt to deal with the different types of ill health absenteeism it is pertinent to categorize the issues. The author suggests various ways of dealing with ill health absenteeism, depending on the facts of each case. A misconduct process should only be applicable in instances where it can be proved that sick leave is used inappropriately or the reason for absence is unknown. Although case law suggests the prevalence of dealing with ill health absence as misconduct, especially in the case of persistent short term absence, these cases rarely prove that abuse is taking place. Suspicions regarding abuse without proper evidence to support such claims will not satisfy the substantive fairness requirements. In the event that illness is of a medium to long term nature, an ill health incapacity process may be the most appropriate process to apply, as in such instances a clearly distinguishable illness exists, which makes accommodation less problematic. Such a process is less suited to persistent short term absence as this can be the result of many illnesses or injuries. In the case of persistent short term absence, the individual may be fully capable of performing their duties upon returning to work, however their frequent absence causes unreliability and inefficiency. It is clear in this instance that accommodation cannot take place due to the unpredictable nature of the absences. The concern with persistent short term absence is less with the illness or illnesses displayed and more with the absences itself. The author suggests that it may be appropriate to deal with such absences on the basis of incapacity due to poor work performance. This assertion is based on the fact that the concern is with frequent short term absence that causes the employee to be unreliable; however the illnesses are not of such a nature that it can warrant accommodation. If it is accepted that the employee is not malingering or if the malingering cannot be proved the employee has failed to meet a performance standard (attendance standard). It is suggested that as part of any incapacity investigation consideration should be given to whether the illness or injury can be deemed a disability. This is necessary as disabled individuals are afforded special protection and treatment. A dismissal of an incapacitated individual that is actually deemed “disabled” could be held to be automatically unfair and therefore it is pertinent that this is established at the outset.
- Full Text:
- Date Issued: 2010
Does reservoir trophic status influence the feeding and growth of the sharptooth catfish, Clarias gariepinus (Teleostei: Clariidae)?
- Potts, Warren M, Hecht, Thomas, Andrew, Timothy G
- Authors: Potts, Warren M , Hecht, Thomas , Andrew, Timothy G
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124309 , vital:35591 , https://doi.org/10.2989/A JAS.2008.33.2.6.503
- Description: The diet and growth of sharptooth catfish, Clarias gariepinus, in an oligotrophic system (Kat River Reservoir, Eastern Cape, South Africa) were compared to those in a eutrophic system (Laing Reservoir, Eastern Cape) to determine if the trophic status of a waterbody had an effect on the growth rate of the species. In order of importance, the diet of catfish in Kat River Reservoir consisted of fish, insects, zooplankton, plant material and other items, while the diet of catfish in Laing Reservoir consisted of fish, plant material, zooplankton, other vertebrates and insects. The diets of catfish in the two reservoirs had a similarity index of 68.1% and there was no significant difference in their nutritional value. Fish prey was the most important dietary component in both reservoirs. Temperature regime and zooplankton and zoobenthos density were similar in both systems. However, fish prey density was significantly higher in the eutrophic Laing Reservoir and catfish grew significantly faster in that system. The slower growth rate in Kat River Reservoir was attributed to the higher energy costs associated with the capture of fish prey, which was less abundant than in Laing Reservoir. Trophic status therefore had an indirect effect on catfish growth by influencing the availability of fish prey.
- Full Text:
- Date Issued: 2010
- Authors: Potts, Warren M , Hecht, Thomas , Andrew, Timothy G
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124309 , vital:35591 , https://doi.org/10.2989/A JAS.2008.33.2.6.503
- Description: The diet and growth of sharptooth catfish, Clarias gariepinus, in an oligotrophic system (Kat River Reservoir, Eastern Cape, South Africa) were compared to those in a eutrophic system (Laing Reservoir, Eastern Cape) to determine if the trophic status of a waterbody had an effect on the growth rate of the species. In order of importance, the diet of catfish in Kat River Reservoir consisted of fish, insects, zooplankton, plant material and other items, while the diet of catfish in Laing Reservoir consisted of fish, plant material, zooplankton, other vertebrates and insects. The diets of catfish in the two reservoirs had a similarity index of 68.1% and there was no significant difference in their nutritional value. Fish prey was the most important dietary component in both reservoirs. Temperature regime and zooplankton and zoobenthos density were similar in both systems. However, fish prey density was significantly higher in the eutrophic Laing Reservoir and catfish grew significantly faster in that system. The slower growth rate in Kat River Reservoir was attributed to the higher energy costs associated with the capture of fish prey, which was less abundant than in Laing Reservoir. Trophic status therefore had an indirect effect on catfish growth by influencing the availability of fish prey.
- Full Text:
- Date Issued: 2010
Dynamic adaptive cost model for wireless Internet connectivity in African rural communities
- Authors: Sibanda, Khulumani
- Date: 2010
- Subjects: Internet , Community development -- South Africa -- Eastern Cape , Cost effectiveness , Wireless communication systems , Rural development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Computer Science)
- Identifier: vital:11389 , http://hdl.handle.net/10353/380 , Internet , Community development -- South Africa -- Eastern Cape , Cost effectiveness , Wireless communication systems , Rural development -- South Africa -- Eastern Cape
- Description: In today’s dynamic technological landscape, wireless communication networks have become an important part of economic development. The emergence of wireless technologies raises hopes to extend communication to remote areas that have not seen any tangible deployment to date. As developing nations pin their hopes to wireless technologies, cost models for wireless communication networks are becoming vital to support the emerging technologies. However, varying cost changes raise critical challenges to the estimation of both capital expenditure and operational expenditure. The network deployment process has numerous events that may cause adjustments to initially estimated project costs. These adjustments are necessary for a cost management plan and this plan includes monitoring cost performance and ensuring that only appropriate changes are made to the network project. The incidents that may cause cost changes can not be entirely predicted as their distribution tend to change dynamically from time to time. Estimating network deployment costs in such a dynamic environment necessitates cost models that can adapt to random occurrence of cost changes. Widely used cost models are usually performed by experienced personnel whose engineering experience is derived from deploying similar networks. In this approach experienced personnel add a certain percentage to the cost estimate to cater for contingency costs. Certainly such an approach depends on individual opinion, making it subjective and void of mathematical estimating relationships which are of paramount importance in ensuring that estimated deployment costs are sufficient to deal with cost uncertainties. We observe that existing approaches can only explore a limited solution space and hence can lead to cost overruns if implemented in dynamically cost changing environments. This thesis presents a wireless communication network deployment cost model that incorporates uncertainties into the final cost estimate. The model is adaptive to unpredictable cost changes since it allows adjustments of confidence levels when calculating contingency costs. This allows dynamically updating the cost changes without the cost model being reconstructed from scratch. We make use of the Poisson process in modeling the occurrence of incidents that are responsible for causing cost changes during network deployment. We also show that the occurrence of the incidents causing cost change are random and tend to follow the Poisson distribution. Using different levels of confidence we model various cost contingencies and make sensitivity analyses to identify the probability of cost overrun when given different contingencies. The dynamic adaptive cost model can be used either at the strategic level to understand the cost of a particular technique or at the operational level, as a way to show how Poisson process in network deployment can compare with engineering experience and other estimating techniques. We believe that the model is useful for remote areas where deployment costs are volatile and the distribution of incidents causing cost change to original cost estimates are diverse and dynamically changing. Further we expect that our research improves the knowledge base of information about the costs for rural communities to connect to the Internet, consequently providing useful input to future policy debates. This work is further poised to be a utility function to help those planning internet infrastructure deployments in least developed regions.
- Full Text:
- Date Issued: 2010
- Authors: Sibanda, Khulumani
- Date: 2010
- Subjects: Internet , Community development -- South Africa -- Eastern Cape , Cost effectiveness , Wireless communication systems , Rural development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Computer Science)
- Identifier: vital:11389 , http://hdl.handle.net/10353/380 , Internet , Community development -- South Africa -- Eastern Cape , Cost effectiveness , Wireless communication systems , Rural development -- South Africa -- Eastern Cape
- Description: In today’s dynamic technological landscape, wireless communication networks have become an important part of economic development. The emergence of wireless technologies raises hopes to extend communication to remote areas that have not seen any tangible deployment to date. As developing nations pin their hopes to wireless technologies, cost models for wireless communication networks are becoming vital to support the emerging technologies. However, varying cost changes raise critical challenges to the estimation of both capital expenditure and operational expenditure. The network deployment process has numerous events that may cause adjustments to initially estimated project costs. These adjustments are necessary for a cost management plan and this plan includes monitoring cost performance and ensuring that only appropriate changes are made to the network project. The incidents that may cause cost changes can not be entirely predicted as their distribution tend to change dynamically from time to time. Estimating network deployment costs in such a dynamic environment necessitates cost models that can adapt to random occurrence of cost changes. Widely used cost models are usually performed by experienced personnel whose engineering experience is derived from deploying similar networks. In this approach experienced personnel add a certain percentage to the cost estimate to cater for contingency costs. Certainly such an approach depends on individual opinion, making it subjective and void of mathematical estimating relationships which are of paramount importance in ensuring that estimated deployment costs are sufficient to deal with cost uncertainties. We observe that existing approaches can only explore a limited solution space and hence can lead to cost overruns if implemented in dynamically cost changing environments. This thesis presents a wireless communication network deployment cost model that incorporates uncertainties into the final cost estimate. The model is adaptive to unpredictable cost changes since it allows adjustments of confidence levels when calculating contingency costs. This allows dynamically updating the cost changes without the cost model being reconstructed from scratch. We make use of the Poisson process in modeling the occurrence of incidents that are responsible for causing cost changes during network deployment. We also show that the occurrence of the incidents causing cost change are random and tend to follow the Poisson distribution. Using different levels of confidence we model various cost contingencies and make sensitivity analyses to identify the probability of cost overrun when given different contingencies. The dynamic adaptive cost model can be used either at the strategic level to understand the cost of a particular technique or at the operational level, as a way to show how Poisson process in network deployment can compare with engineering experience and other estimating techniques. We believe that the model is useful for remote areas where deployment costs are volatile and the distribution of incidents causing cost change to original cost estimates are diverse and dynamically changing. Further we expect that our research improves the knowledge base of information about the costs for rural communities to connect to the Internet, consequently providing useful input to future policy debates. This work is further poised to be a utility function to help those planning internet infrastructure deployments in least developed regions.
- Full Text:
- Date Issued: 2010
E-mail forensic authorship attribution
- Authors: Lalla, Himal
- Date: 2010
- Subjects: Electronic evidence , Electronic mail systems , Authorship , Electronic mail messages , Signatures (Writing) , Writing -- Identification , Forensic accounting
- Language: English
- Type: Thesis , Masters , MCom (Information Systems)
- Identifier: vital:11128 , http://hdl.handle.net/10353/360 , Electronic evidence , Electronic mail systems , Authorship , Electronic mail messages , Signatures (Writing) , Writing -- Identification , Forensic accounting
- Description: E-mails have become the standard for business as well as personal communication. The inherent security risks within e-mail communication present the problem of anonymity. If an author of an e-mail is not known, the digital forensic investigator needs to determine the authorship of the e-mail using a process that has not been standardised in the e-mail forensic field. This research project examines many problems associated with e-mail communication and the digital forensic domain; more specifically e-mail forensic investigations, and the recovery of legally admissible evidence to be presented in a court of law. The Research Methodology utilised a comprehensive literature review in combination with Design Science which results in the development of an artifact through intensive research. The Proposed E-Mail Forensic Methodology is based on the most current digital forensic investigation process and further validation of the process was established via expert reviews. The opinions of the digital forensic experts were an integral portion of the validation process which adds to the credibility of the study. This was performed through the aid of the Delphi technique. This Proposed E-Mail Forensic Methodology adopts a standardised investigation process applied to an e-mail investigation and takes into account the South African perspective by incorporating various checks with the laws and legislation. By following the Proposed E-mail Forensic Methodology, e-mail forensic investigators can produce evidence that is legally admissible in a court of law.
- Full Text:
- Date Issued: 2010
- Authors: Lalla, Himal
- Date: 2010
- Subjects: Electronic evidence , Electronic mail systems , Authorship , Electronic mail messages , Signatures (Writing) , Writing -- Identification , Forensic accounting
- Language: English
- Type: Thesis , Masters , MCom (Information Systems)
- Identifier: vital:11128 , http://hdl.handle.net/10353/360 , Electronic evidence , Electronic mail systems , Authorship , Electronic mail messages , Signatures (Writing) , Writing -- Identification , Forensic accounting
- Description: E-mails have become the standard for business as well as personal communication. The inherent security risks within e-mail communication present the problem of anonymity. If an author of an e-mail is not known, the digital forensic investigator needs to determine the authorship of the e-mail using a process that has not been standardised in the e-mail forensic field. This research project examines many problems associated with e-mail communication and the digital forensic domain; more specifically e-mail forensic investigations, and the recovery of legally admissible evidence to be presented in a court of law. The Research Methodology utilised a comprehensive literature review in combination with Design Science which results in the development of an artifact through intensive research. The Proposed E-Mail Forensic Methodology is based on the most current digital forensic investigation process and further validation of the process was established via expert reviews. The opinions of the digital forensic experts were an integral portion of the validation process which adds to the credibility of the study. This was performed through the aid of the Delphi technique. This Proposed E-Mail Forensic Methodology adopts a standardised investigation process applied to an e-mail investigation and takes into account the South African perspective by incorporating various checks with the laws and legislation. By following the Proposed E-mail Forensic Methodology, e-mail forensic investigators can produce evidence that is legally admissible in a court of law.
- Full Text:
- Date Issued: 2010
Ecological impacts of small dams on South African rivers Part 1: Drivers of change–water quantity and quality
- Mantel, Sukhmani K, Hughes, Denis A, Muller, Nikite W J
- Authors: Mantel, Sukhmani K , Hughes, Denis A , Muller, Nikite W J
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438099 , vital:73435 , ISBN 1816-7950 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2398.pdf
- Description: Impacts of large dams are well-known and quantifiable, while small dams have generally been perceived as benign, both socially and envi-ronmentally. The present study quantifies the cumulative impacts of small dams on the water quality (physico-chemistry and invertebrate biotic indices) and quantity (discharge) of downstream rivers in 2 South African regions. The information from 2 South African national data-bases was used for evaluating the cumulative impacts on water quality and quantity. Physico-chemistry and biological data were obtained from the River Health Programme, and discharge data at stream flow gauges was obtained from the Hydrological Information System. Multivariate analyses were conducted to establish broad patterns for cumulative impacts of small dams across the 2 regions–Western Cape (winter rain-fall, temperate, south-western coast) and Mpumalanga (summer rain-fall, tropical, eastern coast). Multivariate analyses found that the chang-es in macroinvertebrate indices and the stream’s physico-chemistry were more strongly correlated with the density of small dams in the catchment (as a measure of cumulative impact potential) relative to the storage capacity of large dams. T-tests on the data, not including sam-ples with upstream large dams, indicated that the high density of small dams significantly reduced low flows and increased certain physico-chemistry variables (particularly total dissolved salts) in both the re-gions, along with associated significant reductions in a macroinverte-brate index (SASS4 average score per taxon). Regional differences were apparent in the results for discharge reductions and the macroin-vertebrate index. The results suggest that the cumulative effect of a high number of small dams is impacting the quality and quantity of wa-ters in South African rivers and that these impacts need to be systemat-ically incorporated into the monitoring protocol of the environmental wa-ter requirements.
