Stability indicating HPLC-ECD method for the analysis of clarithromycin in pharmaceutical dosage forms: Method scaling versus re-validation.
- Makoni, Pedzisai A, Chikukwa, Mellisa T R, Khamanga, Sandile M, Walker, Roderick B
- Authors: Makoni, Pedzisai A , Chikukwa, Mellisa T R , Khamanga, Sandile M , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183387 , vital:43984 , xlink:href="https://doi.org/10.3390/scipharm87040031"
- Description: An isocratic high-performance liquid chromatographic method using electrochemical detection (HPLC-ECD) for the quantitation of clarithromycin (CLA) was developed using Response Surface Methodology (RSM) based on a Central Composite Design (CCD). The method was validated using International Conference on Harmonization (ICH) guidelines with an analytical run time of 20 min. Method re-validation following a change in analytical column was successful in reducing the analytical run time to 13 min, decreasing solvent consumption thus facilitating environmental and financial sustainability. The applicability of using the United States Pharmacopeia (USP) method scaling approach in place of method re-validation using a column with a different L–designation to the original analytical column, was investigated. The scaled method met all USP system suitability requirements for resolution, tailing factor and % relative standard deviation (RSD). The re-validated and scaled method was successfully used to resolve CLA from manufacturing excipients in commercially available dosage forms. Although USP method scaling is only permitted for columns within the same L-designation, these data suggest that it may also be applicable to columns of different designation.
- Full Text:
- Authors: Makoni, Pedzisai A , Chikukwa, Mellisa T R , Khamanga, Sandile M , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183387 , vital:43984 , xlink:href="https://doi.org/10.3390/scipharm87040031"
- Description: An isocratic high-performance liquid chromatographic method using electrochemical detection (HPLC-ECD) for the quantitation of clarithromycin (CLA) was developed using Response Surface Methodology (RSM) based on a Central Composite Design (CCD). The method was validated using International Conference on Harmonization (ICH) guidelines with an analytical run time of 20 min. Method re-validation following a change in analytical column was successful in reducing the analytical run time to 13 min, decreasing solvent consumption thus facilitating environmental and financial sustainability. The applicability of using the United States Pharmacopeia (USP) method scaling approach in place of method re-validation using a column with a different L–designation to the original analytical column, was investigated. The scaled method met all USP system suitability requirements for resolution, tailing factor and % relative standard deviation (RSD). The re-validated and scaled method was successfully used to resolve CLA from manufacturing excipients in commercially available dosage forms. Although USP method scaling is only permitted for columns within the same L-designation, these data suggest that it may also be applicable to columns of different designation.
- Full Text:
Stakeholder relationship management of a Chinese Mining Organisation in Zimbabwe
- Authors: Chodokufa, Kudakwashe
- Date: 2019
- Subjects: Industrial management -- Zimbabwe , Mineral industries -- Zimbabwe -- Management , Investments, Chinese -- Zimbabwe
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/115127 , vital:34080
- Description: Media reports and research has pointed out problems in the way that Chinese mining organisations in Zimbabwe are managing stakeholder relationships. The problems ranging from disgruntled communities and allegations of labour violations. Taking into account the impact that China’s FDI has had on the ailing Zimbabwean economy research into the management of stakeholder relationships becomes imperative to understand how Chinese mining organisations build and manage stakeholder relationships. A review of stakeholder theory has revealed that there is not much emphasis by researchers on how organisations manage their stakeholder relationships, but rather on the identification and analysis of stakeholders. Research that has focused on stakeholder relationships has focused on different elements found in stakeholder relationship management and not necessarily on how stakeholder relationships should be managed. On the other hand, stakeholder theory does not seem to include social licence to operate which is important in stakeholder relationship management within the mining context. The purpose of this study is to develop a multidimensional stakeholder relationship management process for the Chinese mining organisation in Zimbabwe, showing dynamic interactions between multiple stakeholder networks with complementary, competitive and/or cooperative interests, while taking into account the possibility that interests may vary according to the underlying context. Thirteen semi-structured in-depth interviews were conducted with three stakeholder groups of a Chinese mining organisation as identified from the literature, namely employees, government and the community. The critical incident technique (CIT) was adopted in developing the interview questions and facilitated the data collection process. Participants described 36 critical incidents. According to multiple stakeholders, the findings suggest that, the Chinese managers built the relationship with multiple stakeholders through friendship, negotiation, pretend not to understand, referral, singing a contract, started with problems, they just arrived and through the government. With the same relationship being managed by the Chinese managers by being hard, rough and ruthless, authoritative, Chinese way of doing things, used avoidance, lack of competency, through a third party and resolving conflict when managing stakeholder relationships. Showing that the building and managing of stakeholder relationships is socially constructed and experienced differently by stakeholders. The positive and negative relationship characteristics influenced how stakeholder relationships are managed by the selected Chinese mining organisation. In the presence of positive relationship characteristics which included, friendship,there was flexibility, power dynamics, accountability depends on situations, commitment a show of investment, do cooperate to a certain extent, trust began with an open mind, shared values: hardwork and profit, shared values: culture was associated with the Chinese managing the relationship through being kind, supportive, motivating and understanding; complaint; through a third party; controlling; Chinese way of doing things; and performance and reward management of stakeholder relationships. Whilst negative relationship characteristics which included fear, their hearts were hardened, Chinese had power, intimidaton, not accountable, lack of commitment, communication understanding, connotations and intretations, communication done through a third party; no cooperation want to cut coners; trust are they conveying what is being said; deception and misrepresentation; trust depends on experience; being told lies and not transparent were associated with negative (being authoritative; hard, rough and ruthless; avoidance; blame shifting and pushy) stakeholder relationship management by the Chinese managers. Hence, a proposition that negative or positive relationship characteristics result in negative or positive stakeholder relationship management by the Chinese managers was propossed. The following challenges were experienced in the management of stakeholder relationships namely, communication, corruption, cheating, political environment, working conditions and broken promises. The dynamic multidimensional stakeholder relationship management process was subsequently revised to accommodate the new relationship characteristics and their positive and negative influence on how stakeholder relationships are managed. The main contribution of this study is the dynamic multidimensional stakeholder relationship management process which was developed within the context of a Chinese mining organisation in Africa. It is recommended that practitioners utilise the dynamic multidimensional stakeholder relationship management process to assist them in understanding and conducting research on stakeholder relationships. Further research is suggested on developing the research proposition made in the study and to empirically test the dynamic multidimension stakeholder relationship management process in other industries that posses different or similar contexts as this study.
- Full Text:
- Authors: Chodokufa, Kudakwashe
- Date: 2019
- Subjects: Industrial management -- Zimbabwe , Mineral industries -- Zimbabwe -- Management , Investments, Chinese -- Zimbabwe
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/115127 , vital:34080
- Description: Media reports and research has pointed out problems in the way that Chinese mining organisations in Zimbabwe are managing stakeholder relationships. The problems ranging from disgruntled communities and allegations of labour violations. Taking into account the impact that China’s FDI has had on the ailing Zimbabwean economy research into the management of stakeholder relationships becomes imperative to understand how Chinese mining organisations build and manage stakeholder relationships. A review of stakeholder theory has revealed that there is not much emphasis by researchers on how organisations manage their stakeholder relationships, but rather on the identification and analysis of stakeholders. Research that has focused on stakeholder relationships has focused on different elements found in stakeholder relationship management and not necessarily on how stakeholder relationships should be managed. On the other hand, stakeholder theory does not seem to include social licence to operate which is important in stakeholder relationship management within the mining context. The purpose of this study is to develop a multidimensional stakeholder relationship management process for the Chinese mining organisation in Zimbabwe, showing dynamic interactions between multiple stakeholder networks with complementary, competitive and/or cooperative interests, while taking into account the possibility that interests may vary according to the underlying context. Thirteen semi-structured in-depth interviews were conducted with three stakeholder groups of a Chinese mining organisation as identified from the literature, namely employees, government and the community. The critical incident technique (CIT) was adopted in developing the interview questions and facilitated the data collection process. Participants described 36 critical incidents. According to multiple stakeholders, the findings suggest that, the Chinese managers built the relationship with multiple stakeholders through friendship, negotiation, pretend not to understand, referral, singing a contract, started with problems, they just arrived and through the government. With the same relationship being managed by the Chinese managers by being hard, rough and ruthless, authoritative, Chinese way of doing things, used avoidance, lack of competency, through a third party and resolving conflict when managing stakeholder relationships. Showing that the building and managing of stakeholder relationships is socially constructed and experienced differently by stakeholders. The positive and negative relationship characteristics influenced how stakeholder relationships are managed by the selected Chinese mining organisation. In the presence of positive relationship characteristics which included, friendship,there was flexibility, power dynamics, accountability depends on situations, commitment a show of investment, do cooperate to a certain extent, trust began with an open mind, shared values: hardwork and profit, shared values: culture was associated with the Chinese managing the relationship through being kind, supportive, motivating and understanding; complaint; through a third party; controlling; Chinese way of doing things; and performance and reward management of stakeholder relationships. Whilst negative relationship characteristics which included fear, their hearts were hardened, Chinese had power, intimidaton, not accountable, lack of commitment, communication understanding, connotations and intretations, communication done through a third party; no cooperation want to cut coners; trust are they conveying what is being said; deception and misrepresentation; trust depends on experience; being told lies and not transparent were associated with negative (being authoritative; hard, rough and ruthless; avoidance; blame shifting and pushy) stakeholder relationship management by the Chinese managers. Hence, a proposition that negative or positive relationship characteristics result in negative or positive stakeholder relationship management by the Chinese managers was propossed. The following challenges were experienced in the management of stakeholder relationships namely, communication, corruption, cheating, political environment, working conditions and broken promises. The dynamic multidimensional stakeholder relationship management process was subsequently revised to accommodate the new relationship characteristics and their positive and negative influence on how stakeholder relationships are managed. The main contribution of this study is the dynamic multidimensional stakeholder relationship management process which was developed within the context of a Chinese mining organisation in Africa. It is recommended that practitioners utilise the dynamic multidimensional stakeholder relationship management process to assist them in understanding and conducting research on stakeholder relationships. Further research is suggested on developing the research proposition made in the study and to empirically test the dynamic multidimension stakeholder relationship management process in other industries that posses different or similar contexts as this study.
