Isolation, propagation and rapid molecular detection of the Kalahari truffle, a mycorrhizal fungus occurring in South Africa
- Authors: Adeleke, Rasheed Adegbola
- Date: 2007 , 2013-04-03
- Subjects: Truffles -- Kalahari Desert , Fungi -- Identification , Mycorrhizal fungi -- South Africa , Edible fungi -- South Africa , Mushroom culture -- South Africa , Fungi -- Cultures and culture media -- South Africa , Truffles -- South Africa , Truffles -- Lifecycles , Mycorrhizal fungi -- Lifecycles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3889 , http://hdl.handle.net/10962/d1002951 , Truffles -- Kalahari Desert , Fungi -- Identification , Mycorrhizal fungi -- South Africa , Edible fungi -- South Africa , Mushroom culture -- South Africa , Fungi -- Cultures and culture media -- South Africa , Truffles -- South Africa , Truffles -- Lifecycles , Mycorrhizal fungi -- Lifecycles
- Description: Terfezia pfeilii is an edible mycorrhizal fungus that thrives in the Kalahari Desert of southern Africa. It is best known by desert dwellers for its flavour and as a source of nutrition. Although the genus Terfezia is generally regarded as being an ectomycorrhizal mycobiont, the exact mycorrhizal type formed by T. pfeilli and its' associated host plants remains uncertain. Discovery of the host plants for T. pfeilii would first be required in order to further investigate the life cycle and cultivation of this truffle. This study focussed on the isolation of mycelia from the ascocarp, optimising the growth conditions of the mycelial cultures, rapid molecular identification of T. pfeilii, investigation of potential helper bacteria and mycorrhizal synthesis experiments. T. pfeilii ascocarps were harvested from the Spitskop Nature Reserve in Upington, South Africa. Ascocarps were successfully identified using both morphological and molecular methods. Despite the delayed growth mostly caused by contaminating microorganisms, the isolation of T. pfeilii mycelia culture was successful. Molecular techniques were used to confirm the identity of the pure culture. Further studies were conducted on ways to improve the growth conditions of the mycelial culture on Fontana medium. An optimum temperature of 32°C, the addition of Bovine Serum Albumin as a nitrogen source and a pH of 7.5 significantly improved the growth of T. pfeilii in vitro. A rapid PeR-based molecular method was developed to speed up the identification of T. pfeilii. Specific primers that can exclusively amplify the ITS region of T. pfeilii were designed and used to identify both the ascocarps and the mycelial culture. The specificity of these primers was confirmed by their inability to amplify DNA from the isolates of contamining fungi obtained during the isolation process. Molecular comparison was made to confirm the reclassification of South African samples of T. pfeilii as Kalaharituber pfeilii as proposed by Ferdman et al.,(2005). However, in this study, the name T. pfeilii has been retained. A total of 17 bacterial isolates were obtained from the fruiting bodies of T. pfeaii and these were tested for stimulation of mycelial growth in vitro, indole production and phosphate solubilising capabilities. Bacterial isolates that showed potential to be Mycorrhization Helper Bacteria (MHB) were identified as Paenibacillus sp., Bacillus sp. and Rhizobium tropici. Selected plant seedlings were inoculated with T. pfeilii cultures or ascocarp slurry in order to re-establish the mycorrhizal association. After 8 months, light microscopy observations revealed an endomycorrhizal type association between Cynodon dactylon and T. pfeilii. This was confirmed with molecular analysis using specific T. pfeilii ITS primers. After 15 months, molecular methods confirmed Acacia erioloba as another host plant. These results have provided essential information paving the way for further investigation into the life cycle and biology of the Kalahari truffle. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Authors: Adeleke, Rasheed Adegbola
- Date: 2007 , 2013-04-03
- Subjects: Truffles -- Kalahari Desert , Fungi -- Identification , Mycorrhizal fungi -- South Africa , Edible fungi -- South Africa , Mushroom culture -- South Africa , Fungi -- Cultures and culture media -- South Africa , Truffles -- South Africa , Truffles -- Lifecycles , Mycorrhizal fungi -- Lifecycles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3889 , http://hdl.handle.net/10962/d1002951 , Truffles -- Kalahari Desert , Fungi -- Identification , Mycorrhizal fungi -- South Africa , Edible fungi -- South Africa , Mushroom culture -- South Africa , Fungi -- Cultures and culture media -- South Africa , Truffles -- South Africa , Truffles -- Lifecycles , Mycorrhizal fungi -- Lifecycles
- Description: Terfezia pfeilii is an edible mycorrhizal fungus that thrives in the Kalahari Desert of southern Africa. It is best known by desert dwellers for its flavour and as a source of nutrition. Although the genus Terfezia is generally regarded as being an ectomycorrhizal mycobiont, the exact mycorrhizal type formed by T. pfeilli and its' associated host plants remains uncertain. Discovery of the host plants for T. pfeilii would first be required in order to further investigate the life cycle and cultivation of this truffle. This study focussed on the isolation of mycelia from the ascocarp, optimising the growth conditions of the mycelial cultures, rapid molecular identification of T. pfeilii, investigation of potential helper bacteria and mycorrhizal synthesis experiments. T. pfeilii ascocarps were harvested from the Spitskop Nature Reserve in Upington, South Africa. Ascocarps were successfully identified using both morphological and molecular methods. Despite the delayed growth mostly caused by contaminating microorganisms, the isolation of T. pfeilii mycelia culture was successful. Molecular techniques were used to confirm the identity of the pure culture. Further studies were conducted on ways to improve the growth conditions of the mycelial culture on Fontana medium. An optimum temperature of 32°C, the addition of Bovine Serum Albumin as a nitrogen source and a pH of 7.5 significantly improved the growth of T. pfeilii in vitro. A rapid PeR-based molecular method was developed to speed up the identification of T. pfeilii. Specific primers that can exclusively amplify the ITS region of T. pfeilii were designed and used to identify both the ascocarps and the mycelial culture. The specificity of these primers was confirmed by their inability to amplify DNA from the isolates of contamining fungi obtained during the isolation process. Molecular comparison was made to confirm the reclassification of South African samples of T. pfeilii as Kalaharituber pfeilii as proposed by Ferdman et al.,(2005). However, in this study, the name T. pfeilii has been retained. A total of 17 bacterial isolates were obtained from the fruiting bodies of T. pfeaii and these were tested for stimulation of mycelial growth in vitro, indole production and phosphate solubilising capabilities. Bacterial isolates that showed potential to be Mycorrhization Helper Bacteria (MHB) were identified as Paenibacillus sp., Bacillus sp. and Rhizobium tropici. Selected plant seedlings were inoculated with T. pfeilii cultures or ascocarp slurry in order to re-establish the mycorrhizal association. After 8 months, light microscopy observations revealed an endomycorrhizal type association between Cynodon dactylon and T. pfeilii. This was confirmed with molecular analysis using specific T. pfeilii ITS primers. After 15 months, molecular methods confirmed Acacia erioloba as another host plant. These results have provided essential information paving the way for further investigation into the life cycle and biology of the Kalahari truffle. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
Catalytic activities of metallophthalocyanines towards detection and transformation of pollutants
- Authors: Agboola, Bolade Oyeyinka
- Date: 2007
- Subjects: Phthalocyanines Electrochemistry Pollutants -- Biodegradation Pollutants -- Measurement
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4427 , http://hdl.handle.net/10962/d1006922
- Description: Syntheses, spectral, electrochemical and spectroelectrochemical studies of new thiol-derivatised MPc complexes were satisfactorily carried out. For the first time, spectroelectrochemistry gave evidence for the formation of Ni²⁺/Ni⁺ process in a NiPc complex. Significant insights as to the nature of Fe⁺Pc and Ni⁺Pc spectra were obtained. Transformations of chlorophenols using chemical and photochemical methods are presented. For cobalt tetrasulphophthalocyanine catalysed oxidation of chlorophenols using hydrogen peroxide as the oxidant, types of oxidation products formed depended on the solvent conditions. Photolysis of aqueous solutions of chlorophenols in the presence of immobilised non-transition metal phthalocyanine photosensitisers onto Amerlite® was carried out. For the first time, MPcS[subscript mix] complexes were immobilised on Amberlite® for use in heterogeneous photocatalysis. Photolysis of the chlorophenols resulted mainly in the formation of chlorobenzoquinone derivatives. The generation of singlet oxygen (¹O₂) by these immobilised MPc photosensitisers was found to play a major role in their photoactivities. Modifications of gold electrodes with the newly synthesised thiol-derivatised MPc complexes via electropolymerisation and SAM techniques are presented. Cyclic voltammetry, impedance spectroscopy (NiPcs only) and spectroelectrochemical techniques (NiPcs only) confirmed that the complexes formed films on gold electrodes. Stable and well packed SAM films as evidenced by the voltammetric characterisation were obtained. For the first time, optimisation of the time for SAM formation based on CV technique was studied. First example of a formation of MnPc-SAM was achieved. Catalytic activities of the NiPc towards chlorophenol depended on the nature of the NiPc in the polymer films and also anti-fouling ability of the films depended on polymer film thickness. The FeTBMPc polymer modified gold electrode showed the best catalytic activity in terms of peak potential, E[subscript p] when compared to reported work in literature for nitrate electrooxidation. Cyclic voltammetry and spectroscopy studies showed that the CoPcs, FePcs and NiPcs catalysed nitrite oxidation involve 2 electrons in total while that of McPcs involve 1 electron. Better catalytic performance towards sulphite electrooxidation were obtained for the CoPcs, FePcs and MnPcs which have metal based redox processes within the range of the sulphite electrooxidation peak while the NiPcs which did not show metal based oxidation reaction performed less.
- Full Text:
- Authors: Agboola, Bolade Oyeyinka
- Date: 2007
- Subjects: Phthalocyanines Electrochemistry Pollutants -- Biodegradation Pollutants -- Measurement
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4427 , http://hdl.handle.net/10962/d1006922
- Description: Syntheses, spectral, electrochemical and spectroelectrochemical studies of new thiol-derivatised MPc complexes were satisfactorily carried out. For the first time, spectroelectrochemistry gave evidence for the formation of Ni²⁺/Ni⁺ process in a NiPc complex. Significant insights as to the nature of Fe⁺Pc and Ni⁺Pc spectra were obtained. Transformations of chlorophenols using chemical and photochemical methods are presented. For cobalt tetrasulphophthalocyanine catalysed oxidation of chlorophenols using hydrogen peroxide as the oxidant, types of oxidation products formed depended on the solvent conditions. Photolysis of aqueous solutions of chlorophenols in the presence of immobilised non-transition metal phthalocyanine photosensitisers onto Amerlite® was carried out. For the first time, MPcS[subscript mix] complexes were immobilised on Amberlite® for use in heterogeneous photocatalysis. Photolysis of the chlorophenols resulted mainly in the formation of chlorobenzoquinone derivatives. The generation of singlet oxygen (¹O₂) by these immobilised MPc photosensitisers was found to play a major role in their photoactivities. Modifications of gold electrodes with the newly synthesised thiol-derivatised MPc complexes via electropolymerisation and SAM techniques are presented. Cyclic voltammetry, impedance spectroscopy (NiPcs only) and spectroelectrochemical techniques (NiPcs only) confirmed that the complexes formed films on gold electrodes. Stable and well packed SAM films as evidenced by the voltammetric characterisation were obtained. For the first time, optimisation of the time for SAM formation based on CV technique was studied. First example of a formation of MnPc-SAM was achieved. Catalytic activities of the NiPc towards chlorophenol depended on the nature of the NiPc in the polymer films and also anti-fouling ability of the films depended on polymer film thickness. The FeTBMPc polymer modified gold electrode showed the best catalytic activity in terms of peak potential, E[subscript p] when compared to reported work in literature for nitrate electrooxidation. Cyclic voltammetry and spectroscopy studies showed that the CoPcs, FePcs and NiPcs catalysed nitrite oxidation involve 2 electrons in total while that of McPcs involve 1 electron. Better catalytic performance towards sulphite electrooxidation were obtained for the CoPcs, FePcs and MnPcs which have metal based redox processes within the range of the sulphite electrooxidation peak while the NiPcs which did not show metal based oxidation reaction performed less.
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Implementation of learner-centred education by Grade 4 BETD in-service teachers in selected Namibia schools
- Authors: Amakali, Amram
- Date: 2007
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1849 , http://hdl.handle.net/10962/d1004457
- Description: Before independence Namibia's education system was predominantly teacher-centred. Soon after its independence Namibia embarked on education restructuring and transformation. A new education system, leamer-centred education, was introduced to cater for the needs of all Namibian learners. It was seen as an effective antidote to the stifling teacher-centred practices of the previous education system. A new programme, the Basic Education Teacher Diploma (BETD) was introduced to prepare teachers to teach in a leamer-centred approach. Research has, however, indicated that many Namibian teachers have a somewhat shallow or naIve understanding oflearner-centred education. This small-scale case study, conducted in Oshikoto region, focuses on two Grade 4 teachers. The study examined the two teachers ' perceptions and experiences oflearnercentred education and the teaching strategies they use to develop learners' understanding. The study uses a qualitative approach in its exploration of teachers ' lived experiences of becoming learner-centred. The data emerging from this case study identify a number of misconceptions and understandings of leamer-centred education and its implementation. The findings suggest that teachers ' misconceptions are caused by a lack of deep understanding about the epistemology and theory of learning which underpins Namibia's reform policies and principles.
- Full Text:
- Authors: Amakali, Amram
- Date: 2007
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1849 , http://hdl.handle.net/10962/d1004457
- Description: Before independence Namibia's education system was predominantly teacher-centred. Soon after its independence Namibia embarked on education restructuring and transformation. A new education system, leamer-centred education, was introduced to cater for the needs of all Namibian learners. It was seen as an effective antidote to the stifling teacher-centred practices of the previous education system. A new programme, the Basic Education Teacher Diploma (BETD) was introduced to prepare teachers to teach in a leamer-centred approach. Research has, however, indicated that many Namibian teachers have a somewhat shallow or naIve understanding oflearner-centred education. This small-scale case study, conducted in Oshikoto region, focuses on two Grade 4 teachers. The study examined the two teachers ' perceptions and experiences oflearnercentred education and the teaching strategies they use to develop learners' understanding. The study uses a qualitative approach in its exploration of teachers ' lived experiences of becoming learner-centred. The data emerging from this case study identify a number of misconceptions and understandings of leamer-centred education and its implementation. The findings suggest that teachers ' misconceptions are caused by a lack of deep understanding about the epistemology and theory of learning which underpins Namibia's reform policies and principles.
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An investigation of interpersonal relationships between management and lecturers in a College of Education in Namibia
- Amushigamo, Angelina Popyeni
- Authors: Amushigamo, Angelina Popyeni
- Date: 2007
- Subjects: Communication in education -- Namibia Teacher morale -- Namibia Employee motivation -- Namibia Teacher-administrator relationships -- Namibia College teachers -- Job satisfaction -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1850 , http://hdl.handle.net/10962/d1004458
- Description: Relationships are regarded as an important aspect of any organization's life. The purpose of this study was to investigate staff perceptions and experiences of interpersonal relationships between management and lecturers in a Namibian College of Education. I conducted a case study at the College where I teach. Two methods were used to collect data. Firstly, semi-structured interviews with two management members, two senior lecturers and two lecturers. Secondly, observation where practical aspects of interpersonal relationships in the College were observed. I used the interpretational data analysis technique to analyse my data. Themes and patterns were identified in the data, coded and sorted into categories. The study revealed staff unhappiness about the current situation in the College as far as communication is concerned. The College's hierarchical structure was described as top-down. As such, it does not allow for face to face communication. There is an absence of any social cohesion or sense of community. Relationships at a College level are characterized by personal conflict and difference. However, the study revealed a satisfaction with communication and relationships at a dl'partmentallevel. Five key features of interpersonal communication that are lacking in the College and that contribute to the unhealthy relationships in the College were identified. These are trust, respect, openness, feedback and the sharing of ideas and knowledge. Due to their absence, the College is divided into cliques. A strong desire for the establishment of interpersonal norms of openness, respect, honesty and trust was expressed. Participants expressed the need to establish an organization structure that allows for interaction with others in the College, flatter structures, teamwork and a collaborative cultu re. The study also emphasized participative democracy in building relationships. Participation in decision making is seen as satisfying the personal need to experience a sense of influence and achievement. There is evidence of a desire for distributed leadership where the College staff as a group of professionals lead the College collectively and collaboratively. There is a strong desire for a College where people are liked , valued, accepted by others and recognized for their efforts. Finally, Organization Development is recommended as an approach to enhance College staff relationships.
- Full Text:
- Authors: Amushigamo, Angelina Popyeni
- Date: 2007
- Subjects: Communication in education -- Namibia Teacher morale -- Namibia Employee motivation -- Namibia Teacher-administrator relationships -- Namibia College teachers -- Job satisfaction -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1850 , http://hdl.handle.net/10962/d1004458
- Description: Relationships are regarded as an important aspect of any organization's life. The purpose of this study was to investigate staff perceptions and experiences of interpersonal relationships between management and lecturers in a Namibian College of Education. I conducted a case study at the College where I teach. Two methods were used to collect data. Firstly, semi-structured interviews with two management members, two senior lecturers and two lecturers. Secondly, observation where practical aspects of interpersonal relationships in the College were observed. I used the interpretational data analysis technique to analyse my data. Themes and patterns were identified in the data, coded and sorted into categories. The study revealed staff unhappiness about the current situation in the College as far as communication is concerned. The College's hierarchical structure was described as top-down. As such, it does not allow for face to face communication. There is an absence of any social cohesion or sense of community. Relationships at a College level are characterized by personal conflict and difference. However, the study revealed a satisfaction with communication and relationships at a dl'partmentallevel. Five key features of interpersonal communication that are lacking in the College and that contribute to the unhealthy relationships in the College were identified. These are trust, respect, openness, feedback and the sharing of ideas and knowledge. Due to their absence, the College is divided into cliques. A strong desire for the establishment of interpersonal norms of openness, respect, honesty and trust was expressed. Participants expressed the need to establish an organization structure that allows for interaction with others in the College, flatter structures, teamwork and a collaborative cultu re. The study also emphasized participative democracy in building relationships. Participation in decision making is seen as satisfying the personal need to experience a sense of influence and achievement. There is evidence of a desire for distributed leadership where the College staff as a group of professionals lead the College collectively and collaboratively. There is a strong desire for a College where people are liked , valued, accepted by others and recognized for their efforts. Finally, Organization Development is recommended as an approach to enhance College staff relationships.
- Full Text:
Investigating grade 10 geography teachers' implementation of a learner-centred approach in selected Namibian schools
- Authors: Angula, Adelheid
- Date: 2007
- Subjects: Geography -- Study and teaching (Secondary) -- Namibia Student-centered learning -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1851 , http://hdl.handle.net/10962/d1004459
- Description: Geography, more than other subjects in the curriculum, plays a central role in general education in equipping learners with skills and competencies needed for modern living and global citizenship. A learner-centred education in Namibia was adopted to provide more opportunities for learners to develop the required skills and competencies irrespective of their different cultural background. This small-scale case study investigated three Grade 10 geography teachers' understanding and implementation ofa learner-centred approach to gain insights into how leamer-centred education is being implemented in the context of Geography. The research design adopted a qualitative approach within an interpretative orientation. Data were collected through interviews, classroom observations and documentary analysis. The research was conducted at three selected schools in Oshikoto Region with three Grade 10 geography teachers The findings revealed, firstly, that teachers have a limited understanding of the key ideas ofLCE, such as, prior knowledge, role of questioning, and social interaction in learning; use of resources and the types of assessment activities which comply with the aims of LCE. Seconclly, the findings revealed that the policy documents, such as syllabuses, that are being used by the participants are not in line with the tenets ofLCE. Thirdly, teachers appeared to have limited subject knowledge, as revealed by their lack of understanding of how to translate the aims and assessment objectives into their daily lessons. The study therefore raises some possibilities for improving the implementation of LCE in the selected schools if the gaps as identified by this study are reduced.
- Full Text:
- Authors: Angula, Adelheid
- Date: 2007
- Subjects: Geography -- Study and teaching (Secondary) -- Namibia Student-centered learning -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1851 , http://hdl.handle.net/10962/d1004459
- Description: Geography, more than other subjects in the curriculum, plays a central role in general education in equipping learners with skills and competencies needed for modern living and global citizenship. A learner-centred education in Namibia was adopted to provide more opportunities for learners to develop the required skills and competencies irrespective of their different cultural background. This small-scale case study investigated three Grade 10 geography teachers' understanding and implementation ofa learner-centred approach to gain insights into how leamer-centred education is being implemented in the context of Geography. The research design adopted a qualitative approach within an interpretative orientation. Data were collected through interviews, classroom observations and documentary analysis. The research was conducted at three selected schools in Oshikoto Region with three Grade 10 geography teachers The findings revealed, firstly, that teachers have a limited understanding of the key ideas ofLCE, such as, prior knowledge, role of questioning, and social interaction in learning; use of resources and the types of assessment activities which comply with the aims of LCE. Seconclly, the findings revealed that the policy documents, such as syllabuses, that are being used by the participants are not in line with the tenets ofLCE. Thirdly, teachers appeared to have limited subject knowledge, as revealed by their lack of understanding of how to translate the aims and assessment objectives into their daily lessons. The study therefore raises some possibilities for improving the implementation of LCE in the selected schools if the gaps as identified by this study are reduced.
- Full Text:
The trouble with culture : Plato's critique of poetry
- Authors: Ansell, James D'Olier
- Date: 2007 , 2013-07-25
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2733 , http://hdl.handle.net/10962/d1004460
- Description: In this thesis I argue that Plato's critique of poetry, taken in its proper context, is a serious and relevant critique of popular culture. In the first chapter I argue that the poetic reforms proposed in Books 2 and 3 and Book 10 of Republic stand at the front of a total reform of Greek culture. I argue for the consistency of Plato's whole argument and then I claim that if we get Plato's targets right, not fine art or literature, and focus on appropriate modern analogues then we can see why his critique is still important. If we share his claim that we are influenced by popular culture in important and often insidious ways and agree that culture can promote corrupt values, then we have accepted the core of Plato's challenge. If we find his solution distasteful, then the task is to come up with a democratic alternative. In the remaining two chapters I focus specifically on the challenge to the poets, putting the other reforms to the side. In the second chapter I consider a possible reply to the challenge focusing on the worth of the poetry that was expelled. I first look elsewhere in the Platonic oeuvre at the account of beauty in Symposium and Phaedrus but I argue that neither of them gives anything like aesthetic value that could be usefully applied to poetry. Next I look to some modern accounts of aesthetic value. I argue that while they might go some of the distance against Plato's challenge, they face a difficult task because it is not sufficient positing the value, an account is needed of their positive benefit. In the third chapter I turn to a more direct response to the challenge. Arguably Aristotle offers such a response in the Poetics, in terms of the notion of katharsis. I consider two interpretative candidates for katharsis. The first takes the benefit of poetry to be psychological - katharsis is a purgation of otherwise pathological emotions. I argue that this fails because it misunderstands precisely what Plato's concerns about poetry are, and, furthermore, this account could even be compatible with Plato's worries. The second interpretation takes the benefit of poetry to be ethical- katharsis is a type of ethical clarification which is beneficial in training our emotional responses. I claim that the clarification, and education, is worryingly conventionalist, and doesn't take seriously that Plato's target was popular culture and not great, educative literature. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Ansell, James D'Olier
- Date: 2007 , 2013-07-25
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2733 , http://hdl.handle.net/10962/d1004460
- Description: In this thesis I argue that Plato's critique of poetry, taken in its proper context, is a serious and relevant critique of popular culture. In the first chapter I argue that the poetic reforms proposed in Books 2 and 3 and Book 10 of Republic stand at the front of a total reform of Greek culture. I argue for the consistency of Plato's whole argument and then I claim that if we get Plato's targets right, not fine art or literature, and focus on appropriate modern analogues then we can see why his critique is still important. If we share his claim that we are influenced by popular culture in important and often insidious ways and agree that culture can promote corrupt values, then we have accepted the core of Plato's challenge. If we find his solution distasteful, then the task is to come up with a democratic alternative. In the remaining two chapters I focus specifically on the challenge to the poets, putting the other reforms to the side. In the second chapter I consider a possible reply to the challenge focusing on the worth of the poetry that was expelled. I first look elsewhere in the Platonic oeuvre at the account of beauty in Symposium and Phaedrus but I argue that neither of them gives anything like aesthetic value that could be usefully applied to poetry. Next I look to some modern accounts of aesthetic value. I argue that while they might go some of the distance against Plato's challenge, they face a difficult task because it is not sufficient positing the value, an account is needed of their positive benefit. In the third chapter I turn to a more direct response to the challenge. Arguably Aristotle offers such a response in the Poetics, in terms of the notion of katharsis. I consider two interpretative candidates for katharsis. The first takes the benefit of poetry to be psychological - katharsis is a purgation of otherwise pathological emotions. I argue that this fails because it misunderstands precisely what Plato's concerns about poetry are, and, furthermore, this account could even be compatible with Plato's worries. The second interpretation takes the benefit of poetry to be ethical- katharsis is a type of ethical clarification which is beneficial in training our emotional responses. I claim that the clarification, and education, is worryingly conventionalist, and doesn't take seriously that Plato's target was popular culture and not great, educative literature. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
Creative misreadings: allegory in Tracey Rose's Ciao Bella
- Authors: Bateman, Genevieve
- Date: 2007
- Subjects: Rose, Tracey, 1974- Artists -- South Africa Women artists -- South Africa Performance artists -- South Africa Women in art
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2473 , http://hdl.handle.net/10962/d1009506
- Description: This thesis will aim to investigate the extent to which Tracey Rose's Ciao Bella can be said to allegorically perform a dialectical enfolding of the dichotomous categories of meaning/nonmeaning; image/text; past/present and original/translation. The dual concepts of performance and performativity will be utilized as a means to explore the notion of interpretation as a meaning-making process and as an engagement between artist, artwork and viewer that is necessarily open-ended and in a state of constant change and flux. Rose's performance of Ciao Bella will be read as one that questions the illusion of unmediated representation by parodying and creatively misreading a multiplicity of visual, textual and musical representations so as to foreground the politics of representation. The representational figure of allegory, as one that defines itself in opposition to the Romantic conception of the unified symbol, will be put to work so as to reveal the ways in which Rose's performance works to critically undermine various positivistic attitudes toward self-identity, gender, race, politics, history, authorial intention and interpretation.
- Full Text:
- Authors: Bateman, Genevieve
- Date: 2007
- Subjects: Rose, Tracey, 1974- Artists -- South Africa Women artists -- South Africa Performance artists -- South Africa Women in art
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2473 , http://hdl.handle.net/10962/d1009506
- Description: This thesis will aim to investigate the extent to which Tracey Rose's Ciao Bella can be said to allegorically perform a dialectical enfolding of the dichotomous categories of meaning/nonmeaning; image/text; past/present and original/translation. The dual concepts of performance and performativity will be utilized as a means to explore the notion of interpretation as a meaning-making process and as an engagement between artist, artwork and viewer that is necessarily open-ended and in a state of constant change and flux. Rose's performance of Ciao Bella will be read as one that questions the illusion of unmediated representation by parodying and creatively misreading a multiplicity of visual, textual and musical representations so as to foreground the politics of representation. The representational figure of allegory, as one that defines itself in opposition to the Romantic conception of the unified symbol, will be put to work so as to reveal the ways in which Rose's performance works to critically undermine various positivistic attitudes toward self-identity, gender, race, politics, history, authorial intention and interpretation.
- Full Text:
The role of the euthecosome pteropod, limacina retroversa, in the polar frontal zone, Southern Ocean
- Authors: Bernard, Kim Sarah
- Date: 2007
- Subjects: Pteropoda Limacidae Zooplankton -- Antarctic Ocean Copepoda Phytoplankton
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5761 , http://hdl.handle.net/10962/d1005449
- Description: The aim of the present study was to assess the ecological role of the euthecosome pteropod, Limacina retroversa, in particular, and the mesozooplankton community, in general, in the pelagic ecosystem of the Polar Frontal Zone (PFZ), Southern Ocean. Data were collected from four oceanographic surveys to the Indian sector of the PFZ during austral autumn 2000, 2002, 2004 and 2005. Copepods, mainly Calanus simillimus, Oithona similis, Clausocalanus spp. and Ctenocalanus spp., typically dominated total mesozooplankton counts, accounting for, on average, between 75.5 % and 88.1 % (Mean = 77.4 %; SD = 13.4 %) of the total, during the present investigation. Results of the study indicate that L. retroversa may, at times, contribute substantially to total mesozooplankton abundances. During the study, L. retroversa contributed between 0.0 and 30.0 % (Mean = 5.3 %; SD = 7.1 %) to total mesozooplankton numbers. Significant small-scale variability in abundance and size structure of L. retroversa and abundance of copepods was minimal. Inter-annual variability, on the other hand, was significant between some years. Total pteropod numbers were greatest during April 2002 and 2004, while copepods exhibited greatest abundances during April 2004 only. Pearson’s Correlation analysis suggested that L. retroversa abundances were positively correlated to total surface chlorophyll-a (chl-a) concentrations. The significantly lower chl-a concentrations recorded during April 2005 may explain the reduced pteropod numbers observed during that survey. The size class structure of L. retroversa comprised mainly small and mediumsized individuals during all four surveys. This corresponds well with records from the northern hemisphere (sub-Arctic and Arctic waters) where Limacina spp. are reported to exhibit maximum spawning during mid to late-summer. Higher abundances of large individuals only occurred during April 2005, when chl-a concentrations were very low; possibly the result of delayed spawning, due to reduced food availability. Ingestion rates of the four most abundant copepods, determined using the gut fluorescence technique, ranged between 159.32 ng (pigm) ind⁻¹ day⁻¹ and 728.36 ng (pigm) ind⁻¹ day⁻¹ (Mean = 321.01 ng (pigm) ind⁻¹ day⁻¹; SD = 173.91 ng (pigm) ind⁻¹ day). Ingestion rates of L. retroversa were much higher, ranging from an average of 4 28.68 ng (pigm) ind⁻¹ day⁻¹ in April 2002 to 4 196.88 ng (pigm) ind⁻¹day⁻¹in April 2005 (Mean = 4157.36 ng (pigm) ind⁻¹ day⁻¹; SD = 35.37 ng (pigm) ind⁻¹day⁻¹). Average daily grazing rates for the pteropod varied between 0.39 mg (pigm) m⁻² day⁻¹ in April 2005 and 17.69 mg (pigm) m-2 day-1 in April 2004 (Mean = 6.13 mg (pigm) m⁻² day⁻¹; SD = 11.04 mg (pigm) m⁻² day⁻¹); corresponding average daily grazing impacts ranged between 8.4 % and 139.8 % of the phytoplankton standing stock in April 2005 and 2004, respectively (Mean = 48.5 %; SD = 84.5 %). Average daily grazing rates of the four copepods ranged from 4.58 mg (pigm) m⁻² day⁻¹ to 8.77 mg (pigm) m⁻² day⁻¹ -1, during April 2002 and 2004, respectively (Mean = 6.28 mg (pigm) m⁻² day⁻¹; SD = 5.94 mg (pigm) m⁻² day⁻¹). Collectively, the copepods removed an average of between 31.6 % and 89.8 % of the phytoplankton standing stock per day, during April 2002 and 2004, respectively (Mean = 70.8 %; SD = 86.7 %). The daily grazing impact of the copepods accounted for an average of between 40.4 % and 87.8 % of the total zooplankton grazing impact, during April 2004 and 2005, respectively (Mean = 75.0 %; SD = 65.5 %). L. retroversa was responsible for an average of 52.4 % and 59.5 % of the total zooplankton grazing impact, during April 2002 and 2004, respectively. However, during April 2005, when L. retroversa numbers were significantly lower than previous years, the pteropod contributed an average of only 7.5 % to the total zooplankton grazing impact. Thus, during the present investigation,the pteropod was responsible for removing a mean of 48.9 % of the available phytoplankton (SD = 74.9 %). The predation impact of the dominant carnivorous macrozooplankton and micronekton in the PFZ was determined during April 2004 and 2005 using daily ration estimates obtained from the literature. Additionally, gut content analysis was used to determine the contribution of L. retroversa to the diet of the dominant predators. Average predation impact ranged from 1.1 % and 5.7 % of the total mesozooplankton standing stock during April 2004 and 2005, respectively (Mean = 3.8 %; SD = 12.3 %). Chaetognaths and euphausiids dominated total carnivore numbers and made the greatest contributions to total predation impact during both years. Copepods appeared to be the main prey item of the dominant carnivorous macrozooplankton-micronekton in the region. L. retroversa was only detected in the gut contents of the amphipod, Themisto gaudichaudi, but not in either of the chaetognath species (Eukrohnia hamata and Sagitta gazellae) or the myctophid fish (Electrona spp.). The pteropod was found in 19 % of amphipod guts dissected. Pearson’s Correlation analyses showed that the four major predatory zooplankton groups found in the PFZ (chaetognaths, euphausiids, amphipods and myctophid fish) were positively correlated to abundances of L. retroversa, suggesting that the pteropod might be an important prey item for many of the carnivorous macrozooplankton/micronekton in the PFZ. To conclude, L. retroversa may play an important role in the pelagic ecosystem of the PFZ, in austral autumn. However, ocean acidification and calcium carbonate undersaturation (as a result of increased anthropogenic carbon dioxide emissions), that is predicted to occur within the next 50 – 100 years, will most likely have significant implications for the Sub-Antarctic pelagic ecosystem if L. retroversa cannot adapt quickly enough to the changes.
- Full Text:
The role of the euthecosome pteropod, limacina retroversa, in the polar frontal zone, Southern Ocean
- Authors: Bernard, Kim Sarah
- Date: 2007
- Subjects: Pteropoda Limacidae Zooplankton -- Antarctic Ocean Copepoda Phytoplankton
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5761 , http://hdl.handle.net/10962/d1005449
- Description: The aim of the present study was to assess the ecological role of the euthecosome pteropod, Limacina retroversa, in particular, and the mesozooplankton community, in general, in the pelagic ecosystem of the Polar Frontal Zone (PFZ), Southern Ocean. Data were collected from four oceanographic surveys to the Indian sector of the PFZ during austral autumn 2000, 2002, 2004 and 2005. Copepods, mainly Calanus simillimus, Oithona similis, Clausocalanus spp. and Ctenocalanus spp., typically dominated total mesozooplankton counts, accounting for, on average, between 75.5 % and 88.1 % (Mean = 77.4 %; SD = 13.4 %) of the total, during the present investigation. Results of the study indicate that L. retroversa may, at times, contribute substantially to total mesozooplankton abundances. During the study, L. retroversa contributed between 0.0 and 30.0 % (Mean = 5.3 %; SD = 7.1 %) to total mesozooplankton numbers. Significant small-scale variability in abundance and size structure of L. retroversa and abundance of copepods was minimal. Inter-annual variability, on the other hand, was significant between some years. Total pteropod numbers were greatest during April 2002 and 2004, while copepods exhibited greatest abundances during April 2004 only. Pearson’s Correlation analysis suggested that L. retroversa abundances were positively correlated to total surface chlorophyll-a (chl-a) concentrations. The significantly lower chl-a concentrations recorded during April 2005 may explain the reduced pteropod numbers observed during that survey. The size class structure of L. retroversa comprised mainly small and mediumsized individuals during all four surveys. This corresponds well with records from the northern hemisphere (sub-Arctic and Arctic waters) where Limacina spp. are reported to exhibit maximum spawning during mid to late-summer. Higher abundances of large individuals only occurred during April 2005, when chl-a concentrations were very low; possibly the result of delayed spawning, due to reduced food availability. Ingestion rates of the four most abundant copepods, determined using the gut fluorescence technique, ranged between 159.32 ng (pigm) ind⁻¹ day⁻¹ and 728.36 ng (pigm) ind⁻¹ day⁻¹ (Mean = 321.01 ng (pigm) ind⁻¹ day⁻¹; SD = 173.91 ng (pigm) ind⁻¹ day). Ingestion rates of L. retroversa were much higher, ranging from an average of 4 28.68 ng (pigm) ind⁻¹ day⁻¹ in April 2002 to 4 196.88 ng (pigm) ind⁻¹day⁻¹in April 2005 (Mean = 4157.36 ng (pigm) ind⁻¹ day⁻¹; SD = 35.37 ng (pigm) ind⁻¹day⁻¹). Average daily grazing rates for the pteropod varied between 0.39 mg (pigm) m⁻² day⁻¹ in April 2005 and 17.69 mg (pigm) m-2 day-1 in April 2004 (Mean = 6.13 mg (pigm) m⁻² day⁻¹; SD = 11.04 mg (pigm) m⁻² day⁻¹); corresponding average daily grazing impacts ranged between 8.4 % and 139.8 % of the phytoplankton standing stock in April 2005 and 2004, respectively (Mean = 48.5 %; SD = 84.5 %). Average daily grazing rates of the four copepods ranged from 4.58 mg (pigm) m⁻² day⁻¹ to 8.77 mg (pigm) m⁻² day⁻¹ -1, during April 2002 and 2004, respectively (Mean = 6.28 mg (pigm) m⁻² day⁻¹; SD = 5.94 mg (pigm) m⁻² day⁻¹). Collectively, the copepods removed an average of between 31.6 % and 89.8 % of the phytoplankton standing stock per day, during April 2002 and 2004, respectively (Mean = 70.8 %; SD = 86.7 %). The daily grazing impact of the copepods accounted for an average of between 40.4 % and 87.8 % of the total zooplankton grazing impact, during April 2004 and 2005, respectively (Mean = 75.0 %; SD = 65.5 %). L. retroversa was responsible for an average of 52.4 % and 59.5 % of the total zooplankton grazing impact, during April 2002 and 2004, respectively. However, during April 2005, when L. retroversa numbers were significantly lower than previous years, the pteropod contributed an average of only 7.5 % to the total zooplankton grazing impact. Thus, during the present investigation,the pteropod was responsible for removing a mean of 48.9 % of the available phytoplankton (SD = 74.9 %). The predation impact of the dominant carnivorous macrozooplankton and micronekton in the PFZ was determined during April 2004 and 2005 using daily ration estimates obtained from the literature. Additionally, gut content analysis was used to determine the contribution of L. retroversa to the diet of the dominant predators. Average predation impact ranged from 1.1 % and 5.7 % of the total mesozooplankton standing stock during April 2004 and 2005, respectively (Mean = 3.8 %; SD = 12.3 %). Chaetognaths and euphausiids dominated total carnivore numbers and made the greatest contributions to total predation impact during both years. Copepods appeared to be the main prey item of the dominant carnivorous macrozooplankton-micronekton in the region. L. retroversa was only detected in the gut contents of the amphipod, Themisto gaudichaudi, but not in either of the chaetognath species (Eukrohnia hamata and Sagitta gazellae) or the myctophid fish (Electrona spp.). The pteropod was found in 19 % of amphipod guts dissected. Pearson’s Correlation analyses showed that the four major predatory zooplankton groups found in the PFZ (chaetognaths, euphausiids, amphipods and myctophid fish) were positively correlated to abundances of L. retroversa, suggesting that the pteropod might be an important prey item for many of the carnivorous macrozooplankton/micronekton in the PFZ. To conclude, L. retroversa may play an important role in the pelagic ecosystem of the PFZ, in austral autumn. However, ocean acidification and calcium carbonate undersaturation (as a result of increased anthropogenic carbon dioxide emissions), that is predicted to occur within the next 50 – 100 years, will most likely have significant implications for the Sub-Antarctic pelagic ecosystem if L. retroversa cannot adapt quickly enough to the changes.
- Full Text:
An investigation into the popularity of Zimbabwe's first health communication soap opera, Studio 263 : a qualitative reception study of Bulawayo students aged between 15 and 20 years
- Authors: Bhebhe-Mpofu, Adilaid
- Date: 2007 , 2014-08-18
- Subjects: Studio 263 (Television program) , Television soap operas -- Zimbabwe , Television viewers -- Zimbabwe , Mass media and children -- Zimbabwe , Television and children -- Zimbabwe , AIDS (Disease) -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3531 , http://hdl.handle.net/10962/d1013310
- Description: Within the context of debates concerning the reception and interpretation of media texts by television audiences, this qualitative reception study explores how a sample of Bulawayo students negotiate meanings from Zimbabwe's first health communication soap opera, Studio 263. The study thus examines the reasons behind the popularity of this programme with this target audience. The findings of the study reveal that meaning making is a complex process that is dependent on a variety of factors which include, among others, the socio-cultural context of media consumption, gender, economic disposition and age. It particularly maintains that gender and lived realities influence the interpretation and negotiation of meanings in this particular study. , Adobe Acrobat Pro 11.0.0 Paper Capture Plug-in
- Full Text:
- Authors: Bhebhe-Mpofu, Adilaid
- Date: 2007 , 2014-08-18
- Subjects: Studio 263 (Television program) , Television soap operas -- Zimbabwe , Television viewers -- Zimbabwe , Mass media and children -- Zimbabwe , Television and children -- Zimbabwe , AIDS (Disease) -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3531 , http://hdl.handle.net/10962/d1013310
- Description: Within the context of debates concerning the reception and interpretation of media texts by television audiences, this qualitative reception study explores how a sample of Bulawayo students negotiate meanings from Zimbabwe's first health communication soap opera, Studio 263. The study thus examines the reasons behind the popularity of this programme with this target audience. The findings of the study reveal that meaning making is a complex process that is dependent on a variety of factors which include, among others, the socio-cultural context of media consumption, gender, economic disposition and age. It particularly maintains that gender and lived realities influence the interpretation and negotiation of meanings in this particular study. , Adobe Acrobat Pro 11.0.0 Paper Capture Plug-in
- Full Text:
Transcending state-centrism: new regionalism and the future of Southern African regional integration
- Authors: Blaauw, Lesley
- Date: 2007
- Subjects: Southern African Development Community Southern African Customs Union Southern African Development Coordination Conference Regionalism -- Africa, Southern Africa, Southern -- Economic integration
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2761 , http://hdl.handle.net/10962/d1002971
- Description: This dissertation argues that in the 1990s and beyond, the character and functions of regions and regionalism have experienced a major transformation. This requires a reconceptualisation of regions and regionalism that transcends state-centrism. The argument here is that the definition of regions and regionalism needs to recognise that other actors also participate in the construction of regions and the practise of regionalism. Up to now, however, theories of integration incompletely deal with outcomes appropriate to developing countries, states and regions. In the context where people remain vulnerable to top-down forms of regionalism driven by the forces of globalisation, this calls for a new approach in the analytical study of regionalism in a transnational context. The contention is that new regionalism, and its variant, developmental regionalism pay attention to the role those organised civil society actors and those marginalised by both globalisation and regionalisation play in promoting regionalism in a transnational context. Historically, state-centric regionalism in southern Africa was not aimed at achieving developmental objectives. In the case of SACU, the argument is that South Africa used its economic strength in a hegemonial way. To counter-act apartheid South Africa’s economic hegemony, SADCC was formed. SADCC achieved limited success in the fields of infrastructural development and in attracting donor aid. The end of the Cold War and the downfall of apartheid compelled these organisations to recast their objectives and purpose. For SACU this meant changing from an organisation dominated by South Africa to a fully-fledged inter-state one. Disconcertedly, however, about the reforms undertook by SACU, is that the disposition of member states remain important in determining the content and scope of regionalism. SADC, on the other hand, has also not sufficiently reform itself to achieve the ambitious goals it set-out for itself. Moreover, while SADC has since its inception in 1992 set-out to involve non-state actors in its regional integration efforts, limited institutional reform in 2000 and beyond, and elites at the forefront of institutional restructuring make it difficult for non-state actors to contribute to sustainable regional integration. In conclusion, this dissertation maintains that sustainable regionalist orders are best built by recognising that beyond the geometry of state-sovereignty, civil society organisations with a regional focus and the ordinary people of the region also contribute to regioness and as such to the re-conceptualisation of regional community in southern Africa.
- Full Text:
Transcending state-centrism: new regionalism and the future of Southern African regional integration
- Authors: Blaauw, Lesley
- Date: 2007
- Subjects: Southern African Development Community Southern African Customs Union Southern African Development Coordination Conference Regionalism -- Africa, Southern Africa, Southern -- Economic integration
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2761 , http://hdl.handle.net/10962/d1002971
- Description: This dissertation argues that in the 1990s and beyond, the character and functions of regions and regionalism have experienced a major transformation. This requires a reconceptualisation of regions and regionalism that transcends state-centrism. The argument here is that the definition of regions and regionalism needs to recognise that other actors also participate in the construction of regions and the practise of regionalism. Up to now, however, theories of integration incompletely deal with outcomes appropriate to developing countries, states and regions. In the context where people remain vulnerable to top-down forms of regionalism driven by the forces of globalisation, this calls for a new approach in the analytical study of regionalism in a transnational context. The contention is that new regionalism, and its variant, developmental regionalism pay attention to the role those organised civil society actors and those marginalised by both globalisation and regionalisation play in promoting regionalism in a transnational context. Historically, state-centric regionalism in southern Africa was not aimed at achieving developmental objectives. In the case of SACU, the argument is that South Africa used its economic strength in a hegemonial way. To counter-act apartheid South Africa’s economic hegemony, SADCC was formed. SADCC achieved limited success in the fields of infrastructural development and in attracting donor aid. The end of the Cold War and the downfall of apartheid compelled these organisations to recast their objectives and purpose. For SACU this meant changing from an organisation dominated by South Africa to a fully-fledged inter-state one. Disconcertedly, however, about the reforms undertook by SACU, is that the disposition of member states remain important in determining the content and scope of regionalism. SADC, on the other hand, has also not sufficiently reform itself to achieve the ambitious goals it set-out for itself. Moreover, while SADC has since its inception in 1992 set-out to involve non-state actors in its regional integration efforts, limited institutional reform in 2000 and beyond, and elites at the forefront of institutional restructuring make it difficult for non-state actors to contribute to sustainable regional integration. In conclusion, this dissertation maintains that sustainable regionalist orders are best built by recognising that beyond the geometry of state-sovereignty, civil society organisations with a regional focus and the ordinary people of the region also contribute to regioness and as such to the re-conceptualisation of regional community in southern Africa.
- Full Text:
The initial grounding of rational numbers : an investigation
- Authors: Brown, Bruce John Lindsay
- Date: 2007
- Subjects: Number theory Numbers, Rational -- Study and teaching (Elementary) Numeracy -- Study and teaching (Elementary) Mathematics -- Study and teaching (Elementary)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1904 , http://hdl.handle.net/10962/d1006351
- Description: This small scale exploratory research project investigated the grounding of rational number concepts in informal, everyday life situations. A qualitative approach was taken to allow for the identification and then in depth investigation, of issues of importance for such a grounding of rational number understanding. The methodology followed could be seen as a combination of grounded theory and developmental research. And the data was generated through in-depth and clinical interviews structured around a number of grounded tasks related to rational numbers. The research comprised three cycles of interviews that were transcribed and then analysed in detail, interspersed with periods of reading and reflection. The pilot cycle involved a single grade three teacher, the second cycle involved 2 grade three teachers and the third cycle involved 2 grade three children. The research identified a number of different perspectives that were all important for the development of a fundamental intuitive understanding that could be considered personally meaningful to the individual concerned and relevant to the development of rational number concepts. Firstly in order to motivate and engage the child on a personal level the grounding situation needed to be seen as personally significant by the child. Secondly, coordinating operations provided a means of developing a fundamental intuitive understanding, through coordination with affording structures of the situation that are relevant to rational numbers. Finally, goal directed actions that are deliberately structured to achieve explicit goals in a situation are important for the development of more explicit concepts and skills fundamental for rational number understanding. Different explicit structures give rise to different interpretations of rational numbers in grounding situations. In addition to these perspectives, it became evident that building and learning representations was important for developing a more particularly mathematical understanding, based on the fundamental understanding derived from the child's grounded experience. The conclusion drawn in this research as a result of this complexity, is that to achieve a comprehensive and meaningful grounding, children's learning of rational numbers will not follow a simple linear trajectory. Rather this process forms a web of learning, threading coordinating operations for intuitive development, interpretations for explicit grounding and representations to develop more formal mathematical conceptions.
- Full Text:
- Authors: Brown, Bruce John Lindsay
- Date: 2007
- Subjects: Number theory Numbers, Rational -- Study and teaching (Elementary) Numeracy -- Study and teaching (Elementary) Mathematics -- Study and teaching (Elementary)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1904 , http://hdl.handle.net/10962/d1006351
- Description: This small scale exploratory research project investigated the grounding of rational number concepts in informal, everyday life situations. A qualitative approach was taken to allow for the identification and then in depth investigation, of issues of importance for such a grounding of rational number understanding. The methodology followed could be seen as a combination of grounded theory and developmental research. And the data was generated through in-depth and clinical interviews structured around a number of grounded tasks related to rational numbers. The research comprised three cycles of interviews that were transcribed and then analysed in detail, interspersed with periods of reading and reflection. The pilot cycle involved a single grade three teacher, the second cycle involved 2 grade three teachers and the third cycle involved 2 grade three children. The research identified a number of different perspectives that were all important for the development of a fundamental intuitive understanding that could be considered personally meaningful to the individual concerned and relevant to the development of rational number concepts. Firstly in order to motivate and engage the child on a personal level the grounding situation needed to be seen as personally significant by the child. Secondly, coordinating operations provided a means of developing a fundamental intuitive understanding, through coordination with affording structures of the situation that are relevant to rational numbers. Finally, goal directed actions that are deliberately structured to achieve explicit goals in a situation are important for the development of more explicit concepts and skills fundamental for rational number understanding. Different explicit structures give rise to different interpretations of rational numbers in grounding situations. In addition to these perspectives, it became evident that building and learning representations was important for developing a more particularly mathematical understanding, based on the fundamental understanding derived from the child's grounded experience. The conclusion drawn in this research as a result of this complexity, is that to achieve a comprehensive and meaningful grounding, children's learning of rational numbers will not follow a simple linear trajectory. Rather this process forms a web of learning, threading coordinating operations for intuitive development, interpretations for explicit grounding and representations to develop more formal mathematical conceptions.
- Full Text:
Determination of the botanical composition of black rhinoceros (Diceros bicornis) dung using the rbcL gene as a molecular marker, and analysis of antioxidant and phenolic content of its browse
- Authors: Bulani, Siyavuya Ishmael
- Date: 2007 , 2013-06-25
- Subjects: Black rhinoceros -- Food , Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- Analysis -- South Africa -- Eastern Cape , Plant ecology -- South Africa -- Eastern Cape , Genetic markers , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4070 , http://hdl.handle.net/10962/d1006468 , Black rhinoceros -- Food , Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- Analysis -- South Africa -- Eastern Cape , Plant ecology -- South Africa -- Eastern Cape , Genetic markers , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants
- Description: The black rhinoceros remains one of the world's extremely endangered species despite a variety of policies to protect it. The black rhinoceros population at the Great Fish River Reserve (GFRR) in the Eastern Cape in South Africa has increased steadily since their re-introduction in 1986. This megaherbivore is a browser, with a diet obtained largely from the short and medium succulent thicket of the GFRR. Knowledge of the preferential diet of the black rhinoceros on the reserve is an important factor for the effective management of the land and the herbivores that compete for its resources. The dietary preferences of the black rhinoceros at the reserve have been established using backtracking methods. In this study the rbcL gene was used to establish an rbcL gene database of the plants from the GFRR and determine the botanical composition of the black rhinoceros dung from the GFRR. Due to the limited number of rbcL gene plant sequences from the GFRR deposited in the GenBank database, 18 plant species from the GFRR were sequenced. Sequence analyses between the partial rbcL gene sequences generated were able to distinguish between plants down to species level. Plant species from the family Euphorbiaceae and Fabaceae showed sequence variation at intra-specific level compared to those of Tiliaceae which were more conserved. The generated rbcL gene sequences from seasonal dung samples were compared to the rbcL gene sequenced from 18 plant species obtained from the GFRR and those from the GenBank database. A wide range of plant species were identified from the dung samples. There were no major differences in botanical composition between the dung samples, except that Grewia spp. were found to dominate in almost all seasons. The results obtained on the free radical scavenging activity of the extracts against 2,2-Diphenyl-l-picrylhydrazyl (DPPH) increased in the order of methanol > ethyl acetate > chloroform. The DPPH free radical scavenging activity of the methanol plant extracts increased in the order Brachylaena elliptica > Plumbago auriculata > Grewia robusta > Azima tetracantha. Methanol extracts on the TLC plate sprayed with Fe³⁺-2,4,6-Tri-2-pyridyl-s-triazine (TPTZ) showed that the compounds present in the extracts react differently to ferric ion, with most compounds unable to reduce ferric ion. Furthermore the methanol extracts were able to exhibit reduction potentials vs. Ag/AgCl at low concentrations. The compounds in the extracts were shown to be phenolic acids and flavonoid glycosides.
- Full Text:
- Authors: Bulani, Siyavuya Ishmael
- Date: 2007 , 2013-06-25
- Subjects: Black rhinoceros -- Food , Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- Analysis -- South Africa -- Eastern Cape , Plant ecology -- South Africa -- Eastern Cape , Genetic markers , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4070 , http://hdl.handle.net/10962/d1006468 , Black rhinoceros -- Food , Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- Analysis -- South Africa -- Eastern Cape , Plant ecology -- South Africa -- Eastern Cape , Genetic markers , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants
- Description: The black rhinoceros remains one of the world's extremely endangered species despite a variety of policies to protect it. The black rhinoceros population at the Great Fish River Reserve (GFRR) in the Eastern Cape in South Africa has increased steadily since their re-introduction in 1986. This megaherbivore is a browser, with a diet obtained largely from the short and medium succulent thicket of the GFRR. Knowledge of the preferential diet of the black rhinoceros on the reserve is an important factor for the effective management of the land and the herbivores that compete for its resources. The dietary preferences of the black rhinoceros at the reserve have been established using backtracking methods. In this study the rbcL gene was used to establish an rbcL gene database of the plants from the GFRR and determine the botanical composition of the black rhinoceros dung from the GFRR. Due to the limited number of rbcL gene plant sequences from the GFRR deposited in the GenBank database, 18 plant species from the GFRR were sequenced. Sequence analyses between the partial rbcL gene sequences generated were able to distinguish between plants down to species level. Plant species from the family Euphorbiaceae and Fabaceae showed sequence variation at intra-specific level compared to those of Tiliaceae which were more conserved. The generated rbcL gene sequences from seasonal dung samples were compared to the rbcL gene sequenced from 18 plant species obtained from the GFRR and those from the GenBank database. A wide range of plant species were identified from the dung samples. There were no major differences in botanical composition between the dung samples, except that Grewia spp. were found to dominate in almost all seasons. The results obtained on the free radical scavenging activity of the extracts against 2,2-Diphenyl-l-picrylhydrazyl (DPPH) increased in the order of methanol > ethyl acetate > chloroform. The DPPH free radical scavenging activity of the methanol plant extracts increased in the order Brachylaena elliptica > Plumbago auriculata > Grewia robusta > Azima tetracantha. Methanol extracts on the TLC plate sprayed with Fe³⁺-2,4,6-Tri-2-pyridyl-s-triazine (TPTZ) showed that the compounds present in the extracts react differently to ferric ion, with most compounds unable to reduce ferric ion. Furthermore the methanol extracts were able to exhibit reduction potentials vs. Ag/AgCl at low concentrations. The compounds in the extracts were shown to be phenolic acids and flavonoid glycosides.
- Full Text:
The cost of credit in the micro-finance industry in South Africa
- Authors: Campbell, Jonathan
- Date: 2007
- Subjects: Contracts -- South Africa , Credit -- Law and legislation -- South Africa , Microfinance -- South Africa , Usury laws -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3667 , http://hdl.handle.net/10962/d1003182 , Contracts -- South Africa , Credit -- Law and legislation -- South Africa , Microfinance -- South Africa , Usury laws -- South Africa
- Description: This thesis analyses the cost of credit in the micro-finance industry in South Africa. The study situates micro-lending agreements within the law of contract, beginning with an examination of contractual fairness in terms of the common law: the fundamental principle of freedom of contract that underpins the common law of contract; the principle that agreements contrary to public policy should not be enforced; and the impetus given by constitutional values that inform public policy. In regard to moneylending transactions, common law usury law will be explained. The study then goes on to trace the origins and rapid growth of the micro-finance industry which was made possible by its exemption in 1992 from the Usury Act 73 of 1968. The upshot of this development was that registered micro-lenders have for nearly 14 years charged excessive interest rates, and continue to do so. The dire socio-economic impact of these high interest rates on individual consumers and lowincome communities is then demonstrated: how borrowers of small loans soon become over-indebted; the loss of billions of rands every year to low-income communities in the form of interest on micro-loans. The study then shifts to the legislative response to the need for consumer protection in regard to consumer credit. The extensive credit law review process is explained, resulting ultimately in the National Credit Act 34 of 2005, which allows the Minister to prescribe limits on interest rates and fees in all sectors of the consumer credit market. The prescribed limits on the cost of credit in the micro-finance sector are thoroughly explained and analysed, with particular reference to the implications of each element of the credit costing structure, and the combined impact of the total cost of credit on different types and sizes of loans. The envisaged maximum interest and fees will markedly alter the positions of micro-lenders and consumers, and receive careful analysis. The study closes with a summary of findings in the thesis, which includes suggested amendments to the National Credit Regulations and a review of possible legal challenges to the high cost of credit on smaller loans.
- Full Text:
- Authors: Campbell, Jonathan
- Date: 2007
- Subjects: Contracts -- South Africa , Credit -- Law and legislation -- South Africa , Microfinance -- South Africa , Usury laws -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3667 , http://hdl.handle.net/10962/d1003182 , Contracts -- South Africa , Credit -- Law and legislation -- South Africa , Microfinance -- South Africa , Usury laws -- South Africa
- Description: This thesis analyses the cost of credit in the micro-finance industry in South Africa. The study situates micro-lending agreements within the law of contract, beginning with an examination of contractual fairness in terms of the common law: the fundamental principle of freedom of contract that underpins the common law of contract; the principle that agreements contrary to public policy should not be enforced; and the impetus given by constitutional values that inform public policy. In regard to moneylending transactions, common law usury law will be explained. The study then goes on to trace the origins and rapid growth of the micro-finance industry which was made possible by its exemption in 1992 from the Usury Act 73 of 1968. The upshot of this development was that registered micro-lenders have for nearly 14 years charged excessive interest rates, and continue to do so. The dire socio-economic impact of these high interest rates on individual consumers and lowincome communities is then demonstrated: how borrowers of small loans soon become over-indebted; the loss of billions of rands every year to low-income communities in the form of interest on micro-loans. The study then shifts to the legislative response to the need for consumer protection in regard to consumer credit. The extensive credit law review process is explained, resulting ultimately in the National Credit Act 34 of 2005, which allows the Minister to prescribe limits on interest rates and fees in all sectors of the consumer credit market. The prescribed limits on the cost of credit in the micro-finance sector are thoroughly explained and analysed, with particular reference to the implications of each element of the credit costing structure, and the combined impact of the total cost of credit on different types and sizes of loans. The envisaged maximum interest and fees will markedly alter the positions of micro-lenders and consumers, and receive careful analysis. The study closes with a summary of findings in the thesis, which includes suggested amendments to the National Credit Regulations and a review of possible legal challenges to the high cost of credit on smaller loans.
- Full Text:
Development and assessment of an oxytocin parenteral dosage form prepared using pluronic ® F127
- Authors: Chaibva, Faith Anesu
- Date: 2007
- Subjects: Oxytocin -- Therapeutic use , Drugs -- Dosage forms , Pregnancy -- Complications -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3747 , http://hdl.handle.net/10962/d1003225 , Oxytocin -- Therapeutic use , Drugs -- Dosage forms , Pregnancy -- Complications -- Management
- Full Text:
- Authors: Chaibva, Faith Anesu
- Date: 2007
- Subjects: Oxytocin -- Therapeutic use , Drugs -- Dosage forms , Pregnancy -- Complications -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3747 , http://hdl.handle.net/10962/d1003225 , Oxytocin -- Therapeutic use , Drugs -- Dosage forms , Pregnancy -- Complications -- Management
- Full Text:
Evaluation of the safety and efficacy of topical mometasone furoate formulations
- Authors: Chamboko, Bernadett Vongayi
- Date: 2007
- Subjects: Adrenocortical hormones -- Physiological effect , Drugs -- Testing , Dermatopharmacology , High performance liquid chromatography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3748 , http://hdl.handle.net/10962/d1003226 , Adrenocortical hormones -- Physiological effect , Drugs -- Testing , Dermatopharmacology , High performance liquid chromatography
- Description: The human skin blanching assay (HSBA) is a well-researched and validated method for the bioequivalence assessment of topical corticosteroids. Traditionally, visual assessment of skin blanching has been used. Such testing methods are not conducive for interlaboratory comparisons. Regulatory bodies prefer less subjective methods of analysis. The FDA released guidelines on the assessment of bioequivalence for topical corticosteroids that recommends the use of a chromameter as a reliable method to measure skin blanching although the use of visual assessment with acceptable validation is also provided for. However, the FDA does not elucidate on the manipulation and handling of the chromameter during skin blanching measurements. The purpose of this project was several fold, which included investigations to standardize the manipulation and handling of a chromameter. In particular, measures to avoid skin whitening resulting from the effects of pressure on the skin during chromameter use were investigated. Other methods of analysis should surpass or at least be comparable to the HSBA if such methods are to be used for the assessment of topical corticosteroids. Microdialysis is a relatively new technique for assessing the rate at which drug penetrates the skin. The advantage of using this method is that there are fewer restrictions for selection of an appropriate study population unlike those required for the HSBA where one has to be both a ‘responder’ and a ‘detector’ for their results to be used in data analysis. Microdialysis was investigated by initially conducting experiments in which microdialysis probes were embedded into topical formulations containing mometasone furoate (MF) and the initial results revealed that relatively low drug was released from the formulations. These results indicated that should microdialysis be applied to measure the in vivo release of MF from such topical formulations following application to the skin, even lower concentrations of MF would likely result in the dialysate, necessitating the need for ultra-high sensitive methods of analysis. Typically, the availability of an appropriate analytical technique such as liquid chromatography coupled with mass spectrometry (LCMS) would be a pre-requisite for such in vivo studies. However, only high-pressure liquid chromatography (HPLC) and other less sensitive equipment was available in the laboratories. The study objectives were therefore focussed on in vitro assessment of the release of MF from topical formulations using microdialysis and Franz cells. In addition, the in vivo release of MF was also studied using the HSBA. Data obtained from the microdialysis experiments were compared with the data obtained from the Franz cell diffusion studies in order to provide information on the pharmaceutical availability of MF from the various topical MF dosage forms. Subsequently, pharmaceutical equivalence was investigated from the comparative pharmaceutical availability data using statistical analysis. An additional objective was to attempt to correlate in vitro with in vivo data (IVIVC) to establish a model that could be used to assess safety and efficacy of generic topical drug products. The in vivo data obtained from the HSBA were processed according to the FDA requirements and these pharmacodynamic data were subsequently compared with the microdialysis and Franz cell results. In summary the objectives of this project were: 1. To develop a system to improve the reproducibility of the use of a Minolta® chromameter and compare this with the standard/normal manipulation and handling of such instruments. 2. To develop and validate an HPLC method for the analysis of MF for use with in vitro diffusion studies using microdialysis and Franz cells. 3. To conduct a comparative HSBA on proprietary MF topical creams from two different countries in accordance with the FDA guidance. 4. To assess the pharmaceutical equivalence of topical formulations containing MF using Franz diffusion cells and in vitro microdialysis. 5. To compare the in vivo data obtained from the HSBA with those obtained in vitro using microdialysis and Franz cells.
- Full Text:
- Authors: Chamboko, Bernadett Vongayi
- Date: 2007
- Subjects: Adrenocortical hormones -- Physiological effect , Drugs -- Testing , Dermatopharmacology , High performance liquid chromatography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3748 , http://hdl.handle.net/10962/d1003226 , Adrenocortical hormones -- Physiological effect , Drugs -- Testing , Dermatopharmacology , High performance liquid chromatography
- Description: The human skin blanching assay (HSBA) is a well-researched and validated method for the bioequivalence assessment of topical corticosteroids. Traditionally, visual assessment of skin blanching has been used. Such testing methods are not conducive for interlaboratory comparisons. Regulatory bodies prefer less subjective methods of analysis. The FDA released guidelines on the assessment of bioequivalence for topical corticosteroids that recommends the use of a chromameter as a reliable method to measure skin blanching although the use of visual assessment with acceptable validation is also provided for. However, the FDA does not elucidate on the manipulation and handling of the chromameter during skin blanching measurements. The purpose of this project was several fold, which included investigations to standardize the manipulation and handling of a chromameter. In particular, measures to avoid skin whitening resulting from the effects of pressure on the skin during chromameter use were investigated. Other methods of analysis should surpass or at least be comparable to the HSBA if such methods are to be used for the assessment of topical corticosteroids. Microdialysis is a relatively new technique for assessing the rate at which drug penetrates the skin. The advantage of using this method is that there are fewer restrictions for selection of an appropriate study population unlike those required for the HSBA where one has to be both a ‘responder’ and a ‘detector’ for their results to be used in data analysis. Microdialysis was investigated by initially conducting experiments in which microdialysis probes were embedded into topical formulations containing mometasone furoate (MF) and the initial results revealed that relatively low drug was released from the formulations. These results indicated that should microdialysis be applied to measure the in vivo release of MF from such topical formulations following application to the skin, even lower concentrations of MF would likely result in the dialysate, necessitating the need for ultra-high sensitive methods of analysis. Typically, the availability of an appropriate analytical technique such as liquid chromatography coupled with mass spectrometry (LCMS) would be a pre-requisite for such in vivo studies. However, only high-pressure liquid chromatography (HPLC) and other less sensitive equipment was available in the laboratories. The study objectives were therefore focussed on in vitro assessment of the release of MF from topical formulations using microdialysis and Franz cells. In addition, the in vivo release of MF was also studied using the HSBA. Data obtained from the microdialysis experiments were compared with the data obtained from the Franz cell diffusion studies in order to provide information on the pharmaceutical availability of MF from the various topical MF dosage forms. Subsequently, pharmaceutical equivalence was investigated from the comparative pharmaceutical availability data using statistical analysis. An additional objective was to attempt to correlate in vitro with in vivo data (IVIVC) to establish a model that could be used to assess safety and efficacy of generic topical drug products. The in vivo data obtained from the HSBA were processed according to the FDA requirements and these pharmacodynamic data were subsequently compared with the microdialysis and Franz cell results. In summary the objectives of this project were: 1. To develop a system to improve the reproducibility of the use of a Minolta® chromameter and compare this with the standard/normal manipulation and handling of such instruments. 2. To develop and validate an HPLC method for the analysis of MF for use with in vitro diffusion studies using microdialysis and Franz cells. 3. To conduct a comparative HSBA on proprietary MF topical creams from two different countries in accordance with the FDA guidance. 4. To assess the pharmaceutical equivalence of topical formulations containing MF using Franz diffusion cells and in vitro microdialysis. 5. To compare the in vivo data obtained from the HSBA with those obtained in vitro using microdialysis and Franz cells.
- Full Text:
Spermiogenesis, sperm ultrastructure and reproductive tract morphology in cicadas implications for systematic relationships
- Chawanji, Abraham Simbarashe
- Authors: Chawanji, Abraham Simbarashe
- Date: 2007
- Subjects: Cicadas Cicadas -- Reproduction Spermiogenesis in animals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5770 , http://hdl.handle.net/10962/d1005458
- Description: Sperm structure in five species of cicadine cicadas (Albanycada albigera, Azanicada zuluensis, Platypleura capensis, P. hirtipennis and Pycna semiclara) and five species of cicadettine cicadas (Melampsalta leucoptera, Quintilia walkeri, Stagira simplex, Xosopsaltria thunbergi and Monomatapa matoposa) was investigated by light and electron microscopy. In addition, spermiogenesis in cicadas was described; the information was derived from two cicadettines (Diceroprocta biconica and M. matoposa) and three cicadines (Kongota punctigera, P. capensis and P. semiclara). Mature spermatozoa of all species investigated are elongate and filiform, consisting of three distinct regions: the head (acrosome and nucleus), mid-piece and tail. All species produce more than one discrete length of nucleated, motile sperm, a form of sperm polymorphism termed polymegaly. Polymegaly is expressed in three ways; sperm have uni-, bi- or trimodal nucleus and tail lengths. Besides the differences in length, there are also notable differences in the size of nuclei. The anterior parts of sperm heads are embedded in an elongate homogenous matrix forming spermatodesmata. The conical acrosome is deeply invaginated posteriorly, and sits on top of the nucleus. The acrosomal contents are differentiated internally with a tubular substructure and a subacrosomal space. The anterior of the nucleus intrudes into the posterior section of the subacrosomal space. Anteriorly the acrosome is laterally flattened; posteriorly it extends as two tubular processes on either side of the nucleus that gradually decrease in diameter. The homogenously electron-dense nucleus is pointed anteriorly and is generally cylindrical, although posteriorly there is a lateral invagination that extends part-way along the nucleus. This invagination houses fine granular material of the putative centriolar adjunct which does not form in close proximity to the centriole and hence may not be a true centriolar adjunct. The lamellate disposition of the centriolar adjunct material within the sperm-midpiece of cicadettine cicadas is distinct, and separates these cicadas from their cicadine counterparts in which the centriolar adjunct material is non-lamellate. Vesicle-like elements that are associated with both the posterior nucleus and the centriolar adjunct are also found within the invagination. Immediately posterior of and adjoining the centriolar adjunct is a pair of mitochondrial derivatives that are elongated and extend for almost the entire length of the tail. Except for size the architecture of short and long spermatozoa is generally similar in all species. The absence of accessory bodies in cicada sperm suggests that within the Cicadomorpha, the families Cicadidae and Cercopidae are closely related. Only long nuclei were observed in the fertilized eggs of A. zuluensis indicating that sperm with long nuclei might be favoured for fertilization. Spermiogenesis involves: (a) development of the acrosome from a proacrosomal granule; (b) development of the nucleus, characterized by elongation and streamlining with a simultaneous condensation of chromatin; (c) development of the axoneme from the centriole; (d) amalgamation of individual small mitochondria to form elongated mitochondrial derivatives in which cristae are arranged into regularly spaced lamellae; and (f) elimination of cytoplasm. The presence of a manchette, a transient microtubular organelle, which surrounds the acrosome, nucleus and mitochondrial derivatives, is a characteristic feature of spermiogenesis. The gross morphology of the reproductive tract in both male and female cicadas exhibits an organization similar to that in most oviparous insects. The non-functional spermatheca is the only exceptional feature in the female reproductive tract. Its role has been taken over by the common oviduct which, subsequently, has become modified into a swollen, differentiated structure with a dual role of receiving oocytes from the paired ovaries and storage of spermatozoa. Testis mass varies between cicada species; this variation might be linked to the intensity of sperm competition which has been found to be positively correlated with relative investment in spermatogenesis. Based on the preliminary findings of this study, K. punctigera, with its larger testis relative to body size, would be the ideal candidate to show the greatest levels of sperm competition. Accessory glands in both male and female A. zuluensis, D. biconica, P. hirtipennis and O. quadraticollis are very long; this character might be of phylogenetic significance. Despite being notoriously refractory spermiocladistics is potentially valuable in systematic and phylogenic studies of cicadas, especially at the subfamily level.
- Full Text:
- Authors: Chawanji, Abraham Simbarashe
- Date: 2007
- Subjects: Cicadas Cicadas -- Reproduction Spermiogenesis in animals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5770 , http://hdl.handle.net/10962/d1005458
- Description: Sperm structure in five species of cicadine cicadas (Albanycada albigera, Azanicada zuluensis, Platypleura capensis, P. hirtipennis and Pycna semiclara) and five species of cicadettine cicadas (Melampsalta leucoptera, Quintilia walkeri, Stagira simplex, Xosopsaltria thunbergi and Monomatapa matoposa) was investigated by light and electron microscopy. In addition, spermiogenesis in cicadas was described; the information was derived from two cicadettines (Diceroprocta biconica and M. matoposa) and three cicadines (Kongota punctigera, P. capensis and P. semiclara). Mature spermatozoa of all species investigated are elongate and filiform, consisting of three distinct regions: the head (acrosome and nucleus), mid-piece and tail. All species produce more than one discrete length of nucleated, motile sperm, a form of sperm polymorphism termed polymegaly. Polymegaly is expressed in three ways; sperm have uni-, bi- or trimodal nucleus and tail lengths. Besides the differences in length, there are also notable differences in the size of nuclei. The anterior parts of sperm heads are embedded in an elongate homogenous matrix forming spermatodesmata. The conical acrosome is deeply invaginated posteriorly, and sits on top of the nucleus. The acrosomal contents are differentiated internally with a tubular substructure and a subacrosomal space. The anterior of the nucleus intrudes into the posterior section of the subacrosomal space. Anteriorly the acrosome is laterally flattened; posteriorly it extends as two tubular processes on either side of the nucleus that gradually decrease in diameter. The homogenously electron-dense nucleus is pointed anteriorly and is generally cylindrical, although posteriorly there is a lateral invagination that extends part-way along the nucleus. This invagination houses fine granular material of the putative centriolar adjunct which does not form in close proximity to the centriole and hence may not be a true centriolar adjunct. The lamellate disposition of the centriolar adjunct material within the sperm-midpiece of cicadettine cicadas is distinct, and separates these cicadas from their cicadine counterparts in which the centriolar adjunct material is non-lamellate. Vesicle-like elements that are associated with both the posterior nucleus and the centriolar adjunct are also found within the invagination. Immediately posterior of and adjoining the centriolar adjunct is a pair of mitochondrial derivatives that are elongated and extend for almost the entire length of the tail. Except for size the architecture of short and long spermatozoa is generally similar in all species. The absence of accessory bodies in cicada sperm suggests that within the Cicadomorpha, the families Cicadidae and Cercopidae are closely related. Only long nuclei were observed in the fertilized eggs of A. zuluensis indicating that sperm with long nuclei might be favoured for fertilization. Spermiogenesis involves: (a) development of the acrosome from a proacrosomal granule; (b) development of the nucleus, characterized by elongation and streamlining with a simultaneous condensation of chromatin; (c) development of the axoneme from the centriole; (d) amalgamation of individual small mitochondria to form elongated mitochondrial derivatives in which cristae are arranged into regularly spaced lamellae; and (f) elimination of cytoplasm. The presence of a manchette, a transient microtubular organelle, which surrounds the acrosome, nucleus and mitochondrial derivatives, is a characteristic feature of spermiogenesis. The gross morphology of the reproductive tract in both male and female cicadas exhibits an organization similar to that in most oviparous insects. The non-functional spermatheca is the only exceptional feature in the female reproductive tract. Its role has been taken over by the common oviduct which, subsequently, has become modified into a swollen, differentiated structure with a dual role of receiving oocytes from the paired ovaries and storage of spermatozoa. Testis mass varies between cicada species; this variation might be linked to the intensity of sperm competition which has been found to be positively correlated with relative investment in spermatogenesis. Based on the preliminary findings of this study, K. punctigera, with its larger testis relative to body size, would be the ideal candidate to show the greatest levels of sperm competition. Accessory glands in both male and female A. zuluensis, D. biconica, P. hirtipennis and O. quadraticollis are very long; this character might be of phylogenetic significance. Despite being notoriously refractory spermiocladistics is potentially valuable in systematic and phylogenic studies of cicadas, especially at the subfamily level.
- Full Text:
A study of the summarizing strategies used by ESL first year science students at the University of Botswana
- Authors: Chimbganda, Ambrose Bruce
- Date: 2007
- Subjects: English language -- Study and teaching (Foreign speakers) -- Botswana English language -- Study and teaching (Higher) -- Botswana Science -- Study and teaching (Higher) -- Botswana Language and education -- Botswana College students -- Botswana -- Language
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2341 , http://hdl.handle.net/10962/d1002623
- Description: One of the major problems faced by speakers of English as a second language (ESL) or non-native speakers of English (NNS) is that when they go to college or university, they find themselves without sufficient academic literacy skills to enable them to navigate their learning successfully, such as the ability to summarize textual material. This thesis examines the summarizing strategies used by ESL first year science students at the University of Botswana. Using multiple data collection methods, otherwise known as triangulation or pluralistic research, which is a combination of quantitative and qualitative methods, one hundred and twenty randomly sampled students completed questionnaires and summarized a scientific text. In order to observe the students more closely, nine students (3 high-, 3 average- and 3 low-proficiency) were purposively selected from the sample and wrote a further summary. The nine students were later interviewed in order to find out from them the kinds of strategies they had used in summarizing the texts. To obtain systematic data, the summaries and the taped interview were coded and analyzed using a hybrid scoring classification previously used by other researchers. The results from the Likert type of questionnaire suggest that the ESL first year science students are 'aware' of the appropriate reading, production and self-assessment strategies to use when summarizing. However, when the data from the questionnaire were cross-checked against the strategies they had used in the actual summarization of the text, most of their claims, especially those of the low-proficiency students, were not sustained. As a whole, the results show that high-proficiency students produce more accurate idea units and are more capable of generalizing ideas than low-proficiency students who prefer to "cut and paste" ideas. There are also significant differences between high- and low proficiency students in the manner in which they decode the text: low-proficiency students produce more distortions in their summaries than high-proficiency students who generally give accurate information. Similarly, high-proficiency students are able to sort out global ideas from a labyrinth of localized ideas, unlike average- and low-proficiency students who include trivial information. The same trend is observed with paraphrasing and sentence combinations: high-proficiency students are generally able to recast and coordinate their ideas, unlike low-proficiency students who produce run-on ideas. In terms of the discrete cognitive and meta-cognitive skills preferred by students, low proficiency students are noticeably unable to exploit pre-summarizing cognitive strategies such as discriminating, selecting, note-making, grouping, inferring meanings of new words and using synonyms to convey the intended meanings. There are also greater differences between high- and low-proficiency students when it comes to the use of meta-cognitive strategies. Unlike high-proficiency students who use their reservoir of meta-cognitive skills such as self-judgment, low-proficiency students ostensibly find it difficult to direct their summaries to the demands of the task and are unable to check the accuracy of their summaries. The findings also show that some of the high-proficiency students and many average- and low-proficiency students distort idea units, find it difficult to use their own words and cannot distinguish between main and supporting details. This resulted in the production of circuitous summaries that often failed to capture the gist of the argument. The way the students processed the main ideas also reveals an inherent weakness: most students of different proficiency levels were unable to combine ideas from different paragraphs to produce a coherent text. Not surprising, then, there were too many long summaries produced by both high- and low-proficiency students. To tackle some of the problems related to summarization, pre-reading strategies can be taught, which activate relevant prior knowledge, so that the learning of new knowledge can be facilitated. During the reading process students can become more meta-cognitively aware by monitoring their level of understanding of the text by using, for example, the strategy suggested by Schraw (1998) of "stop, read and think". Text analysis can also be used to help the students identify the main themes or macro-propositions in a text, and hence gain a more global perspective of the content, which is important for selecting the main ideas in a text. A particularly useful approach to fostering a deeper understanding of content is to use a form of reciprocal or peer-mediated teaching, in which students in pairs can articulate to each other their understanding of the main ideas expressed in the text. As part of the solution to the problems faced by students when processing information, we need to take Sewlall's (2000: 170) advice that there should be "a paradigm shift in the learning philosophy from content-based to an emphasis on the acquisition of skills". In this regard, both content and ESL teachers need to train their students in the explicit use of summarizing strategies, and to plan interwoven lessons and learning activities that develop the learners' intellectual ways of dealing with different learning problems so that they can make learning quicker, easier, more effective and exciting.
- Full Text:
- Authors: Chimbganda, Ambrose Bruce
- Date: 2007
- Subjects: English language -- Study and teaching (Foreign speakers) -- Botswana English language -- Study and teaching (Higher) -- Botswana Science -- Study and teaching (Higher) -- Botswana Language and education -- Botswana College students -- Botswana -- Language
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2341 , http://hdl.handle.net/10962/d1002623
- Description: One of the major problems faced by speakers of English as a second language (ESL) or non-native speakers of English (NNS) is that when they go to college or university, they find themselves without sufficient academic literacy skills to enable them to navigate their learning successfully, such as the ability to summarize textual material. This thesis examines the summarizing strategies used by ESL first year science students at the University of Botswana. Using multiple data collection methods, otherwise known as triangulation or pluralistic research, which is a combination of quantitative and qualitative methods, one hundred and twenty randomly sampled students completed questionnaires and summarized a scientific text. In order to observe the students more closely, nine students (3 high-, 3 average- and 3 low-proficiency) were purposively selected from the sample and wrote a further summary. The nine students were later interviewed in order to find out from them the kinds of strategies they had used in summarizing the texts. To obtain systematic data, the summaries and the taped interview were coded and analyzed using a hybrid scoring classification previously used by other researchers. The results from the Likert type of questionnaire suggest that the ESL first year science students are 'aware' of the appropriate reading, production and self-assessment strategies to use when summarizing. However, when the data from the questionnaire were cross-checked against the strategies they had used in the actual summarization of the text, most of their claims, especially those of the low-proficiency students, were not sustained. As a whole, the results show that high-proficiency students produce more accurate idea units and are more capable of generalizing ideas than low-proficiency students who prefer to "cut and paste" ideas. There are also significant differences between high- and low proficiency students in the manner in which they decode the text: low-proficiency students produce more distortions in their summaries than high-proficiency students who generally give accurate information. Similarly, high-proficiency students are able to sort out global ideas from a labyrinth of localized ideas, unlike average- and low-proficiency students who include trivial information. The same trend is observed with paraphrasing and sentence combinations: high-proficiency students are generally able to recast and coordinate their ideas, unlike low-proficiency students who produce run-on ideas. In terms of the discrete cognitive and meta-cognitive skills preferred by students, low proficiency students are noticeably unable to exploit pre-summarizing cognitive strategies such as discriminating, selecting, note-making, grouping, inferring meanings of new words and using synonyms to convey the intended meanings. There are also greater differences between high- and low-proficiency students when it comes to the use of meta-cognitive strategies. Unlike high-proficiency students who use their reservoir of meta-cognitive skills such as self-judgment, low-proficiency students ostensibly find it difficult to direct their summaries to the demands of the task and are unable to check the accuracy of their summaries. The findings also show that some of the high-proficiency students and many average- and low-proficiency students distort idea units, find it difficult to use their own words and cannot distinguish between main and supporting details. This resulted in the production of circuitous summaries that often failed to capture the gist of the argument. The way the students processed the main ideas also reveals an inherent weakness: most students of different proficiency levels were unable to combine ideas from different paragraphs to produce a coherent text. Not surprising, then, there were too many long summaries produced by both high- and low-proficiency students. To tackle some of the problems related to summarization, pre-reading strategies can be taught, which activate relevant prior knowledge, so that the learning of new knowledge can be facilitated. During the reading process students can become more meta-cognitively aware by monitoring their level of understanding of the text by using, for example, the strategy suggested by Schraw (1998) of "stop, read and think". Text analysis can also be used to help the students identify the main themes or macro-propositions in a text, and hence gain a more global perspective of the content, which is important for selecting the main ideas in a text. A particularly useful approach to fostering a deeper understanding of content is to use a form of reciprocal or peer-mediated teaching, in which students in pairs can articulate to each other their understanding of the main ideas expressed in the text. As part of the solution to the problems faced by students when processing information, we need to take Sewlall's (2000: 170) advice that there should be "a paradigm shift in the learning philosophy from content-based to an emphasis on the acquisition of skills". In this regard, both content and ESL teachers need to train their students in the explicit use of summarizing strategies, and to plan interwoven lessons and learning activities that develop the learners' intellectual ways of dealing with different learning problems so that they can make learning quicker, easier, more effective and exciting.
- Full Text:
Women living with HIV/AIDS: a phenomenological intergenerational interpretation of their experiences
- Chisaka, Janet Kaemba Chishimba
- Authors: Chisaka, Janet Kaemba Chishimba
- Date: 2007
- Subjects: AIDS (Disease) in women -- South Africa -- Case studies HIV positive women -- South Africa -- Case studies Poor women -- South Africa -- Case studies
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3307 , http://hdl.handle.net/10962/d1003095
- Description: This study deals with the impact of HIV/AIDS on women living in chronic poverty. The question arises: Do we focus on their HIV/AIDS stories only or do we include their other lived experiences? This phenomenological study, on two sets of three generations of women infected and affected by HIV/AIDS and living in poverty, is an attempt at understanding the way the women experience their lifeworlds, not only their HIV/AIDS stories. One set includes a grandmother, her daughter who is living with full-blown AIDS, and her granddaughter, while the other includes a grandmother, her daughter and her granddaughter infected with HIV. The initial focus of the study was on the women’s HIV/AIDS narratives. However as the study progressed, especially during the interviews, it became apparent that the women’s generational poverty or chronic poverty was of greater concern to them than the HIV/AIDS that they were experiencing. Of the six participants, only one woman centred her life story on HIV/AIDS. This finding echoes other studies on HIV/AIDS among poor women: that chronic poverty is more threatening to the women than the risk or reality of AIDS. As a phenomenological researcher my aim was to focus on the participants’ own interpretations of the studied phenomenon. However, this was inadequate in accounting for the role that social structures play in shaping and informing the women’s subjective consciousness and experience. For this reason, I used feminist ideas to understand and interpret the women’s patriarchal experiences.
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Women living with HIV/AIDS: a phenomenological intergenerational interpretation of their experiences
- Authors: Chisaka, Janet Kaemba Chishimba
- Date: 2007
- Subjects: AIDS (Disease) in women -- South Africa -- Case studies HIV positive women -- South Africa -- Case studies Poor women -- South Africa -- Case studies
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3307 , http://hdl.handle.net/10962/d1003095
- Description: This study deals with the impact of HIV/AIDS on women living in chronic poverty. The question arises: Do we focus on their HIV/AIDS stories only or do we include their other lived experiences? This phenomenological study, on two sets of three generations of women infected and affected by HIV/AIDS and living in poverty, is an attempt at understanding the way the women experience their lifeworlds, not only their HIV/AIDS stories. One set includes a grandmother, her daughter who is living with full-blown AIDS, and her granddaughter, while the other includes a grandmother, her daughter and her granddaughter infected with HIV. The initial focus of the study was on the women’s HIV/AIDS narratives. However as the study progressed, especially during the interviews, it became apparent that the women’s generational poverty or chronic poverty was of greater concern to them than the HIV/AIDS that they were experiencing. Of the six participants, only one woman centred her life story on HIV/AIDS. This finding echoes other studies on HIV/AIDS among poor women: that chronic poverty is more threatening to the women than the risk or reality of AIDS. As a phenomenological researcher my aim was to focus on the participants’ own interpretations of the studied phenomenon. However, this was inadequate in accounting for the role that social structures play in shaping and informing the women’s subjective consciousness and experience. For this reason, I used feminist ideas to understand and interpret the women’s patriarchal experiences.
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The microbial ecology of sulphidogenic lignocellulose degradation
- Authors: Clarke, Anna Maria
- Date: 2007
- Subjects: Microbial ecology , Lignocellulose , Sulfides , Lignin , Lignocellulose -- Biodegradation , Mines and mineral resources -- Waste disposal , Acid mine drainage
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4094 , http://hdl.handle.net/10962/d1008181
- Description: Acid mine drainage is a well known environmental pollutant, not only in South Africa, but throughout the world, and the use of microbial processes in the treatment of these wastes has been the subject of investigation over past decades. Lignocellulose packed-bed reactors have been used in passive treatment systems, and, although effective initially, they show early decline in performance while the packing material remains largely un-utilized. Little is known about this phenomenon which remains a severe constraint in the development of efficient passive mine water treatment systems. It has been proposed that the degradation pathways of the complex lignocellulose substrate may be limited in some way in these systems during the manifestation of this effect. This study has addressed the problem using a molecular microbial ecology methodology in an attempt to relate trophic functions of the microbial population to the physico-chemical data of the system. A field-scale lignocellulose packed-bed reactor located at Vryheid Coronation Colliery (Northern Kwa-Zulu Natal province, South Africa) was monitored for six years and the results showed the classic profile of performance decline related to a slowdown in sulphate reduction and alkalinity production. The reactor was decommissioned , comprehensive samples were collected along the depth profile and the microbial populations investigated by means of 16S rRNA gene methodology. The population was found to include cellulolytic Clostridia spp., CytophagaIFlavobacterlBacteroidetes, Sphingomonadaceae and as yet uncultured microorganisms related to microbiota identified in the rumen and termite gut. These are all known to be involved as primary fermenters of cellulose. Oesulphosporosinus was present as sulphate reducer. A comparison of substrata sampling and population distribution suggested that spatial and temporal gradients within the system may become established over the course of its operation. Based on these findings, a laboratory-scale reactor was constructed to simulate the performance of the packed-bed reactor under controlled experimental conditions. The laboratory-scale reactor was operated for 273 days and showed comparable performance to that in the field in both biomolecular and physicochemical data. Clearly defined trophic niches were observed. These results suggested that a sequence of events does occur in lignocellulose degradation over time. Based on the spatial and temporal column studies, a descriptive model was proposed to account for these events. It was found that fermentative organisms predominate in the inlet zone of the system using easily extractable compounds from the wood, thus providing feedstock for sulphate reduction occurring in the succeeding compartments. Production of sulphide and alkalinity appears to be involved in the enhancement of lignin degradation and this, in turn, appears to enhance access to the cellulose fraction. However, once the readily extractables are exhausted, the decline in sulphide and alkalinity production leads inexorably to a decline in the overall performance of the system as a sulphate reducing unit operation. These observations led to the proposal that with the addition of a limited amount of a readily available carbon source, such as molasses, in the initial zone of the the reactor, the ongoing generation of sulphide would be sustained and this in turn would sustain the microbial attack on the lignocellulose complex. This proposal was tested in scale-up studies and positive results indicate that the descriptive model may, to some extent, provide an account of events occurring in these systems. The work on sustaining lignocellulose degradation through the maintenance of sulphate reduction in the initial stages of the reactor flow path has led to the development of the Degrading Packed-bed Reactor concept and that, has subsequently been successfully evaluated in the field.
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- Authors: Clarke, Anna Maria
- Date: 2007
- Subjects: Microbial ecology , Lignocellulose , Sulfides , Lignin , Lignocellulose -- Biodegradation , Mines and mineral resources -- Waste disposal , Acid mine drainage
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4094 , http://hdl.handle.net/10962/d1008181
- Description: Acid mine drainage is a well known environmental pollutant, not only in South Africa, but throughout the world, and the use of microbial processes in the treatment of these wastes has been the subject of investigation over past decades. Lignocellulose packed-bed reactors have been used in passive treatment systems, and, although effective initially, they show early decline in performance while the packing material remains largely un-utilized. Little is known about this phenomenon which remains a severe constraint in the development of efficient passive mine water treatment systems. It has been proposed that the degradation pathways of the complex lignocellulose substrate may be limited in some way in these systems during the manifestation of this effect. This study has addressed the problem using a molecular microbial ecology methodology in an attempt to relate trophic functions of the microbial population to the physico-chemical data of the system. A field-scale lignocellulose packed-bed reactor located at Vryheid Coronation Colliery (Northern Kwa-Zulu Natal province, South Africa) was monitored for six years and the results showed the classic profile of performance decline related to a slowdown in sulphate reduction and alkalinity production. The reactor was decommissioned , comprehensive samples were collected along the depth profile and the microbial populations investigated by means of 16S rRNA gene methodology. The population was found to include cellulolytic Clostridia spp., CytophagaIFlavobacterlBacteroidetes, Sphingomonadaceae and as yet uncultured microorganisms related to microbiota identified in the rumen and termite gut. These are all known to be involved as primary fermenters of cellulose. Oesulphosporosinus was present as sulphate reducer. A comparison of substrata sampling and population distribution suggested that spatial and temporal gradients within the system may become established over the course of its operation. Based on these findings, a laboratory-scale reactor was constructed to simulate the performance of the packed-bed reactor under controlled experimental conditions. The laboratory-scale reactor was operated for 273 days and showed comparable performance to that in the field in both biomolecular and physicochemical data. Clearly defined trophic niches were observed. These results suggested that a sequence of events does occur in lignocellulose degradation over time. Based on the spatial and temporal column studies, a descriptive model was proposed to account for these events. It was found that fermentative organisms predominate in the inlet zone of the system using easily extractable compounds from the wood, thus providing feedstock for sulphate reduction occurring in the succeeding compartments. Production of sulphide and alkalinity appears to be involved in the enhancement of lignin degradation and this, in turn, appears to enhance access to the cellulose fraction. However, once the readily extractables are exhausted, the decline in sulphide and alkalinity production leads inexorably to a decline in the overall performance of the system as a sulphate reducing unit operation. These observations led to the proposal that with the addition of a limited amount of a readily available carbon source, such as molasses, in the initial zone of the the reactor, the ongoing generation of sulphide would be sustained and this in turn would sustain the microbial attack on the lignocellulose complex. This proposal was tested in scale-up studies and positive results indicate that the descriptive model may, to some extent, provide an account of events occurring in these systems. The work on sustaining lignocellulose degradation through the maintenance of sulphate reduction in the initial stages of the reactor flow path has led to the development of the Degrading Packed-bed Reactor concept and that, has subsequently been successfully evaluated in the field.
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Securing media streams in an Asterisk-based environment and evaluating the resulting performance cost
- Authors: Clayton, Bradley
- Date: 2007 , 2007-01-08
- Subjects: Asterisk (Computer file) , Computer networks -- Security measures , Internet telephony -- Security measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4647 , http://hdl.handle.net/10962/d1006606 , Asterisk (Computer file) , Computer networks -- Security measures , Internet telephony -- Security measures
- Description: When adding Confidentiality, Integrity and Availability (CIA) to a multi-user VoIP (Voice over IP) system, performance and quality are at risk. The aim of this study is twofold. Firstly, it describes current methods suitable to secure voice streams within a VoIP system and make them available in an Asterisk-based VoIP environment. (Asterisk is a well established, open-source, TDM/VoIP PBX.) Secondly, this study evaluates the performance cost incurred after implementing each security method within the Asterisk-based system, using a special testbed suite, named DRAPA, which was developed expressly for this study. The three security methods implemented and studied were IPSec (Internet Protocol Security), SRTP (Secure Real-time Transport Protocol), and SIAX2 (Secure Inter-Asterisk eXchange 2 protocol). From the experiments, it was found that bandwidth and CPU usage were significantly affected by the addition of CIA. In ranking the three security methods in terms of these two resources, it was found that SRTP incurs the least bandwidth overhead, followed by SIAX2 and then IPSec. Where CPU utilisation is concerned, it was found that SIAX2 incurs the least overhead, followed by IPSec, and then SRTP.
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- Authors: Clayton, Bradley
- Date: 2007 , 2007-01-08
- Subjects: Asterisk (Computer file) , Computer networks -- Security measures , Internet telephony -- Security measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4647 , http://hdl.handle.net/10962/d1006606 , Asterisk (Computer file) , Computer networks -- Security measures , Internet telephony -- Security measures
- Description: When adding Confidentiality, Integrity and Availability (CIA) to a multi-user VoIP (Voice over IP) system, performance and quality are at risk. The aim of this study is twofold. Firstly, it describes current methods suitable to secure voice streams within a VoIP system and make them available in an Asterisk-based VoIP environment. (Asterisk is a well established, open-source, TDM/VoIP PBX.) Secondly, this study evaluates the performance cost incurred after implementing each security method within the Asterisk-based system, using a special testbed suite, named DRAPA, which was developed expressly for this study. The three security methods implemented and studied were IPSec (Internet Protocol Security), SRTP (Secure Real-time Transport Protocol), and SIAX2 (Secure Inter-Asterisk eXchange 2 protocol). From the experiments, it was found that bandwidth and CPU usage were significantly affected by the addition of CIA. In ranking the three security methods in terms of these two resources, it was found that SRTP incurs the least bandwidth overhead, followed by SIAX2 and then IPSec. Where CPU utilisation is concerned, it was found that SIAX2 incurs the least overhead, followed by IPSec, and then SRTP.
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