NetwIOC: a framework for the automated generation of network-based IOCS for malware information sharing and defence
- Authors: Rudman, Lauren Lynne
- Date: 2018
- Subjects: Malware (Computer software) , Computer networks Security measures , Computer security , Python (Computer program language)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60639 , vital:27809
- Description: With the substantial number of new malware variants found each day, it is useful to have an efficient way to retrieve Indicators of Compromise (IOCs) from the malware in a format suitable for sharing and detection. In the past, these indicators were manually created after inspection of binary samples and network traffic. The Cuckoo Sandbox, is an existing dynamic malware analysis system which meets the requirements for the proposed framework and was extended by adding a few custom modules. This research explored a way to automate the generation of detailed network-based IOCs in a popular format which can be used for sharing. This was done through careful filtering and analysis of the PCAP hie generated by the sandbox, and placing these values into the correct type of STIX objects using Python, Through several evaluations, analysis of what type of network traffic can be expected for the creation of IOCs was conducted, including a brief ease study that examined the effect of analysis time on the number of IOCs created. Using the automatically generated IOCs to create defence and detection mechanisms for the network was evaluated and proved successful, A proof of concept sharing platform developed for the STIX IOCs is showcased at the end of the research.
- Full Text:
- Date Issued: 2018
- Authors: Rudman, Lauren Lynne
- Date: 2018
- Subjects: Malware (Computer software) , Computer networks Security measures , Computer security , Python (Computer program language)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60639 , vital:27809
- Description: With the substantial number of new malware variants found each day, it is useful to have an efficient way to retrieve Indicators of Compromise (IOCs) from the malware in a format suitable for sharing and detection. In the past, these indicators were manually created after inspection of binary samples and network traffic. The Cuckoo Sandbox, is an existing dynamic malware analysis system which meets the requirements for the proposed framework and was extended by adding a few custom modules. This research explored a way to automate the generation of detailed network-based IOCs in a popular format which can be used for sharing. This was done through careful filtering and analysis of the PCAP hie generated by the sandbox, and placing these values into the correct type of STIX objects using Python, Through several evaluations, analysis of what type of network traffic can be expected for the creation of IOCs was conducted, including a brief ease study that examined the effect of analysis time on the number of IOCs created. Using the automatically generated IOCs to create defence and detection mechanisms for the network was evaluated and proved successful, A proof of concept sharing platform developed for the STIX IOCs is showcased at the end of the research.
- Full Text:
- Date Issued: 2018
New thiazolidine-2,4-dione derivatives combined with organometallic ferrocene: Synthesis, structure and antiparasitic activity
- Oderinlo, Ogunyemi O, Tukulula, Matshawandile, Isaacs, Michelle, Taylor, Dale, Smith, Vincent J, Khanye, Setshaba D, Hoppe, Heinrich C
- Authors: Oderinlo, Ogunyemi O , Tukulula, Matshawandile , Isaacs, Michelle , Taylor, Dale , Smith, Vincent J , Khanye, Setshaba D , Hoppe, Heinrich C
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/122978 , vital:35382 , https://doi.org/10.1002/aoc.4385
- Description: Favourable physicochemical properties of an organometallic ferrocene and antiplasmodial potency of compounds containing the thiazolidine‐2,4‐dione framework (TZD‐4) prompted us to explore compounds containing both the thiazolidine‐2,4‐dione core and the ferrocenyl unit with the primary aim of identifying compounds with promising antiprotozoal activities. Thus, a new series of rationally designed ferrocene‐based thiazolidine‐2,4‐dione derivatives, containing a selection of secondary cyclic amines, was synthesised and fully characterised using standard spectroscopic techniques. The resulting compounds were screened for their antiplasmodial and antitrypanosomal activities against both the chloroquine‐resistant (Dd2) strain of Plasmodium falciparum and the Nagana Trypanosoma brucei brucei 427. The general trend that emerged indicated that the target compounds were more selective towards T. b. brucei compared to the P. falciparum parasite. Moreover, the analogues bearing methylpiperazine (8a) and piperidine (8b) rings were more active against T. b. brucei compared to hit compound TZD‐4. Except compound 8b, which appeared promising, none of the synthesised compounds showed better activity than TZD‐4 against the P. falciparum parasite. All the synthesised compounds were non‐toxic and often showed >90% viability of the HeLa cell line screened.
- Full Text:
- Date Issued: 2018
- Authors: Oderinlo, Ogunyemi O , Tukulula, Matshawandile , Isaacs, Michelle , Taylor, Dale , Smith, Vincent J , Khanye, Setshaba D , Hoppe, Heinrich C
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/122978 , vital:35382 , https://doi.org/10.1002/aoc.4385
- Description: Favourable physicochemical properties of an organometallic ferrocene and antiplasmodial potency of compounds containing the thiazolidine‐2,4‐dione framework (TZD‐4) prompted us to explore compounds containing both the thiazolidine‐2,4‐dione core and the ferrocenyl unit with the primary aim of identifying compounds with promising antiprotozoal activities. Thus, a new series of rationally designed ferrocene‐based thiazolidine‐2,4‐dione derivatives, containing a selection of secondary cyclic amines, was synthesised and fully characterised using standard spectroscopic techniques. The resulting compounds were screened for their antiplasmodial and antitrypanosomal activities against both the chloroquine‐resistant (Dd2) strain of Plasmodium falciparum and the Nagana Trypanosoma brucei brucei 427. The general trend that emerged indicated that the target compounds were more selective towards T. b. brucei compared to the P. falciparum parasite. Moreover, the analogues bearing methylpiperazine (8a) and piperidine (8b) rings were more active against T. b. brucei compared to hit compound TZD‐4. Except compound 8b, which appeared promising, none of the synthesised compounds showed better activity than TZD‐4 against the P. falciparum parasite. All the synthesised compounds were non‐toxic and often showed >90% viability of the HeLa cell line screened.
- Full Text:
- Date Issued: 2018
Newspaper coverage of the 2016 #feesmustfall students' protests in Eastern Cape universities : a content analysis of daily dispatch
- Ayodeji-Falade, Monisola Bolajoko
- Authors: Ayodeji-Falade, Monisola Bolajoko
- Date: 2018
- Subjects: Journalism -- South Africa -- Eastern Cape Mass media -- Political aspects -- South Africa Press -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , Communication
- Identifier: http://hdl.handle.net/10353/9894 , vital:35115
- Description: This study evaluated the coverage of the 2016 #FeeMustFall students’ protests in Eastern Cape Universities by the Daily Dispatch, which is a daily newspaper published in the Eastern Cape Province. The study employed both quantitative and qualitative research methods. Quantitative data were collected and analyzed through content analysis of the Daily Dispatch Newspaper while the qualitative data collected through focus group discussions among selected students of the University of Fort Hare were analyzed using thematic analysis. The study revealed that 31 stories were published by the Daily Dispatch Newspaper during the period of the protest. The tone of the stories suggested that the Daily Dispatch Newspaper was objective in its reportage. Furthermore, framing analysis of the stories showed that conflict news frame was most prominent in the #FeeMustFall students’ protest stories followed by the attribution of responsibility and human-interest frames. Thematic analysis of the focus group discussions revealed that the type of news frame used for the #FeeMustFall student’s protest stories influenced the thoughts and perceptions of readers as the news frames generated similar audience frames. These findings confirm the views highlighted by the agenda setting and framing theories, which underpin this study. This study indicates that news framing plays a significant role in readers’ perception and as well, defines the way information is presented by readers.
- Full Text:
- Date Issued: 2018
- Authors: Ayodeji-Falade, Monisola Bolajoko
- Date: 2018
- Subjects: Journalism -- South Africa -- Eastern Cape Mass media -- Political aspects -- South Africa Press -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , Communication
- Identifier: http://hdl.handle.net/10353/9894 , vital:35115
- Description: This study evaluated the coverage of the 2016 #FeeMustFall students’ protests in Eastern Cape Universities by the Daily Dispatch, which is a daily newspaper published in the Eastern Cape Province. The study employed both quantitative and qualitative research methods. Quantitative data were collected and analyzed through content analysis of the Daily Dispatch Newspaper while the qualitative data collected through focus group discussions among selected students of the University of Fort Hare were analyzed using thematic analysis. The study revealed that 31 stories were published by the Daily Dispatch Newspaper during the period of the protest. The tone of the stories suggested that the Daily Dispatch Newspaper was objective in its reportage. Furthermore, framing analysis of the stories showed that conflict news frame was most prominent in the #FeeMustFall students’ protest stories followed by the attribution of responsibility and human-interest frames. Thematic analysis of the focus group discussions revealed that the type of news frame used for the #FeeMustFall student’s protest stories influenced the thoughts and perceptions of readers as the news frames generated similar audience frames. These findings confirm the views highlighted by the agenda setting and framing theories, which underpin this study. This study indicates that news framing plays a significant role in readers’ perception and as well, defines the way information is presented by readers.
- Full Text:
- Date Issued: 2018
Niq Mhlongo told us# FeesMustFall, or why the surface matters in Dog Eat Dog:
- Authors: Dass, Minesh
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142609 , vital:38095 , DOI: 10.4314/eia.v45i3.6
- Description: In this paper, I investigate some of the reasons for the relative paucity of scholarly attention given to Niq Mhlongo’s debut novel, Dog Eat Dog. I argue that this text anticipates and articulates themes that are vital to contemporary South African culture generally, and to the academic space of the university specifically. For this reason, I contend that it is a work worthy of consideration, both because of its unusual form (it is a novel of ordeal rather than a Bildungsroman), and its prescient depiction of issues to do with institutional racism and academic exclusion – subjects which were central during the student-led protests on South African campuses in 2015 and 2016. A principal thesis of this article is that one of the reasons for literary study’s unwillingness to engage with the novel is the discipline’s predisposition to a hermeneutics of suspicion, a method of analysis that I show is unsuited to Mhlongo’s text. Instead, I argue for the use of surface reading as a valid and appropriate praxis given the form and the content of Dog Eat Dog.
- Full Text:
- Date Issued: 2018
- Authors: Dass, Minesh
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142609 , vital:38095 , DOI: 10.4314/eia.v45i3.6
- Description: In this paper, I investigate some of the reasons for the relative paucity of scholarly attention given to Niq Mhlongo’s debut novel, Dog Eat Dog. I argue that this text anticipates and articulates themes that are vital to contemporary South African culture generally, and to the academic space of the university specifically. For this reason, I contend that it is a work worthy of consideration, both because of its unusual form (it is a novel of ordeal rather than a Bildungsroman), and its prescient depiction of issues to do with institutional racism and academic exclusion – subjects which were central during the student-led protests on South African campuses in 2015 and 2016. A principal thesis of this article is that one of the reasons for literary study’s unwillingness to engage with the novel is the discipline’s predisposition to a hermeneutics of suspicion, a method of analysis that I show is unsuited to Mhlongo’s text. Instead, I argue for the use of surface reading as a valid and appropriate praxis given the form and the content of Dog Eat Dog.
- Full Text:
- Date Issued: 2018
NMR structural elucidation of channaine, an unusual alkaloid from Sceletium tortuosum:
- Veale, Clinton G L, Chen, Weiyang, Chaudhary, Sushil, Kituyi, Sarah N, Isaacs, Michelle, Hoppe, Heinrich C, Edkins, Adrienne L, Combrinck, Sandra, Mehari, Bewketu, Viljoen, Alvaro
- Authors: Veale, Clinton G L , Chen, Weiyang , Chaudhary, Sushil , Kituyi, Sarah N , Isaacs, Michelle , Hoppe, Heinrich C , Edkins, Adrienne L , Combrinck, Sandra , Mehari, Bewketu , Viljoen, Alvaro
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/164345 , vital:41110 , DOI: 10.1016/j.phytol.2017.11.018
- Description: Chemical interrogation of the Sceletium genus and Amaryllidaceae family of plants has yielded a diverse array of aryl-hydroindole containing alkaloids. Included in this class is channaine, which was tentatively identified, without comprehensive structural elucidation from Sceletium tortuosum in 1957. Following its isolation from S. strictum, the structure of channaine was eventually resolved by X-ray crystallographic analysis, which revealed an unusual cage-like ring structure at the interface of two aryl-hydroindole subunits. However, since this report in 1978, channaine has not re-appeared in the literature. In this letter, the full NMR characterisation of channaine, isolated from S. tortuosum collected from St Helena in the Western Cape Province of South Africa, is reported for the first time.
- Full Text:
- Date Issued: 2018
- Authors: Veale, Clinton G L , Chen, Weiyang , Chaudhary, Sushil , Kituyi, Sarah N , Isaacs, Michelle , Hoppe, Heinrich C , Edkins, Adrienne L , Combrinck, Sandra , Mehari, Bewketu , Viljoen, Alvaro
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/164345 , vital:41110 , DOI: 10.1016/j.phytol.2017.11.018
- Description: Chemical interrogation of the Sceletium genus and Amaryllidaceae family of plants has yielded a diverse array of aryl-hydroindole containing alkaloids. Included in this class is channaine, which was tentatively identified, without comprehensive structural elucidation from Sceletium tortuosum in 1957. Following its isolation from S. strictum, the structure of channaine was eventually resolved by X-ray crystallographic analysis, which revealed an unusual cage-like ring structure at the interface of two aryl-hydroindole subunits. However, since this report in 1978, channaine has not re-appeared in the literature. In this letter, the full NMR characterisation of channaine, isolated from S. tortuosum collected from St Helena in the Western Cape Province of South Africa, is reported for the first time.
- Full Text:
- Date Issued: 2018
No evidence for association between APOL1 kidney disease risk alleles and Human African Trypanosomiasis in two Ugandan populations:
- Kimuda, Magambo P, Noyes, Harry, Mulindwa, Julius, Enyaru, John, Alibu, Vincent P, Sidibe, Issa, Mumba Ngoyi, Dieuodonne, Hertz-Fowler, Christiane, MacLeod, Annette, Tastan Bishop, Özlem, Matovu, Enock
- Authors: Kimuda, Magambo P , Noyes, Harry , Mulindwa, Julius , Enyaru, John , Alibu, Vincent P , Sidibe, Issa , Mumba Ngoyi, Dieuodonne , Hertz-Fowler, Christiane , MacLeod, Annette , Tastan Bishop, Özlem , Matovu, Enock
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/162924 , vital:40997 , https://doi.org/10.1371/journal.pntd.0006300
- Description: Human African trypanosomiasis (HAT) manifests as an acute form caused by Trypanosoma brucei rhodesiense (Tbr) and a chronic form caused by Trypanosoma brucei gambiense (Tbg). Previous studies have suggested a host genetic role in infection outcomes, particularly for APOL1. We have undertaken candidate gene association studies (CGAS) in a Ugandan Tbr and a Tbg HAT endemic area, to determine whether polymorphisms in IL10, IL8, IL4, HLAG, TNFA, TNX4LB, IL6, IFNG, MIF, APOL1, HLAA, IL1B, IL4R, IL12B, IL12R, HP, HPR, and CFH have a role in HAT.
- Full Text:
- Date Issued: 2018
- Authors: Kimuda, Magambo P , Noyes, Harry , Mulindwa, Julius , Enyaru, John , Alibu, Vincent P , Sidibe, Issa , Mumba Ngoyi, Dieuodonne , Hertz-Fowler, Christiane , MacLeod, Annette , Tastan Bishop, Özlem , Matovu, Enock
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/162924 , vital:40997 , https://doi.org/10.1371/journal.pntd.0006300
- Description: Human African trypanosomiasis (HAT) manifests as an acute form caused by Trypanosoma brucei rhodesiense (Tbr) and a chronic form caused by Trypanosoma brucei gambiense (Tbg). Previous studies have suggested a host genetic role in infection outcomes, particularly for APOL1. We have undertaken candidate gene association studies (CGAS) in a Ugandan Tbr and a Tbg HAT endemic area, to determine whether polymorphisms in IL10, IL8, IL4, HLAG, TNFA, TNX4LB, IL6, IFNG, MIF, APOL1, HLAA, IL1B, IL4R, IL12B, IL12R, HP, HPR, and CFH have a role in HAT.
- Full Text:
- Date Issued: 2018
Non-farm enterprises and rural development in South Africa : a case of the Eastern Cape
- Authors: Dapira, Clarah
- Date: 2018
- Subjects: Rural development--South Africa--Eastern Cape--Case studies Rural development--South Africa South Africa--Economic conditions
- Language: English
- Type: Thesis , Doctoral , Development Studies
- Identifier: http://hdl.handle.net/10353/15463 , vital:40410
- Description: There is growing recognition that the limited success in rural development policies in many developing countries, including South Africa, is mainly a result of the failure to conceptualize such interventions beyond agriculture and incorporate non-farm enterprises into the mix. Non-farm enterprises are increasingly viewed as having the potential to become one of the drivers of rural development. However, it is an area that remains poorly documented and dimly understood as it has received limited scholarly attention in recent years. The study was carried out in the rural areas of Port St John’s Local Municipality in the Eastern Cape Province of South Africa. The study was premised on the assumption that non-farm enterprises have the potential to become one of the drivers of rural development in terms of employment creation, income generation and diversification of the rural economy. The thesis demonstrates that the hope that non-farm enterprises can add value to the rural economy in terms of creating the much needed employment opportunities is still a goal to be realised. Nevertheless, the income generated by these enterprises is contributing immensely to household welfare, especially improving accessibility to food by poor households. The study recommends the implementation of tailor made capacity building and training programmes aimed at enhancing the skills of rural artisans. This is an area that requires state-mediated intervention to augment the rural economy in order to redress the uneven development of the past.
- Full Text:
- Date Issued: 2018
- Authors: Dapira, Clarah
- Date: 2018
- Subjects: Rural development--South Africa--Eastern Cape--Case studies Rural development--South Africa South Africa--Economic conditions
- Language: English
- Type: Thesis , Doctoral , Development Studies
- Identifier: http://hdl.handle.net/10353/15463 , vital:40410
- Description: There is growing recognition that the limited success in rural development policies in many developing countries, including South Africa, is mainly a result of the failure to conceptualize such interventions beyond agriculture and incorporate non-farm enterprises into the mix. Non-farm enterprises are increasingly viewed as having the potential to become one of the drivers of rural development. However, it is an area that remains poorly documented and dimly understood as it has received limited scholarly attention in recent years. The study was carried out in the rural areas of Port St John’s Local Municipality in the Eastern Cape Province of South Africa. The study was premised on the assumption that non-farm enterprises have the potential to become one of the drivers of rural development in terms of employment creation, income generation and diversification of the rural economy. The thesis demonstrates that the hope that non-farm enterprises can add value to the rural economy in terms of creating the much needed employment opportunities is still a goal to be realised. Nevertheless, the income generated by these enterprises is contributing immensely to household welfare, especially improving accessibility to food by poor households. The study recommends the implementation of tailor made capacity building and training programmes aimed at enhancing the skills of rural artisans. This is an area that requires state-mediated intervention to augment the rural economy in order to redress the uneven development of the past.
- Full Text:
- Date Issued: 2018
Non-government organizations’ adoption of knowledge management systems to enhance service delivery of projects in Grahamstown in the Makana region of the Eastern Cape Province, South Africa
- Authors: Sherif, Nabiha Mohammed
- Date: 2018
- Subjects: Knowledge management , Organizational learning , Non-governmental organizations South Africa Makhanda , Human services South Africa Makhanda
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/61723 , vital:28052
- Description: The object of this research is to enhance the performance of non-government organizations in the Makana region of the Eastern Cape Province of South Africa by the use of knowledge management practices and principles. Non-government organizations face several service delivery challenges that affect their performance. Knowledge management assists in enhancing performance by means of organizational learning. However, the adoption of knowledge management systems has been limited to the profit-making sector. This study includes an evaluation of the contributing factors influencing the adoption of knowledge management and the extent to which non-government organizations use knowledge management to promote organizational learning. An interpretivist, qualitative case study approach was used on five non-government organizations cases from the Makana region of the Eastern Cape Province of South Africa. A suitability profile sampling method was developed to select the non-government organization cases. The participants in the research include non-government organizations’ managers, employees and volunteers. Literature was explored to gain a better understanding of the research area. The research was initiated by an open-ended questionnaire to gather data from the participants, followed by a focus group to enrich the interpretation of the findings. The research proposes a framework to facilitate the adoption of knowledge management systems in non-government organizations. The findings of the research are intended to enhance the performance of non-government organizations projects by means of the use of knowledge management systems.
- Full Text:
- Date Issued: 2018
- Authors: Sherif, Nabiha Mohammed
- Date: 2018
- Subjects: Knowledge management , Organizational learning , Non-governmental organizations South Africa Makhanda , Human services South Africa Makhanda
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/61723 , vital:28052
- Description: The object of this research is to enhance the performance of non-government organizations in the Makana region of the Eastern Cape Province of South Africa by the use of knowledge management practices and principles. Non-government organizations face several service delivery challenges that affect their performance. Knowledge management assists in enhancing performance by means of organizational learning. However, the adoption of knowledge management systems has been limited to the profit-making sector. This study includes an evaluation of the contributing factors influencing the adoption of knowledge management and the extent to which non-government organizations use knowledge management to promote organizational learning. An interpretivist, qualitative case study approach was used on five non-government organizations cases from the Makana region of the Eastern Cape Province of South Africa. A suitability profile sampling method was developed to select the non-government organization cases. The participants in the research include non-government organizations’ managers, employees and volunteers. Literature was explored to gain a better understanding of the research area. The research was initiated by an open-ended questionnaire to gather data from the participants, followed by a focus group to enrich the interpretation of the findings. The research proposes a framework to facilitate the adoption of knowledge management systems in non-government organizations. The findings of the research are intended to enhance the performance of non-government organizations projects by means of the use of knowledge management systems.
- Full Text:
- Date Issued: 2018
Nontimber forest products as ecological and biocultural keystone species
- Shackleton, Charlie M, Ticktin, Tamara, Cunningham, Anthony B
- Authors: Shackleton, Charlie M , Ticktin, Tamara , Cunningham, Anthony B
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180388 , vital:43359 , xlink:href="https://doi.org/10.5751/ES-10469-230422"
- Description: Nontimber forests products (NTFPs) are the mainstay of rural livelihoods and local economies the world over. As such they are of interest to a wide disciplinary range of researchers and development and government agencies seeking to promote livelihoods, incomes, and ecologically sustainable practices. With the attention on the various human uses of NTFPs, their role and networks in the broader biological communities in which they are located are frequently overlooked. Harvesting of many NTFPs has effects not only at the organism and population scales, but also on co-occurring species, some of which may also be NTFPs. Thus, reduction or loss of one NTFP population or species in a specific area may have cascade effects on other NTFP species, including those used for cultural purposes. We illustrate the little appreciated importance of NTFPs in broader ecological and social systems by assessing and illustrating the importance of NTFP species as ecological or biocultural keystones in providing regulating and supporting ecological services to other species and cultural services to people. We present a number of examples where NTFP species act as keystones in ecological and cultural systems, including food, pollination and dispersal, animal health, nutrients, shelter and protection, and cultural symbolism, most of which have not been considered by NTFP researchers and practitioners. From these examples we distill six propositions regarding NTFPs and discuss the value of recognizing some NTFPs as biocultural keystones to acknowledge and highlight their roles at broader scales.
- Full Text:
- Date Issued: 2018
- Authors: Shackleton, Charlie M , Ticktin, Tamara , Cunningham, Anthony B
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180388 , vital:43359 , xlink:href="https://doi.org/10.5751/ES-10469-230422"
- Description: Nontimber forests products (NTFPs) are the mainstay of rural livelihoods and local economies the world over. As such they are of interest to a wide disciplinary range of researchers and development and government agencies seeking to promote livelihoods, incomes, and ecologically sustainable practices. With the attention on the various human uses of NTFPs, their role and networks in the broader biological communities in which they are located are frequently overlooked. Harvesting of many NTFPs has effects not only at the organism and population scales, but also on co-occurring species, some of which may also be NTFPs. Thus, reduction or loss of one NTFP population or species in a specific area may have cascade effects on other NTFP species, including those used for cultural purposes. We illustrate the little appreciated importance of NTFPs in broader ecological and social systems by assessing and illustrating the importance of NTFP species as ecological or biocultural keystones in providing regulating and supporting ecological services to other species and cultural services to people. We present a number of examples where NTFP species act as keystones in ecological and cultural systems, including food, pollination and dispersal, animal health, nutrients, shelter and protection, and cultural symbolism, most of which have not been considered by NTFP researchers and practitioners. From these examples we distill six propositions regarding NTFPs and discuss the value of recognizing some NTFPs as biocultural keystones to acknowledge and highlight their roles at broader scales.
- Full Text:
- Date Issued: 2018
Novel nano-dyad of homoleptic sandwich-type phthalocyanines with nitrogen doped graphene quantum dots for nonlinear optics
- Oluwole, David O, Nwaji, Njemuwa, Nene, Lindokuhle C, Mokone, Lesedi, Dube, Edith, Nyokong, Tebello
- Authors: Oluwole, David O , Nwaji, Njemuwa , Nene, Lindokuhle C , Mokone, Lesedi , Dube, Edith , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233386 , vital:50086 , xlink:href="https://doi.org/10.1039/C8NJ01707G"
- Description: The syntheses of neodymium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (2), bis europium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (3), bis dysprosium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (4) and their conjugated analogues with nitrogen doped quantum dots (NGQDs) are reported herein. The optical nonlinearity of the sandwich-type phthalocyanine complexes and their conjugates with NGQDs were studied in dimethyl sulfoxide using the open aperture Z-scan technique at an excitation wavelength of 532 nm with a 10 ns pulse. The nonlinear absorption coefficient (βeff) value of the samples ranges from 15 cm GW−1 to 89.6 cm GW−1. Complex 4 and its conjugates afforded a strong optical limiting behaviour compared to the other samples. These fabricated complexes and their conjugates with NGQDs could serve as a plausible nonlinear optical (NLO) material due to their fascinating NLO properties.
- Full Text:
- Date Issued: 2018
- Authors: Oluwole, David O , Nwaji, Njemuwa , Nene, Lindokuhle C , Mokone, Lesedi , Dube, Edith , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233386 , vital:50086 , xlink:href="https://doi.org/10.1039/C8NJ01707G"
- Description: The syntheses of neodymium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (2), bis europium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (3), bis dysprosium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (4) and their conjugated analogues with nitrogen doped quantum dots (NGQDs) are reported herein. The optical nonlinearity of the sandwich-type phthalocyanine complexes and their conjugates with NGQDs were studied in dimethyl sulfoxide using the open aperture Z-scan technique at an excitation wavelength of 532 nm with a 10 ns pulse. The nonlinear absorption coefficient (βeff) value of the samples ranges from 15 cm GW−1 to 89.6 cm GW−1. Complex 4 and its conjugates afforded a strong optical limiting behaviour compared to the other samples. These fabricated complexes and their conjugates with NGQDs could serve as a plausible nonlinear optical (NLO) material due to their fascinating NLO properties.
- Full Text:
- Date Issued: 2018
Occurrence of mugilid and sparid fishes in Zostera capensis and bare sediment habitats of the Knysna Estuary
- Authors: Pollard, Melissa
- Date: 2018
- Subjects: Gray mullets South Africa Knysna Lagoon , Sparidae South Africa Knysna Lagoon , Seagrasses South Africa Knysna Lagoon , Eelgrass South Africa Knysna Lagoon , Gray mullets Habitat South Africa Knysna Lagoon , Sparidae Habitat South Africa Knysna Lagoon , Underwater videography in wildlife monitoring , Seining , Zostera capensis Setchel
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54979 , vital:26641
- Description: Seagrass meadows are regarded as one of the most unique and valuable ecosystems in the biosphere, primarily because of the variety of services that they provide. Seagrass meadows serve as nursery grounds for many species and often play an important role in the juvenile stages of economically and recreationally important fish. Zostera capensis Setchell is one of the most dominant submerged macrophytes and the most common seagrass in South African estuaries and is often referred to as eelgrass. Zostera capensis meadows occupy a large area within the Knysna Estuary but little is known about their importance to associated fish assemblages. With Z. capensis meadows being under increased pressure from anthropogenic influences, it is important to establish which fish species and families utilize these habitats and what role they play in the ecology of fish assemblages within the Knysna Estuary. The primary objective of this study was to compare the use of Z. capensis and adjacent bare sediment areas by mainly large juvenile and subadult sparids and mugilids using different techniques. The two main hypotheses were as follows; 1) Mugilidae are likely to be more dominant in the unvegetated areas of the estuary littoral and Sparidae are likely to predominate within the Z. capensis bed areas of the estuary littoral. 2) The non-destructive underwater video monitoring method would yield similar fish composition data to seine netting sampling of the identical sites. Both hypotheses were assessed using data collected during this study and the analysis of historical unpublished data. Overall, Mugilidae were more abundant at bare unvegetated areas where they did most of their foraging. Sparidae were more abundant in the Z. capensis beds, which was also the habitat where they primarily foraged. With regards to the comparison of two different sampling methods, namely underwater video monitoring and seine netting, similar patterns arose with regards to the fish species observed in camera footage and those captured in the seine net, although the abundances were not always comparable.
- Full Text:
- Date Issued: 2018
- Authors: Pollard, Melissa
- Date: 2018
- Subjects: Gray mullets South Africa Knysna Lagoon , Sparidae South Africa Knysna Lagoon , Seagrasses South Africa Knysna Lagoon , Eelgrass South Africa Knysna Lagoon , Gray mullets Habitat South Africa Knysna Lagoon , Sparidae Habitat South Africa Knysna Lagoon , Underwater videography in wildlife monitoring , Seining , Zostera capensis Setchel
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54979 , vital:26641
- Description: Seagrass meadows are regarded as one of the most unique and valuable ecosystems in the biosphere, primarily because of the variety of services that they provide. Seagrass meadows serve as nursery grounds for many species and often play an important role in the juvenile stages of economically and recreationally important fish. Zostera capensis Setchell is one of the most dominant submerged macrophytes and the most common seagrass in South African estuaries and is often referred to as eelgrass. Zostera capensis meadows occupy a large area within the Knysna Estuary but little is known about their importance to associated fish assemblages. With Z. capensis meadows being under increased pressure from anthropogenic influences, it is important to establish which fish species and families utilize these habitats and what role they play in the ecology of fish assemblages within the Knysna Estuary. The primary objective of this study was to compare the use of Z. capensis and adjacent bare sediment areas by mainly large juvenile and subadult sparids and mugilids using different techniques. The two main hypotheses were as follows; 1) Mugilidae are likely to be more dominant in the unvegetated areas of the estuary littoral and Sparidae are likely to predominate within the Z. capensis bed areas of the estuary littoral. 2) The non-destructive underwater video monitoring method would yield similar fish composition data to seine netting sampling of the identical sites. Both hypotheses were assessed using data collected during this study and the analysis of historical unpublished data. Overall, Mugilidae were more abundant at bare unvegetated areas where they did most of their foraging. Sparidae were more abundant in the Z. capensis beds, which was also the habitat where they primarily foraged. With regards to the comparison of two different sampling methods, namely underwater video monitoring and seine netting, similar patterns arose with regards to the fish species observed in camera footage and those captured in the seine net, although the abundances were not always comparable.
- Full Text:
- Date Issued: 2018
Offline-First Design for Fault Tolerant Applications.
- Linklater, Gregory, Marais, Craig, Herbert, Alan, Irwin, Barry V W
- Authors: Linklater, Gregory , Marais, Craig , Herbert, Alan , Irwin, Barry V W
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427683 , vital:72455 , https://www.researchgate.net/profile/Barry-Irwin/publication/327624337_Offline-First_Design_for_Fault_Tolerant_Applications/links/5b9a50a1458515310584ebbe/Offline-First-Design-for-Fault-Tolerant-Applications.pdf
- Description: Faults are inevitable and frustrating, as we increasingly depend on network access and the chain of services that provides it, we suffer a greater loss in productivity when any of those services fail and service delivery is suspended. This research explores connectivity and infrastructure fault tolerance through offline-first application design using techniques such as CQRS and event sourcing. To apply these techniques, this research details the design, and implementation of LOYALTY TRACKER; an offline-first, PoS system for the Android platform that was built to operate in the context of a small pub where faults are commonplace. The application demonstrates data consistency and integrity and a complete feature set that continues to operate while offline but is limited by scalability. The application successfully achieves it’s goals in the limited capacity for which it was designed.
- Full Text:
- Date Issued: 2018
- Authors: Linklater, Gregory , Marais, Craig , Herbert, Alan , Irwin, Barry V W
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427683 , vital:72455 , https://www.researchgate.net/profile/Barry-Irwin/publication/327624337_Offline-First_Design_for_Fault_Tolerant_Applications/links/5b9a50a1458515310584ebbe/Offline-First-Design-for-Fault-Tolerant-Applications.pdf
- Description: Faults are inevitable and frustrating, as we increasingly depend on network access and the chain of services that provides it, we suffer a greater loss in productivity when any of those services fail and service delivery is suspended. This research explores connectivity and infrastructure fault tolerance through offline-first application design using techniques such as CQRS and event sourcing. To apply these techniques, this research details the design, and implementation of LOYALTY TRACKER; an offline-first, PoS system for the Android platform that was built to operate in the context of a small pub where faults are commonplace. The application demonstrates data consistency and integrity and a complete feature set that continues to operate while offline but is limited by scalability. The application successfully achieves it’s goals in the limited capacity for which it was designed.
- Full Text:
- Date Issued: 2018
On becoming literate in English: a literate life history study of selected Grade 12 learners in a Namibian secondary school
- Authors: Kangootui, Angela Lydia
- Date: 2018
- Subjects: English language -- Study and teaching (Secondary) -- Namibia -- Omaheke , Second language acquisition -- Omaheke , Language and languages -- Study and teaching -- Namibia -- Omaheke , Namibia. Ministry of Basic Education, Sport, and Culture
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/62252 , vital:28147
- Description: This study sought to investigate English literate journeys of selected Grade 12 learners who come from educationally disempowering home backgrounds, and who ‘meet’ informal and/or formal exposure to English language mainly within the confines of school hours. Located within the qualitative, interpretive life history study design, the study used questionnaire and learners’ autobiographies to generate data. These data were then subjected to explore the literate journey of these learners in English as a second language through a comprehensive descriptive analysis. The study was conducted in an urban high school in Omaheke region, Namibia, and the research site and study participants were selected purposively. Theoretically, the study drew from Krashen’s (1981) Second Language Acquisition Theory, which offered this study the five hypotheses that were used as categories to generate, analyse, interpret and discuss data. Research findings reveal that, for various reasons discussed in the study, there is minimal parental involvement in the English literacy journey of their children at home. These include parents not reading regularly to their children, not encouraging visits to the library and the shortage of literacy materials such as newspapers and magazines. The educational level of parents is also a major contributing factor in the literacy journey of their children. The contribution of the community towards the literacy journey in English as a second language of these learners was minimal since the vernacular languages or Afrikaans were used to communicate. At the school level it was found that the attitude of some teachers was a hindrance, as was the way they taught. The use of the mother tongue during teaching also had an effect on the literacy development of the learners. Although the different methods used by various teachers at school level contributed in a way towards literacy development of the learners at school, the huge number of learners in the classrooms was a force to be reckoned with. It is hoped that the study’s findings will assist the Ministry of Basic Education Arts and Culture (MBEAC) in Namibia in informing the type of syllabus content and pedagogical practices to be utilised in teaching English as a Second Language.