- Full Text:
- Date Issued: 2010
- Authors: Mantel, Sukhmani K , Hughes, Denis A , Muller, Nikite W J
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438099 , vital:73435 , ISBN 1816-7950 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2398.pdf
- Description: Impacts of large dams are well-known and quantifiable, while small dams have generally been perceived as benign, both socially and envi-ronmentally. The present study quantifies the cumulative impacts of small dams on the water quality (physico-chemistry and invertebrate biotic indices) and quantity (discharge) of downstream rivers in 2 South African regions. The information from 2 South African national data-bases was used for evaluating the cumulative impacts on water quality and quantity. Physico-chemistry and biological data were obtained from the River Health Programme, and discharge data at stream flow gauges was obtained from the Hydrological Information System. Multivariate analyses were conducted to establish broad patterns for cumulative impacts of small dams across the 2 regions–Western Cape (winter rain-fall, temperate, south-western coast) and Mpumalanga (summer rain-fall, tropical, eastern coast). Multivariate analyses found that the chang-es in macroinvertebrate indices and the stream’s physico-chemistry were more strongly correlated with the density of small dams in the catchment (as a measure of cumulative impact potential) relative to the storage capacity of large dams. T-tests on the data, not including sam-ples with upstream large dams, indicated that the high density of small dams significantly reduced low flows and increased certain physico-chemistry variables (particularly total dissolved salts) in both the re-gions, along with associated significant reductions in a macroinverte-brate index (SASS4 average score per taxon). Regional differences were apparent in the results for discharge reductions and the macroin-vertebrate index. The results suggest that the cumulative effect of a high number of small dams is impacting the quality and quantity of wa-ters in South African rivers and that these impacts need to be systemat-ically incorporated into the monitoring protocol of the environmental wa-ter requirements.
- Full Text:
- Date Issued: 2010
Ecological impacts of small dams on South African rivers Part 2: Biotic response – abundance and composition of macroinvertebrate communities
- Mantel, Sukhmani K, Muller, Nikite W J, Hughes, Denis A
- Authors: Mantel, Sukhmani K , Muller, Nikite W J , Hughes, Denis A
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:7095 , http://hdl.handle.net/10962/d1012437
- Description: This paper investigates the cumulative impacts of small dams on invertebrate communities in 2 regions of South Africa – the Western Cape and Mpumalanga. Previous research found reduced discharge, increased total dissolved salts, and a decrease in average score per taxon (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigated using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catchment in foothill-gravel streams (in both Western Cape and Mpumalanga) and in foothill-cobble streams (in Western Cape only). Opportunistic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and seasons) and detailed (at species level) collection of data to verify the results of cumulative effects of small dams. This can further the development of a framework for small-dam construction and management that will limit their impact on river catchments.
- Full Text:
- Date Issued: 2010
- Authors: Mantel, Sukhmani K , Muller, Nikite W J , Hughes, Denis A
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:7095 , http://hdl.handle.net/10962/d1012437
- Description: This paper investigates the cumulative impacts of small dams on invertebrate communities in 2 regions of South Africa – the Western Cape and Mpumalanga. Previous research found reduced discharge, increased total dissolved salts, and a decrease in average score per taxon (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigated using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catchment in foothill-gravel streams (in both Western Cape and Mpumalanga) and in foothill-cobble streams (in Western Cape only). Opportunistic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and seasons) and detailed (at species level) collection of data to verify the results of cumulative effects of small dams. This can further the development of a framework for small-dam construction and management that will limit their impact on river catchments.
- Full Text:
- Date Issued: 2010
Ecological impacts of small dams on South African rivers Part 2: Biotic response–abundance and composition of macroinvertebrate communities
- Mantel, Sukhmani K, Muller, Nikite W J, Hughes, Denis A
- Authors: Mantel, Sukhmani K , Muller, Nikite W J , Hughes, Denis A
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438087 , vital:73434 , ISBN 1816-7950 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2354.pdf
- Description: This paper investigates the cumulative impacts of small dams on inver-tebrate communities in 2 regions of South Africa–the Western Cape and Mpumalanga. Previous research found reduced discharge, in-creased total dissolved salts, and a decrease in average score per tax-on (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigat-ed using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catch-ment in foothill-gravel streams (in both Western Cape and Mpuma-langa) and in foothill-cobble streams (in Western Cape only). Opportun-istic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and sea-sons) and detailed (at species level) collection of data to verify the re-sults of cumulative effects of small dams. This can further the devel-opment of a framework for small-dam construction and management that will limit their impact on river catchments.
- Full Text:
- Date Issued: 2010
- Authors: Mantel, Sukhmani K , Muller, Nikite W J , Hughes, Denis A
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438087 , vital:73434 , ISBN 1816-7950 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2354.pdf
- Description: This paper investigates the cumulative impacts of small dams on inver-tebrate communities in 2 regions of South Africa–the Western Cape and Mpumalanga. Previous research found reduced discharge, in-creased total dissolved salts, and a decrease in average score per tax-on (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigat-ed using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catch-ment in foothill-gravel streams (in both Western Cape and Mpuma-langa) and in foothill-cobble streams (in Western Cape only). Opportun-istic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and sea-sons) and detailed (at species level) collection of data to verify the re-sults of cumulative effects of small dams. This can further the devel-opment of a framework for small-dam construction and management that will limit their impact on river catchments.
- Full Text:
- Date Issued: 2010
Ecology and degree of specialization of South African milkweeds with diverse pollination systems
- Authors: Coombs, Gareth
- Date: 2010
- Subjects: Milkweeds -- South Africa Milkweeds -- South Africa -- Ecology Milkweeds -- South Africa -- Pollination Allee effect Self-pollination Pollination by insects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4189 , http://hdl.handle.net/10962/d1003758
- Description: Like orchids, the complexity of flowers found in asclepiads (Asclepiadoideae, Apocynaceae) and the fact that pollen is presented as pollinaria, offers excellent opportunities to study various aspects of plant-pollinator interactions. In this thesis I investigated two broad themes: ecological aspects of the pollination biology of hymenopteran and fly-pollinated asclepiads as well as the degree of specialization to certain pollinators in these species. Colonizing plants often reproduce through self-pollination, or have highly generalized pollination systems, or both. These characteristics facilitate establishment in small founding populations and generates the prediction that reproductive success should be independent of population size in these species. Chapter one examines the pollination biology of Gomphocarpus physocarpus, an indigenous, weedy species and investigates the relationship between reproductive success and population size. In this species, there is no evidence of an Allee effect and reproductive success is not correlated with population size. In addition G. physocarpus is not capable of self-pollination, suggesting it is completely reliant on pollinators for seed set. The lack of a relationship between pollination success and population size is therefore likely explained by the generalized wasp pollination system of this species. Several milkweeds are invasive outside of their native ranges. Invasive species either need to co-opt native pollinators in order to reproduce or reduce their reliance on pollinators through having the ability to self-pollinate. Co-opting native pollinators is expected to be easier in species that have generalized pollination systems, alternatively species with specialized flower morphologies need to rely on similar functional groups of pollinators to be present within the invaded range. Chapter two investigates the pollination biology and pollination success of the invasive milkweed, Araujia sericifera, and finds that in South Africa, this species is visited mainly by native honeybees and nocturnal moths. Moths however contribute little to pollen removal, and deposition. Based on the apparent morphological mismatch between the flower of A. sericifera and native honeybees, I propose that the native pollinators of this species are likely to be larger Hymenoptera (e.g. Bumblebees). Data from a breeding system study, indicated that this species is not capable of automatic self-pollination, but could set fruit from geitonogamous self-pollinations pointing to the importance of native pollinators for successful reproduction. The pollinaria of milkweeds can accumulate on pollinators to form pollen masses large enough to physically interfere with the foraging behaviour of pollinating insects. In chapter three I describe the pollination biology of Cynanchum ellipticum and find that this species is mainly pollinated by honeybees although this species is visited by several other members of Hymenoptera, Lepidoptera and Diptera. Due to the structure of the pollinaria, these chain together relatively efficiently and frequently form large pollinarium loads on the mouthparts of honeybees. However there is little evidence that these pollinarium loads influence the foraging times of pollinators and only a few individual honeybees exhibited longer foraging times and most honeybees were unaffected by the presence of large pollinarium loads. Within the genus Cynanchum there is large variation in the gynostegium structure that may influence the pattern of pollinarium loading on pollinators as well as pollen reception as shown in chapter three. In Chapter four, the pollination biology of Cynanchum obtusifolium is examined, and like that of C. ellipticum, this species is visited by a wide diversity of pollinators but honeybees appear to be the primary pollinators. More importantly this species is shown to be andromonoecious and produces two morphologically different flower types, that may be distinguished based on differences in the gynostegium structure. These two types of flower could mainly be distinguished by the length of the anther wings. I found that flowers with short anther wings function as male flowers by only exporting- and rarely receiving pollinia. Flowers with longer anther wings function as hermaphrodite flowers and can both export and receive pollinia. The ratio of male to hermaphrodite flowers varied at different times during the flowering season, but preliminary data suggested that this was not related to levels of pollination success. The genera Stapelia and Ceropegia are well known for their intricate floral adaptations that mimic the brood and feeding substrates of pollinating flies. Despite several studies that have documented the various adaptations to fly pollination in different species, there is a lack of natural history studies documenting different flower visitors, pollen loads and long term levels of pollination success in these species. In Chapter six I document the pollination biology of Ceropegia ampliata by documenting different pollinators and quantifying average levels of pollination success and the nectar reward. I also experimentally manipulated the trapping hairs of this species to determine whether trapping hairs influence average levels of pollen export and receipt. I show that Ceropegia ampliata is pollinated by a generalist guild of flies (mainly Tachinidae, Sarcophagidae, Muscidae and Lauxaniidae) and produces minute quantities of relatively dilute nectar as a reward. Pollination success was generally low in this species and increases periodically suggesting that the abundance of pollinators is patchy. I found that flowers with trapping hairs that had already wilted had higher levels of pollinarium removal than flowers with erect hairs, however experimentally removing the hairs had no significant effect on pollen export and receipt. In Chapter seven, I document the pollinators, pollen loads and long term levels of pollination success in Stapelia hirsuta var. bayllissi, a rare sapromyiophilous stapeliad. I find that, in contrast to C. ampliata, this species was specialized to pollination by small flies of the family Anthomyiidae. Similar to the results from Chapter seven, I find that long term levels of pollination success were typically low but could increase periodically, although such increases were generally unpredictable. There are currently very few records documenting pollinator interactions in the Periplocoideae. Many species within this subfamily exhibit open-access flowers suggestive of pollination by short-tongued insects. I investigated the pollination biology of Chlorocyathus lobulata, a rare species with a highly localized distribution. I aimed to determine the pollinators, average levels of pollination success and demography of this species in order to determine whether this rare species is suffering from the collapse of a highly specialized pollinator mutualism. I also quantified the high incidence of flower herbivory caused by larvae of the moth, Bocchoris onychinalis. I find that C. lobulata has a highly generalized fly pollination system and average levels of pollination success suggested that a large proportion of flowers had pollen removed and deposited suggesting that this species is not experiencing pollination failure. The large numbers of juveniles present also indicated that recruitment is taking place.
- Full Text:
- Date Issued: 2010
- Authors: Coombs, Gareth
- Date: 2010
- Subjects: Milkweeds -- South Africa Milkweeds -- South Africa -- Ecology Milkweeds -- South Africa -- Pollination Allee effect Self-pollination Pollination by insects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4189 , http://hdl.handle.net/10962/d1003758
- Description: Like orchids, the complexity of flowers found in asclepiads (Asclepiadoideae, Apocynaceae) and the fact that pollen is presented as pollinaria, offers excellent opportunities to study various aspects of plant-pollinator interactions. In this thesis I investigated two broad themes: ecological aspects of the pollination biology of hymenopteran and fly-pollinated asclepiads as well as the degree of specialization to certain pollinators in these species. Colonizing plants often reproduce through self-pollination, or have highly generalized pollination systems, or both. These characteristics facilitate establishment in small founding populations and generates the prediction that reproductive success should be independent of population size in these species. Chapter one examines the pollination biology of Gomphocarpus physocarpus, an indigenous, weedy species and investigates the relationship between reproductive success and population size. In this species, there is no evidence of an Allee effect and reproductive success is not correlated with population size. In addition G. physocarpus is not capable of self-pollination, suggesting it is completely reliant on pollinators for seed set. The lack of a relationship between pollination success and population size is therefore likely explained by the generalized wasp pollination system of this species. Several milkweeds are invasive outside of their native ranges. Invasive species either need to co-opt native pollinators in order to reproduce or reduce their reliance on pollinators through having the ability to self-pollinate. Co-opting native pollinators is expected to be easier in species that have generalized pollination systems, alternatively species with specialized flower morphologies need to rely on similar functional groups of pollinators to be present within the invaded range. Chapter two investigates the pollination biology and pollination success of the invasive milkweed, Araujia sericifera, and finds that in South Africa, this species is visited mainly by native honeybees and nocturnal moths. Moths however contribute little to pollen removal, and deposition. Based on the apparent morphological mismatch between the flower of A. sericifera and native honeybees, I propose that the native pollinators of this species are likely to be larger Hymenoptera (e.g. Bumblebees). Data from a breeding system study, indicated that this species is not capable of automatic self-pollination, but could set fruit from geitonogamous self-pollinations pointing to the importance of native pollinators for successful reproduction. The pollinaria of milkweeds can accumulate on pollinators to form pollen masses large enough to physically interfere with the foraging behaviour of pollinating insects. In chapter three I describe the pollination biology of Cynanchum ellipticum and find that this species is mainly pollinated by honeybees although this species is visited by several other members of Hymenoptera, Lepidoptera and Diptera. Due to the structure of the pollinaria, these chain together relatively efficiently and frequently form large pollinarium loads on the mouthparts of honeybees. However there is little evidence that these pollinarium loads influence the foraging times of pollinators and only a few individual honeybees exhibited longer foraging times and most honeybees were unaffected by the presence of large pollinarium loads. Within the genus Cynanchum there is large variation in the gynostegium structure that may influence the pattern of pollinarium loading on pollinators as well as pollen reception as shown in chapter three. In Chapter four, the pollination biology of Cynanchum obtusifolium is examined, and like that of C. ellipticum, this species is visited by a wide diversity of pollinators but honeybees appear to be the primary pollinators. More importantly this species is shown to be andromonoecious and produces two morphologically different flower types, that may be distinguished based on differences in the gynostegium structure. These two types of flower could mainly be distinguished by the length of the anther wings. I found that flowers with short anther wings function as male flowers by only exporting- and rarely receiving pollinia. Flowers with longer anther wings function as hermaphrodite flowers and can both export and receive pollinia. The ratio of male to hermaphrodite flowers varied at different times during the flowering season, but preliminary data suggested that this was not related to levels of pollination success. The genera Stapelia and Ceropegia are well known for their intricate floral adaptations that mimic the brood and feeding substrates of pollinating flies. Despite several studies that have documented the various adaptations to fly pollination in different species, there is a lack of natural history studies documenting different flower visitors, pollen loads and long term levels of pollination success in these species. In Chapter six I document the pollination biology of Ceropegia ampliata by documenting different pollinators and quantifying average levels of pollination success and the nectar reward. I also experimentally manipulated the trapping hairs of this species to determine whether trapping hairs influence average levels of pollen export and receipt. I show that Ceropegia ampliata is pollinated by a generalist guild of flies (mainly Tachinidae, Sarcophagidae, Muscidae and Lauxaniidae) and produces minute quantities of relatively dilute nectar as a reward. Pollination success was generally low in this species and increases periodically suggesting that the abundance of pollinators is patchy. I found that flowers with trapping hairs that had already wilted had higher levels of pollinarium removal than flowers with erect hairs, however experimentally removing the hairs had no significant effect on pollen export and receipt. In Chapter seven, I document the pollinators, pollen loads and long term levels of pollination success in Stapelia hirsuta var. bayllissi, a rare sapromyiophilous stapeliad. I find that, in contrast to C. ampliata, this species was specialized to pollination by small flies of the family Anthomyiidae. Similar to the results from Chapter seven, I find that long term levels of pollination success were typically low but could increase periodically, although such increases were generally unpredictable. There are currently very few records documenting pollinator interactions in the Periplocoideae. Many species within this subfamily exhibit open-access flowers suggestive of pollination by short-tongued insects. I investigated the pollination biology of Chlorocyathus lobulata, a rare species with a highly localized distribution. I aimed to determine the pollinators, average levels of pollination success and demography of this species in order to determine whether this rare species is suffering from the collapse of a highly specialized pollinator mutualism. I also quantified the high incidence of flower herbivory caused by larvae of the moth, Bocchoris onychinalis. I find that C. lobulata has a highly generalized fly pollination system and average levels of pollination success suggested that a large proportion of flowers had pollen removed and deposited suggesting that this species is not experiencing pollination failure. The large numbers of juveniles present also indicated that recruitment is taking place.
- Full Text:
- Date Issued: 2010
Econometric determinants of liquidity of the South African bond market
- Mingiri, Kapingura Forget https://orcid.org/0000-0002-5808-5612
- Authors: Mingiri, Kapingura Forget https://orcid.org/0000-0002-5808-5612
- Date: 2010
- Subjects: Economic indicators , Economic forecasting -- Africa , Bond market
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/26346 , vital:65243
- Description: The importance of the bond market to the financial system and broader economy of a country cannot be underestimated. It is important to analyse factors which determine liquidity in this essential market. This study seeks to establish the determinants of liquidity in the South African bond market using monthly data covering the period 1995 to 2009. It begins by providing an updated overview of the South African bond market and an analysis of the relevant literature. Two models linking bond market liquidity to its theoretical determinants were specified. In contrast to the available literature, this study analyses liquidity at both macroeconomic and market microstructure level using two measures of liquidity, volume and the bid-ask spread, applying the VAR approach and two-stage least squares for robust check. All macroeconomic variables (except stock market) were identified to have an impact on bond market liquidity in the long-run. As far as market microstructure factors are concerned, both volume and volatility were established to be important determinants of liquidity in the South African bond market. The study recommended that, as for macroeconomic factors, authorities should keep inflation at low and stables levels as well as a stable currency. Also, offering bond investors certain facilities and the removal of restrictions on foreign investor activities are other important conditions to improve bond market liquidity. As far as market microstructure factors are concerned, we suggest that, ways to safe-guard against excessive volatility include the creation of a vibrant derivative market, development of a more active and well-functioning repurchase market./ , Thesis (MCom) -- Faculty of Management and Commerce, 2010
- Full Text:
- Date Issued: 2010
- Authors: Mingiri, Kapingura Forget https://orcid.org/0000-0002-5808-5612
- Date: 2010
- Subjects: Economic indicators , Economic forecasting -- Africa , Bond market
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/26346 , vital:65243
- Description: The importance of the bond market to the financial system and broader economy of a country cannot be underestimated. It is important to analyse factors which determine liquidity in this essential market. This study seeks to establish the determinants of liquidity in the South African bond market using monthly data covering the period 1995 to 2009. It begins by providing an updated overview of the South African bond market and an analysis of the relevant literature. Two models linking bond market liquidity to its theoretical determinants were specified. In contrast to the available literature, this study analyses liquidity at both macroeconomic and market microstructure level using two measures of liquidity, volume and the bid-ask spread, applying the VAR approach and two-stage least squares for robust check. All macroeconomic variables (except stock market) were identified to have an impact on bond market liquidity in the long-run. As far as market microstructure factors are concerned, both volume and volatility were established to be important determinants of liquidity in the South African bond market. The study recommended that, as for macroeconomic factors, authorities should keep inflation at low and stables levels as well as a stable currency. Also, offering bond investors certain facilities and the removal of restrictions on foreign investor activities are other important conditions to improve bond market liquidity. As far as market microstructure factors are concerned, we suggest that, ways to safe-guard against excessive volatility include the creation of a vibrant derivative market, development of a more active and well-functioning repurchase market./ , Thesis (MCom) -- Faculty of Management and Commerce, 2010
- Full Text:
- Date Issued: 2010
Economic consequences of ecological change: restoration options for the Mfolozi floodplain and implications for Lake St. Lucia, South Africa
- Authors: Collings, Sandy Lyn
- Date: 2010
- Subjects: Lake ecology -- South Africa -- Saint Lucia, Lake , Ecology -- Economic aspects -- South Africa -- Kwazulu-Natal , Wetland ecology -- South Africa -- Kwazulu-Natal , Ecosystem services -- South Africa -- Kwazulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4744 , http://hdl.handle.net/10962/d1006950 , Lake ecology -- South Africa -- Saint Lucia, Lake , Ecology -- Economic aspects -- South Africa -- Kwazulu-Natal , Wetland ecology -- South Africa -- Kwazulu-Natal , Ecosystem services -- South Africa -- Kwazulu-Natal
- Description: Lake St Lucia in northern KwaZulu-Natal, South Africa, experiences severe ecological stress during dry periods largely as a result of diminishing freshwater supplies and conditions of hypersalinity. Possible intervention involves diverting the Mfolozi River to the St Lucia Lake system. However, due to high sediment loading, water from the Mfolozi river requires considerable filtration before a link can be established. A suggested option considered in this study is to restore the existing sugarcane farmlands on the Mfolozi Floodplain (~20 800 ha) to previous wetland conditions to reinstate a sediment removal function amongst other benefits. Proposed restoration will have a direct impact on the industries currently supported by the iSimangaliso Wetland Park and the Mfolozi Floodplain (tourism, sugar, conservation). to understand a measure of such impacts, ecosystem services for both Lake St Lucia and the Mfolozi Floodplain were analysed (flood alleviation, water provision, water purification, sediment regulation, tourism, fisheries, vegetation for harvest, existence, cultural and research). Annual economic values for each ecosystem service were determined by means of valuation methods that included benefit transfer and replacement cost. Results showed a current annual minimum value of the Mfolozi Floodplain and Lake St Lucia as greater than R21 million and R1.1 billion respectively. Partial restoration of the floodplain (~6 000 ha) is expected to increase the sum of all ecosystem services values by approximately 26% for the Mfolozi Floodplain and by 23% for the St Lucia System. Full restoration (~20 800 ha) increases the total ecosystem services value by 88% and 50% for the Mfolozi Floodplain and St Lucia System respectively. Results showed that economic values for existence, fisheries, tourism and water provision increase by the greatest percentage for the St Lucia System under both restoration scenarios. Partial and full restoration of the floodplain will result in the greatest increases in economic value for the services existence, tourism, fisheries and the harvesting of vegetation on the Mfolozi Floodplain.
- Full Text:
- Date Issued: 2010
- Authors: Collings, Sandy Lyn
- Date: 2010
- Subjects: Lake ecology -- South Africa -- Saint Lucia, Lake , Ecology -- Economic aspects -- South Africa -- Kwazulu-Natal , Wetland ecology -- South Africa -- Kwazulu-Natal , Ecosystem services -- South Africa -- Kwazulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4744 , http://hdl.handle.net/10962/d1006950 , Lake ecology -- South Africa -- Saint Lucia, Lake , Ecology -- Economic aspects -- South Africa -- Kwazulu-Natal , Wetland ecology -- South Africa -- Kwazulu-Natal , Ecosystem services -- South Africa -- Kwazulu-Natal
- Description: Lake St Lucia in northern KwaZulu-Natal, South Africa, experiences severe ecological stress during dry periods largely as a result of diminishing freshwater supplies and conditions of hypersalinity. Possible intervention involves diverting the Mfolozi River to the St Lucia Lake system. However, due to high sediment loading, water from the Mfolozi river requires considerable filtration before a link can be established. A suggested option considered in this study is to restore the existing sugarcane farmlands on the Mfolozi Floodplain (~20 800 ha) to previous wetland conditions to reinstate a sediment removal function amongst other benefits. Proposed restoration will have a direct impact on the industries currently supported by the iSimangaliso Wetland Park and the Mfolozi Floodplain (tourism, sugar, conservation). to understand a measure of such impacts, ecosystem services for both Lake St Lucia and the Mfolozi Floodplain were analysed (flood alleviation, water provision, water purification, sediment regulation, tourism, fisheries, vegetation for harvest, existence, cultural and research). Annual economic values for each ecosystem service were determined by means of valuation methods that included benefit transfer and replacement cost. Results showed a current annual minimum value of the Mfolozi Floodplain and Lake St Lucia as greater than R21 million and R1.1 billion respectively. Partial restoration of the floodplain (~6 000 ha) is expected to increase the sum of all ecosystem services values by approximately 26% for the Mfolozi Floodplain and by 23% for the St Lucia System. Full restoration (~20 800 ha) increases the total ecosystem services value by 88% and 50% for the Mfolozi Floodplain and St Lucia System respectively. Results showed that economic values for existence, fisheries, tourism and water provision increase by the greatest percentage for the St Lucia System under both restoration scenarios. Partial and full restoration of the floodplain will result in the greatest increases in economic value for the services existence, tourism, fisheries and the harvesting of vegetation on the Mfolozi Floodplain.
- Full Text:
- Date Issued: 2010