Enhanced nonlinear optical response of benzothiazole substituted ball-type phthalocyanines in the presence of metallic nanoparticles
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188149 , vital:44727 , xlink:href="https://doi.org/10.1016/j.optmat.2018.05.052"
- Description: The synthesis of zinc-zinc, gallium-gallium and indium-indium ball-type phthalocyanines (complexes 4, 5 and 6) and the surface assembly of the complexes onto metallic gold and silver nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical dynamics were investigated. Decreases in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to complexes 4, 5 and 6 alone were observed. The mechanism of strong reverse saturable absorption observed was found to be predominantly dependent on excited state absorption. The optical limiting thresholds range from 0.09 to 0.19 J/cm2. Enhanced triplet parameters and nonlinear optical responses were found when the complexes were conjugated to metallic nanoparticles.
- Full Text:
- Date Issued: 2018
Enhanced nonlinear optical response of benzothiazole substituted ball-type phthalocyanines in the presence of metallic nanoparticles
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187719 , vital:44690 , xlink:href="https://doi.org/10.1016/j.optmat.2018.05.052"
- Description: The synthesis of zinc-zinc, gallium-gallium and indium-indium ball-type phthalocyanines (complexes 4, 5 and 6) and the surface assembly of the complexes onto metallic gold and silver nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical dynamics were investigated. Decreases in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to complexes 4, 5 and 6 alone were observed. The mechanism of strong reverse saturable absorption observed was found to be predominantly dependent on excited state absorption. The optical limiting thresholds range from 0.09 to 0.19 J/cm2. Enhanced triplet parameters and nonlinear optical responses were found when the complexes were conjugated to metallic nanoparticles.
- Full Text:
- Date Issued: 2018
Nonlinear optical dynamics of benzothiazole derivatized phthalocyanines in solution, thin films and when conjugated to nanoparticles
- Authors: Nwaji, Njemuwa , Jones, Benjamin , Mack, John , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190426 , vital:44993 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.05.042"
- Description: Benzothiazole phthalocynines complexes: tetrakis[(benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] indium(III) chloride (1) and tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] indium(III) chloride (2) were synthesisized and their nanosecond nonlinear optical behaviours in solution, solid state and when conjugated to metallic nanoparticles were examined and compared to those of the corresponding ZnPc and GaPc which are designated as: tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] zinc(II) (3), tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5) and tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6). Trends in the electronic structures were identified through a comparison of the UV–vis absorption and magnetic circular dichroism (MCD) spectroscopy of the complexes and calculated spectra predicted by time dependent density functional theory (TD-DFT). Of all the complexes and nanoconjugates, complex 2 (containing sulphur linkages and In as a central metal) gave the best optical limiting behaviour.
- Full Text:
- Date Issued: 2017
Synthesis, photophysical and nonlinear optical properties of a series of ball-type phthalocyanines in solution and thin films
- Authors: Nwaji, Njemuwa , Mack, John , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188976 , vital:44803 , xlink:href="https://doi.org/10.1039/C6NJ03662G"
- Description: In this study, we report on the enhanced nonlinear optical properties of novel tetrakis-4-(hexadecane-1,2-dioxyl)-bis(phthalocyaninato zinc(II)) (4), tetrakis-4-(hexadecane-1,2-dioxyl)-bis(phthalocyaninato gallium chloride) (5) and tetrakis-4-(hexadecane-1,2-dioxyl)-bis(phthalocyaninato indium chloride) (6) both in solution and when embedded in polymer thin films. Complexes 5 and 6 bearing heavy atoms showed enhanced triplet quantum yield and nonlinear optical response. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. Time dependent density functional theory (TD-DFT) calculations were performed in order to explain the origin of the observed UV-vis and magnetic circular dichroism (MCD) spectra of the complexes.