- Full Text:
Statistical Analysis of the Radio-Interferometric Measurement Equation, a derived adaptive weighting scheme, and applications to LOFAR-VLBI observation of the Extended Groth Strip
- Authors: Bonnassieux, Etienne
- Date: 2019
- Subjects: Radio astronomy , Astrophysics , Astrophysics -- Instruments -- Calibration , Imaging systems in astronomy , Radio interferometers , Radio telescopes , Astronomy -- Observations
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/93789 , vital:30942
- Description: J.R.R Tolkien wrote, in his Mythopoeia, that “He sees no stars who does not see them first, of living silver made that sudden burst, to flame like flowers beneath the ancient song”. In his defense of myth-making, he formulates the argument that the attribution of meaning is an act of creation - that “trees are not ‘trees’ until so named and seen” - and that this capacity for creation defines the human creature. The scientific endeavour, in this context, can be understood as a social expression of a fundamental feature of humanity, and from this endeavour flows much understanding. This thesis, one thread among many, focuses on the study of astronomical objects as seen by the radio waves they emit. What are radio waves? Electromagnetic waves were theorised by James Clerk Maxwell (Maxwell 1864) in his great theoretical contribution to modern physics, their speed matching the speed of light as measured by Ole Christensen R0mer and, later, James Bradley. It was not until Heinrich Rudolf Hertz’s 1887 experiment that these waves were measured in a laboratory, leading to the dawn of radio communications - and, later, radio astronomy. The link between radio waves and light was one of association: light is known to behave as a wave (Young double-slit experiment), with the same propagation speed as electromagnetic radiation. Light “proper” is also known to exist beyond the optical regime: Herschel’s experiment shows that when diffracted through a prism, sunlight warms even those parts of a desk which are not observed to be lit (first evidence of infrared light). The link between optical light and unseen electromagnetic radiation is then an easy step to make, and one confirmed through countless technological applications (e.g. optical fiber to name but one). And as soon as this link is established, a question immediately comes to the mind of the astronomer: what does the sky, our Universe, look like to the radio “eye”? Radio astronomy has a short but storied history: from Karl Jansky’s serendipitous observation of the centre of the Milky Way, which outshines our Sun in the radio regime, in 1933, to Grote Reber’s hand-built back-yard radio antenna in 1937, which successfully detected radio emission from the Milky Way itself, to such monumental projects as the Square Kilometer Array and its multiple pathfinders, it has led to countless discoveries and the opening of a truly new window on the Universe. The work presented in this thesis is a contribution to this discipline - the culmination of three years of study, which is a rather short time to get a firm grasp of radio interferometry both in theory and in practice. The need for robust, automated methods - which are improving daily, thanks to the tireless labour of the scientists in the field - is becoming ever stronger as the SKA approaches, looming large on the horizon; but even today, in the precursor era of LOFAR, MeerKAT and other pathfinders, it is keenly felt. When I started my doctorate, the sheer scale of the task at hand felt overwhelming - to actually be able to contribute to its resolution seemed daunting indeed! Thankfully, as the saying goes, no society sets for itself material goals which it cannot achieve. This thesis took place at an exciting time for radio interferometry: at the start of my doctorate, the LOFAR international stations were - to my knowledge - only beginning to be used, and even then, only tentatively; MeerKAT had not yet shown its first light; the techniques used throughout my work were still being developed. At the time of writing, great strides have been made. One of the greatest technical challenges of LOFAR - imaging using the international stations - is starting to become reality. This technical challenge is the key problem that this thesis set out to address. While we only achieved partial success so far, it is a testament to the difficulty of the task that it is not yet truly resolved. One of the major results of this thesis is a model of a bright resolved source near a famous extragalactic field: properly modeling this source not only allows the use of international LOFAR stations, but also grants deeper access to the extragalactic field itself, which is otherwise polluted by the 3C source’s sidelobes. This result was only achieved thanks to the other major result of this thesis: the development of a theoretical framework with which to better understand the effect of calibration errors on images made from interferometric data, and an algorithm to strongly mitigate them. The structure of this manuscript is as follows: we begin with an introduction to radio interferometry, LOFAR, and the emission mechanisms which dominate for our field of interest. These introductions are primarily intended to give a brief overview of the technical aspects of the data reduced in this thesis. We follow with an overview of the Measurement Equation formalism, which underpins our theoretical work. This is the keystone of this thesis. We then show the theoretical work that was developed as part of the research work done during the doctorate - which was published in Astronomy & Astrophysics. Its practical application - a quality-based weighting scheme - is used throughout our data reduction. This data reduction is the next topic of this thesis: we contextualise the scientific interest of the data we reduce, and explain both the methods and the results we achieve.
- Full Text:
- Authors: Bonnassieux, Etienne
- Date: 2019
- Subjects: Radio astronomy , Astrophysics , Astrophysics -- Instruments -- Calibration , Imaging systems in astronomy , Radio interferometers , Radio telescopes , Astronomy -- Observations
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/93789 , vital:30942
- Description: J.R.R Tolkien wrote, in his Mythopoeia, that “He sees no stars who does not see them first, of living silver made that sudden burst, to flame like flowers beneath the ancient song”. In his defense of myth-making, he formulates the argument that the attribution of meaning is an act of creation - that “trees are not ‘trees’ until so named and seen” - and that this capacity for creation defines the human creature. The scientific endeavour, in this context, can be understood as a social expression of a fundamental feature of humanity, and from this endeavour flows much understanding. This thesis, one thread among many, focuses on the study of astronomical objects as seen by the radio waves they emit. What are radio waves? Electromagnetic waves were theorised by James Clerk Maxwell (Maxwell 1864) in his great theoretical contribution to modern physics, their speed matching the speed of light as measured by Ole Christensen R0mer and, later, James Bradley. It was not until Heinrich Rudolf Hertz’s 1887 experiment that these waves were measured in a laboratory, leading to the dawn of radio communications - and, later, radio astronomy. The link between radio waves and light was one of association: light is known to behave as a wave (Young double-slit experiment), with the same propagation speed as electromagnetic radiation. Light “proper” is also known to exist beyond the optical regime: Herschel’s experiment shows that when diffracted through a prism, sunlight warms even those parts of a desk which are not observed to be lit (first evidence of infrared light). The link between optical light and unseen electromagnetic radiation is then an easy step to make, and one confirmed through countless technological applications (e.g. optical fiber to name but one). And as soon as this link is established, a question immediately comes to the mind of the astronomer: what does the sky, our Universe, look like to the radio “eye”? Radio astronomy has a short but storied history: from Karl Jansky’s serendipitous observation of the centre of the Milky Way, which outshines our Sun in the radio regime, in 1933, to Grote Reber’s hand-built back-yard radio antenna in 1937, which successfully detected radio emission from the Milky Way itself, to such monumental projects as the Square Kilometer Array and its multiple pathfinders, it has led to countless discoveries and the opening of a truly new window on the Universe. The work presented in this thesis is a contribution to this discipline - the culmination of three years of study, which is a rather short time to get a firm grasp of radio interferometry both in theory and in practice. The need for robust, automated methods - which are improving daily, thanks to the tireless labour of the scientists in the field - is becoming ever stronger as the SKA approaches, looming large on the horizon; but even today, in the precursor era of LOFAR, MeerKAT and other pathfinders, it is keenly felt. When I started my doctorate, the sheer scale of the task at hand felt overwhelming - to actually be able to contribute to its resolution seemed daunting indeed! Thankfully, as the saying goes, no society sets for itself material goals which it cannot achieve. This thesis took place at an exciting time for radio interferometry: at the start of my doctorate, the LOFAR international stations were - to my knowledge - only beginning to be used, and even then, only tentatively; MeerKAT had not yet shown its first light; the techniques used throughout my work were still being developed. At the time of writing, great strides have been made. One of the greatest technical challenges of LOFAR - imaging using the international stations - is starting to become reality. This technical challenge is the key problem that this thesis set out to address. While we only achieved partial success so far, it is a testament to the difficulty of the task that it is not yet truly resolved. One of the major results of this thesis is a model of a bright resolved source near a famous extragalactic field: properly modeling this source not only allows the use of international LOFAR stations, but also grants deeper access to the extragalactic field itself, which is otherwise polluted by the 3C source’s sidelobes. This result was only achieved thanks to the other major result of this thesis: the development of a theoretical framework with which to better understand the effect of calibration errors on images made from interferometric data, and an algorithm to strongly mitigate them. The structure of this manuscript is as follows: we begin with an introduction to radio interferometry, LOFAR, and the emission mechanisms which dominate for our field of interest. These introductions are primarily intended to give a brief overview of the technical aspects of the data reduced in this thesis. We follow with an overview of the Measurement Equation formalism, which underpins our theoretical work. This is the keystone of this thesis. We then show the theoretical work that was developed as part of the research work done during the doctorate - which was published in Astronomy & Astrophysics. Its practical application - a quality-based weighting scheme - is used throughout our data reduction. This data reduction is the next topic of this thesis: we contextualise the scientific interest of the data we reduce, and explain both the methods and the results we achieve.
- Full Text:
Statistical study of traveling ionospheric disturbances over South Africa
- Authors: Mahlangu, Daniel Fiso
- Date: 2019
- Subjects: Ionosphere -- Research , Sudden ionospheric disturbances , Gravity waves , Magnetic storms
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76387 , vital:30556
- Description: This thesis provides a statistical analysis of traveling ionospheric disturbances (TIDs) in South Africa. The velocities of the TIDs were determined from total electron content (TEC) maps using particle image velocimetry (PIV). The periods were determined using Morlet function in wavelet analysis. The TIDs were grouped into four categories: daytime, twilight, nighttime TIDs, and those TIDs that occurred during magnetic storms. It was found that daytime medium scale TIDs (MSTIDs) propagated equatorward in all seasons (summer, autumn, winter, and spring), with velocities of about 114 to 213 m/s. Their maximum occurrence was in winter between 15:00 and 16:00 LT. The daytime large scale (TIDs) LSTIDs propagated equatorward with velocities of approximately 455 to 767 m/s. Their highest occurrence was in summer, between 12:00-13:00 LT. Most of the these TIDs (about 78%) were observed during the passing of the morning solar terminator. This implied that the morning terminator was more effective in instigating TIDs. Only a few nighttime TIDs were observed and therefore their behavior could not be statistically inferred. The TIDs that occurred during magnetically disturbed conditions propagated equatorward. This indicated that their source mechanism was atmospheric gravity waves generated at the onset of geomagnetic storms.
