Design ethnography: methodological considerations for rebalancing socio-technical phenomena in CMS performativity
- Authors: Jordaan, Leandra
- Date: 2020
- Subjects: Database management -- Social aspects , Information technology -- Social aspects , Management information systems -- Social aspects , Database management -- Philosophy , Information technology -- Philosophy , Management information systems -- Philosophy
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/164781 , vital:41164
- Description: As a practitioner, I had been part of two Content Management System (CMS) Projects in a particular setting that did not deliver on the expected outcomes. The expected outcomes of the projects included streamlined processes, better access to information, functionalities to drive engagement, reduced time searching for information, and improved reusability of content. As I began to reflect on the projects, a certain discomfort developed when the social aspect was ignored in favour of the technological. I sought a better understanding, but I was unaware of the fact at first. The techno-centricity as a concept found in literature and my experience as content management (CM) practitioner – together informed my interest in rebalancing the social and the technological. Thus, I focused on conduct in performing of tasks and emphasised attention on the practices of experts who gave insight into context of CM and use. The research participants are communication practitioners who have the responsibility to communicate internally and externally on behalf of a publicly-funded university in South Africa. Guided by the abductive argument and literature, the key themes for the research focused on technology, individuals and the organisation. The focus on technology (CMS as a subfield of Information Systems) began with my involvement in two CMS Projects. What came to the fore was that the practitioner perspective, and thus their experiential knowledge are neglected in research and that it may be an over-emphasis on techno-centrism in CMS research. I sought to better balance the social and technological aspects. The second focus on individuals (communication practitioners) was to value the stakeholder who was considered representative of the worldviews of the community. I sought to support corporate communication practices in the task of relationship building with stakeholders. The findings showed that the culture of informatio sharing was low at the University. The third focus on the organisation (the University) was to prioritise the success of the communication undertaken by the University. I interrogated the role of power. I demonstrated how the role of power could be seen as productive and positive in the context of HE, the social reality of CUT, and this IS research itself. I positioned the research as interpretivistic. I used hermeneutics as a mode of analysis because as researcher-practitioner, I am part of the social reality of the research. A safeguard against my subjectivity was the use of Phronesis as an orientation to knowledge. An organisation with a shared understanding of ethics and values will balance instrumental rationality (scientific and technical reasoning) with value-rationality (moral reasoning about right and wrong actions). Phronesis is the virtue that should ensure ethical behaviour in actions, yet over time, social science research, in a quest to mimic the natural sciences, centred on episteme and techne. I constructed the lens by particularising the four value-rational questions of Flyvbjerg’s contemporary Phronesis to the performative perspective of the research. My interest in social reality, as well as socio-technical aspects, have led to design-ethnography (D-E) to emerge as the most suitable and most appropriate approach to the research. D-E asked the prescriptive ‘How’ and descriptive ‘What’ questions, whilst the Flyvbjergian Phronesis lens brought focus on the ‘Why’ question. D-E emphasised the betterment of the interaction and synergy between research conducted and practice. My status as an immersed researcher needed careful consideration, and D-E accepted that a certain level of immersion is necessary, D-E has short interventional fieldwork, and D-E has future-oriented engagement. The contemporary Phronesis used in the research is to enact D-E and not an all-encompassing guide for doing Phronesis research The key contributions to the research are predominantly methodological. The claims draw on evidence focused on the three themes technology, individuals and organisation, and the phenomena of interest which are to rebalance the social and the technological in CM practices. The first claim is that immersion in the context is possible and supported by the specific particularised approaches to the research. The second claim suggests a way to rebalance the socio-technical nature of Information Systems (IS). The third claim suggests that there is a viewpoint for power that is not focused on power’s oppressive nature which could see a diverging focus on power in IS research in future. In this viewpoint, the status quo of social reality is not questioned, nor are their emancipatory ambitions. The fourth and final claim suggests that Phronesis as a lens could enact D-E, which in turn is a method that assists in valuing the experience of the practitioner and the support of collaborative work. The research is recommended for IT/IS practitioners who prefer to value participants’ views in design. The approaches used could be of value for researchers who consider the context of their research to be of higher importance than the generalisation of outcomes. Researchers who find themselves in the position of being immersed in the context but question the correctness of active engagement in the field may discover some value from the research approaches and my experience. Also, researchers or practitioners who have an interest in the balance between social and the technological aspects of IS projects. Researchers or practitioners interested in Phronesis, and perhaps the viewpoint of a lens may also find value in this research.
- Full Text:
- Date Issued: 2020
- Authors: Jordaan, Leandra
- Date: 2020
- Subjects: Database management -- Social aspects , Information technology -- Social aspects , Management information systems -- Social aspects , Database management -- Philosophy , Information technology -- Philosophy , Management information systems -- Philosophy
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/164781 , vital:41164
- Description: As a practitioner, I had been part of two Content Management System (CMS) Projects in a particular setting that did not deliver on the expected outcomes. The expected outcomes of the projects included streamlined processes, better access to information, functionalities to drive engagement, reduced time searching for information, and improved reusability of content. As I began to reflect on the projects, a certain discomfort developed when the social aspect was ignored in favour of the technological. I sought a better understanding, but I was unaware of the fact at first. The techno-centricity as a concept found in literature and my experience as content management (CM) practitioner – together informed my interest in rebalancing the social and the technological. Thus, I focused on conduct in performing of tasks and emphasised attention on the practices of experts who gave insight into context of CM and use. The research participants are communication practitioners who have the responsibility to communicate internally and externally on behalf of a publicly-funded university in South Africa. Guided by the abductive argument and literature, the key themes for the research focused on technology, individuals and the organisation. The focus on technology (CMS as a subfield of Information Systems) began with my involvement in two CMS Projects. What came to the fore was that the practitioner perspective, and thus their experiential knowledge are neglected in research and that it may be an over-emphasis on techno-centrism in CMS research. I sought to better balance the social and technological aspects. The second focus on individuals (communication practitioners) was to value the stakeholder who was considered representative of the worldviews of the community. I sought to support corporate communication practices in the task of relationship building with stakeholders. The findings showed that the culture of informatio sharing was low at the University. The third focus on the organisation (the University) was to prioritise the success of the communication undertaken by the University. I interrogated the role of power. I demonstrated how the role of power could be seen as productive and positive in the context of HE, the social reality of CUT, and this IS research itself. I positioned the research as interpretivistic. I used hermeneutics as a mode of analysis because as researcher-practitioner, I am part of the social reality of the research. A safeguard against my subjectivity was the use of Phronesis as an orientation to knowledge. An organisation with a shared understanding of ethics and values will balance instrumental rationality (scientific and technical reasoning) with value-rationality (moral reasoning about right and wrong actions). Phronesis is the virtue that should ensure ethical behaviour in actions, yet over time, social science research, in a quest to mimic the natural sciences, centred on episteme and techne. I constructed the lens by particularising the four value-rational questions of Flyvbjerg’s contemporary Phronesis to the performative perspective of the research. My interest in social reality, as well as socio-technical aspects, have led to design-ethnography (D-E) to emerge as the most suitable and most appropriate approach to the research. D-E asked the prescriptive ‘How’ and descriptive ‘What’ questions, whilst the Flyvbjergian Phronesis lens brought focus on the ‘Why’ question. D-E emphasised the betterment of the interaction and synergy between research conducted and practice. My status as an immersed researcher needed careful consideration, and D-E accepted that a certain level of immersion is necessary, D-E has short interventional fieldwork, and D-E has future-oriented engagement. The contemporary Phronesis used in the research is to enact D-E and not an all-encompassing guide for doing Phronesis research The key contributions to the research are predominantly methodological. The claims draw on evidence focused on the three themes technology, individuals and organisation, and the phenomena of interest which are to rebalance the social and the technological in CM practices. The first claim is that immersion in the context is possible and supported by the specific particularised approaches to the research. The second claim suggests a way to rebalance the socio-technical nature of Information Systems (IS). The third claim suggests that there is a viewpoint for power that is not focused on power’s oppressive nature which could see a diverging focus on power in IS research in future. In this viewpoint, the status quo of social reality is not questioned, nor are their emancipatory ambitions. The fourth and final claim suggests that Phronesis as a lens could enact D-E, which in turn is a method that assists in valuing the experience of the practitioner and the support of collaborative work. The research is recommended for IT/IS practitioners who prefer to value participants’ views in design. The approaches used could be of value for researchers who consider the context of their research to be of higher importance than the generalisation of outcomes. Researchers who find themselves in the position of being immersed in the context but question the correctness of active engagement in the field may discover some value from the research approaches and my experience. Also, researchers or practitioners who have an interest in the balance between social and the technological aspects of IS projects. Researchers or practitioners interested in Phronesis, and perhaps the viewpoint of a lens may also find value in this research.
- Full Text:
- Date Issued: 2020
Design of Immunobiosensors for Detection of Tumor-Associated Anti-P53 Autoantibodies: Method Development
- Authors: Adeniyi, Omotayo Kayode
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/162988 , vital:41002 , 10.21504/10962/162988
- Description: Introduction -- Experimental -- Label-Free Impedimetric Sensing of Anti-P53ab... -- Fluorescent detection of Anti-P53ab -- Peroxidase-like activity of Fe3O4@SiNP-APTES-Au@Pd... -- Colorimetric detection of Anti-P53ab , Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020. , Detection and profiling of circulating tumor-associated autoantibodies (TAAbs) are useful for screening and early-stage diagnosis of asymptomatic lung cancer. Immunobiosensor technologies aimed to accomplish the highly sensitive, rapid and low-cost detection of TAAbs can improve the early-stage detection of lung cancer. Immunobiosensors for the detection of anti-P53-tumour associated autoantibodies have been developed in this work. The design of sensing interfaces with immobilized P53 protein (P53ag) as a sensing element layer on a solid interface was investigated. Several methods of detecting anti-P53-antibodies (anti-P53ab) were investigated. These methods are label-free detection using electrochemical impedance spectroscopy (EIS) and two label techniques. The label-free electrochemical techniques utilize gold electrode pre-modified with a conducting layer of electrochemically grafted phenylethylamine for covalent immobilization of P53ag. The limit of anti-P53ab detection with the label-free EIS was 103.0 pg.ml-1. The labeled technique developed utilizes fluorescent, and peroxidase-like nanomaterial labeled antibody as a detection probe. For the fluorescence detection, fluorescent silica nanoparticles were synthesized by overloading FITC into the silica matrix and conjugated to detection antibody (anti-IgG). The detection of the anti-P53ab was based on the dissolution of the silica nanoparticles to release the loaded dye as a signal amplification strategy. The fluorescence detection was carried out on a microplate, and magnetic bead modified P53-antigen platforms and limit of detection (LoD) were 42.0 fg.ml-1 and 3.3 fg.ml-1 for anti-P53ab; respectively. Fe3O4@SiNP-APTES-Au@Pd hybrid nanoparticles were synthesized, and their peroxidase-like activity and colorimetric detection were evaluated. The Fe3O4@SiNP-APTES-Au@Pd exhibited comparable activity to HRP. The Fe3O4@SiNP-APTES-Au@Pd was conjugated to protein-G-anti-IgG for the detection of anti-P53ab on a microplate and cellulose paper platforms. The LoD was 20.0 fg.ml-1 and 63.0 fg.ml-1 for the microplate and cellulose paper platform; respectively. The potential application of the designed immunobiosensor was evaluated in simulated serum samples. The developed sensors showed higher detection sensitivity, stability and had a lower detection limit for anti-P53ab when compared with the ELISA based detection. The results have provided alternative and effective quantification approaches to ELISA and a promising future for multiplexed detection of tumor-associated autoantibodies. The developed methodologies in this thesis could be applied for the detection of other autoantibodies in other cancer types and auto-immune diseases.
- Full Text:
- Date Issued: 2020
- Authors: Adeniyi, Omotayo Kayode
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/162988 , vital:41002 , 10.21504/10962/162988
- Description: Introduction -- Experimental -- Label-Free Impedimetric Sensing of Anti-P53ab... -- Fluorescent detection of Anti-P53ab -- Peroxidase-like activity of Fe3O4@SiNP-APTES-Au@Pd... -- Colorimetric detection of Anti-P53ab , Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020. , Detection and profiling of circulating tumor-associated autoantibodies (TAAbs) are useful for screening and early-stage diagnosis of asymptomatic lung cancer. Immunobiosensor technologies aimed to accomplish the highly sensitive, rapid and low-cost detection of TAAbs can improve the early-stage detection of lung cancer. Immunobiosensors for the detection of anti-P53-tumour associated autoantibodies have been developed in this work. The design of sensing interfaces with immobilized P53 protein (P53ag) as a sensing element layer on a solid interface was investigated. Several methods of detecting anti-P53-antibodies (anti-P53ab) were investigated. These methods are label-free detection using electrochemical impedance spectroscopy (EIS) and two label techniques. The label-free electrochemical techniques utilize gold electrode pre-modified with a conducting layer of electrochemically grafted phenylethylamine for covalent immobilization of P53ag. The limit of anti-P53ab detection with the label-free EIS was 103.0 pg.ml-1. The labeled technique developed utilizes fluorescent, and peroxidase-like nanomaterial labeled antibody as a detection probe. For the fluorescence detection, fluorescent silica nanoparticles were synthesized by overloading FITC into the silica matrix and conjugated to detection antibody (anti-IgG). The detection of the anti-P53ab was based on the dissolution of the silica nanoparticles to release the loaded dye as a signal amplification strategy. The fluorescence detection was carried out on a microplate, and magnetic bead modified P53-antigen platforms and limit of detection (LoD) were 42.0 fg.ml-1 and 3.3 fg.ml-1 for anti-P53ab; respectively. Fe3O4@SiNP-APTES-Au@Pd hybrid nanoparticles were synthesized, and their peroxidase-like activity and colorimetric detection were evaluated. The Fe3O4@SiNP-APTES-Au@Pd exhibited comparable activity to HRP. The Fe3O4@SiNP-APTES-Au@Pd was conjugated to protein-G-anti-IgG for the detection of anti-P53ab on a microplate and cellulose paper platforms. The LoD was 20.0 fg.ml-1 and 63.0 fg.ml-1 for the microplate and cellulose paper platform; respectively. The potential application of the designed immunobiosensor was evaluated in simulated serum samples. The developed sensors showed higher detection sensitivity, stability and had a lower detection limit for anti-P53ab when compared with the ELISA based detection. The results have provided alternative and effective quantification approaches to ELISA and a promising future for multiplexed detection of tumor-associated autoantibodies. The developed methodologies in this thesis could be applied for the detection of other autoantibodies in other cancer types and auto-immune diseases.
- Full Text:
- Date Issued: 2020
Design of immunosensor for the detection of C-reactive protein using oriented antibody immobilization
- Authors: Adesina, Abiola Olanike
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163080 , vital:41010 , https://dx.doi.org/10.21504/10962/163080
- Description: Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020.
- Full Text:
- Date Issued: 2020
- Authors: Adesina, Abiola Olanike
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163080 , vital:41010 , https://dx.doi.org/10.21504/10962/163080
- Description: Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020.
- Full Text:
- Date Issued: 2020
Designing a parental involvement programme to enhance parental engagement in the educational support programme at a disadvantaged primary school in the Nelson Mandela Bay Metropole, South Africa through participatory action research
- WIlliams, Pearl Juanita Cherrol
- Authors: WIlliams, Pearl Juanita Cherrol
- Date: 2020
- Subjects: Education -- Parent participation -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47303 , vital:39841
- Description: Over the past decades parental involvement in education has increased rapidly within disadvantaged schools in South Africa. This transformation is evident in the legislation of the country which celebrates a spirit of Ubuntu in a democratised society, and, education at large. The ideal of effective school-home partnership across racial boundaries are, for example, emphasised and strengthened via parental involvement at all public schools. Parents, according to the Department of Education (DoE, 1996b:11; 2000c:29; 2001b:29; 2008:23; 2009:17; 2014b:27; n.d.:6), are considered key role-players in school governance and encouraged to support equal educational opportunities for all learners. It implies that the praxis of parental involvement – especially at disadvantaged schools – is a huge benefit to learners with existing backlogs in education. In relation to this view, Stofile and Green (2007:63) emphasise the significance of parental involvement in school life as it can assist greatly in addressing the divere needs of disadvantaged learners. The dynamics associated with parental involvement are investigated in this study through two cycles of participatory action research. Initially ten parents from one of the disadvantaged primary schools within the Nelson Mandela Bay Metropole were purposively selected to participate in an in-depth qualitative research study pertaining to the design of a suitable parental involvement programme for disadvantaged learners. All the relevant information was gathered during action learning sets, individual interviews, and observations to triangulate the data and fill in possible gaps. This data was coded and categorised throughout the cyclical process via inductive participatory data analysis, as described by Patton (2015:216 & 551). Three main themes with sub-themes emerged from the study, namely (1) deficits of the academic programme: remedial education, teacher-assistants, homeworksupport, technical abilities; (2) the neglect of social wellness programmes: need for parental guidance, necessary professional assistance, upgrading of safety measures, availability of clothing bank, sustainability of a nutritional programme; and (3) voids in communication and relationships: the home environment, community, school environment. These themes and sub-themes successfully answered all the research questions. An increasing number of learners at disadvataged primary schools are neglected and/or leave school at a very young age. This scenario is often linked to poor communication and/or a lack of adequate educational support programmes to enhance better learning outcomes. The design of a PIP aimed to address the diverse needs of learners at a specific disadvantaged primary school with the full cooperation of their parents. Nested within the Ecological Model of Bronfenbrenner, the participating parents were engaged in comprehensive discussions about educational support programmes that the school could embark on with them. Numerous programmes were identified as fundamental to transforming the quality of education for many disadvantaged learners. This research therefore encouraged greater parental involvement at disadvantaged primary schools in order to sustain better learning outcomes.
- Full Text:
- Date Issued: 2020
- Authors: WIlliams, Pearl Juanita Cherrol
- Date: 2020
- Subjects: Education -- Parent participation -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47303 , vital:39841
- Description: Over the past decades parental involvement in education has increased rapidly within disadvantaged schools in South Africa. This transformation is evident in the legislation of the country which celebrates a spirit of Ubuntu in a democratised society, and, education at large. The ideal of effective school-home partnership across racial boundaries are, for example, emphasised and strengthened via parental involvement at all public schools. Parents, according to the Department of Education (DoE, 1996b:11; 2000c:29; 2001b:29; 2008:23; 2009:17; 2014b:27; n.d.:6), are considered key role-players in school governance and encouraged to support equal educational opportunities for all learners. It implies that the praxis of parental involvement – especially at disadvantaged schools – is a huge benefit to learners with existing backlogs in education. In relation to this view, Stofile and Green (2007:63) emphasise the significance of parental involvement in school life as it can assist greatly in addressing the divere needs of disadvantaged learners. The dynamics associated with parental involvement are investigated in this study through two cycles of participatory action research. Initially ten parents from one of the disadvantaged primary schools within the Nelson Mandela Bay Metropole were purposively selected to participate in an in-depth qualitative research study pertaining to the design of a suitable parental involvement programme for disadvantaged learners. All the relevant information was gathered during action learning sets, individual interviews, and observations to triangulate the data and fill in possible gaps. This data was coded and categorised throughout the cyclical process via inductive participatory data analysis, as described by Patton (2015:216 & 551). Three main themes with sub-themes emerged from the study, namely (1) deficits of the academic programme: remedial education, teacher-assistants, homeworksupport, technical abilities; (2) the neglect of social wellness programmes: need for parental guidance, necessary professional assistance, upgrading of safety measures, availability of clothing bank, sustainability of a nutritional programme; and (3) voids in communication and relationships: the home environment, community, school environment. These themes and sub-themes successfully answered all the research questions. An increasing number of learners at disadvataged primary schools are neglected and/or leave school at a very young age. This scenario is often linked to poor communication and/or a lack of adequate educational support programmes to enhance better learning outcomes. The design of a PIP aimed to address the diverse needs of learners at a specific disadvantaged primary school with the full cooperation of their parents. Nested within the Ecological Model of Bronfenbrenner, the participating parents were engaged in comprehensive discussions about educational support programmes that the school could embark on with them. Numerous programmes were identified as fundamental to transforming the quality of education for many disadvantaged learners. This research therefore encouraged greater parental involvement at disadvantaged primary schools in order to sustain better learning outcomes.
- Full Text:
- Date Issued: 2020
Determination of nonlinear optical properties of phthalocyanine regioisomers using computational models
- Date: 2020
- Subjects: Electrochemistry , Phthalocyanines , Nanoparticles , Nonlinear optics , Nonlinear optical spectroscopy , Refraction
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/166197 , vital:41337
- Description: This work investigates the effects of the nonlinear optical properties of four different constitutional isomers (C4h, C2v, Cs, and D2h) of a series of tetrasubstituted phthalocyanines (free-base 3-4-tert-butylphenoxyether phthalocyanines, free-base 4-4-tertbutylphenoxyether phthalocyanines, SnCl2 tetra substituted 3-4-tert-butylphenoxyether phthalocyanine, and SnCl2 tetra substituted 4-4-tert-butylphenoxyether phthalocyanine). The properties investigated were the real and imaginary components of the 3rd order hyperpolarizability, as well as the excited state absorption and refraction cross sections. The investigations were performed with a z-scan over a range of laser beam intensities. This work determined the imaginary component of the 3rd order hyperpolarizability for the free-base and SnCl2 3-4-tert-butylphenoxyether phthalocyanines and 4-4-tert-butylphenoxyether phthalocyanines to be highly dependent on the excited state cross sections. The refraction caused due to the real component of the 3rd order hyperpolarizability of the phthalocyanines was also investigated, however, the values found were strongly dependent on the laser beam intensity and the cause of this was investigated. A Five-level model was developed and run on GPGPU computing devices in order to isolate the absorption and refractive cross sections. Theeffects of the regio substitution on the excited state cross sections were also investigated, and the 1st singlet excited state and 1st triplet state absorption cross sections were calculated for all constitutional isomers. It was found that the symmetry of the constitutional isomers have a disproportionately large effect on the excited state absorption when compared to the ground state absorption. The nonlinear refractive properties of all constitutional isomers were also investigated, and the values of the parametric susceptibility are reported herein. The nonlinear refraction was found to have less effect than was seen in the nonlinear absorption. The 1st singlet excited state and 1st triplet state refractive cross sections of all constitutional isomer was determined. The results indicated that if more than one excited state was present and contributing to the nonlinear refraction, then more data than was collected here would be required. However, the 1st singlet excited state cross section were successfully determined for the free-base constitutional isomers. This work concluded that the region substitution affected the excited states more than the ground state.
- Full Text:
- Date Issued: 2020
- Date: 2020
- Subjects: Electrochemistry , Phthalocyanines , Nanoparticles , Nonlinear optics , Nonlinear optical spectroscopy , Refraction
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/166197 , vital:41337
- Description: This work investigates the effects of the nonlinear optical properties of four different constitutional isomers (C4h, C2v, Cs, and D2h) of a series of tetrasubstituted phthalocyanines (free-base 3-4-tert-butylphenoxyether phthalocyanines, free-base 4-4-tertbutylphenoxyether phthalocyanines, SnCl2 tetra substituted 3-4-tert-butylphenoxyether phthalocyanine, and SnCl2 tetra substituted 4-4-tert-butylphenoxyether phthalocyanine). The properties investigated were the real and imaginary components of the 3rd order hyperpolarizability, as well as the excited state absorption and refraction cross sections. The investigations were performed with a z-scan over a range of laser beam intensities. This work determined the imaginary component of the 3rd order hyperpolarizability for the free-base and SnCl2 3-4-tert-butylphenoxyether phthalocyanines and 4-4-tert-butylphenoxyether phthalocyanines to be highly dependent on the excited state cross sections. The refraction caused due to the real component of the 3rd order hyperpolarizability of the phthalocyanines was also investigated, however, the values found were strongly dependent on the laser beam intensity and the cause of this was investigated. A Five-level model was developed and run on GPGPU computing devices in order to isolate the absorption and refractive cross sections. Theeffects of the regio substitution on the excited state cross sections were also investigated, and the 1st singlet excited state and 1st triplet state absorption cross sections were calculated for all constitutional isomers. It was found that the symmetry of the constitutional isomers have a disproportionately large effect on the excited state absorption when compared to the ground state absorption. The nonlinear refractive properties of all constitutional isomers were also investigated, and the values of the parametric susceptibility are reported herein. The nonlinear refraction was found to have less effect than was seen in the nonlinear absorption. The 1st singlet excited state and 1st triplet state refractive cross sections of all constitutional isomer was determined. The results indicated that if more than one excited state was present and contributing to the nonlinear refraction, then more data than was collected here would be required. However, the 1st singlet excited state cross section were successfully determined for the free-base constitutional isomers. This work concluded that the region substitution affected the excited states more than the ground state.
