BODIPY and porphyrin dyes for direct glucose sensing and optical limiting applications
- Authors: Ndebele, Nobuhle
- Date: 2019
- Subjects: Boron compounds , Boric acid , Porphyrins , Dyes and dying -- Chemistry
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97221 , vital:31412
- Description: A series of BODIPY dyes functionalised with boronic acid in the 3,5-positions were successfully synthesised and characterised by using various analytical techniques. The dyes were prepared through a slight modification of the conventional acid catalysed condensation method. Phenylboronic acid moieties were added as styryl groups at the 3,5-positions of the 1,3,5,7-tetrametylBODIPY cores using a modified Knoevengal condensation method. The addition of the styryls resulted in the main absorption band of the dyes red-shifting to the 630−650 nm region. The photophysical and electrochemical properties of these dyes were studied to determine whether the dyes are suitable for use in the fluorescent, colourimetric and electrochemical detection of glucose. Boronic acid moieties were added as bioreceptor recognition elements because they have an affinity for carbohydrates and therefore would be able to bind and “detect” glucose. The series of BODIPY dyes did not show a “turn-on” fluorescence effect upon addition with glucose at the physiological pH. This was attributed on the basis of molecular modelling to the absence of an MO localised on the boronic-acid-substituted styryl moieties that lie close in energy to the HOMO and LUMO that facilitates the formation of an intramolecular charge transfer state. However, colourimetric changes that are visible to the naked eye are observed at basic pH when glucose was added to the dye solutions. The dyes exhibited favourable electrochemical behaviour and were able to detect glucose directly in this context when glassy carbon electrodes are modified through the drop dry method. A series of Sn(IV) porphyrins with thienyl and phenyl groups at the meso-positions were successfully synthesised and characterised. Pyridine and tetrabutyl axial ligands were added to the porphyrins to limit aggregation. The optical limiting properties of these porphyrins and three styrylated BODIPY dyes were studied in benzene and dichloromethane. Dyes were also embedded in polystyrene and studied as thin films to further gauge their suitability for use in optical limiting applications. Second-order hyperpolarizability, third-order susceptibly, non-linear absorption with reversible saturable absorption and the optical limiting threshold, were the parameters studied. Three of the four porphyrins and the three styrylated BODIPY dyes showed favourable optical limiting behaviour, which was further enhanced when the dyes are embedded in polymer thin films.
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Bolvedere: a scalable network flow threat analysis system
- Authors: Herbert, Alan
- Date: 2019
- Subjects: Bolvedere (Computer network analysis system) , Computer networks -- Scalability , Computer networks -- Measurement , Computer networks -- Security measures , Telecommunication -- Traffic -- Measurement
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/71557 , vital:29873
- Description: Since the advent of the Internet, and its public availability in the late 90’s, there have been significant advancements to network technologies and thus a significant increase of the bandwidth available to network users, both human and automated. Although this growth is of great value to network users, it has led to an increase in malicious network-based activities and it is theorized that, as more services become available on the Internet, the volume of such activities will continue to grow. Because of this, there is a need to monitor, comprehend, discern, understand and (where needed) respond to events on networks worldwide. Although this line of thought is simple in its reasoning, undertaking such a task is no small feat. Full packet analysis is a method of network surveillance that seeks out specific characteristics within network traffic that may tell of malicious activity or anomalies in regular network usage. It is carried out within firewalls and implemented through packet classification. In the context of the networks that make up the Internet, this form of packet analysis has become infeasible, as the volume of traffic introduced onto these networks every day is so large that there are simply not enough processing resources to perform such a task on every packet in real time. One could combat this problem by performing post-incident forensics; archiving packets and processing them later. However, as one cannot process all incoming packets, the archive will eventually run out of space. Full packet analysis is also hindered by the fact that some existing, commonly-used solutions are designed around a single host and single thread of execution, an outdated approach that is far slower than necessary on current computing technology. This research explores the conceptual design and implementation of a scalable network traffic analysis system named Bolvedere. Analysis performed by Bolvedere simply asks whether the existence of a connection, coupled with its associated metadata, is enough to conclude something meaningful about that connection. This idea draws away from the traditional processing of every single byte in every single packet monitored on a network link (Deep Packet Inspection) through the concept of working with connection flows. Bolvedere performs its work by leveraging the NetFlow version 9 and IPFIX protocols, but is not limited to these. It is implemented using a modular approach that allows for either complete execution of the system on a single host or the horizontal scaling out of subsystems on multiple hosts. The use of multiple hosts is achieved through the implementation of Zero Message Queue (ZMQ). This allows for Bolvedre to horizontally scale out, which results in an increase in processing resources and thus an increase in analysis throughput. This is due to ease of interprocess communications provided by ZMQ. Many underlying mechanisms in Bolvedere have been automated. This is intended to make the system more userfriendly, as the user need only tell Bolvedere what information they wish to analyse, and the system will then rebuild itself in order to achieve this required task. Bolvedere has also been hardware-accelerated through the use of Field-Programmable Gate Array (FPGA) technologies, which more than doubled the total throughput of the system.
