A potential biological role for microcystin in photosynthesis in Microcystis Aeruginosa
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
A preliminary investigation and photographic atlas of nodules found in the Bokkelveld group (Gydo formation), Steytlerville district, South Africa
- Authors: Browning, Claire
- Date: 2009
- Subjects: Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10656 , http://hdl.handle.net/10948/927 , Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Description: Nodules within the lower Bokkeveld shales often contain well-preserved invertebrate fossil material. The aim of this study was to describe some characteristics seen at various scales (macro-, micro- and ultra -) within nodules that might contribute to an understanding of aspects of nodule formation and the reasons for the excellent preservation of the fossil material within these nodules. Detailed, high quality macro-photographs were taken of sliced and whole nodule surfaces and a catalogue was produced to tentatively identify fossils present and illustrate the variations seen within nodules. Selected nodules were then subjected to petrographic, ultra-structural (SEM) and some chemical (EDS, XRD & XRF) analysis to investigate the possible reasons for these variations. The chemical results have indicated that nodules are enriched with quartz compared to the surrounding shale. Quartz is also the dominant mineral replacing trilobite carapace material within nodules, while trilobite material within shales is replaced with equal proportions of hematite, biotite and quartz. It appears that the higher resistance of quartz to weathering is the dominant factor leading to the preservation of both nodules within the shales and trilobite material within the nodules examined. A comparison with some Western Cape nodules highlighted possible variations in overall nodule chemical composition along strike. Western Cape nodules are predominantly composed of apatite whereas the Cockscomb nodules are mainly composed of quartz. This quartz-apatite compositional variation in nodules occurring within a single formation has been reported from nodules found in the Armorican Massif of France which are very similar in a number of respects to the Bokkeveld nodules described in this study. Based on various features of the fossils present and the structure of nodules they were probably formed during early diagenesis within an epeiric marine deposit greatly affected by sea level fluctuations.
- Full Text:
- Date Issued: 2009
- Authors: Browning, Claire
- Date: 2009
- Subjects: Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10656 , http://hdl.handle.net/10948/927 , Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Description: Nodules within the lower Bokkeveld shales often contain well-preserved invertebrate fossil material. The aim of this study was to describe some characteristics seen at various scales (macro-, micro- and ultra -) within nodules that might contribute to an understanding of aspects of nodule formation and the reasons for the excellent preservation of the fossil material within these nodules. Detailed, high quality macro-photographs were taken of sliced and whole nodule surfaces and a catalogue was produced to tentatively identify fossils present and illustrate the variations seen within nodules. Selected nodules were then subjected to petrographic, ultra-structural (SEM) and some chemical (EDS, XRD & XRF) analysis to investigate the possible reasons for these variations. The chemical results have indicated that nodules are enriched with quartz compared to the surrounding shale. Quartz is also the dominant mineral replacing trilobite carapace material within nodules, while trilobite material within shales is replaced with equal proportions of hematite, biotite and quartz. It appears that the higher resistance of quartz to weathering is the dominant factor leading to the preservation of both nodules within the shales and trilobite material within the nodules examined. A comparison with some Western Cape nodules highlighted possible variations in overall nodule chemical composition along strike. Western Cape nodules are predominantly composed of apatite whereas the Cockscomb nodules are mainly composed of quartz. This quartz-apatite compositional variation in nodules occurring within a single formation has been reported from nodules found in the Armorican Massif of France which are very similar in a number of respects to the Bokkeveld nodules described in this study. Based on various features of the fossils present and the structure of nodules they were probably formed during early diagenesis within an epeiric marine deposit greatly affected by sea level fluctuations.
- Full Text:
- Date Issued: 2009
A resource allocation system for invasive alien plant control on the St. Francis Conservancy
- Authors: Reeves, Brian
- Date: 2009
- Subjects: Alien plants -- Control -- South Africa , Plant invasions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10634 , http://hdl.handle.net/10948/1073 , Alien plants -- Control -- South Africa , Plant invasions -- South Africa
- Description: Alien invasive species pose a great threat to ecosystems and human communities (Richardson & van Wilgen 2004; Hobbs & Humphries 1995). On private lands, there is a need to find institutional, administrative and scientific responses to the alien plant problem that operate beyond the scale imposed by property boundaries (Slocombe 1998; Grumbine 1994). One such response is the development and support of institutions, such as the St Francis Conservancy, that foster cross-boundary management of landscapes (Hurley et al. 2002). This study seeks to promote collective decision-making and collaborative management by private landowners through the development of a resource allocation system for the control of alien invasive plants on the St Francis Conservancy. The conservancy is located in the south-eastern lowlands of the Cape Floristic Region, between the villages of Cape St Francis and Oyster Bay, and is comprised of the properties of multiple landowners. Mutliple Criteria Decision Analysis (MCDA) and Geographical Information Systems (GIS) techniques were integrated to provide a spatially explicit resource allocation system that considered environmental, social and economic concerns. The MCDA technique selected for use was the Analytical Hierarchy Process (AHP). This technique has a record of providing robust, defensible decisions and enabled the resource allocation decision-problem to be decomposed into a hierarchy of objectives, criteria and indicators. Stakeholders participated in the development of the resource allocation system, especially through providing input into the determination of the relative importance of criteria and indicators through the assignment of weights. Various weighting scenarios were presented and these were interpreted into an ii implementation plan. The costs and effort required to clear alien plants were estimated, and obstacles facing the implementation of the plan were identified.
- Full Text:
- Date Issued: 2009
- Authors: Reeves, Brian
- Date: 2009
- Subjects: Alien plants -- Control -- South Africa , Plant invasions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10634 , http://hdl.handle.net/10948/1073 , Alien plants -- Control -- South Africa , Plant invasions -- South Africa
- Description: Alien invasive species pose a great threat to ecosystems and human communities (Richardson & van Wilgen 2004; Hobbs & Humphries 1995). On private lands, there is a need to find institutional, administrative and scientific responses to the alien plant problem that operate beyond the scale imposed by property boundaries (Slocombe 1998; Grumbine 1994). One such response is the development and support of institutions, such as the St Francis Conservancy, that foster cross-boundary management of landscapes (Hurley et al. 2002). This study seeks to promote collective decision-making and collaborative management by private landowners through the development of a resource allocation system for the control of alien invasive plants on the St Francis Conservancy. The conservancy is located in the south-eastern lowlands of the Cape Floristic Region, between the villages of Cape St Francis and Oyster Bay, and is comprised of the properties of multiple landowners. Mutliple Criteria Decision Analysis (MCDA) and Geographical Information Systems (GIS) techniques were integrated to provide a spatially explicit resource allocation system that considered environmental, social and economic concerns. The MCDA technique selected for use was the Analytical Hierarchy Process (AHP). This technique has a record of providing robust, defensible decisions and enabled the resource allocation decision-problem to be decomposed into a hierarchy of objectives, criteria and indicators. Stakeholders participated in the development of the resource allocation system, especially through providing input into the determination of the relative importance of criteria and indicators through the assignment of weights. Various weighting scenarios were presented and these were interpreted into an ii implementation plan. The costs and effort required to clear alien plants were estimated, and obstacles facing the implementation of the plan were identified.
- Full Text:
- Date Issued: 2009
A Speciation study of the chloro-hydroxo complexes of Pt(II)
- Authors: Davis, John Christopher
- Date: 2009
- Subjects: Platinum , Platinum -- Separation , Platinum compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10388 , http://hdl.handle.net/10948/1213 , Platinum , Platinum -- Separation , Platinum compounds
- Description: In this study a method was developed to identify and quantify platinum(II) complexes of the type [PtCl4-n(OH)n]2- and [PtCl4-n(H2O)n]2-n. Separation of the various species was achieved with the aid of a hyphenated reversed phase HPLC-ICP-MS technique coupled with an ion-pairing reagent, HMHDCl2. The adsorption of HMHD2+ onto a C-18 column was investigated by generating a series of breakthrough curves. It was found that the selectivity for high charge density anions originates from its low surface coverage relative to TBA+, which on the other hand could not separate Pt(II) complexes. The peaks in the chromatographic traces were assigned by following the stepwise ligand substitution of [PtCl4]2- in hydroxide medium with UV/Vis spectrophotometry and HPLC-ICP-MS simultaneously. A computer program was written by the author to analyse chromatographic data by deconvoluting the chromatogram into its individual components and calculating the mole fraction of each component. The validity of the consecutive pseudo-first order model was validated by constructing 3D Mauser diagrams with the raw spectrophotometric data (A1 vs A2 vs A3). Additional software was used to simulate the raw spectrophotometric data and processed chromatographic data. The pseudo-first order rate constants obtained in both cases were in agreement with each other. Hence, peaks were assigned to [PtCl4]2-, [PtCl3(OH)]2-, [PtCl2(OH)2]2-, [PtCl3(H2O)]-. The molar extinction coefficient spectra of [PtCl3(OH)]2- and [PtCl2(OH)2]2- were obtained by simulating the spectrophotometric data at wavelengths from 280 to 450 nm. The reaction of [PtCl4]2- with sodium hydroxide was investigated with UV/Vis spectrophotometry at 25 °C. A rate constant consisting of a first and second order term was obtained. The first order term agreed with what has been reported in the literature for aquation of [PtCl4]2- at 25 degrees C. The influence of temperature was established by conducting the experiment at different temperatures. It was found that the reaction proceeds essentially via aquation at elevated temperatures.
- Full Text:
- Date Issued: 2009
- Authors: Davis, John Christopher
- Date: 2009
- Subjects: Platinum , Platinum -- Separation , Platinum compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10388 , http://hdl.handle.net/10948/1213 , Platinum , Platinum -- Separation , Platinum compounds
- Description: In this study a method was developed to identify and quantify platinum(II) complexes of the type [PtCl4-n(OH)n]2- and [PtCl4-n(H2O)n]2-n. Separation of the various species was achieved with the aid of a hyphenated reversed phase HPLC-ICP-MS technique coupled with an ion-pairing reagent, HMHDCl2. The adsorption of HMHD2+ onto a C-18 column was investigated by generating a series of breakthrough curves. It was found that the selectivity for high charge density anions originates from its low surface coverage relative to TBA+, which on the other hand could not separate Pt(II) complexes. The peaks in the chromatographic traces were assigned by following the stepwise ligand substitution of [PtCl4]2- in hydroxide medium with UV/Vis spectrophotometry and HPLC-ICP-MS simultaneously. A computer program was written by the author to analyse chromatographic data by deconvoluting the chromatogram into its individual components and calculating the mole fraction of each component. The validity of the consecutive pseudo-first order model was validated by constructing 3D Mauser diagrams with the raw spectrophotometric data (A1 vs A2 vs A3). Additional software was used to simulate the raw spectrophotometric data and processed chromatographic data. The pseudo-first order rate constants obtained in both cases were in agreement with each other. Hence, peaks were assigned to [PtCl4]2-, [PtCl3(OH)]2-, [PtCl2(OH)2]2-, [PtCl3(H2O)]-. The molar extinction coefficient spectra of [PtCl3(OH)]2- and [PtCl2(OH)2]2- were obtained by simulating the spectrophotometric data at wavelengths from 280 to 450 nm. The reaction of [PtCl4]2- with sodium hydroxide was investigated with UV/Vis spectrophotometry at 25 °C. A rate constant consisting of a first and second order term was obtained. The first order term agreed with what has been reported in the literature for aquation of [PtCl4]2- at 25 degrees C. The influence of temperature was established by conducting the experiment at different temperatures. It was found that the reaction proceeds essentially via aquation at elevated temperatures.
- Full Text:
- Date Issued: 2009
Advances in platinum-amine chemotherapeutic agents : their chemistry and applicationc
- Authors: Jaganath, Yatish
- Date: 2009
- Subjects: Coordination compounds , Antineoplastic antibiotics , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10446 , http://hdl.handle.net/10948/d1021222
- Description: The research conducted in this study focussed on advancing the knowledge database of diamineplatinum complexes on two frontiers: 1) the development of novel anticancer complexes, and 2) improvements in their synthetic chemistry. Novel square-planar dichloro and oxalato platinum(II) complexes were synthesized as potential anticancer agents in accordance with a comprehensive set of factors identified as being significant in optimizing such action. The nonleaving ligands consisted of asymmetric chelating chiral diamines of the form 1- (1-R-imidazol-2yl)(R')methanamine (R representing methyl, butyl and R' methyl, phenyl). The complexes were characterized by a host of spectral, thermal and crystallographic techniques. In addition, the stabilities of the complexes were monitored in aqueous and saline solutions. Cytotoxicity screening on three cultured cancer cell lines (MCF-7, HeLa and HT29) indicated the compounds, present as their respective racemates, to have rather modest activities relative to cisplatin; with complexes having the smallest substituents, R,R' = methyl, being most active. In recognition of the limitations of traditional silver-based syntheses of oxalatoplatinum(II) complexes, innovative non-silver methods were developed using the well known cancer drug, oxaliplatin, (trans-R,R-1,2- diaminocyclohexane)oxalatoplatinum(II), as a prototype. These involved direct ligand exchange reactions of the dichloro precursor, (trans-R,R-1,2- diaminocyclohexane)dichloroplatinum(II), with tetrabutylammonium oxalate in essentially non-aqueous solvents. A 90:10 mixture of isoamyl alcohol (3-methyl- 1-butanol):water, proved to be a promising solvent, enabling the recovery of pure oxaliplatin (~98 percent) after 9 hours at 88 °C in yields of up to 86 percent. In light of the perceived unique mode of anticancer action available to mononitroplatinum(IV) complexes (i.e. their STAT3-binding potential), octahedral diamineoxalatoplatinum(IV) complexes containing axially-coordinated nitro and halo co-ligands were synthesized and extensively characterized. Electrochemical studies revealed trends in reduction potential which could be correlated to structural / chemical traits of the coordinated diamine and axial ligands. The similarities of the determined cytotoxicities of the platinum(IV) compounds and their respective platinum(II) analogues, implicated reduction as a means of activation of the platinum(IV) complexes.
- Full Text:
- Date Issued: 2009
- Authors: Jaganath, Yatish
- Date: 2009
- Subjects: Coordination compounds , Antineoplastic antibiotics , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10446 , http://hdl.handle.net/10948/d1021222
- Description: The research conducted in this study focussed on advancing the knowledge database of diamineplatinum complexes on two frontiers: 1) the development of novel anticancer complexes, and 2) improvements in their synthetic chemistry. Novel square-planar dichloro and oxalato platinum(II) complexes were synthesized as potential anticancer agents in accordance with a comprehensive set of factors identified as being significant in optimizing such action. The nonleaving ligands consisted of asymmetric chelating chiral diamines of the form 1- (1-R-imidazol-2yl)(R')methanamine (R representing methyl, butyl and R' methyl, phenyl). The complexes were characterized by a host of spectral, thermal and crystallographic techniques. In addition, the stabilities of the complexes were monitored in aqueous and saline solutions. Cytotoxicity screening on three cultured cancer cell lines (MCF-7, HeLa and HT29) indicated the compounds, present as their respective racemates, to have rather modest activities relative to cisplatin; with complexes having the smallest substituents, R,R' = methyl, being most active. In recognition of the limitations of traditional silver-based syntheses of oxalatoplatinum(II) complexes, innovative non-silver methods were developed using the well known cancer drug, oxaliplatin, (trans-R,R-1,2- diaminocyclohexane)oxalatoplatinum(II), as a prototype. These involved direct ligand exchange reactions of the dichloro precursor, (trans-R,R-1,2- diaminocyclohexane)dichloroplatinum(II), with tetrabutylammonium oxalate in essentially non-aqueous solvents. A 90:10 mixture of isoamyl alcohol (3-methyl- 1-butanol):water, proved to be a promising solvent, enabling the recovery of pure oxaliplatin (~98 percent) after 9 hours at 88 °C in yields of up to 86 percent. In light of the perceived unique mode of anticancer action available to mononitroplatinum(IV) complexes (i.e. their STAT3-binding potential), octahedral diamineoxalatoplatinum(IV) complexes containing axially-coordinated nitro and halo co-ligands were synthesized and extensively characterized. Electrochemical studies revealed trends in reduction potential which could be correlated to structural / chemical traits of the coordinated diamine and axial ligands. The similarities of the determined cytotoxicities of the platinum(IV) compounds and their respective platinum(II) analogues, implicated reduction as a means of activation of the platinum(IV) complexes.
- Full Text:
- Date Issued: 2009
An investigation into a natural language interface for contact centers
- Authors: Sankar, Gopal Ravi
- Date: 2009
- Subjects: Call centers -- Management , Customer services -- Management , Telephone selling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10468 , http://hdl.handle.net/10948/890 , Call centers -- Management , Customer services -- Management , Telephone selling
- Description: Contact centres are the first point of contact between a company and a customer after the purchase of a product or service. These centres make use of contact centre agents to service customer queries. In the past contact centres hired as many agents as they could in order to service customers, which have led to an increase in personnel costs causing contact centres to become costly to run. Automation techniques were introduced to decrease personnel costs and one such technique is the Interactive Voice Response (IVR). The usability of IVR systems is, however, dismal. Customers would rather speak to a contact centre agent than navigate through the menu structure found in these systems. The menu structure has come under scrutiny because it is difficult to use and navigate, is often not aligned to caller usage patterns, and the menu options are long and vague. This research investigated whether a Natural Language Interface (NLI) could alleviate the problems inherent to IVR. NLIs, however, come with their own disadvantages of which the main ones are ambiguity and the loss of context of a conversation. Two prototypes were implemented, one of which resembled an IVR and the other an NLI (using ALICE concepts). An evaluation of two prototypes confirmed the advantages and disadvantages of these concepts in accordance to theory. A Hybrid prototype was proposed with the aid of two models. The model which proposed an NLI using a rule base was chosen for implementation. The Hybrid prototype was then evaluated against the NLI and IVR prototypes to deduce which prototype was the most effective, efficient and satisfying. The evaluation through the aid of descriptive and inferential statistics showed that the Hybrid prototype was the most usable prototype. The evaluation of the Hybrid prototype confirmed that a Hybrid approach could limit the shortcomings of IVR through the elimination of the menu structure found in these systems, thereby allowing users to state their queries in natural language. The incorporated rule base provided the Hybrid system with long term memory, eliminating one of the main disadvantages of NLIs.
- Full Text:
- Date Issued: 2009
- Authors: Sankar, Gopal Ravi
- Date: 2009
- Subjects: Call centers -- Management , Customer services -- Management , Telephone selling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10468 , http://hdl.handle.net/10948/890 , Call centers -- Management , Customer services -- Management , Telephone selling
- Description: Contact centres are the first point of contact between a company and a customer after the purchase of a product or service. These centres make use of contact centre agents to service customer queries. In the past contact centres hired as many agents as they could in order to service customers, which have led to an increase in personnel costs causing contact centres to become costly to run. Automation techniques were introduced to decrease personnel costs and one such technique is the Interactive Voice Response (IVR). The usability of IVR systems is, however, dismal. Customers would rather speak to a contact centre agent than navigate through the menu structure found in these systems. The menu structure has come under scrutiny because it is difficult to use and navigate, is often not aligned to caller usage patterns, and the menu options are long and vague. This research investigated whether a Natural Language Interface (NLI) could alleviate the problems inherent to IVR. NLIs, however, come with their own disadvantages of which the main ones are ambiguity and the loss of context of a conversation. Two prototypes were implemented, one of which resembled an IVR and the other an NLI (using ALICE concepts). An evaluation of two prototypes confirmed the advantages and disadvantages of these concepts in accordance to theory. A Hybrid prototype was proposed with the aid of two models. The model which proposed an NLI using a rule base was chosen for implementation. The Hybrid prototype was then evaluated against the NLI and IVR prototypes to deduce which prototype was the most effective, efficient and satisfying. The evaluation through the aid of descriptive and inferential statistics showed that the Hybrid prototype was the most usable prototype. The evaluation of the Hybrid prototype confirmed that a Hybrid approach could limit the shortcomings of IVR through the elimination of the menu structure found in these systems, thereby allowing users to state their queries in natural language. The incorporated rule base provided the Hybrid system with long term memory, eliminating one of the main disadvantages of NLIs.
- Full Text:
- Date Issued: 2009
An investigation into the use of guidelines and patterns in the interaction design process
- Authors: Cowley, Niel Lester Orr
- Date: 2009
- Subjects: Human-computer interaction , Web sites -- Design , User interfaces (Computer systems) -- Design
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10466 , http://hdl.handle.net/10948/1062 , Human-computer interaction , Web sites -- Design , User interfaces (Computer systems) -- Design
- Description: Design guidelines are used in interaction design (IxD) for physical design and for evaluating the usability of designs and interactive products. Guidelines are widely used for physical design and evaluation, but have a number of problems. IxD patterns have been proposed as an alternative to guidelines, as they are claimed to have several advantages over guidelines. A small number of empirical studies provide evidence that patterns are beneficial when used in IxD. Additional research on the usefulness of IxD patterns is required. The primary research question investigated in this thesis was thus: How useful are IxD patterns as physical design and evaluation aids in IxD, as compared to design guidelines? The role of guidelines and patterns as design and evaluation aids in IxD was investigated and a comparison of guidelines and patterns, based on a set of guideline and pattern properties, was conducted. The concept of pattern and guideline usefulness was explored and a research agenda for guidelines and patterns was identified, together with a set of research questions for an empirical study. The empirical study of the use of patterns for evaluation, redesign and new design, as compared to guidelines, was conducted at the Nelson Mandela Metropolitan University in 2004. The participants were a purposive sample of post-graduate Computing students, who were regarded as novice interaction designers. Two equivalent groups were formed, one that used patterns and one that used guidelines. Patterns were found to be as useful as guidelines when used as evaluation aids. Guidelines and patterns were identified as effective tools for identifying and explaining usability issues and design features. Best-effort matched sets of guidelines and patterns produced substantially different result sets when used to identify issues and features, with fairly low overlap. A substantial evaluator effect was observed for the use of guidelines and patterns for evaluation, and the results obtained were similar to those obtained by Molich et al. in their Comparative Usability Evaluation (CUE) studies. There was no statistically significant difference between the effectiveness of guidelines and patterns for evaluation. There was also no statistically significant difference between the perceived efficiency, effectiveness and satisfaction in use of guidelines and patterns for evaluation. Guidelines and patterns were found to be used in similar ways for evaluation. Patterns were found to be more effective than guidelines for redesign. Patterns were found to be as useful as guidelines when used for new design. There was no statistically significant difference between the effectiveness of guidelines and patterns for new design. There was also no statistically significant difference between the perceived efficiency, effectiveness and satisfaction in use of guidelines and patterns for redesign and new design. Guidelines and patterns were found to be used in similar ways for design. There was no statistically significant difference between the perceived usefulness of the format, content, ease of learning, and usefulness as personal and shared design languages, of guidelines and patterns. Both participant groups were equally agreeable to using guidelines and patterns in the future. The perceived usefulness of pattern collections was found to depend on the usability of the collection interface and the content quality of the patterns. The results of the empirical study thus provided empirical evidence that patterns were as useful as guidelines for evaluation and new design, and were perceived as positively as guidelines were. Patterns were found to be superior to guidelines for redesign. Patterns can therefore be used with a measure of confidence as early stage design aids for physical design and evaluation in the future. In addition to these findings, a number of opportunities for further research were identified.
- Full Text:
- Date Issued: 2009
- Authors: Cowley, Niel Lester Orr
- Date: 2009
- Subjects: Human-computer interaction , Web sites -- Design , User interfaces (Computer systems) -- Design
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10466 , http://hdl.handle.net/10948/1062 , Human-computer interaction , Web sites -- Design , User interfaces (Computer systems) -- Design
- Description: Design guidelines are used in interaction design (IxD) for physical design and for evaluating the usability of designs and interactive products. Guidelines are widely used for physical design and evaluation, but have a number of problems. IxD patterns have been proposed as an alternative to guidelines, as they are claimed to have several advantages over guidelines. A small number of empirical studies provide evidence that patterns are beneficial when used in IxD. Additional research on the usefulness of IxD patterns is required. The primary research question investigated in this thesis was thus: How useful are IxD patterns as physical design and evaluation aids in IxD, as compared to design guidelines? The role of guidelines and patterns as design and evaluation aids in IxD was investigated and a comparison of guidelines and patterns, based on a set of guideline and pattern properties, was conducted. The concept of pattern and guideline usefulness was explored and a research agenda for guidelines and patterns was identified, together with a set of research questions for an empirical study. The empirical study of the use of patterns for evaluation, redesign and new design, as compared to guidelines, was conducted at the Nelson Mandela Metropolitan University in 2004. The participants were a purposive sample of post-graduate Computing students, who were regarded as novice interaction designers. Two equivalent groups were formed, one that used patterns and one that used guidelines. Patterns were found to be as useful as guidelines when used as evaluation aids. Guidelines and patterns were identified as effective tools for identifying and explaining usability issues and design features. Best-effort matched sets of guidelines and patterns produced substantially different result sets when used to identify issues and features, with fairly low overlap. A substantial evaluator effect was observed for the use of guidelines and patterns for evaluation, and the results obtained were similar to those obtained by Molich et al. in their Comparative Usability Evaluation (CUE) studies. There was no statistically significant difference between the effectiveness of guidelines and patterns for evaluation. There was also no statistically significant difference between the perceived efficiency, effectiveness and satisfaction in use of guidelines and patterns for evaluation. Guidelines and patterns were found to be used in similar ways for evaluation. Patterns were found to be more effective than guidelines for redesign. Patterns were found to be as useful as guidelines when used for new design. There was no statistically significant difference between the effectiveness of guidelines and patterns for new design. There was also no statistically significant difference between the perceived efficiency, effectiveness and satisfaction in use of guidelines and patterns for redesign and new design. Guidelines and patterns were found to be used in similar ways for design. There was no statistically significant difference between the perceived usefulness of the format, content, ease of learning, and usefulness as personal and shared design languages, of guidelines and patterns. Both participant groups were equally agreeable to using guidelines and patterns in the future. The perceived usefulness of pattern collections was found to depend on the usability of the collection interface and the content quality of the patterns. The results of the empirical study thus provided empirical evidence that patterns were as useful as guidelines for evaluation and new design, and were perceived as positively as guidelines were. Patterns were found to be superior to guidelines for redesign. Patterns can therefore be used with a measure of confidence as early stage design aids for physical design and evaluation in the future. In addition to these findings, a number of opportunities for further research were identified.
- Full Text:
- Date Issued: 2009
An investigation of the factors influencing vegetation stress in a part of the Keiskamma catchment, Eastern Cape : a remote sensing and GIS approach
- Haindongo, Priscilla Nauwanga
- Authors: Haindongo, Priscilla Nauwanga
- Date: 2009
- Subjects: Plants, Effect of stress on -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Vegetation and climate -- South Africa -- Eastern Cape , Ecology -- South Africa -- Eastern Cape -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10652 , http://hdl.handle.net/10948/975 , Plants, Effect of stress on -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Vegetation and climate -- South Africa -- Eastern Cape , Ecology -- South Africa -- Eastern Cape -- Remote sensing
- Description: Vegetation stress as a form of degradation is a widespread problem in many catchments in the Eastern Cape province. The Keiskamma is one of the catchments where considerable parts of the thicket biome are stressed. This necessitates an assessment of the status of the thicket biome by way of detecting vegetation stress in the area. The underpinnings of vegetation stress are investigated in this study. As a basic method to evaluate the thicket condition, remotely sensed data were acquired. High resolution ASTER imagery for the Keiskamma area at two different dates (2001 and 2005) was used to compute SVI and NDVI as indicators of vegetation stress conditions. A Digital Elevation Model (DEM) was used to derive slope angle and aspect. By way of digitizing from ortho-photo maps, various land-use types were mapped using Arc View GIS. The relationship between land use, terrain, soil erosion and vegetation stress was established. Field based techniques comprising stomatal conductance measurements were used and compared to remotely sensed data. The SVI and NDVI resultant images expressed similarities in areas depicting vegetation stress conditions at both epochs. A strong linear regression between NDVI and stomatal conductance measurements (mmol/m²) serve to confirm that the NDVI is a reliable indicator of vegetation stress condition. Slope angle and aspect were found to have a significant influence on vegetation stress conditions. Similarly variations in soil moisture and soil surface condition have strong implications for vegetation stress. Amongst other land-use types, abandoned lands were found to have the lowest NDVI values implying an association with the worst vegetation stress scenarios. It was concluded that an element of persistent stress conditions exists amongst the thicket vegetation of the Keiskamma catchment. This was mainly due to land use activities in the area.
- Full Text:
- Date Issued: 2009
- Authors: Haindongo, Priscilla Nauwanga
- Date: 2009
- Subjects: Plants, Effect of stress on -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Vegetation and climate -- South Africa -- Eastern Cape , Ecology -- South Africa -- Eastern Cape -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10652 , http://hdl.handle.net/10948/975 , Plants, Effect of stress on -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Vegetation and climate -- South Africa -- Eastern Cape , Ecology -- South Africa -- Eastern Cape -- Remote sensing
- Description: Vegetation stress as a form of degradation is a widespread problem in many catchments in the Eastern Cape province. The Keiskamma is one of the catchments where considerable parts of the thicket biome are stressed. This necessitates an assessment of the status of the thicket biome by way of detecting vegetation stress in the area. The underpinnings of vegetation stress are investigated in this study. As a basic method to evaluate the thicket condition, remotely sensed data were acquired. High resolution ASTER imagery for the Keiskamma area at two different dates (2001 and 2005) was used to compute SVI and NDVI as indicators of vegetation stress conditions. A Digital Elevation Model (DEM) was used to derive slope angle and aspect. By way of digitizing from ortho-photo maps, various land-use types were mapped using Arc View GIS. The relationship between land use, terrain, soil erosion and vegetation stress was established. Field based techniques comprising stomatal conductance measurements were used and compared to remotely sensed data. The SVI and NDVI resultant images expressed similarities in areas depicting vegetation stress conditions at both epochs. A strong linear regression between NDVI and stomatal conductance measurements (mmol/m²) serve to confirm that the NDVI is a reliable indicator of vegetation stress condition. Slope angle and aspect were found to have a significant influence on vegetation stress conditions. Similarly variations in soil moisture and soil surface condition have strong implications for vegetation stress. Amongst other land-use types, abandoned lands were found to have the lowest NDVI values implying an association with the worst vegetation stress scenarios. It was concluded that an element of persistent stress conditions exists amongst the thicket vegetation of the Keiskamma catchment. This was mainly due to land use activities in the area.
- Full Text:
- Date Issued: 2009
Chang liver cell line as a model for Type II Diabetes in the liver and possible reversal of this condition by an indigenous medicinal plant
- Authors: Williams, Saralene Iona
- Date: 2009
- Subjects: Diabetes -- Alternative treatment , Medicinal plants , Traditional medicine , Liver -- Diseases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10339 , http://hdl.handle.net/10948/d1016179
- Description: The incidence of Type 2 Diabetes Mellittus (T2DM) is increasing world wide. In Africa the limited access to health care and the insidious course of the disease lead to more severe illness and diabetic complications. There is a need to find alternative approaches to treatment and prevention that address the problems and needs of Africa. Sutherlandia frutescens (S.frutescens) is a traditional herbal plant with known anti-diabetic properties, the precise mechanism of action of S.frutescens is not known. In order to develop new approaches for treatment and prevention of T2DM the pathophysiology of T2DM must be understood. T2DM is the final outcome of a multi-organ disease characterized by early defects in muscle, adipocytes, hepatocytes and pancreatic β-cells. In this study the role of the liver was investigated because of its central role in glucose and lipid metabolism. It is hard to differentiate between all the influences in an in vivo model, so the aim of this study was to develop an in vitro model of T2DM in Chang liver cells and to determine if S.frutescens can reverse the state of insulin resistance in this model. Different culture media conditions were screened to identify a method that can be used as the T2DM model in Chang liver cells. Serum free medium (MCBD-201) supplemented with human diabetic serum, (2.5%-10%), high insulin concentrations (0.1μM-1μM), high fructose concentrations (1-10mM). and a combination of high insulin and high fructose was used for this screening. Chang liver cells cultured in MCBD-201 medium supplemented with 1mM fructose and 0.1μM insulin showed reduced glucose uptake and increased lipid accumulation. The effect of two S.frutescens extracts, two anti-diabetic drugs, metformin and ciglitazone, and a hypolipidemic drug ciprofibrate were determined and shown to increase glucose uptake and reduce lipid accumulation. It was postulated that exposing the cells to excess nutrients in the form of high fructose would stimulate the cells to become adipogenic and accumulate lipids, which would interfere with the glucose uptake and induce insulin resistance. Gene expression of PPARγ, PPARα, and SREBP-1 transcription factors regulating lipid metabolism was determined in Chang liver cells cultured in insulin resistance inducing medium over a 48 hour time course. The expression of PPARγ, known to stimulate adipogenesis was increased after 6, 24 and 48 hours of exposure (P(H1)<0.0001). The expression of PPARα, known to stimulate β-oxidation expression, was significantly decreased after 24 hours of exposure (P(H1)<0.0001). The presence of the plant extracts in the insulin resistance inducing media protect against this increase in adipogenesis and decrease in β-oxidation after 48 hours of exposure by increasing PPARα expression and decreasing PPARγ expression. A PCR Array was performed which identified 32 more potential molecular targets of S.frutescens. Five of the 32 targets identified with the PCR Array were validated using qRT-PCR. These genes play a role in lipid and glucose metabolism and protection against oxidative stress and inflammation. In summary a cellular model of insulin resistace in hepatocytes has been established and the capacity of S.frutescens to reverse this process has been demonstrated by acting as a dual PPARγ/α agonist. New genes have been identified in the development of insulin resistance and as targets of S.frutescens.
- Full Text:
- Date Issued: 2009
- Authors: Williams, Saralene Iona
- Date: 2009
- Subjects: Diabetes -- Alternative treatment , Medicinal plants , Traditional medicine , Liver -- Diseases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10339 , http://hdl.handle.net/10948/d1016179
- Description: The incidence of Type 2 Diabetes Mellittus (T2DM) is increasing world wide. In Africa the limited access to health care and the insidious course of the disease lead to more severe illness and diabetic complications. There is a need to find alternative approaches to treatment and prevention that address the problems and needs of Africa. Sutherlandia frutescens (S.frutescens) is a traditional herbal plant with known anti-diabetic properties, the precise mechanism of action of S.frutescens is not known. In order to develop new approaches for treatment and prevention of T2DM the pathophysiology of T2DM must be understood. T2DM is the final outcome of a multi-organ disease characterized by early defects in muscle, adipocytes, hepatocytes and pancreatic β-cells. In this study the role of the liver was investigated because of its central role in glucose and lipid metabolism. It is hard to differentiate between all the influences in an in vivo model, so the aim of this study was to develop an in vitro model of T2DM in Chang liver cells and to determine if S.frutescens can reverse the state of insulin resistance in this model. Different culture media conditions were screened to identify a method that can be used as the T2DM model in Chang liver cells. Serum free medium (MCBD-201) supplemented with human diabetic serum, (2.5%-10%), high insulin concentrations (0.1μM-1μM), high fructose concentrations (1-10mM). and a combination of high insulin and high fructose was used for this screening. Chang liver cells cultured in MCBD-201 medium supplemented with 1mM fructose and 0.1μM insulin showed reduced glucose uptake and increased lipid accumulation. The effect of two S.frutescens extracts, two anti-diabetic drugs, metformin and ciglitazone, and a hypolipidemic drug ciprofibrate were determined and shown to increase glucose uptake and reduce lipid accumulation. It was postulated that exposing the cells to excess nutrients in the form of high fructose would stimulate the cells to become adipogenic and accumulate lipids, which would interfere with the glucose uptake and induce insulin resistance. Gene expression of PPARγ, PPARα, and SREBP-1 transcription factors regulating lipid metabolism was determined in Chang liver cells cultured in insulin resistance inducing medium over a 48 hour time course. The expression of PPARγ, known to stimulate adipogenesis was increased after 6, 24 and 48 hours of exposure (P(H1)<0.0001). The expression of PPARα, known to stimulate β-oxidation expression, was significantly decreased after 24 hours of exposure (P(H1)<0.0001). The presence of the plant extracts in the insulin resistance inducing media protect against this increase in adipogenesis and decrease in β-oxidation after 48 hours of exposure by increasing PPARα expression and decreasing PPARγ expression. A PCR Array was performed which identified 32 more potential molecular targets of S.frutescens. Five of the 32 targets identified with the PCR Array were validated using qRT-PCR. These genes play a role in lipid and glucose metabolism and protection against oxidative stress and inflammation. In summary a cellular model of insulin resistace in hepatocytes has been established and the capacity of S.frutescens to reverse this process has been demonstrated by acting as a dual PPARγ/α agonist. New genes have been identified in the development of insulin resistance and as targets of S.frutescens.
- Full Text:
- Date Issued: 2009
Characterization of hydrogen and helium implanted silicon carbide
- Authors: O'Connell, Jacques Herman
- Date: 2009
- Subjects: Silicon carbide , Hydrogen , Helium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10539 , http://hdl.handle.net/10948/979 , Silicon carbide , Hydrogen , Helium
- Description: This dissertation focuses on the characterization of hydrogen implanted 3C-SiC and helium implanted 6H-SiC and the interaction of silver and palladium with the SiC. The main technique used for the analysis of the implanted SiC was transmission electron microscopy (TEM), although scanning electron microscopy (SEM) and nanoindentation hardness testing were also used. Both H and He implantations were done at an ion energy of 100 keV and the total dose for both species was 1017 ions/cm2. Specimens were annealed at 1000 °C for 20 min in an inert atmosphere. The observed depth of ion damage agreed closely with that predicted by TRIM 2008. The damaged region in the He implanted specimens had a high density of small bubbles but no cracks were observed. Severe cracking was observed along the damaged region in the H implanted specimens. A second phase hexagonal (4H-SiC) was detected in two grains in the 3C-SiC and some grown in voids were also observed. The wettability of SiC by a 2:1 by volume mixture of Ag and Pd is extremely low but is significantly increased through the addition of Si to the mixture. The Si containing metal mixture was found to migrate along the grain boundaries of polycrystalline 3CSiC while sealing the point of entry. Pd attacks SiC and severe etching was observed on the surface of 6H-SiC. An epitaxially orientated Pd2Si inclusion was observed in the 6H-SiC. No effect of implantation damage on the interaction of Pd and Ag with SiC was observed. Pd etched the surface of the He implanted 6H-SiC down through the damaged region with no evidence of implantation damage left after 67 hours of annealing and thus no conclusions could be drawn. The metal mixture interacted with the non implanted surface of the H implanted 3C-SiC after dissolving the Si substrate and therefore the effect of the ion damage on the interaction could not be investigated. Nanoindentation hardness measurements showed a marked increase in hardness of He implanted 6H-SiC annealed for 20 min at 1000 °C over that of as implanted and virgin material. There was also a large decrease in hardness corresponding to the depth of the ion damage.
- Full Text:
- Date Issued: 2009
- Authors: O'Connell, Jacques Herman
- Date: 2009
- Subjects: Silicon carbide , Hydrogen , Helium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10539 , http://hdl.handle.net/10948/979 , Silicon carbide , Hydrogen , Helium
- Description: This dissertation focuses on the characterization of hydrogen implanted 3C-SiC and helium implanted 6H-SiC and the interaction of silver and palladium with the SiC. The main technique used for the analysis of the implanted SiC was transmission electron microscopy (TEM), although scanning electron microscopy (SEM) and nanoindentation hardness testing were also used. Both H and He implantations were done at an ion energy of 100 keV and the total dose for both species was 1017 ions/cm2. Specimens were annealed at 1000 °C for 20 min in an inert atmosphere. The observed depth of ion damage agreed closely with that predicted by TRIM 2008. The damaged region in the He implanted specimens had a high density of small bubbles but no cracks were observed. Severe cracking was observed along the damaged region in the H implanted specimens. A second phase hexagonal (4H-SiC) was detected in two grains in the 3C-SiC and some grown in voids were also observed. The wettability of SiC by a 2:1 by volume mixture of Ag and Pd is extremely low but is significantly increased through the addition of Si to the mixture. The Si containing metal mixture was found to migrate along the grain boundaries of polycrystalline 3CSiC while sealing the point of entry. Pd attacks SiC and severe etching was observed on the surface of 6H-SiC. An epitaxially orientated Pd2Si inclusion was observed in the 6H-SiC. No effect of implantation damage on the interaction of Pd and Ag with SiC was observed. Pd etched the surface of the He implanted 6H-SiC down through the damaged region with no evidence of implantation damage left after 67 hours of annealing and thus no conclusions could be drawn. The metal mixture interacted with the non implanted surface of the H implanted 3C-SiC after dissolving the Si substrate and therefore the effect of the ion damage on the interaction could not be investigated. Nanoindentation hardness measurements showed a marked increase in hardness of He implanted 6H-SiC annealed for 20 min at 1000 °C over that of as implanted and virgin material. There was also a large decrease in hardness corresponding to the depth of the ion damage.
- Full Text:
- Date Issued: 2009
Compensation for polarization mode dispersion and nonlinear birefringence in a multichannel optical fibre system
- Authors: Waswa, David Wafula
- Date: 2009
- Subjects: Fiber optics , Nonlinear optics , Polarization (Light)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10375 , http://hdl.handle.net/10948/885 , Fiber optics , Nonlinear optics , Polarization (Light)
- Description: Polarization mode dispersion (PMD) is stochastic in nature and continues evolving in an unpredictable manner according to the changing environment. Nonlinear birefringence in multichannel systems alters the polarization states of the bits, so that they vary from one bit to the next in a way that is difficult to predict. These are the two major signal-impairment effects that are inherent in optical fibre transmission links which can seriously degrade network performance. It is therefore extremely challenging to compensate for both linear and nonlinear birefringence in multichannel systems. The purpose of this thesis is to investigate the interaction between PMD and nonlinear induced birefringence in a fibre with consideration of mode coupling. A sound knowledge of this interaction is necessary in designing a linear and nonlinear polarization mode dispersion compensator for WDM systems, as was successfully carried out in this study. The investigation shows that the effect of nonlinear birefringence alone depolarizes the signal, while in high PMD links where polarization mode coupling is high, the nonlinear birefringence effect couples with second-order PMD such that it may reduce the penalty and improve the signal DOP. Further investigation shows that when nonlinear birefringence becomes significant, asymmetry arises between the two principal axes of the fibre, such that it is only one axis which experiences the effect of nonlinear birefringence. It is found out that along this vii axis, there exists a critical point in pump power where the nonlinear birefringence cancels PMD in the link and improves the signal. An adaptive compensator to cancel PMD and nonlinear birefringence was designed based on feedforward DOP-monitoring signal. The compensator was tested both at laboratory level and on the Telkom buried fibre link and found to be functioning as intended. It was able to adaptively track and compensate PMD in the link in less than a second. The compensator was able to cancel PMD in the link up to a maximum of 30 ps. The compensator improved the DOP of the worst signal by more than 100 percent.
- Full Text:
- Date Issued: 2009
- Authors: Waswa, David Wafula
- Date: 2009
- Subjects: Fiber optics , Nonlinear optics , Polarization (Light)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10375 , http://hdl.handle.net/10948/885 , Fiber optics , Nonlinear optics , Polarization (Light)
- Description: Polarization mode dispersion (PMD) is stochastic in nature and continues evolving in an unpredictable manner according to the changing environment. Nonlinear birefringence in multichannel systems alters the polarization states of the bits, so that they vary from one bit to the next in a way that is difficult to predict. These are the two major signal-impairment effects that are inherent in optical fibre transmission links which can seriously degrade network performance. It is therefore extremely challenging to compensate for both linear and nonlinear birefringence in multichannel systems. The purpose of this thesis is to investigate the interaction between PMD and nonlinear induced birefringence in a fibre with consideration of mode coupling. A sound knowledge of this interaction is necessary in designing a linear and nonlinear polarization mode dispersion compensator for WDM systems, as was successfully carried out in this study. The investigation shows that the effect of nonlinear birefringence alone depolarizes the signal, while in high PMD links where polarization mode coupling is high, the nonlinear birefringence effect couples with second-order PMD such that it may reduce the penalty and improve the signal DOP. Further investigation shows that when nonlinear birefringence becomes significant, asymmetry arises between the two principal axes of the fibre, such that it is only one axis which experiences the effect of nonlinear birefringence. It is found out that along this vii axis, there exists a critical point in pump power where the nonlinear birefringence cancels PMD in the link and improves the signal. An adaptive compensator to cancel PMD and nonlinear birefringence was designed based on feedforward DOP-monitoring signal. The compensator was tested both at laboratory level and on the Telkom buried fibre link and found to be functioning as intended. It was able to adaptively track and compensate PMD in the link in less than a second. The compensator was able to cancel PMD in the link up to a maximum of 30 ps. The compensator improved the DOP of the worst signal by more than 100 percent.
- Full Text:
- Date Issued: 2009
Complexes of the ReO³⁺/Re(CO)₃cores with multidentate N,O-Donor chelates
- Authors: Potgieter, Kim Carey
- Date: 2009
- Subjects: Rhenium , Schiff bases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10387 , http://hdl.handle.net/10948/1225 , Rhenium , Schiff bases
- Description: This study investigates the coordination modes of multidentate N,O-donor ligands toward the [ReVO]3+ and fac-[ReI(CO)3]+ cores. The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with 4-aminoantipyrine (H2pap) were studied, and the complexes cis-[ReX2(pap)(H2pap)(PPh3)](ReO4) were isolated. The X-ray crystal structures show that both complexes display a distorted octahedral geometry around the central rhenium atom, and are mirror images of each other. The ligand pap is coordinated monodentately through the doubly deprotonated amino nitrogen as an imide, and H2pap acts as a neutral bidentate chelate, with coordination through the neutral amino nitrogen and the ketonic oxygen. The attempted synthesis of the potentially hexadentate Schiff base ligand 1,2-bis(2-{(Z)- [(2-hydroxyphenyl)imido]methyl}phenoxy)benzene from the condensation reaction of 2- (2-((2-aminophenoxy)methyl)benzyloxy)benzenamine and salicylaldehyde produced the zwitterion derivative (H2ono) of 2-{(Z)-[2-(hydroxyphenyl)imino]methyl}phenol. The tridentate Schiff bases (Z)-2-(2-aminobenzylideneamino)phenol (H3onn) and (Z)-2-(2- (methylthio)benzylideneamino)phenol (Hons) were prepared in a similar manner. The reaction of H2ono with trans-[ReOBr3(PPh3)2] surprisingly led to the isolation of the rhenium(III) complex [ReBr(PPh3)2(ono)], in which ono acts as a dianionic tridentate ligand. The reaction of H3onn with trans-[ReOBr3(PPh3)2] produced the imidorhenium(V) complex salt [ReBr(PPh3)2(onn)]Br, in which onn is coordinated as a trianionic tridentate imidoiminophenolate. The reaction of Hons with [Re(CO)5Br] led to the further decomposition of the Hons ligand, and the rhenium(I) product fac- [Re(CO)3(ons)(Hno)] (Hno = 2-aminophenol) was isolated, with ons coordinated as a monoanionic bidentate chelate (with a free SCH3 group), and Hno present as a neutral monodentate ligand with coordination through the amino nitrogen atom. Abstract Nelson Mandela Metropolitan University vi The reactions of the potentially hexadentate ligand N,N’-{ethane-1,2- diylbis[nitrilomethylidenebenzene-1,2-diyl]}bis(2-aminobenzeneimine) (H2ted) with rhenium(V) starting materials resulted in the decomposition of the H2ted molecule to give different coordinated multidentate ligands coordinated to the rhenium(V) centers. In the reaction of H2ted with trans-[ReOBr3(PPh3)2] in ethanol, the highly unusual ‘3+3’ complex cation [Re(tnn)(Htnn)]Br2 was isolated, in which tnn is coordinated as a tridentate imido-imino-amine, and Htnn is present as a tridentate monoanionic amidoimino- amine chelate (H2tnn = N-(2-aminophenylmethylidene)ethane-1,2-diamine). With trans-[ReO2(py)4]Cl as starting material, the neutral complex [ReO(dne)] was found, in which the tetradentate chelate dne acts as a triamido-imine. The reaction of cis- [ReO2I(PPh3)2] with H2ted led to the formation of the monocationic complex salt [ReO(ane)]PF6, with ane acting as a tetradentate dianionic diamidodiimine (H2ane = N,N’-bis[(2-aminophenyl)methylidene] ethane-1,2-diamine). The seven-coordinate rhenium(III) complex cation [Re(dhp)(PPh3)2]+ (H2dhp = 2,6-bis(2- hydroxyphenyliminomethyl)pyridine) was isolated as the iodide salt from the reaction of cis-[ReO2I(PPh3)2] with H2dhp in ethanol and as the perrhenate salt from the reaction of trans-[ReOBr3(PPh3)2] with H2dhp in methanol. Both products result from a disproportionation reaction with perrhenate also being produced in the process. The complex fac-[Re(CO)3(H2dhp)Br] was prepared from [Re(CO)5Br] and H2dhp in toluene, where the H2dhp ligand acts as a neutral bidentate NN-donor chelate. The metal is coordinated to three carbonyl donors in a facial orientation, to a neutral imino nitrogen, a pyridinic nitrogen and a bromide.
- Full Text:
- Date Issued: 2009
- Authors: Potgieter, Kim Carey
- Date: 2009
- Subjects: Rhenium , Schiff bases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10387 , http://hdl.handle.net/10948/1225 , Rhenium , Schiff bases
- Description: This study investigates the coordination modes of multidentate N,O-donor ligands toward the [ReVO]3+ and fac-[ReI(CO)3]+ cores. The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with 4-aminoantipyrine (H2pap) were studied, and the complexes cis-[ReX2(pap)(H2pap)(PPh3)](ReO4) were isolated. The X-ray crystal structures show that both complexes display a distorted octahedral geometry around the central rhenium atom, and are mirror images of each other. The ligand pap is coordinated monodentately through the doubly deprotonated amino nitrogen as an imide, and H2pap acts as a neutral bidentate chelate, with coordination through the neutral amino nitrogen and the ketonic oxygen. The attempted synthesis of the potentially hexadentate Schiff base ligand 1,2-bis(2-{(Z)- [(2-hydroxyphenyl)imido]methyl}phenoxy)benzene from the condensation reaction of 2- (2-((2-aminophenoxy)methyl)benzyloxy)benzenamine and salicylaldehyde produced the zwitterion derivative (H2ono) of 2-{(Z)-[2-(hydroxyphenyl)imino]methyl}phenol. The tridentate Schiff bases (Z)-2-(2-aminobenzylideneamino)phenol (H3onn) and (Z)-2-(2- (methylthio)benzylideneamino)phenol (Hons) were prepared in a similar manner. The reaction of H2ono with trans-[ReOBr3(PPh3)2] surprisingly led to the isolation of the rhenium(III) complex [ReBr(PPh3)2(ono)], in which ono acts as a dianionic tridentate ligand. The reaction of H3onn with trans-[ReOBr3(PPh3)2] produced the imidorhenium(V) complex salt [ReBr(PPh3)2(onn)]Br, in which onn is coordinated as a trianionic tridentate imidoiminophenolate. The reaction of Hons with [Re(CO)5Br] led to the further decomposition of the Hons ligand, and the rhenium(I) product fac- [Re(CO)3(ons)(Hno)] (Hno = 2-aminophenol) was isolated, with ons coordinated as a monoanionic bidentate chelate (with a free SCH3 group), and Hno present as a neutral monodentate ligand with coordination through the amino nitrogen atom. Abstract Nelson Mandela Metropolitan University vi The reactions of the potentially hexadentate ligand N,N’-{ethane-1,2- diylbis[nitrilomethylidenebenzene-1,2-diyl]}bis(2-aminobenzeneimine) (H2ted) with rhenium(V) starting materials resulted in the decomposition of the H2ted molecule to give different coordinated multidentate ligands coordinated to the rhenium(V) centers. In the reaction of H2ted with trans-[ReOBr3(PPh3)2] in ethanol, the highly unusual ‘3+3’ complex cation [Re(tnn)(Htnn)]Br2 was isolated, in which tnn is coordinated as a tridentate imido-imino-amine, and Htnn is present as a tridentate monoanionic amidoimino- amine chelate (H2tnn = N-(2-aminophenylmethylidene)ethane-1,2-diamine). With trans-[ReO2(py)4]Cl as starting material, the neutral complex [ReO(dne)] was found, in which the tetradentate chelate dne acts as a triamido-imine. The reaction of cis- [ReO2I(PPh3)2] with H2ted led to the formation of the monocationic complex salt [ReO(ane)]PF6, with ane acting as a tetradentate dianionic diamidodiimine (H2ane = N,N’-bis[(2-aminophenyl)methylidene] ethane-1,2-diamine). The seven-coordinate rhenium(III) complex cation [Re(dhp)(PPh3)2]+ (H2dhp = 2,6-bis(2- hydroxyphenyliminomethyl)pyridine) was isolated as the iodide salt from the reaction of cis-[ReO2I(PPh3)2] with H2dhp in ethanol and as the perrhenate salt from the reaction of trans-[ReOBr3(PPh3)2] with H2dhp in methanol. Both products result from a disproportionation reaction with perrhenate also being produced in the process. The complex fac-[Re(CO)3(H2dhp)Br] was prepared from [Re(CO)5Br] and H2dhp in toluene, where the H2dhp ligand acts as a neutral bidentate NN-donor chelate. The metal is coordinated to three carbonyl donors in a facial orientation, to a neutral imino nitrogen, a pyridinic nitrogen and a bromide.
- Full Text:
- Date Issued: 2009
Detecting changes in elephant body condition in relation to resource quality
- Authors: De Klerk, Christelle
- Date: 2009
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10704 , http://hdl.handle.net/10948/939 , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: Elephants, as megaherbivores, are known to have extensive impacts on vegetation, especially in enclosed areas. This raises the issue that elephants in enclosed areas may become limited by resource availability. Resource limitation is generally expressed via density dependence, but elephants, due to their slow demography, may not be affected by initial changes in resource availability. This highlights the need for a more sensitive measure of resource limitation to allow for the detection of energy stress within a population before changes in vital rates occur. This study investigated visual changes in elephant body condition in relation to resource availability in a number of Eastern Cape reserves to assess whether body condition could be used to detect life stages, as well as seasons and sites which may be resource limited. Elephant life stages were divided into energy stressed (newly weaned calves, lactating females, and old females) and non-energy stressed classes (sub-adults and non-lactating females) to determine whether energy stressed life stages were more vulnerable to resource limitation. In the AENP it was found that lactating and old females exhibited significantly poorer body condition than non-energy stressed individuals, but that weaned calves had body conditions similar to non-energy stressed individuals. Comparisons between seasons revealed that all life stages exhibited better condition in winter than summer or spring, with lactating females showing little recovery of condition over time. Seasonal body conditions were correlated with rainfall recorded in the Addo Elephant National Park. Comparisons of elephant body condition between sites (n = 6) revealed that body condition varied across sites, with poorer body condition associated with areas of higher elephant density and low rainfall during the study period. Comparisons with faecal dietary quality data both between sites and seasons indicated that body condition also responded to changes in the availability of protein and neutral detergent fibre (NDF) of plant resources, with higher protein and lower values associated with better condition. Based on condition estimates of elephants occurring in the Addo Main Camp, it was established that this population is experiencing nutritional stress, with energy stressed individuals exhibiting the lowest body conditions. This was supported by dietary quality measures. Our findings suggest that elephant body condition is a good measure for detecting resource limitation, both within populations and between seasons, and that elephant body condition respond to relatively small changes in resource conditions, thus making it an effective measure for the detection of nutritional stress. Additionally, our findings show that energy stressed individuals, particularly lactating and old females are more vulnerable to resource limitation. This demonstrates the importance of monitoring these life stages for the detection of density dependence within populations. Finally, our data suggest that threshold values of faecal dietary quality may exist at which body condition within a population begins to deteriorate, making it possible to determine the condition of a population through values obtained in faecal samples.
- Full Text:
- Date Issued: 2009
- Authors: De Klerk, Christelle
- Date: 2009
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10704 , http://hdl.handle.net/10948/939 , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: Elephants, as megaherbivores, are known to have extensive impacts on vegetation, especially in enclosed areas. This raises the issue that elephants in enclosed areas may become limited by resource availability. Resource limitation is generally expressed via density dependence, but elephants, due to their slow demography, may not be affected by initial changes in resource availability. This highlights the need for a more sensitive measure of resource limitation to allow for the detection of energy stress within a population before changes in vital rates occur. This study investigated visual changes in elephant body condition in relation to resource availability in a number of Eastern Cape reserves to assess whether body condition could be used to detect life stages, as well as seasons and sites which may be resource limited. Elephant life stages were divided into energy stressed (newly weaned calves, lactating females, and old females) and non-energy stressed classes (sub-adults and non-lactating females) to determine whether energy stressed life stages were more vulnerable to resource limitation. In the AENP it was found that lactating and old females exhibited significantly poorer body condition than non-energy stressed individuals, but that weaned calves had body conditions similar to non-energy stressed individuals. Comparisons between seasons revealed that all life stages exhibited better condition in winter than summer or spring, with lactating females showing little recovery of condition over time. Seasonal body conditions were correlated with rainfall recorded in the Addo Elephant National Park. Comparisons of elephant body condition between sites (n = 6) revealed that body condition varied across sites, with poorer body condition associated with areas of higher elephant density and low rainfall during the study period. Comparisons with faecal dietary quality data both between sites and seasons indicated that body condition also responded to changes in the availability of protein and neutral detergent fibre (NDF) of plant resources, with higher protein and lower values associated with better condition. Based on condition estimates of elephants occurring in the Addo Main Camp, it was established that this population is experiencing nutritional stress, with energy stressed individuals exhibiting the lowest body conditions. This was supported by dietary quality measures. Our findings suggest that elephant body condition is a good measure for detecting resource limitation, both within populations and between seasons, and that elephant body condition respond to relatively small changes in resource conditions, thus making it an effective measure for the detection of nutritional stress. Additionally, our findings show that energy stressed individuals, particularly lactating and old females are more vulnerable to resource limitation. This demonstrates the importance of monitoring these life stages for the detection of density dependence within populations. Finally, our data suggest that threshold values of faecal dietary quality may exist at which body condition within a population begins to deteriorate, making it possible to determine the condition of a population through values obtained in faecal samples.
- Full Text:
- Date Issued: 2009
Detection of contaminants in wool bales using nuclear techniques
- Authors: Rapakgadi, Jim
- Date: 2009
- Subjects: Wool scouring , Mohair , X-rays
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10448 , http://hdl.handle.net/10948/993 , Wool scouring , Mohair , X-rays
- Description: To improve the quality and the marketability of wool and mohair, it is important to encourage, ensure and preferable certify that the baled fibre is free of contaminants. Anything other than the fibre that is within the bale can be classified as contaminants; this may be in the form of metal and wooden objects, plastic materials, paints, and vegetable matter such as grass and seed. The internationally accepted method for detecting and classifying these contaminants are highly labour intensive and costly. The ultimate goal of the present research is to develop a non-invasive and nondestructive technique that can be used to detect contaminants, particularly plastic (polymer) materials within wool and mohair bales. Such a technique can be implemented in the wool industry and also could be applied to other fibres, such as cotton. The immediate objective of this study was to evaluate the capability and the limitation of X-rays as a technique to detect such contaminants. It was found that X-rays were suitable for detecting foreign objects, or contaminants, such as metals, but not for detecting plastic materials, such as polypropylene and polyethylene.
- Full Text:
- Date Issued: 2009
- Authors: Rapakgadi, Jim
- Date: 2009
- Subjects: Wool scouring , Mohair , X-rays
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10448 , http://hdl.handle.net/10948/993 , Wool scouring , Mohair , X-rays
- Description: To improve the quality and the marketability of wool and mohair, it is important to encourage, ensure and preferable certify that the baled fibre is free of contaminants. Anything other than the fibre that is within the bale can be classified as contaminants; this may be in the form of metal and wooden objects, plastic materials, paints, and vegetable matter such as grass and seed. The internationally accepted method for detecting and classifying these contaminants are highly labour intensive and costly. The ultimate goal of the present research is to develop a non-invasive and nondestructive technique that can be used to detect contaminants, particularly plastic (polymer) materials within wool and mohair bales. Such a technique can be implemented in the wool industry and also could be applied to other fibres, such as cotton. The immediate objective of this study was to evaluate the capability and the limitation of X-rays as a technique to detect such contaminants. It was found that X-rays were suitable for detecting foreign objects, or contaminants, such as metals, but not for detecting plastic materials, such as polypropylene and polyethylene.
- Full Text:
- Date Issued: 2009
Development of a process for the preparation of linalool from CIS-2-pinanol
- Authors: Buddoo, Subash Ramnarain
- Date: 2009
- Subjects: Odors , Perfumes -- History , Perfumes -- Formulae , Fermentation
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10425 , http://hdl.handle.net/10948/d1016219
- Description: Linalool is a key intermediate for the production of important fragrance chemicals such as geraniol, nerol, geranial, and neral. Linalool can be produced via a two-step process from α-pinene which is a major component of crude sulphated turpentine (CST) a foul-smelling, volatile waste product of the pulp and paper industry. The key step in this process is the pyrolysis step which involves the isomerisation of cis-2-pinanol to linalool and requires high temperatures (600-650°C) and is not very selective due to the decomposition of the product itself under these conditions. A client of the CSIR, Teubes Pty. Ltd., is a manufacturer of flavour and fragrance compounds for the local and international fragrance market and expressed an interest in producing linalool since the company would then gain access to other valuable fragrance chemicals via relatively simple processes. Earlier work conducted by AECI, R & D did not meet with much success since the selectivity to linalool was very poor and the process could hardly be deemed as scalable. The main objective of this project was therefore to develop a process for the selective isomerisation of cis-2-pinanol to linalool with minimum by-product formation and using process equipment that could be scaled to full-scale production. Since cis-2- pinanol could not be purchased in sufficient quantities for process development, a process had to be developed for the bench-scale preparation of kilogram quantities of cis-2-pinanol from α-pinene obtained from the client. Although this synthesis formed a minor part of this investigation, several process improvements and innovations were introduced to produce high quality cis-2-pinanol, in very good yields at kilogram scale. A major part of this investigation was the design and set up of a pyrolyis rig capable of operating at elevated temperatures (400 - 750°C) for the evaluation of various process parameters. Various vaporizer, reactor, and condensation systems were evaluated for their ability to cope with the demanding conditions on a consistent basis. The initial part of the investigation was a screening exercise to evaluate various process parameters as well as solvents, materials of construction, catalysts, etc. A comprehensive statistical design was also conducted to determine the critical process parameters and the model obtained was used to predict the optimum conditions required for the preparation of in-specification product on a consistent basis. These conditions were used in the preparation of a 1kg sample which was required by theclient for market evaluation purposes. The use of a novel microreactor system was also evaluated for the pinanol pyrolysis reaction. To our knowledge, this is the first time that a microreactor has been successfully used for this type of reaction in the Fragrance industry and a patent application is being filed by the CSIR. The kinetics of the reaction in both the tubular reactor system and the microreactor system was investigated. Computer modelling studies on both the systems were also conducted. The raw material cost to produce a kilogram of linalool is $1.40. There is a significant margin of 60.8 percent between the raw material cost of linalool and the current selling price ($3.57/kg). This clearly indicates that the project is potentially feasible from an economic point of view and we can now proceed with confidence to the next stage which is the engineering design, building and commissioning of the large scale pyrolysis rig. The rest of the process steps will be conducted on existing equipment currently present at the CSIR’s large scale facility (Imbiza in Isando, Gauteng).
- Full Text:
- Date Issued: 2009
- Authors: Buddoo, Subash Ramnarain
- Date: 2009
- Subjects: Odors , Perfumes -- History , Perfumes -- Formulae , Fermentation
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10425 , http://hdl.handle.net/10948/d1016219
- Description: Linalool is a key intermediate for the production of important fragrance chemicals such as geraniol, nerol, geranial, and neral. Linalool can be produced via a two-step process from α-pinene which is a major component of crude sulphated turpentine (CST) a foul-smelling, volatile waste product of the pulp and paper industry. The key step in this process is the pyrolysis step which involves the isomerisation of cis-2-pinanol to linalool and requires high temperatures (600-650°C) and is not very selective due to the decomposition of the product itself under these conditions. A client of the CSIR, Teubes Pty. Ltd., is a manufacturer of flavour and fragrance compounds for the local and international fragrance market and expressed an interest in producing linalool since the company would then gain access to other valuable fragrance chemicals via relatively simple processes. Earlier work conducted by AECI, R & D did not meet with much success since the selectivity to linalool was very poor and the process could hardly be deemed as scalable. The main objective of this project was therefore to develop a process for the selective isomerisation of cis-2-pinanol to linalool with minimum by-product formation and using process equipment that could be scaled to full-scale production. Since cis-2- pinanol could not be purchased in sufficient quantities for process development, a process had to be developed for the bench-scale preparation of kilogram quantities of cis-2-pinanol from α-pinene obtained from the client. Although this synthesis formed a minor part of this investigation, several process improvements and innovations were introduced to produce high quality cis-2-pinanol, in very good yields at kilogram scale. A major part of this investigation was the design and set up of a pyrolyis rig capable of operating at elevated temperatures (400 - 750°C) for the evaluation of various process parameters. Various vaporizer, reactor, and condensation systems were evaluated for their ability to cope with the demanding conditions on a consistent basis. The initial part of the investigation was a screening exercise to evaluate various process parameters as well as solvents, materials of construction, catalysts, etc. A comprehensive statistical design was also conducted to determine the critical process parameters and the model obtained was used to predict the optimum conditions required for the preparation of in-specification product on a consistent basis. These conditions were used in the preparation of a 1kg sample which was required by theclient for market evaluation purposes. The use of a novel microreactor system was also evaluated for the pinanol pyrolysis reaction. To our knowledge, this is the first time that a microreactor has been successfully used for this type of reaction in the Fragrance industry and a patent application is being filed by the CSIR. The kinetics of the reaction in both the tubular reactor system and the microreactor system was investigated. Computer modelling studies on both the systems were also conducted. The raw material cost to produce a kilogram of linalool is $1.40. There is a significant margin of 60.8 percent between the raw material cost of linalool and the current selling price ($3.57/kg). This clearly indicates that the project is potentially feasible from an economic point of view and we can now proceed with confidence to the next stage which is the engineering design, building and commissioning of the large scale pyrolysis rig. The rest of the process steps will be conducted on existing equipment currently present at the CSIR’s large scale facility (Imbiza in Isando, Gauteng).
- Full Text:
- Date Issued: 2009
Development of biological control strategies against sirex noctilio (Fabricius) on Sappi Forests (Ltd) Landholdings in the summer rainfall regions of South Africa
- Authors: Verleur, Peter Marcel
- Date: 2009
- Subjects: Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10741 , http://hdl.handle.net/10948/1273 , Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Description: The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.
- Full Text:
- Date Issued: 2009
- Authors: Verleur, Peter Marcel
- Date: 2009
- Subjects: Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10741 , http://hdl.handle.net/10948/1273 , Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Description: The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.
- Full Text:
- Date Issued: 2009
Ecological role of estuarine brachyuran crabs in mangrove and salt marsh estuaries, Eastern Cape, South Africa
- Authors: Vorsatz, Jeanne Pauline
- Date: 2009
- Subjects: Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10698 , http://hdl.handle.net/10948/1108 , Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Description: Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
- Full Text:
- Date Issued: 2009
- Authors: Vorsatz, Jeanne Pauline
- Date: 2009
- Subjects: Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10698 , http://hdl.handle.net/10948/1108 , Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Description: Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
- Full Text:
- Date Issued: 2009
Ecosystem health of the Nelson Mandela Bay sandy beaches
- Authors: Yani, Vuyolwethu Veronica
- Date: 2009
- Subjects: Seashore ecology -- South Africa -- Eastern Cape , Sand dune ecology -- South Africa -- Eastern Cape , Coastal ecology -- South Africa -- Eastern Cape , Beaches -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10600 , http://hdl.handle.net/10948/1075 , Seashore ecology -- South Africa -- Eastern Cape , Sand dune ecology -- South Africa -- Eastern Cape , Coastal ecology -- South Africa -- Eastern Cape , Beaches -- South Africa -- Eastern Cape
- Description: An investigation of ecosystem functioning of sandy beaches in the Nelson Mandela Bay Municipality (NMBM) was carried out with the aim of describing their type and pollution status. Water salinity, temperature, pH, beach slope, water inorganic nutrient concentrations, urea, and chlorophyll-a concentration as well as the composition of zooplankton, phytoplankton, meiofauna, benthic microalgae and bacteria were examined at thirteen beaches. The beaches were classified into three types: short beaches; long beaches with surf diatoms; and long beaches that import biomass (without surf diatoms). Of the thirteen beaches, five were non-polluted and eight polluted with polluting human activities in and around them. Most beaches were dominated by fine sand except for St. Georges Strand where the particles were medium to fine sand and Maitland’s River Beach, Bluewater Bay and Sardinia Bay that had coarse sand. Nutrient concentrations ranged from 1.98 ± 0.10 μM to 19.30 ± 3.02 μM nitrate; 4.88 ± 1.00 μM to 11.97 ± 1.00 μM ammonium; 0.67 ± 0.00 μM to 2.31 ±1.00 μM soluble reactive phosphorus; and 0.00 to 0.03 ± 0.00 μg l-1 urea-N. Chlorophyll-a concentrations ranged from 0.04 ± 0.02 to 1.57 ± 0.11 μg l-1. Chlorophyll-a concentrations were negatively correlated to ammonium for all beach types (short beaches: r = 0.94; long importing beaches: r = 0.95 and surf diatom beaches: 0.94) and to nitrate for short and long importing beaches (short: r = 0.97 and long importing: r = 0.85). By contrast, a positive correlation was found between observed between chlorophyll-a concentrations and urea for surf diatom beaches (r = 0.93) and for long importing beaches (r = 0.73). Chlorophyll-a concentrations were negatively correlated to short beaches (r = 0.99) and long importing beaches (r = 0.76). The E. coli and total coliforms in all the sampled beaches were within the recommended South African water quality guidelines for contact recreation as specified by DWAF (1995) except at New Brighton Beach (2 419 total coliforms/100 ml and 1 853 E. coli cells/100 ml) and St. Georges Strand (274 total coliforms/100 ml). Diatoms dominated the phytoplankton and benthic microflora; calanoid copepods dominated the zooplankton and deposit-feeding nematodes dominated the meiofauna in all the beaches with no changes found at polluted beaches.
- Full Text: false
- Date Issued: 2009
- Authors: Yani, Vuyolwethu Veronica
- Date: 2009
- Subjects: Seashore ecology -- South Africa -- Eastern Cape , Sand dune ecology -- South Africa -- Eastern Cape , Coastal ecology -- South Africa -- Eastern Cape , Beaches -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10600 , http://hdl.handle.net/10948/1075 , Seashore ecology -- South Africa -- Eastern Cape , Sand dune ecology -- South Africa -- Eastern Cape , Coastal ecology -- South Africa -- Eastern Cape , Beaches -- South Africa -- Eastern Cape
- Description: An investigation of ecosystem functioning of sandy beaches in the Nelson Mandela Bay Municipality (NMBM) was carried out with the aim of describing their type and pollution status. Water salinity, temperature, pH, beach slope, water inorganic nutrient concentrations, urea, and chlorophyll-a concentration as well as the composition of zooplankton, phytoplankton, meiofauna, benthic microalgae and bacteria were examined at thirteen beaches. The beaches were classified into three types: short beaches; long beaches with surf diatoms; and long beaches that import biomass (without surf diatoms). Of the thirteen beaches, five were non-polluted and eight polluted with polluting human activities in and around them. Most beaches were dominated by fine sand except for St. Georges Strand where the particles were medium to fine sand and Maitland’s River Beach, Bluewater Bay and Sardinia Bay that had coarse sand. Nutrient concentrations ranged from 1.98 ± 0.10 μM to 19.30 ± 3.02 μM nitrate; 4.88 ± 1.00 μM to 11.97 ± 1.00 μM ammonium; 0.67 ± 0.00 μM to 2.31 ±1.00 μM soluble reactive phosphorus; and 0.00 to 0.03 ± 0.00 μg l-1 urea-N. Chlorophyll-a concentrations ranged from 0.04 ± 0.02 to 1.57 ± 0.11 μg l-1. Chlorophyll-a concentrations were negatively correlated to ammonium for all beach types (short beaches: r = 0.94; long importing beaches: r = 0.95 and surf diatom beaches: 0.94) and to nitrate for short and long importing beaches (short: r = 0.97 and long importing: r = 0.85). By contrast, a positive correlation was found between observed between chlorophyll-a concentrations and urea for surf diatom beaches (r = 0.93) and for long importing beaches (r = 0.73). Chlorophyll-a concentrations were negatively correlated to short beaches (r = 0.99) and long importing beaches (r = 0.76). The E. coli and total coliforms in all the sampled beaches were within the recommended South African water quality guidelines for contact recreation as specified by DWAF (1995) except at New Brighton Beach (2 419 total coliforms/100 ml and 1 853 E. coli cells/100 ml) and St. Georges Strand (274 total coliforms/100 ml). Diatoms dominated the phytoplankton and benthic microflora; calanoid copepods dominated the zooplankton and deposit-feeding nematodes dominated the meiofauna in all the beaches with no changes found at polluted beaches.
- Full Text: false
- Date Issued: 2009
Efficacy of selected Kenyan medicinal plants used in the treatment and management of Type II Diabetes
- Authors: Karachi, Jacqueline
- Date: 2009
- Subjects: Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10327 , http://hdl.handle.net/10948/1049 , Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Description: In Kenya, the prevalence of diabetes is estimated at 3-10 percent of the population. These figures could be higher because most type 2 diabetics are diagnosed many years after onset. Out of this number, 15 percent are people below 30 years of age who need prompt education to avoid complications that are associated with diabetes (DMI centre, 2004). Due to inadequate or lack of proper information, most patients especially those with type 2 diabetes are diagnosed through complications. Untreated or poorly managed diabetes is now the leading cause of eye disease and kidney failure in the world. Diabetes is the largest cause of kidney failure in the developed world, and is the fourth leading cause of global death by disease in the world (IDF, 2007). At the Kenyatta National Hospital in Nairobi, Kenya, it is the leading cause of all non-accident related amputations. It is with such statistics in mind and the grim reality of poor and inadequate health services that this research is based. The wide use of selected medicinal plants for the treatment and management of diabetes warrants the further study of these plants for potential use and commercialization. The data obtained can also be invaluable for use and reference when using these plants for medicinal purposes. The medicinal plant studied in the research is widely used in Kenya by many communities and was chosen based on ethno-pharmacological references using traditional medicinal practitioners as well as patient’s recommendations. Different in vitro and in vivo assays were studied to try and elucidate the mechanisms of action as well as the organs targeted during treatment using this plant.
- Full Text:
- Date Issued: 2009
- Authors: Karachi, Jacqueline
- Date: 2009
- Subjects: Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10327 , http://hdl.handle.net/10948/1049 , Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Description: In Kenya, the prevalence of diabetes is estimated at 3-10 percent of the population. These figures could be higher because most type 2 diabetics are diagnosed many years after onset. Out of this number, 15 percent are people below 30 years of age who need prompt education to avoid complications that are associated with diabetes (DMI centre, 2004). Due to inadequate or lack of proper information, most patients especially those with type 2 diabetes are diagnosed through complications. Untreated or poorly managed diabetes is now the leading cause of eye disease and kidney failure in the world. Diabetes is the largest cause of kidney failure in the developed world, and is the fourth leading cause of global death by disease in the world (IDF, 2007). At the Kenyatta National Hospital in Nairobi, Kenya, it is the leading cause of all non-accident related amputations. It is with such statistics in mind and the grim reality of poor and inadequate health services that this research is based. The wide use of selected medicinal plants for the treatment and management of diabetes warrants the further study of these plants for potential use and commercialization. The data obtained can also be invaluable for use and reference when using these plants for medicinal purposes. The medicinal plant studied in the research is widely used in Kenya by many communities and was chosen based on ethno-pharmacological references using traditional medicinal practitioners as well as patient’s recommendations. Different in vitro and in vivo assays were studied to try and elucidate the mechanisms of action as well as the organs targeted during treatment using this plant.
- Full Text:
- Date Issued: 2009
Habitat and foraging models as aids in the identification of priority areas for mitigating actions to reduce the incidence of electrocutions of the threatened Cape Griffon Gyps coprotheres in the Eastern Cape
- Authors: Minnie, Johan Charles
- Date: 2009
- Subjects: Gyps -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10658 , http://hdl.handle.net/10948/1047 , http://hdl.handle.net/10948/d1012887 , Gyps -- South Africa -- Eastern Cape
- Description: The Cape Griffon Gyps coprotheres is listed as a globally threatened species, because of threats posed by, inter alia, poisoning, loss of habitat, food shortages, electrocutions and drowning in high-walled farm reservoirs. The Cape Griffon has undergone major decline in South Africa, including the Eastern Cape. A detailed investigation into the causes of this decline is vital to ensure the survival of the species. Since it is known that electrocution on powerlines is a major cause of mortality of the griffons in the Eastern Cape, the study therefore focuses on this factor in this region. More specifically, the overall aim or objective of the study is to investigate, through the application of appropriate GIS techniques, the use of descriptive, empirical, habitat and foraging models to prioritise powerline networks, in the Eastern Cape, for mitigation to prevent electrocution of Cape Griffons Gyps coprotheres. The specific activities associated with the aim of the study are: (1) to identify the broad habitat types used by the griffons, (2) to determine the mean daily foraging range size of the griffons, (3) to map currently active foraging ranges and to categorise them according to their role, and the level of importance, in the foraging and breeding behaviour of the species, (4) to map the locations of networks of griffon-unfriendly powerline networks, and (5) to integrate the outcomes of (1) to (4) above, to produce a spatially explicit product that ranks griffon-unfriendly powerline networks according to their priority level for mitigation. The study uses simple descriptive models to investigate, spatially, the threat posed by griffon-unfriendly powerlines to the Cape Griffon in the Eastern Cape. The modelling approach includes a broad level simple habitat model (Categorical model), a Maxent model, a spatial foraging model and an electrocution model. Several map outputs were produced from the analyses. Cape Griffon habitat was successfully modelled using ecological input variables: biome, vegetation xvii type (suitable/unsuitable for griffon foraging), stock (cattle, sheep and goats), and stock farming types (commercial & communal). All outputs were modelled through the use of a Geographical Information System (GIS). Opportunistic sightings data were used for the study, which means that the data were collected on a non-systematic basis and are therefore considered incomplete. In ecology and zoogeography, incomplete datasets are common. To address this issue, a maximum entropy (Maxent) model was applied to the available dataset. Maxent produces predictions or conclusions from incomplete information, and was therefore useful for this study. The mean daily foraging area (coverage) of the Cape Griffon in the study area was estimated from published and unpublished marked bird studies conducted elsewhere, but in generally similar habitats. Based on all the data from these studies, it was considered appropriate to use a circular area, with a radius of 40 km, to represent the mean daily foraging range of the Cape Griffon in the Eastern Cape. It was considered appropriate to use a roughly circular area to depict the daily foraging area, given that the Cape Griffon qualifies as a central place forager. This means that the griffons are tied to a permanent site (roosting site or breeding site) and forage within a certain area around that central site. The mean daily foraging area (40 km) was applied to the currently active griffon sites: breeding sites, regular roosting sites, seasonal/occasional sites, and roosting sites (uncertain status). This produced four foraging area types, which formed the basis for the creation of two spatial foraging area models: Hierarchical Foraging Area Model (HFAM) and the Intersecting Foraging Area Model (IFAM). The HFAM produced three outputs: Primary, Secondary and Tertiary Foraging Areas. These three areas represent the hierarchical presentation of the relative importance of the four foraging area types. The outcome was areas of different predicted griffon occurrence: ‘high’, ‘medium’, ‘low’. The IFAM is essentially an extension of the HFAM, which represents a single area where foraging ranges based on all four types are intersected. The outcome represents the area of predicted highest griffon occurrence. The identified areas of different predicted griffon occurrence, or density (outputs of the HFAM and IFAM), were individually intersected with the layer that indicates the locations of the ‘unsafe’ powerlines. These intersects are depicted in hierarchical mode and expressed according to a number of four risk categories (very high, high, medium and low). The final spatial output of the study is a map that identifies priority powerlines for mitigation against griffon mortality caused by electrocutions and collisions with powerline infrastructure.
- Full Text:
- Date Issued: 2009
- Authors: Minnie, Johan Charles
- Date: 2009
- Subjects: Gyps -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10658 , http://hdl.handle.net/10948/1047 , http://hdl.handle.net/10948/d1012887 , Gyps -- South Africa -- Eastern Cape
- Description: The Cape Griffon Gyps coprotheres is listed as a globally threatened species, because of threats posed by, inter alia, poisoning, loss of habitat, food shortages, electrocutions and drowning in high-walled farm reservoirs. The Cape Griffon has undergone major decline in South Africa, including the Eastern Cape. A detailed investigation into the causes of this decline is vital to ensure the survival of the species. Since it is known that electrocution on powerlines is a major cause of mortality of the griffons in the Eastern Cape, the study therefore focuses on this factor in this region. More specifically, the overall aim or objective of the study is to investigate, through the application of appropriate GIS techniques, the use of descriptive, empirical, habitat and foraging models to prioritise powerline networks, in the Eastern Cape, for mitigation to prevent electrocution of Cape Griffons Gyps coprotheres. The specific activities associated with the aim of the study are: (1) to identify the broad habitat types used by the griffons, (2) to determine the mean daily foraging range size of the griffons, (3) to map currently active foraging ranges and to categorise them according to their role, and the level of importance, in the foraging and breeding behaviour of the species, (4) to map the locations of networks of griffon-unfriendly powerline networks, and (5) to integrate the outcomes of (1) to (4) above, to produce a spatially explicit product that ranks griffon-unfriendly powerline networks according to their priority level for mitigation. The study uses simple descriptive models to investigate, spatially, the threat posed by griffon-unfriendly powerlines to the Cape Griffon in the Eastern Cape. The modelling approach includes a broad level simple habitat model (Categorical model), a Maxent model, a spatial foraging model and an electrocution model. Several map outputs were produced from the analyses. Cape Griffon habitat was successfully modelled using ecological input variables: biome, vegetation xvii type (suitable/unsuitable for griffon foraging), stock (cattle, sheep and goats), and stock farming types (commercial & communal). All outputs were modelled through the use of a Geographical Information System (GIS). Opportunistic sightings data were used for the study, which means that the data were collected on a non-systematic basis and are therefore considered incomplete. In ecology and zoogeography, incomplete datasets are common. To address this issue, a maximum entropy (Maxent) model was applied to the available dataset. Maxent produces predictions or conclusions from incomplete information, and was therefore useful for this study. The mean daily foraging area (coverage) of the Cape Griffon in the study area was estimated from published and unpublished marked bird studies conducted elsewhere, but in generally similar habitats. Based on all the data from these studies, it was considered appropriate to use a circular area, with a radius of 40 km, to represent the mean daily foraging range of the Cape Griffon in the Eastern Cape. It was considered appropriate to use a roughly circular area to depict the daily foraging area, given that the Cape Griffon qualifies as a central place forager. This means that the griffons are tied to a permanent site (roosting site or breeding site) and forage within a certain area around that central site. The mean daily foraging area (40 km) was applied to the currently active griffon sites: breeding sites, regular roosting sites, seasonal/occasional sites, and roosting sites (uncertain status). This produced four foraging area types, which formed the basis for the creation of two spatial foraging area models: Hierarchical Foraging Area Model (HFAM) and the Intersecting Foraging Area Model (IFAM). The HFAM produced three outputs: Primary, Secondary and Tertiary Foraging Areas. These three areas represent the hierarchical presentation of the relative importance of the four foraging area types. The outcome was areas of different predicted griffon occurrence: ‘high’, ‘medium’, ‘low’. The IFAM is essentially an extension of the HFAM, which represents a single area where foraging ranges based on all four types are intersected. The outcome represents the area of predicted highest griffon occurrence. The identified areas of different predicted griffon occurrence, or density (outputs of the HFAM and IFAM), were individually intersected with the layer that indicates the locations of the ‘unsafe’ powerlines. These intersects are depicted in hierarchical mode and expressed according to a number of four risk categories (very high, high, medium and low). The final spatial output of the study is a map that identifies priority powerlines for mitigation against griffon mortality caused by electrocutions and collisions with powerline infrastructure.
- Full Text:
- Date Issued: 2009