- Full Text:
- Date Issued: 2017
Photophysical and strong optical limiting properties of ball-type phthalocyanines dimers and their monomeric analogues
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187930 , vital:44711 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.10.045"
- Description: The nonlinear optical behaviors of ball-type phthalocyanine complexes: 1′,11,’15′,25′-tetrakis-[4,4′-((4-formyl-1,2-bisphenoxyl))bis(phthalocyaninato zinc (II)] (5), 1′,11,’15′,25′-tetrakis-[4,4′-((4-formyl-1,2-bisphenoxyl) bis(phthalocyaninato gallium (III) chloride)] (6), and 1′, 11,’15′,25′-tetrakis-4,4′-((4-formyl-1,2-phenoxyl)bis(phthalocyaninato indium (III) chloride)] (7) and the corresponding monomeric derivatives 8–10 were investigated using nanosecond pulse open aperture Z-scan technique at 532 nm. The nonlinear response showed strong reverse saturable absorption for all the complexes both in solution and when embedded in polymer matrix. The dimeric complexes showed better optical limiting properties compared to the monomeric derivatives. The βeff values for the dimeric complexes 5–7 were found to be 48.5, 55.2, and 60.1 cm/GW for 5, 6A, and 7 respectively, higher than the corresponding monomeric derivatives 8–10. Enhanced optical limiting properties were observed when the complexes were formulated in thin films. The second order hyperpolarizability values were in order of 10−28–10−26 esu in solution and 10−27–10−26 in films.
- Full Text:
- Date Issued: 2018
Photophysical and nonlinear optical study of benzothiazole substituted phthalocyanines in solution and thin films
- Authors: Nwaji, Njemuwa , Bankole, Owolabi M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233088 , vital:50055 , xlink:href="https://doi.org/10.1142/S1088424617500079"
- Description: In this study, the photophysical, nonlinear absorption and nonlinear optical limiting properties of zinc and gallium phthalocyanine complexes: tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato]zinc(II) (3), tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6), were investigated both in solution and when embedded in polystyrene thin films using 532 nm laser excitation at 10 ns pulses. It was also observed that complexes that have higher triplet state absorption also possessed enhanced nonlinear and optical limiting behavior. Superior optical performance was observed when the complexes were embedded in thin films compared to when they are in solution. Complex 6 in thin films gave the highest imaginary third-order susceptibility (Imm[X(3)(3)]) and hyperpolarizability (γ)γ) at 4.61 × 10-7-7 esu and 3.44 × 10-26-26 esu, respectively, with a low Ilimlim value of 0.06 J.cm-2.
- Full Text:
- Date Issued: 2017
4-Bis (4-aminophenoxy) phenoxy derivitized phthalocyanine conjugated to metallic nanoparticles
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188965 , vital:44802 , xlink:href="https://doi.org/10.1039/C7NJ02718D"
- Description: In this study, the photophysical, nonlinear absorption and nonlinear optical limiting properties of 4-(2,4-bis(4-aminophenoxy)phenoxy) phthalocyinato zinc(II) phthalocyanine (6) conjugated to metallic nanoparticles have been investigated using open aperture Z-scan techniques using 532 nm nanosecond pulses. The nonlinear optical response demonstrated that the studied complex and the nanoconjugates exhibit higher excited state absorption cross-section compared to ground state absorption. Enhanced optical limiting performance was observed when complex 6 was conjugated to nanoparticles with 6CB-AuNPs (CB = covalent bond) showing the highest optical limiting threshold of 0.36 J cm−2.
- Full Text:
- Date Issued: 2017
Nanosecond optical nonlinearities in low symmetry phthalocyanine nanoconjugates studied using the Z-scan technique
- Authors: Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188172 , vital:44729 , xlink:href="https://doi.org/10.1016/j.jlumin.2017.08.053"
- Description: In this study, the photophysical, and nonlinear optical limiting properties of low symmetry tris[(4-benzo[d] thiazol-2-ylphenoxy)-2-phenoxyl acetic acid phthalocyaninato] zinc (II) (3) conjugated to metallic nanoparticles have been investigated using open aperture Z-scan techniques at 532 nm. The nonlinear optical response demonstrated that the studied complex and the nanoconjugates exhibits higher excited state absorption cross-section resulting from S1 and T1 compared to ground state absorption. Enhanced optical limiting performance was observed when the complex was conjugated to nanoparticles with 3SA-AuNPs showing the best optical limiting threshold of 0.39 J/cm2.
- Full Text:
- Date Issued: 2017
Photophysical and enhanced nonlinear optical response in asymmetric benzothiazole substituted phthalocyanine covalently linked to semiconductor quantum dots
- Authors: Nwaji, Njemuwa , Dingiswayo, Somila , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187851 , vital:44703 , xlink:href="https://doi.org/10.1016/j.saa.2018.06.098"
- Description: The synthesis of asymmetric benzothiazole substituted phthalocyanines (complexes 3 to 5) and their covalent attachment to glutathione (GSH) functionalized quantum dots (QDs) are reported in this work. Additionally, their photophysical and nonlinear optical properties were investigated. A decrease in the fluorescence quantum yield with corresponding increase in the triplet quantum yield was observed when the complexes were covalently linked to glutathione (GSH) functionalized cadmium telluride (CdTe) quantum dots. Reverse saturable absorption was found to be predominantly dominated by excited state absorption. The observed limiting threshold values range from 0.29–0.75 J/cm2.
- Full Text:
- Date Issued: 2019
Nonlinear optical responses of targeted phthalocyanines when conjugated with nanomaterials or fabricated into polymer thin films
- Authors: Nwaji, Njemuwa Njoku
- Date: 2019
- Subjects: Electrochemistry , Phthalocyanines , Nanoparticles , Bioconjugates , Thin films , Polymers , Nonlinear optics , Nonlinear optical spectroscopy , Nanostructured materials , Raman effect
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/71625 , vital:29926
- Description: A number of zinc, gallium and indium metallophthalocyanines (MPcs) with diverse substituents have been synthesized and characterized using various characterization tools such as proton nuclear magnetic resonance (1HNMR), matrix assisted laser desorption time of flight (MALDI-TOF) mass spectrometry, Fourier-transformed infra-red (FT-IR), Ultraviolet-visible (Uv-vis) spectrophotometry, magnetic circular dichroism and CHNS elemental analysis. The time dependent density functional theory was employed to probe the origin of spectroscopic information in these complexes. Complexes with gallium and indium as central metal showed higher triplet quantum yield compared to the zinc derivatives. Some of the MPcs were covalently linked to nanomaterials such as CdTe, CdTeSe, CdTeSe/ZnO, graphene quantum dots (GQDs) as well as metallic gold (AuNPs) and silver (AgNPs) nanoparticles. Others were either surface assembled onto AuNPs and AgNPs or embedded into polystyrene as polymer source. The phthalocyanine-nanomaterial composites (Pc-NMCs) were characterized with FT-IR, UV-visible spectrophotometry, transmission electron microscopy (TEM), dynamic light scattering (DLS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD). The thickness of the thin films was determined by utilization of the knife edge attachment of the A Bruker D8 Discover X-ray diffraction. The optical limiting properties (using the open-aperture Z-scan technique) of the MPcs and the Pc-NMCs were investigated. The investigated MPcs complexes generally showed good optical limiting properties. The nonlinear optical response of the MPcs were improved in the presence of nanomaterials such as the semiconductor quantum dots (SQDs), graphene quantum dots (GQDs) as well as metallic AuNPs and AgNPs with MPc-QDs showing the best optical limiting behavior. The optical limiting properties of the MPcs were greatly enhanced in the presence of polymer thin films.
- Full Text:
- Date Issued: 2019
Gulende, gulende
- Authors: Nwatamula Machatini , performer not specified , Tracey, Hugh
- Date: 1949
- Subjects: Folk Music , Field recordings , Africa, Sub-Saharan , Africa Mozambique city not specified f-mz
- Language: Chopi
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/360647 , vital:65110 , International Library of African Music, Rhodes University, Makhanda, South Africa , Hugh Tracey Commercial Records, Rhodes University, Makhanda, South Africa , AC0066-CM17
- Description: Indigenous music
- Full Text: false
- Date Issued: 1949
Social entrepreneurship and development in Nelson Mandela Bay Municipality
- Authors: Nwauche, Sokeibelemaye
- Date: 2017
- Subjects: Social entrepreneurship -- South Africa -- Nelson Mandela Bay Municipality Entrepreneurship -- South Africa -- Nelson Mandela Bay Municipality , Economic development -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/19817 , vital:28976
- Description: Focusing on the policy context for social entrepreneurship in Nelson Mandela Bay Municipality (NMBM), this dissertation examines the processes through which social entrepreneurs participate in the processes of development of the municipality because; social entrepreneurship is increasingly being recognised as a mechanism for creating social and economic value. Social entrepreneurs play a significant role in fulfilling unmet societal needs and in filling gaps, particularly in areas where government and the market fall short. Based on this view, this study raises questions about the integrated policy guiding social entrepreneurship for better development outcomes. It aims to contribute to the body of literature on social entrepreneurship and development by examining the processes through which social entrepreneurs participate in the development of the communities at the local level. Using the Grounded Theory method, this study found that there is no integrated policy on social entrepreneurship in the NMBM and that the deficiency created by the lack of an integrated policy engenders Social Revisioning. The substantive theory of Social Revisioning emerged from the data to explain the processes through which social entrepreneurs participate in the development of communities when there is no integrated policy on social entrepreneurship. In response to the deficiencies in the policy context, differentiated and autonomous entities within and outside of the municipal government step in and support social entrepreneurs to provide services and participate in the processes of development. However, even though Social Revisioning can be used to address the policy deficiencies in social entrepreneurship and development, the differentiations and autonomy that characterise the entities, role players and processes embodied in Social Revisioning prevent cohesion among them and again beg for an integrated policy that will incorporate them.
- Full Text:
- Date Issued: 2017
A framework to integrate social entrepreneurship into development planning in South Africa
- Authors: Nwauche, Sokeibelemaye
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52982 , vital:44881
- Description: The thesis presents a framework to integrate social entrepreneurship (SE) into development planning in South Africa. Even though there is no consensus on a universally accepted definition of the term, there is concurrence that SE brings about social change that can influence the overall development of the community. In South Africa, SE is thus conceived of as one of the mechanisms for addressing the wicked and persistent socio-economic challenges that face the country. Social entrepreneurship occurs in areas such as education, health, skills development, youth programmes, rehabilitation, safety, food security, poverty, job creation, human rights activism, environmental issues, arts and culture, among others. However, it remains unclear how SE is integrated into the development planning and implementation processes. Questions of integrating SE into development planning are asked within the context of South Africa as a democratic developmental state that intervenes in the development process. It emphasises the mobilization of and engagement with all sectors towards the achievement of its development objectives as articulated in the national development plan (NDP). Also, government recognizes organizations in the social enterprise sector (such as NPOs and NPCs) as stakeholders and development partners who deliver relevant services towards the achievement of these development objectives. However, there is a lack of framework to mobilize and integrate the social enterprise sector and SE into the development planning process. Social entrepreneurship, therefore, tends to occur in insolation from other development programmes. , Thesis (PhD) -- Faculty of Business and Economic Sciences, School of Economics, Development and Tourism, 2021
- Full Text: false
- Date Issued: 2021-04
Design and Characterization of a 5 kw Xe-Lamp Solar Simulator
- Authors: Nwodo, Julian Chizoba
- Date: 2019
- Subjects: Solar energy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14671 , vital:40042
- Description: The design and characterisation of a 5kW Xenon lamp solar simulator is presented. This was accomplished through considering the design features of an ellipsoidal reflector, Xe lamp characteristics and casing, and power supply; assembly of an ellipsoidal, Xe-lamp simulator; design and building of an automated control system capable of remotely controlling the operating mode of the simulator; establishing the 3 scenarios that must be met to conform to a AAA class simulator; characterization of the simulator in terms of temporal stability, irradiance uniformity and spectral match; and application of the simulator and comparing it with STC rated values. The considerations for the type of material used for housing the components of the solar simulator were made. A 5kW DC power supply and igniter for the Xe-lamp was carefully selected since they provide necessary power for running the simulator. The simulator has the ability to be used in either horizontal or vertical position by adjusting the reflector. An automated control system capable of remotely controlling the operating mode of the simulator was built for this study, this system enables the simulator to be operated in either auto or manual modes. It also incorporates an irradiance, temperature, current and voltage feedback. The characterisation of the solar simulator was over a 2.1 m X 1.6 m test plane. The area under which the characterisation was carried out within the test plane is 110 cm x 129.5 cm. At the end of the steady state large area solar simulator characterisation, a class A spectral match, class A spatial uniformity, and a class B temporal instability was obtained
- Full Text:
- Date Issued: 2019
Rights as trumps in African communitarian ethics
- Authors: Nwogbo, Johnbosco
- Date: 2017
- Subjects: Communitarianism Human rights Social values
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10353/12282 , vital:39249
- Description: The notion of rights is among the most basic ideas of contemporary political philosophy on the continent and elsewhere. Although rights are common-place in political philosophy it is fair to say that the discussion around it has been nothing short of contested. On the whole, there have been two kinds of questions to which most of the discussion about rights in political philosophy have been answers, namely, (i) what are rights?, and (ii) to what do people have rights? The first has to do with the nature of rights, while the second has to the nature of that to which people may be said to have rights. This research falls neatly within the parlance of the first kind of questions (i.e., the question of what rights are). Specifically, in this research, I am concerned with the question of whether the radical and moderate African communitarian rights theses of Ifeanyi Menkiti and Kwame Gyekye measure up to what rights are commonly understood to be. I argue that if rights are trumps, which override competing societal and communal considerations, then Menkiti’s and Gyekye’s theories of rights fall short of this fairly standard and typical conception of rights.
- Full Text:
- Date Issued: 2017
The Moderating Influence of Psychological Empowerment in the relationship between Job Insecurity and Organizational Citizenship Behaviour among the Eastern Cape Department of Health Employees
- Authors: Nwokolo, Echezona E
- Date: 2019
- Subjects: Job security -- South Africa -- Eastern Cape Organizational commitment Employee assistance programs
- Language: English
- Type: Thesis , Doctoral , D.Com (Industrial Psychology)
- Identifier: http://hdl.handle.net/10353/13881 , vital:39722
- Description: The unabated focus of many organizations on competition and profitability has amplified the threats of real or anticipated job loss resulting in the feelings of insecurity for employees about their job and future work life. The research investigated the role of psychological empowerment as moderator of the relationship between job insecurity and organizational citizenship behavior among the Eastern Cape Department of Health employees, in Eastern Cape Province of South Africa. The study adopted an exploratory and correlational research design to understand the relationships that exist between the study variables. Respondents were selected using convenience sampling technique, where a sample size of 357 respondents was selected from sample frame of 4847 employees. Seven-point and Five-point likert scale were used to measure the responses. The data analysis methods used include descriptive statistics, regression analysis, ANOVA and Structural Equation Modeling. The reliability, factor analysis and research hypotheses of the research instruments were tested using the aforementioned statistical techniques. The findings reveal a significant negative correlation between job insecurity and Organizational Citizenship Behaviour, a significant positive correlation between psychological empowerment and OCB. It also revealed that job insecurity and psychological empowerment combined account for a significant higher proportion of variance in OCB than any of the two separately, and that significantly and positively moderates the relationship between job insecurity and OCB. Recommendations to promote psychological empowerment in the organization in order to increase organizational citizenship behavior and decrease job insecurity among employees were suggested to leadership of the government departments, organizations and practicing managers.
- Full Text:
- Date Issued: 2019
Classification of Distinct Fuzzy Subgroups of the Dihedral Group Dp nq for p and q distinct primes and n ∈ N
- Authors: Nxala, Baphumelele Ellen
- Date: 2018
- Subjects: Fuzzy mathematics Fuzzy sets
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14516 , vital:39997
- Description: In this dissertation, we classify distinct fuzzy subgroups of the dihedral group Dpnq, for p and q distinct primes and n ∈ N, under a natural equivalence relation of fuzzy subgroups and a fuzzy isomorphism. We aim to present formulae for the number of maximal chains and the number of distinct fuzzy subgroups of this group. Our study will include some theory on non-abelian groups since the classification of distinct fuzzy subgroups of this group relies on the crisp characterization of maximal chains. We give the definition of a natural equivalence relation introduced by Murali and Makamba in [67] which we will use in this study. Based on this definition, we introduce two counting techniques that we will use to compute the number of distinct fuzzy subgroups of Dpnq. In this dissertation, we use the criss-cut counting technique as our primary method of enumeration, and the cross-cut method serves as a means of verifying results we obtain from our primary method. To classify distinct fuzzy subgroups of this group, we begin by investigating the dihedral groups Dpnq, for p and q distinct primes and specific values of n = 2 and 3 to observe a trend. We classify the flags of these groups using the characterization of flags introduced in [93]. From this characterization, we then present formulae for the number of distinct fuzzy subgroups attributed to the flags of Dp 2q and Dp 3q . To generalise results for Dpnq, for p and q distinct primes and n ∈ N, we characterize the flags of this group and classify them as either cyclic, mdcyclic for 1 ≤ m ≤ n, or b-cyclic. Finally, we establish a general formula for the number of distinct fuzzy subgroups obtainable from these flags. We conclude by comparing results obtained from using our general formula to those obtained by other researchers for the same group. Based on the results from this study, we give an outline of future research work
- Full Text:
- Date Issued: 2018
A study of the southwestern Karoo basin in South Africa using magnetic and gravity data
- Authors: Nxantsiya, Zusakhe
- Date: 2017
- Subjects: Groundwater -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14043 , vital:39800
- Description: The early efforts of Booth, Johnson, Rubidge, Catuneanu, de Wit, Chevallier, Stankiewicz, Weckmann and many other scientists in studying the Karoo Supergroup has led to comprehensive documentation of the geology on the main Karoo Basin with regards to understanding the age, sedimentology, sedimentary facies and depositional environments. In spite of these studies, the subsurface structure, variations in thickness of various formations in large parts of the basin, the location and orientation of subsurface dolerite intrusions, and the depth to magnetic and gravity sources remains poorly documented. A geological study with the aid of geophysical techniques, magnetic and gravity, was conducted in the southwestern part of the main Karoo Basin. The objectives of the study were to construct numerous models of the main basin that image the crust to a depth of 45 km, to determine thicknesses of various formations, to relate observed geophysical anomalies with geological bodies and lineaments, to estimate the depth of existing anomalous bodies, to determine densities and porosity of various formations, as well as to determine the mineralogy of various rocks in the Karoo Basin. In total, seventy one rock samples were collected in the main Karoo Basin for density and mineralogical studies. The density results showed that the Beaufort and Ecca Group rocks have the low mean density of 2.490 g/cm3 amongst the rocks while the dolerite intrusions have the highest mean density of 2.697 g/cm3. The porosities of various rocks determined from the measured rock densities revealed that the Ecca Group shales, particularly the Whitehill Formation has the highest porosity of 4.5percent, while the Collingham Formation has the least porosity of 1.4 percent amongst the Ecca Group shales. Mineralogical analysis of seventeen XRD samples and 26 thin sections indicate that quartz, kaolinite, and plagioclase occur as the major mineral in most sandstones and shales in the Karoo Basin, while the pyrophyllite, smectite, and talc occur as minor minerals. Other mineral constituents include, calcite, mica, and amphibole. The 2½ dimensional (2½ D) gravity modelling along seven selected profiles, across the Beattie Magnetic Anomaly (BMA), revealed that the Ecca Group sediments, a target for shale gas exploration in the Karoo, occurs within a depth range of 0 - 4000 m from the surface. The basin deepens to a depth of 4600 m in the southwestern region, near the front of the Cape Fold Belt. It was observed as well that the Karoo dolerite sills are connected at depths and are mostly concentrated at the centre, the deepest part of the basin with some having saucer shape - like structure. These observations correspond well with the borehole data from AB 1/65 and QU 1/65 presented in Linol and de Wit (2016). Thickness isochore maps that were extracted from the gravity models indicate that the Ecca Group, which is the main target for hydrocarbon exploration, thickens to the south away from the centre of the basin and reaches thicknesses of greater than 3680 m. The Beaufort Group proves to be the thickest succession in the Karoo Basin with an estimated thickness of up to 6046 m. Constructed geophysical maps with the geology overlain reveal that most magnetic anomalies are due to dolerite intrusions, while gravity lows are due to less dense shales of the Ecca Group. The depth slices of magnetic data indicate that near surface magnetic bodies occur within the depth of 42 m from the surface whereas deep seated ones occur as deep as 9488 m and possibly deeper. Gravity depth slices reveal signatures that are predominant at depth of 2403 m are of short wavelength and are mainly lineaments and circular structures. They ultimately disappear at depth of 7120 m. The depth slices further indicate that the intensity of both magnetic and gravity long wavelength signatures become stronger with increasing depths.
- Full Text:
- Date Issued: 2017
A study of the southwestern Karoo basin in South Africa using magnetic and gravity data
- Authors: Nxantsiya, Zusakhe
- Date: 2017
- Subjects: Groundwater -- South Africa -- Karoo Aquifers -- South Africa -- Karoo Hydrology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/4748 , vital:28509
- Description: The early efforts of Booth, Johnson, Rubidge, Catuneanu, de Wit, Chevallier, Stankiewicz, Weckmann and many other scientists in studying the Karoo Supergroup has led to comprehensive documentation of the geology on the main Karoo Basin with regards to understanding the age, sedimentology, sedimentary facies and depositional environments. In spite of these studies, the subsurface structure, variations in thickness of various formations in large parts of the basin, the location and orientation of subsurface dolerite intrusions, and the depth to magnetic and gravity sources remains poorly documented. A geological study with the aid of geophysical techniques, magnetic and gravity, was conducted in the southwestern part of the main Karoo Basin. The objectives of the study were to construct numerous models of the main basin that image the crust to a depth of 45 km, to determine thicknesses of various formations, to relate observed geophysical anomalies with geological bodies and lineaments, to estimate the depth of existing anomalous bodies, to determine densities and porosity of various formations, as well as to determine the mineralogy of various rocks in the Karoo Basin.
- Full Text:
- Date Issued: 2017
Nontsizi Mgqwetho’s the nation’s bounty: a prophetic voice towards an African literary theory
- Authors: Nxasana, Thulani
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/4547 , vital:20687
- Description: This thesis seeks to examine the ways in which Africans and African scholarship in particular have relied on the West to lead the way in scientific inquiry, theory and ways of approaching literary texts thus the stunting effects of this in the growth and development of uniquely African literary scholarship and theorising. In his seminal work, Decolonising the Mind, Wa Thiong’o (1987a) stresses that “...how we view ourselves, our environment even, is very much dependent on where we stand in relationship to imperialism in its colonial and neocolonial stages; that if we are to do anything about our individual and collective being today, then we have to coldly and consciously look at what imperialism has been doing to us and to our view of ourselves in the universe” (Wa Thiong’o, 1987a, p.88). Although most African countries obtained their liberation decades ago, seemingly western cultural imperialism still dominates and plagues the African psyche; hence they largely look to the West and ways of the West for established and emergent theoretical conceptions. This thesis aims to interrogate popular western literary theories unquestioningly used to analyse African works, particularly feminism and post-colonial theory; furthermore, to show crucial factors not taken into account such as the evolving power dynamics in African societies, the role of the “sacred” or spirituality which often forms and informs the dynamics of the text, and lastly, based on the poetry of Nontsizi Mgqwetho, to advocate for the need for an African literary theory and put forward the essential tenets of such a theory. The poetry of Xhosa poet, Nontsizi Mgqwetho, is used to analyse the complexities and dynamics of African literary production written in African languages; her poetry is written in isiXhosa to a Xhosa audience, a far cry from the assumption that African literary texts are concerned with writing to the “centre” as post-colonial theorists claim. Her work explicitly provides Africans with an approach to overcome territorial and cultural imperialism; she sees within the African psyche and traditional values empowering modes of resistance against any type of domination and through her poetry illustrates meaningful ways that Africans can critically engage with and examine the positives and negatives of cultural exchange and or assimilation, and the effects thereof while at the same time remaining proudly Africa.
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- Date Issued: 2017