Synthesis of 2,4-Xylidine in continuous flow systems
- Authors: Sagandira, Mellisa Brenda
- Date: 2020
- Subjects: Chemistry, Physical and theoretical -- Research , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49270 , vital:41616
- Description: The continuous flow synthesis of 2,4-xylidine, an important compound in the fine chemical, pharmaceutical as well as the dyes and pigments industries was investigated in this study utilizing 1,3-dimethylbenzene as starting material. The first step involves the highly exothermic nitration of 1,3-dimethylbenzene with mixed acid to afford two nitro isomers, namely 1,3-dimethyl-2-nitrobenzene and 2,4-dimethyl-1-nitrobenzene. Since 2,4-xylidine is the targeted isomer, it is important to get a higher proportion of its nitration precursor 2,4-dimethyl-1-nitrobenzene. A safe and efficient synthesis of 2,4-dimethyl-1-nitrobenzene was therefore developed in continuous flow. This was aided by the micro reactor’s large surface area-to-volume ratio, one of the many features of continuous flow synthesis that enable rapid dissipation of heat allowing exothermic reactions to be conducted safely at ambient or higher temperatures. Two nitration protocols were developed using different micro reactors, a sonicated 1 ml PTFE tube reactor and 2 ml Uniqsis chip reactor. Using a sonicated PTFE tube reactor at room temperature and 15 min residence time, 2,4-dimethyl-1-nitrobenzene was afforded in 100 % conversion and 80 % selectivity. An increase in selectivity to 95 % and 90 % conversion towards 2,4-dimethyl-1-nitrobenzene was achieved using a 2 ml Uniqsis chip reactor at room temperature in 6 min residence time. This was accounted for due to efficient mixing of the two phases brought about by the reactor’s mixing structures, which are designed to create turbulent mixing. Scale-up synthesis of 2,4-dimethyl-1-nitrobenzene was conducted in a 4.5 ml LTF-XXL-ST-04 reactor at room temperature and 6 min residence time affording 90 % conversion and 95 % selectivity with a throughput of 16.6 g/h. Subsequently, reduction of 2,4-dimethyl-1-nitrobenzene to afford 2,4-xylidine was investigated in a 1 ml PTFE tube reactor (0.8 mm ID) using hydrazine in the presence of iron (III) 2,4-pentanedionate catalyst. Maximum conversion of 75 % was achieved at 170 °C in 15 min residence time. A more efficient reduction protocol was developed in a 2.7 ml packed column reactor (10 mm ID) using hydrazine in the presence of Pd/C at 50 °C and 2.5 min residence time affording 94 % conversion towards 2,4-xylidine. Lastly, multistep synthesis of 2,4-xylidine was performed using optimum conditions found using the 2 ml Uniqsis chip reactor and 2.7 ml packed column reactor with the incorporation of a phase separator. Joining the two reactors into a single continuous step afforded 100 % conversion and 95 % selectivity towards 2,4-xylidine with 8 min total residence time. Nitration of other organic compounds followed by reduction of the resultant nitro products was also investigated under respective optimum conditions determined for nitration of 1,3-dimethylbenzene and reduction of 2,4-dimethyl-1-nitrobenzene.
- Full Text:
- Date Issued: 2020
- Authors: Sagandira, Mellisa Brenda
- Date: 2020
- Subjects: Chemistry, Physical and theoretical -- Research , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49270 , vital:41616
- Description: The continuous flow synthesis of 2,4-xylidine, an important compound in the fine chemical, pharmaceutical as well as the dyes and pigments industries was investigated in this study utilizing 1,3-dimethylbenzene as starting material. The first step involves the highly exothermic nitration of 1,3-dimethylbenzene with mixed acid to afford two nitro isomers, namely 1,3-dimethyl-2-nitrobenzene and 2,4-dimethyl-1-nitrobenzene. Since 2,4-xylidine is the targeted isomer, it is important to get a higher proportion of its nitration precursor 2,4-dimethyl-1-nitrobenzene. A safe and efficient synthesis of 2,4-dimethyl-1-nitrobenzene was therefore developed in continuous flow. This was aided by the micro reactor’s large surface area-to-volume ratio, one of the many features of continuous flow synthesis that enable rapid dissipation of heat allowing exothermic reactions to be conducted safely at ambient or higher temperatures. Two nitration protocols were developed using different micro reactors, a sonicated 1 ml PTFE tube reactor and 2 ml Uniqsis chip reactor. Using a sonicated PTFE tube reactor at room temperature and 15 min residence time, 2,4-dimethyl-1-nitrobenzene was afforded in 100 % conversion and 80 % selectivity. An increase in selectivity to 95 % and 90 % conversion towards 2,4-dimethyl-1-nitrobenzene was achieved using a 2 ml Uniqsis chip reactor at room temperature in 6 min residence time. This was accounted for due to efficient mixing of the two phases brought about by the reactor’s mixing structures, which are designed to create turbulent mixing. Scale-up synthesis of 2,4-dimethyl-1-nitrobenzene was conducted in a 4.5 ml LTF-XXL-ST-04 reactor at room temperature and 6 min residence time affording 90 % conversion and 95 % selectivity with a throughput of 16.6 g/h. Subsequently, reduction of 2,4-dimethyl-1-nitrobenzene to afford 2,4-xylidine was investigated in a 1 ml PTFE tube reactor (0.8 mm ID) using hydrazine in the presence of iron (III) 2,4-pentanedionate catalyst. Maximum conversion of 75 % was achieved at 170 °C in 15 min residence time. A more efficient reduction protocol was developed in a 2.7 ml packed column reactor (10 mm ID) using hydrazine in the presence of Pd/C at 50 °C and 2.5 min residence time affording 94 % conversion towards 2,4-xylidine. Lastly, multistep synthesis of 2,4-xylidine was performed using optimum conditions found using the 2 ml Uniqsis chip reactor and 2.7 ml packed column reactor with the incorporation of a phase separator. Joining the two reactors into a single continuous step afforded 100 % conversion and 95 % selectivity towards 2,4-xylidine with 8 min total residence time. Nitration of other organic compounds followed by reduction of the resultant nitro products was also investigated under respective optimum conditions determined for nitration of 1,3-dimethylbenzene and reduction of 2,4-dimethyl-1-nitrobenzene.
- Full Text:
- Date Issued: 2020
Synthesis, characterisation and antitumour activities of lanthanide complexes with hydrazones and carboxylic acid ligands
- Authors: Madanhire, Tatenda
- Date: 2020
- Subjects: Organic acids
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48456 , vital:40878
- Description: The tridentate hydrazone ligands, (E)-N'-(2-hydroxybenzylidene)benzohydrazide (H2phen) and (E)-N'-(2-hydroxybenzylidene)nicotinohydrazide (H2Nic), were synthesised and complexed to Ln(III) acetates. The centrosymmetric, acetato-bridged dinuclear coordination compounds with the formulae, [La2(Hphen)2(OAc)4(H2O)2]·DMF·H2O (1), [Ln2(HNic)2(OAc)4(H2O)2]·DMF·H2O (Ln = La (2) and Nd (3)) and [Ln2(HNic)2(OAc)4(H2O)2]·DMF (Ln = Er (4) and Yb (5)) were isolated and characterised by elemental analyses, IR spectroscopy, UV-Vis spectroscopy, X-ray diffraction studies and SHAPE 2.1. The nine-coordinate complexes 1–3 crystallise in the triclinic space group P-1, with the metal centres having the distorted spherical capped square antiprism geometry (C4v), while the eight-coordinate Er(III) and Yb(III) complexes (monoclinic system, space group P21/c) display the geometry of distorted triangular dodecahedron (D2d). Geometry optimisation of the monoanionic forms of the hydrazone ligands (Hphen– and HNic– ) were performed using Density Functional Theory (DFT) with Becke’s three parameter hybrid method and correlation functional of Lee, Yang and Parr (B3LYP) with augcc-pVTZ basis set. Natural population analysis (NPA) and molecular electrostatic potential (MEP) maps indicated that the most preferred sites for electrophilic attack in the anionic ligands are the phenolate and carbonyl oxygens, and the azomethine nitrogens. The evaluation of the cytotoxic activity of the compounds on breast cancer (MCF-7), the endometrial carcinoma (HEC-1A) and the human monocytic (THP-1) cell lines using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) assay revealed that the hydrazone ligands and complexes 1–4 are partially cytotoxic against MCF-7 cells, while the Schiff bases and complexes 3–5 significantly inhibit cell growth in HEC-1A cells. The complexation reactions of Ce(III), Nd(III), Gd(III) and Er(III) with the chelating/ bridging monoanionic ligand N-(2,6-dimethylphenyl)oxamate (Hpma– ) in basic media were performed in view of the potential applications of oxamate derivatives as cytotoxic agents. The coordination compounds were characterised by different Abstract T. Madanhire Nelson Mandela University xxvi physico-chemical techniques: elemental analysis, conductivity measurements, IR, 1 H NMR and UV-Vis-NIR spectroscopy. The anionic Hpma– was obtained through conversion of the proligand ethyl (2,6-dimethylphenylcarbamoyl)formate (Hdmp). The reactions afforded lanthanide(III)–oxamate coordination polymers of formulae: {[Ln(Hpma)3(MeOH)(H2O)]∙2MeOH}n (Ln = Ce (1) and Nd (2)), {[Gd2(Hpma)6(MeOH)4]∙6MeOH}n (3), {[Er2(Hpma)6(MeOH)(H2O)3]∙2MeOH}n (4) and [Ln2Na2(Hpma)8(EtOH)(H2O)6]n (Ln = Nd (5) and Gd (6)). The polymeric complexes feature Ln-Hpma moieties bridged by μ2-η 1 :η 1 :η 1 Hpma– , giving onedimensional zig-zag chains of the –Ln–O–C–O–Ln– type. Atomic charge analysis and the MEP map of the Hpma– moiety done using the DFT/B3LYP method were found to be consistent with the chelating and bridging modes of the anionic ligand through all the oxygen atoms. The evaluation of the cytotoxic activities of the metal salts, the proligand and the novel lanthanide complexes on MCF-7, HEC-1A and THP-1 cell lines revealed that only the rare-earth metal salts [Ce(NO3)3∙6H2O] and [Nd(NO3)3∙6H2O] showed modest cytotoxicity against MCF-7 and HEC-1A cells, respectively.
- Full Text:
- Date Issued: 2020
- Authors: Madanhire, Tatenda
- Date: 2020
- Subjects: Organic acids
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48456 , vital:40878
- Description: The tridentate hydrazone ligands, (E)-N'-(2-hydroxybenzylidene)benzohydrazide (H2phen) and (E)-N'-(2-hydroxybenzylidene)nicotinohydrazide (H2Nic), were synthesised and complexed to Ln(III) acetates. The centrosymmetric, acetato-bridged dinuclear coordination compounds with the formulae, [La2(Hphen)2(OAc)4(H2O)2]·DMF·H2O (1), [Ln2(HNic)2(OAc)4(H2O)2]·DMF·H2O (Ln = La (2) and Nd (3)) and [Ln2(HNic)2(OAc)4(H2O)2]·DMF (Ln = Er (4) and Yb (5)) were isolated and characterised by elemental analyses, IR spectroscopy, UV-Vis spectroscopy, X-ray diffraction studies and SHAPE 2.1. The nine-coordinate complexes 1–3 crystallise in the triclinic space group P-1, with the metal centres having the distorted spherical capped square antiprism geometry (C4v), while the eight-coordinate Er(III) and Yb(III) complexes (monoclinic system, space group P21/c) display the geometry of distorted triangular dodecahedron (D2d). Geometry optimisation of the monoanionic forms of the hydrazone ligands (Hphen– and HNic– ) were performed using Density Functional Theory (DFT) with Becke’s three parameter hybrid method and correlation functional of Lee, Yang and Parr (B3LYP) with augcc-pVTZ basis set. Natural population analysis (NPA) and molecular electrostatic potential (MEP) maps indicated that the most preferred sites for electrophilic attack in the anionic ligands are the phenolate and carbonyl oxygens, and the azomethine nitrogens. The evaluation of the cytotoxic activity of the compounds on breast cancer (MCF-7), the endometrial carcinoma (HEC-1A) and the human monocytic (THP-1) cell lines using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) assay revealed that the hydrazone ligands and complexes 1–4 are partially cytotoxic against MCF-7 cells, while the Schiff bases and complexes 3–5 significantly inhibit cell growth in HEC-1A cells. The complexation reactions of Ce(III), Nd(III), Gd(III) and Er(III) with the chelating/ bridging monoanionic ligand N-(2,6-dimethylphenyl)oxamate (Hpma– ) in basic media were performed in view of the potential applications of oxamate derivatives as cytotoxic agents. The coordination compounds were characterised by different Abstract T. Madanhire Nelson Mandela University xxvi physico-chemical techniques: elemental analysis, conductivity measurements, IR, 1 H NMR and UV-Vis-NIR spectroscopy. The anionic Hpma– was obtained through conversion of the proligand ethyl (2,6-dimethylphenylcarbamoyl)formate (Hdmp). The reactions afforded lanthanide(III)–oxamate coordination polymers of formulae: {[Ln(Hpma)3(MeOH)(H2O)]∙2MeOH}n (Ln = Ce (1) and Nd (2)), {[Gd2(Hpma)6(MeOH)4]∙6MeOH}n (3), {[Er2(Hpma)6(MeOH)(H2O)3]∙2MeOH}n (4) and [Ln2Na2(Hpma)8(EtOH)(H2O)6]n (Ln = Nd (5) and Gd (6)). The polymeric complexes feature Ln-Hpma moieties bridged by μ2-η 1 :η 1 :η 1 Hpma– , giving onedimensional zig-zag chains of the –Ln–O–C–O–Ln– type. Atomic charge analysis and the MEP map of the Hpma– moiety done using the DFT/B3LYP method were found to be consistent with the chelating and bridging modes of the anionic ligand through all the oxygen atoms. The evaluation of the cytotoxic activities of the metal salts, the proligand and the novel lanthanide complexes on MCF-7, HEC-1A and THP-1 cell lines revealed that only the rare-earth metal salts [Ce(NO3)3∙6H2O] and [Nd(NO3)3∙6H2O] showed modest cytotoxicity against MCF-7 and HEC-1A cells, respectively.
- Full Text:
- Date Issued: 2020
Synthesis, crystal structures and characterization of metal–organic framework architectures involving dinuclear copper(ii) benzoic acid derivative complexes
- Authors: Ndima, Lubabalo
- Date: 2020
- Subjects: Supramolecular chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46783 , vital:39657
- Description: Structural copper(II) complexes with aromatic carboxylic acids show a wide spectrum of coordination schemes. Studies of dicopper(II) carboxylates have been associated with a variety of interests for their catalytic, biological and magnetic applications [1]. Various novel dinuclear copper(II) complexes [Cu2(X-benzoate)4L2] with varying substituents (X = CH3, F, Cl, Br, I, NO2 & OCH3) with a desired octahedral geometry have been synthesized. The various complexes were characterized by single crystal X-ray diffraction studies, spectroscopic and thermal methods (UV/Vis, FTIR and TGA, DSC). In most cases, the structures consists of centrosymmetric dimers in which the Cu atoms show a square pyramidal CuO5 coordination. In all cases, dimeric paddle wheel complexes where two copper(II) ions are held together by four benzoates (forming syn– syn bridges between the copper atoms) and the apical coordination site occupied by a solvent ligand (L) or supramolecular linker were obtained. The dimers are extended into 1D chains that result from hydrogen bonding between the coordinated methanol (solvent ligand) on one Cu(II) and the carboxylate group on an adjacent Cu(II) dimer, including interactions arising from various substituents. π–π Stacking interactions are found to be present in the various crystal structures forming 3D supramolecular array. FTIR and UV/Vis spectra of each complex have shown how the resonance and inductive effect of each substituent affects spectral data of each complex.
- Full Text:
- Date Issued: 2020
- Authors: Ndima, Lubabalo
- Date: 2020
- Subjects: Supramolecular chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46783 , vital:39657
- Description: Structural copper(II) complexes with aromatic carboxylic acids show a wide spectrum of coordination schemes. Studies of dicopper(II) carboxylates have been associated with a variety of interests for their catalytic, biological and magnetic applications [1]. Various novel dinuclear copper(II) complexes [Cu2(X-benzoate)4L2] with varying substituents (X = CH3, F, Cl, Br, I, NO2 & OCH3) with a desired octahedral geometry have been synthesized. The various complexes were characterized by single crystal X-ray diffraction studies, spectroscopic and thermal methods (UV/Vis, FTIR and TGA, DSC). In most cases, the structures consists of centrosymmetric dimers in which the Cu atoms show a square pyramidal CuO5 coordination. In all cases, dimeric paddle wheel complexes where two copper(II) ions are held together by four benzoates (forming syn– syn bridges between the copper atoms) and the apical coordination site occupied by a solvent ligand (L) or supramolecular linker were obtained. The dimers are extended into 1D chains that result from hydrogen bonding between the coordinated methanol (solvent ligand) on one Cu(II) and the carboxylate group on an adjacent Cu(II) dimer, including interactions arising from various substituents. π–π Stacking interactions are found to be present in the various crystal structures forming 3D supramolecular array. FTIR and UV/Vis spectra of each complex have shown how the resonance and inductive effect of each substituent affects spectral data of each complex.
- Full Text:
- Date Issued: 2020
Synthesis, crystal structures and molecular modelling of rare earth complexes with bis(2-pyridylmethyl)amine and its derivatives : a quantum chemical investigation of ligand conformational space, complex intramolecular rearrangement and stability
- Authors: Matthews, Cameron
- Date: 2020
- Subjects: Rare earths , Complex compounds , Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46229 , vital:39517
- Description: Limited research has been performed on the coordination behaviour of hybrid aliphatic and heterocyclic polyamines with trivalent rare earth elements. The rare earth coordination properties of several Nalkylated derivatives of the tridentate ligand bis(2-pyridylmethyl)amine (DPA, HL1) backbone - involving the rare earth elements Y, La-Nd, Sm, Eu and Tb-Lu - have been investigated in this study However, the structural and energetic characteristics of DPA coordination with rare earth elements (REE) have not been studied thus far. Potential applications of DPA-based rare earth complexes are primarily dependent on their electronic and magnetic characteristics, which are affected weakly by the coordination environment, where potential applications may include use as Lanthanide Shift Reagents (LSR), Luminescence probes and small-molecule magnets (SMM). A systematic conformational search of DPA was carried out in this study in order to identify the global minimum conformer and for comparison of the free and coordinated geometries, using the M06(D3) functional belonging to the Density Functional Theory (DFT) family of model chemistries. An understanding of the aforementioned would play an important role in analysis of bulk characterization and the prediction of the reactivity of DPA. Final geometries and electronic energies were obtained from the ‘domain based local pair natural orbital’ (DLPNO)-Møller-Plesset and -coupled cluster theoretical methods, as follows: DLPNO-CCSD(T0)/aug-cc-pVQZ//DLPNO-MP2/aug-cc-pVTZ. Fifteen Single-crystal X-ray diffractometer (SC-XRD) crystal structures of mononuclear rare earth chloride coordination complexes with DPA (RE = La-Nd, Sm, Eu, Tb-Lu and Y) were obtained and geometrically analysed in this study. Three isostructural series of constitutional isomers were identified, consisting of one series of nine-coordinate molecule (M1) and two series of eight-coordinate ion pairs (M2 and M3). This conformational diversity is most likely due the flexible nature of the DPA backbone, as well as the additional stability gained from reduced coordination spheres as a function of decreasing rare earth ionic radii across the lanthanide series (Lanthanide contraction). A Quantum Theory of Atoms-in-Molecules (QTAIM) topological analysis was performed in order to identify and characterise potential hydrogen bonding interactions in H-optimised crystal structures. The crystal structures of five dinuclear (RE = Tb-Tm) and two tetranuclear (RE = Yb and Lu) rare earth chloride complexes with DPA have also been structurally analysed. Furthermore, one mononuclear (RE = Dy), two dinuclear complexes (RE = Dy and Lu) with EtDPA, and one mononuclear complex with the DPA-derivative HL4 (RE = Dy) were structurally characterised. A DFT study of the theoretical interconversion of one real- and two hypothetical- mononuclear lanthanum containing isostructural series (cf. aforementioned crystal structures) was undertaken in order to gain a deeper understanding of the processes involved, in terms of the participating minimum energy paths (MEPs), intermediates and transition states – as determined via the Nudged-Elastic Band (NEB) procedure. This hypothesis is supported by the well-known conformational lability of rare earth complexes, due to the weak/minor covalency of their coordination bonds. An attempt was made to determine the respective energies of one real- and two hypothetical diamagnetic or ‘closed-shell’ constitutional isomers containing the rare earth ions La3+(M1), Y3+(M2) and Lu3+ (M3). It was assumed that the most stable isomers have a greater probability of being observed as the asymmetric unit of the complex crystal structure – assuming weak contributions of lattice or intermolecular interactions towards the geometry of the asymmetric unit.
- Full Text:
- Date Issued: 2020
- Authors: Matthews, Cameron
- Date: 2020
- Subjects: Rare earths , Complex compounds , Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46229 , vital:39517
- Description: Limited research has been performed on the coordination behaviour of hybrid aliphatic and heterocyclic polyamines with trivalent rare earth elements. The rare earth coordination properties of several Nalkylated derivatives of the tridentate ligand bis(2-pyridylmethyl)amine (DPA, HL1) backbone - involving the rare earth elements Y, La-Nd, Sm, Eu and Tb-Lu - have been investigated in this study However, the structural and energetic characteristics of DPA coordination with rare earth elements (REE) have not been studied thus far. Potential applications of DPA-based rare earth complexes are primarily dependent on their electronic and magnetic characteristics, which are affected weakly by the coordination environment, where potential applications may include use as Lanthanide Shift Reagents (LSR), Luminescence probes and small-molecule magnets (SMM). A systematic conformational search of DPA was carried out in this study in order to identify the global minimum conformer and for comparison of the free and coordinated geometries, using the M06(D3) functional belonging to the Density Functional Theory (DFT) family of model chemistries. An understanding of the aforementioned would play an important role in analysis of bulk characterization and the prediction of the reactivity of DPA. Final geometries and electronic energies were obtained from the ‘domain based local pair natural orbital’ (DLPNO)-Møller-Plesset and -coupled cluster theoretical methods, as follows: DLPNO-CCSD(T0)/aug-cc-pVQZ//DLPNO-MP2/aug-cc-pVTZ. Fifteen Single-crystal X-ray diffractometer (SC-XRD) crystal structures of mononuclear rare earth chloride coordination complexes with DPA (RE = La-Nd, Sm, Eu, Tb-Lu and Y) were obtained and geometrically analysed in this study. Three isostructural series of constitutional isomers were identified, consisting of one series of nine-coordinate molecule (M1) and two series of eight-coordinate ion pairs (M2 and M3). This conformational diversity is most likely due the flexible nature of the DPA backbone, as well as the additional stability gained from reduced coordination spheres as a function of decreasing rare earth ionic radii across the lanthanide series (Lanthanide contraction). A Quantum Theory of Atoms-in-Molecules (QTAIM) topological analysis was performed in order to identify and characterise potential hydrogen bonding interactions in H-optimised crystal structures. The crystal structures of five dinuclear (RE = Tb-Tm) and two tetranuclear (RE = Yb and Lu) rare earth chloride complexes with DPA have also been structurally analysed. Furthermore, one mononuclear (RE = Dy), two dinuclear complexes (RE = Dy and Lu) with EtDPA, and one mononuclear complex with the DPA-derivative HL4 (RE = Dy) were structurally characterised. A DFT study of the theoretical interconversion of one real- and two hypothetical- mononuclear lanthanum containing isostructural series (cf. aforementioned crystal structures) was undertaken in order to gain a deeper understanding of the processes involved, in terms of the participating minimum energy paths (MEPs), intermediates and transition states – as determined via the Nudged-Elastic Band (NEB) procedure. This hypothesis is supported by the well-known conformational lability of rare earth complexes, due to the weak/minor covalency of their coordination bonds. An attempt was made to determine the respective energies of one real- and two hypothetical diamagnetic or ‘closed-shell’ constitutional isomers containing the rare earth ions La3+(M1), Y3+(M2) and Lu3+ (M3). It was assumed that the most stable isomers have a greater probability of being observed as the asymmetric unit of the complex crystal structure – assuming weak contributions of lattice or intermolecular interactions towards the geometry of the asymmetric unit.
- Full Text:
- Date Issued: 2020
The application value and most appropriate mapping scales for site classification and evaluation in the South African forest industry
- Authors: Sibhakabhaka, Thembisa
- Date: 2020
- Subjects: Forests and forestry -- South Africa , Forest products industry -- South Africa Geographic information systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49281 , vital:41617
- Description: The South African forest industry is challenged with aspects related to socio-political developments, conflicts with biodiversity values, uncertainties related to climate change, several biotic and abiotic risks, and a limited potential for expansion. For this reason, efficient and optimal land-use is essential, which requires sustainable forest management practices and accurate information and decision support systems. Tree growth patterns, productivity and risks vary according to changes in geology, topography, climate and soil conditions. It is therefore required that forest managers, planners and researchers have a conceptual understanding of the concept of forest site classification and evaluation. This is essential not only for improved levels resilience, but also to maintain a competitive industry in terms of socio-economic and environmental performance. The first chapter of the study aimed to investigate the perceptions and interpretations of a range of representative stakeholders from the forestry industry regarding the value, shortcomings, requirements and design of forest site classification and evaluation systems in use in the local industry. A questionnaire with 16 questions was used for this purpose, and data was analysed using quantitative and qualitative techniques. Results indicated variable levels of understanding amongst respondents of terminology and the nature of systems used in industry. Trends in responses were influenced by the background of stakeholders, the role of individuals in the value chain of forestry as well as past experiences. The perceived importance and value of potential site evaluation applications varied substantially amongst different stakeholders. Results point towards a narrow-focus application for site classification and evaluation systems for site-specific forestry, with a lesser regard with aspects of risk management and environmental performance. Several technical aspects related to site variables, data resolution and scale of presentation were also questioned by participants. Listed priorities for research and development include the integration of site classification and evaluation systems into corporate information systems, modernizing technology, more appropriate site evaluation models, advanced climatic modelling and the development of indices of water and nutrient availability related to forest productivity. There is general agreement for the development of a national forest site classification system. The value of this part of the study lies in the contribution it makes towards our knowledge of stakeholder perceptions regarding site classification and evaluation, as well as the valuable comments made by participants for the refinement of such systems that can serve as indicators for entities involved in education, governance and strategic forest management. The second data chapter of the study involved the development of high-resolution site classification systems in the form of Site Types for two selected study areas in South Africa, one located in Mpumalanga, and the other in the southern Cape. This enabled a comparative analysis with existing low-resolution Land Type classifications that were developed by different authors for the same two study areas, in terms of its reliability, accuracy and general usefulness for applications in the plantation forestry value chain. The comparison of the two types of classification systems revealed that the climate data forming part of the database were of equal accuracy and resolution. However, an obvious difference was detected in the information pertaining to soil in terms of descriptive and spatial data. In the case of both study areas, the Site Type classification systems revealed many soil and geological features that were not indicated by the lower-resolution Land Type systems. Variation in characteristics related to parent material, soil classification, soil depth, intensity of subsoil wetness and soil organic matter were not adequately reflected in these systems. This can potentially have important implications for applications such as species choice, predictions of yield, nutrient optimization, ratings of soil resilience, biodiversity management and evaluations for carbon sequestration potential. The data forming part of this study indicate that although Land Type classification systems can provide valuable support at strategic levels of planning and management, there are several limitations for use at finer scales of resolution. The final chapter of the study includes an investigation and qualitative comparison of the usefulness of Site Type vs. Land Type classification systems, based on existing knowledge in the industry. The two systems are compared in terms of its input towards the following applications: site-species matching, timber yield prediction, site amelioration / site preparation requirements, nutrient management requirements, vegetation management / weed control, management of pests and diseases, determination of risk for soil compaction, soil erosion and nutrient loss, decision making regarding forest engineering operations, prediction of wood / fibre properties, biodiversity management and lastly planning of research activities / priorities. This analysis indicated that applications that require data on only climate and general soil patterns can be supported with equal success by both types of site classification systems. On the other hand, in cases where high-resolution data on site factors are required, Land Type classification systems had numerous shortcomings and received a much lower rating of suitability. The outcome of the study can provide guidance on the development and design of future site classification and evaluation systems for the South African forest industry. High-resolution databases of key site factors should receive priority, together with the development of decision support systems based on causal relationships. This will contribute to the resilience and sustainability of an industry that is increasingly confronted with questions related to the placement, design and management of forest plantations.
- Full Text:
- Date Issued: 2020
- Authors: Sibhakabhaka, Thembisa
- Date: 2020
- Subjects: Forests and forestry -- South Africa , Forest products industry -- South Africa Geographic information systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49281 , vital:41617
- Description: The South African forest industry is challenged with aspects related to socio-political developments, conflicts with biodiversity values, uncertainties related to climate change, several biotic and abiotic risks, and a limited potential for expansion. For this reason, efficient and optimal land-use is essential, which requires sustainable forest management practices and accurate information and decision support systems. Tree growth patterns, productivity and risks vary according to changes in geology, topography, climate and soil conditions. It is therefore required that forest managers, planners and researchers have a conceptual understanding of the concept of forest site classification and evaluation. This is essential not only for improved levels resilience, but also to maintain a competitive industry in terms of socio-economic and environmental performance. The first chapter of the study aimed to investigate the perceptions and interpretations of a range of representative stakeholders from the forestry industry regarding the value, shortcomings, requirements and design of forest site classification and evaluation systems in use in the local industry. A questionnaire with 16 questions was used for this purpose, and data was analysed using quantitative and qualitative techniques. Results indicated variable levels of understanding amongst respondents of terminology and the nature of systems used in industry. Trends in responses were influenced by the background of stakeholders, the role of individuals in the value chain of forestry as well as past experiences. The perceived importance and value of potential site evaluation applications varied substantially amongst different stakeholders. Results point towards a narrow-focus application for site classification and evaluation systems for site-specific forestry, with a lesser regard with aspects of risk management and environmental performance. Several technical aspects related to site variables, data resolution and scale of presentation were also questioned by participants. Listed priorities for research and development include the integration of site classification and evaluation systems into corporate information systems, modernizing technology, more appropriate site evaluation models, advanced climatic modelling and the development of indices of water and nutrient availability related to forest productivity. There is general agreement for the development of a national forest site classification system. The value of this part of the study lies in the contribution it makes towards our knowledge of stakeholder perceptions regarding site classification and evaluation, as well as the valuable comments made by participants for the refinement of such systems that can serve as indicators for entities involved in education, governance and strategic forest management. The second data chapter of the study involved the development of high-resolution site classification systems in the form of Site Types for two selected study areas in South Africa, one located in Mpumalanga, and the other in the southern Cape. This enabled a comparative analysis with existing low-resolution Land Type classifications that were developed by different authors for the same two study areas, in terms of its reliability, accuracy and general usefulness for applications in the plantation forestry value chain. The comparison of the two types of classification systems revealed that the climate data forming part of the database were of equal accuracy and resolution. However, an obvious difference was detected in the information pertaining to soil in terms of descriptive and spatial data. In the case of both study areas, the Site Type classification systems revealed many soil and geological features that were not indicated by the lower-resolution Land Type systems. Variation in characteristics related to parent material, soil classification, soil depth, intensity of subsoil wetness and soil organic matter were not adequately reflected in these systems. This can potentially have important implications for applications such as species choice, predictions of yield, nutrient optimization, ratings of soil resilience, biodiversity management and evaluations for carbon sequestration potential. The data forming part of this study indicate that although Land Type classification systems can provide valuable support at strategic levels of planning and management, there are several limitations for use at finer scales of resolution. The final chapter of the study includes an investigation and qualitative comparison of the usefulness of Site Type vs. Land Type classification systems, based on existing knowledge in the industry. The two systems are compared in terms of its input towards the following applications: site-species matching, timber yield prediction, site amelioration / site preparation requirements, nutrient management requirements, vegetation management / weed control, management of pests and diseases, determination of risk for soil compaction, soil erosion and nutrient loss, decision making regarding forest engineering operations, prediction of wood / fibre properties, biodiversity management and lastly planning of research activities / priorities. This analysis indicated that applications that require data on only climate and general soil patterns can be supported with equal success by both types of site classification systems. On the other hand, in cases where high-resolution data on site factors are required, Land Type classification systems had numerous shortcomings and received a much lower rating of suitability. The outcome of the study can provide guidance on the development and design of future site classification and evaluation systems for the South African forest industry. High-resolution databases of key site factors should receive priority, together with the development of decision support systems based on causal relationships. This will contribute to the resilience and sustainability of an industry that is increasingly confronted with questions related to the placement, design and management of forest plantations.
- Full Text:
- Date Issued: 2020
The characterization and application of novel xanthenyland thioxanthenyl-derived compounds as hosts in the presence of various applicable guest mixtures
- Authors: Jooste, Daniel Victor
- Date: 2020
- Subjects: Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/49104 , vital:41601
- Description: In this work, the host potential of four novel, structurally-related compounds, trans- N,N’-bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine (1,2-DAX), trans-N,N’-bis(9- phenyl-9-thioxanthenyl)cyclohexane-1,2-diamine (1,2-DAT), trans-N,N’-bis(9-phenyl- 9-xanthenyl)cyclohexane-1,4-diamine (1,4-DAX), and trans-N,N’-bis(9-phenyl-9- thioxanthenyl)cyclohexane-1,4-diamine (1,4-DAT), were investigated for their possible employment in the separation of isomers and other related compounds using host– guest chemistry. These hosts were synthesized following a Grignard reaction with phenylmagnesium bromide on either xanthone or thioxanthone. The resultant alcohol was treated with perchloric acid, before finally being linked with either trans-1,2- or trans-1,4-diaminocyclohexane to afford the four title host compounds. Initially, the feasibility of these hosts for separating isomers and related compounds was investigated by recrystallizing each one independently from various guest compounds including the methylpyridines and pyridine, xylenes and ethylbenzene, heterocyclic six-membered ring compounds, aniline, N-methylaniline and N,Ndimethylaniline, and also the alkylbenzenes toluene, cumene and ethylbenzene. 1HNMR spectroscopy was used to ascertain if inclusion of the guest species had occurred in this manner and, if so, the host:guest ratio of the complex. Guest–guest competitions were subsequently conducted in order to establish the selectivity of the hosts when presented with a mixture of guests, and if the host would be able to discriminate between them. Gas chromatography-mass spectrometry (GC-MS) was the analytical method of choice here if 1H-NMR spectroscopy was not suitable owing to guest–guest signal overlap. Here, the host was recrystallized from binary, ternary and quaternary mixed guests, where each was present in equimolar amounts. Additionally, binary competition experiments were conducted in mixed guest solvents where the molar ratios of the guests were varied, and host selectivity for these guests evaluated visually by means of selectivity profiles. Single crystal X-ray diffraction (SC-XRD) and thermal analysis were performed on any complexes that afforded crystals of suitable quality in order to relate inherent host–guest interactions and thermal stability to the observed host selectivity from the competition experiments. The more prevalent interactions that were evident in these inclusion complexes between host and guest species were, more usually, and interactions, as well as other short contacts. Hydrogen bonding interactions were observed in only a few of the complexes. Guest accommodation type was also investigated, and these species resided in either discrete cavities or channels within the host crystal, depending on the guest. For the most part, traces obtained from thermal analyses were highly convoluted and difficult to interpret. As a result, guest release onset temperatures could not be determined for all of the inclusion complexes. In some cases, however, this temperature was successfully measured and correlated directly with the observed selectivity order of the host suggested by the competition experiments. Both enhanced and contrasting results were obtained for the four host compounds. In all cases, 1,2-DAX and 1,2-DAT successfully formed complexes with each of the guest species from each series. Interestingly, the 1,4-derived hosts, however, were more selective in that 1,4-DAX did not complex with only one of the guest solvents, while 1,4-DAT did not enclathrate as many as ten of these solvents. The competition investigations showed that, in most of these experiments, the host compounds displayed selectivity for one of the guests present in the mixture, and in some cases, this selectivity was pronounced, alluding to the feasibility of separating related guests from one another through host–guest chemistry principles. Computational calculations were, additionally, conducted on each of the host molecules in order to gain a better understanding of their geometries, and to compare these with the apohost crystal structures. Significant geometry differences were noted between the calculated and crystal structures.
- Full Text:
- Date Issued: 2020
- Authors: Jooste, Daniel Victor
- Date: 2020
- Subjects: Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/49104 , vital:41601
- Description: In this work, the host potential of four novel, structurally-related compounds, trans- N,N’-bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine (1,2-DAX), trans-N,N’-bis(9- phenyl-9-thioxanthenyl)cyclohexane-1,2-diamine (1,2-DAT), trans-N,N’-bis(9-phenyl- 9-xanthenyl)cyclohexane-1,4-diamine (1,4-DAX), and trans-N,N’-bis(9-phenyl-9- thioxanthenyl)cyclohexane-1,4-diamine (1,4-DAT), were investigated for their possible employment in the separation of isomers and other related compounds using host– guest chemistry. These hosts were synthesized following a Grignard reaction with phenylmagnesium bromide on either xanthone or thioxanthone. The resultant alcohol was treated with perchloric acid, before finally being linked with either trans-1,2- or trans-1,4-diaminocyclohexane to afford the four title host compounds. Initially, the feasibility of these hosts for separating isomers and related compounds was investigated by recrystallizing each one independently from various guest compounds including the methylpyridines and pyridine, xylenes and ethylbenzene, heterocyclic six-membered ring compounds, aniline, N-methylaniline and N,Ndimethylaniline, and also the alkylbenzenes toluene, cumene and ethylbenzene. 1HNMR spectroscopy was used to ascertain if inclusion of the guest species had occurred in this manner and, if so, the host:guest ratio of the complex. Guest–guest competitions were subsequently conducted in order to establish the selectivity of the hosts when presented with a mixture of guests, and if the host would be able to discriminate between them. Gas chromatography-mass spectrometry (GC-MS) was the analytical method of choice here if 1H-NMR spectroscopy was not suitable owing to guest–guest signal overlap. Here, the host was recrystallized from binary, ternary and quaternary mixed guests, where each was present in equimolar amounts. Additionally, binary competition experiments were conducted in mixed guest solvents where the molar ratios of the guests were varied, and host selectivity for these guests evaluated visually by means of selectivity profiles. Single crystal X-ray diffraction (SC-XRD) and thermal analysis were performed on any complexes that afforded crystals of suitable quality in order to relate inherent host–guest interactions and thermal stability to the observed host selectivity from the competition experiments. The more prevalent interactions that were evident in these inclusion complexes between host and guest species were, more usually, and interactions, as well as other short contacts. Hydrogen bonding interactions were observed in only a few of the complexes. Guest accommodation type was also investigated, and these species resided in either discrete cavities or channels within the host crystal, depending on the guest. For the most part, traces obtained from thermal analyses were highly convoluted and difficult to interpret. As a result, guest release onset temperatures could not be determined for all of the inclusion complexes. In some cases, however, this temperature was successfully measured and correlated directly with the observed selectivity order of the host suggested by the competition experiments. Both enhanced and contrasting results were obtained for the four host compounds. In all cases, 1,2-DAX and 1,2-DAT successfully formed complexes with each of the guest species from each series. Interestingly, the 1,4-derived hosts, however, were more selective in that 1,4-DAX did not complex with only one of the guest solvents, while 1,4-DAT did not enclathrate as many as ten of these solvents. The competition investigations showed that, in most of these experiments, the host compounds displayed selectivity for one of the guests present in the mixture, and in some cases, this selectivity was pronounced, alluding to the feasibility of separating related guests from one another through host–guest chemistry principles. Computational calculations were, additionally, conducted on each of the host molecules in order to gain a better understanding of their geometries, and to compare these with the apohost crystal structures. Significant geometry differences were noted between the calculated and crystal structures.
- Full Text:
- Date Issued: 2020
The effect of bioslurry effluent on growth and development of swiss chard (beta vulgaris l.)
