Characterisation of the cellulolytic and hemicellulolytic system of Bacillus Licheniformis SVD1 and the isolation and characterisation of a multi-enzyme complex
- Authors: Van Dyk, Jacoba Susanna
- Date: 2009
- Subjects: Lignocellulose Lignocellulose -- Biotechnology Lignocellulose -- Biodegradation Plant biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3936 , http://hdl.handle.net/10962/d1003995
- Description: The biological degradation of lignocellulose into fermentable sugars for the production of liquid transportation fuels is feasible and sustainable, but equires a variety of enzymes working in synergy as lignocellulose is a complex and recalcitrant substrate. The cellulosome is a multi-enzyme complex (MEC) with a variety of cellulolytic and hemicellulolytic enzymes that appears to facilitate an enhanced synergy and efficiency, as compared to free enzymes, for the degradation of recalcitrant substrates such as lignocellulose and plant cell walls. Most of the studies on cellulosomes have focused on a few organisms; C. thermocellum, C. cellulovorans and C. cellulolyticum, and there is only limited knowledge vailable on similar complexes in other organisms. Some MECs have been identified in aerobic bacteria such as Bacillus circulans and Paenibacillus curdlanolyticus, but the nature of these MECs have not been fully elucidated. This study investigated the cellulolytic and emi-cellulolytic system of Bacillus licheniformis SVD1 with specific reference to the presence of a MEC, which has never been reported in the literature for B. licheniformis. A MEC of approximately 2,000 kDa in size, based on size exclusion chromatography using Sepharose 4B, was purified from a culture of B. licheniformis. When investigating the presence of enzyme activity in the total crude fraction as well as the MEC of a birchwood xylan culture, B. licheniformis was found to display a variety of enzyme activities on a range of substrates, although xylanases were by far the predominant enzyme activity present in both the crude and MEC fractions. Based on zymogram analysis there were three CMCases, seven xylanases, three mannanases and two pectinases in the crude fraction, while the MEC had two CMCases, seven xylanases, two mannanases and one pectinase. The pectinases in the crude could be identified as a pectin methyl esterase and a lyase, while the methyl esterase was absent in the MEC. Seventeen protein species could be detected in the MEC but only nine of these displayed activity on the substrates tested. The possible presence of a β-xylosidase in the crude fraction was deduced from thin layer chromatography (TLC) which demonstrated the production of xylose by the crude fraction. It was furthermore established that B. licheniformis SVD1 was able to regulate levels of enzyme expression based on the substrate the organism was cultured on. It was found that complexed xylanase activity had a pH optimum of between pH 6.0 and 7.0 and a temperature optimum of 55oC. Complexed xylanase activity was found to be slightly inhibited by CaCl2 and inhibited to a greater extent by EDTA. Complexed xylanase activity was further shown to be activated in the presence of xylose and xylobiose, both compounds which are products of enzymatic degradation. Ethanol was found to inhibit complexed xylanase activity. The kinetic parameters for complexed xylanase activity were measured and the Km value was calculated as 2.84 mg/ml while the maximal velocity (Vmax) was calculated as 0.146 U (μmol/min/ml). Binding studies, transmission electron microscopy (TEM) and a bioinformatic analysis was conducted to investigate whether the MEC in B. licheniformis SVD1 was a putative cellulosome. The MEC was found to be unable to bind to Avicel, but was able to bind to insoluble birchwood xylan, indicating the absence of a CBM3a domain common to cellulosomal scaffoldin proteins. TEM micrographs revealed the presence of cell surface structures on cells of B. licheniformis SVD1 cultured on cellobiose and birchwood xylan. However, it could not be established whether these cell surface structures could be ascribed to the presence of the MECs on the cell surface. Bioinformatic analysis was conducted on the available genome sequence of a different strain of B. licheniformis, namely DSM 13 and ATCC 14580. No sequence homology was found with cohesin and dockerin sequences from various cellulosomal species, indicating that these strains most likely do not encode for a cellulosome. This study described and characterised a MEC that was a functional enzyme complex and did not appear to be a mere aggregation of proteins. It displayed a variety of hemi-cellulolytic activities and the available evidence suggests that it is not a cellulosome, but should rather be termed a xylanosome. Further investigation should be carried out to determine the structural basis of this MEC.
- Full Text:
- Authors: Van Dyk, Jacoba Susanna
- Date: 2009
- Subjects: Lignocellulose Lignocellulose -- Biotechnology Lignocellulose -- Biodegradation Plant biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3936 , http://hdl.handle.net/10962/d1003995
- Description: The biological degradation of lignocellulose into fermentable sugars for the production of liquid transportation fuels is feasible and sustainable, but equires a variety of enzymes working in synergy as lignocellulose is a complex and recalcitrant substrate. The cellulosome is a multi-enzyme complex (MEC) with a variety of cellulolytic and hemicellulolytic enzymes that appears to facilitate an enhanced synergy and efficiency, as compared to free enzymes, for the degradation of recalcitrant substrates such as lignocellulose and plant cell walls. Most of the studies on cellulosomes have focused on a few organisms; C. thermocellum, C. cellulovorans and C. cellulolyticum, and there is only limited knowledge vailable on similar complexes in other organisms. Some MECs have been identified in aerobic bacteria such as Bacillus circulans and Paenibacillus curdlanolyticus, but the nature of these MECs have not been fully elucidated. This study investigated the cellulolytic and emi-cellulolytic system of Bacillus licheniformis SVD1 with specific reference to the presence of a MEC, which has never been reported in the literature for B. licheniformis. A MEC of approximately 2,000 kDa in size, based on size exclusion chromatography using Sepharose 4B, was purified from a culture of B. licheniformis. When investigating the presence of enzyme activity in the total crude fraction as well as the MEC of a birchwood xylan culture, B. licheniformis was found to display a variety of enzyme activities on a range of substrates, although xylanases were by far the predominant enzyme activity present in both the crude and MEC fractions. Based on zymogram analysis there were three CMCases, seven xylanases, three mannanases and two pectinases in the crude fraction, while the MEC had two CMCases, seven xylanases, two mannanases and one pectinase. The pectinases in the crude could be identified as a pectin methyl esterase and a lyase, while the methyl esterase was absent in the MEC. Seventeen protein species could be detected in the MEC but only nine of these displayed activity on the substrates tested. The possible presence of a β-xylosidase in the crude fraction was deduced from thin layer chromatography (TLC) which demonstrated the production of xylose by the crude fraction. It was furthermore established that B. licheniformis SVD1 was able to regulate levels of enzyme expression based on the substrate the organism was cultured on. It was found that complexed xylanase activity had a pH optimum of between pH 6.0 and 7.0 and a temperature optimum of 55oC. Complexed xylanase activity was found to be slightly inhibited by CaCl2 and inhibited to a greater extent by EDTA. Complexed xylanase activity was further shown to be activated in the presence of xylose and xylobiose, both compounds which are products of enzymatic degradation. Ethanol was found to inhibit complexed xylanase activity. The kinetic parameters for complexed xylanase activity were measured and the Km value was calculated as 2.84 mg/ml while the maximal velocity (Vmax) was calculated as 0.146 U (μmol/min/ml). Binding studies, transmission electron microscopy (TEM) and a bioinformatic analysis was conducted to investigate whether the MEC in B. licheniformis SVD1 was a putative cellulosome. The MEC was found to be unable to bind to Avicel, but was able to bind to insoluble birchwood xylan, indicating the absence of a CBM3a domain common to cellulosomal scaffoldin proteins. TEM micrographs revealed the presence of cell surface structures on cells of B. licheniformis SVD1 cultured on cellobiose and birchwood xylan. However, it could not be established whether these cell surface structures could be ascribed to the presence of the MECs on the cell surface. Bioinformatic analysis was conducted on the available genome sequence of a different strain of B. licheniformis, namely DSM 13 and ATCC 14580. No sequence homology was found with cohesin and dockerin sequences from various cellulosomal species, indicating that these strains most likely do not encode for a cellulosome. This study described and characterised a MEC that was a functional enzyme complex and did not appear to be a mere aggregation of proteins. It displayed a variety of hemi-cellulolytic activities and the available evidence suggests that it is not a cellulosome, but should rather be termed a xylanosome. Further investigation should be carried out to determine the structural basis of this MEC.
- Full Text:
Characterisation of the plasmodium falciparum Hsp40 chaperones and their partnerships with Hsp70
- Authors: Botha, Melissa
- Date: 2009
- Subjects: Heat shock proteins Plasmodium falciparum Protein folding Molecular chaperones Malaria
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3938 , http://hdl.handle.net/10962/d1003997
- Description: Central to this research, 40 kDa Heat shock proteins (Hsp40s) are known to partner (or cochaperone) 70 kDa Heat shock proteins (Hsp70s), facilitating the selection and transfer of protein substrate to Hsp70 and the stimulation of the protein folding ability of Hsp70. Members of the diverse Hsp70-Hsp40 protein complement of Plasmodium falciparum have been implicated in the cytoprotection of this malaria parasite, and are thought to facilitate the protein folding, assembly and translocation tasks required by the parasite to commandeer the infected human erythrocyte subsequent to invasion. In particular, the parasite has evolved an expanded and specialised 43- member suite of Hsp40 proteins, 19 of which bear an identifiable export motif for secretion into the infected erythrocyte cytoplasm where they potentially interact with human Hsp70. Although type I Hsp40 proteins are representative of typical regulators of Hsp70 activity, only two of these proteins are apparent in the parasite’s Hsp40 complement. These include a characteristic type I Hsp40 termed PfHsp40, and a larger, atypical type I Hsp40 termed Pfj1. Both Hsp40 proteins are predicted to be parasite-resident and are most likely to facilitate the co-chaperone regulation of the highly abundant and stress-inducible Hsp70 homolog, PfHsp70-I. In this work, the co-chaperone functionality of PfHsp40 and Pfj1 was elucidated using in vivo and in vitro assays. Purified recombinant PfHsp40 was shown to stimulate the ATPase activity of PfHsp70-I in in vitro single turnover and steady state ATPase assays, and co-operate with PfHsp70-I in in vitro aggregation suppression assays. In these in vitro assays, heterologous partnerships could be demonstrated between PfHsp70-I and the human Hsp40, Hsj1a, and human Hsp70 and PfHsp40, suggesting a common mode of Hsp70-Hsp40 interaction in the parasite and host organism. The functionality of the signature Hsp40 domain, the Jdomain, of Pfj1 was demonstrated by its ability to replace the equivalent domain of the A. tumefaciens Hsp40, Agt DnaJ, in interactions with the prokaryotic Hsp70, DnaK, in the thermosensitive dnaJ cbpA E. coli OD259 deletion strain. An H33Q mutation introduced into the invariant and crucial HPD tripeptide motif abrogated the functionality of the J-domain in the in vivo complementation system. These findings provide the first evidence for the conservation of the prototypical mode of J-domain based interaction of Hsp40 with Hsp70 in P. falciparum. Immunofluorescence staining revealed the localisation of PfHsp40 to the parasite cytoplasm, and Pfj1 to the parasite cytoplasm and nucleus in cultured intraerythrocytic stage P. falciparum parasites. PfHsp70-I was also shown to localise to the parasite cytoplasm and nucleus in these stages, consistent with the literature. Overall we propose that PfHsp40 and Pfj1 co-localise with and regulate the chaperone activity of PfHsp70-I in P. falciparum. This is the first study to identify and provide evidence for a functional Hsp70-Hsp40 partnership in P. falciparum, and provides a platform for future studies to elucidate the importance of these chaperone partnerships in the establishment and survival of the parasite in the intraerythrocytic-stages of development.
- Full Text:
- Authors: Botha, Melissa
- Date: 2009
- Subjects: Heat shock proteins Plasmodium falciparum Protein folding Molecular chaperones Malaria
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3938 , http://hdl.handle.net/10962/d1003997
- Description: Central to this research, 40 kDa Heat shock proteins (Hsp40s) are known to partner (or cochaperone) 70 kDa Heat shock proteins (Hsp70s), facilitating the selection and transfer of protein substrate to Hsp70 and the stimulation of the protein folding ability of Hsp70. Members of the diverse Hsp70-Hsp40 protein complement of Plasmodium falciparum have been implicated in the cytoprotection of this malaria parasite, and are thought to facilitate the protein folding, assembly and translocation tasks required by the parasite to commandeer the infected human erythrocyte subsequent to invasion. In particular, the parasite has evolved an expanded and specialised 43- member suite of Hsp40 proteins, 19 of which bear an identifiable export motif for secretion into the infected erythrocyte cytoplasm where they potentially interact with human Hsp70. Although type I Hsp40 proteins are representative of typical regulators of Hsp70 activity, only two of these proteins are apparent in the parasite’s Hsp40 complement. These include a characteristic type I Hsp40 termed PfHsp40, and a larger, atypical type I Hsp40 termed Pfj1. Both Hsp40 proteins are predicted to be parasite-resident and are most likely to facilitate the co-chaperone regulation of the highly abundant and stress-inducible Hsp70 homolog, PfHsp70-I. In this work, the co-chaperone functionality of PfHsp40 and Pfj1 was elucidated using in vivo and in vitro assays. Purified recombinant PfHsp40 was shown to stimulate the ATPase activity of PfHsp70-I in in vitro single turnover and steady state ATPase assays, and co-operate with PfHsp70-I in in vitro aggregation suppression assays. In these in vitro assays, heterologous partnerships could be demonstrated between PfHsp70-I and the human Hsp40, Hsj1a, and human Hsp70 and PfHsp40, suggesting a common mode of Hsp70-Hsp40 interaction in the parasite and host organism. The functionality of the signature Hsp40 domain, the Jdomain, of Pfj1 was demonstrated by its ability to replace the equivalent domain of the A. tumefaciens Hsp40, Agt DnaJ, in interactions with the prokaryotic Hsp70, DnaK, in the thermosensitive dnaJ cbpA E. coli OD259 deletion strain. An H33Q mutation introduced into the invariant and crucial HPD tripeptide motif abrogated the functionality of the J-domain in the in vivo complementation system. These findings provide the first evidence for the conservation of the prototypical mode of J-domain based interaction of Hsp40 with Hsp70 in P. falciparum. Immunofluorescence staining revealed the localisation of PfHsp40 to the parasite cytoplasm, and Pfj1 to the parasite cytoplasm and nucleus in cultured intraerythrocytic stage P. falciparum parasites. PfHsp70-I was also shown to localise to the parasite cytoplasm and nucleus in these stages, consistent with the literature. Overall we propose that PfHsp40 and Pfj1 co-localise with and regulate the chaperone activity of PfHsp70-I in P. falciparum. This is the first study to identify and provide evidence for a functional Hsp70-Hsp40 partnership in P. falciparum, and provides a platform for future studies to elucidate the importance of these chaperone partnerships in the establishment and survival of the parasite in the intraerythrocytic-stages of development.
- Full Text:
Characterisation of Trypanosomal Type III and Type IV Hsp40 proteins
- Louw, Cassandra Alexandrovna
- Authors: Louw, Cassandra Alexandrovna
- Date: 2009
- Subjects: Trypanosoma Heat shock proteins African trypanosomiasis Epidemic encephalitis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3926 , http://hdl.handle.net/10962/d1003985
- Description: The heat shock protein-70 (Hsp70) family of molecular chaperones are ubiquitous highly conserved proteins that are critical for the viability of cellular homeostasis. The ATPase activity of Hsp70 proteins is critical to their function as the affinity of a given Hsp70 for non-native substrate is modulated by ATP binding and hydrolysis. When bound to ATP, Hsp70s possess a low affinity for a given substrate protein, while the hydrolysis of ATP to ADP causes a conformational change that results in a high affinity for substrate proteins. The basal ATPase activity of Hsp70s is too low to facilitate their function in vivo, and co-chaperones are essential to modulate the efficient protein folding by Hsp70. Heat shock protein-40 (Hsp40) heat shock proteins are essential for the in vivo function of Hsp70s by stimulating the ATPase activity of these proteins and facilitating transfer of substrates. The Type III class of Hsp40 proteins have not been well characterised due to their poor levels of conservation at the primary sequence level. This is due to the fact that Type III Hsp40s only contain a J-domain and a poorly conserved C-terminal region. The newly identified Type IV class of Hsp40s, contain an abrogated HPD tripeptide motif in the J-domain and have also not been extensively studied. Trypanosoma brucei (T. brucei) is a unicellular flagellated protozoan parasite. It is the causative agent of Human African Trypansomiasis (HAT) which results in thousands of deaths and devastating agricultural losses in many parts of Africa. T. brucei undergoes a complex lifecycle that is characterised by the transition from an insect vector to a mammalian host in markedly different conditions of temperature, pH, nutrient availability and respiratory requirements. It has been proposed that molecular chaperones may enhance the survival of these parasites due to their cytoprotective effect in combating cellular stress. Due to the fact that T. brucei infection is invariably fatal if left untreated, and that no novel treatment regimens have been developed recently, the identification of potential novel drug targets among proteins essential to the parasite’s survival in the host organism is an attractive aspect of T. brucei research. Because Type III Hsp40s are poorly conserved with respect to Hsp40s found in the human host, the identification of any of these proteins found to be essential to T. brucei survival in humans could potentially make attractive novel drug targets. An in depth in silico investigation into the Type III Hsp40 complement as well as partner Hsp70 proteins in T.brucei was performed. T. brucei possesses 65 Hsp40 proteins, of which 47 were classed as Type III and 6 of which were identified as being putative Type IV Hsp40s. A small but significant number (5) of Type III TbHsp40s contained tetratricopeptide (TPR) domains in addition to the J-domain. The J-domains of the Type III TbHsp40 complement were found to be conserved with respect to those of canonical Hsp40 proteins, although the mutation of certain residues that play a key role in Hsp40-Hsp70 interaction was noted. Potential partnerships of these proteins in the parasite was also investigated. The coding regions of three previously uncharacterised TbHsp40s were successfully amplified from T. brucei TREU927 genomic DNA and cloned into an expression vector. Tbj1, a Tcj1 ortholog, was selected for further study and successfully expressed and biochemically characterised. Tbj1 expressed in E. coli was found to be insoluble, but large amounts were recovered with the aid of a denaturing purification followed by refolding elution strategies, and the bulk of the protein recovered was in compact monomeric form as determined by size-exclusion chromatography fast protein liquid chromatography (SEC-FPLC). The addition of Tbj1 to a thermally aggregated substrate resulted in increased levels of aggregation, although Tbj1 was able to assist two Hsp70 proteins in the suppression of aggregation. Tbj1 proved unable to stimulate the ATPase activity of these same Hsp70s, and could not rescue temperature sensitive cells when replacing E.coli DnaJ and CbpA. It was concluded that Tbj1 does not possess independent chaperone activity, but could display Hsp40 co-chaperone properties under certain circumstances. This could allude to a specialised function in the T. brucei parasite. The lack of human orthologues to Tbj1 could result in the attractiveness of this protein as a novel drug target.
