A capillary zone electrophoresis (CZE) method for the determination of cyclizine hydrochloride in tablets and suppositories
- Mohammadi, I, Kanfer, Isadore, Walker, Roderick B
- Authors: Mohammadi, I , Kanfer, Isadore , Walker, Roderick B
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6406 , http://hdl.handle.net/10962/d1006479
- Description: Current compendial methods of assay for the analysis of cyclizine tablets involve the use of UV spectrophotometry. Since this is a non-selective technique its application to more complex dosage forms, such as suppositories, is unlikely to be appropriate. There is therefore a need for the development of a highly specific quantitative analytical method, such as high performance liquid chromatography (HPLC) or capillary electrophoresis (CE). The latter technique was chosen in view of some specific advantages over HPLC, such as the use of relatively non-toxic aqueous buffers, as opposed to organic solvents, which obviates the use of expensive HPLC grade solvents making CE more cost effective. Cyclizine was analyzed in 50 mM phosphate buffer (pH 2.3) and run at an applied voltage 25 kV. Detection sensitivity was enhanced by using a wavelength of 200 nm and samples were loaded hydrodynamically onto an uncoated fused-silica capillary (60 cm×50 mm i.d.). Chlorcyclizine was used as the internal standard and resolution of both compounds was achieved in less than 7 min. Stress testing was undertaken in order to investigate the appearance of breakdown products. The method has the requisite accuracy, selectivity, sensitivity and precision to assay cyclizine in tablets and suppositories. Degradation products resulting from the stress studies did not interfere with the detection of cyclizine and the assay is thus stability-indicating.
- Full Text:
- Date Issued: 2004
- Authors: Mohammadi, I , Kanfer, Isadore , Walker, Roderick B
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6406 , http://hdl.handle.net/10962/d1006479
- Description: Current compendial methods of assay for the analysis of cyclizine tablets involve the use of UV spectrophotometry. Since this is a non-selective technique its application to more complex dosage forms, such as suppositories, is unlikely to be appropriate. There is therefore a need for the development of a highly specific quantitative analytical method, such as high performance liquid chromatography (HPLC) or capillary electrophoresis (CE). The latter technique was chosen in view of some specific advantages over HPLC, such as the use of relatively non-toxic aqueous buffers, as opposed to organic solvents, which obviates the use of expensive HPLC grade solvents making CE more cost effective. Cyclizine was analyzed in 50 mM phosphate buffer (pH 2.3) and run at an applied voltage 25 kV. Detection sensitivity was enhanced by using a wavelength of 200 nm and samples were loaded hydrodynamically onto an uncoated fused-silica capillary (60 cm×50 mm i.d.). Chlorcyclizine was used as the internal standard and resolution of both compounds was achieved in less than 7 min. Stress testing was undertaken in order to investigate the appearance of breakdown products. The method has the requisite accuracy, selectivity, sensitivity and precision to assay cyclizine in tablets and suppositories. Degradation products resulting from the stress studies did not interfere with the detection of cyclizine and the assay is thus stability-indicating.
- Full Text:
- Date Issued: 2004
A Trypanosoma cruzi heat shock protein 40 is able to stimulate the adenosine triphosphate hydrolysis activity of heat shock protein 70 and can substitute for a yeast heat shock protein 40
- Edkins, Adrienne L, Ludewig, M H, Blatch, Gregory L
- Authors: Edkins, Adrienne L , Ludewig, M H , Blatch, Gregory L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6465 , http://hdl.handle.net/10962/d1005794 , http://dx.doi.org/10.1016/j.biocel.2004.01.016
- Description: The process of assisted protein folding, characteristic of members of the heat shock protein 70 (Hsp70) and heat shock protein 40 (Hsp40) molecular chaperone families, is important for maintaining the structural integrity of cellular protein machinery under normal and stressful conditions. Hsp70 and Hsp40 cooperate to bind non-native protein conformations in a process of adenosine triphosphate (ATP)-regulated assisted protein folding. We have analysed the molecular chaperone activity of the cytoplasmic inducible Hsp70 from Trypanosoma cruzi (TcHsp70) and its interactions with its potential partner Hsp40s (T. cruzi DnaJ protein 1 [Tcj1] and T. cruzi DnaJ protein 2 [Tcj2]). Histidine-tagged TcHsp70 (His-TcHsp70), Tcj1 (Tcj1-His) and Tcj2 (His-Tcj2) were over-produced in Escherichia coli and purified by nickel affinity chromatography. The in vitro basal specific ATP hydrolysis activity (ATPase activity) of His-TcHsp70 was determined as 40 nmol phosphate/min/mg protein, significantly higher than that reported for other Hsp70s. The basal specific ATPase activity was stimulated to a maximal level of 60 nmol phosphate/min/mg protein in the presence of His-Tcj2 and a model substrate, reduced carboxymethylated α-lactalbumin. In vivo complementation assays showed that Tcj2 was able to overcome the temperature sensitivity of the ydj1 mutant Saccharomyces cerevisiae strain JJ160, suggesting that Tcj2 may be functionally equivalent to the yeast Hsp40 homologue (yeast DnaJ protein 1, Ydj1). These data suggest that Tcj2 is involved in cytoprotection in a similar fashion to Ydj1, and that TcHsp70 and Tcj2 may interact in a nucleotide-regulated process of chaperone-assisted protein folding.