- Authors: Dumani, Azile
- Date: 2020
- Subjects: Sewage sludge -- Seedlings , Swiss chard -- Seedlings
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48268 , vital:40837
- Description: Studies were conducted at Döhne Agricultural Development Institute (DADI) (32°31’ 34.077” S; 27°27’ 37.473” E) in Stutterheim, Eastern Cape, South Africa, 2017 and 2018. The objectives of this study were (i) to evaluate the effect of bioslurry effluent on seedling growth of Swiss chard (Beta vulgaris L.), (ii) to study the effect of bioslurry effluent on growth, development and the nutrient content of Swiss chard and (iii) to evaluate the residual effect of bioslurry on biological yield and nutrient content of Swiss chard. Experiment 1 was conducted in a glasshouse using two cultivars (Fordhook giant and Star 1801) seeds planted in 200 cavity trays using Hygromix. The treatments were: control (no fertiliser), 50%Bioslurry, 100%Bioslurry, 200%Bioslurry and the recommended rate of 2:3:4 (30) NPK fertilizer. The experiment was arranged in a randomized complete block design replicated three times. At four weeks after germination, ten seedlings per treatment were destructively sampled randomly to determine shoot height and root length, seedling mass, fresh shoot and fresh root mass, dry mass and nutrient content of leaves. The results showed that fertilization with 100%Bioslurry produced significantly taller seedlings (16.33cm) and shoot height (8.72cm), while the shortest seedlings were obtained from the recommended inorganic fertilizer. Fertilization with 200%Bioslurry and the control treatment produced significantly higher biological yield. compared to other treatments. The interaction between fertilizer treatments, cultivar and season indicated that summer season performed better compared to winter in seedling growth and development, and Fordhook giant fertilized with 100% and 200%Bioslurry was superior compared to Star 1801. Fertilization with 50%Bioslurry resulted in seedlings with higher sodium, while the seedlings grown in the control treatment showed higher copper content. The highest manganese was obtained from the seedlings fertilized with the inorganic fertilizer. In Experiment 2, 10 plots of 4.5m² were established in a greenhouse and were replicated three times, using the same cultivars and fertilizer treatments as in Experiment 1. One seedling was planted per hill at a spacing of 0.25m between plants and 0.5 m between rows and this accommodated 28plants per plot. At 20-day intervals, five plants were randomly selected for data collection until 60 days after transplanting. The cultivar significantly affected growth and biological yield parameters, with Fordhook giant performing better in all the three sampling intervals compared to Star 1801 during summer growing season. Fertilizer application positively affected growth and biological yield parameters and plants treated with 200%Bioslurry and the recommended rate of inorganic fertiliser produced the best results. Experiment 3 was carried out in the same manner as experiment two, except that no fertilizer was applied and the seedlings were planted in corresponding treatment to evaluate the residual effect of bioslurry and inorganic fertilizer. The inorganic fertilizer had the highest residual effect compared to bioslurry. Although not necessarily performing significantly better in terms of the residual effects, the bioslurry showed a good potential as an alternative fertilizer source.
- Full Text:
- Date Issued: 2020
- Authors: Dumani, Azile
- Date: 2020
- Subjects: Sewage sludge -- Seedlings , Swiss chard -- Seedlings
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48268 , vital:40837
- Description: Studies were conducted at Döhne Agricultural Development Institute (DADI) (32°31’ 34.077” S; 27°27’ 37.473” E) in Stutterheim, Eastern Cape, South Africa, 2017 and 2018. The objectives of this study were (i) to evaluate the effect of bioslurry effluent on seedling growth of Swiss chard (Beta vulgaris L.), (ii) to study the effect of bioslurry effluent on growth, development and the nutrient content of Swiss chard and (iii) to evaluate the residual effect of bioslurry on biological yield and nutrient content of Swiss chard. Experiment 1 was conducted in a glasshouse using two cultivars (Fordhook giant and Star 1801) seeds planted in 200 cavity trays using Hygromix. The treatments were: control (no fertiliser), 50%Bioslurry, 100%Bioslurry, 200%Bioslurry and the recommended rate of 2:3:4 (30) NPK fertilizer. The experiment was arranged in a randomized complete block design replicated three times. At four weeks after germination, ten seedlings per treatment were destructively sampled randomly to determine shoot height and root length, seedling mass, fresh shoot and fresh root mass, dry mass and nutrient content of leaves. The results showed that fertilization with 100%Bioslurry produced significantly taller seedlings (16.33cm) and shoot height (8.72cm), while the shortest seedlings were obtained from the recommended inorganic fertilizer. Fertilization with 200%Bioslurry and the control treatment produced significantly higher biological yield. compared to other treatments. The interaction between fertilizer treatments, cultivar and season indicated that summer season performed better compared to winter in seedling growth and development, and Fordhook giant fertilized with 100% and 200%Bioslurry was superior compared to Star 1801. Fertilization with 50%Bioslurry resulted in seedlings with higher sodium, while the seedlings grown in the control treatment showed higher copper content. The highest manganese was obtained from the seedlings fertilized with the inorganic fertilizer. In Experiment 2, 10 plots of 4.5m² were established in a greenhouse and were replicated three times, using the same cultivars and fertilizer treatments as in Experiment 1. One seedling was planted per hill at a spacing of 0.25m between plants and 0.5 m between rows and this accommodated 28plants per plot. At 20-day intervals, five plants were randomly selected for data collection until 60 days after transplanting. The cultivar significantly affected growth and biological yield parameters, with Fordhook giant performing better in all the three sampling intervals compared to Star 1801 during summer growing season. Fertilizer application positively affected growth and biological yield parameters and plants treated with 200%Bioslurry and the recommended rate of inorganic fertiliser produced the best results. Experiment 3 was carried out in the same manner as experiment two, except that no fertilizer was applied and the seedlings were planted in corresponding treatment to evaluate the residual effect of bioslurry and inorganic fertilizer. The inorganic fertilizer had the highest residual effect compared to bioslurry. Although not necessarily performing significantly better in terms of the residual effects, the bioslurry showed a good potential as an alternative fertilizer source.
- Full Text:
- Date Issued: 2020
The effect of gamma radiation on the physical and chemical properties of wool
- Authors: Rapakgadi, Jim
- Date: 2020
- Subjects: Semiconductors -- Effect of radiation on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47668 , vital:40263
- Description: Pathogens (e.g. viruses, spores and bacteria) remain one of the biggest threats to trading and the economy of natural fibre products, such as wool, mohair and cotton. One of the means to kill or eliminate pathogens is by radiation sterilisation, involving electromagnetic radiation (e.g. gamma radiation and UV light). The research, reported in this thesis, was aimed at establishing the effect of gamma irradiation dosage on the various quality related physical and chemical characteristics of four different types of merino wool when treated in situ in scoured and greasy state in mini-bale form. Specific properties studied include wool colour (yellowness and brightness), solubility (alkali solubility and urea bisulphite solubility), fibre diameter and tensile properties (staple strength and bundle tenacity). Standard analytical and diagnostic techniques were used to assess changes, if any, in the above mentioned properties due to the radiation treatment. Nominal radiation dosages, ranging from 25 kGy to 75 kGy (actual measured from 0 kGy to 92.2 kGy) were used, 50 kGy normally being regarded as sufficient to destroy the pathogens in question. It was found that nominial gamma radiation dosages of up to 92.2 kGy did not significantly affect fibre diameter or staple length, indicating that no irreversible swelling of the wool fibres occurred as a result of gamma irradiation. Alkali and urea bisulphite solubility as well as yellowness, on the other hand, showed a systematic increase with an increase in irradiation dose, indicating that changes occurred at molecular level. Fibre tensile properties (staple strength and bundle tenacity) were also affected but to a much lesser extent than solubility and colour. The various merino wool types studied showed similar reactions to the radiation treatment, irrespective of the wool quality and type and also whether they were treated in greasy or scoured form.
- Full Text:
- Date Issued: 2020
- Authors: Rapakgadi, Jim
- Date: 2020
- Subjects: Semiconductors -- Effect of radiation on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47668 , vital:40263
- Description: Pathogens (e.g. viruses, spores and bacteria) remain one of the biggest threats to trading and the economy of natural fibre products, such as wool, mohair and cotton. One of the means to kill or eliminate pathogens is by radiation sterilisation, involving electromagnetic radiation (e.g. gamma radiation and UV light). The research, reported in this thesis, was aimed at establishing the effect of gamma irradiation dosage on the various quality related physical and chemical characteristics of four different types of merino wool when treated in situ in scoured and greasy state in mini-bale form. Specific properties studied include wool colour (yellowness and brightness), solubility (alkali solubility and urea bisulphite solubility), fibre diameter and tensile properties (staple strength and bundle tenacity). Standard analytical and diagnostic techniques were used to assess changes, if any, in the above mentioned properties due to the radiation treatment. Nominal radiation dosages, ranging from 25 kGy to 75 kGy (actual measured from 0 kGy to 92.2 kGy) were used, 50 kGy normally being regarded as sufficient to destroy the pathogens in question. It was found that nominial gamma radiation dosages of up to 92.2 kGy did not significantly affect fibre diameter or staple length, indicating that no irreversible swelling of the wool fibres occurred as a result of gamma irradiation. Alkali and urea bisulphite solubility as well as yellowness, on the other hand, showed a systematic increase with an increase in irradiation dose, indicating that changes occurred at molecular level. Fibre tensile properties (staple strength and bundle tenacity) were also affected but to a much lesser extent than solubility and colour. The various merino wool types studied showed similar reactions to the radiation treatment, irrespective of the wool quality and type and also whether they were treated in greasy or scoured form.
- Full Text:
- Date Issued: 2020
The effect of top dressing treatments on stolon weaning and keeping quality on two potato cultivars in the Gamtoos river valley
- Authors: Murray, Roger Benjamin
- Date: 2020
- Subjects: Plants -- Effect of nitrates on
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/48522 , vital:40884
- Description: Potatoes are an important crop in the Eastern Cape, and in South Africa as a whole, as a nutritious staple food. For consumers, they provide a quality, relatively low-priced form of carbohydrate and, for farmers, they are a valuable cash crop. The nutritional requirements of Solanum tuberosum L., in particular its nitrogen (N) needs, during cultivation is an aspect warranting further research. The Eastern Cape is a prime potato-producing region and, as such, is an appropriate and logical choice in terms of a suitable location for the required study. Improper farming practices with regards to improper fertilizer application techniques can adversely affect yields, and excessive application of fertilizer is fundamentally economically unsound, adverse towards the environment and potentially detrimental to the crop. It is therefore imperative that nutrients – and nitrogen in particular – are available to the crop in the correct quantities at the correct time. The objective of this dissertation was to accurately identify the nitrogen fertilizer needs of potatoes – with specific emphasis on whether or not nitrogen affects stolon growth and development. The potato cultivar used in the research trial was Mondial, which is a cultivar well-established in the region. Nitrogen applications needed to be closely monitored with regards to the total seasonal amount of nitrogen applied, the timing of applications and the amount applied at each application. Meaningful data accumulated from this study will help farmers in the area to accurately assess the efficiency of their farming operations. Excessive or insufficient plant nutrition affects tuber bulking and quality. The objective was to accurately identify this “sweet spot” (i.e. the optimal measure and timing) with regards to fertilization, especially nitrogen, while also taking into account various other factors that affect healthy tuber development and stolon formation. The untested assertion that prompted this study was that too much nitrogen adversely affects the number of stolons – and therefore, the number of tubers, since tubers grow from the stolons. It is generally accepted that too little N will adversely affect yields and yield potential will not be achieved, and that too much N will adversely affect yields, incur unnecessary costs and potentially degrade the environment. Optimum nitrogen application quantities were therefore identified, along with points at which deviations from optimum yields occurred. There were 8 distinct treatment combinations – namely: a rate of 150kg/ha, 250kg/ha, 350kg/ha and 450kg/ha – of nitrogen (N) throughout the growing season, administered at 2 different timings (hereafter referred to as the Application Timings). The applications of nitrogen were administered as follows: Application Timing 1 (50% N at planting : 25% N as Topdressing 1 : 25% N as Topdressing 2) and Application Timing 2 (75% N at planting : 12.5% N as Topdressing 1 : 12.5% N as Topdressing 2). The findings suggest that while nitrogen played a role in increasing yield, there was no conclusive evidence to suggest that stolons were weaned by excessive amounts of nitrogen throughout the growing season. The results obtained from statistical analysis showed that, between Application Timing 1 (50%:25%:25%) and Application Timing 2 (75%:12.5%:12.5%), neither split application timing was superior to the other in terms of tuber yield or effect on the average number of stolons when data from all three plantings were combined. In some instances, high stolon numbers were observed in the high N application plots. The highest stolon count in a single data collection in Planting 1 was in the 450kg/ha App. 1 plots in the 3rd data collection. The highest stolon count in a single data collection in Planting 2 was in the 250kg/ha App. 2 plots in the 2nd data collection. The highest stolon count in a single data collection was in the 350kg/ha App. 2 plots in the 3rd data collection. The conjecture that excessive nitrogen causes stolon weaning in potatoes was not supported by the findings of the experiments conducted in the three trial plantings which constituted this research study.
- Full Text:
- Date Issued: 2020
- Authors: Murray, Roger Benjamin
- Date: 2020
- Subjects: Plants -- Effect of nitrates on
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/48522 , vital:40884
- Description: Potatoes are an important crop in the Eastern Cape, and in South Africa as a whole, as a nutritious staple food. For consumers, they provide a quality, relatively low-priced form of carbohydrate and, for farmers, they are a valuable cash crop. The nutritional requirements of Solanum tuberosum L., in particular its nitrogen (N) needs, during cultivation is an aspect warranting further research. The Eastern Cape is a prime potato-producing region and, as such, is an appropriate and logical choice in terms of a suitable location for the required study. Improper farming practices with regards to improper fertilizer application techniques can adversely affect yields, and excessive application of fertilizer is fundamentally economically unsound, adverse towards the environment and potentially detrimental to the crop. It is therefore imperative that nutrients – and nitrogen in particular – are available to the crop in the correct quantities at the correct time. The objective of this dissertation was to accurately identify the nitrogen fertilizer needs of potatoes – with specific emphasis on whether or not nitrogen affects stolon growth and development. The potato cultivar used in the research trial was Mondial, which is a cultivar well-established in the region. Nitrogen applications needed to be closely monitored with regards to the total seasonal amount of nitrogen applied, the timing of applications and the amount applied at each application. Meaningful data accumulated from this study will help farmers in the area to accurately assess the efficiency of their farming operations. Excessive or insufficient plant nutrition affects tuber bulking and quality. The objective was to accurately identify this “sweet spot” (i.e. the optimal measure and timing) with regards to fertilization, especially nitrogen, while also taking into account various other factors that affect healthy tuber development and stolon formation. The untested assertion that prompted this study was that too much nitrogen adversely affects the number of stolons – and therefore, the number of tubers, since tubers grow from the stolons. It is generally accepted that too little N will adversely affect yields and yield potential will not be achieved, and that too much N will adversely affect yields, incur unnecessary costs and potentially degrade the environment. Optimum nitrogen application quantities were therefore identified, along with points at which deviations from optimum yields occurred. There were 8 distinct treatment combinations – namely: a rate of 150kg/ha, 250kg/ha, 350kg/ha and 450kg/ha – of nitrogen (N) throughout the growing season, administered at 2 different timings (hereafter referred to as the Application Timings). The applications of nitrogen were administered as follows: Application Timing 1 (50% N at planting : 25% N as Topdressing 1 : 25% N as Topdressing 2) and Application Timing 2 (75% N at planting : 12.5% N as Topdressing 1 : 12.5% N as Topdressing 2). The findings suggest that while nitrogen played a role in increasing yield, there was no conclusive evidence to suggest that stolons were weaned by excessive amounts of nitrogen throughout the growing season. The results obtained from statistical analysis showed that, between Application Timing 1 (50%:25%:25%) and Application Timing 2 (75%:12.5%:12.5%), neither split application timing was superior to the other in terms of tuber yield or effect on the average number of stolons when data from all three plantings were combined. In some instances, high stolon numbers were observed in the high N application plots. The highest stolon count in a single data collection in Planting 1 was in the 450kg/ha App. 1 plots in the 3rd data collection. The highest stolon count in a single data collection in Planting 2 was in the 250kg/ha App. 2 plots in the 2nd data collection. The highest stolon count in a single data collection was in the 350kg/ha App. 2 plots in the 3rd data collection. The conjecture that excessive nitrogen causes stolon weaning in potatoes was not supported by the findings of the experiments conducted in the three trial plantings which constituted this research study.
- Full Text:
- Date Issued: 2020
The effect of waste tyre pyrolysis-derived carbon black on the various properties of natural rubber/styrene-butadiene rubber blends
- Authors: Ketelo, Sisonke
- Date: 2020
- Subjects: Rubber chemistry , Rubber Polymers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49115 , vital:41602
- Description: Disposal of waste tyres into landfills is common in developing countries, including South Africa. This behaviour is detrimental to human health as well as other living organisms and the environment itself. There are several recycling methods and processes that have been adopted in various countries to mitigate the situation. These include the recovery of materials such as rubber for re-use; shredding of tyres into small crumb particles for secondary applications in various industries such as civil engineering and the automotive sector; and commonly through heating tyres under a controlled environment to produce oil in a process called pyrolysis. The latter is of interest to the study, with a specific interest in valorization of the process’ resultant char/pyrolysis carbon black. In principle, this study considers the advancement of waste tyre material recovery by finding applications for pyrolysis-derived carbon black (pCB) recovered from waste tyres as it is one of the significant products of pyrolysis. The study involved investigating the effectiveness of pyrolysis-derived carbon black in its ability to improve the properties of natural rubber/styrene-butadiene rubber blends for the conveyor belting industry and other related industries. The pyrolysis-derived carbon black was characterized and compared to commercial grades of carbon blacks on properties such as surface area, thermal stability, heat absorption, structure and morphology using various laboratory techniques such as XRD, XRF, TGA, BET, DSC and SEM. It was found that the properties of the unmodified pCB closely matched those of commercial carbon black grade N660. Through internal mixing, rubber compounds were prepared using 40 phr of pCB and of the selected carbon black grades. Improvements were observed in the mechanical properties of the polymer for application specifications, especially tensile properties and abrasion resistance. Pyrolysis-derived carbon black improved tensile properties to a similar magnitude as a reinforcing carbon black grade and produced similar cure times. Partial replacement of a commercial carbon black grade with pCB of 5 to 20 phr in NR/SBR yielded intermediate results. The unmodified pCB can be used to improve the physical properties of natural rubber/styrene-butadiene rubber blends because it exhibits filler behaviour.
- Full Text:
- Date Issued: 2020
- Authors: Ketelo, Sisonke
- Date: 2020
- Subjects: Rubber chemistry , Rubber Polymers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49115 , vital:41602
- Description: Disposal of waste tyres into landfills is common in developing countries, including South Africa. This behaviour is detrimental to human health as well as other living organisms and the environment itself. There are several recycling methods and processes that have been adopted in various countries to mitigate the situation. These include the recovery of materials such as rubber for re-use; shredding of tyres into small crumb particles for secondary applications in various industries such as civil engineering and the automotive sector; and commonly through heating tyres under a controlled environment to produce oil in a process called pyrolysis. The latter is of interest to the study, with a specific interest in valorization of the process’ resultant char/pyrolysis carbon black. In principle, this study considers the advancement of waste tyre material recovery by finding applications for pyrolysis-derived carbon black (pCB) recovered from waste tyres as it is one of the significant products of pyrolysis. The study involved investigating the effectiveness of pyrolysis-derived carbon black in its ability to improve the properties of natural rubber/styrene-butadiene rubber blends for the conveyor belting industry and other related industries. The pyrolysis-derived carbon black was characterized and compared to commercial grades of carbon blacks on properties such as surface area, thermal stability, heat absorption, structure and morphology using various laboratory techniques such as XRD, XRF, TGA, BET, DSC and SEM. It was found that the properties of the unmodified pCB closely matched those of commercial carbon black grade N660. Through internal mixing, rubber compounds were prepared using 40 phr of pCB and of the selected carbon black grades. Improvements were observed in the mechanical properties of the polymer for application specifications, especially tensile properties and abrasion resistance. Pyrolysis-derived carbon black improved tensile properties to a similar magnitude as a reinforcing carbon black grade and produced similar cure times. Partial replacement of a commercial carbon black grade with pCB of 5 to 20 phr in NR/SBR yielded intermediate results. The unmodified pCB can be used to improve the physical properties of natural rubber/styrene-butadiene rubber blends because it exhibits filler behaviour.
- Full Text:
- Date Issued: 2020
The effects of vascular targeted bi-functionalized aunps on hepatic lipid metabolism of a diet-induced rats
- Authors: Singo, Dakalo Gladwell
- Date: 2020
- Subjects: Bile acids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47072 , vital:39780
- Description: Introduction: Obesity is a metabolic disease in which the accumulation of excessive fat in the adipose tissue may interfere with the normal maintenance of a healthy state. However, there is only a limited number of drugs approved for the treatment of obesity. For this purpose, target therapies are receiving more attention as a preferred treatment to reduce the burden of chronic diseases which are associated with the current strategies. Nanotechnology is a highly promising field that offers a nanotechnology-based drug delivery system as a novel means of solving issues associated with the toxicity of conventional anti-obesity drugs. Vascular targeted nanotherapy (targeted bi-functionalized nanoparticles) as a strategy that can overcome the current available anti-obesity drugs. Aim: This study sought to understand the effects of nanotherapy in the hepatic lipid metabolism and secretion of bile acids Research focus: The effects of gold nanotherapy on the bile acid biosynthetic enzymes, transporters and lipogenic enzymes of rats that were on a high fat diet. Conclusion: The study shows low expression in the majority of genes responsible for bile acid synthesis and a lipogenic pathway; therefore, the effects of nanotherapy exhibit low toxicity in the hepatic lipid metabolism.
- Full Text:
- Date Issued: 2020
- Authors: Singo, Dakalo Gladwell
- Date: 2020
- Subjects: Bile acids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47072 , vital:39780
- Description: Introduction: Obesity is a metabolic disease in which the accumulation of excessive fat in the adipose tissue may interfere with the normal maintenance of a healthy state. However, there is only a limited number of drugs approved for the treatment of obesity. For this purpose, target therapies are receiving more attention as a preferred treatment to reduce the burden of chronic diseases which are associated with the current strategies. Nanotechnology is a highly promising field that offers a nanotechnology-based drug delivery system as a novel means of solving issues associated with the toxicity of conventional anti-obesity drugs. Vascular targeted nanotherapy (targeted bi-functionalized nanoparticles) as a strategy that can overcome the current available anti-obesity drugs. Aim: This study sought to understand the effects of nanotherapy in the hepatic lipid metabolism and secretion of bile acids Research focus: The effects of gold nanotherapy on the bile acid biosynthetic enzymes, transporters and lipogenic enzymes of rats that were on a high fat diet. Conclusion: The study shows low expression in the majority of genes responsible for bile acid synthesis and a lipogenic pathway; therefore, the effects of nanotherapy exhibit low toxicity in the hepatic lipid metabolism.
- Full Text:
- Date Issued: 2020
The Geography of Inequality in Port Elizabeth : Post-apartheid Trends
- Authors: Mc Arthur, Brogan Erin
- Date: 2020
- Subjects: Equality -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48478 , vital:40880
- Description: This study aims to identify post-apartheid trends of inequality within Port Elizabeth, by analysing the spatial distribution of social well-being from 1996 to 2011. The spatial distribution of social well-being highlights the geography of inequality within Port Elizabeth, focusing on social indicators as a measure of social well-being. Mapping of these social indicators illustrates various levels of social well-being throughout Port Elizabeth based on the formulation of social indicators, application of these social indicators to census data, data processing and mapping. This results in the mapping of poverty, employment, education and standard of living for the census years of 1996, 2001 and 2011. From the mapping process, trends of social well-being and the associated inequality are illustrated and analysed, while providing insight into the progress of social well-being within a South African city. The findings of this study suggest that social well-being has incurred changes over time which have aided in the improvement of social well-being throughout Port Elizabeth. This improvement is marked by the relative increase and decrease of selected social indicators and their interrelated nature. The various social indicators, although focused on different datasets, highlight similar patterns of progress throughout their spatial distribution over time. As such, similar patterns of inequality can be noted throughout Port Elizabeth for various social indicators. Based on these similarities and the trends identified within the spatial distribution of inequality in Port Elizabeth, a progression towards a more even distribution throughout the study area was noted from 1996 through to 2011.
- Full Text:
- Date Issued: 2020
- Authors: Mc Arthur, Brogan Erin
- Date: 2020
- Subjects: Equality -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48478 , vital:40880
- Description: This study aims to identify post-apartheid trends of inequality within Port Elizabeth, by analysing the spatial distribution of social well-being from 1996 to 2011. The spatial distribution of social well-being highlights the geography of inequality within Port Elizabeth, focusing on social indicators as a measure of social well-being. Mapping of these social indicators illustrates various levels of social well-being throughout Port Elizabeth based on the formulation of social indicators, application of these social indicators to census data, data processing and mapping. This results in the mapping of poverty, employment, education and standard of living for the census years of 1996, 2001 and 2011. From the mapping process, trends of social well-being and the associated inequality are illustrated and analysed, while providing insight into the progress of social well-being within a South African city. The findings of this study suggest that social well-being has incurred changes over time which have aided in the improvement of social well-being throughout Port Elizabeth. This improvement is marked by the relative increase and decrease of selected social indicators and their interrelated nature. The various social indicators, although focused on different datasets, highlight similar patterns of progress throughout their spatial distribution over time. As such, similar patterns of inequality can be noted throughout Port Elizabeth for various social indicators. Based on these similarities and the trends identified within the spatial distribution of inequality in Port Elizabeth, a progression towards a more even distribution throughout the study area was noted from 1996 through to 2011.
- Full Text:
- Date Issued: 2020
The impact of the slum upgrading approach on the livelihoods of scheme participants in Uganda : using the sustainable livelihoods framework
- Authors: Karungi, Doreen
- Date: 2020
- Subjects: Slums -- Public welfare -- Uganda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48412 , vital:40874
- Description: International and local agencies recommend implementing slum upgrading projects in slum areas for slum improvement. However, with no model or guiding principles provided to slum upgrading project implementers on how to upgrade a slum, slum clearance and redevelopment are implemented rather than slum upgrading consequently projects fail to benefit the target group, slum dwellers. Data collection, took place in five areas in Uganda that implemented slum upgrading. In depth interviews were held with project beneficiaries, local council officials and association executives, and government officials at the Ministry of Lands, Housing and Urban Development. Field observation, and document analysis was carried out. Data analysis involved the use of the sustainable livelihoods framework. This study demonstrates that the slum upgrading approach adopted in Uganda exhibited low sustainability and undercut the sustainability of livelihoods of scheme participants. Slum dwellers faced vulnerabilities from loss of land, characterized by rights based actions resulting in minimal to no compensation or eviction and loss of existing livelihoods. Slum upgrading projects introduced new livelihood opportunities that were too few for slum dwellers, were not sustainable and ended during or with project implementation, leaving beneficiaries without employment or income opportunities. Increased vulnerability was observed as slum dwellers that did not benefit from the project were displaced to worse conditions while slum dwellers that benefitted, project beneficiaries remained poor and in debt, with project loans to repay. Although project beneficiaries were provided with access to assets, they were unable to draw on these to build their livelihoods. Some beneficiaries sold plots and project houses allocated to them and moved to adjacent slums, where they lived in worse conditions. At the time of the current research, good quality houses in the slum upgrading areas did not belong to the original beneficiaries old dilapidated structures were occupied by project beneficiaries. This study shows that income earning activities carried out at the time of the study were similar to those carried out prior to the introduction of slum upgrading in project areas and were destroyed during project implementation or banned by implementers. These activities were however carried out in incomplete houses, vacant plots, temporary structures in project areas and in adjacent swamps and forest. Generally, after completion of slum upgrading projects, project areas, adjacent swamps and forest were characterized by haphazard developments including: rentals, informal businesses, farming, brewing and distilling local alcohol used by beneficiaries to derive livelihoods, in other words, slums were recreated, a problem slum upgrading project implementers set out to solve - except in one study area where the project was implemented differently as a result of persist rights based actions.
- Full Text:
- Date Issued: 2020
- Authors: Karungi, Doreen
- Date: 2020
- Subjects: Slums -- Public welfare -- Uganda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48412 , vital:40874
- Description: International and local agencies recommend implementing slum upgrading projects in slum areas for slum improvement. However, with no model or guiding principles provided to slum upgrading project implementers on how to upgrade a slum, slum clearance and redevelopment are implemented rather than slum upgrading consequently projects fail to benefit the target group, slum dwellers. Data collection, took place in five areas in Uganda that implemented slum upgrading. In depth interviews were held with project beneficiaries, local council officials and association executives, and government officials at the Ministry of Lands, Housing and Urban Development. Field observation, and document analysis was carried out. Data analysis involved the use of the sustainable livelihoods framework. This study demonstrates that the slum upgrading approach adopted in Uganda exhibited low sustainability and undercut the sustainability of livelihoods of scheme participants. Slum dwellers faced vulnerabilities from loss of land, characterized by rights based actions resulting in minimal to no compensation or eviction and loss of existing livelihoods. Slum upgrading projects introduced new livelihood opportunities that were too few for slum dwellers, were not sustainable and ended during or with project implementation, leaving beneficiaries without employment or income opportunities. Increased vulnerability was observed as slum dwellers that did not benefit from the project were displaced to worse conditions while slum dwellers that benefitted, project beneficiaries remained poor and in debt, with project loans to repay. Although project beneficiaries were provided with access to assets, they were unable to draw on these to build their livelihoods. Some beneficiaries sold plots and project houses allocated to them and moved to adjacent slums, where they lived in worse conditions. At the time of the current research, good quality houses in the slum upgrading areas did not belong to the original beneficiaries old dilapidated structures were occupied by project beneficiaries. This study shows that income earning activities carried out at the time of the study were similar to those carried out prior to the introduction of slum upgrading in project areas and were destroyed during project implementation or banned by implementers. These activities were however carried out in incomplete houses, vacant plots, temporary structures in project areas and in adjacent swamps and forest. Generally, after completion of slum upgrading projects, project areas, adjacent swamps and forest were characterized by haphazard developments including: rentals, informal businesses, farming, brewing and distilling local alcohol used by beneficiaries to derive livelihoods, in other words, slums were recreated, a problem slum upgrading project implementers set out to solve - except in one study area where the project was implemented differently as a result of persist rights based actions.
- Full Text:
- Date Issued: 2020
The influence of anthropogenic and environmental covariates on the habitat use and density of sympatric carnivores, Limpopo Province, South Africa
- Authors: Faure, J Philip B
- Date: 2020
- Subjects: Carnivorous animals -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48302 , vital:40840
- Description: Carnivores are declining and undergoing substantial range contractions which have largely been attributed to anthropogenic related. Globally, there has been an increase in establishing protected areas for species conservation. However, protected areas may not always effectively conserve all biodiversity, where some areas are too small for viable populations of wide-ranging species, such as leopards Panthera pardus, spotted hyaenas Crocuta crocuta, and brown hyaenas Parahyaena brunnea. The importance of privately-owned areas are gaining increasing recognition for their role in conserving species, and ecosystems. Though such areas may provide key opportunities for the conservation and persistence of biodiversity, little attention (with regards to species conservation planning) is given to these areas. Furthermore, large carnivore populations increasingly have to share the landscapes with humans as the global human population increase. Though anthropogenic impacts can be limited within protected areas, human activities on privately-owned farmlands are mostly dictated by economic activity to sustain human presence (often leading to humancarnivore conflicts). Platjan (South Africa) is one such area. It comprise a matrix of agricultural practices and land-use types, dominated by humans. Consequently, it presented an ideal landscape to investigate how humans and carnivores coexist. Spatial capture-recapture modelling suggest stable populations manifested through low densities for leopards, spotted hyaenas, brown hyaenas, and Africa civet Civettictis civetta within the study area. Densities of the focal species were more similar to what has been found in more arid environments. Though it should be noted, that population fluctuations are common in nature, and this study only provide a brief snapshot of the population. Nonetheless, it provides baseline carnivore density estimates for the area. Single-season, single-species occupancy modelling was used to determine the influence of anthropogenic variables on species probability of site use. Results suggested that leopards and spotted hyaenas avoided crop fields (possibly due to higher human activity in these areas). Whereas black-backed jackal Canis mesomelas were positively influenced by the proportion of survey sites containing human infrastructure (possibly due to additional food sources provided by human presence). The covariates did not suggest any effect on brown hyaena and African civet probability of site use, which may be explained by temporal niche partitioning between the species and humans. Kernel density estimation and selectivity ratios revealed that all carnivores were predominantly crepuscular-nocturnal, with the exception of brown hyaenas which were strictly nocturnal. Among the focal species, brown hyaenas and African civets had the lowest temporal overlap with humans, which may explain why they weren’t affected by any of the anthropogenic variables. Whereas, jackal had the highest overlap, supporting a notion that they may be more tolerant of human presence than the other study animals. Overall, it seems that carnivores are able to coexist with humans on privately-owned farmlands through temporal niche partitioning, but manifest at rather low densities. Nonetheless, this study adds to the current understanding of human-carnivore coadaptation, and provides the first carnivore density estimates for the Platjan region.
- Full Text:
- Date Issued: 2020
- Authors: Faure, J Philip B
- Date: 2020
- Subjects: Carnivorous animals -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48302 , vital:40840
- Description: Carnivores are declining and undergoing substantial range contractions which have largely been attributed to anthropogenic related. Globally, there has been an increase in establishing protected areas for species conservation. However, protected areas may not always effectively conserve all biodiversity, where some areas are too small for viable populations of wide-ranging species, such as leopards Panthera pardus, spotted hyaenas Crocuta crocuta, and brown hyaenas Parahyaena brunnea. The importance of privately-owned areas are gaining increasing recognition for their role in conserving species, and ecosystems. Though such areas may provide key opportunities for the conservation and persistence of biodiversity, little attention (with regards to species conservation planning) is given to these areas. Furthermore, large carnivore populations increasingly have to share the landscapes with humans as the global human population increase. Though anthropogenic impacts can be limited within protected areas, human activities on privately-owned farmlands are mostly dictated by economic activity to sustain human presence (often leading to humancarnivore conflicts). Platjan (South Africa) is one such area. It comprise a matrix of agricultural practices and land-use types, dominated by humans. Consequently, it presented an ideal landscape to investigate how humans and carnivores coexist. Spatial capture-recapture modelling suggest stable populations manifested through low densities for leopards, spotted hyaenas, brown hyaenas, and Africa civet Civettictis civetta within the study area. Densities of the focal species were more similar to what has been found in more arid environments. Though it should be noted, that population fluctuations are common in nature, and this study only provide a brief snapshot of the population. Nonetheless, it provides baseline carnivore density estimates for the area. Single-season, single-species occupancy modelling was used to determine the influence of anthropogenic variables on species probability of site use. Results suggested that leopards and spotted hyaenas avoided crop fields (possibly due to higher human activity in these areas). Whereas black-backed jackal Canis mesomelas were positively influenced by the proportion of survey sites containing human infrastructure (possibly due to additional food sources provided by human presence). The covariates did not suggest any effect on brown hyaena and African civet probability of site use, which may be explained by temporal niche partitioning between the species and humans. Kernel density estimation and selectivity ratios revealed that all carnivores were predominantly crepuscular-nocturnal, with the exception of brown hyaenas which were strictly nocturnal. Among the focal species, brown hyaenas and African civets had the lowest temporal overlap with humans, which may explain why they weren’t affected by any of the anthropogenic variables. Whereas, jackal had the highest overlap, supporting a notion that they may be more tolerant of human presence than the other study animals. Overall, it seems that carnivores are able to coexist with humans on privately-owned farmlands through temporal niche partitioning, but manifest at rather low densities. Nonetheless, this study adds to the current understanding of human-carnivore coadaptation, and provides the first carnivore density estimates for the Platjan region.
- Full Text:
- Date Issued: 2020
The jackal as a mesopredator : dietary response to an apex predator and role as an endozoochore
- Authors: Favaretto, Bianca Sashika
- Date: 2020
- Subjects: Jackal buzzard
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48313 , vital:40841
- Description: Interactions between apex predators, mesopredators and their impacts on trophic dynamics have been well documented. However, the influence of apex predators, through the provision of carrion, on the foraging ecology of African mesopredators is poorly understood. To investigate such resource supplementation by apex predators for mesopredators, the black-backed jackal Canis mesomelas, a generalist mesopredator, was used as a model species to improve our understanding of this topic in South African ecosystems. To do this, I compared the diet of jackal at replicated sites with and without cheetah in the eastern Karoo, South Africa. Scat samples were macroscopically categorized into six broad dietary categories: mammal, reptile, bird, fruit, forage and insect. Mammalian prey was further identified to species and grouped into six functional dietary categories: carnivore, large ungulate, small ungulate, small mammal, and unknown mammal. Jackal diets were dominated by mammal prey, with significant differences in the biomass and frequency of occurrence of mammals by jackal at sites with cheetah and without cheetah. Mammal consumption, showed limited variation amongst seasons. Resource supplementation provided by predator derived carrion is an important factor influencing jackal foraging ecology. The emergent hypothesis that jackal may show demographic responses (increased fecundity, survival, density) to this supplementation needs to be tested. This study also provided an opportunity to investigate the potential role of jackal as an endozoochore. Jackal consume fruits and their seeds, yet to our knowledge, an investigation into their seed dispersing abilities is yet to be investigated. This study assessed the viability and germination capacity of ingested seeds extracted from jackal scat samples using the tetrazolium tests and germination trials. Seed viability and germination of all three species (Grewia occidentalis, Pappea capensis and Diospyros lycioides) were significantly lower than uningested seeds. These results suggest that jackal gut passage is acting severely on ingested seeds. This study represents a novel investigation into differences in jackal diet in sites with and without cheetah as well as the role jackal play in endozoochory, contributing to improved understanding of the ecological role of jackal.
- Full Text:
- Date Issued: 2020
- Authors: Favaretto, Bianca Sashika
- Date: 2020
- Subjects: Jackal buzzard
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48313 , vital:40841
- Description: Interactions between apex predators, mesopredators and their impacts on trophic dynamics have been well documented. However, the influence of apex predators, through the provision of carrion, on the foraging ecology of African mesopredators is poorly understood. To investigate such resource supplementation by apex predators for mesopredators, the black-backed jackal Canis mesomelas, a generalist mesopredator, was used as a model species to improve our understanding of this topic in South African ecosystems. To do this, I compared the diet of jackal at replicated sites with and without cheetah in the eastern Karoo, South Africa. Scat samples were macroscopically categorized into six broad dietary categories: mammal, reptile, bird, fruit, forage and insect. Mammalian prey was further identified to species and grouped into six functional dietary categories: carnivore, large ungulate, small ungulate, small mammal, and unknown mammal. Jackal diets were dominated by mammal prey, with significant differences in the biomass and frequency of occurrence of mammals by jackal at sites with cheetah and without cheetah. Mammal consumption, showed limited variation amongst seasons. Resource supplementation provided by predator derived carrion is an important factor influencing jackal foraging ecology. The emergent hypothesis that jackal may show demographic responses (increased fecundity, survival, density) to this supplementation needs to be tested. This study also provided an opportunity to investigate the potential role of jackal as an endozoochore. Jackal consume fruits and their seeds, yet to our knowledge, an investigation into their seed dispersing abilities is yet to be investigated. This study assessed the viability and germination capacity of ingested seeds extracted from jackal scat samples using the tetrazolium tests and germination trials. Seed viability and germination of all three species (Grewia occidentalis, Pappea capensis and Diospyros lycioides) were significantly lower than uningested seeds. These results suggest that jackal gut passage is acting severely on ingested seeds. This study represents a novel investigation into differences in jackal diet in sites with and without cheetah as well as the role jackal play in endozoochory, contributing to improved understanding of the ecological role of jackal.
- Full Text:
- Date Issued: 2020
The potential of Raman spectroscopy in distinguishing between wool and mohair fibres
- Authors: Notayi, Mzwamadoda
- Date: 2020
- Subjects: Textile fabrics , Textile fibers -- Mechanical properties Wool -- Dissertations Mohair -- Dissertations
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49248 , vital:41614
- Description: The possible application of the FT Raman, Raman micro-spectroscopy and ATR-FTIR micro-spectroscopy, have been investigated for distinguishing between wool and mohair. Highly identical Raman and FTIR spectra were obtained from the two fibre types, indicating that indeed they share similar basic molecular structural chemistry. The analysis of the amide I through curve fitting of wool and mohair FT Raman spectra showed that the protein and polypeptide secondary structure exists mainly in the α-helical structural conformation with smaller proportions of β-pleated sheet and β-Turns. These proportions, however, could not be used to distinguish between wool and mohair, due to the significant overlap observed between the two fibres. This study also determined the disulphide contents for possibly distinguishing between wool and mohair fibres, with the average and standard deviation values of 0.20±0.04 and 0.17±0.03 for wool and mohair, respectively, being found. Despite the mean values being found to differ statistically significant (p<0.05), a considerable overlap was observed, posing a doubt in the possible application of the method for distinguishing between the two fibres and blend composition analysis of the two fibres. The application of ratiometric analysis, based on the relative peak heights of certain FT Raman bands, showed that a combination of ratios A (I2932/I1450) and D (I508/I1450) could hold great potential in distinguishing between wool and mohair fibre samples. The individual values of ratios A and D varied a great deal from one mohair sample to the other and even more from one wool sample to another, with the individual values for ratio A ranging from 2.71-3.68 and 2.35-3.08 for wool and mohair, respectively, while ratio D ranged from 0.18-0.32 and 0.17-0.22 for wool and mohair, respectively. An important observation from this study is that if, for an unknown sample, if individual values of ratios A and D exceed 3.1 and 0.22, respectively, are found then the sample is most likely to be either a pure wool or blend of wool and mohair, whereas if all the values fall below the two threshold values, then the unknown sample can be declared a pure mohair sample. A Raman spectral database or library of approximately 100 high quality Raman average spectra of wool and mohair fibres has been established for the Bruker 80V FTIR/Raman spectrophotometer at the Nelson Mandela University (NMU). Although this has not been fully validated due to the unforeseen frequent breakdown encountered with the FT Raman system, at this stage, it has been realized that verification of unknown materials is highly possible. A great need for the development of a classification model based on multivariate or chemometrics has been realized. An ATR-FTIR LUMOS micro-spectroscopic system was also investigated for the possible application in distinguishing between wool and mohair single fibres. The amide I/II band ratios were determined for both wool and mohair fibres to distinguish between the two fibre types. The mean and standard deviation values of 1.20±0.02 and 1.21±0.01 for mohair and wool, respectively, were found and were shown not to differ statistically significant (p˃0.05). The secondary structure analysis showed that the content of the α-helical secondary structure might be different between the two fibre types, with a great overlap of individual values, however, being observed between the two fibre types (wool and mohair), raising concerns in the possible application of the α-helical content for distinguishing the two fibres.
- Full Text:
- Date Issued: 2020
- Authors: Notayi, Mzwamadoda
- Date: 2020
- Subjects: Textile fabrics , Textile fibers -- Mechanical properties Wool -- Dissertations Mohair -- Dissertations
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49248 , vital:41614
- Description: The possible application of the FT Raman, Raman micro-spectroscopy and ATR-FTIR micro-spectroscopy, have been investigated for distinguishing between wool and mohair. Highly identical Raman and FTIR spectra were obtained from the two fibre types, indicating that indeed they share similar basic molecular structural chemistry. The analysis of the amide I through curve fitting of wool and mohair FT Raman spectra showed that the protein and polypeptide secondary structure exists mainly in the α-helical structural conformation with smaller proportions of β-pleated sheet and β-Turns. These proportions, however, could not be used to distinguish between wool and mohair, due to the significant overlap observed between the two fibres. This study also determined the disulphide contents for possibly distinguishing between wool and mohair fibres, with the average and standard deviation values of 0.20±0.04 and 0.17±0.03 for wool and mohair, respectively, being found. Despite the mean values being found to differ statistically significant (p<0.05), a considerable overlap was observed, posing a doubt in the possible application of the method for distinguishing between the two fibres and blend composition analysis of the two fibres. The application of ratiometric analysis, based on the relative peak heights of certain FT Raman bands, showed that a combination of ratios A (I2932/I1450) and D (I508/I1450) could hold great potential in distinguishing between wool and mohair fibre samples. The individual values of ratios A and D varied a great deal from one mohair sample to the other and even more from one wool sample to another, with the individual values for ratio A ranging from 2.71-3.68 and 2.35-3.08 for wool and mohair, respectively, while ratio D ranged from 0.18-0.32 and 0.17-0.22 for wool and mohair, respectively. An important observation from this study is that if, for an unknown sample, if individual values of ratios A and D exceed 3.1 and 0.22, respectively, are found then the sample is most likely to be either a pure wool or blend of wool and mohair, whereas if all the values fall below the two threshold values, then the unknown sample can be declared a pure mohair sample. A Raman spectral database or library of approximately 100 high quality Raman average spectra of wool and mohair fibres has been established for the Bruker 80V FTIR/Raman spectrophotometer at the Nelson Mandela University (NMU). Although this has not been fully validated due to the unforeseen frequent breakdown encountered with the FT Raman system, at this stage, it has been realized that verification of unknown materials is highly possible. A great need for the development of a classification model based on multivariate or chemometrics has been realized. An ATR-FTIR LUMOS micro-spectroscopic system was also investigated for the possible application in distinguishing between wool and mohair single fibres. The amide I/II band ratios were determined for both wool and mohair fibres to distinguish between the two fibre types. The mean and standard deviation values of 1.20±0.02 and 1.21±0.01 for mohair and wool, respectively, were found and were shown not to differ statistically significant (p˃0.05). The secondary structure analysis showed that the content of the α-helical secondary structure might be different between the two fibre types, with a great overlap of individual values, however, being observed between the two fibre types (wool and mohair), raising concerns in the possible application of the α-helical content for distinguishing the two fibres.
- Full Text:
- Date Issued: 2020
The profile of local hunters in South Africa
- Du Plessis, Madelaine Patricia
- Authors: Du Plessis, Madelaine Patricia
- Date: 2020
- Subjects: Hunters -- Economic conditions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48324 , vital:40847
- Description: The South African hunting industry, but more specifically local hunting, is regarded as one of the key sectors within South Africa’s wildlife industry – not only for the significant economic contribution it makes, but also from an equally vital conservation point of view. Despite this, local hunters are neglected in the sense that hunting accommodation and hunting packages provided by the majority of game ranches mainly focus on accommodating trophy hunters. This study investigated the profile of local hunters in South Africa. The objectives of this study were the following: establishing the factors which determine the profile of local hunters and then comparing the results to existing information, as well as identifying the economic contribution local hunters make towards South Africa’s economy. The study commenced with a literature review of existing research on the local hunting industry and on the profile of local hunters. Thereafter, a self-administered questionnaire was developed and conducted amongst active local hunters via the CHASA hunting confederation website, by means of which the primary data for the current study were collected. The study concluded that the profile of the South African local hunter has undergone slight changes from what previous research had established. This was attributed to several external as well as internal factors. The current research would assist hunting farms in approaching the local hunting sector with up-to-date information in order to accurately tailor their packages and marketing in line with the evidence presented in this dissertation regarding the changes in the profile of the South African local hunter.
- Full Text:
- Date Issued: 2020
- Authors: Du Plessis, Madelaine Patricia
- Date: 2020
- Subjects: Hunters -- Economic conditions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48324 , vital:40847
- Description: The South African hunting industry, but more specifically local hunting, is regarded as one of the key sectors within South Africa’s wildlife industry – not only for the significant economic contribution it makes, but also from an equally vital conservation point of view. Despite this, local hunters are neglected in the sense that hunting accommodation and hunting packages provided by the majority of game ranches mainly focus on accommodating trophy hunters. This study investigated the profile of local hunters in South Africa. The objectives of this study were the following: establishing the factors which determine the profile of local hunters and then comparing the results to existing information, as well as identifying the economic contribution local hunters make towards South Africa’s economy. The study commenced with a literature review of existing research on the local hunting industry and on the profile of local hunters. Thereafter, a self-administered questionnaire was developed and conducted amongst active local hunters via the CHASA hunting confederation website, by means of which the primary data for the current study were collected. The study concluded that the profile of the South African local hunter has undergone slight changes from what previous research had established. This was attributed to several external as well as internal factors. The current research would assist hunting farms in approaching the local hunting sector with up-to-date information in order to accurately tailor their packages and marketing in line with the evidence presented in this dissertation regarding the changes in the profile of the South African local hunter.
- Full Text:
- Date Issued: 2020
The role of elephants in Hluhluwe-iMfolozi Park: Perceived versus measured effects on woody vegetation
- Authors: Mbongwa, Siphesihle
- Date: 2020
- Subjects: Woody plants -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48467 , vital:40879
- Description: Elephants were successfully reintroduced into the 900 km2 fenced Hluhluwe-iMfolozi Park (HiP) from 1981 onwards and their population has increased exponentially since. Their initial reintroduction was motivated by the need to control bush encroachment and to maintain ecosystems such as grassland and open woodland, and to restore ecological processes offered by elephants. The subject of the HiP elephant population and their impact on vegetation in the Park has become controversial; with some concerns being raised that the population is too high and is negatively affecting the vegetation. An absence of a vegetation monitoring programme in protected areas with elephants creates uncertainty leading to an ‗elephant impact‘ debate. This study aimed to compare the perceptions of stakeholders regarding the issue of elephant impact in HiP with measured elephant impact on the vegetation in the Park. The perceptions and concerns of stakeholders regarding the effects of elephants on vegetation in HiP were investigated using a questionnaire. Stakeholders reported that elephants and fire were the main factors shaping vegetation change in HiP over the past decade. Sclerocarya birrea, Senegalia burkei and Schotia brachypetala were reported as the most negatively affected species. Also reported that they are concerned about the effects of elephants on the number of tall trees in the park, tree mortality and elephant‘s effect on rare indigenous vegetation. Most interestingly, the results showed that the groups of stakeholders had different perceptions of the level of elephant impact on the vegetation in the park; except for researchers and tourists whose were not significantly different from each other. Managers had the most respondents that reported that the level of elephant impact is unacceptable, while most researchers and tourists reported that the level of elephant impact is at an acceptable level. Vegetation plots that had been surveyed in 1999, 2003 and 2007, were resurveyed in this study during 2017 to assess elephant impact on vegetation over time. Comparison between the years sampled showed that there was a decrease in the density of tall trees, while the density of trees in 0.5-2 and 2-4 m height classes increased over the same period. Elephants had a strong preference for utilizing tall trees (>4 m) and a strong avoidance for trees in the height range from 0.5-2m tall (Jacobs selection index 0.56 and -0.69, respectively). This trend was apparent for all sample periods. In addition, elephants also showed a strong preference for some rare species including S. brachypetala and Sideroxylon inerme. Between 1999 and 2017, the density of preferred species has decreased while the density of avoided species has increased. I conclude that elephants are having a noticeable impact on the vegetation at HiP by changing vegetation structure to a shrub dominated vegetation, and causing a shift in species composition towards avoided species. The findings of this study show that the perceptions of stakeholders on the effects of elephants and the level of elephant impact on vegetation match the results from measured elephant impact - vegetation survey. However, Thresholds of Potential Concern (TPCs) should be outlined in the elephant management plan and are required to determine whether the levels of elephant impact at HiP have exceeded an acceptable level or not. This study conforms to previous research that an uncontrolled elephant population can have substantial impacts in fenced reserves. This study shows the importance for long-term and continuous vegetation monitoring programme to obtain reliable data to determine trends in vegetation changes over time.
- Full Text:
- Date Issued: 2020
- Authors: Mbongwa, Siphesihle
- Date: 2020
- Subjects: Woody plants -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48467 , vital:40879
- Description: Elephants were successfully reintroduced into the 900 km2 fenced Hluhluwe-iMfolozi Park (HiP) from 1981 onwards and their population has increased exponentially since. Their initial reintroduction was motivated by the need to control bush encroachment and to maintain ecosystems such as grassland and open woodland, and to restore ecological processes offered by elephants. The subject of the HiP elephant population and their impact on vegetation in the Park has become controversial; with some concerns being raised that the population is too high and is negatively affecting the vegetation. An absence of a vegetation monitoring programme in protected areas with elephants creates uncertainty leading to an ‗elephant impact‘ debate. This study aimed to compare the perceptions of stakeholders regarding the issue of elephant impact in HiP with measured elephant impact on the vegetation in the Park. The perceptions and concerns of stakeholders regarding the effects of elephants on vegetation in HiP were investigated using a questionnaire. Stakeholders reported that elephants and fire were the main factors shaping vegetation change in HiP over the past decade. Sclerocarya birrea, Senegalia burkei and Schotia brachypetala were reported as the most negatively affected species. Also reported that they are concerned about the effects of elephants on the number of tall trees in the park, tree mortality and elephant‘s effect on rare indigenous vegetation. Most interestingly, the results showed that the groups of stakeholders had different perceptions of the level of elephant impact on the vegetation in the park; except for researchers and tourists whose were not significantly different from each other. Managers had the most respondents that reported that the level of elephant impact is unacceptable, while most researchers and tourists reported that the level of elephant impact is at an acceptable level. Vegetation plots that had been surveyed in 1999, 2003 and 2007, were resurveyed in this study during 2017 to assess elephant impact on vegetation over time. Comparison between the years sampled showed that there was a decrease in the density of tall trees, while the density of trees in 0.5-2 and 2-4 m height classes increased over the same period. Elephants had a strong preference for utilizing tall trees (>4 m) and a strong avoidance for trees in the height range from 0.5-2m tall (Jacobs selection index 0.56 and -0.69, respectively). This trend was apparent for all sample periods. In addition, elephants also showed a strong preference for some rare species including S. brachypetala and Sideroxylon inerme. Between 1999 and 2017, the density of preferred species has decreased while the density of avoided species has increased. I conclude that elephants are having a noticeable impact on the vegetation at HiP by changing vegetation structure to a shrub dominated vegetation, and causing a shift in species composition towards avoided species. The findings of this study show that the perceptions of stakeholders on the effects of elephants and the level of elephant impact on vegetation match the results from measured elephant impact - vegetation survey. However, Thresholds of Potential Concern (TPCs) should be outlined in the elephant management plan and are required to determine whether the levels of elephant impact at HiP have exceeded an acceptable level or not. This study conforms to previous research that an uncontrolled elephant population can have substantial impacts in fenced reserves. This study shows the importance for long-term and continuous vegetation monitoring programme to obtain reliable data to determine trends in vegetation changes over time.
- Full Text:
- Date Issued: 2020
The spatiotemporal aspects of predation on the Cape gannet Morus capensis population at the Lambert’s Bay gannet colony, Western Cape, South Africa
- Authors: Schoeman, Zanri
- Date: 2020
- Subjects: Sea birds -- South Africa -- Western Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47656 , vital:40262
- Description: Seabirds are one of the most threatened groups of birds with 29% of seabird species at some risk of extinction. As a result of multiple human-induced threats, seabird species including the Cape gannet Morus capensis which is endemic to southern Africa population experience significant declines and is now classified as Endangered. The Cape gannet faces predation threats from a variety of different species. The current predators of concern at Lambert’s Bay gannet colony are both the Cape fur seal Arctocephalus pusillus pusillus and the Kelp gull Larus dominancus. The former predates on fledglings and the latter predates on eggs. In the 2005/06 breeding season the entire Cape gannet population deserted the Lambert’s Bay gannet colony due to predation by the Cape fur seal. Although the Cape gannets have subsequently recovered to approximately 8000 pairs, seal predation on Cape gannet fledglings continues, together with predation by Kelp gulls. This has caused concern over the impact of predation on this species at the Lambert’s Bay colony, particularly given the species’ conservation status, its small breeding range and its current population trend. CapeNature, the conservation agency involved at this colony has been monitoring and managing the predation on Cape gannets and are interested in evaluating the success of their efforts. Therefore the aim of this study was to determine the spatial and temporal aspects of predation on the Cape gannet population at Lambert’s Bay gannet colony. When examining the influence of fish availability on predation intensity, we found that in years with an increase in fish biomass there was a decrease in predation probability by Cape fur seals. This increase in fish biomass not only led to decreased predation on the fledglings it also led to increased breeding success of the Cape gannets. In determining the effect of predation within the Cape gannet breeding colony we found that the probability of predation by Kelp gulls decreased in years with increased adult gannet density. Indirectly, Cape gannet population growth should lead to a decrease in Kelp gull predation as a higher gannet density increases the risk of injury to the Kelp gulls. This suggests that if Cape gannet populations continue to decline, they may become increasingly vulnerable to Kelp gull predation which can result in a further population decline. In terms of past management actions, the selective culling of predatory Cape fur seals and Kelp gulls, was evaluated. It was found that in the years in which culling of Cape fur seals and Kelp gulls was implemented, a decrease in predation was observed. This indicated that culling reduced predation in the short-term. Predation is inevitable, but due to the Cape gannet’s conservation status we suggest that additional, long-term, and more sustainable methods to reduce predation should be explored. Our research emphasises the need for improving food availability to Cape gannets as food security is paramount to their long-term survival and population growth. Colony management in isolation from other management strategies, is not efficient for conserving a species. We therefore suggest that sound management of predation at the terrestrial habitats are required but that effective management of fisheries are also required for the successful conservation of the Cape gannet. Food security for Cape gannets could be improved by, for example, establishing some ways that we suggest improving the food security for Cape gannets would be to establish Marine Protected Areas (MPAs) with dynamic boundaries around Cape gannet colonies, and to have locate the MPAs close to breeding and foraging hotspots where these areas are closed to fishing thus reducing the competition between commercial fisheries and marine predators, such as the Cape gannet. Another way to improve food security for the gannets are to promote the efforts of focussing on developing and implementing an ecosystem approach to fisheries management in which fishing quotas account for the needs of marine predators. The findings of this study have not only aided the understanding of the dynamics of predation on the Cape gannets and highlighted the extent that predation takes place on them but can also guide future management decisions regarding predation on this endemic and endangered species.
- Full Text:
- Date Issued: 2020
- Authors: Schoeman, Zanri
- Date: 2020
- Subjects: Sea birds -- South Africa -- Western Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47656 , vital:40262
- Description: Seabirds are one of the most threatened groups of birds with 29% of seabird species at some risk of extinction. As a result of multiple human-induced threats, seabird species including the Cape gannet Morus capensis which is endemic to southern Africa population experience significant declines and is now classified as Endangered. The Cape gannet faces predation threats from a variety of different species. The current predators of concern at Lambert’s Bay gannet colony are both the Cape fur seal Arctocephalus pusillus pusillus and the Kelp gull Larus dominancus. The former predates on fledglings and the latter predates on eggs. In the 2005/06 breeding season the entire Cape gannet population deserted the Lambert’s Bay gannet colony due to predation by the Cape fur seal. Although the Cape gannets have subsequently recovered to approximately 8000 pairs, seal predation on Cape gannet fledglings continues, together with predation by Kelp gulls. This has caused concern over the impact of predation on this species at the Lambert’s Bay colony, particularly given the species’ conservation status, its small breeding range and its current population trend. CapeNature, the conservation agency involved at this colony has been monitoring and managing the predation on Cape gannets and are interested in evaluating the success of their efforts. Therefore the aim of this study was to determine the spatial and temporal aspects of predation on the Cape gannet population at Lambert’s Bay gannet colony. When examining the influence of fish availability on predation intensity, we found that in years with an increase in fish biomass there was a decrease in predation probability by Cape fur seals. This increase in fish biomass not only led to decreased predation on the fledglings it also led to increased breeding success of the Cape gannets. In determining the effect of predation within the Cape gannet breeding colony we found that the probability of predation by Kelp gulls decreased in years with increased adult gannet density. Indirectly, Cape gannet population growth should lead to a decrease in Kelp gull predation as a higher gannet density increases the risk of injury to the Kelp gulls. This suggests that if Cape gannet populations continue to decline, they may become increasingly vulnerable to Kelp gull predation which can result in a further population decline. In terms of past management actions, the selective culling of predatory Cape fur seals and Kelp gulls, was evaluated. It was found that in the years in which culling of Cape fur seals and Kelp gulls was implemented, a decrease in predation was observed. This indicated that culling reduced predation in the short-term. Predation is inevitable, but due to the Cape gannet’s conservation status we suggest that additional, long-term, and more sustainable methods to reduce predation should be explored. Our research emphasises the need for improving food availability to Cape gannets as food security is paramount to their long-term survival and population growth. Colony management in isolation from other management strategies, is not efficient for conserving a species. We therefore suggest that sound management of predation at the terrestrial habitats are required but that effective management of fisheries are also required for the successful conservation of the Cape gannet. Food security for Cape gannets could be improved by, for example, establishing some ways that we suggest improving the food security for Cape gannets would be to establish Marine Protected Areas (MPAs) with dynamic boundaries around Cape gannet colonies, and to have locate the MPAs close to breeding and foraging hotspots where these areas are closed to fishing thus reducing the competition between commercial fisheries and marine predators, such as the Cape gannet. Another way to improve food security for the gannets are to promote the efforts of focussing on developing and implementing an ecosystem approach to fisheries management in which fishing quotas account for the needs of marine predators. The findings of this study have not only aided the understanding of the dynamics of predation on the Cape gannets and highlighted the extent that predation takes place on them but can also guide future management decisions regarding predation on this endemic and endangered species.
- Full Text:
- Date Issued: 2020
The taxonomic status of dolphins Tursiops spp. and Delphinus in South African waters
- Authors: Ngqulana, Sibusisiwe Gloria
- Date: 2020
- Subjects: Dolphins -- Classification -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48566 , vital:40891
- Description: There is a need for identifying important sites, taxonomic units or populations and the usual criterion used is species identification. The species is the most important taxonomic unit to define in taxonomy, as it is the primary unit of concern in biodiversity, conservation and other biological issues. Thus, taxonomy plays an important role in conservation biology. Additionally, taxonomy can contribute to the development of analytical systems that will provide information on priorities for reaching defensible targets for established conservation. This poses a problem for cetaceans as basic information is frequently deficient and therefore not suitable for conservation planning purposes. This leads to difficulties in identifying and prioritizing areas for the monitoring, management and for the protection of species or populations. Morphological and geographic data used to be the primary means used by taxonomists to define species and subspecies, and due to this, most extant species have been classified by morphological characteristics. However, in the recent years, molecular analyses have been introduced and subsequently stable isotopes were also included to assist in interpreting results. Thereafter, it became a common approach to use more than one technique or a combination of independent datasets to resolve taxonomic uncertainties. This has resulted to a proposed term known as integrative taxonomy. Integrative taxonomy has recently been used in most studies that deal with taxonomy or population structure. The use of multiple lines of evidence, which is sometimes referred to as integrative taxonomy, raises the level of confidence in clearly delineating species. Cetaceans are the most taxonomically diverse group of aquatic mammals, with 93 living species accepted. Previously, their taxonomy was based on morphological characters. However, cetaceans have recently been subjected to intense phylogenetic investigations using both morphological and molecular data. These problems are not only prevalent in larger whales, but the small toothed whales also have these challenges, particularly family Delphinidae. This family is known to be the most diverse among the toothed whales. This is because this family diverged recently, and the divergence occurred relatively fast. This study aimed to clarify the taxonomic status of Tursiops spp. and Delphinus in the family Delphinidae, inhabiting the South African waters, using a combination of morphological and molecular methods. For skull morphology, geometric morphometrics were used, while for molecular methods, the D-loop region in the mitochondrial DNA was used to detect any differences within each genus. For the genus Tursiops, this study showed the consistency of results in all analyses used to investigate the presence of two species in the genus Tursiops in South African waters. This study only analysed sequences from the mitochondrial D-loop region and has re-confirmed the presence of the two species in South Africa. Skull and external morphology both show T. truncatus to be bigger and more robust, and to have a shorter rostrum compared with T. aduncus. These external observations are helpful when identifying the species in the field. Providing evidence supporting the presence of two Tursiops species in South Africa does not only contribute to the global context of the taxonomy of this genus, but also in the local context. This study also gives insight on the distribution of the two species in the region. For the genus Delphinus, molecular analysis did not reveal any clustering in South African Delphinus specimens, which suggested a single species, D. delphis, and that this species is morphologically highly variable. Both skull and external morphology did not reflect the molecular results, supporting suggestions that morphology in this genus does not reflect genetic differences. It has been shown that morphological variation reflects feeding specialization rather than speciation. This may also reflect local adaptations. Both skull and external morphology in this study showed no significant differences. This study did not investigate the phylogeographic details of the species in South Africa and further molecular work including a larger sample size from the west coast of South Africa is needed. By attempting to unravel the taxonomy of these dolphins in South African waters, the findings of this study will be very useful in the development of effective conservation and management strategies for these dolphins.
- Full Text:
- Date Issued: 2020
- Authors: Ngqulana, Sibusisiwe Gloria
- Date: 2020
- Subjects: Dolphins -- Classification -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48566 , vital:40891
- Description: There is a need for identifying important sites, taxonomic units or populations and the usual criterion used is species identification. The species is the most important taxonomic unit to define in taxonomy, as it is the primary unit of concern in biodiversity, conservation and other biological issues. Thus, taxonomy plays an important role in conservation biology. Additionally, taxonomy can contribute to the development of analytical systems that will provide information on priorities for reaching defensible targets for established conservation. This poses a problem for cetaceans as basic information is frequently deficient and therefore not suitable for conservation planning purposes. This leads to difficulties in identifying and prioritizing areas for the monitoring, management and for the protection of species or populations. Morphological and geographic data used to be the primary means used by taxonomists to define species and subspecies, and due to this, most extant species have been classified by morphological characteristics. However, in the recent years, molecular analyses have been introduced and subsequently stable isotopes were also included to assist in interpreting results. Thereafter, it became a common approach to use more than one technique or a combination of independent datasets to resolve taxonomic uncertainties. This has resulted to a proposed term known as integrative taxonomy. Integrative taxonomy has recently been used in most studies that deal with taxonomy or population structure. The use of multiple lines of evidence, which is sometimes referred to as integrative taxonomy, raises the level of confidence in clearly delineating species. Cetaceans are the most taxonomically diverse group of aquatic mammals, with 93 living species accepted. Previously, their taxonomy was based on morphological characters. However, cetaceans have recently been subjected to intense phylogenetic investigations using both morphological and molecular data. These problems are not only prevalent in larger whales, but the small toothed whales also have these challenges, particularly family Delphinidae. This family is known to be the most diverse among the toothed whales. This is because this family diverged recently, and the divergence occurred relatively fast. This study aimed to clarify the taxonomic status of Tursiops spp. and Delphinus in the family Delphinidae, inhabiting the South African waters, using a combination of morphological and molecular methods. For skull morphology, geometric morphometrics were used, while for molecular methods, the D-loop region in the mitochondrial DNA was used to detect any differences within each genus. For the genus Tursiops, this study showed the consistency of results in all analyses used to investigate the presence of two species in the genus Tursiops in South African waters. This study only analysed sequences from the mitochondrial D-loop region and has re-confirmed the presence of the two species in South Africa. Skull and external morphology both show T. truncatus to be bigger and more robust, and to have a shorter rostrum compared with T. aduncus. These external observations are helpful when identifying the species in the field. Providing evidence supporting the presence of two Tursiops species in South Africa does not only contribute to the global context of the taxonomy of this genus, but also in the local context. This study also gives insight on the distribution of the two species in the region. For the genus Delphinus, molecular analysis did not reveal any clustering in South African Delphinus specimens, which suggested a single species, D. delphis, and that this species is morphologically highly variable. Both skull and external morphology did not reflect the molecular results, supporting suggestions that morphology in this genus does not reflect genetic differences. It has been shown that morphological variation reflects feeding specialization rather than speciation. This may also reflect local adaptations. Both skull and external morphology in this study showed no significant differences. This study did not investigate the phylogeographic details of the species in South Africa and further molecular work including a larger sample size from the west coast of South Africa is needed. By attempting to unravel the taxonomy of these dolphins in South African waters, the findings of this study will be very useful in the development of effective conservation and management strategies for these dolphins.
- Full Text:
- Date Issued: 2020