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Book Review: From the Outside In
- Authors: Magadla, Siphokazi
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/298628 , vital:57722 , xlink:href="https://doi.org/10.1080/10220461.2019.1610042"
- Description: From the Outside In: Domestic Actors and South Africa’s Foreign Policy presents an exciting collection of chapters that explore various and often-ignored domestic actors and their relationships within the state, including government departments and local government; and non-governmental organisations such as labour unions, big business and social movements. The editors evoke the imagery of the ‘chess game of foreign policy’, used by scholars such as Joseph Nye,1 to argue that power in international relations is distributed like a ‘three-dimensional chessboard’ consisting of military power, economic power and transnational relations.
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Book Review: Herman Wasserman, Media, Geopolitics and Power
- Authors: Garman, Anthea
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158449 , vital:40187 , https://0-doi.org.wam.seals.ac.za/10.1177/0021909619851645
- Description: The strength of this book is not only that Herman Wasserman gives us a comprehensive overview of the major changes in South Africa’s journalism industries since the transition to democracy, but that he does it through the theoretical lens of Global South thinking. In order to cover the terrain thoroughly Wasserman draws on years of careful observation of – and his previous writings on – the shifts in the institutions and practices of journalism.
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Boundary-crossing learning in agricultural learning systems: formative interventions for water and seed provision in southern Africa
- Authors: Pesanayi, Victor Tichaona
- Date: 2019
- Subjects: Agriultural extension work -- Africa, Southern , Agriultural colleges -- Africa, Southern , Farmers -- Education -- Africa, Southern , Agriculture and state -- Africa, Southern , Sustainable agriculture -- Africa, Southern
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/94067 , vital:30997
- Description: This research was conducted in the Amathole rural district of the Eastern Cape Province of South Africa, and in Zvishavane and Zhombe rural districts of the Midlands Province of Zimbabwe over a period of four years. In the first two years of this period I was involved in co-engaged boundary-crossing expansive learning processes with research participants from agricultural education (agricultural college lecturers, principals and university lecturers), extension services (extension officers, advisors and workers), small-scale farmers and a local economic development (LED) agency as agricultural learning activity systems. The latter was applicable only to the South African nested case while the rest applied to both country nested cases. The study focusses on the boundary-crossing learning of sustainable agricultural water relevant for small-scale farming contexts under rain-fed and climate constrained conditions with specific attention to rainwater harvesting and conservation and climate-adaptive seed. The study employed cultural-historical activity theory (CHAT) and developmental work research methodology developed by Yrjö Engeström and his colleagues at the Centre for Researching Activity Development and Learning (CRADLE) at the University of Helsinki in Finland. The study was guided by three objectives. The first objective was to find out how the different groups represented across the activity systems listed above learn together to mediate and communicate sustainable agricultural water and seed saving. To address this objective I conducted focus groups and interviews with key informants, made observations and analysed documents. The second objective was to explore and document the socio-ecological histories of rainwater harvesting and conservation, locally-adaptive seed systems and associated value chains, and socio-cultural histories of agricultural learning systems in the context of small-scale farming using historical and ethnographic research techniques. The third objective was to understand how learning, curriculum innovation and mediation tools for agricultural extension education and farmer training that can expand learning of rainwater harvesting and conservation sustainable practices for improved local agricultural water and climate-adaptive non-formal seed systems in agricultural education and small-scale farmer activity systems could be co-generated. This third objective constituted the boundary-crossing expansive learning that emerged from change laboratory workshops carefully designed to explore the common water for food object across the different but related activity systems. The study reveals historically-persisting tensions and contradictions in the work of agricultural college lecturers, small-scale farmers and extension workers that limit their ability to work together relationally leaving them operating in isolated ‘silos’. The industrially-driven agricultural college curriculum promoting conventional irrigated agriculture conflicted with the college’s objective of producing extension workers who will work with resource-poor small-scale farmers in rain-fed farming systems. This conflict was aggravated by the work of extension workers who had little to no knowledge regarding how to support small-scale farmers facing persistent drought and consequent crop failure due to poor and erratic rainfall. At the same time extension services promoting genetically modified (GMO) seed in South Africa were in conflict with some small-scale farmers’ demands for seed that was adapted to their changing climate and their ability to operate independently with access to and ownership of land. This study shows that the work of agricultural colleges and extension services often defeats its intended structural objectives due to historically-constituted power relations around knowledge. This study has demonstrated the effectiveness of co-generative formative interventions in boundary-crossing scenarios in learning network contexts for expansion of activity in farming communities, agricultural colleges and extension services, with emphasis of transformed activity towards engaging a collective object of rainwater harvesting and conservation for more sustainable agriculture and poverty alleviation. The study shows that diverse combinations of change practice courses, change laboratories, demonstration sites and media engagements as mediation processes in the context of learning networks strengthened the possibility for boundary-crossing expansive learning across activity systems of agricultural college lecturers, smallholder farmers, extension workers and local economic development agency facilitators. Three of the five mediation processes emerged out of the formative intervention processes in both the South African and Zimbabwean case studies while two were not realised in the Zimbabwean case study, namely the change practice course and media engagements, due to different formative intervention conditions, inadequate time and resources. Boundary-crossing was enabled by a variety of actions including understanding and identifying with the context of the other (i.e. developing empathy) as a result of change laboratory workshops that also ensured confrontation with relational contradictions. The study concludes that it is possible for historically-constituted contradictions around water for food to be resolved when participants from different agricultural learning systems co-engage as equals in boundary-crossing change laboratory fora mediated by appropriate tools and processes. The study contributes to innovation in agricultural learning systems in southern Africa, in particular to means of engaging across boundaries of previously largely disconnected activity systems in ways that benefit smallholder farmers who have previously been marginalised from mainstream agricultural learning systems.
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Bushmeat use is widespread but under-researched in rural communities of South Africa
- Authors: Martins, Vusumzi , Shackleton, Charlie M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179745 , vital:43167 , xlink:href="https://doi.org/10.1016/j.gecco.2019.e00583"
- Description: Bushmeat hunting and consumption is common throughout sub-Saharan Africa. Yet, a recent review indicated that the prevalence and nature of bushmeat hunting was little researched or understood in southern African savannas. Here we present information from a number of rural livelihoods studies in South Africa that indicate that bushmeat consumption is common, with typically between 30 and 60% of rural households in the communal tenure regions stating that they consume it. Yet there are only five studies in the country explicitly investigating bushmeat hunting practices, motivations, offtake and target species. A review of the five studies indicates that bushmeat hunting is largely a male activity and that motivations and practices vary between sites. Hunting with dogs is the most common method, targeting multiple small and medium-sized species. With such widespread consumption, it is possible that bushmeat hunting may have significant effects on the population status of some target species and consequently requires urgent and in-depth research of both practices and effects
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Busy as a Bee: Breeding Industrious Bees in Malawi
- Authors: Kasumba, Arnold M , Pullanikkatil, Deepa
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/433537 , vital:72982 , ISBN 978-3-319-75580-9 , https://link.springer.com/chapter/10.1007/978-3-319-75580-9_14
- Description: A trial and error venture at beekeeping by Arnold Kasumbu in central Malawi, is now a successful integrated farming enterprise incorporating 160 beehives and producing honey for customers in Malawi and Kenya. It is also a site for educational visits for university students learning about agriculture. Arnold’s parents were tobacco farmers living in the Mitundu area of Lilongwe District in central Malawi. He recalls that his childhood was steeped in poverty as he observed his father put in a lot of effort in his farm with diminutive returns. Being the eldest of three children in the household, Arnold was forced to end his schooling in Standard 8, as his family could not afford the school fees. Resolving that he would not do tobacco farming, he began exploring other means of income generation that would entail fewer struggles. He wanted to become wealthy and take care of his family. Through his integrated farm and beekeeping, he has done exactly that! This is Arnold’s life story.
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Careerism and capitalism as women’s emancipation: a critical analysis of Rand Merchant Bank’s ‘Athena Programme', South Africa
- Authors: Mosesi, Poloko Prudence
- Date: 2019
- Subjects: Rand Merchant Bank (South Africa) , Women in economic development -- South Africa , Women in finance -- South Africa , Neoliberalism -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSocSc
- Identifier: http://hdl.handle.net/10962/140344 , vital:37881
- Description: Against the backdrop of debates on feminism and neo– liberalism, this thesis presents a critical analysis of Rand Merchant Bank’s (RMB) Athena programme in South Africa – an award– winning programme run by women, which aims to develop women as senior managers – and of the type of feminism it represents, using a Marxist feminist theoretical framework. Rand Merchant Bank’s is one of the largest investment banks in Africa, part of the giant First Rand Group (FRG) alongside First National Bank (FNB) group. The thesis, based on a detailed case study using qualitative methods, argues that Athena is a very much product of its time: it advances the argument that if more women were in position of power, women in general would be free, and it views the problem of women’s oppression with an individualist lens, which focuses on attitudes and confidence. Athena, like many initiatives of the neo– liberal era, such as Sandberg’s Lean– In philosophy and the Nike Foundation’s ‘Girl Effect’ promote individual understanding and emancipation of women, which sees emancipation in terms of creating a neo– liberal subject that operates more effectively within a capitalist framework, sees capitalism as the solution – rather than the cause – of women’s unequal circumstance and ignores structural issues like class. In effect, Athena argues that the free market and big corporations are neutral tools that can answer the question of women equality, if only women had the correct attitudes, and so long as corporate hierarchies and profits are accepted as fair, and women are seen as an untapped resource that can be used in a ‘smart economics.’ What all these initiatives have in common is shifting the burden and responsibility to women without proper interrogation of the systems that perpetuate inequalities, and a trickle– down theory, according to which more women capitalists and more women in the ruling class will empower the women in the working class.
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Categorising Network Telescope data using big data enrichment techniques
- Authors: Davis, Michael Reginald
- Date: 2019
- Subjects: Denial of service attacks , Big data , Computer networks -- Security measures
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/92941 , vital:30766
- Description: Network Telescopes, Internet backbone sampling, IDS and other forms of network-sourced Threat Intelligence provide researchers with insight into the methods and intent of remote entities by capturing network traffic and analysing the resulting data. This analysis and determination of intent is made difficult by the large amounts of potentially malicious traffic, coupled with limited amount of knowledge that can be attributed to the source of the incoming data, as the source is known only by its IP address. Due to the lack of commonly available tooling, many researchers start this analysis from the beginning and so repeat and re-iterate previous research as the bulk of their work. As a result new insight into methods and approaches of analysis is gained at a high cost. Our research approaches this problem by using additional knowledge about the source IP address such as open ports, reverse and forward DNS, BGP routing tables and more, to enhance the researcher's ability to understand the traffic source. The research is a BigData experiment, where large (hundreds of GB) datasets are merged with a two month section of Network Telescope data using a set of Python scripts. The result are written to a Google BigQuery database table. Analysis of the network data is greatly simplified, with questions about the nature of the source, such as its device class (home routing device or server), potential vulnerabilities (open telnet ports or databases) and location becoming relatively easy to answer. Using this approach, researchers can focus on the questions that need answering and efficiently address them. This research could be taken further by using additional data sources such as Geo-location, WHOIS lookups, Threat Intelligence feeds and many others. Other potential areas of research include real-time categorisation of incoming packets, in order to better inform alerting and reporting systems' configuration. In conclusion, categorising Network Telescope data in this way provides insight into the intent of the (apparent) originator and as such is a valuable tool for those seeking to understand the purpose and intent of arriving packets. In particular, the ability to remove packets categorised as non-malicious (e.g. those in the Research category) from the data eliminates a known source of `noise' from the data. This allows the researcher to focus their efforts in a more productive manner.
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Centralising a counter public: an ethnographic study of the interpretation of mainstream news media by young adults in Joza
- Authors: Ponono, Mvuzo
- Date: 2019
- Subjects: African National Congress Mass media -- Political aspects -- South Africa Press and politics -- South Africa , South Africa -- Politics and government -- 21st century Zuma, Jacob -- Political and social views , Political corruption -- 21st century Elections -- South Africa Voting -- South Africa Misconduct in office -- South Africa Abuse of administrative power -- South Africa Young adults -- Political activity -- South Africa -- Grahamstown Young adults -- Politics and government
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/65033 , vital:28655
- Description: The 2014 national general elections were characterised by a cloud of scandal hanging over the ANC, and the ANC president Jacob Zuma. The biggest and darkest cloud was the Nkandla scandal. Owing to a reported R246 million spent by the state to refurbish his private home, the president stood accused of wasteful expenditure and financial irregularity. In a country reeling from the continued effects of apartheid, which include high unemployment and poverty, the scandal was a bombshell. According to a vocal and often adversarial mainstream media sphere, the ANC went into those elections with an albatross around its neck. The dominant thought was that the ruling party would suffer a heavy loss of votes. This outcome did not materialise. The ANC lost a marginal share of its previous vote. Mainstream media and civil society were confounded. What had happened? Why had poor black South Africans continued to vote for a party that was obviously in breach of the constitutional order? Against the mismatch between what was predicted or purported and the outcome, this study investigates how young people in the township of Joza, Grahamstown, interpreted one of the biggest political scandals in South Africa’s fledgling democracy. Using a combination of subaltern studies, counter public sphere and audience study, the research looks into the interpretation of a mainstream media scandal that was supposed to diminish the chances of the ANC retaining power, but, instead, barely dented its majority. Through a combination of interviews and participant observation, the study found that young people in the township of Joza demonstrated that they chose to ignore the messages about the corruption of the ANC. The data suggests that they did so, not because of overt racial solidarity, but due to the fact that in a context of high inequality, and continued limitations on economic emancipation, the party shone brightly as a vehicle for economic development. Overall, the study argues that the seemingly dubious undertaking to continue with the ANC is a calculated decision that makes sense when viewed within a given socio-economic context.
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Changes and continuities over time in the cultural significance of the Nyaminyami water spirit among the BaTonga people of northwestern Zimbabwe
- Authors: Matanzima, Joshua
- Date: 2019
- Subjects: Water spirits -- Zimbabwe , Tsonga (African people) -- Zimbabwe , Tsonga (African people) -- Zimbabwe -- Religion , Tsonga (African people) -- Zimbabwe -- Rites and ceremonies , Tsonga (African people) -- Zimbabwe -- Social life and customs , Mythology, Tsonga , Mythology, Zimbabwean , Nyaminyami (Spirit)
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/94189 , vital:31015
- Description: Research attests that beliefs in water spirits are an integral part of cultures of many indigenous communities across the globe. These water spirits play significant political, religious and socio-economic roles for the people concerned. However, the functions of water spirits are not constant, but change over time, especially when the people believing in water spirits undergo drastic socio- economic processes of change. It is in this context that this thesis traces the cultural significance over time, of the Nyaminyami water spirit, among some BaTonga people, living in the immediate vicinity of the Kariba gorge area, in north-western Zimbabwe. While previous studies document the existence of beliefs in Nyaminyami, none of these has systematically traced the historical significance of Nyaminyami, in terms of changes and continuities over time. Thus, this thesis makes a valuable contribution to knowledge with regards to the history and religion of the BaTonga people. The thesis argues that Nyaminyami‘s cultural significance or functions evolved over time, due to numerous socio- economic and political processes of change. The major changes that significantly influenced the practices relating to Nyaminyami include colonialism, Kariba dam construction and resettlement, the migration after resettlement in the 1960s and 1970s, the independence of Zimbabwe, and the alienation of the Kariba waterscape from the BaTonga. To be able to arrive at specific findings and conclusions, the thesis is underpinned by theories about resettlement, approaches to water divinities, and theories of religion and social change. The thesis has five ethnographic chapters that focus on specific time periods, illustrating the major socio- economic changes of each epoch, and showing how these changes impacted upon practices and beliefs relating to Nyaminyami. The thesis also documents how Nyaminyami beliefs are variedly distributed along different social variables that include gender, age, income and geographical location. In order to achieve the findings presented, the thesis utilized ethnographic evidence obtained from semi- structured interviews, participant observation, anthropology of extraordinary experience, document review and archival research.
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Changes in household use and sale of locally collected environmental resources over a 15-year period in a rural village, South Africa
- Authors: Falayi, Menelisi , Shackleton, Sheona E , Kemp, Georgina Cundill , Shackleton, Charlie M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398196 , vital:69383 , xlink:href="https://doi.org/10.1080/14728028.2019.1568309"
- Description: Many rural areas are experiencing rapid social-ecological changes, impacting livelihoods and creating less certain futures. Despite several decades of research on the use of locally collected environmental resources there have been few repeat studies, especially in South and Southern Africa, to consider how households may be altering such use alongside other changes. This paper explores changes in the use of environmental resources by communities in the Kat River Valley, South Africa over a fifteen-year period, between 2000 and 2015, using a repeat survey, key informant interviews and other data from a larger study relating to social-ecological change. The proportion of households collecting different environmental resources was similar between the two periods. However, the mean quantities used per household had declined for several resources . Consequently, the monetary contribution or worth of these to livelihoods also declined, except for fuelwood and river sand. These changes can be related to, amongst others, transformations in both the local landscape and socio-economic environment, such as increases in state social welfare, a decline in agricultural production, woody plant encroachment, generational preferences, and the expansion of supermarket retailers. Understanding such trends is important for considering the sustainable management of landscapes and livelihoods into the future.
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Characterization and computational studies of 2-(benzamido) thiazol-5-yl benzoate
- Authors: Odame, Felix , Hosten, Eric C , Betz, Richard , Lobb, Kevin A , Tshentu, Zenixole R
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447003 , vital:74576 , xlink:href="https://doi.org/10.1134/S0022476619010190"
- Description: Thiazoles have shown a broad range of biological activities and are found in many potent biologically active molecules such as Sulfathiazol (antimicrobial drug), Ritonavir (antiretroviral drug), Abafungin (antifungal drug), and Tiazofurin (antineoplastic drug) [1]. They have exhibited some degree of plant growth regulatory and antifungal activities [2], whilst some thiazoles have shown anti-infective [3] as well as antibacterial activities [4]. The regio-controlled synthesis of 2,5-disubstituted and 2,4,5-trisubstituted thiazoles from ethyl-2-bromo-5-chloro-4-thiazolecarboxylates using sequential palladium-catalyzed coupling reactions has been reported [5]. An efficient general method for the preparation of 2,4-di- and trisubsituted thiazoles is via P–TsOH. H2O-Catalyzed cyclization of trisubstituted propargylic alcohols with thioamides has been accomplished with moderate to excellent product yields under mild and standard conditions [6]. In the presence of triethylamine, (Z)-(2-acetoxyl-1-alkenyl) phenyl-λ3 iodanes reacts with thioureas or thioamides in methanol to afford 2,4- disubstituted thiazoles in good yields. The reaction is thought to proceed by the generation of highly reactive α-λ3 iodanyl ketones through ester exchange of the β-acetoxy group with liberation of methyl acetate, followed by nucleophilic substitutions with thioureas or thioamides [7].
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Characterization of electrodes modified with nanocomposites of cobalt tetraaminophenoxyphthalocyanine, reduced graphene and multi-walled carbon nanotubes
- Authors: Shumba, Munyaradz , Nyoni, Stephen , Britton, Jonathan , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187003 , vital:44555 , xlink:href="https://doi.org/10.1080/00958972.2019.1621299"
- Description: Glassy carbon electrodes or plates were modified with nanocomposites consisting of cobalt tetraaminophenoxyphthalocyanine (CoTAPhPc), reduced graphene oxide nanosheets (rGONs) and multi-walled carbon nanotubes (MWCNTs). The modified electrodes were characterized using cyclic voltammetry, scanning electrochemical microscopy (SECM) and time-of-flight-secondary ion mass spectrometer (TOF-SIMS). The electrocatalytic activity of the modified electrode was tested for detection of L-cysteine. The presence of CoTAPhPc on sequential layers of MWCNT and rGONs resulted in improved detection currents compared to CoTAPhPc alone or when MWCNT/rGONs are mixed in CoTAPhPc–MWCNT/ rGONs (mix)–glassy carbon electrode (GCE). CoTAPhPc–MWCNT–GCE (without rGONS) showed higher sensitivity toward L-cysteine as compared to the probes incorporating rGONs with a catalytic rate constant of 4.62x104 M-1 s-1 and a detection limit of 30 nM. The presence of rGONs improved the stability of the electrode.
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Characterization of termite Trinervitermes trinervoides metagenome-derived glycoside hydrolases, the formulation of synergistic core enzyme sets for effective sweet sorghum and corncob saccharification, and their potential industrial applications
- Authors: Mafa, Mpho Stephen
- Date: 2019
- Subjects: Termites , Metagenomics , Glucosides , Hydrolases , Enzymes , Feedstock
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/72414 , vital:30044 , DOI https://doi.org/10.21504/10962/72414
- Description: The current study investigated the biochemical properties of endo-glucanase (GH5E), exo-glucanase (GH5D), xylanase (GH5H) and endo-glucanase/xylanase (GH45), derived from the hindgut bacterial symbionts of a termite (Trinervitermes trinervoides) for their potential role in the biotechnology industry. All these enzymes, except GH5D, exhibited activities on cellulosic and xylan-rich polymeric substrates, which only displayed activity on p-nitrophenyl cellobioside. GH5D, GH5E, GH5H and GH45 enzymes retained more than 80% of their activities at pH 5.5 and also retained more than 80% of their activities at 40ºC. Furthermore, these enzymes were thermostable at 37ºC for 72 hours. GH5E, GH5H and GH45 were generally stable over a range of metal-ion. The kinetic parameters for GH5E were 5.68 mg/ml (KM) and 34.36 U/mg protein (Vmax). GH5D activity did not follow classical Michaelis-Menten kinetics, suggesting product inhibition. GH5H displayed KM values of 5.53, 95.03 and 2.10 mg/ml and Vmax values of 112.36, 144.45 and 180.32 U/mg protein on beechwood xylan, CMC, and xyloglucan, respectively. GH45 displayed a KM of 6.94 mg/ml and a Vmax of 12.30 U/mg protein on CMC. GH5D [cellobiohydrolase (CBH)] and a commercial CBHII (GH6) enzyme outperformed a commercial CBHI (GH7) enzyme when these enzymes hydrolysed β-glucan. GH5D and CBHII also displayed a higher degree of synergy on β-glucan but failed to show synergy on Avicel. We therefore concluded that GH5D and CBHII are β-glucan-specific cellobiohydrolases. The corncob (CC) and sweet sorghum bagasse (SSB) substrates were pretreated with lime, NaOH and NaClO2. Subsequent to pretreatment, these substrates were used to investigate if GH5D, GH5E, GH5H and GH45 could operate in synergy. Results revealed that out of 12 possible core enzyme sets constructed, only two (referred to as CES-E and CES-H) displayed higher activities on pretreated CC or SSB. Simultaneous synergy was generally the most effective mode of synergy during hydrolysis of alkaline pretreated SSB and CC samples by both CES-E and CES-H. Both core enzyme sets did not display synergy on oxidative pretreated substrates. These findings suggest that lime and NaOH are more effective pretreatments for CC and SSB substrates. We used PRotein Interactive MOdeling (PRIMO) software to demonstrate that GH5D protein structure is an (α/β)8 barrel with a tunnel-like active site. Enzymes with this type of protein structure are able to perform transglycosylation, a process in which GH5D produced methyl, ethyl and propyl cellobiosides. We concluded that the GH5D, GH5E, GH5H and GH45 enzymes possess novel biochemical properties and that they form synergy during the hydrolysis of complex substrates (SSB and CC). GH5D transglycosylation could be used to produce novel biodegradable chemicals with special properties (e.g. anti-microbial properties). In conclusion, our findings suggest that GH5D, GH5E, GH5H and GH45 can potentially be used to improve biorefinery processes. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
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Charting freedom: inequality beliefs, preferences for redistribution, and distributive social policy in contemporary South Africa
- Authors: Roberts, Benjamin J
- Date: 2019
- Subjects: South Africa -- Economic conditions South Africa -- Economic policy South Africa -- Social policy , Democracy -- Economic conditions -- South Africa Race discrimination -- South Africa Poverty -- South Africa Equality -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64999 , vital:28644
- Description: While the transition to democracy in South Africa extended civil and political rights and freedoms to all South Africans, there has been disagreement over the preferred nature and scope of social rights within post-apartheid society, reflecting debates over the trajectory of economic policy. Appreciable developmental gains have been made by the state over the last quarter-century, yet the challenges of poverty, unemployment and inequality persist, coupled with mounting popular discontent with the pace of transformation and political accountability. This has led to fundamental questions about social justice, restitution, and the kind of society we wish to promote. Appeals for a more inclusive, transformative social policy have also emerged, arguing that a wider vision of society is required involving multiple government responsibilities and informed by an ethic of equality and social solidarity. Against this background, in this thesis I study the views of the South African public towards economic inequality, general preferences for government-led redistribution, as well as support for social policies intended to promote racial and economic transformation. The research has been guided by several overarching questions: To what extent do South Africans share common general beliefs about material inequality? Does the public exhibit a preference for government redistribution in principle? And how unified or polarised are South Africans in their support for specific redress policies in the country? Responding to these questions has been achieved by drawing on unique, nationally representative data from the South African Social Attitudes Survey (SASAS), which has enabled me to chart social attitudes over a period of almost fifteen years between late 2003 and early 2017. Use has also been made of social citizenship as a guiding conceptual framework to understanding social policy predispositions and analysing attitudinal change. The results demonstrate that the public is united in its awareness of and deep concern about economic inequality. Since the early 2000s, a significant majority has consistently expressed the view that the income gap in the country is too large, articulated a strong preference for a more equitable social structure, and acknowledged the class and social tensions that economic inequality has produced. There is also a preference for a narrowing of earnings disparities, a more generous minimum wage, and regulatory limits on executive pay. While this suggests a desire for fair and legitimate remuneration, the analysis also reveals that South Africans are willing to tolerate fairly high levels of inequality. Nonetheless, these beliefs are generally interpreted as a desire for a more equitable and fair society. This preference for change is reflected in a fairly strong belief that government should assume responsibility for reducing material disparities. One’s social position, mobility history, awareness of inequality, political leaning and racial attitudes all have a bearing on how weak and strong this predisposition is, but the normative demand for political redistribution remains fairly widely shared irrespective of these individual traits. Greater polarisation is however evident with respect to redistributive social policy, especially measures designed to overcome historical racial injustice (affirmative action, sports quotas, and land reform). These intergroup differences converge considerably when referring to class-based policy measures. One surprising finding is the evidence that South Africa’s youngest generation, the so-called ‘Born Frees’, tend to adopt a similar predisposition to redress policy as older generations, thus confounding expectations of a post-apartheid value change. I conclude by arguing that there seems to be a firmer basis for a social compact about preferences for interventions designed to produce a more just society than is typically assumed. Intractably high levels of economic inequality during the country’s first quarter-century of democracy is resulting in a growing recognition of the need for a stronger policy emphasis on economic inequality in South Africa over coming decades if the vision enshrined in the Freedom Charter and the Constitution is to be realised. South Africans may not be able to fully agree about the specific elements that constitute a socially just response to economic inequality. Yet, the common identification of and concern with redressable injustice, coupled with a broad-based commitment to government redistribution and classbased social policies, could serve as a foundation on which to rekindle the solidaristic spirit of 1994 and forge progress towards a more equitable society.
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Checklist, endemism, English vernacular names and identification of the cicadas (Insecta, Hemiptera, Cicadidae) of KwaZulu-Natal, South Africa:
- Authors: Armstrong, Adrian J , Villet, Martin H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140586 , vital:37901 , DOI: 10.3897/afrinvertebr.60.35130
- Description: Public understanding of the goals of applied biology and conservation is promoted by showcasing charismatic or significant organisms using vernacular names. Conservation activities in the province of KwaZulu-Natal, South Africa, are prioritising taxa that have high rates of provincial endemism, such as snails, earthworms, millipedes and cicadas. To assist wider public engagement in these activities, an assessment of endemism of the cicadas of KwaZulu-Natal is presented along with a dichotomous, 37-couplet key for the identification of males, based mainly on externally visible morphology and colouration. Standardised English vernacular names coined following a simple naming convention are proposed. Forty-two percent (16 out of 38) of the cicada species known from KwaZulu-Natal are endemic to the province. Photographs of some of the species are included to facilitate their identification. Photographs can be used for identification of various species providing that the diagnostic characters are visible in the photographs. For this purpose, photographs may have to be taken of hand-held individuals. Some of the endemic species are of particular concern for conservation because they are not known to occur in statutory protected areas or are only known from relatively small protected areas. The latter may not be able to ensure the long-term survival of the species. The rate and extent of loss of habitat outside protected areas is likely to be a grave threat to species that are not protected or that are inadequately conserved in statutory protected areas. The standardised vernacular names proposed here provide a tool for communicating provincial conservation plans and concerns with stakeholders in KwaZulu-Natal and for stimulating interest in cicadas amongst land users, environmental impact assessment practitioners, biologists, naturalists and citizen scientists.
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Chinese engagement of Zimbabwe and the limits of elite agency:
- Authors: Chipaike, Ronald , Bischoff, Paul, 1954-
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/161548 , vital:40637 , https://0-doi.org.wam.seals.ac.za/10.1177/0021909619848783
- Description: This article contends that Zimbabwe’s agency in its engagement with China has been limited and at best circumscribed. This owes to factors such as indifference by state authorities to cooperation with civil society actors in negotiating with Chinese actors, the desperation of the The Zimbabwe African National Union – Patriotic Front regime in the face of isolation by erstwhile partners as well as the opacity and secrecy that characterizes significant areas of the Zimbabwe–China relationship. The pressing need for critical institutions such as parliament to play independent oversight roles as well as the creation of space for civil society watchdog functions are highlighted as key enablers if Zimbabwean agency is to generate positive gains from the country’s engagement with China.
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Chiral Modulation from Molecular to Macroscopic levels by synthetic chiral-amide-bonded porphyrin dimers
- Authors: Liang, Xu , Qin, Mingfeng , Zhang, Xiaomei , Mack, John , Soy, Rodah , Nyokong, Tebello , Zhu, Weihua
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186802 , vital:44535 , xlink:href="https://doi.org/10.1016/j.dyepig.2019.107637"
- Description: Six different nanoarchitectures were constructed by a series of synthetic bio-inspired chiral porphyrin dimers through molecular self-assembly behaviour. A plausible mechanism of chiral expression from the molecular to the macroscopic levels was investigated through an analysis of the optical spectroscopy and theoretical calculations.
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Chitin hydrolysis with chitinolytic enzymes for the production of chitooligomers with antimicrobial properties
- Authors: Oree, Glynis
- Date: 2019
- Subjects: Chitin -- Biotechnology , Enzymes -- Biotechnology , Hydrolysis , Chitooligomers -- Biotechnology
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67887 , vital:29165
- Description: There are many diseases and illnesses in the world that require new drug treatments and chitin has been shown to produce chitooligomeric derivatives which exhibit promising antimicrobial and immune-enhancing properties. However, the rate-limiting step is associated with the high recalcitrance of chitinous substrates, and low hydrolytic activities of chitinolytic enzymes, resulting in low product release. To improve and create a more sustainable and economical process, enhancing chitin hydrolysis through various treatment procedures is essential for obtaining high enzyme hydrolysis rates, resulting in a higher yield of chitooligomers (CHOS). In literature, pre-treatment of insoluble biomass is generally associated with an increase in accessibility of the carbohydrate to hydrolytic enzymes, thus generating more products. The first part of this study investigated the effect of alkali- (NaOH) and acid pre-treatments (HCl and phosphoric acid) on chitin biomass, and chemical and morphological modifications were assessed by the employment of scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray spectrometery (EDX) and x-ray diffraction (XRD). Data obtained confirmed that pre-treated substrates were more chemically and morphologically modified. These results confirmed the fact that pre-treatment of chitin disrupts the structure of the biomass, rendering the polymer more accessible for enzymatic hydrolysis. The commercial chitinases from Bacillus cereus and Streptomyces griseus (CHB and CHS) are costly. Bio-prospecting for other chitin-degrading enzymes from alternate sources such as Oidiodendron maius, or the recombinant expression of CHOS, was a more economically feasible avenue. The chit1 gene from Thermomyces lanuginosus, expressed in Pichia pastoris, produced a large range CHOS with a degree of polymerisation (DP) ranging from 1 to above 6. TLC analysis showed that O. maius exhibited chitin-degrading properties by producing CHOS with a DP length of 1 to 3. These two sources were therefore successful in producing chitin-degrading enzymes. The physico-chemical properties of commercial (CHB and CHS) and expressed (Chit1) chitinolytic enzymes were investigated, to determine under which biochemical conditions and on which type of biomass they can function on optimally, for the production of value-added products such as CHOS. Substrate affinity assays were conducted on the un-treated and pre-treated biomass. TLC revealed that chitosan hydrolysis by the commercial chitinases produced the largest range of CHOS with a DP length ranging from 1 to 6. A range of temperatures (35-90oC) were investigated and CHB, CHS and Chit1 displayed optimum activities at 50, 40 and 45 oC, respectively. Thermostability studies that were conducted at 37 and 50oC revealed that CHB and CHS were most stable at 37oC. Chit1 showed great thermostablity at both temperatures, rendering this enzyme suitable for industrial processes at high temperatures. pH optima studies demonstrated that the pH optima for CHB, CHS and Chit1 was at a pH of 5.0, with specific activities of 33.459, 46.2 and 5.776 μmol/h/mg, respectively. The chain cleaving patterns of the commercial enzymes were determined and exo-chitinase activity was exhibited, due to the production of CHOS that were predominantly of a DP length of 2. Enzyme binary synergy studies were conducted with commercial chitinases (CHB and CHS) on colloidal chitin. Studies illustrated that the simultaneous combination of CHB 75%: CHS 25% produced the highest specific activity (3.526 μmol/h/mg), with no synergy. TLC analysis of this enzyme combination over time revealed that predominantly chitobiose was produced. This suggested that the substrate crystallinity and morphology played an important role in the way the enzymes cleaved the carbohydrate. Since CHOS have shown great promise for their antimicrobial properties, the CHOS generated from the chitinous substrates were tested for antimicrobial properties on Bacillus subtilis, Escherichia coli, Klebsiella and Staphlococcus aureus. This study revealed that certain CHOS produced have inhibitory effects on certain bacteria and could potentially be used in the pharamceutical or medical industries. In conclusion, this study revealed that chitinases can be produced and found in alternate sources and be used for the hydrolysis of chitinous biomass in a more sustainabe and economically viable manner. The chitinases investigated (CHB, CHS and Chit1) exhibited different cleaving patterns of the chitinous substrates due to the chemical and morphological properties of the biomass. CHOS produced from chitinous biomass exhibited some inhibitory effects on bacterial growth and show potential for use in the medical industry.
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