Tuning the redox properties of Co-N4 macrocyclic complexes for the catalytic electrooxidation of glucose
- Villagra, Evelyn, Bedioui, Fethi, Nyokong, Tebello, Canales, J Carlos, Sancy, Mamie, Páez, Maritza A, Costamagna, Juan, Zagal, Jose H
- Authors: Villagra, Evelyn , Bedioui, Fethi , Nyokong, Tebello , Canales, J Carlos , Sancy, Mamie , Páez, Maritza A , Costamagna, Juan , Zagal, Jose H
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268675 , vital:54221 , xlink:href="https://doi.org/10.1016/j.electacta.2008.02.006"
- Description: Graphite electrodes modified with four different cobalt N4 macrocyclics, namely Co tetrapentapyridinophthalocyanine, (CoTPenPyrPc), Co tetrapyridinoporphyrazine (CoTPyPz), Co octa(hydroxyethylthio)phthalocyanine (CoOEHTPc) and Co tetranitrophthalocyanine (CoTNPc) exhibit catalytic activity for the oxidation of glucose in alkaline media. The purpose of this work is to establish correlations between the catalytic activity of these complexes and their redox potential. The activity of the different modified electrodes was tested by linear voltammetry under hydrodynamic conditions using the rotating disk technique. Tafel plots constructed from mass-transport corrected currents give slopes ranging from 0.080 to 0.160 V/decade for the different catalysts which suggests that a first one-electron step is rate controlling with the symmetry of the energy barrier depending on the nature of the ligand of the Co complex. A plot of log I versus the Co(II)/(I) formal potential gives a volcano curve that also includes catalysts studied previously. This illustrates the concept that the formal potential of the catalyst needs to be tuned to a certain value for achieving maximum activity. A theoretical interpretation of these results is given in terms of Langmuir isotherms for the adsorption of glucose on the Co sites of the surface-confined metal complexes.
- Full Text:
- Date Issued: 2008
- Authors: Villagra, Evelyn , Bedioui, Fethi , Nyokong, Tebello , Canales, J Carlos , Sancy, Mamie , Páez, Maritza A , Costamagna, Juan , Zagal, Jose H
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268675 , vital:54221 , xlink:href="https://doi.org/10.1016/j.electacta.2008.02.006"
- Description: Graphite electrodes modified with four different cobalt N4 macrocyclics, namely Co tetrapentapyridinophthalocyanine, (CoTPenPyrPc), Co tetrapyridinoporphyrazine (CoTPyPz), Co octa(hydroxyethylthio)phthalocyanine (CoOEHTPc) and Co tetranitrophthalocyanine (CoTNPc) exhibit catalytic activity for the oxidation of glucose in alkaline media. The purpose of this work is to establish correlations between the catalytic activity of these complexes and their redox potential. The activity of the different modified electrodes was tested by linear voltammetry under hydrodynamic conditions using the rotating disk technique. Tafel plots constructed from mass-transport corrected currents give slopes ranging from 0.080 to 0.160 V/decade for the different catalysts which suggests that a first one-electron step is rate controlling with the symmetry of the energy barrier depending on the nature of the ligand of the Co complex. A plot of log I versus the Co(II)/(I) formal potential gives a volcano curve that also includes catalysts studied previously. This illustrates the concept that the formal potential of the catalyst needs to be tuned to a certain value for achieving maximum activity. A theoretical interpretation of these results is given in terms of Langmuir isotherms for the adsorption of glucose on the Co sites of the surface-confined metal complexes.
- Full Text:
- Date Issued: 2008
Underlying mechanisms affecting institutionalisation of environmental education courses in Southern Africa
- Authors: Lupele, Justin
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386926 , vital:68188 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122773"
- Description: This paper discusses the underlying causal mechanisms that enabled or constrained institutionalisation of environmental education in 12 institutions in eight countries in southern Africa. The study was carried out in the context of the Southern Africa Development Community Regional Environmental Education Support Programme’s Course Development Network (CDN). This paper reports on part of the author's doctoral study and draws on critical realism as the ontological lens. Data analysis was done by means of a retroductive mode of inference, as articulated by Danermark, Ekström, Jakosben and Karlsson (2002). The paper demonstrates that there are a number of underlying causal mechanisms, which may enable or constrain institutionalisation of environmental education. They include factors at play at both national and institutional level; namely, responsiveness to national and institutional needs, recognition and ownership, accreditation and certification, institutional culture and politics, short course support structure and support from colleagues. As part of the discussions of the results of the study, I have advanced some retroductive theories that suggest causal mechanisms beyond the empirical data based on the participants’ experiences and events in the CDN.
- Full Text:
- Date Issued: 2008
- Authors: Lupele, Justin
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386926 , vital:68188 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122773"
- Description: This paper discusses the underlying causal mechanisms that enabled or constrained institutionalisation of environmental education in 12 institutions in eight countries in southern Africa. The study was carried out in the context of the Southern Africa Development Community Regional Environmental Education Support Programme’s Course Development Network (CDN). This paper reports on part of the author's doctoral study and draws on critical realism as the ontological lens. Data analysis was done by means of a retroductive mode of inference, as articulated by Danermark, Ekström, Jakosben and Karlsson (2002). The paper demonstrates that there are a number of underlying causal mechanisms, which may enable or constrain institutionalisation of environmental education. They include factors at play at both national and institutional level; namely, responsiveness to national and institutional needs, recognition and ownership, accreditation and certification, institutional culture and politics, short course support structure and support from colleagues. As part of the discussions of the results of the study, I have advanced some retroductive theories that suggest causal mechanisms beyond the empirical data based on the participants’ experiences and events in the CDN.
- Full Text:
- Date Issued: 2008
Understanding and improving the residual efficacy of the cryptophlebia leucotreta granulovirus (Cryptogran)
- Authors: Kirkman, Wayne
- Date: 2008
- Subjects: Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5794 , http://hdl.handle.net/10962/d1005482 , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Description: False codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyr) (Lepidoptera: Tortricidae), is one of the most important pests on citrus. The Cryptophlebia leucotreta granulovirus (CrleGV) has been developed into a successful biological control agent, registered under the name Cryptogran, and is currently the preferred product for the control of FCM on citrus in South Africa. A prerequisite to the continued success of Cryptogran as a means of controlling false codling moth is to understand the factors affecting field persistence of the virus, and to find ways to improve it. The aim of this study was to gain a clearer understanding of the product and the abiotic and biotic factors affecting its persistence in the field, and to investigate methods to improve this persistence. The effect of UV-irradiation on the virus was determined, and various products were tested as UV protectants in laboratory bioassays. Lignin was the most effective additive, and was tested in several field trials, where it also enhanced the efficacy of Cryptogran. Laboratory trials indicated that Cryptogran is rainfast. Cryptogran applications early in the season had a longer period of residual activity than sprays applied closer to harvest. Daytime applications were less effective that evening sprays. Sprays applied coinciding with peaks in pheromone moth trap catches were more effective than those applied between peaks. Biotic factors influencing persistence were investigated. Residual efficacy was longer when treatments were applied to blocks than as single tree treatments. Attempts were made to quantify the effect of the navel end of a navel orange on the field persistence of Cryptogran. Cryptogran was shown to be compatible with many agricultural chemicals used on citrus. Economic thresholds and various cost-benefit analyses are discussed. A list of practical recommendations to growers was drawn up, and possibilities for future research are presented.
- Full Text:
- Date Issued: 2008
- Authors: Kirkman, Wayne
- Date: 2008
- Subjects: Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5794 , http://hdl.handle.net/10962/d1005482 , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Description: False codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyr) (Lepidoptera: Tortricidae), is one of the most important pests on citrus. The Cryptophlebia leucotreta granulovirus (CrleGV) has been developed into a successful biological control agent, registered under the name Cryptogran, and is currently the preferred product for the control of FCM on citrus in South Africa. A prerequisite to the continued success of Cryptogran as a means of controlling false codling moth is to understand the factors affecting field persistence of the virus, and to find ways to improve it. The aim of this study was to gain a clearer understanding of the product and the abiotic and biotic factors affecting its persistence in the field, and to investigate methods to improve this persistence. The effect of UV-irradiation on the virus was determined, and various products were tested as UV protectants in laboratory bioassays. Lignin was the most effective additive, and was tested in several field trials, where it also enhanced the efficacy of Cryptogran. Laboratory trials indicated that Cryptogran is rainfast. Cryptogran applications early in the season had a longer period of residual activity than sprays applied closer to harvest. Daytime applications were less effective that evening sprays. Sprays applied coinciding with peaks in pheromone moth trap catches were more effective than those applied between peaks. Biotic factors influencing persistence were investigated. Residual efficacy was longer when treatments were applied to blocks than as single tree treatments. Attempts were made to quantify the effect of the navel end of a navel orange on the field persistence of Cryptogran. Cryptogran was shown to be compatible with many agricultural chemicals used on citrus. Economic thresholds and various cost-benefit analyses are discussed. A list of practical recommendations to growers was drawn up, and possibilities for future research are presented.
- Full Text:
- Date Issued: 2008
Using assessment and reflexive teaching practices to inform and guide changes to the teaching and learning activities in Introductory Accounting
- Authors: Bezuidenhout, L Peta
- Date: 2008
- Language: English
- Type: Conference paper
- Identifier: vital:6081 , http://hdl.handle.net/10962/d1008585
- Description: Teaching accounting to first year university students in higher education institutions is becoming increasingly complex as we deal with increasing class sizes, increasing diversity and a student body which appears to be less inclined to study without external motivating factors, while to be successful in studying accounting requires more than passive learning. Our aim was to make our students active participants in their accounting studies. After studying established research into assessment and approaches to student learning, changes were made to our course to ensure increased and active participation from our students. Critical to this change was guiding students in making the shift from a surface approach to learning, to a deep approach to learning where they would engage with the subject matter in a manner more likely to result in truly understanding the concepts and principles being taught. An important part of implementing these changes was asking our students to evaluate the innovations after they had taken place. Feedback received from our students resulted in the use of a new and unplanned innovation in the form of the setting of regular mini-tests. This was arguably the most successful of all the interventions introduced during the year and resulted in our journey being more exciting and less predictable than expected.
- Full Text:
- Date Issued: 2008
- Authors: Bezuidenhout, L Peta
- Date: 2008
- Language: English
- Type: Conference paper
- Identifier: vital:6081 , http://hdl.handle.net/10962/d1008585
- Description: Teaching accounting to first year university students in higher education institutions is becoming increasingly complex as we deal with increasing class sizes, increasing diversity and a student body which appears to be less inclined to study without external motivating factors, while to be successful in studying accounting requires more than passive learning. Our aim was to make our students active participants in their accounting studies. After studying established research into assessment and approaches to student learning, changes were made to our course to ensure increased and active participation from our students. Critical to this change was guiding students in making the shift from a surface approach to learning, to a deep approach to learning where they would engage with the subject matter in a manner more likely to result in truly understanding the concepts and principles being taught. An important part of implementing these changes was asking our students to evaluate the innovations after they had taken place. Feedback received from our students resulted in the use of a new and unplanned innovation in the form of the setting of regular mini-tests. This was arguably the most successful of all the interventions introduced during the year and resulted in our journey being more exciting and less predictable than expected.
- Full Text:
- Date Issued: 2008
Using assessment and reflexive teaching practices to inform and guide changes to the teaching and learning activities in Introductory Accounting
- Authors: Bezuidenhout, L Peta
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: Conference paper
- Identifier: vital:6068 , http://hdl.handle.net/10962/d1004622
- Description: Teaching accounting to first year university students in higher education institutions is becoming increasingly complex as we deal with increasing class sizes, increasing diversity and a student body which appears to be less inclined to study without external motivating factors, while to be successful in studying accounting requires more than passive learning. Our aim was to make our students active participants in their accounting studies. After studying established research into assessment and approaches to student learning, changes were made to our course to ensure increased and active participation from our students. Critical to this change was guiding students in making the shift from a surface approach to learning, to a deep approach to learning where they would engage with the subject matter in a manner more likely to result in truly understanding the concepts and principles being taught. An important part of implementing these changes was asking our students to evaluate the innovations after they had taken place. Feedback received from our students resulted in the use of a new and unplanned innovation in the form of the setting of regular mini-tests. This was arguably the most successful of all the interventions introduced during the year and resulted in our journey being more exciting and less predictable than expected.
- Full Text:
- Date Issued: 2008
- Authors: Bezuidenhout, L Peta
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: Conference paper
- Identifier: vital:6068 , http://hdl.handle.net/10962/d1004622
- Description: Teaching accounting to first year university students in higher education institutions is becoming increasingly complex as we deal with increasing class sizes, increasing diversity and a student body which appears to be less inclined to study without external motivating factors, while to be successful in studying accounting requires more than passive learning. Our aim was to make our students active participants in their accounting studies. After studying established research into assessment and approaches to student learning, changes were made to our course to ensure increased and active participation from our students. Critical to this change was guiding students in making the shift from a surface approach to learning, to a deep approach to learning where they would engage with the subject matter in a manner more likely to result in truly understanding the concepts and principles being taught. An important part of implementing these changes was asking our students to evaluate the innovations after they had taken place. Feedback received from our students resulted in the use of a new and unplanned innovation in the form of the setting of regular mini-tests. This was arguably the most successful of all the interventions introduced during the year and resulted in our journey being more exciting and less predictable than expected.
- Full Text:
- Date Issued: 2008
Using inetvis to evaluate snort and bro scan detection on a network telescope
- Irwin, Barry V W, van Riel, J P
- Authors: Irwin, Barry V W , van Riel, J P
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429981 , vital:72656 , https://doi.org/10.1007/978-3-540-78243-8_17
- Description: This paper presents an investigative analysis of net-work scans and scan detection algorithms. Visualisa-tion is employed to review network telescope traffic and identify incidents of scan activity. Some of the identified phenomena appear to be novel forms of host discovery. Scan detection algorithms used by the Snort and Bro intrusion detection systems are cri-tiqued by comparing the visualised scans with alert output. Where human assessment disagrees with the alert output, explanations are sought by analysing the detection algorithms. The Snort and Bro algorithms are based on counting unique connection attempts to destination addresses and ports. For Snort, notable false positive and false negative cases result due to a grossly oversimplified method of counting unique destination addresses and ports.
- Full Text:
- Date Issued: 2008
- Authors: Irwin, Barry V W , van Riel, J P
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429981 , vital:72656 , https://doi.org/10.1007/978-3-540-78243-8_17
- Description: This paper presents an investigative analysis of net-work scans and scan detection algorithms. Visualisa-tion is employed to review network telescope traffic and identify incidents of scan activity. Some of the identified phenomena appear to be novel forms of host discovery. Scan detection algorithms used by the Snort and Bro intrusion detection systems are cri-tiqued by comparing the visualised scans with alert output. Where human assessment disagrees with the alert output, explanations are sought by analysing the detection algorithms. The Snort and Bro algorithms are based on counting unique connection attempts to destination addresses and ports. For Snort, notable false positive and false negative cases result due to a grossly oversimplified method of counting unique destination addresses and ports.
- Full Text:
- Date Issued: 2008
Utility of the cognitive assessment system (CAS) to predict reading proficiency in grade 1
- Authors: Hüttenrauch, Maria Eleonore
- Date: 2008
- Subjects: Das-Naglieri Cognitive Assessment System , Intelligence tests for preliterates , Cognition in children , Reading disability
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9839 , http://hdl.handle.net/10948/965 , Das-Naglieri Cognitive Assessment System , Intelligence tests for preliterates , Cognition in children , Reading disability
- Description: Reading disability, as the most commonly diagnosed learning disability, continues to pose a tenacious problem to teachers, practitioners and researchers. In an effort to understand the causes of reading disability, voluminous research has been undertaken over the past decades to pinpoint its causes or developmental stumbling blocks. One approach, the Planning, Attention, Simultaneous, and Successive processing (PASS) model, combines neuropsychological theory with elements from cognitive psychology. Based on this model, the Cognitive Assessment System (CAS), as well as methods of intervention for reading disability were developed. Although many studies have been conducted that investigated reading disability in terms of PASS cognitive processes, the final version of the CAS and its predictive utility with respect to reading disability has not been explored to date. The present study aimed to investigate the utility of the CAS, administered at the beginning of grade 1, to predict reading proficiency at the end of grade 1. The sample was comprised of 119 “average” (i.e., belonging to the general population) grade 1 students from schools of the Calgary Board of Education (CBE). The Basic Battery of the CAS was administered to the children in the sample at the beginning of grade 1, as well as four reading subtests of the Woodcock-Johnson Tests of Achievement – Third Edition (WJ-III ACH) at the end of grade 1. The WJ-III ACH yielded a cluster score for basic reading and one for reading comprehension. Correlational and regression analyses were used to address the first aim of this study, namely to explore the relationship between students’ scores on the CAS and their later reading proficiency. To this end, the children’s CAS Full Scale scores and WJ-III ACH cluster scores were subjected to a hierarchical regression analysis, whereby age, gender, and - xviii - SES were kept constant by entering them first in the equation. Next, the relationship between students’ PASS scale scores and the CAS subtest scores respectively and scores on the WJ-III ACH Basic Reading and Reading Comprehension Cluster scores was explored by means of stepwise regression analysis. To improve on the generalizability of results, the regression analyses were conducted on a randomly drawn analysis sample consisting of 80% of the sample, and cross-validated on the remaining 20% of the sample. The second aim of the present study was to ascertain whether clusters could be identified on the basis of CAS performance as well as levels of reading proficiency. To this end, the children’s CAS FS scores, PASS scale scores, and CAS subtest scores were subjected to cluster analyses. The investigation of aim 1 yielded some encouraging results, in that it was found that, together with the covariates: • The CAS FS emerged as a moderately strong predictor of both basic reading and reading comprehension; • Successive processing, in particular the Word Series subtest, significantly predicted basic reading skills; • Successive and simultaneous processing, particularly the Nonverbal Matrices and Sentence Repetition subtests, were significant predictors of reading comprehension; The second aim, which explored the relationship between patterns of CAS cognitive processes and their relationship with reading proficiency, yielded: • Two clusters with distinctly different PASS scale scores and with significant differences between their levels of reading proficiency. Higher PASS scales scores, particularly on the Attention and Planning scales, were associated with higher reading proficiency scores. • Four clusters with distinctly different CAS subtest scores that were also associated with distinctly different levels of reading performance. Good - xix - reading proficiency was associated with good CAS performance, whereas weaker reading proficiency was linked to weaker CAS performance. Biographical variables, such as age and SES were found to be related to performance on the CAS and reading proficiency, while gender did not emerge as an important predictor variable. The present study demonstrated the usefulness of the CAS, particularly its Successive and Simultaneous scales, as potential early predictor of reading disability. An exploration of the relationship between patterns of CAS cognitive processes and later reading proficiency also yielded encouraging and interesting results.
- Full Text:
- Date Issued: 2008
- Authors: Hüttenrauch, Maria Eleonore
- Date: 2008
- Subjects: Das-Naglieri Cognitive Assessment System , Intelligence tests for preliterates , Cognition in children , Reading disability
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9839 , http://hdl.handle.net/10948/965 , Das-Naglieri Cognitive Assessment System , Intelligence tests for preliterates , Cognition in children , Reading disability
- Description: Reading disability, as the most commonly diagnosed learning disability, continues to pose a tenacious problem to teachers, practitioners and researchers. In an effort to understand the causes of reading disability, voluminous research has been undertaken over the past decades to pinpoint its causes or developmental stumbling blocks. One approach, the Planning, Attention, Simultaneous, and Successive processing (PASS) model, combines neuropsychological theory with elements from cognitive psychology. Based on this model, the Cognitive Assessment System (CAS), as well as methods of intervention for reading disability were developed. Although many studies have been conducted that investigated reading disability in terms of PASS cognitive processes, the final version of the CAS and its predictive utility with respect to reading disability has not been explored to date. The present study aimed to investigate the utility of the CAS, administered at the beginning of grade 1, to predict reading proficiency at the end of grade 1. The sample was comprised of 119 “average” (i.e., belonging to the general population) grade 1 students from schools of the Calgary Board of Education (CBE). The Basic Battery of the CAS was administered to the children in the sample at the beginning of grade 1, as well as four reading subtests of the Woodcock-Johnson Tests of Achievement – Third Edition (WJ-III ACH) at the end of grade 1. The WJ-III ACH yielded a cluster score for basic reading and one for reading comprehension. Correlational and regression analyses were used to address the first aim of this study, namely to explore the relationship between students’ scores on the CAS and their later reading proficiency. To this end, the children’s CAS Full Scale scores and WJ-III ACH cluster scores were subjected to a hierarchical regression analysis, whereby age, gender, and - xviii - SES were kept constant by entering them first in the equation. Next, the relationship between students’ PASS scale scores and the CAS subtest scores respectively and scores on the WJ-III ACH Basic Reading and Reading Comprehension Cluster scores was explored by means of stepwise regression analysis. To improve on the generalizability of results, the regression analyses were conducted on a randomly drawn analysis sample consisting of 80% of the sample, and cross-validated on the remaining 20% of the sample. The second aim of the present study was to ascertain whether clusters could be identified on the basis of CAS performance as well as levels of reading proficiency. To this end, the children’s CAS FS scores, PASS scale scores, and CAS subtest scores were subjected to cluster analyses. The investigation of aim 1 yielded some encouraging results, in that it was found that, together with the covariates: • The CAS FS emerged as a moderately strong predictor of both basic reading and reading comprehension; • Successive processing, in particular the Word Series subtest, significantly predicted basic reading skills; • Successive and simultaneous processing, particularly the Nonverbal Matrices and Sentence Repetition subtests, were significant predictors of reading comprehension; The second aim, which explored the relationship between patterns of CAS cognitive processes and their relationship with reading proficiency, yielded: • Two clusters with distinctly different PASS scale scores and with significant differences between their levels of reading proficiency. Higher PASS scales scores, particularly on the Attention and Planning scales, were associated with higher reading proficiency scores. • Four clusters with distinctly different CAS subtest scores that were also associated with distinctly different levels of reading performance. Good - xix - reading proficiency was associated with good CAS performance, whereas weaker reading proficiency was linked to weaker CAS performance. Biographical variables, such as age and SES were found to be related to performance on the CAS and reading proficiency, while gender did not emerge as an important predictor variable. The present study demonstrated the usefulness of the CAS, particularly its Successive and Simultaneous scales, as potential early predictor of reading disability. An exploration of the relationship between patterns of CAS cognitive processes and later reading proficiency also yielded encouraging and interesting results.
- Full Text:
- Date Issued: 2008
Variation in the essential oil composition of Calendula Officinalis L
- Authors: Okoh, Omobola Oluranti
- Date: 2008
- Subjects: Calendula (Genus) , Essences and essential oils , Medicinal plants , Calendula officinalis
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11334 , http://hdl.handle.net/10353/d1001150 , Calendula (Genus) , Essences and essential oils , Medicinal plants , Calendula officinalis
- Description: Variations in the yield, chemical composition, antibacterial, and antioxidant properties of the essential oils of Rosmarinus officinalis L. cultivated in Alice, Eastern Cape of South Africa over a period of 12 months using the solvent-free microwave extraction and traditional hydrodistillation methods were evaluated. The GC-MS analyses of the essential oils revealed the presence of 33 compounds with 1,8-cineole, a-pinene, camphor, verbenone, bornyl acetate and camphene constituting about 80 percent of the oils throughout the period of investigation, with the solvent-free microwave extraction method generally yielding more of the major components than the hydrodistillation method. Each of the major components of the oils varied in quantity and quality of yield at different periods of the year. The method of extraction and time of harvest are of importance to the quantity and quality of essential oil of Rosmarinus officinalis. Higher amounts of oxygenated monoterpenes such as borneol, camphor, terpene- 4-ol, linalool, a-terpeneol were present in the oil of SFME in comparison with HD. However, HD oil contained more monoterpene hydrocarbons such as a-pinene, camphene, β-pinene, myrcene, a-phellanderene, 1,8-cineole, trans- β-ocimene, γ-teprinene, and cis-sabinene hydrate than SFME extracted oil. Accumulation of monoterpene alcohols and ketones was observed during maturation process of Rosmarinus leaves. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration values were determined using a serial microplate dilution method. The essential oils obtained using both methods of extraction were active against all the bacteria tested at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the SFME extracted oils ranged between 0.23 and 1.88 mg mL-1, while those of the HD extracted oils varied between 0.94 and 7.5 mg mL-1, thus suggesting that the oil obtained by solvent free microwave extraction was more active against bacteria than the oil obtained through hydrodistillation. The antioxidant and free radical scavenging activity of the obtained oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay and β- carotene bleaching test. In the DPPH+ assay, while the free radical scavenging activity of the oil obtained by SFME method showed percentage inhibitions of between 48.8 percent and 67 percent, the HD derived oil showed inhibitions of between 52.2 percent and 65.30 percent at concentrations of 0.33, 0.50 and 1.0 mg mL-1, respectively. In the β-carotene bleaching assay, the percentage inhibition increased with increasing concentration of both oils with a higher antioxidant activity of the oil obtained through the SFME than the HD method. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i. e. CEF, BEA and EMW and sprayed with vanillin-sulfuric acid. The chemical composition of the different extracts was similar with the exception of methanol and water extracts which had only one or two visible compounds after treating with vanillin-spray reagent. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against two most important nosocomial microorganisms. S. aureus (Gram positive) and E. coli (Gram negative). Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of E. coli. The hexane extract had the most lines of inhibition followed by ethyl acetate. Bioassay-guided fractionation against E. coli was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the hexane fraction. Furthermore we tried to complete the characterization by extracting and studying other biologically important plant metabolites such as phenolic compounds to evaluate the antioxidant capacity of Rosmarinus extracts
- Full Text:
- Date Issued: 2008
- Authors: Okoh, Omobola Oluranti
- Date: 2008
- Subjects: Calendula (Genus) , Essences and essential oils , Medicinal plants , Calendula officinalis
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11334 , http://hdl.handle.net/10353/d1001150 , Calendula (Genus) , Essences and essential oils , Medicinal plants , Calendula officinalis
- Description: Variations in the yield, chemical composition, antibacterial, and antioxidant properties of the essential oils of Rosmarinus officinalis L. cultivated in Alice, Eastern Cape of South Africa over a period of 12 months using the solvent-free microwave extraction and traditional hydrodistillation methods were evaluated. The GC-MS analyses of the essential oils revealed the presence of 33 compounds with 1,8-cineole, a-pinene, camphor, verbenone, bornyl acetate and camphene constituting about 80 percent of the oils throughout the period of investigation, with the solvent-free microwave extraction method generally yielding more of the major components than the hydrodistillation method. Each of the major components of the oils varied in quantity and quality of yield at different periods of the year. The method of extraction and time of harvest are of importance to the quantity and quality of essential oil of Rosmarinus officinalis. Higher amounts of oxygenated monoterpenes such as borneol, camphor, terpene- 4-ol, linalool, a-terpeneol were present in the oil of SFME in comparison with HD. However, HD oil contained more monoterpene hydrocarbons such as a-pinene, camphene, β-pinene, myrcene, a-phellanderene, 1,8-cineole, trans- β-ocimene, γ-teprinene, and cis-sabinene hydrate than SFME extracted oil. Accumulation of monoterpene alcohols and ketones was observed during maturation process of Rosmarinus leaves. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration values were determined using a serial microplate dilution method. The essential oils obtained using both methods of extraction were active against all the bacteria tested at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the SFME extracted oils ranged between 0.23 and 1.88 mg mL-1, while those of the HD extracted oils varied between 0.94 and 7.5 mg mL-1, thus suggesting that the oil obtained by solvent free microwave extraction was more active against bacteria than the oil obtained through hydrodistillation. The antioxidant and free radical scavenging activity of the obtained oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay and β- carotene bleaching test. In the DPPH+ assay, while the free radical scavenging activity of the oil obtained by SFME method showed percentage inhibitions of between 48.8 percent and 67 percent, the HD derived oil showed inhibitions of between 52.2 percent and 65.30 percent at concentrations of 0.33, 0.50 and 1.0 mg mL-1, respectively. In the β-carotene bleaching assay, the percentage inhibition increased with increasing concentration of both oils with a higher antioxidant activity of the oil obtained through the SFME than the HD method. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i. e. CEF, BEA and EMW and sprayed with vanillin-sulfuric acid. The chemical composition of the different extracts was similar with the exception of methanol and water extracts which had only one or two visible compounds after treating with vanillin-spray reagent. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against two most important nosocomial microorganisms. S. aureus (Gram positive) and E. coli (Gram negative). Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of E. coli. The hexane extract had the most lines of inhibition followed by ethyl acetate. Bioassay-guided fractionation against E. coli was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the hexane fraction. Furthermore we tried to complete the characterization by extracting and studying other biologically important plant metabolites such as phenolic compounds to evaluate the antioxidant capacity of Rosmarinus extracts
- Full Text:
- Date Issued: 2008
Verification of Ionospheric tomography using MIDAS over Grahamstown, South Africa
- Authors: Katamzi, Zama Thobeka
- Date: 2008
- Subjects: Ionosphere -- Remote sensing -- South Africa , Atmosphere, Upper , Tomography -- Scientific applications -- South Africa , Global Positioning System
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5497 , http://hdl.handle.net/10962/d1005283 , Ionosphere -- Remote sensing -- South Africa , Atmosphere, Upper , Tomography -- Scientific applications -- South Africa , Global Positioning System
- Description: Global Positioning System (GPS) satellites and receivers are used to derive total electron content (TEC) from the time delay and phase advance of the radiowaves as they travels through the ionosphere. TEC is defined as the integralof the electron density along the satellite-receiver signal path. Electron densityprofiles can be determined from these TEC values using ionospheric tomographic inversion techniques such as Multi-Instrument Data Analysis System (MIDAS).This thesis reports on a study aimed at evaluating the suitability of ionospheric tomography as a tool to derive one-dimensional electron density profiles, using the MIDAS inversion algorithm over Grahamstown, South Africa (33.30◦S, 26.50◦E). The evaluation was done by using ionosonde data from the Louisvale (28.50◦S, 21.20◦E) and Madimbo (22.40◦S, 30.90◦E) stations to create empirical orthonormal functions (EOFs). These EOFs were used by MIDAS in the inversion process to describe the vertical variation of the electron density. Profiles derived from the MIDAS algorithm were compared with profiles obtained from the international Reference Ionosphere (IRI) 2001 model and with ionosonde profiles from the Grahamstown ionosonde station. The optimised MIDAS profiles show a good agreement with the Grahamstown ionosonde profiles. The South African Bottomside Ionospheric Model (SABIM) was used to set the limits within which MIDAS was producing accurate peak electron density (NmF2) values and to define accuracy in this project, with the understanding that the national model (SABIM) is currently the best model for the Grahamstown region. Analysis show that MIDAS produces accurate results during the winter season, which had the lowest root mean square (rms) error of 0.37×1011[e/m3] and an approximately 86% chance of producing NmF2 closer to the actual NmF2 value than the national model SABIM. MIDAS was found to also produce accurate NmF2 values at 12h00 UT, where an approximately 88% chance of producing an accurate NmF2 value, which may deviate from the measured value by 0.72×1011[e/m3], was determined. In conclusion, ionospheric tomographic inversion techniques show promise in the reconstruction of electron density profiles over South Africa, and are worth pursuing further in the future.
- Full Text:
- Date Issued: 2008
- Authors: Katamzi, Zama Thobeka
- Date: 2008
- Subjects: Ionosphere -- Remote sensing -- South Africa , Atmosphere, Upper , Tomography -- Scientific applications -- South Africa , Global Positioning System
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5497 , http://hdl.handle.net/10962/d1005283 , Ionosphere -- Remote sensing -- South Africa , Atmosphere, Upper , Tomography -- Scientific applications -- South Africa , Global Positioning System
- Description: Global Positioning System (GPS) satellites and receivers are used to derive total electron content (TEC) from the time delay and phase advance of the radiowaves as they travels through the ionosphere. TEC is defined as the integralof the electron density along the satellite-receiver signal path. Electron densityprofiles can be determined from these TEC values using ionospheric tomographic inversion techniques such as Multi-Instrument Data Analysis System (MIDAS).This thesis reports on a study aimed at evaluating the suitability of ionospheric tomography as a tool to derive one-dimensional electron density profiles, using the MIDAS inversion algorithm over Grahamstown, South Africa (33.30◦S, 26.50◦E). The evaluation was done by using ionosonde data from the Louisvale (28.50◦S, 21.20◦E) and Madimbo (22.40◦S, 30.90◦E) stations to create empirical orthonormal functions (EOFs). These EOFs were used by MIDAS in the inversion process to describe the vertical variation of the electron density. Profiles derived from the MIDAS algorithm were compared with profiles obtained from the international Reference Ionosphere (IRI) 2001 model and with ionosonde profiles from the Grahamstown ionosonde station. The optimised MIDAS profiles show a good agreement with the Grahamstown ionosonde profiles. The South African Bottomside Ionospheric Model (SABIM) was used to set the limits within which MIDAS was producing accurate peak electron density (NmF2) values and to define accuracy in this project, with the understanding that the national model (SABIM) is currently the best model for the Grahamstown region. Analysis show that MIDAS produces accurate results during the winter season, which had the lowest root mean square (rms) error of 0.37×1011[e/m3] and an approximately 86% chance of producing NmF2 closer to the actual NmF2 value than the national model SABIM. MIDAS was found to also produce accurate NmF2 values at 12h00 UT, where an approximately 88% chance of producing an accurate NmF2 value, which may deviate from the measured value by 0.72×1011[e/m3], was determined. In conclusion, ionospheric tomographic inversion techniques show promise in the reconstruction of electron density profiles over South Africa, and are worth pursuing further in the future.
- Full Text:
- Date Issued: 2008
Viewpoint: reading conference recommendations in a wider context of social change
- Authors: Lotz-Sisitka, Heila
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67411 , vital:29085 , https://www.ajol.info/index.php/sajee/article/view/122783
- Description: publisher version , This short Viewpoint paper considers the role and value of conference recommendations in shaping the field of environmental education. It explores the social politics, and often contested nature, of conference recommendations and their institutional histories, arguing that the act of producing conference recommendations forms part of the practices of new social movements. The paper recommends historicising conference recommendations and OEcross readings‚ to consider changing discourses and new developments in the field. Accompanying the short Viewpoint paper, are two sets of recently produced conference recommendations, one from the 4th International Environmental Education Conference held in Ahmedabad, India, and the other from the 1st International Conference on Mainstreaming Environment and Sustainability in African Universities held in Nairobi, Kenya.
- Full Text:
- Date Issued: 2008
- Authors: Lotz-Sisitka, Heila
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67411 , vital:29085 , https://www.ajol.info/index.php/sajee/article/view/122783
- Description: publisher version , This short Viewpoint paper considers the role and value of conference recommendations in shaping the field of environmental education. It explores the social politics, and often contested nature, of conference recommendations and their institutional histories, arguing that the act of producing conference recommendations forms part of the practices of new social movements. The paper recommends historicising conference recommendations and OEcross readings‚ to consider changing discourses and new developments in the field. Accompanying the short Viewpoint paper, are two sets of recently produced conference recommendations, one from the 4th International Environmental Education Conference held in Ahmedabad, India, and the other from the 1st International Conference on Mainstreaming Environment and Sustainability in African Universities held in Nairobi, Kenya.
- Full Text:
- Date Issued: 2008
Visit to my mother
- Authors: Berold, Robert
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , poem
- Identifier: http://hdl.handle.net/10962/462525 , vital:76311 , ISBN 0028-4459 , https://journals.co.za/doi/epdf/10.10520/EJC47798
- Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
- Full Text:
- Date Issued: 2008
- Authors: Berold, Robert
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , poem
- Identifier: http://hdl.handle.net/10962/462525 , vital:76311 , ISBN 0028-4459 , https://journals.co.za/doi/epdf/10.10520/EJC47798
- Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
- Full Text:
- Date Issued: 2008
Volcano correlations for the reactivity of surface-confined cobalt N4-macrocyclics for the electrocatalytic oxidation of 2-mercaptoacetate
- Claußen, Jan A, Ochoa, Gonzalo, Páez, Maritza, Costamagno, Juan, Gulppi, Miguel, Nyokong, Tebello, Bedioui, Fethi, Zagal, José H
- Authors: Claußen, Jan A , Ochoa, Gonzalo , Páez, Maritza , Costamagno, Juan , Gulppi, Miguel , Nyokong, Tebello , Bedioui, Fethi , Zagal, José H
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268688 , vital:54222 , xlink:href="https://doi.org/10.1007/s10008-007-0336-y"
- Description: We have investigated the electrocatalytic activity of several substituted and unsubstituted cobalt–phthalocyanines of substituted tetraphenyl porphyrins and of vitamin B12, for the electro-oxidation of 2-mercaptoacetate, with the complexes pre-adsorbed on a pyrolytic graphite electrode. Several N4-macrocyclic were used to have a wide variety of Co(II)/(I) formal potentials. The electrocatalytic activity, measured as current at constant potential, increases with the Co(II)/(I) redox potential for porphyrins as Co–pentafluorotetraphenylporphyrin larger than Co–tetrasulfonatotetraphenylporphyrin larger than Co-2,2′,2″,2‴tetra-aminotetraphenylporphyrin and decreases for cobalt phthalocyanines as Co-3,4-octaethylhexyloxyphthalocyanine > Co–octamethoxyphthalocyanine > Co–tetranitrophthalocyanine Co–tetraaminophthalocyanine > Co–unsubstituted phthalocyanine > Co–tetrasulfonatophthalocyanine > Co–perfluorinated phthalocyanine. Vitamin B12 exhibits the maximum activity. A correlation of log I (at constant potential) versus the Co(II)/(I) formal potential of the catalysts gives a volcano curve. This clearly shows that the search for better catalysts for this reaction point to those N4-macrocyclic complexes with Co(II)/(I) formal potentials close to −0.84 V versus SCE, which correspond to an optimum situation for the interaction of the thiol with the active site.
- Full Text:
- Date Issued: 2008
- Authors: Claußen, Jan A , Ochoa, Gonzalo , Páez, Maritza , Costamagno, Juan , Gulppi, Miguel , Nyokong, Tebello , Bedioui, Fethi , Zagal, José H
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268688 , vital:54222 , xlink:href="https://doi.org/10.1007/s10008-007-0336-y"
- Description: We have investigated the electrocatalytic activity of several substituted and unsubstituted cobalt–phthalocyanines of substituted tetraphenyl porphyrins and of vitamin B12, for the electro-oxidation of 2-mercaptoacetate, with the complexes pre-adsorbed on a pyrolytic graphite electrode. Several N4-macrocyclic were used to have a wide variety of Co(II)/(I) formal potentials. The electrocatalytic activity, measured as current at constant potential, increases with the Co(II)/(I) redox potential for porphyrins as Co–pentafluorotetraphenylporphyrin larger than Co–tetrasulfonatotetraphenylporphyrin larger than Co-2,2′,2″,2‴tetra-aminotetraphenylporphyrin and decreases for cobalt phthalocyanines as Co-3,4-octaethylhexyloxyphthalocyanine > Co–octamethoxyphthalocyanine > Co–tetranitrophthalocyanine Co–tetraaminophthalocyanine > Co–unsubstituted phthalocyanine > Co–tetrasulfonatophthalocyanine > Co–perfluorinated phthalocyanine. Vitamin B12 exhibits the maximum activity. A correlation of log I (at constant potential) versus the Co(II)/(I) formal potential of the catalysts gives a volcano curve. This clearly shows that the search for better catalysts for this reaction point to those N4-macrocyclic complexes with Co(II)/(I) formal potentials close to −0.84 V versus SCE, which correspond to an optimum situation for the interaction of the thiol with the active site.
- Full Text:
- Date Issued: 2008
Walter Oakley West (1930-2007) : obituary
- Authors: Lewis, Colin A
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6703 , http://hdl.handle.net/10962/d1006739
- Full Text:
- Date Issued: 2008
- Authors: Lewis, Colin A
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6703 , http://hdl.handle.net/10962/d1006739
- Full Text:
- Date Issued: 2008
Water quality, abalone growth and the potential for integrated mariculture on a South African abalone Haliotis midae L. farm
- Authors: Yearsley, Rowan David
- Date: 2008
- Subjects: Abalones -- South Africa Abalone culture -- South Africa Abalones -- Growth Mariculture -- South Africa Water quality -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5334 , http://hdl.handle.net/10962/d1005180
- Description: Abalone Haliotis midae farming in South Africa is highly intensive, employing pump-ashore, flow-through systems. Despite the known sensitivity of abalone to water quality, there is only a rudimentary understanding of water quality dynamics on South African abalone farms and its effects on abalone production. Furthermore, the potential for reusing the relatively dilute abalone farm effluent to culture other animal species has not been investigated. This study investigated the dynamics of water quality and growth on a South African abalone farm and assessed the suitability of the effluent for the culture of silver kob Argyrosomus inodorus and bloodworm Arenicola loveni loveni. Monitoring of water quality and abalone growth in abalone tanks revealed that oxygen concentrations decreased, while H⁺ ion and free-ammonia (NH₃) concentration increased in a gradient between the inflow and outflow. Abalone growth was positively correlated with oxygen concentration and negatively correlated with free-ammonia and H⁺ ion concentration. The oxygen (O) concentration of the farm influent was dependent upon the influents’ temperature (T) and was described by the relationship O (mg L⁻¹) = 11.244 – 0.208T (r²=0.74). Linear regression analysis of data collected from abalone farm tanks revealed that the concentration of total ammonia at the outflow of abalone tanks (μg TAN L⁻¹) was dependant upon temperature (°C), flow-rate (L s⁻¹ kg⁻¹ H. midae), abalone size (g) and length of time since the tank was last cleaned (d) (n = 125, r² = 0.80). The production of total ammonia (μg TAN s⁻¹ kg⁻¹) was related to temperature, abalone size and days that the tanks remained un-cleaned (n = 125; r² = 0.81). A diurnal cycle of respiration was evident in abalone tanks with higher oxygen consumption and H+ ion production at night. The oxygen concentration of farm effluent was related to temperature, farm biomass and flow rate by means of a linear regression equation (n = 40; r² = 0.69). The results demonstrated the importance of optimising the flow-rate per unit of biomass for various temperatures and sizes of abalone. As abalone size and temperature cannot be controlled under farm conditions, the flow-rate per unit of biomass which the abalone culture system receives will determine the quality of the culture water. The specific growth rate (0.48 ± 0.01 % BW d⁻¹), mortality (1.8 ± 0.5 %), feed conversion ratio (3.0 ± 0.2) and protein efficiency ratio (1.0 ± 0.1) of silver kob kept in either abalone farm effluent or control seawater for 120 days did not differ significantly (t-test, P>0.05). A 90 day growth trial indicated that abalone farm effluent is a suitable culture medium for bloodworm. Bloodworm supplied with control seawater lost weight at 0.19 ± 0.04 % BW d-1, while those given abalone effluent grew at 0.39 ± 0.07 % BW d⁻¹. Mortality was 6 ± 3 % in effluent and 11 ± 8 % in seawater. The bloodworm were efficient at processing solid waste. Abalone farm effluent initially contained 7.7 ± 13 mg L⁻¹ more suspended solids than control seawater, which contained 3.5 ± 0.5 mg L⁻¹, but after passing through bloodworm systems the concentration in abalone effluent was reduced to only 1.4 ± 3.5 mg L⁻¹ above that in control seawater. Therefore, abalone farm effluent could be reused as a culture medium for both silver kob and bloodworm. Future work is needed to investigate aspects of the feasibility of such systems such as growth rates at different sizes and stocking densities.
- Full Text:
- Date Issued: 2008
- Authors: Yearsley, Rowan David
- Date: 2008
- Subjects: Abalones -- South Africa Abalone culture -- South Africa Abalones -- Growth Mariculture -- South Africa Water quality -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5334 , http://hdl.handle.net/10962/d1005180
- Description: Abalone Haliotis midae farming in South Africa is highly intensive, employing pump-ashore, flow-through systems. Despite the known sensitivity of abalone to water quality, there is only a rudimentary understanding of water quality dynamics on South African abalone farms and its effects on abalone production. Furthermore, the potential for reusing the relatively dilute abalone farm effluent to culture other animal species has not been investigated. This study investigated the dynamics of water quality and growth on a South African abalone farm and assessed the suitability of the effluent for the culture of silver kob Argyrosomus inodorus and bloodworm Arenicola loveni loveni. Monitoring of water quality and abalone growth in abalone tanks revealed that oxygen concentrations decreased, while H⁺ ion and free-ammonia (NH₃) concentration increased in a gradient between the inflow and outflow. Abalone growth was positively correlated with oxygen concentration and negatively correlated with free-ammonia and H⁺ ion concentration. The oxygen (O) concentration of the farm influent was dependent upon the influents’ temperature (T) and was described by the relationship O (mg L⁻¹) = 11.244 – 0.208T (r²=0.74). Linear regression analysis of data collected from abalone farm tanks revealed that the concentration of total ammonia at the outflow of abalone tanks (μg TAN L⁻¹) was dependant upon temperature (°C), flow-rate (L s⁻¹ kg⁻¹ H. midae), abalone size (g) and length of time since the tank was last cleaned (d) (n = 125, r² = 0.80). The production of total ammonia (μg TAN s⁻¹ kg⁻¹) was related to temperature, abalone size and days that the tanks remained un-cleaned (n = 125; r² = 0.81). A diurnal cycle of respiration was evident in abalone tanks with higher oxygen consumption and H+ ion production at night. The oxygen concentration of farm effluent was related to temperature, farm biomass and flow rate by means of a linear regression equation (n = 40; r² = 0.69). The results demonstrated the importance of optimising the flow-rate per unit of biomass for various temperatures and sizes of abalone. As abalone size and temperature cannot be controlled under farm conditions, the flow-rate per unit of biomass which the abalone culture system receives will determine the quality of the culture water. The specific growth rate (0.48 ± 0.01 % BW d⁻¹), mortality (1.8 ± 0.5 %), feed conversion ratio (3.0 ± 0.2) and protein efficiency ratio (1.0 ± 0.1) of silver kob kept in either abalone farm effluent or control seawater for 120 days did not differ significantly (t-test, P>0.05). A 90 day growth trial indicated that abalone farm effluent is a suitable culture medium for bloodworm. Bloodworm supplied with control seawater lost weight at 0.19 ± 0.04 % BW d-1, while those given abalone effluent grew at 0.39 ± 0.07 % BW d⁻¹. Mortality was 6 ± 3 % in effluent and 11 ± 8 % in seawater. The bloodworm were efficient at processing solid waste. Abalone farm effluent initially contained 7.7 ± 13 mg L⁻¹ more suspended solids than control seawater, which contained 3.5 ± 0.5 mg L⁻¹, but after passing through bloodworm systems the concentration in abalone effluent was reduced to only 1.4 ± 3.5 mg L⁻¹ above that in control seawater. Therefore, abalone farm effluent could be reused as a culture medium for both silver kob and bloodworm. Future work is needed to investigate aspects of the feasibility of such systems such as growth rates at different sizes and stocking densities.
- Full Text:
- Date Issued: 2008
Water, salt and nutrient budgets of the Swartkops and Sundays river estuaries using the loicz biogeochemical budgeting protocol
- Authors: Potgieter, Matthys Johannes
- Date: 2008
- Subjects: Estuarine oceanography , Groundwater flow -- South Africa -- Swartkops River Estuary
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10705 , http://hdl.handle.net/10948/903 , Estuarine oceanography , Groundwater flow -- South Africa -- Swartkops River Estuary
- Description: The Swartkops River and Sundays River Estuaries are different in terms of morphology and the level of human impact. Budget models of DIP and DIN were constructed for each estuary at different riverine flow rates, using the Land-Ocean Interactions in the Coastal Zone (LOICZ) protocol. Nutrient dynamics in the estuaries were investigated using nutrient data and the results of the models. The Swartkops River Estuary acted as a sink of DIP and DIN, while being net heterotrophic. The Sundays River Estuary acted as a source of DIP and DIN, while being net autotrophic. Both systems were net denitrifying. The Swartkops River Estuary shows greater anthropogenic impacts in terms of nutrient loads than the Sundays River Estuary. A shift in nutrient concentration trends and system properties occurred between conditions of low and high riverine flow rates. The Swartkops River and Sundays River Estuaries were shown to be ‘outwellers’ of DIN and DIP, while having an important influence on the ratio of DIN:DIP exported to the adjacent ocean. Comparisons with other estuaries suggested that riverine flow into estuaries in the Eastern Cape region may display natural DIN:DIP ratios which are lower than the global average for “pristine” systems. Such ratios would be decreased further by increased water extraction for human activities.
- Full Text:
- Date Issued: 2008
- Authors: Potgieter, Matthys Johannes
- Date: 2008
- Subjects: Estuarine oceanography , Groundwater flow -- South Africa -- Swartkops River Estuary
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10705 , http://hdl.handle.net/10948/903 , Estuarine oceanography , Groundwater flow -- South Africa -- Swartkops River Estuary
- Description: The Swartkops River and Sundays River Estuaries are different in terms of morphology and the level of human impact. Budget models of DIP and DIN were constructed for each estuary at different riverine flow rates, using the Land-Ocean Interactions in the Coastal Zone (LOICZ) protocol. Nutrient dynamics in the estuaries were investigated using nutrient data and the results of the models. The Swartkops River Estuary acted as a sink of DIP and DIN, while being net heterotrophic. The Sundays River Estuary acted as a source of DIP and DIN, while being net autotrophic. Both systems were net denitrifying. The Swartkops River Estuary shows greater anthropogenic impacts in terms of nutrient loads than the Sundays River Estuary. A shift in nutrient concentration trends and system properties occurred between conditions of low and high riverine flow rates. The Swartkops River and Sundays River Estuaries were shown to be ‘outwellers’ of DIN and DIP, while having an important influence on the ratio of DIN:DIP exported to the adjacent ocean. Comparisons with other estuaries suggested that riverine flow into estuaries in the Eastern Cape region may display natural DIN:DIP ratios which are lower than the global average for “pristine” systems. Such ratios would be decreased further by increased water extraction for human activities.
- Full Text:
- Date Issued: 2008
WET-Origins: controls on the distribution and dynamics of wetlands in South Africa
- Ellery, William F N, Grenfell, Michael C, Grenfell, Suzanne E, Kotze, Donovan C, McCarthy, Terence S, Tooth, Stephen, Grundling, Piet-Louis, Beckedahl, Heinz, Le Maitre, David C, Ramsay, Lisa F
- Authors: Ellery, William F N , Grenfell, Michael C , Grenfell, Suzanne E , Kotze, Donovan C , McCarthy, Terence S , Tooth, Stephen , Grundling, Piet-Louis , Beckedahl, Heinz , Le Maitre, David C , Ramsay, Lisa F
- Date: 2008
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/176598 , vital:40091 , ISBN 978-77005-633-6 , https://www.wrc.org.za/mdocs-posts/wetland-management-series-wet-origins-controls-on-the-distribution-and-dynamics-of-wetlands-in-south-africa/
- Description: The need for wetland rehabilitation in South Africa is compelling: loss and degradation of wetlands have been great and national policy and legislation provide clear direction and support for rehabilitation. However, rehabilitating wetlands is often complex because wetlands and their links with people are complex (e.g. through the ways that people use wetlands and the different benefits that people receive from the ecosystem services that wetlands supply).
- Full Text:
- Date Issued: 2008
- Authors: Ellery, William F N , Grenfell, Michael C , Grenfell, Suzanne E , Kotze, Donovan C , McCarthy, Terence S , Tooth, Stephen , Grundling, Piet-Louis , Beckedahl, Heinz , Le Maitre, David C , Ramsay, Lisa F
- Date: 2008
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/176598 , vital:40091 , ISBN 978-77005-633-6 , https://www.wrc.org.za/mdocs-posts/wetland-management-series-wet-origins-controls-on-the-distribution-and-dynamics-of-wetlands-in-south-africa/
- Description: The need for wetland rehabilitation in South Africa is compelling: loss and degradation of wetlands have been great and national policy and legislation provide clear direction and support for rehabilitation. However, rehabilitating wetlands is often complex because wetlands and their links with people are complex (e.g. through the ways that people use wetlands and the different benefits that people receive from the ecosystem services that wetlands supply).
- Full Text:
- Date Issued: 2008
What future subordinates will value in their leaders
- Cox, Andrea, Amos, Trevor L, Baxter, Jeremy
- Authors: Cox, Andrea , Amos, Trevor L , Baxter, Jeremy
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270992 , vital:54499 , xlink:href="https://hdl.handle.net/10520/EJC51031"
- Description: Leaders should not randomly choose a leadership style. To be effective, leaders need to ensure that their leadership style is congruent with what subordinates value. The focus of this study is on what the future South African graduate workforce will value in a leader. The female and male respondents in this study emphasise similar leadership values, indicating that there is no distinct set of competencies that will be valued separately by males and females. The same was found for respondents of different cultures, namely African, Coloured, Indian, White and other. With respect to both gender and culture, the respondents emphasise a mixture of African and Western leadership values. This supports the idea that to be effective in South Africa, leaders need to understand the prevailing national cultural values before simply applying ''foreign'' leadership models and theories based upon cultural values found in the West. This research finds that irrespective of gender and culture in the South African workplace, to be effective, leaders need to be loyal and inspirational, have vision and integrity and must be open and honest with their subordinates. Leaders should avoid being autocratic, strict, religious, ritualistic and traditional. They should also avoid using consensus and perceived external control.
- Full Text:
- Date Issued: 2008
- Authors: Cox, Andrea , Amos, Trevor L , Baxter, Jeremy
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270992 , vital:54499 , xlink:href="https://hdl.handle.net/10520/EJC51031"
- Description: Leaders should not randomly choose a leadership style. To be effective, leaders need to ensure that their leadership style is congruent with what subordinates value. The focus of this study is on what the future South African graduate workforce will value in a leader. The female and male respondents in this study emphasise similar leadership values, indicating that there is no distinct set of competencies that will be valued separately by males and females. The same was found for respondents of different cultures, namely African, Coloured, Indian, White and other. With respect to both gender and culture, the respondents emphasise a mixture of African and Western leadership values. This supports the idea that to be effective in South Africa, leaders need to understand the prevailing national cultural values before simply applying ''foreign'' leadership models and theories based upon cultural values found in the West. This research finds that irrespective of gender and culture in the South African workplace, to be effective, leaders need to be loyal and inspirational, have vision and integrity and must be open and honest with their subordinates. Leaders should avoid being autocratic, strict, religious, ritualistic and traditional. They should also avoid using consensus and perceived external control.
- Full Text:
- Date Issued: 2008
When commercial can also be community:
- Authors: du Toit, Peter , Rau, Asta
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159322 , vital:40287 , https://hdl.handle.net/10520/EJC140094
- Description: Questions of ownership, control and profit distribution are widely used to distinguish between commercial and community media ventures, but an over-reliance on such distinctions may eclipse other important considerations in a way that impacts negatively on media diversity.
- Full Text:
- Date Issued: 2008
- Authors: du Toit, Peter , Rau, Asta
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159322 , vital:40287 , https://hdl.handle.net/10520/EJC140094
- Description: Questions of ownership, control and profit distribution are widely used to distinguish between commercial and community media ventures, but an over-reliance on such distinctions may eclipse other important considerations in a way that impacts negatively on media diversity.
- Full Text:
- Date Issued: 2008
Whole body vibration training and physical fitness of persons with diabetes melitus type II
- Authors: Bekker, Lindy
- Date: 2008
- Subjects: Diabetes -- Exercise therapy , Vibration -- Physiological effect
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10096 , http://hdl.handle.net/10948/672 , Diabetes -- Exercise therapy , Vibration -- Physiological effect
- Description: The aim of this study was to determine the effect of whole body vibration training on selected health and fitness parameters, including: blood glucose levels, blood pressure, anthropometric profile, muscular flexibility, muscular strength, muscular endurance, and aerobic endurance of persons with diabetes mellitus type II. The study was conducted in a descriptive, explorative manner utilizing a quasiexperimental design with an equistatic approach, employing match-pair design to participant grouping. The experimental design was a non-randomized two-group pre- and post-test design, in which approximately 16 male and female participants, who were chosen through convenience and snowball sampling with diabetes mellitus type II, completed the study. Pre- and post-test analysis was performed at the Biokinetics and Sport Science Unit. The whole body vibration training (experimental) group, trained three times a week for a period of ten weeks, performing exercises on the vibration platform with progressive increments in the intensity, duration, and number of the exercises. The control group remained sedentary throughout the intervention period. The dependant variables were analyzed using descriptive statistics. ANOVA was done to determine pre- and post-test differences for both the experimental and control groups for all the variables. Post-Hoc analysis was done to determine and compare differences which may have existed between the experimental and control groups, with practical significance being determined by Cohen’s D analysis. The analysis of the results revealed significant improvements in systolic blood pressure, muscular strength, muscular endurance, and aerobic endurance.
- Full Text:
- Date Issued: 2008
- Authors: Bekker, Lindy
- Date: 2008
- Subjects: Diabetes -- Exercise therapy , Vibration -- Physiological effect
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10096 , http://hdl.handle.net/10948/672 , Diabetes -- Exercise therapy , Vibration -- Physiological effect
- Description: The aim of this study was to determine the effect of whole body vibration training on selected health and fitness parameters, including: blood glucose levels, blood pressure, anthropometric profile, muscular flexibility, muscular strength, muscular endurance, and aerobic endurance of persons with diabetes mellitus type II. The study was conducted in a descriptive, explorative manner utilizing a quasiexperimental design with an equistatic approach, employing match-pair design to participant grouping. The experimental design was a non-randomized two-group pre- and post-test design, in which approximately 16 male and female participants, who were chosen through convenience and snowball sampling with diabetes mellitus type II, completed the study. Pre- and post-test analysis was performed at the Biokinetics and Sport Science Unit. The whole body vibration training (experimental) group, trained three times a week for a period of ten weeks, performing exercises on the vibration platform with progressive increments in the intensity, duration, and number of the exercises. The control group remained sedentary throughout the intervention period. The dependant variables were analyzed using descriptive statistics. ANOVA was done to determine pre- and post-test differences for both the experimental and control groups for all the variables. Post-Hoc analysis was done to determine and compare differences which may have existed between the experimental and control groups, with practical significance being determined by Cohen’s D analysis. The analysis of the results revealed significant improvements in systolic blood pressure, muscular strength, muscular endurance, and aerobic endurance.
- Full Text:
- Date Issued: 2008
Whole body vibration training effects on asthma specific pulmonary variables
- Authors: Mansell, Ingrid Joan
- Date: 2008
- Subjects: Vibration -- Physiological effect , Asthma -- Exercise therapy , Asthma -- Treatment
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10112 , http://hdl.handle.net/10948/d1020953
- Description: The aim of the study was to determine and document evidence of the comparative effect of a 12- week whole body vibration training programme, exercise training programme and sedentary control group on the anthropometric profile, aerobic capacity, lung volumes and hence, the pulmonary capacity in people with asthma. The study used a descriptive, exploratory, quasi-experimental research approach employing randomised pairing to classify participants into either the whole body vibration therapy or exercise training group. Accidental and snowball sampling was used to identify and obtain a base of volunteers. A three-group pre-test/post-test design was employed to gain insight into statistical differences that might be apparent between the whole body vibration therapy group, the exercise group and the control group, and which could potentially be attributed to participation in the whole body vibration exercise programme. Randomised pairing for participant selection was selected because of the potential effects varying pulmonary variables might have had on the reliability of the study. A Physical Activity Selection Criteria Questionnaire was completed by participants to ascertain baseline physical activity readiness and as a means of determining selection criteria for their allocation to the whole body vibration training group, the experimental exercise group or the true control group. The pre-test/post-test assessment made use of a combination evaluation that incorporated an anthropometric profile assessment of height, weight, biceps, triceps, subscapular and suprailliac skinfolds, waist and hip circumference and posture, an aerobic capacity evaluation that incorporated aspects of both the YMCA and Astrand and Rhyming Physical Work Capacity (PWC) evaluation on a cycle ergometer and, lastly, a pulmonary variable assessment that made use of both the Datospir Peak-10 peak flow meter and the Spirovit SP-100AT spirometry unit integrated into the Cardiovit AT-6 model for all spirometry measurements. Participants were required to complete either the whole-body vibration or the exercise training programme a minimum of twice a week and a maximum of four times over the same period. The duration of the intervention programmes was approximately 30 minutes and consisted of three sections including a warm-up comprising flexibility exercises, whole body strength training exercises, and a cool-down which, in turn, consisted of massage exercises or replicated flexibility exercises. The main difference between the whole body vibration and exercise training group thus lay in the exclusion of the use of vibration for those participants assigned to the exercise training programme. Analysis of data was performed using descriptive and inferential statistics with the help of a qualified statistician. The identified variables were tested at a 95 percent level of probability (p<0.05) as recommended by Thomas and Nelson (1996:117). Descriptive data, in the form of a statistical mean, standard deviation, minimum, median and maximum values, obtained during this study were reported in the form of a t-score for selected anthropometric and pulmonary variables. The 12-week intervention programme, on analysis of the results, produced statistically insignificant improvements in the variables of anthropometric profile, aerobic capacity and lung volumes identified as determinants of, and factors influencing, the cardiorespiratory fitness level of participants with asthma and hence, the subsequent severity of this chronic condition. However, slight mean increases for the whole body vibration training group were evident for certain variables identified in this study. Based on the results, the inference could be made that whole body vibration therapy and exercise were both effective modes of training to improve the cardiorespiratory fitness level of people with asthma, but the results of the study did not show sufficient practical or statistical significance to verify the assumption that whole body vibration training was a method superior to conventional exercise training. Hence, the significance of whole body vibration training on the pulmonary variables of people with asthma could not be determined. The researcher recommends that future studies be undertaken to verify whether whole body vibration training incorporating larger participant groups could produce significant improvements in pulmonary variables in people with asthma.
- Full Text:
- Date Issued: 2008
- Authors: Mansell, Ingrid Joan
- Date: 2008
- Subjects: Vibration -- Physiological effect , Asthma -- Exercise therapy , Asthma -- Treatment
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10112 , http://hdl.handle.net/10948/d1020953
- Description: The aim of the study was to determine and document evidence of the comparative effect of a 12- week whole body vibration training programme, exercise training programme and sedentary control group on the anthropometric profile, aerobic capacity, lung volumes and hence, the pulmonary capacity in people with asthma. The study used a descriptive, exploratory, quasi-experimental research approach employing randomised pairing to classify participants into either the whole body vibration therapy or exercise training group. Accidental and snowball sampling was used to identify and obtain a base of volunteers. A three-group pre-test/post-test design was employed to gain insight into statistical differences that might be apparent between the whole body vibration therapy group, the exercise group and the control group, and which could potentially be attributed to participation in the whole body vibration exercise programme. Randomised pairing for participant selection was selected because of the potential effects varying pulmonary variables might have had on the reliability of the study. A Physical Activity Selection Criteria Questionnaire was completed by participants to ascertain baseline physical activity readiness and as a means of determining selection criteria for their allocation to the whole body vibration training group, the experimental exercise group or the true control group. The pre-test/post-test assessment made use of a combination evaluation that incorporated an anthropometric profile assessment of height, weight, biceps, triceps, subscapular and suprailliac skinfolds, waist and hip circumference and posture, an aerobic capacity evaluation that incorporated aspects of both the YMCA and Astrand and Rhyming Physical Work Capacity (PWC) evaluation on a cycle ergometer and, lastly, a pulmonary variable assessment that made use of both the Datospir Peak-10 peak flow meter and the Spirovit SP-100AT spirometry unit integrated into the Cardiovit AT-6 model for all spirometry measurements. Participants were required to complete either the whole-body vibration or the exercise training programme a minimum of twice a week and a maximum of four times over the same period. The duration of the intervention programmes was approximately 30 minutes and consisted of three sections including a warm-up comprising flexibility exercises, whole body strength training exercises, and a cool-down which, in turn, consisted of massage exercises or replicated flexibility exercises. The main difference between the whole body vibration and exercise training group thus lay in the exclusion of the use of vibration for those participants assigned to the exercise training programme. Analysis of data was performed using descriptive and inferential statistics with the help of a qualified statistician. The identified variables were tested at a 95 percent level of probability (p<0.05) as recommended by Thomas and Nelson (1996:117). Descriptive data, in the form of a statistical mean, standard deviation, minimum, median and maximum values, obtained during this study were reported in the form of a t-score for selected anthropometric and pulmonary variables. The 12-week intervention programme, on analysis of the results, produced statistically insignificant improvements in the variables of anthropometric profile, aerobic capacity and lung volumes identified as determinants of, and factors influencing, the cardiorespiratory fitness level of participants with asthma and hence, the subsequent severity of this chronic condition. However, slight mean increases for the whole body vibration training group were evident for certain variables identified in this study. Based on the results, the inference could be made that whole body vibration therapy and exercise were both effective modes of training to improve the cardiorespiratory fitness level of people with asthma, but the results of the study did not show sufficient practical or statistical significance to verify the assumption that whole body vibration training was a method superior to conventional exercise training. Hence, the significance of whole body vibration training on the pulmonary variables of people with asthma could not be determined. The researcher recommends that future studies be undertaken to verify whether whole body vibration training incorporating larger participant groups could produce significant improvements in pulmonary variables in people with asthma.
- Full Text:
- Date Issued: 2008