- Full Text:
- Date Issued: 2020
Developing macroinvertebrate trait- and taxonomically-based approaches for biomonitoring wadeable riverine systems in the Niger delta, Nigeria
- Authors: Edegbene, Ovie Augustine
- Date: 2020
- Subjects: Water – Pollution -- Nigeria -- Niger River Delta , Stream health -- Nigeria -- Niger River Delta , Water -- Pollution -- Measurement , Environmental monitoring -- Nigeria -- Niger River Delta , Water quality -- Nigeria -- Niger River Delta , Water quality biological assessment -- Nigeria -- Niger River Delta , Aquatic invertebrates -- Nigeria -- Niger River Delta , Stream restoration -- Nigeria -- Niger River Delta , Urban agriculture -- Nigeria -- Niger River Delta , Stream ecology -- Nigeria -- Niger River Delta
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/140660 , vital:37907
- Description: Riverine systems are increasingly subjected to pollution due to rapid urbanisation, industrialisation, and agricultural activities. Increasing pollution in freshwater systems impairs water quality, causes biodiversity loss and impairs aquatic ecosystem functionality and supply of ecosystem services. Rivers in the Niger Delta region of Nigeria are particularly vulnerable to urban pollution and agricultural activities as natural forests are increasingly replaced by urbanisation and agriculture. The differential effects of these pressures on the ecological processes of these river systems are poorly explored, as is the development of appropriate biomonitoring tools for routine monitoring of river health. In this study, a physico-chemically-based approach and macroinvertebrate trait- and taxonomic- approaches were developed to better understand the effects of multiple pressures on riverine systems, while developing multimetric indices to enable sustainable management of rivers within the region. Sixty-six stations in 20 river systems within the Edo and Delta States of the Niger Delta ecoregion were monitored seasonally for a period of five (2008–2012) years. The physico-chemically based approach makes apparent the extent of degradation of rivers and streams in the Niger Delta. For each dominant land use type, river stations were classified into least impacted stations (LIS), moderately impacted stations (MIS) or heavily impacted stations (HIS). Of 11 stations within urban catchments, only two were considered least impacted, suggesting that urgent measures are necessary to revise the current trajectories of urban rivers within the region. Most of the stations designated as MIS and HIS in the urban and urban-agriculture catchments were found to be significantly correlated with increased nutrients, EC and BOD5. Characteristics of most of the MIS and HIS within rivers in urban catchments evidenced the so-called urban stream syndrome, a state of persistent degradation of urban streams. The results of the traits and ecological preferences approach showed traits sensitive to urban and urban-agriculture pollution. Traits and ecological preferences that were associated with the LIS include the possession of hardshell, moderate and high sensitivities to oxygen depletion, very large body sized individuals (>20-40mm), swimmers, flattened body shape, a preference for temporary attachment, crawling, respiration with aerial/vegetation, possession of breathing tubes, possession of strap or other apparatus for respiration, streamlined body, and a high sensitivity to oxygen depletion. Permanent attachment as an ecological preference associated with LIS was also positively correlated with increasing dissolved oxygen (DO) and was deemed a pollution sensitive ecological preference. The possession of very small body size (<5mm), associated with HIS, was deemed a pollution-tolerant trait and was negatively correlated with DO, confirming the deteriorating state of the urban and urban-agricultural rivers. The impact of urban-forestry pollution on the distribution pattern of macroinvertebrate traits and ecological preferences was also explored in the selected rivers. Traits and ecological preferences such as possession of hard-shell, large body size, and grazing as a feeding preference which were significantly positively associated with the LIS, were also either significantly positively correlated with DO, or significantly negatively correlated with increasing any two of flow velocity, water temperature, BOD5 and nutrient. These traits and ecological preferences were deemed sensitive in forested rivers receiving urban pollution. Further, burrowing, the pupa aquatic stage, and predation which were significantly positively associated with HIS on the RLQ ordination, were also significantly negatively associated with DO. These traits were deemed tolerant of forested systems receiving urban pollution. Multimetric indices (MMI) were developed, validated and applied for urban, urban-agriculture and urban-forested (MMI-urban, MMI-urban-agric and urban-forest) areas. Of the 26 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban, only five metric were retained for integration into MMI-urban, they are log VeL, Hemiptera abundance, % Coleoptera + Hemiptera, % Chironomidae + Oligochaeta and Evenness index. Further, of the 18 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban-agric, only 12 metrics were retained and nine proved to be redundant. The nine metrics represent different measures; two of them were retained in addition to Chironomidae/Diptera abundance, % Odonata and Oligochaeta richness. The two metrics selected in addition to the hironomidae/Diptera abundance, % Odonata and Oligochaeta richness were the Margalef index and the logarithm of relative abundance of sprawler. For the MMI-urban-forest, 14 metrics satisfactorily discriminated between the LIS, the MIS, and the HIS, and 12 metrics were retained and 11 proved to be redundant. The non-redundant metric was Trichoptera abundance. Three metrics were further selected in addition to the Trichoptera abundance which include % Chironomidae + Oligochaeta, Coleoptera + Hemiptera richness and Shannon diversity. The MMI-urban and MMI-urban-agric indices performed better for LIS designated stations compared to the MIS and HIS deignated stations. The developed indices proved effective as biomonitoring tools for assessing the ecological health of rivers in the urban and urban-agriculture catchments within the Niger Delta. Overall, the results of the macroinvertebrate traits and ecological preferences, and taxonomic approaches showed the strength in the complementarity of both approaches in developing biomonitoring tools for assessing levels of deterioration in riverine systems. The study contributes significantly to understanding the ecology of riverine systems in the Niger Delta, particularly those subject to urban stresses, agricultural activities and urban pollution in forested systems, and thus makes an important contribution to the science and practice of biomonitoring in Nigeria where such studies are sparse.
- Full Text:
- Date Issued: 2020
- Authors: Edegbene, Ovie Augustine
- Date: 2020
- Subjects: Water – Pollution -- Nigeria -- Niger River Delta , Stream health -- Nigeria -- Niger River Delta , Water -- Pollution -- Measurement , Environmental monitoring -- Nigeria -- Niger River Delta , Water quality -- Nigeria -- Niger River Delta , Water quality biological assessment -- Nigeria -- Niger River Delta , Aquatic invertebrates -- Nigeria -- Niger River Delta , Stream restoration -- Nigeria -- Niger River Delta , Urban agriculture -- Nigeria -- Niger River Delta , Stream ecology -- Nigeria -- Niger River Delta
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/140660 , vital:37907
- Description: Riverine systems are increasingly subjected to pollution due to rapid urbanisation, industrialisation, and agricultural activities. Increasing pollution in freshwater systems impairs water quality, causes biodiversity loss and impairs aquatic ecosystem functionality and supply of ecosystem services. Rivers in the Niger Delta region of Nigeria are particularly vulnerable to urban pollution and agricultural activities as natural forests are increasingly replaced by urbanisation and agriculture. The differential effects of these pressures on the ecological processes of these river systems are poorly explored, as is the development of appropriate biomonitoring tools for routine monitoring of river health. In this study, a physico-chemically-based approach and macroinvertebrate trait- and taxonomic- approaches were developed to better understand the effects of multiple pressures on riverine systems, while developing multimetric indices to enable sustainable management of rivers within the region. Sixty-six stations in 20 river systems within the Edo and Delta States of the Niger Delta ecoregion were monitored seasonally for a period of five (2008–2012) years. The physico-chemically based approach makes apparent the extent of degradation of rivers and streams in the Niger Delta. For each dominant land use type, river stations were classified into least impacted stations (LIS), moderately impacted stations (MIS) or heavily impacted stations (HIS). Of 11 stations within urban catchments, only two were considered least impacted, suggesting that urgent measures are necessary to revise the current trajectories of urban rivers within the region. Most of the stations designated as MIS and HIS in the urban and urban-agriculture catchments were found to be significantly correlated with increased nutrients, EC and BOD5. Characteristics of most of the MIS and HIS within rivers in urban catchments evidenced the so-called urban stream syndrome, a state of persistent degradation of urban streams. The results of the traits and ecological preferences approach showed traits sensitive to urban and urban-agriculture pollution. Traits and ecological preferences that were associated with the LIS include the possession of hardshell, moderate and high sensitivities to oxygen depletion, very large body sized individuals (>20-40mm), swimmers, flattened body shape, a preference for temporary attachment, crawling, respiration with aerial/vegetation, possession of breathing tubes, possession of strap or other apparatus for respiration, streamlined body, and a high sensitivity to oxygen depletion. Permanent attachment as an ecological preference associated with LIS was also positively correlated with increasing dissolved oxygen (DO) and was deemed a pollution sensitive ecological preference. The possession of very small body size (<5mm), associated with HIS, was deemed a pollution-tolerant trait and was negatively correlated with DO, confirming the deteriorating state of the urban and urban-agricultural rivers. The impact of urban-forestry pollution on the distribution pattern of macroinvertebrate traits and ecological preferences was also explored in the selected rivers. Traits and ecological preferences such as possession of hard-shell, large body size, and grazing as a feeding preference which were significantly positively associated with the LIS, were also either significantly positively correlated with DO, or significantly negatively correlated with increasing any two of flow velocity, water temperature, BOD5 and nutrient. These traits and ecological preferences were deemed sensitive in forested rivers receiving urban pollution. Further, burrowing, the pupa aquatic stage, and predation which were significantly positively associated with HIS on the RLQ ordination, were also significantly negatively associated with DO. These traits were deemed tolerant of forested systems receiving urban pollution. Multimetric indices (MMI) were developed, validated and applied for urban, urban-agriculture and urban-forested (MMI-urban, MMI-urban-agric and urban-forest) areas. Of the 26 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban, only five metric were retained for integration into MMI-urban, they are log VeL, Hemiptera abundance, % Coleoptera + Hemiptera, % Chironomidae + Oligochaeta and Evenness index. Further, of the 18 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban-agric, only 12 metrics were retained and nine proved to be redundant. The nine metrics represent different measures; two of them were retained in addition to Chironomidae/Diptera abundance, % Odonata and Oligochaeta richness. The two metrics selected in addition to the hironomidae/Diptera abundance, % Odonata and Oligochaeta richness were the Margalef index and the logarithm of relative abundance of sprawler. For the MMI-urban-forest, 14 metrics satisfactorily discriminated between the LIS, the MIS, and the HIS, and 12 metrics were retained and 11 proved to be redundant. The non-redundant metric was Trichoptera abundance. Three metrics were further selected in addition to the Trichoptera abundance which include % Chironomidae + Oligochaeta, Coleoptera + Hemiptera richness and Shannon diversity. The MMI-urban and MMI-urban-agric indices performed better for LIS designated stations compared to the MIS and HIS deignated stations. The developed indices proved effective as biomonitoring tools for assessing the ecological health of rivers in the urban and urban-agriculture catchments within the Niger Delta. Overall, the results of the macroinvertebrate traits and ecological preferences, and taxonomic approaches showed the strength in the complementarity of both approaches in developing biomonitoring tools for assessing levels of deterioration in riverine systems. The study contributes significantly to understanding the ecology of riverine systems in the Niger Delta, particularly those subject to urban stresses, agricultural activities and urban pollution in forested systems, and thus makes an important contribution to the science and practice of biomonitoring in Nigeria where such studies are sparse.
- Full Text:
- Date Issued: 2020
Development of a UV-tolerant strain of the South African isolate of Cryptophlebia leucotreta granulovirus for use as an enhanced biopesticide for Thaumatotibia leucotreta control on citrus
- Authors: Mwanza, Patrick
- Date: 2020
- Subjects: Baculoviruses -- South Africa , Ultraviolet astronomy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48533 , vital:40885
- Description: Baculoviruses are pathogenic to insects in the orders Diptera, Hymenoptera, and Lepidoptera. As a result of this natural relationship with insects they provide an environmentally friendly method to combat crop and forest pests. As such, a number of baculoviruses have been formulated into biopesticides. The use of baculovirus biopesticides is gaining popularity as the use of chemical pesticides has come under stringent regulatory conditions imposed by governments and continental blocks such as the European Union. Baculoviruses have a narrow host range and therefore do not harm non-pests or humans who consume the crops. One such baculovirus is Cryptophlebia leucotreta granulovirus (CrleGV), which is pathogenic to the citrus pest Thaumatotibia leucotreta, commonly referred to as the false codling moth (FCM). CrleGV has an occlusion body (OB) that encloses a single virion. Several CrleGV biopesticides have been registered in South Africa for use on citrus, avocadoes, macadamias, grapes and other crops by two commercial producers, River Bioscience (SA) and Andermatt (Switzerland). These biopesticides are used as part of the FCM integrated pest management (IPM) programme, a multifacetted approach to controlling FCM. However, baculoviruses are susceptible to the ultraviolet (UV) radiation component of sunlight and lose their activity within hours to a few days, after exposure to UV. Several substances have been tested as UV protectants to improve the persistence of baculovirus biopesticides in the field. These include optical brighteners, UV absorbers and anti-oxidants. While very promising in the laboratory, UV-protectants have not been as successful in the field. A few published reports have reported, that UV-tolerant baculoviruses could be isolated from a population by repeatedly exposing and re-exposing the virus to UV irradiation with a propagation step in insect host fourth or fifth instars between each exposure cycle. In this study, the South African isolate of Cryptophlebia leucotreta (CrleGV-SA) was exposed to UV irradiation for 5 exposure cycles in a Q-Sun Xe-3 HC test chamber (Qlab, USA) with parameters set to mimic a typical summer day in the Sundays River Valley, Eastern Cape Province, in South Africa. In between exposures the virus survivors were allowed to multiply in FCM fifth instars. Surface dose bioassays were also conducted to determine the LC50 of the virus after each exposure cycle. Samples from exposure cycle 1 and cycle 5 (UV-tolerant) irradiated for 72 h were prepared for Next Generation Sequencing (NGS) of DNA. The resultant sequence data were analysed using the Geneious R11 software (New Zealand) and compared with the unexposed CrleGV-SA sequence. In-silico restriction enzyme analsysis (REN) with several enzymes was also carried on both the cycle 1 and cycle 5 exposed samples and the resulting digestion patterns were compared with the original CrleGV-SA digestion patterns. The same samples were also analysed by transmission electron microscopy (TEM) and Attenuated Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) to evaluate the effect of UV irradiation on the structure of the CrleGV-SA OB. In addition, three UV protectants, lignin sulphate (Sappi, SA), BREAK-THRU®OE446 (OE446) (Evonik Industries, Germany) and Uvinul Easy (BASF, Germany) were prepared with CrleGV-SA to give final protectant concentrations of 0.09 %, 0.9 % and 9 %. The protectant-virus suspensions were exposed to UV for 24 h in the Q-Sun test chamber and bioassays conducted to determine the protective effect of each protectant concentration. The most successful protectants were then combined with the UV-tolerant CrleGV-SA and exposed to UV for 24 h in the Q-Sun test chamber and surface dose bioassays conducted afterwards. Samples exposed to UV in cycle 5 had lower LC50 values compared to samples in the early cycles. With each re-exposure cycle the LC50 values moved closer to that of the unexposed control. The LC50 of virus samples decreased from 2.89 x 108 OBs/ml after 24 h UV-exposure in cycle 1 to 2.16 x 105 OBs/ml after the same duration of exposure in cycle 5; and from 2.11 x 109 OBs/ml in cycle 1 after 72 h UV-exposure to 1.73 x 106 OBs/ml after the same duration of exposure. This represented a 1338-fold difference and a 1220-fold difference, respectively. When the UV-tolerant samples were sequenced seven SNPs were identified in cycle 1, which were thought to help establish UV tolerance, while a further seven SNPs were identified in cycle 5 samples; these were thought to further establish and maintain the UV-tolerance. Additionally, REN analysis with EcoR1 for both test samples yielded digestion patterns that were different from those of the original CrleGV-SA. TEM data showed that UV damages the virion as well as the crystalline structure of the OB. This is the first time visual evidence for UV damage to baculoviruses has been published. Comparison of cycle 1 and cycle 5 UV exposed OBs revealed that the cycle 5 OBs were significantly larger than the cycle 1 OBs (P<0.05). In addition, several peaks in the fingerprint region were shown to have either appeared or disapeered from the ATR-FTIR spectra after UV irradiation. However, there was no difference in the spectra of the Cycle 1 and Cycle 5 virus samples. The tests with potential UV-protectants revealed that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy were the most effective in protecting the virus from UV. However, there was no significant difference in their protection of UV tolerant CrleGV-SA and wild type CrleGV-SA. Going forward, it is recommended that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy combinations be explored further in future studies, particulary in the field. This study therefore forms an important foundation for the development of UV-tolerant baculovirus that will last longer in the field.
- Full Text:
- Date Issued: 2020
- Authors: Mwanza, Patrick
- Date: 2020
- Subjects: Baculoviruses -- South Africa , Ultraviolet astronomy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48533 , vital:40885
- Description: Baculoviruses are pathogenic to insects in the orders Diptera, Hymenoptera, and Lepidoptera. As a result of this natural relationship with insects they provide an environmentally friendly method to combat crop and forest pests. As such, a number of baculoviruses have been formulated into biopesticides. The use of baculovirus biopesticides is gaining popularity as the use of chemical pesticides has come under stringent regulatory conditions imposed by governments and continental blocks such as the European Union. Baculoviruses have a narrow host range and therefore do not harm non-pests or humans who consume the crops. One such baculovirus is Cryptophlebia leucotreta granulovirus (CrleGV), which is pathogenic to the citrus pest Thaumatotibia leucotreta, commonly referred to as the false codling moth (FCM). CrleGV has an occlusion body (OB) that encloses a single virion. Several CrleGV biopesticides have been registered in South Africa for use on citrus, avocadoes, macadamias, grapes and other crops by two commercial producers, River Bioscience (SA) and Andermatt (Switzerland). These biopesticides are used as part of the FCM integrated pest management (IPM) programme, a multifacetted approach to controlling FCM. However, baculoviruses are susceptible to the ultraviolet (UV) radiation component of sunlight and lose their activity within hours to a few days, after exposure to UV. Several substances have been tested as UV protectants to improve the persistence of baculovirus biopesticides in the field. These include optical brighteners, UV absorbers and anti-oxidants. While very promising in the laboratory, UV-protectants have not been as successful in the field. A few published reports have reported, that UV-tolerant baculoviruses could be isolated from a population by repeatedly exposing and re-exposing the virus to UV irradiation with a propagation step in insect host fourth or fifth instars between each exposure cycle. In this study, the South African isolate of Cryptophlebia leucotreta (CrleGV-SA) was exposed to UV irradiation for 5 exposure cycles in a Q-Sun Xe-3 HC test chamber (Qlab, USA) with parameters set to mimic a typical summer day in the Sundays River Valley, Eastern Cape Province, in South Africa. In between exposures the virus survivors were allowed to multiply in FCM fifth instars. Surface dose bioassays were also conducted to determine the LC50 of the virus after each exposure cycle. Samples from exposure cycle 1 and cycle 5 (UV-tolerant) irradiated for 72 h were prepared for Next Generation Sequencing (NGS) of DNA. The resultant sequence data were analysed using the Geneious R11 software (New Zealand) and compared with the unexposed CrleGV-SA sequence. In-silico restriction enzyme analsysis (REN) with several enzymes was also carried on both the cycle 1 and cycle 5 exposed samples and the resulting digestion patterns were compared with the original CrleGV-SA digestion patterns. The same samples were also analysed by transmission electron microscopy (TEM) and Attenuated Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) to evaluate the effect of UV irradiation on the structure of the CrleGV-SA OB. In addition, three UV protectants, lignin sulphate (Sappi, SA), BREAK-THRU®OE446 (OE446) (Evonik Industries, Germany) and Uvinul Easy (BASF, Germany) were prepared with CrleGV-SA to give final protectant concentrations of 0.09 %, 0.9 % and 9 %. The protectant-virus suspensions were exposed to UV for 24 h in the Q-Sun test chamber and bioassays conducted to determine the protective effect of each protectant concentration. The most successful protectants were then combined with the UV-tolerant CrleGV-SA and exposed to UV for 24 h in the Q-Sun test chamber and surface dose bioassays conducted afterwards. Samples exposed to UV in cycle 5 had lower LC50 values compared to samples in the early cycles. With each re-exposure cycle the LC50 values moved closer to that of the unexposed control. The LC50 of virus samples decreased from 2.89 x 108 OBs/ml after 24 h UV-exposure in cycle 1 to 2.16 x 105 OBs/ml after the same duration of exposure in cycle 5; and from 2.11 x 109 OBs/ml in cycle 1 after 72 h UV-exposure to 1.73 x 106 OBs/ml after the same duration of exposure. This represented a 1338-fold difference and a 1220-fold difference, respectively. When the UV-tolerant samples were sequenced seven SNPs were identified in cycle 1, which were thought to help establish UV tolerance, while a further seven SNPs were identified in cycle 5 samples; these were thought to further establish and maintain the UV-tolerance. Additionally, REN analysis with EcoR1 for both test samples yielded digestion patterns that were different from those of the original CrleGV-SA. TEM data showed that UV damages the virion as well as the crystalline structure of the OB. This is the first time visual evidence for UV damage to baculoviruses has been published. Comparison of cycle 1 and cycle 5 UV exposed OBs revealed that the cycle 5 OBs were significantly larger than the cycle 1 OBs (P<0.05). In addition, several peaks in the fingerprint region were shown to have either appeared or disapeered from the ATR-FTIR spectra after UV irradiation. However, there was no difference in the spectra of the Cycle 1 and Cycle 5 virus samples. The tests with potential UV-protectants revealed that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy were the most effective in protecting the virus from UV. However, there was no significant difference in their protection of UV tolerant CrleGV-SA and wild type CrleGV-SA. Going forward, it is recommended that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy combinations be explored further in future studies, particulary in the field. This study therefore forms an important foundation for the development of UV-tolerant baculovirus that will last longer in the field.
- Full Text:
- Date Issued: 2020
Development of bio-based xylan composites for food packaging applications
- Authors: Naidu, Darrel Sarvesh
- Date: 2020
- Subjects: Xylanases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48544 , vital:40886
- Description: Currently a large number of chemicals and plastics are produced from petroleum-based resources. However, due to the concerns surrounding the depletion of petroleum resources and growing carbon emissions, there is a desire to produce chemicals and plastics from renewable and carbon natural sources. Lignocellulosic biomass (biomass consisting of cellulose, lignin and hemicellulose) is the most common biomass on earth and is renewable and carbon neutral. Of the three main constituents of lignocellulosic biomass, hemicellulose is composed of a mixture of sugars which can be converted into chemicals and plastics. The most common form of hemicellulose found in nature is xylan. This study is aimed at extracting xylan from maize stalk waste residues and the development of xylan films with properties that are suitable for food packaging applications. Xylan was extracted from maize stalk waste residues using an alkaline pre-treatment method. The effects of bleaching conditions (time, temperature and bleach concentration) prior to alkaline treatment on the yield and purity of xylan extracted was studied using a Box-Behnken experimental design. It was observed that the experimental conditions tested had no effect on the yield of the xylan extracted but the bleach concentration had a significant effect on the purity of the xylan extracted. The samples with the lowest lignin content were found to be the samples treated with 3wt% bleach prior to alkaline pre-treatment. One of the main disadvantages of xylan is that it has poor film forming properties, a method of overcoming this is to combine it with another abundantly available biopolymer that has good film forming properties, such as alginate. The effect of xylan, alginate and glycerol content on the mechanical, thermal, moisture uptake and water barrier properties of the films were investigated. It was observed that with an increase in the alginate content there was an increase in the tensile strength and Young’s modulus of the films, whereas the water vapour permeability (WVP) of the films decreased. This was attributed to the greater cohesion between alginate polymer chains compared to the cohesion between xylan polymer chains. The xylanalginate films exhibited better optical and water sorption properties at higher xylan content. In order to improve the inherently poor mechanical and barrier properties of the xylan-alginate films, bentonite and halloysite were incorporated into the films. It was found that 5wt% incorporation of either bentonite or halloysite resulted in a 49% decrease of the WVP, which was attributed to water vapour impermeable nature of the silicate layers that make up both clays. The incorporation of the clays into the xylan-alginate matrix resulted in a significant
- Full Text:
- Date Issued: 2020
- Authors: Naidu, Darrel Sarvesh
- Date: 2020
- Subjects: Xylanases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48544 , vital:40886
- Description: Currently a large number of chemicals and plastics are produced from petroleum-based resources. However, due to the concerns surrounding the depletion of petroleum resources and growing carbon emissions, there is a desire to produce chemicals and plastics from renewable and carbon natural sources. Lignocellulosic biomass (biomass consisting of cellulose, lignin and hemicellulose) is the most common biomass on earth and is renewable and carbon neutral. Of the three main constituents of lignocellulosic biomass, hemicellulose is composed of a mixture of sugars which can be converted into chemicals and plastics. The most common form of hemicellulose found in nature is xylan. This study is aimed at extracting xylan from maize stalk waste residues and the development of xylan films with properties that are suitable for food packaging applications. Xylan was extracted from maize stalk waste residues using an alkaline pre-treatment method. The effects of bleaching conditions (time, temperature and bleach concentration) prior to alkaline treatment on the yield and purity of xylan extracted was studied using a Box-Behnken experimental design. It was observed that the experimental conditions tested had no effect on the yield of the xylan extracted but the bleach concentration had a significant effect on the purity of the xylan extracted. The samples with the lowest lignin content were found to be the samples treated with 3wt% bleach prior to alkaline pre-treatment. One of the main disadvantages of xylan is that it has poor film forming properties, a method of overcoming this is to combine it with another abundantly available biopolymer that has good film forming properties, such as alginate. The effect of xylan, alginate and glycerol content on the mechanical, thermal, moisture uptake and water barrier properties of the films were investigated. It was observed that with an increase in the alginate content there was an increase in the tensile strength and Young’s modulus of the films, whereas the water vapour permeability (WVP) of the films decreased. This was attributed to the greater cohesion between alginate polymer chains compared to the cohesion between xylan polymer chains. The xylanalginate films exhibited better optical and water sorption properties at higher xylan content. In order to improve the inherently poor mechanical and barrier properties of the xylan-alginate films, bentonite and halloysite were incorporated into the films. It was found that 5wt% incorporation of either bentonite or halloysite resulted in a 49% decrease of the WVP, which was attributed to water vapour impermeable nature of the silicate layers that make up both clays. The incorporation of the clays into the xylan-alginate matrix resulted in a significant
- Full Text:
- Date Issued: 2020
Development of paper-based aptasensors for detection of Plasmodium falciparum lactate dehydrogenase in malaria
- Ogunmolasuyi, Adewoyin Martin
- Authors: Ogunmolasuyi, Adewoyin Martin
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/164601 , vital:41147 , doi:10.21504/10962/164601
- Description: Thesis (PhD)--Rhodes University, Faculty of Science, Biotechnology Innovation Centre, 2020
- Full Text:
- Date Issued: 2020
- Authors: Ogunmolasuyi, Adewoyin Martin
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/164601 , vital:41147 , doi:10.21504/10962/164601
- Description: Thesis (PhD)--Rhodes University, Faculty of Science, Biotechnology Innovation Centre, 2020
- Full Text:
- Date Issued: 2020
Dynamics of stimulated luminescence in natural quartz: Thermoluminescence and phototransferred thermoluminescence
- Authors: Folley, Damilola Esther
- Date: 2020
- Subjects: Thermoluminescence , Quartz
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/146255 , vital:38509
- Description: Natural quartz has remained an important mineral that is of topical interest in luminescence and dosimetry-related research. We investigate the dynamics of stimulated luminescence on this material through thermoluminescence (TL) and phototransferred thermoluminescence (PTTL). Measurements were made on unannealed natural quartz as well as quartz annealed at 800 and 1000̊C. The samples were annealed for 10 minutes and for 1 hour. The material, in its un- and annealed state has its main peak between 68 and 72̊C when measured at 1Cs ̃1 after a dose of 50 Gy. A study of dosimetric features and kinetic analysis was carried out on two prominent peaks, peak I and III for all the samples. The peaks show a sublinear dose response for irradiation doses between 10 and 300 Gy. Kinetic analysis shows that peak I is a first-order peak and peak III a general-order peak. Interestingly, we observe for peak I for the sample annealed at 800̊C for 1 hour an inverse thermal quenching behaviour. We demonstrate that a peak affected with an inverse thermal quenching-like behaviour can still show effect of thermal quenching when the dose the sample is irradiated to is significantly reduced. We ascribe the apparent dependence of thermal quenching on dose to competition between radiative and non-radiative transitions at the recombination centre. Peaks I, II, and III for all the samples were reproduced under phototransfer when the peaks, initially removed by preheating to a certain temperature are exposed to 470 and 525 nm light. The infuence of duration of illumination on the PTTL intensity of these peaks corresponding to various preheating temperatures is modelled using coupled first-order dfferential equations. The model is based on systems of acceptors and donors whose number and role depends on preheating temperature
- Full Text:
- Date Issued: 2020
- Authors: Folley, Damilola Esther
- Date: 2020
- Subjects: Thermoluminescence , Quartz
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/146255 , vital:38509
- Description: Natural quartz has remained an important mineral that is of topical interest in luminescence and dosimetry-related research. We investigate the dynamics of stimulated luminescence on this material through thermoluminescence (TL) and phototransferred thermoluminescence (PTTL). Measurements were made on unannealed natural quartz as well as quartz annealed at 800 and 1000̊C. The samples were annealed for 10 minutes and for 1 hour. The material, in its un- and annealed state has its main peak between 68 and 72̊C when measured at 1Cs ̃1 after a dose of 50 Gy. A study of dosimetric features and kinetic analysis was carried out on two prominent peaks, peak I and III for all the samples. The peaks show a sublinear dose response for irradiation doses between 10 and 300 Gy. Kinetic analysis shows that peak I is a first-order peak and peak III a general-order peak. Interestingly, we observe for peak I for the sample annealed at 800̊C for 1 hour an inverse thermal quenching behaviour. We demonstrate that a peak affected with an inverse thermal quenching-like behaviour can still show effect of thermal quenching when the dose the sample is irradiated to is significantly reduced. We ascribe the apparent dependence of thermal quenching on dose to competition between radiative and non-radiative transitions at the recombination centre. Peaks I, II, and III for all the samples were reproduced under phototransfer when the peaks, initially removed by preheating to a certain temperature are exposed to 470 and 525 nm light. The infuence of duration of illumination on the PTTL intensity of these peaks corresponding to various preheating temperatures is modelled using coupled first-order dfferential equations. The model is based on systems of acceptors and donors whose number and role depends on preheating temperature
- Full Text:
- Date Issued: 2020
Ecological assessment of a temperate river system using biomonitoring techniques: a case study of the Bloukrans River system, South Africa
- Authors: Magadze, Tinotenda
- Date: 2020
- Subjects: Bloukrans River , Ecological assessment (Biology) -- South Africa , Stream ecology -- South Africa , Rivers -- Environmental aspects -- South Africa , Benthic animals -- Effect of human beings on -- South Africa , Water quality biological assessment -- South Africa , Diatoms -- South Africa -- Data processing
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/142933 , vital:38177
- Description: Escalating pressures from growing human populations and environmental impacts increasingly imperil freshwater ecosystems. The Bloukrans River, which drains an urbanised and agricultural catchment in the Eastern Cape province of South Africa, is no exception. Detailed knowledge of the structure and function of the aquatic ecosystems is required in order to create models and matrices that predict, guide assessment and direct intervention on ecological integrity and water quality management in these systems. The main objectives of this research were to: examine the effects of urbanization on the benthic macroinvertebrate functional feeding guild structure among different stream orders; determine if benthic diatoms can be used as effective and reliable indicators of ionic composition and conductivity in different stream order categories and finally; to evaluate the applicability of the South African Diatom Index (SADI) and other indices in the Eastern Cape region of South Africa. Field studies were carried out to explore temporal patterns in community structure (macroinvertebrates and diatoms) and ecosystem function related to land-use patterns, instream habitat availability, and water quality parameters in the Bloukrans River system across four study periods: February (summer) and July (winter) 2016 and February (summer) and May/July (winter) 2018. The study was conducted along a gradient of impacts from less impacted agricultural headwaters to highly impacted urban sites located immediately downstream of the city of Makhanda. Macroinvertebrates were separated into functional feeding groups (FFGs) (i.e. collector-gatherer, collector-filterer, scraper, shredder, and predator) which were then used to assess the effects of selected physico-chemical variables and riparian zone condition on FFG organization. Collector-gatherers were the most abundant in the Bloukrans River and represented 71.3 % of the macroinvertebrate assemblages. Stream order 1species such as Nitzschia palea, Gomphonema parvulum, Tryblionella apiculata, Diploneis vulgaris and Staurosira elliptica. Multivariate analysis (Canonical correspondence analysis (CCA)) indicated that differences in diatom community assemblages were best explained by calcium, magnesium, pH, phosphate, nitrate, dissolved oxygen, sediment nitrate, conductivity and salinity. These results indicate that diatoms can be used as bioindicators for monitoring highly impacted river systems and to also further examine pollution gradients and impacts of specific/point pollution sources. In order to further test the application of diatom indices, nine sites with contrasting water quality were sampled along the length river system in February, May and July 2018. Diatom-based indices incorporated in OMNIDIA software were applied to assess the integrity of the water quality as indicated by diatom communities. For comparative purposes, several foreign indices (e.g. the trophic diatom index (TDI), the percentage pollution-tolerant valves (%PTV), biological diatom index (BDI)) and the South African Diatom Index (SADI) were used in the study. From the results, the Percentage Pollution-Tolerant Valves (%PTV) of most urban sites in the Bloukrans River was above the 20% limit indicating the presence of organic pollutants. Although the foreign diatom indices were applicable in the study, the SADI had significant correlations with most water quality variables (p < 0.05) compared to other indices such as Watanabe Index (WAT), Biological Index of Water Quality Trophic Index (BIWQ) and Trophic Index (TI)). These results support wider use of the SADI as an indicator of water quality conditions in South African river systems. Finally, the observed variations in diatom community structure and composition as a result of changes in water quality were broadly in agreement with the results of macroinvertebrate FFG structure indicating that the two biological indicators can, and should, be used as complementary techniques in the biomonitoring of rivers and streams in South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Magadze, Tinotenda
- Date: 2020
- Subjects: Bloukrans River , Ecological assessment (Biology) -- South Africa , Stream ecology -- South Africa , Rivers -- Environmental aspects -- South Africa , Benthic animals -- Effect of human beings on -- South Africa , Water quality biological assessment -- South Africa , Diatoms -- South Africa -- Data processing
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/142933 , vital:38177
- Description: Escalating pressures from growing human populations and environmental impacts increasingly imperil freshwater ecosystems. The Bloukrans River, which drains an urbanised and agricultural catchment in the Eastern Cape province of South Africa, is no exception. Detailed knowledge of the structure and function of the aquatic ecosystems is required in order to create models and matrices that predict, guide assessment and direct intervention on ecological integrity and water quality management in these systems. The main objectives of this research were to: examine the effects of urbanization on the benthic macroinvertebrate functional feeding guild structure among different stream orders; determine if benthic diatoms can be used as effective and reliable indicators of ionic composition and conductivity in different stream order categories and finally; to evaluate the applicability of the South African Diatom Index (SADI) and other indices in the Eastern Cape region of South Africa. Field studies were carried out to explore temporal patterns in community structure (macroinvertebrates and diatoms) and ecosystem function related to land-use patterns, instream habitat availability, and water quality parameters in the Bloukrans River system across four study periods: February (summer) and July (winter) 2016 and February (summer) and May/July (winter) 2018. The study was conducted along a gradient of impacts from less impacted agricultural headwaters to highly impacted urban sites located immediately downstream of the city of Makhanda. Macroinvertebrates were separated into functional feeding groups (FFGs) (i.e. collector-gatherer, collector-filterer, scraper, shredder, and predator) which were then used to assess the effects of selected physico-chemical variables and riparian zone condition on FFG organization. Collector-gatherers were the most abundant in the Bloukrans River and represented 71.3 % of the macroinvertebrate assemblages. Stream order 1species such as Nitzschia palea, Gomphonema parvulum, Tryblionella apiculata, Diploneis vulgaris and Staurosira elliptica. Multivariate analysis (Canonical correspondence analysis (CCA)) indicated that differences in diatom community assemblages were best explained by calcium, magnesium, pH, phosphate, nitrate, dissolved oxygen, sediment nitrate, conductivity and salinity. These results indicate that diatoms can be used as bioindicators for monitoring highly impacted river systems and to also further examine pollution gradients and impacts of specific/point pollution sources. In order to further test the application of diatom indices, nine sites with contrasting water quality were sampled along the length river system in February, May and July 2018. Diatom-based indices incorporated in OMNIDIA software were applied to assess the integrity of the water quality as indicated by diatom communities. For comparative purposes, several foreign indices (e.g. the trophic diatom index (TDI), the percentage pollution-tolerant valves (%PTV), biological diatom index (BDI)) and the South African Diatom Index (SADI) were used in the study. From the results, the Percentage Pollution-Tolerant Valves (%PTV) of most urban sites in the Bloukrans River was above the 20% limit indicating the presence of organic pollutants. Although the foreign diatom indices were applicable in the study, the SADI had significant correlations with most water quality variables (p < 0.05) compared to other indices such as Watanabe Index (WAT), Biological Index of Water Quality Trophic Index (BIWQ) and Trophic Index (TI)). These results support wider use of the SADI as an indicator of water quality conditions in South African river systems. Finally, the observed variations in diatom community structure and composition as a result of changes in water quality were broadly in agreement with the results of macroinvertebrate FFG structure indicating that the two biological indicators can, and should, be used as complementary techniques in the biomonitoring of rivers and streams in South Africa.
- Full Text:
- Date Issued: 2020
Effect of increasing fossil shell flour levels on digestive and metabolic utilization, health, body weight change and wool production, and quality in Dohne-Merino wethers
- Authors: Ikusika, Olusegun Oyebade
- Date: 2020
- Subjects: Merino sheep Sheep -- Quality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/18465 , vital:42542
- Description: The study's broad objective was to assess growth performance, blood and parasitic profiles, wool parameters, methane emission, and nutritional status of Dohne-Merino wethers fed diets supplemented with varying levels of fossil shell flour. Twenty-four Dohne-Merino wethers, averagely weighing 20.0±1.50 kg, were divided into four groups and used in this study. The effects of varying inclusion levels of fossil shell flour (FSF) (0, 2, 4, and 6 %) on feed intake, water intake, nutrient digestibility, N-retention, hematobiochemical and parasitic profiles, body condition scores, feed preference, wool parameters and methane output were determined. The influence of FSF's varying inclusion levels on fermentation parameters, in vitro true digestibility, and relative feed values were also determined. Wethers fed with 4% FSF inclusion level diet showed the highest (P<0.05) values for dry matter intake, average daily weight gain, N retention, (Nitrogen retention) and apparent digestibility of crude protein (CP), Ether Extract (EE) and Ash 6 % (P < 0.05). The urinary N and fecal N were lowest in wethers fed 4% FSF inclusion level and highest in those fed on diets without FSF (P < 0.05). Water intake was highest in wethers fed 0% FSF diet, followed by those fed on 4% and lowest in 6% FSF (P< 0.05). There was a significant increase in white blood cell counts in wethers fed on a diet with 4% and 6% FSF inclusion levels from day 10 to 100 compared to wethers fed on a diet with 0% and 2% FSF (P <0.05). Red blood cell counts also increased significantly in wethers fed on a diet containing 4% FSF, but a slight increase in wethers with 6 % FSF diet, throughout the experimental period (P < 0.05). Blood urea was highest in wethers fed 0% FSF inclusion level and lowest in 6% at day 30 to day 100. Wethers on 4% FSF diet showed an increase in blood urea from day 30 to day 100 (P < 0.05) while wethers on 0% and 2% remained unchanged (P<0.05) during this period and not different (P > 0.05) from wethers on 4% FSF as well. The total protein concentration, albumin, total bilirubin, Na, K, glucose, cholesterol, and liver enzymes were normal for wethers. However, serum creatinine level was lower in wethers fed on 4% FSF than those on 0% FSF (P < 0.01). Haemonchus and Coccidian fecal egg counts were low in wethers fed diets with 2%, 4%, and 6 % FSF (P < 0.01) compared 11 with wethers fed with 0% FSF inclusion level during the same period. The body condition score of wethers fed on diets with 2%, 4%, and 6% FSF inclusion levels were higher than those on 0% (P < 0.05). Wool yield, staple length, the coefficient variation of the fibre diameter, and fibre of wethers fed on diets with FSF were higher than those without FSF (P < 0.05). The fibre diameter of the wethers fed on FSF supplemented diets was the same as those on 0 % FSF (P > 0.05). The wethers spent more time on FSF supplemented diets and consumed more feed compared to that without FSF supplemented (P < 0.05). The levels of FSF inclusion in the diet affected the enteric methane output (ppm-m), where 4 % FSF had the highest enteric methane output while wethers on 2 % FSF had the lowest methane output (P < 0.05). Resting wethers produced more methane (g/day) than those feeding or standing (P < 0.05). Increasing levels of FSF did not affect ruminal temperature and pH. Ammonia-N increased with increasing FSF except in wethers fed on a diet with 4% FSF (P < 0.01). The total molar concentrations of the wethers' volatile fatty acids decreased with increasing FSF levels (P > 0.05). The acetic propionic ratio of the wethers also decreased except at a 4% inclusion level. The in vitro true digestibility dry matter (IVTDDM), in vitro true digestibility neutral detergent fibre (IVTDNDF), and in vitro true digestibility acid detergent fibre (IVTDADF) of the wethers decreased up to 4% FSF inclusion but tended to increase at 6% inclusion. This study's result as one of the pioneer studies in Dohne-Marino wethers showed that FSF treatment has the potential to improve the nutritional status of the animal and the animal performance and wool quality. Health-wise, FSF decrease nematode population and boost animal immunity as seen in RBC and WBC counts. It also can play a major role in protecting the environment, as seen in its reduction in feacal and urinary nitrogen, which is heavily involved in environmental pollution. Result also confirmed that the best period to target for methane mitigation in ruminants is the resting period. In conclusion, the inclusion of FSF in the diet of Dohne-Merino wethers has the potential to improve the overall performance, with a 4% FSF inclusion level having optimal productivity. However, future research is required to investigate FSF's effect on meat quality, rumen microbial community, in-vivo digestibility, and milk production.
- Full Text:
- Date Issued: 2020
- Authors: Ikusika, Olusegun Oyebade
- Date: 2020
- Subjects: Merino sheep Sheep -- Quality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/18465 , vital:42542
- Description: The study's broad objective was to assess growth performance, blood and parasitic profiles, wool parameters, methane emission, and nutritional status of Dohne-Merino wethers fed diets supplemented with varying levels of fossil shell flour. Twenty-four Dohne-Merino wethers, averagely weighing 20.0±1.50 kg, were divided into four groups and used in this study. The effects of varying inclusion levels of fossil shell flour (FSF) (0, 2, 4, and 6 %) on feed intake, water intake, nutrient digestibility, N-retention, hematobiochemical and parasitic profiles, body condition scores, feed preference, wool parameters and methane output were determined. The influence of FSF's varying inclusion levels on fermentation parameters, in vitro true digestibility, and relative feed values were also determined. Wethers fed with 4% FSF inclusion level diet showed the highest (P<0.05) values for dry matter intake, average daily weight gain, N retention, (Nitrogen retention) and apparent digestibility of crude protein (CP), Ether Extract (EE) and Ash 6 % (P < 0.05). The urinary N and fecal N were lowest in wethers fed 4% FSF inclusion level and highest in those fed on diets without FSF (P < 0.05). Water intake was highest in wethers fed 0% FSF diet, followed by those fed on 4% and lowest in 6% FSF (P< 0.05). There was a significant increase in white blood cell counts in wethers fed on a diet with 4% and 6% FSF inclusion levels from day 10 to 100 compared to wethers fed on a diet with 0% and 2% FSF (P <0.05). Red blood cell counts also increased significantly in wethers fed on a diet containing 4% FSF, but a slight increase in wethers with 6 % FSF diet, throughout the experimental period (P < 0.05). Blood urea was highest in wethers fed 0% FSF inclusion level and lowest in 6% at day 30 to day 100. Wethers on 4% FSF diet showed an increase in blood urea from day 30 to day 100 (P < 0.05) while wethers on 0% and 2% remained unchanged (P<0.05) during this period and not different (P > 0.05) from wethers on 4% FSF as well. The total protein concentration, albumin, total bilirubin, Na, K, glucose, cholesterol, and liver enzymes were normal for wethers. However, serum creatinine level was lower in wethers fed on 4% FSF than those on 0% FSF (P < 0.01). Haemonchus and Coccidian fecal egg counts were low in wethers fed diets with 2%, 4%, and 6 % FSF (P < 0.01) compared 11 with wethers fed with 0% FSF inclusion level during the same period. The body condition score of wethers fed on diets with 2%, 4%, and 6% FSF inclusion levels were higher than those on 0% (P < 0.05). Wool yield, staple length, the coefficient variation of the fibre diameter, and fibre of wethers fed on diets with FSF were higher than those without FSF (P < 0.05). The fibre diameter of the wethers fed on FSF supplemented diets was the same as those on 0 % FSF (P > 0.05). The wethers spent more time on FSF supplemented diets and consumed more feed compared to that without FSF supplemented (P < 0.05). The levels of FSF inclusion in the diet affected the enteric methane output (ppm-m), where 4 % FSF had the highest enteric methane output while wethers on 2 % FSF had the lowest methane output (P < 0.05). Resting wethers produced more methane (g/day) than those feeding or standing (P < 0.05). Increasing levels of FSF did not affect ruminal temperature and pH. Ammonia-N increased with increasing FSF except in wethers fed on a diet with 4% FSF (P < 0.01). The total molar concentrations of the wethers' volatile fatty acids decreased with increasing FSF levels (P > 0.05). The acetic propionic ratio of the wethers also decreased except at a 4% inclusion level. The in vitro true digestibility dry matter (IVTDDM), in vitro true digestibility neutral detergent fibre (IVTDNDF), and in vitro true digestibility acid detergent fibre (IVTDADF) of the wethers decreased up to 4% FSF inclusion but tended to increase at 6% inclusion. This study's result as one of the pioneer studies in Dohne-Marino wethers showed that FSF treatment has the potential to improve the nutritional status of the animal and the animal performance and wool quality. Health-wise, FSF decrease nematode population and boost animal immunity as seen in RBC and WBC counts. It also can play a major role in protecting the environment, as seen in its reduction in feacal and urinary nitrogen, which is heavily involved in environmental pollution. Result also confirmed that the best period to target for methane mitigation in ruminants is the resting period. In conclusion, the inclusion of FSF in the diet of Dohne-Merino wethers has the potential to improve the overall performance, with a 4% FSF inclusion level having optimal productivity. However, future research is required to investigate FSF's effect on meat quality, rumen microbial community, in-vivo digestibility, and milk production.
- Full Text:
- Date Issued: 2020
Exploring and modelling the effects of agricultural land management and climate change on agroecosystem services in the Eastern Cape, South Africa
- Authors: Choruma, Dennis Junior
- Date: 2020
- Subjects: Agricultural ecology -- South Africa -- Eastern Cape , Agriculture -- Environmental aspects -- South Africa -- Eastern Cape , Crops and climate -- South Africa -- Eastern Cape , Corn -- Climatic factors -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/146756 , vital:38554
- Description: The aims of this study were to evaluate the impacts of agricultural land management strategies and climate change on irrigated maize production in the Eastern Cape, South Africa. To achieve these aims, the study was guided by two overarching research questions, subsequently broken down into more specific questions. The first research question examined the reasons behind farmers’ current agricultural land management practices, the values they assigned to different agroecosystem services, their perceptions of climate change and the adaptation strategies they used to address challenges associated with agricultural crop production and climate change. To answer these questions, a survey of conventional farmers in the Eastern Cape was carried out. The survey targeted farmers who used fertilisers and irrigation water in their day to day farming. Results showed that farmers recognised the different benefits that agroecosystems provided even though they were not familiar with the term ‘ecosystem services.’ Farmers assigned a high value to food provisioning compared to other agroecosystem services and managed their farms for maximum crop yields or maximum crop quality. Fertiliser and irrigation water management decisions were based on multiple factors such as cost, availability of farming equipment and crop yield or crop quality considerations. Survey results showed that while most farmers were able to state the amount of fertiliser used per growing season, the majority of farmers did not know the amount of water they used per growing season. From the farmers’ survey it was recommended that extension services and agricultural education programmes be strengthened in the region to increase farmers’ knowledge on effective agricultural land management strategies that support sustainable intensification. The second research question investigated the effects of agricultural land management strategies and climate change on crop yields in the Eastern Cape. This investigation was done in three steps. First, a crop model, the Environmental Policy Integrated Climate (EPIC) model was calibrated and validated using limited field data from maize variety trials carried out at the Cradock Research Farm in the Eastern Cape. Calibration and validation results proved satisfactory with model efficiencies (Nash Sutcliffe, NSE) greater than 0.5 for both calibration and validation. It was concluded that limited data from field trials on maize that only included grain yield and agricultural land management dates can be used for the calibration of the EPIC model to simulate maize production under South African conditions. In the second step, the calibrated model was applied to simulate different irrigation and fertiliser management strategies for maize production in the Eastern Cape. Different irrigation and Nitrogen (N) fertiliser levels were compared to find optimal irrigation and N fertiliser management strategies that would increase maize yields while minimising environmental pollution (nitrate leaching). Model outputs were also compared to the average yields obtained in the field trials (baseline) and to maize yields reported by farmers in the farmers’ survey. Results showed that improved management of irrigation water and N fertiliser could improve farmers’ maize yields from approximately 7.2 t ha-1 to approximately 12.2 t ha-1, an increase of approximately 69%. Results also revealed a trade-off between food provision and nitrate leaching. Simulations showed that increasing N fertiliser application under sufficient irrigation water levels would increase maize yields, however, this would be accompanied by an increase in N leaching. Lastly, the EPIC model was then applied to simulate the effects of future climate change on irrigated maize production in the Eastern Cape. For these simulations, the model was driven by statistically downscaled climate data derived from three General Circulation Models (GCMs) for two future climate periods, (2040-2069) and (2070-2099), under two Representative Concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. Future maize yields were compared to the baseline (1980-2010) maize yield average. All three climate models predicted a decline in maize yields, with yields declining by as much as 23.8% in RCP 8.5, 2070-2099. Simulations also predicted increases in average daily maximum and minimum temperatures for both the two future climate periods under both RCPs. Results also indicated a decrease in seasonal irrigation water requirements. Nitrate leaching was projected to significantly increase towards the end of the century, increasing by as much as 373.8% in RCP 8.5 2070-2099. Concerning farmers’ perceptions of climate change, results showed that farmers were aware of climate change and identified temperature and rainfall changes as the most important changes in climate that they had observed. To adapt to climate change, farmers used a variety of adaptation strategies such as crop rotations and intercropping. Apart from challenges posed by climate change, farmers also faced other challenges such as access to markets and access to financial credit lines, challenges that prevented them from effectively adapting to climate change. The study therefore recommended that appropriate and adequate strategies be designed to help farmers in the region offset the projected decrease in maize production and increase crop yields while minimising negative environmental impacts.
- Full Text:
- Date Issued: 2020
- Authors: Choruma, Dennis Junior
- Date: 2020
- Subjects: Agricultural ecology -- South Africa -- Eastern Cape , Agriculture -- Environmental aspects -- South Africa -- Eastern Cape , Crops and climate -- South Africa -- Eastern Cape , Corn -- Climatic factors -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/146756 , vital:38554
- Description: The aims of this study were to evaluate the impacts of agricultural land management strategies and climate change on irrigated maize production in the Eastern Cape, South Africa. To achieve these aims, the study was guided by two overarching research questions, subsequently broken down into more specific questions. The first research question examined the reasons behind farmers’ current agricultural land management practices, the values they assigned to different agroecosystem services, their perceptions of climate change and the adaptation strategies they used to address challenges associated with agricultural crop production and climate change. To answer these questions, a survey of conventional farmers in the Eastern Cape was carried out. The survey targeted farmers who used fertilisers and irrigation water in their day to day farming. Results showed that farmers recognised the different benefits that agroecosystems provided even though they were not familiar with the term ‘ecosystem services.’ Farmers assigned a high value to food provisioning compared to other agroecosystem services and managed their farms for maximum crop yields or maximum crop quality. Fertiliser and irrigation water management decisions were based on multiple factors such as cost, availability of farming equipment and crop yield or crop quality considerations. Survey results showed that while most farmers were able to state the amount of fertiliser used per growing season, the majority of farmers did not know the amount of water they used per growing season. From the farmers’ survey it was recommended that extension services and agricultural education programmes be strengthened in the region to increase farmers’ knowledge on effective agricultural land management strategies that support sustainable intensification. The second research question investigated the effects of agricultural land management strategies and climate change on crop yields in the Eastern Cape. This investigation was done in three steps. First, a crop model, the Environmental Policy Integrated Climate (EPIC) model was calibrated and validated using limited field data from maize variety trials carried out at the Cradock Research Farm in the Eastern Cape. Calibration and validation results proved satisfactory with model efficiencies (Nash Sutcliffe, NSE) greater than 0.5 for both calibration and validation. It was concluded that limited data from field trials on maize that only included grain yield and agricultural land management dates can be used for the calibration of the EPIC model to simulate maize production under South African conditions. In the second step, the calibrated model was applied to simulate different irrigation and fertiliser management strategies for maize production in the Eastern Cape. Different irrigation and Nitrogen (N) fertiliser levels were compared to find optimal irrigation and N fertiliser management strategies that would increase maize yields while minimising environmental pollution (nitrate leaching). Model outputs were also compared to the average yields obtained in the field trials (baseline) and to maize yields reported by farmers in the farmers’ survey. Results showed that improved management of irrigation water and N fertiliser could improve farmers’ maize yields from approximately 7.2 t ha-1 to approximately 12.2 t ha-1, an increase of approximately 69%. Results also revealed a trade-off between food provision and nitrate leaching. Simulations showed that increasing N fertiliser application under sufficient irrigation water levels would increase maize yields, however, this would be accompanied by an increase in N leaching. Lastly, the EPIC model was then applied to simulate the effects of future climate change on irrigated maize production in the Eastern Cape. For these simulations, the model was driven by statistically downscaled climate data derived from three General Circulation Models (GCMs) for two future climate periods, (2040-2069) and (2070-2099), under two Representative Concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. Future maize yields were compared to the baseline (1980-2010) maize yield average. All three climate models predicted a decline in maize yields, with yields declining by as much as 23.8% in RCP 8.5, 2070-2099. Simulations also predicted increases in average daily maximum and minimum temperatures for both the two future climate periods under both RCPs. Results also indicated a decrease in seasonal irrigation water requirements. Nitrate leaching was projected to significantly increase towards the end of the century, increasing by as much as 373.8% in RCP 8.5 2070-2099. Concerning farmers’ perceptions of climate change, results showed that farmers were aware of climate change and identified temperature and rainfall changes as the most important changes in climate that they had observed. To adapt to climate change, farmers used a variety of adaptation strategies such as crop rotations and intercropping. Apart from challenges posed by climate change, farmers also faced other challenges such as access to markets and access to financial credit lines, challenges that prevented them from effectively adapting to climate change. The study therefore recommended that appropriate and adequate strategies be designed to help farmers in the region offset the projected decrease in maize production and increase crop yields while minimising negative environmental impacts.
- Full Text:
- Date Issued: 2020
Exploring teaching and learning German as a foreign language at a South African institution of higher education: blended learning and collocations
- Authors: Ortner, Gwyndolen Jeanie
- Date: 2020
- Subjects: German language -- Study and teaching (Higher) -- South Africa , German language -- Study and teaching (Higher) -- Foreign speakers -- South Africa , German language -- Study and teaching (Higher) -- English speakers -- South Africa , Rhodes University -- Students , Rhodes University. German Studies
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167295 , vital:41465
- Description: German Studies students at Rhodes University have normally never studied the German language before enrolling for the first-year course and face the challenge of a fairly rapid linguistic advancement, in a context with very limited exposure to the foreign language outside the classroom. Free writing is an area which students find particularly challenging as it requires students to syndissertatione grammatical and vocabulary knowledge. Furthermore, South African students are often underprepared for the challenges they face at university regarding language, technology and finance, as they try to to assimilate to the academic environment and gain epistemological access to their various subjects, in this case, language acquisition and the attendant modules of translation, literature and cultural studies. The use of technology in teaching and learning, known as blended learning, is said to produce better results than face-to face teaching alone, through creating opportunities for more autonomous student learning. Scholars of instructed second-language acquisition also suggest using technology to improve language instruction. One particular area which is gaining ground is teaching students collocational structures through exploring large language corpora, to improve students’ language competencies such as writing fluency. However, both blended learning practices and corpus-based teaching practices suggested by scholars are often not reported on in a particular teaching and learning context, taking into account factors such as institutional infrastructure, student and staff backgrounds and preparedness, and larger socio-political factors. Thus, it remains unclear how these practices (blended learning and corpus-based teaching of collocations) may be integrated into standard urricula, particularly for languages other than English, which have been severely under-researched. The purpose of this research is to take a context-based approach to language teaching and thereby investigate current blended learning practices for German Studies at Rhodes University in South Africa and explore through an action research approach how to integrate collocational awareness into the curriculum, within the blended learning model. Insights from corpus linguistics guide an adaptation of teaching practice, helping students develop skills to aid with writing fluency, seeking to make the patterned nature of language salient to our students. This is undertaken in a scaffolded way, within the curriculum, making use firstly of the texts to which students are exposed in the textbook (comprehensible input) as a source of collocational examples, and following this by making use of reallife language data from an online German corpus, DWDS. Findings from the study reveal a number of best practices related to the use of blended learning and teaching collocations in context of the German foreign language curriculum at a South African institution of higher education.
- Full Text:
- Date Issued: 2020
- Authors: Ortner, Gwyndolen Jeanie
- Date: 2020
- Subjects: German language -- Study and teaching (Higher) -- South Africa , German language -- Study and teaching (Higher) -- Foreign speakers -- South Africa , German language -- Study and teaching (Higher) -- English speakers -- South Africa , Rhodes University -- Students , Rhodes University. German Studies
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167295 , vital:41465
- Description: German Studies students at Rhodes University have normally never studied the German language before enrolling for the first-year course and face the challenge of a fairly rapid linguistic advancement, in a context with very limited exposure to the foreign language outside the classroom. Free writing is an area which students find particularly challenging as it requires students to syndissertatione grammatical and vocabulary knowledge. Furthermore, South African students are often underprepared for the challenges they face at university regarding language, technology and finance, as they try to to assimilate to the academic environment and gain epistemological access to their various subjects, in this case, language acquisition and the attendant modules of translation, literature and cultural studies. The use of technology in teaching and learning, known as blended learning, is said to produce better results than face-to face teaching alone, through creating opportunities for more autonomous student learning. Scholars of instructed second-language acquisition also suggest using technology to improve language instruction. One particular area which is gaining ground is teaching students collocational structures through exploring large language corpora, to improve students’ language competencies such as writing fluency. However, both blended learning practices and corpus-based teaching practices suggested by scholars are often not reported on in a particular teaching and learning context, taking into account factors such as institutional infrastructure, student and staff backgrounds and preparedness, and larger socio-political factors. Thus, it remains unclear how these practices (blended learning and corpus-based teaching of collocations) may be integrated into standard urricula, particularly for languages other than English, which have been severely under-researched. The purpose of this research is to take a context-based approach to language teaching and thereby investigate current blended learning practices for German Studies at Rhodes University in South Africa and explore through an action research approach how to integrate collocational awareness into the curriculum, within the blended learning model. Insights from corpus linguistics guide an adaptation of teaching practice, helping students develop skills to aid with writing fluency, seeking to make the patterned nature of language salient to our students. This is undertaken in a scaffolded way, within the curriculum, making use firstly of the texts to which students are exposed in the textbook (comprehensible input) as a source of collocational examples, and following this by making use of reallife language data from an online German corpus, DWDS. Findings from the study reveal a number of best practices related to the use of blended learning and teaching collocations in context of the German foreign language curriculum at a South African institution of higher education.
- Full Text:
- Date Issued: 2020
Financial integration in the BRICS countries
- Authors: Nach, Marida Nephertiti
- Date: 2020
- Subjects: Autogression (Statistics) -- mathematical models , Monetary policy -- Econometric models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/50609 , vital:42278
- Description: An optimum currency area (OCA) owes its definition to Robert Mundell (1961). In his seminal paper, Mundell (1961) defines an OCA as an area for which the costs of relinquishing the exchange rate as an internal instrument of adjustments are outweighed by the benefits of adopting a single currency or a fixed exchange rate regime. Mundell (1961) emphasises two major benefits of adopting a single currency: the elimination of transaction costs and a better performance of money as a medium of exchange and as a unit of account. Thus far, OCA theory has served as the framework for the discussion about monetary integration and has provided an explanation for the monetary integration processes around the world both developed and developing countries in Europe, Asia, Africa, and Latin America. The emergence of the BRICS (Brazil, Russia, India, China, South Africa) countries can be a model and a representation of developing and emerging countries in the global economic and financial system. Hence, this has made the BRICS economies the object of many discussions and recent empirical researches. The research presented in this thesis uses a structural vector autoregression (SVAR) econometric model to explore whether there is a feasibility of macroeconomic convergence among the BRICS economies. The SVAR model permitted to examine the symmetry of shocks (supply, demand and monetary) among the five BRICS countries. The findings of this research showed that there was some degree of symmetry of shocks among the BRICS countries. Nevertheless, there is a need for more policy coordination in order to achieve the desired level of symmetry of shocks among these countries.
- Full Text:
- Date Issued: 2020
- Authors: Nach, Marida Nephertiti
- Date: 2020
- Subjects: Autogression (Statistics) -- mathematical models , Monetary policy -- Econometric models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/50609 , vital:42278
- Description: An optimum currency area (OCA) owes its definition to Robert Mundell (1961). In his seminal paper, Mundell (1961) defines an OCA as an area for which the costs of relinquishing the exchange rate as an internal instrument of adjustments are outweighed by the benefits of adopting a single currency or a fixed exchange rate regime. Mundell (1961) emphasises two major benefits of adopting a single currency: the elimination of transaction costs and a better performance of money as a medium of exchange and as a unit of account. Thus far, OCA theory has served as the framework for the discussion about monetary integration and has provided an explanation for the monetary integration processes around the world both developed and developing countries in Europe, Asia, Africa, and Latin America. The emergence of the BRICS (Brazil, Russia, India, China, South Africa) countries can be a model and a representation of developing and emerging countries in the global economic and financial system. Hence, this has made the BRICS economies the object of many discussions and recent empirical researches. The research presented in this thesis uses a structural vector autoregression (SVAR) econometric model to explore whether there is a feasibility of macroeconomic convergence among the BRICS economies. The SVAR model permitted to examine the symmetry of shocks (supply, demand and monetary) among the five BRICS countries. The findings of this research showed that there was some degree of symmetry of shocks among the BRICS countries. Nevertheless, there is a need for more policy coordination in order to achieve the desired level of symmetry of shocks among these countries.
- Full Text:
- Date Issued: 2020
Foraging for fruits: natural resource use and its conservation potential in urban environments
- Authors: Sardeshpande, Mallika
- Date: 2020
- Subjects: Non-timber forest products , Wild plants, Edible , Urban plants , Urban ecology (Biology) , Open spaces , Environmental protection -- Citizen participation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167465 , vital:41483
- Description: Wild edible fruits (WEFs) are a type of natural resource that humans across the world collect from diverse natural landscapes. They are among the most used non-timber forest products (NTFPs) and wild foods, and often serve more than a nutritional purpose for humans, in the form of fibre, fuel, medicine, and other products. The use of WEFs may augment household dietary diversity, food security, and income in some contexts. The prevalence of WEF species across the spectrum of natural to modified ecosystems presents the potential for integrated landscape-level conservation efforts centred on these species. The first half of this thesis investigates the state of knowledge about this versatile and ubiquitous resource in the wider context of other wild foods and NTFPs, and compares the patterns of use of WEFs with those of other wild foods and NTFPs. Through these studies, I find that WEFs are indeed a widely occurring, resilient, and useful resource along the rural-urban gradient. They are unique in that their use transcends the geographical and socio-economic criteria that influence the use of other wild foods and NTFPs. Based on these findings, in the second half of the thesis, I propose the use-based conservation of WEF species in urban landscapes through the practice of urban foraging. Through interviews with urban land managers and foragers, I describe the state of urban green space management and urban foraging, and identify synergies between the two. Green space management is increasingly devolved and well-defined in developed cities, and relatively diffused in smaller towns, but nevertheless supportive of use-based biodiversity conservation. Planting and foraging for WEFs in urban green spaces ties in with local and national objectives of urban land use management policy. However, the lack of information on species, spaces, and sustainability related to foraging are a hindrance to addressing this activity and harnessing its conservation potential. Foragers use a variety of WEF species collected from natural as well as highly used and urbanised areas in their cities. Although most foragers consider foraging as a cultural and recreational activity, many of them agreed with the prospect of commercialising or popularising it to protect and promote the biodiversity and culture associated with their foraging spaces. The synthesis of this study presents four possible pathways to conserve the diversity of WEF species, and to extend the benefits of WEF use to landscape stewardship. It identifies key stakeholders in implementing these pathways and possible collaborations between these stakeholders; the multiple conservation objectives and policies these pathways respond to; and context-specific considerations for policy and implementation related to planting and foraging of WEFs.
- Full Text:
- Date Issued: 2020
- Authors: Sardeshpande, Mallika
- Date: 2020
- Subjects: Non-timber forest products , Wild plants, Edible , Urban plants , Urban ecology (Biology) , Open spaces , Environmental protection -- Citizen participation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167465 , vital:41483
- Description: Wild edible fruits (WEFs) are a type of natural resource that humans across the world collect from diverse natural landscapes. They are among the most used non-timber forest products (NTFPs) and wild foods, and often serve more than a nutritional purpose for humans, in the form of fibre, fuel, medicine, and other products. The use of WEFs may augment household dietary diversity, food security, and income in some contexts. The prevalence of WEF species across the spectrum of natural to modified ecosystems presents the potential for integrated landscape-level conservation efforts centred on these species. The first half of this thesis investigates the state of knowledge about this versatile and ubiquitous resource in the wider context of other wild foods and NTFPs, and compares the patterns of use of WEFs with those of other wild foods and NTFPs. Through these studies, I find that WEFs are indeed a widely occurring, resilient, and useful resource along the rural-urban gradient. They are unique in that their use transcends the geographical and socio-economic criteria that influence the use of other wild foods and NTFPs. Based on these findings, in the second half of the thesis, I propose the use-based conservation of WEF species in urban landscapes through the practice of urban foraging. Through interviews with urban land managers and foragers, I describe the state of urban green space management and urban foraging, and identify synergies between the two. Green space management is increasingly devolved and well-defined in developed cities, and relatively diffused in smaller towns, but nevertheless supportive of use-based biodiversity conservation. Planting and foraging for WEFs in urban green spaces ties in with local and national objectives of urban land use management policy. However, the lack of information on species, spaces, and sustainability related to foraging are a hindrance to addressing this activity and harnessing its conservation potential. Foragers use a variety of WEF species collected from natural as well as highly used and urbanised areas in their cities. Although most foragers consider foraging as a cultural and recreational activity, many of them agreed with the prospect of commercialising or popularising it to protect and promote the biodiversity and culture associated with their foraging spaces. The synthesis of this study presents four possible pathways to conserve the diversity of WEF species, and to extend the benefits of WEF use to landscape stewardship. It identifies key stakeholders in implementing these pathways and possible collaborations between these stakeholders; the multiple conservation objectives and policies these pathways respond to; and context-specific considerations for policy and implementation related to planting and foraging of WEFs.
- Full Text:
- Date Issued: 2020
Formulation and characterisation of a combination captopril and hydrochlorothiazide microparticulate dosage form for paediatric use
- Chikukwa, Mellisa Tafadzwa Ruramai
- Authors: Chikukwa, Mellisa Tafadzwa Ruramai
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163216 , vital:41019 , doi:10.21504/10962/163216
- Description: Thesis (PhD)--Rhodes University, Pharmacy Faculty, Department of Pharmaceutics, 2020
- Full Text:
- Date Issued: 2020
- Authors: Chikukwa, Mellisa Tafadzwa Ruramai
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163216 , vital:41019 , doi:10.21504/10962/163216
- Description: Thesis (PhD)--Rhodes University, Pharmacy Faculty, Department of Pharmaceutics, 2020
- Full Text:
- Date Issued: 2020
Formulation development, manufacture and evaluation of a lamivudine-zidovudine nano co-crystal thermo-responsive suspension
- Authors: Witika, Bwalya Angel
- Date: 2020
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/140546 , vital:37897 , http://dx.doi.org/10.21504/10962/140546
- Description: Expected release date-April 2021
- Full Text:
- Date Issued: 2020
- Authors: Witika, Bwalya Angel
- Date: 2020
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/140546 , vital:37897 , http://dx.doi.org/10.21504/10962/140546
- Description: Expected release date-April 2021
- Full Text:
- Date Issued: 2020
Formulation, development and assessment of devil’s claw loaded phyto-elastosomes in thermo-responsive hydrogels
- Authors: Ntemi, Pascal Vitalis
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/164568 , vital:41139 , doi:10.21504/10962/164568
- Description: Thesis (PhD)--Rhodes University, Faculty of Pharmacy, Pharmaceutics, 2020
- Full Text:
- Date Issued: 2020
- Authors: Ntemi, Pascal Vitalis
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/164568 , vital:41139 , doi:10.21504/10962/164568
- Description: Thesis (PhD)--Rhodes University, Faculty of Pharmacy, Pharmaceutics, 2020
- Full Text:
- Date Issued: 2020
Genetic connectivity in sandy beach macroinfauna with contrasting life histories and zonation patterns
- Authors: Bezuidenhout, Karien
- Date: 2020
- Subjects: Fishes -- Genetics , Seashore ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/45944 , vital:39380
- Description: Open-ocean sandy beaches are highly dynamic ecosystems that continuously respond to waves, tides and storms. These beaches support a suite of uniquely adapted fauna that exhibits a high degree of endemism. This diversity, which also includes some economically important resource species, contributes to the great socio-economic and ecological value of sandy beach systems, which provide ecosystem services such as nutrient recycling and water purification, fish nursery habitat (surf zone), and natural buffering against storms. Despite their broad global distribution comprising ~70 % of the world’s ice-free coastline, beaches are naturally fragmented by other intertidal marine habitats and extensive coastal development. Sea-level rise is now threatening beaches, particularly along developed coasts through coastal squeeze, with an increased risk of habitat loss and exacerbated fragmentation. Such habitat loss has important implications for population and species persistence, depending on the level of connectivity among populations. While sandy beach macroinfauna tend to be highly mobile across and along shore, they also show a strong bias towards direct, or aplanktonic, development; the latter could reduce opportunities for dispersal and sustained population connectivity. However, comparatively little is known about population connectivity on sandy beaches, limiting scientifically sound management of much of the world’s coastline. This study aims to address this knowledge gap by working towards a conceptual model quantifying population connectivity, and by investigating the specific roles of life history, across-shore zonation, and geographic range as putative indicators and possibly drivers of genetic differentiation (ΦST) and connectivity (gene flow) among beach macroinvertebrate populations. The main hypotheses are that 1) species with a pelagic larval stage will display lower genetic differentiation with higher rates of gene flow among populations than species with a benthic lecithotrophic larval stage or direct development; and 2) genetic differentiation among populations will decrease along an across-shore axis, from the supratidal to the low water mark. Two opposing hypotheses were tested concerning the relationship between genetic structure and distributional range: 3a) Species with a large range (measured as distance and number of latitudes) will show less genetic differentiation than those with a narrow range, because they are more able to disperse; or 3b) more widely distributed species may occur across more phylogenetic | v breaks, and thus show higher genetic differentiation than species restricted to a smaller ranges and single biogeographic provinces. First, the extent and likely drivers of population connectivity were investigated for a suite of temperate South African macroinfauna. Very low, non-significant genetic differentiation was demonstrated for the beach clam Donax serra, thus supporting the hypothesis that pelagic larval dispersers display low/no genetic differentiation among populations (Chapter 2). Statistical power of the COI locus was, however, low in this species, due to reduced genetic variability which could be attributed to an expansion from a small source population into extant habitats. The results highlighted the need for caution when interpreting a lack of genetic differentiation as evidence for population connectivity. Nevertheless, COI sequences verified that D. serra occupying the cool and warm-temperate regions of the South African coast, constitute a single species, despite morphological and behavioural differences between inhabitants of these two bioregions. D. sordidus, a congener of D. serra, and endemic to the warm-temperate (Agulhas) bioregion of South Africa, was investigated to test two opposing hypotheses (Chapter 3): 1) this pelagic larval disperser lack genetic differentiation with high rates of gene flow across its range, or alternatively 2) these clams are genetically structured across their range due to the influence of freshwater input (measured as distance to nearest estuary), and morphodynamics of the surf zone (represented by surf-zone width). Significant global ΦST was estimated for D. sordidus, with differentiation predominantly driven by haplotype frequencies at a single study site and estimates of gene flow among most sample locations generally high. Tentative evidence suggested that natural selection driven by differences in water salinity due to estuarine runoff and surf-zone width, might be maintaining two dominant haplotypes across the range of this species. Beach clams from the Southern Hemisphere, occupying different distributional ranges, were compared to test the hypothesis that genetic structure decreases with an increase in range. This hypothesis was poorly supported by the results; opposite (yet mostly non-significant) trends demonstrated for ΦST and haplotype diversity, thus providing some support for the alternative hypothesis that more phylogeographic breaks in broad-ranging species results in higher estimates of genetic structure in these species.
- Full Text:
- Date Issued: 2020
- Authors: Bezuidenhout, Karien
- Date: 2020
- Subjects: Fishes -- Genetics , Seashore ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/45944 , vital:39380
- Description: Open-ocean sandy beaches are highly dynamic ecosystems that continuously respond to waves, tides and storms. These beaches support a suite of uniquely adapted fauna that exhibits a high degree of endemism. This diversity, which also includes some economically important resource species, contributes to the great socio-economic and ecological value of sandy beach systems, which provide ecosystem services such as nutrient recycling and water purification, fish nursery habitat (surf zone), and natural buffering against storms. Despite their broad global distribution comprising ~70 % of the world’s ice-free coastline, beaches are naturally fragmented by other intertidal marine habitats and extensive coastal development. Sea-level rise is now threatening beaches, particularly along developed coasts through coastal squeeze, with an increased risk of habitat loss and exacerbated fragmentation. Such habitat loss has important implications for population and species persistence, depending on the level of connectivity among populations. While sandy beach macroinfauna tend to be highly mobile across and along shore, they also show a strong bias towards direct, or aplanktonic, development; the latter could reduce opportunities for dispersal and sustained population connectivity. However, comparatively little is known about population connectivity on sandy beaches, limiting scientifically sound management of much of the world’s coastline. This study aims to address this knowledge gap by working towards a conceptual model quantifying population connectivity, and by investigating the specific roles of life history, across-shore zonation, and geographic range as putative indicators and possibly drivers of genetic differentiation (ΦST) and connectivity (gene flow) among beach macroinvertebrate populations. The main hypotheses are that 1) species with a pelagic larval stage will display lower genetic differentiation with higher rates of gene flow among populations than species with a benthic lecithotrophic larval stage or direct development; and 2) genetic differentiation among populations will decrease along an across-shore axis, from the supratidal to the low water mark. Two opposing hypotheses were tested concerning the relationship between genetic structure and distributional range: 3a) Species with a large range (measured as distance and number of latitudes) will show less genetic differentiation than those with a narrow range, because they are more able to disperse; or 3b) more widely distributed species may occur across more phylogenetic | v breaks, and thus show higher genetic differentiation than species restricted to a smaller ranges and single biogeographic provinces. First, the extent and likely drivers of population connectivity were investigated for a suite of temperate South African macroinfauna. Very low, non-significant genetic differentiation was demonstrated for the beach clam Donax serra, thus supporting the hypothesis that pelagic larval dispersers display low/no genetic differentiation among populations (Chapter 2). Statistical power of the COI locus was, however, low in this species, due to reduced genetic variability which could be attributed to an expansion from a small source population into extant habitats. The results highlighted the need for caution when interpreting a lack of genetic differentiation as evidence for population connectivity. Nevertheless, COI sequences verified that D. serra occupying the cool and warm-temperate regions of the South African coast, constitute a single species, despite morphological and behavioural differences between inhabitants of these two bioregions. D. sordidus, a congener of D. serra, and endemic to the warm-temperate (Agulhas) bioregion of South Africa, was investigated to test two opposing hypotheses (Chapter 3): 1) this pelagic larval disperser lack genetic differentiation with high rates of gene flow across its range, or alternatively 2) these clams are genetically structured across their range due to the influence of freshwater input (measured as distance to nearest estuary), and morphodynamics of the surf zone (represented by surf-zone width). Significant global ΦST was estimated for D. sordidus, with differentiation predominantly driven by haplotype frequencies at a single study site and estimates of gene flow among most sample locations generally high. Tentative evidence suggested that natural selection driven by differences in water salinity due to estuarine runoff and surf-zone width, might be maintaining two dominant haplotypes across the range of this species. Beach clams from the Southern Hemisphere, occupying different distributional ranges, were compared to test the hypothesis that genetic structure decreases with an increase in range. This hypothesis was poorly supported by the results; opposite (yet mostly non-significant) trends demonstrated for ΦST and haplotype diversity, thus providing some support for the alternative hypothesis that more phylogeographic breaks in broad-ranging species results in higher estimates of genetic structure in these species.
- Full Text:
- Date Issued: 2020