- Full Text:
- Date Issued: 2004
- Authors: Edkins, Adrienne L , Ludewig, M H , Blatch, Gregory L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6465 , http://hdl.handle.net/10962/d1005794 , http://dx.doi.org/10.1016/j.biocel.2004.01.016
- Description: The process of assisted protein folding, characteristic of members of the heat shock protein 70 (Hsp70) and heat shock protein 40 (Hsp40) molecular chaperone families, is important for maintaining the structural integrity of cellular protein machinery under normal and stressful conditions. Hsp70 and Hsp40 cooperate to bind non-native protein conformations in a process of adenosine triphosphate (ATP)-regulated assisted protein folding. We have analysed the molecular chaperone activity of the cytoplasmic inducible Hsp70 from Trypanosoma cruzi (TcHsp70) and its interactions with its potential partner Hsp40s (T. cruzi DnaJ protein 1 [Tcj1] and T. cruzi DnaJ protein 2 [Tcj2]). Histidine-tagged TcHsp70 (His-TcHsp70), Tcj1 (Tcj1-His) and Tcj2 (His-Tcj2) were over-produced in Escherichia coli and purified by nickel affinity chromatography. The in vitro basal specific ATP hydrolysis activity (ATPase activity) of His-TcHsp70 was determined as 40 nmol phosphate/min/mg protein, significantly higher than that reported for other Hsp70s. The basal specific ATPase activity was stimulated to a maximal level of 60 nmol phosphate/min/mg protein in the presence of His-Tcj2 and a model substrate, reduced carboxymethylated α-lactalbumin. In vivo complementation assays showed that Tcj2 was able to overcome the temperature sensitivity of the ydj1 mutant Saccharomyces cerevisiae strain JJ160, suggesting that Tcj2 may be functionally equivalent to the yeast Hsp40 homologue (yeast DnaJ protein 1, Ydj1). These data suggest that Tcj2 is involved in cytoprotection in a similar fashion to Ydj1, and that TcHsp70 and Tcj2 may interact in a nucleotide-regulated process of chaperone-assisted protein folding.
- Full Text:
- Date Issued: 2004
APDUSA Views
- Date: 1990-09
- Subjects: Government, Resistance to -- South Africa , South Africa -- History -- 20th century , South Africa -- Politics and government
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/33620 , vital:32908 , Bulk File 7
- Description: APDUSA Views was published by the African People’s Democratic Union of Southern Africa (Natal), an affiliate of the New Unity Movement.
- Full Text: false
- Date Issued: 1990-09
- Date: 1990-09
- Subjects: Government, Resistance to -- South Africa , South Africa -- History -- 20th century , South Africa -- Politics and government
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/33620 , vital:32908 , Bulk File 7
- Description: APDUSA Views was published by the African People’s Democratic Union of Southern Africa (Natal), an affiliate of the New Unity Movement.
- Full Text: false
- Date Issued: 1990-09
Automated estimation and analyses of meteorological drought characteristics from monthly rainfall data
- Smakhtin, V U, Hughes, Denis A
- Authors: Smakhtin, V U , Hughes, Denis A
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:7078 , http://hdl.handle.net/10962/d1009746
- Description: The paper describes a new software package for automated estimation, display and analyses of various drought indices – continuous functions of precipitation that allow quantitative assessment of meteorological drought events to be made. The software at present allows up to five different drought indices to be estimated. They include the Decile Index (DI), the Effective Drought Index (EDI), the Standardized Precipitation Index (SPI) and deviations from the long-term mean and median value. Each index can be estimated from point and spatially averaged rainfall data and a number of options are provided for months' selection and the type of the analysis, including a running mean, single value or multiple annual values. The software also allows spell/run analysis to be performed and maps of a specific index to be constructed. The software forms part of the comprehensive computer package, developed earlier and designed to perform the multitude of water resources analyses and hydro-meteorological data processing. The 7-step procedure of setting up and running a typical drought assessment application is described in detail. The examples of applications are given primarily in the specific context of South Asia where the software has been used.
- Full Text:
- Date Issued: 2007
- Authors: Smakhtin, V U , Hughes, Denis A
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:7078 , http://hdl.handle.net/10962/d1009746
- Description: The paper describes a new software package for automated estimation, display and analyses of various drought indices – continuous functions of precipitation that allow quantitative assessment of meteorological drought events to be made. The software at present allows up to five different drought indices to be estimated. They include the Decile Index (DI), the Effective Drought Index (EDI), the Standardized Precipitation Index (SPI) and deviations from the long-term mean and median value. Each index can be estimated from point and spatially averaged rainfall data and a number of options are provided for months' selection and the type of the analysis, including a running mean, single value or multiple annual values. The software also allows spell/run analysis to be performed and maps of a specific index to be constructed. The software forms part of the comprehensive computer package, developed earlier and designed to perform the multitude of water resources analyses and hydro-meteorological data processing. The 7-step procedure of setting up and running a typical drought assessment application is described in detail. The examples of applications are given primarily in the specific context of South Asia where the software has been used.
- Full Text:
- Date Issued: 2007
Bioremediation of trace organic compounds found in precious metals refineries wastewaters: A review of potential options
- Barbosa, V L, Tandlich, Roman, Burgess, Jo E
- Authors: Barbosa, V L , Tandlich, Roman , Burgess, Jo E
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6469 , http://hdl.handle.net/10962/d1005798 , http://dx.doi.org/10.1016/j.chemosphere.2007.01.018 , http://www.sciencedirect.com/science/article/pii/S0045653507001026
- Description: Platinum group metal (PGM) refining processes produce large quantities of wastewater, which is contaminated with the compounds that make up the solvents/extractants mixtures used in the process. These compounds often include solvesso, β-hydroxyxime, amines, amides and methyl isobutyl ketone. A process to clean up PGM refinery wastewaters so that they could be re-used in the refining process would greatly contribute to continual water storage problems and to cost reduction for the industry. Based on the concept that organic compounds that are produced biologically can be destroyed biologically, the use of biological processes for the treatment of organic compounds in other types of waste stream has been favoured in recent years, owing to their low cost and environmental acceptability. This review examines the available biotechnologies and their effectiveness for treating compounds likely to be contained in precious metal extraction process wastewaters. The processes examined include: biofilters, fluidized bed reactors, trickle-bed bioreactors, bioscrubbers, two-phase partitioning bioreactors, membrane bioreactors and activated sludge. Although all processes examined showed adequate to excellent removal of organic compounds from various gaseous and fewer liquid waste streams, there was a variation in their effectiveness. Variations in performance of laboratory-scale biological processes are probably due to the inherent change in the microbial population composition due to selection pressure, environmental conditions and the time allowed for adaptation to the organic compounds. However, if these factors are disregarded, it can be established that activated sludge and membrane bioreactors are the most promising processes for use in the treatment of PGM refinery wastewaters.
- Full Text:
- Date Issued: 2007
- Authors: Barbosa, V L , Tandlich, Roman , Burgess, Jo E
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6469 , http://hdl.handle.net/10962/d1005798 , http://dx.doi.org/10.1016/j.chemosphere.2007.01.018 , http://www.sciencedirect.com/science/article/pii/S0045653507001026
- Description: Platinum group metal (PGM) refining processes produce large quantities of wastewater, which is contaminated with the compounds that make up the solvents/extractants mixtures used in the process. These compounds often include solvesso, β-hydroxyxime, amines, amides and methyl isobutyl ketone. A process to clean up PGM refinery wastewaters so that they could be re-used in the refining process would greatly contribute to continual water storage problems and to cost reduction for the industry. Based on the concept that organic compounds that are produced biologically can be destroyed biologically, the use of biological processes for the treatment of organic compounds in other types of waste stream has been favoured in recent years, owing to their low cost and environmental acceptability. This review examines the available biotechnologies and their effectiveness for treating compounds likely to be contained in precious metal extraction process wastewaters. The processes examined include: biofilters, fluidized bed reactors, trickle-bed bioreactors, bioscrubbers, two-phase partitioning bioreactors, membrane bioreactors and activated sludge. Although all processes examined showed adequate to excellent removal of organic compounds from various gaseous and fewer liquid waste streams, there was a variation in their effectiveness. Variations in performance of laboratory-scale biological processes are probably due to the inherent change in the microbial population composition due to selection pressure, environmental conditions and the time allowed for adaptation to the organic compounds. However, if these factors are disregarded, it can be established that activated sludge and membrane bioreactors are the most promising processes for use in the treatment of PGM refinery wastewaters.
- Full Text:
- Date Issued: 2007
Changes in fuelwood use and selection following electrification in the Bushbuckridge lowveld, South Africa
- Madubansi, Mainza, Shackleton, Charlie M
- Authors: Madubansi, Mainza , Shackleton, Charlie M
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6641 , http://hdl.handle.net/10962/d1006867
- Description: Fuelwood is the primary energy source for domestic purposes throughout the developing world, in both urban and rural environments. Due to the detrimental impacts of biomass use on human and environmental health, many governments have sought to reduce its use through provision of potentially cleaner energies, of which electricity is the dominant form. Yet there are surprisingly few studies of changes in fuelwood use following the introduction of electricity, especially in rural areas of Africa. This paper reports on a longitudinal study of fuelwood use, using identical approaches, in five rural villages in the Bushbuckridge region of South Africa, spanning the period over which electricity became widely available. Almost a decade after the introduction of electricity, over 90% of households still used fuelwood for thermal purposes, especially cooking, and the mean household consumption rates over the 11-year period had not changed, even with a policy of 6 kWh per month of free electricity. The proportion of households purchasing fuelwood had increased, probably in response to a number of factors, including (i) increased fuelwood scarcity in the local environment as reflected by increased fuelwood collection times, changes in fuelwood species preferences, and ranking of scarcity by local collectors, and (ii) increases in the price of fuelwood well below that of other fuels and the prevailing inflation rate. Overall, there was an increase in the number of species harvested over the 11-year period. The implications of these findings for rural energy provision are discussed.
- Full Text:
- Date Issued: 2007
- Authors: Madubansi, Mainza , Shackleton, Charlie M
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6641 , http://hdl.handle.net/10962/d1006867
- Description: Fuelwood is the primary energy source for domestic purposes throughout the developing world, in both urban and rural environments. Due to the detrimental impacts of biomass use on human and environmental health, many governments have sought to reduce its use through provision of potentially cleaner energies, of which electricity is the dominant form. Yet there are surprisingly few studies of changes in fuelwood use following the introduction of electricity, especially in rural areas of Africa. This paper reports on a longitudinal study of fuelwood use, using identical approaches, in five rural villages in the Bushbuckridge region of South Africa, spanning the period over which electricity became widely available. Almost a decade after the introduction of electricity, over 90% of households still used fuelwood for thermal purposes, especially cooking, and the mean household consumption rates over the 11-year period had not changed, even with a policy of 6 kWh per month of free electricity. The proportion of households purchasing fuelwood had increased, probably in response to a number of factors, including (i) increased fuelwood scarcity in the local environment as reflected by increased fuelwood collection times, changes in fuelwood species preferences, and ranking of scarcity by local collectors, and (ii) increases in the price of fuelwood well below that of other fuels and the prevailing inflation rate. Overall, there was an increase in the number of species harvested over the 11-year period. The implications of these findings for rural energy provision are discussed.
- Full Text:
- Date Issued: 2007
Cholera in KwaZulu-Natal : probing institutional governmentality and indigenous hand-washing practices
- Authors: O’Donoghue, Rob
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6094 , http://hdl.handle.net/10962/d1008616
- Description: The paper reviews education activities in a successful anti-cholera campaign amongst rural communities in eastern southern Africa. It is centred on probing how a modern institutional governmentality was relatively blind to an historical legacy of Nguni hand-washing practices and came to exclude use of simple tests for coliform contamination in rural health education activities. The study examines institutional processes, probing discontinuities between the health education message and the complex social ecology of cholera. In so doing, it uncovers how a post-apartheid institutional rhetoric of participation, empowerment and social transformation is playing out in communicative interventions to instil healthier practices amongst the rural poor. Institutional perspectives such as this are rooted in an institutional legacy of appropriation and control. Despite the current rhetoric of participation, instrumental orientations are being sustained as the radical critique of struggle for freedom and change gives way, through comfortable submission and intellectual conformity, to an instrumental conservatism in many post-apartheid institutional settings today. The study notes and probes a surprising resonance between the ecology of the disease and an intergenerational social capital of indigenous hand-washing practices. The evidence suggests that these patterns of hand-washing practice would have served to contain the disease in earlier times and points to this social capital as a focus for co-engaged action on environment and health concerns. The findings suggest that an opposing of institutional and indigenous knowledge is not a simple matter and that moving beyond a legacy of cultural exclusion and marginalisation remains a challenge as the first decade of post-apartheid democratic governance comes to a close.
- Full Text:
- Date Issued: 2005
- Authors: O’Donoghue, Rob
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6094 , http://hdl.handle.net/10962/d1008616
- Description: The paper reviews education activities in a successful anti-cholera campaign amongst rural communities in eastern southern Africa. It is centred on probing how a modern institutional governmentality was relatively blind to an historical legacy of Nguni hand-washing practices and came to exclude use of simple tests for coliform contamination in rural health education activities. The study examines institutional processes, probing discontinuities between the health education message and the complex social ecology of cholera. In so doing, it uncovers how a post-apartheid institutional rhetoric of participation, empowerment and social transformation is playing out in communicative interventions to instil healthier practices amongst the rural poor. Institutional perspectives such as this are rooted in an institutional legacy of appropriation and control. Despite the current rhetoric of participation, instrumental orientations are being sustained as the radical critique of struggle for freedom and change gives way, through comfortable submission and intellectual conformity, to an instrumental conservatism in many post-apartheid institutional settings today. The study notes and probes a surprising resonance between the ecology of the disease and an intergenerational social capital of indigenous hand-washing practices. The evidence suggests that these patterns of hand-washing practice would have served to contain the disease in earlier times and points to this social capital as a focus for co-engaged action on environment and health concerns. The findings suggest that an opposing of institutional and indigenous knowledge is not a simple matter and that moving beyond a legacy of cultural exclusion and marginalisation remains a challenge as the first decade of post-apartheid democratic governance comes to a close.
- Full Text:
- Date Issued: 2005
Creating international support for the development of the news media in Africa
- Authors: Banda, Fackson
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6326 , http://hdl.handle.net/10962/d1008301
- Description: This article analyses the issues associated with providing support mechanisms for strengthening media institutions in Africa. It takes a historical look at the involvement of international actors in the evolution of African media, arguing that ideology plays a key role in the way international support is crafted for Africa's development, including media development.
- Full Text:
- Date Issued: 2006
- Authors: Banda, Fackson
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6326 , http://hdl.handle.net/10962/d1008301
- Description: This article analyses the issues associated with providing support mechanisms for strengthening media institutions in Africa. It takes a historical look at the involvement of international actors in the evolution of African media, arguing that ideology plays a key role in the way international support is crafted for Africa's development, including media development.
- Full Text:
- Date Issued: 2006
Cryptic variation in an ecological indicator organism: mitochondrial and nuclear DNA sequence data confirm distinct lineages of Baetis harrisoni Barnard (Ephemeroptera: Baetidae) in Southern Africa
- Pereira-da-Conceicoa, Lyndall L, Price, Benjamin W, Barber-James, Helen M, Barker, Nigel P, De Moor, Ferdy C, Villet, Martin H
- Authors: Pereira-da-Conceicoa, Lyndall L , Price, Benjamin W , Barber-James, Helen M , Barker, Nigel P , De Moor, Ferdy C , Villet, Martin H
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6535 , http://hdl.handle.net/10962/d1005976 , https://dx.doi.org/10.1186/1471-2148-12-26
- Description: Baetis harrisoni Barnard is a mayfly frequently encountered in river studies across Africa, but the external morphological features used for identifying nymphs have been observed to vary subtly between different geographic locations. It has been associated with a wide range of ecological conditions, including pH extremes of pH 2.9–10.0 in polluted waters. We present a molecular study of the genetic variation within B. harrisoni across 21 rivers in its distribution range in southern Africa.
- Full Text:
- Date Issued: 2012
- Authors: Pereira-da-Conceicoa, Lyndall L , Price, Benjamin W , Barber-James, Helen M , Barker, Nigel P , De Moor, Ferdy C , Villet, Martin H
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6535 , http://hdl.handle.net/10962/d1005976 , https://dx.doi.org/10.1186/1471-2148-12-26
- Description: Baetis harrisoni Barnard is a mayfly frequently encountered in river studies across Africa, but the external morphological features used for identifying nymphs have been observed to vary subtly between different geographic locations. It has been associated with a wide range of ecological conditions, including pH extremes of pH 2.9–10.0 in polluted waters. We present a molecular study of the genetic variation within B. harrisoni across 21 rivers in its distribution range in southern Africa.
- Full Text:
- Date Issued: 2012
Cryptic variation in an ecological indicator organism: mitochondrial and nuclear DNA sequence data confirm distinct lineages of Baetis harrisoni Barnard (Ephemeroptera: Baetidae) in southern Africa
- Pereira-da-Conceicoa, L L, Price, Benjamin W, Barber-James, Helen M
- Authors: Pereira-da-Conceicoa, L L , Price, Benjamin W , Barber-James, Helen M
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:7151 , http://hdl.handle.net/10962/d1011855
- Description: Baetis harrisoni Barnard is a mayfly frequently encountered in river studies across Africa, but the external morphological features used for identifying nymphs have been observed to vary subtly between different geographic locations. It has been associated with a wide range of ecological conditions, including pH extremes of pH 2.9–10.0 in polluted waters. We present a molecular study of the genetic variation within B. harrisoni across 21 rivers in its distribution range in southern Africa.
- Full Text:
- Date Issued: 2012
- Authors: Pereira-da-Conceicoa, L L , Price, Benjamin W , Barber-James, Helen M
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:7151 , http://hdl.handle.net/10962/d1011855
- Description: Baetis harrisoni Barnard is a mayfly frequently encountered in river studies across Africa, but the external morphological features used for identifying nymphs have been observed to vary subtly between different geographic locations. It has been associated with a wide range of ecological conditions, including pH extremes of pH 2.9–10.0 in polluted waters. We present a molecular study of the genetic variation within B. harrisoni across 21 rivers in its distribution range in southern Africa.
- Full Text:
- Date Issued: 2012
Description and identification of white grubs (Coleoptera: Scarabaeidae) attacking pineapple crops in South Africa
- Smith, Tamara J, Petty, G, Villet, Martin H
- Authors: Smith, Tamara J , Petty, G , Villet, Martin H
- Date: 1995
- Language: English
- Type: text , Article
- Identifier: vital:6853 , http://hdl.handle.net/10962/d1011134
- Description: Larvae of five species of scarabaeid beetles, Asthenopholis subfasciata Blanchard, Trochalus politus Moser, Macrophylla ciliata Herbst, Congela valida Peringuey and Adoretus ictericus Burmeister, and adults of a sixth species, Heteronychus arator (Fabricius), cause considerable economic damage to the root systems of pineapple plants. The biologies of the species differ, making reliable identification essential. Since no convenient method is available to identify them, both field and laboratory keys are provided for the identification of third instar larvae of the six species, and detailed, illustrated descriptions for confirming their identifications
- Full Text:
- Date Issued: 1995
- Authors: Smith, Tamara J , Petty, G , Villet, Martin H
- Date: 1995
- Language: English
- Type: text , Article
- Identifier: vital:6853 , http://hdl.handle.net/10962/d1011134
- Description: Larvae of five species of scarabaeid beetles, Asthenopholis subfasciata Blanchard, Trochalus politus Moser, Macrophylla ciliata Herbst, Congela valida Peringuey and Adoretus ictericus Burmeister, and adults of a sixth species, Heteronychus arator (Fabricius), cause considerable economic damage to the root systems of pineapple plants. The biologies of the species differ, making reliable identification essential. Since no convenient method is available to identify them, both field and laboratory keys are provided for the identification of third instar larvae of the six species, and detailed, illustrated descriptions for confirming their identifications
- Full Text:
- Date Issued: 1995
Ectomycorrhizas in association with Pinus patula in Sabie, South Africa
- Hawley, Greer L, Taylor, A F S, Dames, Joanna F
- Authors: Hawley, Greer L , Taylor, A F S , Dames, Joanna F
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6475 , http://hdl.handle.net/10962/d1006163 , http://www.scielo.org.za/scielo.php?pid=S0038-23532008000400011&script=sci_arttext
- Description: Forestry is an economically important industry in South Africa,involving extensive exotic plantations of Eucalyptus, Pinus and Acacia species. These tree species have fungal associations, such as ectomycorrhizas, that have become locally naturalized. The forestry industry is increasingly faced with problems of long-term sustainability, increasing soil acidity and depletion of soil nutrients. It is, therefore, essential that the fundamental importance of the ectomycorrhizal (ECM) symbioses in the nutrient cycling, growth, health and survival of these tree species should not be ignored. Research on the species diversity of ECM fungi associated with forestry plant species has been hampered by the difficulty of identifying the fungi involved in the symbiosis. This investigation focused on the ECM fungi associated with Pinus patula (Schlecht. et Cham.) grown in managed plantations in the Sabie region, Mpumalanga province, South Africa. ECM roots were morphotyped and DNA was extracted. The internal transcribed spacer (ITS) region was amplified using the ITS 1F and ITS 4 primers. The sequences were BLASTed using the GenBank and UNITE databases. Twenty-seven extractions were successfully amplified representing 17 different morphotypes. Of the 27 sequences, 21 were identified as ECM fungi and, from the BLAST results, eleven different ECM species could be identified. Selected ECM root types were morphologically and anatomically described according to root morphology, mantle structure, specialized hyphae and rhizomorph arrangement. Seven dominant field types were described and identified as two Amanita species, Scleroderma citrinum, a suilloid species, Thelephora terrestris, a tometelloid species and one resembled an Albatrellus species.
- Full Text:
- Date Issued: 2008
- Authors: Hawley, Greer L , Taylor, A F S , Dames, Joanna F
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6475 , http://hdl.handle.net/10962/d1006163 , http://www.scielo.org.za/scielo.php?pid=S0038-23532008000400011&script=sci_arttext
- Description: Forestry is an economically important industry in South Africa,involving extensive exotic plantations of Eucalyptus, Pinus and Acacia species. These tree species have fungal associations, such as ectomycorrhizas, that have become locally naturalized. The forestry industry is increasingly faced with problems of long-term sustainability, increasing soil acidity and depletion of soil nutrients. It is, therefore, essential that the fundamental importance of the ectomycorrhizal (ECM) symbioses in the nutrient cycling, growth, health and survival of these tree species should not be ignored. Research on the species diversity of ECM fungi associated with forestry plant species has been hampered by the difficulty of identifying the fungi involved in the symbiosis. This investigation focused on the ECM fungi associated with Pinus patula (Schlecht. et Cham.) grown in managed plantations in the Sabie region, Mpumalanga province, South Africa. ECM roots were morphotyped and DNA was extracted. The internal transcribed spacer (ITS) region was amplified using the ITS 1F and ITS 4 primers. The sequences were BLASTed using the GenBank and UNITE databases. Twenty-seven extractions were successfully amplified representing 17 different morphotypes. Of the 27 sequences, 21 were identified as ECM fungi and, from the BLAST results, eleven different ECM species could be identified. Selected ECM root types were morphologically and anatomically described according to root morphology, mantle structure, specialized hyphae and rhizomorph arrangement. Seven dominant field types were described and identified as two Amanita species, Scleroderma citrinum, a suilloid species, Thelephora terrestris, a tometelloid species and one resembled an Albatrellus species.
- Full Text:
- Date Issued: 2008
Evaluating the impact of the Institutional Repository, or positioning innovation between a rock and a hard place
- Authors: Thomas, G M E
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6988 , http://hdl.handle.net/10962/d1012411
- Description: Repositories remain an innovative but marginalized technology largely because there is no consensus about an agreed set of Performance Indicators (PIs) that demonstrate their overall impact on the research enterprise of our universities. A successful Institutional Repository should be evaluated in terms of the extent to which the open access repository builds a critical mass of scholarly content which is sustained and available through active university community engagement and ongoing scholarly contributions (faculty, researchers & students) that, when managed efficiently and effectively, ultimately strengthen, promote and give visibility to the research enterprise of the institution, and bring benefit to broader society. However, librarians are grappling with what and how best to demonstrate ‘institutional good’ but without clear evidence, assessment is fed by perception based on limited information which leads to diminished impact and value of the facility, a tyranny described as being caught between a rock and a hard place. Using Illuminative Evaluation to design a series of quantitative and qualitative metrics, it is proposed that a distinction be made between significant and secondary Performance Indicators where the former gather evidence to demonstrate the overall effect or impact of the IR on the individual and collective research community.
- Full Text:
- Date Issued: 2007
- Authors: Thomas, G M E
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6988 , http://hdl.handle.net/10962/d1012411
- Description: Repositories remain an innovative but marginalized technology largely because there is no consensus about an agreed set of Performance Indicators (PIs) that demonstrate their overall impact on the research enterprise of our universities. A successful Institutional Repository should be evaluated in terms of the extent to which the open access repository builds a critical mass of scholarly content which is sustained and available through active university community engagement and ongoing scholarly contributions (faculty, researchers & students) that, when managed efficiently and effectively, ultimately strengthen, promote and give visibility to the research enterprise of the institution, and bring benefit to broader society. However, librarians are grappling with what and how best to demonstrate ‘institutional good’ but without clear evidence, assessment is fed by perception based on limited information which leads to diminished impact and value of the facility, a tyranny described as being caught between a rock and a hard place. Using Illuminative Evaluation to design a series of quantitative and qualitative metrics, it is proposed that a distinction be made between significant and secondary Performance Indicators where the former gather evidence to demonstrate the overall effect or impact of the IR on the individual and collective research community.
- Full Text:
- Date Issued: 2007
First evidence for the Cenomanian-Turonian oceanic anoxic event (OAE2, Bonarelli event) from the Ionian Zone, western continental Greece
- Karakitsios, V, Tsikos, Harilaos, Van Breugel, Y, Koletti, L, Sinninghe Damsté, J S, Jenkyns, H C
- Authors: Karakitsios, V , Tsikos, Harilaos , Van Breugel, Y , Koletti, L , Sinninghe Damsté, J S , Jenkyns, H C
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6735 , http://hdl.handle.net/10962/d1007547
- Description: Integrated biostratigraphic (planktonic foraminifera, calcareous nannofossils), chemostratigraphic (bulk C and O isotopes) and compound-specific organic geochemical studies of a mid-Cretaceous pelagic carbonate—black shale succession of the Ionian Zone (western Greece), provide the first evidence for the Cenomanian–Turonian oceanic anoxic event (OAE2, ‘Bonarelli’ event) in mainland Greece. The event is manifested by the occurrence of a relatively thin (35 cm), yet exceptionally organic carbon-rich (44.5 wt% TOC), carbonate-free black shale, near the Cenomanian–Turonian boundary within the Vigla limestone formation (Berriasian–Turonian). Compared to the ‘Bonarelli’ black-shale interval from the type locality of OAE2 in Marche–Umbria, Italy, this black shale exhibits greatly reduced stratigraphic thickness, coupled with a considerable relative enrichment in TOC. Isotopically, enriched δ[superscript 13]C values for both bulk organic matter (−22.2‰) and specific organic compounds are up to 5‰ higher than those of underlying organic-rich strata of the Aptian-lower Albian Vigla Shale member, and thus compare very well with similar values of Cenomanian–Turonian black shale occurrences elsewhere. The relative predominance of bacterial hopanoids in the saturated, apolar lipid fraction of the OAE2 black shale of the Ionian Zone supports recent findings suggesting the abundance of N[subscript 2]-fixing cyanobacteria in Cretaceous oceans during the Cenomanian–Turonian and early Aptian oceanic anoxic events.
- Full Text:
- Date Issued: 2007
- Authors: Karakitsios, V , Tsikos, Harilaos , Van Breugel, Y , Koletti, L , Sinninghe Damsté, J S , Jenkyns, H C
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6735 , http://hdl.handle.net/10962/d1007547
- Description: Integrated biostratigraphic (planktonic foraminifera, calcareous nannofossils), chemostratigraphic (bulk C and O isotopes) and compound-specific organic geochemical studies of a mid-Cretaceous pelagic carbonate—black shale succession of the Ionian Zone (western Greece), provide the first evidence for the Cenomanian–Turonian oceanic anoxic event (OAE2, ‘Bonarelli’ event) in mainland Greece. The event is manifested by the occurrence of a relatively thin (35 cm), yet exceptionally organic carbon-rich (44.5 wt% TOC), carbonate-free black shale, near the Cenomanian–Turonian boundary within the Vigla limestone formation (Berriasian–Turonian). Compared to the ‘Bonarelli’ black-shale interval from the type locality of OAE2 in Marche–Umbria, Italy, this black shale exhibits greatly reduced stratigraphic thickness, coupled with a considerable relative enrichment in TOC. Isotopically, enriched δ[superscript 13]C values for both bulk organic matter (−22.2‰) and specific organic compounds are up to 5‰ higher than those of underlying organic-rich strata of the Aptian-lower Albian Vigla Shale member, and thus compare very well with similar values of Cenomanian–Turonian black shale occurrences elsewhere. The relative predominance of bacterial hopanoids in the saturated, apolar lipid fraction of the OAE2 black shale of the Ionian Zone supports recent findings suggesting the abundance of N[subscript 2]-fixing cyanobacteria in Cretaceous oceans during the Cenomanian–Turonian and early Aptian oceanic anoxic events.
- Full Text:
- Date Issued: 2007
From panic disorder to complex traumatic stress disorder : retrospective reflections on the case of Tariq
- Authors: Edwards, David J A
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6234 , http://hdl.handle.net/10962/d1007784
- Description: This is a phenomenological-hermeneutic case study of Tariq who initially presented with panic disorder. It documents how, as therapy proceeded, the underlying meaning of his initial panic deepened as its roots in traumatic memories of childhood emerged. There were four spaced phases of treatment over four years. The first focused on anxiety management; the second was conceptualized within schema-focused therapy, and evoked and worked with childhood memories using inner child guided imagery; in the third and fourth phases insights gained led to an authentic re-engagement with family members in relationships that had been problematic. The panic attacks resolved and there were two dreams representing a reconfiguring of his relationship with his deceased father. The first two phases were the focus of an unpublished case study presented at a conference in 1995. This article incorporates material from that study and looks back at the case both in light of developments in phases two and three and also in light of theoretical developments in our understanding of complex trauma since the initial presentation.
- Full Text:
- Date Issued: 2013
- Authors: Edwards, David J A
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6234 , http://hdl.handle.net/10962/d1007784
- Description: This is a phenomenological-hermeneutic case study of Tariq who initially presented with panic disorder. It documents how, as therapy proceeded, the underlying meaning of his initial panic deepened as its roots in traumatic memories of childhood emerged. There were four spaced phases of treatment over four years. The first focused on anxiety management; the second was conceptualized within schema-focused therapy, and evoked and worked with childhood memories using inner child guided imagery; in the third and fourth phases insights gained led to an authentic re-engagement with family members in relationships that had been problematic. The panic attacks resolved and there were two dreams representing a reconfiguring of his relationship with his deceased father. The first two phases were the focus of an unpublished case study presented at a conference in 1995. This article incorporates material from that study and looks back at the case both in light of developments in phases two and three and also in light of theoretical developments in our understanding of complex trauma since the initial presentation.
- Full Text:
- Date Issued: 2013
Generic substitution: the use of medicinal products containing different salts and implications for safety and efficacy
- Verbeeck, R K, Kanfer, Isadore, Walker, Roderick B
- Authors: Verbeeck, R K , Kanfer, Isadore , Walker, Roderick B
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6445 , http://hdl.handle.net/10962/d1006632
- Description: In their quest to gain early entry of new generic products into the market prior to patent expiration, one of the strategies pursued by generic drug product manufacturers is to incorporate different salts of an approved active pharmaceutical ingredient (API) in a brand company's marketed dosage form and subject such dosage forms to bioequivalence assessment. These initiatives present challenges to regulatory authorities where the decision to approve bioequivalent products containing such pharmaceutical alternatives must be considered in the light of safety and efficacy, and more particularly, with respect to their substitutability. This article describes the various issues and contentions associated with the concept of pharmaceutical alternatives, specifically with respect to the uses of different salts and the implications for safety, efficacy and generic substitution.
- Full Text:
- Date Issued: 2006
- Authors: Verbeeck, R K , Kanfer, Isadore , Walker, Roderick B
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6445 , http://hdl.handle.net/10962/d1006632
- Description: In their quest to gain early entry of new generic products into the market prior to patent expiration, one of the strategies pursued by generic drug product manufacturers is to incorporate different salts of an approved active pharmaceutical ingredient (API) in a brand company's marketed dosage form and subject such dosage forms to bioequivalence assessment. These initiatives present challenges to regulatory authorities where the decision to approve bioequivalent products containing such pharmaceutical alternatives must be considered in the light of safety and efficacy, and more particularly, with respect to their substitutability. This article describes the various issues and contentions associated with the concept of pharmaceutical alternatives, specifically with respect to the uses of different salts and the implications for safety, efficacy and generic substitution.
- Full Text:
- Date Issued: 2006
How entrepreneurs deal with ethical challenges : an application of the Business Ethics Synergy Star Technique
- Robinson, David A, Davidsson, Per, Van der Mescht, Hennie, Court, Philip
- Authors: Robinson, David A , Davidsson, Per , Van der Mescht, Hennie , Court, Philip
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6079 , http://hdl.handle.net/10962/d1006123
- Description: Entrepreneurs typically live with the ever present threat of business failure arising from limited financial resources and aggressive competition in the marketplace. Under these circumstances, conflicting priorities arise and the entrepreneur is thus faced with certain dilemmas. In seeking to resolve these, entrepreneurs must often rely on their own judgment to determine ‘‘what is right’’. There is thus a need for a technique to assist them decide on a course of action when no precedent or obvious solution exists. This research paper examines how entrepreneurs experience and deal with these dilemmas. The research is based on interviews with seven entrepreneurs in established service-oriented ventures, which gave rise to 26 dilemmas. These dilemmas were analyzed by making use of the Synergy Star technique, which is introduced here as a tool that is useful in defining any dilemma, isolating the ethical component, and resolving the dilemma in a way that is congruent with the entrepreneur’s personal world-view.
- Full Text:
- Date Issued: 2007
- Authors: Robinson, David A , Davidsson, Per , Van der Mescht, Hennie , Court, Philip
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6079 , http://hdl.handle.net/10962/d1006123
- Description: Entrepreneurs typically live with the ever present threat of business failure arising from limited financial resources and aggressive competition in the marketplace. Under these circumstances, conflicting priorities arise and the entrepreneur is thus faced with certain dilemmas. In seeking to resolve these, entrepreneurs must often rely on their own judgment to determine ‘‘what is right’’. There is thus a need for a technique to assist them decide on a course of action when no precedent or obvious solution exists. This research paper examines how entrepreneurs experience and deal with these dilemmas. The research is based on interviews with seven entrepreneurs in established service-oriented ventures, which gave rise to 26 dilemmas. These dilemmas were analyzed by making use of the Synergy Star technique, which is introduced here as a tool that is useful in defining any dilemma, isolating the ethical component, and resolving the dilemma in a way that is congruent with the entrepreneur’s personal world-view.
- Full Text:
- Date Issued: 2007
How taboo are taboo words for girls?
- Authors: De Klerk, Vivian A
- Date: 1992
- Language: English
- Type: Article
- Identifier: vital:6143 , http://hdl.handle.net/10962/d1011596
- Description: In the past five years, there has been much interest in the question of whether women are really as concerned about politeness and status as they have been made out to be by such writers as Baroni and D'Urso (1984), Crosby and Nyquist (1977), Lakoff (1973), Spender (1980), and Trudgill (1972). Despite the commonly held perception that it is only males who bandy about derogatory and taboo words (Bailey 1985; Flexner 1975), Risch (1987) provided counterevidence based on data obtained in the United States. The results of the present study, based on data obtained in South Africa, strongly support her findings and challenge the assumption that women stick to standard speech, citing evidence that young females are familiar with, and use, a wide range of highly taboo/slang items themselves. In particular, attention is devoted to the question of pejorative words applicable to males and females, respectively, and the view that there are only a few pejorative terms commonly used to describe males (particularly by females) is challenged. (Women's language, politeness, linguistic taboo, stereotypes, slang, expletives, prestige forms).
- Full Text:
- Date Issued: 1992
- Authors: De Klerk, Vivian A
- Date: 1992
- Language: English
- Type: Article
- Identifier: vital:6143 , http://hdl.handle.net/10962/d1011596
- Description: In the past five years, there has been much interest in the question of whether women are really as concerned about politeness and status as they have been made out to be by such writers as Baroni and D'Urso (1984), Crosby and Nyquist (1977), Lakoff (1973), Spender (1980), and Trudgill (1972). Despite the commonly held perception that it is only males who bandy about derogatory and taboo words (Bailey 1985; Flexner 1975), Risch (1987) provided counterevidence based on data obtained in the United States. The results of the present study, based on data obtained in South Africa, strongly support her findings and challenge the assumption that women stick to standard speech, citing evidence that young females are familiar with, and use, a wide range of highly taboo/slang items themselves. In particular, attention is devoted to the question of pejorative words applicable to males and females, respectively, and the view that there are only a few pejorative terms commonly used to describe males (particularly by females) is challenged. (Women's language, politeness, linguistic taboo, stereotypes, slang, expletives, prestige forms).
- Full Text:
- Date Issued: 1992
Impact of nutrients and herbivory by Eccritotarsus catarinensis on the biological control of water hyacinth, Eichhornia crassipes
- Coetzee, Julie A, Byrne, Marcus J, Hill, Martin P
- Authors: Coetzee, Julie A , Byrne, Marcus J , Hill, Martin P
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6945 , http://hdl.handle.net/10962/d1011973 , https://orcid.org/0000-0003-0579-5298
- Description: Many water hyacinth infestations in South Africa are the symptom of eutrophication, and as a result, biological control of this weed is variable. This study examined the effects of herbivory by the mirid, Eccritotarsus catarinensis, on water hyacinth grown at high, medium and low nitrogen (N) and phosphorus (P) nutrient concentrations. Water nutrient concentration appears to be the overriding factor affecting plant growth parameters of water hyacinth plants—at high nutrient concentrations, leaf and daughter plant production were more than double than at low nutrient concentrations, while stem length was twice as great at high nutrient concentrations compared to low concentrations. Chlorophyll content was also twice as high at high nutrient concentrations than low concentrations. Conversely, flower production at high nutrient concentrations was less than half that at low concentrations. Herbivory by E. catarinensis did not have as great an effect on water hyacinth vigour as nutrient concentration did, although it significantly reduced the production of daughter plants by 23 ± 9%, the length of the second petiole by 13 ± 5%, and chlorophyll content of water hyacinth leaves by 15 ± 6%. In terms of insect numbers, mirids performed better on plants grown under medium nutrient conditions (99 ± 28 S.E.), compared to high nutrient concentrations (52 ± 27 S.E.), and low nutrient concentrations (25 ± 30 S.E.). Thus, these results suggest that the fastest and most significant reduction in water hyacinth proliferation would be reached by lowering the water nutrient concentrations, and herbivory by E. catarinensis alone is not sufficient to reduce all aspects of water hyacinth vigour, especially at very high nutrient concentrations.
- Full Text:
- Date Issued: 2007
- Authors: Coetzee, Julie A , Byrne, Marcus J , Hill, Martin P
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6945 , http://hdl.handle.net/10962/d1011973 , https://orcid.org/0000-0003-0579-5298
- Description: Many water hyacinth infestations in South Africa are the symptom of eutrophication, and as a result, biological control of this weed is variable. This study examined the effects of herbivory by the mirid, Eccritotarsus catarinensis, on water hyacinth grown at high, medium and low nitrogen (N) and phosphorus (P) nutrient concentrations. Water nutrient concentration appears to be the overriding factor affecting plant growth parameters of water hyacinth plants—at high nutrient concentrations, leaf and daughter plant production were more than double than at low nutrient concentrations, while stem length was twice as great at high nutrient concentrations compared to low concentrations. Chlorophyll content was also twice as high at high nutrient concentrations than low concentrations. Conversely, flower production at high nutrient concentrations was less than half that at low concentrations. Herbivory by E. catarinensis did not have as great an effect on water hyacinth vigour as nutrient concentration did, although it significantly reduced the production of daughter plants by 23 ± 9%, the length of the second petiole by 13 ± 5%, and chlorophyll content of water hyacinth leaves by 15 ± 6%. In terms of insect numbers, mirids performed better on plants grown under medium nutrient conditions (99 ± 28 S.E.), compared to high nutrient concentrations (52 ± 27 S.E.), and low nutrient concentrations (25 ± 30 S.E.). Thus, these results suggest that the fastest and most significant reduction in water hyacinth proliferation would be reached by lowering the water nutrient concentrations, and herbivory by E. catarinensis alone is not sufficient to reduce all aspects of water hyacinth vigour, especially at very high nutrient concentrations.
- Full Text:
- Date Issued: 2007
Mapping GPS-derived ionospheric Total Electron Content over Southern Africa during different epochs of solar cycle 23
- Moeketsi, D M, Combrinck, W L, McKinnell, Lee-Anne, Fedrizz, M
- Authors: Moeketsi, D M , Combrinck, W L , McKinnell, Lee-Anne , Fedrizz, M
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6802 , http://hdl.handle.net/10962/d1004165
- Description: The Southern African Development Community and the International Global Navigation Satellite Systems Service (GNSS) network of dual frequency Global Positioning System (GPS) receivers provide an opportunity to determine Total Electron Content (TEC) over Southern Africa by taking advantage of the dispersive nature of the ionospheric medium. For this task, the University of New Brunswick (UNB) ionospheric modelling technique which applies a spatial linear approximation of the vertical TEC above each station using stochastic parameters in Kalman filter estimation, primed with data from the Southern Africa GPS network, was used for mapping TEC at South African locations during selected days and hours of different epochs of solar cycle 23. Significant enhancements in the TEC value and features, which could be associated with frequent solar events, are evident around a day of extreme solar maximum. These observations are discussed and further investigated by analyzing the GOES 8 and 10 satellites X-ray flux (0.1–0.8 nm) and SOHO Solar EUV Monitor (26.0–34.0 nm) higher resolution data. Comparison of these physical quantities reveals that for each X-ray flare observed, there is an associated EUV flare event. The latter phenomenon causes photoionisation in the daytime ionosphere which results in significant TEC enhancement. The daytime UNB TEC compared with the International Reference Ionosphere (IRI) 2001 predicted TEC found both models to show a good agreement.
- Full Text:
- Date Issued: 2007
- Authors: Moeketsi, D M , Combrinck, W L , McKinnell, Lee-Anne , Fedrizz, M
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6802 , http://hdl.handle.net/10962/d1004165
- Description: The Southern African Development Community and the International Global Navigation Satellite Systems Service (GNSS) network of dual frequency Global Positioning System (GPS) receivers provide an opportunity to determine Total Electron Content (TEC) over Southern Africa by taking advantage of the dispersive nature of the ionospheric medium. For this task, the University of New Brunswick (UNB) ionospheric modelling technique which applies a spatial linear approximation of the vertical TEC above each station using stochastic parameters in Kalman filter estimation, primed with data from the Southern Africa GPS network, was used for mapping TEC at South African locations during selected days and hours of different epochs of solar cycle 23. Significant enhancements in the TEC value and features, which could be associated with frequent solar events, are evident around a day of extreme solar maximum. These observations are discussed and further investigated by analyzing the GOES 8 and 10 satellites X-ray flux (0.1–0.8 nm) and SOHO Solar EUV Monitor (26.0–34.0 nm) higher resolution data. Comparison of these physical quantities reveals that for each X-ray flare observed, there is an associated EUV flare event. The latter phenomenon causes photoionisation in the daytime ionosphere which results in significant TEC enhancement. The daytime UNB TEC compared with the International Reference Ionosphere (IRI) 2001 predicted TEC found both models to show a good agreement.
- Full Text:
- Date Issued: 2007