- Full Text:
- Date Issued: 2018
- Authors: Kangootui, Angela Lydia
- Date: 2018
- Subjects: English language -- Study and teaching (Secondary) -- Namibia -- Omaheke , Second language acquisition -- Omaheke , Language and languages -- Study and teaching -- Namibia -- Omaheke , Namibia. Ministry of Basic Education, Sport, and Culture
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/62252 , vital:28147
- Description: This study sought to investigate English literate journeys of selected Grade 12 learners who come from educationally disempowering home backgrounds, and who ‘meet’ informal and/or formal exposure to English language mainly within the confines of school hours. Located within the qualitative, interpretive life history study design, the study used questionnaire and learners’ autobiographies to generate data. These data were then subjected to explore the literate journey of these learners in English as a second language through a comprehensive descriptive analysis. The study was conducted in an urban high school in Omaheke region, Namibia, and the research site and study participants were selected purposively. Theoretically, the study drew from Krashen’s (1981) Second Language Acquisition Theory, which offered this study the five hypotheses that were used as categories to generate, analyse, interpret and discuss data. Research findings reveal that, for various reasons discussed in the study, there is minimal parental involvement in the English literacy journey of their children at home. These include parents not reading regularly to their children, not encouraging visits to the library and the shortage of literacy materials such as newspapers and magazines. The educational level of parents is also a major contributing factor in the literacy journey of their children. The contribution of the community towards the literacy journey in English as a second language of these learners was minimal since the vernacular languages or Afrikaans were used to communicate. At the school level it was found that the attitude of some teachers was a hindrance, as was the way they taught. The use of the mother tongue during teaching also had an effect on the literacy development of the learners. Although the different methods used by various teachers at school level contributed in a way towards literacy development of the learners at school, the huge number of learners in the classrooms was a force to be reckoned with. It is hoped that the study’s findings will assist the Ministry of Basic Education Arts and Culture (MBEAC) in Namibia in informing the type of syllabus content and pedagogical practices to be utilised in teaching English as a Second Language.
- Full Text:
- Date Issued: 2018
On high-altitude and high- latitude frost environments
- Authors: Hansen, Christel Dorothee
- Date: 2018
- Subjects: Frost -- Drakensberg Mountains , Frost -- Prince Edward Islands -- Marion Island , Frost -- Antarctica -- Queen Maud Land , Climatic geomorphology -- Southern Hemisphere , Permafrost -- Southern Hemisphere , Periglacial processes -- Southern Hemisphere , Frost environments -- Southern Hemisphere
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62383 , vital:28169
- Description: Frost environments occur throughout the world, with associated processes occurring across climatic zones. Climatic geomorphology proposes that climatic zones, largely derived from annual average air temperature and precipitation values, have specific landforms and processes active within that zone. This study offers unique insights into the frost environments of three locations in the Southern Hemisphere, namely the Eastern Cape Drakensberg of South Africa, sub-Antarctic Marion Island, and Dronning Maud Land of Antarctica. The Drakensberg ranges from temperate to alpine, Marion Island is hyper-maritime, and Dronning Maud Land a polar desert. Drivers and forcings on the ground frost regime are identified, as are future climatic scenarios. Altitude and latitude were identified as the most important locational drivers, while air temperature showed highest correlation with freezing events. The initiation of a freeze event correlated strongly with maximum ground temperatures. Vegetation cover was found to ameliorate frost cycles, thereby increasing ground temperatures. Dronning Maud Land of Antarctica is characterised by annual frost (permafrost), with limited seasonal thaw in summer. Thawing cycles reflected the depth of the active layer, which ranged from just under 60 cm for Robertskollen (at lowest altitude) to less than 15 cm on Slettfjell (at greatest altitude). Marion Island had the most active frost environment, exhibiting both seasonal frost, and ubiquitous shallow diurnal frost cycles. The Drakensberg were largely frost-free, with limited seasonal frost and few diurnal freeze- thaw events. Diurnal frost processes were found to be azonal, and present at all three study locations. Evidence of landforms derived from diurnal frost processes were evident in each zone. Equifinality/convergence of form was present to a degree. The presence of patterned ground, which was not wholly derived from frost processes, suggests a measure of equifinality. Furthermore, openwork block deposits, of which not all are either blockstreams nor blockfields, are not necessarily the result of frost processes. The periglacial environment is poorly defined and methods to delineate this environment, as well as other climatic zones, should include additional parameters. Delineating zones on annual (and limited) monthly averages based on predominantly temperature, is not sufficient. While concepts of climatic geomorphology may be applied in a general sense, this framework is not suited to working at smaller scales. Specifically, periglacial environments should be delineated using ground moisture, as well as air temperature. Furthermore, vegetation and snow cover are important, as are soil textural properties.
- Full Text:
- Date Issued: 2018
- Authors: Hansen, Christel Dorothee
- Date: 2018
- Subjects: Frost -- Drakensberg Mountains , Frost -- Prince Edward Islands -- Marion Island , Frost -- Antarctica -- Queen Maud Land , Climatic geomorphology -- Southern Hemisphere , Permafrost -- Southern Hemisphere , Periglacial processes -- Southern Hemisphere , Frost environments -- Southern Hemisphere
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62383 , vital:28169
- Description: Frost environments occur throughout the world, with associated processes occurring across climatic zones. Climatic geomorphology proposes that climatic zones, largely derived from annual average air temperature and precipitation values, have specific landforms and processes active within that zone. This study offers unique insights into the frost environments of three locations in the Southern Hemisphere, namely the Eastern Cape Drakensberg of South Africa, sub-Antarctic Marion Island, and Dronning Maud Land of Antarctica. The Drakensberg ranges from temperate to alpine, Marion Island is hyper-maritime, and Dronning Maud Land a polar desert. Drivers and forcings on the ground frost regime are identified, as are future climatic scenarios. Altitude and latitude were identified as the most important locational drivers, while air temperature showed highest correlation with freezing events. The initiation of a freeze event correlated strongly with maximum ground temperatures. Vegetation cover was found to ameliorate frost cycles, thereby increasing ground temperatures. Dronning Maud Land of Antarctica is characterised by annual frost (permafrost), with limited seasonal thaw in summer. Thawing cycles reflected the depth of the active layer, which ranged from just under 60 cm for Robertskollen (at lowest altitude) to less than 15 cm on Slettfjell (at greatest altitude). Marion Island had the most active frost environment, exhibiting both seasonal frost, and ubiquitous shallow diurnal frost cycles. The Drakensberg were largely frost-free, with limited seasonal frost and few diurnal freeze- thaw events. Diurnal frost processes were found to be azonal, and present at all three study locations. Evidence of landforms derived from diurnal frost processes were evident in each zone. Equifinality/convergence of form was present to a degree. The presence of patterned ground, which was not wholly derived from frost processes, suggests a measure of equifinality. Furthermore, openwork block deposits, of which not all are either blockstreams nor blockfields, are not necessarily the result of frost processes. The periglacial environment is poorly defined and methods to delineate this environment, as well as other climatic zones, should include additional parameters. Delineating zones on annual (and limited) monthly averages based on predominantly temperature, is not sufficient. While concepts of climatic geomorphology may be applied in a general sense, this framework is not suited to working at smaller scales. Specifically, periglacial environments should be delineated using ground moisture, as well as air temperature. Furthermore, vegetation and snow cover are important, as are soil textural properties.
- Full Text:
- Date Issued: 2018
On the characterization of solar cells using advanced imaging techniques
- Authors: Dix-Peek, Ross Michael
- Date: 2018
- Subjects: Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/17944 , vital:28544
- Description: Photovoltaic (PV) cells are devices capable of producing electricity - in particular, from the abundant resource of sunlight. Solar energy (from PV cells) provides a sustainable alternative to fossil fuel energy sources such as coal and oil. PV cells are typically strung in series in PV modules to generate the current and voltage required for commercial use. However, PV cell performance can be limited by defects and degradation. Under operational conditions due to mismatch and shading, individual cells within a PV module can be forced to operate in their reverse bias regime. Depending on the severity of the reverse bias and the defects present in the cell, the longevity of the cell and/or the module can be affected. Reverse bias (assuming bypass diodes are absent) can result in localised heating that can affect the encapsulant polymer’s longevity as well as degrade the cell’s performance over time. However, under more severe reverse bias, the cell could fail, drastically affecting the performance of the module. PV cells can be characterised using various opto-electronic non-destructive techniques, this provides a set of powerful tools which allow the application of multiple such techniques to the same sample. Furthermore, this allows for an in-depth study of the device. Dark Current-Voltage (I-V) measurements, Electroluminescence (EL), Infrared (IR) thermography, Light Beam Induced Current (LBIC) measurements, and the associated techniques are all examples of such tools and are used within this study. An experimental setup was developed to perform dark I-V measurements, EL imaging, IR thermography and LBIC measurements. Part of the development of the experimental setup was the design of an enclosure in which to perform all the measurements. The enclosure minimised internal reflection, and isolated the experiment from electromagnetic radiation. Due to the complex mathematical model applied to the I-V curve, an Evolutionary Algorithm was used to determine optimal parameter values for the equation. More specifically, a Genetic Algorithm was used in the Parameter Optimisation (or Extraction) of the dark I-V parameters based upon the two-diode model for PV cells. The resulting parameters give an indication of the material and device quality. However, to determine the spatial distribution of the defects that effect the I-V response of the device, various imaging techniques were utilised. LBIC is a technique that uses a focussed light beam to raster scan across the surface of a PV cell. The local photo-induced current/voltage can then be measured and compiled into a response map. LBIC was used to determine the local current response across the device. The intensity distribution of EL signal is related to the local junction voltage and the local quantum efficiency. EL intensity imaging with a Si CCD camera was used to determine the spatial distribution of features visible both in the forward bias and in the reverse bias. The experimental setup utilised had a micron scale resolution. A voltage dependent approach was utilised to further characterise features observed. In forward bias, the local junction varies across the device due to parasitic resistances such as series and shunt resistance. At higher forward bias conditions (in the vicinity of and higher than maximum power voltage), series resistance becomes a limiting factor. Therefore, utilising a voltage dependent approach allows for the determination of a series resistance map from voltage dependent EL images. In reverse bias, localised radiative processes can be imaged. These radiative processes are related to defects in the device, such as Al stains, FeSi2 needles and avalanche breakdown. The processes are related to highly localised current flow; this causes localised heating which degrades the device. The voltage dependent Reverse Bias EL (ReBEL) imaging was also used to determine the local breakdown voltage of radiative reverse features. Dark IR thermography is a technique used in the identification of high current sites that leads to localised Joule heating, particularly in reverse bias. In this study, thermography was used to identify breakdown sites and shunts. The results of this study allow for an in-depth analysis of defects found in multi-crystalline Si PV cells using the opto-electronic techniques mentioned above. The multi-pronged approach allowed from a comparison of the various opto-electronic techniques, as well as a more in-depth characterisation of the defects than if only one technique was used.
- Full Text:
- Date Issued: 2018
- Authors: Dix-Peek, Ross Michael
- Date: 2018
- Subjects: Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/17944 , vital:28544
- Description: Photovoltaic (PV) cells are devices capable of producing electricity - in particular, from the abundant resource of sunlight. Solar energy (from PV cells) provides a sustainable alternative to fossil fuel energy sources such as coal and oil. PV cells are typically strung in series in PV modules to generate the current and voltage required for commercial use. However, PV cell performance can be limited by defects and degradation. Under operational conditions due to mismatch and shading, individual cells within a PV module can be forced to operate in their reverse bias regime. Depending on the severity of the reverse bias and the defects present in the cell, the longevity of the cell and/or the module can be affected. Reverse bias (assuming bypass diodes are absent) can result in localised heating that can affect the encapsulant polymer’s longevity as well as degrade the cell’s performance over time. However, under more severe reverse bias, the cell could fail, drastically affecting the performance of the module. PV cells can be characterised using various opto-electronic non-destructive techniques, this provides a set of powerful tools which allow the application of multiple such techniques to the same sample. Furthermore, this allows for an in-depth study of the device. Dark Current-Voltage (I-V) measurements, Electroluminescence (EL), Infrared (IR) thermography, Light Beam Induced Current (LBIC) measurements, and the associated techniques are all examples of such tools and are used within this study. An experimental setup was developed to perform dark I-V measurements, EL imaging, IR thermography and LBIC measurements. Part of the development of the experimental setup was the design of an enclosure in which to perform all the measurements. The enclosure minimised internal reflection, and isolated the experiment from electromagnetic radiation. Due to the complex mathematical model applied to the I-V curve, an Evolutionary Algorithm was used to determine optimal parameter values for the equation. More specifically, a Genetic Algorithm was used in the Parameter Optimisation (or Extraction) of the dark I-V parameters based upon the two-diode model for PV cells. The resulting parameters give an indication of the material and device quality. However, to determine the spatial distribution of the defects that effect the I-V response of the device, various imaging techniques were utilised. LBIC is a technique that uses a focussed light beam to raster scan across the surface of a PV cell. The local photo-induced current/voltage can then be measured and compiled into a response map. LBIC was used to determine the local current response across the device. The intensity distribution of EL signal is related to the local junction voltage and the local quantum efficiency. EL intensity imaging with a Si CCD camera was used to determine the spatial distribution of features visible both in the forward bias and in the reverse bias. The experimental setup utilised had a micron scale resolution. A voltage dependent approach was utilised to further characterise features observed. In forward bias, the local junction varies across the device due to parasitic resistances such as series and shunt resistance. At higher forward bias conditions (in the vicinity of and higher than maximum power voltage), series resistance becomes a limiting factor. Therefore, utilising a voltage dependent approach allows for the determination of a series resistance map from voltage dependent EL images. In reverse bias, localised radiative processes can be imaged. These radiative processes are related to defects in the device, such as Al stains, FeSi2 needles and avalanche breakdown. The processes are related to highly localised current flow; this causes localised heating which degrades the device. The voltage dependent Reverse Bias EL (ReBEL) imaging was also used to determine the local breakdown voltage of radiative reverse features. Dark IR thermography is a technique used in the identification of high current sites that leads to localised Joule heating, particularly in reverse bias. In this study, thermography was used to identify breakdown sites and shunts. The results of this study allow for an in-depth analysis of defects found in multi-crystalline Si PV cells using the opto-electronic techniques mentioned above. The multi-pronged approach allowed from a comparison of the various opto-electronic techniques, as well as a more in-depth characterisation of the defects than if only one technique was used.
- Full Text:
- Date Issued: 2018
On the development of ZnO nanorods on silicon substrate for light-emitting diode applications
- Djiokap, Stive Roussel Tankio
- Authors: Djiokap, Stive Roussel Tankio
- Date: 2018
- Subjects: Zinc oxide , Chemical reactions , Compound semiconductors
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/29973 , vital:30802
- Description: The interest in zinc oxide (ZnO), a promising material for blue/ultraviolet light emitting devices, arises from its large exciton binding energy (60 meV). The main challenge associated with this promising compound semiconductor, however, arises from the difficulty to achieve stable and/or reproducible p-type doping. Since silicon (Si) technology still dominates the semiconductor industry, the objective of this thesis is to probe into the possibility of using ZnO nanorods (NRs) on p-type silicon for opto-electronic devices. ZnO NRs have been grown on seeded Si, as well as on nickel oxide (NiO) and aluminum nitride (AlN) coated Si, using a two-step chemical bath deposition (CBD) process. Various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM), have been used to characterize the samples. The electrical characteristics of the heterojunction between the substrate and the ZnO nanostructures were evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. SEM and XRD studies have confirmed that, irrespective of the orientation of the Si substrate (Si (100) and Si (111)), the two-step CBD process yielded NRs that crystallised in the wurtzite structure and exhibited a hexagonal shape. Most of the rods developed perpendicularly to the surface of the substrate, with the orientation and distribution of the rods dictated by the seed layer density. Similarly, irrespective of the substrate, the luminescence of the ZnO nanostructures is dominated by near band edge (NBE) emission in the UV region (~ 3.29 eV) and deep level emission (DLE) in the visible region (2 eV to 2.6 eV). Annealing at moderate temperatures (~ 300 °C) increased the NBE emission and decreased the DLE. The removal of surface adsorbed impurities and enhanced defect passivation by hydrogen are responsible for these changes. The diode characteristics of the ZnO/Si heterojunction was studied by I-V and C-V measurements. Rectification was observed when the Si substrate had a relatively low acceptor density of ~1016 cm-3, while diodes produced on substrate with p ~1018 cm-3 were ohmic. From the C-V analysis the donor density in the ZnO was deduced to be ~1018 cm-3. In the case of rectifying junctions, thermionic emission did not dominate the charge transport. The carrier transport mechanism was therefore probed by the temperature dependent I-V xiii measurements (100 K to 295 K). Defect-assisted multistep tunneling was deduced to dominate in the n-ZnO/p-Si diodes at low forward bias. The band alignment between n-ZnO and p-Si predicts a much smaller barrier for electrons than for holes at the interface, which results in recombination on the Si side of the junction for a forward-biased diode. NiO intermediate layers (formed on Si by the thermal oxidation of Ni) were used to reduce electron injection from ZnO into Si. Scanning probe microscopy (SPM) and XRD analysis showed that while the grain size of the poly-crystalline NiO increased with NiO film thickness, the orientation and distribution of the subsequently grown ZnO nanorods were unaffected by the underlying NiO layer. Also, the photoluminescence response of the ZnO rods remained unchanged. I-V measurements did illustrate rectifying behaviour, with both the forward and reverse currents strongly decreased due to the resistive nature of the NiO. In another attempt at confining electrons to the ZnO side of the junction, AlN-coated Si (111) was used as a substrate for ZnO nanorods. CBD parameters that normally yield nanorods resulted in a plate-like architecture of the ZnO. By modifying the ZnO seed density on the AlN/Si substrate, the rod-like morphology could be recovered. Both the forward and reverse current decreased in these diodes. From studies aimed at identifying the transport mechanism it was concluded that trap-assisted tunnelling, resulting from a high density of defects in the seed layer, dominates in these devices. In conclusion, while no ZnO electroluminescence could be achieved from any of the devices, this study provides insight into the transport mechanisms in n-ZnO/barrier/p-Si heterostructures and highlights the importance of the heterointerface quality for light emitting devices.
- Full Text:
- Date Issued: 2018
- Authors: Djiokap, Stive Roussel Tankio
- Date: 2018
- Subjects: Zinc oxide , Chemical reactions , Compound semiconductors
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/29973 , vital:30802
- Description: The interest in zinc oxide (ZnO), a promising material for blue/ultraviolet light emitting devices, arises from its large exciton binding energy (60 meV). The main challenge associated with this promising compound semiconductor, however, arises from the difficulty to achieve stable and/or reproducible p-type doping. Since silicon (Si) technology still dominates the semiconductor industry, the objective of this thesis is to probe into the possibility of using ZnO nanorods (NRs) on p-type silicon for opto-electronic devices. ZnO NRs have been grown on seeded Si, as well as on nickel oxide (NiO) and aluminum nitride (AlN) coated Si, using a two-step chemical bath deposition (CBD) process. Various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM), have been used to characterize the samples. The electrical characteristics of the heterojunction between the substrate and the ZnO nanostructures were evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. SEM and XRD studies have confirmed that, irrespective of the orientation of the Si substrate (Si (100) and Si (111)), the two-step CBD process yielded NRs that crystallised in the wurtzite structure and exhibited a hexagonal shape. Most of the rods developed perpendicularly to the surface of the substrate, with the orientation and distribution of the rods dictated by the seed layer density. Similarly, irrespective of the substrate, the luminescence of the ZnO nanostructures is dominated by near band edge (NBE) emission in the UV region (~ 3.29 eV) and deep level emission (DLE) in the visible region (2 eV to 2.6 eV). Annealing at moderate temperatures (~ 300 °C) increased the NBE emission and decreased the DLE. The removal of surface adsorbed impurities and enhanced defect passivation by hydrogen are responsible for these changes. The diode characteristics of the ZnO/Si heterojunction was studied by I-V and C-V measurements. Rectification was observed when the Si substrate had a relatively low acceptor density of ~1016 cm-3, while diodes produced on substrate with p ~1018 cm-3 were ohmic. From the C-V analysis the donor density in the ZnO was deduced to be ~1018 cm-3. In the case of rectifying junctions, thermionic emission did not dominate the charge transport. The carrier transport mechanism was therefore probed by the temperature dependent I-V xiii measurements (100 K to 295 K). Defect-assisted multistep tunneling was deduced to dominate in the n-ZnO/p-Si diodes at low forward bias. The band alignment between n-ZnO and p-Si predicts a much smaller barrier for electrons than for holes at the interface, which results in recombination on the Si side of the junction for a forward-biased diode. NiO intermediate layers (formed on Si by the thermal oxidation of Ni) were used to reduce electron injection from ZnO into Si. Scanning probe microscopy (SPM) and XRD analysis showed that while the grain size of the poly-crystalline NiO increased with NiO film thickness, the orientation and distribution of the subsequently grown ZnO nanorods were unaffected by the underlying NiO layer. Also, the photoluminescence response of the ZnO rods remained unchanged. I-V measurements did illustrate rectifying behaviour, with both the forward and reverse currents strongly decreased due to the resistive nature of the NiO. In another attempt at confining electrons to the ZnO side of the junction, AlN-coated Si (111) was used as a substrate for ZnO nanorods. CBD parameters that normally yield nanorods resulted in a plate-like architecture of the ZnO. By modifying the ZnO seed density on the AlN/Si substrate, the rod-like morphology could be recovered. Both the forward and reverse current decreased in these diodes. From studies aimed at identifying the transport mechanism it was concluded that trap-assisted tunnelling, resulting from a high density of defects in the seed layer, dominates in these devices. In conclusion, while no ZnO electroluminescence could be achieved from any of the devices, this study provides insight into the transport mechanisms in n-ZnO/barrier/p-Si heterostructures and highlights the importance of the heterointerface quality for light emitting devices.
- Full Text:
- Date Issued: 2018
On Their Own: women, Urbanization, and the Right to the City in South Africa, by Allison GoebelUbuntu und die Post-Development-Debatte. A review
- Authors: Matthews, Sally
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142169 , vital:38055 , DOI: 10.1080/14616742.2017.1400210
- Description: Allison Goebel's book gives much-needed attention to the experiences of women in South African cities. While there is plenty of literature on the urban experience in South Africa, such literature does not often give much attention to gender. Goebel's book draws on the experiences of poorer women living in informal and township areas in the Msunduzi Municipality in KwaZulu-Natal. Goebel has conducted extensive fieldwork in the area and uses this fieldwork to provide the reader with a sense of South African women's experiences of urban living.
- Full Text:
- Date Issued: 2018
- Authors: Matthews, Sally
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142169 , vital:38055 , DOI: 10.1080/14616742.2017.1400210
- Description: Allison Goebel's book gives much-needed attention to the experiences of women in South African cities. While there is plenty of literature on the urban experience in South Africa, such literature does not often give much attention to gender. Goebel's book draws on the experiences of poorer women living in informal and township areas in the Msunduzi Municipality in KwaZulu-Natal. Goebel has conducted extensive fieldwork in the area and uses this fieldwork to provide the reader with a sense of South African women's experiences of urban living.
- Full Text:
- Date Issued: 2018
One-pot synthesis of graphene quantum dots–phthalocyanines supramolecular hybrid and the investigation of their photophysical properties
- Fomo, Gertrude, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Fomo, Gertrude , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188126 , vital:44725 , xlink:href="https://doi.org/10.1007/s10853-017-1539-y"
- Description: The synthesis of graphene quantum dots (GQDs) using organic compounds as carbon sources via bottom-up approaches has been widely developed, whereas their hybrids with other materials have been previously achieved post-synthetically via multi-step procedures. A novel approach for the preparation of supramolecular hybrid conjugates of GQDs and phthalocyanines (Pcs) via an in situ one-step bottom-up route was employed in this study. The as-synthesized GQDs and their Pc conjugates were characterized using different spectroscopic techniques and their photophysicochemical properties evaluated. Notably, the singlet oxygen quantum yields of the Pcs in the presence of GQDs were found to be 0.51 and 0.74 for 1-GQDs and 2-GQDs, respectively, as compared to the Pcs alone (0.18 and 0.70 for complex 1 and 2, respectively). The increase in triplet quantum yield (ΦT) values is complemented by a decrease in fluorescence quantum yield (ΦF). ΦT value of 0.96 obtained for the complex 2 after conjugation with GQDs is better or higher than the value of 0.74 as reported in the literature when complex 2 was conjugated to semiconductor QDs. Hence, this novel approach resulted in the derivation of hybrid materials with potentials for various photophysicochemical applications such as photodynamic therapy and photocatalysis.
- Full Text:
- Date Issued: 2018
- Authors: Fomo, Gertrude , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188126 , vital:44725 , xlink:href="https://doi.org/10.1007/s10853-017-1539-y"
- Description: The synthesis of graphene quantum dots (GQDs) using organic compounds as carbon sources via bottom-up approaches has been widely developed, whereas their hybrids with other materials have been previously achieved post-synthetically via multi-step procedures. A novel approach for the preparation of supramolecular hybrid conjugates of GQDs and phthalocyanines (Pcs) via an in situ one-step bottom-up route was employed in this study. The as-synthesized GQDs and their Pc conjugates were characterized using different spectroscopic techniques and their photophysicochemical properties evaluated. Notably, the singlet oxygen quantum yields of the Pcs in the presence of GQDs were found to be 0.51 and 0.74 for 1-GQDs and 2-GQDs, respectively, as compared to the Pcs alone (0.18 and 0.70 for complex 1 and 2, respectively). The increase in triplet quantum yield (ΦT) values is complemented by a decrease in fluorescence quantum yield (ΦF). ΦT value of 0.96 obtained for the complex 2 after conjugation with GQDs is better or higher than the value of 0.74 as reported in the literature when complex 2 was conjugated to semiconductor QDs. Hence, this novel approach resulted in the derivation of hybrid materials with potentials for various photophysicochemical applications such as photodynamic therapy and photocatalysis.
- Full Text:
- Date Issued: 2018
Online Appendix: The Best and Worst Times of Life for South Africans: Evidence of universal reference standards in evaluations of personal well-being using Bernheim’s ACSA
- Moller, Valerie, Roberts, Benjamin J
- Authors: Moller, Valerie , Roberts, Benjamin J
- Date: 2018
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10962/67024 , vital:29021
- Description: Online appendix to the authors’ paper published in Social Indicators Research under the title: ‘The Best and Worst Times of Life for South Africans: Evidence of universal reference standards in evaluations of personal well‐being using Bernheim’s ACSA’. From the introduction: The Anamnestic Comparative Self‐Assessment (Bernheim’s ACSA), a measure of personal well‐being, was applied in the 10th annual round of the nationally representative South African Social Attitudes Survey (SASAS), a research infrastructure that has been administered by the Human Sciences Research Council (HSRC) since 2003. The target population for the survey was individuals aged 16 and over who live in South Africa. The multi‐stage sampling frame used by SASAS is based on census enumerator areas and data is weighted to the South African population using Statistics South Africa’s mid‐year population estimates as a benchmark. A total of 2’521 persons were interviewed in October and November 2012 by trained fieldworkers in their homes. Each interview was conducted in the respondent’s home language. ACSA was translated into the eleven official national languages. The SASAS 2012 study of ACSA follows on two earlier South African studies conducted in the Eastern Cape Province: a small pilot study conducted in 2005/6, followed by a larger representative community survey with some 1’000 respondents in 2007. ACSA uses a self‐anchoring scale. SASAS 2012 survey respondents were asked to think, first of their best period in life, and then of their worst period in life. These two periods represent the anchors of an 11‐ point scale running from ‐5 over a mid‐point (0), to +5. Text placed above the negative ‐5 anchor of the scale read: ‘As bad as the WORST period in my life’; text above the positive +5 anchor read: ‘As good as the BEST period in my life’. The respondents were asked to rate their present well‐being relative to these two periods on the scale. Their descriptions of these two extreme periods were recorded verbatim at the time of the interview. Later they were classified by domain in life based on the guidelines for the standard multiple‐choice format provided for recording ACSA anchors. This classification system is recommended by the ACSA scales’ initiator, Jan Bernheim and his colleagues. This online appendix to our Social Indicators Research article (‘The best and worst times of life for South Africans: Evidence of universal reference standards in evaluations of personal well‐being using Bernheim’s ACSA’) reports in greater detail the substantive contents of the survey responses to the ACSA anchoring process. The anchors of the ACSA scale serve as the reference standards for evaluating one’s life. Importantly, our 2012 SASAS survey respondents were invited to make explicit their choice of reference standards when reviewing their lives. This data offers a unique opportunity to gain rich insights into what matters for South Africans when they think about their quality of life and personal well‐being.
- Full Text:
- Date Issued: 2018
- Authors: Moller, Valerie , Roberts, Benjamin J
- Date: 2018
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10962/67024 , vital:29021
- Description: Online appendix to the authors’ paper published in Social Indicators Research under the title: ‘The Best and Worst Times of Life for South Africans: Evidence of universal reference standards in evaluations of personal well‐being using Bernheim’s ACSA’. From the introduction: The Anamnestic Comparative Self‐Assessment (Bernheim’s ACSA), a measure of personal well‐being, was applied in the 10th annual round of the nationally representative South African Social Attitudes Survey (SASAS), a research infrastructure that has been administered by the Human Sciences Research Council (HSRC) since 2003. The target population for the survey was individuals aged 16 and over who live in South Africa. The multi‐stage sampling frame used by SASAS is based on census enumerator areas and data is weighted to the South African population using Statistics South Africa’s mid‐year population estimates as a benchmark. A total of 2’521 persons were interviewed in October and November 2012 by trained fieldworkers in their homes. Each interview was conducted in the respondent’s home language. ACSA was translated into the eleven official national languages. The SASAS 2012 study of ACSA follows on two earlier South African studies conducted in the Eastern Cape Province: a small pilot study conducted in 2005/6, followed by a larger representative community survey with some 1’000 respondents in 2007. ACSA uses a self‐anchoring scale. SASAS 2012 survey respondents were asked to think, first of their best period in life, and then of their worst period in life. These two periods represent the anchors of an 11‐ point scale running from ‐5 over a mid‐point (0), to +5. Text placed above the negative ‐5 anchor of the scale read: ‘As bad as the WORST period in my life’; text above the positive +5 anchor read: ‘As good as the BEST period in my life’. The respondents were asked to rate their present well‐being relative to these two periods on the scale. Their descriptions of these two extreme periods were recorded verbatim at the time of the interview. Later they were classified by domain in life based on the guidelines for the standard multiple‐choice format provided for recording ACSA anchors. This classification system is recommended by the ACSA scales’ initiator, Jan Bernheim and his colleagues. This online appendix to our Social Indicators Research article (‘The best and worst times of life for South Africans: Evidence of universal reference standards in evaluations of personal well‐being using Bernheim’s ACSA’) reports in greater detail the substantive contents of the survey responses to the ACSA anchoring process. The anchors of the ACSA scale serve as the reference standards for evaluating one’s life. Importantly, our 2012 SASAS survey respondents were invited to make explicit their choice of reference standards when reviewing their lives. This data offers a unique opportunity to gain rich insights into what matters for South Africans when they think about their quality of life and personal well‐being.
- Full Text:
- Date Issued: 2018
Optical limiting properties of 3, 5-dipyrenylvinyleneBODIPY dyes at 532 nm
- Kubheka, Gugu, Sanusi, Kayode, Mack, John, Nyokong, Tebello
- Authors: Kubheka, Gugu , Sanusi, Kayode , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237938 , vital:50567 , xlink:href="https://doi.org/10.1016/j.saa.2017.10.021"
- Description: The optical limiting (OL) properties of 3,5-dipyrenylvinyleneBODIPY dyes that contain both electron withdrawing and donating moieties have been investigated by using the z-scan technique at 532 nm in the nanosecond pulse range. The extension of the π-conjugation at the 3,5-positions with pyrenylvinylene groups results in a ca. 200 nm red shift of the main BODIPY spectral band to ca. 700 nm, so there is relatively weak absorbance at 532 nm under ambient light conditions. Reverse saturable absorbance (RSA) profiles are observed in response to incident pulsed laser light that is consistent with a two photon absorption-assisted excited state absorption (ESA) mechanism in CH2Cl2 solution and when the dyes are embedded in poly(bisphenol carbonate A) (PBC) polymer thin films. This demonstrates that 3,5-divinyleneBODIPY dyes are potentially suitable for use in OL applications, since limiting threshold fluence (Ilim) values of below 0.95 J cm−2 are observed when thin films are prepared.
- Full Text:
- Date Issued: 2018
- Authors: Kubheka, Gugu , Sanusi, Kayode , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237938 , vital:50567 , xlink:href="https://doi.org/10.1016/j.saa.2017.10.021"
- Description: The optical limiting (OL) properties of 3,5-dipyrenylvinyleneBODIPY dyes that contain both electron withdrawing and donating moieties have been investigated by using the z-scan technique at 532 nm in the nanosecond pulse range. The extension of the π-conjugation at the 3,5-positions with pyrenylvinylene groups results in a ca. 200 nm red shift of the main BODIPY spectral band to ca. 700 nm, so there is relatively weak absorbance at 532 nm under ambient light conditions. Reverse saturable absorbance (RSA) profiles are observed in response to incident pulsed laser light that is consistent with a two photon absorption-assisted excited state absorption (ESA) mechanism in CH2Cl2 solution and when the dyes are embedded in poly(bisphenol carbonate A) (PBC) polymer thin films. This demonstrates that 3,5-divinyleneBODIPY dyes are potentially suitable for use in OL applications, since limiting threshold fluence (Ilim) values of below 0.95 J cm−2 are observed when thin films are prepared.
- Full Text:
- Date Issued: 2018