Isocyanide complexes of rhenium
- Authors: Schoultz, Xandri
- Date: 2013
- Subjects: Isocyanides , Rhenium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10360 , http://hdl.handle.net/10948/d1021069
- Description: This study investigates the synthesis of rhenium(III)-isocyanide complexes with potentially bidentate ligands, as well as the reactivity of isocyanide ligands toward rhenium(I) and (V). The crystal structures of all the complexes have been determined by X-ray diffraction methods. The coordination behaviour of trans-[ReIIICl3(t-BuNC)(PPh3)2] with aniline and its derivatives were investigated. The isocyanide-containing rhenium(V) complexes [ReCl3(t-BuNC)(L)(PPh3)] were isolated, with the ligands H2L (aniline, o-phenylenediamine and anthranilic acid). In all these complexes the dianionic ligands L are coordinated monodentately as the imide. However, with 2-aminophenol the complexes [ReVCl2(t-BuNC)(L)(PPh3)2](ReO4) and [ReIIICl2(t-BuNC)(ibq)(PPh3)2] (ibq- = 2-iminobenzoquinonate) were identified as the products. [ReCl2(t-BuNC)(L)(PPh3)2](ReO4) is the product of a disproportionation reaction from Re(III) to Re(VII) and Re(V). All the above complexes show a distorted octahedral geometry around the rhenium. The products of the reaction of the Re(I) complex [Re(CO)5Cl] with isocyanides (tert-butyl- and cyclohexylisocyanide) are reported. Rhenium(I) tricarbonyl complexes of the form [Re(CO)3(CNR)2Cl] were isolated and they were characterized structurally and spectroscopically. The tricarbonyls are coordinated in the typical facial-fashion, whereas the isocyanides are coordinated cis to each other. The reaction of [Re(CO)3(t-BuNC)2Cl] with H2O led to the formation of the rhenium(I) complex [Re(CO)3(t-BuNC)2(OH2)] in which the aquo ligand can readily be substituted by a more complex ligand. The reaction of the rhenium(V) complexes cis-[ReO2I(PPh3)2] and mer-[ReOCl3(SMe2)(OPPh3)] with isocyanides were studied. The seven-coordinate trigonal prismatic, square faced monocapped rhenium(III) complex [ReI3(t-BuNC)3(PPh3)] was surprisingly isolated upon reacting cis-[ReO2I(PPh3)2] with tert-butyl isocyanide. The dimeric complex (μ-O)[ReOCl2(CNC6H11)2]2 was obtained from the reaction of mer-[ReOCl3(SMe2)(OPPh3)] with cyclohexyl isocyanide.
- Full Text:
- Date Issued: 2013
- Authors: Schoultz, Xandri
- Date: 2013
- Subjects: Isocyanides , Rhenium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10360 , http://hdl.handle.net/10948/d1021069
- Description: This study investigates the synthesis of rhenium(III)-isocyanide complexes with potentially bidentate ligands, as well as the reactivity of isocyanide ligands toward rhenium(I) and (V). The crystal structures of all the complexes have been determined by X-ray diffraction methods. The coordination behaviour of trans-[ReIIICl3(t-BuNC)(PPh3)2] with aniline and its derivatives were investigated. The isocyanide-containing rhenium(V) complexes [ReCl3(t-BuNC)(L)(PPh3)] were isolated, with the ligands H2L (aniline, o-phenylenediamine and anthranilic acid). In all these complexes the dianionic ligands L are coordinated monodentately as the imide. However, with 2-aminophenol the complexes [ReVCl2(t-BuNC)(L)(PPh3)2](ReO4) and [ReIIICl2(t-BuNC)(ibq)(PPh3)2] (ibq- = 2-iminobenzoquinonate) were identified as the products. [ReCl2(t-BuNC)(L)(PPh3)2](ReO4) is the product of a disproportionation reaction from Re(III) to Re(VII) and Re(V). All the above complexes show a distorted octahedral geometry around the rhenium. The products of the reaction of the Re(I) complex [Re(CO)5Cl] with isocyanides (tert-butyl- and cyclohexylisocyanide) are reported. Rhenium(I) tricarbonyl complexes of the form [Re(CO)3(CNR)2Cl] were isolated and they were characterized structurally and spectroscopically. The tricarbonyls are coordinated in the typical facial-fashion, whereas the isocyanides are coordinated cis to each other. The reaction of [Re(CO)3(t-BuNC)2Cl] with H2O led to the formation of the rhenium(I) complex [Re(CO)3(t-BuNC)2(OH2)] in which the aquo ligand can readily be substituted by a more complex ligand. The reaction of the rhenium(V) complexes cis-[ReO2I(PPh3)2] and mer-[ReOCl3(SMe2)(OPPh3)] with isocyanides were studied. The seven-coordinate trigonal prismatic, square faced monocapped rhenium(III) complex [ReI3(t-BuNC)3(PPh3)] was surprisingly isolated upon reacting cis-[ReO2I(PPh3)2] with tert-butyl isocyanide. The dimeric complex (μ-O)[ReOCl2(CNC6H11)2]2 was obtained from the reaction of mer-[ReOCl3(SMe2)(OPPh3)] with cyclohexyl isocyanide.
- Full Text:
- Date Issued: 2013
Management of capital expenditure for infrastructure programmes in the North-West Province
- Authors: Norgbey, Wisdom Selorm
- Date: 2013
- Subjects: Construction industry -- Capital investments , Infrastructure (Economics) -- Management , Expenditures, Public
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9718 , http://hdl.handle.net/10948/d1021075
- Description: The need for programme management to align, coordinate and manage a portfolio of construction projects to deliver benefits that would not be achievable if the projects were managed independently in a turbulent economic environment, limitations of project management, and increasing stakeholder expectations cannot be over emphasised. In the construction industry, the implementation of programme management has been bedevilled with major challenges of which the North West Department of Public Works (DPW) CAPEX programme is no exception. The CAPEX programme has been noted for delivering fewer infrastructure projects as planned in terms of budget, time, and other expectations. The research documented in this treatise thus examined the existing programme management approach of the North West DPW CAPEX programme with respect to generally accepted standards and practices. A mixed research approach was used to identify problems such as delays in payment of works, poor reporting standards, improper planning of works, procurement difficulties, and inadequate management structures. The results point to excessive bureaucratic processes, improper information management systems and lack of commitment and ownership towards government works as the major underlying causes of the programme predicaments. Dogmatic implementation of government’s black economic empowerment policies and inadequate in-house capacity were also contributing factors. The research findings imply that effective processes should be laid for prompt payment of works certificates and invoices. Improved reporting standards and proper planning of the programme as a whole and its constituent projects is necessary for the attainment of stipulated goals. In particular, it is crucial to ensure that adequate management considerations in terms of capacity, infrastructure, structures and expertise are put in place while the procurement processes should be continually reviewed for programme success purposes.
- Full Text:
- Date Issued: 2013
- Authors: Norgbey, Wisdom Selorm
- Date: 2013
- Subjects: Construction industry -- Capital investments , Infrastructure (Economics) -- Management , Expenditures, Public
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9718 , http://hdl.handle.net/10948/d1021075
- Description: The need for programme management to align, coordinate and manage a portfolio of construction projects to deliver benefits that would not be achievable if the projects were managed independently in a turbulent economic environment, limitations of project management, and increasing stakeholder expectations cannot be over emphasised. In the construction industry, the implementation of programme management has been bedevilled with major challenges of which the North West Department of Public Works (DPW) CAPEX programme is no exception. The CAPEX programme has been noted for delivering fewer infrastructure projects as planned in terms of budget, time, and other expectations. The research documented in this treatise thus examined the existing programme management approach of the North West DPW CAPEX programme with respect to generally accepted standards and practices. A mixed research approach was used to identify problems such as delays in payment of works, poor reporting standards, improper planning of works, procurement difficulties, and inadequate management structures. The results point to excessive bureaucratic processes, improper information management systems and lack of commitment and ownership towards government works as the major underlying causes of the programme predicaments. Dogmatic implementation of government’s black economic empowerment policies and inadequate in-house capacity were also contributing factors. The research findings imply that effective processes should be laid for prompt payment of works certificates and invoices. Improved reporting standards and proper planning of the programme as a whole and its constituent projects is necessary for the attainment of stipulated goals. In particular, it is crucial to ensure that adequate management considerations in terms of capacity, infrastructure, structures and expertise are put in place while the procurement processes should be continually reviewed for programme success purposes.
- Full Text:
- Date Issued: 2013
On meshless methods : a novel interpolatory method and a GPU-accelerated implementation
- Authors: Hamed, Maien Mohamed Osman
- Date: 2013
- Subjects: Engineering mathematics , Numerical analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10509 , http://hdl.handle.net/10948/d1018227
- Description: Meshless methods have been developed to avoid the numerical burden imposed by meshing in the Finite Element Method. Such methods are especially attrac- tive in problems that require repeated updates to the mesh, such as problems with discontinuities or large geometrical deformations. Although meshing is not required for solving problems with meshless methods, the use of meshless methods gives rise to different challenges. One of the main challenges associated with meshless methods is imposition of essential boundary conditions. If exact interpolants are used as shape functions in a meshless method, imposing essen- tial boundary conditions can be done in the same way as the Finite Element Method. Another attractive feature of meshless methods is that their use involves compu- tations that are largely independent from one another. This makes them suitable for implementation to run on highly parallel computing systems. Highly par- allel computing has become widely available with the introduction of software development tools that enable developing general-purpose programs that run on Graphics Processing Units. In the current work, the Moving Regularized Interpolation method has been de- veloped, which is a novel method of constructing meshless shape functions that achieve exact interpolation. The method is demonstrated in data interpolation and in partial differential equations. In addition, an implementation of the Element-Free Galerkin method has been written to run on a Graphics Processing Unit. The implementation is described and its performance is compared to that of a similar implementation that does not make use of the Graphics Processing Unit.
- Full Text:
- Date Issued: 2013
- Authors: Hamed, Maien Mohamed Osman
- Date: 2013
- Subjects: Engineering mathematics , Numerical analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10509 , http://hdl.handle.net/10948/d1018227
- Description: Meshless methods have been developed to avoid the numerical burden imposed by meshing in the Finite Element Method. Such methods are especially attrac- tive in problems that require repeated updates to the mesh, such as problems with discontinuities or large geometrical deformations. Although meshing is not required for solving problems with meshless methods, the use of meshless methods gives rise to different challenges. One of the main challenges associated with meshless methods is imposition of essential boundary conditions. If exact interpolants are used as shape functions in a meshless method, imposing essen- tial boundary conditions can be done in the same way as the Finite Element Method. Another attractive feature of meshless methods is that their use involves compu- tations that are largely independent from one another. This makes them suitable for implementation to run on highly parallel computing systems. Highly par- allel computing has become widely available with the introduction of software development tools that enable developing general-purpose programs that run on Graphics Processing Units. In the current work, the Moving Regularized Interpolation method has been de- veloped, which is a novel method of constructing meshless shape functions that achieve exact interpolation. The method is demonstrated in data interpolation and in partial differential equations. In addition, an implementation of the Element-Free Galerkin method has been written to run on a Graphics Processing Unit. The implementation is described and its performance is compared to that of a similar implementation that does not make use of the Graphics Processing Unit.
- Full Text:
- Date Issued: 2013
Production of recombinant human CD21 and CD23 : towards a better understanding of their interaction
- Authors: Van Zyl, Dwain George
- Date: 2013
- Subjects: Immunoglobulins , Fc receptors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10365 , http://hdl.handle.net/10948/d10211135
- Description: The prevalence of allergic diseases has dramatically increased over the last three decades. Presently, it is estimated that 20-30 per cent of the developed world suffers from allergic diseases. The majority of allergic diseases are rooted in the activities of IgE; an immunoglobulin which exerts its effector functions by interacting with a network of proteins. This network includes its low affinity receptor CD23. Cross linking of membrane IgE and CD21 by soluble CD23 results in an increase in IgE synthesis. This marks the interaction between CD23 and CD21 as an attractive therapeutic target. However, details regarding this interaction are inadequate for rational drug design. To obtain a deeper understanding of the CD23-CD21 interaction recombinant human CD21 (SCR1-2 and SCR5-8) and CD23 (16 kD and 25 kDa) were produced. The cloning, expression and purification of recombinant proteins comprised a significant portion of this study. Recombinant CD23 was expressed as inclusion bodies, refolded by rapid dilution and purified by size exclusion chromatography. Conversely, recombinant CD21 was expressed as soluble MBP-fusions and purified with an amylose affinity resin. The interaction between recombinant CD23 and CD21 was analysed by flow cytometry and ELISA experiments. Flow cytometry showed that 16 kDa and 25 kDa CD23 interacted with SCR5-8 to the same extent. Semi-quantitative ELISA experiments showed that both SCR1-2 and SCR5-8 were able to interact with 16 kDa and 25 kDa CD23. This suggests that the binding sites of SCR1-2 and SCR5-8 occur on 16 kDa CD23. Furthermore, since proteins were expressed in E. coli it suggests that the CD23-CD21 interaction does not require glycosylation. Furthermore, considering what is known about the SCR1-2-CD23 interaction from previous NMR studies; i.e. that the C-terminal tail (residues residues 289-298) of CD23 is responsible for binding SCR1-2, indicates that SCR5-8 binds somewhere within the lectin domain of CD23. This indicates that the CD23-CD21 interaction involves C-terminal tail-SCR1-2 and lectin domain-SCR5-8 interactions.
- Full Text:
- Date Issued: 2013
- Authors: Van Zyl, Dwain George
- Date: 2013
- Subjects: Immunoglobulins , Fc receptors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10365 , http://hdl.handle.net/10948/d10211135
- Description: The prevalence of allergic diseases has dramatically increased over the last three decades. Presently, it is estimated that 20-30 per cent of the developed world suffers from allergic diseases. The majority of allergic diseases are rooted in the activities of IgE; an immunoglobulin which exerts its effector functions by interacting with a network of proteins. This network includes its low affinity receptor CD23. Cross linking of membrane IgE and CD21 by soluble CD23 results in an increase in IgE synthesis. This marks the interaction between CD23 and CD21 as an attractive therapeutic target. However, details regarding this interaction are inadequate for rational drug design. To obtain a deeper understanding of the CD23-CD21 interaction recombinant human CD21 (SCR1-2 and SCR5-8) and CD23 (16 kD and 25 kDa) were produced. The cloning, expression and purification of recombinant proteins comprised a significant portion of this study. Recombinant CD23 was expressed as inclusion bodies, refolded by rapid dilution and purified by size exclusion chromatography. Conversely, recombinant CD21 was expressed as soluble MBP-fusions and purified with an amylose affinity resin. The interaction between recombinant CD23 and CD21 was analysed by flow cytometry and ELISA experiments. Flow cytometry showed that 16 kDa and 25 kDa CD23 interacted with SCR5-8 to the same extent. Semi-quantitative ELISA experiments showed that both SCR1-2 and SCR5-8 were able to interact with 16 kDa and 25 kDa CD23. This suggests that the binding sites of SCR1-2 and SCR5-8 occur on 16 kDa CD23. Furthermore, since proteins were expressed in E. coli it suggests that the CD23-CD21 interaction does not require glycosylation. Furthermore, considering what is known about the SCR1-2-CD23 interaction from previous NMR studies; i.e. that the C-terminal tail (residues residues 289-298) of CD23 is responsible for binding SCR1-2, indicates that SCR5-8 binds somewhere within the lectin domain of CD23. This indicates that the CD23-CD21 interaction involves C-terminal tail-SCR1-2 and lectin domain-SCR5-8 interactions.
- Full Text:
- Date Issued: 2013
Relating vegetation condition to grazing management systems in the central Keiskamma catchment, Eastern Cape Province, South Africa
- Authors: Ndou, Naledzani Nyahman
- Date: 2013
- Subjects: Grazing -- Management , Grazing -- South Africa -- Management , Vegetation and climate -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10673 , http://hdl.handle.net/10948/d1020645
- Description: Vegetation degradation in South Africa has been identified as a serious environmental problem, especially impacting communal areas. This study investigated the spatial distribution of vegetative condition, along with related changes, deterioration and trends, across the communal villages of the central Keiskamma catchment, Eastern Cape Province. The principal hypothesis of this study was that differences in grazing management strategies may explain the variations in vegetation condition within these communal areas. This investigation assessed the status and condition of vegetation in relation to local institutional grazing management systems, in association with factoring in relevant topographical and physical elements. Topographic homogeneity of the study area was tested by extracting topographic parameters from a DEM and performing a Chi squared test. Remote sensing techniques were used to analyse the spatial and temporal variations in vegetation condition between the villages. Landsat TM images, from 1984 and 1999, in conjunction with SPOT imagery of 2011, were used to assess the spatial trends in vegetation. Land use and cover maps were generated, comprising five categories of land cover, viz. intact vegetation; transformed vegetation; degraded vegetation; bare surfaces; and water. The classification of the images was achieved using the supervised object-oriented classification techniques, which aggregates pixels of each class into homogeneous objects. Information regarding existence and functionality of local institutional structures was obtained through structured interview method. Vegetation condition was correlated to grazing management systems, with the logistic regression confirming a significant relationship between vegetation condition and grazing management systems. Analysis of vegetation condition trends revealed a decline in pristine vegetation with an increase in degraded vegetation and exposed soil throughout the villages. However, it was observed that the decrease in pristine vegetation, with the associated increase in degraded vegetation and soil, do not occur evenly among the villages of the central Keiskamma catchment; the communal areas surrounding certain villages exhibited severe degradation of soil and vegetation, while other villages demonstrated less or minimal deterioration in their environs. The topographic homogeneity of the study locale lent credence to the theory that the uneven distribution of vegetation conditions between the villages is not controlled by topographic factors. Analysis of the data, collected through interviews, revealed differences in the functionality of institutional structures between villages. A statistically significant correlation between the vegetative condition and implementation of grazing management systems, supports the postulated concept that the variances in vegetation condition of the central Keiskamma catchment reflect the efficacy or inefficiency of the settlements‘ grazing management systems. Through gathering, analysing and assessing all the data, a conclusion was drawn, which advances that the primary requirement for remedial action in reversing the current decline in vegetation condition is strengthening the local institutional management regimes throughout all villages under study.
- Full Text:
- Date Issued: 2013
- Authors: Ndou, Naledzani Nyahman
- Date: 2013
- Subjects: Grazing -- Management , Grazing -- South Africa -- Management , Vegetation and climate -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10673 , http://hdl.handle.net/10948/d1020645
- Description: Vegetation degradation in South Africa has been identified as a serious environmental problem, especially impacting communal areas. This study investigated the spatial distribution of vegetative condition, along with related changes, deterioration and trends, across the communal villages of the central Keiskamma catchment, Eastern Cape Province. The principal hypothesis of this study was that differences in grazing management strategies may explain the variations in vegetation condition within these communal areas. This investigation assessed the status and condition of vegetation in relation to local institutional grazing management systems, in association with factoring in relevant topographical and physical elements. Topographic homogeneity of the study area was tested by extracting topographic parameters from a DEM and performing a Chi squared test. Remote sensing techniques were used to analyse the spatial and temporal variations in vegetation condition between the villages. Landsat TM images, from 1984 and 1999, in conjunction with SPOT imagery of 2011, were used to assess the spatial trends in vegetation. Land use and cover maps were generated, comprising five categories of land cover, viz. intact vegetation; transformed vegetation; degraded vegetation; bare surfaces; and water. The classification of the images was achieved using the supervised object-oriented classification techniques, which aggregates pixels of each class into homogeneous objects. Information regarding existence and functionality of local institutional structures was obtained through structured interview method. Vegetation condition was correlated to grazing management systems, with the logistic regression confirming a significant relationship between vegetation condition and grazing management systems. Analysis of vegetation condition trends revealed a decline in pristine vegetation with an increase in degraded vegetation and exposed soil throughout the villages. However, it was observed that the decrease in pristine vegetation, with the associated increase in degraded vegetation and soil, do not occur evenly among the villages of the central Keiskamma catchment; the communal areas surrounding certain villages exhibited severe degradation of soil and vegetation, while other villages demonstrated less or minimal deterioration in their environs. The topographic homogeneity of the study locale lent credence to the theory that the uneven distribution of vegetation conditions between the villages is not controlled by topographic factors. Analysis of the data, collected through interviews, revealed differences in the functionality of institutional structures between villages. A statistically significant correlation between the vegetative condition and implementation of grazing management systems, supports the postulated concept that the variances in vegetation condition of the central Keiskamma catchment reflect the efficacy or inefficiency of the settlements‘ grazing management systems. Through gathering, analysing and assessing all the data, a conclusion was drawn, which advances that the primary requirement for remedial action in reversing the current decline in vegetation condition is strengthening the local institutional management regimes throughout all villages under study.
- Full Text:
- Date Issued: 2013
Revision of Aloiampelos Klopper & Gideon F.Sm. (xanthorrhoeaceae subfam. asphodeloideae)
- Authors: Ellis, Kristen
- Date: 2013
- Subjects: Xanthorrhoeaceae , Asparagales
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10642 , http://hdl.handle.net/10948/d1020955
- Description: The genus Aloiampelos Klopper & Gideon F.Sm., previously treated as Aloe L. Ser. Macrifoliae (Sect. Prolongatae), comprises seven species with barely succulent leaves that are popularly known as rambling, scrambling or climbing aloes, because they make use of surrounding trees and shrubs for support. The rambling aloes are centered in the Eastern Cape but some species have disjunct distributions in the Western Cape and KwaZulu-Natal. Many are widely used in gardens and landscaping. With their rambling habit and weakly succulent leaves, the genus is widely considered to be an old lineage among alooid genera. Species concepts within the genus remain contentious, with disagreement amongst taxonomists with respect to the recognition of some taxa at the rank of variety. Morphology, historical taxonomy, palynology and phylogenetics of the genus were investigated. The occasional presence of minute cilia on the sheathing leaf bases and distinct lineation of the leaf sheaths of Aloiampelos tenuior var. decidua and Aloiampelos tenuior var. rubriflora were the most important outcomes of the morphological study. The pollen grains of all species studied were very similar in grain shape and exine surface pattern, with only minor differences in grain size. Ordination analyses showed that grain length and muri length were useful at the infraspecific level, with Aloiampelos tenuior “orange” separating clearly from the other varieties. Pollen morphology was therefore not informative as a taxonomic character at species level when used in isolation, but may be useful when used in conjunction with other characteristics. Preliminary analyses of two plastid barcoding regions (matK and rbcL) and nuclear ITS have confirmed that Aloiampelos is monophyletic. These barcoding markers were not informative in assessing the species boundaries among the closely related taxa in the genus and morphological assessments were therefore used to elucidate relationships at the species rank. A key is given for the genus, integrating the findings of the study.
- Full Text:
- Date Issued: 2013
- Authors: Ellis, Kristen
- Date: 2013
- Subjects: Xanthorrhoeaceae , Asparagales
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10642 , http://hdl.handle.net/10948/d1020955
- Description: The genus Aloiampelos Klopper & Gideon F.Sm., previously treated as Aloe L. Ser. Macrifoliae (Sect. Prolongatae), comprises seven species with barely succulent leaves that are popularly known as rambling, scrambling or climbing aloes, because they make use of surrounding trees and shrubs for support. The rambling aloes are centered in the Eastern Cape but some species have disjunct distributions in the Western Cape and KwaZulu-Natal. Many are widely used in gardens and landscaping. With their rambling habit and weakly succulent leaves, the genus is widely considered to be an old lineage among alooid genera. Species concepts within the genus remain contentious, with disagreement amongst taxonomists with respect to the recognition of some taxa at the rank of variety. Morphology, historical taxonomy, palynology and phylogenetics of the genus were investigated. The occasional presence of minute cilia on the sheathing leaf bases and distinct lineation of the leaf sheaths of Aloiampelos tenuior var. decidua and Aloiampelos tenuior var. rubriflora were the most important outcomes of the morphological study. The pollen grains of all species studied were very similar in grain shape and exine surface pattern, with only minor differences in grain size. Ordination analyses showed that grain length and muri length were useful at the infraspecific level, with Aloiampelos tenuior “orange” separating clearly from the other varieties. Pollen morphology was therefore not informative as a taxonomic character at species level when used in isolation, but may be useful when used in conjunction with other characteristics. Preliminary analyses of two plastid barcoding regions (matK and rbcL) and nuclear ITS have confirmed that Aloiampelos is monophyletic. These barcoding markers were not informative in assessing the species boundaries among the closely related taxa in the genus and morphological assessments were therefore used to elucidate relationships at the species rank. A key is given for the genus, integrating the findings of the study.
- Full Text:
- Date Issued: 2013
Rhenium (I), (III) and (V) complexes with potentially multidentate N, O-Donor ligands
- Authors: Habarurema, Gratien
- Date: 2013
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10441 , http://hdl.handle.net/10948/d1020952
- Description: This study investigates the coordination modes of potential multidentate N,O-donor Schiff base ligands to the [ReVO]3+ and fac-[ReI(CO)3]+ cores. The project is aimed at the synthesis of tridentate, tetradentate and pentadentate Schiff bases ligands derived from the condensation reactions of benzaldehyde with different primary amines. The structures of these Schiff bases and their complexes were confirmed by using physical characterization methods, namely melting points, UV-Visible, UV-emission, 1H NMR and IR spectroscopy, X-ray diffractometry and elemental analysis. To further understand the coordination chemistry of rhenium, the prepared diiminediphenol N2O2-donor Schiff base ligand N N′-o-phenylene-bis(salicylaldimine) (H2salphen) was reacted with trans-[ReOCl3(PPh3)2] to yield cis-[ReCl2(ophsal)(PPh3)], whereas its reaction with trans-[ReOBr3(PPh3)2] resulted in the formation of the cis-[ReBr2(aphsal)(PPh3)].2CH3CN complex. In the above complexes the H2salphen ligand was cleaved leading to the coordinated tridentate ophsal NO2- and aphsal N2O-donor ligands. The reaction of H3aphsal with trans-[ReOBr3(PPh3)2] in toluene led to an unexpected compound, trans- [{[ReBr(aphsal)(PPh3)2]Br}{[ReBr(aphsal)(PPh3)2](ReO4)}] with an imido [ReNR]3+core. The ligand aphsal was coordinated tridentately with the doubly deprotonated amino nitrogen leading to Re(V)-imido complexes. The reaction of 2-((Z)-(2-aminoethylimino)methyl)phenol (H3amphol) with [Re(CO)5Cl] led to the rhenium(I) product fac-[Re(CO)3(H3amphol)] with H3amphol coordinated as a monoanionic tridentate chelate through its phenolate oxygen and amino nitrogen atoms. The X-ray crystal structures showed that all complexes display a distorted octahedral geometry around the central rhenium atom. The reaction of 2,6-bis(2-hydroxyphenylimino)pyridine (H2hpp) with cis-[ReO2I(PPh3)2] resulted in the reduced Re(III) product trans-[Re(hpp)(PPh3)2]I, while trans-[Re(hpp)(PPh3)2](ReO4) was isolated from its reaction with trans-[ReOCl3(PPh3)2]. The H2hpp ligand acts as a pentadentate N3O2-donor ligand where the two phenolic protons undergo deprotonation and its three nitrogens act as neutral donor atoms. Both compounds resulted from a disproportionation reaction characterized by the produced perrhenate counter-ion. The complex fac-[Re(CO)3(H2hpp)Cl] was prepared from [Re(CO)5Cl] and H2hpp in toluene. The H2hpp ligand acted as a neutral bidentate N,N-donor chelate. The metal is coordinated to three carbonyl donors in a facial orientation, two neutral nitrogen atoms and a chloride ligand. The reactions of the potentially tetradentate ligand N,N'-ethylenebis(salicylideneimine) (H2salen) with different rhenium(V) precursors resulted in the formation of two dimeric oxorhenium (V) compounds. In the reaction of H2salen with trans-[ReOCl3(PPh3)2] in ethanol, the highly unusual distorted dimeric complex (μ-salen)[ReOCl2(PPh3)]2 was isolated, in which salen2- is coordinated as a tetradentate to two oxorhenium(V) centres, and salen2- is present as a bidentate monoanionic ligand on each rhenium center. The reaction of cis- [ReO2I(PPh3)2] with H2salen led to the formation of the neutral dimeric oxorhenium(V) complex (μ-O)[ReO(salen)]2 in which the tetradentate chelate salen acts as a tetradentate dianionic ligand through its phenolate oxygens and nitrogen atoms of the azomethine groups. In its reaction with H2hmp the compound (μ-O)[ReO(hmp)]2 was isolated. In this product the pentadentate ligand H2hmp coordinated as tetradentate via its phenolic oxygen and nitrogen atoms. The reaction of the potentially tetradentate N1,N2-bis(aminobenzylidene)-1,2-ethylenediamine (H2amben) with trans-[ReOCl3(PPh3)2] led to the formation of the monocationic square-pyramidal complex salt [ReO(amben)](ReO4.
- Full Text:
- Date Issued: 2013
- Authors: Habarurema, Gratien
- Date: 2013
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10441 , http://hdl.handle.net/10948/d1020952
- Description: This study investigates the coordination modes of potential multidentate N,O-donor Schiff base ligands to the [ReVO]3+ and fac-[ReI(CO)3]+ cores. The project is aimed at the synthesis of tridentate, tetradentate and pentadentate Schiff bases ligands derived from the condensation reactions of benzaldehyde with different primary amines. The structures of these Schiff bases and their complexes were confirmed by using physical characterization methods, namely melting points, UV-Visible, UV-emission, 1H NMR and IR spectroscopy, X-ray diffractometry and elemental analysis. To further understand the coordination chemistry of rhenium, the prepared diiminediphenol N2O2-donor Schiff base ligand N N′-o-phenylene-bis(salicylaldimine) (H2salphen) was reacted with trans-[ReOCl3(PPh3)2] to yield cis-[ReCl2(ophsal)(PPh3)], whereas its reaction with trans-[ReOBr3(PPh3)2] resulted in the formation of the cis-[ReBr2(aphsal)(PPh3)].2CH3CN complex. In the above complexes the H2salphen ligand was cleaved leading to the coordinated tridentate ophsal NO2- and aphsal N2O-donor ligands. The reaction of H3aphsal with trans-[ReOBr3(PPh3)2] in toluene led to an unexpected compound, trans- [{[ReBr(aphsal)(PPh3)2]Br}{[ReBr(aphsal)(PPh3)2](ReO4)}] with an imido [ReNR]3+core. The ligand aphsal was coordinated tridentately with the doubly deprotonated amino nitrogen leading to Re(V)-imido complexes. The reaction of 2-((Z)-(2-aminoethylimino)methyl)phenol (H3amphol) with [Re(CO)5Cl] led to the rhenium(I) product fac-[Re(CO)3(H3amphol)] with H3amphol coordinated as a monoanionic tridentate chelate through its phenolate oxygen and amino nitrogen atoms. The X-ray crystal structures showed that all complexes display a distorted octahedral geometry around the central rhenium atom. The reaction of 2,6-bis(2-hydroxyphenylimino)pyridine (H2hpp) with cis-[ReO2I(PPh3)2] resulted in the reduced Re(III) product trans-[Re(hpp)(PPh3)2]I, while trans-[Re(hpp)(PPh3)2](ReO4) was isolated from its reaction with trans-[ReOCl3(PPh3)2]. The H2hpp ligand acts as a pentadentate N3O2-donor ligand where the two phenolic protons undergo deprotonation and its three nitrogens act as neutral donor atoms. Both compounds resulted from a disproportionation reaction characterized by the produced perrhenate counter-ion. The complex fac-[Re(CO)3(H2hpp)Cl] was prepared from [Re(CO)5Cl] and H2hpp in toluene. The H2hpp ligand acted as a neutral bidentate N,N-donor chelate. The metal is coordinated to three carbonyl donors in a facial orientation, two neutral nitrogen atoms and a chloride ligand. The reactions of the potentially tetradentate ligand N,N'-ethylenebis(salicylideneimine) (H2salen) with different rhenium(V) precursors resulted in the formation of two dimeric oxorhenium (V) compounds. In the reaction of H2salen with trans-[ReOCl3(PPh3)2] in ethanol, the highly unusual distorted dimeric complex (μ-salen)[ReOCl2(PPh3)]2 was isolated, in which salen2- is coordinated as a tetradentate to two oxorhenium(V) centres, and salen2- is present as a bidentate monoanionic ligand on each rhenium center. The reaction of cis- [ReO2I(PPh3)2] with H2salen led to the formation of the neutral dimeric oxorhenium(V) complex (μ-O)[ReO(salen)]2 in which the tetradentate chelate salen acts as a tetradentate dianionic ligand through its phenolate oxygens and nitrogen atoms of the azomethine groups. In its reaction with H2hmp the compound (μ-O)[ReO(hmp)]2 was isolated. In this product the pentadentate ligand H2hmp coordinated as tetradentate via its phenolic oxygen and nitrogen atoms. The reaction of the potentially tetradentate N1,N2-bis(aminobenzylidene)-1,2-ethylenediamine (H2amben) with trans-[ReOCl3(PPh3)2] led to the formation of the monocationic square-pyramidal complex salt [ReO(amben)](ReO4.
- Full Text:
- Date Issued: 2013
Social network analysis of stakeholders in the Duiwenhoks Water Catchment
- Authors: Whyte, Michelle
- Date: 2013
- Subjects: Conservation of natural resources -- South Africa , Conservation plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10756 , http://hdl.handle.net/10948/d1020995
- Description: Social-ecological systems are facing complex social, political, economic and environmental problems beyond the capacity of one group of stakeholders or organization to solve in isolation. Ecosystem degradation causes major environmental and economic concern, due to the loss of ecosystem services which river and wetland ecosystems provide. Stakeholder communities who depend on natural resources need to identify the social processes which are underlying causes to unsuccessful natural resource management and thus environmental degradation. The study is primarily aimed at identifying and understanding the structural and functional properties of the stakeholder network in the Duiwenhoks River catchment in the Western Cape, South Africa. Through analyzing the social network properties the study identifies and describes the main stakeholders involved with natural resource management in the Duiwenhoks water catchment area. How the individual actors from the diverse stakeholder groups are connected through communication ties were assessed. Furthermore, issues and factors which limit the effectiveness of the social network were identified. The main factors include a lack of communication and collaboration between key local resource users and governance officials caused by conflicting perspectives regarding resource management and societal conflicts caused by asymmetries in power distribution favoring government institutions. The lack of collaboration between stakeholders was identified as a contributing factor that links to the resource degradation experienced in the catchment. Ultimately means of overcoming the limitations to effective social networking, in order to manage the challenges related to natural resource management were identified. Management recommendations include the development of bridging ties and collaboration between diverse stakeholders, whilst facilitating participatory processes aimed at participatory problem solving and adaptive co-management of natural resources. Government institutions were identified as being dominant stakeholders in the network and should be mobilized to perform a stronger bridging role to connect disconnected actors. The findings of the study may inform future efforts of researchers and facilitators to implement strategies which promote social networking, social learning and ultimately adaptive co-management in the study area or other similar social-ecological systems. Ultimately, collaboration can be achieved between the diverse stakeholders to successfully improve ecosystem management and resilience in the Duiwenhoks water catchment.
- Full Text:
- Date Issued: 2013
- Authors: Whyte, Michelle
- Date: 2013
- Subjects: Conservation of natural resources -- South Africa , Conservation plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10756 , http://hdl.handle.net/10948/d1020995
- Description: Social-ecological systems are facing complex social, political, economic and environmental problems beyond the capacity of one group of stakeholders or organization to solve in isolation. Ecosystem degradation causes major environmental and economic concern, due to the loss of ecosystem services which river and wetland ecosystems provide. Stakeholder communities who depend on natural resources need to identify the social processes which are underlying causes to unsuccessful natural resource management and thus environmental degradation. The study is primarily aimed at identifying and understanding the structural and functional properties of the stakeholder network in the Duiwenhoks River catchment in the Western Cape, South Africa. Through analyzing the social network properties the study identifies and describes the main stakeholders involved with natural resource management in the Duiwenhoks water catchment area. How the individual actors from the diverse stakeholder groups are connected through communication ties were assessed. Furthermore, issues and factors which limit the effectiveness of the social network were identified. The main factors include a lack of communication and collaboration between key local resource users and governance officials caused by conflicting perspectives regarding resource management and societal conflicts caused by asymmetries in power distribution favoring government institutions. The lack of collaboration between stakeholders was identified as a contributing factor that links to the resource degradation experienced in the catchment. Ultimately means of overcoming the limitations to effective social networking, in order to manage the challenges related to natural resource management were identified. Management recommendations include the development of bridging ties and collaboration between diverse stakeholders, whilst facilitating participatory processes aimed at participatory problem solving and adaptive co-management of natural resources. Government institutions were identified as being dominant stakeholders in the network and should be mobilized to perform a stronger bridging role to connect disconnected actors. The findings of the study may inform future efforts of researchers and facilitators to implement strategies which promote social networking, social learning and ultimately adaptive co-management in the study area or other similar social-ecological systems. Ultimately, collaboration can be achieved between the diverse stakeholders to successfully improve ecosystem management and resilience in the Duiwenhoks water catchment.
- Full Text:
- Date Issued: 2013
Statistical analysis of electricity demand profiles
- Authors: Mangisa, Siphumlile
- Date: 2013
- Subjects: Electric power consumption -- Forecasting , Energy consumption , Electric power consumption
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10572 , http://hdl.handle.net/10948/d1011548 , Electric power consumption -- Forecasting , Energy consumption , Electric power consumption
- Description: An electricity demand profile is a graph showing the amount of electricity used by customers over a unit of time. It shows the variation in electricity demand versus time. In the demand profiles, the shape of the graph is of utmost importance. The variations in demand profiles are caused by many factors, such as economic and en- vironmental factors. These variations may also be due to changes in the electricity use behaviours of electricity users. This study seeks to model daily profiles of energy demand in South Africa with a model which is a composition of two de Moivre type models. The model has seven parameters, each with a natural interpretation (one parameter representing minimum demand in a day, two parameters representing the time of morning and afternoon peaks, two parameters representing the shape of each peak, and two parameters representing the total energy per peak). With the help of this model, we trace change in the demand profile over a number of years. The proposed model will be helpful for short to long term electricity demand forecasting.
- Full Text:
- Date Issued: 2013
- Authors: Mangisa, Siphumlile
- Date: 2013
- Subjects: Electric power consumption -- Forecasting , Energy consumption , Electric power consumption
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10572 , http://hdl.handle.net/10948/d1011548 , Electric power consumption -- Forecasting , Energy consumption , Electric power consumption
- Description: An electricity demand profile is a graph showing the amount of electricity used by customers over a unit of time. It shows the variation in electricity demand versus time. In the demand profiles, the shape of the graph is of utmost importance. The variations in demand profiles are caused by many factors, such as economic and en- vironmental factors. These variations may also be due to changes in the electricity use behaviours of electricity users. This study seeks to model daily profiles of energy demand in South Africa with a model which is a composition of two de Moivre type models. The model has seven parameters, each with a natural interpretation (one parameter representing minimum demand in a day, two parameters representing the time of morning and afternoon peaks, two parameters representing the shape of each peak, and two parameters representing the total energy per peak). With the help of this model, we trace change in the demand profile over a number of years. The proposed model will be helpful for short to long term electricity demand forecasting.
- Full Text:
- Date Issued: 2013
Statistical model for risk diversification in renewable energy
- Authors: Ahame, Edmund
- Date: 2013
- Subjects: Renewable energy sources -- Statistics , Diversification in industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10564 , http://hdl.handle.net/10948/d1008399 , Renewable energy sources -- Statistics , Diversification in industry
- Description: The growth of the industry and population of South Africa urges to seek new sources of electric power, hence the need to look at alternative power sources. Power output from some renewable energy sources is highly volatile. For instance power output from wind turbines or photovoltaic solar panels fluctuates between zero and the maximum rated power out. To optimize the overall power output a model was designed to determine the best trade-off between production from two or more renewable energy sources putting emphasis on wind and solar. Different measures of risk, such as coefficient of variation (CV) and value at risk (VAR), were used to determine the best hybrid renewable energy system (HRES) configuration. Depending on the investors’ expected returns (demand) and risk averseness, they will be able to use the model to choose the best configuration that suites their needs. In general it was found that investing in a diversified HRES is better than investing in individual power sources.
- Full Text:
- Date Issued: 2013
- Authors: Ahame, Edmund
- Date: 2013
- Subjects: Renewable energy sources -- Statistics , Diversification in industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10564 , http://hdl.handle.net/10948/d1008399 , Renewable energy sources -- Statistics , Diversification in industry
- Description: The growth of the industry and population of South Africa urges to seek new sources of electric power, hence the need to look at alternative power sources. Power output from some renewable energy sources is highly volatile. For instance power output from wind turbines or photovoltaic solar panels fluctuates between zero and the maximum rated power out. To optimize the overall power output a model was designed to determine the best trade-off between production from two or more renewable energy sources putting emphasis on wind and solar. Different measures of risk, such as coefficient of variation (CV) and value at risk (VAR), were used to determine the best hybrid renewable energy system (HRES) configuration. Depending on the investors’ expected returns (demand) and risk averseness, they will be able to use the model to choose the best configuration that suites their needs. In general it was found that investing in a diversified HRES is better than investing in individual power sources.
- Full Text:
- Date Issued: 2013
Strategic management of construction companies
- Authors: Van Rooyen, Roelof Petrus
- Date: 2013
- Subjects: Construction industry -- Planning , Business planning -- South Africa -- Eastern Cape , Corporate turnarounds -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9712 , http://hdl.handle.net/10948/d1020407
- Description: The research emanated from an investigation of GB7, GB8 and GB9 main contractors in the Eastern Cape Province of South Africa. The study was focussed on the strident economic times in the construction industry following the FIFA Soccer World Cup from August 2010 to December 2012. The research was conducted to identify the key strategy or combination of strategies keeping construction entities in operation. The study further investigates the key elements of a successful turnaround strategy as well as the most effective methods in implementing strategies within construction organizations. The research took the form of an empirical quantitative study where a descriptive survey was used to collect data. Structured interviews were held with the target population to collect data in the field. The study established that geographic diversification was the most effective method utilized by main contractors for survival during the study timeframe. The study also found that lowering of profit margins and preliminary and general amounts were most effective methods in the use of turn around strategies. The study finally concluded that effective steps were taken by main contractors in the Eastern Cape to implement corporate strategies within their organizations. Step by step guidance to all employees on new processes was the key element in successful strategic implementation of a strategy within construction organizations. The research conducted contributes to the strategic management competency within the built environment as well as the existing body of knowledge within the construction industry. All members of the construction industry in South Africa involved with strategic level planning of entities would value the study.
- Full Text:
- Date Issued: 2013
- Authors: Van Rooyen, Roelof Petrus
- Date: 2013
- Subjects: Construction industry -- Planning , Business planning -- South Africa -- Eastern Cape , Corporate turnarounds -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9712 , http://hdl.handle.net/10948/d1020407
- Description: The research emanated from an investigation of GB7, GB8 and GB9 main contractors in the Eastern Cape Province of South Africa. The study was focussed on the strident economic times in the construction industry following the FIFA Soccer World Cup from August 2010 to December 2012. The research was conducted to identify the key strategy or combination of strategies keeping construction entities in operation. The study further investigates the key elements of a successful turnaround strategy as well as the most effective methods in implementing strategies within construction organizations. The research took the form of an empirical quantitative study where a descriptive survey was used to collect data. Structured interviews were held with the target population to collect data in the field. The study established that geographic diversification was the most effective method utilized by main contractors for survival during the study timeframe. The study also found that lowering of profit margins and preliminary and general amounts were most effective methods in the use of turn around strategies. The study finally concluded that effective steps were taken by main contractors in the Eastern Cape to implement corporate strategies within their organizations. Step by step guidance to all employees on new processes was the key element in successful strategic implementation of a strategy within construction organizations. The research conducted contributes to the strategic management competency within the built environment as well as the existing body of knowledge within the construction industry. All members of the construction industry in South Africa involved with strategic level planning of entities would value the study.
- Full Text:
- Date Issued: 2013
Sustainable harvesting of wild populations of Cyclopia intermedia in Kouga, Eastern Cape, South Africa
- Authors: Barnardo, Nadia
- Date: 2013
- Subjects: Wild plants, Edible -- South Africa -- Eastern Cape , Rooibos tea industry -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10639 , http://hdl.handle.net/10948/d1020195
- Description: Cyclopia intermedia E. Mey is harvested from the wild to produce honeybush tea. The presence of a lignotuber and its slow growth seems to hinder the cultivation of this species and wild harvesting is likely to continue. Species distribution modelling indicated that C. intermedia has a climate envelope that spans from the Eastern Cape to the Western Cape along the Cape Fold mountains. This regional distribution is threatened under future climate change scenarios with a range loss and shift identified for climate conditions predicted for 2050. More specifically, its niche was identified as south-facing slopes with sandy to loamy sand soils and water holding capacity that is higher than the surrounding areas. Some keystone Fynbos species were found to share this niche: Leucadendron salignum, Leucospermum cuneiforme, Protea neriifolia, Protea repens, Elegia filacea and Rhodocoma fruticosa. Cyclopia intermedia grows throughout the summer with flowering buds developing in autumn. These enlarge during winter with the flowers opening in early spring. Pods develop in November and seed set occurs during December. Harvesting plants increases their fecundity with cut plants producing more than twice the number of pods and seeds compared to their non-harvested counterparts. This is because resprouting plants produce more flowering stems than uncut plants. Controlled harvesting or localised short-cycle burning could be considered as a management option to improve fecundity of declining Cyclopia intermedia populations in protected areas. C. intermedia harvesting could occur every third year and stem colour was identified as a measure of harvest maturity. Where at least 30 percent of the population has orange (RHS colour 163A) stems the population is suitable for harvesting.
- Full Text:
- Date Issued: 2013
- Authors: Barnardo, Nadia
- Date: 2013
- Subjects: Wild plants, Edible -- South Africa -- Eastern Cape , Rooibos tea industry -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10639 , http://hdl.handle.net/10948/d1020195
- Description: Cyclopia intermedia E. Mey is harvested from the wild to produce honeybush tea. The presence of a lignotuber and its slow growth seems to hinder the cultivation of this species and wild harvesting is likely to continue. Species distribution modelling indicated that C. intermedia has a climate envelope that spans from the Eastern Cape to the Western Cape along the Cape Fold mountains. This regional distribution is threatened under future climate change scenarios with a range loss and shift identified for climate conditions predicted for 2050. More specifically, its niche was identified as south-facing slopes with sandy to loamy sand soils and water holding capacity that is higher than the surrounding areas. Some keystone Fynbos species were found to share this niche: Leucadendron salignum, Leucospermum cuneiforme, Protea neriifolia, Protea repens, Elegia filacea and Rhodocoma fruticosa. Cyclopia intermedia grows throughout the summer with flowering buds developing in autumn. These enlarge during winter with the flowers opening in early spring. Pods develop in November and seed set occurs during December. Harvesting plants increases their fecundity with cut plants producing more than twice the number of pods and seeds compared to their non-harvested counterparts. This is because resprouting plants produce more flowering stems than uncut plants. Controlled harvesting or localised short-cycle burning could be considered as a management option to improve fecundity of declining Cyclopia intermedia populations in protected areas. C. intermedia harvesting could occur every third year and stem colour was identified as a measure of harvest maturity. Where at least 30 percent of the population has orange (RHS colour 163A) stems the population is suitable for harvesting.
- Full Text:
- Date Issued: 2013
Synthesis and characterisation of oxorhenium(V) and tricarbonylrhenium(I) complexes with biologically active N, O and N, S-Donor ligands
- Authors: Mukiza, Janvier
- Date: 2013
- Subjects: Rhenium , Rhenium compounds , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10437 , http://hdl.handle.net/10948/d1020769
- Description: This study investigated the synthesis of rhenium(I) and rhenium(V) complexes with a variety of multidentate NS, NSO, NO and SO-donor ligands. It also investigated the synthesis of dinuclear dihalogeno- and trihalogeno-bridged rhenium(I) complexes based on the fac-[Re(CO)3]+ core. The reactions of hydrated folic acid with [Re(CO)5X] (X = Cl, Br) were studied, and the complexes [Re(CO)3(H2O)3]+[Re2(μ-X)3CO)6]−.5H2O [X= Br (1), Cl(2)] were isolated. The reaction of orotic acid potassium salt [Re(CO)5Br] was performed, and the complex [Re2(μ-Br)2(CO)8] was isolated. The reaction of bis(piperidin-1- yl)methanone with [Re(CO)5Cl] followed by recrystallisation of the resulting precipitate in dichloromethane/acetontrile resulted in the complex [Re2(μ- Cl)2(CO)6(MeCN)2]. The X-ray crystal structures show that all these complexes display a distorted octahedral geometry around the central rhenium atoms. The reactions of aroylhydrazone-based ligands such as 3-((pyridin- 2yl)methyleneamino)-2,3-dihydro-2-pyridin-2yl)quinazolin-4-(1H)-one (Hppq) and N-(di(pyridin-2-yl)methylene)benzohydrazide (Hdpmb) with [Re(CO)5Cl] were studied and led to the formation of the complexes [Re(CO)3Cl(Hdpmb)] and [Re(CO)3Cl(Hppq)]. The Hdpmb and Hppq coordinated to the fac-[Re(CO)3]+ core as neutral bidentate chalates via the pyridinic nitrogens (for Hdpmb) and via imino and pyridinic nitrogens for Hppq. The X-ray crystal structures show that the geometry around the rhenium in both complexes is a distorted octahedral. The treatment of the dithizone (H2dz) ligand with rhenium(V) precursors containing a triphenylphosphine group (PPh3) led to the decomposition of dithizone. The decomposition product reacted with the triphenylphosphine group and generated a new ligand triphenylphosphazeno-N-phenylmethanethiohydrazide (H2L). The reaction of trans-[ReOX3(PPh3)2] (X = Cl, Br) with dithizone (H2dz) led to the complex [ReO(dz)2][ReO(HL)2]. The reaction of trans-[ReOI2(OEt)(PPh3)2] with H2dz led to the same product. The reaction of cis-[ReO2I(PPh3)2] with H2dz in methanol led to [ReO(dz)2][ReO(HL)2](MeOH)2 in which methanol bonded to HLvia hydrogen bonds. The H2dz was doubly deprotonated and coordinated to the [ReO]3+ moiety via a thiolate sulfur and deprotonated hydrazinic nitrogen to yield [ReO(dz)2]−, while the H2L was singly deprotonated and coordinated to [ReO]3+ moiety via the neutral sulfur atom and deprotonated hydrazinic nitrogen to yield [ReO(HL)2]+. The X-ray crystal structure show that in both [ReO(HL)2]+ and [ReO(dz)2]−, the rhenium atoms are five-coordinated and adopt a distorted squarebased pyramidal geometry. The reaction of thiosemicarbazones such as salcylidene-4- phenylthiosemicarbazide (H3salpt) with cis-[ReO2I(PPh3)2] was investigated and led to the complex [ReO(Hsalpt)(H2salpt)]. The X-ray study reveals that Hsalpt is present as a tridentate chelate coordinating via the thiolate sulfur, imino nitrogen and phenolic oxygen, while H2salpt coordinates as a bidentate chelate via the thiolate sulfur and imino nitrogen atoms. The geometry around rhenium is distorted octahedral. The coordination mode of the benzoylthiourea derivatives 4-tert-butyl-N- (diphenylcarbamothioyl)benzamide (Htpb) and N-(diethylcarbamothioyl)benzamide (Heb) to the [Re2O3]4+ and fac-[Re(CO)3]+ cores were investigated. The reaction of [Re(CO)5Cl] in presence of sodium acetate with Htpb led to the dimeric complex [Re(CO)3(tpb)]2 in which the tpb coordinated to the fac-[Re(CO)3]+ core via the ketonic oxygen and bridging thiolate sulfur. The same reaction with Heb led to the monomeric complex [Re(CO)3(eb)(Heb)], in which the eb coordinates to the fac-[Re(CO)3]+core via thiolate sulfur and ketonic oxygen with Heb binding via the neutral sulfur atom. The reaction of Heb with cis-[ReO2I(PPh3)2] at room temperature with excess of sodium acetate led to the dimeric complex (μ-O)[ReO(eb)2]2 in which Heb is present as a monoanionic (deprotonated) bidentate with coordination through the thiolate sulfur and ketonic oxygen.
- Full Text:
- Date Issued: 2013
- Authors: Mukiza, Janvier
- Date: 2013
- Subjects: Rhenium , Rhenium compounds , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10437 , http://hdl.handle.net/10948/d1020769
- Description: This study investigated the synthesis of rhenium(I) and rhenium(V) complexes with a variety of multidentate NS, NSO, NO and SO-donor ligands. It also investigated the synthesis of dinuclear dihalogeno- and trihalogeno-bridged rhenium(I) complexes based on the fac-[Re(CO)3]+ core. The reactions of hydrated folic acid with [Re(CO)5X] (X = Cl, Br) were studied, and the complexes [Re(CO)3(H2O)3]+[Re2(μ-X)3CO)6]−.5H2O [X= Br (1), Cl(2)] were isolated. The reaction of orotic acid potassium salt [Re(CO)5Br] was performed, and the complex [Re2(μ-Br)2(CO)8] was isolated. The reaction of bis(piperidin-1- yl)methanone with [Re(CO)5Cl] followed by recrystallisation of the resulting precipitate in dichloromethane/acetontrile resulted in the complex [Re2(μ- Cl)2(CO)6(MeCN)2]. The X-ray crystal structures show that all these complexes display a distorted octahedral geometry around the central rhenium atoms. The reactions of aroylhydrazone-based ligands such as 3-((pyridin- 2yl)methyleneamino)-2,3-dihydro-2-pyridin-2yl)quinazolin-4-(1H)-one (Hppq) and N-(di(pyridin-2-yl)methylene)benzohydrazide (Hdpmb) with [Re(CO)5Cl] were studied and led to the formation of the complexes [Re(CO)3Cl(Hdpmb)] and [Re(CO)3Cl(Hppq)]. The Hdpmb and Hppq coordinated to the fac-[Re(CO)3]+ core as neutral bidentate chalates via the pyridinic nitrogens (for Hdpmb) and via imino and pyridinic nitrogens for Hppq. The X-ray crystal structures show that the geometry around the rhenium in both complexes is a distorted octahedral. The treatment of the dithizone (H2dz) ligand with rhenium(V) precursors containing a triphenylphosphine group (PPh3) led to the decomposition of dithizone. The decomposition product reacted with the triphenylphosphine group and generated a new ligand triphenylphosphazeno-N-phenylmethanethiohydrazide (H2L). The reaction of trans-[ReOX3(PPh3)2] (X = Cl, Br) with dithizone (H2dz) led to the complex [ReO(dz)2][ReO(HL)2]. The reaction of trans-[ReOI2(OEt)(PPh3)2] with H2dz led to the same product. The reaction of cis-[ReO2I(PPh3)2] with H2dz in methanol led to [ReO(dz)2][ReO(HL)2](MeOH)2 in which methanol bonded to HLvia hydrogen bonds. The H2dz was doubly deprotonated and coordinated to the [ReO]3+ moiety via a thiolate sulfur and deprotonated hydrazinic nitrogen to yield [ReO(dz)2]−, while the H2L was singly deprotonated and coordinated to [ReO]3+ moiety via the neutral sulfur atom and deprotonated hydrazinic nitrogen to yield [ReO(HL)2]+. The X-ray crystal structure show that in both [ReO(HL)2]+ and [ReO(dz)2]−, the rhenium atoms are five-coordinated and adopt a distorted squarebased pyramidal geometry. The reaction of thiosemicarbazones such as salcylidene-4- phenylthiosemicarbazide (H3salpt) with cis-[ReO2I(PPh3)2] was investigated and led to the complex [ReO(Hsalpt)(H2salpt)]. The X-ray study reveals that Hsalpt is present as a tridentate chelate coordinating via the thiolate sulfur, imino nitrogen and phenolic oxygen, while H2salpt coordinates as a bidentate chelate via the thiolate sulfur and imino nitrogen atoms. The geometry around rhenium is distorted octahedral. The coordination mode of the benzoylthiourea derivatives 4-tert-butyl-N- (diphenylcarbamothioyl)benzamide (Htpb) and N-(diethylcarbamothioyl)benzamide (Heb) to the [Re2O3]4+ and fac-[Re(CO)3]+ cores were investigated. The reaction of [Re(CO)5Cl] in presence of sodium acetate with Htpb led to the dimeric complex [Re(CO)3(tpb)]2 in which the tpb coordinated to the fac-[Re(CO)3]+ core via the ketonic oxygen and bridging thiolate sulfur. The same reaction with Heb led to the monomeric complex [Re(CO)3(eb)(Heb)], in which the eb coordinates to the fac-[Re(CO)3]+core via thiolate sulfur and ketonic oxygen with Heb binding via the neutral sulfur atom. The reaction of Heb with cis-[ReO2I(PPh3)2] at room temperature with excess of sodium acetate led to the dimeric complex (μ-O)[ReO(eb)2]2 in which Heb is present as a monoanionic (deprotonated) bidentate with coordination through the thiolate sulfur and ketonic oxygen.
- Full Text:
- Date Issued: 2013
Synthesis of fluorescent polymers with coumarin backbones by "click" polymerization
- Authors: Okerio, Jaspher Mosomi
- Date: 2013
- Subjects: Polymerization , Fluorescent polymers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10431 , http://hdl.handle.net/10948/d1020132
- Description: Click chemistry is one of the growing areas of research which is applied in the design and synthesis of a wide range of polymeric architectures. This investigation focuses on the synthesis of fluorescent coumarin based polymers by “click” A-B step growth polymerization process and evaluation of their photophysical properties. Non-fluorescent azide-alkyne functionalized coumarin-based monomers were synthesized in multiple steps from 2,4-dihydroxybenzaldehyde in reasonable yields. Polymers with coumarin backbone were synthesized from azide-alkyne functionalized coumarin monomers via the Cu(I) catalyzed 1,3-dipolar cycloaddition reaction between azides and alkynes, a typical click reaction, to form polymers whose repeating units are connected by a 1,2,3-triazole ring. The structures of the synthesized polymers were confirmed by NMR and FT-IR spectroscopy. Finally, the photophysical properties of the synthesized monomers and polymers were evaluated in DMF. All coumarin based monomers showed reduced fluorescent properties due to the quenching effect from the azido group. Although all polymers absorbed at maximum wavelength of 340 nm, a characteristic for coumarin chromophore, the homo-polymers emitted at a shorter wavelength of 413 nm as compared to the co-polymers which emitted at 421 nm.
- Full Text:
- Date Issued: 2013
- Authors: Okerio, Jaspher Mosomi
- Date: 2013
- Subjects: Polymerization , Fluorescent polymers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10431 , http://hdl.handle.net/10948/d1020132
- Description: Click chemistry is one of the growing areas of research which is applied in the design and synthesis of a wide range of polymeric architectures. This investigation focuses on the synthesis of fluorescent coumarin based polymers by “click” A-B step growth polymerization process and evaluation of their photophysical properties. Non-fluorescent azide-alkyne functionalized coumarin-based monomers were synthesized in multiple steps from 2,4-dihydroxybenzaldehyde in reasonable yields. Polymers with coumarin backbone were synthesized from azide-alkyne functionalized coumarin monomers via the Cu(I) catalyzed 1,3-dipolar cycloaddition reaction between azides and alkynes, a typical click reaction, to form polymers whose repeating units are connected by a 1,2,3-triazole ring. The structures of the synthesized polymers were confirmed by NMR and FT-IR spectroscopy. Finally, the photophysical properties of the synthesized monomers and polymers were evaluated in DMF. All coumarin based monomers showed reduced fluorescent properties due to the quenching effect from the azido group. Although all polymers absorbed at maximum wavelength of 340 nm, a characteristic for coumarin chromophore, the homo-polymers emitted at a shorter wavelength of 413 nm as compared to the co-polymers which emitted at 421 nm.
- Full Text:
- Date Issued: 2013
Synthesis of fluorescent polymers with pendant triazole-substituted coumarin side-chains via a combination of click chemistry and raft-mediated polymerization
- Authors: Wali, Nwabisa Whitney
- Date: 2013
- Subjects: Fluorescent polymers , Polymerization , Macromolecules -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10432 , http://hdl.handle.net/10948/d1020142
- Description: This research project focuses on the synthesis of fluorescent polymers with pendant triazole-substituted coumarin side chain units. Copper(I)-catalyzed Huisgen’s 1,3-dipolar cycloaddition of alkynes with azides to form a 1,2,3-triazole ring, a typical example of “click” reaction, has been utilized for the synthesis of a novel vinyl monomer, 2-oxo-3-(4- vinyl-1H-1,2,3-triazol-1-yl)-2H-chromen-7-yl acetate 62. The monomer and its precursors were synthesised and characterized using 1D- and 2D-NMR and FT-IR. Coumarin-containing triazole polymers were synthesised using free radical polymerization. Reversible Addition-Fragmentation Chain Transfer (RAFT)-mediated polymerization was used to synthesise well defined coumarin-containing triazole polymers with moderate PDI values. The polymers were characterised using 1H-NMR and FT-IR. Modelling of the monomer precursor 61 and the monomer 62 at DFT level of approximation provided useful insights into possible conformations adopted by the monomer precursor 61 and the monomer 62. The photophysical properties of the novel monomer and the synthesised polymers were investigated in a polar solvent.
- Full Text:
- Date Issued: 2013
- Authors: Wali, Nwabisa Whitney
- Date: 2013
- Subjects: Fluorescent polymers , Polymerization , Macromolecules -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10432 , http://hdl.handle.net/10948/d1020142
- Description: This research project focuses on the synthesis of fluorescent polymers with pendant triazole-substituted coumarin side chain units. Copper(I)-catalyzed Huisgen’s 1,3-dipolar cycloaddition of alkynes with azides to form a 1,2,3-triazole ring, a typical example of “click” reaction, has been utilized for the synthesis of a novel vinyl monomer, 2-oxo-3-(4- vinyl-1H-1,2,3-triazol-1-yl)-2H-chromen-7-yl acetate 62. The monomer and its precursors were synthesised and characterized using 1D- and 2D-NMR and FT-IR. Coumarin-containing triazole polymers were synthesised using free radical polymerization. Reversible Addition-Fragmentation Chain Transfer (RAFT)-mediated polymerization was used to synthesise well defined coumarin-containing triazole polymers with moderate PDI values. The polymers were characterised using 1H-NMR and FT-IR. Modelling of the monomer precursor 61 and the monomer 62 at DFT level of approximation provided useful insights into possible conformations adopted by the monomer precursor 61 and the monomer 62. The photophysical properties of the novel monomer and the synthesised polymers were investigated in a polar solvent.
- Full Text:
- Date Issued: 2013
Synthesis, optical and morphological characterization of CdSe/ZnSe quantum dots for cytotoxicity studies
- Authors: Nkaule, Anati Nomxolisi
- Date: 2013
- Subjects: Quantum dots , Quantum dots -- Optical properties
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10434 , http://hdl.handle.net/10948/d1020637
- Description: Colon cancer (CC) ranks high in morbidity and mortality amongst the most frequent occurring cancers worldwide. Mortality rates are mostly caused by mis-diagnosis and the poor efficacy of treatment. The aim of this study was to enhance our insights of quantum dots, for early detection and targeted drug delivery, thereby reducing toxicity to normal cells and reducing side effects that are caused by previous colon cancer medicine. The synthesis, characterization and cytotoxicity studies of CdSe/ZnSe quantum dots (QDs), nanocrystals are reported. Toxicological properties of the Cd2+ core are reduced by capping quantum dots with ZnSe, varying chain length and functional group ligands. Fluorescence wavelength and their size is improved by varying Cd2+ source and varying nanocrystal synthesis growth temperature. CdSe/ZnSe quantum dots are characterized with FT-IR to elucidate their structure. High-resolution transmission electron microscopy (HRTEM), X-Ray Diffraction (EDX), Photoluminescence spectroscopy (PL) and Ultraviolet-visible spectroscopy (UV-Vis) are used to measure their size and composition. Ligand exchange reactions are conducted with the use of 3-Mercaptopropanoic acid (3-MPA) to facilitate bio-compatibility and stability of CdSe/ZnSe QDs. Temperature stability of various ligand capped and stabilized CdSe/ZnSe QDs are measured by using thermogravimetric analysis (TGA). Caco-2 cell line is cultured from colon cancer, and cytotoxic studies are conducted to test for cell viability of various capped 3-Mercaptopropanoic acid (3-MPA) CdSe/ZnSe quantum dots at various concentrations. Myristic acid capped CdSe/ZnSe quantum dots produce high fluorescing mono-disperse quantum dots. The capping material, synthesis temperature and Cd2+ source of CdSe/ZnSe QDs affect fluorescence wavelength and thermal stability of quantum dots. Fluorescence wavelength is improved by using CdCl2.7H2O source of Cd2+. Cytotoxicity was found to be dependent on the concentration and the capping material of quantum dots. CdSe/ZnSe quantum dots toxicity is adjusted and reduced by varying the length, size and type of the capping ligand on the surface of quantum dots.
- Full Text:
- Date Issued: 2013
- Authors: Nkaule, Anati Nomxolisi
- Date: 2013
- Subjects: Quantum dots , Quantum dots -- Optical properties
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10434 , http://hdl.handle.net/10948/d1020637
- Description: Colon cancer (CC) ranks high in morbidity and mortality amongst the most frequent occurring cancers worldwide. Mortality rates are mostly caused by mis-diagnosis and the poor efficacy of treatment. The aim of this study was to enhance our insights of quantum dots, for early detection and targeted drug delivery, thereby reducing toxicity to normal cells and reducing side effects that are caused by previous colon cancer medicine. The synthesis, characterization and cytotoxicity studies of CdSe/ZnSe quantum dots (QDs), nanocrystals are reported. Toxicological properties of the Cd2+ core are reduced by capping quantum dots with ZnSe, varying chain length and functional group ligands. Fluorescence wavelength and their size is improved by varying Cd2+ source and varying nanocrystal synthesis growth temperature. CdSe/ZnSe quantum dots are characterized with FT-IR to elucidate their structure. High-resolution transmission electron microscopy (HRTEM), X-Ray Diffraction (EDX), Photoluminescence spectroscopy (PL) and Ultraviolet-visible spectroscopy (UV-Vis) are used to measure their size and composition. Ligand exchange reactions are conducted with the use of 3-Mercaptopropanoic acid (3-MPA) to facilitate bio-compatibility and stability of CdSe/ZnSe QDs. Temperature stability of various ligand capped and stabilized CdSe/ZnSe QDs are measured by using thermogravimetric analysis (TGA). Caco-2 cell line is cultured from colon cancer, and cytotoxic studies are conducted to test for cell viability of various capped 3-Mercaptopropanoic acid (3-MPA) CdSe/ZnSe quantum dots at various concentrations. Myristic acid capped CdSe/ZnSe quantum dots produce high fluorescing mono-disperse quantum dots. The capping material, synthesis temperature and Cd2+ source of CdSe/ZnSe QDs affect fluorescence wavelength and thermal stability of quantum dots. Fluorescence wavelength is improved by using CdCl2.7H2O source of Cd2+. Cytotoxicity was found to be dependent on the concentration and the capping material of quantum dots. CdSe/ZnSe quantum dots toxicity is adjusted and reduced by varying the length, size and type of the capping ligand on the surface of quantum dots.
- Full Text:
- Date Issued: 2013
Technology transfer of antibacterial oral solid dosage form in a pharmaceutical industry
- Authors: Ramloll, Jason
- Date: 2013
- Subjects: Clinical pharmacology Pharmacy -- Research , Pharmaceutical industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47913 , vital:40398
- Description: Technology transfer (TT) looks at the transfer of intellectual property from one manufacturing site to another. If carried out successfully, a TT can increase the leveraging capability of the company acquiring the intellectual property together with its brand strength. This in turn aids in a decreased time to market of the final dosage form produced. The aim of the research was to assess the TT of an antibacterial oral solid dosage form from one manufacturing site to another. An expected change of manufacturing equipment from a single-pot to a multi-phase system took place due to the equipment available at the receiving unit. The assessment done by the researcher was performed in the capacity of an observer. The assessment of the TT was performed by observing the critical stages during the transfer process, namely the development and validation stages. Prior to the start of the development stage, a characterisation of innovator was performed. At this stage, innovator batches received from the Sending Unit (SU) were characterised to allow for a means of comparison. The development stage allows for the determination of the robustness of the formulation to be used whilst the validation stage will look at the reproducibility of the chosen formulation. During the development stage, small scale trials were manufactured with amendments made to the original formulation. The amendments allowed for a formulation more comparable to the innovator product with regards to its dissolution profile. The comparable batch produced at a small scale was then up-scaled to a production scale batch and these were compared to the innovator products. The amendments made were on the amount of granulation fluid and binder as well as the method of addition of the disintegrant. When a large scale batch comparable to that of the innovator product was produced, the validation stage was started. With the aim of showing reproducibility of the Receiving Unit (RU) at producing large scale batches, three batches were produced. These were tested for all critical parameters, namely through the loss on drying, particle size distribution, hardness, disintegration and dissolution tests and, the results of the tests were compared to the specifications set by the SU. They were also compared to each other, enabling statistical determination of any significant difference across the batches through the use of comparative statistical analyses. Comparison of batches, at the development and validation stage, was done using the dissolution potential of the batches. These were performed through the use of statistical analyses. The RU made use of the similarity factor (F2) to compare the dissolution profiles. For the purpose of this research, the 1-Way analysis of variance was also used, which compared to the similarity factor, took in consideration the level of variance of the batches produced. Results and discussion: During the development stage amendments were made to produce a batch comparable to the innovator product. The amendments that led to the production of a comparable batch consisted of an extra 14 % of granulation fluid as well as 50 % of the disintegrant being added intra-granularly with the other 50 % added extra-granularly. The amendments were added on top of the amount suggested by the SU. This formulation was used and three batches produced consecutively. On comparison to the specifications set by the SU, the three batches were seen to be within the specifications. On comparison to each other, the dissolution profiles were seen to be different. Conclusion and recommendation: The development stage producing batches within the specifications set by the SU but also comparable with regards to its dissolution profile, was seen to be successful. The validation stage was seen to be unsuccessful. Even though the results of the critical parameters were within specifications, when compared to each other, the batches were seen to be significantly different. This led to the research looking at the TT as a whole as being unsuccessful. The researcher then determined what stage could be improved and how this could be done. The various stages seen as having associated problems were determined and ways to mitigate those were determined. A guideline in the form of a flow chart was proposed to aid a manufacturing facility undertaking a TT to shorten the period of time to completion as well as increase the chance of success.
- Full Text:
- Date Issued: 2013
- Authors: Ramloll, Jason
- Date: 2013
- Subjects: Clinical pharmacology Pharmacy -- Research , Pharmaceutical industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47913 , vital:40398
- Description: Technology transfer (TT) looks at the transfer of intellectual property from one manufacturing site to another. If carried out successfully, a TT can increase the leveraging capability of the company acquiring the intellectual property together with its brand strength. This in turn aids in a decreased time to market of the final dosage form produced. The aim of the research was to assess the TT of an antibacterial oral solid dosage form from one manufacturing site to another. An expected change of manufacturing equipment from a single-pot to a multi-phase system took place due to the equipment available at the receiving unit. The assessment done by the researcher was performed in the capacity of an observer. The assessment of the TT was performed by observing the critical stages during the transfer process, namely the development and validation stages. Prior to the start of the development stage, a characterisation of innovator was performed. At this stage, innovator batches received from the Sending Unit (SU) were characterised to allow for a means of comparison. The development stage allows for the determination of the robustness of the formulation to be used whilst the validation stage will look at the reproducibility of the chosen formulation. During the development stage, small scale trials were manufactured with amendments made to the original formulation. The amendments allowed for a formulation more comparable to the innovator product with regards to its dissolution profile. The comparable batch produced at a small scale was then up-scaled to a production scale batch and these were compared to the innovator products. The amendments made were on the amount of granulation fluid and binder as well as the method of addition of the disintegrant. When a large scale batch comparable to that of the innovator product was produced, the validation stage was started. With the aim of showing reproducibility of the Receiving Unit (RU) at producing large scale batches, three batches were produced. These were tested for all critical parameters, namely through the loss on drying, particle size distribution, hardness, disintegration and dissolution tests and, the results of the tests were compared to the specifications set by the SU. They were also compared to each other, enabling statistical determination of any significant difference across the batches through the use of comparative statistical analyses. Comparison of batches, at the development and validation stage, was done using the dissolution potential of the batches. These were performed through the use of statistical analyses. The RU made use of the similarity factor (F2) to compare the dissolution profiles. For the purpose of this research, the 1-Way analysis of variance was also used, which compared to the similarity factor, took in consideration the level of variance of the batches produced. Results and discussion: During the development stage amendments were made to produce a batch comparable to the innovator product. The amendments that led to the production of a comparable batch consisted of an extra 14 % of granulation fluid as well as 50 % of the disintegrant being added intra-granularly with the other 50 % added extra-granularly. The amendments were added on top of the amount suggested by the SU. This formulation was used and three batches produced consecutively. On comparison to the specifications set by the SU, the three batches were seen to be within the specifications. On comparison to each other, the dissolution profiles were seen to be different. Conclusion and recommendation: The development stage producing batches within the specifications set by the SU but also comparable with regards to its dissolution profile, was seen to be successful. The validation stage was seen to be unsuccessful. Even though the results of the critical parameters were within specifications, when compared to each other, the batches were seen to be significantly different. This led to the research looking at the TT as a whole as being unsuccessful. The researcher then determined what stage could be improved and how this could be done. The various stages seen as having associated problems were determined and ways to mitigate those were determined. A guideline in the form of a flow chart was proposed to aid a manufacturing facility undertaking a TT to shorten the period of time to completion as well as increase the chance of success.
- Full Text:
- Date Issued: 2013
The diet of the Subantarctic (A. Tropicalis) and Antarctic (A. Gazella) Fur seal at Marion Island
- Mgibantaka, Nonkoliso Felicia
- Authors: Mgibantaka, Nonkoliso Felicia
- Date: 2013
- Subjects: Southern fur seals -- Feeding and feeds -- Antarctica , Seals (Animals) -- Antarctica , Marine ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10729 , http://hdl.handle.net/10948/d1021104
- Description: Studying the diet of marine top predators is important for understanding the trophic ecology of the predators but also the distribution, abundance and seasonal variation of prey species. Dietary studies on subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) is important for assessing their role as predators in the Southern Ocean. Seven hundred and sixty four scats were collected from an A. tropicalis colony at Cape Davis while 659 scats were collected from an A. gazella colony at Watertunnel stream from April 2006 to March 2010. Hard remains such as fish otoliths and cephalopod beaks were used for identification and quantification of prey. A. tropicalis diet comprised of three animal groups (fish, cephalopod and crustaceans) while A. gazella diet was made up of four animal groups (fish, cephalopods, crustaceans and seabirds). Fish contributed substantially more than other prey items in the diet of both fur seal species over the study period. Both species fed predominantly on fish of the family Myctophidae which constituted a numerical abundance of 98.9 percent in scats for both species combined. A. tropicalis fed on fish prey species from eight families, namely: Myctophidae, Notosudidae, Paralepididae, Nototheniidae, Bathylagidae, Chlorophthalmidae, Sternoptychidae and Photichthyidae while A. gazella fed on fish from six of these families, with Chlorophthalmidae and Photichthyidae not represented in its diet. Cephalopods and crustaceans were found in low numbers in the diet of both seal species and seabird remains were only found in the diet of A. gazella. Numerically, the most dominant species were from the genus Gymnoscopelus followed by Protomyctophum and then Electrona. In the diet of A. tropicalis, Gymnoscopelus contributed 66 percent, Protomyctophum 18 percent and Electrona 5.9 percent while in the diet of A. gazella Gymnoscopelus, Protomyctophum and Electrona contributed 59.43 percent, 20.24 percent and 14.24 percent respectively. Gymnoscopelus species comprised G. piabilis, G. bolini, G. braueri, G. fraseri, and G. nicholsi; Protomyctophum comprised Protomyctophum bolini, P. choriodon and P. tenisoni while Electrona comprised Electrona antarctica, E. carlsbergi and E. subaspera. Gymnoscopelus piabilis was the most dominant species from this genus while Electrona carlsbergi and Protomyctophum tenisoni dominated the genus Electrona and Protomyctophum respectively. The total number of fish species utilised by A. tropicalis was twenty four while twenty three fish species were identified in A. gazella diet. Bathysauropsis gracilis only featured in the diet of A. tropicalis while Lampanyctus ater and Lepidonotothen larseni were only found in the diet of A. gazella. To compare the diet of the seal species between seasons, a year was divided into three seasons, early summer, late summer and winter. Their diet was also compared between years from 2006 to 2010. Myctophid fish species showed substantial seasonal and annual fluctuations in the diet of the two fur seal species. E. carlsbergi, G. nicholsi and G. piabilis increased in numerical abundance in winter while Melectrona ventralis increased in late summer. The numerical abundance of G. fraseri and P. tenisoni increased in early summer. Generally, the two fur seal species fed on the same prey species. However, there was a significant difference when the diet of both fur seals was compared seasonally. There was no significant difference when the diet of A. gazella was compared annually, although such a difference was apparent for A. tropicalis.
- Full Text:
- Date Issued: 2013
- Authors: Mgibantaka, Nonkoliso Felicia
- Date: 2013
- Subjects: Southern fur seals -- Feeding and feeds -- Antarctica , Seals (Animals) -- Antarctica , Marine ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10729 , http://hdl.handle.net/10948/d1021104
- Description: Studying the diet of marine top predators is important for understanding the trophic ecology of the predators but also the distribution, abundance and seasonal variation of prey species. Dietary studies on subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) is important for assessing their role as predators in the Southern Ocean. Seven hundred and sixty four scats were collected from an A. tropicalis colony at Cape Davis while 659 scats were collected from an A. gazella colony at Watertunnel stream from April 2006 to March 2010. Hard remains such as fish otoliths and cephalopod beaks were used for identification and quantification of prey. A. tropicalis diet comprised of three animal groups (fish, cephalopod and crustaceans) while A. gazella diet was made up of four animal groups (fish, cephalopods, crustaceans and seabirds). Fish contributed substantially more than other prey items in the diet of both fur seal species over the study period. Both species fed predominantly on fish of the family Myctophidae which constituted a numerical abundance of 98.9 percent in scats for both species combined. A. tropicalis fed on fish prey species from eight families, namely: Myctophidae, Notosudidae, Paralepididae, Nototheniidae, Bathylagidae, Chlorophthalmidae, Sternoptychidae and Photichthyidae while A. gazella fed on fish from six of these families, with Chlorophthalmidae and Photichthyidae not represented in its diet. Cephalopods and crustaceans were found in low numbers in the diet of both seal species and seabird remains were only found in the diet of A. gazella. Numerically, the most dominant species were from the genus Gymnoscopelus followed by Protomyctophum and then Electrona. In the diet of A. tropicalis, Gymnoscopelus contributed 66 percent, Protomyctophum 18 percent and Electrona 5.9 percent while in the diet of A. gazella Gymnoscopelus, Protomyctophum and Electrona contributed 59.43 percent, 20.24 percent and 14.24 percent respectively. Gymnoscopelus species comprised G. piabilis, G. bolini, G. braueri, G. fraseri, and G. nicholsi; Protomyctophum comprised Protomyctophum bolini, P. choriodon and P. tenisoni while Electrona comprised Electrona antarctica, E. carlsbergi and E. subaspera. Gymnoscopelus piabilis was the most dominant species from this genus while Electrona carlsbergi and Protomyctophum tenisoni dominated the genus Electrona and Protomyctophum respectively. The total number of fish species utilised by A. tropicalis was twenty four while twenty three fish species were identified in A. gazella diet. Bathysauropsis gracilis only featured in the diet of A. tropicalis while Lampanyctus ater and Lepidonotothen larseni were only found in the diet of A. gazella. To compare the diet of the seal species between seasons, a year was divided into three seasons, early summer, late summer and winter. Their diet was also compared between years from 2006 to 2010. Myctophid fish species showed substantial seasonal and annual fluctuations in the diet of the two fur seal species. E. carlsbergi, G. nicholsi and G. piabilis increased in numerical abundance in winter while Melectrona ventralis increased in late summer. The numerical abundance of G. fraseri and P. tenisoni increased in early summer. Generally, the two fur seal species fed on the same prey species. However, there was a significant difference when the diet of both fur seals was compared seasonally. There was no significant difference when the diet of A. gazella was compared annually, although such a difference was apparent for A. tropicalis.
- Full Text:
- Date Issued: 2013
The diversity and distribution patterns of intertidal fish in the Agulhas bioregion
- Authors: Roux, Maryanne
- Date: 2013
- Subjects: Intertidal fishes , Marine fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10723 , http://hdl.handle.net/10948/d1019712
- Description: This study aimed to expand the existing knowledge on the diversity and distribution patterns of intertidal fishes in the Sardinia Bay MPA and adjacent open access areas. It focussed particularly on in intertidal fish communities along the Agulhas Bioregion coast which has been understudied, especially in recent years. Typical resident species belonging to the family Clinidae were the most abundant, conforming to previous studies. Species from the family Gobiidae were the second most abundant in this study but this family was not previously recorded as being abundant. Transient species were unimportant in the current study which is in contrast to previous studies in the region and suggests a change in species composition. Certain transient species utilised intertidal rockpools as part of their nursery areas in the Eastern Cape, as has previously been found around Algoa Bay. A decrease in species richness from east to west was recorded in this study which has been noted by previous authors and the diversity and distribution patterns of the intertidal fish in the current study conformed to patterns found previously. The position of the biogeographic boundary between the Agulhas and Natal Bioregions could not be confirmed but Wavecrest (along the Transkei coastline) appeared to be part of a transition zone rather than a fixed break. More sampling around this area is recommended to determine the location and understand the dynamic nature of this boundary. The fish species were found to be vertically distributed across the shore with most of the resident species being more abundant across the low shore while the transient species were more abundant in the middle to low shore pools. This vertical distribution has been found at many sites around the world. The volume of the pools proved to be the primary controlling factor while the effect of temperature on vertical distribution could not be demonstrated. The benefits of the Sardinia Bay Marine Protected Area on this unexploited community of fishes could not be demonstrated but the long term benefit of protection has yet to be shown. Results from this study suggest that despite the correspondence with general biogeographic trends, the intertidal fish community has changed in composition (at least in terms of transient species) during the last 30 years and the cause for these changes may in part be reduced recruitment from exploited linefish.
- Full Text:
- Date Issued: 2013
- Authors: Roux, Maryanne
- Date: 2013
- Subjects: Intertidal fishes , Marine fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10723 , http://hdl.handle.net/10948/d1019712
- Description: This study aimed to expand the existing knowledge on the diversity and distribution patterns of intertidal fishes in the Sardinia Bay MPA and adjacent open access areas. It focussed particularly on in intertidal fish communities along the Agulhas Bioregion coast which has been understudied, especially in recent years. Typical resident species belonging to the family Clinidae were the most abundant, conforming to previous studies. Species from the family Gobiidae were the second most abundant in this study but this family was not previously recorded as being abundant. Transient species were unimportant in the current study which is in contrast to previous studies in the region and suggests a change in species composition. Certain transient species utilised intertidal rockpools as part of their nursery areas in the Eastern Cape, as has previously been found around Algoa Bay. A decrease in species richness from east to west was recorded in this study which has been noted by previous authors and the diversity and distribution patterns of the intertidal fish in the current study conformed to patterns found previously. The position of the biogeographic boundary between the Agulhas and Natal Bioregions could not be confirmed but Wavecrest (along the Transkei coastline) appeared to be part of a transition zone rather than a fixed break. More sampling around this area is recommended to determine the location and understand the dynamic nature of this boundary. The fish species were found to be vertically distributed across the shore with most of the resident species being more abundant across the low shore while the transient species were more abundant in the middle to low shore pools. This vertical distribution has been found at many sites around the world. The volume of the pools proved to be the primary controlling factor while the effect of temperature on vertical distribution could not be demonstrated. The benefits of the Sardinia Bay Marine Protected Area on this unexploited community of fishes could not be demonstrated but the long term benefit of protection has yet to be shown. Results from this study suggest that despite the correspondence with general biogeographic trends, the intertidal fish community has changed in composition (at least in terms of transient species) during the last 30 years and the cause for these changes may in part be reduced recruitment from exploited linefish.
- Full Text:
- Date Issued: 2013
The effect of in vitro digestion on selected biological activities of Hypoxis sobolifera corms
- Authors: Van Rooyen, Anzel
- Date: 2013
- Subjects: Potatoes -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10344 , http://hdl.handle.net/10948/d1020058
- Description: In South Africa part of the cultural and religious beliefs of the African people is the use of traditional remedies to treat diseases. These remedies are obtained from medicinal plants (Steenkamp, 2003). One of the most frequently traded plants in the Eastern Cape is Hypoxis, commonly known as Afrika patat, or African potato. South African traditional healers instruct patients to brew the fresh Hypoxis corm as a tea and then ingest it (Steenkamp, 2006a). This prompted an investigation into the digestive stability of a traditionally prepared Hypoxis extract. The H. sobolifera extracts were digested using a simulated gastric/small intestinal digestion and their biological activity determined. The hot water H. sobolifera extract before digestion only showed cytotoxic activity against cancer cell lines at very high concentrations which are not likely to be achieved under normal ingestion circumstances. In Chang liver cells on the other hand, chronic exposure to the hot water H. sobolifera extract increased glucose uptake in amounts similar to that of metformin. On the negative side, the glucose utilization stimulation was lost due to the simulated digestion process. The significant inhibition of AGEs by hot water H. sobolifera extract (IC50 of 6.3 Ig/ml) is a very encouraging result as treatment in the management of diabetes. This activity was only slightly reduced by the in vitro digestion process. Also observed was enzyme inhibition activity by traditionally prepared H. sobolifera, with ∝-amylase being inhibited (IC50 of approximately 250 Ig/ml) and therefore preventing or limiting starch breakdown. From the DPPH results it was clear that H. sobolifera, even when digested, is a potent anti-oxidant (IC50 of 134.4 Ig/ml when undigested compared to 162.9 when digested with β-glucosidase added to stomach digestive step). HPLC and TLC experiments revealed that rooperol which has previously been thought to be the compound responsible for the anti-oxidant activity in Hypoxis extracts, was absent from the traditional extract of H. sobolifera and therefore cannot be the sole compound exhibiting anti-oxidant activity; other compounds such as phenolics may be contributing. The phenolic and flavonoid content results revealed very highconcentrations of these compounds in the traditionally prepared H. sobolifera extract. These compounds may therefore play major roles in all of the biological activities observed from treatment with Hypoxis spp. The ROS results yielded interesting and promising results. Using standard or traditionally prepared H. sobolifera extracts, activation of differentiated U937 cells with PMA was greatly enhanced by cotreatment with the extracts, while extracts on their own did not cause significant activation. Future studies should investigate this property of the extracts as a promising immune boosterThe HPLC results showed that hypoxoside was undetectable in the hot water traditional extract and the TLC anti-oxidant experiment proved that rooperol is not present in the hot water traditional extract after treatment with β-glucosidase. This indicates that neither one of the Hypoxis compounds previously believed to be responsible for the biological activities observed are present in the extract when prepared the traditional way. Therefore, the biological activities observed in this study can be attributed to other phytochemical compounds.
- Full Text:
- Date Issued: 2013
- Authors: Van Rooyen, Anzel
- Date: 2013
- Subjects: Potatoes -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10344 , http://hdl.handle.net/10948/d1020058
- Description: In South Africa part of the cultural and religious beliefs of the African people is the use of traditional remedies to treat diseases. These remedies are obtained from medicinal plants (Steenkamp, 2003). One of the most frequently traded plants in the Eastern Cape is Hypoxis, commonly known as Afrika patat, or African potato. South African traditional healers instruct patients to brew the fresh Hypoxis corm as a tea and then ingest it (Steenkamp, 2006a). This prompted an investigation into the digestive stability of a traditionally prepared Hypoxis extract. The H. sobolifera extracts were digested using a simulated gastric/small intestinal digestion and their biological activity determined. The hot water H. sobolifera extract before digestion only showed cytotoxic activity against cancer cell lines at very high concentrations which are not likely to be achieved under normal ingestion circumstances. In Chang liver cells on the other hand, chronic exposure to the hot water H. sobolifera extract increased glucose uptake in amounts similar to that of metformin. On the negative side, the glucose utilization stimulation was lost due to the simulated digestion process. The significant inhibition of AGEs by hot water H. sobolifera extract (IC50 of 6.3 Ig/ml) is a very encouraging result as treatment in the management of diabetes. This activity was only slightly reduced by the in vitro digestion process. Also observed was enzyme inhibition activity by traditionally prepared H. sobolifera, with ∝-amylase being inhibited (IC50 of approximately 250 Ig/ml) and therefore preventing or limiting starch breakdown. From the DPPH results it was clear that H. sobolifera, even when digested, is a potent anti-oxidant (IC50 of 134.4 Ig/ml when undigested compared to 162.9 when digested with β-glucosidase added to stomach digestive step). HPLC and TLC experiments revealed that rooperol which has previously been thought to be the compound responsible for the anti-oxidant activity in Hypoxis extracts, was absent from the traditional extract of H. sobolifera and therefore cannot be the sole compound exhibiting anti-oxidant activity; other compounds such as phenolics may be contributing. The phenolic and flavonoid content results revealed very highconcentrations of these compounds in the traditionally prepared H. sobolifera extract. These compounds may therefore play major roles in all of the biological activities observed from treatment with Hypoxis spp. The ROS results yielded interesting and promising results. Using standard or traditionally prepared H. sobolifera extracts, activation of differentiated U937 cells with PMA was greatly enhanced by cotreatment with the extracts, while extracts on their own did not cause significant activation. Future studies should investigate this property of the extracts as a promising immune boosterThe HPLC results showed that hypoxoside was undetectable in the hot water traditional extract and the TLC anti-oxidant experiment proved that rooperol is not present in the hot water traditional extract after treatment with β-glucosidase. This indicates that neither one of the Hypoxis compounds previously believed to be responsible for the biological activities observed are present in the extract when prepared the traditional way. Therefore, the biological activities observed in this study can be attributed to other phytochemical compounds.
- Full Text:
- Date Issued: 2013