- Full Text:
- Authors: Mahlangu, Daniel Fiso
- Date: 2019
- Subjects: Ionosphere -- Research , Sudden ionospheric disturbances , Gravity waves , Magnetic storms
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76387 , vital:30556
- Description: This thesis provides a statistical analysis of traveling ionospheric disturbances (TIDs) in South Africa. The velocities of the TIDs were determined from total electron content (TEC) maps using particle image velocimetry (PIV). The periods were determined using Morlet function in wavelet analysis. The TIDs were grouped into four categories: daytime, twilight, nighttime TIDs, and those TIDs that occurred during magnetic storms. It was found that daytime medium scale TIDs (MSTIDs) propagated equatorward in all seasons (summer, autumn, winter, and spring), with velocities of about 114 to 213 m/s. Their maximum occurrence was in winter between 15:00 and 16:00 LT. The daytime large scale (TIDs) LSTIDs propagated equatorward with velocities of approximately 455 to 767 m/s. Their highest occurrence was in summer, between 12:00-13:00 LT. Most of the these TIDs (about 78%) were observed during the passing of the morning solar terminator. This implied that the morning terminator was more effective in instigating TIDs. Only a few nighttime TIDs were observed and therefore their behavior could not be statistically inferred. The TIDs that occurred during magnetically disturbed conditions propagated equatorward. This indicated that their source mechanism was atmospheric gravity waves generated at the onset of geomagnetic storms.
- Full Text:
Strength and Sprint Time Changes in Response to Repeated Shuttles Between the Wickets During Batting in Cricket
- Christie, Candice J, Sheppard, Bronwyn J, Goble, David, Pote, Lee, Noakes, Timothy
- Authors: Christie, Candice J , Sheppard, Bronwyn J , Goble, David , Pote, Lee , Noakes, Timothy
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127133 , vital:35959 , https://doi.org/10.1519/jsc.0000000000002585
- Description: Christie CJ, Sheppard B, Goble D, Pote L, and Noakes TD. Strength and sprint time changes in response to repeated shuttles between the wickets during batting in cricket. J Strength Cond Res XX(X): 000–000, 2018—No studies have investigated the impact of repeated sprints between the wickets on lower-limb strength and sprint performance. Therefore, the purpose of this study was to assess changes in knee extensor (EXT) and flexor (FLEX) strength after repeated sprints between the wickets and to relate these to changes in sprint times. Twenty batters completed 2 conditions: onewas high-volume running (HVR-twelve sprints per over) and the other, moderate-volume running (MVR-6 sprints per over) between the wickets (42 deliveries in both). Peak isokinetic torque was measured before and after each condition and sprint times were recorded. Eccentric and concentric peak torque decreased significantly (p , 0.05) at 1.05 rad˙s ̄1 for knee EXT in both conditions. There was an 18% (HVR) and 10% (MVR) decline in concentric and eccentric knee EXT peak torque. Peak FLEX torques were significantly (p , 0.05) reduced after HVR (16.7%) but not after the MVR condition (8%). There were similar declines in eccentric FLEX peak torque. Sprint times increased significantly (p , 0.05) during the HVR condition but not in the MVR condition; sprint times in the HVR condition were compromised as early as the third over. We conclude that a high volume of runs significantly reduces muscle function in the lower limbs, partly explaining the impairment in sprint performance. However, because batters slowed as early as the third over in the HVR condition, there may be some form of strategy used in anticipation of a higher overall workload. More middle wicket practices, focusing on repeat shuttle sprints while batting, should be included in the coaching program.
- Full Text:
- Authors: Christie, Candice J , Sheppard, Bronwyn J , Goble, David , Pote, Lee , Noakes, Timothy
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127133 , vital:35959 , https://doi.org/10.1519/jsc.0000000000002585
- Description: Christie CJ, Sheppard B, Goble D, Pote L, and Noakes TD. Strength and sprint time changes in response to repeated shuttles between the wickets during batting in cricket. J Strength Cond Res XX(X): 000–000, 2018—No studies have investigated the impact of repeated sprints between the wickets on lower-limb strength and sprint performance. Therefore, the purpose of this study was to assess changes in knee extensor (EXT) and flexor (FLEX) strength after repeated sprints between the wickets and to relate these to changes in sprint times. Twenty batters completed 2 conditions: onewas high-volume running (HVR-twelve sprints per over) and the other, moderate-volume running (MVR-6 sprints per over) between the wickets (42 deliveries in both). Peak isokinetic torque was measured before and after each condition and sprint times were recorded. Eccentric and concentric peak torque decreased significantly (p , 0.05) at 1.05 rad˙s ̄1 for knee EXT in both conditions. There was an 18% (HVR) and 10% (MVR) decline in concentric and eccentric knee EXT peak torque. Peak FLEX torques were significantly (p , 0.05) reduced after HVR (16.7%) but not after the MVR condition (8%). There were similar declines in eccentric FLEX peak torque. Sprint times increased significantly (p , 0.05) during the HVR condition but not in the MVR condition; sprint times in the HVR condition were compromised as early as the third over. We conclude that a high volume of runs significantly reduces muscle function in the lower limbs, partly explaining the impairment in sprint performance. However, because batters slowed as early as the third over in the HVR condition, there may be some form of strategy used in anticipation of a higher overall workload. More middle wicket practices, focusing on repeat shuttle sprints while batting, should be included in the coaching program.
- Full Text:
Students’ perceptions of their employability as revealed by their understandings of the South African Labour Market
- Authors: Gabobegwe, Maoshadi Keletso
- Date: 2019
- Language: English
- Type: text , Thesis , Masters , MSocSc
- Identifier: http://hdl.handle.net/10962/71482 , vital:29857
- Description: The state of the South African labour market is characterized −among other things− by inequalities and the chronic issue of unemployment, with a rate that has come up to 27.7% in the third quarter of 2017. Considering this, unemployment in South Africa is explained by numerous authors as a structural issue. In a sense that unemployed people do not have the skills required by the labour market. But, since education attainment improves an individuals’ employment prospects and outcome. It would be expected that people with higher education would have high prospects of getting employment. Yet, people with higher education qualifications also face challenges of obtaining employment. Even though research finds that graduate unemployment is not as bad when compared to general and overall unemployment of the country. It still remains that skills shortages and/or mismatch are deemed to be the main contributor of the South African graduate unemployment. Existing research finds that just as the labour market is characterized with differences on the grounds of gender and race. This also reflects on how graduates enter the labour market. With the white race having more employment outcomes than blacks and males than females. It is against this background that this dissertation set out to explore what Rhodes University final-year students’ −who are nearing the transition from varsity to the labour market− perceive to be their employment prospects and outcomes. Taking into consideration the issue of unemployment and inequalities in the labour market. In essence, one of the key issues that the dissertation focuses on, is what students think of their employability based on their understanding of the labour market. More than that, the dissertation investigates how aspects such as the student’s field of study, race and gender factor into how students understand the labour market and ultimately how they perceive their employment prospects and outcomes. As a consequence, evidence suggests that students’ perceptions of the labour market influences how they perceive their employability. Over and above, the research finds that the students field of study especially, features significantly in how students perceive the labour market and their employability. While race and gender also factored in students’ responses, it was not as significant as compared to their field of study respectively. The general finding is that students are well aware of the issues of the labour market and are concerned about the implications of these issues on their employability. This awareness and concern varied based on students’ field of study, race and gender.
- Full Text:
- Authors: Gabobegwe, Maoshadi Keletso
- Date: 2019
- Language: English
- Type: text , Thesis , Masters , MSocSc
- Identifier: http://hdl.handle.net/10962/71482 , vital:29857
- Description: The state of the South African labour market is characterized −among other things− by inequalities and the chronic issue of unemployment, with a rate that has come up to 27.7% in the third quarter of 2017. Considering this, unemployment in South Africa is explained by numerous authors as a structural issue. In a sense that unemployed people do not have the skills required by the labour market. But, since education attainment improves an individuals’ employment prospects and outcome. It would be expected that people with higher education would have high prospects of getting employment. Yet, people with higher education qualifications also face challenges of obtaining employment. Even though research finds that graduate unemployment is not as bad when compared to general and overall unemployment of the country. It still remains that skills shortages and/or mismatch are deemed to be the main contributor of the South African graduate unemployment. Existing research finds that just as the labour market is characterized with differences on the grounds of gender and race. This also reflects on how graduates enter the labour market. With the white race having more employment outcomes than blacks and males than females. It is against this background that this dissertation set out to explore what Rhodes University final-year students’ −who are nearing the transition from varsity to the labour market− perceive to be their employment prospects and outcomes. Taking into consideration the issue of unemployment and inequalities in the labour market. In essence, one of the key issues that the dissertation focuses on, is what students think of their employability based on their understanding of the labour market. More than that, the dissertation investigates how aspects such as the student’s field of study, race and gender factor into how students understand the labour market and ultimately how they perceive their employment prospects and outcomes. As a consequence, evidence suggests that students’ perceptions of the labour market influences how they perceive their employability. Over and above, the research finds that the students field of study especially, features significantly in how students perceive the labour market and their employability. While race and gender also factored in students’ responses, it was not as significant as compared to their field of study respectively. The general finding is that students are well aware of the issues of the labour market and are concerned about the implications of these issues on their employability. This awareness and concern varied based on students’ field of study, race and gender.
- Full Text:
Students’ perspectives on the language question in South African Higher Education: the expression of marginalized linguistic identities on Rhodes University students’ Facebook pages
- Authors: Resha, Babalwa
- Date: 2019
- Subjects: Language policy -- South Africa -- Makhanda , Language and education -- South Africa -- Makhanda , Sociolinguistics -- South Africa -- Makhanda , Language and languages -- Study and teaching -- Social aspects -- South Africa -- Makhanda , Linguistic rights -- South Africa , Translanguaging (Linguistics) , Multilingual education -- South Africa -- Makhanda , Educational change -- South Africa -- Makhanda , South Africa – Makhanda -- Language and languages -- Political aspects , Student movements -- South Africa -- Makhanda , Online social networks -- South Africa -- Makhanda , Rhodes University -- Sociological aspects , Facebook (Firm) , UCKAR
- Language: English
- Type: text , Thesis , Doctoral , MA
- Identifier: http://hdl.handle.net/10962/119813 , vital:34785
- Description: The study analyses students’ engagement with the language question in South African Higher Education (HE) and their use of African languages on the institutional Facebook pages, namely UCKAR and RHODES SRC, during the student protests of 2015 to early 2017. Extensive use of social media is a salient feature of the protests as indicated by the hashtag prefixes such as #RhodesMustFall and #FeesMustFall. On these platforms, disgruntled students use their multiple languages to interact, establish a sense of belonging and power to challenge different forms of exclusionary institutional culture, including language policies and practices in HE. The research examines and explores students’ perspectives on the language question in Higher Education Institutions (HEIs) on the two institutional Facebook pages, and how mother tongue speakers of indigenous African languages use these languages to express their marginalized linguistic identities in HEIs in South Africa. Theoretically, the study uses the notion of linguistic imperialism to provide a broad context for understanding the language question in South African HE and its significance in transformation. The engagement with the language question on the UCKAR and RHODES SRC Facebook pages is carried out from the lenses of citizen sociolinguistics while the new theory of translanguaging offers the analysis on language usage and alternative ways of addressing linguistic hegemony in educational environments. The translanguaging approach has the capacity to demonstrate multi-layered linguistic practices and reflections on the UCKAR and RHODES pages. It is the interest of the researcher to investigate how students with various linguistic and other backgrounds engage the language question and perform linguistic identities. Language usage on the two Rhodes University institutional Facebook pages and its implications on students’ engagement with issues, is used to provide insight towards the implementation of multilingualism in the university. The study is virtual ethnographic in nature. Virtual ethnography is an online research method that employs ethnographic research to study online social interactions. To analyse data, the study used a textual analysis technique as it looks at any analysis of texts broadly. Critical Discourse Analysis approach was used to analyse language debates. Purposive sampling was also used to select Facebook posts and comments on the language question and those written in African languages, and interviews were conducted with key members of Rhodes University, to bring forth their perspectives on the institution’s language policy and to figure out what plans are put into place to engage students in debates on the language question because students are important stakeholders of the university, and at the same time some of these students are also speakers of indigenous African languages. In general, the research findings have shown that students as users of languages in HEIs are capable of engendering debates that could be used as solutions to the language question and transformation in the South African HEIs. Thus, this study offers a different approach into engaging with students, their perspective and debates through institutional Facebook pages. In addition, it offers students’ perspectives on the curriculum of the university and how the university can go about its transformation. This study provides evidence that the use of indigenous African languages by mother tongue speakers of these languages in institutes of higher learning and their related institutional Facebook pages and social media in general, is an expression of marginalized linguistic identities of these language speakers. Sometimes these identities are multiple, and students use different modalities to express them, hence the notion of translanguaging.
- Full Text:
- Authors: Resha, Babalwa
- Date: 2019
- Subjects: Language policy -- South Africa -- Makhanda , Language and education -- South Africa -- Makhanda , Sociolinguistics -- South Africa -- Makhanda , Language and languages -- Study and teaching -- Social aspects -- South Africa -- Makhanda , Linguistic rights -- South Africa , Translanguaging (Linguistics) , Multilingual education -- South Africa -- Makhanda , Educational change -- South Africa -- Makhanda , South Africa – Makhanda -- Language and languages -- Political aspects , Student movements -- South Africa -- Makhanda , Online social networks -- South Africa -- Makhanda , Rhodes University -- Sociological aspects , Facebook (Firm) , UCKAR
- Language: English
- Type: text , Thesis , Doctoral , MA
- Identifier: http://hdl.handle.net/10962/119813 , vital:34785
- Description: The study analyses students’ engagement with the language question in South African Higher Education (HE) and their use of African languages on the institutional Facebook pages, namely UCKAR and RHODES SRC, during the student protests of 2015 to early 2017. Extensive use of social media is a salient feature of the protests as indicated by the hashtag prefixes such as #RhodesMustFall and #FeesMustFall. On these platforms, disgruntled students use their multiple languages to interact, establish a sense of belonging and power to challenge different forms of exclusionary institutional culture, including language policies and practices in HE. The research examines and explores students’ perspectives on the language question in Higher Education Institutions (HEIs) on the two institutional Facebook pages, and how mother tongue speakers of indigenous African languages use these languages to express their marginalized linguistic identities in HEIs in South Africa. Theoretically, the study uses the notion of linguistic imperialism to provide a broad context for understanding the language question in South African HE and its significance in transformation. The engagement with the language question on the UCKAR and RHODES SRC Facebook pages is carried out from the lenses of citizen sociolinguistics while the new theory of translanguaging offers the analysis on language usage and alternative ways of addressing linguistic hegemony in educational environments. The translanguaging approach has the capacity to demonstrate multi-layered linguistic practices and reflections on the UCKAR and RHODES pages. It is the interest of the researcher to investigate how students with various linguistic and other backgrounds engage the language question and perform linguistic identities. Language usage on the two Rhodes University institutional Facebook pages and its implications on students’ engagement with issues, is used to provide insight towards the implementation of multilingualism in the university. The study is virtual ethnographic in nature. Virtual ethnography is an online research method that employs ethnographic research to study online social interactions. To analyse data, the study used a textual analysis technique as it looks at any analysis of texts broadly. Critical Discourse Analysis approach was used to analyse language debates. Purposive sampling was also used to select Facebook posts and comments on the language question and those written in African languages, and interviews were conducted with key members of Rhodes University, to bring forth their perspectives on the institution’s language policy and to figure out what plans are put into place to engage students in debates on the language question because students are important stakeholders of the university, and at the same time some of these students are also speakers of indigenous African languages. In general, the research findings have shown that students as users of languages in HEIs are capable of engendering debates that could be used as solutions to the language question and transformation in the South African HEIs. Thus, this study offers a different approach into engaging with students, their perspective and debates through institutional Facebook pages. In addition, it offers students’ perspectives on the curriculum of the university and how the university can go about its transformation. This study provides evidence that the use of indigenous African languages by mother tongue speakers of these languages in institutes of higher learning and their related institutional Facebook pages and social media in general, is an expression of marginalized linguistic identities of these language speakers. Sometimes these identities are multiple, and students use different modalities to express them, hence the notion of translanguaging.
- Full Text:
Substituent effects on the electrocatalytic activity of cobalt phthalocyanine in the presence of graphene quantum dots
- Centane, Sixolile Sibongiseni
- Authors: Centane, Sixolile Sibongiseni
- Date: 2019
- Subjects: Phthalocyanines , Quantum dots , Electrocatalysis , Electrochemistry
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67614 , vital:29121
- Description: The electrocatalytic activity of metallophthalocyanines derivatives is explored. Cobalt monocarboxyphenoxy phthalocyanine (1), cobalt tetracarboxyphenoxy phthalocyanine (2), cobalt tetraaminophenoxy phthalocyanine (3) and cobalt tris-(tert-butylphenoxy) monocarboxyphenoxy phthalocyanine (4) are the phthalocyanines employed in this work. The metallophthalocyanines were employed alone as well as in the presence of the carbon based graphene quantum dots. The electrocatalytic behaviour of functionalized GQDs is also explored herein. The catalytic processes studies were conducted on a glassy carbon electrode surface. Modification of the electrode was achieved by the adsorption method. The materials were adsorbed either alone, as premixed/covalently linked GQDs/Pc conjugates or sequentially. Sequentially adsorbed electrodes involved the phthalocyanines on top or beneath GQDs. Sequentially modified electrodes where the phthalocyanine had higher currents and low detection limits than when the phthalocyanine is underneath. Premixed conjugates showed better activity than the covalently formed conjugates. The nanomaterials synthesized and used in this work were characterized using transmission electron microscopy, UV-Vis spectroscopy, dynamic light scattering, Raman spectroscopy, X-ray diffraction, Atomic Force Microscopy and X-ray photoelectron spectroscopy. The modified electrodes were characterized using cyclic voltammetry and scanning electrochemical spectroscopy. The electrocatalytic activity of the modified electrodes towards the oxidation of hydrazine was evaluated using cyclic voltammetry and chronoamperometry. Superior catalytic activity was observed for the conjugates compared to that of the individual conjugates.
- Full Text:
- Authors: Centane, Sixolile Sibongiseni
- Date: 2019
- Subjects: Phthalocyanines , Quantum dots , Electrocatalysis , Electrochemistry
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67614 , vital:29121
- Description: The electrocatalytic activity of metallophthalocyanines derivatives is explored. Cobalt monocarboxyphenoxy phthalocyanine (1), cobalt tetracarboxyphenoxy phthalocyanine (2), cobalt tetraaminophenoxy phthalocyanine (3) and cobalt tris-(tert-butylphenoxy) monocarboxyphenoxy phthalocyanine (4) are the phthalocyanines employed in this work. The metallophthalocyanines were employed alone as well as in the presence of the carbon based graphene quantum dots. The electrocatalytic behaviour of functionalized GQDs is also explored herein. The catalytic processes studies were conducted on a glassy carbon electrode surface. Modification of the electrode was achieved by the adsorption method. The materials were adsorbed either alone, as premixed/covalently linked GQDs/Pc conjugates or sequentially. Sequentially adsorbed electrodes involved the phthalocyanines on top or beneath GQDs. Sequentially modified electrodes where the phthalocyanine had higher currents and low detection limits than when the phthalocyanine is underneath. Premixed conjugates showed better activity than the covalently formed conjugates. The nanomaterials synthesized and used in this work were characterized using transmission electron microscopy, UV-Vis spectroscopy, dynamic light scattering, Raman spectroscopy, X-ray diffraction, Atomic Force Microscopy and X-ray photoelectron spectroscopy. The modified electrodes were characterized using cyclic voltammetry and scanning electrochemical spectroscopy. The electrocatalytic activity of the modified electrodes towards the oxidation of hydrazine was evaluated using cyclic voltammetry and chronoamperometry. Superior catalytic activity was observed for the conjugates compared to that of the individual conjugates.
- Full Text:
Suicide and the South African business cycle
- Authors: Botha, Ferdi , Pitot, A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396138 , vital:69153 , xlink:href="https://hdl.handle.net/10520/EJC-18880c26e4"
- Description: Using monthly data for January 2006 - December 2015, this study explores the relationship between suicide and the South African business cycle. Contrary to most previous research, the findings reveal that suicide is pro-cyclical.
- Full Text:
- Authors: Botha, Ferdi , Pitot, A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396138 , vital:69153 , xlink:href="https://hdl.handle.net/10520/EJC-18880c26e4"
- Description: Using monthly data for January 2006 - December 2015, this study explores the relationship between suicide and the South African business cycle. Contrary to most previous research, the findings reveal that suicide is pro-cyclical.
- Full Text:
Sulphide textures and compositions associated with the hydrothermal/magmatic system of the Twangiza gold deposit (South Kivu, DRC)
- Authors: Busane, Emmanuel Aganze
- Date: 2019
- Subjects: Gold mines and mining -- Congo (Democratic Republic) , Geology -- Congo (Democratic Republic) , Hydrothermal alteration -- Congo (Democratic Republic) , Sulphide minerals -- Congo (Democratic Republic) , Gold ores -- Geology -- Congo (Democratic Republic) , Geochemistry -- Congo (Democratic Republic) , Twangiza Mine (Congo (Democratic Republic))
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76588 , vital:30610
- Description: Twangiza mine is a gold deposit situated in the eastern Democratic Republic of Congo. The rock types at the Twangiza Mine consist of black shale, including carbonaceous mudstone and thin intercalated layers of siltstone, and feldspar-rich granitoid intrusive sills, referred to as albitite, folded into a major antiformal structure. The gold mineralization at the mine is commonly found associated with sulphides. The sulphide textures and compositions of mineralized and unmineralized samples of black shales, albitite sills and hydrothermal veins in the mine are considered for the understanding of the spatial association of gold with sulphides and gold mineralization history of the mine. The sulphides within the Twangiza mine consist of pyrite, arsenopyrite, pyrrhotite, chalcopyrite and rare cobaltite. The primary pyrite texture occurs in unmineralized black shale and is interpreted to be diagenetic. It consists of fine-grained anhedral pyrite crystals aggregating into spherical nodules and formed in replacement of organic material during the diagenesis process. The secondary pyrite textures resulted from the hydrothermal fluids activity and include (i) aggregates of annealed anhedral crystals into sulphide-rich lenses; (ii) elongated anhedral pyrite in the form of short stringers; (iii) fine-grained subhedral to euhedral pyrite randomly distributed within the rock matrix; (iv) euhedral zoned pyrite crystals occurring within veins; (v) aggregations of fine-grained anhedral pyrite, locally distributed in the matrix; (vi) abundant dissemination of fine-grained subhedral to anhedral pyrite crystals within the vein selvedge in the host rock; (vii) and coarse-grained massive pyrite bodies. The pyrite major elemental composition does not vary significantly in the different textures and sample types. The Fe content ranges from 44.57 to 46.40 wt. %, and the S content ranges from 53.75 to 55.25 wt. %. Pyrite from mineralized black shale and hydrothermal veins contains relatively higher concentrations of As (~ 1 wt. %) than pyrite from other sample types. The arsenopyrite commonly occurs as fine-grained anhedral crystals as inclusions within pyrite, medium-grained crystal intergrowing with pyrite and/or as coarse-grained massive arsenopyrite bodies in the massive sulphide veins. The arsenopyrite composition is uniform in all textural and sample type with Fe content ranging from 33.44 to 35.20 wt. %, S content ranging from 21.13 to 22.55 wt. % and As content ranging from 42.20 to 43.97 wt. %. In mineralized black shale and unmineralized black shale, the arsenopyrite shows, however, minor concentrations of Ni with 0.39 and 0.70 wt. % respectively. The pyrrhotite occurs as fine-grained anhedral patchy crystals randomly distributed within the rock matrix of unmineralized black shale and unmineralized granitoid, and / or as inclusions within pyrite in mineralized granitoid. The pyrrhotite shows a uniform composition in all samples and textural types, though minor concentrations of Ni (2.06 wt. %) content are reported in unmineralized granitoid. Chalcopyrite occurs as fine-grained crystals in inclusions within pyrite; and cobaltite occurs as rare fine-grained anhedral crystals occasionally disseminated in the albitite sill matrix. The chalcopyrite composition does not vary considerably in all sample and textural types, and cobaltite shows minor concentrations of Ni (4.55 wt. %) and Fe (3.45 wt. %). Native gold grains are commonly found associated with the secondary pyrite texture especially within the sulphide-rich lenses and in the massive sulphide veins, and are almost pure with ~97 wt. %. A Na-rich hydrothermal fluid from low-grade metamorphism associated with the E-W compressive tectonic event, which caused formation of the antiform structure which control the mineralization in the deposit area, led to the albitization of the deposit rocks and specially the alteration of the granitic assemblage to form albitite, and the deposition of aggregates of fine-grained anhedral crystals and growth and annealing of pyrite in sulphide-rich lenses. Afterward, the CO2-rich hydrothermal fluids influx circulated through reactivated structures, including quartz veins, and led to the precipitation of dolomite, ankerite, siderite and magnesite. They also led to the precipitation of pyrite of secondary textures as well as arsenopyrite, chalcopyrite and formation of pyrrhotite from the desulphurization of early pyrite. The CO2-rich hydrothermal fluids probably leached gold and other trace elements such as As, Co, etc. from the sedimentary host rocks and deposited them into suitable traps, such as the sulphide-rich lenses and massive sulphide bodies, preferably within the hinge zone of anticline axis constituting a hydrothermal fluid pathway.
- Full Text:
- Authors: Busane, Emmanuel Aganze
- Date: 2019
- Subjects: Gold mines and mining -- Congo (Democratic Republic) , Geology -- Congo (Democratic Republic) , Hydrothermal alteration -- Congo (Democratic Republic) , Sulphide minerals -- Congo (Democratic Republic) , Gold ores -- Geology -- Congo (Democratic Republic) , Geochemistry -- Congo (Democratic Republic) , Twangiza Mine (Congo (Democratic Republic))
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76588 , vital:30610
- Description: Twangiza mine is a gold deposit situated in the eastern Democratic Republic of Congo. The rock types at the Twangiza Mine consist of black shale, including carbonaceous mudstone and thin intercalated layers of siltstone, and feldspar-rich granitoid intrusive sills, referred to as albitite, folded into a major antiformal structure. The gold mineralization at the mine is commonly found associated with sulphides. The sulphide textures and compositions of mineralized and unmineralized samples of black shales, albitite sills and hydrothermal veins in the mine are considered for the understanding of the spatial association of gold with sulphides and gold mineralization history of the mine. The sulphides within the Twangiza mine consist of pyrite, arsenopyrite, pyrrhotite, chalcopyrite and rare cobaltite. The primary pyrite texture occurs in unmineralized black shale and is interpreted to be diagenetic. It consists of fine-grained anhedral pyrite crystals aggregating into spherical nodules and formed in replacement of organic material during the diagenesis process. The secondary pyrite textures resulted from the hydrothermal fluids activity and include (i) aggregates of annealed anhedral crystals into sulphide-rich lenses; (ii) elongated anhedral pyrite in the form of short stringers; (iii) fine-grained subhedral to euhedral pyrite randomly distributed within the rock matrix; (iv) euhedral zoned pyrite crystals occurring within veins; (v) aggregations of fine-grained anhedral pyrite, locally distributed in the matrix; (vi) abundant dissemination of fine-grained subhedral to anhedral pyrite crystals within the vein selvedge in the host rock; (vii) and coarse-grained massive pyrite bodies. The pyrite major elemental composition does not vary significantly in the different textures and sample types. The Fe content ranges from 44.57 to 46.40 wt. %, and the S content ranges from 53.75 to 55.25 wt. %. Pyrite from mineralized black shale and hydrothermal veins contains relatively higher concentrations of As (~ 1 wt. %) than pyrite from other sample types. The arsenopyrite commonly occurs as fine-grained anhedral crystals as inclusions within pyrite, medium-grained crystal intergrowing with pyrite and/or as coarse-grained massive arsenopyrite bodies in the massive sulphide veins. The arsenopyrite composition is uniform in all textural and sample type with Fe content ranging from 33.44 to 35.20 wt. %, S content ranging from 21.13 to 22.55 wt. % and As content ranging from 42.20 to 43.97 wt. %. In mineralized black shale and unmineralized black shale, the arsenopyrite shows, however, minor concentrations of Ni with 0.39 and 0.70 wt. % respectively. The pyrrhotite occurs as fine-grained anhedral patchy crystals randomly distributed within the rock matrix of unmineralized black shale and unmineralized granitoid, and / or as inclusions within pyrite in mineralized granitoid. The pyrrhotite shows a uniform composition in all samples and textural types, though minor concentrations of Ni (2.06 wt. %) content are reported in unmineralized granitoid. Chalcopyrite occurs as fine-grained crystals in inclusions within pyrite; and cobaltite occurs as rare fine-grained anhedral crystals occasionally disseminated in the albitite sill matrix. The chalcopyrite composition does not vary considerably in all sample and textural types, and cobaltite shows minor concentrations of Ni (4.55 wt. %) and Fe (3.45 wt. %). Native gold grains are commonly found associated with the secondary pyrite texture especially within the sulphide-rich lenses and in the massive sulphide veins, and are almost pure with ~97 wt. %. A Na-rich hydrothermal fluid from low-grade metamorphism associated with the E-W compressive tectonic event, which caused formation of the antiform structure which control the mineralization in the deposit area, led to the albitization of the deposit rocks and specially the alteration of the granitic assemblage to form albitite, and the deposition of aggregates of fine-grained anhedral crystals and growth and annealing of pyrite in sulphide-rich lenses. Afterward, the CO2-rich hydrothermal fluids influx circulated through reactivated structures, including quartz veins, and led to the precipitation of dolomite, ankerite, siderite and magnesite. They also led to the precipitation of pyrite of secondary textures as well as arsenopyrite, chalcopyrite and formation of pyrrhotite from the desulphurization of early pyrite. The CO2-rich hydrothermal fluids probably leached gold and other trace elements such as As, Co, etc. from the sedimentary host rocks and deposited them into suitable traps, such as the sulphide-rich lenses and massive sulphide bodies, preferably within the hinge zone of anticline axis constituting a hydrothermal fluid pathway.
- Full Text:
Syntheses and photophysico-chemical properties of phthalocyanines in the presence of silica nanoparticles
- Authors: Peteni, Siwaphiwe
- Date: 2019
- Subjects: Phthalocyanines , Silica , Nanoparticles , Bioconjugates
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67592 , vital:29118
- Description: This thesis reports on the syntheses and characterizationof symmetrical (charged and neutral), asymmetrical (neutral) metallophthalocyanines (MPcs) and subphthalocyanines (SubPcs). The charged and neutral Pcs were physically doped onto silica nanoparticles (SiNPs). The asymmetrical MPc was also chemically linked to SiNPs. Spectroscopic and microscopic techniques were used to confirm the formation of SiNPs-MPc conjugates. The photophysics and photochemistry of the MPcs were assessed when alone and in conjugates (with SiNPs). The studies showed no significant changes in fluorescence quantum yields (ϕF) and fluorescence lifetimes (ϕF) of MPcs following doping except for 2-SiNPs (2 = Zn tetraaminophenoxyphthalocyanines) and 6-SiNPs (doped) (6 = Zn tris[(4-(pyridine-4-ylthio)2-thio-4-methylthiazol-5yl) acetic acid phthalocyanine) where there was a decrease in the ϕF value. Also for 1-SiNPs (1 = unsubstituted ZnPc) there was an elongation in τF which could be due to the protection offered by SiNPs. Both charged/neutral MPcs displayed high triplet quantum yields (ϕT) and singlet quantum yields (ϕΔ) following doping except for 2-SiNPs where there was a decrease in the latter. For 1-SiNPs there was an increase in ϕT but a decrease inϕΔ .There wasa decrease in ϕT and an increase in ϕΔfor4-SiNPs (4 = Zn tetrasulfophenoxyphthalocyanine), the decrease in ϕT could be due to the orientation of theMPc in SiNPs. An increase in both ϕT and ϕΔ for 6-SiNPs (linked) compared to 6-SiNPs (doped) was observed. Complex 5 (5 = Zn tetra-kis-(dodecylmercapto) phthalocyanine) showed a low ϕΔ value.
- Full Text:
- Authors: Peteni, Siwaphiwe
- Date: 2019
- Subjects: Phthalocyanines , Silica , Nanoparticles , Bioconjugates
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67592 , vital:29118
- Description: This thesis reports on the syntheses and characterizationof symmetrical (charged and neutral), asymmetrical (neutral) metallophthalocyanines (MPcs) and subphthalocyanines (SubPcs). The charged and neutral Pcs were physically doped onto silica nanoparticles (SiNPs). The asymmetrical MPc was also chemically linked to SiNPs. Spectroscopic and microscopic techniques were used to confirm the formation of SiNPs-MPc conjugates. The photophysics and photochemistry of the MPcs were assessed when alone and in conjugates (with SiNPs). The studies showed no significant changes in fluorescence quantum yields (ϕF) and fluorescence lifetimes (ϕF) of MPcs following doping except for 2-SiNPs (2 = Zn tetraaminophenoxyphthalocyanines) and 6-SiNPs (doped) (6 = Zn tris[(4-(pyridine-4-ylthio)2-thio-4-methylthiazol-5yl) acetic acid phthalocyanine) where there was a decrease in the ϕF value. Also for 1-SiNPs (1 = unsubstituted ZnPc) there was an elongation in τF which could be due to the protection offered by SiNPs. Both charged/neutral MPcs displayed high triplet quantum yields (ϕT) and singlet quantum yields (ϕΔ) following doping except for 2-SiNPs where there was a decrease in the latter. For 1-SiNPs there was an increase in ϕT but a decrease inϕΔ .There wasa decrease in ϕT and an increase in ϕΔfor4-SiNPs (4 = Zn tetrasulfophenoxyphthalocyanine), the decrease in ϕT could be due to the orientation of theMPc in SiNPs. An increase in both ϕT and ϕΔ for 6-SiNPs (linked) compared to 6-SiNPs (doped) was observed. Complex 5 (5 = Zn tetra-kis-(dodecylmercapto) phthalocyanine) showed a low ϕΔ value.
- Full Text:
Synthesis and elaboration of critical realist methodology for green skills research
- Authors: Rosenberg, Eureta
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/436119 , vital:73228 , ISBN 9780429279362 , https://www.taylorfrancis.com/chapters/edit/10.4324/9780429279362-13/synthesis-elaboration-critical-realist-methodology-green-skills-research-eureta-rosenberg
- Description: In the concluding section of the book, this penultimate chapter elaborates on the central quest for research design that approaches green skills questions as inextricably linked to complex economic, environmental and social justice contexts that are systemic and emergent in nature, therefore necessitating a depth ontology and a dialectic approach, given the transformative intent of researching towards a more just and sustainable society. The chapter highlights methodological insights from the studies reviewed in this book, and provides guidance for green skills research design. It does so in relation to four interacting domains that research and programme planners need to consider in relation to each other. These are: the political-institutional context; theory and conceptual considerations; researchers’ personal-professional commitments; and the aligned methodological considerations. The meta-theory underlabouring the work in this book is Bhaskar’s dialectical critical realism, and its practical implications are illustrated and elaborated here with reference to the most pertinent features including lamination, systems, emergence, absence and associated approaches to analysis. The result is not a blueprint for a single research design, but considerations that could give rise to a variety of different designs for green skills research.
- Full Text:
- Authors: Rosenberg, Eureta
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/436119 , vital:73228 , ISBN 9780429279362 , https://www.taylorfrancis.com/chapters/edit/10.4324/9780429279362-13/synthesis-elaboration-critical-realist-methodology-green-skills-research-eureta-rosenberg
- Description: In the concluding section of the book, this penultimate chapter elaborates on the central quest for research design that approaches green skills questions as inextricably linked to complex economic, environmental and social justice contexts that are systemic and emergent in nature, therefore necessitating a depth ontology and a dialectic approach, given the transformative intent of researching towards a more just and sustainable society. The chapter highlights methodological insights from the studies reviewed in this book, and provides guidance for green skills research design. It does so in relation to four interacting domains that research and programme planners need to consider in relation to each other. These are: the political-institutional context; theory and conceptual considerations; researchers’ personal-professional commitments; and the aligned methodological considerations. The meta-theory underlabouring the work in this book is Bhaskar’s dialectical critical realism, and its practical implications are illustrated and elaborated here with reference to the most pertinent features including lamination, systems, emergence, absence and associated approaches to analysis. The result is not a blueprint for a single research design, but considerations that could give rise to a variety of different designs for green skills research.
- Full Text:
Synthesis and photophysicochemical properties of novel axially di-substituted silicon (IV) phthalocyanines and their photodynamic antimicrobial chemotherapy (PACT) activity against Staphylococcus aureus
- Sen, Pinar, Sindelo, Azole, Mafukidze, Donovan M, Nyokong, Tebello
- Authors: Sen, Pinar , Sindelo, Azole , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186757 , vital:44531 , xlink:href="https://doi.org/10.1016/j.synthmet.2019.116203"
- Description: In this study, novel silicon (IV) phthalocyanine axially di-substituted with benzimidazole moieties (3) and its quaternized derivative (4) have been synthesized and fully characterized. The photophysical and photochemical properties of both phthalocyanines such as absorption, fluorescence and, singlet oxygen quantum yields, triplet state quantum yields and exited state lifetimes were investigated in solutions. These new silicon phthalocyanines exhibited low fluorescence but produced high singlet oxygen yields in both DMSO (compound 3 and 4) and aqueous media (compound 4). The quaternization of Si(IV)Pc (3) improved the triplet state quantum yield (ΦT) 0.61 to 0.83, consequently singlet oxygen generation (ΦΔ) increased to 0.69 from 0.42. Photodynamic antimicrobial chemotherapy activities (PACT) of Si(IV)Pc photosensitizers were determined towards Staphylococcus aureus. The higher efficiency was obtained with cationic derivative (4) giving reduction percentage value of 99.75%.
- Full Text:
- Authors: Sen, Pinar , Sindelo, Azole , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186757 , vital:44531 , xlink:href="https://doi.org/10.1016/j.synthmet.2019.116203"
- Description: In this study, novel silicon (IV) phthalocyanine axially di-substituted with benzimidazole moieties (3) and its quaternized derivative (4) have been synthesized and fully characterized. The photophysical and photochemical properties of both phthalocyanines such as absorption, fluorescence and, singlet oxygen quantum yields, triplet state quantum yields and exited state lifetimes were investigated in solutions. These new silicon phthalocyanines exhibited low fluorescence but produced high singlet oxygen yields in both DMSO (compound 3 and 4) and aqueous media (compound 4). The quaternization of Si(IV)Pc (3) improved the triplet state quantum yield (ΦT) 0.61 to 0.83, consequently singlet oxygen generation (ΦΔ) increased to 0.69 from 0.42. Photodynamic antimicrobial chemotherapy activities (PACT) of Si(IV)Pc photosensitizers were determined towards Staphylococcus aureus. The higher efficiency was obtained with cationic derivative (4) giving reduction percentage value of 99.75%.
- Full Text:
Synthesis and properties of chiral amide-bonded porphyrin dimers with various functional bridging blocks
- Zhu, Weihua, Haider, Syed Najeeb-uz-Zaman, Zhang, Honglin, Attatsi, Isaac K, Mack, John, Dingiswayo, Somila, Nyokong, Tebello, Song, Yuting, Xu, Haijun, Liang, Xu
- Authors: Zhu, Weihua , Haider, Syed Najeeb-uz-Zaman , Zhang, Honglin , Attatsi, Isaac K , Mack, John , Dingiswayo, Somila , Nyokong, Tebello , Song, Yuting , Xu, Haijun , Liang, Xu
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186791 , vital:44534 , xlink:href="https://doi.org/10.1016/j.dyepig.2019.107740"
- Description: Eight porphyrin dimers with various functional bridging blocks and chiral amide-bonds were synthesized and characterized. An analysis of the spectroscopy and electrochemistry has been carried out to demonstrate that the chiral properties can be modified by changing the interchromophoric through-space coupling distance between the two porphyrin chromophores by introducing various bonding and bridging blocks.
- Full Text:
- Authors: Zhu, Weihua , Haider, Syed Najeeb-uz-Zaman , Zhang, Honglin , Attatsi, Isaac K , Mack, John , Dingiswayo, Somila , Nyokong, Tebello , Song, Yuting , Xu, Haijun , Liang, Xu
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186791 , vital:44534 , xlink:href="https://doi.org/10.1016/j.dyepig.2019.107740"
- Description: Eight porphyrin dimers with various functional bridging blocks and chiral amide-bonds were synthesized and characterized. An analysis of the spectroscopy and electrochemistry has been carried out to demonstrate that the chiral properties can be modified by changing the interchromophoric through-space coupling distance between the two porphyrin chromophores by introducing various bonding and bridging blocks.
- Full Text:
Synthesis of indium phthalocyanines for photodynamic antimicrobial chemotherapy and photo-oxidation of pollutants
- Authors: Sindelo, Azole
- Date: 2019
- Subjects: Phthalocyanines , Azo dyes , Indium compounds , Photochemotherapy , Nanoparticles , Photodegradation , Pollutants , Water -- Purification
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67581 , vital:29116
- Description: Indium (III) octacarboxyl phthalocyanine (ClInOCPc) alone and when conjugated to magnetic nanoparticles (MNP-ClInOCPc), 2(3),9(10),16(17),23(24)-octapyridylsulfanyl phthalocyaninato chloroindium (III) (ClInOPyPc) and its quaternized derivative 2(3),9(10),16(17),23(24)-octamethylpyridylsulfanyl phthalocyaninato chloroindium (III) (ClInOMePyPc) were synthesized. All Pcs were tested for both photodynamic antimicrobial chemotherapy (PACT) of an unknown water sample and photo-degradation of methyl red (MR). The singlet quantum yield (ΦΔ) for the ClInOCPc and MNP-ClInOCPc in PAN polymer fibers were 0.36 and 0.20 respectively using ADMA as a quencher in water. The photo-inactivation of bacteria in a water sample with unknown microbes was tested, with the MNP-ClInOCPc inactivating 90.6 % of the microbes and the ClInOCPc with 84.8 %. When embedded to the polymer, there was 48% bacterial clearance for ClInOCPc and 64% clearance for the MNP-ClInOCPc. The rate of degradation of MR increased with decrease of the MR concentration, with the MNP-ClInOCPc having the fastest rate. For ClInOPyPc and ClInOMePyPc, the singlet quantum yields were 0.46 and 0.33 in dimethylformamide (DMF), respectively. The PACT activity of ClInOMePyPc (containing 8 positive charges) was compared to those of 9(10),16(17),23(24)-tri-N-methyl-4-pyridylsulfanyl-2(3)-(4-aminophenoxy) phthalocyaninato chloro indium (III) triiodide (1) (containing 3 positive charges) and 2-[4-(N-methylpyridyloxy) phthalocyaninato] chloroindium (III) iodide (2) (containing 4 positive charges). When comparing ClInOMePyPc, 1 and 2, the largest log reduction for E. coli were obtained for complex 2 containing four positive charges hence showing it is not always the charge that determines the PACT activity, but the bridging atom in the phthalocyanine plays a role.
- Full Text:
- Authors: Sindelo, Azole
- Date: 2019
- Subjects: Phthalocyanines , Azo dyes , Indium compounds , Photochemotherapy , Nanoparticles , Photodegradation , Pollutants , Water -- Purification
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67581 , vital:29116
- Description: Indium (III) octacarboxyl phthalocyanine (ClInOCPc) alone and when conjugated to magnetic nanoparticles (MNP-ClInOCPc), 2(3),9(10),16(17),23(24)-octapyridylsulfanyl phthalocyaninato chloroindium (III) (ClInOPyPc) and its quaternized derivative 2(3),9(10),16(17),23(24)-octamethylpyridylsulfanyl phthalocyaninato chloroindium (III) (ClInOMePyPc) were synthesized. All Pcs were tested for both photodynamic antimicrobial chemotherapy (PACT) of an unknown water sample and photo-degradation of methyl red (MR). The singlet quantum yield (ΦΔ) for the ClInOCPc and MNP-ClInOCPc in PAN polymer fibers were 0.36 and 0.20 respectively using ADMA as a quencher in water. The photo-inactivation of bacteria in a water sample with unknown microbes was tested, with the MNP-ClInOCPc inactivating 90.6 % of the microbes and the ClInOCPc with 84.8 %. When embedded to the polymer, there was 48% bacterial clearance for ClInOCPc and 64% clearance for the MNP-ClInOCPc. The rate of degradation of MR increased with decrease of the MR concentration, with the MNP-ClInOCPc having the fastest rate. For ClInOPyPc and ClInOMePyPc, the singlet quantum yields were 0.46 and 0.33 in dimethylformamide (DMF), respectively. The PACT activity of ClInOMePyPc (containing 8 positive charges) was compared to those of 9(10),16(17),23(24)-tri-N-methyl-4-pyridylsulfanyl-2(3)-(4-aminophenoxy) phthalocyaninato chloro indium (III) triiodide (1) (containing 3 positive charges) and 2-[4-(N-methylpyridyloxy) phthalocyaninato] chloroindium (III) iodide (2) (containing 4 positive charges). When comparing ClInOMePyPc, 1 and 2, the largest log reduction for E. coli were obtained for complex 2 containing four positive charges hence showing it is not always the charge that determines the PACT activity, but the bridging atom in the phthalocyanine plays a role.
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Synthesis of N-Substituted phosphoramidic acid esters as “reverse” fosmidomycin analogues
- Adeyemi, Christiana M, Hoppe, Heinrich C, Isaacs, Michelle, Klein, Rosalyn, Lobb, Kevin A, Kaye, Perry T
- Authors: Adeyemi, Christiana M , Hoppe, Heinrich C , Isaacs, Michelle , Klein, Rosalyn , Lobb, Kevin A , Kaye, Perry T
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443238 , vital:74101 , https://doi.org/10.1016/j.tet.2019.02.003
- Description: An efficient synthetic pathway to a series of novel “reverse” fosmidomycin analogues has been developed, commencing from substituted benzylamines. In these analogues, the fosmidomycin hydroxamate moiety is reversed and the tetrahedral methylene carbon adjacent to the phosphonate moiety is replaced by a nitrogen atom bearing different benzyl groups. The resulting phosphonate esters were designed as potential antimalarial “pro-drugs”.
- Full Text:
- Authors: Adeyemi, Christiana M , Hoppe, Heinrich C , Isaacs, Michelle , Klein, Rosalyn , Lobb, Kevin A , Kaye, Perry T
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443238 , vital:74101 , https://doi.org/10.1016/j.tet.2019.02.003
- Description: An efficient synthetic pathway to a series of novel “reverse” fosmidomycin analogues has been developed, commencing from substituted benzylamines. In these analogues, the fosmidomycin hydroxamate moiety is reversed and the tetrahedral methylene carbon adjacent to the phosphonate moiety is replaced by a nitrogen atom bearing different benzyl groups. The resulting phosphonate esters were designed as potential antimalarial “pro-drugs”.
- Full Text:
Synthesis of N-Substituted phosphoramidic acid esters as “reverse” fosmidomycin analogues
- Adeyemi, Christiana M, Hoppe, Heinrich C, Isaacs, Michelle, Klein, Rosalyn, Lobb, Kevin A, Kaye, Perry T
- Authors: Adeyemi, Christiana M , Hoppe, Heinrich C , Isaacs, Michelle , Klein, Rosalyn , Lobb, Kevin A , Kaye, Perry T
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447196 , vital:74591 , xlink:href="https://doi.org/10.1016/j.tet.2019.02.003"
- Description: An efficient synthetic pathway to a series of novel “reverse” fosmidomycin analogues has been developed, commencing from substituted benzylamines. In these analogues, the fosmidomycin hydroxamate moiety is reversed and the tetrahedral methylene carbon adjacent to the phosphonate moiety is replaced by a nitrogen atom bearing different benzyl groups. The resulting phosphonate esters were designed as potential antimalarial “pro-drugs”.
- Full Text:
- Authors: Adeyemi, Christiana M , Hoppe, Heinrich C , Isaacs, Michelle , Klein, Rosalyn , Lobb, Kevin A , Kaye, Perry T
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447196 , vital:74591 , xlink:href="https://doi.org/10.1016/j.tet.2019.02.003"
- Description: An efficient synthetic pathway to a series of novel “reverse” fosmidomycin analogues has been developed, commencing from substituted benzylamines. In these analogues, the fosmidomycin hydroxamate moiety is reversed and the tetrahedral methylene carbon adjacent to the phosphonate moiety is replaced by a nitrogen atom bearing different benzyl groups. The resulting phosphonate esters were designed as potential antimalarial “pro-drugs”.
- Full Text:
Synthesis of pH responsive carriers for pulmonary drug delivery of anti-tuberculosis therapeutics: mesoporous silica nanoparticles and gelatin nanoparticles
- Authors: Ngoepe, Mpho Phehello
- Date: 2019
- Subjects: Drug delivery systems , Pulmonary pharmacology , Nanosilicon , Nanomedicine , Nanoparticles , Mesoporous materials , Silica , Tuberculosis -- Treatment
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/76519 , vital:30590
- Description: Pulmonary drug delivery has historically been used as a route for delivery of therapeutics for respiratory disease management. However, while there are many advantages, there are also some serious limitations, arising mostly from the physical aspects of the inhaler devices. This is more profound when the devices are the driving force for controlling particle size generation, which results in non-uniform particles that end up being swallowed/wasted/expelled. One promising solution to overcome this limitation is to pre-formulate nano/microscale particles with a high degree of manufacturing control. Nanomedicine has advanced such that there are already several nanoparticle formulations commercially available. In the case of tuberculosis treatment, there is an opportunity not only to examine the use of nanoparticles for inhalation therapy, but to take advantage of the fact that the physiochemical environment of diseased tissue is significantly different to health lung tissue (lower pH and increased enzyme concentrations). We formulated two series of nanoparticles, whose design included moieties that could respond to pH and enzymes. To address variability, a Box-Behnken statistical approach was followed to construct mesoporous silica nanoparticles. These “hard nanoparticles” can entrap both lipophilic and hydrophilic drugs and were coated with a pH-sensitive hydrazone linker. It was observed that pH, calcination temperature and ratio of water to silica source played the greatest role, not only in controlling the physicochemical properties of the nanoparticles but also the drug release rate. A second series of nanoparticles were synthesized based on gelatin. This was done partly to add support the comparison of hard (inorganic silica) versus soft, organic particles, but also to enable enzymatic degradation and drug release. Again, diseased lung tissue expresses increased concentrations of gelatinase enzymes that could be used to stimulate drug release at the site of the disease. In addition, it was observed that the non-ionic surfactant C12E10 could interact with the protein via hydrophobic interactions thus affecting the gelatin folding. The folding states affected crosslinking with the pH responsive linker, which in turn affected the rate of drug release. To support the synthetic work, we sought to develop a unique 3D lung model directly from MRI data of tuberculosis infected lungs. This would not only permit the evaluation of our nanoparticles but could be used as a proxy for in-vivo studies in future to predict lung deposition in diseased lung. Thus, this study shows that it is possible to synthesize pH and enzyme sensitive nanoparticles for pulmonary drug delivery in the treatment and management of pulmonary tuberculosis. These particles could be loaded with either hydrophobic or hydrophilic drugs and their distribution in the airway modelled using an in-silico 3D model based on real data. Further development and verification of these results should improve treatment for pulmonary diseases and conditions such as tuberculosis. This is especially urgent in the face of multi-drug resistance and poor side effects profiles for current treatment.
- Full Text:
- Authors: Ngoepe, Mpho Phehello
- Date: 2019
- Subjects: Drug delivery systems , Pulmonary pharmacology , Nanosilicon , Nanomedicine , Nanoparticles , Mesoporous materials , Silica , Tuberculosis -- Treatment
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/76519 , vital:30590
- Description: Pulmonary drug delivery has historically been used as a route for delivery of therapeutics for respiratory disease management. However, while there are many advantages, there are also some serious limitations, arising mostly from the physical aspects of the inhaler devices. This is more profound when the devices are the driving force for controlling particle size generation, which results in non-uniform particles that end up being swallowed/wasted/expelled. One promising solution to overcome this limitation is to pre-formulate nano/microscale particles with a high degree of manufacturing control. Nanomedicine has advanced such that there are already several nanoparticle formulations commercially available. In the case of tuberculosis treatment, there is an opportunity not only to examine the use of nanoparticles for inhalation therapy, but to take advantage of the fact that the physiochemical environment of diseased tissue is significantly different to health lung tissue (lower pH and increased enzyme concentrations). We formulated two series of nanoparticles, whose design included moieties that could respond to pH and enzymes. To address variability, a Box-Behnken statistical approach was followed to construct mesoporous silica nanoparticles. These “hard nanoparticles” can entrap both lipophilic and hydrophilic drugs and were coated with a pH-sensitive hydrazone linker. It was observed that pH, calcination temperature and ratio of water to silica source played the greatest role, not only in controlling the physicochemical properties of the nanoparticles but also the drug release rate. A second series of nanoparticles were synthesized based on gelatin. This was done partly to add support the comparison of hard (inorganic silica) versus soft, organic particles, but also to enable enzymatic degradation and drug release. Again, diseased lung tissue expresses increased concentrations of gelatinase enzymes that could be used to stimulate drug release at the site of the disease. In addition, it was observed that the non-ionic surfactant C12E10 could interact with the protein via hydrophobic interactions thus affecting the gelatin folding. The folding states affected crosslinking with the pH responsive linker, which in turn affected the rate of drug release. To support the synthetic work, we sought to develop a unique 3D lung model directly from MRI data of tuberculosis infected lungs. This would not only permit the evaluation of our nanoparticles but could be used as a proxy for in-vivo studies in future to predict lung deposition in diseased lung. Thus, this study shows that it is possible to synthesize pH and enzyme sensitive nanoparticles for pulmonary drug delivery in the treatment and management of pulmonary tuberculosis. These particles could be loaded with either hydrophobic or hydrophilic drugs and their distribution in the airway modelled using an in-silico 3D model based on real data. Further development and verification of these results should improve treatment for pulmonary diseases and conditions such as tuberculosis. This is especially urgent in the face of multi-drug resistance and poor side effects profiles for current treatment.
- Full Text:
Synthesis, characterisation and biological evaluation of novel anti-infective compounds bearing ferrocene, arylpyrrole, thiazolidinedione, quinoline and triazole moieties
- Authors: Oderinlo, Ogunyemi Olajide
- Date: 2019
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/114714 , vital:34016 , 10.21504/10962/114714
- Description: Expected release date-April 2022
- Full Text: false
- Authors: Oderinlo, Ogunyemi Olajide
- Date: 2019
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/114714 , vital:34016 , 10.21504/10962/114714
- Description: Expected release date-April 2022
- Full Text: false
Synthesis, characterisation and spectroscopic studies of diazine-N-oxide complexes of iron(II) towards the development of sensors
- Authors: Mpiti, Unako Bongani
- Date: 2019
- Subjects: Diazines , Ligands , Iron
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94753 , vital:31075
- Description: The characteristic magnetic and spectroscopic features associated with the red monomeric or dimeric, and polymeric pyrazine-N-oxide (PyzNO) iron(II) perchlorate complexes; Fen(μ1,1-pyzNO)2n-2(pyzNO)3n+2(ClO4)2n (n = {1, 2}*, and the novel compound {Fe(μ-pyzNO-κN,κO)n-1(pyzNO-κN)2(pyzNO-κO)2}n(ClO4)2n†, respectively, were investigated. These properties are altered substantially when the complexes are hydrated; for instance, by atmospheric exposure. The resulting species; Fe(pyzNO)5(H2O)3(ClO4)2* and [Fe(pyzNO-κN)4(H2O)2](ClO4)2.2H2O†, which have different hues of a bright yellow colour, were found to exhibit strong paramagnetism, in contrast to their anhydrous precursors, which are ‘EPR silent’. A low spin → high spin crossover (LS→HS, SCO) transition was therefore proposed to occur as the complexes become hydrated by atmospheric moisture. The red→yellow colour change is reversible, and dehydration of the yellow species by heating regenerates the red variant, a feature which lends itself to the potential applicability of the system as a sensor. Further emphasis on this potential derives from the fact that the hydration/dehydration process, and its accompanying physical changes, appears reversible even after many such treatments. It became of interest, then, to determine if these changes were limited to water-exposed samples, or if they occurred under more diverse solvent atmospheres. The reversibility of such exposure on the structure of the novel polynuclear complex was therefore investigated. In general, it was found that there occurred a strong solvent-complex association for the more polar solvents. Red→yellow, LS→HS events were seen when the complex was exposed to the vapours of p-dioxane, acetaldehyde and formaldehyde, and to a lesser extent, to that of methanol. In each case, significant structural changes were seen, as evidenced be comparative XRPD and thermo-analytical studies. Some of these changes have however been ascribed to the effects of partial dissolution upon extended exposure of the complex to the associated media. Exposure to less polar solvent atmospheres, such as those of cyclohexane, toluene, diethyl ether, etc., showed some signs of mild solvent surface adhesion, but were unaccompanied by discernible magnetic and colour changes. Another novel complex was produced during attempts to synthesize the PyzNO complexes from a mixture of a 2,2’-dimethoxypropane (DMP) and ethanol (1:1, v/v), rather than the methanol/DMP mixture which had been alternately used. The formula of the resulting complex is Fe(pyzNO)6(ClO4)2.3EtOH*. This EPR inactive product was orange in colour, and transformed into a bright yellow, strongly paramagnetic species upon atmospheric exposure. Further solvent studies showed that this species interacted significantly with all solvents tested, but generally more strongly with increasing solvent polarity. Orange→yellow colour changes occurred in environments saturated with p-dioxane, acetaldehyde and formaldehyde vapours. The DMSO-exposed sample transformed to dark red, due to suspected PyzNO substitution by the solvent. The red→yellow and orange→yellow colour changes were ascribed to the formal substitution of O-coordinated PyzNO (μ-PyzNO in the polymeric complex) by the incoming solvent. The resulting structural and geometric changes stimulated a redistribution of d electrons among the new constituent molecular orbitals of altered energy and symmetry. Therefore, although the colour changes were not conventionally solvatochromic - in that the original structure was lost on exposure – data suggested that it was the coordination of species of higher donor strength that produced the observed bathochromic shifts. A novel 4,4’-bipyridine-N-oxide Fe(II) perchlorate complex, Fe2(bipyNO)5(ClO4)4.6MeOH†, was also produced, primarily for physicochemical comparison with the PyzNO complexes. No colour or magnetic changes were seen on atmospheric exposure. The original complex was observed to be inherently paramagnetic, and no SCO events occurred upon solvent exposure. Despite this, thermal analyses showed that the complex did exhibit the strong uptake of polar solvents in general, but particularly with acetaldehyde. Significant structural changes upon exposure were limited to surface phenomena, with the exception of the acetaldehyde-exposed sample.
- Full Text:
- Authors: Mpiti, Unako Bongani
- Date: 2019
- Subjects: Diazines , Ligands , Iron
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94753 , vital:31075
- Description: The characteristic magnetic and spectroscopic features associated with the red monomeric or dimeric, and polymeric pyrazine-N-oxide (PyzNO) iron(II) perchlorate complexes; Fen(μ1,1-pyzNO)2n-2(pyzNO)3n+2(ClO4)2n (n = {1, 2}*, and the novel compound {Fe(μ-pyzNO-κN,κO)n-1(pyzNO-κN)2(pyzNO-κO)2}n(ClO4)2n†, respectively, were investigated. These properties are altered substantially when the complexes are hydrated; for instance, by atmospheric exposure. The resulting species; Fe(pyzNO)5(H2O)3(ClO4)2* and [Fe(pyzNO-κN)4(H2O)2](ClO4)2.2H2O†, which have different hues of a bright yellow colour, were found to exhibit strong paramagnetism, in contrast to their anhydrous precursors, which are ‘EPR silent’. A low spin → high spin crossover (LS→HS, SCO) transition was therefore proposed to occur as the complexes become hydrated by atmospheric moisture. The red→yellow colour change is reversible, and dehydration of the yellow species by heating regenerates the red variant, a feature which lends itself to the potential applicability of the system as a sensor. Further emphasis on this potential derives from the fact that the hydration/dehydration process, and its accompanying physical changes, appears reversible even after many such treatments. It became of interest, then, to determine if these changes were limited to water-exposed samples, or if they occurred under more diverse solvent atmospheres. The reversibility of such exposure on the structure of the novel polynuclear complex was therefore investigated. In general, it was found that there occurred a strong solvent-complex association for the more polar solvents. Red→yellow, LS→HS events were seen when the complex was exposed to the vapours of p-dioxane, acetaldehyde and formaldehyde, and to a lesser extent, to that of methanol. In each case, significant structural changes were seen, as evidenced be comparative XRPD and thermo-analytical studies. Some of these changes have however been ascribed to the effects of partial dissolution upon extended exposure of the complex to the associated media. Exposure to less polar solvent atmospheres, such as those of cyclohexane, toluene, diethyl ether, etc., showed some signs of mild solvent surface adhesion, but were unaccompanied by discernible magnetic and colour changes. Another novel complex was produced during attempts to synthesize the PyzNO complexes from a mixture of a 2,2’-dimethoxypropane (DMP) and ethanol (1:1, v/v), rather than the methanol/DMP mixture which had been alternately used. The formula of the resulting complex is Fe(pyzNO)6(ClO4)2.3EtOH*. This EPR inactive product was orange in colour, and transformed into a bright yellow, strongly paramagnetic species upon atmospheric exposure. Further solvent studies showed that this species interacted significantly with all solvents tested, but generally more strongly with increasing solvent polarity. Orange→yellow colour changes occurred in environments saturated with p-dioxane, acetaldehyde and formaldehyde vapours. The DMSO-exposed sample transformed to dark red, due to suspected PyzNO substitution by the solvent. The red→yellow and orange→yellow colour changes were ascribed to the formal substitution of O-coordinated PyzNO (μ-PyzNO in the polymeric complex) by the incoming solvent. The resulting structural and geometric changes stimulated a redistribution of d electrons among the new constituent molecular orbitals of altered energy and symmetry. Therefore, although the colour changes were not conventionally solvatochromic - in that the original structure was lost on exposure – data suggested that it was the coordination of species of higher donor strength that produced the observed bathochromic shifts. A novel 4,4’-bipyridine-N-oxide Fe(II) perchlorate complex, Fe2(bipyNO)5(ClO4)4.6MeOH†, was also produced, primarily for physicochemical comparison with the PyzNO complexes. No colour or magnetic changes were seen on atmospheric exposure. The original complex was observed to be inherently paramagnetic, and no SCO events occurred upon solvent exposure. Despite this, thermal analyses showed that the complex did exhibit the strong uptake of polar solvents in general, but particularly with acetaldehyde. Significant structural changes upon exposure were limited to surface phenomena, with the exception of the acetaldehyde-exposed sample.
- Full Text: