A raman spectroscopy study of semiconducting thin films
- Authors: Goosen, William Edward
- Date: 2006
- Subjects: Raman spectroscopy , Semiconductor films , Thin films
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10514 , http://hdl.handle.net/10948/426 , Raman spectroscopy , Semiconductor films , Thin films
- Description: A home-built Raman system, utilizing a pseudo-backscattering geometry, was built in the Physics Department at the Nelson Mandela Metropolitan University (NMMU). The system was then used to analyse a variety of bulk and thin film semiconducting materials currently being studied in the Physics Department. Silicon wafers were exposed to hydrogen plasma. Raman analysis of hydrogen induced platelets (HIPs), resulting from hydrogen plasma treatment of silicon, is reported. ZnO layers were deposited on glass, GaAs, Si, sapphire and SiC-Si substrates by metalorganic chemical vapour deposition (MOCVD) in the Physics Department at the NMMU. It was found that the ZnO layers grown by MOCVD all exhibited a strong E2 (high) phonon mode that dominated the Raman spectra. Furthermore, the spectra lacked the A1 (LO) phonon mode which is usually associated with the O-vacancy, the Zn-interstitial, or complexes of the two, indicating that the layers were all of good quality. The influence of depositing the ZnO thin film on a 3 mm thick SiC layer was also investigated and compared with the deposition of ZnO on Si substrate, in order to reduce the lattice mismatch between ZnO and the Si substrate. The possible shift of the Raman peaks due to the residual strain in the film, if present, could not be resolved. Characterization of GaN and AlxGa1-xN produced by MOCVD at the CRHEA laboratory of the CNRS in Valbonne, France is reported. A sharp peak at 567 cm-1 corresponding to the E2 (high) mode of GaN broadens and shifts to higher wavenumbers as the aluminium content of the AlxGa1-xN is increased. The shift is accompanied by a decrease in the intensity and a broadening of this peak. The broadening was attributed to a general decrease in the quality of the layers which accompanies increased aluminium content in AlxGa1-xN.
- Full Text:
- Date Issued: 2006
- Authors: Goosen, William Edward
- Date: 2006
- Subjects: Raman spectroscopy , Semiconductor films , Thin films
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10514 , http://hdl.handle.net/10948/426 , Raman spectroscopy , Semiconductor films , Thin films
- Description: A home-built Raman system, utilizing a pseudo-backscattering geometry, was built in the Physics Department at the Nelson Mandela Metropolitan University (NMMU). The system was then used to analyse a variety of bulk and thin film semiconducting materials currently being studied in the Physics Department. Silicon wafers were exposed to hydrogen plasma. Raman analysis of hydrogen induced platelets (HIPs), resulting from hydrogen plasma treatment of silicon, is reported. ZnO layers were deposited on glass, GaAs, Si, sapphire and SiC-Si substrates by metalorganic chemical vapour deposition (MOCVD) in the Physics Department at the NMMU. It was found that the ZnO layers grown by MOCVD all exhibited a strong E2 (high) phonon mode that dominated the Raman spectra. Furthermore, the spectra lacked the A1 (LO) phonon mode which is usually associated with the O-vacancy, the Zn-interstitial, or complexes of the two, indicating that the layers were all of good quality. The influence of depositing the ZnO thin film on a 3 mm thick SiC layer was also investigated and compared with the deposition of ZnO on Si substrate, in order to reduce the lattice mismatch between ZnO and the Si substrate. The possible shift of the Raman peaks due to the residual strain in the film, if present, could not be resolved. Characterization of GaN and AlxGa1-xN produced by MOCVD at the CRHEA laboratory of the CNRS in Valbonne, France is reported. A sharp peak at 567 cm-1 corresponding to the E2 (high) mode of GaN broadens and shifts to higher wavenumbers as the aluminium content of the AlxGa1-xN is increased. The shift is accompanied by a decrease in the intensity and a broadening of this peak. The broadening was attributed to a general decrease in the quality of the layers which accompanies increased aluminium content in AlxGa1-xN.
- Full Text:
- Date Issued: 2006
Factors influencing species richness, cover and composition of vegetation on Namaqualand quartz fields
- Authors: Van Tonder, Carlo
- Date: 2006
- Subjects: Plant diversity -- South Africa -- Namaqualand , Soil biology -- South Africa -- Namaqualand
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10752 , http://hdl.handle.net/10948/630 , Plant diversity -- South Africa -- Namaqualand , Soil biology -- South Africa -- Namaqualand
- Description: Quartz fields contribute significantly to plant diversity in the Succulent Karoo biome. They are distinctly different from surrounding habitats and have high levels of plant endemism. Biological soil crusts are features of quartz field soils and fulfill a vital function in that they stabilize soils. It is important for managers of nature reserves and agricultural rangelands to know what factors influence quartz field soils and vegetation. Both stakeholders could benefit from new information that would allow for informed decision-making regarding land-use on quartz fields. The present study took place in the Namaqua National Park that contains a significant proportion of the Riethuis-Wallekraal quartz fields phytochorion. The first part of the study aimed to understand whether certain land-use activities potentially destabilize quartz field soils, which might have possible ramifications for associated biological soil crusts and vegetation. It was followed by relating variation in soil stability with species richness, cover and species composition of quartz field vegetation. Overall, positions assumed to be impacted by land-use activities had less stable soils compared to positions assumed not be impacted. Soil stability had a significant influence on species richness and cover but to a lesser degree on species composition. Quartz field vegetation was significantly influenced by soil physical and chemical properties as well as location in the quartz fields landscape. The second part of the study aimed at understanding how species richness of isolated quartz outcrops is related to their size compared to that of a mainland body of quartz outcrops. No clear species-area relationships emerged from the study. There were significant differences between isolated outcrops and mainland outcrops in substrate and vegetation composition. Findings are discussed in relation to Island Biogeography Theory.
- Full Text:
- Date Issued: 2006
- Authors: Van Tonder, Carlo
- Date: 2006
- Subjects: Plant diversity -- South Africa -- Namaqualand , Soil biology -- South Africa -- Namaqualand
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10752 , http://hdl.handle.net/10948/630 , Plant diversity -- South Africa -- Namaqualand , Soil biology -- South Africa -- Namaqualand
- Description: Quartz fields contribute significantly to plant diversity in the Succulent Karoo biome. They are distinctly different from surrounding habitats and have high levels of plant endemism. Biological soil crusts are features of quartz field soils and fulfill a vital function in that they stabilize soils. It is important for managers of nature reserves and agricultural rangelands to know what factors influence quartz field soils and vegetation. Both stakeholders could benefit from new information that would allow for informed decision-making regarding land-use on quartz fields. The present study took place in the Namaqua National Park that contains a significant proportion of the Riethuis-Wallekraal quartz fields phytochorion. The first part of the study aimed to understand whether certain land-use activities potentially destabilize quartz field soils, which might have possible ramifications for associated biological soil crusts and vegetation. It was followed by relating variation in soil stability with species richness, cover and species composition of quartz field vegetation. Overall, positions assumed to be impacted by land-use activities had less stable soils compared to positions assumed not be impacted. Soil stability had a significant influence on species richness and cover but to a lesser degree on species composition. Quartz field vegetation was significantly influenced by soil physical and chemical properties as well as location in the quartz fields landscape. The second part of the study aimed at understanding how species richness of isolated quartz outcrops is related to their size compared to that of a mainland body of quartz outcrops. No clear species-area relationships emerged from the study. There were significant differences between isolated outcrops and mainland outcrops in substrate and vegetation composition. Findings are discussed in relation to Island Biogeography Theory.
- Full Text:
- Date Issued: 2006
A structural study of Witteberg group rocks (Cape supergroup) in the Cape fold belt, Steytlerville district, Eastern Cape
- Authors: Brunsdon, Gideon
- Date: 2006
- Subjects: Geology, Structural|zSouth Africa|zEastern Cape , Faults (Geology)|zSouth Africa|zEastern Cape , Folds (Geology)|zSouth Africa|zEastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10666 , http://hdl.handle.net/10948/d1019682
- Description: A structural study of Witteberg Group Rocks was conducted along the Soutkloof River, approximately 14 km east of Steytlerville, Eastern Cape Province of South Africa. Here a north to south geotraverse was studied in an attempt at unravelling the structural geology of the rocks belonging to the Upper Devonian to Lower Carboniferous Witteberg Group (Upper Cape Supergroup). These rocks are mostly arenaceous and include quartzite, sandstone, siltstone and shale which have been folded, faulted and metamorphosed. Thrust, normal and strike-slip faulting occur in the area. Shallow south-dipping low-angle thrust fault planes are displaced by steep south-dipping thrust planes and subordinate north-dipping backthrusts. Displacement along thrust planes is predominantly northwards. Steeply dipping thrust fault planes are often reactivated as east-west striking normal faults. Strike-slip faulting postdates all observed structural features and displaces normal and thrust fault planes. Open to tight folds are present and are mostly northvergent and often steepened or truncated by steep south-dipping thrust fault planes. South-vergent folds are related to backthrusting and post-fold faulting. The study has revealed that the current geological map and the local stratigraphy were compiled without recognising major structural features such as thrust, normal and strike-slip faulting and their (the map and currently accepted stratigraphy) validity are therefore questioned. The presence of extensive faulting suggests that the conventional stratigraphic interpretation of the Witteberg Group should be revised.
- Full Text:
- Date Issued: 2006
- Authors: Brunsdon, Gideon
- Date: 2006
- Subjects: Geology, Structural|zSouth Africa|zEastern Cape , Faults (Geology)|zSouth Africa|zEastern Cape , Folds (Geology)|zSouth Africa|zEastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10666 , http://hdl.handle.net/10948/d1019682
- Description: A structural study of Witteberg Group Rocks was conducted along the Soutkloof River, approximately 14 km east of Steytlerville, Eastern Cape Province of South Africa. Here a north to south geotraverse was studied in an attempt at unravelling the structural geology of the rocks belonging to the Upper Devonian to Lower Carboniferous Witteberg Group (Upper Cape Supergroup). These rocks are mostly arenaceous and include quartzite, sandstone, siltstone and shale which have been folded, faulted and metamorphosed. Thrust, normal and strike-slip faulting occur in the area. Shallow south-dipping low-angle thrust fault planes are displaced by steep south-dipping thrust planes and subordinate north-dipping backthrusts. Displacement along thrust planes is predominantly northwards. Steeply dipping thrust fault planes are often reactivated as east-west striking normal faults. Strike-slip faulting postdates all observed structural features and displaces normal and thrust fault planes. Open to tight folds are present and are mostly northvergent and often steepened or truncated by steep south-dipping thrust fault planes. South-vergent folds are related to backthrusting and post-fold faulting. The study has revealed that the current geological map and the local stratigraphy were compiled without recognising major structural features such as thrust, normal and strike-slip faulting and their (the map and currently accepted stratigraphy) validity are therefore questioned. The presence of extensive faulting suggests that the conventional stratigraphic interpretation of the Witteberg Group should be revised.
- Full Text:
- Date Issued: 2006
Optimisation of an in vitro model for anti-diabetic screening
- Authors: Wilson, Gayle Pamela
- Date: 2006
- Subjects: Hypoglycemic agents , Diabetes -- Treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10308 , http://hdl.handle.net/10948/428 , Hypoglycemic agents , Diabetes -- Treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Description: The need for alternative strategies for the prevention and treatment of diabetes is growing rapidly as type II diabetes is reaching epidemic status in our society. This need was the basis for the creation of this study, as it was necessary to start looking towards medicinal plants as potential antidiabetic treatment and no comprehensive in vitro model existed. In creating a model for determining the effects of alternative traditional medicines as antidiabetic potentiates, it was necessary that two metabolic pathways, namely glucose uptake and insulin secretion, which play a significant role in glucose homeostasis, be at the centre of our investigations. The objective of this project was to optimize the methodology required to screen and ultimately determine the effectiveness of the plant extracts Kankerbos and MRC2003, as antidiabetic potentiates, through observing their effects on glucose utilisation and insulin secretion. If these medicinal plants are going to make a positive contribution to the health of type II diabetic South Africans, then the determination of their efficacy is essential. The cell lines used in this study included 3T3-L1 preadipocytes, Chang liver, C2C12 muscle and INS-1 rat pancreatic cells. Each cell line represents a different in vivo organ that is known to have an influence on glucose homeostasis in our bodies, each with its own unique metabolic pathways and mechanisms of activity, thereby making each one a vital component in the study. The positive controls for the two models were insulin and metformin (glucose utilisation) and glibenclamide (insulin secretion). Insulin was shown to provide a significant increase in the amount of glucose taken up in C2C12 muscle and Chang liver cells for acute conditions. Chronic treatments with metformin provided a significant increase in glucose utilised by Chang liver cells. Glibenclamide was an effective positive control for stimulating insulin secretion by INS-1 cells under acute conditions as there was a significant increase in the amount of insulin secreted. MRC2003 did not show any significant antidiabetic activity. Sutherlandia frutescens (Kankerbos) showed biological activities comparable to some of the more recognized antidiabetic compounds throughout the study. With regards to the glucose utilisation model, Kankerbos was seen to have both acute and chronic effects in different cell lines. In the C2C12 muscle cell line, Kankerbos significantly increased glucose uptake when they were exposed to acute conditions. Kankerbos also had a significant effect on the Chang liver cells as it was observed that under both acute and chronic conditions, this plant extract induced the uptake of glucose into these cells. With respect to the insulin secretion model involving INS-1 cells, no significant effect was seen during acute exposure with Kankerbos treatment. However during chronic exposure, an increase in insulin secretion was initiated by this plant extract. Overall, the results of this study suggest that Kankerbos has a twofold mechanism of action for its glucose-lowering effects. Given that Kankerbos is widely available in South Africa, this study was valuable as it provided an indication that Kankerbos has antidiabetic activities and could possibly be used as an alternative antidiabetic medication.
- Full Text:
- Date Issued: 2006
- Authors: Wilson, Gayle Pamela
- Date: 2006
- Subjects: Hypoglycemic agents , Diabetes -- Treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10308 , http://hdl.handle.net/10948/428 , Hypoglycemic agents , Diabetes -- Treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Description: The need for alternative strategies for the prevention and treatment of diabetes is growing rapidly as type II diabetes is reaching epidemic status in our society. This need was the basis for the creation of this study, as it was necessary to start looking towards medicinal plants as potential antidiabetic treatment and no comprehensive in vitro model existed. In creating a model for determining the effects of alternative traditional medicines as antidiabetic potentiates, it was necessary that two metabolic pathways, namely glucose uptake and insulin secretion, which play a significant role in glucose homeostasis, be at the centre of our investigations. The objective of this project was to optimize the methodology required to screen and ultimately determine the effectiveness of the plant extracts Kankerbos and MRC2003, as antidiabetic potentiates, through observing their effects on glucose utilisation and insulin secretion. If these medicinal plants are going to make a positive contribution to the health of type II diabetic South Africans, then the determination of their efficacy is essential. The cell lines used in this study included 3T3-L1 preadipocytes, Chang liver, C2C12 muscle and INS-1 rat pancreatic cells. Each cell line represents a different in vivo organ that is known to have an influence on glucose homeostasis in our bodies, each with its own unique metabolic pathways and mechanisms of activity, thereby making each one a vital component in the study. The positive controls for the two models were insulin and metformin (glucose utilisation) and glibenclamide (insulin secretion). Insulin was shown to provide a significant increase in the amount of glucose taken up in C2C12 muscle and Chang liver cells for acute conditions. Chronic treatments with metformin provided a significant increase in glucose utilised by Chang liver cells. Glibenclamide was an effective positive control for stimulating insulin secretion by INS-1 cells under acute conditions as there was a significant increase in the amount of insulin secreted. MRC2003 did not show any significant antidiabetic activity. Sutherlandia frutescens (Kankerbos) showed biological activities comparable to some of the more recognized antidiabetic compounds throughout the study. With regards to the glucose utilisation model, Kankerbos was seen to have both acute and chronic effects in different cell lines. In the C2C12 muscle cell line, Kankerbos significantly increased glucose uptake when they were exposed to acute conditions. Kankerbos also had a significant effect on the Chang liver cells as it was observed that under both acute and chronic conditions, this plant extract induced the uptake of glucose into these cells. With respect to the insulin secretion model involving INS-1 cells, no significant effect was seen during acute exposure with Kankerbos treatment. However during chronic exposure, an increase in insulin secretion was initiated by this plant extract. Overall, the results of this study suggest that Kankerbos has a twofold mechanism of action for its glucose-lowering effects. Given that Kankerbos is widely available in South Africa, this study was valuable as it provided an indication that Kankerbos has antidiabetic activities and could possibly be used as an alternative antidiabetic medication.
- Full Text:
- Date Issued: 2006
A Hall-effect study of as-grown and hydrogenerated n-type ZnO layers grown by MOCVD
- Somhlahlo, Nomabali Nelisiwe
- Authors: Somhlahlo, Nomabali Nelisiwe
- Date: 2006
- Subjects: Hall effect , Electric currents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10535 , http://hdl.handle.net/10948/444 , http://hdl.handle.net/10948/d1012014 , Hall effect , Electric currents
- Description: A series of as-grown ZnO layers have been electrically characterised by the temperature dependent (20 – 300 K) Hall-effect technique. The ZnO layers were grown by metal organic chemical vapour deposition (MOCVD) on glass substrates under various growth conditions. The temperature dependent Hall-effect technique produced mobility and carrier concentration measurements. These measurements were found to be reproducible and reliable. The carrier concentration data for the layers was fitted by the charge balance equation to accurately determine the donor level and corresponding donor concentration as well as the acceptor concentration for each sample. The measured donor levels were found to vary from sample to sample and there is evidence from the results that the variations are related to the differing growth conditions of the layers. The mobility data was also fitted to establish the dominant electron scattering mechanisms in the layers. The dominant scattering mechanisms were found to vary from sample to sample. For most of the layers studied, the dominant scattering mechanism was found to be both the ionised impurity scattering at low temperatures (20 – 100 K) and grain boundary scattering at higher temperatures (100 – 300 K). The effects of exposing the ZnO layers to hydrogen plasma were also investigated by the temperature dependent Hall-effect technique. Findings indicate that hydrogen is readily incorporated in ZnO, leading always to an increased carrier concentration. It was further noted that incorporating hydrogen into ZnO in some layers increased the mobility while in other layers it caused a decrease in the mobility. The hydrogenated samples were subsequently annealed at 600 °C for 1 hour in argon ambient resulting in the carrier concentration reducing to its original value. This effect is attributed to hydrogen diffusing out of ZnO.
- Full Text:
- Date Issued: 2006
- Authors: Somhlahlo, Nomabali Nelisiwe
- Date: 2006
- Subjects: Hall effect , Electric currents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10535 , http://hdl.handle.net/10948/444 , http://hdl.handle.net/10948/d1012014 , Hall effect , Electric currents
- Description: A series of as-grown ZnO layers have been electrically characterised by the temperature dependent (20 – 300 K) Hall-effect technique. The ZnO layers were grown by metal organic chemical vapour deposition (MOCVD) on glass substrates under various growth conditions. The temperature dependent Hall-effect technique produced mobility and carrier concentration measurements. These measurements were found to be reproducible and reliable. The carrier concentration data for the layers was fitted by the charge balance equation to accurately determine the donor level and corresponding donor concentration as well as the acceptor concentration for each sample. The measured donor levels were found to vary from sample to sample and there is evidence from the results that the variations are related to the differing growth conditions of the layers. The mobility data was also fitted to establish the dominant electron scattering mechanisms in the layers. The dominant scattering mechanisms were found to vary from sample to sample. For most of the layers studied, the dominant scattering mechanism was found to be both the ionised impurity scattering at low temperatures (20 – 100 K) and grain boundary scattering at higher temperatures (100 – 300 K). The effects of exposing the ZnO layers to hydrogen plasma were also investigated by the temperature dependent Hall-effect technique. Findings indicate that hydrogen is readily incorporated in ZnO, leading always to an increased carrier concentration. It was further noted that incorporating hydrogen into ZnO in some layers increased the mobility while in other layers it caused a decrease in the mobility. The hydrogenated samples were subsequently annealed at 600 °C for 1 hour in argon ambient resulting in the carrier concentration reducing to its original value. This effect is attributed to hydrogen diffusing out of ZnO.
- Full Text:
- Date Issued: 2006
Horticultural propagation of the threatened species, Syncarpha revurvata (L.f.)B. Nord
- Authors: Swart, Pierre André
- Date: 2006
- Subjects: Horticultural crops -- Propagation , Plant propagation , Horticulture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10624 , http://hdl.handle.net/10948/613 , Horticultural crops -- Propagation , Plant propagation , Horticulture
- Description: Syncarpha recurvata (L.f.) B. Nord. (Asteraceae, Gnaphalieae) is listed as a vulnerable (intermediate priority) species. The propagation methods of achene germination, stem cuttings, air layering and micropropagation were investigated to obtain an efficient propagation method. Smoke water dilutions of 1:100, 1:50 and 1:10 significantly increased germination, with the 1:100 smoke water dilutions showing the highest germination percentage (22.4 percent). Achenes collected between August and October 2005 showed higher germination and viability than achenes collected between May and July 2006. Fifty percent of the stem cuttings and 32 percent of the airlayered branches rooted. Embryo culture was the only successful culture type out of the four attempted. Two embryos germinated and four became photosynthetic. Two of the germinated embryos also produced callus cells, a medium supplemented with 5 μM IAA may be used to test for a suitable plant regulator for organogenesis or embryogenesis. Syncarpha recurvata plants were also transplanted into pots and 60 percent survived. A growth rate of 1.466 mm y-1 was obtained from total shoot length measurements. In this study, it was found that air-layering branches of transplanted Syncarpha recurvata plants is the most efficient propagation method.
- Full Text:
- Date Issued: 2006
- Authors: Swart, Pierre André
- Date: 2006
- Subjects: Horticultural crops -- Propagation , Plant propagation , Horticulture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10624 , http://hdl.handle.net/10948/613 , Horticultural crops -- Propagation , Plant propagation , Horticulture
- Description: Syncarpha recurvata (L.f.) B. Nord. (Asteraceae, Gnaphalieae) is listed as a vulnerable (intermediate priority) species. The propagation methods of achene germination, stem cuttings, air layering and micropropagation were investigated to obtain an efficient propagation method. Smoke water dilutions of 1:100, 1:50 and 1:10 significantly increased germination, with the 1:100 smoke water dilutions showing the highest germination percentage (22.4 percent). Achenes collected between August and October 2005 showed higher germination and viability than achenes collected between May and July 2006. Fifty percent of the stem cuttings and 32 percent of the airlayered branches rooted. Embryo culture was the only successful culture type out of the four attempted. Two embryos germinated and four became photosynthetic. Two of the germinated embryos also produced callus cells, a medium supplemented with 5 μM IAA may be used to test for a suitable plant regulator for organogenesis or embryogenesis. Syncarpha recurvata plants were also transplanted into pots and 60 percent survived. A growth rate of 1.466 mm y-1 was obtained from total shoot length measurements. In this study, it was found that air-layering branches of transplanted Syncarpha recurvata plants is the most efficient propagation method.
- Full Text:
- Date Issued: 2006
SL-model for paired comparisons
- Authors: Sjölander, Morné Rowan
- Date: 2006
- Subjects: Paired comparisons (Statistics) , Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10574 , http://hdl.handle.net/10948/605 , Paired comparisons (Statistics) , Mathematical statistics
- Description: The method of paired comparisons can be found all the way back to 1860, where Fechner made the first publication in this method, using it for his psychometric investigations [4]. Thurstone formalised the method by providing a mathematical background to it [9-11] and in 1927 the method’s birth took place with his psychometric publications, one being “a law of comparative judgment” [12-14]. The law of comparative judgment is a set of equations relating the proportion of times any stimulus k is judged greater on a given attribute than any other stimulus j to the scales and discriminal dispersions of the two stimuli on the psychological continuum. The amount of research done for discrete models of paired comparisons is not a lot. This study develops a new discrete model, the SL-model for paired comparisons. Paired comparisons data processing in which objects have an upper limit to their scores was also not yet developed, and making such a model is one of the aims of this report. The SLmodel is thus developed in this context; however, the model easily generalises to not necessarily having an upper limit on scores.
- Full Text:
- Date Issued: 2006
- Authors: Sjölander, Morné Rowan
- Date: 2006
- Subjects: Paired comparisons (Statistics) , Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10574 , http://hdl.handle.net/10948/605 , Paired comparisons (Statistics) , Mathematical statistics
- Description: The method of paired comparisons can be found all the way back to 1860, where Fechner made the first publication in this method, using it for his psychometric investigations [4]. Thurstone formalised the method by providing a mathematical background to it [9-11] and in 1927 the method’s birth took place with his psychometric publications, one being “a law of comparative judgment” [12-14]. The law of comparative judgment is a set of equations relating the proportion of times any stimulus k is judged greater on a given attribute than any other stimulus j to the scales and discriminal dispersions of the two stimuli on the psychological continuum. The amount of research done for discrete models of paired comparisons is not a lot. This study develops a new discrete model, the SL-model for paired comparisons. Paired comparisons data processing in which objects have an upper limit to their scores was also not yet developed, and making such a model is one of the aims of this report. The SLmodel is thus developed in this context; however, the model easily generalises to not necessarily having an upper limit on scores.
- Full Text:
- Date Issued: 2006
An investigation of the binding capacities of recombinant domain mutants of the human Polymeric Immunoglobulin Receptor (pIgR)
- Authors: Prinsloo, Earl Adin Gerard
- Date: 2006
- Subjects: Immunoglobulins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10307 , http://hdl.handle.net/10948/403 , Immunoglobulins
- Description: The membrane bound glycoprotein, polymeric immunoglobulin receptor (pIgR) is the primary transport molecule of the polymeric immunoglobulins, dimeric IgA and pentameric IgM, across epithelial cells. This process, known as transcytosis, is essential in order to establish immunity at mucosal surfaces. Typically, pIgR binds to the polymeric immunoglobulin at the basolateral surface of the epithelial cell, via five homologous immunoglobulin-like domains of the ectodomain. Binding is covalent to IgA and non-covalent to IgM; the IgM binding varying among species. The pIgR-bound complex is released at the apical surface of the cell after cleavage of pIgR at Arg585, thereafter referred to as secretory component (SC). SC confers protective and immunologic functions to the polymeric immunoglobulin. Free SC, i.e. not complexed with polymeric immunoglobulins, is also known to be released into mucosal secretions; and binds to pathogenic bacteria and bacterial products. It is known that domain I of the ectodomain is the primary domain in the interaction with polymeric immunoglobulins, while domain V is involved in a covalent linkage with IgA. However, little is known of domains II-IV and their role in immunoglobulin binding, particularly to IgM. This study aimed to characterize the binding of recombinant human pIgR domain mutants to polymeric IgM using immunological, biophysical and cell based techniques; thereby allowing greater insight into the contribution of each of the five domains. The unique domain structure allowed for selective amplification of single and multiple domain mutants from cloned human PIGR ectodomain cDNA. Mutants were cloned and expressed in Esherichia coli BL21 (DE3) as inclusion bodies. Recombinant mutant proteins were refolded in vitro by equilibrium gradient dialysis and purified to homogeneity. Equilibrium binding data show significant contributions to specific binding as a factor of domain presence. Binding kinetics determined by biophysical surface plasmon resonance measurements show the interplay between association and dissociation rates as defined by individual domains. In vitro competitive binding studies using the human intestinal carcinoma, HT29, known to constitutively express pIgR, show that the constructed recombinant domain mutants outcompete native pIgR. The level of competition is shown to be dependant on the domains downstream of domain I. The data also confirm the biological activity of the first in vitro refolded recombinant human SC.
- Full Text:
- Date Issued: 2006
- Authors: Prinsloo, Earl Adin Gerard
- Date: 2006
- Subjects: Immunoglobulins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10307 , http://hdl.handle.net/10948/403 , Immunoglobulins
- Description: The membrane bound glycoprotein, polymeric immunoglobulin receptor (pIgR) is the primary transport molecule of the polymeric immunoglobulins, dimeric IgA and pentameric IgM, across epithelial cells. This process, known as transcytosis, is essential in order to establish immunity at mucosal surfaces. Typically, pIgR binds to the polymeric immunoglobulin at the basolateral surface of the epithelial cell, via five homologous immunoglobulin-like domains of the ectodomain. Binding is covalent to IgA and non-covalent to IgM; the IgM binding varying among species. The pIgR-bound complex is released at the apical surface of the cell after cleavage of pIgR at Arg585, thereafter referred to as secretory component (SC). SC confers protective and immunologic functions to the polymeric immunoglobulin. Free SC, i.e. not complexed with polymeric immunoglobulins, is also known to be released into mucosal secretions; and binds to pathogenic bacteria and bacterial products. It is known that domain I of the ectodomain is the primary domain in the interaction with polymeric immunoglobulins, while domain V is involved in a covalent linkage with IgA. However, little is known of domains II-IV and their role in immunoglobulin binding, particularly to IgM. This study aimed to characterize the binding of recombinant human pIgR domain mutants to polymeric IgM using immunological, biophysical and cell based techniques; thereby allowing greater insight into the contribution of each of the five domains. The unique domain structure allowed for selective amplification of single and multiple domain mutants from cloned human PIGR ectodomain cDNA. Mutants were cloned and expressed in Esherichia coli BL21 (DE3) as inclusion bodies. Recombinant mutant proteins were refolded in vitro by equilibrium gradient dialysis and purified to homogeneity. Equilibrium binding data show significant contributions to specific binding as a factor of domain presence. Binding kinetics determined by biophysical surface plasmon resonance measurements show the interplay between association and dissociation rates as defined by individual domains. In vitro competitive binding studies using the human intestinal carcinoma, HT29, known to constitutively express pIgR, show that the constructed recombinant domain mutants outcompete native pIgR. The level of competition is shown to be dependant on the domains downstream of domain I. The data also confirm the biological activity of the first in vitro refolded recombinant human SC.
- Full Text:
- Date Issued: 2006
Volhoubaarheid van die kommersiële benutting van inheemse dekriet (Thamnochortus insignis) in die Suid-Kaap
- Authors: Horn, Johan Andries Muller
- Date: 2006
- Subjects: Fynbos -- Harvesting -- South Africa , Thatched roofs -- South Africa
- Language: Afrikaans
- Type: Thesis , Masters , MTech
- Identifier: vital:10591 , http://hdl.handle.net/10948/836 , http://hdl.handle.net/10948/d1012882 , Fynbos -- Harvesting -- South Africa , Thatched roofs -- South Africa
- Description: Thamnochortus insignis (Albertinia thatching reed) is a restio specie which is endemic in the narrow (20 km wide) coastal dune veld, from the Gouritz River in the east to the Breede River in the west (120 km). The area within this belt, where this reed is the dominant restio, covers 65 500 hectares. The culms of the reed is harvested as a natural product from the veld and used as thatch on roofs of houses. The traditional use has been as roofing material in Cape Dutch architecture. At this time, thatch roofs are regarded as a luxury commodity and are used in prestigious residential areas and also eco-friendly housing developments. The first section of the research project was based on a Delphi technique questionnaire completed first by 37 and secondly by 10 stakeholders in the industry. This group of growers, contract harvesters, crop agents and thatchers represented 80 percent percent of the estimated 2005 harvest and 87 percent of the estimated farm gate crop value. The thatching reed industry is the main agricultural enterprise situated in the coastal dune veld of the Southern Cape, i.e. 55 percent of total Gross Product Value generated by the survey respondents. The second section is based on an analysis of experimental harvest plots (50 m2), selected at random (4 replications per site) in the 2 x 3 different production systems, i.e. traditional harvest from natural veld, harvest from veld which had been subjected to mechanical injury ("sleep") and harvest from established orchard-type lands. Harvest data was collected at each site in terms of the following components, i.e. number of harvestable tussocks, circumference of tussocks and number of reed bundles (minimum circumference 210 mm, minimum length 1,2 m). The gross income per site was calculated on the basis of R1,80 per bundle (2006-price level). Economic analysis (Gross Margin above selected costs) indicates that plant density (reed tussocks/ha) is a critical factor, in order to offset the establishment cost of R2 100/ha in established lands, which is not incurred in the other two production systems. Economic returns from the first planted lands (2 100 and 2 900 plants/ha) averaged R7 666/ha against R8 781/ha for the mechanical-injury plants. However, at a density of 5 000 plants/ha, the projected Gross Margin increases to R15 765/ha. The use of mechanicalinjury and natural vegetation production systems both interfere with biodiversity and raise major concerns with regard to sustainability of the sensitive coastal dune fynbos. ANOVA-analysis of the data indicates a highly significant difference (p = 0,01) for all sites and production systems. Statistical analysis of averages indicates that mechanical injury treatment results in a significant increase in the number of tussocks, when compared to established and natural veld, respectively. The variance in the circumference of tussocks was greatest in natural veld (55 to 71 percent) and mechanical injury (54 to 61 percent). Tussocks harvested from established plantings reflected the least level of variance (28 to 38 percent). The larger reed tussocks in the established lands produced more bundles of marketable reed (8 200/ha) than the mechanical-injury (7 625/ha) and natural veld (3 450/ha) respectively. Establishment of T. insignis plantlets in an "orchard" system at spacings of 2 m x 1 m on previous winter cereal lands or old pastures, is shown to meet all the requirements within a sustainable production system, i.e. viability, productivity, environmental-friendly, risk management and social acceptance. Furthermore, the quality of the yield was in line with the proposed grading standard for thatching reed, i.e. minimum circumference 210 mm, minimum length 1,2 m and less than 6,5 percent grey culm content.
- Full Text:
- Date Issued: 2006
- Authors: Horn, Johan Andries Muller
- Date: 2006
- Subjects: Fynbos -- Harvesting -- South Africa , Thatched roofs -- South Africa
- Language: Afrikaans
- Type: Thesis , Masters , MTech
- Identifier: vital:10591 , http://hdl.handle.net/10948/836 , http://hdl.handle.net/10948/d1012882 , Fynbos -- Harvesting -- South Africa , Thatched roofs -- South Africa
- Description: Thamnochortus insignis (Albertinia thatching reed) is a restio specie which is endemic in the narrow (20 km wide) coastal dune veld, from the Gouritz River in the east to the Breede River in the west (120 km). The area within this belt, where this reed is the dominant restio, covers 65 500 hectares. The culms of the reed is harvested as a natural product from the veld and used as thatch on roofs of houses. The traditional use has been as roofing material in Cape Dutch architecture. At this time, thatch roofs are regarded as a luxury commodity and are used in prestigious residential areas and also eco-friendly housing developments. The first section of the research project was based on a Delphi technique questionnaire completed first by 37 and secondly by 10 stakeholders in the industry. This group of growers, contract harvesters, crop agents and thatchers represented 80 percent percent of the estimated 2005 harvest and 87 percent of the estimated farm gate crop value. The thatching reed industry is the main agricultural enterprise situated in the coastal dune veld of the Southern Cape, i.e. 55 percent of total Gross Product Value generated by the survey respondents. The second section is based on an analysis of experimental harvest plots (50 m2), selected at random (4 replications per site) in the 2 x 3 different production systems, i.e. traditional harvest from natural veld, harvest from veld which had been subjected to mechanical injury ("sleep") and harvest from established orchard-type lands. Harvest data was collected at each site in terms of the following components, i.e. number of harvestable tussocks, circumference of tussocks and number of reed bundles (minimum circumference 210 mm, minimum length 1,2 m). The gross income per site was calculated on the basis of R1,80 per bundle (2006-price level). Economic analysis (Gross Margin above selected costs) indicates that plant density (reed tussocks/ha) is a critical factor, in order to offset the establishment cost of R2 100/ha in established lands, which is not incurred in the other two production systems. Economic returns from the first planted lands (2 100 and 2 900 plants/ha) averaged R7 666/ha against R8 781/ha for the mechanical-injury plants. However, at a density of 5 000 plants/ha, the projected Gross Margin increases to R15 765/ha. The use of mechanicalinjury and natural vegetation production systems both interfere with biodiversity and raise major concerns with regard to sustainability of the sensitive coastal dune fynbos. ANOVA-analysis of the data indicates a highly significant difference (p = 0,01) for all sites and production systems. Statistical analysis of averages indicates that mechanical injury treatment results in a significant increase in the number of tussocks, when compared to established and natural veld, respectively. The variance in the circumference of tussocks was greatest in natural veld (55 to 71 percent) and mechanical injury (54 to 61 percent). Tussocks harvested from established plantings reflected the least level of variance (28 to 38 percent). The larger reed tussocks in the established lands produced more bundles of marketable reed (8 200/ha) than the mechanical-injury (7 625/ha) and natural veld (3 450/ha) respectively. Establishment of T. insignis plantlets in an "orchard" system at spacings of 2 m x 1 m on previous winter cereal lands or old pastures, is shown to meet all the requirements within a sustainable production system, i.e. viability, productivity, environmental-friendly, risk management and social acceptance. Furthermore, the quality of the yield was in line with the proposed grading standard for thatching reed, i.e. minimum circumference 210 mm, minimum length 1,2 m and less than 6,5 percent grey culm content.
- Full Text:
- Date Issued: 2006
A model for information architecture of government web sites in Southern Africa
- Authors: Bernardo, Tomás
- Date: 2006
- Subjects: Information storage and retrieval systems , Web sites -- Design , Government information -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10479 , http://hdl.handle.net/10948/459 , Information storage and retrieval systems , Web sites -- Design , Government information -- South Africa
- Description: The main purpose of this research is to investigate the Information Architecture (IA) of government web sites in Southern Africa. The government web sites of Mozambique and South Africa were selected for the purpose of this research. A further aim of this research was to derive a model for the IA of government web sites. The model was based on IA components and guidelines as well as on web site components and E-government requirements. The IA guidelines in the model were derived from general design guidelines and guidelines for government web sites. The IA guidelines in the proposed model were used to conduct an analytical and empirical evaluation of the selected sites. The selection of the sites was based on similarities in the Information and Communication Technology (ICT) strategies and policies, the annual Internet growth rates, the Internet user profiles and the Egovernment initiatives in both countries. Differences between the sites also contributed to their selection. Mozambique is one of the least developed countries in the world, while South Africa is one of the most developed countries in Africa. Heuristic evaluation was used for the analytical evaluation while questionnaires and user testing were used for the empirical evaluation. Some of the usability problems identified in the heuristic evaluation, such as incorrect organisation of information and navigation issues, were also identified in the empirical evaluation, confirming to the existence of these usability problems. The results of this research show that the IA of government web sites has an impact on user performance and satisfaction and that the proposed model can be used to design and evaluate the IA of government web sites in Southern Africa.
- Full Text:
- Date Issued: 2006
- Authors: Bernardo, Tomás
- Date: 2006
- Subjects: Information storage and retrieval systems , Web sites -- Design , Government information -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10479 , http://hdl.handle.net/10948/459 , Information storage and retrieval systems , Web sites -- Design , Government information -- South Africa
- Description: The main purpose of this research is to investigate the Information Architecture (IA) of government web sites in Southern Africa. The government web sites of Mozambique and South Africa were selected for the purpose of this research. A further aim of this research was to derive a model for the IA of government web sites. The model was based on IA components and guidelines as well as on web site components and E-government requirements. The IA guidelines in the model were derived from general design guidelines and guidelines for government web sites. The IA guidelines in the proposed model were used to conduct an analytical and empirical evaluation of the selected sites. The selection of the sites was based on similarities in the Information and Communication Technology (ICT) strategies and policies, the annual Internet growth rates, the Internet user profiles and the Egovernment initiatives in both countries. Differences between the sites also contributed to their selection. Mozambique is one of the least developed countries in the world, while South Africa is one of the most developed countries in Africa. Heuristic evaluation was used for the analytical evaluation while questionnaires and user testing were used for the empirical evaluation. Some of the usability problems identified in the heuristic evaluation, such as incorrect organisation of information and navigation issues, were also identified in the empirical evaluation, confirming to the existence of these usability problems. The results of this research show that the IA of government web sites has an impact on user performance and satisfaction and that the proposed model can be used to design and evaluate the IA of government web sites in Southern Africa.
- Full Text:
- Date Issued: 2006
A comparison framework for server virtualisation systems a case study
- Authors: Van Tonder, Martin Stephen
- Date: 2006
- Subjects: Virtual computer systems -- South Africa Case studies , Virtual storage (Computer science) -- South Africa Case studies
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10481 , http://hdl.handle.net/10948/439 , http://hdl.handle.net/10948/d1012009 , Virtual computer systems -- South Africa Case studies , Virtual storage (Computer science) -- South Africa Case studies
- Description: Recent years have seen a revival of interest in virtualisation research. Although this term has been used to refer to various systems, the focus of this research is on systems which partition a single physical server into multiple virtual servers. It is difficult for researchers and practitioners to get a clear picture of the state of the art in server virtualisation. This is due in part to the large number of systems available. Another reason is that information about virtualisation systems lacks structure, and is dispersed among multiple sources. Practitioners, such as data centre managers and systems administrators, may be familiar with virtualisation systems from a specific vendor, but generally lack a broader view of the field. This makes it difficult to make informed decisions when selecting these systems. Researchers and vendors who are developing virtualisation systems also lack a standard framework for identifying the strengths and weaknesses of their systems, compared to competing systems. It is also time-consuming for researchers who are new to the field to learn about current virtualisation systems. The purpose of this research was to develop a framework to solve these problems. The objectives of the research correspond to the applications of the framework. These include conducting comparative evaluations of server virtualisation systems, identifying strengths and weaknesses of particular virtualisation systems, specifying virtualisation system requirements to facilitate system selection, and gathering information about current virtualisation systems in a structured form. These four objectives were satisfied. The design of this framework was also guided by six framework design principles. These principles, or secondary objectives, were also met. The framework was developed based on an extensive literature study of data centres, virtualisation and current virtualisation systems. Criteria were selected through an inductive process. The feasibility of conducting evaluations using the framework was demonstrated by means of literature-based evaluations, and a practical case study. The use of the framework to facilitate virtualisation system selection was also demonstrated by means of a case study featuring the NMMU Telkom CoE data centre. This framework has a number of practical applications, ranging from the facilitation of decision-making to identifying areas for improvement in current virtualisation systems. The information resulting from evaluations using the framework is also a valuable resource for researchers who are new to the field. The literature study which forms the theoretical foundation of this work is particularly useful in this regard. A future extension to this work would be to develop a decision support system based on the framework. Another possibility is to make the framework, and evaluations, available on-line as a resource for data center managers, vendors and researchers. This would also enable other researchers to provide additional feedback, enabling the framework to be further refined
- Full Text:
- Date Issued: 2006
- Authors: Van Tonder, Martin Stephen
- Date: 2006
- Subjects: Virtual computer systems -- South Africa Case studies , Virtual storage (Computer science) -- South Africa Case studies
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10481 , http://hdl.handle.net/10948/439 , http://hdl.handle.net/10948/d1012009 , Virtual computer systems -- South Africa Case studies , Virtual storage (Computer science) -- South Africa Case studies
- Description: Recent years have seen a revival of interest in virtualisation research. Although this term has been used to refer to various systems, the focus of this research is on systems which partition a single physical server into multiple virtual servers. It is difficult for researchers and practitioners to get a clear picture of the state of the art in server virtualisation. This is due in part to the large number of systems available. Another reason is that information about virtualisation systems lacks structure, and is dispersed among multiple sources. Practitioners, such as data centre managers and systems administrators, may be familiar with virtualisation systems from a specific vendor, but generally lack a broader view of the field. This makes it difficult to make informed decisions when selecting these systems. Researchers and vendors who are developing virtualisation systems also lack a standard framework for identifying the strengths and weaknesses of their systems, compared to competing systems. It is also time-consuming for researchers who are new to the field to learn about current virtualisation systems. The purpose of this research was to develop a framework to solve these problems. The objectives of the research correspond to the applications of the framework. These include conducting comparative evaluations of server virtualisation systems, identifying strengths and weaknesses of particular virtualisation systems, specifying virtualisation system requirements to facilitate system selection, and gathering information about current virtualisation systems in a structured form. These four objectives were satisfied. The design of this framework was also guided by six framework design principles. These principles, or secondary objectives, were also met. The framework was developed based on an extensive literature study of data centres, virtualisation and current virtualisation systems. Criteria were selected through an inductive process. The feasibility of conducting evaluations using the framework was demonstrated by means of literature-based evaluations, and a practical case study. The use of the framework to facilitate virtualisation system selection was also demonstrated by means of a case study featuring the NMMU Telkom CoE data centre. This framework has a number of practical applications, ranging from the facilitation of decision-making to identifying areas for improvement in current virtualisation systems. The information resulting from evaluations using the framework is also a valuable resource for researchers who are new to the field. The literature study which forms the theoretical foundation of this work is particularly useful in this regard. A future extension to this work would be to develop a decision support system based on the framework. Another possibility is to make the framework, and evaluations, available on-line as a resource for data center managers, vendors and researchers. This would also enable other researchers to provide additional feedback, enabling the framework to be further refined
- Full Text:
- Date Issued: 2006
On the characterisation of copper indium diselenide based photovoltaic devices
- Authors: Thantsha, Nicolas Matome
- Date: 2006
- Subjects: Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10536 , http://hdl.handle.net/10948/443 , Photovoltaic cells
- Description: Photovoltaic (PV) modules based on thin film systems of CuInSe2 (CIS) and its alloys on low cost substrates are promising candidates to meet the long term efficiency, reliability and manufacturing cost goals. The attention to the CIS solar cell technology is because of the high absorption coefficient of the solar cell absorber layer. Solar cells and PV modules are conventionally assessed by measuring the currentvoltage characteristic of the device. This thesis presents an assessment procedure developed capable of assessing the device parameters with reference to I-V measurements. This thesis then characterizes the performance of the CIS based solar cells and modules in conjunction with other PV modules of different technologies such as crystalline Silicon modules by analyzing the light and dark I-V measurements of the devices. The light and dark I-V characteristics of PV devices were investigated and device parameters were extracted from the I-V data. The extraction and interpretation of these device parameters has a variety of important applications. It has been proven that the device parameters can be used for quality control during production and to provide insights into the operation of the PV devices, thereby improving the efficiency of the devices. The assessment comprises light I-V measurements at standard test conditions (STC), irradiance dependence measurements, parasitic series and shunt resistances measurements and the dark I-V measurements of the PV devices. The PV modules assessed comprise different technologies, namely, thin film based modules (CIS and a-Si) and multicrystalline Si and Edged-defined Film-fed Growth Si (EFG-Si). The dark I-V measurements results showed that the EFG-Si module has acceptable shunt (900 W) and series (0.4 W) resistances, thereby leading to the higher power output depicted from the light I-V measurements. The low quality cells of a-Si module were so low that the fill factor was the smallest (43%). In addition, the dark I-V measurements results revealed that CIS modules are less dependent to temperature at high voltages.
- Full Text:
- Date Issued: 2006
- Authors: Thantsha, Nicolas Matome
- Date: 2006
- Subjects: Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10536 , http://hdl.handle.net/10948/443 , Photovoltaic cells
- Description: Photovoltaic (PV) modules based on thin film systems of CuInSe2 (CIS) and its alloys on low cost substrates are promising candidates to meet the long term efficiency, reliability and manufacturing cost goals. The attention to the CIS solar cell technology is because of the high absorption coefficient of the solar cell absorber layer. Solar cells and PV modules are conventionally assessed by measuring the currentvoltage characteristic of the device. This thesis presents an assessment procedure developed capable of assessing the device parameters with reference to I-V measurements. This thesis then characterizes the performance of the CIS based solar cells and modules in conjunction with other PV modules of different technologies such as crystalline Silicon modules by analyzing the light and dark I-V measurements of the devices. The light and dark I-V characteristics of PV devices were investigated and device parameters were extracted from the I-V data. The extraction and interpretation of these device parameters has a variety of important applications. It has been proven that the device parameters can be used for quality control during production and to provide insights into the operation of the PV devices, thereby improving the efficiency of the devices. The assessment comprises light I-V measurements at standard test conditions (STC), irradiance dependence measurements, parasitic series and shunt resistances measurements and the dark I-V measurements of the PV devices. The PV modules assessed comprise different technologies, namely, thin film based modules (CIS and a-Si) and multicrystalline Si and Edged-defined Film-fed Growth Si (EFG-Si). The dark I-V measurements results showed that the EFG-Si module has acceptable shunt (900 W) and series (0.4 W) resistances, thereby leading to the higher power output depicted from the light I-V measurements. The low quality cells of a-Si module were so low that the fill factor was the smallest (43%). In addition, the dark I-V measurements results revealed that CIS modules are less dependent to temperature at high voltages.
- Full Text:
- Date Issued: 2006
Impacts of impala on subtropical thicket in the Shamwari Game Reserve, Eastern Cape
- Authors: Gerber, Johann
- Date: 2006
- Subjects: Impala -- Feeding and feeds -- South Africa -- Eastern Cape , Impala -- Habitat -- South Africa -- Eastern Cape , Savannas -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10627 , http://hdl.handle.net/10948/509 , http://hdl.handle.net/10948/d1012011 , Impala -- Feeding and feeds -- South Africa -- Eastern Cape , Impala -- Habitat -- South Africa -- Eastern Cape , Savannas -- South Africa -- Eastern Cape
- Description: Subtropical thicket supports a large variety of indigenous browsing herbivores, such as elephants, black rhino, kudu and bushbuck, but impala historically never occurred in the Eastern Cape. The aim of this study was to determine what impacts extralimital impala (Aepyceros melampus) have on subtropical thicket. The thicket of the Shamwari Game Reserve, Eastern Cape, was used for the study. To quantify the effects of impala, feeding behaviour and diet was investigated during summer and winter. Sixteen impala were also enclosed in a camp of subtropical thicket where they would be limited to feedings on thicket. Vegetation composition and structure were monitored for a period of 12 months in the enclosure. Impala followed the expected high percentage graze and a low percentage browse in thicket in summer. However, the expected was not observed during winter: at this time grazing and browsing were equally important. Field collection of feeding behaviour data showed that impala are attracted to fringes of intact bush clumps or degraded thicket. Analysis of the impala diet confirmed this, with a significantly higher percentage graze (48 percent) than browse (22 percent) during summer. However, during winter, diet analysis indicated grazing to be much higher (36 percent) than browsing (6 percent) with the impala temporarily taking advantage of nutritious grasses still present. The enclosed portion of thicket was originally at 80 percent ecological status but it showed significant changes after addition of 16 impala. Animal trails increased in number and in width, resulting in a trampling effect. Grass cover was significantly different inside the enclosure after 12 months compared to outside. The amount of available browse of the enclosed thicket was also significantly different after addition of the impala. It is concluded that impala have a negative effect on thicket, with trampling the most significant effect. Long term monitoring of the effects of extralimital impala in different types of thicket will be required to accurately quantify their direct effects on subtropical thicket in the Eastern Cape. The main aim of this study was to determine the impacts of impala on Thicket. The study showed significant impacts on Thicket as found in Shamwari, and therefore the aim of the study was achieved.
- Full Text:
- Date Issued: 2006
- Authors: Gerber, Johann
- Date: 2006
- Subjects: Impala -- Feeding and feeds -- South Africa -- Eastern Cape , Impala -- Habitat -- South Africa -- Eastern Cape , Savannas -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10627 , http://hdl.handle.net/10948/509 , http://hdl.handle.net/10948/d1012011 , Impala -- Feeding and feeds -- South Africa -- Eastern Cape , Impala -- Habitat -- South Africa -- Eastern Cape , Savannas -- South Africa -- Eastern Cape
- Description: Subtropical thicket supports a large variety of indigenous browsing herbivores, such as elephants, black rhino, kudu and bushbuck, but impala historically never occurred in the Eastern Cape. The aim of this study was to determine what impacts extralimital impala (Aepyceros melampus) have on subtropical thicket. The thicket of the Shamwari Game Reserve, Eastern Cape, was used for the study. To quantify the effects of impala, feeding behaviour and diet was investigated during summer and winter. Sixteen impala were also enclosed in a camp of subtropical thicket where they would be limited to feedings on thicket. Vegetation composition and structure were monitored for a period of 12 months in the enclosure. Impala followed the expected high percentage graze and a low percentage browse in thicket in summer. However, the expected was not observed during winter: at this time grazing and browsing were equally important. Field collection of feeding behaviour data showed that impala are attracted to fringes of intact bush clumps or degraded thicket. Analysis of the impala diet confirmed this, with a significantly higher percentage graze (48 percent) than browse (22 percent) during summer. However, during winter, diet analysis indicated grazing to be much higher (36 percent) than browsing (6 percent) with the impala temporarily taking advantage of nutritious grasses still present. The enclosed portion of thicket was originally at 80 percent ecological status but it showed significant changes after addition of 16 impala. Animal trails increased in number and in width, resulting in a trampling effect. Grass cover was significantly different inside the enclosure after 12 months compared to outside. The amount of available browse of the enclosed thicket was also significantly different after addition of the impala. It is concluded that impala have a negative effect on thicket, with trampling the most significant effect. Long term monitoring of the effects of extralimital impala in different types of thicket will be required to accurately quantify their direct effects on subtropical thicket in the Eastern Cape. The main aim of this study was to determine the impacts of impala on Thicket. The study showed significant impacts on Thicket as found in Shamwari, and therefore the aim of the study was achieved.
- Full Text:
- Date Issued: 2006
Epitaxial growth and characterisation of CuGaS2
- Authors: Branch, Matthew Stewart
- Date: 2006
- Subjects: Epitaxy , Chalcopyrite , Semiconductors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10541 , http://hdl.handle.net/10948/438 , http://hdl.handle.net/10948/d1012893 , Epitaxy , Chalcopyrite , Semiconductors
- Description: In this work, the growth and characterisation of the chalcopyrite semiconductor CuGaS2 is presented. The purpose of this study is to gain a better understanding of the defect chemistry of this class of materials through a systematic study relating the structural and optical properties to the composition of thin films grown by metalorganic vapour phase epitaxy. Details associated with the optimisation of the growth process are presented in a format relating the changes in the composition and morphology to variations in the growth process. The structural properties of thin films grown on GaAs(001) substrates are described. A dominance of polycrystalline growth is found to occur for Cu-rich material, whereas near-stoichiometric to Ga-rich material is typified by epitaxial growth. Secondary phases are identified by X-ray diffractometry and Raman spectroscopy for severely non-stoichiometric material. In some cases, the formation of the cubic zincblende and CuPt polytype of CuGaS2 are identified by transmission electron microscopy. It will be shown that changes in the Cu/Ga ratio of the solid strongly influence the photoluminescence response of the layers. Weak excitonic luminescence is observed for both slightly Ga-rich and Cu-rich material. Near stoichiometric layers exhibit luminescence centered at ~2.4 eV. Cu-rich layers are dominated by a line occurring at ~2.1 eV, whereas a different line at ~2.25 eV dominates for Ga-rich layers. A clear picture emerges of the radiative mechanisms dominating for Cu-rich and Ga-rich layers.
- Full Text:
- Date Issued: 2006
- Authors: Branch, Matthew Stewart
- Date: 2006
- Subjects: Epitaxy , Chalcopyrite , Semiconductors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10541 , http://hdl.handle.net/10948/438 , http://hdl.handle.net/10948/d1012893 , Epitaxy , Chalcopyrite , Semiconductors
- Description: In this work, the growth and characterisation of the chalcopyrite semiconductor CuGaS2 is presented. The purpose of this study is to gain a better understanding of the defect chemistry of this class of materials through a systematic study relating the structural and optical properties to the composition of thin films grown by metalorganic vapour phase epitaxy. Details associated with the optimisation of the growth process are presented in a format relating the changes in the composition and morphology to variations in the growth process. The structural properties of thin films grown on GaAs(001) substrates are described. A dominance of polycrystalline growth is found to occur for Cu-rich material, whereas near-stoichiometric to Ga-rich material is typified by epitaxial growth. Secondary phases are identified by X-ray diffractometry and Raman spectroscopy for severely non-stoichiometric material. In some cases, the formation of the cubic zincblende and CuPt polytype of CuGaS2 are identified by transmission electron microscopy. It will be shown that changes in the Cu/Ga ratio of the solid strongly influence the photoluminescence response of the layers. Weak excitonic luminescence is observed for both slightly Ga-rich and Cu-rich material. Near stoichiometric layers exhibit luminescence centered at ~2.4 eV. Cu-rich layers are dominated by a line occurring at ~2.1 eV, whereas a different line at ~2.25 eV dominates for Ga-rich layers. A clear picture emerges of the radiative mechanisms dominating for Cu-rich and Ga-rich layers.
- Full Text:
- Date Issued: 2006
Cytokine signalling functions of human soluble IgE receptors in peripheral blood mononuclear cells from normal and hyper-allergic individuals and in B-lymphoblastoid and monocytic cell lines
- Authors: Askew, Sandra Lyn
- Date: 2006
- Subjects: Ligands , Cell receptors , Cellular signal transduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10305 , http://hdl.handle.net/10948/455 , Ligands , Cell receptors , Cellular signal transduction
- Description: CD23 is a multifunctional receptor/ligand, found in a variety of cell types, such as human peripheral blood mononuclear cells (PBMCs), B-lymphoblastoid cell lines, mast cells and basophils. It is also found on a variety of haematopoietic cell lines. As the low-affinity receptor for immunoglobulin E (IgE), CD23 plays a role in antigen-presentation and macrophage activation. As a surface molecule cleaved from the cell membrane, soluble CD23 (sCD23) can act as an adhesion molecule and a cytokine. Perturbances of such molecular interactions may lead to various diseases such as allergies and other inflammatory diseases. It has been speculated that elevated levels of sCD23 may be used to bind secreted IgE, thus preventing it from binding to membrane CD23 on haematopoietic cells, preventing B cells from being activated into IgE producing cells. Signal transduction by sCD23 is dependent on cell subsets, ligands and co-factors required for its function. sCD23 plays a direct role in inducing tumour necrosis factor alpha (TNFα), interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β) and soluble IL-1 receptor from activated human monocytes and PBMCs in vitro. Recombinant forms of 25 and 37 kDa human sCD23 were produced by polymerase chain reaction (PCR)-cloning into pET23a, a bacterial expression vector. The proteins were expressed and refolded, followed by purification by gel filtration chromatography. The purified proteins were biochemically characterized to ensure purity and biological activity, by observing the binding to human IgE both in enzyme-linked immunosorbant assay (ELISA) and surface plasmon resonance (SPR) spectroscopy. ELISA showed KD values of 7.23 x 10-9M and 8.12 x 10-9M for the 25 and 37 kDa proteins, respectively. These values were significantly lower than that of Hibbert et al., (2005). SPR data obtained for the 25 kDa CD23 was not of reliable quality but SPR for the 33kDa sCD23 showed a KD of 1.18 x 10-7M, close to that of Hibbert et al., (2005), J. Exp. Med, 202: 751-760. To test the therapeutic potential of the recombinant molecule, a B-lymphoblastoid cell line (Raji), a pre-monocytic cell line (U937), and PBMCs from normal and hyper-allergic individuals were used. All cells showed no change in production of cytokines. It is essential to investigate further cytokine functions and production implicated by recombinant forms of sCD23, as well as binding of sCD23 to CD21 and CD11b/c, and in vivo IgE regulation before a conclusion can be drawn as to whether recombinant sCD23 is a potential therapeutic target against allergic disease.
- Full Text:
- Date Issued: 2006
- Authors: Askew, Sandra Lyn
- Date: 2006
- Subjects: Ligands , Cell receptors , Cellular signal transduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10305 , http://hdl.handle.net/10948/455 , Ligands , Cell receptors , Cellular signal transduction
- Description: CD23 is a multifunctional receptor/ligand, found in a variety of cell types, such as human peripheral blood mononuclear cells (PBMCs), B-lymphoblastoid cell lines, mast cells and basophils. It is also found on a variety of haematopoietic cell lines. As the low-affinity receptor for immunoglobulin E (IgE), CD23 plays a role in antigen-presentation and macrophage activation. As a surface molecule cleaved from the cell membrane, soluble CD23 (sCD23) can act as an adhesion molecule and a cytokine. Perturbances of such molecular interactions may lead to various diseases such as allergies and other inflammatory diseases. It has been speculated that elevated levels of sCD23 may be used to bind secreted IgE, thus preventing it from binding to membrane CD23 on haematopoietic cells, preventing B cells from being activated into IgE producing cells. Signal transduction by sCD23 is dependent on cell subsets, ligands and co-factors required for its function. sCD23 plays a direct role in inducing tumour necrosis factor alpha (TNFα), interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β) and soluble IL-1 receptor from activated human monocytes and PBMCs in vitro. Recombinant forms of 25 and 37 kDa human sCD23 were produced by polymerase chain reaction (PCR)-cloning into pET23a, a bacterial expression vector. The proteins were expressed and refolded, followed by purification by gel filtration chromatography. The purified proteins were biochemically characterized to ensure purity and biological activity, by observing the binding to human IgE both in enzyme-linked immunosorbant assay (ELISA) and surface plasmon resonance (SPR) spectroscopy. ELISA showed KD values of 7.23 x 10-9M and 8.12 x 10-9M for the 25 and 37 kDa proteins, respectively. These values were significantly lower than that of Hibbert et al., (2005). SPR data obtained for the 25 kDa CD23 was not of reliable quality but SPR for the 33kDa sCD23 showed a KD of 1.18 x 10-7M, close to that of Hibbert et al., (2005), J. Exp. Med, 202: 751-760. To test the therapeutic potential of the recombinant molecule, a B-lymphoblastoid cell line (Raji), a pre-monocytic cell line (U937), and PBMCs from normal and hyper-allergic individuals were used. All cells showed no change in production of cytokines. It is essential to investigate further cytokine functions and production implicated by recombinant forms of sCD23, as well as binding of sCD23 to CD21 and CD11b/c, and in vivo IgE regulation before a conclusion can be drawn as to whether recombinant sCD23 is a potential therapeutic target against allergic disease.
- Full Text:
- Date Issued: 2006
Metabolic effects brought about by tricyclic antidepressants and the contribution of a medicinal plant in alleviating high fat diet induced insulin resistance in male wistar rats
- Authors: Chadwick, Wayne
- Date: 2006
- Subjects: Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10329 , http://hdl.handle.net/10948/461 , Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
- Description: Type II diabetes is becoming a growing problem in developed countries worldwide. The median age for diagnosis was around sixty, but recent surveys have shown that the entire age distribution curve shifting left. The incidence of type II diabetes is thought to be parallel with the growing rate of obesity associated with an unhealthy western diet. Type II diabetes is an expensive disease to manage, it is for this reason that cheaper medication needs to be investigated in the form of traditional plants, such as Sutherlandia frutescens. Prescription medication, such as tricyclic antidepressants, may also increase body weight thereby playing a role in obesity. The cause of weight gain in such cases may go unrecognized or lead to cessation of the medication with or without the practitioner’s knowledge or approval. It is therefore necessary to investigate the causative agents responsible for the excessive weight gain. Drinking water containing extracts of S. frutescens or metformin was administered to two groups of eleven insulin resistant male Wistar rats. The insulin resistant control group received water without any medication. Rats were sacrificed after 8 weeks allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. The effect of the medication and the diet on muscle post receptor insulin signaling proteins was determined through Western blots. Liver proteomics was also performed using 2-D electrophoresis. In a separate experiment 26 male Wistar rats were exposed to strepotozotocin toxin, 7 of these rats received intravenous insulin treatment, 7 rats received S. frutescens extract and 7 rats received a combination of both medications, the remaining 5 received no treatment and served as the control. Rats were sacrificed after 6 days allowing for fasting blood glucose, insulin and tissue glycogen content determination. Two groups of 14 male Wistar rats received amitriptyline or trimipramine (common tricyclic antidepressants) in their drinking water, the control group (30 rats) received water without any medication. The rats’ weight and food consumption was monitored throughout the trial and their oxygen consumption was also determined. Rats were sacrificed after 6 weeks or 14 weeks of medicinal compliance allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. S. frutescens treatment normalized circulating serum insulin levels and significantly increased the rate of glucose clearance. Certain post receptor insulin signaling proteins were also significantly increased relative to the insulin resistant control group. 2-D electrophoresis identified the normalization of protein levels associated with the urea cycle. S. frutescens was also able to, independently; maintain normoglycaemic levels in the strepotozotocin treated group. The tricyclic antidepressants significantly increased blood glucose levels while significantly reducing tissue glycogen levels for both sacrifice periods. Serum insulin remained unchanged while a significant increase in insulin degradation and insulin degrading enzyme levels were found for both antidepressants. S. frutescens shows promise as a low cost antidiabetic medication for future use. Although the antidepressants did not promote weight gain, the increase in blood glucose levels may be cause for concern in patients with a pre-disposition toward developing diabetes.
- Full Text:
- Date Issued: 2006
- Authors: Chadwick, Wayne
- Date: 2006
- Subjects: Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10329 , http://hdl.handle.net/10948/461 , Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
- Description: Type II diabetes is becoming a growing problem in developed countries worldwide. The median age for diagnosis was around sixty, but recent surveys have shown that the entire age distribution curve shifting left. The incidence of type II diabetes is thought to be parallel with the growing rate of obesity associated with an unhealthy western diet. Type II diabetes is an expensive disease to manage, it is for this reason that cheaper medication needs to be investigated in the form of traditional plants, such as Sutherlandia frutescens. Prescription medication, such as tricyclic antidepressants, may also increase body weight thereby playing a role in obesity. The cause of weight gain in such cases may go unrecognized or lead to cessation of the medication with or without the practitioner’s knowledge or approval. It is therefore necessary to investigate the causative agents responsible for the excessive weight gain. Drinking water containing extracts of S. frutescens or metformin was administered to two groups of eleven insulin resistant male Wistar rats. The insulin resistant control group received water without any medication. Rats were sacrificed after 8 weeks allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. The effect of the medication and the diet on muscle post receptor insulin signaling proteins was determined through Western blots. Liver proteomics was also performed using 2-D electrophoresis. In a separate experiment 26 male Wistar rats were exposed to strepotozotocin toxin, 7 of these rats received intravenous insulin treatment, 7 rats received S. frutescens extract and 7 rats received a combination of both medications, the remaining 5 received no treatment and served as the control. Rats were sacrificed after 6 days allowing for fasting blood glucose, insulin and tissue glycogen content determination. Two groups of 14 male Wistar rats received amitriptyline or trimipramine (common tricyclic antidepressants) in their drinking water, the control group (30 rats) received water without any medication. The rats’ weight and food consumption was monitored throughout the trial and their oxygen consumption was also determined. Rats were sacrificed after 6 weeks or 14 weeks of medicinal compliance allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. S. frutescens treatment normalized circulating serum insulin levels and significantly increased the rate of glucose clearance. Certain post receptor insulin signaling proteins were also significantly increased relative to the insulin resistant control group. 2-D electrophoresis identified the normalization of protein levels associated with the urea cycle. S. frutescens was also able to, independently; maintain normoglycaemic levels in the strepotozotocin treated group. The tricyclic antidepressants significantly increased blood glucose levels while significantly reducing tissue glycogen levels for both sacrifice periods. Serum insulin remained unchanged while a significant increase in insulin degradation and insulin degrading enzyme levels were found for both antidepressants. S. frutescens shows promise as a low cost antidiabetic medication for future use. Although the antidepressants did not promote weight gain, the increase in blood glucose levels may be cause for concern in patients with a pre-disposition toward developing diabetes.
- Full Text:
- Date Issued: 2006
The effect of different slaughter age regimes on the primary and secondary production parameters of Ostriches (Struthio Camelus Domesticus) and the economic consequences of different slaughter ages
- Authors: Bhiya, Clovis Solomon
- Date: 2006
- Subjects: Slaughtering and slaughter-houses -- South Africa , Ostrich farming -- South Africa , Ostriches -- Breeding -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10735 , http://hdl.handle.net/10948/837 , Slaughtering and slaughter-houses -- South Africa , Ostrich farming -- South Africa , Ostriches -- Breeding -- South Africa
- Description: The South African ostrich industry is presently characterised by a drastic decline in the slaughter price of slaughter birds, due to the drop in the price of meat as well as leather. As a result, the economic viability of ostrich farming is severely hampered by these developments, and many generally accepted industry practices have to be reviewed. Among the practices under review is the possibility of slaughtering ostriches at an earlier age than the traditional slaughter age of 12 - 14 months, in order to minimise feed costs and the incidence of damage to the skin. However, little information is available on the effect of the slaughter age on the yield and quality of the economically important end-products. The effect of slaughter age on production and the economic viability of a commercially intensive ostrich production system was consequently evaluated in a completely randomised experimental design involving two batches (n= 81 and n= 94) of ostriches. The experiments took place at Kromme Rhee experimental farm of the Elsenburg Research Centre near Stellenbosch. The birds were subject to experimental treatment at the age of 4 months (n= 81, from May 2004 to March 2005) and 6 months (n= 94, from August 2004 to August 2005) respectively. The ostriches were randomly divided into 10 groups of between 16 and 20 birds per group. Standard production practices, as applied in an intensive ostrich production unit, were implemented. Clean drinking water and self-mixed grower diet (min 15 percent crude protein, 0.68 percent lysine and 11.4 MJ ME per kg feed) and finisher diet (min 14 percent crude protein, 0.55 percent lysine and 9.8 MJ ME per kg feed) were provided ad libitum to the birds. Birds were slaughtered at the ages of 8.5, 10.5, 12.5, 14.5, and 16.5 months respectively. Data on feed intake and yields of cold carcass, crust skin size, skin grade and total feathers was recorded for birds slaughtered at the respective ages. Data was analysed according to the analysis of variances. Values for meat yield, skin size yield and feed intake were predicted by regression analysis based on experimental values. Industry figures and norms were used as proxy for other production inputs and costs. A gross margin type analysis was performed to evaluate the effect of different slaughter ages on the profitability of each production system. There was a positive correlation between age and feed intake (r2= 0.40), slaughter weight (r2= 0.97), cold carcass yield (r2= 0.48), skin surface area (r2= 0.39), skin grade (r2= 0.19) and total yield of feathers (r2= 0.29). The dry skin grade showed deterioration as slaughter age was prolonged. Highly significant differences (P< 0.01) in slaughter weight, cold carcass yield, skin surface area, dry skin grade and total feathers were detected at the different slaughter ages. There were no significant differences (P> 0.05) with respect to gender for slaughter weight, skin surface area and dry skin grade within the different age groups. Males had significantly higher (P< 0.05) cold carcass yield and total feather yield than their female counterparts. From this study it can be concluded that an increase in slaughter age significantly increases feed intake, slaughter weight, cold carcass yield, and skin surface area. It is also clear that an increase in slaughter age can be detrimental to dry skin grade. The relative income contribution of the three main products (skin: meat: feathers) occurred in a ratio of 47:53:0, 52:47:1, 47:50:3, 44:51:5, 39:56:5 at the respective slaughter ages. Total income revealed an increase of 26 percent from 8.5 to 10.5 months slaughtering, an increase of 4 percent between 10.5 and 12.5 months, and an increase of 11 percent between 12.5 and 14.5 months. The income dropped by 0.3 percent between 14.5 and 16.5 months slaughtering. Total costs increased with slaughter age, particularly feed costs which showed an increase (at a decreasing rate) between the different slaughter ages. The margin above specified cost per bird was the highest for birds slaughtered at the age of 10.5 months. The margin above cost showed a steady decline as birds were slaughtered at higher ages. Slaughtering at 16.5 months revealed a negative margin. To compare the effect of differences in time span on different slaughter age regimes, margin above costs for each system over 5 years were discounted to a present value. In this study, with current feed costs and income from end products, slaughtering at 10.5 months revealed the highest present value for the margin above cost. Furthermore, slaughtering at 16.5 months revealed a negative present value on the margin above cost after 5 years. Financial viability calculations are relevant and valid for data obtained in this case study. Financial viability is however case-specific and may vary between producers, depending on their individual management practices, production systems and cost structures. Results from this study may be of significant value to managerial decision-making in the ostrich industry.
- Full Text:
- Date Issued: 2006
- Authors: Bhiya, Clovis Solomon
- Date: 2006
- Subjects: Slaughtering and slaughter-houses -- South Africa , Ostrich farming -- South Africa , Ostriches -- Breeding -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10735 , http://hdl.handle.net/10948/837 , Slaughtering and slaughter-houses -- South Africa , Ostrich farming -- South Africa , Ostriches -- Breeding -- South Africa
- Description: The South African ostrich industry is presently characterised by a drastic decline in the slaughter price of slaughter birds, due to the drop in the price of meat as well as leather. As a result, the economic viability of ostrich farming is severely hampered by these developments, and many generally accepted industry practices have to be reviewed. Among the practices under review is the possibility of slaughtering ostriches at an earlier age than the traditional slaughter age of 12 - 14 months, in order to minimise feed costs and the incidence of damage to the skin. However, little information is available on the effect of the slaughter age on the yield and quality of the economically important end-products. The effect of slaughter age on production and the economic viability of a commercially intensive ostrich production system was consequently evaluated in a completely randomised experimental design involving two batches (n= 81 and n= 94) of ostriches. The experiments took place at Kromme Rhee experimental farm of the Elsenburg Research Centre near Stellenbosch. The birds were subject to experimental treatment at the age of 4 months (n= 81, from May 2004 to March 2005) and 6 months (n= 94, from August 2004 to August 2005) respectively. The ostriches were randomly divided into 10 groups of between 16 and 20 birds per group. Standard production practices, as applied in an intensive ostrich production unit, were implemented. Clean drinking water and self-mixed grower diet (min 15 percent crude protein, 0.68 percent lysine and 11.4 MJ ME per kg feed) and finisher diet (min 14 percent crude protein, 0.55 percent lysine and 9.8 MJ ME per kg feed) were provided ad libitum to the birds. Birds were slaughtered at the ages of 8.5, 10.5, 12.5, 14.5, and 16.5 months respectively. Data on feed intake and yields of cold carcass, crust skin size, skin grade and total feathers was recorded for birds slaughtered at the respective ages. Data was analysed according to the analysis of variances. Values for meat yield, skin size yield and feed intake were predicted by regression analysis based on experimental values. Industry figures and norms were used as proxy for other production inputs and costs. A gross margin type analysis was performed to evaluate the effect of different slaughter ages on the profitability of each production system. There was a positive correlation between age and feed intake (r2= 0.40), slaughter weight (r2= 0.97), cold carcass yield (r2= 0.48), skin surface area (r2= 0.39), skin grade (r2= 0.19) and total yield of feathers (r2= 0.29). The dry skin grade showed deterioration as slaughter age was prolonged. Highly significant differences (P< 0.01) in slaughter weight, cold carcass yield, skin surface area, dry skin grade and total feathers were detected at the different slaughter ages. There were no significant differences (P> 0.05) with respect to gender for slaughter weight, skin surface area and dry skin grade within the different age groups. Males had significantly higher (P< 0.05) cold carcass yield and total feather yield than their female counterparts. From this study it can be concluded that an increase in slaughter age significantly increases feed intake, slaughter weight, cold carcass yield, and skin surface area. It is also clear that an increase in slaughter age can be detrimental to dry skin grade. The relative income contribution of the three main products (skin: meat: feathers) occurred in a ratio of 47:53:0, 52:47:1, 47:50:3, 44:51:5, 39:56:5 at the respective slaughter ages. Total income revealed an increase of 26 percent from 8.5 to 10.5 months slaughtering, an increase of 4 percent between 10.5 and 12.5 months, and an increase of 11 percent between 12.5 and 14.5 months. The income dropped by 0.3 percent between 14.5 and 16.5 months slaughtering. Total costs increased with slaughter age, particularly feed costs which showed an increase (at a decreasing rate) between the different slaughter ages. The margin above specified cost per bird was the highest for birds slaughtered at the age of 10.5 months. The margin above cost showed a steady decline as birds were slaughtered at higher ages. Slaughtering at 16.5 months revealed a negative margin. To compare the effect of differences in time span on different slaughter age regimes, margin above costs for each system over 5 years were discounted to a present value. In this study, with current feed costs and income from end products, slaughtering at 10.5 months revealed the highest present value for the margin above cost. Furthermore, slaughtering at 16.5 months revealed a negative present value on the margin above cost after 5 years. Financial viability calculations are relevant and valid for data obtained in this case study. Financial viability is however case-specific and may vary between producers, depending on their individual management practices, production systems and cost structures. Results from this study may be of significant value to managerial decision-making in the ostrich industry.
- Full Text:
- Date Issued: 2006
An investigation of the in vitro anticancer properties of selected platinum compounds
- Authors: Du Plessis-Stoman, Debbie
- Date: 2006
- Subjects: Antineoplastic agents , Platinum compounds , Cancer -- Immunological aspects , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10334 , http://hdl.handle.net/10948/498 , http://hdl.handle.net/10948/d1012002 , Antineoplastic agents , Platinum compounds , Cancer -- Immunological aspects , Cancer -- Chemotherapy
- Description: This dissertation mainly deals with some biochemical aspects regarding the efficacy of novel platinum anticancer compounds, as part of a broader study in which both chemistry and biochemistry are involved. Various novel diamine and N-S donor chelate compounds of platinum II and IV have been developed in which factors such as stereochemistry, ligand exchange rate and biocompatibility were considered as additional parameters. In the first order testing, each of these compounds was tested with reference to their “killing” potential by comparing their rate of killing, over a period of 48 hours with those of cisplatin and oxaliplatin. Some 80 compounds were tested in this way. Although only a few could be regarded as equal to or even better than cisplatin and oxaliplatin, the testing of these compounds on cancer cells provided useful knowledge for the further development of novel compounds. Four of the better compounds, namely Y9, Y14, Y16 and Lt16.2 were selected for further studies to obtain more detailed knowledge of their anticancer action, including some flow cytometric studies. In addition to the above, cisplatin resistant cells were produced for each of the three different cell lines tested, namely, HeLa, HT29 and MCF7 cancer cell lines, by intermittent and incremental exposure to cisplatin (all the cell lines tested became resistant to cisplatin). Each of the selected compounds were exposed to the cells in the same manner, in order to attempt the induction of resistance against these compounds in the three cell lines tested (i.e. whether these cells will become resistant to the various compounds). Each of these selected platinum containing compounds were subsequently tested against the “cisplatin resistant” cell lines in order to determine their efficacy against such cells. One such compound could be singled out, since cervical cancer cells (HeLa cells) do not become resistant to it. This behaviour is similar to that of oxaliplatin against cervical cancer and colon cancer (HT29) cells (oxaliplatin is the number one treatment for colon cancer at present). This compound also proved to be more active against cisplatin resistant cell lines. It was found that all the compounds induced apoptosis in the cell lines tested as well as inhibit the DNA cycle at one or more phase. Finally, an effort was made to evaluate the different compounds by comparing them with respect to their properties relating to anticancer action.
- Full Text:
- Date Issued: 2006
- Authors: Du Plessis-Stoman, Debbie
- Date: 2006
- Subjects: Antineoplastic agents , Platinum compounds , Cancer -- Immunological aspects , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10334 , http://hdl.handle.net/10948/498 , http://hdl.handle.net/10948/d1012002 , Antineoplastic agents , Platinum compounds , Cancer -- Immunological aspects , Cancer -- Chemotherapy
- Description: This dissertation mainly deals with some biochemical aspects regarding the efficacy of novel platinum anticancer compounds, as part of a broader study in which both chemistry and biochemistry are involved. Various novel diamine and N-S donor chelate compounds of platinum II and IV have been developed in which factors such as stereochemistry, ligand exchange rate and biocompatibility were considered as additional parameters. In the first order testing, each of these compounds was tested with reference to their “killing” potential by comparing their rate of killing, over a period of 48 hours with those of cisplatin and oxaliplatin. Some 80 compounds were tested in this way. Although only a few could be regarded as equal to or even better than cisplatin and oxaliplatin, the testing of these compounds on cancer cells provided useful knowledge for the further development of novel compounds. Four of the better compounds, namely Y9, Y14, Y16 and Lt16.2 were selected for further studies to obtain more detailed knowledge of their anticancer action, including some flow cytometric studies. In addition to the above, cisplatin resistant cells were produced for each of the three different cell lines tested, namely, HeLa, HT29 and MCF7 cancer cell lines, by intermittent and incremental exposure to cisplatin (all the cell lines tested became resistant to cisplatin). Each of the selected compounds were exposed to the cells in the same manner, in order to attempt the induction of resistance against these compounds in the three cell lines tested (i.e. whether these cells will become resistant to the various compounds). Each of these selected platinum containing compounds were subsequently tested against the “cisplatin resistant” cell lines in order to determine their efficacy against such cells. One such compound could be singled out, since cervical cancer cells (HeLa cells) do not become resistant to it. This behaviour is similar to that of oxaliplatin against cervical cancer and colon cancer (HT29) cells (oxaliplatin is the number one treatment for colon cancer at present). This compound also proved to be more active against cisplatin resistant cell lines. It was found that all the compounds induced apoptosis in the cell lines tested as well as inhibit the DNA cycle at one or more phase. Finally, an effort was made to evaluate the different compounds by comparing them with respect to their properties relating to anticancer action.
- Full Text:
- Date Issued: 2006
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