A histological description of ovarian recrudescence in two Labeo victorianus populations
- Booth, Anthony J, Hecht, Thomas
- Authors: Booth, Anthony J , Hecht, Thomas
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123564 , vital:35455 , https://doi.org/10.2989/16085910409503813
- Description: The ovaries of Labeo victorianus are paired organs situated in the peritoneal cavity and suspended on either side of the midline by a mesovarium. A capsule, composed of dense, regularly-arranged collagen and elastic fibres mixed with a few smooth muscle cells, enclosed the ovaries and gave off connective tissue septa, forming the ovigerous lamellae, which contained germ and follicle cells. Eight discrete stages of recrudescence were identified: oogonia, chromatin nucleolar oocytes, perinucleolar oocytes, primary yolk vesicle oocytes, secondary yolk vesicle oocytes, tertiary yolk vesicle oocytes, post-ovulatory follicles and atretic oocytes. Ovulation seemed to be synchronised with the onset of rainfall, with some deviations in the Sio River population. Gonadosomatic index variation followed a bimodal pattern, with maxima between January–February and between September–October for both populations. The same pattern was exhibited for both rainfall and water levels at the two study sites. Successful ovulation was followed by the formation of post-ovulatory follicles and Type I atresia, while failed spawning was characterised by Type II atresia. Clearance of post-ovulatory follicles was by phagocytosis and formation of melanomacrophage centres. There were variations in post-ovulatory changes between the two populations. Reproductive patterns in the Kagera River population conformed to the ‘norm’ in African labeines of the synchronisation of spawning with rainfall. Slight deviations from this pattern were, however, observed in the Sio River population where spawning occurred prior to the onset of rainfall.
- Full Text:
- Date Issued: 2010
- Authors: Booth, Anthony J , Hecht, Thomas
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123564 , vital:35455 , https://doi.org/10.2989/16085910409503813
- Description: The ovaries of Labeo victorianus are paired organs situated in the peritoneal cavity and suspended on either side of the midline by a mesovarium. A capsule, composed of dense, regularly-arranged collagen and elastic fibres mixed with a few smooth muscle cells, enclosed the ovaries and gave off connective tissue septa, forming the ovigerous lamellae, which contained germ and follicle cells. Eight discrete stages of recrudescence were identified: oogonia, chromatin nucleolar oocytes, perinucleolar oocytes, primary yolk vesicle oocytes, secondary yolk vesicle oocytes, tertiary yolk vesicle oocytes, post-ovulatory follicles and atretic oocytes. Ovulation seemed to be synchronised with the onset of rainfall, with some deviations in the Sio River population. Gonadosomatic index variation followed a bimodal pattern, with maxima between January–February and between September–October for both populations. The same pattern was exhibited for both rainfall and water levels at the two study sites. Successful ovulation was followed by the formation of post-ovulatory follicles and Type I atresia, while failed spawning was characterised by Type II atresia. Clearance of post-ovulatory follicles was by phagocytosis and formation of melanomacrophage centres. There were variations in post-ovulatory changes between the two populations. Reproductive patterns in the Kagera River population conformed to the ‘norm’ in African labeines of the synchronisation of spawning with rainfall. Slight deviations from this pattern were, however, observed in the Sio River population where spawning occurred prior to the onset of rainfall.
- Full Text:
- Date Issued: 2010
An assessment of a light-attraction fishery in southern Lake Malawi
- Weyl, Olaf L F, Kazembe, Jacqueline, Booth, Anthony J, Mandere, D S
- Authors: Weyl, Olaf L F , Kazembe, Jacqueline , Booth, Anthony J , Mandere, D S
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123683 , vital:35472 , https://doi.org/10.2989/16085910409503787
- Description: This study provides the first quantitative assessment of the light-attraction component of a small-scale purse seine, locally known as a chilimira net, fishery in two areas of southern Lake Malawi. For monitoring purposes the shoreline of Lake Malawi is divided into a number of statistical strata. Two strata (‘2.1’ in the southeast arm and ‘3.1’ in the southwest arm of the lake) were selected for this study. Catch per unit effort in stratum 2.1 was generally lower than that recorded in stratum 3.1 but nets in stratum 2.1 fished more frequently, leading to similar annual catches in the two strata. Annual catch was estimated as 19.4 (CI = 15.9–23.5) tons net–1 year–1 in stratum 2.1 and 23.5 (CI = 19.5–28.1) tons net–1 year–1 in stratum 3.1 respectively. A total of 62 species from 28 cichlid genera, and 13 species from nine non-cichlid genera, were identified from the samples. Of the 37 genera identified, only five; Copadichromis, Dimidiochromis, Engraulicypris, Oreochromis and Rhamphochromis, contributed more than 5% to the total annual catch in either stratum. Their combined contribution to the annual catch was in excess of 85% in both strata. Comparisons showed that catch-composition was dependent on area. Length-frequency distributions of major target species in the catch showed that the fishery targeted juveniles in stratum 2.1, while in stratum 3.1 most individuals were harvested after reaching their lengthat-maturity. The dependence of catch-composition and size-selection on area indicates that management interventions for this fishery need to be area-specific. Since the fishery targets a diverse species assemblage, effort limitation or area closure may be the only viable management options, until such time as additional biological and fisheries data are available for the application of stock assessment models.
- Full Text:
- Date Issued: 2010
- Authors: Weyl, Olaf L F , Kazembe, Jacqueline , Booth, Anthony J , Mandere, D S
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123683 , vital:35472 , https://doi.org/10.2989/16085910409503787
- Description: This study provides the first quantitative assessment of the light-attraction component of a small-scale purse seine, locally known as a chilimira net, fishery in two areas of southern Lake Malawi. For monitoring purposes the shoreline of Lake Malawi is divided into a number of statistical strata. Two strata (‘2.1’ in the southeast arm and ‘3.1’ in the southwest arm of the lake) were selected for this study. Catch per unit effort in stratum 2.1 was generally lower than that recorded in stratum 3.1 but nets in stratum 2.1 fished more frequently, leading to similar annual catches in the two strata. Annual catch was estimated as 19.4 (CI = 15.9–23.5) tons net–1 year–1 in stratum 2.1 and 23.5 (CI = 19.5–28.1) tons net–1 year–1 in stratum 3.1 respectively. A total of 62 species from 28 cichlid genera, and 13 species from nine non-cichlid genera, were identified from the samples. Of the 37 genera identified, only five; Copadichromis, Dimidiochromis, Engraulicypris, Oreochromis and Rhamphochromis, contributed more than 5% to the total annual catch in either stratum. Their combined contribution to the annual catch was in excess of 85% in both strata. Comparisons showed that catch-composition was dependent on area. Length-frequency distributions of major target species in the catch showed that the fishery targeted juveniles in stratum 2.1, while in stratum 3.1 most individuals were harvested after reaching their lengthat-maturity. The dependence of catch-composition and size-selection on area indicates that management interventions for this fishery need to be area-specific. Since the fishery targets a diverse species assemblage, effort limitation or area closure may be the only viable management options, until such time as additional biological and fisheries data are available for the application of stock assessment models.
- Full Text:
- Date Issued: 2010
More media for Southern Africa?: the place of politics, economics and convergence in developing media density
- Authors: Berger, Guy
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147825 , vital:38676 , https://0-doi.org.wam.seals.ac.za/10.1080/02560240485310041
- Description: In line with global trends, media in Southern Africa in the past decade has been moving slowly towards mergers, partnerships and multi-platform publishing. Driven by politics and facilitated by technology, the process has had to confront the difficulty of establishing viable economic models, the lack of regional integration within Southern African countries, and what is sometimes a difficult political environment. Markets remain largely national or local and economically weak. Print media faces huge hurdles. Broadcast media density is improving, partly through noncommercial mechanisms. News websites are understaffed, lacking in viable survival strategies and skills, and are incompletely integrated with parent media platforms. Economic pressures, however, are likely to force Southern African media operations into greater synergies in search of survival. The various convergences entailed may increase media density.
- Full Text:
- Date Issued: 2007
- Authors: Berger, Guy
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147825 , vital:38676 , https://0-doi.org.wam.seals.ac.za/10.1080/02560240485310041
- Description: In line with global trends, media in Southern Africa in the past decade has been moving slowly towards mergers, partnerships and multi-platform publishing. Driven by politics and facilitated by technology, the process has had to confront the difficulty of establishing viable economic models, the lack of regional integration within Southern African countries, and what is sometimes a difficult political environment. Markets remain largely national or local and economically weak. Print media faces huge hurdles. Broadcast media density is improving, partly through noncommercial mechanisms. News websites are understaffed, lacking in viable survival strategies and skills, and are incompletely integrated with parent media platforms. Economic pressures, however, are likely to force Southern African media operations into greater synergies in search of survival. The various convergences entailed may increase media density.
- Full Text:
- Date Issued: 2007
Transforming the media: a cultural approach
- Authors: Steenveld, Lynette N
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147891 , vital:38682 , DOI: 10.1080/02560240485310061
- Description: The change from an Apartheid state to a liberal democratic one has wrought many changes at all levels of South African society: the economic, social, political, cultural. This paper explores the impacts of these changes on the South African print media industry, with a view to assessing their contribution to the development of a democratic citizenship. While acknowledging the constraining effects of economic structures of ownership, the paper locates these within the broader social and political context of post-apartheid South Africa. It thus attempts to synthesise elements of both a political economy and cultural approach to the analysis of cultural production.
- Full Text:
- Date Issued: 2007
- Authors: Steenveld, Lynette N
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147891 , vital:38682 , DOI: 10.1080/02560240485310061
- Description: The change from an Apartheid state to a liberal democratic one has wrought many changes at all levels of South African society: the economic, social, political, cultural. This paper explores the impacts of these changes on the South African print media industry, with a view to assessing their contribution to the development of a democratic citizenship. While acknowledging the constraining effects of economic structures of ownership, the paper locates these within the broader social and political context of post-apartheid South Africa. It thus attempts to synthesise elements of both a political economy and cultural approach to the analysis of cultural production.
- Full Text:
- Date Issued: 2007
"My novel, Hill of Fools"
- Peteni, R L, Wright, Laurence
- Authors: Peteni, R L , Wright, Laurence
- Date: 2004
- Language: English
- Type: text , article
- Identifier: vital:7038 , http://hdl.handle.net/10962/d1007376 , http://hdl.handle.net/10520/EJC47869
- Description: preprint , R.L. Peteni - 'There is a tendency in human beings to pay no heed to events in small remote areas. They would rather concern themselves only with those events which make headlines, with political upheavals and industrial conflicts centred in large metropolitan regions. Yet there is always drama and human conflict in the humblest rural village. In selecting a pastoral theme and small fictitious villages in an obscure corner of Keiskammahoek as the setting of the novel, I had an ironic intention. Themes illustrated in these obscure villages would, I believed, have more universal application than they would if I had selected a larger centre, identifiable personages and known political trends. I did not want anybody to sit back, complacent, feeling that the spotlight was on Lennox Sebe’s Ciskei alone, or Kaiser Matanzima’s Transkei, or John Vorster’s apartheid South Africa. The spotlight is on the Ciskei, yes, on Transkei, on South Africa, on any other country where public life and personal relationships are bedevilled by tribalism or racialism or any form of sectionalism.
- Full Text:
- Date Issued: 2004
- Authors: Peteni, R L , Wright, Laurence
- Date: 2004
- Language: English
- Type: text , article
- Identifier: vital:7038 , http://hdl.handle.net/10962/d1007376 , http://hdl.handle.net/10520/EJC47869
- Description: preprint , R.L. Peteni - 'There is a tendency in human beings to pay no heed to events in small remote areas. They would rather concern themselves only with those events which make headlines, with political upheavals and industrial conflicts centred in large metropolitan regions. Yet there is always drama and human conflict in the humblest rural village. In selecting a pastoral theme and small fictitious villages in an obscure corner of Keiskammahoek as the setting of the novel, I had an ironic intention. Themes illustrated in these obscure villages would, I believed, have more universal application than they would if I had selected a larger centre, identifiable personages and known political trends. I did not want anybody to sit back, complacent, feeling that the spotlight was on Lennox Sebe’s Ciskei alone, or Kaiser Matanzima’s Transkei, or John Vorster’s apartheid South Africa. The spotlight is on the Ciskei, yes, on Transkei, on South Africa, on any other country where public life and personal relationships are bedevilled by tribalism or racialism or any form of sectionalism.
- Full Text:
- Date Issued: 2004
A fuzzy classification technique for predicting species' distributions: applications using invasive alien plants and indigenous insects
- Robertson, Mark P, Villet, Martin H, Palmer, Anthony R
- Authors: Robertson, Mark P , Villet, Martin H , Palmer, Anthony R
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6897 , http://hdl.handle.net/10962/d1011659 , http://dx.doi.org/10.1111/j.1366-9516.2004.00108.x
- Description: A new predictive modelling technique called the fuzzy envelope model (FEM) is introduced. The technique can be used to predict potential distributions of organisms using presence-only locality records and a set of environmental predictor variables. FEM uses fuzzy logic to classify a set of predictor variable maps based on the values associated with presence records and combines the results to produce a potential distribution map for a target species. This technique represents several refinements of the envelope approach used in the BIOCLIM modelling package. These refinements are related to the way in which FEMs deal with uncertainty, the way in which this uncertainty is represented in the resultant potential distribution maps, and the way that these maps can be interpreted and applied. To illustrate its potential use in biogeographical studies, FEM was applied to predicting the potential distribution of three invasive alien plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.), and three native cicada species (Capicada decora Germar, Platypleura deusta Thun. and P. capensis L.) in South Africa, Lesotho and Swaziland. These models were quantitatively compared with models produced by means of the algorithm used in the BIOCLIM modelling package, which is referred to as a crisp envelope model (the CEM design). The average performance of models of the FEM design was consistently higher than those of the CEM design. There were significant differences in model performance among species but there was no significant interaction between model design and species. The average maximum kappa value ranged from 0.70 to 0.90 for FEM design and from 0.57 to 0.89 for the CEM design, which can be described as 'good' to 'excellent' using published ranges of agreement for the kappa statistic. This technique can be used to predict species' potential distributions that could be used for identifying regions at risk from invasion by alien species. These predictions could also be used in conservation planning in the case of native species.
- Full Text:
- Date Issued: 2004
- Authors: Robertson, Mark P , Villet, Martin H , Palmer, Anthony R
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6897 , http://hdl.handle.net/10962/d1011659 , http://dx.doi.org/10.1111/j.1366-9516.2004.00108.x
- Description: A new predictive modelling technique called the fuzzy envelope model (FEM) is introduced. The technique can be used to predict potential distributions of organisms using presence-only locality records and a set of environmental predictor variables. FEM uses fuzzy logic to classify a set of predictor variable maps based on the values associated with presence records and combines the results to produce a potential distribution map for a target species. This technique represents several refinements of the envelope approach used in the BIOCLIM modelling package. These refinements are related to the way in which FEMs deal with uncertainty, the way in which this uncertainty is represented in the resultant potential distribution maps, and the way that these maps can be interpreted and applied. To illustrate its potential use in biogeographical studies, FEM was applied to predicting the potential distribution of three invasive alien plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.), and three native cicada species (Capicada decora Germar, Platypleura deusta Thun. and P. capensis L.) in South Africa, Lesotho and Swaziland. These models were quantitatively compared with models produced by means of the algorithm used in the BIOCLIM modelling package, which is referred to as a crisp envelope model (the CEM design). The average performance of models of the FEM design was consistently higher than those of the CEM design. There were significant differences in model performance among species but there was no significant interaction between model design and species. The average maximum kappa value ranged from 0.70 to 0.90 for FEM design and from 0.57 to 0.89 for the CEM design, which can be described as 'good' to 'excellent' using published ranges of agreement for the kappa statistic. This technique can be used to predict species' potential distributions that could be used for identifying regions at risk from invasion by alien species. These predictions could also be used in conservation planning in the case of native species.
- Full Text:
- Date Issued: 2004
A new broom: feature
- Cocks, Michelle L, Dold, Anthony P, Sizane, Nomtunzi
- Authors: Cocks, Michelle L , Dold, Anthony P , Sizane, Nomtunzi
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141404 , vital:37969 , https://hdl.handle.net/10520/EJC112779
- Description: Traditional grass brooms keep certain cultural practices alive in urban areas and provide rural people with a means to earn an income.
- Full Text:
- Date Issued: 2004
- Authors: Cocks, Michelle L , Dold, Anthony P , Sizane, Nomtunzi
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141404 , vital:37969 , https://hdl.handle.net/10520/EJC112779
- Description: Traditional grass brooms keep certain cultural practices alive in urban areas and provide rural people with a means to earn an income.
- Full Text:
- Date Issued: 2004
An analysis of automatically scaled F1 layer data over Grahamstown, South Africa
- Jacobs, Linda, Poole, Allon W V, McKinnell, Lee-Anne
- Authors: Jacobs, Linda , Poole, Allon W V , McKinnell, Lee-Anne
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6808 , http://hdl.handle.net/10962/d1004194
- Description: This paper describes an analysis of automatically scaled F1 layer data over Grahamstown, South Africa (33.3°S, 26.5°E). An application for real time raytracing through the South African ionosphere was identified, and for this application real time evaluation of the electron density profile is essential. Raw real time virtual height data are provided by a Lowell Digisonde (DPS), which employs the automatic scaling software, ARTIST whose output includes the virtual-to-real height data conversion. Experience has shown that there are times when the raytracing performance is degraded because of difficulties surrounding the real time characterisation of the F1 region by ARTIST. The purpose of this investigation is to establish the extent of the problem, the times and conditions under which it occurs, with a view to formulating remedial alternative strategies, such as predictive modelling.
- Full Text:
- Date Issued: 2004
- Authors: Jacobs, Linda , Poole, Allon W V , McKinnell, Lee-Anne
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6808 , http://hdl.handle.net/10962/d1004194
- Description: This paper describes an analysis of automatically scaled F1 layer data over Grahamstown, South Africa (33.3°S, 26.5°E). An application for real time raytracing through the South African ionosphere was identified, and for this application real time evaluation of the electron density profile is essential. Raw real time virtual height data are provided by a Lowell Digisonde (DPS), which employs the automatic scaling software, ARTIST whose output includes the virtual-to-real height data conversion. Experience has shown that there are times when the raytracing performance is degraded because of difficulties surrounding the real time characterisation of the F1 region by ARTIST. The purpose of this investigation is to establish the extent of the problem, the times and conditions under which it occurs, with a view to formulating remedial alternative strategies, such as predictive modelling.
- Full Text:
- Date Issued: 2004
An introduction: Peteni in context
- Authors: Wright, Laurence
- Date: 2004
- Language: English
- Type: text , article
- Identifier: vital:7036 , http://hdl.handle.net/10962/d1007372 , http://hdl.handle.net/10520/EJC47870
- Description: preprint , It is rare for a writer to make a literary impact with only one novel. It is even more unusual when that work is written by a novice author in his early sixties. Yet such is the case of R.L. Peteni, whose novel, Hill of Fools, was published by David Philip in South Africa in 1976, and internationally in the same year by Heinemann in the African Writers Series. Four years later, in 1980, the book was translated by the author into Xhosa as Kwazidenge and published by the Lovedale Press. Twenty years after initial publication, in 1996, there came a television version of Kwazidenge broadcast by the SABC, starring Willie Thambo and Amanda Quwe, though the locale was translated – in the bizarre logic of television – to an urban environment on the Cape Flats. The transposition, though pragmatic in terms of television demographics, destroyed much of the point of Peteni’s work, for Hill of Fools is South Africa’s first regional novel in English by a black writer. It is also the first novel in English by a Xhosa-speaker.
- Full Text:
- Date Issued: 2004
- Authors: Wright, Laurence
- Date: 2004
- Language: English
- Type: text , article
- Identifier: vital:7036 , http://hdl.handle.net/10962/d1007372 , http://hdl.handle.net/10520/EJC47870
- Description: preprint , It is rare for a writer to make a literary impact with only one novel. It is even more unusual when that work is written by a novice author in his early sixties. Yet such is the case of R.L. Peteni, whose novel, Hill of Fools, was published by David Philip in South Africa in 1976, and internationally in the same year by Heinemann in the African Writers Series. Four years later, in 1980, the book was translated by the author into Xhosa as Kwazidenge and published by the Lovedale Press. Twenty years after initial publication, in 1996, there came a television version of Kwazidenge broadcast by the SABC, starring Willie Thambo and Amanda Quwe, though the locale was translated – in the bizarre logic of television – to an urban environment on the Cape Flats. The transposition, though pragmatic in terms of television demographics, destroyed much of the point of Peteni’s work, for Hill of Fools is South Africa’s first regional novel in English by a black writer. It is also the first novel in English by a Xhosa-speaker.
- Full Text:
- Date Issued: 2004
Catalytic activity of iron and cobalt phthalocyanine complexes towards the oxidation of cyclohexene using tert-butylhydroperoxide and chloroperoxybenzoic acid
- Sehlotho, Nthapo, Nyokong, Tebello
- Authors: Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/290257 , vital:56729 , xlink:href="https://doi.org/10.1016/j.molcata.2003.08.014"
- Description: Cyclohexene oxidation using tert-butylhydroperoxide (TBHP) or chloroperoxybenzoic acid (CPBA) in the presence of iron(II) polychlorophthalocyanine (Cl16PcFe), iron(II) phthalocyanine (PcFe) and cobalt(II) phthalocyanine (PcCo), results in the formation of the following products: cyclohexene oxide, 2-cyclohexene-1-ol and 2-cyclohexene-1-one. Adipic acid was also formed after long reaction times. The selectivity for 2-cyclohexene-1-one is favoured when Cl16PcFe or PcCo catalysts are employed, while PcFe is selective towards the formation of 2-cyclohexene-1-ol. The Cl16PcFe catalyst is transformed into a μ-oxo dimer (Cl16PcFeIIIOIIIFePcCl16) during the oxidation process. The catalytic process using the unsubstituted PcCoII and PcFeII catalysts involved PcMIII species as an intermediate. The active form of the Cl16PcFe catalyst was stable to degradation in that it was still active even after 4 weeks of continued catalysis.
- Full Text:
- Date Issued: 2004
- Authors: Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/290257 , vital:56729 , xlink:href="https://doi.org/10.1016/j.molcata.2003.08.014"
- Description: Cyclohexene oxidation using tert-butylhydroperoxide (TBHP) or chloroperoxybenzoic acid (CPBA) in the presence of iron(II) polychlorophthalocyanine (Cl16PcFe), iron(II) phthalocyanine (PcFe) and cobalt(II) phthalocyanine (PcCo), results in the formation of the following products: cyclohexene oxide, 2-cyclohexene-1-ol and 2-cyclohexene-1-one. Adipic acid was also formed after long reaction times. The selectivity for 2-cyclohexene-1-one is favoured when Cl16PcFe or PcCo catalysts are employed, while PcFe is selective towards the formation of 2-cyclohexene-1-ol. The Cl16PcFe catalyst is transformed into a μ-oxo dimer (Cl16PcFeIIIOIIIFePcCl16) during the oxidation process. The catalytic process using the unsubstituted PcCoII and PcFeII catalysts involved PcMIII species as an intermediate. The active form of the Cl16PcFe catalyst was stable to degradation in that it was still active even after 4 weeks of continued catalysis.
- Full Text:
- Date Issued: 2004
Competition for attachment of aquaculture candidate probiotic and pathogenic bacteria on fish intestinal mucus:
- Vine, Niall G, Leukes, W D, Kaiser, Horst, Daya, Santylal, Baxter, Jeremy, Hecht, Thomas
- Authors: Vine, Niall G , Leukes, W D , Kaiser, Horst , Daya, Santylal , Baxter, Jeremy , Hecht, Thomas
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142819 , vital:38120 , DOI: 10.1111/j.1365-2761.2004.00542.x
- Description: Probiotics for aquaculture are generally only selected by their ability to produce antimicrobial metabolites; however, attachment to intestinal mucus is important in order to remain within the gut of its host. Five candidate probiotics (AP1–AP5), isolated from the clownfish, Amphiprion percula (Lacepéde), were examined for their ability to attach to fish intestinal mucus and compete with two pathogens, Aeromonas hydrophila and Vibrio alginolyticus. Two different radioactive isotopes were used to quantify competition between pathogens and probionts. Attachment of the pathogens was enhanced by the presence of the candidate probiotics. However, the addition of the candidate probiotics after the pathogens resulted in reduced pathogen attachment.
- Full Text:
- Date Issued: 2004
- Authors: Vine, Niall G , Leukes, W D , Kaiser, Horst , Daya, Santylal , Baxter, Jeremy , Hecht, Thomas
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142819 , vital:38120 , DOI: 10.1111/j.1365-2761.2004.00542.x
- Description: Probiotics for aquaculture are generally only selected by their ability to produce antimicrobial metabolites; however, attachment to intestinal mucus is important in order to remain within the gut of its host. Five candidate probiotics (AP1–AP5), isolated from the clownfish, Amphiprion percula (Lacepéde), were examined for their ability to attach to fish intestinal mucus and compete with two pathogens, Aeromonas hydrophila and Vibrio alginolyticus. Two different radioactive isotopes were used to quantify competition between pathogens and probionts. Attachment of the pathogens was enhanced by the presence of the candidate probiotics. However, the addition of the candidate probiotics after the pathogens resulted in reduced pathogen attachment.
- Full Text:
- Date Issued: 2004
Determination of 2′, 3′-Dideoxyinosine Using Iron (II) Phthalocyanine Modified Carbon Paste Electrode
- Ozoemena, Kenneth I, Stefan, Raluca-Ioana, Nyokong, Tebello
- Authors: Ozoemena, Kenneth I , Stefan, Raluca-Ioana , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300298 , vital:57914 , xlink:href="https://doi.org/10.1081/AL-200031940"
- Description: An amperometric sensor, based on carbon paste impregnated with iron (II) phthalocyanine complex (FePc), has been constructed for the assay of anti‐HIV agent dideoxyinosine (didanosine, DDI). Using chronoamperometry (E = +1.04 V versus Ag/AgCl) technique, the amperometric sensor can be used reliably for dideoxyinosine assay at pH 7.4 phosphate buffer in the 1.5–9.5 nmol/L concentration range with a detection limit of 5.7 × 10−10 mol/L. The surface of the electrode can easily be regenerated by simple polishing, obtaining a fresh surface ready for use in a new assay. The new amperometric sensor proved to be highly reliable for the assay of dideoxyinosine purity in raw material as well as for the uniformity content test of Videx® tablets.
- Full Text:
- Date Issued: 2004
- Authors: Ozoemena, Kenneth I , Stefan, Raluca-Ioana , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300298 , vital:57914 , xlink:href="https://doi.org/10.1081/AL-200031940"
- Description: An amperometric sensor, based on carbon paste impregnated with iron (II) phthalocyanine complex (FePc), has been constructed for the assay of anti‐HIV agent dideoxyinosine (didanosine, DDI). Using chronoamperometry (E = +1.04 V versus Ag/AgCl) technique, the amperometric sensor can be used reliably for dideoxyinosine assay at pH 7.4 phosphate buffer in the 1.5–9.5 nmol/L concentration range with a detection limit of 5.7 × 10−10 mol/L. The surface of the electrode can easily be regenerated by simple polishing, obtaining a fresh surface ready for use in a new assay. The new amperometric sensor proved to be highly reliable for the assay of dideoxyinosine purity in raw material as well as for the uniformity content test of Videx® tablets.
- Full Text:
- Date Issued: 2004
Discourse domination?: the role of gender in seminar interaction
- De Klerk, Vivian A, Hunt, Sally
- Authors: De Klerk, Vivian A , Hunt, Sally
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/139160 , vital:37710 , https://www.ajol.info/index.php/salas/article/view/6501
- Description: This paper focuses on the effect of the gender of participants on the discourse patterns of university seminars, and compares the interaction patterns in two undergraduate seminars with those in two post-graduate seminars at Rhodes University. In the undergraduate seminars, two different groups of students at first year level in different disciplines were videotaped. The major difference was in terms of composition: in one seminar, there were equal numbers of male and female students, while in the other, female students dominated numerically (75%). In addition, five of the six formed a close-knit group of friends, which proved to be an important factor in the analysis. At the postgraduate level, the student participants were identical and met in the same venue and at the same time on two successive days to discuss the same topic (affirmative action in the workplace). The important difference between the two classes was the fact that the first seminar was led by a female tutor and the second seminar by a male tutor, both under 40 years of age and white, both members of staff in the department, and both known to the students. The discourse patterns in these two sets of seminars were analysed in order to investigate the ways in which the gender of tutors and students influenced the floor-winning and floor-holding conventions of participants.
- Full Text:
- Date Issued: 2004
- Authors: De Klerk, Vivian A , Hunt, Sally
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/139160 , vital:37710 , https://www.ajol.info/index.php/salas/article/view/6501
- Description: This paper focuses on the effect of the gender of participants on the discourse patterns of university seminars, and compares the interaction patterns in two undergraduate seminars with those in two post-graduate seminars at Rhodes University. In the undergraduate seminars, two different groups of students at first year level in different disciplines were videotaped. The major difference was in terms of composition: in one seminar, there were equal numbers of male and female students, while in the other, female students dominated numerically (75%). In addition, five of the six formed a close-knit group of friends, which proved to be an important factor in the analysis. At the postgraduate level, the student participants were identical and met in the same venue and at the same time on two successive days to discuss the same topic (affirmative action in the workplace). The important difference between the two classes was the fact that the first seminar was led by a female tutor and the second seminar by a male tutor, both under 40 years of age and white, both members of staff in the department, and both known to the students. The discourse patterns in these two sets of seminars were analysed in order to investigate the ways in which the gender of tutors and students influenced the floor-winning and floor-holding conventions of participants.
- Full Text:
- Date Issued: 2004
Distinct kimberlite pipe classes with contrasting eruption processes
- Skinner, E M W, Marsh, Julian S
- Authors: Skinner, E M W , Marsh, Julian S
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150603 , vital:38988 , https://doi.org/10.1016/j.lithos.2004.03.044
- Description: Field and Scott Smith [Field, M., Scott Smith, B.H., 1999. Contrasting geology and near-surface emplacement of kimberlite pipes in southern Africa and Canada. Proc. 7th Int. Kimb. Conf. (Eds. Gurney et al.) 1, 214–237.] propose that kimberlite pipes can be grouped into three types or classes. Classical or Class 1 pipes are the only class with characteristic low temperature, diatreme-facies kimberlite in addition to hypabyssal- and crater-facies kimberlite. Class 2 and 3 pipes are characterized only by hypabyssal-and crater-facies kimberlite.
- Full Text: false
- Date Issued: 2004
- Authors: Skinner, E M W , Marsh, Julian S
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150603 , vital:38988 , https://doi.org/10.1016/j.lithos.2004.03.044
- Description: Field and Scott Smith [Field, M., Scott Smith, B.H., 1999. Contrasting geology and near-surface emplacement of kimberlite pipes in southern Africa and Canada. Proc. 7th Int. Kimb. Conf. (Eds. Gurney et al.) 1, 214–237.] propose that kimberlite pipes can be grouped into three types or classes. Classical or Class 1 pipes are the only class with characteristic low temperature, diatreme-facies kimberlite in addition to hypabyssal- and crater-facies kimberlite. Class 2 and 3 pipes are characterized only by hypabyssal-and crater-facies kimberlite.
- Full Text: false
- Date Issued: 2004
Electrochemical and catalytic properties of chromium tetraaminophthalocyanine
- Obirai, Joe, Nyokong, Tebello
- Authors: Obirai, Joe , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300310 , vital:57915 , xlink:href="https://doi.org/10.1016/j.jelechem.2004.06.026"
- Description: Chromium tetraaminophthalocyanine (CrIIITAPc) has been synthesized and its electrochemical and spectroelectrochemical properties reported. The first reduction and oxidation in this complex occur at the central metal, giving CrIITAPc and CrIVTAPc complexes, respectively, the latter having been observed for the first time. The CrIIITAPc species was polymerized onto glassy carbon (GCE) or indium tin oxide (ITO) electrodes and the polymer evolution confirmed by UV/Visible spectroscopy and by scanning electron microscopy. The polymers were employed for the catalytic oxidation of nitrite or nitric oxide, and the catalysis involved the CrIVTAPc−1 species.
- Full Text:
- Date Issued: 2004
- Authors: Obirai, Joe , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300310 , vital:57915 , xlink:href="https://doi.org/10.1016/j.jelechem.2004.06.026"
- Description: Chromium tetraaminophthalocyanine (CrIIITAPc) has been synthesized and its electrochemical and spectroelectrochemical properties reported. The first reduction and oxidation in this complex occur at the central metal, giving CrIITAPc and CrIVTAPc complexes, respectively, the latter having been observed for the first time. The CrIIITAPc species was polymerized onto glassy carbon (GCE) or indium tin oxide (ITO) electrodes and the polymer evolution confirmed by UV/Visible spectroscopy and by scanning electron microscopy. The polymers were employed for the catalytic oxidation of nitrite or nitric oxide, and the catalysis involved the CrIVTAPc−1 species.
- Full Text:
- Date Issued: 2004
Electrochemical studies of manganese tetraamminophthalocyanine monomer and polymer
- Obirai, Joseph, Nyokong, Tebello
- Authors: Obirai, Joseph , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/290330 , vital:56738 , xlink:href="https://doi.org/10.1016/j.electacta.2003.11.006"
- Description: Manganese tetraaminophthalocyanine (MnTAPc) has been synthesised. The cyclic voltammetry and spectroelectrochemistry of the complex have been examined. Spectroelectrochemistry has been used to confirm that the species synthesised in this work contains MnIII, giving (OH)MnIIITAPc. The oxidation and reduction couples obtained from cyclic voltammetry have been assigned to MnIVPc−/MnIVPc2− (couple I), MnIVPc2−/MnIIIPc2− (couple I′), MnIIIPc2−/MnIIPc2− (couple II) and MnIIPc2−/MnIIPc3− (couple III). Electropolymerization of the MnTAPc onto either the indium tin oxide or glassy carbon electrode results in the in the formation of a poly-MnTAPc. The poly-MnTAPc shows improved reversibility at low pH. The poly-MnTAPc electrode was employed to analyse glycine.
- Full Text:
- Date Issued: 2004
- Authors: Obirai, Joseph , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/290330 , vital:56738 , xlink:href="https://doi.org/10.1016/j.electacta.2003.11.006"
- Description: Manganese tetraaminophthalocyanine (MnTAPc) has been synthesised. The cyclic voltammetry and spectroelectrochemistry of the complex have been examined. Spectroelectrochemistry has been used to confirm that the species synthesised in this work contains MnIII, giving (OH)MnIIITAPc. The oxidation and reduction couples obtained from cyclic voltammetry have been assigned to MnIVPc−/MnIVPc2− (couple I), MnIVPc2−/MnIIIPc2− (couple I′), MnIIIPc2−/MnIIPc2− (couple II) and MnIIPc2−/MnIIPc3− (couple III). Electropolymerization of the MnTAPc onto either the indium tin oxide or glassy carbon electrode results in the in the formation of a poly-MnTAPc. The poly-MnTAPc shows improved reversibility at low pH. The poly-MnTAPc electrode was employed to analyse glycine.
- Full Text:
- Date Issued: 2004
Emerging patterns of abstraction in environmental education: A review of materials, methods and professional development perspectives
- O'Donoghue, Rob B, Russo, Vladimir
- Authors: O'Donoghue, Rob B , Russo, Vladimir
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/373610 , vital:66707 , xlink:href="https://doi.org/10.1080/1350462042000258170"
- Description: The epistemic unconscious is the history of the field. And it is clear that, to secure some chance of really knowing what one is doing, one has to unfold what is inscribed in the various relations of implication in which the thinker and his thoughts are caught up, that is, the presuppositions he engages and the inclusions and exclusions he unwittingly performs. (Bourdieu, 2000, p. 99).
- Full Text:
- Date Issued: 2004
- Authors: O'Donoghue, Rob B , Russo, Vladimir
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/373610 , vital:66707 , xlink:href="https://doi.org/10.1080/1350462042000258170"
- Description: The epistemic unconscious is the history of the field. And it is clear that, to secure some chance of really knowing what one is doing, one has to unfold what is inscribed in the various relations of implication in which the thinker and his thoughts are caught up, that is, the presuppositions he engages and the inclusions and exclusions he unwittingly performs. (Bourdieu, 2000, p. 99).
- Full Text:
- Date Issued: 2004
Endothermy in African Platypleurine Cicadas: the influence of body size and habitat (Hemiptera: Cicadidae)
- Sanborn, Allen F, Villet, Martin H, Phillips, P K
- Authors: Sanborn, Allen F , Villet, Martin H , Phillips, P K
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6925 , http://hdl.handle.net/10962/d1011912
- Description: The platypleurine cicadas have a wide distribution across Africa and southern Asia. We investigate endothermy as a thermoregulatory strategy in 11 South African species from five genera, with comparisons to the lone ectothermic platypleurine we found, in an attempt to ascertain any influence that habitat and/or body size have on the expression of endothermy in the platypleurine cicadas. Field measurements of body temperature (Tb) show that these animals regulate Tb through endogenous heat production. Heat production in the laboratory elevated Tb to the same range as in animals active in the field. Maximum Tb measured during calling activity when there was no access to solar radiation ranged from 13.2° to 22.3°C above ambient temperature in the five species measured. The mean Tb during activity without access to solar radiation did not differ from the mean Tb during diurnal activity. All platypleurines exhibit a unique behavior for cicadas while warming endogenously, a temperature- dependent telescoping pulsation of the abdomen that probably functions in ventilation. Platypleurines generally call from trunks and branches within the canopy and appear to rely on endothermy even when the sun is available to elevate Tb, in contrast to the facultative endothermy exhibited by New World endothermic species. The two exceptions to this generalization we found within the platypleurines are Platypleura wahlbergi and Albanycada albigera, which were the smallest species studied. The small size of P. wahlbergi appears to have altered their thermoregulatory strategy to one of facultative endothermy, whereby they use the sun when it is available to facilitate increases in Tb. Albanycada albigera is the only ectothermic platypleurine we found. The habitat and host plant association of A. albigera appear to have influenced the choice of ectothermy as a thermoregulatory strategy, as the species possesses the metabolic machinery to elevate to the Tb range observed in the endothermic species. Therefore, size and habitat appear to influence the expression of thermoregulatory strategies in African platypleurine cicadas.
- Full Text:
- Date Issued: 2004
- Authors: Sanborn, Allen F , Villet, Martin H , Phillips, P K
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6925 , http://hdl.handle.net/10962/d1011912
- Description: The platypleurine cicadas have a wide distribution across Africa and southern Asia. We investigate endothermy as a thermoregulatory strategy in 11 South African species from five genera, with comparisons to the lone ectothermic platypleurine we found, in an attempt to ascertain any influence that habitat and/or body size have on the expression of endothermy in the platypleurine cicadas. Field measurements of body temperature (Tb) show that these animals regulate Tb through endogenous heat production. Heat production in the laboratory elevated Tb to the same range as in animals active in the field. Maximum Tb measured during calling activity when there was no access to solar radiation ranged from 13.2° to 22.3°C above ambient temperature in the five species measured. The mean Tb during activity without access to solar radiation did not differ from the mean Tb during diurnal activity. All platypleurines exhibit a unique behavior for cicadas while warming endogenously, a temperature- dependent telescoping pulsation of the abdomen that probably functions in ventilation. Platypleurines generally call from trunks and branches within the canopy and appear to rely on endothermy even when the sun is available to elevate Tb, in contrast to the facultative endothermy exhibited by New World endothermic species. The two exceptions to this generalization we found within the platypleurines are Platypleura wahlbergi and Albanycada albigera, which were the smallest species studied. The small size of P. wahlbergi appears to have altered their thermoregulatory strategy to one of facultative endothermy, whereby they use the sun when it is available to facilitate increases in Tb. Albanycada albigera is the only ectothermic platypleurine we found. The habitat and host plant association of A. albigera appear to have influenced the choice of ectothermy as a thermoregulatory strategy, as the species possesses the metabolic machinery to elevate to the Tb range observed in the endothermic species. Therefore, size and habitat appear to influence the expression of thermoregulatory strategies in African platypleurine cicadas.
- Full Text:
- Date Issued: 2004
Environmental education research and social change: Southern African perspectives
- Authors: Lotz-Sisitka, Heila
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182709 , vital:43855 , xlink:href="https://doi.org/10.1080/1350462042000258143"
- Description: Environmental issues and risks in southern Africa have, like elsewhere in the world, their roots in the structures and orientations of modern societies. In modernist fashion, we draw on education and research to address socio-ecological concerns. In 1995 Eureta Janse van Rensburg, then Murray and Roberts Chair of Environmental Education at Rhodes University,1 undertook a study to identify environmental education research priorities, and through her study she provided a description of research in environmental education as a ‘landscape of shifting priorites’ (Janse van Rensburg, 1995). The papers in this journal offer a contemporary ‘snapshot’ of the landscape of environmental education research in southern Africa, illustrating a fresh range of ‘shifting priorities’.
- Full Text:
- Date Issued: 2004
- Authors: Lotz-Sisitka, Heila
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182709 , vital:43855 , xlink:href="https://doi.org/10.1080/1350462042000258143"
- Description: Environmental issues and risks in southern Africa have, like elsewhere in the world, their roots in the structures and orientations of modern societies. In modernist fashion, we draw on education and research to address socio-ecological concerns. In 1995 Eureta Janse van Rensburg, then Murray and Roberts Chair of Environmental Education at Rhodes University,1 undertook a study to identify environmental education research priorities, and through her study she provided a description of research in environmental education as a ‘landscape of shifting priorites’ (Janse van Rensburg, 1995). The papers in this journal offer a contemporary ‘snapshot’ of the landscape of environmental education research in southern Africa, illustrating a fresh range of ‘shifting priorities’.
- Full Text:
- Date Issued: 2004
Harvesting impacts on commonly used medicinal tree species (Catha edulis and Rapanea melanophloeos) under different land management regimes in the Mpumalanga Lowveld, South Africa
- Botha, Jenny, Witkowski, Ed T F, Shackleton, Charlie M
- Authors: Botha, Jenny , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181379 , vital:43728 , xlink:href="https://doi.org/10.4102/koedoe.v47i2.77"
- Description: Harvesting of products from plants in the wild is widespread throughout southern Africa. Particularly important products are plant parts used in traditional medicine. However, the impacts of harvesting practices are rarely quantified, with as yet insufficient generic rules across species and life forms. This limits the predictive ability to monitor and manage the affected populations. This paper examines the harvesting impact on two popular woody medicinal species used throughout sub-Saharan Africa, namely Catha edulis (Vahl) Forssk. ex Endl. (bushman’s tea) and Rapanea melanophloeos (L.) Mez. (Cape beech). In both species, basal diameters, heights, and the number of size classes in the harvested populations were lower than in unharvested. Densities of harvested populations were higher in both species, including densities of young plants, but the frequency of individuals in larger size classes was lower. The populations of both species being harvested for medicinal products appeared to be withstanding the current levels of harvesting, but the population structure of C. edulis populations being harvested for poles on the roadside and near human settlements had been substantially altered. Despite the resilience of the two species to harvesting for medicinal products, loss of habitat or changes in land use pose a threat to a number of the assessed populations.
- Full Text:
- Date Issued: 2004
- Authors: Botha, Jenny , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181379 , vital:43728 , xlink:href="https://doi.org/10.4102/koedoe.v47i2.77"
- Description: Harvesting of products from plants in the wild is widespread throughout southern Africa. Particularly important products are plant parts used in traditional medicine. However, the impacts of harvesting practices are rarely quantified, with as yet insufficient generic rules across species and life forms. This limits the predictive ability to monitor and manage the affected populations. This paper examines the harvesting impact on two popular woody medicinal species used throughout sub-Saharan Africa, namely Catha edulis (Vahl) Forssk. ex Endl. (bushman’s tea) and Rapanea melanophloeos (L.) Mez. (Cape beech). In both species, basal diameters, heights, and the number of size classes in the harvested populations were lower than in unharvested. Densities of harvested populations were higher in both species, including densities of young plants, but the frequency of individuals in larger size classes was lower. The populations of both species being harvested for medicinal products appeared to be withstanding the current levels of harvesting, but the population structure of C. edulis populations being harvested for poles on the roadside and near human settlements had been substantially altered. Despite the resilience of the two species to harvesting for medicinal products, loss of habitat or changes in land use pose a threat to a number of the assessed populations.
- Full Text:
- Date Issued: 2004