- Full Text:
- Authors: Louw, Cassandra Alexandrovna
- Date: 2009
- Subjects: Trypanosoma Heat shock proteins African trypanosomiasis Epidemic encephalitis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3926 , http://hdl.handle.net/10962/d1003985
- Description: The heat shock protein-70 (Hsp70) family of molecular chaperones are ubiquitous highly conserved proteins that are critical for the viability of cellular homeostasis. The ATPase activity of Hsp70 proteins is critical to their function as the affinity of a given Hsp70 for non-native substrate is modulated by ATP binding and hydrolysis. When bound to ATP, Hsp70s possess a low affinity for a given substrate protein, while the hydrolysis of ATP to ADP causes a conformational change that results in a high affinity for substrate proteins. The basal ATPase activity of Hsp70s is too low to facilitate their function in vivo, and co-chaperones are essential to modulate the efficient protein folding by Hsp70. Heat shock protein-40 (Hsp40) heat shock proteins are essential for the in vivo function of Hsp70s by stimulating the ATPase activity of these proteins and facilitating transfer of substrates. The Type III class of Hsp40 proteins have not been well characterised due to their poor levels of conservation at the primary sequence level. This is due to the fact that Type III Hsp40s only contain a J-domain and a poorly conserved C-terminal region. The newly identified Type IV class of Hsp40s, contain an abrogated HPD tripeptide motif in the J-domain and have also not been extensively studied. Trypanosoma brucei (T. brucei) is a unicellular flagellated protozoan parasite. It is the causative agent of Human African Trypansomiasis (HAT) which results in thousands of deaths and devastating agricultural losses in many parts of Africa. T. brucei undergoes a complex lifecycle that is characterised by the transition from an insect vector to a mammalian host in markedly different conditions of temperature, pH, nutrient availability and respiratory requirements. It has been proposed that molecular chaperones may enhance the survival of these parasites due to their cytoprotective effect in combating cellular stress. Due to the fact that T. brucei infection is invariably fatal if left untreated, and that no novel treatment regimens have been developed recently, the identification of potential novel drug targets among proteins essential to the parasite’s survival in the host organism is an attractive aspect of T. brucei research. Because Type III Hsp40s are poorly conserved with respect to Hsp40s found in the human host, the identification of any of these proteins found to be essential to T. brucei survival in humans could potentially make attractive novel drug targets. An in depth in silico investigation into the Type III Hsp40 complement as well as partner Hsp70 proteins in T.brucei was performed. T. brucei possesses 65 Hsp40 proteins, of which 47 were classed as Type III and 6 of which were identified as being putative Type IV Hsp40s. A small but significant number (5) of Type III TbHsp40s contained tetratricopeptide (TPR) domains in addition to the J-domain. The J-domains of the Type III TbHsp40 complement were found to be conserved with respect to those of canonical Hsp40 proteins, although the mutation of certain residues that play a key role in Hsp40-Hsp70 interaction was noted. Potential partnerships of these proteins in the parasite was also investigated. The coding regions of three previously uncharacterised TbHsp40s were successfully amplified from T. brucei TREU927 genomic DNA and cloned into an expression vector. Tbj1, a Tcj1 ortholog, was selected for further study and successfully expressed and biochemically characterised. Tbj1 expressed in E. coli was found to be insoluble, but large amounts were recovered with the aid of a denaturing purification followed by refolding elution strategies, and the bulk of the protein recovered was in compact monomeric form as determined by size-exclusion chromatography fast protein liquid chromatography (SEC-FPLC). The addition of Tbj1 to a thermally aggregated substrate resulted in increased levels of aggregation, although Tbj1 was able to assist two Hsp70 proteins in the suppression of aggregation. Tbj1 proved unable to stimulate the ATPase activity of these same Hsp70s, and could not rescue temperature sensitive cells when replacing E.coli DnaJ and CbpA. It was concluded that Tbj1 does not possess independent chaperone activity, but could display Hsp40 co-chaperone properties under certain circumstances. This could allude to a specialised function in the T. brucei parasite. The lack of human orthologues to Tbj1 could result in the attractiveness of this protein as a novel drug target.
- Full Text:
Characterization of manganese tetraarylthiosubstituted phthalocyanines self assembled monolayers
- Matemadombo, Fungisai, Durmus, Mahmut, Togo, Chamunorwa, Limson, Janice L, Nyokong, Tebello
- Authors: Matemadombo, Fungisai , Durmus, Mahmut , Togo, Chamunorwa , Limson, Janice L , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263364 , vital:53621 , xlink:href="https://doi.org/10.1016/j.electacta.2009.04.059"
- Description: Manganese tetraarylthiosubstituted phthalocyanines (complexes 1–5) have been deposited on Au electrode surfaces through the self assembled monolayer (SAM) technique. SAM characteristics reported in this work are: ion barrier factor (∼1); interfacial capacitance (303–539 μF cm−2) and surface coverage (1.06 × 10−10–2.80 × 10−10 mol cm−2). Atomic force microscopy was employed in characterizing a SAM. SAMs of complexes 1–5 were employed to detect L-cysteine (with limit of detection ranging from 2.83 × 10−7 to 3.14 × 10−7 M at potentials of 0.68–0.75 V vs. Ag|AgCl) and nitrite (limit of detection ranging from 1.78 × 10−7 to 3.02 × 10−7 M at potentials of 0.69–0.76 V vs. Ag|AgCl).
- Full Text:
- Authors: Matemadombo, Fungisai , Durmus, Mahmut , Togo, Chamunorwa , Limson, Janice L , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263364 , vital:53621 , xlink:href="https://doi.org/10.1016/j.electacta.2009.04.059"
- Description: Manganese tetraarylthiosubstituted phthalocyanines (complexes 1–5) have been deposited on Au electrode surfaces through the self assembled monolayer (SAM) technique. SAM characteristics reported in this work are: ion barrier factor (∼1); interfacial capacitance (303–539 μF cm−2) and surface coverage (1.06 × 10−10–2.80 × 10−10 mol cm−2). Atomic force microscopy was employed in characterizing a SAM. SAMs of complexes 1–5 were employed to detect L-cysteine (with limit of detection ranging from 2.83 × 10−7 to 3.14 × 10−7 M at potentials of 0.68–0.75 V vs. Ag|AgCl) and nitrite (limit of detection ranging from 1.78 × 10−7 to 3.02 × 10−7 M at potentials of 0.69–0.76 V vs. Ag|AgCl).
- Full Text:
Characterization of nickel tetrahydroxy phthalocyanine complexes and the electrocatalytic oxidation of 4-chlorophenol
- Khene, Samson M, Lobb, Kevin A, Nyokong, Tebello
- Authors: Khene, Samson M , Lobb, Kevin A , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263308 , vital:53616 , xlink:href="https://doi.org/10.1016/j.ica.2009.08.019"
- Description: This work reports on the use of nickel(II) tetrahydroxy (NiPc(OH)4) and (poly-Ni(OH)Pc(OH)4) phthalocyanine complexes as films on ordinary poly graphite electrode (OPGE) for the electrochemical oxidation of 4-chlorophenol (4-CP). The NiPc(OH)4 film was electrotransformed to Ni(OH)Pc(OH)4 film in aqueous 0.1 M NaOH solution to the ‘O–Ni–O oxo’ bridge form. The result showed that the Ni(OH)Pc(OH)4 film on OPGE was more electroactive in terms of increase in current and less catalytic in terms of potential compared to the adsorbed NiPc(OH)4 on OPGE. The reactivity of the two molecules was explained by theoretical calculations. The energies of the frontier orbitals of NiPc(OH)4, Ni(OH)Pc(OH)4 and 4-chlorophenol were calculated using density functional theory (DFT) method. The inter molecular hardness (η) and donor–acceptor hardness (ηDA) of Ni(OH)Pc(OH)4, NiPc(OH)4, Ni(OH)Pc(OH)4/4-chlorophenol and NiPc(OH)4/4-chlorophenol were estimated. The Ni(OH)Pc(OH)4, showed stronger interaction with 4-chlorophenol than NiPc(OH)4. DFT method was also used to model IR and Raman spectrum of H2Pc(OH)4 and NiPc(OH)4.
- Full Text:
- Authors: Khene, Samson M , Lobb, Kevin A , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263308 , vital:53616 , xlink:href="https://doi.org/10.1016/j.ica.2009.08.019"
- Description: This work reports on the use of nickel(II) tetrahydroxy (NiPc(OH)4) and (poly-Ni(OH)Pc(OH)4) phthalocyanine complexes as films on ordinary poly graphite electrode (OPGE) for the electrochemical oxidation of 4-chlorophenol (4-CP). The NiPc(OH)4 film was electrotransformed to Ni(OH)Pc(OH)4 film in aqueous 0.1 M NaOH solution to the ‘O–Ni–O oxo’ bridge form. The result showed that the Ni(OH)Pc(OH)4 film on OPGE was more electroactive in terms of increase in current and less catalytic in terms of potential compared to the adsorbed NiPc(OH)4 on OPGE. The reactivity of the two molecules was explained by theoretical calculations. The energies of the frontier orbitals of NiPc(OH)4, Ni(OH)Pc(OH)4 and 4-chlorophenol were calculated using density functional theory (DFT) method. The inter molecular hardness (η) and donor–acceptor hardness (ηDA) of Ni(OH)Pc(OH)4, NiPc(OH)4, Ni(OH)Pc(OH)4/4-chlorophenol and NiPc(OH)4/4-chlorophenol were estimated. The Ni(OH)Pc(OH)4, showed stronger interaction with 4-chlorophenol than NiPc(OH)4. DFT method was also used to model IR and Raman spectrum of H2Pc(OH)4 and NiPc(OH)4.
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Characterization of polymeric film of a new manganese phthalocyanine complex octa-substituted with 2-diethylaminoethanethiol, and its use for the electrochemical detection of bentazon
- Akinbulu, Isaac A, Nyokong, Tebello
- Authors: Akinbulu, Isaac A , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262568 , vital:53534 , xlink:href="https://doi.org/10.1016/j.electacta.2009.07.074"
- Description: Manganese acetate octakis-(2-diethyaminoethanethiol) phthalocyanine (AcMnODEAETPc) was newly synthesized and characterized by spectroscopic and electrochemical methods. Solution electrochemistry of the complex showed three redox processes assigned to MnIIIPc−1/MnIIIPc−2, MnIIIPc−2/MnIIPc−2 and MnIIPc−2/MnIIPc−3 species. The new molecule was polymerized onto a glassy carbon electrode (GCE) to form thin films of different thickness, giving poly-10-AcMnODEAETPc-GCE, poly-20-AcMnODEAETPc-GCE and poly-30-AcMnODEAETPc-GCE, where 10, 20 and 30 represent the number of voltammetry scans during polymerization. Three distinct redox processes were observed on the modified electrode in 0.1 M phosphate buffer solution, pH 5, which confirmed the formation of the polymer. The current signal due to the herbicide, bentazon, was dependent on film thickness; the best signal was obtained on poly-20-AcMnODEAETPc-GCE while poly-10-AcMnODEAETPc-GCE gave the least signal. However, the signals due to the herbicide were better on the different films compared to the bare electrode. Electrochemical impedance spectroscopy (EIS) technique revealed that differences in film thickness offered different charge transfer resistances, Rct, hence difference in current signals for bentazon oxidation were observed on these films. A Tafel slope of 77 mV/decade, obtained for the herbicide on poly-20-AcMnODEAETPc-GCE, denotes a fast one electron transfer followed by a slow chemical step in the electro-oxidation of bentazon. The voltammetry signals of the herbicide on the films indicated the likely involvement of ring-based redox processes in the detection of the herbicide. A plot of background corrected current response, on this film, versus the concentration of bentazon was linear within the range 50–750 μM with a detection limit of 2.48 × 10−7 M.
- Full Text:
- Authors: Akinbulu, Isaac A , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262568 , vital:53534 , xlink:href="https://doi.org/10.1016/j.electacta.2009.07.074"
- Description: Manganese acetate octakis-(2-diethyaminoethanethiol) phthalocyanine (AcMnODEAETPc) was newly synthesized and characterized by spectroscopic and electrochemical methods. Solution electrochemistry of the complex showed three redox processes assigned to MnIIIPc−1/MnIIIPc−2, MnIIIPc−2/MnIIPc−2 and MnIIPc−2/MnIIPc−3 species. The new molecule was polymerized onto a glassy carbon electrode (GCE) to form thin films of different thickness, giving poly-10-AcMnODEAETPc-GCE, poly-20-AcMnODEAETPc-GCE and poly-30-AcMnODEAETPc-GCE, where 10, 20 and 30 represent the number of voltammetry scans during polymerization. Three distinct redox processes were observed on the modified electrode in 0.1 M phosphate buffer solution, pH 5, which confirmed the formation of the polymer. The current signal due to the herbicide, bentazon, was dependent on film thickness; the best signal was obtained on poly-20-AcMnODEAETPc-GCE while poly-10-AcMnODEAETPc-GCE gave the least signal. However, the signals due to the herbicide were better on the different films compared to the bare electrode. Electrochemical impedance spectroscopy (EIS) technique revealed that differences in film thickness offered different charge transfer resistances, Rct, hence difference in current signals for bentazon oxidation were observed on these films. A Tafel slope of 77 mV/decade, obtained for the herbicide on poly-20-AcMnODEAETPc-GCE, denotes a fast one electron transfer followed by a slow chemical step in the electro-oxidation of bentazon. The voltammetry signals of the herbicide on the films indicated the likely involvement of ring-based redox processes in the detection of the herbicide. A plot of background corrected current response, on this film, versus the concentration of bentazon was linear within the range 50–750 μM with a detection limit of 2.48 × 10−7 M.
- Full Text:
Children navigating rural poverty: Rural children's use of wild resources to counteract food insecurity in the Eastern Cape, South Africa
- McGarry, Dylan K, Shackleton, Charlie M
- Authors: McGarry, Dylan K , Shackleton, Charlie M
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181191 , vital:43706 , xlink:href="https://doi.org/10.1080/10796120802677594"
- Description: This paper analyzes the role of natural resources in the lives of rural children experiencing heightened vulnerability to poverty and the impact of HIV/AIDS, a subject that previously has been unexplored. The authors highlight wild-food use by rural children as a regular activity that supplements their domestic diets. Over the course of 18 months in the Eastern Cape of South Africa, the authors used a broad quantitative and qualitative methodology to explore the food acquisition and consumption patterns for 850 children. They found that the quality of children's domestic diets was, on average, 60% lower than the Food and Agricultural Organization (FAO) guidelines. This occurred in a population where 62% of the children surveyed were supplementing their diets with wild foods; and 30% with over half their diet supplemented in this way. Significantly, dietary diversity increased by 13% when wild food supplementation occurred. Another result was the commercialization of wild foods (observed among 47% of the children), wherein significantly more vulnerable children sold these foods. Considering the heightened nutritional and energy needs of children, combined with the impact of poverty and HIV/AIDS on household food access, wild foods represent the last freely attainable food sources available to them.
- Full Text:
- Authors: McGarry, Dylan K , Shackleton, Charlie M
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181191 , vital:43706 , xlink:href="https://doi.org/10.1080/10796120802677594"
- Description: This paper analyzes the role of natural resources in the lives of rural children experiencing heightened vulnerability to poverty and the impact of HIV/AIDS, a subject that previously has been unexplored. The authors highlight wild-food use by rural children as a regular activity that supplements their domestic diets. Over the course of 18 months in the Eastern Cape of South Africa, the authors used a broad quantitative and qualitative methodology to explore the food acquisition and consumption patterns for 850 children. They found that the quality of children's domestic diets was, on average, 60% lower than the Food and Agricultural Organization (FAO) guidelines. This occurred in a population where 62% of the children surveyed were supplementing their diets with wild foods; and 30% with over half their diet supplemented in this way. Significantly, dietary diversity increased by 13% when wild food supplementation occurred. Another result was the commercialization of wild foods (observed among 47% of the children), wherein significantly more vulnerable children sold these foods. Considering the heightened nutritional and energy needs of children, combined with the impact of poverty and HIV/AIDS on household food access, wild foods represent the last freely attainable food sources available to them.
- Full Text:
Chromone Studies. Part 17. Tricyclic Scaffolds from Reactions of chromone-3-carbaldehydes and methyl vinyl ketone under Baylis–Hillman conditions
- Ganto, Mlungiseleli M, Molefe, Duduzile M, Lobb, Kevin A, Kaye, Perry T
- Authors: Ganto, Mlungiseleli M , Molefe, Duduzile M , Lobb, Kevin A , Kaye, Perry T
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449321 , vital:74811 , xlink:href="https://doi.org/10.3184/030823409X4652"
- Description: Reaction of a series of chromone-3-carbaldehydes with methyl vinyl ketone under Baylis–Hillman conditions, using 3-hydroxyquinuclidine in chloroform or DABCO in 1-methyl-2-pyrrolidinone, affords unprecedented tricylic chromone derivatives which, depending on the conditions, may be accompanied by the normal Baylis–Hillman products or their respective tricyclic dimers.
- Full Text:
- Authors: Ganto, Mlungiseleli M , Molefe, Duduzile M , Lobb, Kevin A , Kaye, Perry T
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449321 , vital:74811 , xlink:href="https://doi.org/10.3184/030823409X4652"
- Description: Reaction of a series of chromone-3-carbaldehydes with methyl vinyl ketone under Baylis–Hillman conditions, using 3-hydroxyquinuclidine in chloroform or DABCO in 1-methyl-2-pyrrolidinone, affords unprecedented tricylic chromone derivatives which, depending on the conditions, may be accompanied by the normal Baylis–Hillman products or their respective tricyclic dimers.
- Full Text:
Civil society's quest for democracy in Zimbabwe: origins,barriers and prospects, 1900-2008
- Authors: Magure, Booker
- Date: 2009
- Subjects: Civil Society -- Zimbabwe Zimbabwe -- Politics and government -- 1980 Zimbabwe -- Economic conditions Zimbabwe -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2798 , http://hdl.handle.net/10962/d1003008
- Description: This thesis is a critical examination of the origins, barriers and prospects for a working class-led civil society as it sought to democratise Zimbabwe’s post-colonial state. It is an interdisciplinary but historically informed analysis of how advanced capitalist development promoted the emergence of social movement unionism with a potentiality to advance democracy in Zimbabwe. Despite occurring on a much smaller and thinner scale, the evolution of civil society in colonial Zimbabwe was akin to what happened in 19th century Britain where capitalist expansion presented a foundation for democratisation. However, big underlying barriers exist in Zimbabwe, resulting from various forms of authoritarian structures and forcible mobilisation strategies emanating from colonialism and the protracted war of liberation. ZANU PF’s violent reaction to memory contests by non-participants in the war of liberation seeking an alternative political agenda attest to the controversial and polemical nature of struggles over memory and forgetting in contemporary Zimbabwean politics. These structural impediments forestalled the organic growth of civil society in Zimbabwe, thereby explaining its inchoate status and the failure to significantly determine the course of public policy. While recognising the democratic aspirations and capacities of the working class in precipitating political change, this thesis takes into consideration the impact of other factors on state-society relations. These include deepening state barbarism, globalisation, and technological advances in communication, transnational civil society, a dysfunctional economy, migration and remittances. Finally this thesis presents an optimistic scenario about the prospects for civil society and democratisation in Zimbabwe. I argue that the revival of the productive sectors of the economy can possibly strengthen the labour movement and revive its capacities for ushering in a democracy.
- Full Text:
- Authors: Magure, Booker
- Date: 2009
- Subjects: Civil Society -- Zimbabwe Zimbabwe -- Politics and government -- 1980 Zimbabwe -- Economic conditions Zimbabwe -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2798 , http://hdl.handle.net/10962/d1003008
- Description: This thesis is a critical examination of the origins, barriers and prospects for a working class-led civil society as it sought to democratise Zimbabwe’s post-colonial state. It is an interdisciplinary but historically informed analysis of how advanced capitalist development promoted the emergence of social movement unionism with a potentiality to advance democracy in Zimbabwe. Despite occurring on a much smaller and thinner scale, the evolution of civil society in colonial Zimbabwe was akin to what happened in 19th century Britain where capitalist expansion presented a foundation for democratisation. However, big underlying barriers exist in Zimbabwe, resulting from various forms of authoritarian structures and forcible mobilisation strategies emanating from colonialism and the protracted war of liberation. ZANU PF’s violent reaction to memory contests by non-participants in the war of liberation seeking an alternative political agenda attest to the controversial and polemical nature of struggles over memory and forgetting in contemporary Zimbabwean politics. These structural impediments forestalled the organic growth of civil society in Zimbabwe, thereby explaining its inchoate status and the failure to significantly determine the course of public policy. While recognising the democratic aspirations and capacities of the working class in precipitating political change, this thesis takes into consideration the impact of other factors on state-society relations. These include deepening state barbarism, globalisation, and technological advances in communication, transnational civil society, a dysfunctional economy, migration and remittances. Finally this thesis presents an optimistic scenario about the prospects for civil society and democratisation in Zimbabwe. I argue that the revival of the productive sectors of the economy can possibly strengthen the labour movement and revive its capacities for ushering in a democracy.
- Full Text:
Clem Sunter's transformational leadership discourse: a linguistic analysis
- Authors: Eley, Georgina Jane
- Date: 2009
- Subjects: Linguistics
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/61994 , vital:28093
- Description: Since the 1970s, two distinct leadership styles have been recognised in the fields of business and organisational research - transactional and transformational leadership. Transactional leadership is seen to resemble managerial-type leadership where followers fulfil their duties in return for rewards that satisfy their self-interest, such as pay or promotion. Transformational leadership, as the label suggests, is leadership that is seen to transform followers from their everyday selves to their better selves (Yukl 1998). Transformational leaders motivate followers by appealing to their higher-order needs, offering incentives for compliance such as feelings of personal empowerment, a sense of moral self-actualisation and an emphasis on the individual's contribution to the community at large (Harvey 2004). These leaders have been observed to emerge and thrive within contexts fraught with socio-political and economic turbulence, where they maximise the uncertainty of the environment to instigate change. Transformational leaders are seen to be especially adept at using discourse to foster strong, persuasive interpersonal relations with their followers. This research reports on, particularly, the interpersonal dimension of Clem Sunter's transformational discourse; he being a prominent South African scenario planner and business leader. It is essentially a qualitative study that describes Sunter's discourse in three of his texts written in 1996. The end to Apartheid in 1994 and transition from White to Black governance meant that the socio-political climate of 1996 South Africa was conducive to the rise of a transformational leader like Sunter. Although the country was, ostensibly, a democracy in 1996, much social transformation was still needed at the time Sunter produced his texts. The analysis are grounded mainly in Systemic Functional Linguistics, specifically APPRAISAL theory and, to some extent, Critical Discourse Analysis theory. However, the analyses do not follow a classic CDA analysis approach, but draw rather from more recent CDA work (cf. Fairclough 2003), such as the analysis of value assumption types within the texts. This analysis clearly demonstrates that Sunter's discourse is congruent 11 with the principal insights of transformational leadership. More than this, it is argued that these findings suggest a close link between transformational leadership and the goals of the latest social order of new capitalism, a link not made in the relevant research to date. The analysis of modes of operation of ideology in the texts (cf. Thompson 1990), also deriving from CDA, reinforces this, indicating that Sunter's transformational discourse promotes and maintains the kinds of power inequalities that underpin new capitalism. The APPRAISAL analysis of Affect choices in the text reveals a high frequency of disquiet, i.e. Sunter's discourse is seen to generate feelings of insecurity and fear. This feature, interestingly, is completely inconsistent with current transformational leadership theory, but would have been an effective motivational technique given the instability of the South African socio-political context in 1996. In addition, the APPRAISAL analysis of Judgement reveals that Sunter evokes high levels of tenacity and appeals to readers' morality, ethics and feelings of group-efficacy - all higher-order needs. The argument here too is that the socio-political context enabled Sunter to stimulate disquiet and tenacity in an effective configuration to mobilise change in his reader and promote the goals of new capitalism. The thesis concludes with a reflection on the limitations of the study and makes various recommendations for future research.
- Full Text:
- Authors: Eley, Georgina Jane
- Date: 2009
- Subjects: Linguistics
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/61994 , vital:28093
- Description: Since the 1970s, two distinct leadership styles have been recognised in the fields of business and organisational research - transactional and transformational leadership. Transactional leadership is seen to resemble managerial-type leadership where followers fulfil their duties in return for rewards that satisfy their self-interest, such as pay or promotion. Transformational leadership, as the label suggests, is leadership that is seen to transform followers from their everyday selves to their better selves (Yukl 1998). Transformational leaders motivate followers by appealing to their higher-order needs, offering incentives for compliance such as feelings of personal empowerment, a sense of moral self-actualisation and an emphasis on the individual's contribution to the community at large (Harvey 2004). These leaders have been observed to emerge and thrive within contexts fraught with socio-political and economic turbulence, where they maximise the uncertainty of the environment to instigate change. Transformational leaders are seen to be especially adept at using discourse to foster strong, persuasive interpersonal relations with their followers. This research reports on, particularly, the interpersonal dimension of Clem Sunter's transformational discourse; he being a prominent South African scenario planner and business leader. It is essentially a qualitative study that describes Sunter's discourse in three of his texts written in 1996. The end to Apartheid in 1994 and transition from White to Black governance meant that the socio-political climate of 1996 South Africa was conducive to the rise of a transformational leader like Sunter. Although the country was, ostensibly, a democracy in 1996, much social transformation was still needed at the time Sunter produced his texts. The analysis are grounded mainly in Systemic Functional Linguistics, specifically APPRAISAL theory and, to some extent, Critical Discourse Analysis theory. However, the analyses do not follow a classic CDA analysis approach, but draw rather from more recent CDA work (cf. Fairclough 2003), such as the analysis of value assumption types within the texts. This analysis clearly demonstrates that Sunter's discourse is congruent 11 with the principal insights of transformational leadership. More than this, it is argued that these findings suggest a close link between transformational leadership and the goals of the latest social order of new capitalism, a link not made in the relevant research to date. The analysis of modes of operation of ideology in the texts (cf. Thompson 1990), also deriving from CDA, reinforces this, indicating that Sunter's transformational discourse promotes and maintains the kinds of power inequalities that underpin new capitalism. The APPRAISAL analysis of Affect choices in the text reveals a high frequency of disquiet, i.e. Sunter's discourse is seen to generate feelings of insecurity and fear. This feature, interestingly, is completely inconsistent with current transformational leadership theory, but would have been an effective motivational technique given the instability of the South African socio-political context in 1996. In addition, the APPRAISAL analysis of Judgement reveals that Sunter evokes high levels of tenacity and appeals to readers' morality, ethics and feelings of group-efficacy - all higher-order needs. The argument here too is that the socio-political context enabled Sunter to stimulate disquiet and tenacity in an effective configuration to mobilise change in his reader and promote the goals of new capitalism. The thesis concludes with a reflection on the limitations of the study and makes various recommendations for future research.
- Full Text:
Clustering algorithms and their effect on edge preservation in image compression
- Authors: Ndebele, Nothando Elizabeth
- Date: 2009
- Subjects: Image compression , Vector analysis , Cluster analysis , Cluster anaylsis -- Data processing , Algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5576 , http://hdl.handle.net/10962/d1008210 , Image compression , Vector analysis , Cluster analysis , Cluster anaylsis -- Data processing , Algorithms
- Description: Image compression aims to reduce the amount of data that is stored or transmitted for images. One technique that may be used to this end is vector quantization. Vectors may be used to represent images. Vector quantization reduces the number of vectors required for an image by representing a cluster of similar vectors by one typical vector that is part of a set of vectors referred to as the code book. For compression, for each image vector, only the closest codebook vector is stored or transmitted. For reconstruction, the image vectors are again replaced by the the closest codebook vectors. Hence vector quantization is a lossy compression technique and the quality of the reconstructed image depends strongly on the quality of the codebook. The design of the codebook is therefore an important part of the process. In this thesis we examine three clustering algorithms which can be used for codebook design in image compression: c-means (CM), fuzzy c-means (FCM) and learning vector quantization (LVQ). We give a description of these algorithms and their application to codebook design. Edges are an important part of the visual information contained in an image. It is essential therefore to use codebooks which allow an accurate representation of the edges. One of the shortcomings of using vector quantization is poor edge representation. We therefore carry out experiments using these algorithms to compare their edge preserving qualities. We also investigate the combination of these algorithms with classified vector quantization (CVQ) and the replication method (RM). Both these methods have been suggested as methods for improving edge representation. We use a cross validation approach to estimate the mean squared error to measure the performance of each of the algorithms and the edge preserving methods. The results reflect that the edges are less accurately represented than the non - edge areas when using CM, FCM and LVQ. The advantage of using CVQ is that the time taken for code book design is reduced particularly for CM and FCM. RM is found to be effective where the codebook is trained using a set that has larger proportions of edges than the test set.
- Full Text:
- Authors: Ndebele, Nothando Elizabeth
- Date: 2009
- Subjects: Image compression , Vector analysis , Cluster analysis , Cluster anaylsis -- Data processing , Algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5576 , http://hdl.handle.net/10962/d1008210 , Image compression , Vector analysis , Cluster analysis , Cluster anaylsis -- Data processing , Algorithms
- Description: Image compression aims to reduce the amount of data that is stored or transmitted for images. One technique that may be used to this end is vector quantization. Vectors may be used to represent images. Vector quantization reduces the number of vectors required for an image by representing a cluster of similar vectors by one typical vector that is part of a set of vectors referred to as the code book. For compression, for each image vector, only the closest codebook vector is stored or transmitted. For reconstruction, the image vectors are again replaced by the the closest codebook vectors. Hence vector quantization is a lossy compression technique and the quality of the reconstructed image depends strongly on the quality of the codebook. The design of the codebook is therefore an important part of the process. In this thesis we examine three clustering algorithms which can be used for codebook design in image compression: c-means (CM), fuzzy c-means (FCM) and learning vector quantization (LVQ). We give a description of these algorithms and their application to codebook design. Edges are an important part of the visual information contained in an image. It is essential therefore to use codebooks which allow an accurate representation of the edges. One of the shortcomings of using vector quantization is poor edge representation. We therefore carry out experiments using these algorithms to compare their edge preserving qualities. We also investigate the combination of these algorithms with classified vector quantization (CVQ) and the replication method (RM). Both these methods have been suggested as methods for improving edge representation. We use a cross validation approach to estimate the mean squared error to measure the performance of each of the algorithms and the edge preserving methods. The results reflect that the edges are less accurately represented than the non - edge areas when using CM, FCM and LVQ. The advantage of using CVQ is that the time taken for code book design is reduced particularly for CM and FCM. RM is found to be effective where the codebook is trained using a set that has larger proportions of edges than the test set.
- Full Text:
Collective forgiving
- Authors: Hamilton, Kelly
- Date: 2009
- Subjects: Forgiveness -- Philosophy Collective behavior -- Philosophy Retribution -- Philosophy Reconciliation -- Philosophy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2709 , http://hdl.handle.net/10962/d1002839
- Description: Forgiveness is traditionally understood as a personal change of heart, in which an individual victim of a wrongdoing overcomes her resentment towards the perpetrator of that wrongdoing. Peter Strawson (1974) famously argued that resentment is a personal participant retributive reactive attitude, and the overcoming of such an attitude through forgiveness is itself a personal reactive attitude – in other words, forgiveness is an affective response to a wrongdoing by an individual victim, that is devoid of a retributive element. Because reactive attitudes are personal, it is argued that collectives – groups of individuals – cannot forgive, since collectives cannot, as collectives, hold reactive attitudes. I argue against this. I show that it is possible for collectives to hold attitudes in a way that is not reducible to individuals holding attitudes as individuals, and yet these attitudes still remain personal. Individuals exist within communities, and are interdependent on one another. Much of an individual‟s beliefs and attitudes depend on the collectives that she is a part of. I argue that an attitude is collective when it is deemed to be the appropriate attitude for members of the collective to hold. Members of the collective will take this attitude on as their own insofar as they identify themselves as members of the collective. Individuals hold the attitude, making the attitude personal, but since the individuals hold the attitude in virtue of their membership to a collective, the attitude is also collective. Given that forgiveness is itself a reactive attitude, and that collectives can hold attitudes, I argue that it is possible for a collective to forgive. Members of a collective will come to forgive when forgiveness is held up as the appropriate attitude for them, and once enough members have taken on the attitude of forgiveness as their own attitude, a collective can be said to have forgiven.
- Full Text:
- Authors: Hamilton, Kelly
- Date: 2009
- Subjects: Forgiveness -- Philosophy Collective behavior -- Philosophy Retribution -- Philosophy Reconciliation -- Philosophy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2709 , http://hdl.handle.net/10962/d1002839
- Description: Forgiveness is traditionally understood as a personal change of heart, in which an individual victim of a wrongdoing overcomes her resentment towards the perpetrator of that wrongdoing. Peter Strawson (1974) famously argued that resentment is a personal participant retributive reactive attitude, and the overcoming of such an attitude through forgiveness is itself a personal reactive attitude – in other words, forgiveness is an affective response to a wrongdoing by an individual victim, that is devoid of a retributive element. Because reactive attitudes are personal, it is argued that collectives – groups of individuals – cannot forgive, since collectives cannot, as collectives, hold reactive attitudes. I argue against this. I show that it is possible for collectives to hold attitudes in a way that is not reducible to individuals holding attitudes as individuals, and yet these attitudes still remain personal. Individuals exist within communities, and are interdependent on one another. Much of an individual‟s beliefs and attitudes depend on the collectives that she is a part of. I argue that an attitude is collective when it is deemed to be the appropriate attitude for members of the collective to hold. Members of the collective will take this attitude on as their own insofar as they identify themselves as members of the collective. Individuals hold the attitude, making the attitude personal, but since the individuals hold the attitude in virtue of their membership to a collective, the attitude is also collective. Given that forgiveness is itself a reactive attitude, and that collectives can hold attitudes, I argue that it is possible for a collective to forgive. Members of a collective will come to forgive when forgiveness is held up as the appropriate attitude for them, and once enough members have taken on the attitude of forgiveness as their own attitude, a collective can be said to have forgiven.
- Full Text:
Comparative electrocatalytic behavior of self-assembled monolayer of thiol derivatised Co (II) phthalocyanines on gold disk, ultramicro cylinder and fiber electrodes
- Nombona, Nolwazi, Geraldo, Daniela A, Hakuzimana, Jean, Schwarz, Anne, Westbroek, Philippe, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Geraldo, Daniela A , Hakuzimana, Jean , Schwarz, Anne , Westbroek, Philippe , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263488 , vital:53632 , xlink:href="https://doi.org/10.1007/s10800-008-9716-y"
- Description: This paper reports on the use of thiol derivatised cobalt phthalocyanines as self assembled monolayers (SAMs) on gold disk electrode, gold ultramicro-cylinder electrode (UMCE) and on gold coated fiber for the detection of L-cysteine. The complexes are peripherally and non-peripherally substituted with phenylthio substituents. The SAM modified electrodes showed enhancement of catalytic currents and overpotential reduction occurred on the gold modified electrodes with different geometries. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultramicro cylinder electrode were less stable towards the electrocatalytic oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential.
- Full Text:
- Authors: Nombona, Nolwazi , Geraldo, Daniela A , Hakuzimana, Jean , Schwarz, Anne , Westbroek, Philippe , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263488 , vital:53632 , xlink:href="https://doi.org/10.1007/s10800-008-9716-y"
- Description: This paper reports on the use of thiol derivatised cobalt phthalocyanines as self assembled monolayers (SAMs) on gold disk electrode, gold ultramicro-cylinder electrode (UMCE) and on gold coated fiber for the detection of L-cysteine. The complexes are peripherally and non-peripherally substituted with phenylthio substituents. The SAM modified electrodes showed enhancement of catalytic currents and overpotential reduction occurred on the gold modified electrodes with different geometries. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultramicro cylinder electrode were less stable towards the electrocatalytic oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential.
- Full Text:
Comparing and contrasting liberal, communitarian and feminist approaches to resolving tensions between customary and constitutional law: the case of polygamy in Swaziland
- Authors: Manson, Katherine Elizabeth
- Date: 2009
- Subjects: Human rights -- Swaziland Constitutional law -- Swaziland Customary law -- Swaziland Culture and law -- Swaziland Women's rights -- Swaziland Sex discrimination against women -- Swaziland Polygamy -- Swaziland Liberalism Communitarianism
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2801 , http://hdl.handle.net/10962/d1003011
- Description: Tensions between the individual rights and freedoms found in constitutional bills of rights and the traditionally prescribed social roles and positions articulated in African customary law systems have often been characterised as tensions between communitarian and liberal philosophies. In particular, the notion of gender equality, which is often a feature of the protections offered by constitutional bills of rights, is seen to be in direct opposition to the overtly patriarchal character of many African customs and traditions. This thesis looks specifically at polygamy, long and widely considered in the West to be an oppressive practice premised on the assumed inferiority of women. The analysis considers the implications of polygamy in a particular cultural context, that of the Kingdom of Swaziland, where the newly instituted constitution is often seen to be incompatible with many aspects of Swazi customary law. Here, the tension between the constitutional commitment to gender equality and the persistence of polygamy as a seemingly discriminatory cultural practice forms a lens through which to view the debate as a whole. The theoretical analysis is supplemented by empirical research sourced from local media archives and in-depth interviews conducted with twelve Swazi women, both unmarried and married in polygamous relationships. Communitarian and liberal approaches to resolving this tension are compared, contrasted and finally critiqued from a feminist standpoint. The feminist critique of both communitarianism and liberalism implies that neither ideology promises much for women and affirms the relatively recent feminist suggestion that the key to resolving tensions between constitutional and customary law in general, and to uplifting the social/legal status of women in particular lies in the enhancement of women’s democratic participation and the improvement of women’s decision-making powers.
- Full Text:
- Authors: Manson, Katherine Elizabeth
- Date: 2009
- Subjects: Human rights -- Swaziland Constitutional law -- Swaziland Customary law -- Swaziland Culture and law -- Swaziland Women's rights -- Swaziland Sex discrimination against women -- Swaziland Polygamy -- Swaziland Liberalism Communitarianism
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2801 , http://hdl.handle.net/10962/d1003011
- Description: Tensions between the individual rights and freedoms found in constitutional bills of rights and the traditionally prescribed social roles and positions articulated in African customary law systems have often been characterised as tensions between communitarian and liberal philosophies. In particular, the notion of gender equality, which is often a feature of the protections offered by constitutional bills of rights, is seen to be in direct opposition to the overtly patriarchal character of many African customs and traditions. This thesis looks specifically at polygamy, long and widely considered in the West to be an oppressive practice premised on the assumed inferiority of women. The analysis considers the implications of polygamy in a particular cultural context, that of the Kingdom of Swaziland, where the newly instituted constitution is often seen to be incompatible with many aspects of Swazi customary law. Here, the tension between the constitutional commitment to gender equality and the persistence of polygamy as a seemingly discriminatory cultural practice forms a lens through which to view the debate as a whole. The theoretical analysis is supplemented by empirical research sourced from local media archives and in-depth interviews conducted with twelve Swazi women, both unmarried and married in polygamous relationships. Communitarian and liberal approaches to resolving this tension are compared, contrasted and finally critiqued from a feminist standpoint. The feminist critique of both communitarianism and liberalism implies that neither ideology promises much for women and affirms the relatively recent feminist suggestion that the key to resolving tensions between constitutional and customary law in general, and to uplifting the social/legal status of women in particular lies in the enhancement of women’s democratic participation and the improvement of women’s decision-making powers.
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Conceptualising the more knowledgeable other within a multi-directional ZPD:
- Authors: Graven, Mellony
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69519 , vital:29545 , https://doi.org/10.1007/s10649-017-9768-1
- Description: From a Marxian/Vygotskian perspective, learning is social in origin and it happens in the presence of others that are more knowledgeable. Extending this view to the learning of mathematics, such learning also becomes inseparable from the presence of others (people and artefacts). Researchers over decades have studied different interactions to see how such learning with others occurs, what is the role of the (more knowledgeable) other, and if at all this role alternates between the participants. In this paper, we looked at a 5-year-old’s (Lila) interaction with her mother (Mellony) and a television remote control as Lila attempted to count in threes using the three by three physical layout of the numbered buttons 1–9 on the remote control. We specifically looked at the emergence of the Zone of Proximal Development (ZPD) as Lila’s attention was caught by the properties of the remote control and by her mother’s questions. We also pay attention to how the role of the more knowledgeable other alternates among the participants. Our findings suggest that Lila, at times, used resources provided by the physical properties of the remote control and sometimes, used resources provided by Mellony to think about the task of counting in threes. In Lila’s interaction, we interpreted a multi-directional ZPD as the role of the more knowledgeable other alternated between Mellony, Lila and the remote control.
- Full Text:
- Authors: Graven, Mellony
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69519 , vital:29545 , https://doi.org/10.1007/s10649-017-9768-1
- Description: From a Marxian/Vygotskian perspective, learning is social in origin and it happens in the presence of others that are more knowledgeable. Extending this view to the learning of mathematics, such learning also becomes inseparable from the presence of others (people and artefacts). Researchers over decades have studied different interactions to see how such learning with others occurs, what is the role of the (more knowledgeable) other, and if at all this role alternates between the participants. In this paper, we looked at a 5-year-old’s (Lila) interaction with her mother (Mellony) and a television remote control as Lila attempted to count in threes using the three by three physical layout of the numbered buttons 1–9 on the remote control. We specifically looked at the emergence of the Zone of Proximal Development (ZPD) as Lila’s attention was caught by the properties of the remote control and by her mother’s questions. We also pay attention to how the role of the more knowledgeable other alternates among the participants. Our findings suggest that Lila, at times, used resources provided by the physical properties of the remote control and sometimes, used resources provided by Mellony to think about the task of counting in threes. In Lila’s interaction, we interpreted a multi-directional ZPD as the role of the more knowledgeable other alternated between Mellony, Lila and the remote control.
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Conflict, contradiction and crisis: an analysis of the politics of AIDS policy in post-Apartheid South Africa
- Authors: Fletcher, Haley Kim
- Date: 2009
- Subjects: AIDS (Disease) -- Political aspects -- Africa, Southern AIDS (Disease) -- Political aspects -- South Africa AIDS (Disease) -- Government policy -- South Africa Africa -- Politics and government
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2775 , http://hdl.handle.net/10962/d1002985
- Description: Despite the profound impacts of HIV and AIDS on all sectors of South African society, governmental responses to the AIDS epidemic have been inundated with contradiction, conflict and contestation. Though governmental leaders have justified not funding HIV treatment programs because they believe that poverty needs to be dealt with first, social spending has been slashed as part of an adherence to a neo-liberal economic model. Though it would seem that the government would seem to have everything to gain by establishing a cooperative relationship with non-governmental actors regarding the epidemic, the relationship between the government and non-governmental actors has instead been described as nothing short of hostile. Though the government enthusiastically backed Virodene, a supposed treatment for AIDS that turned out to be no more than an industrial solvent, other ‘scientifically backed’ AIDS treatments have been treated with caution and skepticism – to the point where the government even refused to provide funding for programs to prevent mother to child transmission of the virus. And perhaps the most perplexing is that although widely respected for his intellect and cool demeanor, former President Mbeki chose to risk his political career on the AIDS issue by shunning away from the mainstream consensus on the biomedical causes of the epidemic and instead surrounded himself and sought advice from AIDS ‘dissidents’ This thesis will seek explanations for these apparent contradictions. Using Bourdieu’s (1986) typology of capitals, it will build on an argument put forward by Helen Schneider (2002): from the South African government’s perspective, the contestation regarding HIV and AIDS policy and implementation is over symbolic capital, or the right to legitimately hold and exercise political power regarding the epidemic. Though this argument helps explain the conflictual relationship between the government and non-governmental actors regarding the AIDS crisis, in order to understand the perplexing contradictions within the governmental policy response, the political context of policy formation must first be taken into consideration.
- Full Text:
- Authors: Fletcher, Haley Kim
- Date: 2009
- Subjects: AIDS (Disease) -- Political aspects -- Africa, Southern AIDS (Disease) -- Political aspects -- South Africa AIDS (Disease) -- Government policy -- South Africa Africa -- Politics and government
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2775 , http://hdl.handle.net/10962/d1002985
- Description: Despite the profound impacts of HIV and AIDS on all sectors of South African society, governmental responses to the AIDS epidemic have been inundated with contradiction, conflict and contestation. Though governmental leaders have justified not funding HIV treatment programs because they believe that poverty needs to be dealt with first, social spending has been slashed as part of an adherence to a neo-liberal economic model. Though it would seem that the government would seem to have everything to gain by establishing a cooperative relationship with non-governmental actors regarding the epidemic, the relationship between the government and non-governmental actors has instead been described as nothing short of hostile. Though the government enthusiastically backed Virodene, a supposed treatment for AIDS that turned out to be no more than an industrial solvent, other ‘scientifically backed’ AIDS treatments have been treated with caution and skepticism – to the point where the government even refused to provide funding for programs to prevent mother to child transmission of the virus. And perhaps the most perplexing is that although widely respected for his intellect and cool demeanor, former President Mbeki chose to risk his political career on the AIDS issue by shunning away from the mainstream consensus on the biomedical causes of the epidemic and instead surrounded himself and sought advice from AIDS ‘dissidents’ This thesis will seek explanations for these apparent contradictions. Using Bourdieu’s (1986) typology of capitals, it will build on an argument put forward by Helen Schneider (2002): from the South African government’s perspective, the contestation regarding HIV and AIDS policy and implementation is over symbolic capital, or the right to legitimately hold and exercise political power regarding the epidemic. Though this argument helps explain the conflictual relationship between the government and non-governmental actors regarding the AIDS crisis, in order to understand the perplexing contradictions within the governmental policy response, the political context of policy formation must first be taken into consideration.
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Conservation, commercialisation and confusion: Harvesting of Ischyrolepis in a coastal forest, South Africa
- Shackleton, Charlie M, Parkin, Fiona, Chauke, Maphambe I, Downsborough, Linda, Olsen, Ashleigh, Brill, Greg, Weideman, Craig I
- Authors: Shackleton, Charlie M , Parkin, Fiona , Chauke, Maphambe I , Downsborough, Linda , Olsen, Ashleigh , Brill, Greg , Weideman, Craig I
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181169 , vital:43704 , xlink:href="https://doi.org/10.1007/s10668-007-9106-3"
- Description: Harvesting of non-timber forest products is an integral component of rural livelihoods throughout the developing world. At times this is at odds with conservation objectives. Reconciliation of the two requires examination of local level contexts and needs. This paper reports on the harvesting needs for Ischyrolepis by a rural community in South Africa, against the setting that they had recently been prohibited from harvesting by the local conservation officials. Interviews were conducted with conservation officials to understand the reasoning for the prohibition. Local demand for Ischyrolepis was assessed by household surveys, as well as in-depth interviews with traders. The density and size class distribution of Ischyrolepis was determined using transects. The total annual demand for Ischyrolepis was determined to be approximately only 2.7% of the standing crop. The bulk of the annual demand was for small-scale trade, the income from which was a primary source of income for the few harvesters. Very little evidence could be found indicating that harvesting was damaging the resource or its habitat, and local knowledge suggested that the abundance of the species was stimulated by harvesting. Even if market demand were to increase, the size of the shoots required means that less than 20% of the standing crop could be harvested annually. Current regulations around harvesting are in a state of revision, and hence confusion prevails regarding if harvesting is permissible, and if so, under what conditions, which is detrimental to both conservation and livelihoods.
- Full Text:
- Authors: Shackleton, Charlie M , Parkin, Fiona , Chauke, Maphambe I , Downsborough, Linda , Olsen, Ashleigh , Brill, Greg , Weideman, Craig I
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181169 , vital:43704 , xlink:href="https://doi.org/10.1007/s10668-007-9106-3"
- Description: Harvesting of non-timber forest products is an integral component of rural livelihoods throughout the developing world. At times this is at odds with conservation objectives. Reconciliation of the two requires examination of local level contexts and needs. This paper reports on the harvesting needs for Ischyrolepis by a rural community in South Africa, against the setting that they had recently been prohibited from harvesting by the local conservation officials. Interviews were conducted with conservation officials to understand the reasoning for the prohibition. Local demand for Ischyrolepis was assessed by household surveys, as well as in-depth interviews with traders. The density and size class distribution of Ischyrolepis was determined using transects. The total annual demand for Ischyrolepis was determined to be approximately only 2.7% of the standing crop. The bulk of the annual demand was for small-scale trade, the income from which was a primary source of income for the few harvesters. Very little evidence could be found indicating that harvesting was damaging the resource or its habitat, and local knowledge suggested that the abundance of the species was stimulated by harvesting. Even if market demand were to increase, the size of the shoots required means that less than 20% of the standing crop could be harvested annually. Current regulations around harvesting are in a state of revision, and hence confusion prevails regarding if harvesting is permissible, and if so, under what conditions, which is detrimental to both conservation and livelihoods.
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Constructing the intellectually disabled person as a subject of education: a discourse analysis using Q-methodology
- Authors: McKenzie, Judith Anne
- Date: 2009
- Subjects: Foucault, Michel, 1926-1984 Learning disabled -- Education -- South Africa Discourse analysis -- Methodology Discourse analysis Children with mental disabilities -- Education -- South Africa Q technique Special education -- South Africa Children with disabilities -- Education -- South Africa Right to education Intelligence tests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3017 , http://hdl.handle.net/10962/d1002526
- Description: The education of intellectually disabled (ID) people is constructed within mass education systems as a problem requiring specialised intervention, separation from “normal” school contexts and the application of professional expertise. A social model of disability resists these practices from a human rights perspective and underpins an inclusive education approach. In this study, a post-structuralist disability studies theoretical framework, drawing particularly on the work of Foucault, was used to examine discourses that construct the intellectually disabled person as a subject of education. The study was conducted in Buffalo City, South Africa at a time when an inclusive education policy is being implemented in the country. The research questions were: What discourses are deployed in the representation and educational practices of those identified as ID? What are the effects of these discourses in constructing the ID subject and associated educational practice? The study utilises Q-methodology, a factor analytic method that yields whole patterns of responses for analysis. A process of sorting selected statements along the dimension of agree to disagree was completed by three groups of participants, namely adults with ID, parents of people with ID and professionals working with ID. Discourses of representation and of educational practice were identified through statistical and interpretive analysis, following the discourse analysis school of Q-methodology. The findings of this study reveal the operation of power in a medico-psychological gaze that makes ID visible and supervises disability expertise within education. Representations of ID suffused with religious notions support the exercise of pastoral power by disability experts. Human rights discourses in education can marginalise ID people if applied uncritically. Fixed notions of impairment constrain an intellectually disabled subject who is vulnerable and incompetent. This study argues instead for a theory of (poss)ability, underpinned by an understanding of the situational and shared nature of competence and a fluid conception of impairment. Human rights should be supplemented by an ethics of care and belonging in the community (ubuntu). A research agenda supporting this effort would examine the ways in which ID people work on themselves as subjects (subjectivisation) and explore the potential for resistance in this process.
- Full Text:
- Authors: McKenzie, Judith Anne
- Date: 2009
- Subjects: Foucault, Michel, 1926-1984 Learning disabled -- Education -- South Africa Discourse analysis -- Methodology Discourse analysis Children with mental disabilities -- Education -- South Africa Q technique Special education -- South Africa Children with disabilities -- Education -- South Africa Right to education Intelligence tests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3017 , http://hdl.handle.net/10962/d1002526
- Description: The education of intellectually disabled (ID) people is constructed within mass education systems as a problem requiring specialised intervention, separation from “normal” school contexts and the application of professional expertise. A social model of disability resists these practices from a human rights perspective and underpins an inclusive education approach. In this study, a post-structuralist disability studies theoretical framework, drawing particularly on the work of Foucault, was used to examine discourses that construct the intellectually disabled person as a subject of education. The study was conducted in Buffalo City, South Africa at a time when an inclusive education policy is being implemented in the country. The research questions were: What discourses are deployed in the representation and educational practices of those identified as ID? What are the effects of these discourses in constructing the ID subject and associated educational practice? The study utilises Q-methodology, a factor analytic method that yields whole patterns of responses for analysis. A process of sorting selected statements along the dimension of agree to disagree was completed by three groups of participants, namely adults with ID, parents of people with ID and professionals working with ID. Discourses of representation and of educational practice were identified through statistical and interpretive analysis, following the discourse analysis school of Q-methodology. The findings of this study reveal the operation of power in a medico-psychological gaze that makes ID visible and supervises disability expertise within education. Representations of ID suffused with religious notions support the exercise of pastoral power by disability experts. Human rights discourses in education can marginalise ID people if applied uncritically. Fixed notions of impairment constrain an intellectually disabled subject who is vulnerable and incompetent. This study argues instead for a theory of (poss)ability, underpinned by an understanding of the situational and shared nature of competence and a fluid conception of impairment. Human rights should be supplemented by an ethics of care and belonging in the community (ubuntu). A research agenda supporting this effort would examine the ways in which ID people work on themselves as subjects (subjectivisation) and explore the potential for resistance in this process.
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Contextualizing the NCS through the use of school gardens in the Butterworth area
- Authors: Rasi, Nandi
- Date: 2009
- Subjects: South African National Biodiversity Institute , Environmental education -- South Africa , School gardens -- South Africa -- Butterworth , Gardening -- Study and teaching (Elementary) -- South Africa -- Butterworth , Environmental education -- Study and teaching (Elementary) -- South Africa -- Butterworth , Teacher participation in curriculum planning -- South Africa -- Butterworth
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1464 , http://hdl.handle.net/10962/d1003345
- Description: The research focuses on how teachers can use school gardens sponsored by South African National Biodiversity Institute as resource materials for teaching and learning. The study also focused on how teachers can integrate local knowledge into the school curriculum. The setting of the research is Zizamele Senior Primary School situated in Zizamele community in Butterworth in the Eastern Cape. The study is designed in portfolio format. It consists of three separate studies: a contextual profile; a stakeholder analysis; and a small-scale action research project, which build on each other. By developing a contextual profile of the research site, and the school community and school gardens project, I was able to collect information that informed the stakeholder analysis and the action research study. Data for the contextual profile was gathered by using a variety of data gathering techniques like questionnaires and interviews. The findings were that: the study area is characterized by socio-economic issues like poverty, unemployment, drug abuse and crime. This requires that the people of the area take responsibility in addressing some of the problems by being involved and knowing where to report issues. The second study, which is the stakeholder analysis, was done to mobilize stakeholders’ contributions to the gardens project in Zizamele School, sponsored by the South African National Biodiversity Institute. Data was collected at meetings and workshops in the schools through interviews. Findings indicated that different stakeholders had various contributions to make and that they were prepared to work with the school and with each other to develop the school garden and the learning potential of the school garden. This paved the way for the small scale action research case study that would follow. The last study, the small scale action research, was undertaken in the same school, Zizamele School, and focused on investigating ways of integrating local knowledge into the curriculum and how teachers use the gardens as resource for teaching and learning, with reference to Life Orientation Learning Area. Data was collected by interviews, questionnaires and worksheets. The study involved two teachers who worked with me on the action research and Grade 5 and 6 learners, as well as some of the community stakeholders. The main finding of the action researched showed the potential for involving community members in the process of integrating local knowledge as a way of implementing aspects of the Life Orientation curriculum requirements. The three studies link with each other, and show that to start with an action research project, one needs to understand the context, and the roles of different stakeholders, and how they might contribute to the programmes in the school. Findings showed that teachers could use gardens as resource materials for teaching and learning, and that they could bring in local knowledge to the school curriculum.
- Full Text:
- Authors: Rasi, Nandi
- Date: 2009
- Subjects: South African National Biodiversity Institute , Environmental education -- South Africa , School gardens -- South Africa -- Butterworth , Gardening -- Study and teaching (Elementary) -- South Africa -- Butterworth , Environmental education -- Study and teaching (Elementary) -- South Africa -- Butterworth , Teacher participation in curriculum planning -- South Africa -- Butterworth
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1464 , http://hdl.handle.net/10962/d1003345
- Description: The research focuses on how teachers can use school gardens sponsored by South African National Biodiversity Institute as resource materials for teaching and learning. The study also focused on how teachers can integrate local knowledge into the school curriculum. The setting of the research is Zizamele Senior Primary School situated in Zizamele community in Butterworth in the Eastern Cape. The study is designed in portfolio format. It consists of three separate studies: a contextual profile; a stakeholder analysis; and a small-scale action research project, which build on each other. By developing a contextual profile of the research site, and the school community and school gardens project, I was able to collect information that informed the stakeholder analysis and the action research study. Data for the contextual profile was gathered by using a variety of data gathering techniques like questionnaires and interviews. The findings were that: the study area is characterized by socio-economic issues like poverty, unemployment, drug abuse and crime. This requires that the people of the area take responsibility in addressing some of the problems by being involved and knowing where to report issues. The second study, which is the stakeholder analysis, was done to mobilize stakeholders’ contributions to the gardens project in Zizamele School, sponsored by the South African National Biodiversity Institute. Data was collected at meetings and workshops in the schools through interviews. Findings indicated that different stakeholders had various contributions to make and that they were prepared to work with the school and with each other to develop the school garden and the learning potential of the school garden. This paved the way for the small scale action research case study that would follow. The last study, the small scale action research, was undertaken in the same school, Zizamele School, and focused on investigating ways of integrating local knowledge into the curriculum and how teachers use the gardens as resource for teaching and learning, with reference to Life Orientation Learning Area. Data was collected by interviews, questionnaires and worksheets. The study involved two teachers who worked with me on the action research and Grade 5 and 6 learners, as well as some of the community stakeholders. The main finding of the action researched showed the potential for involving community members in the process of integrating local knowledge as a way of implementing aspects of the Life Orientation curriculum requirements. The three studies link with each other, and show that to start with an action research project, one needs to understand the context, and the roles of different stakeholders, and how they might contribute to the programmes in the school. Findings showed that teachers could use gardens as resource materials for teaching and learning, and that they could bring in local knowledge to the school curriculum.
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Continuous assessment in Oshikwanyama: a case study
- Nghiueuelekuah, Soini Tuhafeni
- Authors: Nghiueuelekuah, Soini Tuhafeni
- Date: 2009
- Subjects: Educational tests and measurements -- Namibia -- Case studies Kuanyama language -- Namibia -- Case studies Kuanyama language -- Study and teaching -- Namibia -- Case studies Language and education -- Namibia -- Case studies
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1465 , http://hdl.handle.net/10962/d1003346
- Description: This study is about Continuous Assessment (CA) in teaching and learning, a new concept and approach in independent Namibia. The country's education system was reformed shortly after independence in 1990 to fulfill the intention for Education for All. The Namibian education system then moved from a behaviorist to constructivist philosophy of education. The move made from one philosophy to another resulted in many changes in teaching and learning including changes in assessment in education. CA is born out of a constructivist philosophy. It is believed to facilitate learning with understanding. In this study I explored the understanding of Oshikwanyama teachers and their practice of CA in teaching and learning. Interviews, classroom observations and document analysis were used. The research focused on 10 participants in the Ohangwena and Oshana regions. The participants ranged from a Head of Department to members of the curriculum panel, subject advisors and Oshikwanyama subject facilitators as well as teachers at the classroom level. It was revealed that generally speaking, CA as a term is understood, but the practice is not well implemented. In the practice of CA, instead of learners being assessed for further learning, the emphasis is on scored marks without further assistance in learning. Further, the collection of marks during CA is often seen as largely for the purpose of contributing to the marks for summative final marks. Informal assessment which is part of CA was not given attention, which is a key factor preventing the effective use of CA in teaching and learning. Methods such as marking grids that are provided in the syllabus, as well as portfolios and learners' profiles, were not mentioned in the interviews nor observed as being in use. Participants in the study did acknowledge that they did not fully understand how best to implement CA. Overall, the evidence pointed to a conclusion that the identified shortcomings in the implementation of formative assessment is limiting the realization of the rich potential for CA as a day-to-day tool to facilitate learning for understanding in the observed classes.
- Full Text:
- Authors: Nghiueuelekuah, Soini Tuhafeni
- Date: 2009
- Subjects: Educational tests and measurements -- Namibia -- Case studies Kuanyama language -- Namibia -- Case studies Kuanyama language -- Study and teaching -- Namibia -- Case studies Language and education -- Namibia -- Case studies
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1465 , http://hdl.handle.net/10962/d1003346
- Description: This study is about Continuous Assessment (CA) in teaching and learning, a new concept and approach in independent Namibia. The country's education system was reformed shortly after independence in 1990 to fulfill the intention for Education for All. The Namibian education system then moved from a behaviorist to constructivist philosophy of education. The move made from one philosophy to another resulted in many changes in teaching and learning including changes in assessment in education. CA is born out of a constructivist philosophy. It is believed to facilitate learning with understanding. In this study I explored the understanding of Oshikwanyama teachers and their practice of CA in teaching and learning. Interviews, classroom observations and document analysis were used. The research focused on 10 participants in the Ohangwena and Oshana regions. The participants ranged from a Head of Department to members of the curriculum panel, subject advisors and Oshikwanyama subject facilitators as well as teachers at the classroom level. It was revealed that generally speaking, CA as a term is understood, but the practice is not well implemented. In the practice of CA, instead of learners being assessed for further learning, the emphasis is on scored marks without further assistance in learning. Further, the collection of marks during CA is often seen as largely for the purpose of contributing to the marks for summative final marks. Informal assessment which is part of CA was not given attention, which is a key factor preventing the effective use of CA in teaching and learning. Methods such as marking grids that are provided in the syllabus, as well as portfolios and learners' profiles, were not mentioned in the interviews nor observed as being in use. Participants in the study did acknowledge that they did not fully understand how best to implement CA. Overall, the evidence pointed to a conclusion that the identified shortcomings in the implementation of formative assessment is limiting the realization of the rich potential for CA as a day-to-day tool to facilitate learning for understanding in the observed classes.
- Full Text: